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Gould and Pyle's Cyclopedia of 
 Practical Medicine and Surgery 
 
 Illustrated* One Volume 
 With 74 Special Contributors 
 
 A Concise Reference Handbook (Alphabetically 
 Arranged) of Medicine, Surgery, Obstetrics, Materia 
 Medica, Therapeutics, and the various specialties, 
 with Particular Reference to Diagnosis and Treat- 
 ment. Compiled under the Editorial Supervision of 
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 spond with Gould's " Illustrated Dictionary." 
 
 Full Sheep or y 2 Dark-Green Leather, net, $10.00 
 
 With Thumb Index, net, $11.00 
 
 Half Russia, Thumb Index, net, $12.00 
 
 The great success of Dr. Gould's " Illustrated Diction- 
 ary of Medicine " suggested the preparation of this com- 
 panion volume, which should be the same trustworthy 
 handbook in the broad field of general medical infor- 
 mation that the Dictionary is in the more special one of 
 the explanation of words and the statement of facts. 
 
 The seventy-four special contributors — the names of 
 whom are given in our special circular — have been selected 
 from all parts of the country in accordance with their fitness 
 for treating special subjects about which they may be 
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 work of the kind. 
 
 A Special Circular with Detail Description of Con- 
 tents, Press Notices, etc., sent free upon application 
 
 P. BLAKISTON'S SON & CO., :: Publishers 
 
PRACTICAL TREATISE 
 
 MECHANICAL DENTISTRY 
 
 BY 
 
 JOSEPH RICHARDSON, M.D., D.D.S. 
 
 LATE PROFESSOR OF THE PRINCIPLES OF PROSTHETIC DENTISTRY IN THE INDIANA DENTAL COLLEGE, 
 
 ETC., ETC. 
 
 SEVENTH EDITION 
 
 REVISED, ENLARGED, AND EDITED BY 
 
 GEORGE W. WARREN, A.M., D.D.S. 
 
 PROFESSOR OF CLINICAL DENTISTRY AND ORAL SURGERY; CHIEF OF THE CLINICAL STAFF, PENNSYLVANIA 
 
 COLLEGE OF DENTAL SURGERY, PHILADELPHIA; AUTHOR OF "A COMPEND ON DENTAL 
 
 PATHOLOGY AND DENTAL MEDICINE," AND " A COMPEND OF 
 
 DENTAL PROSTHESIS AND METALLURGY'." 
 
 WITH SIX HUNDRED AND NINETY-ONE ILLUSTRATIONS 
 
 MANY OF WHICH ARE FROM NEW AND ORIGINAL DRAWINGS 
 
 PHILADELPHIA 
 P. BLAKISTON'S SON & CO. 
 
 IOI2 WALNUT STREET 
 I9O3 
 
Entered according to Act of Congress, in the year 1897, by 
 
 P. BLAKISTON, SON & CO., 
 
 In the Office of the Librarian of Congress, at Washington, D. C. 
 
 
 JbJft 
 
 I « / Q 
 
Co 
 
 THE MEMORY OF THE LATE 
 
 JAMES TAYLOR, M.D., D.D.S., 
 
 FORMERLY EMERITUS PROFESSOR OF THE INSTITUTES OF DENTAL SCIENCE 
 IN THE OHIO COLLEGE OF DENTAL SURGERY, 
 
 ACKNOWLEDGMENT OF PROFESSIONAL EMINENCE 
 AND PRIVATE WORTH, 
 
 Ctyis Volumt ts gratefullg inscrffieo, 
 
 BY 
 HIS FORMER PUPIL, 
 
 THE AUTHOR. 
 
NOTE. 
 
 In preparing the seventh edition of this work, the editor's effort 
 has been to make it preeminently practical as a text-book for 
 students, and a guide for young practitioners, — an exponent of the 
 present status of dental prosthesis. Much of the text has been 
 rewritten; three new chapters, new appliances, and systems have 
 been introduced; while useless methods and obsolete theories have 
 been eliminated, thus keeping the dimensions of the book convenient 
 and compact. 
 
 The editor desires to acknowledge his indebtedness to the writ- 
 ings of Professors Wilbur F. Litch, C. J. Essig, L. P. Haskell, and 
 Drs. George Evans, James W. White, Eben F. Flagg, John Allen, 
 
 Theo. F. Chupein, and others. 
 
 Geo. W. Warren. 
 
 Philadelphia, April, 1897. 
 
PREFACE TO FIFTH EDITION. 
 
 The demand for a fifth edition of the present work, following 
 •closely upon the publication of the one immediately preceding, 
 affords gratifying assurance of the profession's recognition of the 
 treatise as a trustworthy exponent of the present status of pros- 
 thetic dentistry as illustrated in the practice and teachings of its 
 representative members. 
 
 Not less obviously does it furnish proof of an increasing inter- 
 est in a department of dental practice that has amply vindicated 
 its claim to rank as a conservative branch of the healing art; a dis- 
 tinction due, in large part, to the introduction and growth of more 
 or less perfected systems of root-crowning and bridge dentures — 
 systems involving processes of repair and methods of curative treat- 
 ment that do not suffer by comparison with those practised at the 
 chair in the important work of restoring to usefulness organs whose 
 natural functions have been impaired or wholly subverted by the 
 ravages of decay. 
 
 It is a suggestive fact, commended to the consideration of those 
 -who characterize prosthetic dentistry as essentially " mechanical," 
 and who seek to disparage the professional and scientific qualifica- 
 tions necessary to success in this department, that the results 
 achieved by the conservative methods alluded to have been reached 
 only through a critical study of tooth-structure and function, a 
 familiar acquaintance with pathological conditions associated with 
 diseased teeth and implicated tissues, a comprehensive knowledge 
 •of the curative resources of dental therapeutics, a broad and intelli- 
 gent apprehension of principles underlying mechanical devices, and 
 a marvelous development of ingenuity and manipulative skill. 
 
 For obvious reasons, therefore, large space is given to the con- 
 sideration of these systems of crown replacement, the value and 
 importance of which command, at this time, general and deserved 
 recognition. Subjected to the crucial tests of time, and amenable 
 
X PREFACE TO FIFTH EDITION. 
 
 to the inexorable verdict of experience, many of them, doubtless, 
 will at no distant day take their place " down among the dead 
 men," while others, in obedience to the operation of laws that de- 
 termine the " survival of the fittest," will live and take a fixed place 
 among other humane devices that have proved lasting benefactions 
 to mankind. 
 
 Without indicating specifically the supplemental contributions 
 incorporated in this edition, it will be sufficient to state that the 
 work has been materially enriched by the introduction of special 
 methods of substitution, and various laboratory appliances, so con- 
 spicuously meritorious that they may properly be said to mark an 
 era in the development of prosthetic practice. 
 
 Joseph Richardson. 
 
 Terre Haute, Ind. 
 
CONTENTS. 
 
 PAGE. 
 
 Dedication, v 
 
 Editor's Note, vii 
 
 Preface, ix 
 
 Introduction, 17 
 
 CHAPTER I. 
 
 Fuels, - 22-30 
 
 Liquid Fuels ; Solid Fuels ; Gaseous Fuels. 
 
 CHAPTER II. 
 
 Appliances used in the Generation and Application of Heat, 31-67 
 
 Lamps ; Burners ; Blowpipes ; Supports ; Furnaces ; Heaters ; Crucibles ; 
 Principles of Soldering. 
 
 CHAPTER III. 
 
 Metals Employed in Dental Laboratory Operations, 68-73 
 
 Gold, Properties of; Properties of Particular Alloys of Gold. 
 
 CHAPTER IV. 
 Refining Gold, Elements Employed, etc., 74-79 
 
 CHAPTER V. 
 
 Alloys of Gold for Dental Purposes, 80-88 
 
 Formulas for Gold Plate used as a Base for Artificial Dentures ; Clasps, 
 Wire, Stays or Backings, Metal Pins, etc. ; Gold Solders, Formulas 
 for ; Method of Reducing Gold to a Lower or Raising to a Higher 
 Standard of Fineness, and of Determining the Carat of any given 
 Alloy. 
 
 CHAPTER VI. 
 
 Method of Converting Gold Alloys into the Required Forms for 
 
 Dental Purposes, 89-97 
 
 Thickness of Gold Plate Required as a Base for Artificial Dentures, 
 Clasps, Backings, etc. ; Reduction of Gold Solders into Proper 
 Form for Use ; Method of Obtaining Gold Wire, Constructing 
 Spiral Springs, etc. 
 
 xi 
 
Xll CONTENTS. 
 
 CHAPTER VII. page. 
 
 Silver, General Properties of, Alloys of, Refining Alloys of, etc.,. . . 98-102 
 Reduction of Silver to Required Forms for Dental Purposes ; Formulas 
 for Silver Solders. 
 
 CHAPTER VIII. 
 Platinum, Platinoid Metals, and their Alloys, 103-106 
 
 CHAPTER IX. 
 Aluminium, General Properties and Alloys of, 1 07-1 10 
 
 CHAPTER X. 
 Copper, Zinc, Lead, Tin, Antimony, and Bismuth, and their Alloys,. 111-116 
 
 CHAPTER XI. 
 
 General Properties of Alloys, and their Treatment and Behavior 
 
 in the Process of Compounding, 11 7-1 19 
 
 CHAPTER XII. 
 
 Treatment of the Mouth Preparatory to the Insertion of Artificial 
 Dentures, and Time Necessary to Elapse After the Extrac- 
 tion of the Teeth Before Inserting Artificial Dentures,.... 120-125 
 
 CHAPTER XIII. 
 
 Materials, Appliances, and Methods Employed in Obtaining Impres- 
 sions of the Mouth 126-147 
 
 CHAPTER XIV. 
 Plaster Models, and Manner of Obtaining Same, 148-155 
 
 CHAPTER XV. 
 
 Metallic Dies and Counter-Dies ; Manner of Obtaining ; Essential 
 
 Properties, etc., 1 56-1 77 
 
 CHAPTER XVI. 
 
 Partial Dentures Retained in the Mouth by Means of Clasps At- 
 tached to the Natural Teeth, 178-197 
 
 Remarks on the Use of Clasps ; The Teeth most Suitable for Clasp- 
 ing ; Separation of the Teeth for the Reception of Clasps ; Modi- 
 fications in the Form of Clasps ; Modifications in the Form of 
 Plates for Partial Dentures Supported by Clasps ; Swaging or 
 Stamping the Plate, etc. 
 
 CHAPTER XVII. 
 
 Partial Dentures Supported in the Mouth by Atmospheric Pres- 
 sure or Adhesion ; Modifications in the Form of the Base, 
 etc 198-201 
 
CONTENTS. Xlll 
 
 CHAPTER XVIII. page, 
 
 Method of Obtaining an Antagonizing Model for Partial Dentures ; 
 Selecting, Arranging, and Antagonizing the Teeth ; Investing, 
 Adjusting Stays, Soldering, etc., • • • 202-212 
 
 CHAPTER XIX. 
 
 Entire Dentures, 213-232 
 
 A Consideration of the Principles and Attendant Phenomena In- 
 volved in the Application of the Forces Utilized as a Means 
 of Attachment; Esthetic Requirements in the Selection and Ar- 
 rangement of the Teeth of Replacement; The Four Basal Tem- 
 peraments and their General Indications ; The Teeth as Indicated 
 by Temperament; Temperament in Relation to the Teeth. 
 
 CHAPTER XX. 
 Entire Dentures Attached to a Swaged Metallic Plate Base, 233-257 
 
 CHAPTER XXI. 
 Manufacture of Porcelain Teeth, 258-263 
 
 CHAPTER XXII. 
 " Continuous-Gum " Dentures, 264-280 
 
 CHAPTER XXIII. 
 Rubber or Vulcanite Base, 281-326 
 
 CHAPTER XXIV. 
 Celluloid Base, 3 2 7~353 
 
 CHAPTER XXV. 
 Attaching Porcelain Teeth to a Metallic Base with Rubber or Cel- 
 luloid, 354-36i 
 
 CHAPTER XXVI. 
 Cast Metal Base, 362-372 
 
 CHAPTER XXVII. 
 Defects of the Palatal Organs and their Treatment by Artificial 
 
 Means, 373-399 
 
 CHAPTER XXVIII. 
 Appliances for the Correction of Fractured Maxillje (Interdental 
 
 Splints), 400-433 
 
XIV CONTENTS. 
 
 CHAPTER XXIX. PAGE . 
 
 Appliances for the Correction of Dental Irregularities, 434-473 
 
 CHAPTER XXX. 
 Artificial Crowns, 474-55 1 
 
 CHAPTER XXXI. 
 Bridge Dentures, . . . 552-654 
 
 CHAPTER XXXII. 
 Electricity, and its Application in Dental Mechanics, 655-670 
 
A TREATISE 
 
 MECHANICAL DENTISTRY. 
 
 INTRODUCTION. 
 
 Before entering upon a detailed account of the agencies, pro- 
 cesses, and methods appertaining to the department of dental 
 practice to which this work relates, some general reflections may 
 not be inappropriate. 
 
 It is not the purpose of the writer to unduly magnify the claims 
 of prosthetic dentistry upon the regard and consideration of the 
 profession. A just estimate of the nature of its requirements, and 
 the results contemplated in its practice, as well as the abundance 
 and sufficiency of its resources in the accomplishment of its high 
 and humane purposes, will, it is believed, amply vindicate its im- 
 portance, its possibilities, and its beneficence as a department of 
 practical dentistry having intimate relation to the necessities of 
 the unfortunate. 
 
 The untimely or premature loss of the natural teeth may be 
 ascribed to a number of diverse causes. Multitudes are lost in 
 consequence of abuse or neglect, or the dread of pain so com- 
 monly associated with the means employed in their preservation ; 
 many from unavoidable accident ; and countless numbers are sac- 
 rificed through the incompetency and dishonesty of ignorant and 
 unscrupulous operators who, in one guise or another, infest and 
 prey upon communities. 
 
 Nor can we exclude from this list of causes another source 
 of loss which, by implication, declares the impotence of the pro- 
 fession's curative resources in the absolute conservation of these 
 
 2 jy 
 
1 8 MECHANICAL DENTISTRY. 
 
 important organs. Whatever sense of humiliation may attend the 
 statement, it is nevertheless true that the highest attainable skill 
 directed to the permanent preservation of the natural teeth must, 
 in the very nature of things, often prove inadequate and abortive, 
 for no proposition is more broadly or more generally recognized 
 by intelligent practitioners than that conservative practice has its 
 limitations growing out of conditions associated with individual 
 organisms and environments wholly beyond the control of the 
 operator. Whatever triumphs (and they are many and conspicu- 
 ous) modern conservative dentistry may have achieved in the way 
 of narrowing the field of prosthetic practice, the prophecy, born of 
 hope, that the time will come when the utmost resources of human 
 skill will, in respect of the teeth, be able to exempt mankind 
 wholly from the penalties of transgressed law, is as Utopian and 
 delusive as the faith that prophylactic or preventive medicine will 
 ultimately eradicate every form of disease that at present afflicts 
 mankind. They are alike the dreams of enthusiasts and vision- 
 aries. Physical infirmity, in one form or another, is the heritage of 
 the race, and human skill, however well directed or conscientiously 
 and intelligently administered, can do little more than mitigate the 
 "pains and penalties" of the primal curse that rests upon all. 
 
 It is the peculiar and distinctive prerogative of prosthetic den- 
 tistry to devise and perfect means for the amelioration of the con- 
 dition of those who, from whatever cause, have suffered one of the 
 gravest forms of mutilation in the loss of organs so essential to the 
 healthful performance of many important functions. In this spe- 
 cial field of humane endeavor the highest order of qualification is 
 imperatively demanded for the complete fulfilment of its diversi- 
 fied and complex requirements. No one can be said to be properly 
 equipped for its duties who has not a more or less familiar ac- 
 quaintance with such of the several branches of Physics and 
 Natural Philosophy as relate in any manner to his special work, 
 while an exact knowledge of the Anatomy, Physiology, and Path- 
 ology of the tissues or structures in any way related to the substi- 
 tute is absolutely indispensable. Added to such qualifications is 
 the essential requirement of the highest order of manipulative 
 skill. But beyond all these qualifications, and supplementing 
 them, is that art culture which is the crown and inspiration of all 
 perfect work in every form of substitution, and without which the 
 
INTRODUCTION. 
 
 19 
 
 best results of mere handcraft are, in the main, but little better than 
 libels and caricatures. In no other department of practical dentis- 
 try is the art instinct so strongly appealed to, or so imperiously 
 demanded as a condition of the highest success. Dr. Eben M. 
 Flagg, in an essay on Dental Art, very aptly says: "There is an 
 element which enters into the conception and execution of every 
 branch of our labor, and more or less forms part of every opera- 
 tion that we are called upon to make, be it surgical, operative, or 
 prosthetic. This element lightens our drudgery, enlarges our 
 souls, gives individuality to our work, and brings satisfaction to 
 ourselves that fully repays the time spent in fulfilling its require- 
 ments. It was born with our race, and has inseparably accompa- 
 nied every movement that has brought comfort and happiness to 
 man. It has contributed its share toward raising the physician 
 from a mere 'bleeding, physicking, leeching' animal, to the posi- 
 tion he occupies to-day, and has shown the mechanic and inventor 
 that, if he would be great, he must be more than an artisan ; he 
 must be an artist. This element — the element of art — whenever 
 it enters the field of human life, has for its function to finish and 
 render attractive the hard labor that preceded it. Thus, we do 
 not find it in its full manifestation except in those departments 
 of labor which have attained scientific certainty." 
 
 Among the unnumbered millions of human beings who have 
 .peopled the earth since the dawn of time, it may be affirmed that 
 no two have been created with faces exactly alike. There is the 
 same aggregate of features, and a pervading general resemblance 
 of one person to another, but there will be found as infinite a multi- 
 plication of distinct shades of facial expression as there are human 
 faces, and each separate shade of expression characteristic of each 
 one, and distinguishing him or her from all others, constitutes fa- 
 cial individuality. Each separate feature — as the eye, the nose, the 
 mouth, the teeth, facial contour, complexion, temperament, etc. — 
 contributes to this individuality, and no one special feature more, 
 perhaps, than the teeth. There are few more repulsive deformities 
 than those inflicted by the loss of these organs, and none more fa- 
 tal to the habitual and characteristic expression of the individual. 
 It is the special mission, as it is the first and highest duty, of the 
 dentist to preserve this individuality intact, and an equally impera- 
 tive duty to restore it as perfectly as possible when impaired. To 
 
20 MECHANICAL DENTISTRY. 
 
 fulfil, in the most perfect manner possible, this most difficult of 
 all the requirements of prosthetic practice implies an art culture 
 that is competent to interpret the distinct play of features asso- 
 ciated with individual physiognomies, to differentiate individual 
 temperaments, and make available the sculptor's and painter's 
 perceptions of the subtle harmonies of form and color. 
 
 To the failure or inability to properly comprehend the practical 
 import or significance of individual characteristics, so far as they 
 find expression in the teeth, and the consequent failure to con- 
 form our methods of replacement to the imperative requirements 
 of art, may be fairly ascribed the deserved reproach into which 
 prosthetic practice has fallen, and not, as is generally charged, to 
 the employment of any particular material or methods concerned 
 in the mechanical execution of the work. 
 
 There is no material classed among the so-called "cheap bases" 
 that does not embody art possibilities far beyond what is being 
 continually illustrated in general practice. Unquestionably they 
 are not the best for the purpose, but they may be greatly en- 
 hanced in value, and rendered more deserving of professional 
 favor, if utilized in conformity with the esthetic requirements im- 
 peratively demanded in all forms of substitution. 
 
 There is an ethical phase of this subject which must enter as an 
 element into the profession's estimate of the suitableness of these 
 inferior forms of replacement — a question of obligation and re- . 
 sponsibility involving a problem the solution of which should be 
 attempted without unreasonable prejudice or unjust discrimina- 
 tion so far as materials and methods are concerned. There are 
 multitudes in every community who, though not in indigent cir- 
 cumstances, are unable to secure expensive services without great 
 hardship, and other multitudes who perforce must suffer lasting 
 harm and prolonged deformity on the same terms. Dentistry, like 
 Medicine, is professedly a humane calling, and it would be well to 
 consider whether the afflicted have not just claims upon the pro- 
 fession's resources in providing them with inexpensive means of 
 relief. Until the time comes when the necessities of this class can 
 be supplied with wholly unobjectionable forms of substitution at a 
 cost that is not oppressive, or that does not altogether deny relief, 
 it will be well to cease indiscriminate condemnation of materials 
 and methods which, when properly considered in relation to their 
 
INTRODUCTION. 2E 
 
 yet undeveloped possibilities, are far from being unmixed evils. 
 That there are radical and inherent objections to the use of vege- 
 table plastics that do not attach to metallic bases is unquestion- 
 able, but it is equally true that the nature, behavior, and proper or 
 scientific treatment of these substances have not been, until quite 
 recently, well understood ; that imperfect appliances have hereto- 
 fore failed to develop their best qualities, and, above all, that there 
 is a prevailing disregard or ignorance of all esthetic requirements 
 in the uses to which they are applied. That the facility they 
 afford for the ready construction of substitutes has attracted to 
 the ranks of the profession a mercenary and unscrupulous class of 
 operators, is as true as it is unfortunate. However powerless the 
 profession may have been in the past to check this evil, the re- 
 sponsibility for its continuance in the future will rest largely with 
 the profession itself. There is a reasonable assurance that the 
 era of irresponsible quackery is fast passing away. The people 
 of three-fourths of the States of the Union have, through their 
 representatives, generously and confidingly relegated to the pro- 
 fession the power of providing a remedy for the evils of char- 
 latanry, and have, under legal forms, designated our colleges and 
 boards of examiners as the proper custodians of the profession's 
 honor and the people's interest. A faithful execution of the trust 
 reposed in these bodies will go far to redeem prosthetic practice 
 from the undeserved reproach brought upon it by a prostitution 
 of its legitimate resources wholly unworthy of toleration and ut- 
 terly destructive of all sense of professional self-respect. 
 
CHAPTER I. 
 
 FUELS EMPLOYED IN LABORATORY PROCESSES. 
 
 It is essential that the mechanical operator should have some 
 intelligent conception of the nature and properties of such com^- 
 bustible substances as are ordinarily used in the dental laboratory 
 for the generation of heat. This, and a somewhat familiar ac- 
 quaintance with approved appliances used in the application of 
 heat and adapted to his peculiar needs, are indispensable requis- 
 ites to the successful practice of the department of practical den- 
 tistry to which this work relates. Only such heat-producing sub- 
 stances as are deemed suitable for dental laboratory operations 
 will be considered with any degree of particularity. 
 
 The general forms of fuel may be classified as Liquid, Solid, and 
 Gaseous. They will be treated of, in more or less detail, under 
 these general heads. 
 
 LIQUID FUELS. 
 
 In connection with lamps designed chiefly for soldering pur- 
 poses and vulcanizing, the substances usually employed are alco- 
 hol, gasolene, or kerosene. When alcohol is employed, the lamp 
 shown in Fig. I is found very convenient and useful. Gasolene is 
 used in connection with the Oxycarbon Forge (see page 43), 
 while good kerosene, uncontaminated with naphtha, may be used 
 with safety, and is, in many cases, a valuable substitute for other 
 combustible materials for general heating purposes, and is largely 
 employed in connection with vulcanite and celluloid work by 
 those unable to command the ordinary illuminating gas. 
 
 SOLID FUELS. 
 
 Under this head are comprehended such combustible substances 
 as are used for fires or draft furnaces, as wood, charcoal, bitumin- 
 ous and anthracite coal, and coke. For baking or muffle furnaces 
 used in tin- construction of continuous-gum work 'and other allied 
 processes, anthracite and coke are esteemed the most suitable on 
 
 22 
 
FUELS EMPLOYED IN LABORATORY PROCESSES. 23 
 
 account of the high temperatures attainable in their use, and the 
 persistent or prolonged heat consequent on the comparatively 
 slow waste of substance in the process of combustion. 
 
 Wood, except when charred, is wholly unsuited for laboratory 
 work. 
 
 Charcoal is the solid residuum of the destructive distillation of 
 wood. It is obtained by igniting wood, and then excluding it 
 from the air while burning; the volatile products are thus driven 
 off, while the carbon remains. The chemical composition of the 
 ordinary charcoal of commerce is given in the following table, in 
 which it will be seen to consist principally of carbon, combined 
 with certain volatile constituents, a considerable percentage of 
 absorbed water, and but little ash : 
 
 Carbon, 70 Nitrogen, 1 
 
 Hydrogen, 5 Ash, 2 
 
 Oxygen, 11 Hygroscopic moisture, .... 11 
 
 During the process of charring, the volatile constituents — hy- 
 drogen, oxygen, and nitrogen — are, in a large measure, driven off, 
 but no temperature that can be commanded, and no time, how- 
 ever prolonged, will wholly expel them. 
 
 Charcoal is insipid and inodorous, is a poor conductor of heat 
 and a good conductor of electricity, is insoluble in water, is at- 
 tacked by nitric acid with difficulty, and is but little affected by 
 the other acids or by alkalies. Its carbon constituent is exceed- 
 ingly refractory to heat, and, if secluded in a retort, will neither 
 fuse nor volatilize under the highest temperature that can be pro- 
 duced. This latter property of carbon, in connection with that 
 of its comparative non-conduction of heat, makes it a valuable in- 
 gredient in the construction of supports used in soldering, repre- 
 sented in the carbon block and cylinder (Figs. 27, 28), and in the 
 devices (Figs. 50, 51) combining crucible and ingot mold. Char- 
 coal retains the organic structure of the wood from which it was 
 produced, except when prepared at a very high temperature, when 
 it becomes a black, shining, porous mass, resembling fossil coal, 
 with a considerable increase in density and without a trace of 
 organic structure. 
 
 When it is desired to maintain a high heat in a small compass, 
 the charcoal best adapted to the purpose is that obtained from 
 what is termed hard wood, as the beech, the oak, the alder, the 
 
24 MECHANICAL DENTISTRY. 
 
 birch, the elm, etc. A cubic foot of charcoal derived from these 
 woods weighs, upon an average, from 12 to 13 pounds, while 
 a similar bulk obtained from soft wood, as the fir, the different 
 kinds of pine, the larch, the linden, the willow, and the poplar, 
 averages only from eight to nine pounds.* There is, therefore, 
 economy in the use of the former when purchased in bulk ; and of 
 this class the beech-wood charcoal is the best on account of its 
 greater specific gravity. Charcoals derived from the hard woods 
 possess the additional advantage of generating a more equable 
 and enduring temperature, and are, therefore, better adapted to 
 operations in the laboratory requiring a prolonged heat. The 
 more heavy charcoals require a stronger draft than those of a 
 lighter character, as a more generous supply of oxygen is neces- 
 sary to their perfect combustion. Charcoal should be kept as dry 
 as practicable, since it readily absorbs moisture from the atmos- 
 phere, by which its calorific energy is materially impaired. 
 
 Bituminous, or pit coals, are generally unfit for the uses re- 
 quired of fuel by the dentist, on account of the excessive carbona- 
 ceous residue accompanying their combustion, and are, therefore, 
 seldom used except when reduced to that form of mineral char- 
 coal known as coke. 
 
 As charcoal, coke, or a mixture of the two, and anthracite coal 
 are the heat-producing substances chiefly used in the processes 
 of the dental laboratory requiring the employment of solid fuels, 
 they will be more particularly described. 
 
 Coke. — This substance is a carbonaceous product obtained from 
 bituminous coal that has been exposed to ignition for some time, 
 excluded from the contact of air, the volatile constituents of the 
 coal, like those of wood, having been driven off by the heat. There 
 are two different varieties of this mineral charcoal, namely, gas 
 coke, obtained from' the retorts of gas works after the gases have 
 been separated ; and oven coke, which is made in ovens or pits, 
 and which is considered by manufacturers as the only true coke, 
 gas coke being merely cinder. There is a marked difference in the 
 appearance of the two kinds of coke, the principal part of that 
 obtained from gas houses being of a dull, iron-black color, very 
 spongy and friable, is more rapidly consumed in the process of 
 
 *Ure. 
 
FUELS EMPLOYED IN LABORATORY PROCESSES. 25 
 
 combustion, and produces less heat than the harder .and more 
 compact variety. The best coke for heating purposes is the oven 
 or pit coke, which has a steel-gray color, with somewhat metallic 
 luster, is compact in structure, and splits into pieces having a 
 longitudinal fracture. Whenever it can be procured, the latter 
 should always be preferred in connection with the use of the bak- 
 ing or muffle furnaces employed in the fabrication of continuous- 
 gum work, porcelain teeth, etc. Until the more recent substitu- 
 tion of anthracite, the former was exclusively employed for these 
 purposes, and is in every way suitable in the production of high 
 and persistent temperatures. It is sometimes used combined 
 with charcoal, but, when fairly ignited, gives an augmented and 
 more lasting heat when used alone. 
 
 Coke does not readily ignite, and at first generally requires the 
 admixture of charcoal to effect its combustion ; it also requires a 
 strong draft to burn it, but when thoroughly ignited it produces 
 an intense and persistent heat. As before stated, it is one of the 
 principal fuels used in baking mineral teeth, porcelain blocks, 
 and the silicious compounds employed in the construction of con- 
 tinuous-gum work. 
 
 Professor Piggot, in his remarks on the comparative value of 
 fuels, observes: "Practically, for the purpose of the chemist, the 
 best fuel is charcoal or coke, or a mixture of the two. The ash of 
 charcoal being infusible, it passes through the bars of the grate as 
 a white powder. Should potash, however, be in large excess, it 
 corrodes the bricks by forming with them a silicate of potash, 
 which runs down the walls and chokes the bars. In small quanti- 
 ties this action is beneficial, as it furnishes a protective varnish, 
 and unites the bricks and lutes by forming a sort of cement, which 
 intimately combines with them. 
 
 "Coke contains a very variable amount of ash, which is com- 
 posed chiefly of oxid of iron and clay. When pure it forms a 
 harmless slag, which injures neither the furnace nor the crucibles. 
 Usually, however, the oxid of iron predominates. In this case 
 the ash is very injurious, for it is reduced to a protoxid, which is 
 not only fusible, but powerfully corrosive to all argillaceous mat- 
 ters, so that both the crucibles and furnaces suffer."* 
 
 * " Dental Chemistry and Metallurgy." 
 
26 MECHANICAL DENTISTRY. 
 
 Anthracite. — Anthracite is the most condensed variety of 
 mineral coal, containing the largest proportion of carbon and the 
 smallest quantity of volatile matter. With the exception of the 
 diamond, it is the purest form of carbon in its natural state. The 
 best specimens contain 95 per cent, carbon, but the average pro- 
 duction of the purest beds of this coal will not exceed 90 per cent., 
 and generally not more than 80 to 87 per cent, carbon. The volatile 
 matter in the dense, hard varieties, is almost exclusively water and 
 earthy impurities, but in common varieties the volatile portion 
 consists of water, hydrogen, oxygen, and nitrogen, while the ash or 
 incombustible matter contains oxid of iron, iron pyrites, silica, alu- 
 mina, magnesia, lime, etc. Anthracite which contains only 80 per 
 cent, carbon, with 20 per cent, water and incombustible matter, 
 is the lowest grade of commercial coal, and of little value as fuel. 
 
 The general features and fractures of hard anthracite are pecu- 
 liar and noticeable to the common observer. They are massive, 
 hard, dense, amorphous or conchoidal in fracture, with fine, sharp 
 edges when broken, and a rich satin or an iron-black sub-metallic 
 luster. With some local exceptions the softer varieties, both red- 
 and white-ash (by which name the Pennsylvania anthracite coals 
 are generally known), are less massive, hard, and dense, more 
 regular and cubical in fracture, and, exclusive of the upper red- 
 ash beds, less rich and lustrous. 
 
 Anthracite coals, in greater or less abundance, and of varying 
 qualities, are found in several of the States and territories of the 
 Union, namely, in Pennsylvania, Massachusetts, Rhode Island, 
 Virginia, Arkansas, Oregon, and in New Mexico and Sonora. Of 
 the European anthracite fields, exclusive of those in Wales, Eng- 
 land, the most prolific and largely developed are those in France, 
 while others of more limited production are found in Spain, Por- 
 tugal, Germany, Austria, and Norway. Anthracite also exists in 
 Persia, India, China, and in South America. The most prominent 
 anthracite fields of the world, however, are those of Pennsylvania 
 and South Wales, which produce nine-tenths of the quantity used. 
 
 The first authentic account which we find of the use of anthracite 
 in the United States was in 1768-69, when it was used by two 
 blacksmiths from Connecticut, named Gore. It did not,on account 
 of the difficulty of making it burn, come into use for domestic pur- 
 poses till 1808, when Judge Fell succeeded in burning "stone coal" 
 
FUELS EMPLOYED IN LABORATORY PROCESSES. 27 
 
 in a grate of his own construction. This was probably the first 
 successful use of anthracite for general purposes in the world. 
 So imperfectly were the properties of this fuel understood, and so 
 little known of its proper management, that four years later, Col. 
 Shoemaker, who had disposed of several loads of it to parties in 
 Philadelphia who were unable to burn it, was arrested, upon a 
 writ obtained from the city authorities, as an impostor and swind- 
 ler, who had sold them rocks for coal. 
 
 Prof. H. D. Rogers explains the formation of anthracite by sup- 
 posing it to be the result of altered bituminous coal metamor- 
 phosed by intense heat, and, of course, by heat induced subse- 
 quent to the formation of the bituminous beds ; and he further 
 explains the escape of the volatile portion of the latter as gas 
 through cracks and openings caused by the plication of the an- 
 thracite strata. This plication follows closely the general type 
 of the paleozoic rocks, which are intensely crushed and folded 
 near the contact of their edges with the igneous or granitic rocks, 
 and much less plicated and distorted in a western direction. This 
 theory, though natural and ingenious, is controverted by others 
 who contend that anthracite is not a metamorphosis of bitumin- 
 ous coal, but as much a normal creation as the bituminous variety 
 itself, from a combination of its constituents under superior heat, 
 however the original elements were produced. 
 
 The particular mineral fuel under consideration has been treated 
 of here somewhat at length, for the reason that it is being more 
 generally employed of late years by the dentist, not only for re- 
 fining and general heating purposes, but more especially in those 
 important processes of the dental laboratory in which more or 
 less refractory silicious substances requiring a high, uniform, and 
 prolonged heat, are employed in compounding body and gum 
 enamels, in baking mineral teeth, and in the construction of con- 
 tinuous-gum work. For the latter especially, it is preferred by 
 many to coke, in connection with solid fuel furnaces. 
 
 Owing to the difficulty of igniting anthracite, it is customary to 
 mix with it at first about an equal quantity of charcoal. Its proper 
 combustion after ignition, when burned alone, requires a strong 
 draft, which is ordinarily attainable in use of the ordinary draft or 
 muffle furnace properly connected with a suitable flue. Under con- 
 ditions that insure more or less complete combustion, the chief of 
 
28 • MECHANICAL DENTISTRY. 
 
 which is a generous supply of oxygen, anthracite will yield a 
 higher temperature than any other kind of solid fuel. The blast 
 furnace is, therefore, best adapted to this end, though for all ordi- 
 nary purposes requiring heat in the dental laboratory the ordinary 
 chimney draft will be sufficient. To recapitulate somewhat, it may 
 be said, not only in reference to anthracite, but to the other solid 
 fuels mentioned, that in order that the greatest amount of heat may 
 be generated, it is necessary that the conditions essential to their 
 most perfect combustion should be strictly observed ; these, as be- 
 fore stated, have reference mainly to an unobstructed circulation 
 of air in order that oxygen may be freely supplied to them. To 
 this end the furnace should be kept clean, the bars of the grate 
 unbroken, and a good draft obtained. The condition in which the 
 fuel is applied will also modify the results. Thus, for example, if 
 the lumps are too large, they will absorb heat, and caloric will be 
 lost ; if too small, they will be too rapidly consumed. It is essen- 
 tial, also, to have the fuel as free as possible from dust and dirt, as 
 these fine particles in any considerable quantities obstruct the 
 draft, and prevent a thorough ignition of the mass. Coke, espe- 
 cially, should be preserved clean, and should be broken into frag- 
 ments not larger than an inch or an inch and a half in diameter,, 
 and, as nearly as possible, in the form of blocks or cubes, as these 
 leave more open spaces for the free circulation of air. 
 
 GASEOUS FUEL. 
 
 Illuminating Gas. — The ordinary illuminating gas, derived from 
 the destructive distillation of bituminous coals, is a form of fuel 
 that, of late years, has largely supplanted the use of the liquid and 
 solid varieties for heating purposes in the dental laboratory. The 
 introduction of gas, for the uses indicated, marks an era in pros- 
 thetic practice, so far as the application of heat for metallurgic 
 purposes is concerned, in which inventive genius has been indus- 
 triously and successively employed in devising and perfecting ap- 
 pliances designed to obviate entirely the necessity of employing 
 other forms of fuel heretofore used, and which are, in many re- 
 spects, inconvenient and objectionable. So fruitful have been these 
 later devices in meeting the necessities of the dental metallurgist, 
 and so reasonably certain is it that more extended experiments in 
 the construction of furnaces adapted to this mode of producing 
 
FUELS EMPLOYED IN LABORATORY PROCESSES. 2Q 
 
 heat will, in the near future, meet all the requirements of ceramic 
 art, as applied to dental prosthetics, that it may be confidently pre- 
 dicted that all solid fuels for these purposes will be wholly ban- 
 ished from the laboratory wherever gas can be commanded for 
 the generation of heat. The latter, intermixed with atmospheric 
 air in proper proportions, and used in connection with burners and 
 furnaces of suitable construction, is, in all essential respects, pref- 
 erable, since it is comparatively free from dirt and smoke, and is 
 capable of producing a rapid, equable, and intense heat, which is 
 completely under the control of the operator as respects duration 
 and the degree of temperature required for any given operation. 
 
 Natural gas has, until recently, been obtained only in very 
 limited quantities. There are many localities where combustible 
 gases have long been known to issue from the earth. Gas has 
 been used in China for centuries, conveyed in bamboo tubes from 
 fissures in salt mines, in excavations from 1200 to 1600 feet in 
 depth. Near the Caspian Sea, in Asia, there are several so-called 
 eternal fires caused by gas issuing from the soil. In parts of New 
 York it issues from bituminous limestone interspersed among the 
 slates and sandstones of the Portage group ; but the most prolific 
 sources of natural gas are in the coal regions of western Pennsyl- 
 vania, where great wells are yielding almost unlimited supplies of 
 this light- and heat-producing combustible, and which, in some of 
 the larger cities, is being utilized not only for illuminating pur- 
 poses, but for fuel in many of the manufacturing establishments. 
 
 The chief supplies of illuminating gas, however, are derived 
 from the destructive distillation of various grades of bituminous 
 coal, and, to a more limited extent, from wood, peat, resin, petro- 
 leum, oils and fats, and from water and coke.. As the gas used in 
 the dental laboratory for the generation of heat is the common 
 house illuminating gas obtained from coal, this variety only will 
 be treated of in this place. 
 
 Bituminous coals, such as English cannel and boghead coals, 
 Ohio cannel, and the coking coals of Pennsylvania, Maryland, and 
 Virginia, are commonly used in the manufacture of illuminating 
 gas. When bituminous coal is heated to redness in the presence 
 of air, it is principally converted into gases which unite with oxy- 
 gen ; but if air is excluded, as when the coal is confined in retorts, 
 the gaseous products, unable to unite with oxygen, may be col- 
 
30 MECHANICAL DENTISTRY. 
 
 lected in receivers and burned in tubes. The products of the 
 destructive distillation of bituminous coal consist of a great 
 number of gases, liquids, and solids, which may be conveniently- 
 included under the following heads, according to an analysis by 
 Bunsen : 
 
 Coke, 68.93 Olefiant gas, 0.78 
 
 Tar, 12.23 Sulphuretted hydrogen, .. 0.75 
 
 Water, 7.40 Hydrogen, 0.50 
 
 Marsh gas, 7.04 Ammonia, 0.17 
 
 Carbonic oxid, 1.13 Nitrogen, 0.03 
 
 Carbonic acid, 1.07 
 
 The illuminating power of the gas may be regarded as depend- 
 ing principally upon the amount of olefiant gas (heavy carburetted 
 hydrogen) which it contains, the bulk of other gases being carriers 
 rather than light-producers. The olefiant gas is separated by igni- 
 tion into marsh gas (light carburetted hydrogen) and carbon, the 
 solid particles of which become incandescent and emit white light, 
 which is observed in the luminous cone of a gas flame, and which 
 has the same constitution as that of a candle. The luminosity of 
 a gas flame depends both upon the percentage of heavy hydro- 
 carbons it contains and the amount of atmospheric air or oxygen 
 mixed with it. With the admixture of air or oxygen, the illumin- 
 ating power of the gas is diminished, while there is at the same 
 time increased evolution of heat. This fact is of interest and value 
 to the dentist, since it underlies the construction of all the modern 
 forms of heating appliances made on the principle of the Bunsen 
 burner, which provides for intermingling currents of atmospheric 
 air and gas. Oxygen thus applied to the gas jet, and combining 
 with the carbon at the moment of ignition, greatly augments the 
 heat of the flame, while the latter becomes almost non-luminous. 
 
 Oxyhydrogen Gas. — A combination of nitrous oxid and illu- 
 minating gas has been used of late in the dental laboratory with 
 highly satisfactory results, forming practically an oxyhydrogen 
 flame of great heating power. (See Dr. Knapp's oxyhydrogen 
 blowpipe, page 44.) 
 
CHAPTER II. 
 
 APPLIANCES USED IN THE GENERATION AND APPLICATION OF 
 HEAT; WITH SOME OBSERVATIONS ON SOLDERING. 
 
 The modes of generating heat, and the appliances used in its ap- 
 plication to the various mechanical processes of the dental labora- 
 tory, will require more or less detailed descriptions of the several 
 agencies employed for these purposes. These relate to Lamps, 
 Burners, Blowpipes, Supports, Crucibles, and Furnaces. As full a 
 description of these several appliances will be given as is compati- 
 
 FlG. I. 
 
 ble with the scope of the present work. The agencies employed 
 in the generation and application of heat alluded to under the head 
 of lamps, burners, supports, and blowpipes, are such as are used 
 chiefly in soldering, one of the most important and not always the 
 least difficult processes of the dental laboratory, while furnaces are 
 largely used for melting and refining purposes, compounding body 
 and gum materials, baking porcelain teeth, and in constructing 
 continuous-gum work. Heaters are adapted to a variety of pur- 
 
32 
 
 MECHANICAL DENTISTRY. 
 
 Fig. 
 
 poses requiring moderate temperatures, as melting some of the 
 more fusible metals, warming water, heating plaster molds pre- 
 paratory to packing plastic substances, etc. 
 
 Lamps. — For all the minor operations of the laboratory requir- 
 ing the application of moderate degrees of heat in the use of 
 either the mouth or the simpler forms of bellows blowpipe, an 
 ordinary alcohol lamp or the gasolene furnace described on page 
 55 will be found serviceable and efficient. When, however, gas 
 can be commanded, it is preferable to the oils or alcohol for heat- 
 producing purposes, on account of its greater convenience and 
 freedom from accident. 
 
 Burners. — The ordinary gas flame is unsuitable for soldering 
 or other operations, by reason of the carbonaceous residue with 
 which it is constantly charged. This source of uncleanliness may 
 be gotten rid of by an admixture of air with the gas flame. This 
 intermingling of gas and air currents for the 
 purpose of augmenting the heat of the gas 
 flame, and of rendering it in other respects 
 more suitable for general metallurgic pur- 
 poses, was first practised by Bunsen, a dis- 
 tinguished German chemist, by means of a 
 simple contrivance represented in Fig. 2. 
 All modern heat-producing appliances usu- 
 ally denominated Bunsen burners utilize 
 the same principle in the generation of 
 heat, and differ only in mechanical con- 
 struction from Bunsen's original device. 
 A very simple contrivance embracing the principle of the Bun- 
 sen burner, is shown in Fig. 3. The gas is supplied through a 
 flexible rubber tube connected with the stem of the burner, and 
 connected at the other end with any ordinary gas burner conve- 
 niently located in the laboratory. For soldering small pieces, 
 and for many other purposes requiring a ready and manageable 
 heat, the writer has used this simple appliance, with great satis- 
 faction. It is especially useful in "waxing up" a base plate, 
 heating water, vulcanizing, and other minor operations requiring 
 a moderate and easily-graduated heat. 
 
 To obtain a flame of greater volume than is possible with the 
 burner just described, one such as shown in Fig. 4 is employed. 
 
GENERATION AND APPLICATION OF HEAT. 
 
 33 
 
 This contrivance is especially adapted to drying and heating up 
 large pieces before soldering, and for melting metals in consider- 
 able quantities. 
 
 Another heating apparatus of recent introduction, designed, in 
 
 Fig. 3. 
 
 Fig. 4. 
 
 part, for soldering with the use of blowpipes, is represented in 
 Fig. 5. It is called the "Perfect Duplex Burner," and will be 
 found very convenient for laboratory use. It is an important ad- 
 
 Fig. s. 
 
 vance beyond the well-known revolving form of duplex burner. 
 Both burners are fixed, and a small jet is placed between them, 
 the gas flow being governed by a knob, a quarter turn of which to 
 the right or left ignites either burner when once the small jet is 
 
 3 
 
34 MECHANICAL DENTISTRY. 
 
 lighted. The plug has a long bearing, and is carefully ground in 
 so as to eliminate wear as far as possible. The knob is not af- 
 fected by the heating up of either burner. The apparatus is well 
 made, with every observed defect of the old form eliminated and 
 every shortcoming remedied. The old form was good ; the new 
 is better, and comes very close to fulfilling the intention of the in- 
 ventor — to supply the need of metal-workers for a perfect self- 
 lighting soldering and Bunsen burner combined. 
 
 BLOWPIPES. 
 
 Following the description of lamps and burners given in the 
 preceding pages, it would seem appropriate to consider next the 
 various forms of blowpipes used in the application of the heat 
 produced by means of the appliances named. 
 
 Various modifications in the form of the blowpipe have been 
 introduced from time to time, and are named according to the 
 means used to produce the blast, as — mouth, bellows, self-acting, 
 or spirit, and the Gasolene or "Oxycarbon" blowpipe. 
 
 In addition to the varieties mentioned, there are others, used in 
 producing extreme degrees of heat, as the "oxygen blowpipe," 
 with which the flame is blown with a jet of oxygen ; and another, 
 with which the two gases, oxygen and hydrogen, are burned, 
 called the "oxyhydrogen blowpipe." The latter is capable of 
 producing a heat that immediately fuses the most refractory sub- 
 stances, as quartz, flint, rock-crystal, plumbago, etc. With it gold 
 is volatilized and iron rapidly consumed when placed in the 
 flame ; while platinum, next to iridium the most infusible of all 
 known metals, has been melted in quantities exceeding ioo ounces 
 by means of this powerful instrument. As, however, these blow- 
 pipes are, for the most part, of no special practical utility in the 
 dental laboratory, reference will be had only to the one recently 
 introduced by Dr. Knapp, of New Orleans, La. Nor is it deemed 
 necessary to embrace descriptions of spirit blowpipes, as they 
 have fallen, of late years, almost wholly into disuse. 
 
 MOUTH BLOWPIPE. 
 
 This instrument has been long in use, is simple in its form and 
 construction, and, for general use in the application of moderate 
 degrees of heat, is both convenient and economical. Those 
 
GENERATION AND APPLICATION OF HEAT. 
 
 35 
 
 accustomed to its use are enabled to produce a continuous blast 
 of considerable force, and soon acquire the facility of regulating 
 the heat produced with equal if not greater precision than can be 
 readily attained in any other way. 
 
 The most simple form of the mouth blowpipe is shown in Fig. 
 6. It consists, usually, of a plain tube of brass, larger at the end 
 applied to the mouth, and tapering gradually to a point at its 
 other extremity, the latter being curved and tipped at the point 
 with a conical-shaped, raised margin, to protect it from the action 
 of the flame ; the caliber of the instrument terminates here in a 
 very small orifice. The point of the instrument, as well as that 
 part of it received into the mouth, is sometimes plated with a 
 less oxidizable metal than brass^ as silver or platinum. The stem 
 is generally from 12 to 20 inches in length, and the mouth ex- 
 tremity from y-2. to Y\ of an inch in diameter. 
 
 In operations requiring protracted blowing, a somewhat dif- 
 ferent form of the instrument will be required, owing to the accu- 
 
 Fig. 6. 
 
 mulation of moisture within the tube, which, being forcibly 
 expelled from the orifice, spurts upon whatever is being heated 
 and interrupts the blast; also, on account of the fatigue, which 
 in process of time renders the muscles of the mouth and face 
 engaged in the act to a great extent powerless. 
 
 The difficulties mentioned may be obviated, in a great measure, 
 by applying the form of blowpipe represented in Fig. 7. To the 
 mouth extremity is attached a circular concave flange or collar 
 which receives and supports the lips. To the shaft, near its 
 curved extremity, is adjusted either a spheric or cylindric chamber 
 which collects and retains the moisture as it forms within the pipe. 
 By allowing that part of the tube connected with the curved end to 
 pass part way into the chamber, a basin is formed at the depending 
 portion of the latter, which, by collecting the fluids, will effectually 
 prevent them from overflowing and passing into the tube beyond. 
 
36 
 
 MECHANICAL DENTISTRY. 
 
 Another form of mouth blowpipe is exhibited in Fig - . 8. It will 
 be seen to be wholly unlike any mouth blowpipe yet devised, and 
 admits of great latitude of movements in the application of heat. 
 This form of the mouthpiece is especially adapted to continued 
 blowing without strain on the lips, while the opening is well 
 under the control of the tongue. The blowpipe proper is held 
 as a pencil, the chamber collecting condensed moisture and pre- 
 
 Fig. 7. 
 
 venting the passage of heat up to the end. The instrument can 
 be readily changed from a cold- to a hot-blast blowpipe by sub- 
 stituting the coil (b) for the plain jet or tip. 
 
 There are other allied forms of the mouth blowpipe, but as they 
 are constructed more especially for chemical examinations or anal- 
 yses, and as they possess no advantages for dental purposes, over 
 those already mentioned, a description of them is not necessary. 
 
 Fig. 8. 
 
 Mechanism Involved in the Act of Producing a Continuous 
 Blast with the Mouth Blowpipe. — As a steady, continuous cur- 
 rent of air from the blowpipe is preferable to the interrupted jet 
 in all those operations where it is desired to produce a steadily 
 augmenting heat, the following remarks explanatory of the 
 method of producing it are subjoined, in the belief that they will 
 render easier a process not always readily acquired. 
 
GENERATION AND APPLICATION OF HEAT. 
 
 37 
 
 "The tongue must be applied to the roof of the mouth, so as to 
 interrupt the communication between the passage of the nostrils 
 and the mouth. The operator now fills his mouth with air, which 
 is to be passed through the pipe by compressing the muscles of 
 the cheeks, while he breathes through the nostrils and uses the 
 palate as a valve. When the mouth becomes nearly empty, it is 
 replenished by the lungs in an instant, while the tongue is mo- 
 mentarily withdrawn from the roof of the mouth. The stream 
 of air can be continued for a long time without the least fatigue 
 or injury to the lungs. 
 
 "The easier way for the student to accustom himself to the use 
 of the blowpipe, is first to learn to fill the mouth with air, and 
 while the lips are kept firmly closed to breathe freely through the 
 nostrils. Having effected this much, he may introduce the mouth- 
 piece of the blowpipe between his lips. By inflating the cheeks 
 and breathing through the nostrils, he will soon learn to use the 
 instrument without the least fatigue. The air is forced through 
 the tube, against the flame, by the action of the muscles of the 
 cheeks, while he continues to breathe, without interruption, 
 through the nostrils. Having become acquainted with this proc- 
 ess, it only requires some practice to produce a steady jet of flame. 
 A defect in the nature of the combustible used, as bad oil, such as 
 fish oil, or oil thickened by long standing or by dirt, dirty cotton 
 wick, or an untrimmed one, or a dirty wick-holder, or a want of 
 steadiness of the hand that holds the blowpipe, will prevent a 
 steady jet of flame. But, frequently, the fault lies in the orifice of 
 the jet, as too small a hole or its partial stoppage by dirt, which will 
 prevent a steadyjet of air and lead to difficulty. With a good blow- 
 pipe, the air projects the entire flame, forming a horizontal, blue 
 cone of flame, which converges to a point at about an inch from the 
 wick, with a larger, longer, and more luminous flame enveloping 
 it, and terminating at a point beyond that of the blue flame." * 
 
 BELLOWS BLOWPIPE. 
 
 There are many processes of the dental laboratory requiring the 
 application of a higher temperature than is obtainable with the 
 mouth blowpipe. A more powerful and persistent air-blast is 
 
 * " The Practical Use of the Blowpipe." — Anon. 
 
38 
 
 MECHANICAL DENTISTRY. 
 
 readily produced by a bellows or foot-blower, used commonly in 
 connection with a burner of suitable form attached to the common 
 gas-jet, by means of which the gas is furnished with the oxygen 
 required for its combustion in a state of intimate mixture. 
 
 A simple and compact form of bellows or foot-blower is shown 
 in Fig. 9. The pressure obtainable with this instrument is contin- 
 uous, equable, and completely under the control of the operator, 
 but the current may be greatly increased in power after the rub- 
 ber disk is distended until forced against the net. 
 
 A bellows of similar construction, but with the position of the 
 blower reversed, is shown in Fig. 10. By this arrangement the 
 disk is less liable to injury, while it prevents the valve from pick- 
 ing up dirt from the floor. 
 
 Fig.- 9. 
 
 Fig. 
 
 A contrivance essentially different in its construction from the 
 ordinary bellows employed to produce the air-jet is shown in Fig. 
 11, and is known as the "Burgess Mechanical Blowpipe." When 
 in use, the air is drawn into a cylinder and condensed in an air- 
 chamber, ready to be used in large or small quantities at the will 
 of the operator, by a rapid or slow movement of the treadle. A 
 pressure of from 2 to 12 pounds is produced at the will of the 
 operator, by accelerating the motion of the foot, and can be. con- 
 tinued with but little exertion. The machine weighs 12 pounds, 
 and measures 22 inches in height. The pump-cylinder is 2J/2 
 inches in diameter, with three-inch stroke. The internal mechan- 
 ism is clearly illustrated in Fig. 11, and its simplicity will be at 
 once appreciated. It requires an occasional drop of oil upon 
 
GENERATION AND APPLICATION OF HEAT. 
 
 39 
 
 the leather packing-ring, and this, with ordinary care, will make 
 the apparatus last for years. When operating, place the entire 
 foot upon the treadle, so that an easy rocking motion is obtained ; 
 by pressing the toe downward, air is drawn into the cylinder, and 
 in reversing the motion it is driven into the air-chamber above. 
 The pipe-outlet is much smaller than in the mouth blowpipe, to 
 
 Fig. ii. 
 
 .... ; 
 
 enable a pressure to be obtained, which is increased or dimin- 
 ished by a quick or slow motion of the treadle. The air-chamber 
 is easily filled, and when so a constant supply of pure air is at the 
 control of the operator. 
 
 The blowpipes used in connection with the bellows are of vari- 
 ous forms. Fig. 12 represents one form of apparatus employed 
 in the application of the air-blast to the gas-flame. 
 
 A movable gas-jet attached to two short arms of an ordinary 
 
4° 
 
 MECHANICAL DENTISTRY. 
 
 gas-pipe is made to receive within it the blowpipe point connected 
 with the rubber tube, the air-tube terminating a little within the 
 open mouth of the gas-jet; it is thus a tube within a tube, with a 
 space between them for the admission and passage of gas. The 
 gas, being admitted by turning the tap connected with the gas- 
 pipe, is ignited, when the current of air from the bellows will 
 strike the center of the flame and project it upon whatever is to be 
 heated. The connected portions of the air- and gas-jets are so 
 attached to the main pipe as to admit of an upward and down- 
 ward motion, while the volume of gas and air is readily gradu- 
 ated by the stop-cocks attached to the air- and gas-tubes. 
 
 A bellows blowpipe, constructed on similar principles, but 
 
 Fig. 12. 
 
 Fig. 13. 
 
 Fig. 14. 
 
 admitting of greater latitude of movements, is exhibited in Fig. 
 13. As will be readily observed, it is capable of being adjusted 
 in any desired position. The jet-tube may be raised or lowered 
 to any height and turned in any direction. A touch will direct 
 the flame on any point while the blowpipe stands in the same 
 position on the table ; there being no necessity for raising, lower- 
 ing, or adjusting work before it. 
 
 Macomber's gas blowpipe, Fig. 14, differs somewhat in construc- 
 tion from the latter, its capability of adjustment being regulated by 
 a ball-and-socket attachment which imparts to it, at the will of the 
 operator, a latitude of movement or adjustment of the blowpipe 
 point that is practically without limit. The direction of the point, 
 1, is regulated by the joint, 3, and the supply of gas controlled by 
 
GENERATION AND APPLICATION OF HEAT. 
 
 41 
 
 the stop-cock, 2. The air is supplied by the bellows through the 
 flexible tube. 
 
 A very convenient, manageable, and effective instrument for 
 many purposes requiring the application of heat in the dental 
 laboratory is the hand blowpipe shown in Fig. 15. It is capable 
 of producing very high degrees of heat, but the intensity of the 
 
 Fig. 15. 
 
 latter may be graduated at the will of the operator, as the stop- 
 cocks, which are both under perfect control of the thumb of 
 the hand which holds the blowpipe, regulate the supply of gas, 
 and control the volume of air. The air-jet is */& of an inch bore, 
 and requires a supply from a bellows. 
 
 Fig. 16. 
 
 Fig. 16 represents an improved pattern of the Fletcher Automa- 
 ton, designed especially for crown- and bridge-work. It is made 
 of smaller tubing than the No. 6 A or B Automaton, the end 
 being bent at an angle to give greater facility in directing the 
 flame. The adjustable nozzle is screwed on and off, instead of 
 operating by a slip-joint, as in other patterns of the automaton 
 
42 MECHANICAL DENTISTRY. 
 
 blowpipe. Its length is increased, removing the hand further 
 from the heat. The supply of gas and air is controlled by a longi- 
 tudinal movement of the tube, instead of a rotative one. A spring 
 opposes the movement of the hand, and a slight variation of press- 
 ure upon the end-piece, when it is held as shown, is sufficient to 
 give either a pointed jet or a full-sized brush flame at pleasure. 
 An improved tip is used on the air-jet, and the small blue-pointed 
 reducing flame is very easily and perfectly produced. 
 
 The gas passage does not close entirely, but allows the passage 
 of enough gas to prevent the flame from going out when the blow- 
 pipe is not in use. It can be hung up by the ring shown on its 
 body, when it is desirable to get it out of the hand. 
 
 The several forms of bellows blowpipe illustrated in these pages 
 are complete and efficient, and admirably adapted to the necessi- 
 ties of the mechanical operator. In most instances, the jet may be 
 elevated or depressed at will, while the force of the air-current 
 and the volume of the gas-flame can as readily be increased or 
 diminished. The operator is thus enabled, with the greatest ease, 
 to produce a heat adapted to the most delicate operations, or to 
 instantly change it to a heat so intense that pure gold in consider- 
 able quantities is almost immediately fused in the flame. They are, 
 therefore, well adapted to all operations in the dental laboratory. 
 
 THE GASOLENE OR OXYCARBON BLOWPIPE. 
 
 Where illuminating gas is not available, the oxycarbon forge 
 or blowpipe will be found most useful. It gives a high, steady, 
 smokeless, and nearly odorless blast, and at the same time does 
 not require either the bellows attachment or lung power. It is 
 less expensive than gas or alcohol, is safe, portable, durable, and 
 is simple to control and handle. It can be changed instantly from 
 an intense heat to a feeble flame, or the reverse. The entire forge 
 is only about 12 inches high, having a base 9 inches in diameter, 
 and can be run all day with y 2 gallon of 74 ° deodorized gasolene 
 (see page 55) without any attention, excepting a few minutes' 
 use with the rubber bulb to keep up the necessary air pressure. 
 This forge is illustrated in Figs. 17, 18, and 19. 
 
 It can be used for vulcanizing, heating investments, soldering, 
 melting metals, annealing plates, for waxing, or any purpose for 
 which heat may be required in the laboratory. 
 
GENERATION AN 
 
 ND APPLICATION OF HEAT. 
 
 43 
 
 Fig. 17- 
 
 Fig. i i 
 
44 
 
 MECHANICAL DENTISTRY. 
 
 OXYHYDROGEN BLOWPIPE. 
 
 No dental laboratory appliance for heating purposes has ever 
 been devised that has attracted so much attention, or elicited such 
 cordial and unreserved praise by expert manipulators, as that 
 invented by Dr. J. Rollo Knapp, of New Orleans, La., and shown 
 in Fig. 20. 
 
 It is described as being to all intents and purposes an oxy- 
 hydrogen blowpipe divested of the cumbersome paraphernalia 
 usually accompanying the latter, and reduced to a practical size 
 
 Fig. 19. 
 
 and shape for soldering operations. It is essentially an apparatus 
 for securing the consumption of hydrogen in a highly oxygenated 
 atmosphere, the resulting flame being second in intensity only to 
 that of the oxyhydrogen blowpipe proper. It will melt gold or its 
 alloys in quantities suited to its capacity almost instantly, without 
 other exertion on the part of the operator than the adjustment of a 
 couple of small levers. It is economical of time and materials, and 
 not the least notable of its good qualities is its cleanliness. Its 
 inventor has been accustomed to do all his soldering of crown- 
 and bridge-work without leaving the operating room. It can be 
 used wherever illuminating gas is available. Any of the soldering 
 
GENERATION AND APPLICATION OF HEAT. 
 
 45 
 
 operations of the laboratory, from the largest piece of bridge- 
 work to the most delicate joining of the narrowest bands or finest 
 wires, are accomplished with equal facility. With illuminating 
 gas of good quality and sufficient pressure, a pennyweight of 20- 
 carat gold can be melted in thirty seconds. When the invest- 
 ment is large, it must first be heated by other means. 
 
 The apparatus consists of the blowpipe attachments, connected 
 to the yoke of a nitrous oxid gas-cylinder, the cylinder being set 
 upright, and secured by a thumb-screw on one end of an iron base 
 
 Fig. 20. 
 
 or stand, at the other end of which is pivoted a table, upon which 
 to rest the work. The blowpipe proper is a continuation of the 
 outlet tube of the gas-cylinder. A lever-valve, G, regulates the 
 supply of nitrous oxid. Just beyond this valve is the mixing 
 chamber K, to which the illuminating gas is conducted from the 
 gas-bracket by means of rubber tubing, entering the bottom of the 
 chamber through the valved tube, C. The lever, D, controls the 
 supply. The mixing chamber is provided with a gauze screen to 
 prevent the flame from being drawn into the supply tubes. Imme- 
 
46 MECHANICAL DENTISTRY. 
 
 diately beyond the mixing chamber the pipe is branched to afford 
 two flames of different sizes, E and F, which can be used inde- 
 pendently of each other or both together. The valve-lever, L, 
 regulates the flame in both. For greater convenience in manipu- 
 lation the pipe-nozzles are connected with the branched pipe by 
 rubber tubing. From the body of the valve L an arm extends, at 
 the end of which is a small scalloped disc as a holder for the 
 flame-nozzles when not in use. In the illustration one of the noz- 
 zles is shown in the holder, the other being directed to the re- 
 volving table. 
 
 SUPPORTS. 
 
 There are many processes in the dental laboratory for which it 
 is necessary to provide a suitable holder or support, as in melting 
 small quantities of gold and silver, and in all the varied opera- 
 tions requiring the use of solder. 
 
 For melting or soldering small pieces, a variety of simple de- 
 vices, easily and economically constructed, may be used, among 
 which are the following: 
 
 Charcoal, either alone or combined with other non-conducting 
 substances, is very commonly employed, and being combustible, 
 adds materially to the heat of the blowpipe-flame. A convenient 
 support of this kind may be made by selecting a fair-sized block 
 of compact, close-grained charcoal, derived from some of the 
 hard woods, such as oak or beech, and investing it in plaster 
 
 ^2 or ^4 of an inch thick, one end or 
 Fig. 2i. side being left open and made concave, to 
 
 ^r^^^^^^^^%. receive whatever is being heated. Or a 
 fj^k B 1 plaster cup, two or three inches deep and 
 
 'v ^5 P^Jl three or four inches in diameter, may be 
 
 ■Ifei ,.,. ..-■risSfiSffl'' used, its interior being filled with a mix- 
 
 ■K WB ture of plaster, sand, asbestos, and pul- 
 
 l|i: '' IIIIIBi^^^ verized charcoal. Coke, encased in the 
 
 same manner as charcoal, may be substi- 
 tuted for the latter, and has the merit of being more lasting, but in 
 all other respects is inferior for the purpose. Supports for the uses 
 under consideration are also sometimes made of pumice-stone. 
 
 Manufactured supports, composed of asbestos and carbon, very 
 convenient and durable, may be obtained at the dental depots. 
 Fig. 21 represents a carbon block designed for melting and solder- 
 
GENERATION AND APPLICATION OF HEAT. 
 
 47 
 
 ing, while Fig. 22 shows an asbestos block manufactured for the 
 same purpose. 
 
 For soldering purposes exclusively, especially in uniting teeth 
 to a metallic base, either of the following means of support for the 
 
 Fig. 22. 
 
 invested piece will be suitable : A simple holder, which the opera- 
 tor himself can easily construct, may be made of a circular or 
 semi-elliptic piece of heavy sheet iron, the margin of which is ser- 
 rated and turned at right angles, forming a cup. To the under 
 side and center of this an iron rod, 10 or 12 inches long, may be 
 
 Fig. 23. 
 
 permanently riveted, or it may be made to revolve on the handle, 
 so that the heat may be thrown directly upon any particular part 
 of the piece to be soldered without disturbing the latter. 
 
 A small hand furnace (Fig. 23) is sometimes used, and will be 
 
4 8 
 
 MECHANICAL DENTISTRY. 
 
 found a very convenient and useful apparatus, not only for solder- 
 ing, but for preparatory heating. It consists of a funnel-shaped 
 receptacle made of sheet iron, with a light grate or perforated 
 plate of the same material adjusted near the bottom, and an open- 
 ing on one side, underneath the grate, for the admission of air. 
 The upper part of the holder is surmounted by a cone-shaped top, 
 which may be readily removed by a handle attached to it, while 
 to the bottom of the furnace is attached an iron rod, five or six 
 inches long and terminating in a wooden handle. The piece to be 
 soldered is placed inside on a bed of charcoal, the top adjusted 
 to its place, and the fuel ignited ; when the case is sufficiently 
 
 Fig. 24. 
 
 heated, the top may be lifted off, and the piece remaining in the 
 furnace soldered with the blowpipe in the usual manner, the fur- 
 nace thus serving the purpose of a holder. 
 
 The Melotte Clamp or Support. — A very simple and conve- 
 nient clamp or support, devised by Dr. George W. Melotte, of 
 Ithaca, N. Y., is shown in Fig. 24 and is especially designed for 
 crown- and bridge-work. 
 
 It is the design of this invention to provide means for holding 
 gold crown collars and their caps so that without change of size 
 or shape their closed joints can be neatly soldered. Fig. 24 ex- 
 hibits a collar thus held. A slight pressure suffices, and this is 
 
GENERATION AND APPLICATION OF HEAT. 
 
 49 
 
 effected by pushing the jaw shank into the handle, which by its 
 spur is then fixed in a piece of charcoal or on the bench ; the jaws 
 turn in the handle to bring the joint into position, when the left 
 hand is set free to manipulate the solder while the blowpipe is 
 directed by the right hand as usual. 
 
 FURNACES. 
 
 It would be inconsistent with the design of the present work 
 to introduce a description of any form of furnace other than those 
 of practical use to the dentist. Many of those used in the arts, or 
 
 Fig. 25. 
 
 for chemical and pharmaceutical purposes, embrace almost end- 
 less varieties, and have no special adaptation to the uses required 
 of them in the dental laboratory. 
 
 Draft or Wind Furnace. — A very convenient, portable, and 
 economical furnace may be made of sheet iron, of any desired 
 shape or dimensions, though usually of small size and cylindric 
 in form. A light grate, or heavy piece of sheet iron, perforated 
 with holes, to admit of the passage of air, should be adjusted near 
 4 
 
5o 
 
 MECHANICAL DENTISTRY. 
 
 the bottom, while above and below the grate are two openings, 
 the lower one communicating with the ash-pit, and the upper one 
 for the introduction of fuel and substances to be heated. By sur- 
 mounting this simple apparatus with a pipe, or connecting it with 
 
 Fig. 26. 
 
 the flue of a chimney, it will be found efficient in many of the 
 minor operations of the shop, as melting metals, heating pieces 
 preparatory to soldering, annealing, etc. 
 
 A more durable and serviceable draft-furnace, however, may be 
 
GENERATION AND APPLICATION OF HEAT. 
 
 51 
 
 Fig. 27. 
 
 built of masonry, a convenient form of which is represented in 
 Fig. 25. The construction of this stationary fixture is so plainly 
 exhibited in the cut that any extended description of it seems 
 unnecessary. The upper holes represent the entrance to the fire 
 chambers, which are distinct from each other ; the lower ones 
 communicate with the ash-pit, which is common to both cham- 
 bers. Two fire apartments are here shown, one for melting and 
 re-fining the more precious metals, heating up for soldering, etc., 
 the other being used exclusively for fusing the baser metals, as 
 zinc, antimony, lead, etc. These furnaces are sometimes con- 
 structed with a single fire-chamber, but the one exhibited is in 
 every way preferable. 
 
 Baking Furnace. — The chief purposes to which these furnaces 
 are applied are the manufacture of por- 
 celain teeth, single and in sectional blocks, 
 the preparation of silicious compounds, 
 and the construction of what is known as 
 "continuous-gum work." An excellent 
 form of furnace is shown in Fig. 26, which 
 is made after the description of Dr. L. P. 
 Haskell, who says of it: "If you wish to 
 shut the heat out of the room, have a wire 
 frame made, over sides and top, and sit- 
 ting against the chimney with a movable 
 front, and holes corresponding with the 
 furnace openings, and cover with asbestos 
 felt." This is shown complete in the il- 
 lustration. 
 
 A furnace especially designed and in- 
 troduced for continuous-gum work, is exhibited in Fig. 27. The 
 fire-pit below the muffle is of more than usual capacity, insuring, 
 it is claimed, perfect results at each baking. The part which is 
 subjected to the greatest heat is free from angles and incased with 
 sheet iron, rendering it less liable to crack from long use. The 
 fire or ashes may be withdrawn by removing the two projecting 
 grate-bars. It is 24 inches high and 12*4 inches in diameter. 
 
 As the purposes, heretofore stated, for which these several fur- 
 naces are designed require a steady, intense, and persistent heat, 
 the fuels commonly used, as fulfilling most perfectly these indi- 
 
52 MECHANICAL DENTISTRY. 
 
 cations, are coke, or a mixture of charcoal and coke, and anthra- 
 cite, preference being given, by many, to the latter. 
 
 It will be observed that, in connection with the several kinds of 
 furnaces heretofore mentioned, heat is generated by the use of 
 solid fuels. Within the past few years, baking- or muffle-furnaces 
 have been constructed with reference to their special adaptability 
 to the use of gas in combination with the air-blast. While these 
 later devices commend themselves on the score of their greater 
 convenience and economy of time in firing, and their freedom from 
 the dirt and smoke attending the use of solid fuels, their successful 
 application to the special uses for which they are mainly designed, 
 has been attended with difficulties which have heretofore been 
 adverse to their general adoption by the profession, and which it 
 has been the aim of inventors to overcome. This has been meas- 
 urably accomplished, and the successes so far attained give fair 
 promise of a complete revolution in the modes of applying heat in 
 all operations concerned in the fabrication of the various forms of 
 dental porcelain. The chief obstacle to the successful use of gas 
 in connection with the air-blast in the processes relating to the 
 manufacture of porcelain teeth, gum-enamels, continuous-gum 
 work, etc., is in the increased liability t© so-called "gasing," or the 
 formation of bubbles, due to absorption and elimination of gas that 
 finds its way into the muffle during the process of baking. The 
 manner in which this accident occurs is thus accounted for in a 
 communication to the author from Dr. C. H. Land, of Detroit, 
 Michigan. Alluding to the kind of furnaces under consideration, 
 the writer says : 
 
 "To be able to fuse the body and enamel of which artificial 
 teeth are composed in an easy and convenient manner is a thing 
 the profession has studiously sought after, realizing that, when 
 properly accomplished, the means to elevate prosthetic dentistry 
 from an ordinary mechanical enterprise to one of true art, would 
 be at hand. The mere construction of a furnace after the usual 
 modes has been simple enough, and the question of securing the 
 necessary degree of heat was long ago accomplished. However, 
 the ideal furnace demanded much more. It must possess not only 
 the capacity of a coal or coke fire, but also accomplish the work 
 in less time, and require but the minimum amount of exertion to 
 operate it. Of the many attempts to produce such, nearly all 
 have failed, owing to technicalities that were not well understood. 
 
GENERATION AND APPLICATION OF HEAT. 
 
 53 
 
 Fig. zi 
 
 "After many experiments, and their accompanying failures, it 
 has been demonstrated that to heat an eight-inch muffle, 3^2 
 by 25/2 inches in diameter, to over 2800 F., represents about 
 a one-man power equivalent to the exertion of running the 
 ordinary foot-lathe or the No. 9 bellows, as manufactured by the 
 Buffalo Dental Manufacturing Company, which gives a working 
 pressure of iy 2 pounds to the square inch, and corresponds 
 exactly to the required amount of air pressure and volume neces- 
 sary to heat an eight-inch muffle to 2800 F. Therefore, to 
 make a furnace larger would 
 require too much power, and 
 one smaller would not do 
 for large pieces of work. In 
 the production of a suitable 
 furnace, the whole working 
 apparatus must be as nearly 
 air-tight as possible, the sup- 
 ply of gas and air must be 
 easily controlled and well bal- 
 anced, with the least amount 
 of friction in the passage 
 through the pipes. These, 
 with many minor details, form 
 the basis of a practical gas- 
 furnace. 
 
 "GASING THE BODY AND ENAMEL 
 
 "The most serious trouble 
 with all gas-furnaces has been 
 the extreme liability of injur- 
 ing the body and enamel by what has been commonly called 'gas- 
 ing.' The accompanying illustration, Fig. 28, will make the phi- 
 losophy of combustion more clear, and give the reasons why teeth 
 are injured. A represents the burner; BBB, fire-brick lining; 
 C C C, combustion chamber; D, interior of muffle. The arrows 
 indicate the direction of the blast. The space in the combustion 
 chamber between the lines E E is where carbon monoxid is 
 formed, a gas containing one equivalent less of oxygen than car- 
 bon dioxid, simply an imperfect state of combustion. It is this gas 
 
54 
 
 MECHANICAL DENTISTRY. 
 
 that injures the body and enamel. By reference to the illustra- 
 tion, it will be seen that the little arrows are made to appear pass- 
 ing through the pores of the muffle, and as the direction of the 
 blast from the burner A is directly against the bottom of the 
 muffle, with a pressure of one pound to the square inch, a portion 
 of the carbon monoxid is extremely liable to be forced through its 
 pores, and will be taken up with the body during the first and sec- 
 ond biscuiting, here to remain until the enameling process, and as 
 this takes a much higher degree of heat, it causes the gas to be 
 eliminated, as shown in the numerous small bubbles on the sur- 
 face. The space between the lines E E, and within the combus- 
 tion chamber C C C, should be known as the first stage of com- 
 bustion, where a certain portion of carbon monoxid is always 
 present, and the space above the line F, within the chamber C, 
 should be known as the second stage, which is perfect combustion. 
 In the first stage of combustion one equivalent of oxygen from the 
 atmosphere unites with the hydrocarbon to form carbon monoxid ; 
 in the second stage, two, or perhaps. three, unite to form carbon 
 dioxid, or carbonic acid. Perfect combustion is always at the 
 extreme point of the blowpipe, as shown in the illustration. 
 
 "The attempt, therefore, should be to place the muffle as nearly 
 as possible in the center of perfect combustion. As carbon mon- 
 oxid is not consumed short of a temperature of over 2200 F., the 
 teeth should be kept in front of the muffle until it approaches a 
 white heat. Starting from a cold muffle this will take about 
 twelve minutes, and they should be gradually carried to the ex- 
 treme end. At a high temperature, there is very little danger of 
 gasing, unless a greater quantity of gas is supplied than the fur- 
 nace is capable of burning. Having constructed a furnace, and 
 being familiar with many other details that provided a means to 
 overcome all the apparent difficulties, the success of properly bak- 
 ing teeth seemed to be assured, until the muffle began to crack, 
 which usually started in the second or third enameling heat. This 
 let in such a quantity of monoxid of carbon as to ruin the teeth. 
 Here was a difficulty that was overcome by forcing a quantity of 
 superheated air into the muffle, and backing all foul gases out. 
 This proved to be a cure for gasing, but added an excess of oxy- 
 gen, and it was found that this had a tendency to bleach the gum- 
 enamel to a lighter shade. The next step was to inject a pure 
 
GENERATION AND APPLICATION OF HEAT. 55 
 
 atmosphere of nitrogen into the muffle, it being a neutral gas, not 
 uniting radically with anything. This was eminently successful, 
 and thoroughly demonstrated the fact that porcelain baked in an 
 atmosphere of nitrogen was absolutely perfect, both in color and 
 texture. It therefore gives me pleasure to be able to announce to 
 the profession that the baking of all kinds of porcelain with any 
 of the hydrocarbons has been brought within the range of every 
 dental practitioner, so that, with a little experience and knowledge 
 of the above facts, artificial teeth can be baked, with unerring pre- 
 cision, in a very comfortable, cheap, and easy manner. By a sim- 
 ple attachment, each furnace produces its own nitrogen as fast as 
 needed, and with recent improvements in the construction of 
 muffles, and the aid of a small motor, the author has been able to 
 maintain a constant and uniform temperature above 2800 F., by 
 which a slab of sectional gum teeth was completed every seven 
 minutes, at the will of the operator. 
 
 " OLEFIANT GAS AND GASOLENE. 
 
 "defiant gas, with which nearly all our cities and towns are 
 supplied, is a compound of hydrogen and carbon. Its symbols are 
 C 2 H 4 , differing from gasolene only in its specific gravity, the com- 
 position of the latter being also C 2 H 4 . The former will rise to the 
 top of a building, while the latter will fall. The former is more 
 penetrating, therefore more liable to gas the teeth, and hence requires 
 more care in handling. The quality varies in different localities, 
 and sometimes, owing to the presence of ammonia, it may injure 
 the teeth, or it may be too thin. When properly purified, it should 
 be a rich hydrocarbon. The uncertainty of its qualities is fre- 
 quently the cause of failure. To be successful with gas-furnaces, 
 it is absolutely necessary to have a pure and rich hydrocarbon. 
 When the gas pressure is weak or the quality is poor, a gasolene 
 generator may be attached to the pipe and the current allowed to 
 pass through. This takes up a large percentage of the gasolene 
 and provides a very rich quality of gas. The 87 per cent, is the 
 best; 74 per cent, is too heavy to use without requiring heat 
 to vaporize it. By applying to the Combination Gas Machine 
 Company a supply can be had. When pure gasolene is used, it 
 is necessary to have a generator so arranged that a portion of the 
 air from the bellows will pass through it. This carries the vapor 
 
56 MECHANICAL DENTISTRY. 
 
 into the furnace, where it becomes mixed with the proper quantity 
 of air, and will produce as good, if not better, results than any 
 other hydrocarbon. All kinds of crucible and muffle work can be 
 done equally well, also soldering and brazing with the blowpipe. 
 One gallon of gasolene costs 15 to 20 cents; this will bake one 
 set of teeth. Therefore it will be seen that dentists living in lo- 
 calities where there is no gas will not be deprived of practically 
 the same advantages as their city brethren." 
 
 The Land Furnace. — The following is a description of a fur- 
 nace, invented by Dr. Land, designed especially to overcome the 
 trouble spoken of above, as well as to provide other advantages : 
 
 Size No. 1 is especially adapted for all kinds of muffle work, 
 crucible work, blowpipe work, forging and brazing, assaying, and 
 small castings of iron, brass, and steel. A muffle 8 inches long, 
 3^2 inches wide, 2^2 inches high, inside measurement, can be 
 heated to over 3240 F. in twenty-five minutes, sufficient to 
 melt wrought iron. Fig. 29 represents the furnace closed and 
 ready for muffle work. A A is an iron pipe, capable of both a 
 sliding and a swinging motion (see L, Fig. 30), to- which the 
 door or plug is securely attached. There is a small hole in the 
 door, covered with a piece of mica, through which all operations 
 can be seen. Observe that the iron pipe is connected with rubber 
 tubing, B, and with pipe having an air-cock, C, which regulates 
 the quantity of air passing into the mouth of the muffle. It will 
 also be noticed that the pipe passes over the two holes, D D; 
 thus by the escaping flame the pipe is heated to redness and pro- 
 vides a superheated air before reaching the muffle ; this column 
 of air forced into the muffle keeps up a counter-pressure within, so 
 much greater than the pressure produced by the blast within the 
 fire-chamber that all foul gases are prevented from entering the 
 muffle even though it is cracked ; thus the most delicate porcelain 
 can be baked without the least danger of so-called gasing. Also, 
 it will be seen that by connecting the rubber pipe with retorts of 
 gasometers any desired vapor or gas could be forced into the 
 muffle, making the furnace invaluable for scientific experiments. 
 
 Fig. 30 illustrates the furnace thrown open, being swung on 
 hinges at the back, exposing the muffle, E. The groove, P P, is 
 packed with asbestos fiber, so that when the sections are brought 
 together the furnace will be perfectly air- and gas-tight. The 
 
GENERATION AND APPLICATION OF HEAT. 
 
 57 
 
 hooks, F F, are to hold the upper section secure to the lower. 
 The gas and air connections are so arranged that the ordinary- 
 blowpipe can be attached, as shown at G. When the muffle, E, 
 is removed, it exposes two burners and a fire-brick surface made 
 to fit the various appliances for crucible, ladle, and blowpipe work. 
 One or both burners can be operated in conjunction with the blow- 
 
 Fig. 29. 
 
 pipe, G. The air-cock, R, is to provide a means for shutting off 
 the air supply from either burner when required. H is the gas 
 supply ; K, air-pipe connecting with the bellows. Size of muffle, 
 inside measurement, 8 inches long, ^A inches wide, 2^ inches 
 high. With gasolene gas porcelain teeth can be enameled in from 
 
58 
 
 MECHANICAL DENTISTRY. 
 
 ten to fifteen minutes ; with ordinary city gas in from fifteen to 
 twenty-five minutes, according to quality. In thirty minutes a 
 heat sufficient to destroy the muffle can be produced, which 
 indicates a temperature of over 3240 F., much higher than is 
 ever needed for any kind of work, except the fusing of platinum. 
 
 Fig. 30. 
 
 Three-eighths of an inch gas-pipe will supply sufficient gas and 
 can be worked with the ordinary foot-bellows. 
 
 The Sharpe Furnace. — One of the simplest and most complete 
 gas muffle-furnaces yet placed upon the market, is that invented 
 by Dr. W. M. Sharpe, of Binghamton, New York, and is exhib- 
 ited in Figs. 31 and 32. 
 
Fig. 31. 
 
 Fig. 32. 
 
6o 
 
 MECHANICAL DENTISTRY, 
 
 Gas Crucible Furnace Without Blast. — Fig. 33 represents a 
 small crucible furnace that will be found very convenient for melt- 
 ing and refining the precious and more infusible metals employed 
 by the dentist. It takes crucibles up to 2.y 2 by 2.]/^ inches outside, 
 and with a three-foot chimney will melt copper, gold, silver, etc., 
 in about ten minutes, or cast iron in thirty minutes from the time 
 the gas is lighted. 
 
 The construction of the burner used with this furnace is illus- 
 trated by the sectional diagram, Fig. 34, and is thus described : 
 
 Fig. 33. 
 
 Fig. 34. 
 
 "The gas enters a chamber at the bottom of the burner, through 
 a device similar to a Bunsen burner, mixing with air as it enters, 
 and is burned at the upper ends of a series of concentric tubes, 
 furnishing air-spaces alternately with those supplying the mix- 
 ture of gas and air. The whole burner is constructed of iron, and 
 will be found better able to withstand an intense heat, more dur- 
 able and quicker in its operation, than the old pattern with gun- 
 metal tubes. In case metal should be spilled into the burner, it 
 can be easily taken apart for its removal. 
 
 "Each part of the burner is lettered, and in case of accident it 
 
GENERATION AND APPLICATION OF HEAT. 
 
 61 
 
 can be supplied at a small expense by specifying the letter on the 
 piece desired. 
 
 "The burner in its present shape is believed to be the most effi- 
 cient and economical yet devised for furnace purposes." 
 
 The following instructions in the use of this furnace should be 
 observed : 
 
 "A chimney or stove-pipe, eight or ten feet high, may be used 
 as a fixture, and the draft partially stopped with a damper or 
 slide when lower temperatures are required, the gas being turned 
 down in proportion; the guide for the proper adjustment being 
 
 that UNDER ALL CIRCUMSTANCES THE FLAME MUST JUST COVER THE 
 
 crucible or muffle, but not extend into the chimney so as to 
 make it red hot. When the flame covers the crucible or muffle the 
 
 Fig. 35. 
 
 gas is doing its extreme duty under the most favorable circum- 
 stances, without waste. Particles of flux should not be allowed to 
 fall on the fire-clay casing, where the parts touch each other ; and 
 the power of the furnace should not be urged too far by the use of 
 very long chimneys, as there is danger of the fusion of the fire- 
 clay parts together, so that they cannot be separated. Fire-clay 
 fittings, as a rule, cannot be safely used for temperatures much 
 exceeding the fusing-point of cast iron. Plumbago fittings and cru- 
 cibles must be heated slowly the first time they are used. After the 
 first time they may be subjected instantly to the full power of the 
 furnace without injury." 
 
 Gas Crucible Furnaces with Blast. — A small, compact, and 
 convenient crucible furnace is shown in Fig. 35. Of this simple 
 but powerful heating-apparatus, which will be found especially 
 
62 MECHANICAL DENTISTRY. 
 
 adapted to the necessities of the dental laboratory, the manufac- 
 turers* observe : 
 
 " Owing to the discovery, by Mr. Fletcher, of a singularly per- 
 fect non-conducting furnace casing, we are enabled to produce the 
 first really simple gas-furnace ever constructed. This material is 
 only about one-sixth the weight of fire-clay, and has not one-tenth 
 its conducting power for heat. 
 
 " The furnace consists of a simple pot — for holding the cruci- 
 ble — with a lid and a blowpipe, all mounted on a suitable cast- 
 iron base. As compared with the ordinary gas-furnace it appears 
 almost a toy, owing to its great simplicity. 
 
 " The casing holds the heat so perfectly that the most refrac- 
 tory substances can be fused with ease, using a common foot- 
 blower. Half a pound of cast iron requires from seven to twelve 
 minutes for perfect fusion, the time depending on the gas supply 
 and pressure of air from the blower. 
 
 " The power which can be obtained is far beyond what is re- 
 quired for most purposes, and is limited only by the fusibility of 
 the crucible and casing. 
 
 " The crucible will hold about ten ounces of gold. 
 
 " An ordinary gas supply pipe, T \ or ■§-, will work it efficiently. 
 It requires a much smaller supply of gas than any other furnace 
 known. About ten cubic feet per hour is sufficient for most pur- 
 poses. 
 
 " Crucibles must not exceed 2% by 2 inches. Any common 
 blowpipe bellows will work the furnace satisfactorily except for 
 very high temperatures (fusion of steel, etc.), for which a heavy 
 pressure of air is necessary. 
 
 " In adjusting this furnace for use, put the gauze-nozzle of the 
 burner closely against the hole in the side of the casing, turn on 
 the gas, and light it in the furnace. Work the bellows and then 
 put the cover on the furnace. The air supply should be such that 
 a flame about two inches long will play out of the hole in the 
 cover, and it may be adjusted by turning the thumb-screw on the 
 side of burner. The amount of air and gas used by this burner is 
 very small. Care should be taken that the right proportion of 
 each should be used. A very light but steady blast of air will give 
 the best results. 
 
 * Buffalo Dental Manufacturing Company. 
 
GENERATION AND APPLICATION OF HEAT. 63 
 
 "A modified pattern of the foregoing furnace (Fig. 36) has 
 been designed, retaining all the peculiar advantages of the one 
 just described, but burning refined petroleum instead of gas as 
 fuel, and is claimed to be equally as efficient as the gas-furnace. 
 
 "The burner of this "furnace is constructed upon the principle 
 of an atomizer ; and this, of course, dispenses with a wick. This 
 method has proven the most efficient of any that has been experi- 
 mented with. 
 
 " The recent improvements consist in a device for regulating 
 the supply of oil, which is operated by the milled nut (marked A) 
 shown on top of the reservoir in the cut, and the addition of an 
 annular jet of air, which is regulated by turning the sleeve 
 (marked B)." 
 
 This is an approved crucible furnace, and is known as Fletch- 
 er's injector gas-furnace, the construction of this apparatus being 
 
 Fig. 36. 
 
 upon the principle of the injector furnace, and it is claimed that 
 its power and speed of working are practically without limit, 
 depending only upon the gas and air supply. It is very simple 
 in construction, and consists of two parts, an upper portion, which 
 forms the cover, and a lower part, which holds the crucible while 
 in operation (see Fig. 36). 
 
 A very useful and almost indispensable heating-apparatus in 
 the dental laboratory, suitable for drying, boiling, melting metals 
 requiring a moderate temperature, as zinc, tin, lead, etc., heating 
 flasks preparatory to packing with rubber, and a variety of other 
 purposes, is exhibited in Fig. 37. 
 
 The burner, consisting, as will be seen, of a circular perforated 
 gas-tube with a central air-jet, gives a complete range of tempera- 
 
64 
 
 MECHANICAL DENTISTRY. 
 
 ture, from a gentle current of warm air to a clear red heat, and is 
 so perfectly tinder control that a common glass bottle may be 
 placed on the tripod and heated to any required temperature with- 
 out the slightest risk of fracture. For very low temperatures the 
 ring must be lighted through the opening B. This gives a steady 
 current of heated air through the gauze above. For boiling, melt- 
 ing, etc., the light must be applied on the surface of the gauze, 
 thereby providing a large body of blue flame, which can be urged 
 by the blastpipe C. This is one of the most generally useful 
 burners, and stands hard, dirty work without injury. The gauze, 
 if choked up with dirt, can be replaced in a few seconds. 
 
 An equally convenient heater for many purposes requiring a 
 diminished temperature, as compared with the air-blast heater 
 
 Fig. 37- 
 
 Fig. 38. 
 
 MS*-- ^ =: 
 
 just described, is exhibited in Fig. 38. A gentle current of air 
 passes through side openings in the end of the injecting tube, 
 mingling with the gas supplied through a rubber tube attached to 
 an ordinary gas-burner. 
 
 An admirably contrived ladle-furnace, designed by Dr. Fletcher, 
 is shown in Fig. 39. This simple contrivance, provided with a 
 heating apparatus similar to the burner last described, is espe- 
 cially well adapted for melting any of the several metals usually 
 employed for dies and counter-dies, as zinc, tin, lead, Babbitt 
 metal, etc. The burner can be removed from the casing and used 
 for other purposes if desired. A cast-iron ladle of suitable form, 
 with a detachable handle, which can be removed during the proc- 
 ess of melting, is also illustrated. 
 
PRINCIPLES OF SOLDERING. 
 
 65 
 
 CRUCIBLES. 
 
 Crucibles are small, conical-shaped vessels used by the dentist 
 principally for the purpose of melting and refining metals used 
 for plates, compounding metallic alloys, preparing and compound- 
 ing the various ingredients employed in the manufacture of 
 porcelain teeth, continuous-gum work, etc. They combine in a 
 high degree the properties of infusibility, exemption from the 
 attack of substances fused in them, the power of resisting sudden 
 alternations of temperature and impermeability to fluids and 
 gases. The Hessian crucibles, which are in most common use 
 among dentists, are composed of silica, alumina, and oxid of iron. 
 
 Fig. 39. 
 
 Plumbago crucibles are also made from special patterns, and ex- 
 pressly designed for Fletcher's furnaces. 
 
 To avoid a possible loss of fused metals, which may occur in 
 consequence of some imperfection in the crucible, a test should 
 be made by placing in it a small quantity of borax and then sub- 
 jecting it to a high heat. If imperfect, the borax, rendered semi- 
 fluid by the heat, will pass through the substance of the crucible 
 and glaze the surface on the outside. 
 
 PRINCIPLES OF SOLDERING. 
 
 Successful soldering is dependent upon several conditions, a 
 disregard of any one of which may mean much difficulty, or a 
 complete failure. By the close observance of these conditions 
 
66 MECHANICAL DENTISTRY. 
 
 the difficulties experienced in soldering - (especially by students) 
 may be reduced to a minimum, in fact the operation becomes very 
 simple. These conditions are : 
 
 First, contact of the two surfaces to be united. If, for instance, 
 the ends of a piece of plate are to be united, as in the formation of 
 a band or ferrule, they must be so shaped as to be in close appo- 
 sition at every point, as solder will not bridge a space. Or, if it 
 be the soldering of an artificial denture, the backings must be in 
 contact with the plate to which they are to be united. In other 
 words, the continuity of the metal must be complete at the points 
 where it is desirous to have the solder flow. 
 
 Second, cleanliness of the surfaces over which the solder is to 
 flow. That cleanliness in soldering operations should be observed, 
 is quite as necessary as that the surfaces to be united should be in 
 perfect contact. The purity of gold or silver is usually reduced 
 by alloying with copper, which readily oxidizes when the metal is 
 heated to redness. This oxidation can be readily removed by 
 immersing the piece, when practicable, in dilute sulphuric acid, 
 slightly heated ; or a strong solution of alum may be used — its 
 solvent properties, however, are not developed until brought to the 
 boiling-point, 212 F. Borax is also employed for this purpose; 
 it accomplishes the same result by dissolving the oxid from the 
 surface of the metal at the points where applied, and at the same 
 time protects it from further oxidation. A good practice is to 
 coat the surfaces to be soldered, before the heat is first applied. 
 
 Third, the proper amount and application of heat. Where arti- 
 ficial teeth are to be soldered the heating process, as well as the 
 cooling, should be gradual. The greater the amount of invest- 
 ment material, the greater the amount of heat required to bring 
 the piece to be soldered to a uniform temperature. It naturally 
 follows that the thickest part of the investment must receive the 
 greatest volume of heat. Solder always flows toward the hottest 
 point; this tendency enables us to direct its course under the 
 blowpipe, by keeping the parts to be soldered at a higher tem- 
 perature than the solder itself. On the other hand, if the heat is 
 directed upon the solder, so that it reaches its fusing-point before 
 the parts upon which it is placed are equally hot or hotter, it rolls 
 up into a ball, a very troublesome feature to the majority of stu- 
 dents. A large flame from the blowpipe should only be employed 
 
PRINCIPLES OF SOLDERING. 67 
 
 in " heating up " the case, not for the soldering- process. If these 
 three stages have been carefully observed, it will be found that 
 with a small pointed flame directed upon the solder and the parts 
 to be united, the solder will flow quickly and leave a smooth, even 
 surface at the completion of the operation. 
 
CHAPTER III. 
 
 METALS EMPLOYED IN DENTAL LABORATORY OPERATIONS. 
 
 GOLD. 
 
 Au (Aurum). 
 
 Gold has been known from a period of great antiquity, having, 
 according to the writings of Moses, been wrought into articles of 
 jewelry more than three thousand years ago. As a base or sup- 
 port for artificial dentures, it has entirely superseded the use of 
 the various animal substances formerly employed, and, by the 
 mass of practitioners at the present time, it continues to be the 
 most highly esteemed metal for the purpose mentioned, notwith- 
 standing the more recent introduction of processes in which, as 
 a base, this metal is wholly discarded. 
 
 Gold is found in nature chiefly in the metallic state, and occurs 
 either crystallized in the cube and its allied forms, or in threads of 
 various sizes, twisted and interlaced into a chain of minute octa- 
 hedral crystals ; also in spangles or roundish grains. These lat- 
 ter, when they occur of a certain magnitude, are called pepitas, 
 some specimens of which have been obtained of great size. In 
 1810 a mass of alluvial gold weighing 28 pounds was found in the 
 gravel-pits of the creeks of Rockhole, in North Carolina. A lump 
 of gold ore weighing three cwt. was forwarded from Chili, South 
 America, as a contribution to the World's Exhibition in London. 
 New Granada, California, Russia, and Australia have each pro- 
 duced pepitas, or masses of gold weighing respectively 27^, 28, 
 70, and 106 pounds. As it occurs in nature, gold is never quite 
 pure, being generally associated with silver, though sometimes it 
 contains small quantities of platinum, iridium, or palladium. 
 
 Geological Situations. — The crystalline primitive rocks, the 
 compact transition rocks, the trachytic and trap rocks, and allu- 
 vial grounds are the formations in which gold occurs. Unlike 
 many other metals, it is never in such large quantities as to con- 
 stitute veins by itself, but is either disseminated through the 
 
 68 
 
METALS EMPLOYED IN DENTAL LABORATORY OPERATIONS. 69 
 
 rocky masses, or spread out in thin plates or grains on their sur- 
 face, or confined in their cavities in the shape of filaments or 
 crystallized twigs. The minerals composing the veins are either 
 quartz, calcspar, or sulphate of baryta. The ores associated with 
 the gold in these veins are principally iron, copper, arsenical 
 pyrites, galena, and blende. The most abundant sources of gold, 
 however, are in alluvial grounds, where it is found distributed in 
 the form of spangles in the sands of certain plains and rivers, 
 especially at their reentering angles, at the season of low water 
 and after storms and temporary floods. Sufficient reasons have 
 been advanced in support of the belief that gold found in alluvial 
 situations belongs to the grounds traversed by these rivers, in- 
 stead of being washed, as was formerly supposed, from the moun- 
 tains in which their waters have their origin. 
 
 Geographical Distribution. — The European mines more par- 
 ticularly distinguished for their richness are in Hungary and 
 Transylvania ; it also occurs, but more sparingly, in Ireland, 
 Sweden, Siberia, Germany, Russia, Spain. In Asia and Africa, the 
 mines which yield most abundantly are situated in the southern 
 portion of these continents. From the latter, the ancients derived 
 the greater portion of their gold. Several of the South American 
 provinces yield this metal in considerable quantities. Washings 
 are also common in several States of the Union, but California 
 stands unrivaled, except by Australia, in the immense productive- 
 ness of its mines, and its resources in respect to this rare and 
 valuable metal are reckoned inexhaustible. 
 
 Properties of Gold. — Pure gold is distinguished from all other 
 metals by its brilliant orange-red or yellow color, being the only 
 simple metal that possesses this complexion. It is susceptible to 
 a high polish, but is inferior in brilliancy to steel, silver, or mer- 
 cury. Its specific gravity varies somewhat, according as it is 
 fused or hammered ; the former having a density of 19.26, the 
 latter ranging from 19.04 to 19.65. It is only excelled in density, 
 therefore, by platinum, the specific gravity of which is 21.25. 
 
 Gold surpasses all other metals in malleability. The average 
 thickness of ordinary gold-leaf is 2T2V00" °^ an i ncn > Dut the 
 ultimate degree of attenuation to which pure gold is susceptible 
 exceeds considerably this estimate. It is also distinguished for 
 its ductility. A single grain of gold may be drawn into wire 50a 
 
7o 
 
 MECHANICAL DENTISTRY. 
 
 feet in length, while an ounce may be made to extend 1300 miles. 
 It is somewhat softer than silver, and possesses great tenacity, 
 though inferior in this quality to iron, copper, platinum, or silver. 
 A thread of gold y|-| -q of an inch in diameter will sustain a weight 
 of 150 pounds. 
 
 The fusing point of gold is 201 6° F. It fuses with consider- 
 able expansion, and on cooling contracts more than any other 
 metal. 
 
 On account of the want of affinity of gold for oxygen, it remains 
 unaltered in the longest exposure ; it is incapable of being oxid- 
 ized in any heat that may be applied to it, and is only volatilized 
 with great difficulty in the resistless heat of the oxyhydrogen 
 blowpipe. It is unaffected by the most concentrated of the sim- 
 ple acids, but is readily soluble in aqua regia or nitro-muriatic acid 
 and nitro-fluoric acid. 
 
 It will thus be seen that gold possesses, in an eminent degree, 
 those general properties which render it peculiarly fit for the 
 purposes to which it is applied in the practice of dental prosthesis. 
 
 Influence of Alloying on the Properties of Gold. — The term 
 alloy signifies a compound of any two or more metals, as brass, 
 which is an alloy of copper and zinc. 
 
 Alloys, in respect of their uses, are practically new metals, and 
 differ in many important respects, both in their chemical and 
 physical characteristics, from the constituent metals of which 
 they are composed. A more particular account of the influence 
 of alloying upon the general properties of metals, and their man- 
 agement and behavior in the process of compounding, will be 
 given under the head of alloys of the baser metals. As gold com- 
 bines readily with most metals, some of the more prominent con- 
 ditions which distinguish its alloys will be given. 
 
 The malleability of gold is, strictly speaking, always impaired 
 by its union with other metals. This effect is eminently charac- 
 teristic of certain contaminations, as those with arsenic, tin, anti- 
 mony, bismuth, lead, etc. ; while with certain other metals, as sil- 
 ver, copper, and platinum, unless in excess, this property of gold 
 is so little affected, as in no material degree to interfere with its 
 being worked into any desired form for dental purposes. The 
 ductility of gold is also usually diminished by its incorporation 
 with foreign metals ; sometimes in a remarkable degree. Gold is 
 
METALS EMPLOYED IN DENTAL LABORATORY OPERATIONS. JI 
 
 always rendered harder, and its tenacity is generally increased, by 
 alloying, while its density varies with the particular metal or met- 
 als with which it is combined. Thus the alloy of gold with either 
 zinc, tin, bismuth, antimony, or cobalt, has a density greater than 
 that of the mean of its constituents, while the alloys of gold hav- 
 ing a less specific gravity than the mean of their components are 
 those with silver, iron, lead, copper, iridium, or nickel. Gold is 
 ordinarily more fusible when alloyed, the alloy always melting at a 
 less heat than that required to fuse the most refractory constituent, and 
 oftentimes less than the more fusible component. The alloy of gold 
 and platinum furnishes an example of the former ; the platinum, 
 which in its uncombined state is infusible in the highest heat of a 
 blast-furnace, forming a fusible compound with gold, the melting- 
 point of which is far below that of platinum. Gold solder, com- 
 posed of gold, copper, and silver, affords a familiar illustration of 
 the latter, the alloy melting at a less heat than that required to 
 fuse its least refractory component, silver. Gold, which in its pure 
 state has less affinity for oxygen than any other metal, is rendered 
 more or less oxidizable when combined with other metals. 
 
 That gold alloys tend to be formed in definite proportions of 
 their constituents would appear from the phenomenon observed 
 in the native gold of the auriferous sands, which is an alloy with 
 silver in the ratio of one atom of silver, united to four, five, six, or 
 twelve atoms of gold, but never with a fractional part of an atom. 
 The same circumstance is noticed in connection with the amalgam 
 of silver and mercury. But as alloys are generally soluble in each 
 other, the definiteness of this atomic combination is obscured and 
 disappears in most cases. 
 
 Properties of Particular Alloys of Gold. — The metals with 
 which gold is liable to be contaminated in the dental laboratory 
 are zinc, tin, lead, antimony, bismuth, iron or steel, mercury, and 
 arsenic ; as also excess of silver, copper, and platinum. As several 
 of these metals when alloyed with gold, even in very minute quan- 
 tities, are highly destructive in their influence upon those proper- 
 ties which adapt this metal to the various .wants of the mechanical 
 operator, and as their separation is often attended with consider- 
 able difficulty, annoyance, and loss of time, it is practically im- 
 portant that care should be taken to prevent, as far as practicable, 
 the admixture of any one or more of them with the gold scrap, fil- 
 
72 MECHANICAL DENTISTRY. 
 
 ings, or sweepings, that are to be reconverted into proper form 
 for use. The accidental intrusion of these metals, however, is, to 
 some extent, unavoidable, and as an acquaintance with the more 
 prominent characteristics or sensible properties of the resulting 
 alloys sometimes furnishes valuable indications in the selection of 
 the proper reagents employed in their purification, a description 
 of individual alloys is introduced. 
 
 Tin, antimony, bismuth, lead, and arsenic, are peculiarly 
 prominent in their effects upon the malleability of gold; either 
 of these metals in exceedingly minute quantities render gold 
 intractable. 
 
 One part of antimony with nine parts of gold, form a pale, brittle 
 alloy, and in the proportion of one part of the former to 1920 of 
 gold, the resulting compound is too brittle to admit of successful 
 lamination. 
 
 An alloy of arsenic with gold containing ^q- of the former is a 
 gray, brittle metal, while in the proportion of -g-jjQ-, the malleabil- 
 ity of the gold is seriously impaired without suffering any change 
 of color. So energetic is the influence of this metal on gold that 
 the latter is rendered brittle when subjected even to the vapor of 
 arsenic. 
 
 Tin, lead, and bismuth are somewhat analogous to arsenic in 
 their influence upon the malleability of gold, either of them, in al- 
 most inappreciable quantities, rendering the latter metal unman- 
 ageable under the rollers. One part of lead or bismuth to 1920 
 of gold converts the latter into an unmalleable metal, while tin 
 exceeds either in its remarkable tendency to render gold hard and 
 brittle. Alloys of gold with tin are of a light color; those with 
 lead are of a darker complexion. 
 
 Zinc .with gold forms a brittle alloy, and when combined in 
 equal proportions is exceedingly hard, white, and brittle. Uniting 
 or incorporating itself less intimately with the gold than either 
 lead or tin, however, it not infrequently happens that portions of 
 the ingot will be brittle while others remain, in some degree, 
 malleable; so that the bar, when rolled out in the form of plate, 
 will be perforated or cracked at those points where the zinc pre- 
 dominates, while remaining portions of the plate retain a moder- 
 ate degree of softness and pliability. 
 
 The working properties of gold are not sensibly affected by the 
 
METALS EMPLOYED IN DENTAL LABORATORY OPERATIONS. 73 
 
 incorporation of very small quantities of iron, as an alloy of these 
 metals, in the proportion of one part of the latter to eleven of 
 gold, remains malleable. 
 
 Platinum, in itself a highly refractory metal, is, as before stated, 
 rendered fusible in combination with other metals. When com- 
 bined with gold in small proportions, the latter is rendered harder 
 and more elastic without having its malleability practically im- 
 paired. Platinum very readily affects the color of gold, the small- 
 est quantities rendering the alloy pale and dull-colored. 
 
 Silver unites with gold in every proportion, and is the chief 
 metal employed in the reduction of gold to the required forms for 
 dental uses. It renders gold more fusible, and imparts to it 
 increased hardness without materially affecting its malleability. 
 The alloy is light-colored in proportion to the amount of silver 
 introduced. 
 
 Copper, like silver, is usually combined with gold in the forma- 
 tion of plate, solders, etc., and hardens and renders gold tougher 
 without practically impairing its malleability. It imparts to the 
 alloy a deeper red color, and in the form of plate is capable of 
 receiving a polish excelling in richness and brilliancy any other 
 metal. 
 
 The foregoing alloys of gold, it will be perceived, are such as 
 result from the incorporation with gold of minute proportions 
 of any one of the base metals mentioned, and possess certain 
 physical characteristics that indicate, with tolerable certainty, the 
 particular alloying component. Thus, for example, if the alloy is 
 light-colored and very brittle, the presence of tin may be sus- 
 pected ; if brittle and dull-colored, lead is indicated ; if grayish or 
 dull-colored, but still malleable, tough, and elastic, platinum is 
 probably present ; if unequally malleable, or brittle in spots, the 
 presence of zinc may be inferred. 
 
 Alloys of gold, however, embracing several or all of these met- 
 als in varying proportions, are sometimes accidentally formed, in 
 which case the more distinctive features which characterize the 
 binary compounds are lost or obscured. 
 
CHAPTER IV. 
 
 REFINING GOLD. 
 
 Elements Employed. — The separation of foreign metals from 
 gold by what is termed the "dry method," or roasting, is effected 
 by the action on them of either oxygen, chlorin, or sulphur, con- 
 verting them into oxids, chlorids, or sulphurets. Certain com- 
 pound substances are used for this purpose which, when heated 
 and decomposed, yield these elements in sufficient quantities for 
 the purposes specified. The refining agents in common use are 
 nitrate of potassa (niter, or saltpeter), which yields oxygen; chlorid 
 of mercury (corrosive sublimate), which yields chlorin; and sul- 
 phuret of antimony (crude antimony), which yields sulphur. Other 
 compounds contain these elements, but those mentioned are 
 generally preferred because they contain them abundantly, are 
 readily decomposed by heat, and do not materially interfere with 
 the process of separation by the introduction of troublesome com- 
 ponents into the alloy. 
 
 Before considering specifically the different modes of refining 
 alloys of gold, it will be convenient to classify the different forms 
 of gold as they occur in working this metal in the laboratory. 
 
 i. Plate-scrap or clippings, and plate-filings. These, if proper 
 care is taken to prevent the introduction of fragments of platinum, 
 impure filings, or particles of base metals, only require, provided 
 they were originally of suitable fineness, to be remelted and again 
 converted into plate or other forms for use. 
 
 2. Mixed filings, and fragments containing solder, platinum, 
 etc. These, when melted alone, produce an alloy more or less 
 impoverished in proportion to the quantity and quality of the 
 foreign metals introduced in finishing pieces constructed of gold, 
 and should either be separately refined by roasting, or reduced to 
 pure gold by the " humid method," to be described hereafter. 
 
 3. Sweepings. This form embraces many impurities, earthy 
 and metallic, and should first be thoroughly washed, to remove 
 
 74 
 
REFINING GOLD. 
 
 75 
 
 the earthy constituents, after which the remaining metals may 
 either be mixed with class second, or separately refined. Another 
 and perhaps better method, is to fuse together the sweepings and 
 substances hereinafter mentioned, in the following proportions : 
 Of sweepings, eight parts ; chlorid of sodium, four parts ; impure 
 carbonate of potassa, four parts ; impure supertartrate of potassa, 
 one part; and nitrate potassa, half part. Mix them thoroughly 
 together, and melt in a crucible. The crucible with its contents 
 should remain in the fire for some time, in order to secure a com- 
 plete separation of the metals from extraneous matter. 
 
 It is evident from the above classification that much time and 
 labor may be saved by preserving these forms of gold separately 
 as they accumulate in the laboratory. Separate lap-skins or recep- 
 tacles, therefore, should be appropriated to the working of gold, 
 one to receive scrap and unmixed plate-filings, which may be 
 reconverted into plate without refining; another to collect the 
 solder-filings, and such impure fragments as require purification. 
 
 Separation of Foreign Metals from Gold. — The most trouble- 
 some ingredients which find their way into gold alloys are what 
 are commonly called base metals, as tin, lead, zinc, iron, antimony, 
 bismuth, etc. In attempting to separate these metals from gold, 
 it is not a matter of indifference what reagent is employed, inas- 
 much as distinct affinities exist, which may be advantageously 
 consulted. If, for example, zinc, or iron, or both of these metals 
 are present in small quantities, any compound which yields oxy- 
 gen will, by virtue of the affinity of the latter for these metals, 
 effect their separation by converting them into oxids ; hence, 
 when these metals are to be got rid of, nitrate of potassa is em- 
 ployed. But oxygen has a feeble affinity for tin, and when this 
 metal is present, its separation is better effected by some com- 
 pound which parts with chlorin in the act of decomposition ; 
 chlorid of mercury is therefore used for the purpose. When the 
 alloy of gold contains a number of these metals at the same time, 
 and is very coarse, sulphuret of antimony, which is a very power- 
 ful and efficient reagent, should be resorted to, unless the opera- 
 tor should prefer, and which is the better way, to reduce the alloy 
 to pure gold by the " humid method." 
 
 The Dry Method. — After all traces of iron or steel have been 
 removed from the gold fragments and filings by passing a magnet 
 
j6 MECHANICAL DENTISTRY. 
 
 repeatedly through them, the latter should be placed in a clean 
 crucible, lined on the inside with borax, and covered either with a 
 piece of fire-clay slab, or broken crucible. Sheet-iron has been 
 recommended for the latter purpose, but should never be used, as, 
 when highly heated, scales form on the surface, and are liable to drop 
 in upon the fused metals. If the operation is likely to be pro- 
 tracted, an inverted crucible, with a hole in the bottom, may be 
 securely luted to the top of the one containing the metals ; the 
 refining agents and fluxes being introduced through the opening 
 in the upper crucible. These are then placed in the furnace, on a 
 bed of charcoal, or what is better, a mixture of charcoal and coke, 
 the latter being built up around the crucible, and over it when 
 covered with a second crucible, care being taken that no frag- 
 ments of fuel are permitted to fall in upon the fused metals. The 
 process is as follows : 
 
 First melt the alloy at a high temperature, to oxidize the 
 base metals ; the refining agents may then be added in small 
 quantities from time to time, and the heat continued from half an 
 hour to an hour, according to the coarseness of the alloy. The 
 agents first employed are borax, and potassium nitrate (KN0 3 ).. 
 The latter assists the oxidation by parting with its oxygen, when 
 the foreign metals will generally become entirely oxidized and 
 dissolved in the slag. 
 
 The crucible should be removed from the fire, and the metals 
 allowed to cool gradually. The crucible may now be broken and 
 the button of gold at the bottom removed and separated from the 
 slag that covers it with a hammer. The gold should then be put 
 into a fresh crucible and remelted for pouring into ingot-molds, 
 which should be previously warmed and oiled (see page 89). 
 This treatment, with nitrate of potassa and borax, will usually be 
 sufficient, as most metals are oxidizable. If, however, after ham- 
 mering, annealing, and rolling the ingot, it should still be found 
 brittle, it must be remelted, and some other refining agent em- 
 ployed to remove the traces of the base metals. If it is known 
 what foreign metal is present, the particular reagent which will 
 most readily attack it should be used. But if, as is often the case, 
 the alloy is of uncertain composition, or contains several metals 
 having distinct affinities, the process becomes to some extent 
 experimental, making it necessary to use first one refining agent 
 
REFINING GOLD. 
 
 77 
 
 and then another, until, from the appearance and the manipula- 
 tion of the gold, it is found to be free from alloy. The special 
 reagents employed are as follows : 
 
 When tin or lead is present, add mercuric chlorid, HgCl 2 (cor- 
 rosive sublimate), and zinc chlorid, ZnCl 4 , or lead chlorid, PbCl,, 
 are formed and with the mercury volatilized by the heat. 
 
 When silver is present, add to the molten alloy from two to 
 four times its weight of antimony sulphid, Sb 2 S 3 ; this must be 
 added carefully and a little at a time. The heat decomposes the 
 sulphid. The sulphur unites with the silver and other base met- 
 als, forming sulphids, while the antimony unites with the gold, 
 forming a leaden-colored alloy. When effervescence has ceased, 
 remove the crucible from the fire and allow it to cool. The anti- 
 mony and gold alloy will be found in the bottom of the crucible, 
 and the sulphids on the surface. 
 
 To separate the antimony from the gold, remelt the alloy and 
 throw upon the molten mass a current of air from a blowpipe. 
 Antimony oxid, Sb 2 3 , is formed and volatilized ; continue the 
 process until fumes cease to be given off. 
 
 When iridium is present, Prof. Essig, in writing upon the sub- 
 ject, says : " The little, hard grains occasionally met with in gold, 
 upon which the file makes no impression, consist of iridium, or a 
 native alloy of osmium and iridium, and are not combined with 
 the gold, but merely disseminated through it. The only dry 
 method of separating it from gold consists in alloying the latter 
 with three times its weight in silver, by which means the specific 
 gravity of the metal is so much lowered that iridium, which is 
 very infusible and of a specific gravity of 21.1, will subside to the 
 bottom of the crucible, when the gold and silver alloy may be 
 poured or ladled off. As some of the gold will remain with the 
 residue, more silver must be melted with it, the operation being 
 repeated several times until nearly all the gold is removed." The 
 gold and silver alloy may then be separated as directed above. 
 
 When Platinum is Present. — If, after treating the alloy with 
 the reagents enumerated, it should be found malleable, but stiff or 
 elastic, and of a rather dull color, it is due to the presence of 
 platinum ; and any further attempts to reduce it by the " dry proc- 
 ess " will prove unavailing. It must then be subjected to what 
 will hereafter be described as the " humid or wet method." 
 
yS MECHANICAL DENTISTRY. 
 
 The Humid Method.- — When it is desired to reduce the alloy 
 to pure gold, which is generally advisable whenever the gold to be 
 refined consists of very coarse filings, fragments of plate contain- 
 ing large quantities of solder, linings with platinum pins attached, 
 particles of base metals, etc., the " humid or wet method," as it is 
 called, should be employed. The solvents in common use for this 
 purpose are nitric, sulphuric, and nitro-muriatic or hydrochloric 
 acid ; but as the desired results can be more conveniently and 
 directly obtained by the use of the latter, or hydrochloric acid, 
 this most available method alone will be given. The following 
 practical remarks on the subject are from an article on the " Man- 
 agement of Gold,"* by Professor George Watt: 
 
 " When the alloy is composed of metals differing but little in 
 their affinities for oxygen, chlorin, etc., we resort to one of the ' wet 
 methods.' And, in connection, we will only describe the one which 
 we consider the most convenient and effectual for the practical 
 dentist. It is effectual in all cases, as it always gives us pure gold. 
 
 " Let us, then, suppose that our gold alloy has become contam- 
 inated with platinum to such an extent that the color and elasticity 
 of the plate are objectionable. The alloy should be dissolved in 
 nitro-muriatic or hydrochloric acid, called aqua regia. The best 
 proportions for aqua regia are three parts of hydrochloric acid 
 to one of nitric. If the acids are at all good, four ounces of 
 the aqua regia will be an abundance for an ounce of the alloy. 
 The advantage of using the acids in the proportion of three to 
 one, instead of two to one, as directed in most of the text-books, 
 is, that when the solution is completed there is but little, if any, 
 excess of nitric acid. If the acids be ' chemically pure,' four parts 
 of the hydrochloric to one of the nitric produces still better re- 
 sults. 
 
 " By this process the metals are all converted into chlorids ; 
 and, as the chlorid of silver is insoluble, and has a greater speci- 
 fic gravity than the liquid, it is found as a grayish-white powder 
 at the bottom of the vessel. The chlorids of the other metals, 
 being soluble, remain in solution. By washing and pouring off, 
 allowing the chlorid of silver time to settle to the bottom, the 
 solution may be entirely separated from it. 
 
 " The object is now to precipitate the gold while the others re- 
 
 * Dental Register of the West, vol. xii, p. 251. 
 
REFINING GOLD. 79 
 
 main in solution. This precipitation may be effected by any one 
 of several different agents, but we will mention only the protosul- 
 phate of iron. 
 
 " This salt is the common green copperas of the shops, and, as 
 it is always cheap and readily obtained, we need look no further. 
 It should be dissolved in clean rain-water, and the solution should 
 be filtered, and allowed to settle until perfectly clear. Then it is 
 to be added gradually to the gold solution as long as a precipitate 
 is formed, and even longer, as an excess .will the better insure the 
 precipitation of all the gold. The gold thus precipitated is a 
 brown powder, having none of the appearances of gold in its 
 ordinary state. The solution should now be filtered, or the gold 
 should be allowed to settle to the bottom, where it may be washed 
 after pouring off the solution. It is better to filter than decant in 
 this case, as, frequently, particles of the gold float on the surface, 
 and would be lost in the washings by the latter process. 
 
 " Minute traces of iron may adhere to the gold thus precipi- 
 tated. These c^n be removed by digesting the gold in dilute sul- 
 phuric acid ; and, when the process is properly conducted thus 
 far, the result is pure gold, which may be melted, under carbonate 
 of potash, in a crucible lined with borax, and reduced to the re- 
 quired carat." 
 
CHAPTER V. 
 
 ALLOYS OF GOLD FOR DENTAL PURPOSES. 
 
 Gold in its pure state is rarely employed by the dentist in lab- 
 oratory processes, on account of its softness and flexibility ; it is, 
 therefore, usually alloyed with such metals as impart to it — with- 
 out practically impairing either its malleability, pliancy, or purity 
 — the degree of hardness, strength, and elasticity necessary to re- 
 sist the wear and strain to which an artificial piece constructed 
 from it is unavoidably exposed in the mouth. 
 
 Reducing Metals. — The metals with which gold is usually 
 combined are copper and silver. It is sometimes reduced with 
 silver alone, many regarding the introduction of copper into the 
 alloy as objectionable, as plate derived from it is supposed to be 
 more readily tarnished and to communicate to the mouth a dis- 
 agreeable metallic taste. This is unquestionably true, if, as is 
 sometimes the case, the copper used is in excess ; when, in addi- 
 tion to the effects mentioned, gold, so debased, may become a 
 source of positive injury to the organs of the mouth, as well as to 
 the general health. The small proportions of copper usually em- 
 ployed in forming gold plate, however, are not likely to produce, 
 in any objectionable degree, the consequences complained of, un- 
 less the fluids of the mouth are greatly perverted. If gold coin is 
 used in the formation of plate, it may be sufficient to add sil- 
 ver alone, inasmuch as copper is already present; though, usually, 
 additional quantities of the latter metal are added. 
 
 Required Fineness of Gold Plate. — Alloys of gold to be per- 
 manently worn in the mouth should be of such purity as will most 
 certainly, under all the contingencies of health and disease, resist 
 any chemical changes that would tend to compromise either the 
 comfort or health of the patient. Evils of no inconsiderable mag- 
 nitude are sometimes inflicted, either through ignorance, careless- 
 ness, or cupidity, by a disregard of this important requirement. If 
 the general health of the patient remained always uniformly unim- 
 
 80 
 
ALLOYS OF GOLD FOR DENTAL PURPOSES. 8 1 
 
 paired, with the secretions of the mouth in their normal state, 
 gold degraded to 18 or even 16 carats fine, would undergo no 
 material changes in the mouth. But it must be remembered 
 that, in addition to the corrosive agents introduced into the 
 mouth from without, a variety of diseases, local and constitutional, 
 effect important changes in the otherwise bland and innoxious 
 fluids contained therein, which, from being alkaline or neutral, be- 
 come more or less acidulated. Indigestion, with acid eructations ; 
 gastro-enteritis ; ague ; inflammatory and typhoid fevers ; brain 
 affections ; eruptive diseases ; rheumatism, gout, etc., are some of 
 the local and constitutional disorders almost uniformly imparting 
 to the mucous and salivary secretions an acid reaction. When 
 this condition of the secretions exists in connection with the use 
 of gold, readily acted on chemically by reason of its impoverish- 
 ment, some degree of irritation of the tissues of the oral cavity is 
 likely to ensue. Gold plate intended to be introduced into the 
 mouth should not, therefore, as a general thing, be of a less stand- 
 ard of fineness than from 18 to 20 carats. It may exceed this 
 degree of purity in some cases, but will rarely or never, unless 
 alloyed with platinum, admit of being used of a higher carat 
 than the present American coin, which is 21.6 carats fine. 
 
 Formulas for Gold Plate used as a Base for Artificial Den- 
 tures. — Any of the following formulas may be employed in the 
 formation of gold plate to be used as a base or support for artifi- 
 cial dentures. The relative proportions of the alloying com- 
 ponents may be varied to suit the peculiar views or necessities of 
 the manipulator. The estimated carat of the appended formulas 
 is based on the fineness of the American gold pieces coined in 
 1837 and thereafter. 
 
 GOLD PLATE EIGHTEEN CARATS FINE. 
 Formula No. 1. Formula No. 2. 
 
 18 dwts. pure gold, 20 dwts. gold coin, 
 
 4 dwts. fine copper, 2 dwts. fine copper, 
 
 2 dwts. fine silver. 2 dwts. fine silver. 
 
 GOLD PLATE NINETEEN CARATS FINE. 
 Formula No. 3. Formula No. 4. 
 
 19 dwts. pure gold, 20 dwts. gold coin, 
 
 3 dwts. copper, 25 grs. copper, 
 
 2 dwts. silver. 40 + g rs - silver. 
 
 6 
 
82 MECHANICAL DENTISTRY. 
 
 GOLD PLATE TWENTY CARATS FINE. 
 Formula No. 5. Formula No. 6. 
 
 20 dwts. pure gold, 20 dwts. gold coin, 
 
 2 dwts. copper, 18 grs. copper, 
 
 2 dwts. silver. 20 + grs. silver. 
 
 GOLD PLATE TWENTY-ONE CARATS FINE. 
 
 Formula No. 7. Formula No. 8. Formula No. 0. 
 
 21 dwts. pure gold, 20 dwts. gold coin, 20 dwts. gold coin, 
 
 2 dwts. copper, 13 + grs. silver. 6 grs. copper, 
 
 1 dwt. silver. ? s grs> platinum. 
 
 GOLD PLATE TWENTY-TWO CARATS FINE. 
 
 Formula No. 10. 
 22 dwts. pure gold, 
 
 1 dwt. fine copper, 
 18 grs. silver, 
 
 6 grs. platinum. 
 
 The union of platinum with gold, as in Formula No. 10, fur- 
 nishes an alloy rich in gold, while it imparts to the plate derived 
 from it a reasonable degree of stiffness and elasticity; preserves 
 in a good degree the characteristic color of fine gold ; and does 
 not materially impair its susceptibility of receiving a high polish. 
 The amount of gold coin given in Formula No. 9 may be reduced 
 with platinum alone, adding to it from eight to twelve grains ; in 
 which case, although the carat of the alloy is lowered, its absolute 
 purity remains unaffected, and plate formed from it will better 
 resist any changes in the mouth than gold coin itself. 
 
 Formulas for Gold Plate used for Clasps, Wire, Stays or 
 Backings, Dowels, etc. — Gold used in the formation of clasps, 
 backings, etc., is improved for these purposes by the addition of 
 sufficient platinum to render it firmer and more elastic than the 
 alloys ordinarily employed in the formation of plate as a base. 
 The advantages of this elastic property, in its application to the 
 purposes under consideration, are, that clasps formed from such 
 alloys will adapt themselves more accurately to the teeth, as, when 
 partially spread apart on being forced over the crowns, they will 
 spring together again and accurately embrace the more contracted 
 portions. In the form of stays or backings, additional strength 
 being imparted, a less amount of substance will be required ; the 
 elasticity of these supports, also, will not only lessen the chances 
 
ALLOYS OF GOLD FOR DENTAL PURPOSES. 83 
 
 of accident to the teeth themselves in mastication and otherwise, 
 but preserve their proper position when temporarily disturbed by 
 any of the forces applied to them. The same advantages last men- 
 tioned are obtained from this property in the use of metallic 
 pivots. 
 
 Formula No. 1. Formula No. 2. 
 
 20 dwts. pure gold, 20 dwts. coin gold, 
 
 2 dwts. fine copper, 8 grs. fine copper, 
 
 1 dwt. fine silver, 10 grs. silver, 
 
 1 dwt. platinum. 20 grs. platinum. 
 
 The alloy derived from either of these formulas will be 20 
 carats fine. 
 
 Gold Solders. — Solders are a class of alloys by means of which 
 the several pieces of the same or of different metals are united to 
 each other. They should be more fusible than the metals to be 
 united, and should consist of such components as possess a strong 
 affinity for the substances to be joined. They should also be as 
 fine as the metals to which they are applied will admit of without 
 endangering the latter. Solders of different degrees of fineness, 
 therefore, should always be provided to make selections from. 
 
 The use of solders of doubtful or unknown composition should 
 be avoided, and hence they should be compounded either from 
 pure gold or gold coin. 
 
 The following formula taken from Prof. Harris's work on 
 " Dental Surgery," page 666, recipe No. 3, may be used in connec- 
 tion with 18 or 20 carat gold plate, and is 16 carats fine : 
 
 6 dwts. pure gold, 
 
 2 dwts. rosette copper, 
 
 1 dwt. fine silver. 
 
 Recipes Nos. 1 and 2, page 663 of same work, are too coarse to 
 be introduced into the mouth ; the former being a fraction below 
 14 carats, while the latter is still more objectionable, exceeding 
 but little i2 J / 2 carats. 
 
 Formula No. I of the following recipes is a fraction over 15 
 carats fine : and No. 2 furnishes a solder 18 carats fine : 
 
 Formula No. i. Formula No. 2. 
 
 6 dwts. gold coin, Gold coin, 30 parts, 
 
 30 grs. silver, Silver, 4 " 
 
 20 grs. copper, Copper, 1 part, 
 
 10 grs. brass. Brass, 1 " 
 
84 MECHANICAL DENTISTRY. 
 
 In the reduction of gold for solders, Dr. Dorrence recommends 
 the use of what he calls " solder alloy." This is derived from the 
 following formula : 
 
 1 part pure silver, 
 
 2 parts pure zinc, 
 
 3 parts pure copper. 
 
 The copper and silver are melted without flux, in a clean cru- 
 cible which is well lined with borax; the zinc is then added in 
 small quantities as rapidly as may be without chilling the molten 
 mass so that it loses its fluidity, meanwhile stirring it with a clay 
 pipe-stem or rod, or a white-wood stick, until the profuse fumes 
 of the burning zinc just pass off, when pour immediately into an 
 ingot-mold, or into clean water in a clean wooden pail. The met- 
 als entering into the composition of this solder alloy should be 
 absolutely pure, especially should they be free of arsenic, anti- 
 mony, cadmium, etc., in which case not only the alloy, but gold 
 and silver solders made from it, will be tough and easy-flowing. 
 Inasmuch as the zinc, in compounding the alloy, has not been pro- 
 tected from oxidation, if it has been cast at the proper moment, it 
 will be found present in about its combining weight. Both gold 
 and silver solders made with this alloy will, as has been stated, be 
 found very tough, and easy-flowing, the range of proportion most 
 desirable being, for gold solder from 20 to 12 carats, or from 15 to 
 50 per cent, of alloy. Dr. D. very properly says, however, that the 
 12 carat or 50 per cent, solder is too coarse for dental work. From 
 to to 15 per cent, of the alloy added to gold coin is recommended 
 as a suitable solder in the construction of coin-gold crowns. 
 
 Zinc, as a constituent of solders, is used principally with a view 
 of rendering them more fusible without materially debasing them 
 if the proper proportion is observed. Its employment under any 
 circumstances has been objected to by some, on the ground that 
 the alloy is more readily tarnished in the mouth, is more brittle, 
 and that it furnishes more favorable conditions for galvanic action. 
 These objections only hold good when zinc is used in excess. 
 When employed in quantities sufficient only to make the gold flow 
 readily and evenly at a diminished heat, it is claimed that the base 
 metal used in these alloys is chiefly consumed in the process of 
 soldering, leaving a residuum of gold alloy equal, or nearly so, in 
 purity to solder not so contaminated. If such is the case they are 
 
ALLOYS OF GOLD FOR DENTAL PURPOSES. 8^ 
 
 acceptable alloys for soldering purposes, inasmuch as it is not 
 only desirable to have an easy-flowing solder, but one which shall 
 have as little affinity as possible for acids often found associated 
 with the fluids of the mouth. Care should be taken to add no 
 more zinc than is necessary to make the solder flow freely under 
 a heat that may be safely applied, without danger of melting the 
 pieces to be united. 
 
 Method of Reducing Gold to a Lower or Raising it to a Higher 
 Standard of Fineness, and of Determining the Carat of any Given 
 Alloy. — In the process of compounding gold for dental purposes, 
 the manipulator should always aim at exactness in the quantity 
 and relative proportions of the reducing components, and should 
 be able to determine precisely the purity of the metals he em- 
 ploys. Gold alloys are too often arbitrarily compounded, and 
 used without any adequate knowledge of their qualities or prop- 
 erties ; and formulas, taken on trust, are employed without any 
 certain knowledge of the quality of the alloys they produce. 
 
 That we may know certainly the quality of the gold alloys used 
 in the laboratory without resorting to the inconvenient process of 
 analysis or assaying, they should always be made either from pure 
 gold or gold coin, the standard of these being definitely fixed. 
 But as the process of procuring pure gold is somewhat tedious and 
 troublesome, gold coin is very generally employed for the purpose. 
 The amount of alloy necessary to reduce either pure or coin gold 
 to any particular standard, and the method of ascertaining the 
 carat or fineness of any given alloy, may be readily determined 
 by a few simple rules. The following practical remarks on the 
 method are taken from an article on " Alloying of Gold,"* by 
 Professor Watt : 
 
 " i. To Ascertain the Carat of any Given Alloy. — The propor- 
 tion may be expressed as follows : 
 
 "As the weight of the alloyed mass is to the weight of gold 
 it contains, so is 24 to the standard sought. Take, for example, 
 Harris's No. 3 gold solder: 
 
 Pure gold, 6 parts. 
 
 " silver, 2 
 
 " copper, 1 part. 
 
 Total, 9 parts. 
 
 * Dental Register of the West, vol. x, p. 396. 
 
86 MECHANICAL DENTISTRY. 
 
 " The total proportion would be expressed thus : 
 
 9 : 6 : : 24 : 16. 
 
 " From this any one can deduce the following : 
 
 " Rule. — Multiply 24 by the weight of gold in the alloyed mass, 
 and divide the product by the weight of the mass ; the quotient is 
 the carat sought. 
 
 " In the above example, 24 multiplied by 6, the quantity of 
 gold, gives 144, which, divided by 9, the weight of the whole 
 mass, gives 16. Hence, an alloy prepared as above is 16 carats 
 fine. 
 
 " As another example, under the same rule, take Harris's No. 
 1 solder: 
 
 22 carat gold, 48 parts. 
 
 Silver 16 
 
 Copper, 12 
 
 Total, 76 parts. 
 
 " Now, as the gold used is but 22 carats fine, one-twelfth of it 
 
 is alloy. The -fa of 48 is 4, which subtracted from 48 leaves 44. 
 
 The statement then is : 
 
 76 : 44 :: 24 : 13.9. 
 
 " This solder, therefore, falls a fraction below 14 carats. 
 
 " 2. To Reduce Gold to a Required Carat. — The proportion 
 may be expressed as follows : 
 
 " As the required carat is to 24, so is the weight of the gold used 
 to the weight of the alloyed mass when reduced. The weight of 
 gold subtracted from this gives the quantity of alloy to be added. 
 
 " For example, reduce six ounces of pure gold to 16 carats. 
 
 " The statement is expressed thus : 
 
 16 : 24 : : 6 : 9. 
 
 " Six subtracted from nine leaves three, which is the quantity 
 of alloy to be added. From this is deduced the following : 
 
 " Rule. — Multiply 24 by the weight of pure gold used, and 
 divide the product by the required carat. The quotient is the 
 weight of the mass when reduced, from which subtract the weight 
 of the gold used, and the remainder is the weight of alloy to be 
 added. 
 
ALLOYS OF GOLD FOR DENTAL PURPOSES. 87 
 
 " As another example under the same rule, reduce one penny- 
 weight of 22 carat gold to 18 carats. 
 
 " As the gold is only 22 carats fine, one-twelfth of it is already 
 alloy. The one pennyweight, therefore, contains but 22 grains of 
 pure gold. The statement is, therefore, thus expressed : 
 
 18 : 24 : : 2.2 : 29J/3. 
 
 " Twenty-two subtracted from 29% leaves 7%. Therefore, 
 each pennyweight of 22 carat gold requires 7% grains of alloy to 
 reduce it to 18 carats. 
 
 " 3. To Raise Gold to a Higher Carat. — This may be done by 
 adding pure gold or a gold alloy finer than that required. The 
 principle of the rule may be set forth in the following general ex- 
 pression : 
 
 " As the alloy in the required carat is to the alloy in the given 
 carat, so is the weight of the alloyed gold used to the weight of 
 the reduced alloy required. The principle may be. practically ap- 
 plied by the following: 
 
 " Rule. — Multiply the weight of the alloyed gold used by the 
 number representing the proportion of alloy in the given carat, 
 and divide the product by that representing the proportion of al- 
 loy in the required carat; the quotient is the weight of the mass 
 when reduced to the required carat by adding fine gold : 
 
 " To illustrate this, take the following example : 
 
 " Raise one pennyweight of 16 carat gold to 18 carats. 
 
 " The numbers representing the proportions of alloy in this ex- 
 ample are found by respectively subtracting 18 and 16 from 24. 
 The statement is, therefore : 
 
 6 : 8 : : 1 : xyi, 
 
 from which it follows that to raise one pennyweight of 16 carat 
 gold to 18 carats, there must be Y$ of a pennyweight of pure gold 
 added to it. 
 
 " But suppose that, instead of pure gold, we wish to effect the 
 change by adding 22 carat gold. The numbers, then, respectively 
 representing the proportions of the alloy would be found by sub- 
 tracting, in the above example, 16 and 18 from 22, and the state- 
 ment would be : 
 
 4 : 6 : : 1 : iV 2 . 
 
88 MECHANICAL DENTISTRY. 
 
 " It follows, then, that to each pennyweight of 16 carat gold y 2 
 of a pennyweight of 22 carat gold must be added to bring it to 18 
 carats. 
 
 " By the above rules, we think the student will be able, in all 
 cases, to calculate the fineness or quality of his gold, and to effect 
 any reduction, whether ascending or descending, which he may 
 desire." 
 
CHAPTER VI. 
 
 METHOD OF CONVERTING GOLD ALLOYS INTO THE REQUIRED 
 FORMS FOR DENTAL PURPOSES. 
 
 Manner of Procuring an Ingot. — The gold to be molded in the 
 form of ingot is put into a clean crucible lined on the inside with 
 borax, and placed in the furnace. When the contained metals are 
 perfectly fused, the crucible should be removed from the fire with 
 a pair of tongs, and the contents poured quickly but carefully into 
 the ingot-molds ; the latter being placed conveniently near the 
 mouth of the furnace, as the molten metals soon become chilled 
 on exposure to the open air. Before pouring, the molds, if made 
 
 Fig. 40. 
 
 of iron, should be moderately heated and oiled, or coated with 
 lamp smoke by holding their inner surfaces over the flame of an 
 oil lamp or gas-jet. 
 
 Ingot-molds are constructed of various substances, but those in 
 most common use are formed of iron, and, for gold, are generally 
 about two inches square and from y% to y^ of an inch thick (Fig. 
 40). They should be slightly concave on their inner surfaces, to 
 compensate for the greater shrinkage of the gold in the center 
 than at the margins of the ingot. 
 
 Soapstone is sometimes employed for the same purpose, and is 
 
 89 
 
9<D MECHANICAL DENTISTRY. 
 
 preferred by some. Molds made from this substance should also 
 be warmed and oiled before pouring the metals. 
 
 Molds are also made from charcoal, which is highly recom- 
 mended for the purpose, though it requires to be frequently re- 
 newed. Prof. Gorgas, in commenting on the relative fitness or 
 value of the several substances mentioned, says : " Iron is perhaps 
 the most convenient ; soapstone gives, with the same gold, a 
 tougher ingot; whilst with charcoal, the greatest toughness of 
 metal is obtained, so far as the nature of the ingot-mold can 
 modify it. Pig-iron, from the same furnace, run into iron molds, 
 may be white and brittle ; or into sand molds, gray and less brit- 
 tle; or into charcoal, dark gray and soft. Some such molecular 
 arrangement of gold, due to its manner of cooling, is probably the 
 correct explanation of the fact that a charcoal mold yields, other 
 things being equal, a tougher ingot than iron." 
 
 Charcoal ingot-molds may be very easily and quickly made as 
 follows : Selecting a close-grained compact piece, of suitable size, 
 cut through it with a saw, and then rub the divided surfaces to- 
 gether until perfect coaptation is secured. The required size- and 
 shape of the mold is then cut out in one section of the block ; or 
 a strip of sheet-iron, a little broader than the required thickness 
 of the ingot, being bent into proper form, is placed between the 
 two pieces, with the edges partially imbedded, and the whole 
 secured in place by binding with wire, or with the use of clamps. 
 
 Asbestos Molds. — Comparatively inexpensive, and at the same 
 time more convenient and durable contrivances designed for the 
 same purpose, combining both crucible and mold, and embracing 
 the special advantages claimed for charcoal, may be obtained at 
 the dental depots. One of the simplest forms of this kind is the 
 asbestos melting and ingot block shown in Fig. 41. When in use, 
 place a piece of charcoal over the bowl-shaped portion of the in- 
 got block, as it facilitates heating the metal. The small asbestos 
 slab being placed in position to complete the mold, and retained 
 in place by clamping, the metal, when sufficiently fused, is poured 
 into the mold by tipping the block. The bowl or crucible has a 
 thin coating of whiting, to prevent borax or other flux from ad- 
 hering. Should this occur, however, rub a little moist whiting in 
 the bowl. The sides of the block are encased in strips of wood, 
 to protect the hands from heat. 
 
FORMING GOLD ALLOYS FOR DENTAL USE. 
 
 91 
 
 Carbon Molds. — A very ingenious, convenient, and useful ap- 
 paratus, combining crucible and ingot-mold, by the use of which 
 ingots of gold, silver, etc., may be quickly obtained without the 
 use of a furnace, is shown in Fig. 42. The crucible is of molded 
 carbon, and is supported in position by an iron side-plate. A 
 
 Fig. 41. 
 
 clamp holds crucible and ingot-mold in position, swiveling on a 
 cast-iron stand. 
 
 The metal to be melted is placed in the crucible, and the flame 
 of the blowpipe directed on it until it is perfectly fused. The 
 waste heat serves to make the ingot-mold hot, and the whole is 
 
 Fig. 42. 
 
 tilted over by means of the upright handle at the back of the 
 mold. With this simple instrument a sound ingot may be ob- 
 tained at any time in about two minutes. 
 
 Aside from the greater convenience and cleanliness, as com- 
 pared with the older method in which draft-furnace heat is used, 
 
92 MECHANICAL DENTISTRY. 
 
 there is great economy of time in the use of the last-named appli- 
 ance combining crucible and mold, since an ingot may be thus 
 obtained, with the use of the bellows blowpipe, in from two to 
 three minutes. It is suitable for melting from two to four ounces 
 of gold or silver. 
 
 It not infrequently happens that, at the first pouring, the metals 
 arrange themselves in the ingot in accordance with the density of 
 the several components, those of greater specific gravity passing to 
 the bottom, and the lighter metals remaining above. Whenever 
 this occurs, the ingot must be broken into pieces and remelted ; 
 this should be repeated, if necessary, until the alloy assumes a per- 
 fectly homogeneous appearance. It should then be annealed in 
 hot ashes, which softens the gold and removes the adhering grease. 
 
 Forging. — Before laminating, the ingot should be reduced 
 somewhat in thickness ( by placing it on an even-faced anvil or 
 other equally smooth and resistant surface, and subjecting it to 
 repeated blows with a tolerably heavy hammer. It should be fre- 
 quently annealed, and the process of forging continued, alter- 
 nately hammering and annealing, until the ingot is reduced one- 
 half or more in thickness. 
 
 Laminating or Rolling. — The reduced ingot, well annealed, is 
 next laminated or spread out into a sheet of greater or less thin- 
 ness by passing it repeatedly between two strong, highly-polished 
 cylindrical steel rollers. The mills used for the purpose are 
 variously constructed, the plainest forms being very simple in 
 their mechanism, while others, or geared mills, are more compli- 
 cated, and are constructed with a view to a greater augmentation 
 of power, precision, and certainty of action. Fig. 43 illustrates 
 such a mill. 
 
 In laminating, the rollers should first be adjusted equidistant 
 at both ends, and this uniformity, as they are approximated from 
 time to time, should be preserved throughout. At every passage 
 of the gold bar between the rollers, the distance between the lat- 
 ter should be diminished, care being taken that the approxima- 
 tion be insufficient to clog or impede the free action of the mills. 
 The gold, which, in time, becomes hard and brittle, and liable to 
 crack in the mills, should be frequently and well annealed by 
 bringing it to a full red heat ; this restores the pliancy of the gold 
 and facilitates the operation in the press. 
 
FORMING GOLD ALLOYS FOR DENTAL USE. 
 
 93 
 
 When the ingot has been extended in one direction as far as 
 may be desired, it should always be reannealed before turning it 
 in the mills ; a neglect of this precaution will seriously interfere 
 with the working of the gold by twisting or doubling the plate 
 upon itself ; and in some instances, provided the gold has not 
 been well annealed throughout the operation, or is in any consid- 
 
 Fig. 43. 
 
 erable degree unmalleable, the plate will be torn across and ren- 
 dered unfit for use. 
 
 A thin or retreating edge may be given to the plate at any de- 
 sired point or points by passing such portions part way between 
 the rollers and withdrawing; repeating this, with the rollers 
 brought a little nearer to each other every time the plate is 
 introduced between them, and decreasing the distance the plate 
 
94 
 
 MECHANICAL DENTISTRY. 
 
 passes each time, until it is reduced to as thin an edge as may be 
 desired. 
 
 Standard Gage Plate. — The degree of attenuation obtained by- 
 rolling is determined by what is called a gage plate (Fig. 44). 
 This instrument is usually circular or oblong in form, and is 
 marked at intervals on its edge by cross-cut grooves, or fissures, 
 which successively diminish in size and are indexed by numbers 
 ranging from 5 to 36. The sizes of the grooves diminish with 
 the ascending numbers. During the operation of rolling, the 
 plate should be tested, from time to time, by the gage, to deter- 
 mine when it has undergone sufficient attenuation. 
 
 Fig. 44. 
 
 Thickness of Gold Plate Required as a Base for Artificial 
 Dentures. — In prescribing the thickness of plate proper for the 
 purpose indicated, no estimate can be given that will apply to all 
 cases, as certain conditions of the mouth, to be mentioned here- 
 after, will suggest some modifications in this respect. Usually, 
 however, plate for entire upper dentures should correspond in thick- 
 ness with number 26 of the gage plate; for the lower jaw, number 
 24 may be used; while for partial upper pieces, an intermediate 
 number may be chosen, unless atmospheric pressure-plates are 
 used, when the number recommended for full upper sets may be 
 employed. 
 
 Thickness of Plate for Clasps, Backings, etc. — Plate for these 
 
FORMING GOLD ALLOYS FOR DENTAL USE. 
 
 95 
 
 purposes should usually correspond with number 22 of the gage ; 
 a less amount of substance, as before stated, being required when 
 the alloy has incorporated with it a small proportion of platinum. 
 
 Reduction of Gold Solders into Proper Form for Use. — The 
 method of converting gold solders into the form of plate does 
 not differ from that already described in the manufacture of plate 
 as a base, except that when zinc or brass is used, the latter should 
 be added after the other constituents are completely fused, and 
 then instantly poured, to prevent undue wasting of the base met- 
 als by a too protracted heat. 
 
 The solder should be reduced to plate somewhat thinner than 
 that used for upper dentures, 28 of the gage plate. It is customary 
 
 Fig. 45. 
 
 © ( ? S vi r i S 1' 8 ?• 
 
 • & • © S • © :£) • 
 
 sometimes to roll the solder into very thin ribbons, but this is 
 objectionable for the reason that a greater amount of the alloy- 
 ing metals, being exposed in a given surface to the action of the 
 heat in soldering, are burnt out or oxidated, which interrupts the 
 flow and weakens the attachment between the solder and plate. 
 
 Method of Obtaining Gold Wire. — To convert gold or its al- 
 loys into the form of wire, the operator should be provided with a 
 draw-plate, a vise, and a pair of flat-nosed pliers. A draw-plate 
 (Fig. 45) is an oblong piece of steel, pierced with a regular grada- 
 tion of holes, or a series of progressively diminishing apertures, 
 through which the gold bar, reduced to a rod, is forced and made 
 to assume the form and dimensions of the hole through which it 
 
9 6 
 
 MECHANICAL DENTISTRY. 
 
 is last drawn. The holes are formed with a steel punch, and are 
 enlarged on the side where the wire enters and diminish with a 
 gradual taper to the other side. A draw-bench is sometimes em- 
 ployed in extending the wire, the power being applied by a 
 toothed-wheel, pinion, and rack-work, and is moved by the hands 
 of one or two persons. For the purposes of the dentist, however, 
 it will be sufficient to fix the draw-plate securely between the jaws 
 of a bench-vise, and, by seizing hold of one end of the gold rod 
 with a strong pair of clamps or flat-nosed pliers, serrated or cut 
 like a file on the inside of the jaws, the wire may be drawn stead- 
 
 FlG. 46. 
 
 ily through the plate, passing from the larger to the smaller holes 
 until a wire of the required size is obtained. 
 
 In drawing the wire, the motion should be steady and uniform, 
 for if drawn interruptedly or by jerks, the wire will be marked by 
 corresponding inequalities. The gold rod should also be annealed 
 from time to time, and the holes kept well greased or waxed. 
 
 The process described above will answer equally well in reduc- 
 ing any of the ductile metals to wire, as silver, copper, platinum, 
 etc., so that any further description of the method, in connection 
 with these metals, will be unnecessary. 
 
 Method of Constructing Spiral Springs. — Inasmuch as spiral 
 springs have been, to a great extent, superseded by more ap- 
 proved agencies employed in the retention of artificial teeth in 
 
FORMING GOLD ALLOYS FOR DENTAL USE. 
 
 97 
 
 the mouth, and as all the principal dental furnishing houses are 
 supplied with these appliances already prepared for use, it does 
 not seem necessary to enter into a description of the various ap- 
 paratus used in making them. 
 
 The following simple contrivance will meet the limited require- 
 ments of those who are obliged or prefer to manufacture their 
 own springs. The wire, obtained as already described, by means 
 of the draw-plate, is held between two blocks of wood fastened 
 between the jaws of a bench-vise, as shown in Fig. 46. By means 
 of a small hand-vise, one end of the wire is clamped to a uniformly 
 cylindrical and well-tempered steel rod or wire, four or six inches 
 long, and about the size of a small knitting-needle, and which 
 being made to revolve while resting on the blocks of wood, the 
 wire is wound firmly and compactly around it, producing a uni- 
 form coil. 
 
CHAPTER VII. 
 
 SILVER. 
 
 Ag (Aigentum). 
 
 General Properties of Silver. — Pure silver, when planished, 
 is the brightest of the metals. Fused, or in the form of ingot, its 
 specific gravity is 10.47; Dut when hammered or condensed in the 
 coining press, its density is increased and its specific gravity be- 
 comes 10.6. It is very malleable and ductile, yielding leaves 
 not more than j-q-^-qqq of an inch thick, and wire 400 feet of 
 which may be drawn weighing but a single grain. It exceeds 
 gold in tenacity or cohesion, but is inferior to platinum in this re- 
 spect. A silver wire .078 of an inch in diameter will sustain a 
 weight of 187.13 pounds. Fine silver is unaffected by moisture or 
 pure atmospheric air, but is readily tarnished with a film of brown 
 sulphuret by exposure to sulphureted hydrogen. The sulphuret 
 of silver thus formed may be easily removed by rubbing the 
 metal with a solution of chameleon mineral, prepared by calcining 
 equal parts of black or peroxid of manganese and niter. Unlike 
 gold and platinum, it is readily soluble in nitric acid, this and sul- 
 phuric acid being the only simple ones that dissolve it. 
 
 Silver fuses at an extreme red heat, generally estimated at 
 1873 ° F. It becomes very brilliant when heated ; boils and vapor- 
 izes above its fusing-point ; and when cooled slowly its surface 
 presents a crystalline appearance. 
 
 Alloys of Silver. — Silver combines readily with most metals, 
 forming compounds of variable degrees of malleability, ductility, 
 density, etc. 
 
 Tin, zinc, antimony, lead, bismuth, and arsenic render it brittle. 
 A very minute quantity of tin is fatal to the ductility of silver. 
 .Silver does not easily combine with iron, although the two metals 
 may be united by fusion. Gold, copper, platinum, iridium, steel, 
 manganese, and mercury also form alloys with silver. 
 
 An alloy of nine parts of silver and one part of copper is the 
 
 98 
 
SILVER. 99 
 
 Government standard of the United States coinage since 1837. To 
 this, three-cent pieces form an exception ; these being composed 
 of three parts silver and two of copper. The coins of silver hav- 
 ing a greater average fineness than those of our own country are 
 Brazil, Britain, Chili, France, Greece, Hindustan, Persia, Portu- 
 gal, Rome, and Tuscany. A common impression prevails that the 
 Mexican silver coin contains more than an average percentage of 
 pure silver, and it is therefore sought after on account of its sup- 
 posed purity. This is true of some pieces coined at different 
 periods, but the average fineness of the Mexican, as well as the 
 Spanish coins, falls below that of the United States mints. 
 
 Refining Alloys of Silver. — The following accounts of the man- 
 ner of obtaining pure, or nearly pure, silver from alloys of that 
 metal by the dry, and wet or humid methods, are given by Prof. 
 Essig in his treatise on "' Dental Metallurgy : " 
 
 " Dry Method. — The dry method or assaying process consists 
 in forming an alloy of the silver with lead, and is especially appli- 
 cable to ores and the sweepings of the dentist's laboratory. The 
 specimen to be treated is heated with from twelve to thirty times 
 its weight of granulated lead, in a bone-ash cupel, which is placed 
 in a muffle so arranged that a current of atmospheric air may pass 
 freely over the vessel and oxidize the lead. This oxid of lead, 
 being quite fusible, combines with any base metal present and 
 oxidizes it, uniting subsequently with the oxid as a fusible slag, 
 while the gold or silver will be held by the unoxidized portion of 
 the lead. In the treatment of specimens of alloy, such as plate 
 or coins, a quantity of the specimen is accurately weighed and 
 mixed with from four to five times its weight of pure granulated 
 lead. It is then placed in the cupel and exposed to heat, as above 
 described, until all the lead is oxidized or converted into litharge, 
 when the remaining button assumes the brilliant apearance of 
 surface to which allusion has been previously made, denoting that 
 the base metals or oxidizable constituents have been oxidized and 
 taken up by the lead oxid. This button is then to be weighed by 
 means of a delicate assay balance, and the loss of weight denotes 
 the amount of alloy that was present. 
 
 "Wet Method. — Pure silver, which is reckoned as 1000 fine, 
 may be obtained from standard or other grades of silver by dis- 
 solving them in nitric acid slightly diluted with water, the solution 
 
IOO MECHANICAL DENTISTRY. 
 
 being much facilitated by exposure to gentle heat. If gold be 
 associated with the alloy it will be found at the bottom of the 
 vessel, in which case it will be necessary to. use a siphon to re- 
 move the argentic nitrate solution. The silver is now to be 
 precipitated in the form of chlorid by the addition of an excess 
 of common salt. When all has subsided, the liquid is carefully 
 poured off, and the chlorid thoroughly washed, to remove all 
 traces of acid. The chlorid is then placed in water acidulated 
 with hydrochloric acid (an ounce of chlorid requiring six to eight 
 ounces of water) and pieces of clean wrought-iron put in it, when 
 a copious evolution of hydrogen follows, which, uniting with the 
 chlorin of the argentic chlorid, liberates metallic silver. The 
 latter should not be disturbed until the last particle of it is thus 
 reduced, when it will be found to be a spongy mass. The un- 
 dissolved iron should now be carefully removed, the ferrous and 
 ferric chlorid carefully decanted, and the silver washed in hot 
 water containing about one-tenth its bulk of hydrochloric acid. 
 This is repeated several times, and finally the silver is again thor- 
 oughly washed with pure hot water. The silver, after drying, is 
 then ready for melting, and if care has been observed in the proc- 
 ess it will be found to be of a fineness of 999.7 parts in 1000, the 
 0.3 of impurity present being due to traces of iron. The chlorids 
 may be acidulated with sulphuric acid, and reduced with zinc in- 
 stead of iron. 
 
 " Another method of precipitating silver in the metallic form 
 consists in placing a sheet of copper in a solution of argentic 
 nitrate. The metal is thrown down in a crystalline form. Silver 
 thus obtained is never free from traces of copper. 
 
 " Pure silver can only be obtained from samples of a lower 
 grade by fusing the pure chlorid with sodium carbonate. The re- 
 action is shown in the following equation : 
 
 sAgCl + Na 2 C0 3 = Ag 2 + sNaCl + O + C0 2 . 
 
 Owing to the copious evolution of carbonic acid gas which takes 
 place during the decomposition, some of the silver may be thrown 
 from the crucible, and loss may occur by the absorption by the 
 crucible of some of the fused chlorid. To avoid this, the sides of 
 the vessel should be coated with a hot saturated solution of borax. 
 " A composition of 100 parts of argentic chlorid, 70.4 of calcic 
 
SILVER. IOt 
 
 carbonate (chalk), and 4.02 of charcoal, has been recommended 
 as a means of obtaining pure silver. This mixture is heated to 
 dull redness for thirty minutes, and then raised to full redness ; 
 carbonic acid and carbonic oxid are given off; the calcic chlorid is 
 converted into calcic oxychlorid, underneath which, in the bottom 
 of the crucible, will be found the button of pure silver." 
 
 Reduction of Silver to the Required Forms for Dental Pur- 
 poses. — Owing to the very soft and flexible nature of silver in its 
 pure state, it is usual, when converting it into plate or other forms 
 for use, to employ an alloy of the metal. Hence silver coins, 
 which are made harder by the copper they contain, are generally 
 selected for the purpose. The employment of silver, thus de- 
 based, as a base for dental substitutes is regarded by many as 
 unsafe and injudicious. Although the influences of an alloy so 
 readily acted upon as this by the various agents which affect it 
 chemically cannot always be certainly predicted in every case, yet 
 no reasonable doubt can be entertained but that, under the favor- 
 ing conditions which usually exist in the mouth, the evils accru- 
 ing, directly and indirectly, to the organs of the mouth, and 
 through them to the general system, are positive and undoubted. 
 If used at all, therefore, it should be alloyed with the least prac- 
 ticable amount of copper, or, what is better, pure silver should be 
 reduced with platinum alone, in sufficient quantities to impart to 
 the plate an adequate degree of strength and elasticity. The ten- 
 dency of silver to tarnish in the mouth when alloyed with copper 
 may be diminished by boiling the finished piece in a solution of 
 cream of tartar and chlorid of soda, or common salt, or by scrub- 
 bing it with aqua ammonia, which removes the superficial par- 
 ticles of copper and exposes a surface of fine silver. When plati- 
 num is introduced as the sole alloying component, the purity of 
 the silver is not only preserved, but the alloy is less easily acted 
 on chemically, while the plate derived from it is rendered suffi- 
 ciently inflexible and elastic. From three to five grains of plati- 
 num may be added to one pennyweight of pure silver. 
 
 On account of the strong affinity of sulphur for silver, the fuel 
 most proper to be used in melting it is charcoal. The various- 
 processes employed in the conversion of silver into the required 
 forms for use are similar to those described for gold, and need not 
 be recapitulated. 
 
102 MECHANICAL DENTISTRY. 
 
 Formulas for Silver Solders. — Silver solders are usually com- 
 posed of silver, copper, and zinc in variable proportions. Alloys 
 formed from the following formulas are such as are generally 
 employed in soldering silver plate, derived from the coins of that 
 metal. Three-cent pieces, composed of two parts silver and one 
 of copper, may be used for the same purpose : 
 
 Formula No. i. Formula No. 2. 
 
 Silver, 66 parts. Silver, 6 parts. 
 
 Copper, 30 " Copper, 2 " 
 
 Zinc, 10 " Brass, 1 part. 
 
 When the material to be united is composed of pure silver and 
 platinum, silver coin alloyed with one-tenth zinc may be used as 
 a solder. 
 
 In compounding silver solders the silver and copper should be 
 first melted, and the zinc or brass afterward added, when they 
 should be quickly poured, to prevent undue waste by oxidation of 
 the more fusible component. The ingot, when cold, should be 
 rolled into a plate a little thicker than that recommended for gold 
 solder. 
 
CHAPTER VIII. 
 
 PLATINUM. 
 Pt. 
 
 General Properties. — Platinum is a grayish- white metal, re- 
 sembling, in some measure, polished steel. It is harder than 
 silver, and has a density greater than any other known metal, its 
 specific gravity being 21.25. It remains unaltered in the highest 
 heat of a smith's forge, and can only be fused by means of the 
 oxyhydrogen blowpipe and galvanism. A white heat does not 
 tarnish it, nor is it in any way affected by exposure, either in the 
 air or water. It is insoluble in any of the simple acids ; nitro- 
 muriatic acid (aqua regia) being the only one that dissolves it. It is 
 sufficiently malleable to be hammered into leaves so thin as to be 
 blown about by the breath. It may be drawn into wire yinnr 
 of an inch in diameter, and a still greater attenuation may be 
 obtained by coating the wire with silver, drawing it out, and 
 dissolving off the latter metal. It expands less by heat than 
 any other metal, and is much inferior to gold, silver, and copper 
 as a conductor of electricity. While it does not oxidize in the air 
 at any temperature, nor is soluble in any one acid, if heated to red- 
 ness in the air, in contact with caustic alkalies or alkaline earths, 
 a hydrated oxid is formed which combines with the alkaline base 
 in a similar manner to palladium. 
 
 Platinum, when absolutely pure, is quite soft and flexible, and 
 when rolled into thin sheets, say 28 or 30 of the gage plate, and 
 well annealed at a strong white heat for eight or ten minutes, it may 
 be readily forced into all the inequalities of a zinc die without 
 producing any appreciable change in the face of the latter. 
 
 The fusing-point of platinum is above 3500 F., to reach which, 
 in the laboratory, it is necessary to employ the oxyhydrogen 
 blowpipe or electric current. 
 
 The following interesting and practical observations on the 
 method of melting platinum scraps are by E. A. L. Roberts. 
 
 103 
 
104 MECHANICAL DENTISTRY. 
 
 By the process of welding, the operator will be enabled to recon- 
 vert his waste scraps of platinum into convenient forms for use, 
 and of which he could not otherwise avail himself, on account of 
 the infusible nature of this metal in its uncombined state : 
 
 " Platinum used by dentists should be soft, tough, and without 
 flaws. These qualities can be attained only by thorough melting 
 and welding. The welding must be done at a white heat. 
 When the surface is cool enough to be visible, the metal is too 
 cool to be welded, and every blow is injurious, because it has a 
 tendency to shatter and shake it to pieces. The necessary deli- 
 cacy of this process and the uncertainty of success has led some 
 writers to declare that platinum is incapable of being welded. 
 The platinum must be perfectly clean, and must be heated in a 
 muffle. When welded, the metal should be handled with tongs 
 plated with platinum, and hammered with a clean hammer on a 
 clean anvil, both of which should be as hot as possible without 
 drawing the temper of the steel. The hammer used in welding 
 should weigh about a pound, to prevent drawing the metal ; but 
 when welded the metal may be forged with a heavier hammer. 
 
 " The scraps or sponge should be condensed in a square mold, 
 very compactly, two pieces of which, weighing from 10 to 20 
 ounces, may be put in a muffle together. When the heat becomes 
 so great that on opening the door the metal becomes invisible, 
 bring one of the pieces, in the tongs, quickly to the anvil, give it 
 three or four quick, sharp blows, in rapid succession. Return the 
 piece to the muffle, and proceed with the other piece in like man- 
 ner, and thus alternately until both are thoroughly welded. 
 
 " Platinum should never be thrown into water while hot, as 
 that tends to make it crystallize. It should be thoroughly ham- 
 mered, which makes it tough and fibrous. 
 
 " The following process gives the best results in melting this 
 metal. Condense the scraps, sponge, or filings in an iron mold. 
 Lay the condensed mass on a concave fire-brick, and heat it to 
 whiteness. Take the brick from the muffle, and place it in a 
 sheet-iron pan, coated with plaster and asbestos. The pan should 
 be deep enough and broad enough to catch all globules and other 
 loose particles of the metal. Place it under the jet of the oxy- 
 hydrogen blowpipe in the following manner: 
 
 " The pan is provided with a handle, opposite to which is a ring, 
 
PLATINUM. 105 
 
 which is to be attached to an iron hook and rod, suspended from 
 the ceiling by a slip of india-rubber, which enables the operator to 
 hold the pan conveniently at any distance from the jet of the burn- 
 ing gases. The hydrogen is first lighted, and gives a powerful 
 flame, but as the oxygen combines with it, the flame subsides into 
 an intense focus of heat, in which the metal is soon brought to a 
 state of fusion. Begin at one end and melt along toward the 
 other, till the whole is fused in one mass. The platinum in this 
 condition, when cool, is quite crystallized and sonorous. It breaks 
 very easily, like spelter-zinc. Heat it very hot and forge it. A 
 continuation of this process renders it soft, tough, and fibrous. 
 When reduced to the width desired, and to the thickness of ^ °f 
 an inch, it should be made very hot and passed instantly through 
 the rollers." 
 
 Use for Dental Purposes. — Platinum, in mechanical practice, is 
 chiefly employed as a base for continuous-gum work ; as a color- 
 ing ingredient of porcelain ; for pins for attaching mineral teeth ; 
 for backings and dowels in crown- and bridge-work; and, to a 
 limited extent, in some of the minor operations of the laboratory. 
 
 Solder for Platinum. — Pure gold is the only proper solder for 
 this metal. 
 
 Alloys of Platinum. — Platinum unites with most of the base 
 metals, forming alloys of variable degrees of hardness, elasticity, 
 brittleness, color, fusibility, etc., but their practical value to the 
 dentist is not sufficient to justify a separate description of their 
 properties. 
 
 Alloyed with gold it forms a straw-colored alloy, the shade de- 
 pending on the quantity of gold added. Silver hardens it, the re- 
 sulting alloy being unaffected by sulphur. 
 
 Platinoid Metals. — The platinoid metals, palladium, iridium, 
 osmium, rhodium, and ruthenium, are native contaminations, the 
 alloys of these metals having a close general resemblance to 
 platinum. 
 
 Among the platinoid metals, palladium and iridium are the only 
 ones that have been used for dental purposes, and these only to a 
 limited extent. Palladium is of a steel-gray color, and when 
 planished, is a brilliant steel-white metal, not liable to tarnish in 
 the air. Though closely resembling platinum, it may be readily 
 distinguished from the latter metal by the following tests: (1) It 
 
I06 MECHANICAL DENTISTRY. 
 
 has little more than one-half the density of platinum. (2) If a 
 piece of it is heated to redness, it assumes a bronze-blue shade, of 
 greater or less intensity, as it is cooled more or less slowly ; but if 
 it is suddenly chilled by immersing it in cold water, it instantly re- 
 sumes its original luster. (3) When a drop of the tincture of io- 
 din is let fall upon its surface and evaporated over the flame of a 
 lamp, a black spot remains, which does not occur with platinum. 
 Palladium melts at about the heat required to fuse malleable iron, 
 and is the most fusible of the platinoid metals. It is soluble in 
 nitric acid, but its best solvent is nitrohydrochloric acid. 
 
 Palladium, being very costly, and possessing no properties that 
 specially recommend it for dental use, is but little employed in 
 prosthetic practice. 
 
 Iridium, though generally found associated with platinum, os- 
 mium, and other allied metals, sometimes occurs native and nearly 
 pure. Like platinum, it is very refractory when exposed to high 
 temperatures, and can only be fused by the oxyhydrogen blowpipe 
 or by the heat of the voltaic current. An alloy of one-fifth plat- 
 inum and four-fifths iridium has been met with in octahedral crys- 
 tals, whiter than platinum, and of specific gravity 22.66. When 
 native platinum is dissolved in nitrohydrochloric acid, black scales 
 remain behind, which are composed of iridium and osmium. These 
 metals may then be separated by one of the methods in use, and 
 the iridium is obtained in a gray metallic powder, resembling 
 spongy platinum. Iridium is very hard, white, and brittle, and 
 has a specific gravity of 21.15. None of the acids attack the pure 
 metal, but when alloyed with platinum it is readily dissolved by 
 aqua regia or nitrohydrochloric acid. If heated in a finely divided 
 state in the open air, iridium absorbs oxygen ; it is also oxidized 
 by niter and caustic potash. 
 
 The extreme hardness and consequent rigidity of iridium ren- 
 ders it, in its unalloyed state, practically unfit for base plates on 
 account of the great difficulty of swaging it into proper form. 
 This, however, may be accomplished in certain cases, as in partial 
 pieces, with the use of zinc dies and counters ; and in these cases 
 it is desirable on account of the increased strength its property of 
 hardness imparts to the plate. It may be used to advantage, how- 
 ever, alloyed with platinum, a small quantity imparting to the 
 latter increased stiffness and elasticity. 
 
CHAPTER IX. 
 
 ALUMINIUM. 
 Al. 
 
 Derivation. — Aluminium is the metallic basis of alumina, the 
 latter being the characteristic ingredient of common clay. It is 
 only within a comparatively few years that the attention of chem- 
 ists has been directed to the production of this metal, with a view 
 to its general introduction into commerce and the arts. Prior to 
 the researches of M. Deville, who, under the patronage of the 
 then Emperor of the French, commenced his researches in 1854 
 for the production of this metal on a large scale, the small quan- 
 tities produced, and the corresponding exorbitant prices it com- 
 manded, rendered it entirely unavailable for other purposes than 
 merely scientific experiment. The improvements in the methods 
 of. obtaining it, however, which have been more recently intro- 
 duced, have rendered its production more economical, and it is 
 now supplied in much larger quantities, and at a corresponding 
 reduction in the cost of the metal. The latest process for ex- 
 tracting aluminium is by the electric current. The Pittsburg 
 Reduction Company, especially, is using this method with much 
 success. 
 
 General Properties. — One of the most striking properties of 
 aluminium is its extreme lightness, its specific gravity being 2.6, 
 nearly that of glass, whilst that of platinum is 21.5, gold 19.5, 
 copper 8.96, zinc 7.2, tin 7.3. 
 
 The metal is very malleable and ductile ; that is, it can be 
 reduced to thin sheets or drawn into very fine threads. Its ten- 
 acity, though superior to that of silver, is less than that of copper ; 
 but no very accurate experiments have been made in this respect. 
 
 When pure it is about as hard as silver, and is about the color 
 of new zinc. Its elasticity is not great. It files readily, and is 
 said not to injure the file. It conducts electricity with great facil- 
 ity, so that it may be considered as one of the best conductors 
 
 107 
 
IOS MECHANICAL DENTISTRY. 
 
 known, almost equal in this respect to silver, and more than eight 
 times a better conductor than iron. 
 
 Fusing-point. — Aluminium melts at about 1160 F. (according 
 to the latest experiments), between zinc and silver. In its chem- 
 ical qualities it would seem to take an intermediate rank between 
 what are termed the noble metals and the common metals, being, 
 as Deville states, one of the most unalterable of metals. 
 
 Corrodibility. — One of the most marked qualities of aluminium 
 is its resistance to oxidation. It might be imagined that it would 
 as readily reassume its oxygen as it parted with it with difficulty 
 when in its state of oxid. This, however, is not the case ; it ap- 
 pears to be as indifferent to oxygen as either platinum or gold. 
 In air and in oxygen it undergoes no sensible alteration, and it 
 even resists it at the highest temperature which Deville could pro- 
 duce in a cupelling furnace, a temperature higher than that em- 
 ployed in assaying gold. Water has no action, according to 
 Deville, on aluminium, either at its ordinary temperature, when 
 boiling, nor even upon the metal at a low, red heat, near its melt- 
 ing-point. According to Professor Crace Calvert, this statement 
 must be received with some degree of caution, as in experiments 
 he has made he considers that oxidation does take place slowly 
 when the metal is immersed in water for any considerable length 
 of time. It is not, however, affected by sulphur or sulphureted 
 hydrogen. 
 
 Solubility. — Aluminium is not acted upon to any considerable 
 degree by any of the oxyacids in the cold ; nitric acid, whether 
 strong or weak, at its ordinary temperature, in no way affects 
 it, though when boiling it acts upon it slowly. Small grains of 
 aluminium, plunged in sulphuric acid for three months, remained 
 apparently unaltered. The vegetable acids, such as acetic, oxalic, 
 and tartaric acids, have scarcely any effect on it at all. The true 
 solvent of the metal is hydrochloric acid, which attacks it rapidly. It 
 appears to resemble tin when brought into contact with hydro- 
 chloric acid and the chlorids. Its absolute harmlessness permits 
 of its being employed in a vast number of cases where the use of 
 tin would not be desirable on account of the extreme facility with 
 which that metal is dissolved in the organic acids. 
 
 Manner of Annealing. — For the purpose of annealing alumin- 
 ium the surface of the plate may be coated with oil, and then 
 
ALUMINIUM. IO9 
 
 passed over the flame of a spirit-lamp or Bunsen burner until the 
 oil is entirely burned off and the plate becomes white, when it is 
 instantly withdrawn. Or it may be accomplished by placing the 
 piece of plate in a furnace muffle, an even heat being maintained 
 until the metal is hot enough to char the end of a pine stick, which 
 should leave a black mark behind it as it is drawn over the plate. 
 The metal on being withdrawn should be allowed to cool slowly. 
 
 Manner of Melting. — Aluminium should be melted in ordinary 
 plumbago crucibles, as it does not absorb or unite with carbon 
 when heating in contact with it. No flux is needed to cover the 
 molten metal, as it is non-volatile at any temperature that can be 
 obtained with an ordinary furnace. 
 
 Casting. — Aluminium is now being used to considerable extent 
 in castings of all descriptions where lightness, non-corrodibility, 
 and silvery color is desired. Either iron, sand, or plaster and 
 marble-dust molds can be used, the metal being poured as cold 
 as possible. 
 
 Polishing. — The truly distinctive and beautiful color of alumin- 
 ium is best brought out in highly polished plate. To polish, use 
 rouge or tripoli ; or " Almeta Polish," which was introduced by 
 the Pittsburg Reduction Co., has earned a well-merited reputation 
 as an aluminium polish. Its formula is as follows : 
 
 Stearic Acid, 1 part. 
 
 Fuller's Earth 1 " 
 
 Rotten Stone, .* 6 parts. 
 
 The whole ground very fine and well mixed. 
 
 On flat surfaces the highest finish can be given with fine emery 
 paper and oil. 
 
 Soldering. — Several methods of soldering aluminium have 
 proven more or less successful for some purposes ; one of the 
 solders is 6 parts aluminium, 4 copper, and 90 zinc, another, rec- 
 ommended by Schlosser, is 30 parts gold, 1 platinum, 20 silver, 
 100 aluminium ; none of them, however, is suitable for attaching 
 •artificial teeth to be worn in the mouth. The only way in which 
 the metal has been successfully employed as a dental base is with 
 the rubber attachment. 
 
 Alloys. — Aluminium, like iron, does not unite with mercury, 
 and scarcely at all with lead. It, however, forms a variety of 
 alloys with other metals. It can be alloyed with iron, and seems 
 
IIO MECHANICAL DENTISTRY. 
 
 to unite readily with zinc ; a variety of alloys with nickel have 
 been made, and that consisting of ioo parts of aluminium and 
 three of nickel is found to work readily, and to have gained hard- 
 ness and rigidity, as compared with the pure metal. The alloys,, 
 however, with copper are the most striking ; they are light and 
 very hard, and capable of a fine polish. In the same degree that 
 copper adds to the hardness of aluminium, so does the latter,, 
 when used in small quantities, give hardness to copper, without,, 
 however, injuring its malleability. It renders it susceptible of a 
 fine polish, and, according as the proportions are varied, the color 
 of the alloy becomes deep or pale gold. Alloys of copper with 
 five and ten per cent, of aluminium resemble gold, perhaps, more 
 than any other metallic alloy hitherto employed. They do not 
 tarnish sensibly by exposure to the air. Aluminium can be de- 
 posited by the battery, and by the same agent it can be gilt or 
 silvered. 
 
 Dental Uses. — For several years past attempts have been made 
 to render aluminium available as a base for artificial dentures, 
 both by the swaging and casting processes, with only partial suc- 
 cess. When in the form of plate no suitable solder has yet been 
 discovered by which the several parts of a dental appliance may 
 be securely united, and experiments in casting have not yet prov- 
 en entirely satisfactory. It is being used to a limited extent, with 
 rubber attachment, and it is hoped that in the near future, upon 
 further acquaintance with its capabilities, it may prove entirely 
 acceptable for dental purposes. 
 
CHAPTER X. 
 
 COPPER, ZINC, LEAD, TIN, ANTIMONY, AND BISMUTH. 
 COPPER. 
 
 Cu (Cuprum). 
 
 General Properties. — Copper is one of the metals most 
 anciently known ; it is of a brownish-red color, with a tinge of 
 yellow ; has a faint but nauseous and disagreeable taste, and im- 
 parts, when exposed to friction, a smell somewhat similar to its 
 taste. Its specific gravity ranges from 8.8 to 8.9. It is both 
 malleable and ductile, but excels in the former property, finer 
 leaves being obtained from it than wire. It is inferior to iron in 
 tenacity, but surpasses gold, silver, and platinum in this respect. 
 The fusing-point of copper is about 2000 F. 
 
 Alloys of Copper. — Copper unites readily with most metals, 
 forming alloys of great practical value in the arts, but which have 
 but a limited application in dental laboratory processes. Many 
 of these alloys are curious and instructive, as illustrating the 
 singular and unaccountable influence of alloying upon the dis- 
 tinctive properties of the component metals. Copper and tin, for 
 example — the former of which is highly ductile, and the latter 
 equally malleable — when combined in the proportion to form 
 speculum metal (9 C: 1 T), form an alloy distinguished for its ex- 
 treme brittleness, with a surface hardness almost equal to steel. 
 By increasing the quantity of tin until the compound assumes the 
 proportions constituting gun-metal (C 2: T 1), the alloy, though 
 neither malleable nor ductile, becomes eminently tough and rigid. 
 Other prominent examples might be given, showing how com- 
 pletely this combining influence defies all calculations in regard 
 to ultimate results. The following summary embraces the names 
 and composition of the more familiar alloys of copper, omitting, 
 as unnecessary in this connection, a description of their individual 
 properties. 
 
 Alloys of Copper with Zinc. — Brass is an alloy of uncertain 
 
 in 
 
112 MECHANICAL DENTISTRY. 
 
 and variable composition, consisting usually, however, of two to 
 five parts of copper and one of zinc. Brass melts at 1869 F. 
 Prince's metal, and its allied compounds, Pinchbeck, Similor, and 
 Mannheim gold, consists of nearly equal parts of copper and zinc. 
 Mosaic gold, consists of 100 parts of copper and from 52 to 55 of 
 zinc. Dutch gold, from which foil of that name was formerly ob- 
 tained, is formed of 11 parts of copper with two of zinc. Bath 
 metal is composed of 32 parts of brass and nine of zinc. 
 
 Brass solder consists of two parts of brass and one of zinc, to 
 which a little tin is occasionally added. 
 
 Alloys of Copper with Tin. — Bell metal usually consists of 
 100 parts of copper with from 60 to 63 parts of tin. Cannon 
 metal is compounded of 90 parts of copper with ten of tin. 
 Cymbals and gongs contain 100 parts of copper and 25 of tin. 
 Speculum metal consists of two parts of copper and one of tin. 
 
 Copper and arsenic form a white-colored alloy, which, in the 
 proportion of nine parts of copper and one of arsenic, is white, 
 slightly ductile, and is denser and more fusible than copper. 
 
 German silver is composed of copper, 40.4; nickel, 31.6; zinc, 
 25.4; iron, 2.6; but the proportions of the metals of this alloy 
 differ according to the various uses to which this compound is 
 applied. 
 
 Babbitt metal is a compound of copper, antimony, and tin, in 
 somewhat varying proportions. The following formula is given by 
 Henry Long Jacob in the British Journal of Dental Science: 
 
 Copper, 2 parts. 
 
 Antimony, 3 
 
 Tin, 12 " 
 
 The following method of preparing it is given by the same 
 writer: 
 
 " In preparing this metal, the copper is first melted in a cruci- 
 ble, with about an equal weight of tin (the copper thus fusing 
 much more readily than by itself), a little more of the tin is then 
 added, next the antimony, and lastly the remainder of the tin by 
 degrees, stirring well during the whole of the time ; the metal can 
 then be poured into sand molds of any convenient form. About 
 a year and a half ago I furnished Mr. Thomas Fletcher with this 
 formula, and I believe it is given in his work on ' Dental Metal- 
 
ZINC. II3 
 
 lurgy.' The melting-point of this metal is lower than that of zinc 
 and somewhat higher than that of lead, so that counter-molds of 
 this latter can be readily made to it with proper care. I am un- 
 der the impression that the original Babbitt metal was said to 
 contain a portion of lead, but this addition was found to be injuri- 
 ous." 
 
 ZINC. 
 Zn (Zincum). 
 
 General Properties. — Zinc is a bluish-white metal, possessing 
 considerable luster when broken. The commercial variety is 
 always impure, containing traces of iron, lead, cadmium, arsenic, 
 carbon, etc. It does not easily tarnish in dry air, but soon be- 
 comes dull on exposure to moisture. In the condition in which 
 it ordinarily occurs it is a brittle metal, but may be rendered 
 malleable by annealing it at certain temperatures. This change 
 in its condition is effected by subjecting it to a heat of from 220 
 to 300 F., at which temperature it may be rolled into sheets, and 
 retain its malleability when cold. The best annealing tempera- 
 ture for zinc is about 245 ° F. A knowledge of this fact will 
 enable the operator to avail himself of the advantages of this 
 property by annealing his zinc die, by which its liability to crack 
 or part under the hammer is diminished. 
 
 The fusing-point of zinc is about 775 ° F., and when heated 
 much above this point in contact with air, it burns with a bril- 
 liant, greenish-white flame, while woolly-looking flocculi rise 
 from the vessel in which it is being heated and float in the air. 
 The specific gravity of zinc varies from 6.9 to 7.2. 
 
 Use for Dental Purposes. — Zinc has been long, and almost ex- 
 clusively, employed in the formation of dies used in swaging 
 metallic plates employed in mounting artificial teeth, and experi- 
 ence has very justly accorded to it undisputed preeminence above 
 all other unalloyed metals for the purpose. A more particular 
 account of its peculiar fitness for dental purposes will be given 
 under the head of Metallic Dies and Counter-Dies. 
 
114 MECHANICAL DENTISTRY. 
 
 LEAD. 
 
 Pb (Plumbum). 
 
 Properties. — Lead has a grayish-blue color, with a bright 
 metallic luster when melted or newly cut, but it soon becomes 
 tarnished and dull-colored when exposed to the air. The specific 
 gravity of commercial lead, which is usually contaminated with 
 other metals, is 11.352. 
 
 The fusing-point of lead is 61 7 F. Exposed to a high heat, 
 it absorbs oxygen rapidly, forming on its surface a gray film of 
 protoxid and metallic lead. It is both malleable and ductile, but 
 soft and perfectly inelastic. 
 
 Its Use in the Laboratory. — Lead, either in its pure state or 
 when alloyed with certain other metals, serves important pur- 
 poses in the dental laboratory. In its simple or uncombined state 
 it is useful only in forming counter-dies. Alloyed with antimony 
 in the proportion of ^4 to ^ of the latter, with the addition some- 
 times of very small portions of copper, tin, and bismuth, it forms 
 different grades of type-metal, which is harder than lead and very 
 brittle, and is sometimes used for dies ; and sometimes, though 
 very rarely, for counter-dies. When type-metal is used as a coun- 
 ter to a zinc die, it is improved for the purpose by adding to it an 
 equal quantity of lead ; it may also be used in the form of a die in 
 connection with a lead counter after rough stamping with zinc. 
 
 Fusible Alloys. — The alloy known as Rose's fusible metal is 
 composed of two parts of bismuth to one of lead and one of tin, 
 and melts at about 200 F. A still more fusible alloy is com- 
 posed of lead three parts, tin two parts, and bismuth five parts, 
 which fuses at 197 . There are other alloys of lead, to be men- 
 tioned hereafter, melting at from 200 to 440 , which may be 
 advantageously employed in forming dies to be used after zinc, 
 where the latter, from its greater shrinkage, fails to bring the 
 plate into accurate adaptation to the mouth. 
 
 Soft solder is an alloy composed of lead and tin in the propor- 
 tion of two parts of the former to one of the latter. 
 
TIN ANTIMONY. 
 
 TIN. 
 Sn (Stannum). 
 
 115 
 
 Properties. — Tin is a brilliant, silver-white metal, the luster of 
 which is not sensibly affected by exposure to the air, but is easily 
 oxidized by heat. It has a slightly disagreeable taste, and emits, 
 when rubbed, a peculiar odor. It is soft, inelastic, and, when 
 bent, emits a peculiar cracking sound called the creaking of tin. 
 It is inferior in tenacity and ductility, but is very malleable, and 
 may be beaten into leaves awg- °f an i ncn m thickness, ordinary 
 tin foil being about y-^Vs" of an inch thick. 
 
 The fusing-point of tin is about 450 F. ; it boils at a white 
 heat, and burns with a blue flame to binoxid. 
 
 The more common alloys of tin with other metals have already 
 been noticed. It was at one time used as a base for artificial 
 teeth, and more recently it has been introduced as a component 
 of " cheoplastic " metal, a compound used for the same purpose. 
 In its pure state, it is sometimes used for counter-dies, and occa- 
 sionally for dies. When employed for the latter purpose in con- 
 nection with a lead counter, the latter should not be obtained 
 directly from the die, as the high temperature of melted lead 
 would produce, when poured upon the tin, partial fusion of the 
 latter and consequent adhesion of the two pieces. Tin is also 
 used by many operators as a trial base-plate for artificial den- 
 tures, instead of wax, gutta-percha, or other more pliable mate- 
 rials. 
 
 ANTIMONY. 
 
 Sb (Stibium). 
 
 General Properties. — Antimony is of a silver-white color, with 
 a tinge of blue, a lamellar texture, and a crystalline fracture. It 
 is brittle and easily pulverized. It enters as an ingredient into 
 the composition of type- and stereotype-metal, music plates, and 
 Britannia metal. It is also a component of certain fusible alloys 
 analogous to those already mentioned under the head of lead, 
 and which, in the form of a die, are sometimes used on account 
 of their slight degree of shrinkage. 
 
 The fusing-point of antimony is 840 F., and when heated at 
 the blowpipe it melts with great readiness, and diffuses white 
 
Il6 MECHANICAL DENTISTRY. 
 
 vapors, emitting- an odor similar to garlic. The specific gravity 
 of the purest variety is 6.715. 
 
 BISMUTH. 
 Bi (Bismuthum). 
 
 General Properties.— Bismuth is a white-colored metal, resem- 
 bling, in some degree, antimony. It is soft, but so brittle as to 
 be easily pulverized. Its specific gravity is 9.83, which may be 
 increased somewhat by hammering. 
 
 The fusing-point of bismuth is about 510 F. When the tem- 
 perature of the metal is raised from 32 to 212 it expands y^- 
 in length. 
 
 Alloyed with Other Metals. — Bismuth has the property, in a 
 high degree, of increasing the fusibility of the metals with which 
 it is incorporated, and is a common ingredient of the more fusible 
 alloys, some of which melt in boiling water. One part of bismuth 
 with 24 of tin is malleable, but the alloy of these metals becomes 
 brittle by the addition of more bismuth. Bismuth unites readily 
 with antimony, and in the proportion of one part or more of the 
 former to two of the latter, it expands in the act of cooling. 
 
 There are many other metals and alloys beside those already 
 enumerated, but which have not been particularly described on 
 account of their inutility in the laboratory for dental purposes. 
 Among these may be mentioned iron, brass, bronze, etc., which are 
 only employed for auxiliary purposes, and are both inconvenient 
 and impracticable for dies by reason of their infusible nature and 
 consequent contraction ; nickel, on account, also, of its extreme 
 infusibility and its tendency to render the alloy of which it is a 
 component less fusible ; sodium, on account of the changes pro- 
 duced on it by exposure to the air ; potassium, on account of its 
 extreme sensitiveness to the influence of low temperatures, being 
 semi-fluid at 6o° F., nearly liquid at 92°, and entirely so at 
 120 ; arsenic, because it volatilizes before fusing; cadmium, with 
 no advantages above tin, on account of its scarcity, costliness, 
 etc. 
 
CHAPTER XI. 
 
 GENERAL PROPERTIES OF ALLOYS, AND THEIR TREATMENT AND 
 BEHAVIOR IN THE PROCESS OF COMPOUNDING. 
 
 All alloys possess metallic luster, are opaque, conduct heat and 
 electricity, and, in a greater or less degree, are ductile, malleable, 
 elastic, and sonorous. Some alloys, as brass and gong metal, are 
 usually malleable in the cold and brittle when hot. 
 
 Metals sometimes unite in atomic ratios, forming compounds 
 of definite or equivalent proportions of the component metals, as 
 certain alloys of copper and zinc, gold and copper, gold and silver, 
 mercurial alloys, etc., while, on the other hand, many are formed 
 in all proportions, like mixtures of salt and water. 
 
 Metals differ in respect to their affinity for each other, and do 
 not, therefore, alloy with equal facility ; thus it is difficult to unite 
 silver and iron, but the former combines readily with gold, cop- 
 per, or lead. 
 
 The ductility of an alloy is, in general, less than that of its 
 constituent metals, and this difference is, in some instances, re- 
 markably prominent, as in the case of certain alloys of copper 
 and tin, already mentioned. 
 
 An alloy is generally harder than the mean hardness of its 
 components, a property which, when taken in connection with 
 their increased fusibility, gives to alloys peculiar value in the for- 
 mation of dies for stamping purposes. To the rule stated, amal- 
 gams, or mercurial alloys, are cited as exceptions. 
 
 The density of an alloy varies with the peculiar metals com- 
 posing it, being generally either greater or less than the mean 
 density of its several components. 
 
 It is impossible to predict with certainty the melting-point of 
 an alloy from that of its separate constituents, but, generally, the 
 fusibility of the alloy is increased, sometimes in a most remark- 
 able degree. The alloy of five parts of bismuth, three of lead, 
 and two of tin is a striking example of this fact, this compound 
 melting at 197 , while the mean melting-point of its constituents 
 
 117 
 
Il8 MECHANICAL DENTISTRY. 
 
 is 514 . Silver solder is also a familiar illustration of the influ- 
 ence of alloying on the fusibility of metals ; copper, melting at 
 1996 , and silver at 1873 , when combined fuse at a heat much 
 below that required to melt silver, the more fusible component of 
 the alloy. Again, iron, which melts at a little less than 3000 , 
 acquires almost the fusibility of gold when alloyed with the lat- 
 ter. Examples might be multiplied, but it will be sufficient to 
 add that, in general, metallic alloys melt at a lower heat than is 
 required to fuse the most refractory or infusible component, and 
 sometimes lower than the most fusible ingredient. 
 
 The color of an alloy cannot, in general, be inferred from that 
 of its component metals ; thus it would be conjectured that copper 
 would be rendered very much paler by adding to it zinc in con- 
 siderable quantities, but the fallacy of such an inference is at once 
 shown by an examination of some of the rich-looking gold-colored 
 varieties of brass, as Prince's metal, pinchbeck, and similor, com- 
 posed each of nearly equal parts of copper and zinc ; and Mann- 
 heim gold, compounded of three parts copper and one of zinc. 
 
 The affinity of an alloy for oxygen is greater than that of the 
 separate metals, a phenomenon that is ascribed by Ure to the 
 increase of affinity for oxygen which results from the tendency of 
 one of the oxids to combine with the other ; by others it is attrib- 
 uted to galvanic action. According to Faraday, 100 parts of steel 
 alloyed with one of platinum is dissolved with effervescence in 
 dilute sulphuric acid too weak to act with perceptible energy on 
 common steel. It is offered in explanation of this fact that the 
 steel js rendered positive by the presence of platinum. A similar 
 illustration is afforded by the action of dilute acid on commercial 
 zinc, which is usually an alloy of zinc with other metals. 
 
 The action of air is, in general, less on alloys than on the sepa- 
 rate metals composing them. To this, however, there are excep- 
 tions, as the alloy of three parts of lead and one of tin, which, 
 when heated to redness, burns briskly into a red oxid. 
 
 Some points of practical interest suggest themselves in connec- 
 tion with the behavior and proper management of alloys in the 
 process of compounding. 
 
 As metallic alloys can only be formed by fusion, and as the 
 affinity of the metals composing them for oxygen is greatly in- 
 creased by heat, especially those denominated base, it is important 
 
PROPERTIES AND TREATMENT OF ALLOYS. 
 
 II 9 
 
 that this tendency, which is incompatible with the proportional 
 accurateness of the compound, should be, as far as practicable, 
 guarded against. Hence, various substances having a greater 
 affinity for oxygen than the metals to be united, as oil or grease, 
 rosin, powdered charcoal, etc., are generally added, coating the 
 surface of the liquid metals, and which, by affording a protective 
 covering, preserve, with little change, the proportions of the alloy. 
 
 The Difficulty of Securing a Homogeneous Alloy, Owing to the 
 Difference in the Specific Gravities of the Metals Composing It. — 
 Some difficulty is occasionally experienced in obtaining a per- 
 fectly uniform alloy, on account of the different specific gravities 
 of the metals composing it — each metal assuming the level due 
 to its density. This partial separation is common to gold and sil- 
 ver, provided they have not been adequately stirred before pour- 
 ing. This result is not so likely to occur when the metals em- 
 ployed are in small quantities, and are suddenly cooled, but when 
 used in considerable masses and allowed to cool slowly, it is 
 much favored by permitting the metals to fix themselves in the 
 order of their separate densities. Hence, whenever a notable dif- 
 ference in the specific gravity of the metals exists, the fused mass 
 should be briskly stirred immediately before the instant of pour- 
 ing it, and should be made to solidify quickly. If uniformity be 
 not obtained in this manner, it will be necessary to remelt, and 
 repeat the process until the alloy is rendered sufficiently homo- 
 geneous. 
 
 The Metals that Should be Melted First. — In alloying three or 
 more metals differing greatly in fusibility, or that have but little 
 affinity for each other, it is better to first unite those which most 
 readily combine, and afterward, these with the remaining metal 
 or metals. If, for example, it is desired to unite a small quantity 
 of lead with brass or bronze, some difficulty would be experienced 
 in forming the alloy by direct incorporation of the metals, but 
 union could be readily effected by first melting the lead with zinc 
 or tin, and then adding the melted copper. 
 
CHAPTER XII. 
 
 TREATMENT OF THE MOUTH PREPARATORY TO THE INSERTION OF 
 ARTIFICIAL DENTURES. 
 
 It rarely occurs that all the structures of the mouth are in such 
 condition as will render it proper to insert an artificial appliance 
 without some preparatory treatment. This important require- 
 ment cannot, in any material respect, be disregarded by the prac- 
 titioner without endangering the utility and permanence of the 
 substitute, and inflicting upon the patient a train of consequences 
 alike distressing and pernicious. Every experienced dentist is 
 familiar with the fact that an artificial substitute, resting upon 
 diseased roots of teeth and impinging continually upon gums al- 
 ready irritated and inflamed, soon becomes a source not only of 
 annoyance and discomfort to the patient, but is rendered, in a 
 great degree, inefficient in the performance of some of its more 
 important offices. There is, besides, a perpetual and cumulative 
 aggravation of the morbid conditions, and sooner or later irre- 
 trievable destruction of the remaining natural organs will be in- 
 duced. These consequences cannot be wholly averted by the 
 most skilful manipulation, but they may be greatly magnified by 
 a defective execution of the work, or by a faulty adaptation of the 
 appliance to the parts in the mouth. 
 
 Patients not infrequently attempt, by every artifice or pretext 
 that caprice or timidity may suggest, to persuade the operator to 
 violate his own clear convictions of duty, but, unless under cir- 
 cumstances of peculiar exigency, he should be careful- to guard 
 himself against the imputation of incompetency or bad faith by 
 being peremptory and unyielding in his demands upon the patient 
 to submit to the necessities and just requirements of the case, 
 and no ordinary circumstance should influence him in opposition 
 to his better informed judgment. 
 
 The conditions usually met with, to which it will be necessary 
 to direct attention in the treatment of the mouth, arc: (i) The 
 presence of useless and diseased remains of teeth. (2) Accumula- 
 
 120 
 
PREPARATORY TREATMENT OF THE MOUTH. 121 
 
 tions of tartar. (3) Diseased states of the gums and mucous 
 membrane. (4) Caries. 
 
 Useless and Diseased Remains of Teeth. — It may be stated, 
 as an absolute rule of practice, that all teeth, or remains of teeth, 
 affected by incurable forms of disease, should be removed before 
 inserting either partial or entire dentures. This recommendation 
 must, however, be construed in the light of the curative resources 
 of dental surgery and therapeutics. Many diseased conditions 
 associated with the teeth that have heretofore been generally re- 
 garded as incurable, have, in the use of more radical and efficient 
 remedial measures, proven amenable to such treatment as assures 
 their retention for many years in a condition fitting them for im- 
 portant uses. A new impulse has of late been given to such con- 
 servative treatment of these organs with the view, chiefly, of 
 utilizing them more generally for purposes of support in setting 
 artificial crowns, and in the method of replacement known as 
 " bridge-work." 
 
 The marked success which of late years has attended the treat- 
 ment of diseased roots, and the increasing importance attached to 
 them for the purposes mentioned, as well also as the essential 
 office they perform in preserving the structural integrity of the 
 associated alveoli, and in maintaining the normal circulation and 
 nutrition of the parts, would seem to justify the conclusion that 
 their extraction is plainly contraindicated, save in rare and excep- 
 tional cases of intractable disease, in which case there is no ques- 
 tion concerning the propriety or necessity of their removal. 
 Their presence in connection with the substitute must, sooner or 
 later, become not only a source of annoyance and distress to the 
 patient, but will, in all probability, lead ultimately to conse- 
 quences of a still graver nature. Inflammation and suppuration 
 will be likely to be induced, or, if already present, will be aggra- 
 vated by the mobility and unaccustomed pressure of the substi- 
 tute in the process of mastication, thus contaminating and vitiat- 
 ing the oral secretions, which act, by reason thereof, with increas- 
 ing energy upon oxidizable materials present in the mouth, as 
 well as upon the remaining natural teeth, while the contiguous 
 parts, through their immediate connection or sympathetic rela- 
 tions with the structures of the mouth, respond to the local dis- 
 turbances, and the case, in time, becomes complicated with those 
 
122 MECHANICAL DENTISTRY. 
 
 various distressing maladies about the head and face so commonly 
 associated with diseased conditions of the oral cavity. At last, 
 the patient, no longer able to endure the offensiveness and dis- 
 tress arising from the presence of the substitute in the mouth, or 
 to properly masticate his food, is compelled to have the offending 
 organs removed. The absorption of the gums and processes 
 which follows this operation, and the corresponding changes 
 which occur therefrom in the form of the alveolar ridge, make it 
 imperative either to reconstruct the piece or to supply the patient 
 with an entirely new substitute ; whereas, if due regard had been 
 given to the proper preparation of the mouth in the first instance, 
 the patient might be spared such inflictions, and the operator the 
 discredit which almost invariably attaches to the neglect of the 
 measures recommended. 
 
 Removal of Salivary Calculus or Tartar. — The deposits of tar- 
 tar which so frequently collect at the necks of the teeth and under 
 the free margins of the gum are a prolific source of evil, inducing 
 ultimate destruction of the investing membranes and contiguous 
 alveoli, and as this deposit is continuous and progressive, follow- 
 ing closely the wasting or destruction of the implicated tissue, 
 teeth originally firm become in time not only unfitted for the 
 proper performance of the functions required of them, but a 
 source of diseased action in surrounding structures. Hence it 
 becomes absolutely necessary, as it relates to the general health 
 of the mouth, to thoroughly remove, with suitable instruments, 
 all traces of this concretion from the teeth. In some complica- 
 tions characterized by suppurating processes and necrosed alve- 
 oli, as in so-called " Rigg's disease," or pyorrhea alveolaris, the 
 treatment must be more thorough and radical. 
 
 Diseased Conditions of the Mucous Membrane and Gums. — 
 It will seldom be necessary to institute treatment for the reduc- 
 tion of inflammation and suppuration of the soft tissues of the 
 mouth after removal of diseased roots and tartar, inasmuch as 
 these conditions, being generally provoked by and associated with 
 the latter, will spontaneously subside with the removal of the 
 exciting causes. If, however, this does not occur within a rea- 
 sonable time, relief may generally be obtained with the use, as a 
 mouth-wash, of any of the remedies ordinarily employed, as 
 dilute tincture of arnica, myrrh, or calendula, phenol sodique, etc. 
 
PREPARATORY TREATMENT OF THE MOUTH. 1 23 
 
 As a means of allaying soreness or tenderness of the gums after 
 extraction, the writer has had gratifying success in the use of 
 Electrozone, or Pond's extract of hamamelis. If there are mor- 
 bid conditions of the soft tissues or osseous structures of the 
 mouth, not immediately arising from the presence of diseased 
 roots and tartar, they should be treated in accordance with the 
 particular pathological conditions present. 
 
 Caries or Decay of the Remaining Teeth. — In order that all the 
 teeth which it is deemed advisable to retain in the mouth may 
 be permanently preserved, it will be necessary to fill, or other- 
 wise treat, such as may be affected by caries. This operation 
 will be attended with more satisfactory results, and be accom- 
 panied with less pain to the patient and diminished risk of failure, 
 when performed after the removal of the roots of teeth and tartar, 
 and the restoration of diseased conditions of the mouth to health, 
 as, in this case, there will be less irritability of the general system 
 and reduced sensitiveness of the teeth operated on. 
 
 Surgical Treatment of the Mouth After the Extraction of 
 Teeth. — In the operation of extracting preparatory to the inser- 
 tion of artificial dentures, especially in cases accompanied by 
 unavoidable fracture of the processes, it sometimes happens that 
 loose and pendulous portions of gum remain, giving temporary 
 annoyance to the patient. Any considerable excess of such tissue 
 may be, in part at least, clipped off, while sharp and protruding 
 portions of processes at other points should be removed, for, if 
 allowed to remain, the gum closing over them will, in a short 
 time, become irritated and inflamed, and exceedingly painful to 
 the slightest pressure. If, in the course of a few weeks, promi- 
 nences still remain, over which the mucous membrane is stretched 
 and irritated or inflamed, as is more frequently the case around 
 the sockets of the cuspid teeth, the membrane should be divided 
 over such points with a lancet, and the sharp points of bone un- 
 derneath broken down with suitable cutting instruments. This 
 condition, however, can usually be obviated, in a measure, by 
 firmly pressing the process together immediately after extraction. 
 
 Time Necessary to Elapse After the Extraction of Teeth 
 Before Inserting Artificial Dentures. — The time that should 
 elapse after extracting the natural teeth, before replacing them 
 with artificial substitutes, will depend upon various circum- 
 
124 MECHANICAL DENTISTRY. 
 
 stances. If the appliance is only intended to meet the wants of 
 the individual until all the changes effected by absorption of the 
 gums and processes are fully completed, it may be inserted in 
 from one to three weeks, depending somewhat upon the number 
 of teeth extracted, the extent of the injuries unavoidably inflicted 
 upon the parts, and the virulence of the diseased action present 
 in the structures of the mouh at the time of the operation. If 
 there are no unusual complications, and the space or spaces to be 
 supplied are such as are made by the loss of only one or two teeth 
 at intervals, the parts quickly assume their normal condition, and 
 the piece to be temporarily worn may be applied within a few 
 days. If, however, a greater number, or all of the teeth have 
 been removed, more or less inflammation and tenderness will be 
 present for from ten days to two or three weeks, rendering the 
 wearing of an artificial piece uncomfortable to the patient, and in 
 some degree mischievous, by aggravating the morbid conditions 
 already existing. Another objection to the too early introduc- 
 tion of artificial substitutes into the mouth arises from the fact 
 that the changes which occur in the ridge are much more rapid 
 within the first few weeks after the extraction of the teeth than at 
 any subsequent period, so that the plate, if inserted immediately 
 or within a few days after such an operation, will soon lose its 
 bearing upon the ridge and become inefficient for masticating 
 purposes, or may even fail to be retained in the mouth without 
 much annoyance to the patient. From two to eight or more 
 weeks should, therefore, elapse before inserting the substitute. 
 In the meantime, the patient should be seen frequently, and such 
 medical or surgical treatment adopted from time to time as the 
 case may demand. 
 
 The time occupied in the completion of those changes which 
 occur in the alveolar border after the extraction of all or any con- 
 siderable number of the teeth cannot be definitely stated, but will 
 range from five to twelve months or more, according to the 
 amount of superfluous structures to be removed, the density of 
 the osseous tissues, and the functional activity of the absorbents. 
 In all cases, ample time should be permitted to elapse in order 
 that no appreciable change in the form of the parts may take place 
 after the appliance has been permanently adjusted. It should be 
 remembered, however, that there is no period of time when the 
 
PREPARATORY TREATMENT OF THE MOUTH. 125 
 
 changes in the maxillary bones which follow the extraction of the 
 natural teeth may be said to be absolutely completed. It is well 
 known that, in exceptional cases, renewed absorption may occur 
 long after the time when it is supposed to be completed, extend- 
 ing in some cases quite beyond the ordinary limits. This is 
 ascribed by many to misfitting plates, or to some particular qual- 
 ity of the material used as a base, notably vulcanized rubber. 
 While there may be some plausibility in this view, it can hardly 
 be accepted as final or conclusive. That the unusual destruction 
 or wasting away of involved tissue is induced by some abnormal 
 action of the absorbent or nutritive processes is without ques- 
 tion, but whether this is induced by local or systemic causes re- 
 mains in doubt. 
 
CHAPTER XIII. 
 
 MATERIALS, APPLIANCES, AND METHODS EMPLOYED IN OBTAIN- 
 ING IMPRESSIONS OF THE MOUTH. 
 
 In the process of constructing a dental substitute, it is of the 
 first importance that as accurate an impression as possible should 
 be obtained of all those parts of the mouth with which the appli- 
 ance is in any way connected. If this important preliminary step is- 
 in any essential respect imperfectly performed, the ultimate utility of 
 the artificial -fixture will either be greatly impaired or wholly de- 
 stroyed, notwithstanding all the subsequent manipulations may 
 be most carefully and skilfully performed. The operator, there- 
 fore, should not only avail himself of every appliance and facility 
 that will enable him to attain the most perfect results, but should 
 have an exact and intelligent acquaintance with the nature, prop- 
 erties, and adaptability of the impression materials used. 
 
 The substances usually employed for this purpose are : bees- 
 wax, modeling composition, and plaster-of-Paris. 
 
 Some diversity of opinion exists as to the relative value of these 
 several impression materials, and the choice of any one of the 
 class is generally determined by individual notions of the indica- 
 tions to be fulfilled in any given case, and the supposed special 
 adaptability of the material to the fulfilment of such indications. 
 
 In the case of entire dentures, where there is a near approach to 
 uniformity of hardness or softness, and consequent uniformity of 
 resistance, in the tissues of the mouth, plaster, of the proper con- 
 sistency, unquestionably takes precedence of all other materials 
 for the purpose, and the almost universal preference given to it in 
 such cases is a virtual confession of its superior fitness. Its capa- 
 bility, beyond that of all the other substances mentioned, of secur- 
 ing the most perfect impression of the several parts in their undis- 
 turbed relation to each other is unquestioned, and it may be 
 affirmed with positiveness that, except, possibly, in the case of 
 plastic bases, where there is no compensation for the slight ex- 
 pansion of the plaster, if all the surfaces on which the substitute 
 
 126 
 
IMPRESSIONS OF THE MOUTH. 
 
 127 
 
 rests were equally pliant or equally resistant to forces applied to 
 them, no other material would be required. But, strictly speak- 
 ing, this condition of uniformity never prevails, and in many cases 
 there is a marked departure from it. The most common and 
 troublesome complication of this kind occurs where there is a 
 more or less pliable or yielding condition of the alveolar ridge 
 associated with a comparatively hard and resistant surface along 
 the median line of the floor of the palate, being more pronounced 
 near the soft palate. In such cases, this inequality of softness 
 and hardness, if considerable, prevents a properly balanced con- 
 tact and pressure of a substitute constructed from an impression 
 of the parts in a state of repose. Thus, for example, in the case 
 of a perfectly fitting denture secured in the manner just stated, if 
 the ridge along the mesial line of the palatal vault is more than 
 usually hard and prominent, and the lateral portion of the arch 
 and alveolar ridge relatively soft and yielding, the substitute, 
 meeting with a fixed point of resistance at the floor of the palate, 
 will prevent the lateral walls and ridge from being sufficiently 
 compressed on the application of retaining forces, whether atmos- 
 pheric, adhesive, or capillary, or all combined. Hence, when 
 forcible pressure is made on one side over the ridge, as in masti- 
 cation, the substitute, impinging or riding upon the central resis- 
 tant surface of the arch, as upon a pivotal point, will be detached 
 and thrown off from the opposite side. If the same yielding con- 
 dition of the anterior portion of the ridge prevails, the appliance, 
 when forces are applied to the front teeth, will be dislodged pos- 
 teriorly. 
 
 The proposed remedy for the instability of the substitute, re- 
 sulting from the conditions mentioned, consists in so constructing 
 the dental appliance that, when applied to the mouth and sub- 
 jected to the action of the retaining forces, a degree of resistance 
 in those parts where the soft tissues are in excess will, through 
 compression of the tissues, be secured, equal, or nearly so, to that 
 presented by the central portion of the arch ; in other words, by 
 establishing an equilibrium of pressure or resistance in all the 
 parts on which the plate rests. 
 
 It is believed by some teachers, that certain forms of impres- 
 sion material, through the pressure they exert, are capable of con- 
 tributing materially to this result. This is predicated on the 
 
128 MECHANICAL DENTISTRY. 
 
 assumption that the pressure they exert is sufficient to compress 
 or displace the tissues in question. The writer, however, thinks 
 it well to inquire if the compressing power of these substances, in 
 the cases under consideration, has not been overrated. If by the 
 term compression, as used in this connection, is meant condensa- 
 tion or diminished bulk of tissue, certainly no such result could 
 be obtained by any force capable of being applied within the 
 mouth, however hard and resistant the material used. Any 
 change in the normal configuration of the arch and ridges possi- 
 ble in the use of such substances must, therefore, result, not in 
 condensation, but in displacement of tissue. It can be readily under- 
 stood how this displacement may occur along the summit line of 
 the ridge in cases characterized by considerable excess of gum 
 material lying in loose and gristly folds, chiefly in front of the 
 bicuspids, and associated generally with the long use of partial 
 dentures. In applying pressure in such cases, the effect would be 
 to force these mobile structures out of their customary relations 
 to the ridge and arch. How far such a procedure is in accordance 
 with the principles of correct practice must be submitted to indi- 
 vidual judgment. That any change in the mere relative position 
 of such loose structures to the ridge would contribute in any 
 appreciable manner to the stability of the substitute is not very 
 apparent. 
 
 Within the limits of the maxillary arch or palatal vault, the 
 fossae or depressions lying on either side of the central line are 
 filled more or less completely with a mass of comparatively soft 
 but elastic areolar, cellular, or connective tissue, which, in its un- 
 changed condition, is thought practically to interfere, in many 
 cases, with a properly balanced contact or bearing of the substi- 
 tute. A partial remedy, at least, it is claimed by many, may be 
 found in the use of some impression material of sufficient firm- 
 ness to compress or displace such tissues sufficiently to afford 
 points of resistance to the substitute equal, or nearly so, to that 
 offered by the median line of the arch. The displacement here, 
 if any, would be in the direction of the least resistance, or toward 
 the velum or soft palate, all portions of the arch anterior to the 
 latter, except in the case of an air-chamber, offering effectual re- 
 sistance to displacement in any other direction. When the nature 
 and relations of these associated soft structures of the mouth are 
 
IMPRESSIONS OF THE MOUTH. 120, 
 
 considered, it is highly improbable, and we think impossible, that 
 any appreciable change of contour within the arch could take 
 place on the application of any force applied in the use of either 
 wax or modeling composition. If these conclusions should be 
 justified by experimental tests, as we believe they would be, it 
 would be practically unimportant, except where the tissues of the 
 ridge are characterized by unusual mobility, what material was 
 used, provided a perfect impression could be obtained with it. 
 The paramount merits of plaster, as a substance capable beyond 
 question of fulfilling perfectly this requirement, would therefore 
 recommend it, in preference to any other material ; and we might 
 add, too, that the more difficulties there are presented in securing an 
 accurate impression, the more reason there is for using plaster-of- 
 Paris as the impression material. 
 
 One possible result of the use of any of the impression mate- 
 rials named, exclusive of plaster, both in full and partial cases, 
 must always render their employment of doubtful expediency 
 whenever plaster can be successfully manipulated for the same 
 purpose, namely, their great liability to distortion on the applica- 
 tion of forces necessary to detach them from the mouth, and the 
 impossibility of detecting any change of form until the error, too 
 late for correction, is revealed in a faulty adaptation of the finished 
 piece to the mouth. It must not, however, be understood from 
 this that it is impossible to secure a practically accurate impres- 
 sion of the parts in the use of these materials. The purpose is, 
 rather, to impress the importance and absolute necessity of extra- 
 ordinary care in their manipulation in order to secure satisfactory 
 results. The relative liability of the several substances named to 
 such disturbance of form, and the precautions necessary to avoid 
 such an unfortunate and generally fatal accident, will be more 
 particularly noticed when we come to treat of them individually 
 as impression materials. This will be done in the order before 
 named. 
 
 Beeswax. — There are two varieties of this substance in common 
 use, the yellow and white wax. The more desirable properties of 
 the yellow wax are often impaired by the admixture with it of 
 tallow, with which it is, for mercenary purposes, frequently con- 
 taminated. The presence of tallow may be detected by its charac- 
 teristic odor, and by the whitish or pale yellow color it imparts to 
 the wax, which in its pure state is of a deep, bright straw color. 
 9 
 
13° 
 
 MECHANICAL DENTISTRY. 
 
 Wax used for impressions should always be kept in convenient 
 form for immediate use, and may be prepared either by warming 
 it until sufficiently soft and then rolling or pressing it into thin 
 sheets ; or, having melted it in a properly formed vessel, immerse 
 in it a strip of thin board, previously moistened, and withdraw 
 quickly ; this is repeated as the successive layers cool, until a coat- 
 ing of sufficient thickness is obtained. The latter is a convenient 
 method of obtaining sheets of wax of a uniform thickness, a form 
 frequently required for various purposes in the dental laboratory. 
 
 The following directions in the use of wax will apply also to its 
 combinations with paraffin and gutta-percha, and also to model- 
 ing compositions. 
 
 Manner of Obtaining an Impression of the Mouth in Wax for 
 Partial Upper Dentures. — Until within the past few years, wax 
 has been used almost exclusively for the purpose of obtaining an 
 impression of the mouth in those cases where any number of the 
 natural teeth remain in either or both jaws; for this purpose it 
 is ordinarily more convenient and manageable than plaster, and, 
 if carefully manipulated, will secure in many cases a sufficiently 
 accurate impression of the parts. 
 
 Before preparing the wax, a suitable impression-cup or tray 
 should be selected, conforming as nearly as possible in size and 
 shape to the general form of the arch and ridge. The proper size 
 should- always be determined by trial of the empty cup in the 
 mouth before taking the impression. 
 
 Impression-cups are made from a variety of substances, as 
 sheet-tin, porcelain, vulcanized rubber, and Britannia metal, and 
 sometimes, in order to meet the requirements of special or excep- 
 tional cases, either brass, copper, block-tin, or gutta-percha may 
 be used. 
 
 Cups constructed of sheet-tin, which any tinner can readily 
 make to order, were formerly very generally used for partial cases, 
 and if proper care is taken not to inflict injury to the lips and soft 
 parts with the thin, sharp edges, when introducing and pressing 
 the cup to its place in the mouth, they may be used with satisfac- 
 tion. 
 
 Porcelain cups are adapted to the use of the several impression 
 materials named, except plaster, the latter being quite liable to 
 part from their glazed surfaces on the application of the necessary 
 force to detach the impression, leaving the plaster in the mouth. 
 Aside from their purity and attractive appearance, they possess 
 
IMPRESSIONS OF THE MOUTH. 
 
 131 
 
 no advantages that would make them preferable to Britannia 
 cups, while they are objectionable because of their liability to in- 
 jury, and entire incapability of being changed in form to meet 
 special requirements. When used in connection with wax, they 
 should be slightly heated before the former is introduced. 
 
 Hard-rubber trays, of any desired form, may be readily made 
 from plaster models by any one accustomed to rubber work, and 
 are chiefly adapted to the use of plaster, as they are not readily 
 cleansed if other than plastic substances are employed. Their 
 form may be materially changed by immersing them for a few 
 moments in boiling water. 
 
 Britannia metal, however, meets most fully all the requirements 
 of an impression-cup, and is well adapted to the use of any of the 
 impression materials commonly employed. The great variety in 
 form and size found at dental depots, will amply meet all the re- 
 
 Fig. 47. 
 
 quirements of ordinary cases. For unusual or abnormal condi- 
 tions requiring exceptional forms of trays, the operator can con- 
 struct for himself, from these, such appliances as will best serve 
 his purpose in the individual case. 
 
 The Form of Cup to Use. — Whatever cup is selected in secur- 
 ing an impression in wax for a partial upper case, it should be 
 large enough to embrace the alveolar ridge, leaving a space of 
 nearly *4 of an inch between the rim and the external wall of the 
 alveolar ridge. In partial upper cases requiring an impression, 
 it may be, of only a limited portion of the arch, as where clasps 
 are used, or of the entire hard palate, the form of cup illustrated 
 in Fig. 47 should be employed. 
 
132 
 
 MECHANICAL DENTISTRY. 
 
 A cup designed for similar cases by Dr. Wardle, exhibited in 
 Fig. 48, is particularly adapted to high arches, being provided 
 with a movable palate plate, by which the central portion of the 
 impression material is effectually forced into the highest portions 
 of the palatal arch, and laterally against the sides and necks of 
 the remaining teeth. The same result can be accomplished, how- 
 ever, by using the ordinary impression-cup, and building up the 
 rear and center of the palatine portion with softened beeswax, 
 before introducing the plaster. 
 
 Having selected a cup of the proper form and size, the wax 
 should be warmed over a spirit-flame until it acquires about the 
 consistency of freshly-made putty. Wax is sometimes softened 
 by immersing it in hot water, but the dry heat is preferable, as the 
 former seems to impair, to some extent, its toughness and con- 
 tinuity. 
 
 Fig. 48. 
 
 The Position of the Operator. — In taking the impression the 
 operator should place himself behind and to the right of the pa- 
 tient, and should be sufficiently raised above the latter to enable 
 him to manipulate with the greatest ease and certainty, and at 
 the same time to command as full and unobstructed a view of the 
 interior of the mouth as possible. 
 
 Manner of Introducing the Cup, etc. — The cup, with the wax 
 arranged should then be introduced into the mouth without un- 
 necessary delay. To do this properly, and without subjecting 
 the patient to annoyance, will occasionally require some care and 
 expertness, on account of the disproportionate size of the cup and 
 orifice of the mouth. An ample and expanded jaw, for example, 
 is frequently associated with a small mouth, and if in addition to 
 this the sphincter muscle of the mouth happens to be rigid and 
 
IMPRESSIONS OF THE MOUTH. 1 33 
 
 unyielding, the introduction of a cup of sufficient size may be 
 attended with some difficulty and embarrassment. This impedi- 
 ment, however, may be readily overcome in most cases by pre- 
 senting the cup obliquely to the mouth, one side resting against, 
 and pressing outward, the corner of the mouth, while — as the 
 opposite corner is extended with the first and second fingers of 
 the left hand — the cup is passed in with a rotary movement. 
 
 When the cup is within the mouth it should be carefully ad- 
 justed over the ridge before pressing it up, so that no portion of 
 the rim may cut into the soft tissues of the mouth, an accident lia- 
 ble to happen without care, and which will make it necessary, in 
 most cases, to withdraw the cup before the impression is com- 
 plete. The proper position of the cup in the mouth secured, it 
 should be held firmly with the thumb resting on the handle above, 
 and two or more of the fingers on the under surface, when it is 
 slowly but steadily and forcibly pressed against the parts above 
 until the ridge is completely imbedded, and the wax carried 
 closely against the roof of the mouth. The cup should then be 
 held stationary with two fingers from each hand; applying equal 
 pressure upon both sides, while with the thumbs the wax around 
 the margins of the cup should be pressed closely into all the 
 depressions occurring on the outside of the ridge between the 
 remaining teeth, or wherever irregularities may present them- 
 selves on the external border of the jaw. 
 
 After the wax has remained in the mouth long enough to be- 
 come in some degree hardened, it should be carefully detached by 
 gentle traction upon the cup, and removed from the mouth in the 
 same manner in which it was introduced, care being taken not to 
 displace the wax or otherwise mar the impression. The force 
 with which the wax impression will adhere to the mucous surfaces 
 on the complete exclusion of air is oftentimes very considerable, 
 and will require a corresponding tractive force to dislodge it. In 
 applying this force, it should be borne in mind that, in the very 
 plastic condition in which the wax is applied to the mouth, it is 
 not only very soft and yielding, but, being wholly inelastic, is incapa- 
 ble of recovering its form when temporarily disturbed, and that, con- 
 sequently, any distortion of the impression occurring from the 
 force applied in removing it from the mouth will be permanent 
 and possibly fatal. It should, therefore, as has already been 
 
134 MECHANICAL DENTISTRY. 
 
 stated, be allowed to remain in the mouth long enough to become 
 somewhat hardened, say from three to five minutes, and this proc- 
 ess may be facilitated by holding against the cup a napkin satur- 
 ated with cold water. The proper degree of hardness will, how- 
 ever, depend upon the circumstances of the case. If the remain- 
 ing teeth present to each other parallel walls, or nearly so, per- 
 mitting an easy escape of the wax from the interdental spaces, the 
 greatest practicable degree of hardness that can be obtained is de- 
 sirable. If, on the other hand, these spaces are V-shaped or dove- 
 tailed, as is very generally the case where the teeth to be replaced 
 have been long absent, the impression should be removed while 
 the wax is somewhat plastic, permitting a ready separation by 
 such displacement of wax immediately around the adjoining teeth 
 as must always occur in these cases in the use of wax. In propor- 
 tion as the wax is rendered hard and unyielding will be the resis- 
 tance to its escape from these spaces, and the danger of change 
 of form in parts of the impression more or less remote from them 
 augmented. It is, therefore, unadvisable in such cases to produce 
 hardness artificially by the application of ice or cold water. Un- 
 der similar conditions, the same precautions should be taken 
 against overhardening in the use of modeling composition. 
 
 Imperfections occurring from 'displacement or dragging of wax 
 on removal from the mouth, if inconsiderable, may be remedied 
 with tolerable accuracy by subsequent carving of the plaster 
 model, and this may be aided by a comparison of the plaster rep- 
 resentation of the teeth with those in the mouth. If, however, 
 the interdental undercuts, and those associated with bell-crowned 
 teeth at other points, are more pronounced, it is better to use 
 either the modeling composition or plaster. 
 
 Inasmuch as it is necessary, in constructing partial sets of teeth 
 where swaged base-plates are used, to be provided with two or 
 more plaster models, and as the latter cannot well be obtained in 
 perfect condition from a single impression, it is better that at least 
 two of the latter should be secured in the first instance. 
 
 Manner of Obtaining an Impression of the Lower Jaw in Wax, 
 for Partial Dentures. — If the case is one where teeth at intervals 
 are to be supplied, the form of cup illustrated in Fig. 49 may be 
 employed. If, however, as is more generally the case, the front 
 teeth remain, and those posterior .to the cuspids or bicuspids are 
 
IMPRESSIONS OF THE MOUTH. 
 
 135 
 
 to be replaced, the form of cup exhibited in Fig. 50 should be 
 used, a portion being cut out from the front part of it, forming a 
 vacuity which receives and permits an unobstructive passage of 
 the front teeth. As the latter are often very long, it is difficult, 
 with the ordinary form of cup, to press the wax down fairly upon 
 the ridge behind without bringing their cutting edges prema- 
 turely in contact with the floor of the cup in front. Instead of 
 the opening represented in the cup, however, it will be sufficient 
 in most cases to have it formed with a depression in front of ade- 
 quate depth to receive the points of the anterior teeth. 
 
 Position of Operator. — In taking an impression of the lower 
 jaw, after having prepared and arranged the wax by softening and 
 filling the groove of the cup flush with the margins, the operator 
 may first take a position to the right and back of the patient and 
 introduce the cup into the mouth in the manner heretofore de- 
 
 Fig. 49. 
 
 Fig. 50. 
 
 scribed, when he may pass a little to the front of the patient, and, 
 having adjusted the cup properly over the ridge, he should then 
 take his place again, at the side or back of the patient, placing his 
 fingers of each hand under each side of the patient's jaw, and the 
 thumbs upon the top of the cup ; then make steady pressure until 
 the ridge is wholly imbedded. Before final adjustment of the 
 wax to the ridge, however, care should be taken not to enclose any 
 loose folds of membrane along the line of junction between the 
 ridge and cheeks, or of loose tissue lying on the inside near the 
 base of the tongue. To avoid the former, immediately before 
 final pressure is made, the cheek should be distended and drawn 
 outward with the finger, first on one side and then on the other, 
 
136 
 
 MECHANICAL DENTISTRY, 
 
 holding the cup, in the meanwhile, steadily in place. The loose 
 and movable tissues on the inside will be drawn away from the 
 ridge somewhat if the patient is directed to raise the tongue well 
 toward the roof of the mouth. Some little additional pressure 
 may then be made upon the cup, after which the wax should be 
 pressed in around the margins of the cup, both externally and 
 within, when the impression is carefully removed from the mouth, 
 observing the precautions stated when treating of wax and other 
 allied substances. 
 
 Manner of Obtaining an Impression of the Mouth in Wax, for 
 Entire Upper Dentures. — The form of cup employed in taking an 
 impression of the upper jaw, in the absence of all the natural 
 teeth, is seen in Fig. 51. A number of these corresponding as 
 nearly as possible in form and size to the various modifications in 
 
 the configuration and dimen- 
 sions of the maxillary arch, 
 should be kept conveniently at 
 hand. If the teeth have been 
 recently extracted, the wax 
 should be prepared somewhat 
 softer than usual, to prevent 
 displacement of the gums, 
 which, in their unabsorbed con- 
 dition, possess more or less mo- 
 bility. The cup should be filled 
 flush with the edges, and built 
 up in the center if the depth 
 of the palatal vault requires it, 
 and the wax properly trimmed; it is then introduced into the 
 mouth and adjusted to the ridge, as already described, and 
 pressed to the jaw with sufficient force to fully encase all the 
 parts to which the substitute is ultimately to be applied. The 
 wax, as the cup is pressed up, has a tendency to roll out at its 
 edges, and thus depart from the upper and outer portions of the 
 ridge ; hence care must be taken to press the wax in around the 
 marginal portions of the cup, as has previously been directed, fill- 
 ing up any depressions or fossae that may occur on the external 
 border of the jaw. It is particularly necessary to observe this 
 precaution whenever the ridge overhangs, as is prominently the 
 case for the first few months after the extraction of the teeth. 
 
IMPRESSIONS OF THE MOUTH. 
 
 137 
 
 Fig. 52. 
 
 If the impression is an accurate one, some difficulty is occa- 
 sionally experienced in detaching it from the mouth, on account 
 of the thorough exclusion of air from between it and the mouth 
 the wax being held firmly in place by adhesive force ; in which 
 event it is only necessary to admit the air between the two ; and 
 this may generally be readily effected by placing the finger against 
 the jaw on one side and above the wax, pressing firmly toward the 
 center of the arch and upward, forcing the muscles and mucous 
 membrane somewhat from the edge of the cup, and at the same 
 time depressing the latter on the same side. A small portion 
 of air being admitted, it will soon diffuse itself between the 
 adhering surfaces and allow the wax to be readily detached. 
 
 To harden the wax, so as to prevent it from dragging at the 
 points where the ridge overhangs, or to prevent any change in its 
 shape on the application of suffi- 
 cient force to detach it from the 
 mouth, inject under the lip and 
 upon the cup a stream of cold 
 water, sufficient to chill the wax. 
 
 The writer would repeat, in this 
 connection, his conviction that it is 
 impracticable, in most cases, to ob- 
 tain a faultless impression of the 
 mouth in wax. There are points, 
 not readily accessible to the fingers, 
 where the wax departs from the ex- 
 ternal and posterior borders of the 
 jaw, and is not, therefore, susceptible of easy correction ; besides, 
 when reached and the remedy applied, there is no certain assur- 
 ance that in pressing the wax in at one point we are not displacing 
 it at another. The same uncertainty, to a less degree, in regard to 
 results also attaches to the use of the modeling composition. For 
 this reason, we almost invariably use plaster, and we have suffi- 
 cient reason to believe that the results are more uniformly suc- 
 cessful. 
 
 Manner of Obtaining an Impression of the Lower Jaw in Wax, 
 for Entire Dentures. — The method pursued in securing an im- 
 pression of the lower jaw; in wax for an entire denture differs in 
 no essential respect from that described when taking an impres- 
 sion for lower partial pieces, the form of cup being represented in 
 Fig. 52. When the parts are imbedded in the wax, the latter 
 
I38 MECHANICAL DENTISTRY. 
 
 should be pressed in around the inner border of the holder, but 
 more especially near the posterior part of the ridge on each side 
 where the latter overhang and approximate each other, forming 
 corresponding excavations underneath. After adjusting the wax 
 to the ridge along the border of the cup, the latter should again 
 be pressed directly down upon the jaw before removing it, to 
 correct any partial deformity that may have occurred during the 
 previous manipulations. 
 
 Modeling composition, of late years, has largely superseded 
 the use of wax for impressions. It is compounded of gum 
 dammar, stearin, French chalk, carmin, for coloring, and some 
 perfume. The consistence of the mass depends upon the relative 
 quantity of stearin and chalk introduced, the grades as manufac- 
 tured being designated as soft, medium, and hard. 
 
 This material takes a sharper impression of the parts than wax, 
 and its elastic property makes it more suitable where there are 
 overhanging ridges, irregularly arranged and bell-crowned teeth, 
 and dovetailed interdental spaces. It is prepared for use by soft- 
 ening it either with dry heat, or by immersing it in hot water. 
 When sufficiently plastic, it is introduced into a cup slightly 
 heated to render the material somewhat adhesive, and then placed 
 in the mouth as has been directed for wax impressions. 
 
 Before removing it from the mouth, it should be cooled some- 
 what in order to preserve its form unchanged. Excessive hard- 
 ness, however, should be avoided where portions are pressed into 
 unusual undercut spaces, as the force necessary to detach it in 
 such cases may produce deformity of the body of the impression, 
 more or less remote from the teeth and spaces mentioned. When 
 removed it should be immediately dipped in cold water. The 
 general manipulation of the compound in the mouth, both in full 
 and partial cases, is the same as that described when wax is used, 
 and the same care should be observed when removing the im- 
 pression from the mouth. 
 
 Moldine. — This plastic compound, originated by Dr. George 
 W. Melotte, and used by him chiefly in connection with crown- 
 and bridge-work, is composed of potter's clay mixed with glycerin 
 to the consistency of stiff putty. With the observance of certain 
 precautions in the use of this material, the operator is enabled 
 very quickly to secure a metallic die and counter-die immediately 
 from the impression. 
 
IMPRESSIONS OF THE MOUTH. 
 
 139 
 
 The following, in substance, is Dr. Melotte's method of using 
 it and of obtaining the die and counter-die. Make the tooth or 
 teeth perfectly dry, and, filling the cup (Fig. 53) nearly full with 
 moldine, coat it with soapstone powder, and take the impression 
 in the usual manner. Carefully remove the cup ; trim off any 
 overhanging material, and place the rubber ring (Fig. 54) over 
 the cup to about one-half the depth of the ring. Melt the fusible 
 metal and pour it as cool as it will run from the iron ladle. As 
 soon as the metal is hard, remove it with the ring, taking care not 
 to impair the impression, which can be used again if the die is 
 found imperfect or is injured in use. Place the die and ring in 
 cold water, to remain until quite cooled. While the die is wet and 
 held over a basin of water, pour into the ring fusible metal which 
 has been stirred until it begins to granulate, and quickly immerse 
 
 Fig. 53. Fig. 54. 
 
 all in the water. The die and counter-die should separate readily 
 by tapping them with a hammer, but if they stick, others can be 
 quickly made from the same impression, by the same method, 
 using more care. 
 
 Plaster-of-Paris. — Plaster-of-Paris, or, technically, calcium sul- 
 phate, has been long employed in taking impressions of the mouth 
 for entire dentures, and of late years it has almost entirely super- 
 seded the use of all other materials, on account of its capability of 
 receiving a practically faultless imprint of the parts on which the 
 substitute rests. The same quality of exactness recommends it 
 also in partial cases where conditions exist that render an accurate 
 impression of the parts with other materials impossible. ' 
 
 Derivation. — Plaster is derived from gypsum by a process of 
 calcination. The latter, or gypsum, is a common mineral, fre- 
 quently crystallized, oftener amorphous, and oftentimes forming 
 rock masses. Its transparent variety, called selenite, sometimes 
 
I_(.0 MECHANICAL DENTISTRY. 
 
 occurs in large plates, which have been used for windows. It also 
 frequently occurs in aggregated needle-like crystals, and is then 
 called fibrous gypsum. In its amorphous condition, when com- 
 pact and translucent, it is named alabaster. More commonly it is 
 white, opaque, and soft, and is then called snowy gypsum. The 
 most important deposits known are those of the Paris basin at 
 Montmartre, from which it has taken the common name of plas- 
 ter-of-Paris. 
 
 Manner of Preparing. — In the preparation of plaster, as used 
 in the arts, the gypsum rock is ground between burstones until it 
 is reduced to a fine powder, when it is calcined by being heated 
 in kettles or stills, the combining water being thus driven off. 
 If, in this condition, it is again mixed with water, the latter re- 
 combines with it, the mass becoming first plastic, and then solid. 
 Hence, it is admirably adapted to a great variety of modeling 
 processes. In its ordinary calcined form, plaster absorbs mois- 
 ture from the atmosphere, and should, therefore, be carefully pro- 
 tected from dampness. Should the latter occur, however, the un- 
 combined moisture may be driven off by exposing the plaster to 
 a moderate heat in a shallow pan or other suitable vessel. 
 
 In the process of hardening, after having been made plastic by 
 the addition of water, more or less expansion of the mass, both 
 during and for a time after solidification takes place, varying 
 with the kind of plaster used and the various methods employed 
 in preparing it for molding purposes. 
 
 To hasten the setting of plaster use warm water for mixing, 
 or add about ten grains of common salt (sodium chlorid) to the 
 water before introducing the plaster, when about to take an im- 
 pression. The salt also makes the plaster more brittle, which is 
 desirable in impressions. It is better to add the salt before the 
 plaster, as it gives it a better opportunity to become uniformly 
 diffused. Other agents, such as chlorate of potash, potassium 
 sulphate, and alum, have been and are used to hasten the setting 
 of plaster; but salt is the least objectionable and answers every 
 purpose. 
 
 Manner of Obtaining an Impression of the Mouth in Plaster, 
 for Partial Upper and Lower Dentures. — In partial cases, 
 whether above or below, there are, almost universally, conditions 
 associated with the presence of the remaining natural teeth, 
 
IMPRESSIONS OF THE MOUTH. I4I 
 
 which, until more recently, have been thought to contraindicate 
 the use of plaster as an impression material, but experience has 
 demonstrated that, with the adoption of certain available means 
 and careful and skilful manipulation, there are few if any cases in 
 which this material may not be successfully employed. Its supe- 
 rior capabilities of receiving a faultless imprint of the mucous 
 surfaces recommend it for this purpose in all suitable cases. 
 
 The conditions mentioned above relate to those cases where 
 the cervical portions of the crowns are relatively small ; or where 
 the teeth are irregularly arranged in the circle, having either an 
 anterior, posterior, or lateral obliquity ; or where there are marked 
 depressions or fossae on the external border of the alveolar ridge ; 
 and especially where there are well-defined dovetailed or wedge- 
 shaped interdental spaces. These conditions prevail in different 
 degrees in individual cases, and the instances are exceedingly rare 
 where some or all of them are not present. As plaster prepared 
 for impressions, in the act of setting or hardening, becomes rigid 
 and unyielding, and therefore practically incapable of any change 
 of form by distortion or dragging of any portion of it on traction, 
 the difficulty, not to say impossibility, of detaching it by the ordi- 
 nary means, where these conditions prevail, will be apparent. In 
 cases of very slight deviation from the normal position of the 
 teeth, sufficient force, judiciously applied, will disengage the im- 
 pression, provided the plaster is not allowed to set hard. 
 
 If the mal-arrangement of the teeth is considerable, or very 
 pronounced, the separation of the plaster impression must be 
 accomplished in some other way than by simple traction. Prof. 
 Charles J. Essig recommends the following method of proce- 
 dure: 
 
 " An impression-cup should first be selected of the proper size 
 and shape — those with the flat floor (Fig. 47) are best for partial 
 cases ; the plaster should be mixed quite thin, adding chlorid of 
 soda to facilitate setting. Plaster mixed in this manner does not 
 become so hard and unyielding as that mixed merely to satura- 
 tion. Now oil the cup so that it will readily separate from the 
 impression when hard ; fill the cup as soon as the plaster thickens 
 sufficiently, then, with a small spatula, place a layer of the soft 
 plaster in upon the palatine surface, otherwise, by enclosing the 
 air in the deep portion of the arch, the accuracy of the impression 
 
142 MECHANICAL DENTISTRY. 
 
 may be impaired. After this precaution, the cup is placed in the 
 mouth, and gently pressed up until its floor comes in contact with 
 the teeth. When the plaster is sufficiently hardened, remove the 
 cup, which, from its having been oiled, is done without difficulty ; 
 with the thumb and index finger break off the outside walls ; the 
 portion covering the palatine surface is then removed by the use 
 of a blunt steel spatula, curved at the end in the form of a hook. 
 The pieces are then placed back into the cup, where they will be 
 found to articulate with perfect accuracy. 
 
 " Should the first attempt be rendered futile, by the tendency to 
 nausea or troublesome gagging on the part of the patient, camphor 
 water, as recommended by Dr. Louis Jack, may be used as a gar- 
 gle, which will, in nearly every case, prove an effectual remedy." 
 
 This device is effectual to the extent described by Prof. Essig r 
 but it affords only a partial remedy for difficulties which present 
 themselves in many of these cases. The most formidable ob- 
 stacle to the removal of a plaster impression will be found gen- 
 erally in that portion of it embraced in wedge-shaped interdental 
 spaces, and undercuts formed by truncated, cone-shaped crowns, 
 and malpositions of the teeth ; and when the outside walls of the 
 impression alone are broken off, and remaining portions are im- 
 bedded in these undercuts, it will rarely be possible to remove 
 the portion covering the palatal surface without further fracture 
 and removal by sections. 
 
 The writer is indebted to Prof. Wilbur F. Litch for the follow- 
 ing description and illustration (Fig. 55) of a method of securing 
 plaster impressions for partial cases : 
 
 " A wax impression-tray is made, and either scored or perfor- 
 ated, to afford anchorage for the plaster. This extends only mid- 
 way of teeth or interspace. After the plaster has hardened, the 
 outer edge is trimmed, notched, and oiled in the mouth, and sec- 
 tions D D of the diagram made by carrying plaster into position 
 by means of a spatula, the outer section being made in two pieces, 
 joined at about the median line. The three pieces are removed 
 separately and joined by means of the notches made in the pala- 
 tine section C, into which notches the plaster of sections D D 
 will fit. After the three sections are cemented together, they may 
 be imbedded in plaster, to more securely hold them together 
 while the model is being poured." 
 
IMPRESSIONS OF THE MOUTH. 
 
 143 
 
 Another method of securing plaster impressions in sections is 
 the following, suggested by Dr. A. G. Bennett: 
 
 " A wax cut-off is placed in the floor of the impression-tray in 
 such manner that it will touch the crowns of the molars and the 
 cutting edges of the incisors about midway between their buccal 
 
 Fig. 55. 
 
 A A. Teeth or interspace. B. Wax impression-tray. C. Plaster impression of 
 palatine vault and palatal half of teeth or interspace. D D. Buccal or labial 
 half of teeth or interspace. E. Palatal vault. 
 
 or labial and palatine walls, as shown in Fig. 56, letters D D. 
 After the wax cut-offs have been firmly attached to the tray by 
 heat, the tray is oiled, filled with plaster, and placed in position in 
 the mouth. After the plaster has hardened, the tray is with- 
 drawn, the plaster remaining in the mouth, when the outer sec- 
 
 A A. Molar teeth. B. Palatine vault. C C C. Impression-tray. D D. Wax 
 cut-offs. E E. Labial sections of plaster impressions. F. Palatal section of 
 impression. 
 
 tions, E E, are readily broken off, and the plaster section, F, with- 
 drawn. The several pieces are then replaced in their proper posi- 
 tion in the tray." 
 
 Another method of procedure in the class of cases under con- 
 sideration is that described by the late Dr. F. M. Dixon, of Phila- 
 delphia, which seems to provide more perfectly for the removal Of 
 the palatal portion of the impression in cases characterized by un- 
 
144 
 
 MECHANICAL DENTISTRY. 
 
 usual inward inclination of the teeth. The process described re- 
 lates to partial upper cases : 
 
 " First take an impression of the whole upper jaw in wax, and 
 harden by applying ice-water. Divide this impression, with a 
 slightly heated knife-blade, into the number of sections desired 
 for the plaster impression. From the inner surfaces of these sec- 
 tions, a sufficient quantity of the wax is cut away to make room 
 for the required amount of plaster. Hard-setting plaster is then 
 poured into one of the palatal sections, and the latter placed in 
 its proper position in the mouth, securing an impression of the 
 palatal surfaces of the teeth of that side, and about one-third of 
 the palate of the same side. When the plaster has hardened suf- 
 ficiently, the section is removed and laid to one side while an 
 impression of the opposite side is secured in the same manner. 
 
 "The patient may now be dismissed with an appointment for 
 another sitting. In the interim, these sections are carefully 
 trimmed in such a manner that the lower or lingual surface shall 
 present a bevel from margins near the mesial line of the palate to 
 the grinding surfaces of the teeth, that the next section may be 
 readily removed after the hardening in the mouth. When the 
 patient returns, the prepared lateral sections, oiled on their under 
 surfaces, are placed in the mouth, and an impression of the cen- 
 tral portion of the palate and palatal surfaces of the incisors is 
 secured as before. The impressions of the buccal surfaces, when 
 needed, are taken in like manner, with the other sections in situ." 
 
 Manner of Obtaining an Impression of the Mouth in Plaster 
 for Entire Upper Dentures. — The form of cup used in securing 
 an impression of the upper jaw for entire sets of teeth differs in 
 no essential respect from that recommended when wax is used for 
 similar purposes (Fig. 51). If the external border of the alveolar 
 ridge is very deep, or there is considerable space intervening 
 between the heel of the cup and the floor of the palate, a rim of 
 wax should be placed across the posterior border of the cup, to 
 carry the plaster well up at this point, so as to secure an accurate 
 impression, and more effectually to confine the plaster within the 
 cup and prevent its escape into the back part of the mouth before 
 it has fairly reached the palatal vault. If the latter is extremely 
 deep, with a marked excavation in its central and anterior por- 
 tion, or if it presents, somewhat, the form of a deep fissure, the 
 
IMPRESSIONS OF THE MOUTH. 1 45 
 
 plaster may fail to be carried perfectly against the floor of the 
 palate, or the air, becoming confined within the central portion of 
 the arch, when the plaster is pressed up, may displace the latter 
 and form corresponding chambers in the impression. If these 
 imperfections are but slight, they may be subsequently remedied 
 either by filling up the cavity or cavities in the impression, or by 
 trimming away at these points from the model. The better plan, 
 however, where these conditions of the vault prevail, is to take 
 up a small portion of plaster on the end of a spatula and apply it 
 to the deeper portions of the arch just before introducing the cup. 
 In preparing plaster for use in these cases, it should be so treated 
 as to insure quick setting when applied to the mouth. This is 
 generally accomplished either by adding to a very thin mixture of 
 plaster and water a small quantity of sodium chlorid or common 
 salt and stirring until it begins to thicken. It then adapts itself 
 readily to the parts, hardens quickly, and is not liable, with ordi- 
 nary care, to incommode the patient by running back too far upon 
 the soft palate or into the fauces. So quickly, indeed, does it con- 
 dense, that unless expeditiously introduced into the mouth, it will 
 begin to " set " before the parts are fairly imbedded. When pre- 
 paring it for use, therefore, the plaster should be mixed at the 
 chair with the cup conveniently at hand, while the patient should 
 be in proper position, and in immediate readiness for the opera- 
 tion. 
 
 In view of the liability of the plaster to run back into the fauces 
 when the cup is pressed to its place in the mouth, producing nau- 
 sea and involuntary retching, and which is very liable to occur 
 whenever the mixture is too thin or is improperly manipulated, 
 it is recommended to instruct the patient to avoid swallowing 
 while the plaster is in the mouth, and to breathe entirely through 
 the nostrils, which act keeps the mouth and throat quiet, and 
 hence less liable to irritation from the impression material, and 
 the accumulation of saliva in the mouth. 
 
 Position of Patient, etc. — The patient being seated as nearly 
 upright in the chair as possible, with the head inclined slightly 
 forward, the cup is filled with the plaster mixture and introduced 
 quickly into the mouth, when it is pressed up slowly and gently 
 (the rear or heel of the cup first, which causes most of the sur- 
 plus plaster to be forced forward), until the parts are completely 
 
I46 MECHANICAL DENTISTRY. 
 
 encased and portions of plaster are seen to protrude from all 
 parts of the margins of the cup, otherwise the impression is liable 
 to be imperfect, either on its outer borders or on its posterior 
 palatal face. Immediately after introducing and pressing up the 
 cup, the lip in front should be extended and drawn down over the 
 cup, when gentle pressure, as the plaster is hardening, may be 
 made upon the lip and cheeks, to force the plaster more perfectly 
 into close contact with the outer surface of the alveolar ridge. 
 
 It is essential to perfect success in this operation that the cup, 
 after the parts are once imbedded, should be held perfectly sta- 
 tionary until the plaster becomes fixed, as the slightest movement 
 when the plaster is in the act of consolidating will derange the 
 impression and render it faulty. Again, if after the parts are im- 
 bedded the operator discovers that they are not sufficiently en- 
 cased, and the plaster has partially set, no further effort should be 
 made to press the plaster up upon the parts, but the cup should be 
 withdrawn and the operation repeated with fresh plaster. 
 
 If the operation has been successfully conducted, the plaster 
 will adhere to the mouth, in most instances, with great tenacity, 
 and it will be necessary to observe some caution in removing it, 
 for, if forcibly detached, injury may be inflicted upon the soft 
 parts by tearing away portions of mucous membrane ; or the im- 
 pression may be badly fractured or otherwise impaired. In addi- 
 tion to the means already alluded to in connection with the 
 method of separating wax impressions from the mouth, resort is 
 sometimes had to the following expedient : The central portion 
 of the cup being pierced with two or three small holes, a blunt- 
 pointed probe is passed at these points through the plaster, before 
 the latter has hardened perfectly, to the roof of the mouth. Into 
 these passages the external air passes and diffuses itself between 
 the surface of the plaster and the palate, when the impression may 
 be readily detached. The writer, however, has succeeded best 
 in detaching impressions in such cases by upward and interrupted 
 traction upon the handle of the cup, which, by depressing the 
 latter posteriorly, more readily permits the introduction of air 
 than by either of the methods commonly employed. 
 
 Manner of Obtaining an Impression of the Mouth in Plaster, 
 for Entire Lower Dentures. — The general form of cup used for 
 the above purpose is shown in Fig. 52. This being filled with the 
 
IMPRESSIONS OF THE MOUTH. 
 
 147 
 
 plaster mixture, prepared as described in connection with full 
 upper pieces, is inverted and quickly introduced into the mouth 
 and pressed down upon the ridge until the latter is completely 
 imbedded, being careful at the same time to draw the lower lip 
 away from the cup, and the cheeks outward, in order to prevent 
 any loose tissues from folding in upon the outer borders of the 
 ridge as the cup is pressed to place, thus seriously marring the 
 impression. 
 
 It is thought by many operators that better results can be 
 secured by first taking the impression in wax, enlarging the im- 
 pression thus secured with suitable instruments, and using this 
 as a tray for plaster. 
 
CHAPTER XIV. 
 
 PLASTER MODELS. 
 
 After an impression of the mouth has been secured in either of 
 the ways mentioned in the preceding chapter, the next step in the 
 process of constructing an artificial denture is to procure from 
 the impression a representation of the parts in plaster. The copy 
 thus secured is called a model, or cast, and if correctly obtained 
 is a true counterpart, or facsimile, of all parts of the mouth rep- 
 resented in the impression. 
 
 Manner of Obtaining a Plaster Model from an Impression in 
 Wax or Modeling Compound, for Partial Dentures. — The im- 
 pression should be first trimmed by cutting away superfluous 
 portions that overhang the borders of the cup, care' being taken 
 not to mar any essential part of the impression. The surface 
 imprinted should then be uniformly and thinly coated with soapy 
 water or oil, applied with a camel's-hair brush. This should not 
 be of too thick a consistency, nor applied in too large quantities, 
 as it will collect in the more depending portions of the impres- 
 sion, and, failing to be displaced by the plaster, leave the model 
 imperfect at these points, especially at the coronal extremities of 
 the plaster teeth. The cup is now surrounded by some substance 
 that will confine the plaster and give proper form to the body of 
 the model. For this purpose any material that is easily shaped 
 may be used, as a thin sheet of lead or wax, paper, strips of oil- 
 or wax-cloth, etc. 
 
 Before pouring the plaster, if it is desired to strengthen any of 
 the plaster teeth — as those adjoining the vacuities in the jaw, or 
 such as are to be used in adjusting clasps — and thus secure them 
 against accident in handling, adequate support may be imparted 
 to them by placing short pieces of stiff wire vertically in the de- 
 pressions made in the impression by the teeth, supporting them 
 in an upright position by imbedding one end in the wax or other 
 material in the center of the bottom of each cavity. 
 
 When the cup is properly inclosed, a batter of plaster, of some- 
 
 148 
 
PLASTER MODELS. 
 
 149 
 
 what thinner consistency than that used for impressions, is 
 poured in upon the surface of the wax in sufficient quantity to 
 give to the body of the model a depth of from one to three inches, 
 according to the particular requirements of the case. The plas- 
 ter should not be poured directly or hastily into the cavities 
 formed by the teeth, but upon points contiguous to them, and 
 from which it should be allowed to run slowly into the depres- 
 sions, by tapping the bottom of the cup gently upon the table, 
 thus expelling the contained oil or air, and filling them perfectly. 
 When the plaster has become sufficiently hard, any portions over- 
 lapping the borders of the impression, and not essential to the 
 form of the model, should be cut away and the two separated by 
 immersion in warm' water until the warmth imparted to the model 
 renders the impression sufficiently soft to allow the former to be 
 removed without fracturing the plaster teeth. 
 
 The general form of the body of a model is shown in Fig. 
 58. Where a swaged base is required, the walls, as will be seen, 
 are made as nearly vertical or parallel as will admit of the model 
 being readily detached from the sand in the process of molding; 
 for if made too flaring or divergent, the metallic die obtained 
 from it will be more liable to crack or spread apart under the 
 repeated strokes of a heavy hammer, or to rock under one-sided 
 blows. 
 
 During the process of stamping or forcing a metallic base into 
 adaptation to the die — which is a metallic counterpart of the 
 model — the plate, when cut to the exact pattern of the parts to be 
 covered by it, is frequently forced or dragged back toward the 
 heel of the die, and is thus drawn from the teeth at the sides and 
 in front. This displacement of the plate may be prevented by 
 cutting away all of the plaster teeth from the model, leaving, how- 
 ever, enough of them remaining where they unite with the body 
 of the model to form a shoulder to each tooth, as in Fig. 57. In 
 this case the plate should be sufficiently ample in its dimensions 
 partially to overlap the border, when, as it is forced into adapta- 
 tion, distinct indentations will be made in it, corresponding ex- 
 actly with the palatal curvatures of the teeth ; the portions of the 
 plate covering the cut ends of the teeth are then cut away with 
 plate forceps or other instruments. If, however, the plate is of 
 the exact size required before stamping, one or two plaster teeth 
 
150 
 
 MECHANICAL DENTISTRY. 
 
 upon each side of the model may be allowed to remain, against 
 
 the anterior face of which the plate is made to rest, holding it 
 
 stationary. 
 
 Fig. 57. 
 
 Manner of Obtaining a Plaster Model from an Impression in 
 Wax or Modeling Compound, for Entire Dentures. — The same 
 general method is pursued in obtaining a plaster model from an 
 
 Fig. 58. 
 
 Fig. 59. 
 
 impression of either the upper or lower jaw for entire dentures 
 with the substances mentioned, as that employed in partial cases. 
 The general form of these pieces is represented in Figs. 58 and 59. 
 
PLASTER MODELS. I5I 
 
 If it is desired to swage a rim to the plate, forming a groove or 
 socket into which the plate extremities of the teeth are received, 
 the model should be formed in the manner represented in the an- 
 nexed cuts ; in which it will be seen that an abrupt shoulder is 
 formed on the external border of the model of the upper jaw (Fig. 
 58), but which on the lower (Fig. 59) is extended round the inner 
 border also, as it is desirable, in the latter case, to give a rounded 
 edge to the lingual border of the plate, and which is accomplished 
 in part by swaging in the first instance and afterward by turning 
 the edge down upon the plate with pliers or by other means. 
 The model is prepared by adjusting a strip of softened wax 
 around the border, and cutting away from its upper surface in 
 such a way as to form a groove, the bottom of which shall be on 
 a line with the extreme edge of the base or plate, which should 
 be indicated upon the model with a pencil mark before applying 
 the roll of wax. 
 
 Rimmed plates, however, are only required when single gum 
 teeth, or sectional, or entire blocks are employed, or when plate 
 teeth are mounted on a platinum base with continuous gum. 
 
 Forming the Air-chamber. — Whenever an air-chamber is to 
 be stamped in the base, the model should be prepared for the pur- 
 pose before casting the metallic swages. The general form and 
 position of the central cavity or chamber in the arch is represented 
 in Fig. 58. The model may be prepared in either of the following 
 ways: 1. The form of the chamber may be cut from the wax or 
 plaster impression, in which case the plaster will be raised at a 
 corresponding point or points upon the model, and will have ex- 
 actly the same form and depth as the cavity in the impression. 2. 
 Cover the palatal face of the model with a sheet of wax equal in 
 thickness to the required depth of the chamber, and cut out from 
 this, at the desired point, the form of the cavity ; fill the latter with 
 plaster, and when hard remove the wax and trim the raised por- 
 tion to the proper form. 3. Cut a pattern, of the required form 
 and depth of chamber, from sheet-wax or lead ; place it in proper 
 position in the arch, and press down with the fingers or burnisher 
 until it conforms to the contour of the palate ; it is then fixed in 
 place either by confining it with a small pin or tack driven through 
 it into the plaster, or by interposing softened wax or other adhe- 
 sive material between the pattern and model. A small brush 
 
i5 2 
 
 MECHANICAL DENTISTRY. 
 
 loaded with a varnish mixture passed around the edge of the pat- 
 tern will insure sufficient adhesion. 
 
 The same general method as that when central chambers are 
 formed is pursued in the preparation of the model when it is de- 
 sired to construct lateral cavities in the plate. The form and 
 position of these on the model will be indicated by inspection of 
 the form of " lateral cavity " plates as exhibited in the chapter on 
 Entire Dentures. 
 
 There are other modifications in the form of cavity plates, some 
 of which are obsolete ; that known as " Cleveland's chamber " is 
 still in limited use, but does not require a model differing in form 
 from the one described in connection with full dentures with 
 central chambers. 
 
 Manner of Obtaining a Plaster Model from an Impression in 
 Plaster, for Partial Dentures. — The surface of the impression in 
 plaster should be first glazed, by applying to it, with a camel's- 
 hair brush, a uniform coating of varnish, to prevent adhesion of 
 the model. Two kinds of varnish are in common use — a trans- 
 parent and a colored. The former is preferred, for the reason 
 that it penetrates the plaster more thoroughly, giving to it a 
 greater depth of surface hardness, while the latter, if not suffi- 
 ciently fluid, forms a somewhat superficial incrustation, which is 
 liable to peel off in handling, leaving portions of the model unpro- 
 tected. Either, however, if properly prepared and applied, may 
 be employed. 
 
 Formula No. I. Formula No. 2. 
 
 TRANSPARENT VARNISH. COLORED VARNISH. 
 
 Gum sandarach, 5 oz. Gum shellac, 5 oz. 
 
 Alcohol, 1 quart. Alcohol, 1 quart. 
 
 The sandarach or shellac should first be freed from all impuri- 
 ties by careful picking and washing; they are then added to the 
 alcohol and digested over a moderate heat until thoroughly dis- 
 solved. Other substances, as gum elcmi, Venice turpentine, etc., 
 have been recommended as additional ingredients, but they are 
 not indispensable, and may be omitted without sensibly impair- 
 ing the properties of the varnish. 
 
 The varnish, or separating fluid, should be kept securely bot- 
 tled, to prevent evaporation of the alcohol, and keep it free from 
 dust and other foreign substances. For this purpose the " Clo- 
 
PLASTER MODELS. 
 
 153 
 
 ver-Leaf Holder " (see Fig. 60) is probably the most convenient, 
 neat, cleanly, and economical receptacle on sale for that purpose. 
 The body is of glass with nickeled mountings and cover. It con- 
 tains two compartments, the larger for the varnish, the smaller 
 for the brushes, of which there are three, a large one attached to 
 the lid, and two smaller ones which depend from the partition 
 between the compartments by means of a little hook. Across the 
 main compartment is a scraper to remove surplus varnish from 
 the brushes. The lid is held in place upon a rubber ring with a 
 firm pressure, by means of a rubber wheel attached to a swinging 
 lever. This makes the holder air-tight and prevents evaporation 
 of the varnish. The brushes are specially made for varnish, of 
 fine goat's hair, which is better for the purpose and more durable 
 
 Fig. 60. 
 
 than camel's-hair. A little alcohol placed in the brush compart- 
 ment keeps the brushes pliable, and is convenient for thinning the 
 varnish when desirable. 
 
 After glazing the surface of the plaster impression with var- 
 nish, a thin and uniform coat of oil or soapy water should be 
 applied ; it is then enveloped, and the model procured in the same 
 manner as when the other plastic materials are used. 
 
 The following method of preparing the plaster impression be- 
 fore it is filled in for the model is recommended by Dr. C. W. 
 Spalding : " After the impression has become hard, coat the sur- 
 face with a lather of soap and water ; wash this off and immerse 
 the model in water. This expels air and avoids liability to poros- 
 ity of the surface of the model. Again coat the surface with a 
 strong lather of soap and water, and wash off as before, when the 
 impression is ready to receive the plaster for the model. I prefer 
 
154 
 
 MECHANICAL DENTISTRY. 
 
 this method to varnishing, for the reason that the varnish used is 
 not always of uniform consistency." 
 
 In separating the model from a plaster impression, for partial 
 cases, it will be necessary to cut the latter away in pieces, as any 
 attempt to separate the two in the ordinary manner would inevi- 
 tably break away the plaster teeth from the model. The impres- 
 sion should be chipped away with care, to avoid defacing the 
 model. To provide more perfectly against this accident, it is 
 better to coat the impression with colored varnish, as this will 
 indicate with greater certainty the line of contact or union be- 
 tween the two pieces. Dr. Spalding suggests a simple and effec- 
 tive device for the same purpose, which consists in coloring the 
 water used to mix the plaster for the impression with anilin red. 
 When separated, the model should be trimmed and formed in the 
 manner before described. 
 
 Manner of Obtaining a Plaster Model from an Impression in 
 Plaster, for Entire Dentures. — The preparation of a plaster im- 
 pression of either the upper or lower jaw, for full dentures, and 
 the method of procuring a model therefrom, differ in no essential 
 respect, except in the mode of separation, from the manipulations 
 required when the impressions have been taken in plaster for 
 partial pieces. A model can, ordinarily, where there are no con- 
 siderable depressions or undercuts on the external face of the 
 ridge, be readily separated, either by taking the model in the hand 
 and tapping the handle of the cup, or by forcing a wedge-shaped 
 instrument between the impression and model at the posterior 
 border. When, however, there are considerable undercuts, such 
 as usually prevail on either side of the median line in front, above 
 and below, or the anterior and middle portions of the ridge are 
 thin, prominent, and overhanging, the application of sufficient 
 force to detach the impression in a body will inevitably fracture 
 such portions of the ridge of the model as are engaged in the con- 
 tracted spaces. In such cases, the cup being removed from the 
 impression, the latter should be grooved as deeply as possible 
 without marring the face of the model, in such a way that, when 
 the instrument is forced in at suitable points, the impression will 
 be fractured on a line with the grooves, and thus be detached in 
 sections. One groove may be made continuously along a line 
 corresponding with the summit of the ridge, and others extending 
 
PLASTER MODELS. I 55 
 
 at right angles with this to the outer borders of the impression. 
 When these external sections are removed separately by wedging 
 at the extreme border of the impression, the whole central portion 
 will be easily detached. Extreme thinness and prominence of 
 the ridge will most generally be found in connection with the 
 lower jaw, and will require cautious manipulation to avoid acci- 
 dent to the model. If any portion of the model should be de- 
 faced, it may be remedied by restoring the contour with plaster. 
 After detaching the model in the manner mentioned, the entire 
 body of it should be glazed and hardened by applying to it a thin 
 and uniform coat of varnish, if it is to be used in obtaining a 
 metallic die. This protective covering will prevent the surface 
 from wearing, render it more pleasant to the touch, facilitate its 
 withdrawal from the sand, and give a more perfect mold. A 
 model may be better prepared for permanent preservation by im- 
 mersing it for a short time in a solution of carbonate of soda, by 
 which its surface is converted into carbonate of lime and thereby 
 rendered hard and durable ; care must be taken not to introduce 
 any of the bicarbonate of soda into the solution. 
 
CHAPTER XV. 
 
 METALLIC DIES AND COUNTER-DIES. 
 
 A metallic die is a facsimile or transcript of the mouth in metal, 
 and is also a copy or likeness of the plaster model. 
 
 A metallic counter-die is a copy of the impression, and is a 
 reversed image of the die and plaster model. 
 
 Manner of Obtaining a Metallic Die. — Two general methods 
 are employed in procuring a metallic counterpart of the model : 
 first, by molding; second, by a process termed " dipping." The 
 first only, however, — being the more practical and more gener- 
 ally used, — will be considered. 
 
 Materials Used in Molding. — For this purpose the best mate- 
 rial is marble-dust, though other substances, as sand, Spanish 
 whiting, etc., have been recommended. Marble-dust has the ad- 
 vantage of being always ready for use, or nearly so, as it absorbs 
 considerable moisture from the atmosphere to render it cohesive, 
 is cleanly, and gives a smooth and uniform surface to the die. 
 When sand is used it should be fine and even-grained, the best 
 for the purpose being that used by brass-founders. It is pre- 
 pared by mixing with it sufficient water to render its particles 
 somewhat adherent, so that when portions of it are pressed in the 
 hand and then parted with the fingers it will break away in well- 
 defined fragments. Excess of water should be avoided, as the 
 vapor formed by the molten metal, when poured upon it, will 
 displace portions of the latter and form cavities or blisters in the 
 face of the die ; nor should the sand used be too dry, as in that 
 case it will crumble away in detaching the model. 
 
 Oil lias been proposed as a substitute for water, in which case 
 it is recommended to add one quart of the former to a peck of 
 sand. It is claimed that the sand so prepared is always in imme- 
 diate readiness for use. 
 
 Preparing Model Previous to Molding. — Tn upper cases, 
 whether partial or full, a shallow groove should be made along 
 
 156 
 
METALLIC DIES AND COUNTER-DIES. 
 
 157 
 
 the posterior plate line, so that when the plate is swaged this 
 edge will press firmly against the roof of the mouth. The cast 
 should also be carved at the points where the integument of the 
 palate is soft and yielding. In some cases the center of the pala- 
 tal portion of the mouth is unusually hard and unyielding ; in fact, 
 large, bony prominences are sometimes found ; these points 
 should have a thin layer of wax placed over them, so as to relieve 
 the pressure, otherwise the plate would rock, thus interfering 
 with the adhesion and the wearer's comfort. The form for the 
 vacuum-chamber should also be built up with wax or other mate- 
 rial, when the cast will be ready to proceed with the molding. 
 
 Manner of Securing Mold. — The molding material being prop- 
 erly prepared, the model is placed with its face uppermost on the 
 molding-board and surrounded with a metallic ring. What is 
 known as the Bailey Molding-flask is used by many operators. 
 A common " wagon-box," however, of which two or three sizes 
 should be had, will answer every purpose in ordinary cases. If 
 sand is used, it should first be well sifted to remove the coarser 
 particles, and then filled into the ring, packing it closely with the 
 fingers around and over the model until even with the upper edge 
 of the box. Some care must be observed in the management of 
 the molding material when packing it, for, if made too compact, 
 the vapor formed in pouring hot metal, failing to pass out readily, 
 will be confined within the cavity and cause imperfections in the 
 face of the die ; or, if too loosely packed, the fluid metal, when 
 poured into the mold, will, to some extent, permeate the pores of 
 the sand or other material, and render the face of the die rough 
 and imperfect. 
 
 Manner of Withdrawing the Cast. — After the sand has been 
 well packed, level off the surface with a rule, lift the flask or ring 
 with its contents from the bench, turn it over carefully, and lay it 
 down with the bottom of the cast up. Now run the point of a 
 tack or the small blade of a knife into the center of the cast with 
 a few gentle taps from the hammer. Grasp the knife or head of 
 the tack firmly between the thumb and fingers, and with a small 
 hammer distribute a few gentle taps over the surface of the cast. 
 If the cast cannot then be withdrawn, continue the process and at 
 the same time distribute a few gentle blows over the edge of the 
 molding-ring, when it will usually be found that the cast can be 
 
158 
 
 MECHANICAL DENTISTRY. 
 
 readily lifted out. All these manipulations must be very gentle 
 or the cast may be tilted or rocked in the sand, and thus make a 
 false impression. 
 
 Another method of removing the cast from the sand, usually 
 given in the text-books, is to reinvert the ring and contents, hold 
 it above the table, and dislodge the cast by tapping it gently un- 
 derneath. The writer would, however, in nearly all cases reject a 
 mold from which the cast had fallen out by its own weight. 
 
 Manner of Molding where Undercuts are Present. — Where we 
 have an overhanging alveolar ridge producing a slight undercut, 
 the front of the cast may be raised by first building an inclined 
 bed of the molding material, and resting the cast upon its highest 
 
 Fig. 6i. 
 
 point with the heel upon the molding-tray or table, as is shown in 
 Fig. 61. It can then, in ordinary cases, be readily withdrawn. 
 
 Molding with Cores. — Where the undercuts are too great to be 
 overcome by the method just described, what is known as core- 
 molding is employed. First set the cast on some smooth surface ; 
 oil at the site of the undercut ; mix plaster and asbestos, or plaster 
 and marble-dust, equal parts. When dry, apply the mixture of 
 proper consistency to the front of the model, from the bottom up 
 to the edge of the alveolar line, spreading it on both sides so as en- 
 tirely to fill up the depression, making the lower edge ^2 of an inch 
 thick, and sloping off toward the alveolar ridge (Fig. 62). When 
 this has hardened, separate it from the model, and draw the top of 
 
METALLIC DIES AND COUNTER-DIES. 
 
 159 
 
 it over sand-paper to obtain a flat edge, and let it dry. Readjust 
 this front piece to the model ; procure a mold in sand or other 
 material, in the usual way; place the extra piece or core back in 
 its proper position in the mold, and proceed to cast for the die. 
 After the mold is secured, the core is removed from the plaster 
 model, replaced in the mold, and the metal poured. 
 
 The Hawes Flask. — The difficulty mentioned above may also 
 be overcome by employing the sectional molding flask invented 
 by Dr. G. W. Hawes, the several parts of which are represented 
 in Figs. 63, 64, and 65. 
 
 Fig. 63 represents the lower ring, composed of three movable 
 pieces, with flange extensions that project in toward the center. 
 
 Fig. 62. 
 
 When used, this portion of the flask is closed and the sections 
 kept in place by pins passing through the joints. Inside of this 
 ring the model is placed face upward, the ridge extending a little 
 above the upper plane of the ring. Sand, well sifted, is then 
 packed in around the model on a level with the most projecting 
 points on the outside of the ridge, as indicated by the dotted line 
 in Fig. 65. The surface of the sand should be trimmed smoothly, 
 and should be cut squarely and at right angles with the ridge to 
 prevent the sand from breaking away when the model is with- 
 drawn. Very finely pulverized charcoal, contained in a loose 
 muslin bag, is now sifted over the exposed surface of the sand to 
 prevent the next portion contained in the upper ring from adher- 
 ing. The plain ring (Fig. 64) is then placed over the one contain- 
 
i6o 
 
 MECHANICAL DENTISTRY. 
 
 ing the model, and is filled with sand well packed over the face of 
 the die. The upper ring is now carefully lifted from the lower 
 one on a line with the pins, thus separating the two portions of 
 sand, and again exposing the uncovered face of the model. One 
 of the pins should then be drawn from the lower ring, the sec- 
 tions of the latter carefully unfolded, and the model withdrawn, 
 when the ring may be again closed and confined by replacing the 
 pin. The upper ring is then readjusted in its proper relation to 
 the lower one, the flask inverted, when the mold, if the process 
 has been accurately conducted, will be found perfect. 
 
 In obtaining a mold from the model of a lower jaw, but little 
 difficulty will ordinarily be experienced in obtaining it perfect in 
 
 Fig. 63. 
 
 Fig. 64. 
 
 Fig. 65. 
 
 the manner first described. The depressions at the posterior and 
 inner border of the ridge are the points most liable to drag or dis- 
 place the sand, and when the latter occurs, the surplus metal in 
 the die at such points must be cut away with suitable instru- 
 ments ; or the cavities in the model may be so filled out with wax 
 before molding as to permit the ready separation of the model 
 without displacing the sand, in which case, also, it will be neces- 
 sary, afterward, to trim the redundant metal from the die. 
 
 The Lewis Molding-flask. — This form of flask, introduced by 
 the Buffalo Dental Manufacturing Co., is an improvement upon 
 the Bailey Flask for making dies ; the top part, which forms the 
 
METALLIC DIES AND COUNTER-DIES. 
 
 161 
 
 zinc die, being entirely new in shape and purpose. By the use of 
 this flask, the metal in the die is concentrated above it, so that it 
 has no outside bearing upon the counter-die ; thus overcoming 
 what is to many dentists a serious objection to dies produced 
 with the ordinary flasks or rings, viz., the bearing of the die 
 upon the counter, outside of the model, preventing the driving of 
 the former into the latter as it yields in swaging, unless the 
 method suggested by Dr. Broomell on page 169 employed. In 
 dies produced by the Lewis Flask, the bearing of the die upon 
 the counter is limited to the model, and a more perfect adaptation 
 can be secured between it and the plate. With this flask a thin 
 model can be used, at the same time all the advantages of the 
 old-fashioned, thick, or built-up model secured. 
 
 Fig. 66 
 
 When this form of flask is employed, the procedure is as fol- 
 lows : A thin plaster cast should be trimmed to give proper draft 
 at the edges ; varnish and dry thoroughly. Before proceeding to 
 mold, dust it with a little finely-powdered charcoal, shaking off all 
 that does not adhere. Invert the top or winged section of the 
 flask, fill its conical cavity with sand, leaving it a little high, and 
 press the back of the model firmly upon it, to secure a solid foun- 
 dation and prevent rocking. Place the ring in position, and sift 
 the sand into it, ramming it down carefully. Strike off the surface 
 of the sand level with the top of the ring. Reverse the flask, hold- 
 ing the sections together securely ; then remove the winged sec- 
 tion and draw the model. Fill the depression in the sand with the 
 molten metal ; then place the upper section of the flask in position 
 — the sand having previously been knocked out of it — and com- 
 plete the pouring of the metal. When the die has cooled, smoke 
 
l62 MECHANICAL DENTISTRY. 
 
 its exposed surface, and replace it in the winged part of the flask ; 
 knock the sand out of the ring, place it in position, and fill with 
 the counter-die metal. 
 
 The Pearsall Molding-flask. — This form of molding-flask, as 
 Mr. Booth Pearsall, the designer, says, is intended to remove 
 some of the many defects found in zinc dies as commonly made 
 by dentists. The molding-plate (Fig. 67) is circular, and has on 
 its upper surface four concentric grooves and four projections or 
 tabs. The grooves hold the sand, and make so many dikes or 
 obstructions to prevent the hot metal from running out between 
 the molding-plate and the sand. The grooves also serve to guide 
 the workman in correctly centering or excentering the position of 
 the model, so that the cone or striking part of the die will come 
 where most strength is required — in other words, where the 
 heaviest hammering is to be done. On the under side of the 
 molding-plate are four webs or feet (C, Fig. 69), running from 
 the circumference of the plate to the conical aperture A, in the 
 middle, by which the truncated cone to be hammered upon is 
 molded. The object of these feet is to make the molding-plate 
 strong enough to bear rough usage, and of sufficient weight to 
 prevent it from being floated off the sand-mold by the weight of 
 the molten metal as it is poured in, as well as to form steady 
 feet for the plate to rest upon on the molding-table. 
 
 The sand-ring is of strong hoop-iron, and should fit easily and 
 truly on the grooved surface of the molding-plate next to the 
 projections or tabs. 
 
 When molding is to be done, the molding-plate is placed in the 
 sand-drawer or on the table, grooved side upward, and on it the 
 shallow plaster model (from Y\ to one inch deep, as may be de- 
 sired) (Fig. 67), in such a position as to bring the cone-shaped 
 aperture where most strength is required in the die. The iron 
 sand-ring is then put on the molding-plate (Fig. 68), and sand is 
 packed in in the usual way. When the packing is finished, the 
 iron ring full of sand, with the molting-plate, are turned upside 
 down (Fig. 69). The molding-plate is then removed, exposing 
 the model, which is withdrawn by the aid of a point and hammer 
 in the usual way. 
 
 The mold having been examined, and any loose particles of 
 sand blown out of it, zinc sufficient to barely fill the mold is 
 
METALLIC DIES AND COUNTER-DIES. 163 
 
 Fig. 67. . Fig. 68. 
 
 Fig. 69. 
 
 Fig. 70. 
 
 Fig. 71. 
 
 Bailey Die 3-Pound Zinc 
 
 Ordinary Die 2VPound Zinc 
 
 Pearsall Die ______ 2-Pound Zinc 
 
164 MECHANICAL DENTISTRY. 
 
 poured in, the molding-plate slightly heated is put over the mold, 
 and the remaining zinc poured into the aperture to make the cone- 
 shaped end of the die. Of course, if the sand-mold is over-filled 
 with zinc in the first instance, there will be difficulty in placing 
 the molding-plate on the sand-mold, but this is easily avoided. 
 
 To make a counter-die, the molding-plate, zinc die, and a coun- 
 ter-die ring are arranged as in Fig. 70, sufficient sand being 
 packed about the die to give the depth of counter-die required. 
 
 In use, the swaging of a plate will be found more certain and 
 accurate, because of the ease with which heavy blows can be 
 struck on the truncated cone, and the hollow formed in the center 
 of the cone by the cooling of the zinc is really a source of 
 strength, so far as construction is concerned. The cone-shaped 
 end, with the model projecting over it, enables the die to be held 
 in a vise in such a way that blows struck on the palate or teeth of 
 the model will not cause it to slip in the jaws of the vise. The 
 die thus has a steady bearing, forming a great contrast to the 
 slippery and uncertain hold of the ordinary form of die when 
 placed in a vise to be filed or hammered. It can also be easily 
 and quickly turned and secured in any desired position by open- 
 ing and instantly reclosing the jaws of the vise, whereas neither 
 the Bailey nor the ordinary form of die can be secured in a vise 
 with the same certainty, precision, or rapidity. 
 
 Attention may also be directed to the ease with which blows 
 can be struck outside the cone on the shoulder formed by the pro- 
 jection of the mold, and such blows are often of the greatest ser- 
 vice in certain cases, instances of which will readily suggest 
 themselves. 
 
 The advantages, as summed up by Mr. Pcarsall, are as follows: 
 
 1 . The shallowness of the model required, and the consequent 
 saving of time in drying it. 
 
 2. The ease with which a shallow plaster model can be re- 
 moved from the sand as compared with a deep one. 
 
 3. Saving in the amount of zinc to be melted. As zinc deteri- 
 orates by constant melting, this is important, and a supply of zinc 
 ought to go further in the constant use of the smaller dies. 
 
 4. The great increase of strength, owing to the improved con- 
 struction of the die, aided by the cooling of the zinc. 
 
 5. The choice offered to the workman in placing the strength 
 
METALLIC DIES AND COUNTER-DIES. 1 65 
 
 or blow-resisting cone, where it is needed to resist heavy ham- 
 mering. 
 
 6. The ease and rapidity with which the new form of die can be 
 secured in any position in the ordinary vise. 
 
 7. The precision of the blow secured by the use of the cone- 
 shaped end of the die. 
 
 Diagram No. 5 (Fig. 71) shows sections of the same model 
 used as a die in the new method, the usual method, and that in- 
 vented by Bailey ; but only a comparison of the actual dies can 
 convey an adequate notion of the advantages of the new form. 
 
 Preparing Cast for Mold, for Partial Dentures. — A die is more 
 readily and accurately obtained from a model for partial den- 
 tures by cutting away the plaster teeth, as before described. The 
 displacement of sand where the ridge overhangs will, as a general 
 thing, be unimportant in these cases, as the base seldom more 
 than partially overlaps the border. 
 
 When whiting or marble-dust is used in molding, it is generally 
 unnecessary to mix water with them, as the moisture which they 
 absorb from the atmosphere will give to them the proper con- 
 sistency. 
 
 Preparing and Pouring Metal for Dies. — Having obtained a 
 mold in either of the ways mentioned, the metal designed for the 
 die should be melted and poured carefully in upon the more 
 prominent portions on the face of the former. If the metal is 
 raised much above its fusing-point, or the sand is quite damp, the 
 former should be poured very slowly into the mold. It is better, 
 however, that the sand should be partially dried before pouring 
 the metal, and the die cast, on the instant of the metal becoming 
 sufficiently fluid. An observance of these precautions will pro- 
 tect the sand from the overaction of heat, prevent ebullition of 
 the fused metal from the too rapid decomposition of the water in 
 the sand, will give a smoother face to the die, and secure the 
 metal or metals from undue waste by oxidation. The opinion is 
 entertained by some, that greater shrinkage of the die occurs 
 when the metallic substance of which it is composed is poured at 
 a temperature much above its fusing-point ; the fallacy of this is 
 made obvious by a moment's reflection, as a simple example will 
 show that any change affecting the face of the die, as a conse- 
 quence of contraction, can only occur in the metal between its 
 
1 66 MECHANICAL DENTISTRY. 
 
 point of solidification or liquefaction — for they are identical — and 
 its working temperature. Zinc, for example, melts at 773°. Now 
 if its temperature be raised to 1200 , it will remain fluid until it 
 reaches 773 °, and in passing through the intermediate degrees of 
 heat, it will, in obedience to gravity, adapt itself perfectly to all 
 parts of the mold ; and this perfect continuity of the two surfaces 
 will remain unaffected by the contraction of the metal until the 
 latter commences to " set " or solidify, after which, and not until 
 then, the zinc begins to part from the face of the mold by con- 
 tracting upon itself between 773 ° and the mean temperature of 
 the air. So far as any change, by contraction, in the face of the 
 die is concerned, therefore, it is obviously immaterial whether the 
 zinc be poured on the instant of melting or at 1200 ; the result 
 will be the same in either case. 
 
 The Franklin Mold.— The author is indebted to Dr. B. W. 
 Franklin for the following method of securing metallic dies and 
 counters by a process which greatly facilitates the operation and 
 insures accurate and satisfactory results : " I take all impressions, 
 full and partial, in plaster. A small hole, less than -Jg- of an inch, 
 is drilled through the highest point of the palatal surface of the 
 impression, through cup and all ; into this place two or three 
 broom splints, cutting them off even with the surface of the plas- 
 ter, to allow any vapors to pass off. I sometimes smoke the sur- 
 face of the impression. Around the impression place sufficient 
 putty to form a ring the size and height required for the die. Into 
 this pour, at as low heat as is consistent with the mobility re- 
 quired for sharp castings, the bismuth alloy known as Sir Isaac 
 Newton metal, or, which is better in some respects, eight parts 
 bismuth and four parts each of tin and lead — the latter composi- 
 tion being a little harder. If a little judgment is exercised in 
 pouring either of the above alloys, a perfect die will be secured 
 from moist plaster impressions without any drying. As the bis- 
 muth is expansive and the alloy is hard and somewhat brittle, I 
 run only a thin casting, not more than l / 2 of an inch in thickness, 
 over the highest portion of the impression. I have cast-iron or 
 brass heads made, 3^4 inches in length, 3 inches in diameter at 
 the large end, and 2 inches at the other; the large end is flat, and 
 well coated with common tinman's solder. This head is heated 
 until the solder begins to soften ; it is then placed in a pan or other 
 convenient vessel, and the die, face side up, is placed upon the 
 tinned surface. When the die begins to melt, and perfect union 
 
METALLIC DIES AND COUNTER -DIES. 1 67 
 
 is secured, cold water is dashed upon the die and head ; and thus 
 we have a sharp die, with an iron head, to sustain the force of the 
 blow in stamping the plate, and by this means preventing any- 
 spreading of the face of the die or liability of breaking in the 
 process of swaging. 
 
 " I now take sheet-lead of the thickness of about No. 24, 
 standard gage, and adapt it to the face of the die by means of a 
 wooden mallet or burnisher, or other convenient means. Trim 
 the lead plate to the size required for the plate to be stamped ; 
 when the lead plate is nicely fitted, remove it carefully from the 
 die and place it in a ring or narrow molding-flask, the palatal side 
 up ; now gently stamp molding sand into the plate and flask, up 
 level with the edges of the flask ; then reverse the flask and cut 
 the sand away clean for y 2 of an inch or more down to the edge of 
 the lead plate all around. Around the plate place a common 
 molding-ring, sufficiently large to form the counter, which is 
 made by pouring melted tin or lead (or any alloys of these met- 
 als) on to the lead plate, being careful not to run the metal so hot 
 as to melt the lead plate. When the counter is cool enough to 
 handle, the adhering sand is brushed or washed away ; the die is 
 then placed into the bed or counter, and, with a moderate-sized 
 hammer, give one or two sharp blows to bring the die and counter 
 together. In swaging gold plates, two, three, or more dies may 
 be required ; these may be made either by running the die metal 
 into the impression (if not broken) or by running into lead plates, 
 gotten up as before described, reserving, of course, the first die 
 and counter for the final swaging of the plate. I have gotten up 
 a die and counter from the impression, with the aid of an assis- 
 tant, in the foregoing manner, in twelve minutes. I usually get 
 out my die immediately after taking the impression ; adapt a wax 
 or gutta-percha plate to the die, and get the articulation before 
 the patient leaves the office." 
 
 In the act of contracting, the central portion of the die, being 
 the last to solidify, is gradually drawn toward the periphery, 
 forming, when the contraction is completed, an excavation of 
 greater or less depth in the center of its base, a form unfavorable 
 to an equal distribution of the force applied in swaging, and 
 greatly increasing the danger of distorting the face of the die by 
 cracking or spreading, especially when zinc is used. To concen- 
 trate and equalize this force is a matter of the first importance. 
 The liability to such an accident may, to some extent, be avoided 
 
1 68 MECHANICAL DEXTISTRY. 
 
 by placing on the die a cone-shaped cap of any hard metal, as zinc, 
 brass, or cast-iron. This, however, while it provides against one- 
 sided blows of the hammer, affords only a partial remedy, since 
 the same danger of spreading the die exists, in consequence of the 
 cap resting on the outer border of the base of the die, with no 
 central bearing whatever. To equalize the force perfectly, the 
 cone-shaped metal cap should be incorporated with, and form part 
 of the body of the die itself. This is partly, if not wholly, accom- 
 plished by Dr. Franklin's expedient. 
 
 Counter-dies. — A counter to the die is generally obtained di- 
 rectly from the latter. The die is placed, face upward, upon the 
 molding-table, and sand, prepared as in molding, built up around 
 it, leaving only the ridge and palatal face exposed. It is then 
 encircled with a cast- or sheet-iron ring two or three inches deep, 
 its edge imbedded in the sand to prevent the escape of the fluid 
 metal ; into this the metal for the counter is poured until nearly 
 or quite full. 
 
 The metal commonly employed for the counter is lead, al- 
 though other substances, as tin, type-metal, some of the more 
 fusible alloys hereafter to be mentioned, etc., are sometimes em- 
 ployed. When the counter is taken by pouring the metal or met- 
 als composing it upon a die fusing at a low heat, some caution 
 should be observed lest the two pieces adhere by partial fusion 
 of the die. In such cases the surface of the die should be well 
 protected with lamp-smoke or whiting ; the lead should be poured 
 at the lowest practical temperature, and the conduction of heat 
 facilitated by surrounding the die with a heavy cast-iron box or 
 ring. 
 
 During the process of forcing a plate into adaptation to the 
 form of the mouth with swages, it not infrequently happens that 
 the marginal portions of the former become wedged or immovably 
 fixed between the outer border of the die and corresponding por- 
 tions of the counter before its central portion is forced into con- 
 tact with the palatal surface of the former, thus rendering it diffi- 
 cult to conform the plate accurately to the parts without the appli- 
 cation of sufficient force to deface or otherwise mar the form of 
 the die. In such cases the central portion of the plate may be 
 first swaged with a partial counter, which is made to receive only 
 the palatal portion and upper surface of the ridge of the die. This 
 method, as practised and described by Dr. I. N. Broomell, of the 
 Pennsylvania College of Dental Surgery, is as follows : 
 
METALLIC DIES AND COUNTER-DIES. 
 
 169 
 
 " Progressive Counter-dies. — It being desirous, in swaging a 
 plate, to have the palatine portion forced into position at the be- 
 ginning, the iirst counter-die should be formed as represented in 
 Fig. 72. To accomplish this the sand must be built entirely over 
 the. ridge, allowing only the palatine portion of the die to be ex- 
 
 Fig. 7; 
 
 Fig. 73- 
 
 Fig. 74- 
 
 posed. The second counter-die should extend just beyond the 
 center of the ridge, as shown in Fig. 73, and the third or final 
 counter may be formed in the usual manner, see Fig. 74. By the 
 judicious construction of this series of counter-dies, more satis- 
 factory results are obtained, and much needless use of the horn 
 mallet dispensed with. It will readily be observed that a coun- 
 ter-die, formed as represented in No. i (Fig. 72), will drive the 
 center of the plate into position without the usual resistance ex- 
 perienced in using the ordinary counter. The use of No. ii (Fig. 
 73) will gradually start the plate over the ridge, and No. iii will 
 readily complete the process." 
 
I/O 
 
 MECHANICAL DENTISTRY. 
 
 As before remarked, preference is usually given to lead in the 
 formation of a counter-die, mainly on account of its greater soft- 
 ness. This property in a counter is practically important. In 
 the process of forcing a metallic plate into adaptation to the 
 mouth, partial displacement or yielding of either the die or 
 counter, or of both, necessarily occurs, and it is scarcely necessary 
 to remark that whatever change of form is produced should take 
 place wholly in the counter, otherwise deformity of the die must 
 ensue. 
 
 Essential Properties of a Die. — There are certain properties 
 which it is indispensable that a metallic die should possess in 
 order to answer fully the requirements of the dentist. 
 
 1. A die should be sufficiently. hard to resist any necessary force 
 applied to it in stamping the plate without suffering any material 
 change in the form of its face, by which latter term is meant that 
 portion of the die with which the plate is brought in contact. 
 This property is most indispensable in those cases where the arch 
 of the mouth is very deep, the rugae prominent and sharply de- 
 fined, and where the alveolar ridge is marked by angular and 
 abrupt prominences and depressions. In such cases, if the die is 
 not sufficiently resistant, the points most prominent upon its face 
 will be bruised or battered down, while the plate will fail to be 
 forced perfectly into the cavities or depressions, and its coapta- 
 tion to the mouth, to that extent, rendered faulty. The case in 
 which a less degree of hardness is admissible is where the arch of 
 the mouth is broad and shallow, the rugae imperfectly defined, and 
 the ridge regular and symmetrical. The conformation of the 
 mouth, therefore, will, in respect to the property of hardness, ad- 
 mit of some latitude in the choice of the metal or alloy employed 
 in the formation of a die. 
 
 2. Another important property of a metallic die is non-contrac- 
 tion, so far, at least, as this is attainable. Inasmuch as the suc- 
 cessful adaptation of the plate depends, in a great measure, upon 
 an accurate representation of the precise form of the mouth in the 
 die, it is of the first importance that the latter, other requisites 
 being secured, should be composed of some metal or metals hav- 
 ing the least possible contraction in cooling. Contraction is, in 
 varying degrees, common to all metals exposed to a decreasing 
 temperature, and it is impossible, therefore, to obtain a perfectly 
 
METALLIC DIES AND COUNTER-DIES. 171 
 
 faultless copy of the mouth in metal. Fortunately, as well for 
 the expert as the unskilled manipulator, the unavoidable shrink- 
 age incurred is partially or wholly compensated for, by the ex- 
 pansion of the plaster model and the yielding condition of the 
 soft tissues of the mouth, but under no circumstances should the 
 accommodation afforded by the condition last mentioned encour- 
 age negligence or unskilfulness in the use of all available means 
 necessary to secure the most accurate adaptation of the base. 
 Ordinarily, a moderate degree of contraction will not materially 
 impair the fit of a plate ; on the contrary, in the case of the upper 
 jaw, it sometimes favors its adhesion and retention in the mouth. 
 Cases, on the other hand, frequently occur where the least prac- 
 ticable amount of shrinkage, even at the partial sacrifice of other 
 properties, becomes indispensable in the die. 
 
 3. A third important requisite of a die is fusibility. Aside from 
 the convenience incident to the use of metals which fuse at a low 
 heat, there is another consideration favoring this property of more 
 practical importance. It is well known that all metals expand by 
 heat and contract by cold. In obedience to this law, metals fus- 
 ing at a high heat suffer a greater aggregate contraction than 
 those melting at a lower temperature, and, as between two metal- 
 lic bodies of equal dimensions, liquefying at different tempera- 
 tures, the difference in contraction will correspond exactly with 
 the difference in the number of degrees through which each passes 
 from the point of solidification to the mean temperature of the air, 
 allowance being made for the difference in their ratios of contrac- 
 tion. The difference in the contraction will be somewhat modified 
 by that in their ratio of contraction, but it will always be found 
 that the more fusible metals have the least aggregate shrinkage 
 whenever any considerable disparity exists between their fusing- 
 points. It is in accordance with the principles here set forth that 
 the more fusible alloys, some of which melt at remarkably low 
 temperatures, are employed whenever it is important to obtain a 
 die as nearly the exact counterpart of the model as possible. 
 
 4. Finally, a die should be sufficiently cohesive to resist the re- 
 peated blows of a heavy hammer without parting or cracking. 
 Many metals, as antimony, bismuth, etc., in other respects suit- 
 able for dies, are objectionable on account of brittleness. But it 
 must not, therefore, be inferred that all metals that are denom- 
 
172 MECHANICAL DENTISTRY. 
 
 inated brittle are inadmissible for this purpose ; for zinc, which in 
 its ordinary condition is ranked as a brittle metal, and type-metal, 
 which is always so, are in no danger of being forced asunder or 
 of suffering displacement when in the compact form of a die, pro- 
 vided the force used in swaging is judiciously applied, or proper 
 form and sufficient depth are given to the body of the die. 
 
 To recapitulate briefly : A die should be formed of some metal 
 or alloy that has a surface hardness sufficient to resist compres- 
 sion ; that fuses at a low temperature ; that does not, in any mate- 
 rial degree, contract in the act of cooling, and whose particles 
 adhere with sufficient cohesive force to maintain perfectly its in- 
 tegrity of form under the hammer. Any one or two of these 
 properties are readily attainable in the same die, but no one 
 known metal or alloy combines all of them perfectly. Thus either 
 cast-iron, brass, bronze, or cannon metal would form an excellent 
 material in respect of surface hardness, and in the compact form 
 of a die would be sufficiently cohesive, but few enjoy convenient 
 facilities for melting them ; besides, their great contraction, con- 
 sequent upon their high fusing-point, would render their employ- 
 ment entirely inadmissible. Again, certain alloys, as those com- 
 posed of lead, tin, and antimony or bismuth, are eminently suit- 
 able on account of their ready fusibility and comparative exemp- 
 tion from shrinkage, but they gain these properties at the expense 
 of that degree of hardness necessary to resist compression. Tin, 
 in its uncombined state, is ordinarily sufficiently fusible, tena- 
 cious, and non-contractile, but is too soft and yielding when 
 forcibly compressed. Antimony and bismuth are sufficiently 
 hard, fusible, and non-contractile, but are objectionable on the 
 score of extreme brittleness. 
 
 Any metallic substance that combines most perfectly the sev- 
 eral properties referred to is, therefore, best adapted to the neces- 
 sities of the mechanical operator, and experience has almost uni- 
 versally accorded preeminence in this respect to zinc. It presents 
 a more resistant surface to the blow of a hammer than either cop- 
 per or brass, three times more so than that of tin, and more than 
 double that of type-metal. As it usually occurs in commerce it 
 may be classed as a brittle metal, but when annealed it is tough 
 and malleable. Tt melts at a heat (773 ) which may be readily 
 commanded, and contracts but little in cooling. The late Pro- 
 
METALLIC DIES AND COUNTER-DIES. 
 
 173 
 
 fessor Austen demonstrated by actual experiments that an aver- 
 age-sized zinc die measuring two inches transversely contracts 
 if o"o" °f an mc ^ f rom outside to outside of the alveolar ridge, being 
 equivalent in thickness to three leaves of this volume. Professor 
 Austen remarks: " In the first case (upper jaw) the plate would 
 ' bind,' and if the ridge were covered by an unyielding mucous 
 membrane it would prevent accuracy of adaptation. In the sec- 
 ond case (under jaw) the plate would have too much lateral 
 ' play/ and consequently lack stability. Again, in a moderately 
 deep arch, say y 2 of an inch in depth, the shrinkage between the 
 level of the ridge and the floor of the palate will be nearly y^-q-q — 
 rather more than one leaf. In the deepest arches this shrinkage 
 becomes a serious difficulty ; in the shallower cases it is not of 
 much moment, as there is no mouth so hard as not to yield the 
 
 T0V0 or TOT of an inch/ ' 
 
 As before stated, a moderate degree of shrinkage in the die 
 
 may, in certain conditions of the mouth, practically favor the ad- 
 hesion and permanent retention of a plate applied to the upper 
 jaw. The conditions alluded to, and which prevail in a greater 
 or less degree in all cases, are soft and yielding ridge, and com- 
 paratively hard and unimpressible palate. Now, if in the first 
 instance the plate is swaged into uniform contact with all parts 
 of the jaw, it will be readily perceived that if pressure is made 
 over the ridge on one side the latter will yield, while the central 
 portion of the plate, meeting with a fixed point of resistance at 
 the floor of the palate, will " ride " upon the latter, and thus throw 
 the plate from the ridge on the opposite side of the jaw. If, how- 
 ever, a space equal to one or two thicknesses of the plate exists 
 between the latter and the roof of the mouth, as a consequence of 
 contraction in the die, the plate, as it is carried against the palate 
 in the act of exhausting the air from beneath it, will, at the same 
 time, forcibly compress the ridge, securing thereby a more resis- 
 tant basis along the border, and providing more certainly against 
 displacement of the base on the application of forces brought to 
 bear upon it in mastication. 
 
 The extent to which the shrinkage of a die may be admitted in 
 any given case will depend partly upon difference in the condi- 
 tions heretofore mentioned in the soft parts of the mouth, and in 
 part, also, upon the general configuration of the jaw. In a me- 
 
174 MECHANICAL DENTISTRY. 
 
 dium-sized mouth, with a depth of say y 2 of an inch to the arch, a 
 moderately soft ridge and resisting palate, the shrinkage incident 
 to zinc will be unimportant, and in many cases will be advantage- 
 ous. If, however, the vault is very deep, even though there be a 
 yielding ridge, the unavoidable contraction of a zinc die will 
 throw the plate so far from the arch as to render it difficult for the 
 patient to exhaust the atmosphere from between it and the floor 
 of the palate, and even when the latter is practicable, the plate 
 will bind with such force upon the outer border of the ridge as not 
 only to produce pain and irritation of the compressed parts, but 
 the resistance afforded at these points will be sufficient, in many 
 cases, to break up the adhesion, and force the plate from the pal- 
 ate. Again, as an extreme case, if the ridge and palate are some- 
 what uniformly unyielding, and the palatal vault is at the same 
 time very deep, a zinc die can only be made available in bringing 
 the base as nearly into adaptation as possible, after which the 
 operation may be completed with a swage having a less degree of 
 shrinkage, and which, as a mere finishing die, need not neces- 
 sarily be so hard as zinc. 
 
 In conforming a plate to the lower jaw, the die should be as 
 free as possible from contraction in all cases. The greatest 
 shrinkage in such cases will be between the posterior extremities 
 of the ridge, giving too much lateral play to the plate ; in addi- 
 tion to which the posterior and inner edge of the base, projecting 
 outward from the ridge, will obstruct the free action of the 
 tongue, while the latter will tend to lift it from the ridge and ren- 
 der it unstable. These conditions may be partially remedied by 
 turning the edge of the plate in against the ridge with pliers ; but 
 this expedient should never be resorted to in any case whenever 
 it is practicable to secure a correct adaptation by swaging. 
 
 In all cases in which a zinc die fails to bring the plate into 
 proper adaptation to the parts, either of the following metallic 
 compounds may be used to complete the process after partial 
 stamping with zinc. 
 
 Type-metal. — Lead, five parts; antimony, one part. Fuses at 
 500 ; contraction less than one-half that of zinc ; more compres- 
 sible than the latter and very brittle. 
 
 Babbitt or Anti-friction Metal. — Copper, three parts ; anti- 
 mony, one part; tin, three parts. First fuse the copper, and then 
 
METALLIC DIES AND COUNTER-DIES. 
 
 175 
 
 add the antimony and tin. Melts at a moderately low heat; con- 
 tracts but little ; is brittle, but may be rendered less so by adding 
 tin. 
 
 Zinc, four parts ; tin, one part. Fuses at a lower heat, contracts 
 less in cooling, and has a less surface hardness than zinc. 
 
 Tin, five parts ; antimony, one part. Melts at a lower heat than 
 either of the preceding alloys; contracts but slightly in cooling; 
 is harder than tin and sufficiently adhesive. It is readily oxid- 
 ized and should be poured as soon as melted. 
 
 Fusible Alloys. — The following tabular view of the more fusi- 
 ble alloys, the respective properties of which are deduced from 
 actual experiments, was given by Professor Austen in a paper on 
 " Metallic Dies." * Zinc is introduced into the table for the pur- 
 pose of comparison. 
 
 1 . Zinc, 
 
 2. Lead, 2, Tin, 1 
 
 3. Lead, 1, Tin, 2, 
 
 4. Lead, 2, Tin, 3, Antimony, 1, 
 
 5. Lead, 5, Tin, 6, Antimony, 1, 
 
 6. Lead, 5, Tin, 6, Antimony, 1, Bismuth, 3, 
 
 7. Lead, 1, Tin, 1, Bismuth, 1, 
 
 8. Lead, 5, Tin, 3, Bismuth, 8, 
 
 9. Lead, 2, Tin, 1, Bismuth, 3, 
 
 Melting- 
 
 Contrac- 
 
 Hardi- 
 
 point. 
 
 tility. 
 
 ness. 
 
 770° 
 
 .OI366 
 
 .Ol8 
 
 440 
 
 .00633 
 
 .050 
 
 340 
 
 .OO50O 
 
 .040 
 
 420 
 
 •OO433 
 
 .026 
 
 320 
 
 .00566 
 
 •035 
 
 3OO 
 
 .00266 
 
 .030 
 
 250 
 
 .OO066 
 
 .042 
 
 200 
 
 .00200 
 
 •045 
 
 200 
 
 .OOI33 
 
 .048 
 
 Brittle- 
 ness. 
 
 In commenting on the preceding table, Professor Austen ob- 
 serves : " The last column contains an approximate estimate of 
 the relative brittleness of the samples given. . As in the other col- 
 umns, the low numbers represent the metals, so far as this prop- 
 erty is concerned, most desirable. Those marked below five are 
 malleable metals ; those above five are brittle ; zinc, marked five, 
 separates these two classes, and belongs to one or the other, ac- 
 cording to the way in which it is managed." Allusion is here 
 made to the process of annealing zinc, which has already been 
 alluded to when considering the latter metal in the former part of 
 the work. The special method employed is thus described by 
 the author already quoted : " The simplest way to anneal a zinc 
 die is to place it in the melting ladle with about a tablespoonful 
 of water, removing it in thirty seconds after the water has boiled 
 
 * American Journal of Dental Science, vol. vi, page 367. 
 
I76 MECHANICAL DENTISTRY. 
 
 away. If the fire is a very hot one, remove it immediately on the 
 disappearance of the water. It will often happen that the die is 
 annealed in the process of taking the counter-die. This will more 
 certainly occur when Nos. 7, 8, or 9 (see table), are used for the 
 counter. For example, take tin, using a mass twice the size of 
 the die; should it be heated to 540 (ioo° above melting-point), 
 it would not, allowing for loss of heat by radiation and contact 
 with the cast-iron ring (if one be used), heat the zinc beyond 
 330 . Lead, cast as cool as it could possibly be poured, unless in 
 a very heavy ring (such as a ' cart-wheel box '), or in quantity too 
 small for a well-shaped Counter, would be apt to raise the zinc at 
 least 400°, and so impair its malleability, whilst, if poured as hot 
 as many are in the habit of doing, the zinc will remain as brittle 
 as when first cast." 
 
 The Parker Swaging Device. — This device for swaging dental 
 plates (Fig. 75) consists of two parts : First, a cup made of cast- 
 iron from 3 to 3^2 inches in diameter, and i 1 /* inches in depth, 
 and a " plunger " or " follower," turned to fit the inside of the cup, 
 with a concussion block in the upper end. The lower edge of the 
 plunger is a concave flange so formed that when forced into the 
 cup the contents of the cup will be forced toward a common 
 center. Shot is here employed as the counter, the finest obtain- 
 able, No. 12 being the best. 
 
 In using this device, first prepare, in any suitable manner, a 
 thin metallic model, ]/\ of an inch in thickness over the palatine 
 arch is sufficient ; over this " rough swage " the metallic blanks 
 with a horn mallet, or in any suitable way, until the edges are 
 brought close to the model ; this is to prevent the shot, or other 
 material used, from passing under the plate. Wrap the model 
 and plate with a few thicknesses of tough manilla tissue-paper; 
 this will keep the shot from getting under the plate, and prevent 
 " leading." Fig. 76 shows the device open, ready to have the 
 model introduced. 
 
 When this is done, pour a layer of shot into the cup, sufficient 
 to give the model an even bearing; place the model and plate in 
 the center, and fill up with shot until both are just covered. 
 Now insert the plunger, and be sure that it rests squarely upon the 
 shot, for if it pinches or binds in the cup, and is then hammered 
 upon, it will be almost certain to fracture the cup, while if the 
 
METALLIC DIES AND COUNTER-DIES. 
 
 177 
 
 follower rests entirely on the material in the cup, it will be driven 
 downward and inward, no lateral strain developing. The cup 
 must stand upon an anvil or some other smooth, solid surface, 
 while the hammering is being done. Any weight of hammer may 
 be used — the heavier the hammer the fewer the blows necessary 
 — until the shot is thoroughly condensed ; then open and pour the 
 contents out of the cup. If, on examination, the edges of the 
 plate are not in close contact with the model, bend them down 
 carefully with pliers, replace them in the cup and reswage until 
 
 Fig. 76. 
 
 Fig. 75 
 
 the plate fits the model perfectly. The pressure is so evenly dis- 
 tributed that no amount of hammering will distort the die, and if 
 desirable, after the plate is well fitted to the metallic model, it 
 may be swaged over the original plaster cast. 
 
 This method can also be employed to good advantage in re- 
 swaging an ill-fitting plate, with the teeth on or off, by securing a 
 new impression, trimming or carving model as the case may indi- 
 cate ; then, adjust plate to the plaster model and swage upon it. 
 
CHAPTER XVI. 
 
 PARTIAL DENTURES RETAINED IN THE MOUTH BY MEANS OF 
 
 CLASPS. 
 
 Introductory Remarks. — The almost unlimited modifications 
 in the form of substitutes designed to supply the loss of a portion 
 only of the natural teeth, and the difficulties oftentimes incident 
 to a harmonious arrangement of the teeth of replacement, as well, 
 also, as the impracticability of always securing a perfectly satis- 
 factory and efficient antagonism or closure of the artificial with 
 the natural organs, frequently surround this process with peculiar 
 embarrassments, and often render their successful application 
 extremely difficult. They will, accordingly, be found to demand 
 of the operator the exercise of greater skill, ingenuity, and dis- 
 crimination than are usually required of him in the construction 
 and application of entire dentures. 
 
 Certain general and characteristic forms of substitutes of the 
 kind under consideration derive their distinctive character from 
 the means employed in fixing or retaining them in the mouth. 
 These means of retention may be classified as: (i) Clasps at- 
 tached to the remaining natural teeth ; (2) atmospheric pressure 
 and adhesion. 
 
 Observations on the Use of Clasps. — Clasps or metallic bands 
 have been long and very generally employed as a means of retain- 
 ing parts of sets of teeth in the mouth, and are still used, to a 
 limited extent, for that purpose by many practitioners. When 
 these appliances are skilfully adjusted, and all the conditions per- 
 taining to the mouth and remaining natural teeth are favorable to 
 their application, they afford a certain, permanent, and satisfac- 
 tory means of supporting partial dentures, and may be employed, 
 under such circumstances, with comparative safety to the natural 
 organs. When it is remembered, however, that in a lamentably 
 large proportion of cases, clasps are carelessly or unskilfully 
 formed and fitted to the teeth ; that the organs of support are 
 often indiscriminately selected, and are neither adapted in form, 
 
 178 
 
PARTIAL DENTURES RETAINED BY CLASPS. 
 
 179 
 
 situation, or structure for such uses ; and that they are frequently- 
 diseased and insecurely attached to the jaw, or are mutilated for 
 the reception of clasps, we can readily understand to what unlim- 
 ited extent this method is subject to abuses. In fact, few other 
 special processes in mechanical practice have been so fruitful of 
 evil as that under consideration, and the opprobrium which but 
 too justly attaches to it in professional as well as popular estima- 
 tion, is chargeable more properly to bad faith and unskilfulness on 
 the part of the operator, and to want of necessary attention to the 
 cleanliness of the substitute and the organs of the mouth on the part 
 of the patient, than to any inherent unsuitableness of the method 
 itself. Nevertheless, it must be admitted that, under the most 
 favorable circumstances, the teeth clasped are not wholly exempt 
 from liability to injury, and this circumstance in itself renders it 
 the more imperative that the process should be surrounded by 
 all the safeguards that skill and ingenuity can devise. 
 
 The opinion, at one time current, that the injury inflicted upon 
 the teeth by clasps was mainly the result of mechanical action, 
 has given place to the more defensible view that the causes con- 
 cerned in its production are chiefly of chemical origin. Thus, 
 the secretions of the mouth, with particles of food being retained 
 between the clasp and the tooth for a sufficient period of time, 
 and exposed to the favoring conditions of warmth and immo- 
 bility, suffer a process of putrefactive decomposition by which 
 acids are eliminated, and which, in their nascent state, act with 
 perceptible energy upon the bone constituents of the tooth, pro- 
 ducing disintegration and ultimate decay. The rapidity and ex- 
 tent of this action will depend much upon the nature and quan- 
 tity of the acids present ; the structural characteristics and vital 
 resistance of the teeth ; the mechanical execution, adaptation, and 
 composition of the plate ; and the personal habits of the patient 
 with respect to cleanliness. 
 
 The most usual seat of structural disorganization in these cases 
 is at the neck of the tooth, where the enamel is thinnest, and is 
 sometimes limited to a circumscribed spot, but oftener extends 
 on a line with the gum, involving nearly or quite all of that part 
 of the neck of the tooth embraced by the clasp. At first the 
 enamel becomes bleached and softened as though macerated, and 
 is ordinarily very sensitive to both chemical and mechanical irri- 
 
l80 MECHANICAL DENTISTRY. 
 
 tants. With a continuance of the cause, the superficial portions 
 of the affected parts become more and more thoroughly disin- 
 tegrated, and sooner or later assume the open form and charac- 
 teristics of ordinary decay. If, as was formerly supposed, decay 
 or solution of tooth-bone in these cases resulted from mechanical 
 attrition, or wearing away of the enamel, the injury would be 
 inflicted at points distant from the neck of the tooth where the 
 clasp lies in more direct and immediate contact with the pro- 
 tuberant portions of the crown ; but we find that decay, from this 
 cause, is not only of infrequent occurrence at such points, but, on 
 the contrary, the enamel here is frequently found condensed and 
 polished by the mechanical action of the clasp. Certain condi- 
 tions of the plate and clasp undoubtedly favor mechanical action 
 and accelerate the destruction of the tooth ; as where the clasp 
 bears unequally with sharp and unfinished edges upon the tooth, 
 or where the base is faulty in its adaptation to the mouth, ad- 
 mitting, by its mobility, of irregular traction or pressure upon 
 the organs of support. Whenever the artificial appliance is thus 
 unskilfully constructed and applied, and free interspaces are. fur- 
 nished for the lodgment and retention of particles of food, and 
 the teeth clasped are defective in structure, and we have con- 
 joined with these, an utter disregard of cleanliness in regard to 
 the substitute and remaining natural teeth, the destruction of the 
 latter is certain, rapid, and generally irretrievable. 
 
 The Teeth to which it is most Proper to Attach Clasps. — The 
 utility, comfort, and appearance of a partial set of artificial teeth 
 in the mouth will depend much upon the fitness of the natural 
 organs- selected for the purpose of support. "A clasp," says 
 Professor Harris, " should never be applied to a loose tooth, or to 
 one situated in a diseased socket, or which is so much affected by 
 caries as to render its perfect restoration and permanent preser- 
 vation impracticable, and when none but such can be had, the 
 proper course to pursue is to extract every tooth in the jaw, and 
 replace the loss of the whole with an entire denture. The appli- 
 cation of clasps to diseased or loose teeth, always aggravates the 
 morbid condition of the parts, and causes the substitute which 
 they sustain to become a source of annoyance to the patient. Be- 
 sides, such teeth can be retained in the mouth only for a short 
 time, and when they give way, the artificial appliance becomes 
 
PARTIAL DENTURES RETAINED BY CLASPS. l8l 
 
 useless, and even while it is worn, it is not held firmly in place, 
 but is moved up and down by the action of the lips and tongue, so 
 that its presence can hardly escape observation from the most 
 casual observer."* 
 
 Teeth, also, that are too short to admit of sufficient breadth to 
 the clasp to impart stability to the substitute, and those that 
 stand very irregularly in the arch, rendering it difficult for the 
 patient to apply and remove the appliance, are unsuitable as 
 organs of support. 
 
 In reference to the individual classes of teeth, it may be ob- 
 served that the incisors, both as regards form and situation, are 
 inadmissible for clasping, and are, therefore, never used for this 
 purpose. The cuspid teeth, likewise, being placed conspicuously 
 in the front part of the mouth, cannot be securely embraced with- 
 out manifest exposure of the clasp ; besides, the conical form of 
 these teeth makes the use of a very slender clasp indispensable ; 
 hence, these teeth are rarely employed, and may only be used 
 when, in the judgment of the operator, the necessities of the 
 patient for the time being seem to require it. 
 
 Either the anterior or the second molars, when sound and firm, 
 offer, in respect of their general conformation and position in the 
 arch, the most desirable and efficient support for parts of sets of 
 teeth. The crowns of these teeth generally afford ample breadth 
 to the clasp ; have nearly parallel walls ; and furnish, by the 
 strength and immobility of their attachments to the jaw, the 
 greatest security to the artificial appliance. The anterior molars 
 are preferable where these are remaining in good condition, or 
 are susceptible of being properly restored and preserved if dis- 
 eased or carious. 
 
 Of the bicuspids, the posterior are to be selected, if practicable, 
 as these better favor the concealment of the clasps ; to effect 
 which more perfectly, in the use of either the first or second 
 bicuspids, it will be sufficient in many cases to embrace only the 
 posterior half of the crown. 
 
 The third molars, or wisdom teeth, will seldom admit of the 
 application of clasps, as the crowns of these teeth are usually very 
 short and cone-shaped, the walls converging abruptly from' the 
 gum ; besides, the retractive forces applied to the anterior teeth of 
 
 *" Principles and Practice of Dental Surgery," page 717. 
 
1 82 MECHANICAL DENTISTRY. 
 
 the substitute would, on account of the increased leverage con- 
 sequent upon the extension of the plate back to these teeth, tend 
 either to disengage the clasps or produce displacement of the 
 teeth to which they are applied. 
 
 In supplying the loss of the inferior incisors, the appliance 
 should, as a general thing, be attached either to the anterior or 
 posterior bicuspids, as these teeth stand more nearly vertical in 
 the arch. In fixing partial lower dentures, it will be sufficient to 
 simply provide against mobility of the base, as they are favored 
 rather than opposed, as above, by gravitation. 
 
 The replacement of the inferior teeth posterior to one or both 
 bicuspids, however, is more frequently demanded ; in which case 
 it is customary to attach the clasps to the teeth immediately in 
 front of and adjoining the vacuities on each side. It will not, 
 however, be necessary to attach clasps in these cases whenever the 
 edentulous portions of the jaw present a distinctly scooped form 
 or marked concavity of outline, forming a kind of bed for the 
 plate. If, on the other hand, the ridge falls back with a tolerably 
 uniform inclination from the teeth in front, with no sufficient ele- 
 vation at the base of the coronoid process, it may become neces- 
 sary to provide against backward displacement of the substitute 
 by attaching clasps, as before stated, to the teeth immediately in 
 front. In any case, if the third molars remain, partial or stay 
 clasps may be attached to each heel of the plate, and so adjusted 
 as to rest against the anterior face of these teeth, obviating en- 
 tirely the necessity of clasps in front. 
 
 Separation of the Teeth for the Reception of Clasps. — The 
 practice of separating the teeth with the file to provide for the ap- 
 plication of clasps should always be avoided, since the liability of 
 the teeth, thus denuded of enamel, to decay is greatly increased 
 under circumstances so favorable to their disintegration. In the 
 case of young subjects, especially, where the teeth are but imper- 
 fectly consolidated, and in adults whose teeth are defectively 
 organized, presenting but a feeble resistance to the disintegrating 
 agents usually present in the mouth, the use of the file, for the 
 purpose indicated, is pernicious, and should never be resorted to. 
 When it is found necessary to separate or straighten up the sides 
 of the teeth for the reception of clasps, a thin diamond disc should 
 be employed, as it is less annoying to the patient, does the work 
 
PARTIAL DENTURES RETAINED BY CLASPS. 
 
 183 
 
 in iess time, and is not so destructive to the tooth structure as 
 the file. 
 
 Whenever a plain necessity for this operation exists, a careful 
 examination of all the teeth to which it is proper to apply clasps 
 should be made, and if decay is found upon their proximate sur- 
 faces, the separation should be made between the teeth so af- 
 fected ; and this circumstance should, in most cases, determine 
 the selection, though the affected tooth or the one adjoining may 
 not be esteemed, in other respects, the best for the purposes of 
 support. If decay exists on the proximate surface of only one of 
 the teeth to be separated, a safe-sided diamond disc, revolved by 
 the dental engine, should be employed, and the cutting confined 
 entirely to the carious tooth, leaving the enamel of the one adjoin- 
 
 Fig. 77. 
 
 ing unbroken. The cavity of decay should be well filled, and the 
 filed surface thoroughly condensed and polished. 
 
 Modifications in the Form of Clasps. — 1. Plain Band. The 
 most usual form of clasp is that shown in Fig. Jj. It consists of 
 a plain metallic band of greater or less width and thickness, and 
 is made to embrace the larger portion of the circumference of the 
 tooth. In regard to the general properties of metallic clasps, it 
 may be said that they should be, as nearly as practicable, of the 
 same quality or fineness as the plate or base to which they are 
 united ; they should be heavy enough to impart adequate security 
 to the attachment — usual thickness, 22 of the gage plate — and 
 sufficiently elastic to embrace accurately the more contracted 
 parts of the teeth after having been temporarily forced apart 
 in passing over the enlarged portions of the crowns. In con- 
 structing a plain band or clasp, a strip of sheet-lead or other 
 
1 84 
 
 MECHANICAL DENTISTRY. 
 
 pliable substance may first be fitted accurately to the plaster 
 tooth, making it of the required width, and shaping the edge 
 next the gum in conformity with the irregularities in the latter 
 around the neck of the tooth ; the exact counterpart of the pattern 
 thus obtained is then cut from the plate to be used in the forma- 
 tion of the clasp. The strip thus obtained is then bent with 
 round-nosed or grooved pliers (Fig. 78), until conformed as per- 
 fectly as possible to every portion of the surface of the tooth em- 
 braced by it. This coaptation should be sufficiently accurate to 
 exclude perfectly all solid substances from between the clasp and 
 the tooth. A more accurate adaptation of the clasp may be se- 
 cured in the following manner: First secure a pattern, as before 
 described, and by this cut from a thin strip of platinum, say No. 
 
 Fig. 78. 
 
 30 or 32 of the gage plate, a band of the required size and form, 
 and press or burnish it accurately to the form of the plaster tooth. 
 The soft and pliant condition of this metal will admit of its being 
 easily adapted to any irregularities upon the lateral walls of the 
 tooth. The band thus molded to the tooth is then carefully re- 
 moved from the model, and its central portion filled with a mix- 
 ture of plaster and sand, with a small metallic wire or bar passing 
 through the center to support it while soldering. The outer or 
 exposed surface is then coated with a mixture of borax, and small 
 scraps or fragments of gold plate of equal fineness with the main 
 plate are placed at intervals and fused with the blowpipe until 
 diffused uniformly over the surface. Small pieces may be added 
 from time to time, until the required thickness of the clasp is ob- 
 tained. The piece should be heated uniformly throughout to in- 
 duce an even flow of the gold over the exterior surface of the 
 
PARTIAL DENTURES RETAINED BY CLASPS. 1 85 
 
 platinum ring. By this method a faultless adaptation of the clasp 
 to the tooth may be secured, provided the form of the latter is 
 correctly represented on the model. In all cases where the plain 
 band is used, it should be made as broad as the tooth will admit 
 of, as a clasp so formed gives greater stability to the plate, and 
 does not endanger the tooth clasped in as great a degree as a 
 narrow one. 
 
 2. Standard Clasp. — To guard more perfectly against the reten- 
 tion of vitiated secretions and particles of food around the neck 
 of the tooth, a method of constructing clasps has been devised 
 and introduced to the notice of the profession by Dr. C. W. Spald- 
 ing, which, by leaving the cervical portion of the tooth in a great 
 degree uncovered, permits, as he claims, the action of the tongue 
 
 Fig. 79. 
 
 and the natural circulation of the fluids of the mouth, to wash or 
 cleanse that portion of the tooth most liable to be injuriously 
 affected. In commenting on this method, Dr. Spalding remarks : 
 " I have for many years been in the habit of employing narrow 
 clasps for the purposes of support, making them of sufficient 
 thickness to give the required strength, and attaching them to the 
 plate by means of standards, so arranged as to induce the re- 
 moval of accumulations between the clasp and tooth, by the cir- 
 culation of the saliva (Fig. 79). The use of one or more stand- 
 ards as a means of attachment also provides, by a variation of 
 their length, for the grasping of the tooth at any desired point. 
 If the tooth is long, and particularly if it is at the same time bell- 
 crowned, the point selected should be toward the grinding sur- 
 
1 86 MECHANICAL DENTISTRY. 
 
 face, as far from the gum as is found practicable. If the tooth is 
 short and of such form that it can be successfully clasped at no 
 other point than that near the gum, the plate should be cut away 
 at least I or 1^2 lines from the tooth, and standards introduced 
 for the purpose of promoting circulation, by affording a free pass- 
 age for the ingress and egress of fluids. These standards should 
 also be narrow, no wider than the clasp itself, and should consti- 
 tute the only point of union between the clasp and plate. Half- 
 round wire will be found to be a very convenient article for mak- 
 ing clasps. The particular form of the clasp is, however, imma- 
 terial if it is both narrow and strong." 
 
 3. Scalloped Clasp. — Somewhat analogous in form to the clasp 
 just described, and constructed with a similar design, is the one 
 recommended by Dr. B. T. Whitney. A plain band of gold is 
 fitted to the tooth in the manner first described, when that por- 
 tion of it next the gum on the lingual side of the tooth is scal- 
 loped or cut away in the form of a semicircle or arch, the ends of 
 the clasp being in like manner narrowed sufficiently to relieve 
 them from contact with the neck of the tooth. The intermediate 
 points of the clasp which serve to unite the latter to the base may 
 be two or more in number, and should be wide enough to impart 
 adequate strength to the attachment. A clasp so formed and ap- 
 plied to the base will present very nearly the appearance of the 
 standard clasp as represented in Fig. 79. Dr. W. recommends 
 soldering but a single point at first, and then having tried the 
 plate in the mouth and adjusted the clasp properly to the tooth, 
 remove and solder the remaining point or points. 
 
 4. Partial or Stay Clasp. — This form of clasp, instead of em- 
 bracing the tooth, is designed to steady or fix the substitute in 
 place, by simply resting against one side of the tooth to which it 
 is applied. They should be so connected to the plate that, when 
 pressed over the enlarged portions of the crowns of the teeth, they 
 will spring readily into place and adapt themselves closely to the 
 more contracted parts near the gum. In cases where there is no 
 adequate opposing force to that exerted by the clasp, care should 
 be taken that no more pressure is produced than is necessary to 
 keep the substitute in place, as, without this precaution, outward 
 displacement of the teeth is liable to occur, and the appliance, 
 losing its bearing upon the teeth, soon becomes loosened and in- 
 
PARTIAL DENTURES RETAINED BY CLASPS. 
 
 I8 7 
 
 secure in the mouth. The result alluded to should be particu- 
 larly guarded against in the case of young subjects, whose teeth 
 are easily moved by the application of very slight forces. 
 
 Modifications in the Form of Plates for Partial Dentures Sup- 
 ported in the Mouth by Clasps. — The particular form and dimen- 
 sions of a plate, when clasps are used, will be mainly determined 
 by the number and position of the teeth to be replaced, and by the 
 location of the natural organs to which the clasps are attached. 
 It will be sufficient in this place to indicate the leading forms as 
 they relate to the substitution of the several classes of teeth. In 
 
 Fig. 80. 
 
 supplying the loss of a superior central or lateral incisor, it will 
 be sufficient in many cases to attach the plate to either a bicuspid 
 or molar on the same side. If two or more of the front teeth, 
 however, are to be replaced, it is better to extend the plate on 
 each side of the palatal arch, and attach to a bicuspid or molar 
 (Fig. 80). In all cases where it is necessary to extend a narrow 
 plate from the extreme front part of the mouth to a single tooth 
 situated posteriorly in the arch, the former should be strength- 
 ened by soldering a narrow rim of plate or half-round wire along 
 the border next the teeth, and the clasp should, whenever prac- 
 ticable, pass in front of and embrace the anterior face of the tooth 
 to which it is applied. 
 
 If an anterior bicuspid is to be replaced, the plate may be 
 attached to the adjoining bicuspid, or if both are absent, then to 
 
I5C MECHANICAL DENTISTRY. 
 
 the first molar, or the clasp may embrace both of the latter if 
 remaining and no separation between them exists. 
 
 Take a case where it is necessary to supply the loss of the two 
 bicuspids on one side, and the first bicuspid and first molar on the 
 opposite, the plate being- attached to an anterior molar and second 
 bicuspid. The antero-posterior extension of the plate, in con- 
 nection with the bicuspid tooth, greatly favors the stability of the 
 substitute, and, provided the plate and clasp are accurately fitted 
 to the parts, the support afforded by a bicuspid tooth under such 
 circumstances is equivalent to that furnished by a clasp about a 
 
 Fig. 8i. 
 
 firm and well-formed molar. A base so supported may be made 
 to sustain a number of teeth with much security. 
 
 Either the anterior or posterior molars, if firm and securely 
 attached in the jaw, will afford adequate support to a plate replac- 
 ing all of the teeth anterior to them. Even a single molar situ- 
 ated on either side of the arch, if similarly circumstanced, may be 
 made to sustain, with tolerable firmness, a base supplying the loss 
 of all the remaining teeth, though, ordinarily, it is better to extract 
 such teeth and substitute an entire upper denture. Tn all cases 
 where any considerable number of teeth anterior to those clasped 
 are to be replaced, and a vacuity on the ridge exists posterior to 
 the latter, the plate should be extended back and overlap the ridge 
 (Fig. 8ij, the latter affording a counterpoint of resistance when 
 traction is made upon the anterior teeth, thus directing the forces 
 
PARTIAL DENTURES RETAINED BY CLASPS. 
 
 189 
 
 applied more on a line with the long axes of the teeth that sustain 
 the appliance. 
 
 In supplying the loss of the inferior molars and bicuspids, or 
 any number of these teeth, the form of plate represented in Fig. 
 82 is generally employed. The parts of the plate overlapping and 
 resting upon the ridge behind are connected with each other by 
 a narrow strip of plate extending round the ridge, hugging the 
 lingual side of the anterior teeth. This latter portion of the plate 
 should be accurately swaged to the form of the gum on which it 
 rests, and should be made narrow enough to avoid encroaching 
 upon the reflected portion of mucous membrane, the glands be- 
 neath the tongue, or the 
 frenum linguae. Fig. 82. 
 
 Reinforcing. — To avoid 
 wounding these parts, and 
 to allow them unobstructed 
 play, it will be necessary to 
 make this portion of the 
 plate quite narrow; and as 
 a single thickness of plate 
 would not impart adequate 
 strength, it is better practice 
 to reinforce or double this 
 connecting band — the dupli- 
 cate band extending back to 
 
 the lateral wings of the plate, and crossing them obliquely, as in- 
 dicated by the lines in Fig. 82. Additional strength will be given 
 by doubling the entire plate, but this is not generally required. 
 The outer border of those portions of the plate overlapping the 
 ridge may be turned up to the depth of from y 2 of a line to a line, 
 to form a groove or socket for the reception of the ends of gum 
 teeth, or blocks, if such are used ; while the inner margins should 
 terminate in a rounded edge, extending from heel to heel of the 
 plate, this form being given to it either by turning the edge over 
 and filling in the groove with solder, or by soldering a narrow 
 strip of plate or half-round gold wire along the border. The cir- 
 cumstances or conditions which make the use of clasps necessary 
 in these cases, as well as those, also, which contraindicate their 
 employment, have already been noticed. The practice of extend- 
 
190 
 
 MECHANICAL DENTISTRY. 
 
 ing a narrow band or wire from the sides of the plate round the 
 outer border of the ridge in front of the anterior teeth, to prevent 
 a backward displacement of the base, is liable to produce irrita- 
 tion and tenderness of the mucous membrane immediately over 
 the roots of the anterior teeth, and should, therefore, never be 
 resorted to unless there are no teeth remaining to which clasps 
 may be applied. 
 
 If the appliance is designed to restore the loss of teeth recently 
 extracted, and where but little or no change has occurred from 
 absorption of the parts, the portions of the plate which pass in 
 between the adjoining teeth should terminate a line or more 
 within the outer circle of the remaining teeth ; and where the 
 space, if it happens in the front part of the mouth, admits of two 
 or more teeth, the edges of the extended portion of plate should 
 be scalloped in correspondence with the festoons of the gum, as 
 seen in Fig. 80. In such cases, plain or plate teeth, by which is 
 meant those which represent only the crowns of the natural or- 
 gans, should be employed; these, resting on the edge of the plate, 
 will overlap somewhat, with their anterior edges resting directly 
 upon the gum in front, taking the place occupied by the crowns 
 of the extracted teeth. On the other hand, if sufficient time has 
 elapsed after the extraction of the teeth to permit the changes in 
 the form of the ridge to occur incident to partial or complete 
 absorption of the parts, and a greater or less concavity exists 
 between and above the teeth on the outside of the jaw, the plate, 
 where it passes into the interspace, should extend some distance 
 over the border of the ridge. 
 
 Swaging the Plate. — Having determined upon the proper form 
 and dimensions of the plate for any given case, its outlines may 
 first be traced upon the model ; from this an exact pattern in lead 
 may be obtained, or the pattern may be sufficiently ample to par- 
 tially overlap the cut extremities of the teeth when the latter are 
 not represented upon the die, having been previously cut from 
 the model, as shown in Fig. 57, page 150. The outlines of the 
 pattern arc then traced upon the plate of gold, or other metal 
 used for the base. The redundant portions of plate are then cut 
 away with plate-shears and forceps, and the edges trimmed 
 smooth with a file. A very convenient and almost indispensable 
 instrument for cutting away the plate in conformity with the 
 
PARTIAL DENTURES RETAINED BY CLASPS. 
 
 191 
 
 Fig. 83. 
 
 palatal curvatures of the teeth, is the plate-forceps as exhibited 
 in Fig. 83. 
 
 The plate cut to the proper form is now placed upon the die and 
 brought as nearly as possible into adaptation with a wooden or 
 horn mallet ; it is then placed between the die and counter, the 
 latter resting on an anvil or other equally resisting surface, when 
 the two metallic pieces are brought forcibly together with a few 
 steady and well-directed blows of a heavy hammer. Tilting of 
 the die, resulting sometimes unavoidably from a one-sided blow, 
 may be obviated by placing a cone-shaped piece of cast-iron, 
 brass, or zinc over the die, the base of the cone resting on the 
 back of the die ; by this expedient the force of the blow is equal- 
 ized and concentrated more directly over the die. The metallic 
 swages should at first be brought cau- 
 tiously together, and should be separated 
 after the first blow or two, to enable the 
 manipulator to detect and remedy any 
 malposition of the plate before it becomes 
 intractable from continued swaging. If, 
 in the process of stamping, any portion 
 of the plate is found cracking or parting, 
 its further extension at that point may be 
 prevented by flowing a little solder at the 
 termination of the fissure. 
 
 Annealing the Plate. — During the pro- 
 gress of swaging the plate should be fre- 
 quently annealed, which is done by bring- 
 ing it to a full red heat under the blow- 
 pipe or by placing it in the furnace ; the 
 plate is thus rendered more pliant, and 
 can be more readily and perfectly forced into adaptation to the 
 irregularities on the face of the die. 
 
 If, after somewhat protracted swaging, the plate is not con- 
 formed perfectly to the face of the die, another and unused coun- 
 ter should be substituted for that in use ; and, indeed, it is better 
 in all cases to have duplicate copies both of the die and counter in 
 reserve with which to complete the swaging, inasmuch as more 
 or less deformity of both swages unavoidably occurs before the 
 plate is brought into very accurate coaptation with the die. The 
 
I92 MECHANICAL DENTISTRY. 
 
 stamping conducted thus far, the plate may be applied to the plas- 
 ter model, and if found too full at any point, it should be trimmed 
 with a file to the exact dimensions required. The margins of the 
 plate adjoining the necks of the teeth should be permitted either 
 to lie closely to them, or should be cut away, leaving a space 
 equal to a line or more between the plate and the teeth; for if 
 but a very narrow line of uncovered gum remains at these points, 
 injury to the parts immediately surrounding the necks of the 
 teeth is more liable to occur from strangulation of the interposed 
 gum, than if the plate were further removed from the teeth or 
 rested directly against them. 
 
 Adjusting and Strengthening the Projections or Tongues of 
 the Plate. — If the portion of the plate which passes in between 
 the remaining teeth is quite narrow, as where but a single tooth 
 is to be supplied, it should be strengthened by wiring the edges or 
 doubling the plate at such a point. It is also advisable in many 
 cases, in order to provide more perfectly against fracture or dis- 
 tortion of the base in mastication, to wire or double the entire 
 border of the plate adjoining the necks of the teeth. Narrow 
 bands of gold resting against the necks of the teeth, constructed 
 and adjusted after the manner of stay clasps, are sometimes sol- 
 dered to the edge of the plate next the teeth ; but unless the sub- 
 stitute is frequently cleansed, as well, also, as the teeth to which 
 the clasps are applied, serious injury is likely to be inflicted upon 
 the teeth implicated. 
 
 The edges of those parts of the plate occupying the vacuities 
 on the ridge should be filed thin to admit of a more accurate adap- 
 tation of the artificial with the natural gum, and should not, as 
 before observed, ordinarily extend beyond the outer circle of the 
 contiguous teeth, allowing the gum extremity of the artificial tooth 
 to overlap and rest directly on the natural gum above. If, how- 
 ever, the concavity between and above the teeth on the external 
 border of the ridge is considerable, the interdentinal portions of 
 the plate should overlap the border completely and underlie the 
 porcelain gum. 
 
 Adjusting Clasps to the Plate. — Having proceeded thus far in 
 the operation, the plate and clasps should next be united to each 
 other, and the utility and comfort of the appliance in the mouth, as 
 well as the safety of the natural organs used for the purpose of sup- 
 
PARTIAL DENTURES RETAINED BY CLASPS. 
 
 193 
 
 port, will depend in a great measure upon the accurateness of the 
 relation of the several parts of the appliance to the organs of the 
 mouth; it being a matter of primary importance that the various 
 parts of the substitute should be so adjusted to the remaining 
 teeth — especially those to which the clasps are applied — and the 
 ridge and palate, that it shall not, in any material degree, act as a 
 retractor upon the organs of support, or furnish interspaces for 
 the lodgment of food, while at the same time it should be so 
 fitted as easily to be removed and readjusted by the patient. 
 
 Manner of Securing Clasps to the Plate. — The clasps having 
 been fitted to the plaster teeth and the base swaged to the form of 
 the palatal arch and ridge, the plate is placed in its proper position 
 in the mouth and an impression in wax taken of the. latter with 
 the plate in place. The impression, with the plate adhering, is 
 then removed from the mouth, its surface oiled, and a model 
 obtained in the manner heretofore described. If, in separating 
 the model and impression, the plate adheres to the latter, it should 
 be detached and adjusted to the model and the clasps arranged 
 upon the plaster teeth. The plate and clasps may now be at- 
 tached to each other temporarily, with adhesive wax, in the rela- 
 tion they occupy on the model, and then removed carefully and 
 the clasps and palatal face of the plate imbedded in a mixture of 
 nearly equal parts of plaster, sand, and asbestos. Before uniting 
 the two pieces on the model with wax, however, the ends of the 
 clasps should be slightly spread apart, in order that they may 
 part readily from the plaster teeth, without, in any degree, chang- 
 ing their exact relation to the plate ; in doing this, it should be 
 observed that all parts of the clasps which are to be united to 
 the plate should remain in close contact with the plaster teeth. 
 After the plaster mixture, in which the plate and clasps are im- 
 bedded, has become sufficiently hard, the portions of wax which 
 temporarily united the latter should be removed, and the surfaces 
 of the clasps and plate, where they unite with each other, coated 
 with borax ground in water to the consistency of cream ; small 
 pieces of solder are then placed along the lines of contact, the in- 
 vestment heated in the furnace until the plate acquires a dull red 
 heat, when it is removed, placed upon a suitable holder, and the 
 solder fused with the blowpipe. 
 
 Whenever the form and inclination of the teeth to be clasped 
 
 13 
 
194 
 
 MECHANICAL DENTISTRY. 
 
 are not fairly represented on the model, owing to dragging or dis- 
 placement of the wax in withdrawing the impression, the difficul- 
 ties of securing a proper relative adjustment of the several parts 
 of the appliance will be increased ; but either of the following 
 methods, if carefully and accurately manipulated, will secure 
 accurate results : 
 
 i. Plaster-of-Paris or modeling compound may be substituted 
 for wax when taking an impression with the plate in the mouth. 
 With the proper use of these materials, the exact form and in- 
 clination of the teeth will be better preserved ; and when em- 
 ployed they should be filled in with plaster for the model imme- 
 diately after removing them from the mouth. The subsequent 
 steps in the operation are precisely similar to those described 
 when wax is used. 
 
 2. Another method is to adjust the clasps and plate to the parts 
 in the mouth, attach them temporarily in their proper relation, 
 and remove, invest, and solder in the usual way. This may be 
 accomplished in the following manner: First, spread apart the 
 ends of the clasp somewhat to permit it easily to be removed from 
 the tooth ; place this upon the tooth in the mouth to be clasped ; 
 then adjust the plate, and attach the two to each other by press- 
 ing a piece of stiff, adhesive wax in against the clasp and plate 
 where they unite ; harden the wax by placing against it, for a few 
 minutes, a pledget of cotton, or the end of a napkin, moist with 
 cold water; then remove the plate and clasp carefully from the 
 mouth, and invest and solder as before. The plate, with one clasp 
 permanently attached, is now placed back in the mouth, and the 
 second clasp adjusted to the tooth on the opposite side in the 
 manner before alluded to ; this is then temporarily fastened to the 
 plate and otherwise treated in like manner as the one first de- 
 scribed. If the teeth to be clasped are favorably formed and 
 regularly arranged in the arch, both clasps may, at the same time, 
 be temporarily attached to the plate in the first instance; if not, 
 it will be impracticable to remove them from the teeth without 
 disturbing the wax and changing their relation to the base and 
 the teeth clasped. The additional labor and consumption of time 
 incident to a separate attachment of the clasps will, in proportion 
 as they secure better results, amply reward the operator for his 
 painstaking. 
 
PARTIAL DENTURES RETAINED BY CLASPS. 
 
 195 
 
 Plaster is sometimes substituted for wax in this process ; in 
 which case it is introduced into the mouth on a small piece of wax 
 or sheet-lead and pressed gently against the uniting portions of 
 the plate and clasp, and allowed to remain until sufficiently hard. 
 Any superfluous portions around the tooth that may hinder the 
 easy removal of the clasp should now be cut away, when the 
 pieces so attached to each other are removed from the mouth. A 
 separation of the plaster from the clasp or plate, or both, may oc- 
 cur when removing the latter ; in this case the several parts may 
 be readily and accurately adjusted to each other again in their 
 exact relation when out of the mouth, as the latter will be plainly 
 indicated by the impression made by the plate and clasp in the 
 plaster. Being readjusted, they may be further secured by stick- 
 ing them together with a little softened wax, when they are in- 
 vested, the temporary fastening of plaster removed, and the pieces 
 united by soldering. The use of plaster in these cases unques- 
 tionably possesses many advantages over wax for the purpose, 
 as the latter is liable, unless most skilfully manipulated, to become 
 
 Fig. 84. 
 
 displaced in removing it from the mouth ; and this change, when 
 it occurs, not being indicated by inspection of the wax, is incapa- 
 ble of timely correction. 
 
 3. Still another method is that contrived by Dr. Fogle and 
 described by Dr. Cushman in the tenth volume of the American 
 Journal of Dental Science. It consists in securing the proper rela- 
 tion of the clasps to the teeth in the mouth by the use, in the first 
 instance, of what are termed " temporary fastenings." The plate 
 
iq6 mechanical dentistry. 
 
 and clasps are first applied to the model, and are then connected 
 by a narrow strip of plate or piece of wire bent in the form of a 
 bow, the concavity facing the model, one end of which is soldered 
 to the palatal side of the clasp, and the other to a contiguous 
 point upon the plate, as exhibited in Fig. 84, and the pieces thus 
 temporarily united are removed from the model and adjusted to 
 the parts in the mouth. If the position of the clasps is found in 
 any respect faulty, they can be easily and accurately adapted to 
 the walls of the teeth by bending or twisting the connecting strip 
 in any desired direction with pliers or other instruments suitable 
 for the purpose. This accomplished, the plate and clasps are 
 removed, and the operation of permanently uniting the clasps to 
 the plate performed in the usual manner. 
 
 In the use of partial dentures, there is always increased liability 
 to injury of the soft parts by reason of pressure being concen- 
 trated upon limited or circumscribed portions of the alveolar ridge 
 embraced in interdental spaces, thereby diminishing resistance to 
 the pressure of the plate at such points. As a consequence, the 
 latter is forced into the soft tissues, producing more or less irrita- 
 tion and inflammation, and consequent tenderness and pain on 
 pressure, and, generally, either partial denudation of the necks of 
 the natural teeth abutting upon the interdental spaces, or stran- 
 gulation, congestion, and hypertrophy of the gum in immediate 
 contact with them. 
 
 Clasps with Spurs. — A simple device, by which the results 
 alluded to may be obviated, consists in attaching to the clasps, 
 above or below, a strip or spur of gold at suitable points, long 
 enough to overlap or rest upon the masticating surface of the 
 tooth clasped, forming a hook or partial crown-cap. These will 
 afford fixed points of resistance to pressure and effectually pre- 
 vent the plate impinging upon the underlying tissues. The same 
 expedient may be adopted also in the case of partial dentures 
 retained by adhesion or atmospheric pressure, by attaching sim- 
 ilar gold spurs or caps to the border of the plate at suitable points 
 contiguous to the bicuspids and molars. 
 
 Charles Rathbun, of London, England, relates, in the Dental 
 Cosmos of December, 1886, a method of constructing partial 
 pieces which embodies the same principle of crown-support as 
 described above, the essential details of which are here given: 
 
PARTIAL DENTURES RETAINED BY CLASPS. 
 
 197 
 
 In Fig. 85 we have the first bicuspid standing; the second bi- 
 cuspid and cuspid in that case filling the role of the lateral, miss- 
 ing from its position. The bicuspid is pear-shaped, its largest 
 diameter being just below the grinding surface, and the molar is 
 a trifle undercut. A No. 7 or 8 English gage gold plate, struck 
 from a model made from a modeling compound impression, would 
 not touch the necks of either the bicuspid or molar, owing to the 
 fact that these teeth would " draw " a little in the impression, and 
 it should be fitted over the shoulder at the neck on the lingual side 
 of the cuspid, left clear of it at the distal side, and have a stay or 
 clip resting just above the prominence on that side of the tooth. 
 A band should be soldered to the plate at the lingual side of the 
 bicuspid, to grasp that tooth at its largest point, viz., about one- 
 third of the distance from the grinding surface to the neck ; also, 
 a band fitted to the molar to reach from about the middle of the 
 lingual side far enough around the mesial face to clasp over the 
 prominence at the mesio-buccal aspect of the tooth ; this band to 
 
 Fig. 85. 
 
 Fig. 86. 
 
 be fitted to grasp the tooth at its fullest part, as in the case of 
 the bicuspid. (See Fig. 86.) Wires or clasps at the necks of 
 teeth of this class do no end of damage to the teeth, and are open 
 to the great objection that a case may go in very hard, and yet 
 when the clasps are past the large part of the teeth the case is 
 quite loose and shaky. The bands I have described do not bear 
 on the teeth at all until the case is within about a line of its place, 
 and then each one bears on its own tooth irrespective of the 
 others, and, be it borne in mind, touches the tooth at a point 
 where the chance of decay is simply infinitesimal. If a porce- 
 lain cuspid and bicuspid be ground in properly, the clasps will 
 not be visible externally, which cannot be said of the broad gold 
 band carried across the buccal face of the natural tooth. 
 
CHAPTER XVII. 
 
 PARTIAL DENTURES SUPPORTED BY ATMOSPHERIC PRESSURE 
 
 OR ADHESION. 
 
 The method of attaching partial sets of teeth to the superior 
 jaw by means of atmospheric pressure, or by adhesion, is much 
 more generally practised than formerly, and whenever the con- 
 dition of the soft parts of the mouth, the general configuration of 
 the palatal arch, and the antagonism or occlusion of the artificial 
 with the natural teeth favor its adoption, there are good and suffi- 
 cient reasons why either of these forces should, in all practicable 
 cases, be utilized in preference to the use of clasps for purposes of 
 attachment. 
 
 Modifications in the Form of the Base. — If vacuities exist at 
 various points on the ridge, the plate on which the teeth of 
 replacement are mounted should be ample in its dimensions, 
 covering nearly or quite all of the hard palate. The general form 
 of the base, where several teeth scattered throughout the arch are 
 required, is shown in Fig. 87. In most cases, whether but one or 
 a greater number of teeth are to be replaced, increased adherence 
 and stability of the substitute will be better secured by permitting 
 the plate to cover the larger portion of the roof of the mouth ; 
 though, in cases that present the best form of the vault, a dimin- 
 ished surface may be given to the base with equally satisfactory 
 results. In the substitution of a single incisor, for example, it will 
 frequently be sufficient to employ a very small plate, covering only 
 a part of the anterior sloping wall of the palate. In the latter case 
 the plate used may be very thin, say No. 30 standard gage ; it 
 will thus impede the movements of the tongue less, and may be 
 swaged more accurately to the parts. If constructed with an air- 
 chamber, the latter should be quite shallow. 
 
 A somewhat anomalous form of atmospheric-pressure plate, 
 employed in the substitution of one or two bicuspid teeth on each 
 side, is described by Professor Taft, the design of which is to 
 secure in such cases increased stability of the substitute, while 
 
 198 
 
PARTIAL DENTURES HELD BY ATMOSPHERIC PRESSURE. 
 
 199 
 
 much of the palatal arch is left uncovered. It consists of two lat- 
 eral cavity plates accurately adjusted to the sloping walls of the 
 palate on each side, immediately adjoining and partly occupying 
 the spaces to be supplied. These lateral plates may be made as 
 large as a dime, or somewhat larger, and of an elliptical shape if 
 both bicuspids on the same side are to be replaced, and are con- 
 nected with each other by a narrow band of gold plate, two lines 
 or more in width, having an anterior curvature, and resting on the 
 front wall of the palate, two or three lines behind the anterior 
 teeth. The entire appliance may be constructed from a single 
 piece of gold plate swaged accurately to the parts ; or the lateral 
 plates and connecting band may be separately swaged and secured 
 
 Fig. 87. 
 
 in their proper relation to each other in the mouth with wax or 
 plaster, when they are carefully removed, invested, and soldered 
 together ; it should then be reswaged to correct any change of re- 
 lation that may have happened during the concluding manipula- 
 tions. The liability of the plate to ride upon the central and raised 
 portion of the palate, when pressure is made upon one side, throw- 
 ing the plate off from the ridge on the other, as in the case of a 
 base extending across the arch, is in a great degree obviated by 
 the method just described. 
 
 Manner of Forming an Air-chamber. — Atmospheric-pressure 
 plates for partial cases are constructed with a central air-cham- 
 ber ; in which case, the part of the model representing the chamber 
 
200 MECHANICAL DENTISTRY. 
 
 may be formed in either of the ways mentioned in the chapter on 
 Plaster Models. The model prepared, the form of the plate to be 
 used is first indicated thereon, and from this a pattern in sheet- 
 lead is obtained, which is placed on the plate of gold or other 
 metal, and its outlines traced with a pointed instrument ; the re- 
 dundant portions are then cut away with plate shears and forceps. 
 The plate is now placed on the die and brought as nearly as pos- 
 sible into adaptation to the latter with the No. i counter-die (see 
 Progressive Counter-dies) ; it is then interposed between the die 
 and the larger counter, and swaged until it conforms perfectly to 
 the face of the former, annealing the plate frequently to render it 
 more pliant and manageable under the hammer. 
 
 The Use of a Tracer in the Swaging Process. — Unless the plate 
 used is purer and thinner than is generally employed, or than is 
 consistent with the required strength, it will fail to be forced per- 
 fectly into the groove around the chamber by the process of swag- 
 ing alone ; a more definite border, however, may be formed by 
 forcing the plate in at this place with a small, smooth-faced stamp 
 or tracer, shaped to the angle of the groove, passing round the 
 chamber and carefully forcing the plate in with the stamp and a 
 small hammer or mallet until a somewhat sharp and abrupt angle 
 is obtained to the palatal edge of the chamber. After the chamber 
 is as perfectly formed as possible in this way, the plate should be 
 well annealed and again swaged to correct any partial deformity 
 occasioned by stamping the chamber. 
 
 The Soldered Air-chamber. — A still more perfectly defined 
 angle may be given to the borders of the chamber in the following 
 manner : After swaging the plate sufficiently to indicate the exact 
 position and form of the chamber, the portion forming the latter 
 should be separated from the main plate by completely dividing it 
 with a saw, or small, sharp, chisel-shaped instrument, cutting on a 
 line with the groove around the chamber until the latter is entirely 
 separated. The cut portion of the main plate is then trimmed 
 evenly with a file, being careful not to enlarge the opening more 
 than is required to remove the irregularities of the edge formed in 
 cutting. The plate, with its central portion removed, is then placed 
 upon the die, when a separate piece of gold cut to the general form 
 of a chamber, but somewhat larger than the opening in the main 
 plate, is adjusted over the chamber, and struck up with the plate 
 
PARTIAL DENTURES HELD BY ATMOSPHERIC PRESSURE. 
 
 20I 
 
 until the overlapping portions of the central piece are forced down 
 upon the plate around the margins of the chamber. It is not, how- 
 ever, always necessary to employ a separate piece of gold for the 
 chamber, as the central portion cut from the plate in the first 
 instance may be sufficiently enlarged for the purpose. This is 
 accomplished by first flattening out the detached portion, anneal- 
 ing it, and then passing successive portions of its edges y-g- of an 
 inch or more between the rollers, the latter being sufficiently ap- 
 proximated to produce a perceptible thinning of the margins. 
 When the entire border of the chamber piece has been thus atten- 
 uated and extended, it will be found so much enlarged that, when 
 adjusted to the die and swaged in connection with the main plate, 
 
 Fig. 88. 
 
 its borders will overlap and rest upon the margins of the opening 
 in the base, as in the other case. 
 
 The portions of the plate and cut chamber lying in contact and 
 temporarily secured in position by means of wire clamps, as 
 shown in Fig. 88, are now coated with borax and pieces of solder 
 placed along the line of union on the lingual side of the plate, when 
 the two pieces, being transferred to a bed of charcoal, are perma- 
 nently united by flowing the solder with a blowpipe. Sufficient* 
 heat should be applied to induce an extension of the solder 
 between the two portions of plate, filling up completely the gap 
 between them to the edge of the orifice in the main plate, forming, 
 at this point, a square and well-defined angle to the margins of the 
 chamber. 
 
CHAPTER XVIII. 
 
 METHOD OF OBTAINING AN ANTAGONIZING MODEL FOR PARTIAL 
 DENTURES; SELECTING, ARRANGING, AND ANTAGONIZING THE 
 TEETH ; INVESTING, ADJUSTING STAYS, SOLDERING, ETC 
 
 Having constructed the plate or base to be used as a support 
 for partial sets of teeth in either of the ways described in the 
 preceding chapter, it will be necessary, before arranging the teeth 
 on the plate, to secure an accurate representation of all the 
 remaining natural teeth of both jaws in plaster, preserving accu- 
 rately the relation which these organs bear to each other in the 
 mouth. This is effected by what is called an antagonising 
 model, and may be secured in the following manner : 
 
 Taking the " Bite." — A roll or strip of adhesive wax is first 
 attached to the lingual border of the plate, and its adhesion 
 secured by holding the opposite side of the plate for a moment 
 over the flame of a Bunsen burner or spirit-lamp. The wax used 
 for articulating purposes should be harder and more tenacious 
 than plain beeswax, and may be compounded from the following 
 formula : 
 
 Beeswax, i pound. 
 
 Gum mastic, 2 ounces. 
 
 Spanish whiting, 1 ounce. 
 
 The wax is first melted in a shallow vessel, and the mastic, 
 finely pulverized, gradually added, and then the whiting, stirring 
 constantly until thoroughly incorporated. The rim of wax being 
 arranged on the plate, all superfluous portions overhanging the 
 margins occupied by the remaining teeth are cut away ; the plate 
 may then be placed on the model and the wax again trimmed, 
 leaving- it somewhat fuller than the outer circle of the teeth, and 
 from one to three lines longer than those immediately adjoining 
 the spaces. The plate, with the wax attached, is then placed in its 
 proper position in the mouth, and the patient instructed to close 
 the jaws naturally until the remaining teeth meet ; one-third or 
 more of the crowns of the opposing teeth opposite the spaces will 
 
 2C2 
 
ANTAGONIZING MODELS, TEETH, ETC., FOR PARTIAL DENTURES. 2O3 
 
 thus be imbedded in the wax. A still fuller impression of the 
 opposing teeth may be obtained, if desired, by pressing the edges 
 of the wax down upon the crowns with the finger. 
 
 The Mesial Line. — If a series of anterior teeth are to be re- 
 placed, the mesial line of the mouth in front should be indicated 
 upon the wax by drawing a line vertically across the latter to 
 serve as a guide in the arrangement of the central incisors and 
 adjoining teeth. The plate and wax are then carefully removed 
 from the mouth and again placed upon the plaster model, the lat- 
 ter having been previously obtained from an impression of the 
 parts with the plate in the mouth. 
 
 Securing the Antagonizing Models. — The method of securing 
 the antagonizing models as practised by many, is to place the 
 model on a slip of paper with the plate and wax upward, and the 
 heel of the model extended from one to two inches posteriorly 
 to form an articulating surface for the remaining portion of 
 the antagonizing model. The added portion of plaster may be 
 confined by a narrow strip of wax or sheet-lead extending back 
 upon each side of the model, into which a batter of plaster is 
 poured to the depth of y 2 or y^ of an inch. When hard, the 
 edges and upper surface of the added plaster should be trimmed 
 smooth, and a crucial groove, or two or three conical-shaped 
 holes, cut in the surface of the latter to secure a fixed and definite 
 relation of the two parts of the model. The articulating surface 
 is then varnished and oiled to prevent the next portion of plaster 
 from adhering; the imprints of the teeth in the wax are also oiled. 
 The open space looking into the palatal vault should be closed 
 with a sheet of softened wax to prevent the next portion of plaster 
 from flowing into the cavity underneath. A batter of plaster is 
 now poured carefully upon the exposed surface of the wax, filling 
 the imprints of the teeth perfectly, and extending back upon the 
 heel of the model until it acquires a depth of y 2 of an inch or more. 
 When sufficiently hard, the two sections of the model are separ- 
 ated, superfluous portions trimmed away, and the entire surface of 
 both pieces glazed with varnish, and if the manipulations have 
 been accurate, this simple contrivance will exhibit all the parts 
 represented in plaster in precisely the same relative position which 
 they occupy in the mouth. The writer feels, however, that a more 
 elegant and accurate method of securing the antagonizing model, 
 
204 MECHANICAL DENTISTRY. 
 
 is to take a full impression of the antagonizing teeth in wax 
 or modeling compound. Secure a plaster cast from same and 
 adjust the two models properly upon an articulator. 
 
 Selecting, Arranging, and Antagonizing the Teeth. — The teeth 
 of replacement should harmonize, as nearly as possible, in size, 
 configuration, and color, with those remaining in the mouth ; and 
 when selecting teeth for any given case, the operator should be 
 provided with a sufficient number of sample teeth to meet every 
 requirement, by comparison, in respect of the various tints or deli- 
 cate shades of color characteristic of the natural teeth and gums. 
 The required size and form of the artificial teeth may be deter- 
 mined with tolerable accuracy by a comparison with those on the 
 plaster model, but the form or figure more ceftainly by a careful 
 inspection of those in the mouth. 
 
 Although there are almost limitless varieties of manufactured 
 teeth, both in respect to form and color, it is not always possible, 
 in partial cases, to obtain such as will harmonize with the natural 
 organs. As to form, a much closer resemblance to the natural 
 organs in immediate relation with those of replacement can be 
 obtained by cutting away more or less freely from the cutting 
 edges of the incisors, and the cusps of bicuspids and molars, in 
 cases where the natural teeth are much worn. The ground sur- 
 faces may afterward be polished with pumice on a buff-wheel, and 
 finished with rotten-stone and oil. The exigencies of practice, in 
 respect of partial sets, will often require the reshaping of ready- 
 made teeth by grinding, and the original form should never be 
 preserved at the sacrifice of utility and appearance. 
 
 To secure harmony of color in the use of manufactured teeth 
 as found in dental depots is not always practicable. There are 
 often conditions of the natural organs associated with decay and 
 organic discolorations which it is impossible to match with porce- 
 lain teeth provided by manufacturers for general purposes. Such 
 needs of the practitioner can only be adequately met by selecting 
 the teeth and having them stained before baking at the dental 
 depot. 
 
 Grinding the Teeth. — A greater or less change in the form of 
 porcelain teeth will be required, in nearly all cases, in fitting them 
 to the vacuities in the jaw; and this is more particularly so in 
 those cases requiring the use of gum teeth. This alteration of form 
 
ANTAGONIZING MODELS, TEETH, ETC., FOR PARTIAL DENTURES. 205 
 
 is effected by grinding away portions of the tooth upon an emery- 
 or corundum-wheel attached to the dental lathe (Fig. 89). If the 
 edentulous portions of the ridge have suffered but little change 
 of form by absorption, as where the teeth have been recently ex- 
 
 tracted, and plain teeth (those representing only the crowns of the 
 natural organs) are used, the posterior portions of the base of the 
 latter resting upon the margins of the plate will only require to be 
 conformed to the irregularities on the surface of the base-plate, 
 grinding sufficiently to give them^the proper length and relative 
 position, while their anterior cervical portion is permitted to over- 
 lap the edge of the plate and rest directly upon the gum in front on a 
 line with the adjoining teeth. When, however, a considerable con- 
 
206 MECHANICAL DENTISTRY. 
 
 cavity exists in the ridge and external border, and single gnm teeth 
 are employed to restore the customary fulness and contour of the 
 parts, the gum portion of the tooth should be ground away on its 
 posterior face sufficiently to restore the circle of the gum on the 
 external border of the alveolus, and from the base of the tooth 
 where it rests upon the plate, to admit of a proper relative position 
 of the artificial crown ; while those portions of the porcelain gum 
 terminating at and adjoining the remaining teeth, next the spaces, 
 should be formed with a thin retreating edge, where it laps upon 
 the natural gum, giving to the parts, when the substitute is ad- 
 justed to the mouth, the appearance of an unbroken denture and a 
 continuous gum. When the space to be supplied requires a series 
 of two or more single gum teeth, the latter should be united to 
 each other with the greatest care and exactness by grinding the 
 proximate edges of the gum portions until the coaptation is such 
 as to render the seams imperceptible in the mouth. In adjusting 
 the porcelain teeth to the. plate, the base of each tooth should be 
 ground to rest as directly and uniformly on the plate as possible ; 
 for if thrown, in any degree, from the plate, the whole strain in 
 mastication will come upon the platinum rivets, and, in' a compara- 
 tively short time, the latter will either be entirely worn or cut off, 
 or the artificial crown will be fractured on a line with the pins. 
 
 Antagonizing Partial Dentures. — In antagonizing partial sets 
 of teeth, the indications pointed out by the customary closure of 
 the natural organs should be followed as nearly as the form and 
 position of the opposing teeth will permit. A changed or abnor- 
 mal relation of the teeth of both jaws, however, frequently ren- 
 ders it difficult to effect a satisfactory adjustment of the teeth of 
 replacement. If, in the case of the bicuspids, for example, one or 
 more teeth in the under jaw project into a vacuity above to the 
 extent of one-third or more of its depth, a direct closure of the 
 substituted organs upon these, in the ordinary manner, would be 
 impracticable without a corresponding shortening of the porcelain 
 teeth, enforcing, in such cases, an inharmonious arrangement, en- 
 tirely inconsistent with the just requirements of the case. The 
 difficulty cited, or any of the various modifications of it, may be 
 overcome wholly, or in part, in one of two or three ways. If the 
 teeth encroaching upon tin- opposite space arc very loose, as is 
 frequently the ease with those thai have become elongated from 
 
ANTAGONIZING MODELS, TEETH, ETC., FOR PARTIAL DENTURES. 20J 
 
 the long-continued want of an adequate opposing force, or are 
 hopelessly carious or otherwise diseased, they should be at once 
 removed. If they remain firm and sound, and stand slightly 
 within the circle of the teeth of the opposite jaw, or if they have 
 somewhat of an inward inclination in the arch, the vacuity oppo- 
 site may be filled with non-masticating teeth, as a cuspid, on the 
 lingual side of which an antagonizing cusp of gold may be con- 
 structed, allowing the point of the cuspid to lap over the labial 
 face of the encroaching tooth or teeth ; or a bicuspid, manufac- 
 tured for the purpose, with the inner cusp near the base of the 
 tooth, may be used instead. Additional room may be provided in 
 such cases for the overlapping portion by grinding away from a 
 corresponding point on the opposing tooth. If, however, taking 
 the most impracticable case, the remaining teeth are sound and 
 firm, and stand vertically in the arch, closing between the oppos- 
 ing teeth on a line with, or somewhat outside of, the outer circle 
 of the latter (the elongation of such teeth being rather relative 
 than absolute, as where it results from a mechanical wearing away 
 of the remaining antagonizing teeth and a corresponding approxi- 
 mation of the jaws), the practitioner will be compelled either to 
 submit to a mal-arrangement of the teeth of replacement by 
 grinding away sufficiently from their masticating surface to per- 
 mit an unobstructed closure of the natural organs, or if the re- 
 maining teeth are few, and poor in structure, extract them, and 
 insert a full denture. 
 
 In view of the difficulties which so frequently present them- 
 selves in connection with the arrangement of artificial teeth in 
 partial cases, it may not be amiss to observe that, however essen- 
 tial to the natural and agreeable expression of the individual an 
 exact and harmonious arrangement of the teeth of replacement 
 may be, this requirement should, in some degree, be disregarded 
 whenever the necessities of the patient, in respect of the comfort 
 and utility of the appliance or the safety of the natural organs, 
 demand it; — to what extent appearances should be sacrificed to 
 these considerations will depend upon the peculiar exigencies of 
 the case, and cannot, therefore, be specifically stated. On the 
 other hand, it may be observed that, if a sufficient number of the 
 natural teeth are remaining in both jaws to enable the patient to 
 perform, with tolerable efficiency, the act of mastication, the mere 
 
208 MECHANICAL DENTISTRY. 
 
 utility of the substitute in regard to the performance of this func- 
 tion, may be partly or wholly disregarded whenever there is 
 sufficient reason to apprehend that the substituted organs cannot 
 be antagonized with a view to the comminution of food without 
 endangering the permanency and usefulness of the appliance, by 
 necessitating the application of forces unfavorably directed. 
 
 Investing. — Having arranged and antagonized the teeth as 
 accurately as possible on the plaster model, the piece should be 
 placed in the mouth to detect and remedy any faultiness that may 
 be found to exist either in the adaptation, position, or antagonism 
 of the artificial teeth. It is then removed and imbedded in a mix- 
 ture of plaster, sand, and asbestos, in the proportion of about two 
 parts of the former and one part each of the latter. The body of 
 the investment may be surrounded by a copper or sheet-iron band 
 to prevent it from breaking away while adjusting the stays or lin- 
 ings to the teeth. All parts of the plate and teeth, except the 
 lingual side of the former and the backs of the latter, should be 
 incased to the depth of y 2 of an inch or more, and when the latter 
 is sufficiently hard all traces of wax from the inside should be 
 carefully detached with suitable instruments. 
 
 Manner of Backing the Teeth. — The piece is now ready for 
 the adjustment of stays or backings, which, when permanently 
 united by soldering to the base and teeth, are designed to sustain 
 the latter in position. These supports are formed from plate some- 
 what thicker than that used for the base, a heavier and stronger 
 stay being necessary when they are not united laterally, and when 
 plate teeth are used. If, however, single gum or block teeth are 
 employed, and the stays are joined, forming a continuous band, 
 plate one-half thicker than that used for the base will, ordinarily, 
 impart adequate security to the attachment. A plain strip, corre- 
 sponding in width with the tooth to be lined, is cut, and the end 
 resting on the main plate conformed accurately with the file, or 
 stone revolved by the dental engine, to the irregularities on the 
 surface of the latter, and in such a manner as to permit the strip to 
 take the direction of the tooth. The general form of the stay may, 
 in the first place, be obtained by cutting a strip from a piece of 
 gold. The points upon the stay to be pierced for the admission of 
 the platinum pins may be ascertained by coating the surface of the 
 former with wax softened in the flame of a spirit-lamp, and press- 
 
ANTAGONIZING MODELS, TEETH, ETC., FOR PARTIAL DENTURES. 200, 
 
 ing it first against the lower pin, the point of which will be indica- 
 ted by an indentation of the wax. The backing is then perforated 
 at this point with a plate-punch, two forms of which are exhibited 
 in Fig. 90, one armed with a tongue, which, when the plate is 
 
 Fig. 90. 
 
 pierced, forces the latter from the punch. The strip is then reap- 
 plied to the upper pin, and the second hole obtained in like manner 
 as the first. Instead of using wax, the ends of the rivets may be 
 stained with some pigment, which will show the points to be 
 pierced in the backing. 
 
 The stay should be adapted accurately to the face of the tooth ; it 
 is then cut to the proper length, reaching nearly or quite to the 
 point of the tooth, and shaped with a file and stone to the general 
 form of the crown. When the backings are to be united, they 
 should be formed with a shoulder at a point corresponding with 
 the neck of the tooth, and the proximate edges below united 
 closely by squares edges, or the latter may be beveled and made 
 to lap upon each other. The process of soldering will be greatly 
 
 14 
 
2IO MECHANICAL DENTISTRY. 
 
 facilitated, and the piece will be more easily and artistically 
 finished, by securing, in the first instance, a perfect coaptation of 
 all the parts which are ultimately to be united. The sides of the 
 holes in the stays facing the plate should now be enlarged or coun- 
 tersunk with a spear-shaped or conical bur-drill, and when applied 
 to the teeth the projecting ends of the platinum pins are cut off 
 even with the backings, and then split and spread apart with a 
 small chisel-shaped instrument ; a head will thus be formed to the 
 rivets when solder is fused upon them, which will prevent them 
 from drawing from the backings. 
 
 The Soldering Process. — All the lines of union between the 
 several pieces should next be well scraped, exposing a clean, 
 bright, metallic surface to the solder (see Principles of Soldering, 
 page 65) ; the seams are then coated with borax, ground or rubbed 
 in clean, soft water to about the consistency of cream ;* after 
 which small pieces of solder are placed along the joints and over 
 the points of the platinum pins. The piece thus prepared is now 
 placed in the furnace or ordinary fireplace, in order to heat the 
 entire mass preparatory to soldering. The fuel most proper for 
 this purpose is charcoal, either alone or combined with coke, the 
 latter being preferable for the reason that charcoal alone is more 
 quickly consumed, and burning away more rapidly underneath, 
 the piece is more liable to drop to the bottom of the furnace. The 
 fuel should be broken into small pieces and built up around the 
 borders of the investment in order that all parts of the latter may 
 be uniformly heated. The heating process should be conducted 
 gradually, for if the piece to be soldered is subjected suddenly to 
 a high heat, the plaster will be displaced by the too rapid evolu- 
 tion of vapor, and the integrity of the porcelain teeth will be en- 
 dangered. The piece may be allowed to remain in the fire until 
 the plate acquires a visible red heat, when it should be removed, 
 placed on a suitable holder, and the solder fused with the blow- 
 pipe. A broad, spreading flame should first be thrown over the 
 entire surface of the plate and border of the plaster, until the tem- 
 perature of the entire mass is nearly that required to fuse the sol- 
 
 * Slate is often used for this purpose, but is unfit, as, in rubbing the borax, 
 loosened particles of the former become mixed with the latter and impede the flow 
 of the solder, and becoming entangled render it unclean and porous. Ground 
 glass or a porcelain slab is the best for the purpose. 
 
ANTAGONIZING MODELS, TEETH, ETC., FOR PARTIAL DENTURES. 211 
 
 der, and which is indicated by the latter settling and contracting 
 upon itself. A small pointed flame, carefully controlled, with very 
 slight pressure upon the bellozvs, may then be concentrated upon a 
 particular point, as at the heel of the plate on one side, passing 
 round from tooth to tooth until all the parts are completely united 
 and the solder is well and uniformly diffused. 
 
 Having united the teeth to the plate, the piece may be allowed 
 to cool gradually, or it may be plunged, after the lapse of a few 
 minutes, into boiling water without risk of injury to the teeth. 
 When cool, the plaster is removed and the plate placed in the acid 
 bath (a solution of equal parts of sulphuric acid and water), where 
 it may be allowed to remain until the discoloration of the plate 
 and the remains of the vitrified borax, incident to the soldering, 
 are removed, or it may be put into a small copper vessel, partly 
 filled with the same solution, and boiled for a few minutes. After 
 removing the plate from the acid, it should be boiled for five or 
 ten minutes in a solution of chlorid of soda, or common salt and 
 water, to remove thoroughly all traces of the acid. 
 
 The Finishing Process. — Superfluous portions of solder are 
 now to be removed, and this at first may be more quickly accom- 
 plished by the use of burs and stones of various forms and sizes 
 attached to the dental engine. After the rougher and more 
 redundant parts are thus cut away, any remaining irregularities 
 upon the surface may be further reduced with sand-paper or 
 emery-discs. Then, with a rapidly-revolving brush attached to a 
 foot-lathe, the final polish or luster may be imparted by the use, 
 first, of finely-powdered pumice-stone, followed by Spanish whit- 
 ing, or prepared chalk, and then rouge mixed with water or alcohol. 
 
 In the final adjustment of the finished piece to the mouth, and 
 after any additional change in the form of the teeth necessary to 
 secure the most perfect antagonism has been made, the patient 
 should, in all cases of partial dentures, receive explicit directions 
 in regard to the general care and management of the appliance 
 and the remaining natural teeth. Ordinarily, there will be but 
 little difficulty experienced by the patient in the immediate and 
 successful use of a substitute supported in the mouth by clasps, or 
 any equivalent means; but in the case of atmospheric-pressure 
 plates, the patient should be candidly advised of the probable 
 want of stability incident to the first use of the appliance, and the 
 
212 MECHANICAL DENTISTRY. 
 
 consequent annoyance which in many cases follows its occasional 
 displacement in mastication until such time as the adaptation of 
 the several parts to each other are perfected, and the patient has 
 acquired a habit of controlling and directing the forces applied to 
 the substitute. The time necessary to accomplish these results 
 will depend much upon the form and condition of the mouth, a 
 favorable or unfavorable antagonism, the adaptation of the plate, 
 and the aptitude and temper of the patient. It will be prudent 
 and but just to the patient to state that the complete utility of an 
 appliance sustained by atmospheric pressure will not, probably, 
 be realized in less time than from one to two weeks, and this esti- 
 mate of time, in a majority of cases, will be fully justified by expe- 
 rience in the cases under consideration. 
 
 The importance of thorough and absolute cleanliness of the 
 substitute and remaining natural teeth, and the reasons therefor, 
 should be clearly stated ; and the comfort, utility, and durability 
 of the artificial fixture, as well as the safety of all the remaining 
 natural organs, will depend, in a great measure, upon the fidelity 
 of the patient with respect to the observance of these injunctions. 
 In those cases especially where clasps are used, the substitute 
 should invariably be removed after each meal and cleansed, while 
 the teeth clasped should, at the same time, be freed from deposits 
 of food or other foreign substances with a brush, and other means 
 usually recommended for the purpose. 
 
CHAPTER XIX. 
 
 ENTIRE DENTURES. 
 
 Preliminary Observations. — Before proceeding to describe in 
 detail the mechanical processes or manipulations concerned in 
 the construction of entire dentures, unnecessary repetition will 
 hereafter be avoided by first considering, in this place, certain 
 underlying principles and fundamental requirements which are 
 common to all the various distinct methods of replacement in 
 edentulous cases. This preliminary treatment of the subject may 
 be comprehended under two general heads: (i) A consideration 
 of the principles and attendant phenomena involved in the appli- 
 cation of the forces commonly utilized as a means of attachment ; 
 and (2) esthetic requirements in the selection and arrangement of 
 the teeth of replacement. There are two forces in nature utilized 
 in the retention of entire dentures, notably in upper cases, — 
 atmospheric pressure and adhesion. We shall consider, first, some 
 of the attributes and phenomena characteristic of these forces, 
 and then endeavor to make some practical applications of them in 
 elucidation of the subject in hand. 
 
 Adhesion may be defined as the force by which the particles of 
 different bodies stick together, in contradistinction to cohesion, 
 which is the force that holds the molecules of the same body 
 together. There are several kinds of adhesion, but our present 
 purpose only contemplates those which relate to the adhesion of 
 solids to solids, and fluids to solids. 
 
 The adhesion of solids to solids is illustrated by pressing to- 
 gether two plates of glass or metal having perfect occluding sur- 
 faces, when they will be found to adhere with force enough to 
 support not only the lower plate, but some additional weight. 
 Very delicate tests have been made by which the adhesive force 
 is accurately measured. An important practical fact, in this con- 
 nection, has been well established, which has a direct bearing on 
 the subject we are considering, namely, that the tenacity with 
 which such plates adhere to each other is not in any manner due 
 
 213 
 
214 
 
 MECHANICAL DENTISTRY. 
 
 to, but wholly independent of, any force exerted by the pressure 
 of the atmosphere, as was supposed by some of the earlier experi- 
 menters. The fact alluded to was conclusively proven by sus- 
 pending the plates, the lower one of which was weighted, in the 
 vacuum of an air-pump, in which case the plates still remained 
 adherent. Examples of this adhesive force as affecting solids 
 might be almost indefinitely multiplied. 
 
 The force of adhesion of solids to liquids is not less pronounced. 
 When a polished plate is suspended on a delicately constructed 
 balance, and brought carefully down on the surface of a liquid, 
 completely excluding the air, adhesion will take place, the force of 
 which will be modified by the kind of liquid in contact with the 
 plate. It has been ascertained by careful experiment that the ad- 
 hevise force of a polished plate of agate, one inch in diameter, in 
 contact with water, is 25 grains ; sulphuric acid, 29 ; hydrochloric 
 acid, 25; solution of saltpeter, 23; of lime, 21; almond-oil, 16; 
 petroleum, 16; turpentine and alcohol, 15; ether, 10. Where, as 
 often happens, drops of the liquid adhere to the plate when separ- 
 ated, it proves that the adhesion of the liquid to the solid is 
 stronger than the cohesion of the liquid itself, and that the num- 
 bers obtained in these experiments express rather the cohesion of 
 particles of the liquid which were separated by the weight, than 
 the adhesion of the plate to the liquid. As in the case of adhesion 
 of solids to solids, it was formerly claimed by some that adhesion 
 in these cases was due to atmospheric pressure, but that was dis- 
 proved in the same manner as the other. Perfect exclusion of air 
 is essential to the operation of this force, a suggestive fact in con- 
 nection with the adaptation and retention of entire dentures. 
 
 Atmospheric pressure is that force exerted by the air by reason 
 of its gravity, one of its mechanical properties being zvcight, which 
 renders it amenable to the same law of attraction that affects all 
 other bodies similarly endowed. It exerts a pressure not only 
 downward, but, according to the law of fluids, sideways, upward, 
 etc., as by the mobility of fluid particles any pressure is trans- 
 mitted in all directions. Superadded to gravity is its clastic force, 
 a property which, like all gaseous bodies, it possesses in a remark- 
 able degree. This property is familiarly demonstrated by filling 
 .-1 bladder with air and exposing it to rarefied air at a great height. 
 The external pressure of the atmosphere at such an altitude being 
 
ENTIRE DENTURES. 21 5 
 
 diminished, the air within tends to expand to the same degree of 
 rarity as that without, and with such force as to burst the bladder. 
 The partial displacement of air by compression within a diving- 
 bell by the pressure of water at a low depth, and the forcible ex- 
 pulsion of the intruding water as the bell is brought to the sur- 
 face, not only illustrates its elasticity, but its impenetrability also, 
 or its property of preventing another body from occupying the 
 space where it is. There are many other examples of the press- 
 ure of the atmosphere and the force exerted by virtue of its elas- 
 tic property, but those of most interest and consequence to the 
 prosthetic specialist relate to their effects on the human organism. 
 It is estimated that the force exerted by the pressure of the atmos- 
 phere on the body of a mediurn-sized man must be about 15 tons, 
 a force sufficient to crush and destroy him if applied only to the 
 external portions of the body. Such pressure, however, is neu- 
 tralized and rendered harmless by counter-pressure from within ; 
 a result due to the elasticity of the air, which exerts a force every- 
 where and in all directions alike, from the external parts inwardly, 
 and from those within outwardly. The tendency in nature every- 
 where is toward the establishment of an equilibrium of atmos- 
 pheric pressure, and when these balanced forces are disturbed, 
 unusual and characteristic phenomena follow. If, as in the case 
 of " cupping," the external pressure of the atmosphere is removed 
 by the formation of a vacuum, the elastic force of the air operat- 
 ing from within, and meeting no counter-force at the point 
 cupped, will, by virtue of its inherent elastic energy, force the soft 
 tissues into the body of the cup as the result of this tendency to 
 an equilibrium. The latter occurs as soon as the unoccupied 
 space forming the vacuum is filled with the tissues, when, the 
 accustomed balance of forces being restored, the cup will loosen 
 and fall off. If the disturbance of the equilibrium of forces act- 
 ing from without and within is general, as in the case of an 
 aeronaut in a balloon at great heights, the result of this tendency 
 may, and often has, put life in jeopardy by expansion of the inter- 
 nal organs. On the contrary, the body exposed to greatly in- 
 creased external pressure of the air, as when the latter is con- 
 densed in the diving-bell at low depths, or in caissons employed 
 in forming a foundation of subaqueous structures, the results may 
 be equally harmful or fatal by compression of the internal organs. 
 
2l6 MECHANICAL DENTISTRY. 
 
 The Application of Atmospheric Pressure and Adhesion in the 
 Retention of Artificial Dentures. — The general proposition that, 
 in the case of entire dentures, retention of the plate in place by 
 atmospheric pressure presupposes a vacuum obtained by exhaus- 
 tion of the air from a cavity, of whatever form, located somewhere 
 between the plate and the mucous surfaces on which the latter 
 rests, and that such cavit}^ implies space. Whenever, therefore, 
 a dental appliance of the kind under consideration is in uniform 
 contact at all points with the parts in the mouth, it is manifestly 
 improper to speak of it as being held in place by atmospheric 
 pressure, or to designate it as an " atmospheric-pressure plate." 
 Uniform contact implies perfect continuity between the plate and 
 the parts on which it rests, and this necessarily precludes the idea 
 of space, and without space a vacuum is impossible, and in the 
 absence of the latter, the atmosphere, as we shall endeavor to 
 show, is wholly inoperative as a retaining force. To comprehend 
 the matter intelligently, we must not lose sight of the important 
 central fact that the atmosphere, in its undisturbed condition, 
 exerts an equal pressure in all directions, a property largely due 
 to its elasticity, and that in obedience to this law, in its operation 
 upon the human organism, the force exerted from without inward 
 is exactly counterbalanced by the same force acting from within 
 outward, thus establishing an equilibrium of the counteracting 
 forces, and a consequent neutralizing of pressure at the surface. 
 This equalized force is an essential condition of human well-being 
 and of human life, as has been heretofore stated and demonstrated 
 by examples. The absurdity, therefore, of attributing the reten- 
 tion of substitutes, adapted in this manner to the mouth, to the 
 pressure of the atmosphere is apparent. There can be no reason- 
 able question but that substitutes so applied are held in situ by 
 that force manifesting itself in adhesion. In all cases where the 
 plate or other base is accurately adapted to the entire mucous 
 surfaces, and the air thoroughly excluded, the essential condi- 
 tions favoring its retention by adhesion is secured, namely, per- 
 fect contact of a solid with the fluids with which the mucous 
 surfaces are constantly bathed. 
 
 Let us now consider, as briefly as possible, the manner in which 
 air-pressure acts as a retaining force when applied to cavity- 
 plates, and in the same connection some of the phenomena result- 
 ing from such action. 
 
ENTIRE DENTURES. 2.1J 
 
 When a plate, provided with a cavity or chamber, is applied to 
 the mouth, two concurrent phenomena are observed : the imme- 
 diate and forcible attachment of the plate to the mucous surfaces, 
 and the obtrusion of the soft tissues into the space from which 
 the air has been exhausted. The first is due to the external press- 
 ure of the atmosphere, the latter to the same force acting from 
 within. Here, again, it is essential to remember the fundamental 
 fact that atmospheric pressure acts equally in all directions. The 
 phenomena to which attention has been called, in the case of an 
 applied cavity-plate, are the result of a disturbance of these ordi- 
 narily balanced forces. When a vacuum, partial or complete, is 
 formed by exhaustion of air from the chamber, the external press- 
 ure of the air meeting with a diminished counter-resistance from 
 within, by reason of the vacuum, forces the plate against the 
 parts, while at the same time the atmospheric pressure acting 
 from within outwardly, meeting with a like diminished resistance 
 at the surface embraced within the limits of the chamber, forces 
 the soft tissues into the chamber. Thus we find displayed the 
 universal tendency to an equilibrium of atmospheric pressure, 
 and a practical illustration of nature's proverbial abhorrence of a 
 vacuum. 
 
 It is not probable that a perfect vacuum is ever secured by the 
 means ordinarily employed by the patient, unless, perhaps, in the 
 case of very shallow cavities. The moment any portion of the 
 contained air is exhausted, there is instant and forcible pressure 
 of the plate upon the soft tissues immediately surrounding the 
 chamber, acting as an effectual mechanical impediment to further 
 egress of air. The power to exhaust is therefore self-limited, and 
 a partial vacuum only the result. Sooner or later, in a large per- 
 centage of cases, even this limited power is rendered inadequate 
 to secure any degree of exhaustion by the intrusion of tissues 
 which, by long-continued and unrelieved pressure, become in time 
 permanently hypertrophied. 
 
 The completeness with which the chamber may become filled 
 with soft tissues will depend partly upon the form of the cavity, 
 and partly upon the abundance and mobility of the tissues. If the 
 cavity is constructed with vertical walls and sharply defined mar- 
 gins, the latter, by becoming quickly imbedded, will act as a 
 mechanical obstruction to any ready, sliding movement of the 
 
2l8 MECHANICAL DENTISTRY. 
 
 tissues into the chamber. Plates so constructed adhere with 
 greater tenacity and more persistency, especially when the parts 
 embraced are rigid and immobile ; but it is at the cost of the max- 
 imum of injury which cavity-plates are capable of inflicting, and 
 which is often, in extreme cases, characterized by rupture of the 
 superficial vessels, wounding of the mucous membrane, and in 
 active inflammatory conditions which not infrequently involve the 
 adjacent tissues. More ready entrance of the tissues into the 
 chamber occurs where the edges of the latter are rounded and the 
 walls slope toward the center, as in the case of those that are 
 swaged, but this form is at the expense of the retaining force, 
 since atmospheric pressure from without is always diminished in 
 proportion as the cavity becomes filled in with the tissues, and 
 ceases entirely when a vacuum no longer exists. The facility 
 with which the chamber will become occupied is greatly increased 
 when the soft tissues are in excess, their softness and mobility 
 offering but a feeble resistance to the atmospheric pressure from 
 within, in which case the cavity soon becomes partly or wholly 
 occupied by them, and what retaining force was originally secured 
 by atmospheric pressure will, in a comparatively short time, be- 
 come greatly impaired or wholly inoperative. 
 
 When it is remembered how transitory are the uses of so-called 
 " air-chambers," and how capable, under ordinary circumstances, 
 they are of inflicting serious injury upon the delicate tissues of the 
 mouth, there would seem to be no sufficient reason or justification 
 for their employment, except possibly in rare and exceptional 
 cases. Experience has amply demonstrated that equally secure and 
 much more enduring attachment of the substitute may be obtained in 
 the utilisation of adhesive force alone — a means of retention wholly 
 exempt from the harmful consequences that too often follow the 
 application of atmospheric pressure consequent on the formation 
 of a vacuum. 
 
 There are, however, many cases where spaces or cavities may 
 be employed to advantage for the purpose of securing, through 
 the temporary pressure of the atmosphere, increased stability of a 
 dental appliance subjected to the forces applied in mastication. 
 There are associated conditions of the mouth which, in their nor- 
 mal and undisturbed relation to each other, prevent, to some ex- 
 tent, a uniform or equalized bearing of the substitute upon the 
 
ENTIRE DENTURES. 2IO, 
 
 parts to which it is applied. These conditions relate to unequal 
 hardness and softness of the tissues, and a consequent inequality 
 of resistance to pressure. Thus, if the ridge is relatively softer 
 and more compressible than the central portion of the arch, the 
 plate, when force is applied over the ridge, will " ride " upon the 
 central portion, as upon a pivot-point, and thus raise or detach the 
 plate from the ridge on the opposite side. This is called " rock- 
 ing " of the plate, the action being illustrated in the sport famil- 
 iarly known as " see-sawing." The remedy for this consists in 
 securing a space between the central portion of the roof of the mouth 
 and the corresponding portions of the plate, so that when the substi- 
 tute is applied to the mouth and the air exhausted, the greatest press- 
 ure will be expanded upon the ridge, and, by compression, equalise 
 the resistance. This space, when the plastic vegetable' bases are 
 used, is obtained by scraping away from the impression at the 
 required points ; raising the central portions of the plaster model 
 with sheet-lead of proper form and thickness ; or by trimming 
 away from the palatal surface of the finished piece. In the case 
 ■of swaged plates, the shrinkage of the metallic die will ordinarily 
 afford the required space. 
 
 In cases where there is approximate uniformity of hardness of 
 the ridge and central line of the arch extending antero-posteriorly, 
 associated with soft and yielding tissues filling the fossae on either 
 side and extending some distance up the lateral walls of the arch, 
 it is customary, in order to equalize the pressure of the plate, or 
 rather, to secure uniformity of resistance to such pressure, to 
 scrape away from such portions of the plaster model as corre- 
 spond with the softer tissues, thus securing in the finished piece 
 an increased convexity or fulness which, on application of the 
 substitute, exerts a compressing force at such points, superadded 
 to that obtained either by atmospheric pressure or adhesion. It 
 may be reasonably objected to this mode of procedure that the 
 augmented compressing force thus applied, being continually an- 
 tagonized by the inherent elastic force of the tissue pressed, must 
 inevitably tend to weaken the attachment of the substitute, and 
 that such repelling force will continue to act, in a diminishing 
 degree, no doubt, until, from long-continued pressure, such of the 
 tissues as are not displaced will become absorbed or atrophied. 
 The objection is emphasized by the further fact that, in such 
 
220 MECHANICAL DENTISTRY. 
 
 cases, the absorption is always preceded and accompanied by 
 forcible displacement of superabundant tissue into the soft palate, 
 inducing more or less irritation and ultimate chronic tumefaction 
 of the displaced tissue at the posterior margin of the plate. The 
 prevalent fallacy that the tissues thus subjected to pressure are 
 condensed thereby has been considered in the initial portion of the 
 chapter on Impressions. 
 
 Xo device will, we believe, so effectually and satisfactorily ful- 
 fil the requirements of the cases last mentioned as the one that 
 provides for displacement of the tissues within the limits of the 
 plate itself. This may be done by securing a graduated space, 
 including a large part of the palatal vault. This space should 
 not be in the form of a cavity with defined walls, but should 
 slope gradually toward the periphery in such manner that its 
 boundaries shall be indistinguishable. By a graduated cavity is 
 meant that, wherever the soft tissues are in excess, there should 
 be a corresponding depth of space to provide for such varying 
 degrees of displacement as are essential in the procurement of an 
 equalized resistance to the pressure of the plate. By this method 
 there is not only no injury or objectionable deformity inflicted,, 
 but the attachment of the substitute, instead of being impaired, as 
 in the other method, is maintained at first by the full and un- 
 obstructed force of atmospheric pressure, and when, finally, the 
 required displacement of tissue is accomplished, by a filling-in of 
 the space, the best practicable adaptation is obtained, and the 
 future stability of the substitute as perfectly provided for as is 
 possible with the resources at our command. 
 
 Esthetic Requirements in the Selection and Arrangement of 
 the Teeth of Replacement. — In selecting teeth for an entire upper 
 and lower denture, the special requirements in regard to size, 
 form, and color, will depend in a great measure upon the com- 
 plexion, age, sex, and general configuration of the face of the 
 patient. Every separate denture, therefore, that is constructed 
 in strict conformity with a faithful interpretation of the special 
 requirements of each individual case, will be characterized by 
 shades of difference in color, form, size, and arrangement of the 
 teeth of replacement. The indication in the fulfilment of such 
 requirements, broadly stated, is, that such selection of the teeth, 
 in any given case, should be made as will, when suitably arranged, 
 most perfectly reproduce the lost proportions of the facial con- 
 tour, and restore the characteristic expression of the individual. 
 
ENTIRE DENTURES. 221 
 
 To accomplish this with fidelity will require a higher order of 
 intelligent discrimination, and a broader art culture than is re- 
 quired in cases where the operator is aided by comparison of the 
 artificial with remaining natural teeth, as in partial dentures. In 
 the present case he has no resources except those that come to 
 him through a critical and conscientious study of the laws of har- 
 mony as displayed in the typical forms of dentures associated 
 with individual physiognomy and temperament. Says Dr. Eben 
 M. Flagg, a thoughtful writer: "We find that the necessity for 
 art in dentistry exists in proportion to the hopelessness of the 
 case. The greater the amount of lost tissue to be replaced, the 
 greater the knowledge of natural form required to properly effect 
 its replacement. Beginning with the restoration of portions of 
 teeth through gold fillings, we come to the loss of the entire 
 crown, and, finally, to that last resort, the replacement of the 
 entire denture. Knowledge of form and color, of expression, 
 character, and effect, now becomes imperative to the dentist. To 
 relieve the condition of his patient, the art of the sculptor and 
 colorist must be studied with more care than many of us are wont 
 to give it, while a knowledge of temperament and physiognomy 
 becomes an important element in our work." 
 
 " No matter how anatomically correct," observes one of the 
 most intelligent contributors to the literature of esthetic dentistry, 
 the late Dr. James W. White, " or how skilfully adapted for 
 speech and mastication an artificial denture may be, yet, if it bear 
 not the relation demanded by age, temperament, facial contour, 
 etc., it cannot be otherwise than that its artificiality will be appar- 
 ent to every beholder. 
 
 " This law of correlation, harmony, running through nature, 
 attracts and enchants us by an infinite diversity of manifesta- 
 tions ; the failure to recognize its demands by art is correspond- 
 ingly abhorrent to our sensibilities. 
 
 " In the social gathering, a lady who appreciates the law of har- 
 mony delights the eye by the taste displayed in her attire ; an- 
 other, though more elaborately and expensively adorned, yet fail- 
 ing to harmonize the details of her costume, attracts attention 
 only by the impression of incongruity. We hear frequently from 
 a lady who is selecting a bonnet, or from a gentleman purchasing 
 a hat or other article of wearing apparel, the question to a friend : 
 ' Does this become me? ' the query indicating the recognition that, 
 however exquisite the material or excellent the manufacture of 
 
222 MECHANICAL DENTISTRY. 
 
 the article, a certain law of fitness prevails, the failure to comply 
 with which makes the wearer appear ridiculous. We meet in the 
 street one the color of whose hair we expect, by the law of asso- 
 ciation, to be fair or sandy, and if otherwise, a wig or a dye is in- 
 stantly suggested. 
 
 " There is a relation between the physical form and the voice, 
 from which we are led to infer in advance the character of the 
 tones which from any given individual may be expected. This 
 law of association in any case having led us to anticipate a bass 
 voice, the anomaly, should a falsetto greet us, is almost ludicrous. 
 
 " There is a similar relation between other physical character- 
 istics and the teeth. A broad, square face or an oval ; a large, 
 coarse-featured man or a delicately-organized woman ; a miss of 
 eighteen or a matron of fifty ; a brunette or a blonde — these and 
 other varieties present as many differing types, with teeth, in size, 
 shape, color, density, etc., corresponding. If, then, teeth, corre- 
 lated in their characteristics to those which nature assigns to one 
 class, be inserted in the mouth of one whose physical organization 
 demands a different order, the effect cannot be otherwise than dis- 
 pleasing to the eye, whether the observer be skilled in perception, 
 or intuitively recognizes inharmony without understanding the 
 cause." 
 
 Written or verbal instructions can do little more than present 
 general principles governing the selection of teeth for any given 
 case. The completeness with which the requirements of indi- 
 vidual cases are fulfilled will largely depend upon the operator's 
 art intuitions, and his ability properly to interpret and apply the 
 basal facts which an intelligent study of the relation of physi- 
 ognomy and temperament to the teeth has revealed. The rela- 
 tions of the latter to the teeth have been clearly and fully set forth 
 in tabulated form by Dr. J. Foster Flagg, which we herewith ap- 
 pend. The first tabic relates to the basal temperaments, namely, 
 bilious, sanguineous, nervous, and lymphatic, and their general 
 indications ; the second, to the teeth as indicated by temperament. 
 
 A careful study of these tables, the subject-matter of which is 
 by far the most valuable contribution that has yet appeared in 
 connection with the subject under consideration, will furnish a 
 helpful means of solving one of the most difficult problems in 
 prosthetic practice. 
 
ENTIRE DENTURES. 223 
 
 The following editorial, by Dr. James W. White, on " Tempera- 
 ment in Relation to Teeth," suggested, doubtless, by Dr. Flagg's 
 tables, embodies not only a discussion of the general subject of 
 temperaments, but some forcible and striking commentaries on 
 the importance and value, esthetically considered, of the indica- 
 tions furnished by temperamental characteristics in the intelligent 
 choice of artificial substitutes for special cases. The importance 
 of the subject to which the article relates will justify its introduc- 
 tion here without abridgment : 
 
 " The animal kingdom is divided into sub-kingdoms, classes, 
 orders, families, genera, species. A further or sub-division in- 
 cludes in minor groups individuals whose salient characteristics 
 are correspondent or similar. Thus every living creature has 
 certain physical peculiarities by which its position in this classifi- 
 cation is determined. Man, as the head of the animal kingdom, 
 besides having his place in this general scale, is distinguished by 
 a still finer classification under the denomination of temperament 
 — an association of several distinguishing characteristics, such as 
 size and form of body, complexion, color of the eyes and hair, 
 and, to a certain extent, the disposition and character of the in- 
 dividual. 
 
 " Temperament may be defined as a constitutional organization, 
 depending primarily upon heredity — national or ancestral — and 
 consisting chiefly in a certain relative proportion of the mechan- 
 ical, nutritive, and nervous systems, and the relative energy of 
 the various functions of the body — the reciprocal action of the 
 digestive, respiratory, circulatory, and nervous systems. The 
 stomach, liver, lungs, heart, and brain — digestion, assimilation, 
 respiration, circulation, and innervation — are all factors in the 
 differentiation of temperament ; and according to the congenital 
 predominance of one or the other, and the relative activity of 
 these functions, is the modification of the characteristics of the 
 individual which assigns him to one or other of the basal or mixed 
 temperaments. Each temperament is the result as well as the 
 indication of the preponderance of one or another of these sys- 
 tems, and of relative functional activity. 
 
 " A perfect equilibrium of the different systems is rarely, if 
 ever, presented in any individual. One having a balance of all 
 the temperaments would be temperamentless, or of no special 
 
224 MECHANICAL DENTISTRY. 
 
 temperament. It is difficult, in some cases, to decide positively 
 to which variety a special case belongs, the several temperaments 
 being combined and blended in such ever-varying proportions. 
 Not infrequently the indications are even contradictory, and the 
 blending of several temperaments requires a nice discrimination 
 to define the admixture. The primary elements of temperament 
 are susceptible of such manifold combinations ; the determining 
 forces are so complex, and our knowledge of their comparative 
 values is so limited, that no rule can be given which will not fail 
 in numerous instances to apply in all respects to individual cases ; 
 but that there is a general relation between constitutional quali- 
 ties and external signs does not admit of question. 
 
 " Temperaments are readily divisible into four basal classes — 
 bilious, sanguineous, nervous, and lymphatic (see tables) ; then 
 again into sub-classes of mixed temperaments — a combination of 
 two or more of the primary divisions. In these combinations one 
 or other of the so-called basal temperaments predominates, and a 
 compound term is used to express the complexity, as, for instance, 
 the nervo-bilious, signifying that the bilious base — the foundation 
 temperament — is qualified by an admixture of the nervous ele- 
 ment, and so throughout the series. Twelve varieties of temper- 
 ament, in addition to the four basal, may thus be designated by 
 the combination in pairs of the original four. The admixture of 
 the peculiarities of three or of all four of the basal temperaments 
 results in what are denominated respectively ternary and quater- 
 nary combinations, which call for nice discrimination in diagno- 
 sis ; but even such complexities are registered in the size, form, 
 and color of the dental organs. 
 
 " The value of a practical application of the study of tempera- 
 ment in the practice of dentistry is apparent. That the relation 
 of the teeth to temperament is, as a rule, ignored by those en- 
 gaged in prosthetic dentistry is evident in the mouths of a ma- 
 jority of those who are so unfortunate as to be under the neces- 
 sity of wearing substitutes for lost natural dentures. 
 
 " A certain law of harmony in nature between the teeth and 
 other physical characteristics necessitates respect to size, shape, 
 color, and other qualities in an artificial denture, in order that it 
 shall correspond with other indications of temperament; and if 
 teeth correlated in their characteristics to those which nature 
 
ENTIRE DENTURES. 
 
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 MECHANICAL DENTISTRY. 
 
 
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ENTIRE DENTURES. 
 
 227 
 
 assigns to one temperament be inserted in the mouth of one 
 whose physical organization demands a different type, the effect 
 is abhorrent. The artificiality of artificial teeth is the subject of 
 remark by those who have little or no conception of the reason 
 therefor — simply an instinctive appreciation of the incongruity 
 and unreality. It is indeed rare to see a case in which there is 
 occasion for a moment's hesitation as to the fact of replacement. 
 There is no dental service that, from the esthetic standpoint, is, 
 as a rule,. so illy performed as the prosthetic. Thousands of den- 
 tures are constructed which serve the needs of the wearer for 
 speech and mastication, but which are, nevertheless, deserving of 
 utter condemnation as art productions. More attention has been 
 paid to the. best methods of restoring impaired function — secur- 
 ing comfort and usefulness in artificial dentures — than to a corre- 
 lation of the substitutes to the physical characteristics of the 
 patient. 
 
 " What is needed is such an appreciation of the law of corres- 
 pondence that the dentist can cipher out, as by the rule of three, 
 the character of teeth required in the case of an edentulous mouth 
 with the same precision as the comparative anatomist can, from a 
 single bone, indicate the anatomical structure of the animal to 
 which it belonged. The probability is that in many, perhaps in 
 most, of the cases of incongruous artificial dentures the fault is 
 not in carelessness or indifference of the dentist, but in failure to 
 recognize the requirements of temperament. A certain family 
 resemblance to each other in a set of teeth is considered essential, 
 but the adaptability of the set as a whole to a given case should 
 be esteemed of even greater importance. Especially is there a 
 notable failure to recognize the color demanded by form. A set 
 of teeth in which not only the relative length and breadth, but 
 every line and curve, characterize it as belonging to a certain tem- 
 perament, is, in contravention of every law of correspondence, 
 made of a color which was never found in nature associated with 
 such forms. Thus we see constantly such incongruities as the 
 association of the massive tooth of the bilious temperament with 
 the pearl-blue color belonging to the nervous temperament, and 
 the long, narrow teeth of the nervous temperament of bronze- 
 yellow color never seen in the mouth of any but those of a bilious 
 temperament. 
 
221 
 
 MECHANICAL DENTISTRY. 
 
 " The trouble is not with the manufacturers ; they supply the 
 demand. The fact is, the requirements of the law of correspond- 
 ence have not been sufficiently studied by the profession. The 
 first study of the dentist who aspires to the dignity of artist, when 
 proposing to replace a lost denture, should be how to restore the 
 natural appearance of his patient, and this can only be effected 
 through an appreciation and observance of the temperamental 
 characteristics and the law of correspondence or harmony. Age 
 and sex may somewhat modify the requirements in a given case, 
 
 Fig. 91. 
 
 Bilious. 
 
 Sanguineous 
 
 but tin- basal fact on which he should proceed is temperament. 
 A failure to recognize its demands will result in failure — from an 
 esthetic standpoint." 
 
 Selection and Arrangement of Artificial Teeth. — A knowledge 
 of the distinguishing characteristics of the various temperaments 
 and the style of teeth which conform to nature's type in the phys- 
 
ENTIRE DENTURES. 
 
 229 
 
 ical organization (see Fig. 91) marks the difference between the 
 dental mechanic and the dental artist ; and the fulfilment of the 
 highest art conceptions in the construction of entire dentures is 
 far from being complete with the mere selection of teeth in con- 
 formity with temperamental and other indications. The essen- 
 tial preliminary step is concerned chiefly with the form and color 
 of substitutes, but the highest attainments in the art of replace- 
 ment can never be attained without an intelligent perception of 
 the esthetic requirements which have inseparable relation to the 
 arrangement of the teeth selected in strict conformity with the 
 same law of harmony or correspondence that' applies to form and 
 color. The art of arrangement is scarcely less difficult, and cer- 
 tainly not less important, than the art of selection, and equal 
 judgment and discrimination will be required to effect such an ad- 
 justment of the teeth as will most faithfully serve to restore the 
 facial contour and characteristic expression of the individual. 
 This will, in most cases, necessitate some deviation from the uni- 
 formly symmetrical or ideal relation of the teeth to each other 
 characteristic of perfect regularity of arrangement, and which 
 rarely exists except in connection with a perfectly balanced devel- 
 opment of the jaws and teeth, a condition which may be said to 
 be almost phenomenal. 
 
 The kind or degree of displacement of any particular tooth or 
 teeth to effect such irregularity of arrangement as would best 
 reproduce the customary expression of the individual in any given 
 case, cannot, of course, be here indicated. The operator is neces- 
 sarily thrown upon his own resources in determining, in this 
 respect, the necessities of individual cases. Generally speaking, 
 the changed relation of the teeth is, in most part, confined to the 
 six anterior teeth, above and below, as they are most largely con- 
 cerned in expression ; but it may often be extended to the bicus- 
 pids and molars, which may be displaced within or without the 
 arch, or given an oblique position, with here and there interdental 
 spaces, some of which may be wide enough to suggest the loss of 
 the natural teeth at intervals. The central incisors may be made 
 to overlap each other, with the laterals in normal position ; or the 
 latter may be given a position inside of the circle, which will give 
 a relative prominence to the centrals and cuspids, or they may be 
 partially rotated while retaining their regular position in the arch, 
 
230 
 
 MECHANICAL DENTISTRY. 
 
 or be made to overlap or underlap the centrals, in which case the 
 latter may be made to diverge somewhat from each other at the 
 points, leaving some space between them. Figs. 92, 93, 94, and 
 95, are given as suggestive both in the selection of teeth and their 
 arrangement. 
 
 There is scarcely any limit to the capability of effecting mal- 
 positions of the teeth of replacement, and this is especially true of 
 
 Fig. 92. 
 
 those forms of substitution known as continuous-gum work, and 
 in the use of celluloid, either process, by admitting of the use of 
 single, plain teeth, affording unlimited opportunities for the op- 
 tional placement of the teeth. In the use of sectional gum teeth, 
 many of the forms of dental irregularity have been faithfully 
 
 Fig. 93. 
 
 reproduced by manufacturers, and, when selected with an intelli- 
 gent apprehension of their fitness for any particular case, will 
 meet the ordinary wants of the practitioner in the use of rubber, 
 or a metallic plate-base with rubber or celluloid attachment. The 
 minimum of capability in effecting irregularity of arrangement is 
 attached to soldered work, where, as is usually the case, single 
 gum teeth are employed. 
 
ENTIRE DENTURES. 
 
 231 
 
 It is possible often, when teeth have been selected conforming 
 as nearly as practicable to the requirements of the case in color, 
 so to change the form of the teeth by judicious grinding of the 
 proximate surfaces, cutting edges of the incisors, and the points 
 
 Fig. 94. 
 
 of the cuspids, and occluding surfaces of bicuspids and molars, as 
 greatly to change the effect in the mouth, giving them an harmo- 
 nious expression impossible in the use of manufactured teeth in 
 their unchanged form. Figs. 92 and 93 indicate the treatment. 
 This is particularly observable when they are ground in imitation 
 
 Fig 
 
 of the partial destruction of the occluding surfaces by erosion, 
 a condition very commonly associated with middle age. The 
 effect is still further enhanced by coloring the portions of the 
 ground surfaces in imitation of the dark discoloration usually 
 
232 
 
 MECHANICAL DENTISTRY. 
 
 associated with exposed dentine. This may be readily done in 
 the manner described in the chapter on partial dentures mounted 
 on metallic plate-base. The same process of coloring may also 
 be applied to single porcelain teeth representing absorption or 
 recession of the gum at the cervix, which is always of a darker 
 hue than the crown (see Fig. 93). An additional device, some- 
 times employed to disguise the fact of artificiality, is that of intro- 
 ducing gold fillings into one or more of the front teeth. Cavities 
 for this purpose are sometimes formed in porcelain teeth at the 
 time of baking. When these are not readily procured, the opera- 
 tor may easily improvise them. A dovetailed slot may be ground 
 in the proximate side of a front tooth with suitably formed cor- 
 undum-discs, or a concave depression made and retaining pits 
 formed with a hard-tempered steel drill. A correspondent of the 
 Cosmos gives the following method of using the drill : " Use a 
 hard-tempered, spear-pointed steel drill in the engine, and while 
 operating keep wet with a solution of spirits of camphor and spir- 
 its of turpentine in equal parts. The cutting will be facilitated by 
 giving the hand-piece a slight rotary motion. If a contour filling 
 is desired, grind off with the corundum-wheel as much as is 
 desired for ' contour,' after which make the retaining portion with 
 the drill." Cavities, however, can be formed with greater facility 
 by the use of the diamond drill. 
 
 With these general reflections concerning full dentures, we re- 
 turn to a consideration of the mechanical or manipulative proc- 
 esses concerned in the construction of an entire denture attached 
 to a swaged metallic plate by soldering. 
 
CHAPTER XX. 
 
 ENTIRE DENTURES ATTACHED TO A SWAGED METALLIC PLATE- 
 BASE. 
 
 Method of Constructing an Entire Upper Denture Mounted on 
 a Swaged Metallic Plate-Base. — The general form and dimen- 
 sions of the required base to be used as a support for a complete 
 denture for the upper jaw may first be indicated by drawn lines 
 upon the plaster model, and a sheet-lead pattern obtained from 
 this is to serve as a guide in securing the form of the plate to be 
 swaged. The plate should be made sufficiently ample in its di- 
 mensions to cover all the hard palate, the alveolar ridge, and all 
 portions of the external borders of the latter not directly en- 
 croached upon by the muscles and reflected portions of the mu- 
 cous membrane of the lips and cheeks. 
 
 Before swaging, the plate should be well annealed, then its 
 central portion is brought as nearly as possible to the form of the 
 palatal face of the die with the No. I or partial counter-die (see 
 page 169), forcing the heel of the plate down with suitable pliers 
 and forceps in advance of the portion covering the more anterior 
 concavity of the arch, preventing thereby a doubling of the pos- 
 terior edge of the plate upon itself. 
 
 Having conformed the plate as nearly as practicable to the die, 
 with the small counter and plate-forceps constructed for the pur- 
 pose (Fig. 96), it should be placed between the die and the larger 
 counters, which are forced together with a heavy hammer until 
 a tolerably accurate coaptation of the plate is obtained, the latter 
 being frequently annealed during the process of stamping to ren- 
 der it more pliable. At first considerable yielding and consequent 
 deformity of the counter-die will occur ; hence, after partial swag- 
 ing, another should be substituted, and the process continued un- 
 til the greatest possible accuracy of adaptation is secured. If 
 the face of the die is marked by prominent and sharply defined 
 rugae, or other irregularities, such points will, to some extent, be 
 bruised or flattened ; it will therefore be expedient in such cases, 
 
 233 
 
234 
 
 MECHANICAL DENTISTRY. 
 
 and better, perhaps, in all, to finish the swaging with a new and 
 unused die and counter, in which case two or three moderate, 
 steady, and well-directed blows of the hammer will be sufficient. 
 If the plate is brought into uniform contact with all parts of the 
 face of the die, this conformity is the only reliable test of its adap- 
 tation out of the mouth. In no case will the swaged plate fit the 
 plaster model perfectly, inasmuch as the unavoidable contraction 
 
 Fig. 96. 
 
 of the die, however slight, will, especially in deep-arched mouths, 
 cause the plate to bind on the posterior and external borders of 
 the ridge, preventing it from touching the floor of the palate ; 
 while the bruising, though inconsiderable, of the more prominent 
 points upon the die, and a corresponding flattening of the plate at 
 such points, will prevent uniform contact of the latter with the 
 unchanged surface of the plaster model. 
 
 After final swaging, the plate should be again annealed with a 
 heat nearly or quite equal to that which will be ultimately re- 
 
ENTIRE DENTURES ATTACHED TO SWAGED PLATE-BASE. 
 
 235 
 
 quired in soldering. After this, any additional swaging should 
 be avoided, unless the plate warps in the heat, which may be de- 
 termined by applying it to the die. If any change has occurred, 
 it should be reswaged, and again annealed at a high heat, and the 
 operation should be repeated, if necessary, until the plate retains 
 its integrity of form after the last annealing. This process of 
 final heating does not apply to silver if in the form of a swaged 
 plate, as this metal invariably suffers some change of form when 
 subjected to an annealing heat. 
 
 Modifications in the Form of Plates for Entire Upper Dentures. 
 — Whenever a central air-chamber is employed, it may be con- 
 structed in either of the ways described when treating of partial 
 
 Fig. 97. 
 
 Fig. 98. 
 
 atmospheric-pressure plates. The general form of an entire up- 
 per denture with a central chamber is exhibited in Fig. 97. Other 
 modifications in the form of cavity-plates for full upper sets are 
 in limited use, as where chambers are arranged one on each side 
 of the sloping walls of the palate, or directly over that portion of 
 the ridge previously occupied by the anterior molar and the bicus- 
 pids on each side, as seen in Fig. 98, called " lateral cavity-plates." 
 Whatever their general utility may be, cases doubtless occur 
 where they may be advantageously employed ; separately, as 
 shown in the illustration, or in combination with the central 
 chamber, as when any great inequality exists in the hardness of 
 the ridge and palate, such as cannot be readily overcome by ordi- 
 nary means. These lateral cavities or chambers are not cut out 
 and soldered as is sometimes done with the central chambers. 
 The cast, and consequently the die, is raised or built up slightly 
 
236 MECHANICAL DENTISTRY. 
 
 at these points, which forms in the plate when swaged, the shal- 
 low cavities shown in the illustration. 
 
 Forming the Borders of the Plate. — In whatever way the plate 
 is formed, a notch or fissure of sufficient depth to receive and 
 permit an unobstructed play of the frenum of the lip should be 
 formed in the front part of the plate, while the borders of the 
 latter nearly opposite the anterior molars on each side should be 
 narrowed to prevent undue contact of its edges with the folds 
 of the mucous membrane stretching obliquely across from the 
 cheeks to the ridge. Care should also be taken to trim away 
 from the heel of the plate any portions that might otherwise en- 
 croach upon the soft palate. 
 
 It is only in the fewest number of cases that a rim can be 
 swaged to form a groove or socket properly situated for the re- 
 ception of the plate extremities of either single gum or block 
 teeth, as it will usually be found impracticable to adjust the gum 
 extremities to the socket thus formed without necessitating, in 
 some degree, a departure from a just arrangement and antagon- 
 ism of the teeth. Whenever it is thought best, therefore, to rim 
 the plate, it will generally be necessary to adjust and solder a 
 separate strip of plate or wire along the outer borders of the 
 plate, covering somewhat the extreme edge of the gum, when 
 gum-teeth are employed, and of the pink rubber-gum, when plain 
 teeth are used. 
 
 Trying the Plate in the Mouth. — After the plate has been 
 worked as nearly as possible into the required form, it should be 
 applied to the mouth of the patient to ascertain the correctness of 
 its adaptation to the parts before proceeding further with the 
 operation. If the adaptation is found imperfect, the fault lies 
 either in the impression or in undue contraction of the die. In 
 the former case, another impression should be taken, and the plate 
 reswaged ; in the latter, a less contractile metal or compound 
 should be employed in the formation of the die. To determine 
 the practical efficiency of the adaptation and adherence of an 
 atmospheric-pressure plate, various tests may be applied. The 
 coaptation of its borders to the external walls of the ridge may 
 be ascertained by inspection, and the patient's sense of contact 
 or non-contact of its central portion with the floor of the palate 
 may, in some degree, be relied on as evidence of the accuracy of 
 
ENTIRE DENTURES ATTACHED TO SWAGED PLATE-BASE. 237 
 
 its adjustment to parts not visible. The tenacity with which the 
 plate adheres on the application of direct traction cannot always 
 be relied upon, inasmuch as a well-fitting plate will sometimes 
 readily be dislodged in this manner, while, on the contrary, one 
 but illy adapted to the parts may require considerable force to 
 separate it from the jaw when acted on in the same way. The most 
 trustworthy test of actual or practical stability is firm pressure applied 
 alternately over the ridge on each side and in front. If the plate 
 maintains its position and remains fixed under repeated trials of press- 
 ure applied in the manner indicated, the adaptation may be safely 
 relied on ; if it slides upon the palate or is easily disengaged from the 
 mouth, the instability of the plate may be referred in many cases, not 
 to a want of coaptation, but to a want of uniformity in the condition 
 of the parts on which the plate rests. These conditions have already 
 been sufficiently considered. 
 
 Method of Constructing an Entire Lower Denture Mounted 
 on a Swaged Metallic Plate-base. — Aside from the differences in 
 the form of the plate, and the manipulations incident thereto, the 
 process of constructing a plate for the under jaw does not differ 
 essentially from that already described in connection with full upper 
 dentures. 
 
 If the lower plate is constructed from a single lamina of gold or 
 other metal, it should be somewhat thicker than that used in upper 
 cases, and should also be of finer quality, as the additional thickness 
 of the plate and the peculiar form of the inferior maxilla render a 
 greater degree of pliancy necessary in swaging it to the form of the 
 ridge. The internal border of the plate should usually be doubled — 
 either by turning the edge over in swaging, or by soldering on a 
 narrow strip of plate or half-round wire as indicated at a, a, Fig. 
 99. 
 
 A more perfect adaptation of the plate to the ridge may be obtained 
 by the use of a double instead of a single plate, in which case a thin 
 plate, not exceeding No. 30 of the gage, should be swaged to the 
 form of the ridge in the first instance, and then a duplicate plate, 
 swaging the two together and uniting them to each other with solder. 
 A plate of the specified thickness may be very readily and accurately 
 conformed to any irregularities in the ridge, and when the two are 
 united the base will be heavier and stronger than a single lamina of 
 the ordinary thickness. Instead, however, of doubling the entire 
 
238 MECHANICAL DENTISTRY. 
 
 plate, it will be sufficient, in most cases, to adapt the second plate 
 only to the lingual surface of the first, extending it up from the 
 lower edge to a point corresponding as nearly as possible with the 
 inner portions of the base of the teeth when the latter are adjusted 
 to the plate, that is, at about the point indicated at a, a, Fig. 99. A 
 moderately thin plate may, in this manner, be used for the primary 
 base, while the duplicate band will impart the requisite strength to 
 the plate, and, at the same time, obviate the necessity of wiring its 
 lingual border. In adopting either of the last-named methods, the 
 plates, after they are united to each other, should be again swaged 
 to correct any change of form incident to the use of solder. 
 
 Fig. 99. 
 
 Antagonizing Model for an Entire Upper and Lower Denture. 
 
 — The following method is adopted in securing an antagonizing 
 model for complete dentures : 
 
 Attach to the ridge of each plate a roll or strip of adhesive wax 
 corresponding in width to the length of the teeth which will be 
 required for each plate respectively; place the plates, with the wax 
 attached, in the mouth, and trim away from the proximate edges of 
 the wax until the two sections close upon each other uniformly 
 throughout the circle ; then cut away from the labial surfaces of the 
 rims of wax, above and below, until the proper fulness and required 
 contour of the parts associated with the lips and mouth are secured. 
 The approximation of the two jaws, when the finished substitutes are 
 ultimately adjusted to the mouth, will depend altogether upon the 
 aggregate width given to the two sections of wax at this stage of 
 the operation, and it is, therefore, important that the " bite " or clos- 
 ure of the jaws secured at this time should be such as will most 
 
ENTIRE DENTURES ATTACHED TO SWAGED PLATE-BASE. 239 
 
 perfectly fulfil the requirements of the case in respect to the utility 
 and comfort of the appliance, and the proper restoration of the nor- 
 mal facial expression. 
 
 Re-posing the Features. — If there is any considerable change 
 produced in the relation of the jaws habitual to them prior to the 
 loss of the natural teeth, the Characteristic expression of the indi- 
 vidual will be very much changed or marred ; an unnatural and re- 
 strained action will be imposed upon the muscles concerned in the 
 movements of the lower jaw, which will render the use of the appli- 
 ances, at least temporarily, if not permanently, uncomfortable and 
 fatiguing, or even painful ; while the utility of the fixtures may be 
 impaired or wholly destroyed by compelling a particular application 
 of forces in mastication inconsistent with their stability in the mouth. 
 No specific directions, of course, can be given that will apply to all 
 cases, but it may be observed that, ordinarily, the two sections of 
 wax should be cut away from their approximating surfaces until the 
 jaws close sufficiently to permit the edges of the lips to rest easily 
 and naturally upon each other when in a relaxed condition, or the 
 upper rim may extend somewhat below the margin of the upper lip, 
 while the lower section of wax is cut away on a level with the lower 
 lip, or a little below it. Cases occur, however, where a less exposure 
 of the upper portion of wax, even though quite narrow, will be re- 
 quired ; as where the alveolar ridge is very deep, and the lip covering 
 it either absolutely or relatively short, or where the latter is retracted, 
 exposing, even when in a state of repose, a greater portion of all of 
 the crowns of the teeth, and in extreme cases the margins of the gum. 
 Between the latter extreme and an inordinate extension of the upper 
 lip below the ridge, all intermediate conditions occur, and the prac- 
 titioner, aiming to produce an agreeable, harmonious, and truthful 
 expression of all the parts, must rely wholly upon his judgment in 
 reference to the necessary approximation of the jaws, the restoration 
 of the natural fulness and contour of the face, and the relative length 
 to be given to the upper and lower teeth. 
 
 The dentist needs to study the face of his patient as the artist 
 studies his picture, for he displays his genius not upon canvas but 
 upon the living features of the face. He should know the origin 
 and insertion of the principal muscles of which the face is formed, 
 and which ones he is to raise, otherwise he will be liable to produce 
 distortion instead of restoration. This improvement consists of 
 
240 
 
 MECHANICAL DENTISTRY. 
 
 prominences made upon the denture of such form and size as to 
 bring out each muscle or sunken portion of the face to its original 
 fulness ; and when these are rightly formed, they are not detected 
 by the closest observer (see Fig. ioo). There are four points of 
 the face (of many persons) which the mere insertion of the teeth 
 does not restore, viz., one upon each side beneath the malar or cheek 
 bone, and also a point upon each side of the base of the nose, in a 
 line toward the front portion of the malar bone. 
 
 The extent of this falling-in varies in different persons, accord- 
 ing to their temperaments. If the lymphatic temperament predomi- 
 nates, the change will be slight. If nervous or sanguine, it may be 
 
 Fig. ioo. 
 
 very great. The muscles situated upon the sides of the face, and 
 which rest upon the molar or back teeth, are the zygomaticus major, 
 masseter, and buccinator. The loss of the upper teeth causes these 
 muscles to fall in. The principal muscles which form the front por- 
 tion of the face and lips are the zygomaticus minor, levator labii 
 superioris alseque nasi, and orbicularis oris. 
 
 These rest upon the incisor, cuspid, and bicuspid teeth, which, 
 when lost, allow the muscles to sink in, thereby changing the form 
 and expression of the mouth. 
 
 The insertion of the front teeth will, in a great measure, bring 
 out the lips, but there are two muscles in the front portion of the 
 face which cannot, in many cases, be thus restored to their original 
 position ; one is the zygomaticus minor, which arises from the front 
 part of the malar bone, and is inserted into the upper lip above the 
 angle of the mouth; the other is the levator muscle, which arises 
 from the nasal process and from the edge of the orbit above the in- 
 
ENTIRE DENTURES ATTACHED TO SWAGED PLATE-BASE. 24 1 
 
 fraorbital foramen. It is inserted into the ala nasi, or wing of the 
 nose and upper lip. 
 
 The prominences before mentioned, applied to these four points 
 of the face, beneath the muscles just described, bring out that nar- 
 rowness and sunken expression about the upper lip and cheeks to 
 the same breadth and fulness which they formerly displayed. If 
 skill and judgment have been exercised in building up and forming 
 the wax bite-pieces and is continued throughout the operation, the 
 result will be highly pleasing and of practical utility. 
 
 Projection of the Lower Jaw. — Patients, when requested to 
 close the mouth naturally, are very liable to project the lower jaw; 
 hence it is well to have them open and close the jaws several times, 
 observing at the same time if the separate portions of wax meet in 
 precisely the same manner at each occlusion. If the bite varies at 
 every approximation of the jaws, directions should then be given to 
 relax and abandon for the moment all control over the muscles of 
 the lower jaw; the patient should then be directed to close lightly 
 upon the wax in the back part of the mouth. The attention thus 
 being drawn in that direction, the jaw will naturally come back and 
 close in the normal position. The median line should then be drawn 
 across both plates, and a cross, or two or three oblique lines made 
 on each side; after this is accomplished, the patient should again be 
 directed to open and close the mouth, and note whether these lines 
 are brought accurately together; if so, it is fair to assume that the 
 bite is correct. We should then have the patient bring slight 
 pressure upon them by closing the jaws a little harder, when, if the 
 occluding surfaces have been previously passed over the flame, they 
 will adhere so firmly that they may be readily removed from the 
 mouth together, without displacement. Or a heated knife-blade 
 may be passed between the two sections, the melted wax temporarily 
 uniting them. Another very convenient and secure method is to 
 attach them together by means of two strips of metal bent in the 
 form of a staple ; these may be warmed in a spirit-flame, and pressed 
 into the wax, one on each side — one end penetrating the upper rim 
 of wax, the other the lower. 
 
 The plates, attached to each other as shown in Fig. 101, may be 
 
 removed from the mouth, plaster mixed and poured into them to 
 
 form temporary models for attachment in the articulator. When 
 
 the plaster is sufficiently condensed, the line across the wax in front 
 
 16 
 
24- 
 
 MECHANICAL DENTISTRY. 
 
 should be extended in a direct line across the borders of the plaster 
 model above and below,, as, in arranging the teeth, the wax will be 
 
 Fig. 
 
 removed, and without this precaution the mesial point of the mouth 
 may be lost. 
 
 Antagonizing Model for an Entire Upper Denture with the 
 Natural Teeth of the Lower Jaw Remaining. — In forming an an- 
 tagonizing model to be used as a guide in arranging and articulating 
 a full upper denture where all or a part of the natural organs of the 
 inferior jaw are remaining, a rim of wax should first be adjusted to 
 the borders of the plate, one or two lines wider than the required 
 length of the artificial teeth. When placed in the mouth, the exterior 
 surface of the wax draft should be cut away or added to, until the 
 proper fullness of the parts is restored. The patient should then 
 close the lower teeth against the wax, imbedding them just sufficiently 
 to indicate the cutting edges and grinding surfaces. The median 
 line of the mouth is then indicated upon the wax and the plate re- 
 moved, when the two casts (the lower having been previously secured 
 from a wax or modeling compound impression) should be secured in 
 the articulator as illustrated in Fig. 102. 
 
 Articulators. — Various articulators have been devised. Fig. 
 103 illustrates one of the simpler forms, while a very ingenious and 
 novel device has been brought to the notice of the profession by 
 Dr. W. G. A. Bonwill, to which we give considerable space. The 
 inventor has characterized it as the " Anatomical Articulator," and 
 describes it as follows : 
 
ENTIRE DENTURES ATTACHED TO SWAGED PLATE-BASE. 
 
 243 
 
 " It is modeled on the same geometrical system as the human jaw. 
 
 " I found by measurement that the average width of the lower 
 jaw from center to center of each condyle was four inches, and from 
 the same center of each condyloid process to the median line of the 
 lower jaw. where the cutting edges of the lower incisors meet, was 
 also four inches, making of the human jaw an equilateral triangle. 
 This holds good in all jaws, and the difference of Y\ of an inch in this 
 
 Fig. 102. 
 
 radius of a circle of four inches would make but little practical dif- 
 ference as to the results. 
 
 " This beautiful law enables us to have the fullest benefit of mas- 
 tication at the least expense of power and motion in the arc of the 
 circle of four inches as a radius. 
 
 " This being an absolute law, I have so made this articulator, and 
 the cast of every case is set therein with the median line at the lower 
 centrals just four inches, by the dividers, from each condyloid pro- 
 cess. If an unusually large jaw, then the cast is put a very little 
 distance further out. 
 
 " For all full sets, the articulation is so perfect, as made in this, in 
 the laboratory, as to need but a trifling touch in fitting: in the mouth. 
 
244 
 
 MECHANICAL DENTISTRY. 
 
 " I found that there is a further positive law in the mechanism of 
 the human jaw that should be regarded in every substitute made 
 therefor, and that is, just in proportion to the depth of overbite of 
 the centrals, there is a curvature from the mesial surface of the first 
 molars back, through the other molars, up the ramus. That this 
 curvature upward and backward at the ramus is due solely to the 
 depth of closure of the upper over the lower jaw. That where there 
 is occlusion or closing of the cutting surfaces of the incisors directly 
 
 Fig. 103. 
 
 upon each other, then a straight line, directly backward, is the conse- 
 quence. If curved at the ramus, in such a case no lateral or forward 
 movement of the lower jaw could occur — only the up and down. 
 
 " When there is l /g of an inch depth- of bite, then, as you go back 
 to the center of motion — the condyloid processes — the cusps in the 
 bicuspids and molars grow less deep, and the curvature at the ramus 
 is ]4>, of an inch out of line. 
 
 " When there is an overbite of J /x of an inch, then, in opening 
 the lower jaw and carrying it forward to use the incisors for cutting, 
 the back teeth of the lower jaw are brought forward; and as the 
 second molar is higher out of line than the first molar, it comes in 
 contact with the distal surface of .the first superior molar, which 
 begins just here to curve upward, and is the highest out of line in 
 
ENTIRE DENTURES ATTACHED TO SWAGED PLATE-BASE. 
 
 245 
 
 the superior jaw, and they meet at the same time that the incisors 
 do. And the same law holds good when the lower jaw is turned to 
 the right or left; the molars are brought in contact to equalize the 
 force which would be brought upon the incisors only. Besides, the 
 recognizing of this law enables the cusps or palatal and lingual sides 
 of the molars of both jaws to be utilized in every position the lower 
 jaw may take in mastication. Upon this plan I make all my arti- 
 ficial dentures, most of their articulating surfaces being utilized at 
 every position of the lower jaw. Any human jaw will show this 
 
 Fig. 104. 
 
 system, which, by this system, can be made just as complete, and 
 more so in many cases, than. the normal, or such as is found in ad- 
 vanced civilization. 
 
 " When a set of teeth is commenced in this articulator with the 
 upper overbiting the lower )/% of an inch, as you set each tooth back- 
 ward toward the condyloid processes they will assume the exact 
 angle and depth of cusps, as well as the curvature at the ramus, as 
 found in nature. If both jaws are in direct opposition at the in- 
 cisors, then all of the teeth must of necessity be on a perfect plane, 
 or but one would touch when in lateral position. 
 
 " With this one base, which Fig. 104 shows, there is a separate 
 bow to each part of base, one for upper and one for lower jaw, which 
 can be removed as soon as the plaster in one case is allowed to harden 
 on the rim. This can be marked and laid away for a vear if neces- 
 
246 MECHANICAL DENTISTRY. 
 
 sary, and then articulated. A pair of bo.ws can be used for as many 
 separate cases, while only one base is required, which should be made 
 absolutely and geometrically exact— approximately so. 
 
 " The set screw in the center is to hold the jaw or casts apart after 
 the proper distance has been secured in taking- the bite. Or this 
 may be regulated on the bite in wax, which, before it is taken off 
 the base-plate, has the exact height marked by a pair of dividers 
 on the plaster at the median line, measuring from the cutting edge 
 of wax, and then, when the first central or block is set, there is no 
 longer any call for a prop to keep open the jaws of the articulator. 
 When this height is taken with the dividers, it is marked on the 
 top of each cast for future reference. The dividers make each cast 
 exact without a scale for measurement. 
 
 " Articulate the upper set first, and retain on the lower base the 
 wax for length and fulness. When the upper are all on, then the 
 lower incisors are gaged as to the height or length by the dividers 
 while the wax is still on the base-plate and taken from the height 
 marked on the lower cast for reference. 
 
 " M ake the lateral movement as soon as the first tooth or block 
 is in position where the case is an upper one with a good lower jaw 
 of natural teeth. 
 
 " When a full set, the upper are first ground on and shaped so as 
 to meet the intended overbite, and when the lower set are ground on, 
 the upper can be changed to suit the lower, so as to allow the whole 
 of every cusp to touch at nearly every lateral movement of jaw. 
 
 " When the plaster case is to be set in the articulator, it must be 
 done with the dividers set just four inches, with one point at the 
 median line as formed by the lower incisors, and the other carried 
 over to each condyloid process as marked on the articulator. This 
 makes the center of jaw equidistant from the condyles. The study 
 of this principle will make one fully realize the beautiful workings 
 of Divinity, which is only governed by positive law in every depart- 
 ment of the universe. With this plan understood, one will never 
 again attempt to articulate a set of teeth on the unwritten law, as 
 now universally made and recognized by every dentist in the land. 
 
 " Until this system is taught in the schools and by private prac- 
 titioners, no truly artistic and fully natural set of teeth can ever be 
 made, for we have been without law in this department. To de- 
 scribe it is not enough. Jt must be seen and demonstrated, one 
 
ENTIRE DENTURES ATTACHED TO SWAGED PLATE-BASE. 247 
 
 tooth at a time, until the whole set is made. Only in this way can 
 it be understood. 
 
 " The construction of this articulator is very simple. It is made 
 of brass wire (y% of an inch in diameter), and brass tubing to allow 
 the size of wire to fit closely, and move freely therein when drawn 
 out or pushed up. The spiral spring on either condyle allows of 
 easy lateral motion to the lower part, and from exactly the same 
 standpoint as in nature; that is, one of the lower condyles moves 
 forward in the glenoid cavity while the other remains still. Every 
 part of it is rigid except the movement at the condyles, and the 
 joints or bows are only temporarily so. There is also an up-and- 
 down motion made at the condyles by raising the bow up or down. 
 
 " No case, when once fixed in it, can become disarranged. If the 
 bite in the wax is not correct, no articulator can make it so. You 
 must go back again to the mouth and retake it, which is easily done 
 at first by asking the patient to swallow, when the jaws will auto- 
 matically close and assume their normal position. If now correct, 
 there is never any necessity for a screw to change it when once in 
 this articulator. 
 
 " There can be no excuse for failure or inartistic work when this 
 instrument is once understood and the law controlling the human 
 jaw. As we may forever have to resort to artificial dentures, we 
 should demand of the colleges that such an instrument be used, and 
 it alone, as furnishing the only hope now offered of an approach to 
 high-toned, artistic, mechanical dentistry. Until we can be taught 
 to appreciate that law is the governor of the universe, and applicable 
 in every branch of dentistry, we are false men, and will set ' false 
 teeth,' and never realize our high destiny." 
 
 Grinding and Adjusting Single Gum Teeth. — In arranging or 
 adjusting single gum teeth to the plate in those cases where the 
 changes in the form of the alveolar ridge, consequent on absorption, 
 are completed, the portions applied to the base should be ground 
 away sufficiently to restore the required fulness of the parts and to 
 give proper length and inclination to the teeth. The coaptation of 
 the ground surfaces to the base should be accurate enough to exclude 
 perfectly particles of food, and to furnish such a basis to each tooth 
 as will provide most effectually against fracture when acted upon by 
 the forces applied to them in the mouth. The gum extremities of 
 the teeth should also be accurately united to each other laterally by 
 
248 MECHANICAL DENTISTRY. 
 
 grinding carefully from their proximate edges until the joints or 
 seams will be rendered incapable of ready detection in the mouth, 
 care being taken that this coaptation of the adjoining surfaces is uni- 
 form, for if confined to the outer edge alone, portions of the gum 
 enamel may be broken away in the process of soldering. 
 
 Arranging for Temporary Plates. — In the construction of sub- 
 stitutes designed to fulfil only a temporary purpose, and where the 
 alveolar processes remain in a great measure unabsorbed, and plain 
 teeth (those representing but the crowns of the natural organs) 'are 
 used, but little skill will ordinarily be required in adjusting and fitting 
 them to the base. If the ridge in front is prominent and but inade- 
 quately concealed by the lip, as where the teeth have been but re- 
 cently extracted, all those portions of the border of the plate in 
 front, anterior to the first or second bicuspid on each side, may be 
 cut away on a line a little within the required circle of the anterior 
 teeth and scalloped, permitting the anterior cervical portions of the 
 artificial incisors and cuspids, and, in some cases, the anterior bicus- 
 pids, to overlap the edge of the plate and rest directly and firmly 
 upon the gum in front. This abridgment of the plate is shown in 
 Figs. 94, 95, page 231, and will not, ordinarily, materially affect the 
 adhesion or stability of the substitute. 
 
 There are cases of a mixed character that render it more difficult 
 to effect a harmonious and symmetrical arrangement of the teeth, 
 as where a limited number of the natural teeth at intervals have been 
 long absent, and the excavations in the ridge consequent on absorp- 
 tion alternate with other points upon the ridge in a comparatively 
 unchanged condition. To give uniformity to the denture by restor- 
 ing perfectly the required circle of the arch in such cases will neces- 
 sitate the employment of plain and single gum teeth conjointly. 
 Whenever necessary, those portions of the base occupied by the plate 
 teeth may be cut away in such a manner as to permit the latter to be 
 adjusted directly to the unabsorbed gum as before described. 
 
 Arranging the Teeth for a Full Upper and Lower Denture. — 
 In the process of grinding the teeth to the base, above and below, the 
 operator should commence by first arranging the superior central 
 incisors, and then the lower, and so, passing back from tooth to 
 tooth, grind and adjust an upper and lower tooth alternately, keep- 
 ing the upper ones in advance of those of the lower jaw. The cen- 
 tral incisors above should be placed parallel with each other, but the 
 
ENTIRE DENTURES ATTACHED TO SWAGED PLATE-BASE. 249 
 
 cutting edges of the laterals and the points of the cuspids should 
 incline slightly toward the median line of the mouth. In arrang- 
 ing the teeth of the upper jaw, the anterior six may be made to 
 describe, with more or less exactness, the segment of a circle, but 
 a somewhat abrupt angle may be 
 given to the arch on each side by FlG- I05- 
 
 placing the first bicuspid within the 
 circle in such a way that, when 
 standing directly in front of the 
 patient and looking into the mouth, 
 only a narrow line of the exterior 
 face of the crowns of these teeth 
 will be seen, while the remaining 
 teeth posterior to them should be 
 arranged nearly on a straight line, 
 diverging as they pass backward. 
 
 When arranged in the manner described, the peripheral outline of 
 the arch will exhibit somewhat the form presented in the diagram 
 (Fig. 105). 
 
 In regard to the practical efficiency of an upper denture retained 
 in the mouth by atmospheric pressure or adhesion, it is important 
 that the teeth engaged in the comminution of food, as the bicuspids 
 and molars, should occupy a position directly over the central line 
 of the ridge, and should either be arranged vertically or with a 
 slight inclination toward the center of the mouth. The liability to 
 displacement of the substitute in mastication will thus be greatly 
 diminished, whereas, if placed outside of the line indicated, and 
 especially with a diverging inclination, the stability of the appliance 
 will be endangered and the functions of mastication impeded, not- 
 withstanding other conditions necessary to complete success have 
 been fully secured. In arranging the upper and posterior teeth as 
 described, it will sometimes be necessary to give to the opposing 
 under teeth a decided inward inclination in order to effect a satis- 
 factory antagonism of the teeth ; and cases occur where a practical 
 articulation cannot be secured without departing in some degree 
 from the arrangement of the upper teeth spoken of, — as where a 
 great disparity exists between the posterior transverse diameters of 
 the two jaws, a medium-sized, or even small arch above being asso- 
 ciated with an expanded ridge below. 
 
25O MECHANICAL DENTISTRY. 
 
 In articulating the upper and lower teeth, the normal occlusion 
 of the natural organs should be imitated as nearly as the other essen- 
 tial requirements of the case .will admit. Hence the upper front 
 teeth, describing the segment of a larger circle than the correspond- 
 ing teeth of the lower jaw, will project beyond and overlap slightly 
 the cutting edges of the latter ; and having a greater width of crown, 
 they will extend latterly beyond the opposing teeth, covering one- 
 third of the crowns of those next adjoining, so that when the cus- 
 pids of the upper jaw are reached, they will close between the" lower 
 cuspids and first bicuspids; and, passing back, the anterior superior 
 bicuspids between the first and second bicuspids below ; the posterior 
 bicuspids above, between the second inferior bicuspids and anterior 
 molars ; the first superior molars between the first and second molars 
 below ; while the anterior half of the posterior molars above will 
 close upon the posterior half of the inferior second molars, the re- 
 maining posterior half of the second molars above extending poste- 
 riorly beyond those of the lower jaw. The outer cusps of the supe- 
 rior bicuspids and molars will overlap those of the inferior teeth; 
 while the inner cusps of the teeth of the superior jaw will pass into 
 the depressions in the lower teeth formed by the internal and exter- 
 nal cusps, and the external cusps of the inferior teeth will, in like 
 manner, be received into the corresponding excavations of the upper 
 teeth. An abnormal relation of the jaws, as where undue projec- 
 tion, absolutely or relatively, of either maxilla exists, or where the 
 lower jaw closes on one side or other of the upper, will frequently 
 compel a departure from the ordinary arrangement of the artificial 
 organs, the extent of which must be determined by the necessities 
 of each individual case. 
 
 In selecting teeth for a full upper denture in those cases where 
 natural organs are remaining below, or vice versa, the color, size, 
 and form of the latter will serve as a guide in the choice of teeth 
 appropriate for the opposite jaw. In fitting and arranging the 
 teeth upon the base, and in antagonizing them with the opposing 
 natural teeth, the same general principles apply as those already 
 adverted to in connection with full upper and lower dentures. 
 
 Having adjusted the teeth to the base, they should be placed in 
 the mouth before uniting them permanently to the plate, to detect 
 and remedy any error of arrangement cither in respect to prominence, 
 position, inclination, length, or antagonism. 
 
ENTIRE DENTURES ATTACHED TO SWAGED PLATE-BASE. 25 1 
 
 Forming a Rim to the Plate. — If the case is one where single 
 gum or block teeth are employed, and it is intended to form a socket 
 or groove upon the borders of the plate for the reception of the plate 
 extremities of the teeth, the rim forming the groove should be fitted 
 and soldered to the base before investing the piece in plaster. If the 
 alveolar ridge above is shallow, and but imperfectly concealed by the 
 lip, a rim to the plate will be inadmissible, as when the mouth is 
 opened and the lip retracted, as in laughing, the metallic band will 
 he exposed to view. A rim may be fitted and attached to the base 
 in either of the following ways : 
 
 1. A strip of plate from one to two lines in width is adjusted to 
 the plate, with one edge resting on the uncovered border of the plate, 
 close to the gum extremities of the teeth, and the other overlapping 
 and embracing the latter. The rim may be more conveniently ad- 
 justed by employing two pieces, extending from each heel of the 
 plate and uniting in front. 
 
 2. A half-round wire with the edge beveled where it joins the 
 ends of the teeth, forming a narrow groove, may, in like manner, 
 be fitted to the plate, furnishing a shallow bed for the gum extrem- 
 ities of the teeth. Or a narrow strip of plate, about the thickness of 
 heavy clasp material, niay be substituted for the half-round wire. 
 In either case, the better plan is first to trace the outlines of the 
 gum portions of the teeth upon the plate with a sharp instrument; 
 remove the wax and teeth from the plate; draw another line a little 
 within the first all round, and solder the rim to the line last drawn ; 
 remove the teeth from the wax, and readjust the latter in. its proper 
 place upon the plate; then fit each tooth separately to the rim by 
 grinding away sufficiently from the end of the tooth to effect an 
 accurate adjustment of it to the socket. The ends of the teeth may 
 be ground away to the rim until the platinum pins freely reenter 
 the rivet-holes in the wax, thus restoring them to their proper posi- 
 tion in relation to the base. 
 
 3. Another method of forming a rim consists in swaging a strip 
 •of plate accurately to the form of the parts to which it is applied. 
 An impression in wax or plaster is first taken of the gum surfaces 
 of the teeth and exposed border of the plate; but as it will be im- 
 possible to detach either wax or plaster in perfect condition when 
 encircling the entire arch, or to swage perfectly with a die so unfa- 
 vorably formed for stamping, separate impressions of the two lateral 
 
252 MECHANICAL DENTISTRY. 
 
 halves of the piece should be taken from these plaster models, and 
 from the latter, dies and counters produced ; — with these, two strips 
 of plate of sufficient width are swaged, each extending from the heel 
 of the plate to a little beyond the median line in front, overlapping 
 slightly at the latter point. The portions of the swaged strips 
 embracing the plate ends of the teeth are then trimmed to the proper 
 width, and scalloped, if desired, in correspondence with the festoons 
 of the artificial gums. In whatever way the rim is formed, when 
 it has been fitted to the plate and teeth it may be held temporarily 
 in place with clamps (such as are shown in soldering air-chamber 
 in plate, page 201) adjusted at two or three points around the plate 
 and then transferred to a piece of charcoal, or soldering block, and 
 secured by first tacking it at two or three points with solder. The 
 groove may then be filled with whiting, mixed with water or alco- 
 hol to prevent the solder from flowing in and filling it up ; after 
 which small pieces of solder are placed along the line of union next 
 the edge of the plate, and the rim permanently united throughout 
 with the blowpipe ; after which the wax and teeth are reapplied to- 
 the plate. 
 
 Constructing and Attaching Spiral Springs. — The success 
 which has been attained in the use of atmospheric pressure and ad- 
 hesive plates has almost entirely superseded the necessity of employ- 
 ing spiral springs as means of support ; nor should the latter be 
 resorted to except under circumstances that preclude the use of the 
 former, as in case of cleft palate, for instance. When applied, they 
 should be attached to the base on each side between the posterior 
 bicuspid and first molar below, and opposite the posterior bicuspid 
 above. To the border of the plate near the base of the teeth a nar- 
 row strip of plate is soldered, extending up and lying closely against 
 the side of the latter, to the end of which, near the grinding sur- 
 faces of the teeth, is adjusted a small, circular cap of gold connected 
 with the standard by a small wire on which the looped extremity 
 of the spring plays. To each end of the spring is attached a gold 
 swivel, one end to enter the hollow in the wire, the other attached 
 to the plate, either by soldering or vulcanizing as the case may be. 
 The appliance is shown in Fig. 106. Figs. 107 and 108 exhibit the 
 application of springs to an upper and lower denture. In this in- 
 stance plain teeth with rubber attachment arc shown, but they may 
 be readily attached to any form of teeth or plate. 
 
ENTIRE DENTURES ATTACHED TO SWAGED PLATE-BASE. 
 
 253 
 
 Investing. — The plate, with the wax and teeth in place, is next 
 incased in a mixture of plaster, preparatory to backing the teeth 
 and uniting them with solder to the base. For this purpose plaster 
 and sand may be employed, using as little of the former as will serve 
 
 Fig. 106. 
 
 to hold the investment together during the subsequent manipula- 
 tions. Asbestos may be added, and is a useful ingredient. Burnt 
 plaster, or that which has been previously used for investing, may 
 be substituted for the sand and asbestos, adding a sufficient quantity 
 
 Fig. 108. 
 
 of unused plaster to effect consolidation. Either of the combina- 
 tions mentioned will suffer but little change in the fire if properly 
 managed. It is customary to incase the piece in the plaster mix- 
 ture to the depth of from ]/ 2 to }i of an inch, leaving only the lingual 
 surfaces of the plate and teeth uncovered. 
 
; 54 
 
 MECHANICAL DENTISTRY, 
 
 Warping or Springing. — However comparatively free from 
 change of form the best combinations of plaster may be, yet some 
 slight contraction of the body of the investment doubtless ensues 
 on the application of heat, and it is probable that so large and re- 
 sistant a mass must tend, in some degree, to produce deformity of 
 the plate in soldering; for, as the investment contracts and the plate 
 at the same time expands when heated, a change in the form of the 
 latter must occur whenever the force exerted by the shrinking plas- 
 ter exceeds the expansive force of the metal ; and when the peculiar 
 form of the upper plate is considered, we can readily conceive how 
 a slight contraction of the plaster of the thickness mentioned may 
 " warp " or " spring " the plate when its uniform linear expansion 
 and contraction is so effectively opposed. The change in the form 
 of the base from this cause will, according to the writer's observa- 
 tions, be found, in an upper plate, to exist on each side of the slop- 
 ing walls of the palate, embracing the posterior half or two-thirds 
 of the plate at these two points — the change manifesting itself in an 
 inward displacement of the lateral walls of the plate midway between 
 the summit of the palatal arch and the most depending portion of 
 the ridge. We would suggest in explanation of this result that, as 
 the plaster contracts with sufficient force to carry the plate with it, 
 the sides of the latter are approximated, while the palatal portion is 
 at the same time lifted up. Now it seems plain, that inasmuch as the 
 portions of plate overlapping the ridge are incased in and embraced 
 by the plaster, and as the palatal portion is arched in form with its 
 convexity presenting to the plaster, and therefore self-sustaining in 
 respect to its own peculiar form, the special configuration of these 
 parts cannot suffer any appreciable change ; but as they are forced 
 toward the common center of the mass, their relation to each other is 
 also changed, and this changed relation must necessarily result in a 
 deformity of those parts of the plate which offer the least resistance 
 to the contractile force of the plaster. In obedience to this neces- 
 sity, the sides of the plate along the sloping walls of the palate, which 
 from their form are neither resistant nor self-sustaining under press- 
 ure, and whose inward displacement is unopposed by any counter- 
 force, are projected in toward the center of the palatal excavation 
 in proportion as the borders and central portions are approximated 
 or converged in the direction of the center of the piece. The prac- 
 tical effect of this approximation of the lateral and posterior borders. 
 
ENTIRE DENTURES ATTACHED TO SWAGED PLATE-BASE. 255 
 
 and internal displacement of the plate is to make the latter " bind " 
 upon the outer and posterior borders of the alveolar ridge, and to 
 throw the central portion of the plate from the roof of the mouth. 
 
 Methods of Overcoming the Tendency to Change in Form. — 
 To obviate, as far as practicable, any change in the form of the plate 
 which may result from the contraction of the plaster investment, 
 various expedients have been suggested, but the following will suf- 
 ficiently counteract the influence of the plaster by permitting an un- 
 obstructed expansion and contraction of the metallic base. Take a 
 band of tolerably thick copper plate, as wide as the plate and teeth 
 are deep ; bend it to the form of the plate, but large enough to leave 
 a space of nearly ^ of an inch between it and the teeth, the ends 
 being united to each other back of the plate by riveting or other- 
 wise. Holes are then made in the band at numerous points through- 
 out its extent, through which wire is introduced and interlaced on 
 the inside in such a way as to form loops, the latter extending in to 
 within a short distance of the teeth. The plaster is then filled into 
 the space between the band and teeth, even with the cutting and 
 grinding surfaces of the latter; the palatal surface of the plate is 
 also covered with plaster and may be connected with the outer por- 
 tion by a very thin layer at the edge of the plate, or the two may 
 be entirely disconnected. The expansion of copper being very nearly 
 that of gold, the body of the plaster, when heat is applied, will be 
 carried in advance of the borders of the plate as the latter expands, 
 while the thin portion of plaster at the edges of the plate will allow 
 the central portion of the latter to expand with but little or no inter- 
 ruption. On cooling, the entire mass will contract and assume its 
 original form, unless warping is induced by other agencies acting 
 independently of the enveloping plaster, as excess or unequal distri- 
 bution of solder, irregular heating, etc. 
 
 It is not, ordinarily, necessary to provide by any special expedient 
 against warping of the lower plate, as any slight change of form 
 consequent on contraction will not materially affect its adaptation to 
 the lower jaw — its only effect being to impart to the substitute a 
 slight lateral play upon the ridge. The plaster on the inside of the 
 lower piece may be cut away to the edge of the plate, while that 
 external to the teeth should not be added in greater quantities than 
 is barely sufficient to hold the latter in place while backing and sol- 
 dering them to the base. 
 
2^6 MECHANICAL DENTISTRY. 
 
 Backing or Lining the Teeth. — The plate being properly in- 
 vested, all portions of the wax attached to the inner surface of the 
 teeth and plate should be thoroughly removed with suitable instru- 
 ments, after - which stays or backings are to be adjusted to the teeth. 
 In reference to the method of forming and adjusting backings, little 
 need be added to what has already been said when treating of par- 
 tial dentures. One method, not there specified, consists in first 
 fitting to each tooth separately, in the usual manner, a thin backing 
 formed of platinum, which is temporarily fastened to the tooth by 
 splitting and spreading apart the ends of the rivets with a small 
 chisel-shaped instrument. The teeth are then removed from the 
 investment and partially imbedded side by side in plaster, the plati- 
 num strips remaining uncovered. The plaster and teeth may then 
 be raised to a full red heat with a blowpipe or by placing them in 
 the furnace. Small pieces of gold plate, of equal fineness with the 
 base, are then placed upon the surfaces of the platinum backings and 
 thoroughly fused with the blowpipe until they flow perfectly in 
 around the rivets, and uniformly over the surface. If sufficient heat 
 is applied, the solder will insinuate itself between the stay and tooth, 
 and thus render the coaptation of the two perfect. Small pieces of 
 gold plate should be added until sufficient thickness is imparted. 
 The backings are then trimmed smoothly, when they may be placed 
 back in the investment in their appropriate places. They may then 
 be united to each other laterally in sections or continuously, when 
 the teeth are joined to each other throughout, a very small quantity 
 of solder being sufficient to support them, provided it is well diffused 
 along the joints, uniting them perfectly at all points. 
 
 Soldering and Finishing. — The process of preparatory heating, 
 soldering, pickling, and finishing the plate is the same in all respects 
 as that described when treating of partial pieces (see p. 210), and 
 need not, therefore, be recapitulated. 
 
 In the final adjustment of the finished piece to the mouth, and 
 after any additional grinding of the masticating surfaces of the teeth 
 necessary to perfect the antagonism has been performed, such in- 
 structions should be given to the patient in regard to the care and 
 management of the appliances as will best promote their immediate 
 and successful use. The wearer should be impressed with the abso- 
 lute necessity of early and prompt attention to any injuries inflicted 
 .upon the soft tissues of the mouth by the substitutes, as much future 
 
ENTIRE DENTURES ATTACHED TO SWAGED PLATE-BASE. 257 
 
 trouble and annoyance, if not permanent mutilation of the parts, may 
 result from neglect, but which may be readily averted, in most in- 
 stances, by a timely removal of the sources of injury. To obviate, 
 in some measure, the tendency to displacement of the base which 
 usually accompanies the first use of artificial teeth, and especially 
 the upper denture, the patient may be directed, when dividing food 
 with the front teeth, to press the substance backward and upward 
 against the cutting edges of the superior incisors at the same time 
 that the opposing teeth are closed upon each other, thus dividing com- 
 pletely the substance seized. In reference to the mastication of food, 
 it has been suggested to instruct the patient to distribute, by the 
 action of the tongue, the portions of food as equally as possible on 
 each side of the mouth, in this manner distributing the forces applied, 
 and thereby lessening the chances of lateral displacement of the sub- 
 stitute. 
 
 17 
 
CHAPTER XXL 
 
 MANUFACTURE OF PORCELAIN TEETH. 
 
 The perfection and completeness of results attained at this day 
 in the production of porcelain teeth, approximating so nearly the 
 natural organs in all their more obvious, physical, and distinctive 
 characteristics as to be almost, if not quite, indistinguishable from 
 the latter when applied in obedience to the esthetic requirements 
 of individual cases, is one of the marvels of ceramic art. Nowhere, 
 perhaps, have the conceptions of genius been embodied in porce- 
 lain with more truthfulness or greater fidelity to nature than in the 
 exquisite and wonderful imitations of the dental manufacturing 
 laboratory. 
 
 So amply and satisfactorily has the intelligent, progressive, and 
 well-directed enterprise of manufacturers provided for all the ordi- 
 nary needs of prosthetic practice in the almost endless variety in 
 size, color, configuration, relation, and adaptability of single and 
 sectional teeth, that the work of hand-carving is now rarely de- 
 manded of the general practitioner, except in extreme cases result- 
 ing either from accident or disease. Thus, as aptly remarked by 
 the late Professor Austen : " The dental depot not only renders ser- 
 vice by the superior excellence of the surgical instruments and 
 prosthetic materials which it supplies, but it directly benefits the 
 science and art of dentistry by releasing the practitioner from man- 
 ufacturing toil, and giving time for the acquirement of increased 
 knowledge and skill. Thus, if the time heretofore given to block- 
 making were devoted to the study of dental esthetics, patients would 
 have the benefit of an artistic selection from a far larger variety of 
 porcelain dentures than could otherwise possibly be made." 
 
 As affording some curious as well as practical information in re- 
 gard to the composition and manufacture of porcelain teeth, the 
 following descriptions will be found of interest: 
 
 Components of Dental Porcelain. — Manufactured single and 
 sectional mineral teeth, carved block-teeth, continuous-gum mate- 
 
 258 
 
MANUFACTURE OF PORCELAIN TEETH. 259 
 
 rial, etc., are composed of two distinct portions — the body, or base', 
 and enamel. The chief mineral substances which compose the body 
 are silex, feldspar, and kaolin. The enamel, both crown and gum, 
 consists principally of feldspar. 
 
 The various tints or shades are imparted to the porcelain by cer- 
 tain metals in a state of minute division, or their oxids. The more 
 general properties of the mineral ingredients will be first described. 
 
 Silex. — Silex, silica, or silicic acid, is a white powder, inodorous 
 and insipid. It forms the chief part of many familiar mineral for- 
 mations, as quartz, rock-crystal, flint, agate, and most sands and 
 sandstones, in some of which it occurs nearly pure. Silica, in its 
 pure state, is insoluble in water or acids, and is infusible in the 
 highest heat of the furnace ; it melts, however, in the flame of the 
 oxyhydrogen blowpipe, passing into a transparent, colorless glass. 
 Its specific gravity is 2.66 ; and it is composed of silicon, 48.04, and 
 oxygen, 51.96. Only the purest varieties of silex are employed in 
 the manufacture of porcelain teeth. It is prepared for use by sub- 
 jecting it to a white heat and then plunging it into cold water, after 
 which it is ground to a very fine powder in a mortar. 
 
 Feldspar. — This mineral substance occurs crystallized in 
 oblique rhomboidal prisms, and is a constant ingredient of granite, 
 trachyte, porphyry, and many of the volcanic rocks. The felds- 
 pathic mineral formations present either a pearly or vitreous luster, 
 and vary in color, being red, green, gray, yellow, brown, flesh- 
 colored, pure white, milky, transparent, or translucent. Feldspar 
 yields no water when calcined, melts at the blowpipe into a white 
 enamel, and is unaffected by acids. It is composed, according to 
 Rose, of silica, 66.75; alumina, 17.50; potash, 12; lime, 125; oxid 
 of iron, 0.75. It is found in various localities throughout the United 
 States, the purest and whitest kinds being employed in the manu- 
 facture of mineral teeth. It is prepared for use in the same manner 
 as silex. 
 
 Feldspar, from its ready fusibility, serves to agglutinate the par- 
 ticles of the more refractory ingredients, silex and kaolin ; and when 
 diffused throughout the mass imparts to the porcelain a semi-trans- 
 lucent appearance. 
 
 Kaolin. — Kaolin, or decomposed feldspar, is a fine white variety 
 of clay, and is composed chiefly of silica and alumina, the latter 
 being; the characteristic ingredient of common clav. It is found in 
 
26o MECHANICAL DENTISTRY. 
 
 various localities throughout the Eastern States and in parts of 
 Asia and Europe. Kaolin is refractory, or fire-proof, but is ren- 
 dered more or less fusible by the contaminations of iron and lime 
 with which it is usually combined. The opaque and lifeless appear- 
 ance characteristic of the earlier manufacture of mineral teeth was 
 due to the introduction of a relatively large proportion of this clay 
 into the body of the porcelain. The peculiar translucent and lifelike 
 expression which distinguishes the beautiful imitations of the pres- 
 ent day is due, in great part, to the comparatively small proportion 
 of kaolin clay, and an increased amount of the more fusible and 
 vitreous component, feldspar. 
 
 Kaolin is prepared for use by washing it in clean water; the 
 coarser particles having settled to the bottom, the water holding 
 the finer ones in solution is poured off, and when the suspended 
 clay is deposited at the bottom of the vessel, the water is again 
 poured off, and the remaining kaolin dried in the sun. 
 
 Coloring Materials. — The following metals and oxids are em- 
 ployed in coloring mineral teeth : titanium, platina sponge, and oxid 
 of gold being those chiefly used in producing the more positive tints, 
 by combining which, in varying proportions, any desired shade or 
 color may be obtained : 
 
 METALS AND OXIDS. COLORS PRODUCED. 
 
 Gold in a state of minute division, Rose red. 
 
 Oxid of gold, Bright rose red. 
 
 Platina sponge, Grayish-blue. 
 
 Oxid of titanium, Bright yellow. 
 
 Purple of Cassius, Rose purple. 
 
 Oxid of uranium, Greenish-yellow. 
 
 Oxid of manganese, Purple. 
 
 Oxid of cobalt, Bright blue. 
 
 Oxid of silver, Lemon yellow. 
 
 Oxid of zinc, Lemon yellow. 
 
 As the preparation of most of the above colors requires great 
 care and a somewhat intimate knowledge of chemistry, and as the 
 most delicate manipulations arc necessary to secure accurate and 
 satisfactory results, it is better for the mechanical operator to pro- 
 cure the coloring ingredients already prepared from some compe- 
 tent chemist, rather than attempt their production himself. 
 
 Manufacture of Porcelain Teeth. — The subjoined account of 
 the processes concerned in the manufacture of porcelain teeth is 
 
MANUFACTURE OF PORCELAIN TEETH. 26l 
 
 descriptive of those at present employed by most of our leading 
 manufacturers. 
 
 The feldspar is first calcined by throwing it in large masses into 
 a furnace and subjecting it to a red heat and then plunging it into 
 water, which renders it brittle and easily broken by the hammer 
 into small pieces, so that all foreign matters, such as mica or iron, 
 with which it may be mixed, can be separated. It is then crushed 
 between flint stones, and, when fine enough, is afterward ground 
 under water in a mill in which heavy blocks of French bur-stone 
 revolve upon a nether millstone of the same material until suffi- 
 ciently pulverized, when it is floated off and allowed to settle. After 
 this the water is drawn off or evaporated, and the deposit of spar 
 dried and sifted. 
 
 The silex is subjected to the same treatment. 
 
 The kaolin, already of the desired consistency as found in na- 
 ture, is prepared for use by first washing out impurities, and then 
 drying. 
 
 The mineral ingredients are ground somewhat coarsely, but the 
 coloring materials are reduced to an impalpable powder by means 
 of a mortar and pestle machine of great power. 
 
 When properly prepared, the several materials are combined in 
 suitable proportions to form the body and enamels, and are then 
 mixed with water and worked into masses of the required consist- 
 ency for molding. The degree of plasticity of the body and enamel 
 pastes differs with the methods of manufacture. Formerly, the 
 teeth, when molded, were first exposed to a heat just sufficient to 
 produce partial baking of the body, and this was called cruising, or 
 bisatiting, after which a thin paste of enamel material was applied 
 with a camel's-hair brush, and the whole subjected to a second heat 
 for complete and final fusion. This preliminary process of biscuit- 
 ing is essential in carved block and continuous-gum work, but in- 
 most of the factories this partial baking is dispensed with, and the 
 body and enamel pastes of the uniform consistency of putty are 
 introduced into the molds, in the first instance, properly distributed, 
 and final fusion effected by a single exposure to heat. 
 
 The molds are made of brass and are in two sections, one-half 
 of the tooth being represented on either side. The exact form of 
 the tooth is carved out with great care and precision, and must be 
 anatomically correct ■ and mechanically perfect, .while the matrix is 
 
262 MECHANICAL DENTISTRY. 
 
 made about one-fifth larger than the required size to compensate for 
 shrinkage of the materials in baking. Holes are drilled in each 
 half of the mold to receive the platinum pins, and the exact closure 
 of the two pieces of the mold secured by guiding pins. 
 
 The molds having been previously oiled, and the platinum pins — 
 which vary in length and thickness to meet special requirements 
 — placed with small tweezers in the holes provided for them, the 
 crown and gum enamels are first carefully laid in with small steel 
 spatulas in the required quantity and position. The body is then 
 added, in quantity exceeding somewhat the capacity of the mold, 
 when the sections of the mold are closed upon each other and sub- 
 jected to a pressure sufficient to insure compactness of the inclosed 
 mass. When thoroughly dried by a slow heat, to which the molds 
 are exposed, the teeth are readily disengaged when the matrix is 
 separated, and will be found at this stage extremely friable and 
 tender, requiring great care in handling them. 
 
 They are then sent from the molding to the trimmer's room, 
 where, after critical inspection, all defective ones are either repaired 
 or condemned, all excess of material cut smoothly away, and the 
 arch of the gum over each tooth made true and smooth with fine 
 pointed instruments. They are then placed on beds of coarse quartz 
 sand, on fire-clay trays or slides ready for the furnace. 
 
 Referring to this stage in the process of manufacture, an intelli- 
 gent observer writes : 
 
 " Beyond this no tool can follow them. Imperfections heretofore 
 could be repaired, but in the future, beyond the fire, the tooth is 
 either perfect or a failure irremediable. The furnace is an institu- 
 tion entitled to respect for its intensity. In its center is a muffle 
 of fire-clay, entirely surrounded by the glowing fuel, a charge of 
 half a ton's weight of coal, itself carefully bricked up before firing, 
 that no impurities of dust or vapor shall reach the teeth. Take 
 out the small, half-oval door of the muffle and you will see an inner 
 glow the eye shrinks from registering, an incandescence that startles 
 you by its fervor. In from fifteen to thirty minutes, teeth and fire- 
 clay slide, glowing like the oven, are taken out finished. The dull 
 enamel has become as glass. The lusterless oxids have yielded 
 their color, and the tooth that went in friable and brittle has come 
 out adamant. But there is an intermediate skill, the acquisition of 
 which is one of the marvels of the mechanic arts. A little too long 
 
MANUFACTURE OF PORCELAIN TEETH. 263 
 
 in that heat and the teeth are ruined, and the evils of ' underdone ' 
 are equally to be guarded against. It is a trained judgment, a skill 
 of eye and handling that enables the burner to lend success to the 
 work of those who have gone before him, and at the precise point 
 where a shade of failure is utter ruin." 
 
 The teeth are now done and ready for the wax cards, on which 
 they sfo to the trade. 
 
CHAPTER XXII. 
 
 " CONTINUOUS-GUM " DENTURES.* 
 
 The process of uniting single mineral teeth to each other and to 
 a metallic base by means of a porcelain cement was attempted as 
 early as 1820, by Delabarre, of Paris, France, but with such imper- 
 fect and unsatisfactory results as induced its early abandonment. 
 At a later period, Dr. John Allen, a distinguished practitioner of 
 dentistry in America, devised a method embracing original and 
 important modifications of practice, both in the preparation and 
 combination of materials and the modes of manipulating them ; and 
 after an extended series of experiments, commencing in 1844, suc- 
 ceeded in obtaining certain mineral compounds which vitrified at a 
 heat much below that employed by Delabarre, and the contraction 
 of which corresponded so nearly with that of the platinum base to 
 which it was applied that the shrinkage incident to baking conflicted 
 in no material degree with the practical utility of the work in the 
 mouth. 
 
 In the construction of dentures upon this principle, plain single 
 teeth, made for the purpose, are arranged and soldered to a plate 
 properly fitted to the mouth, after which different mineral com- 
 pounds, made to represent the natural gum tissues, etc., are applied 
 
 * The attentive reader of the early editions of this work will not fail to note 
 that the statements involving the question of priority, contained in the introduc- 
 tory portion of the above chapter, are at variance with those originally published. 
 A more extended examination and careful analysis of the evidences as they ap- 
 pear upon record — evidences not fully accessible to the author at that time — 
 established beyond reasonable doubt the just claims of Dr. Allen as the originator 
 of that special and distinctive method here considered, by which the attachment 
 of the teeth to the plate is effected by direct fusion of the gum material. Dr. 
 Hunter's earliest and contemporaneous experiments contemplated simply a union 
 of all the teeth by means of a fusible cement, forming a single, continuous block, 
 which was afterward united to the base by riveting or soldering. 
 
 This brief explanation is here introduced as an act of simple justice to the late 
 Dr. Allen, who devoted the best energies of his life to the successful development 
 of a process which stands unrivaled in all the chief requisites of an artificial 
 denture. 
 
 264 
 
" CONTINUOUS-GUM " DENTURES. 265 
 
 to the plate and teeth in a plastic state, then carved and trimmed 
 in proper form, and by means of a strong furnace heat, these com- 
 pounds, called the body and the gum enamel, are fused, producing 
 a continuous and seamless artificial gum and palate resembling 
 closely the natural structures. 
 
 The compounds at present employed in this process, as well as 
 the more fusible preparations used for repairing purposes, are man- 
 ufactured in quantities sufficient to meet the wants of the profes- 
 sion, and may be procured at all the dental furnishing houses 
 throughout the United States. 
 
 The intimate but later identification of Dr. W. M. Hunter with the 
 above process has rendered his name familiar as one whose skill 
 and devotion to this specialty of mechanical practice has contributed 
 to its development in a modified form. Dr. Hunter's formulas and 
 modes of manipulating his compounds will be introduced hereafter. 
 
 Following Dr. Hunter's descriptions, the reader will find practical 
 and valuable instructions in this method of substitution, contributed, 
 at the solicitation of the author of this work, by Professors S. P. 
 Haskell, of Chicago, 111., and George S. Field, of Detroit, Mich., 
 also the late Dr. Ambler Tees, of Philadelphia, Pa., whose long 
 experience and intimate familiarity with the most approved methods 
 of constructing continuous-gum dentures impart special value to 
 the subject-matter of their communications. 
 
 Before introducing an account of Dr. Allen's modes of procedure, 
 we would premise that it is unnecessary to repeat in this connection 
 what has already been fully described in regard to impressions of 
 the mouth, or the . manipulations connected with the formation of 
 plaster models and metallic swages, these processes being essentially 
 the same as in the construction of ordinary gold work. 
 
 An ingenious method of attachment has been devised by Dr. C. 
 H. Land, of Detroit, Mich. The improvement, in its application 
 to continuous-gum work, is in the construction of the teeth, which 
 are provided with three pins arranged transversely in the cervical 
 portion of the tooth — one in the center and one upon either side on 
 the posterior lateral aspect of the cervix, the latter being somewhat 
 longer than the center pin. The long pins at the sides are so 
 arranged that, when the teeth are in position, the lateral pins of 
 all the teeth will cross each other, as shown in Fig. 109. The pins 
 so crossed, and also the center pins, are pressed down closely upon 
 
266 MECHANICAL DENTISTRY. 
 
 the plate, and the whole united to each other and to the base by 
 flowing solder at the points where they cross, and at their line of 
 junction with the base. 
 
 These teeth are designed more especially for continuous-gum 
 work, but are applicable to dentures attached to gold plates by 
 rubber or celluloid, and may be used also to advantage, in a modi- 
 fied form, in the use of rubber or celluloid alone. 
 
 The particular advantages claimed for these teeth are, that in their 
 use in continuous-gum cases, equal or greater strength is imparted 
 to a plate made much thinner than those ordinarily employed, say 
 32 to 33 Stub's gage, thus materially reducing the weight of the 
 piece, while at the same time they offer greater facility and certainty 
 in the manipulation of the gum body. 
 
 Fig. 109. 
 
 Dr. Allen's Methods. — The following descriptions embrace the 
 methods and manipulations practised by the late Dr. John Allen in 
 the construction of artificial dentures with continuous gums. 
 
 The plate or base is formed of platinum, or platinum and iridium. 
 The plate being properly fitted to the mouth, and wax placed upon 
 it for the bite, as in ordinary plate work, the teeth are arranged 
 thereon with special reference to the requirements of the case. 
 They are then covered with a thin coating of plaster mixed with 
 water to the consistency of cream. After this has become firmly 
 set, another mixture of plaster and asbestos with water, somewhat 
 thicker or more plastic than the first, is placed round on the out- 
 side of the previous covering and the plate. A convenient way of 
 applying the second covering is to turn the mixture out of the 
 vessel upon a piece of tin, say four or five inches square, thus form- 
 
" CONTINUOUS-GUM " DENTURES. 267 
 
 ing a cone, upon which the plate, .with the teeth upward, is pressed 
 gently down until within an inch or less from the tin. Then with 
 a spatula the mixture is brought up over the teeth, forming an in- 
 vestment that will not crack in the process of soldering. Sand 
 may be used with the plaster for this purpose, but asbestos is prefer- 
 able. 
 
 Attaching the Teeth. — When the covering has become suffici 7 
 ently hard, the wax is removed, and a rim of platinum' is then fitted 
 to the lingual side of the teeth, below the pins, and to the base- 
 plate. The pins in the teeth are then bent down upon the rim, and 
 soldered with pure gold, or a mixture of gold and platinum, at the 
 same time the rim is soldered to the plate. This rim, which forms 
 the lining for the teeth, is usually about the thickness of the plate 
 upon which they are set, say 28 to 30; but should the case require 
 more than ordinary strength, a' double or triple thickness of rim 
 should be used. This may become necessary in cases where the 
 natural molar teeth are standing firmly in the opposite jaw, and 
 antagonize with the artificial piece, or where from any cause an 
 undue strain is brought to bear upon the artificial teeth. To attain 
 successful results, the dentist must take into consideration all the 
 circumstances or conditions of each particular case, and then exer- 
 cise his best judgment in executing the work. 
 
 In soldering platinum with pure gold, flat surfaces of this metal 
 should be brought into positive contact, in order to become firmly 
 united. Therefore, in mounting teeth upon a plate of this kind, the 
 backing or inside rim should be a little wider than the distance 
 between the pins in the teeth and the plate, say from y% to y± of an 
 inch. This extra width of rim should be bent at right angles along 
 the base of the teeth, so as to admit of being pressed down upon 
 the plate after the rim is adjusted to the teeth, and the pins bent 
 down firmly upon it. In this way flat surfaces of the rim and plate 
 are brought together and soldered. The pins in the teeth are also 
 soldered to the rim at the same time. When the parts are thus 
 united, they will remain so during the subsequent bakings ; but if 
 the edge of the rim only is fitted to the plate and soldered like gold 
 or silver work, the subsequent heatings for baking the body and 
 gum will cause the gold to become absorbed in the platinum, and 
 leave the joints not united. It is sometimes asked, Why not use 
 common eold solder for this stvle of work ? To this we would 
 
268 MECHANICAL DENTISTRY. 
 
 answer, because the alloy in the solder will greatly injure the color 
 of the gum enamel in baking. For instance, copper alloy will turn 
 it to a greenish shade, and silver will give it a yellow tinge. Al- 
 though pure gold requires more intense heat to melt it (being about 
 2000 ) than ordinary gold solder, yet when melted it flows much 
 more freely than the latter. The best way to solder the teeth upon 
 platinum plate is to place small pieces of gold upon the joints or 
 parts to be soldered, with wet ground borax, and then slowly intro- 
 duce the piece with the investment into a heated muffle, and bring 
 the whole mass up to a red heat ; then withdraw it from the furnace, 
 and bring it quickly under the blowpipe to flow the gold. In this 
 way the teeth do not become etched, as they are liable to be if the 
 soldering is done in the furnace. 
 
 The piece being soldered and cooled, the covering is removed 
 from the teeth, taking care to preserve the base unbroken for the 
 plate to sit upon during the subsequent bakings of the body and gum 
 enamel. 
 
 Preparing and Applying the Body. — All particles of plaster or 
 other foreign matter should be removed from the teeth and plate by 
 thoroughly washing and brushing them. It is well to immerse the 
 piece for a short time in sulphuric acid, after which rinse and brush 
 it well with water. This done, a colorless mineral compound, called 
 the body, is applied in a plastic state (with spatulas or small instru- 
 ments for the purpose) to the teeth and plate. It is then carved 
 to represent the gum, roof, and rugse of the mouth, taking care to 
 keep the crowns of the teeth well defined. Small, clean cuts with 
 a thin knife-blade should then be made, one between each of the 
 teeth. Commencing with the space between the molars, the cuts 
 should be made, externally and internally, entirely through the body 
 to the stay and the plate. The object of these separations is to 
 prevent movement on the part of the teeth from contraction of the 
 body in baking, compelling the material to shrink toward the teeth 
 and unite with them, leaving smooth and irregular openings where 
 the incisions were made, into .which more material is readily intro- 
 duced and baked. 
 
 First Baking. — The piece is then placed on the base upon which 
 it was soldered, and set upon a slide on the apron in front of one 
 of the upper muffles of the heated furnace; and every few minutes 
 it should he moved forward into the muffle, say two or three inches 
 
CONTINUOUS-GUM DENTURES. 
 
 269 
 
 each time, until the piece shall have passed the center of the same, 
 which should be at a red heat. It is then withdrawn and passed 
 into a lower muffle, where the heat is greater, in which the body 
 
 Fig. iio. 
 
 ;soon becomes semi-vitrified, which is sufficient for the first bake. 
 It is then taken out and, together with the slide on which it was 
 baked, placed in a cooling muffle, the mouth of which should be 
 
 Fig. hi. 
 
 -closed to prevent the change of temperature from being too rapid 
 .and causing the teeth to become brittle. Fig. no shows a case 
 .after the first heating. When the piece is sufficiently cool to handle, 
 
2JO MECHANICAL DENTISTRY. 
 
 a second application of body is made for the purpose of repairing 
 any defects that may have occurred in the baking; this done, the 
 piece is again introduced as before into the upper muffle, then into 
 the lower, allowing the second bake to become a little harder than 
 the first, but not so much as to appear glossy. It is then withdrawn, 
 and cooled as described above. 
 
 Applying the Gum Enamel. — A flesh-colored compound is then 
 applied, which is called the gum enamel. This is also made plastic 
 with water, and a thin coating is put over the body and closely 
 packed and carved around the teeth with small instruments made for 
 the purpose, still taking care to keep the crowns of the teeth clean 
 and well defined. Small camel's-hair brushes are used wet with 
 water to cause the gum enamel, and also the body, to settle more 
 closely around the necks of the teeth ; other brushes are also used 
 dry to remove all particles of body, gum, or other substances from 
 the crowns of the teeth. 
 
 Final Baking.— After the application of the gum enamel, the 
 piece is again subjected to the heat of the furnace as described for 
 baking the body, with this difference : The heat should be a little 
 greater than for either of the preceding bakes. It should be a 
 strong, sharp heat, in order to produce a smooth, glossy appearance, 
 which is required for the enamel. These different degrees of heat 
 for the first, second, and third baking should be carefully observed 
 for the purpose of getting an even temper in the piece, and thereby 
 preventing it from crazing or cracking in cooling. 
 
 The enamel being thoroughly fused, the piece is withdrawn from 
 tbe heated muffle, and passed into another, outside of the furnace. 
 This muffle should be made quite hot before the denture is placed 
 in it, in order to prolong the cooling process; for if the piece is 
 cooled too rapidly it is rendered more fragile. It is well to let the 
 case remain in the cooling muffle, with the mouth of it closed, sev- 
 eral hours before exposing it to the air. By baking just at night 
 the piece will be in proper condition to finish up the next morning. 
 Fig. in shows the case completed. 
 
 The finishing process consists simply in smoothing and polish- 
 ing the plate and burnishing the rim. It is then ready to be adjusted 
 to the mouth. In baking, great care is necessary to prevent the 
 piece from becoming gassed. This can be avoided by allowing the 
 gas to escape entirely from the burning coal or coke in the furnace 
 
CONTINUOUS-GUM DENTURES. 27 1 
 
 before the piece is introduced into the muffle. The presence of gas 
 is indicated by the blue flame escaping from the coal. When the 
 fire becomes clear, it is then safe to introduce the case to be baked 
 (as before described) into the muffle. Pure anthracite coal is the 
 best for this purpose .when the ordinary furnaces are employed, as 
 it maintains a longer and stronger heat than coke. Bituminous 
 coal is not good for this kind of work unless first converted into 
 coke. With the electric furnace, however, the danger or possibility 
 of gassing is entirely overcome. 
 
 It often occurs that the natural gums will change more or less 
 after the teeth are inserted. In such cases a new impression should 
 be taken from the mouth and a fusible die formed. The denture is 
 then placed upon the die, and it will be seen at once where the 
 change has taken place ; then, with the piece resting upon the die, 
 the artificial gum may be chipped off with a small hammer and 
 chisel. The platinum plate, being soft, can be refitted to the die 
 very accurately with a burnisher, hammer, and small driver made 
 for the purpose. A new coat of body is then applied where the 
 plate has been refitted, and then baked, cooled, enameled, and baked 
 again — still observing the same directions as detailed in the manage- 
 ment of new pieces. 
 
 Repairing. — If the tooth gets broken (a mishap which seldom 
 occurs by use in the mouth) it can be replaced with another by 
 grinding out the remaining portion of the broken tooth, and the gum 
 covering the neck of same, and then fitting a new one in its place. 
 This tooth need not be soldered to the inside rim; it is sufficient to 
 grind a small notch or groove in the enamel which covers the lingual 
 side of the rim for the pin of the tooth to fit into. The pin resting 
 in the groove is covered with the body at the same time it is applied 
 around the base of the tooth, and when this body is baked the tooth 
 will become firmly fastened in place of the broken one. Any num- 
 ber of teeth that may be required can be replaced in this way. If it 
 is desired to change the position of one or more teeth, or to make 
 ' them longer, this can also be done as described above, with the addi- 
 tional precaution, to press softened wax upon the inside of the teeth 
 and palatal arch of the denture before the others are removed — this 
 wax will serve as a guide or index as to the relative change to be 
 made, and also to sustain the teeth in place while they are being 
 fitted as desired to the denture. The wax soon becomes hard, and 
 
-/- 
 
 MECHANICAL DEXTISTRV. 
 
 is readily removed as each successive tooth is ground and adjusted 
 in its proper place. 
 
 When the teeth are thus fitted with each pin accurately pressed 
 into the groove prepared for it, and the wax being placed upon the 
 inside to support the teeth in the proper position, body is filled in 
 around the base of the new ones, which are carved, trimmed, and 
 brushed, so as to save the crowns of the teeth clean and properly 
 defined. The wax is then carefully removed from the piece, and 
 more body is filled in around the teeth upon the inside — filling up 
 the grooves over the pins, and then carving, trimming, etc., as be- 
 fore, to give it the desired form. This done, if the teeth are set a 
 little apart, and it is desired to keep them in that position, take a 
 little piece of asbestos and gently press it in between the teeth at 
 the cutting edges ; this will prevent them from being drawn to- 
 gether when the body is being baked. The piece is now ready for 
 the furnace, but it should not be baked hard enough to gloss the 
 newly-applied body ; it should have more the appearance of Parian 
 marble. 
 
 This being done, it is then withdrawn from the furnace and trans- 
 ferred to a cooling muffle, as before described. When sufficiently 
 cool, the gum enamel is applied and baked with a sharp heat until 
 it becomes smooth and glossy. To prevent the old gum from bleach- 
 ing or becoming lighter colored in consequence of repeated bakings, 
 a very thin coating of fresh gum enamel should be lightly brushed 
 over the entire enameled surface of the piece. The enamel thus 
 applied should be mixed with water, quite thin, so as to flow evenly 
 over the surface when applied with a camel's-hair brush. This 
 should be done before the last baking, that the whole may be fused 
 at the same time. Experience and judgment are essential requisites 
 in order to produce good practical results. For example, if the 
 carving of the body is not properly clone, the form and shading of 
 the gum and roof will not appear natural when the work is finished ; 
 if the gum enamel is put on too thick, it will produce a dark red 
 color; if not thick enough, it will be too light; if fused too hard, it 
 will be liable to craze or crack; if not hard enough, it will be rough 
 or granular; if the piece becomes gassed in baking, it will be porous 
 and of a bluish color. 
 
 Dr. Haskell's Methods. — " It should be borne in mind," says 
 Dr. Haskell, " that the strength of this work depends mainly 
 
CONTINUOUS-GUM DENTURES. 273 
 
 upon the metal, and not upon the porcelain, though the latter adds 
 to its strength. While platinum is a very soft metal, yet, by means 
 of various devices, the plate, with the teeth properly soldered on, 
 and ready for the porcelain, can be made very stiff and strong, there- 
 fore everything that can be done to secure a strong foundation should 
 be carefully observed. 
 
 " The plate should be of the best French material (not melted 
 scraps and old plates), 29 to 30 gage for the upper, and 26 to 28 for 
 the lower, and should be swaged on Babbitt metal dies. The plate 
 is then tried in the mouth, and if the fit is found to be correct, 
 arrange the articulating wax, secure the ' bite,' and make the articu- 
 lating model. 
 
 " The back of the plate should be doubled, for the following rea- 
 sons : It imparts increased strength ; leaves some margin for change, 
 in case of necessity, after the work is in the mouth; protects the 
 edge of the porcelain, and admits of a neater finish. This ' doubler ' 
 should be about -^ of an inch wide, with the edge turned up slightly 
 to receive the porcelain. Around the outer edge, solder a flattened 
 wire, Jg of an inch wide, or less, and 22 gage, bringing the ends to 
 meet the turned edge of the doubler. This strengthens the plate, 
 and affords a good round finish to the edge, as well as protection to 
 the porcelain. This is easily put on after a little practice, and is far 
 preferable to turning the edge of the plate with pliers, or otherwise. 
 Pure gold should always be used for soldering, and with just enough 
 borax (using very little) to give direction to the flow of solder. 
 
 " Then comes the arrangement of the teeth, and this should al- 
 ways be done in the mouth, the articulating model being only a pre- 
 liminary guide ; for by the mouth alone can one determine the correct 
 expression and arrangement desired; and it is just here that three- 
 fourths or more of the artificial dentures fail in an utter lack of 
 artistic skill. In this work there is ample opportunity for the dis- 
 play of taste and skill, so that perfection itself is attained at the 
 hands of the true artist. 
 
 " The investing process comes next. First, a coat of shellac over 
 the teeth to prevent etching (although, if this occurs, it is not a 
 matter of much account, as the baking remedies it). Then a thin 
 coat of clear plaster; next plaster and asbestos, one part of the lat- 
 ter to two of the former. Let the portion under the plate extend 
 18 
 
2/4 MECHANICAL DENTISTRY. 
 
 at least one inch back of the latter, as this bottom portion is to be 
 retained on which to bake the case; invest the whole ^ of an inch 
 thick. Warm the case until the plate is sufficiently heated to remove 
 the wax easily; dash boiling water over it (this is the best method 
 to remove wax adhering to teeth and plate in all kinds of work). 
 The backings should be continuous and be lapped on to the plate, 
 for in this is the mainstay of the work for strength. Cut patterns 
 in tin or lead, three pieces, one for the six front teeth, and one for 
 each side, lapping over the cuspid teeth ; the foot-piece should lap 
 on to the plate about -^ of an inch. No borax is needed. The gold 
 should be melted and rolled into a ribbon as thin as possible, and 
 cut in small pieces and laid under the lap, or foot-piece, and a piece 
 under each pin. The backings can be fitted more easily by splitting 
 the foot-piece. The most convenient method of soldering is in the 
 furnace, being careful not to let it remain too long, so as to fuse 
 the enamel on the teeth. If a pin should fail to solder, it is imma- 
 terial, as the ' body ' will hold it. 
 
 " After cooling, remove the plaster and save the base. Place the 
 plate on the articulating model, and if it is sprung, press it into place, 
 which is very readily done. 
 
 " Apply the ' body ' mixed with water, quite thin, by means of an 
 oval-pointed knife, occasionally jarring with handle of spatula, and 
 as the moisture comes to the surface, absorb with a cloth ; after it is 
 well filled into all interstices, apply it thicker, jarring, absorbing, and 
 packing hard, until enough is on the outside to produce the proper 
 shape and contour of the lips. Then apply, with the curved point 
 of the knife, the body to the lingual side of the plate, same as on 
 the outside, but only a thin coat on the plate. Trim around the necks 
 of the teeth, remove all particles from between with a quill tooth- 
 pick, and brush all particles off the surface of the teeth and exposed 
 portions of plate, and the case is ready for baking. 
 
 " The furnace shown in Fig. 26 is preferable ; and in setting the 
 ' muffle,' see that the vent hole in the top is clear; this is for escape 
 of gas that may be in the muffle and would injure the work. Fasten 
 the front end with fire-clay, but leave the back end free. Set the 
 case 10 or 12 inches from the opening, move forward, every few 
 minutes, a couple of inches, until it is in the muffle; place it within 
 two inches of the back, and close the door. If the heat is right, 
 
" CONTINUOUS-GUM " DENTURES. 275 
 
 five or ten minutes will suffice ; still, it must be looked at so as not 
 to get too much heat. This first bake should be only a glaze. Re- 
 move to a muffle on the hearth and close up tight. When cool, place 
 on the model, and, if sprung, press it into place. Next fill up all 
 the cracks with very thin body, jarring with handle of the spatula 
 often, so that the material will fill up thoroughly ; then spread on 
 thicker until the proper shape and fullness are secured, trimming 
 around the teeth, and doing as previously described, and bake as 
 before. After cooling, the enamel is to be put on the same as the 
 body, applying only a thin and uniform coat. The rugae can be 
 produced in the body or in the gum. The enamel should have a 
 thoroughly glossy appearance when ready to be removed from the 
 furnace. . Heated cooling muffles are unnecessary, as the case itself 
 will heat the muffle all that is necessary. 
 
 " Lower sets are better without a binding, as it is sometimes 
 necessary to file or grind away the edge. 
 
 " The case is finished by filing and polishing the exposed metal 
 surface, not doing anything to the upper surface. 
 
 " A ' defined ' air-chamber is rarely necessary ; a Cleveland cham- 
 ber never. Raise the plate over the hard palate with a thin film of 
 wax on the plaster cast, chamfering off the edges completely ; scrape 
 the plaster model across the back, except right in the center, accord- 
 ing to the softness of the palate. 
 
 " This work is not advisable for partial sets, except in some par- 
 tial lower cases where there are no detached teeth. In these cases 
 the plate should be at least two thicknesses across the back of the 
 front teeth, and resting well up on the necks of the same. 
 
 " Repairing. — Very few seem to know how to prepare a case for 
 repairing. Invest it in plaster and asbestos at least ]/ 2 of an inch 
 deep ; place in the muffle before lighting the fire, and allow it to 
 remain with the door open, as the fire comes up, until it is red hot; 
 then remove, cool, and thoroughly clean off the plaster, preserving 
 the base, and it can be run into the furnace with as little danger of 
 cracking as if it had never been worn. 
 
 " Grind out the remains of the teeth below the margins of the 
 gum ; select a rubber tooth, as it is easier to get and just as good 
 as one made for this work, filing off the'pins; hold with wax until 
 a little plaster and asbestos can be placed over it and the adjoining 
 
2^6 MECHANICAL DENTISTRY. 
 
 teeth; thoroughly remove the wax and put on repairing body, and 
 bake; cool, put on the gum, having previously ground off a portion 
 of the old gum if it is a very old case, and put on just a little new, 
 and bake as at first. 
 
 " If blisters occur, grind into them and fill with body and gum, 
 three to one, press hard, and enamel." 
 
 Dr. Ambler Tees' Methods and Formulas. — The late Dr. Tees 
 described his work as follows : " Continuous-gum work is mounted 
 upon a swaged plate of pure platina, about No. 29, American gage. 
 The lowest plate, to insure strength, is made of two pieces soldered 
 together, one being large enough to allow for a rim. In a partial 
 lower set, an additional piece of iridionized platina is soldered to the 
 part covering the lingual gums of the remaining natural teeth. Plain 
 teeth, with single long pins, made for the purpose by tooth manu- 
 facturers, are soldered to the plate with pure gold (24 k.), which 
 alone is used as a solder in this work, since the copper and silver con- 
 tained in alloyed gold will discolor the gum enamel. The silicious 
 materials called body and gum enamel are then applied around the 
 necks of the teeth, and upon the lingual portion of the plate, by 
 means of small spatulas, and carved to imitate the contour of the 
 gum. 
 
 ' The investment used for retaining the teeth in position while 
 being soldered is composed of two parts of plaster and one of asbes- 
 tos ; before applying this, the teeth should be coated with a thick 
 varnish of shellac and alcohol, to prevent the teeth being etched in 
 soldering. The backing is fitted most conveniently by making it of 
 three pieces ; the pins are bent down over it, and soldered with pure 
 gold. After soldering, the investment is removed, and the teeth and 
 the plate brushed with soap-suds and powdered pumice-stone and 
 washed off with clean water. The first coat of body is then applied, 
 moistened with clean water to the consistency of soft putty, as a 
 foundation, no effort being made to imitate the contour of the gums ; 
 separations, however, are made between the teeth, so that the body 
 may fuse around each tooth separately, and prevent it being drawn 
 from position by the shrinkage of the body. It is then fused in the 
 muffle, and placed in a cool muffle for thirty minutes. After adjust- 
 ing it upon the articulator, it is ready for the second coat of body. 
 In applying this, an artistic effort is made to imitate the contour of 
 the gums ; and by making elevations and depressions in appropriate 
 
CONTINUOUS-GUM " DENTURES. 277 
 
 position, the lights and shades of the natural gums may be simu- 
 lated, especial attention being paid to the rugae. This coat is vitri- 
 fied and not fused. After it is cool and again adjusted upon the 
 articulator, the gum enamel is applied, the spatulas being used for 
 the purpose. It is moistened with clean water, a little thinner than 
 the body, and laid on a little at a time, about the thickness of 26 
 plate. This is fused and allowed to remain in the cool muffle for 
 an hour and a half. The platina is then rubbed with pumice-stone, 
 an orange-wood stick being used, and the rim filed, stoned, and bur- 
 nished, when the set will be ready for the mouth. 
 
 " When a set is to be repaired, the mucus should be burnt off 
 before any fresh body is applied. To accomplish this, it should be 
 invested in plaster and asbestos, and heated to redness over a gas 
 or coal-oil stove, or upon the coals in a range. The investment 
 should then be removed, the set washed with soap-suds and pumice- 
 stone, and again heated to redness upon a slide in the muffle. The 
 new tooth, after being carefully ground against the gum, is held in 
 position by plaster and asbestos on the palatine surface, a very small 
 quantity being sufficient ; after it has set, gum enamel is worked into 
 the joint at the neck and fused in the muffle. The body and gum 
 enamel are then applied to the palatine surface, after the pin is sol- 
 dered to the old backing, and then fused. This plan obviates the 
 old method of investing the whole set in plaster and asbestos." 
 
 Body and gum enamel for continuous-gum work was manufac- 
 tured by the late Dr. Tees, according to the following formulas and 
 methods of compounding : 
 
 He furnished three shades of gum enamel — pale, medium, and 
 dark. The body as made by him is composed of : 
 
 Feldspar, 2 ozs. 
 
 Dental glass, 8 dwts. 
 
 Kaolin, 3 dwts. 
 
 The materials are ground together in a moistened state, in a 
 wedgewood mortar, for about an hour ; then dried ; again ground 
 for ten minutes, and fused in a crucible in a coke fire, or upon a 
 slide in the muffle. After being pulverized, two grains of titanium 
 to each ounce are added and thoroughlv mixed. 
 
2j8 MECHANICAL DENTISTRY. 
 
 The gum enamel is composed of : 
 
 Feldspar, 2 ozs. 
 
 Dental glass 10 dwts. 
 
 Gum frit, Vi dwt. 
 
 These materials are ground together in a moistened state, for 
 about an hour, in a wedgewood mortar; then dried, ground again 
 for ten minutes, and fused — upon a slide rubbed with fine, dry silex 
 — in the muffle of the furnace ; again pulverized, and sufficient addi- 
 tional gum frit mixed in with a spatula to give the desired shade. 
 
 The materials fuse readily and will not check in cooling. 
 
 Application of Continuous Gum to Partial Sets. — The follow- 
 ing method of constructing partial sets of artificial teeth with con- 
 tinuous gum is taken from a practical paper on this process by Dr. 
 W. B. Roberts: 
 
 " Partial cases may be made of continuous gum ; but the work 
 is so various in its nature that the dentist must necessarily depend 
 much upon his own judgment. Difficult cases will constantly pre- 
 sent themselves that will require the exercise of much study and 
 ingenuity, in which the general instruction that can be given in words 
 may be of but little service. The first attempt of this kind in my 
 own experience was in replacing two central incisors. Taking two 
 continuous-gum teeth, I placed upon them a platinum lining, slitting 
 this down along the edge of one tooth nearly through the piece and 
 up the edge of the other tooth by a parallel cut, leaving the two 
 parts joined together by a narrow slip. This allowed sufficient mo- 
 tion between the teeth, so that they could be adjusted as desired. I 
 then placed a small piece of tissue-paper on the plaster model, cover- 
 ing the spot to be occupied by the teeth and gum, to prevent the 
 adhesion of the body to the plaster, and holding the two incisors in 
 their places, worked the body into all the depressions of the gum 
 and around the roots of the teeth. It was then all removed from 
 the model, and placed in a paste of pulverized silex, or plaster and 
 asbestos, upon a slide, and baked as described for full sets. The 
 little slip of platinum kept the two teeth in place. The work shrunk 
 somewhal ; but this was remedied by again placing the piece upon 
 the model with the intervention of tissue-paper covered with a thin 
 coating of body. Into this I pressed the piece till it occupied its 
 true place, and then filled in again with more body all the crevices 
 an mud the roots of the teeth, and rebaked. 
 
" CONTINUOUS-GUM " DENTURES. 279 
 
 "After enameling, if the work has been carefully and skilfully 
 done upon this plan, it will be as fine a piece in appearance and fit 
 as can be made. It may then be soldered to a gold plate, and the 
 little strip of platinum between the teeth be cut out. With the 
 body and gum formerly in use many difficulties were encountered 
 from discoloration of the gum, or from other injuries incurred in 
 soldering. But with Roberts' material these are easily avoided, and 
 the piece can be treated the same as block or single gum teeth. In 
 partial sets on entire plates of platinum trouble has sometimes been 
 experienced by the enamel giving way upon the small narrow points 
 that connect the teeth with the plate by the shock occasioned in bit- 
 ing, consequently I have left these points uncovered, and used two 
 or three thicknesses of platinum to give greater strength. But 
 where this is likely to occur, gold plates would be preferable, if 
 nicely adapted with single gum teeth, or blocks of continuous gum, 
 as the case might require. I have also applied continuous gum in 
 cases where the natural teeth, from one to five in number, were 
 left in the mouth, by making the plates as in full sets, cutting out 
 around the natural ones, and raising a small bead, or placing a light 
 wire around, about }i of an inch or more from the teeth, against 
 which the gum or body is to be finished. The points around the 
 teeth are to be left free, in order to be burnished down in cases of 
 imperfections caused by the difficulty of obtaining exact impressions 
 in these places. In such cases I sometimes form a strong standard 
 of several thicknesses of platinum fitting closely against one or more 
 natural teeth, leaving a loophole through which to run a gold clasp 
 for afterward securing the artificial set. 
 
 " I have also secured the gold to the standard by rivets of plati- 
 num, and sometimes by two or three gold screws, not providing, in 
 these cases, the loophole. These methods are to be preferred to 
 using solder for fastening ; for, in case of repair, the clasps are easily 
 removed without leaving any foreign substance; but in case of 
 soldering, however carefully they may be removed, there will remain 
 some alloy, which in the baking heat to which the piece is to be 
 exposed will be incorporated with the platinum. Even so small an 
 amount of silver as may be in gold coin used for solder will com- 
 municate a yellowish tinge to the gum, spoiling the whole work. 
 Many operators in their early practice experienced this result, and 
 learned that no alloys, especially of silver or copper, can be admis- 
 
280 MECHANICAL DENTISTRY. 
 
 sible for soldering this work. I have tried platinum clasps without 
 success, as no elasticity could be obtained, and therefore would not 
 hold upon the teeth. Another source of mischief may properly be 
 noticed in this place. In baking, especially with a new furnace, or 
 with muffles lately renewed, either at the first or second heat, or it 
 may be enameling, the piece is sometimes changed in its texture and 
 color, as is supposed, by the gases present, and the phenomenon is 
 called gassing the piece. The body becomes porous and of a bluish 
 color. When this occurs there is no remedy but to place it on the 
 metallic die, remove the whole of the injured part, and replace it 
 with a new coating of body and gum. The teeth are seldom, if ever, 
 thus affected. As a precaution, the muffles should be well ventilated 
 with holes for the passage of the heated air and gases." 
 
CHAPTER XXIII. 
 RUBBER OR VULCANITE BASE. 
 
 While there are undoubtedly many important uses to which vul- 
 canized india-rubber may be applied in the practical departments 
 of dentistry, and for which it would be difficult to find an adequate 
 substitute, yet there are accumulating evidences leading- to the con- 
 clusion that its abandonment, as a base for artificial dentures, by 
 intelligent and conscientious practitioners, except in rare cases, or 
 where, for pecuniary reasons, a more expensive base is not admissible, 
 is an event of the not distant future. 
 
 This anticipated result, in respect of a material which has been 
 almost universally employed as a base for the past twenty years, is 
 assured by the confirmed and steadily increasing distrust of its suit- 
 ableness for the purpose indicated, and the growing tendency in the 
 profession to return to higher and less objectionable forms of sub- 
 stitution in respect to material and construction. 
 
 While the statements made in former editions of this work in 
 regard to rubber as a base reflected, as the author believed, the esti- 
 mate of its fitness by the profession generally, what is now written, 
 the editor believes, embodies the present judgment of the mass of 
 enlightened practitioners in reference to its unsuitableness as a base 
 for artificial dentures. 
 
 General Properties of India-rubber. — Caoutchouc, gum-elastic, 
 or india-rubber exists as a milky juice in several plants, but is ex- 
 tracted chiefly from the Siphonia cahuca, which grows in South 
 America and Java. It is discharged through the numerous inci- 
 sions made in the tree through the bark, and is spread upon clay 
 molds, and dried in the sun, or with the smoke of a fire, which black- 
 ens it. The juice when first obtained is of a pale yellow color, of 
 about the consistency of cream, and has a specific gravity of about 
 1.012. In the process of drying 55 per cent, is lost, the residuary 
 45 being elastic gum. It immediately coagulates, by reason of its 
 albumin, on application of heat, the elastic gum rising to the sur- 
 
 281 
 
282 MECHANICAL DENTISTRY. 
 
 face. The specific gravity of the juice is diminished by inspissa- 
 tion, becoming 0.925 when hard, and cannot be permanently in- 
 creased by any degree of pressure. When once stiffened by cold 
 or continued quiescences it cannot be restored to its original condi- 
 tion of juiciness. 
 
 The inspissated juice, or crude rubber of commerce, is altogether 
 insoluble in water or alcohol, but is readily soluble in ether deprived 
 of its alcohol by washing, affording a colorless solution. On evap- 
 oration of the ether, the gum resumes its original condition. It 
 swells to thirty times its bulk when treated with hot naphtha, and if 
 triturated in this condition in a mortar, and pressed through a sieve, 
 furnishes a homogeneous varnish employed in the preparation of a 
 waterproof cloth. 
 
 Caoutchouc is soluble in the fixed oils, but is not readily decom- 
 posed by cold sulphuric acid or diluted nitric acid, and is unaffected 
 by either muriatic acid gas, sulphurous acid gas, fluosilicic acid, am- 
 monia, or chlorin, nor is it dissolved by the strongest caustic potash 
 lye. even at a boiling heat, and is therefore highly esteemed as an 
 appliance of the chemical laboratory. According to the experiments 
 of Ure, Faraday, and others, caoutchouc contains no oxygen, as al- 
 most all other solid vegetable products do, but is a mere compound 
 of carbon and hydrogen, in the proportion of three atoms of the for- 
 mer to two of the latter. From this property of resisting the corro- 
 sive action of acid vapors, and its tenacity of adhesion to glass, 
 caoutchouc, when melted, forms a very excellent lute for chemical 
 apparatus. 
 
 Such are some of the properties of this remarkable product, the 
 uses of which have been almost immeasurably extended since the 
 first successful efforts to produce artificial induration by Charles 
 Goodyear in 1844. 
 
 Compounding Rubber for Dental Purposes. — India-rubber is 
 prepared for vulcanizing by incorporating with it, in varying pro- 
 portions, either sulphur alone or some of its compounds, sulphur 
 being an essential component of all vulcanizable gum compounds. 
 For dental purposes, the coloring is effected in most preparations by 
 the introduction of vermilion (sulphuret of mercury). These sub- 
 stances, properly combined, are subjected to artificial heat for a 
 specified time, producing a hard, horn-like substance, possessing 
 the qualities of lightness, strength, durability, imperviousness to 
 
RUBBER OR VULCANITE BASE. 283 
 
 fluids, insolubility in the oral secretions, unchangeableness on ex- 
 posure to ordinary temperatures, etc. 
 
 Method of Constructing an Entire Denture in a Base of Rub- 
 ber. — As the manipulations concerned in the construction of a 
 full upper set differ in no essential respect from those required in 
 the formation of a denture for the inferior arch, except as the two 
 differ in conformation, requiring corresponding modifications of 
 practice which will readily suggest themselves, it will be sufficient 
 to describe the method of constructing an entire denture for the 
 upper jaw. 
 
 An impression of the mouth is first secured in the usual manner, 
 and, as has been stated, plaster-of-Paris is preferable to any other 
 material for the purpose. As rubber, when rendered plastic by heat 
 and subjected to pressure, receives a distinct and perfect impress of 
 the face of the model, it is important that the latter should be as 
 smooth upon its surface, and as free from faultiness of form or 
 surface blemish, as possible. From the impression a plaster model 
 is obtained, and if an air-chamber is required, it may be secured 
 either by cutting out from the impression before filling in with 
 plaster, for the model, or it may be raised upon the model after 
 the latter has been separated from the impression. For the latter 
 purpose lead is often used, but sheet-tin, cut to the required form, 
 is preferable, as the former leaves a tenacious coating of oxid adher- 
 ing to the plate. 
 
 A temporary or model base-plate is next conformed as accurately 
 as possible to the face of the model, and for this purpose the pre- 
 pared gutta-percha, paraffin, and wax, or modeling compound 
 worked into thin sheets may be used, or a die may be secured and 
 a trial plate struck up from block tin. Though the latter requires 
 more labor, it gives more satisfactory and accurate results. The 
 former may be softened either by subjecting them to a dry heat 
 until sufficiently plastic, or by immersing in hot water. The face 
 of the model being previously well saturated with cold water to 
 prevent the wax or gutta-percha from adhering, the latter is 
 pressed or .molded accurately to the model with the fingers moist- 
 ened with cold water, heating such portions from time to time as 
 'do not readily yield to pressure until an accurate adaptation of all 
 •portions of the plate is secured ; then trim to the required dimen- 
 sions. 
 
284 MECHANICAL DENTISTRY. 
 
 Having fitted the temporary plate to the model, it is placed in 
 the mouth with a wax guide or rim attached, when the latter is 
 trimmed to the required width, fullness, and contour, and the 
 " bite " of the under teeth secured ; it is then removed and placed 
 in its proper position on the model, which is placed in an articu- 
 lator, with the antagonizing model, the latter being obtained in the 
 manner described in connection with the metallic plate-base (page 
 242). The mode of procedure in cases of entire dentures for the 
 upper and lower jaws differs in no respect from that practised when 
 gold or other metallic plate is used as a base. 
 
 Arranging the Teeth. — Having secured an antagonizing model, 
 the teeth are selected and arranged upon the temporary plate in the 
 usual manner. The porcelain teeth used in this process are more 
 commonly in the form of blocks or sections. Figs. 112 and 113 
 
 Fig. 112. 
 
 exhibit the marked peculiarities, and the proper arrangement of an 
 artistically designed set of gum or block teeth. The increased 
 strength of attachment formed by the greater number of pins also 
 renders them more permanent and enduring than single gum teeth. 
 Teeth made expressly for rubber base were originally manufactured 
 with plain platina pins, longer and heavier than those used in con- 
 nection with metallic plates. These, when used, were curved and 
 pressed together, forming loops or hooks to prevent them with- 
 drawing from the rubber. Subsequently, however, the detachment 
 of the teeth was more securely and certainly provided against by 
 the substitution of headed pins, which rendered their withdrawal 
 from the rubber impossible. For this valuable improvement the 
 profession is indebted to the late Dr. S. S. White, whose genius, 
 enterprise, and intelligence were so long and unceasingly tributary 
 to the needs of the dental practitioner. 
 
RUBBER OR VULCANITE BASE. 
 Fig. 113. 
 
 ^°: 
 
 Fig. 114. 
 
 <Jflk] 
 
 f 
 
 ^iittiiUMi^iiiiiiiliiiiiUJ^ 
 
 ri r\ 
 
 J L_ i \<.J V 1 
 
 W\m 
 
 ^\r\t 
 
 m\M 
 
 ^ ! ^ 
 
286 MECHANICAL DENTISTRY. 
 
 The latest design in the construction of porcelain teeth is shown 
 in Fig. 114. The base of the tooth is countersunk, with headed pins 
 inclosed within the cavity. It is claimed that their close conformity 
 in contour to the natural organs makes them much more acceptable 
 to the tongue than teeth backed in the ordinary manner, renders 
 articulation easier and more distinct, and prevents disclosure of 
 artificiality when the mouth is opened. In addition to these advan- 
 tages, they allow greater facility of adaptation to the maxillary 
 ridge. They are particularly adapted to rubber base with cellu- 
 loid facing, or to celluloid base alone. Other forms of plain teeth 
 are placed upon the market, and when they can be employed more 
 artistic results may be secured than is possible with the gum 
 teeth. 
 
 Grinding and Jointing the Teeth. — In arranging the teeth, por- 
 tions of the wax rim are cut away to form a bed for each tooth 
 or block, as the case may be, grinding from the base of the latter 
 and from their proximate edges until the proper position is assigned 
 to the teeth, and the required antagonism is secured. When gum 
 teeth are used; whether single or in the form of blocks, they should 
 be united to each other laterally with the greatest possible accuracy, 
 to prevent, as far as practicable, the intrusion of the gum material 
 between them. To further provide against this, various expedients 
 have been resorted to with the view of cementing or packing the 
 joints in order to render them impervious to the rubber. The sub- 
 stances usually recommended for this purpose are plaster or finely- 
 pulverized silex or feldspar moistened with dilute liquid silex, os- 
 artificial, soluble glass, gold, or tin-foil, or fusible metal packed into 
 the joints, etc. Of the more destructible substances mentioned, Pro- 
 fessor Wildman very justly observes : " All of these, in course of 
 time, will yield to the action of the fluids of the mouth ; and then 
 the ill-fitted joints will be receptacles for soft particles of food, 
 which will be more objectionable than having them filled with good, 
 solid rubber. The best filling is an accurately fitted joint; when so 
 made, if the enveloping plaster is of good quality and properly 
 mixed, and no undue force is used in bringing the section of the 
 fla-1: together, there is little danger of the rubber insinuating itself 
 into the joints." As properly remarked, there is no expedient which 
 will so certainly and effectually exclude the rubber as close-fitting 
 joints, and if the precaution is taken to secure an accurate and uni- 
 
RUBBER OR VULCANITE BASE. 
 
 287 
 
 form coaptation of the ground surfaces 
 where they unite in front, and the " en- 
 veloping plaster is of good quality and 
 properly mixed, and no undue force is 
 used in bringing the sections of the flask 
 together," there will, at most, be but a 
 very thin film of rubber, nearly imper- 
 ceptible in the finished work, and wholly 
 so in the mouth. To better effect the 
 object stated, the writer has been accus- 
 tomed, when uniting porcelain blocks, 
 to use a small magnifying glass, which 
 reveals inaccuracies of coaptation not 
 apparent to the naked eye. 
 
 The teeth having thus been properly 
 united and arranged, the wax rim 
 supporting them on the lingual side 
 should be cut away and carved with 
 heated instruments, especially designed 
 for that purpose, as represented in 
 Fig. 115, until the required form and 
 fullness are obtained, adding wax, if 
 necessary, to the palatal portion of 
 the plate, making it just enough thicker 
 than that required in the completed 
 set to compensate for waste in the 
 process of final finishing. Any con- 
 siderable excess of material should be 
 avoided, since it will not only mate- 
 rially increase the labor of dressing 
 the vulcanized plate, but tend to in- 
 duce porosity or sponginess of the rub- 
 ber under heat. A rim of wax should 
 also be extended around the front and 
 lateral borders of the plate, overlapping 
 somewhat the extremities of the gum 
 portions of the teeth. Wax used for 
 the purposes indicated should be of the 
 cleanest and purest varieties. A set 
 
 Fig. 115. 
 
288 
 
 MECHANICAL DENTISTRY, 
 
 modeled in the manner described will present the appearance rep- 
 resented in Fig. 116. 
 
 Flasking. — The process having been conducted thus far — any 
 defects in the arrangement of the teeth having been previously 
 corrected upon trial of the plate in the mouth — the next step in the 
 operation is the formation of a mold or matrix in which the gum 
 material is packed and pressed preparatory to being vulcanized. 
 In forming a matrix, a vulcanizing flask is used, the forms of 
 which are separately represented in Figs. 1 21-125. The lower 
 section of the flask is first filled one-half or two-thirds full of plaster 
 mixed with water to the consistency of cream. Into this the base 
 
 Fig. 116. 
 
 of the model, previously moistened with water (the plate and teeth 
 being attached to the model), is immersed and additional portions 
 of the plaster added, if necessary, filling the cup even with the 
 upper edge, and extending it up the sides of the model, to the lower 
 edge of the external rim of wax attached to the borders of the gum 
 plate. The base of the model should be cut away, so that when 
 placed in the flask the lower edge of the gum plate will extend but 
 little above the level of the upper borders of the cup. The surface 
 of the plaster is then trimmed smoothly, and coated with varnish 
 and then oiled ; all the exposed portions of the gum plate and wax 
 are also oiled, leaving the surfaces of the teeth untouched. The 
 
RUBBER OR VULCANITE BASE. 289 
 
 several parts will now present the appearance represented in Fig. 
 116. The upper section of the flask is next placed in its proper 
 position over the lower — the slides formed in one, and correspond- 
 ing grooves in the other, determining an accurate relation of the 
 two pieces. Into the upper rim of the flask, plaster, mixed to the 
 consistency before mentioned, is now poured, filling it completely. 
 The lid or cap is then applied to the opening above, and the several 
 parts of the flask brought firmly together, forcing the excess 
 through the joints of the flask. As soon as condensation of the 
 plaster takes place, the flask should be placed in a hot-air chamber 
 or on a stove, and heated throughout just sufficiently to soften, but 
 not melt the wax. The flask should be heated gradually, otherwise 
 the contents may be suddenly and forcibly ejected, in consequence 
 of the too rapid evolution of vapor. The two sections of the flask 
 are then carefully separated by forcing the blade of a knife or a small 
 chisel-shaped instrument in at different points between them, the lid 
 closing the opening above remaining in place. On separating the 
 flask, the teeth, with the wax and temporary plate, will be found 
 attached to the section of the matrix last formed, the portions of the 
 crowns of the teeth not covered with wax being imbedded in the 
 plaster and their plate extremities presenting toward the matrix, as 
 seen in Fig. 117. The base-plate and wax should now be carefully 
 detached with such instruments as will best enable the operator to 
 work out confined portions around the platinum pins and from the 
 interstices between the teeth, being careful at the same time not to 
 deface the plaster surface of the mold. To relieve the matrix more 
 perfectly of all traces of wax not accessible to instruments, the 
 section containing the teeth may be subjected to a small stream of 
 boiling water, which should be dashed upon it until every trace of 
 wax is removed. 
 
 Before packing the material, provision should be made for the 
 escape of any excess when the matrix is filled and the two sections 
 of the flask are forced together, permitting the latter to close upon 
 each other in exactly the same manner as before the introduction 
 of the gum. If the vulcanizable substance becomes engaged be- 
 tween the surfaces of the plaster around the matrix, the vulcan- 
 ized base will be increased in thickness just in proportion to that of 
 the interposed layer of gum, and hence the teeth of replacement 
 will be relatively elongated. This increased thickness of the base 
 19 
 
290 
 
 MECHANICAL DENTISTRY. 
 
 and consequent changed relation of the teeth to the maxillary ridge 
 and to those of the opposing jaw, if but slight, may be immaterial 
 in the application of full sets of teeth ; but it is far different in the 
 construction of partial pieces, where the perfection of the finished 
 work depends in so great a degree upon a faultless preservation of 
 the exact position originally assigned to the organs of replacement 
 in the several vacuities on the ridge. If, for example, in replacing 
 
 Fig. 117. 
 
 the superior incisors, the approximation of the two sections form- 
 ing the mold is obstructed by the intrusion of the gum material 
 between the plaster surfaces, the teeth, whether plate or gum, will 
 be relatively elongated in proportion to the increased thickness im- 
 parted to the base consequent upon the incomplete closure of the 
 flask, and however accurately or skilfully the porcelain teeth may 
 have been originally fitted to the vacuity in front, the artificial will 
 be found to depart from the natural gum, while the porcelain crowns 
 
RUBBER OR VULCANITE BASE. 
 
 29I 
 
 will be displaced and projected below those of the contiguous 
 natural organs. Such displacement in the cases last referred to, 
 however small in degree, cannot fail either to impair or destroy the 
 value, both as respects appearance and utility, of the substitute. 
 The method of furnishing an exit to redundant material, as usually 
 practised, is to form a series of conduits or grooves in the surface 
 of the plaster, extending them from the edge of the matrix to the 
 rim of the cup. The escape of the gum will be facilitated by cutting 
 
 Fig. ii< 
 
 notches at intervals around the rim of the flask, making the grooves 
 in the plaster continuous with them, the grooves being about Y\ of 
 an inch apart. To still more effectually prevent the intrusion of 
 the vulcanite material between the surfaces of the opposing sections 
 of plaster, a circular groove may be cut in the plaster within a line 
 or two of the margins of the matrix, as is shown in the illustration, 
 Fig. 118, into which narrow channels at short distances are made, 
 leading from the mold ; others, again, are made at wider intervals 
 
292 
 
 MECHANICAL DENTISTRY. 
 
 from the circular groove to the outer margins of the flask, termi- 
 nating as before in small notches found in the rim of the cup. The 
 two pieces when closed upon each other form a matrix. Into the 
 grooved section of the mold, the vulcanizable substance is packed 
 previous to being indurated. It is at this stage that the materials 
 employed to exclude the rubber from between the teeth, and noticed 
 in another place, are packed into the joints before the gum material 
 is introduced. The face of the model should also be coated with 
 some substance which will prevent the rubber from penetrating the 
 pores of the plaster and its adhesion to the surface of the model. 
 Preference is given by Professor Wildman to liquid silex, as being 
 more readily detached from the surface in finishing than the prepa- 
 rations mentioned. Whatever is used, it should be allowed to dry 
 perfectly before packing. Other methods, and good ones, are to 
 burnish a sheet of tin-foil over the cast, or sprinkle lycopodium 
 or soapstone upon the surface of the cast. These latter should be 
 
 Fig. 119. 
 
 brushed off with a jeweler's brush or a soft brush wheel, which will 
 leave the surface of the model with a high polish. 
 
 Packing the Mold. — The portion of the flask containing the 
 teeth should be first heated in an oven or furnace, or over the flame 
 of a spirit-lamp, until the temperature of the whole is sufficient to 
 render the rubber soft and pliable as successive portions are ap- 
 plied and pressed into the mold, and to retain it in that condition 
 until the operation of. packing is completed. Narrow strips of the 
 rubber should first be worked carefully into the contracted groove 
 underneath the platinum pins with small curved or straight- 
 pointed spear-shaped steel instruments (Fig. 119), adding on small 
 pieces at a time after each successive portion is thoroughly im- 
 pacted, until the main groove of the matrix over the base of the 
 teeth is partially filled. The palatal convexity of the mold may 
 tli en be covered with a single piece cut to the form of the uncov- 
 ered space; a smaller piece of the same general form as the latter 
 may then be added, giving to the central portion a double thick- 
 ii' ;s of the gum-plate material, so that when the two sections of 
 
RUBBER OR VULCANITE BASE. 
 
 293 
 
 the flask are brought together, the excess of gum in the center will 
 be forced gradually to the margins of the mold, diminishing, 
 thereby, the liability of the grooves becoming prematurely clogged 
 with the material before the opposing sections of the flask close 
 upon each other. Especial care should be taken in the process of 
 packing to avoid contact of the instruments with the surface of the 
 
 Fig. 120. 
 
 mold, as fragments of the broken plaster are liable to mix with the 
 gum and render the surface of the finished work imperfect by 
 forming small pits wherever such particles occur. 
 
 In regard to the quantity of rubber necessary perfectly to fill 
 the matrix, experience in its use will enable the operator to esti- 
 mate the capacity of the mold with tolerable accuracy. Some 
 
294 MECHANICAL DENTISTRY. 
 
 Small excess of rubber should always be provided. The required 
 quantity, however, can be more certainly determined by measure- 
 ment. A very simple instrument (Fig. 120), contrived by Dr. E. 
 T. Starr, may be used to determine the quantity by measurement. 
 The vessel being partly filled with water, the lower point is 
 adjusted and fixed with a screw to mark its height. Into this 
 every particle of the trial base-plate is immersed, and the rise of 
 water indicated in the same manner by the upper point. The 
 vessel is then emptied and well cleansed, clean water filled in to 
 the level of the lower point, when rubber is added in sufficient 
 quantity to bring the surface of the water on a level with the upper 
 point ; to this is to be added the necessary excess of rubber before 
 recommended. 
 
 Having completed the packing of the mold, the two portions of 
 the flask are reapplied to each other in exactly their original rela- 
 tion, being careful that the apposition of the two is such that, when 
 approximated, the guides attached to one division of the flask shall 
 pass directly and without obstruction into the grooves or slots in 
 the one opposite. With the flasks first introduced, some difficulty 
 and uncertainty were experienced in effecting the desired closure of 
 the flask on account of inherent defects of construction, but more 
 recent improvements have entirely obviated this difficulty. 
 
 What is known as the " Starr Flask," highly commended as ful- 
 filling very perfectly the requirements of practice, and as happily 
 meeting some important indications, is represented in Fig. 121. 
 Every operator of experience is familiar with the annoyance and 
 difficulty sometimes attending a satisfactory adjustment of models 
 of unusual depth, often of lower sets, and partial pieces, where the 
 porcelain teeth are secured by the surrounding plaster to the model 
 — difficulties arising from the shallowness of the lower section of 
 flasks as ordinarily constructed. The " Reversible Flask," invented 
 by Dr. E. T. Starr, the different parts of which are represented in 
 the accompanying cut, provides very perfectly for any exigency that 
 may arise in the class of cases mentioned. The following descrip- 
 tion of this flask is taken from the Dental Cosmos: 
 
 'The rings are of different widths, either of them fitting the top 
 or bottom accurately, as may be required. 
 
 " By using the wide ring next to the bottom, an admirable flask- 
 is obtained for dec]) cases and partial sets, or where the artificial 
 
RUBBER OR VULCANITE BASE. 
 
 295 
 
 gum rests on the natural. The narrow ring is used next the bottom 
 
 plate, for whole dentures, where the parting is at the rim of the 
 
 plate. The bottom has three countersunk holes, through which the 
 
 plaster runs, and, when set, holds the accompanying ring securely 
 
 to it. The fastenings of the flask are T-shaped at one end, and fit 
 
 the slots in the bottom plate ; and, being free at both ends, are more 
 
 easily adjusted than ordinary bolts. The flask being in four pieces 
 
 (two rings and two plates), the plaster is removed without the usual 
 
 trouble." 
 
 Fig. i2i. 
 
 The writer has, for several years, used with much satisfaction a 
 flask constructed with detached T-shaped bolts fitting accurately 
 into slots or grooves extending continuously from top to bottom of 
 the flask, as represented in Fig. 122. The closure of the sections 
 bv this arrangement, with the bolts in place, is unerring, and is 
 accomplished with the greatest facility. It is known as the " Im- 
 proved Anchor Flask." Another useful form of flask is that de- 
 vised by Dr. I. N. Broomell, and is represented in Fig. 123. 
 
 Fig. 124 represents an oblong, or " box flask," designed for 
 
296 
 
 MECHANICAL DENTISTRY. 
 Fig. 122. 
 
RUBBER OR VULCANITE BASE. 
 
 297 
 
 exceptionally large cases, splints for fractures, artificial palates, 
 etc. 
 
 Whatever flask is used, the entire mass of inclosed rubber should 
 be rendered uniformly plastic, after packing, by subjecting it to 
 either a dry heat, such as may be obtained with a conveniently con- 
 structed sheet-iron furnace, the baking apartment of an ordinary 
 cooking stove, or any other available means by which a diffused and 
 uniform temperature may be secured, being careful not to overheat; 
 or, if moist heat is employed, by immersing the flask in boiling 
 
 Fig. 125. 
 
 water for a time sufficient to soften the rubber. The approximation 
 of the sections of the flask should be effected interruptedly — alter- 
 nately heating the entire mass and tightening by means of the 
 screw-bolts until all the redundant material is expelled by degrees 
 through the outlets provided for it, and the sections of the flask 
 close accurately upon each other. 
 
 The Brown Clamp Flask. — This simple and effective appliance, 
 devised by Dr. Wister P. Brown, is intended principally to do 
 away with all bolts, and to give a more even and ready distribution 
 of pressure in closing the flask. With three screws we may move 
 
298 MECHANICAL DENTISTRY. 
 
 the rubber to any portion of the flask desired, which is impossible 
 with a one-screw flask-press. If more space is desired between 
 flask and clamp, the top plate of flask may be removed and turned 
 bottom upward, when the flat surface of the clamp bottom will 
 answer same as top plate. Fig. 125 illustrates this form of flask. 
 The holder (a), key (b), and a brass wire lifter (c), prevent any 
 burning or soiling of hands. Clamps and flasks are made all sizes, 
 so that two of each may go in any two-flask vulcanizer. If the 
 screws of the clamp are kept lubricated with oil, they will last for 
 many years. 
 
 Vulcanizing. — The process of vulcanizing or hardening the 
 various rubber compounds employed for dental purposes is effected 
 by subjecting them for variable periods of time to the action of 
 heat, the substances to be acted on being confined within a chamber 
 constructed for the purpose. 
 
 As introductory to a consideration of the usual methods and 
 appliances employed in the process of vulcanizing, considerable 
 space is given to the following abstract of a paper by F. Alb. Boeck, 
 of Berlin, Germany, translated by Dr. Louis Ottofy, of Chicago. 
 The discussion embodies a somewhat exhaustive consideration of 
 the rationale of the process of vulcanizing, and is introduced in this 
 connection not only as a matter of curious scientific interest, but as 
 of practical importance in the proper treatment of a plastic material 
 which still continues to be largely used as a base for artificial den- 
 tures. The writer says : 
 
 " The rubber we use, as is well known, is common rubber mixed 
 with sulphur, to which is added certain coloring materials. Of the 
 latter I will speak later in the course of this paper. Though they 
 may influence the hardening of the rubber indirectly, they have 
 no other direct influence. This rubber mixed with sulphur forms 
 our ' dental rubber.' The rubber which we obtain from the dental 
 depots is already ' vulcanized,' as this latter simply means mixing 
 the sulphur. We know that when it is heated it becomes hard. 
 The circumstances under which this takes place leads us to several 
 questions: Is it the heat, or the steam pressure, or the melting of 
 the sulphur, which causes the change in the rubber? 
 
 " Konnerly, the impression prevailed that the hardening took 
 place from the influence of the steam. In the first vulcanizers 
 the flask stood on a stand in the vulcanizers above the water; but 
 
RUBBER OR VULCANITE BASE. 
 
 299 
 
 as once, in 1856, the flask fell into the water, the vulcanizing took 
 place as usual, the mistake was corrected. Later it was found that 
 the process would take place even if the heat was passed through 
 oil or sand, and that the same was the case with glycerin and par- 
 affin. Certainly, under these circumstances, the time of vulcanizing 
 was longer than when steam was used ; this circumstance, at that 
 time, however, was of no particular consequence, as it took from 
 three to four hours to vulcanize it by steam. I will return to this 
 difference of time later ; suffice it to state here that vulcanizing can 
 take place in the absence of steam. 
 
 " It is clear, therefore, that it is the heat alone which causes the 
 hardening of the rubber. In order to answer the question of why 
 this takes place, it will be necessary to turn into the domain of 
 chemistry. 
 
 " The rubber is a vegetable product ; it is the sap of certain trees, 
 which hardens on exposure to the air. As a vegetable product it 
 is liable to the changes of all other vegetable substances, and all 
 changes which it undergoes are found equally effective on other 
 vegetable substances. From this fact it is very simple to draw con- 
 clusions for our purpose. 
 
 " Chemistry teaches that all vegetable products, such as wood, 
 starch, the leaves and sap of plants, consist of four elements, 
 oxygen, nitrogen, hydrogen, and carbon. In no plant, or the 
 product of a plant, is carbon absent, and it is mostly in connection 
 with hydrogen and oxygen, whereas nitrogen is but seldom present. 
 From these few elements nature has produced all that earth pos- 
 sesses of vegetable growth, the variety and difference being some- 
 times only the different proportion of union of the elements, or the 
 addition of a small amount of acids, bitter substances, coloring 
 matters, or salts. Rubber consists only of the above elements, 
 namely, C 16 H 7 ; it belongs, therefore, to the class known as the 
 hydrocarbons, and to that class of these in which C predominates. 
 It is interesting to notice here that the change from the soft to the 
 hard, as is the case with rubber, is the property of all vegetable 
 products. We know that the change takes place by the application 
 of heat, that hydrogen sulphid (H 2 S) is formed, and that the proc- 
 ess takes place during the exclusion of air. This process is chem- 
 ically the same as takes place in the dry distillation of wood, in the 
 changing of wood into coal, and of resin into amber. If wood is 
 
300 
 
 MECHANICAL DENTISTRY. 
 
 heated in the open air it burns; the same is the case with rubber, 
 only that the latter bums slower on account of its larger percentage 
 of C. If wood is, however, heated in the absence of air, as is the 
 case in making illuminating gas, quite peculiar substances are 
 eliminated from the wood, the illuminating gas, which escapes, and 
 three substances; a watery pyroligneous acid (wood-vinegar), a 
 thick, viscid liquid (wood-tar), and a solid mass (charcoal). 
 
 " The wood-tar is, like the rubber, of a resinous nature ; it con- 
 sists of the oil of wood-tar and a liquid substance, burnt resin. 
 Both become hard on cooling; the former is the well-known paraffin, 
 the latter the equally well-known pitch. 
 
 " The rubber undergoes similar changes. If it is heated while 
 excluded from the air, as is the case in vulcanizing, there escapes 
 (as in the case of wood, illuminating gas), the hydrogen sulphid, 
 and there remains a plastic, which hardens on cooling, as in the 
 case of pitch or paraffin, and we have our hard rubber. 
 
 " If we think over this subject, it becomes clear to us why 
 sulphur is added to the rubber. By dry distillation one or more 
 equivalents of hydrogen separate from the mass and remain gaseous, 
 or unite with other substances present and form a liquid, thus 
 leaving behind a hard substance, which consists mainly of C. It 
 is well known that the hardest substance, the diamond, is pure C. 
 The more equivalents of H that remain, the softer is the substance, 
 as in the following scale : coal, resin, pitch, axle grease, oil, ethereal 
 oils, gases. The same is the case in the reversed order. If from 
 the soft rubber hard rubber is to be made, it is necessary to remove 
 from it one or more equivalents of H. This is the case in dry dis- 
 tillation. If there was no dry distillation, if the rubber was heated 
 under free admission of air, the C would immediately unite with 
 the O of the air, forming carbonic acid, combustion would take 
 place, even though it would be slow and difficult. That cannot 
 take place when the air is excluded, the carbon remains unchanged, 
 whereas the H finds a substance with which it is more than willing 
 to unite at a high temperature. This substance is the S, and the 
 union of these forms H 2 S, which is well known to us by its odor. 
 When this union has taken place a chemical change has been 
 accomplished, a new substance has been produced, the gas escapes, 
 the remainder, the product of the distillation, contains less H than 
 the raw rubber, and on cooling, like pitch, it becomes a harder 
 
RUBBER OR VULCANITE BASE. ; 3OI 
 
 substance by its containing more C than before. Hard rubber, 
 therefore, is one step nearer to resin than soft rubber. All resins 
 are, as is well known, involatile substances, and they possess the 
 power to prevent other substances from becoming volatile; they 
 are insoluble in water, and, consequently, tasteless; they are soluble 
 in volatile oils, as turpentine oil, benzene, etc. It is known that 
 hard rubber does not only possess these characteristics, but resem- 
 bles the resins, by its easy electrification, to a remarkable degree. 
 
 " My hypothesis, therefore, leads me to the following conclusion : 
 
 " The hardening, or so-called vulcanising of rubber, is the changing 
 of caoutchouc into a resin-resembling substance, by the process of dry 
 distillation; that is, by the removal of one equivalent of H. The 
 addition of S serves only as a base, which is indifferent toward C, but 
 unites with H by virtue of a strong chemical affinity existing between 
 H and S, which form a new compound, H 2 S, which escapes as a gas. 
 
 " You will notice I do not agree with the opinion that the 
 sulphur, by melting and hardening, exerts the influence required 
 to harden the rubber. The hypothesis was laid down in some 
 American dental journal, that just as is the case with camphor 
 and celluloid, it is with sulphur and rubber; that is, that the 
 sulphur is the medium which brings the particles of rubber into 
 the plastic condition, and afterward retains them in the hardened 
 condition. 
 
 " We know that a portion of the original composition of the 
 rubber has disappeared, and we know that some of the sulphur 
 and hydrogen disappear. It is natural that if more sulphur is 
 present than can combine with one equivalent of hydrogen, the 
 remainder is in mechanical union with the rubber. If hard rubber 
 be heated to a degree somewhat higher than the boiling-point of 
 water, it loses its hardness. This fact might lead to the conclusion 
 that the sulphur melts, and thus influences the hardness of the 
 rubber. If, however, the correctness of my theory be granted — 
 that is, that hard rubber is nothing but the resinous state of the 
 original product — we observe that it must soften, as the melting- 
 point of the resins is about the same as that of sulphur. Further- 
 more, we know that sulphur hardens slowly, whereas resins become 
 hard more rapidly, as is the case with shellac and sealing-wax; 
 the same is the case with heated hard rubber. Hard rubber, when 
 undergoing the change from its melted condition into the hard 
 
302 
 
 MECHANICAL DENTISTRY. 
 
 condition, does not change the character of its molecular relation,, 
 remaining amorphous ; resembling in its structural appearance 
 molten glass. All resins, gum, glue, tar, etc., show the same char- 
 acteristics. Sulphur, on the contrary, when changing from its 
 molten condition, either crystallizes or becomes crystalline in ap- 
 pearance. 
 
 " I do not wish to prove anything further by this theory. It 
 may, however, be mentioned, that if it be correct, some important 
 results may be accomplished. I will mention, for one, the fact 
 that the scraps and filings of hard rubber, which are now useless 
 and thrown away, may be made valuable and useful. Lately, a 
 patent has been obtained by which useless vulcanized rubber may 
 be made useful. 
 
 " Leaving this subject, we now arrive at one not less important, 
 namely, the influence of steam pressure on vulcanization. 
 
 " It has been previously stated that vulcanized rubber may be 
 hardened without steam. This teaches us that hardening is not 
 produced by steam. The theory which has been discussed gives 
 us the reason. The question arises, why do we use steam? The 
 answer is, steam has no direct influence in vulcanizing; it only serves, 
 the same as oil, sand, paraffin, or glycerin, for the transmission of 
 the heat. This takes place by use of steam, faster and with more 
 precision and certainty than with other substances. Furthermore, 
 it will be shown further on that for other reasons steam is the best 
 vehicle for the purpose. 
 
 " As with oil, by using steam the heat is equally distributed 
 and the temperature rises evenly. Changes of temperature, as is 
 the case in dry vulcanization or overheated steam, are also pre- 
 vented. It also has the important advantage of causing the 
 hardening to take place more rapidly. This latter fact is known 
 to us by experience ; it only remains to explain the reason why 
 this is so. 
 
 " By the use of steam, hardening takes place in from fifteen to 
 seventy-five minutes, according to the temperature, the quality of 
 the rubber and its thickness ; by the use of dry heat or oil the 
 process requires from two to three hours, and the requisite degree 
 of heat must be reached gradually. What is the reason that by 
 use of steam and a high degree of heat it takes less time to 
 vulcanize? It must he remembered that the higher the tempera- 
 
RUBBER OR VULCANITE BASE. 
 
 303 
 
 ture, the less time is required to vulcanize. The reason of this is 
 clear, if we remember that, according to my theory, hardening is 
 subservient to the escape of a certain amount of hydrogen from the 
 rubber. 
 
 " The greater the heat, the easier is the separation of the un- 
 natural union, as it were, of the hydrogen with the carbon of 
 the rubber, and it also facilitates the union of this H with the S, 
 which is in a molten condition. This takes place in accordance 
 with the laws of chemical affinity and relation. It is a sort of 
 magnetic power which the sulphur exerts upon the hydrogen, and 
 which becomes firmer and more powerful the higher the tempera- 
 ture. Here the steam does not take any part, as it only does the 
 same thing that oil or sand would do, and that is to transmit the 
 heat. There must be another reason why the use of steam per- 
 mits us to increase the temperature and shorten the time. We 
 know that we cannot do so when using sand or oil, as in that case 
 the rubber becomes porous. If we can find the reason why the 
 rubber becomes porous, we can ascertain the influence of the steam 
 when used a shorter time. 
 
 " A great deal has been written and said in regard to the poros- 
 ity of rubber. This takes place when the escape of the gas is re- 
 tarded or prevented in certain places. This may take place when 
 the heat was applied rapidly or unevenly, or when it was not equally 
 distributed to all parts of the rubber. In the latter case, such 
 parts as are more exposed to the radiating heat than others become 
 hard much sooner, because the H escapes quicker. In the former 
 case, that is, by rapid increase of heat, the outer surface of the 
 rubber hardens sooner than the inner, to which the heat only 
 reaches gradually. Rubber is, as is well known, the poorest of 
 conductors. It is clear, therefore, that the thicker a piece is, the 
 longer it takes it to become heated in all parts, and the more 
 gradual must be the heating, in order that an even hardening, or 
 rather an even drying, of the mass may take place, so as not to 
 produce a hardened outer rim when the inner substance is yet soft, 
 i. c, contains more H. The H, which is becoming rarefied by the 
 increase of heat, has not the power to force itself through the 
 hardened parts ; it, however, possesses a considerable power of ex- 
 pansion, which increases by the constant application of heat ; it 
 
304 
 
 MECHANICAL DENTISTRY. 
 
 therefore forms a cavity for itself in which the yet unhardened 
 rubber deposits its H as long as it escapes from the rubber, and 
 until it is free from it and becomes hard. This is a supposition 
 which becomes more clear by future statements. 
 
 " Accordingly, in order to prevent porosity, nothing else is neces- 
 sary than to heat it in such a manner that the heat is equally dis- 
 tributed. This result is obtained by observing : 
 
 " i. That the heat is equal on all surfaces, and 
 
 " 2. That the heat be gradually raised and continued, according 
 to the thickness of the plate. 
 
 " In making plates of considerable thickness, experience taught 
 us to observe the above rules, or the strength would be lessened. 
 
 " It was mentioned before that steam, like oil or paraffin, serves 
 simply to convey the heat. It furthermore possesses two other 
 properties which make it more valuable than the other substances : 
 i. Its well-known property of conducting heat. 2. Its elasticity. 
 In consequence of its conductibility, it distributes the heat evenly; 
 and in consequence of its elasticity, it prevents an uneven rise of 
 its temperature, while oil, e. g., will follow any change in the tem- 
 perature that may be caused by the applied heat. Consequently, 
 steam serves as a reservoir of heat, as a balance-wheel serves as a 
 reservoir of power; as the latter distributes the force, so does steam 
 distribute evenly the over-abundance of heat from one point where 
 the flame is larger, or for a moment when the heat is greater it is 
 equalized over the surface and over several minutes of time. There- 
 fore, if the rubber exposed to it is not too thick, so that its influence 
 can reach through the whole mass of the poorly conducting rubber, 
 one may be certain that by the use of steam the heat exerts its in- 
 fluence evenly and the temperature also rises equally. There need 
 be no fear, therefore, that one place will be harder than another, as 
 is often the case with oil; also the temperature may be raised 
 higher, and, consequently, less time required for the process, and no 
 fear entertained on account of porosity. 
 
 " Another property of steam may here be considered which 
 exerts a still greater influence than cither its conductibility or 
 elasticity, and which also hastens the process I have illustrated, 
 chemical affinity; viz., the magnetic — that is, the power of sub- 
 stances to form certain compounds. 
 
RUBBER OR VULCANITE BASE. 
 
 305 
 
 " The steam acts like a magnet upon the sulphureted hydrogen, 
 dissolving this gas with a great deal of alacrity, forming a solution 
 of sulphureted hydrogen. 
 
 " It is true that the property of steam is contradictory to the 
 formation of H 2 S within the rubber. The hardening, in my opinion, 
 is nothing more than dry distillation, and this is nothing more 
 than ' slow burning by the exclusion of air.' This takes place more 
 rapidly the better the provisions are for carrying away the products 
 of combustion, such as carbonic acid, oxid of carbon, etc., and the 
 same is the case in any chemical change. 
 
 " What the chimney is in the burning of wood, the steam is in 
 vulcanization. In the latter, the product — that is, the H 2 S — is 
 readily taken up by the steam, thus furnishing the opportunity for 
 more to be formed, and permitting the rubber to harden quickly. 
 This is the main reason why we can vulcanize faster when using 
 steam than either oil or sand. 
 
 " The other properties of steam permit of raising the temperature 
 rapidly, and by absorbing the gas which is formed, serve as a proof 
 of the foregoing assertion, that the hardening of rubber takes place 
 by the escape of one equivalent of H 2 , and that porosity is caused 
 by hindering the escape of this gas." 
 
 The Time and Temperature Necessary. — As solid fuel is no 
 longer employed in vulcanizing, any description of the apparatus 
 especially adapted to this mode of producing heat is deemed un- 
 necessary. They have been entirely superseded by others of 
 improved form and construction adapted to the use of either gas, 
 alcohol, or coal-oil and its products, for heating purposes. After 
 the lamp or burner has been lighted, it should be so regulated as 
 to require a half hour to raise the temperature to the vulcanizing- 
 point, 320 F., or 120 lbs. pressure by steam-gage. This, of course, 
 is for ordinary work; where for any reason the rubber is unusually 
 thick the time for running it up to the vulcanizing-point should be 
 extended to one hour or more, according to the thickness of the 
 mass, as the heat, if run up too rapidly, will cause the rubber to 
 become spongy or porous. 
 
 Fig. 117 represents the Hayes vulcanizer with capacity for from 
 one to three cases. The iron-clad improvement in these machines 
 is designed as a protection, from the dangers of explosion conse- 
 quent upon a gradual thinning of the copper boiler from corrosion, 
 
;o6 
 
 MECHANICAL DENTISTRY. 
 
 a safeguard of great practical value and concern to those who are 
 continually exposed to the perils of such an accident. The shell 
 is made of malleable iron, }£ of an inch thick, strong enough to 
 resist many times the strain required, and can never be exposed 
 to deterioration. The copper lining is made the same thickness as 
 the copper boilers now in use, and the machine may be used with 
 
 Fig. 126. 
 
 perfect safety, even when the copper has become as thin as paper; 
 and then, when an opening has been fairly eaten through, steam will 
 escape from between it and the iron shell, below the packing joint, 
 giving timely notice that a new lining is required, which can be 
 inserted at moderate expense, and render the vessel good, and safe 
 as new. 
 
 A peculiar and important feature of these vulcanizers is in placing 
 
RUBBER OR VULCANITE BASE. 3O7 
 
 the thermometer bulb within a mercury bath, outside the steam- 
 chamber, relieving it entirely from the danger of being crushed or 
 checked by the pressure of steam, as is liable to happen when it is 
 exposed to the steam itself, necessitating its frequent replacement. 
 
 In the accompanying illustration the time and gas regulator is 
 also shown. This regulator (the Coolidge-Lewis) is without doubt 
 the most convenient and perfect in its action and adjustment of any 
 yet constructed. 
 
 The pointer is so constructed that it acts as a stop by coming in 
 contact with the inlet tube. This stop prevents the regulator from 
 being set either by design or accident to maintain a higher tem- 
 perature than the highest graduation on the base, and endangering 
 the safety of the vulcanizer. It also requires no special adjustment 
 after leaving the factory. 
 
 To vulcanize at any of the degrees of temperature marked on 
 the graduated base, all that is required is to turn the milled hand- 
 plate till the pointer is over the degree desired. This can be done 
 either before or after lighting the gas under the vulcanizer. 
 
 It should not be forgotten when vulcanizing at a low heat to 
 extend the time of vulcanization. 
 
 Better results are obtained by running the vulcanizer from an 
 hour and a half to two hours — exclusive of the time of heating up 
 — at a low heat. 
 
 This graduated gas regulator is provided with a by-pass screw 
 adjustable to different pressures of gas. The adjustment, as it 
 leaves the factory, is for coal gas — low pressure. If the regulator 
 is to be used with natural gas, at a high pressure, too much gas 
 will be passed after the proper temperature has been reached. A 
 readjustment of the by-pass will then be required. This is accom- 
 plished by turning the small screw on the side of the gas-chamber 
 till the flame maintains the heat at the proper temperature. Fuller 
 instructions accompany these regulators when sold to the profes- 
 sion. 
 
 The Whitney Vulcanizer. — A not less convenient, safe, and 
 reliable vulcanizer is that known as Dr. Whitney's, represented in 
 Fig. 127, having a steam-chamber capacity for from one to three 
 flasks. 
 
 The Mann Vulcanizer is shown in Figs. 128 and 129. The 
 
3 o8 
 
 MECHANICAL DENTISTRY, 
 Fig. 127. 
 
 Fig. 128. 
 
 Fig. 129. 
 
RUBBER OR VULCANITE BASE. 
 
 309 
 
 same apparatus has stove attachment for the use of kerosene, and 
 admits of the use of thermometer or steam-gage. 
 
 The. facility with which this vulcanizer may be operated is one 
 of its distinctive features. The lid, instead of being screwed on to 
 the boiler, is fitted neatly, and rests on a shoulder formed on the 
 casting, and is secured by a heavy steel clamping-bar and screw- 
 bolt. One end of the bar is hinged to the side of the boiler, the 
 outer end being slotted to receive the screw-bolt, which is hinged 
 to the other side of the boiler. Rubber packing between the lid 
 and the shoulder on which it rests makes the joint steam-tight. 
 The lid is removed by unscrewing the nut of the screw-bolt a turn 
 or two, when the bolt drops out of the slot and the bar is turned 
 back, leaving the lid free to be removed. This method, while it 
 gives as perfect a fastening as the usual plan, affords very much 
 greater facility for opening and closing the boiler. Should it stick, 
 by reason of the packing becoming chilled (a common occurrence 
 with all vulcanizers), it is pried off with very much less trouble than 
 is required when the top screws on. 
 
 Another advantage is the bail, a simple but heretofore un- 
 thought-of device, which greatly facilitates the handling of the vul- 
 canizer, especially when hot. Thus the boiler can be opened for 
 the removal of one case and the placing of another. The nut of 
 the clamping-bolt is loosened a little at a time, allowing the steam 
 to escape gradually until the bolt is released, when the bar can be 
 thrown back and the top of the boiler raised. The bail is also 
 useful in removing the boiler from the jacket, in tightening or 
 loosening the screw-bolt when closing or opening the boiler, and 
 at all times when the boiler is to be lifted. When not in use it is 
 readily removed. 
 
 The Boston Vulcanizer. — This vulcanizer, manufactured by 
 the Boston Dental Manufacturing Co., is made of the best bronze, 
 so-called " gun-metal," and is tested at 1000 pounds hydraulic 
 pressure. It will hold three flasks, and allow plenty of room 
 for handling. The packing is molded instead of being cut in 
 strips, and it is claimed will last for years without being re- 
 newed. The cover can be screwed steam-tight without the use 
 of a wrench, the same being necessary only to open after being 
 heated. The small quantity of water used (one gill) produces 
 vulcanizing by steam, instead of water, thus giving better results. 
 
3io 
 
 MECHANICAL DENTISTRY. 
 
 The bed-plate jacket, which is screwed to the bench, allows 
 an easy and ready method of handling. It is illustrated in Fig. 
 130. 
 
 The Philadelphia Vulcanizer. — The several parts of this vul- 
 canizer are illustrated in Fig. 131. Its simplicity is shown in a, 
 b, and c. a represents the copper bowl ; b, the ring or socket 
 
 Fig. 130. 
 
 Wm<\ 
 
 EMONT::- 
 
 w. >■? 
 
 lite*'" 
 
 with an annular rib on the top, which supports the copper bowl, 
 while C shows the tripod yoke or lid. There are no bolts, nuts, 
 wrench, nor bed-plate required, making it altogether the simplest 
 and oii<- of the most convenient vulcanizers extant. 
 
 In vulcanizing, the heat should he maintained at 320 for about 
 one hour and ten or twenty minutes. Vulcanization may be effected 
 
RUBBER OR VULCANITE BASE. 
 
 311 
 
 at a lower heat, but the time must be proportionately extended; 
 or a higher heat being employed, a less time will be required 
 to vulcanize. Care should be taken, however, not to overheat, 
 as the rubber is thereby rendered dark and brittle, and the 
 important property of elasticity impaired. The time and degrees 
 of heat mentioned, therefore, may be regarded as the safest, 
 and as yielding the best results, though with other rubber com- 
 pounds, and the use of modified forms of vulcanizers, corre- 
 sponding differences in time and temperature may be required, 
 and which can only be accurately determined by vulcanizing test- 
 pieces of rubber. 
 
 In this connection the reader's attention is called to some practi- 
 cal observations on the subject of steam pressure in vulcanizing, 
 
 and the reliability of thermometers as indicators of heat, and which 
 acquire additional interest if it be true, as alleged, that many of the 
 vulcanizers in use by dentists are insecure by reason of inherent 
 defects of construction or faultiness in the modes of indicating the 
 elastic force of steam. In commenting on this subject the late Prof. 
 Wildman observes : 
 
 " As high steam is used in vulcanizing, it is important that the 
 operator should be conversant with the nature of the agent which 
 he employs to accomplish this end. It is perfectly safe; but the 
 following will show him that it must be used with discretion and 
 judgment. Numerous experiments have been made by scientific 
 men to ascertain the elastic force of steam at different temperatures. 
 The results of their investigations are not uniform, although they all 
 agree in showing the immense force exerted bv this agent at high 
 
312 
 
 MECHANICAL DENTISTRY. 
 
 temperatures. HasweU's tables are looked upon as good authority. 
 The results of the investigations of the Franklin Institute Com- 
 mittee, in the higher degrees, give a greater elastic force than the 
 table below quoted. I shall, however, quote the results of the experi- 
 ments of the commission of the French Academy, appointed by the 
 French government to investigate this subject, for the reasons that, 
 from the manner in which they were conducted, they are probably 
 as reliable as any, and that they are extended to a more elevated 
 temperature than the others. 
 
 Elasticity of steam, taking 
 
 
 Pressure, per square inch, 
 
 atmospheric pressure as unity. 
 
 Temperature F. 
 
 pounds. 
 
 I 
 
 212° 
 
 14.7 
 
 lV2 
 
 233. 96° 
 
 22.05 
 
 2 
 
 250.52° 
 
 29.4 
 
 2V2 
 
 263.84° 
 
 36.75 
 
 3 
 
 275.18° 
 
 44.I 
 
 lY* 
 
 285.08° 
 
 51-45 
 
 4 
 
 293.72° 
 
 58.8 
 
 4 l /2 
 
 300.28° 
 
 66.15 
 
 5 
 
 307-05 
 
 73-5 
 
 SH • 
 
 314.24° 
 
 80.85 
 
 6 
 
 320.36° 
 
 88.2 
 
 6y 2 
 
 326.26° 
 
 95-55 
 
 7 
 
 331-70° 
 
 102.9 
 
 7Y2 
 
 336.86° 
 
 110.85 
 
 8 
 
 341-78° 
 
 1 1 7.6 
 
 9 
 
 350.78° 
 
 132.3 
 
 10 
 
 358.88° 
 
 147 
 
 ii 
 
 366.85° 
 
 161. 7 
 
 12 
 
 374.00° 
 
 176.4 
 
 13 
 
 380.66° 
 
 191.1 
 
 14 
 
 386.94° 
 
 205.8 
 
 15 
 
 392.86° 
 
 220.5 
 
 16 
 
 398-48° 
 
 235-2 
 
 17 
 
 403.82° 
 
 . 249-9 
 
 18 
 
 408.92° 
 
 264.6 
 
 19 
 
 413-78° 
 
 279-3 
 
 20 
 
 418.46° 
 
 294 
 
 " I would here call the attention of those using high steam to 
 an important consideration. In raising steam, the ratio of increase 
 of pressure or elastic force is far greater than that of the increase of 
 temperature. 
 
 " By referring to the above table, commencing at 212 and tak- 
 
RUBBER OR VULCANITE BASE. 313 
 
 ing steps as near 50 as is given in the ascending scale, we find this 
 exemplified. Thus : 
 
 Increase of force per Giving a force per 
 Increase of temperature. square inch. square inch. 
 
 From 212 to 263.84 — 51.85° 22.05 lbs. 36.75 lbs. 
 
 " 263.84° to 314.24° = 50.40° 44.10 lbs. 80.85 K>s. 
 
 " 314.24° to 366.85° =: 52.61° 80.85 tt)S. 161.85 lbs. 
 
 " 366.85° to 418.46° = 51.61° 132.15 lbs. 294 lbs. 
 
 " This comparison shows clearly how rapidly the pressure in- 
 creases at high temperatures, and warns the operator that a strong 
 instrument, combined with care and judgment in its treatment, are 
 indispensable to safety. Besides the rapid increase of pressure, it 
 must be borne in mind that at high temperatures, copper, of which 
 the boiler is composed, becomes weakened, and in a measure loses 
 its power to resist this great imprisoned force. Copper, in passing 
 from 212 to 230 F., loses about one-tenth of its strength, and at 
 550 it has lost one-fourth of its tenacity." 
 
 In a paper read before the Massachusetts Dental Association, 
 January, 1865, Dr. A. Lawrence affirms that : " Most vulcanizers 
 are now made of sheet-copper -i of an inch in thickness, and, 
 agreeably to the foregoing facts, have a tensile strength of 1875 
 pounds ; and one four inches in diameter will not sustain a pressure 
 of more than 150 pounds per square inch, or a temperature of 
 
 363°- 
 
 " Let us next ascertain what force of steam is exerted upon the 
 boiler within a short range of temperatures. We find by the tables 
 of Haswell, King, and others, that at 320 the pressure is 85 
 pounds; at 324 , 90 pounds; at 328°, 95 pounds; and at 332 it is 
 100 pounds per square inch. These figures I have verified by a 
 steam-gage connected with my own vulcanizer, and which I now 
 use in preference to a thermometer, as I consider it more convenient, 
 safer, and less liable to accidents. 
 
 " Practical engineers concur in the opinion that a force of not 
 over one-half the sustaining capacity of the boiler can be safely 
 applied." 
 
 Thermometers as Indicators of Heat. — Immediately connected 
 with the process of vulcanizing is the question of the reliability 
 of thermometers as indicators of heat or steam pressure. Dr. 
 Lawrence, commenting on this subject, says: "Suppose the bulb 
 
3I4 MECHANICAL DENTISTRY. 
 
 of the thermometer gets slightly fractured, and, the accident not 
 being discovered, the vulcanizer is put to use, what then? 
 
 " If the damage is slight, the mercury may still be made to rise 
 in the tube at high temperatures, but will not truly indicate the 
 full heat or force within. Some time ago I had some difficulty 
 in producing a desirable shade in my vulcanite work ; it was too 
 dark, as is the case when overheated, and I came to the conclu- 
 sion that the gum had deteriorated in quality. Other samples of 
 gum were tried, and at varying lengths of time, yet with the same 
 result. 
 
 " No defect could be discovered in the thermometer by the naked 
 eye, but a microscope revealed a slight crack in the bulb, and the 
 mystery was solved. But what force of steam was produced dur- 
 ing these almost despondent trials? 
 
 " Although my vulcanizer would safely bear a pressure of 100 
 pounds per square inch, I concluded to use a steam-gage for the 
 future, and now feel a security in its use positively refreshing." 
 
 The unreliability of thermometers in connection with vulcanizers 
 has been recognized by many in the profession who have testified 
 to their uncertainty and insecurity as a means of determining with 
 exactness at all times the amount of steam pressure employed in 
 the process of vulcanizing at a high heat. 
 
 The steam-gage spoken of by Dr. Lawrence seems very per- 
 fectly to fulfil the requirements of the dentist, and may justly 
 claim favorable consideration from the commendation bestowed 
 upon it by the distinguished gentleman who has brought it to 
 the notice of the profession. It is shown in Fig. 128. The follow- 
 ing is the author's own account of the instrument : " The gage 
 most suitable for the purpose in question somewhat resembles a 
 small, circular clock, is about six inches in diameter, and marked to 
 register 140 or 180 pounds pressure, with pound dots near the outer 
 circle of the dial. A pointer indicates the force which moves it. 
 
 " This size is better than a smaller one, because the spring inside, 
 not being crowded to its utmost capacity in vulcanizing, will, of 
 course, retain its working integrity longer; in fact, as long as any 
 dentist now living will be personally interested in the matter. They 
 can be used with all vulcanizers generating steam, connecting by 
 means of three or four feet, or as much more as may be convenient, 
 of small pipe having a U-shaped bend, or a single coil near and 
 
RUBBER OR VULCANITE BASE. 315 
 
 under the gage to receive the condensed steam, as water alone should 
 enter this instrument. 
 
 " The following table exhibits a range of pressure sufficient for 
 vulcanizing purposes, with the temperature necessary to produce the 
 same : 
 
 Pressure 
 in lbs. 
 
 Tempera- 
 ture. 
 
 Pressure 
 in lbs. 
 
 Tempe ra ■ 
 ture. 
 
 Pressure 
 in lbs. 
 
 Tempera- 
 ture. 
 
 Pressure 
 
 in lbs. 
 
 Tempera- 
 ture. 
 
 60 
 
 295° 
 
 69 
 
 3°S° 
 
 78 
 
 314° 
 
 95 
 
 328° 
 
 61 
 
 296 
 
 70 
 
 306 
 
 79 
 
 314° 
 
 100 
 
 332° 
 
 62 
 
 298 
 
 71 
 
 307° 
 
 80 
 
 315° 
 
 105 
 
 335° 
 
 63 
 
 299 
 
 72 
 
 308° 
 
 81 
 
 316 
 
 no 
 
 339° 
 
 64 
 
 300 
 
 73 
 
 3°9° 
 
 82 
 
 317° 
 
 115 
 
 342° 
 
 65 
 
 301° 
 
 74 
 
 310 
 
 83 
 
 318° 
 
 120 
 
 345° 
 
 66 
 
 302 
 
 75 
 
 3i i.° 
 
 84 
 
 319° 
 
 125 
 
 349° 
 
 67 
 
 303° 
 
 76 
 
 312° 
 
 85 
 
 320° 
 
 130 
 
 352° 
 
 68 
 
 304° 
 
 77 
 
 313° 
 
 90 
 
 324 
 
 
 
 " It will readily be seen by the above that a pressure of 60 pounds 
 requires a temperature of 295 ° by Fahrenheit's scale to produce it, 
 and 85 pounds 320 , at which latter pressure I vulcanize, running 
 •one hour, and with the most satisfactory results." 
 
 Removing the Flask after Vulcanizing. — When the process 
 -of vulcanizing has been conducted a sufficient length of time, the 
 flame is turned off and the steam discharged through the safety- 
 valve, if the vulcanizer is provided with one; or the lower half of 
 the boiler may be placed in cold water until the contents are cooled 
 down to about 200 . When time will permit, however, it is better 
 to let the vulcanizer cool gradually. The top is then taken off and 
 the flasks removed. The latter should always be allowed to cool 
 gradually, as the immersion of the flask, while hot, in cold water 
 will endanger the porcelain teeth by a too sudden change of tem- 
 perature. Neither should the flask be opened while hot, for the 
 plate, being pliable when heated, would be liable to suffer some 
 change of form in forcing the sections of the flask apart, or in 
 removing the piece after separation of the flask. When the plate 
 is removed from the flask, detach carefully all adhering plaster with 
 a pointed knife, and cleanse well by washing with a stiff brush. 
 
 The Finishing Process. — The rougher and more redundant por- 
 tions of the rubber are first removed with coarse files or rasps, fol- 
 lowing with those of a finer cut (Fig. 132) or lathe burs (Fig. 134), 
 until all parts of the piece accessible to such instruments are 
 
316 MECHANICAL DENTISTRY. 
 
 reduced to nearly the thickness required. The excess of material 
 Fig. 132. Fig. 133. 
 
 on the lingual side of the plate and other points not admitting of 
 the use of the file is removed with scrapers of various forms, some 
 
RUBBER OR VULCANITE BASE. 317 
 
 of which are shown in Fig. 133. After nearly the desired thickness 
 is thus obtained, and the surface rendered somewhat smooth and 
 uniform, a still further reduction is obtained with the use of sand- 
 paper, using first the coarser and finishing with the finer numbers. 
 The final polish is then given to the surface, first with the use of 
 finely-pulverized pumice-stone, and afterward with either prepared 
 chalk or whiting. The best method of applying the pumice is with 
 flat, circular pieces of cork of various sizes, which may be readily 
 formed by attaching them to the lathe and reducing them to the 
 proper size and shape with a file while revolving. The chalk or 
 whiting may be applied upon a cotton or ordinary brush wheel. 
 In the use of the polishing materials, the latter should be kept 
 constantly and freely saturated with cold water throughout the 
 operation. 
 
 Partial Dentures Constructed on a Base of Rubber. — The fore- 
 going description of the method of forming entire dentures on a 
 base of rubber, together with a knowledge of the manner of con- 
 structing parts of sets of teeth mounted on metallic plates, will 
 render any extended description of the former process, as it relates 
 to partial pieces, unnecessary. A base-plate of the required thick- 
 ness and dimensions is accurately adapted to a model of the parts, 
 the narrower portions passing into the spaces between the teeth 
 being stiffened by doubling the plate at these points with an addi- 
 tional strip of the material used. The central portion of the plate 
 may also be temporarily supported, and its form preserved, by fill- 
 ing in the concavity with a layer of stiffened wax. A rim of wax 
 is then attached in the usual manner to those portions of the plate 
 occupying the vacuities on the ridge, when the plate is placed in 
 the mouth and an impression of the points of the opposing teeth 
 secured; it is then removed, reapplied to the model, and the heel 
 of the latter extended posteriorly to form an articulating surface 
 for the remaining portion of the antagonizing model — the latter 
 being formed in the ordinary way. The teeth are then fitted to the 
 Vacuities in precisely the same manner as when metallic plates are 
 used, and the wax trimmed to the required fullness. The plate, 
 with the teeth attached, is then placed in the mouth and any neces- 
 sary corrections made in the arrangement of the teeth; after which 
 it is removed and readjusted. 
 
 In constructing partial sets of vulcanite, it is of the first im- 
 
318 MECHANICAL DENTISTRY. 
 
 portance, when forming- the mold, that the relation of the porcelain 
 teeth to the model of the mouth should be accurately maintained, 
 the reasons for which are fully set forth when treating- of the 
 formation of the mold or matrix for full sets. To secure this result 
 with certainty the following method should be adopted. Having 
 adjusted the plate and teeth upon the model, with the wax trimmed 
 and carved to the required fullness, place the model in the lower 
 section of the flask and fill in with plaster, extending it up to the 
 points of the teeth, binding them to the model, and making the 
 line of separation of the sections of the flask at that point. The 
 ends of the plaster teeth should be cut away sufficiently to allow of 
 a ready separation of the sections. Plaster is then poured in for 
 the upper section of the mold, and, when hard, the flask is parted 
 and the wax removed from the model and teeth, the latter being 
 retained in the lower instead of the upper section as in full cases. 
 Metallic Clasps Attached to Rubber Plates. — Although at- 
 
 Fig. 135. Fig. 136. 
 
 mospheric pressure or adhesion should be made available in all 
 practicable cases as a means of retaining parts of sets of teeth in 
 the mouth, yet cases frequently present themselves necessitating 
 the employment of clasps. These may be of rubber, but those 
 formed of gold, or gold alloyed with platinum, are more reliable 
 and better adapted to those cases where the spaces between the 
 teeth are contracted. 
 
 In constructing a clasp, first bend the clasp to fit the tooth accu- 
 rately; then make the attachment by which it is to be held to the 
 rubber (this may be done by soldering a thin plate of gold or pla- 
 tina to the clasp in such a position that it will be inclosed in the 
 rubber) ; then perforate the plate with numerous small holes, which 
 should be countersunk on both sides (Fig. 135). This plate enter- 
 ing the base, the rubber filling the holes forms pins which rivet the 
 clasp securely to the rubber plate. 
 
 ( h the attachment may be made in this manner: On the parts 
 
RUBBER OR VULCANITE BASE. 319 
 
 of the clasp that can be covered with rubber drill one, two, or three 
 holes, as the space may admit; insert gold or platina wire, solder 
 with gold solder, then cut off at proper length, and head them 
 (Fig. 136) ; these act in retaining the clasp in the same manner as 
 the double-headed pins in securing the tooth to the base, and offer 
 the advantage over the perforated plate of being more easily 
 manipulated and less liable to become displaced in packing the 
 mold. The clasp is to be attached to the model plate, and will re- 
 main secured in the mold when it is opened. 
 
 Substitution of Plate for Rubber Teeth. — An ordinary plate 
 tooth, such as is commonly used in connection with a metallic 
 plate-base, can be readily rendered suitable for a rubber base. 
 This is done by soldering a narrow strip of gold plate to the ends 
 of the platinum pins, forming a loop or staple, and which, imbedded 
 in the rubber, renders the attachment very secure. A narrow arm 
 of rubber extending to a single tooth may be materi- 
 ally strengthened by placing a metallic backing on Fig. 137. 
 the tooth and permitting the gold strip, perforated 
 with holes or roughened on its edges, to pass some 
 distance into the rubber, as seen in Fig. 137. This 
 method may be resorted to with signal advantage in 
 cases of very close bite; that is, where, on closure of 
 the jaws, the points of the opposing teeth encroach 
 unduly upon the space to be filled, extending nearly to the gum, 
 requiring the tooth of replacement to be as thinly formed through- 
 out its length as possible. 
 
 Repairing. — If a tooth or block has been broken, or any change 
 is to be made in the position of either, the teeth or fragments 
 thereof are removed, and an irregularly shaped groove or dove- 
 tail formed in the base occupying the space to be supplied; into 
 this space the tooth or teeth are properly arranged and supported 
 with wax ; the dovetail is then filled in with wax, giving some 
 additional fullness to compensate for waste in finishing. All por- 
 tions of the piece except the lingual face of the plate and teeth are 
 then imbedded in plaster in the lower section of the flask. The 
 upper section of the mold is obtained in the usual way. When 
 separated and all traces of wax removed, the gum is packed into 
 the cavity around the tooth or teeth. Grooves are then cut ex- 
 tending out from the mold, the two sections heated and forced 
 
320 
 
 MECHANICAL DENTISTRY. 
 
 together, and the process of vulcanizing conducted in the usual 
 manner, the same time and degrees of heat being required as in the 
 first instance. The renewed heat employed renders the surface of 
 the material previously vulcanized somewhat darker, to remove 
 which it is recommended to moisten the surface with dilute nitric 
 acid for a short time, after which the piece is thoroughly washed, 
 and then placed for a few minutes in an alkaline solution to remove 
 any remaining traces of acid. It is also recommended to immerse 
 the case in alcohol for five or six hours, and then expose it to the 
 rays of the sun for a like period of time. 
 
 Dr. A. A. Blount, of Geneva, Switzerland, in the Ohio State 
 Journal, suggests the following method of replacing a broken 
 crown without removing the entire section : " Finding it impossible 
 to match the injured block," he says, " I ground the broken tooth 
 down to the gum, as one would for a pivot tooth, and, as I had often 
 done before in mending a continuous-gum piece, selecting a plain 
 rubber tooth the exact size and shape, ground it carefully and 
 accurately to fit, cementing it in place with a plastic cement, which 
 served to hold it firm and prevent the rubber from coming through 
 to the front. The plate being prepared as usual for mending, the 
 piece was vulcanized. After being finished, no one could tell that 
 the block had ever been fractured. This method of repairing 
 broken blocks, mounted upon Watt's metal, will be found very prac- 
 tical, as it is somewhat difficult to replace a broken block upon that 
 base." 
 
 One of the most frequent repairs we are called upon to make is 
 a fracture through the center of an upper partial denture, the 
 break extending from the region of the central incisors backward. 
 The method of repair in such cases is quite simple, consisting in 
 first accurately adjusting the two parts of the plate and fastening 
 them in their correct relation to each other with adhesive wax or 
 shellac. This should be dropped over the entire length of the 
 crack by an assistant, while the sections of the plate are being 
 held in correct apposition. Plaster is then mixed and poured into 
 the plate, forming a cast of the palatine surface of the mouth. 
 After this hardens sufficiently, the wax or shellac is removed, 
 which permits the sections of the plate to be taken up separately. 
 The line of the fracture is now cut out or enlarged upon either 
 side with a large bur revolved by the dental engine, or it may be 
 
RUBBER OR VULCANITE BASE. 
 
 321 
 
 accomplished with a file or saw. Dovetails are then cut on either 
 side with a jeweler's saw, and the sections replaced upon the cast. 
 The work at this stage is shown in Fig. 138. 
 
 The opening between the two halves and the dovetailed spaces 
 are then covered with wax, the case invested in a flask in the 
 usual way, the flask reopened, and wax removed. The space 
 between the two halves, with the dovetailed spaces, are then care- 
 fully packed with rubber, when it is vulcanized and finished in the 
 usual way. 
 
 The whole subject of repairing rubber plates is so fully and 
 clearly described by Dr. George B. Snow, in an article entitled, 
 " Repairing Vulcanite Plates," that his processes are here given in 
 
 Fig. 138. 
 
 detail. The writer would premise that he has long since abandoned 
 the older method of " under cutting " in repairing rubber plates, 
 and would emphasize what is stated by Dr. Snow, " that perfect 
 union can be obtained in such cases if the surfaces of contact are 
 freshly cut, absolutely clean, and properly roughened. 
 
 " It is not unusual to see vulcanite plates which have been cracked 
 or broken, and repaired by what may be termed the ' hole and 
 plaster ' system. Holes are drilled through the plate along the 
 edges of the crack, and a new thickness of rubber superimposed 
 upon a mass which, possibly, is already too thick for comfort or 
 convenience, the old crack still remaining as a weak point to occa- 
 sion further breakage. No advantage was taken of any possibility 
 
322 
 
 MECHANICAL DENTISTRY. 
 
 of union between the old and new material, the dentist having been 
 obviously ignorant of the fact that perfect union can be obtained in 
 such cases if the surfaces of contact are freshly cut, absolutely clean, 
 and properly roughened. 
 
 " The great point to be remembered in repairing or making any 
 addition to a vulcanite plate is that the new and old material will 
 unite perfectly, and with such firm adhesion that the plate will be 
 practically as good as new, if the surfaces of the old plate where 
 union with the new material is desired are freshly filed, absolutely 
 clean, properly roughened, and of sufficient area. To insure these 
 results, wax should not be melted upon the surfaces of union in 
 waxing up, and removal of the wax from the mold should be accom- 
 plished by means of instruments, and not by hot water, unless, 
 possibly, for the removal of very small particles which cannot other- 
 wise be gotten rid of. Any amount of the old material desired may 
 be cut away, and its place supplied by new ; and thus any change 
 wished may be effected. In case of breakage or cracking, the plate 
 should be cut away so that the old defects will be wholly obliter- 
 ated and new material supplied. 
 
 " As a first instance, suppose a partial lower plate, supplying the 
 loss of the bicuspids and molars on both sides of the mouth, to be 
 broken through the bar which extends from one side of the mouth 
 to the other behind the incisors. The fracture is generally a clean 
 one, resembling that of glass or porcelain, and the two pieces may 
 be brought into apposition with certainty. The dentist holding the 
 parts together in exactly the right position, the assistant covers the 
 lingual side of the plate at the point of fracture with a few drops of 
 hot shellac from a shellac stick. A little cold water follows, and 
 the two parts of the plate are firmly cemented together. A brace 
 is now extended across from the molars on one side to those on the 
 other, by laying a burnt match on the grinding surfaces of the 
 respective teeth, and fastening both ends with a few drops of hot 
 wax. By this means sufficient strength is obtained to allow of the 
 plate being safely handled. A piece of paper or sheet-wax is cut 
 to fit and reach across the lingual space at the lower edge of the 
 plate, and fastened therein with wax, a coat of shellac varnish 
 is applied to the paper, the surface lathered with soap-suds, and 
 rinsed, and a model run in the same manner as in filling an impres- 
 sion. 
 
RUBBER OR VULCANITE BASE. 323 
 
 " After this has hardened, the plate is removed from the model, 
 which is then given a coating of liquid silex. This is always pref- 
 erably done in repairing plates, at the time when the plate is first 
 removed from the model. The rubber bar may now be cut away, 
 on either side of the fracture, by a jeweler's saw, the cut being made 
 diagonally, so as to make what is termed a ' scarf ' joint. The sur- 
 faces should be further roughened by making a series of shallow 
 parallel cuts across them with the saw, a thick separating file, or a 
 thin wheel-bur. The parts of the plate are then placed upon the 
 model, waxed up, and flasked, the model and buccal surfaces of the 
 teeth being covered with plaster, and the parting made so that the 
 plate will be retained upon the model, while the pieces of the bar 
 can be readily removed. After the flask is opened, the pieces are 
 removed, the usual gateways cut, and the packing, vulcanizing, and 
 finishing done as usual. 
 
 " In the case of an entire lower set broken through the center, it 
 will be seen that the same directions will apply, excepting as to the 
 amount of rubber to be cut away. A free cut should be made on 
 the lingual side, extending through under the teeth, to and includ- 
 ing the labial band; so that the broken surfaces will be entirely 
 obliterated, and at least x /% of an inch in width of new rubber sup- 
 plied between the cut surfaces. An engine-bur will do much of 
 this work nicely, and a wheel-bur is very convenient for the purpose 
 of scoring the surface. Making the model, flasking, and packing 
 will be done as before. 
 
 " If one of the incisor blocks be broken, and needs replacement, 
 a new one can be fitted after the model is obtained, and the remain- 
 ing steps of the process followed as has been described. 
 
 " Upper plates are sometimes cracked in the center, the crack 
 extending from under and between the incisor teeth backward over 
 the palate. This often happens from the amount of rubber just 
 behind the incisors being insufficient. It is not unusual to see it 
 cut away at this point, so that the pins are almost or quite ex- 
 posed, the plate having its usual thickness at a very short distance 
 behind the teeth. A much larger amount of material will be toler- 
 ated here than is usually employed, and often with benefit, not 
 only to the strength of the plate but to the articulation of the wearer. 
 The curve of the surface of the plate should be made to re- 
 semble that of the palate before the removal of the teeth, and it 
 
3 2 4 
 
 MECHANICAL DENTISTRY. 
 
 will be found that the extra thickness may extend for y 2 of an 
 inch behind the teeth without annoyance to the. patient. 
 
 " A proper curvature to the surface of the plate, just behind the 
 incisors, will do much to prevent the disagreeable whistling in mak- 
 ing the s sound, and will assist in giving the correct enunciation to 
 sh, zh, and other Unguals. 
 
 " If the cracked plate fits a flat mouth, a model can often be 
 drawn from it as it is; but if the arch is high, and the gums pro- 
 jecting, it is better, after thoroughly cleansing and drying the 
 plate, to finish the cracking by breaking the plate entirely in two. 
 The two halves may now be fastened together by dropping shellac 
 upon the lingual side, and a model secured, from which either 
 half of the plate can be easily removed. The whole palatal por- 
 tion of the plate can then be removed by a saw cut, leaving only 
 a narrow margin on the lingual surface inside the teeth. The 
 remainder of the surfaces of fracture are cut away as directed in 
 case of the lower plate, the new surfaces roughened, the pieces of 
 the old plate replaced upon the model (which has received its 
 coating of liquid silex), waxed up, flasked, packed, and vulcanized, 
 the teeth being retained upon the model as before described. 
 The plate, when finished, will show the old rim and a margin of 
 the old rubber inside the teeth. 
 
 " It is sometimes desirable to change the substance of the plate 
 entirely, as in case of supposed mercurial poisoning by red rubber; 
 or at least to put what red rubber there may be about the plate 
 entirely out of sight, and to reduce its quantity to a minimum. 
 If this is to be done to the plate last under consideration, it should 
 be prepared for flasking as described, excepting that the labial 
 band should be cut away, and everything arranged so that the 
 plate can be separated from the model when flasked. The parts 
 cut away should, of course, be replaced by wax. The cast is now 
 set in the flask so as to leave the parting at the upper edges of the 
 gums. The plaster is varnished and oiled, and more plaster built 
 on against the labial sides of the teeth, extending from their cut- 
 ting edges to the edge of the flask, and again varnished and oiled, 
 so that the appearance will now be precisely similar to a plate 
 flasked so as to be retained upon the model. The ring of the 
 flask is now put in place and filled, and the plaster allowed to 
 harden. 
 
RUBBER OR VULCANITE BASE. 325 
 
 " When the flask is separated, the teeth will be found in its ring 
 section. A few blows of the hammer will dislodge them, with the 
 piece of plaster built against their labial surfaces. This is care- 
 fully broken away, in two pieces, if possible, which are preserved, 
 and the teeth and rubber incasing them are left. The rubber is 
 now filed away as much as is practicable, leaving none of the old 
 rubber in sight, and removing enough from the palatal surface to 
 make a new fit to the model. The teeth and plaster are replaced 
 in the flask, and the case is ready for packing and vulcanizing; 
 when finished, none of the old rubber will be seen, and the plate 
 will be practically as good as though the teeth had been removed 
 from the old plate and reset. 
 
 " It is evident that the change from red to black rubber just 
 described, can be made with a whole plate or a broken one indif- 
 ferently. If a change of articulation and a new fit to the mouth 
 is also desired, on account of shrinkage of the gums, the plate 
 should be prepared so as to draw from the model, and a few small 
 pieces of wax put in the palatal side to bear upon the alveolar 
 ridge, and give the right articulation by trial in the mouth, the 
 center of the plate being cut away to facilitate the fitting of the 
 plate to the model. A fresh model of the mouth being secured 
 from an impression, the plate is waxed on to it, the case is flasked 
 with a false piece of plaster built against the labial sides of the 
 teeth, as has been described, and the plate removed and cut away 
 as much as desired, a considerable amount being always taken 
 from its palatal surface." 
 
 Beaded or Grooved Dentures. — For the exclusion of air and 
 moisture from between the artificial denture and the mucous 
 membrane of the mouth, a groove may be cut in the plaster cast, as 
 shown in Fig. 139, which is taken from an article in the Dental 
 Cosmos, contributed by Dr. W. Storer How. The bead must be 
 carried continuously around the outer portion of the cast, just 
 inside the plate line. This inclosure will produce a chamber-like 
 function of the entire inner surface of the denture, see Fig. 140. 
 The resulting greatly increased adhesion, especially noticeable in 
 mouths having flat and soft surfaces, is a gratifying effect of the 
 device. 
 
 Partial dentures, as shown in Fig. 141, may thus be securely re- 
 tained, and the simplicity of the process is hardly less remarkable 
 
\z6 
 
 MECHANICAL DENTISTRY. 
 
 than the successful result. It is only essential that the scraper 
 shall be shaped and operated to produce a suitably smooth, nar- 
 
 FlG. 139. 
 
 row, half-round groove in the model, and follow previously studied 
 lines along the palatal soft parts and at the merging of the muscles 
 in the gums. The inclosures may be of any size or shape or 
 
 Fig. 140. 
 
 Fig. 141. 
 
 number that a careful preobservation of the character and confor- 
 mation of the mouth may indicate. 
 
CHAPTER XXIV. 
 
 CELLULOID BASE. 
 
 The employment of celluloid in prosthetic dentistry, notwith- 
 standing the very general failure which attended its first intro- 
 duction into practice, came rapidly into general professional favor 
 as a cheap, convenient, and serviceable base for artificial dentures. 
 With the more recent improvements in the manufacture and sea- 
 soning of blanks, more perfectly adapted appliances for molding, 
 and a more extended acquaintance with the peculiar and distinctive 
 characteristics of this material, it has, in the practice of many, 
 superseded, in a great measure, other plastic vegetable substances 
 for the purpose indicated. 
 
 It is more in harmony with the soft tissues of the mouth, more 
 cohesive in texture, approximates more nearly the natural gum 
 color, contains less vermilion pigment in its composition than 
 does rubber, and is less objectionable by reason of the comparative 
 cleanliness accompanying its manipulation. 
 
 Celluloid, as at present produced, and when properly manipu- 
 lated, does not, in any appreciable degree, undergo change of form 
 after molding by warping either in or out of the mouth, as was 
 formerly the case. It loses somewhat the freshness and clearness 
 of its original pink color, however, after having been in use for 
 some time, in many cases in a very marked degree. 
 
 Though not bearing so perfect a resemblance to the complexion 
 of the healthy gum tissue as the porcelain imitations, yet the near 
 approximation of celluloid to the desired color makes the use of 
 single plain teeth admissible for permanent dentures, and this is 
 unquestionably its crowning merit, and makes it the most desirable 
 of all the so-called " cheap bases." The indiscriminate and almost 
 universal employment of block or sectional gum teeth in con- 
 nection with rubber has done more to degrade the prosthetic 
 department of dental practice than all other causes combined. 
 The optional arrangement of each individual tooth to meet the 
 
 3 2 7 
 
328 
 
 MECHANICAL DENTISTRY. 
 
 requirements of special cases in respect to expression, articulation, 
 and antagonism is one of the absolute and indispensable require- 
 ments of a perfect artificial denture. 
 
 Composition and Manufacture. — The following is the sub- 
 stance of Dr. C. J. Essig's account of the composition and manu- 
 facture of celluloid: 
 
 Celluloid is derived from cellulose, a woody fiber, constituting 
 the framework or foundation of plants. 
 
 Linen, cotton-wool, hemp, etc., are examples of cellulose. For 
 the manufacture of celluloid, the cellulose is first converted into 
 paper; hemp is the form of cellulose employed for this purpose, 
 because it has been found to make the strongest paper, and the 
 stronger the paper the better the celluloid. 
 
 The hemp is first converted into paper in the usual way by 
 paper machines. By this process the form of the material under- 
 goes a physical change only, while chemically it remains the same, 
 viz., nearly pure cellulose, and has a formula of C 6 H 10 O 5 . The 
 cellulose, now in the form of hemp-paper, is converted into pyrox- 
 ylin by a process technically known as " conversion," this change 
 being effected by immersing the hemp-paper in a strong mixture 
 of nitric and sulphuric acids for a sufficient length of time, when it 
 is removed from the acids and washed thoroughly. 
 
 It is now still in the form of paper, but it will be found to have 
 increased in weight about 70 per cent., and to have become highly 
 explosive, taking fire at about 300 ° F. 
 
 Pyroxylin, then, is the chief ingredient in celluloid, and is 
 reduced to a pulp in a machine similar to that used in paper- 
 making; a thorough mixture is then made of: 
 
 Pyroxylin, ioo parts. 
 
 Camphor, 4° 
 
 Oxid of zinc, 2 
 
 Vermilion, 0.6 
 
 Some alcohol is used to soften the camphor. The mass is now 
 put under a hydraulic pressure of 2000 pounds to the square inch. 
 The cylinders in which it is pressed have a small orifice in the side 
 near the bottom, and when pressure is made the celluloid is forced 
 out through this orifice. 
 
 The immense pressure is to condense or solidify the celluloid, 
 
CELLULOID BASE. 
 
 329 
 
 and as it is forced out it is cut off in pieces of the proper size, and 
 molded by pressure and heat to the forms in which we receive it. 
 At this point the blanks are still soft, and require to be seasoned; 
 this requires about two months, during which time they are kept 
 in a room at a temperature of 160 F. 
 
 Processes Preliminary to Molding. — While many of the proc- 
 esses entering into the construction of artificial dentures, with cel- 
 luloid as a base, are essentially the same as those required when 
 rubber is used, yet there are, in many important respects, modifica- 
 tions of practice made necessary by the peculiar nature and behavior 
 of the material employed. 
 
 When the distinctive characteristics of celluloid are well under- 
 stood, and the operator is familiar with the approved methods of 
 working it, no unusual difficulties attend its successful manipula- 
 tion. To attain uniformity and satisfactory results, however, it is 
 absolutely necessary that there should be a faithful compliance 
 with every manipulative detail, however seemingly unimportant, 
 which experience in the use of this substance has demonstrated to 
 be essential. 
 
 Plaster Model. — The inferior plasticity of celluloid, compared 
 with vulcanizable rubber, when exposed to the action of heat, and 
 the consequent greater pressure necessary to mold it into any 
 given form, makes it necessary to give to the plaster model the 
 greatest practicable hardness and strength. To secure these im- 
 portant qualities it is recommended to use the best quality of 
 coarse builder's plaster, which, though it does not set so quickly 
 as the finer and whiter varieties, becomes much harder and more 
 resistant to pressure when thoroughly dried. Increased hardness 
 will be secured by adding to the plaster mixture a small quantity 
 of clean white river or lake sand or marble dust. 
 
 A smoother face will be given to the model by .first coating the 
 surface of the impression with a moderately thin mixture of fine 
 plaster, and, as this begins to set, fill in with the coarser variety for 
 the body of the model. 
 
 The plaster for the model should be mixed as thick as can be 
 well poured, taking care, as it is slowly introduced, to expel any 
 confined air by tapping or shaking the impression-tray as the plas- 
 ter flows in. 
 
 In cases where there is any considerable anterior projection of 
 
33° 
 
 MECHANICAL DENTISTRY. 
 
 the alveolar ridge in front, above or below, the corresponding 
 portion of the plaster model is liable to be crushed under the 
 pressure necessary to mold celluloid. To prevent such accident, 
 it has been recommended, in addition to the expedient to be 
 mentioned hereafter, to place in the front part of the impression 
 a curved piece of brass plate punched full of holes, }/ 2 or Y\ of an 
 inch wide, which, when the impression is filled, will be imbedded in 
 the central portion of the plaster ridge, and extend some distance 
 into the body of the model. 
 
 Metal Casts. — In extreme cases, where the ridge is very thin 
 and the projection spoken of excessive, it is safer and better 
 practice to substitute metal for plaster in forming the model. In 
 this case the latter may be obtained by pouring block-tin or 
 Babbitt metal directly into the plaster impression, which should 
 first be thoroughly dried, and the cavity for the air-chamber formed 
 before pouring. 
 
 A solid metal cast, however, should never be employed when 
 there is any considerable undercutting, as is often the case on 
 either side of the median line in front, forming the canine fossa, 
 and posteriorly underneath the maxillary tuberosities, since, in 
 such cases, it will be impossible to detach the metal cast from the 
 case when molded. The separation can be readily effected by 
 substituting a metal shell for the solid cast. The shell is formed 
 in the following manner : Secure a perfect mold of the plaster 
 model in sand, and pour into this fused block-tin of the purest 
 kind, pouring it as hot as can be without producing bubbling 
 of the metal. As the metal cools first at the surface, a shell will 
 form externally in a few seconds, when the box containing the 
 mold should be inverted and the central fluid mass poured out 
 quickly at the back part of the mold in order to secure the 
 thinnest portion, of the shell in front, where it should not be 
 thicker than ordinary card paper. A little practice, with a few 
 failures at first, will enable the operator to secure the desired thick- 
 ness of the shell with tolerable exactness. When obtained, the 
 shell is filled in with hard-setting plaster to form the metal-faced 
 model to be used in molding the celluloid. When the case is 
 finished and the plaster removed from the shell, the overlapping 
 borders of the latter may be readily drawn in toward the center 
 with pliers, and the shell disengaged from the undercut spaces. 
 
CELLULOID BASE. 
 
 331 
 
 To facilitate its removal, the shell, before 
 filling in with plaster, may be divided 
 vertically at intervals with a fine saw, 
 extending the cuts from the margins to 
 near the summit of the ridge. 
 
 Waxing or Modeling. — After hav- 
 ing arranged the teeth for any given 
 case, place them with the trial plate on 
 the model, and build out with wax, 
 paraffin and wax, or modeling com- 
 pound. In carving or modeling these 
 materials, much time and labor may be 
 saved in final finishing of the piece, and 
 a more compact surface given to the 
 celluloid, by securing in the first place 
 the exact form and fullness required in 
 the completed set. When this is done 
 with instruments especially adapted to 
 the purpose, the general forms of which 
 are represented in Fig. 142, additional 
 smoothness of the surface may be ob- 
 tained with a blowpipe flame 'applied in 
 such a way as to produce simple surface 
 fusion of the wax or other material. 
 The palatal and exterior surfaces may 
 then be covered with No. 60 tin-foil, 
 carefully burnished into close contact. 
 A closer imitation of the granular ap- 
 pearance of the natural gum exteriorly 
 may be obtained by pitting or " stip- 
 pling " the surface with a small pointed 
 instrument, care being taken not to per- 
 forate, but simply indent, the foil ; or a 
 flat-faced serrated plugger may be used 
 for the same purpose. 
 
 Investing. — The piece prepared as 
 above is then placed in a flask especi- 
 ally designed for celluloid (see Fig. 
 143), invested in plaster, and 'the mold 
 
 Fig. 142. 
 
 / 
 
33 2 
 
 MECHANICAL DENTISTRY, 
 
 or matrix formed in the same manner as practised when rubber is 
 used. In case the ridge overhangs, or is undercut, the model, 
 before being incased in the lower section of the flask, should be 
 cut across diagonally, with the slope toward the heel of the model, 
 thus depressing the latter posteriorly. By this means the projecting 
 portion of the ridge will be brought more directly in a line with the 
 pressure in closing the flask. 
 
 It is quite as important that the incasing plaster forming the 
 matrix should be as hard and resistant to pressure as that entering 
 into the composition of the plaster model. If this condition is not 
 secured, there will be great danger, not only of fracture of the 
 
 Fig. 143. 
 
 model for the want of adequate lateral support, but of displacement 
 of the teeth by being forced into the plaster. So important is the 
 right condition and manipulation of plaster in the use of celluloid, 
 that the writer feels warranted in adding, to what has already been 
 said in this connection, the following judicious comments contained 
 in a pamphlet issued by the manufacturers of celluloid: 
 
 " Plaster should always be mixed as thick as possible, and, if con- 
 venient, allowed to set over night, with the flask open, and dried in 
 a warm place, as it is thereby rendered much harder. Simple as the 
 operation is, comparatively few understand how to mix plaster so 
 as to get the greatest strength and resistance to pressure. The 
 
CELLULOID BASE. 
 
 333 
 
 proper way to mix plaster for both models and filling flask is as 
 follows : First, stir the plaster as thick as can be well poured, taking 
 care that there is no excess of water; pour some of this into the 
 flask or impression to be filled, and shake down well. Then, into 
 what remains in the bowl, stir more plaster until you have a mass 
 so thick that it can be piled up. With this the flask is filled up and 
 thoroughly shaken down. It is surprising how much plaster can 
 be stirred in after the first is poured out, and also how thick a mass, 
 such as described, will settle down in the flask without bubbles. 
 The thinner plaster first poured in will run and be driven, by the 
 thicker afterward added, into all the crevices, and most of it will 
 escape from the flask, leaving a body of solid, resisting plaster that 
 cannot be obtained by the ordinary method of mixing." 
 
 In flasking the case, the line of separation between the upper and 
 lower sections should be along the borders of the plate. This is par- 
 ticularly necessary when the gum is " stippled." When the piece 
 is incased, and the plaster has sufficiently hardened, the two sec- 
 tions of the flask should be carefully separated, and this can be 
 done with greater safety to the model and other portions of the 
 matrix, and with less liability of loosening and detaching the teeth 
 from the plaster, by first applying just sufficient heat to the flask to 
 soften the wax and trial plate, being careful not to melt the wax by 
 too great or long-continued heat. 
 
 When the flask is separated, all portions of wax or other material 
 should be carefully and thoroughly removed from the mold, and if 
 any remain, not accessible to instruments, the section or sections 
 of the flask containing remains of wax should be placed in a clean 
 vessel under clean water and well boiled until all is expelled. The 
 thin, frail edges encircling the matrix in both sections of the flask 
 should then be cut away somewhat, and well rounded to prevent 
 fracture and consequent mixing of particles of plaster with the cel- 
 luloid in molding. When this is done, put the flask together and 
 see if there is ample room for the " nose " of the model to pass the 
 edge of the matrix. 
 
 To permit the escape of surplus material in molding, either of 
 the following plans may be adopted : I . Cut two concentric grooves 
 in the plaster of the upper or lower section completely encircling 
 the matrix, the inner one not less than %. or j4 of an inch from the 
 margin of the mold, and the other at the border of the flask, the 
 
334 
 
 MECHANICAL DENTISTRY. 
 
 inner side of the latter forming a part of the outer groove. 2. 
 Bevel the plaster around the mold, commencing at the margins of 
 the tin-foil C, and extending it to the sides of the flask, as shown at 
 B, Fig. 144. 
 
 In no case should cross grooves be made communicating with the 
 matrix, as these afford too ready an exit for surplus material, and 
 prevent that " back pressure " so essential to a complete and com- 
 pact filling of the mold. The grooves should be deep and ample 
 enough to receive all surplus, otherwise it would be difficult,, 
 if not impossible, to close the flask perfectly. In the use of gum 
 teeth, holes may be drilled in the matrix inside the teeth, opposite 
 
 Fig. 144. 
 
 each joint, not over ^ of an inch in diameter, and as deep as it may 
 be deemed necessary. These act as waste' gates, and relieve the 
 blocks from pressure. 
 
 Selection and Preparation of the Celluloid Plate or Blank. — 
 The mold having been prepared in the manner described, a suit- 
 able blank should be selected, and, as it is important that this 
 should be, as nearly as possible, the size and general form of the 
 mold, a good assortment of plates, for both entire and partial 
 pieces, should be at command from which to select for any given 
 case. Special attention is directed to this important requirement. 
 Celluloid does not, like rubber, flow together and intimately inter- 
 
CELLULOID BASE. 335 
 
 mix when exposed to heat and pressure. If, therefore, the blank is, 
 in any considerable degree, wider than the model, or its central or 
 palatal portion fuller and deeper than that of the model, the material, 
 when under pressure, will lap or fold upon itself along the lateral 
 walls of the arch, and, failing to unite, will form grooves or fissures. 
 On the other hand, if it is not wide or deep enough, the material is 
 liable to be stretched and torn. The blank should be just large 
 enough to fill all parts of the mold perfectly, with some slight ex- 
 cess, and the central portion should always be somewhat thicker 
 than the corresponding part of the trial or pattern plate. 
 
 As celluloid cannot be depended on to flow from one part of the 
 mold to another, it is important that there should not only be an 
 excess of material, but that this excess should be, as nearly as 
 practicable, distributed throughout all portions of the matrix. A 
 neglect of this precaution will result either in an imperfect filling of 
 the mold in some places, and consequent defect of the plate, or a 
 porous condition of the celluloid will be found wherever the mate- 
 rial, though apparently filling the mold, has not been impacted with 
 sufficient force. 
 
 The selected blank should be conformed as nearly as possible to 
 the shape of the mold by heating it in boiling water and pressing it 
 with the fingers into the section of the matrix containing the teeth ; 
 after which the necessary fullness of the several parts of the blank 
 may be obtained by dressing away redundant portions with files, a 
 small bracket-saw, or the knife, first softening the plate in boiling 
 water before using the latter. 
 
 Greater exactness in the required amount of celluloid necessary 
 in any given case may be obtained by measurement, the simplest 
 method being by the use of the Starr instrument for measuring, 
 illustrated in the chapter on Vulcanite. It must be remembered, 
 however, that this device only determines the aggregate amount of 
 material necessary, and that, while it may be a safe guide in the use 
 of rubber, which flows freely, it may lead to failure when celluloid 
 is employed, unless care is taken that all parts of the blank corre- 
 spond with the capacity of the mold. 
 
 A more reliable though somewhat tedious method of securing 
 exactness in the quantity and distribution of material necessary, 
 and which acquires special value in cases where there is unusual 
 danger of fracture of the model or teeth, and especially of the latter 
 
336 MECHANICAL DENTISTRY. 
 
 when glim teeth are used and these are ground very thin, is the 
 following, given by a correspondent of the Dental Cosmos: " After 
 preparing the case ready to flask, remove the teeth from the pat- 
 tern, stop the pin-holes, then remove the pattern and carefully flask 
 it. When the mold is ready, remove all the wax or material of the 
 pattern ; place the celluloid ' blank ' ; apply heat, and cast the same 
 as if for final case. Remove the flask from the heater; place it in 
 the clamp and cool rapidly. When it is entirely cool, remove it 
 from the flask, and trim as carefully as for final case until the 
 blank is almost the same as the pattern in thickness (it always 
 comes out thicker) . Now you have a blank with but little excess ; 
 — only what the vacuum and pins displace, or slightly more, and 
 exactly the shape of the pattern, minus the teeth. Set up the 
 case again, being careful to make the pattern the same size; flask, 
 and when ready remove the pattern; if doubtful as to amount of 
 excess, pare the edges of the mold slightly, which will be all 
 that is needed. Replace the blank; apply heat, when but moderate 
 pressure will be found necessary to bring the flask entirely to- 
 gether. If dry heat is preferred, dip the edges of the blank to 
 come in contact with the pins in spirit of camphor for a few min- 
 utes before casting." 
 
 Before the blank is placed in the flask preparatory to molding, 
 some provision should be made against adhesion of the plaster to 
 the plate. This may be done by oiling the surface of the model, 
 or by coating it and other portions of the matrix with either collo- 
 dion or liquid silex, or by rubbing the surfaces well with French 
 chalk or powdered soapstone; or a layer of tin-foil may be inter- 
 posed between the model and blank. The following novel method 
 of coating the surface of the model with tin is recommended by 
 Charles P. Alker, of Bordeaux, France : " Reduce ordinary col- 
 lodion with about three times its bulk of ether, and add pow- 
 dered tin until the solution is well impregnated with the metal. 
 The tin is the same that is sometimes used for coating plaster 
 images. When properly mixed and applied with a brush, an even 
 covering of- tin is formed upon the model, so dense as to closely 
 resemble tin-foil, and so firm as to not be detached by boiling 
 water or heat. The plate is readily cleansed with a coarse brush, 
 and presents the appearance of having been made in a metallic 
 mold." 
 
CELLULOID BASE. 
 
 337 
 
 More perfect results, however, it is believed, can be obtained in 
 the use of a metal-faced model in connection with the use of tin-foil, 
 as before described. A piece thus incased in metal will require no 
 more final finishing" than is necessary to remove surplus material 
 and dress and polish edges. 
 
 The case, thus described, is now ready for molding. 
 
 Molding. — The various machines or heaters now generally 
 employed in molding celluloid into dental plates contemplate the 
 use of either glycerin or oil, steam or dry heat, for the purpose 
 of producing the requisite plasticity of the material subjected to 
 pressure. There is considerable diversity in the form and con- 
 struction of heaters designed to utilize the several mediums for 
 the conduction of heat, as well as differences in the modes of 
 applying pressure, and while each has, doubtless, some special 
 points of merit not possessed by others, satisfactory results may, 
 with careful and intelligent manipulation, be attained by the use of 
 any one of the many recommended. The limits of this work will 
 only permit the introduction of such as are believed to be in most 
 general use. 
 
 Hot Moist Air (so-called " Dry-Heat ") Machines. — In the use 
 of these heaters, the water with which the plaster is impreg- 
 nated is relied upon to produce the steam necessary to carry off 
 all excess of camphor from the celluloid in the process of molding. 
 An essential point by this method is to have the plaster in the 
 flask thoroughly wet, and this may be better attained by setting 
 the flask in a vessel of water before placing it in the heater. To 
 provide against insufficiency of moisture in the plaster, a small 
 quantity of water may be introduced into the tank before applying 
 heat. 
 
 Fig. 145 represents a modeling or packing machine of the class 
 here spoken of, and is designated as the " Best." The inside 
 chamber is of cast-iron, surrounded by a sheet-iron casing. The 
 lid, of cast-iron, forming a part of the clamp, is pierced for the 
 passage of three wrought-iron screw-bolts — the nuts being on 
 the upper side and easy of access. When these nuts are turned 
 for the purpose of closing the clamp, the bottom portion of the 
 clamp is drawn up by each revolution away from the flame, thus 
 avoiding the danger of overheating the plate, and securing a 
 uniform heat. The bottom of the cast-iron chamber and the lid 
 
338 MECHANICAL DENTISTRY. 
 
 are pierced with holes, to allow a circulation through the chamber, 
 for the purpose of carrying off the camphor which is disengaged 
 in the process. 
 
 With the celluloid blank adjusted to its proper position in the 
 flask, the latter is placed in the clamp and the top screwed down 
 until it slightly presses the clamp. It is then placed in the oven or 
 tank and heat applied. 
 
 If gas is used, the form of burner shown underneath the heater in 
 Fig. 145, which gives a pure blue flame without smoke, may be used. 
 If gas cannot be commanded, however, any of the alcohol or kero- 
 sene lamps commonly employed in vulcanizing may be substituted; 
 or the " Hot Blast Oil Stove," especially adapted to the " Best " 
 machine, and exhibited in connection with the latter in Fig. 146. 
 
 Having applied the heat, it is of the first importance that un- 
 remitting attention should be given to the process of molding until 
 it is completed. If pressure is applied before the celluloid is ren- 
 dered somewhat plastic, or too great force is exerted during the 
 earlier stages of the process, and without sufficient intervals of 
 rest, there is danger of crushing or fracturing the model and of 
 impairing the articulation by displacement of the teeth. On the 
 other hand, the nature of celluloid is such that if it is exposed to 
 a temperature of 270 , without being under pressure, the camphor 
 evaporates, and the material, besides being rendered hard and in- 
 tractable, is puffed up, exactly as a loaf of bread is raised by yeast, 
 and filled with air-cells, and thus rendered porous. 
 
 Celluloid begins to soften at about 225 °, and will then yield 
 slightly to pressure, but this should be applied very gently at first, 
 with no more force than can be readily exerted with the thumb 
 and finger. As the heat increases, and the celluloid becomes 
 more and more plastic and yielding, the pressure should be corre- 
 spondingly increased, but always interruptedly, giving the material 
 time, between each turn of the screw or nuts, to escape from under 
 the pressure. No considerable amount of pressure will be re- 
 quired in any case until near the close of the operation, when the 
 mold is completely impacted, and the excess is being forced into 
 the grooves or gateways as the flask comes together. 
 
 At this point considerable force will be necessary to close the 
 flask perfectly, and somewhat longer intervals of time should occur 
 between each turn of the screw or nuts. 
 
CELLULOID BASE. 
 Fig. 145. 
 
 339 
 
 Fig. 146. 
 
340 
 
 MECHANICAL DENTISTRY, 
 
 During the progress of the molding, the flask should be with- 
 drawn occasionally for inspection. If, in the case of central 
 pressure, the flask is found to be closing unevenly, it should be 
 loosened in the clamp and readjusted in such manner as to correct 
 the faulty approximation. No difficulty will be experienced in 
 this respect in the use of clamps provided with screw-bolts, as 
 pressure may be applied at any point, and the flask be made to 
 close uniformly without the necessity of shifting the latter. 
 
 The moment the flask is completely closed the heat should be 
 turned off, and the piece allowed to cool gradually. In no in- 
 stance should the flask be removed from the clamp until it is 
 stone cold. In cases where the material is of extra thickness, or 
 where the shape of the blank is totally altered, longer season- 
 ing is advisable, and the flask should be placed near a stove or 
 over a register (keeping it closed by a clamp, or by an instru- 
 ment or piece of iron put through the holes in the standard) for 
 half a day or more, at a temperature not over 140 . If these 
 directions are observed, no trouble from warping plates will be 
 experienced. 
 
 Molding in Steam. — In using the steam machine, care should 
 be taken to keep it in good order. The screw should be well oiled 
 with only the best sperm oil, which will not gum, and kept so that it 
 can be easily turned with the thumb and finger. If the machine, 
 when received from the depot, works hard, the screw should be run 
 out, the gland unscrewed, and the rubber packing loosened up, so 
 that it will not bind the screw. Do not turn it down tight again 
 until you heat it up, when, if it begins to leak, it can easily be tight- 
 ened. Bear in mind that turning this gland merely, prevents the 
 escape of steam, and does not affect the pressure on the flask. 
 
 The safety-valve should be kept free from gum, and if either it 
 or the screw is clogged, it should be well cleansed with kerosene. 
 This valve, in the machine now sold, is so constructed that it 
 blows off at about 275 °, a temperature that celluloid will bear very 
 well ; and as the heat, so long as water remains in the boiler, cannot, 
 if the safety-valve is kept in order, be raised above that point, it is 
 impossible to barn a plate in this machine. While this is true, it 
 is also true that too long an exposure to even 275 ° in steam 
 tends to injure the quality of the celluloid, and for this reason the 
 heat should be continued no longer than necessary, but should be 
 
CELLULOID BASE. 34 1 
 
 reduced at- once by blowing off steam as soon as the molding is 
 completed. The first machines were constructed with the safety- 
 valve much heavier, and all in one piece, and were adjusted to a 
 temperature of nearly 300 , which was higher than necessary or 
 advisable. It is recommended, therefore, that those having that 
 style of valve should cut off about one-fourth in weight from the 
 lead weight, which can easily be done by removing a little wire 
 which passes through the stem and weight. A modern valve will 
 be furnished when ordered. When molding, fill the boiler partly- 
 full of water. The amount is not material, but there should always 
 be enough to cover the ribs at the bottom. Have the screw well 
 turned back, until the plunger, when placed in position, will rest 
 against the top of the boiler, otherwise the flask may be pressed 
 upon while screwing down the cover and the cast injured. Turn 
 down the cover snugly ; see that the gland is turned back, and the 
 screw works freely. Many failures have occurred by neglecting 
 this simple matter. If it works hard, it is impossible to tell how 
 much or how little pressure is being exerted ; there may be too 
 much, and blocks or cast be broken ; or too little, and the plate 
 made porous. In all methods of working celluloid, the sense of 
 feeling is the best guide as to when and how hard to turn; but in 
 order to have this, there must be perfect freedom of motion of the 
 parts. The time elapsing before turning is not reliable, as it varies 
 with the heat employed, the temperature at starting, the amount of 
 water in the boiler, the drafts of air to which the flame may be 
 subjected, etc. 
 
 After placing the flasks in position, turn down the screw very 
 gently, with thumb and finger, until you feel it touch the flask. 
 Fill the cup with alcohol and light it, or light the gas. The safety- 
 valve is made in two parts. The upper portion may be suspended 
 by the pins in the lead weight ; the valve will now blow off steam 
 (if in proper order) at a temperature of 225 °. Until this occurs, no 
 particular attention is necessary, but from that time the exclusive 
 attention of the operator should be given to the molding. Many 
 failures occur from the want of this, for the plate may be easily 
 injured from too much heat without proper pressure. But fifteen 
 or twenty minutes, at the most, will be required from this point, 
 with proper heat, and nothing else should be attended to. 
 
 At the point when the steam escapes from the valve with the 
 
3-P MECHANICAL DENTISTRY. 
 
 upper portion suspended, the plate will soften, and the screw will 
 be felt to yield to light pressure with thumb and finger. The upper 
 weight should now be dropped down. Turn the screw very care- 
 fully, stopping when you feel the resistance increase; as soon as it 
 yields again, turn it more, going slowly and carefully at first, but 
 increasing the pressure somewhat as the steam gets up, which you 
 will know by occasionally raising the valve. It is just here that 
 judgment is required to avoid, on the one hand, too much pressure 
 before the material is sufficiently softened, which would result in 
 fracture of the cast or blocks, disarranging the articulation, or a 
 " flaky " plate ; and, on the other, too little pressure after the heat 
 is up, which would result in injuring the quality of the material. 
 The pressure should be followed up as the heat rises and the screw 
 yields, the object being to get the whole of the plate under pressure, 
 in every part of the mold, by the time the steam blows off quite 
 sharply and steadily on raising the safety-valve. After this the 
 pressure should be increased, but time should always be given 
 between the turns for the slowly flowing celluloid to escape from 
 under the pressure. Toward the close of the process, the pressure 
 should be considerable ; in fact, about all that can be applied with 
 the machine, and should be continued as long as the screw can be 
 turned. If the operation has been properly timed, the s,team will 
 blow off at the safety-valve at about the time the molding is com- 
 pleted and the alcohol in the cup is consumed. If it should blow 
 off before that, no harm would be done, as the heat cannot become 
 too great if the safety-valve is kept in proper condition. These 
 remarks apply to the use of alcohol in the cup furnished with the 
 machine. If any other heat is used, the flame should be sufficient 
 to complete the process within thirty to forty minutes. If more 
 than this time is consumed in the molding, the quality of the plate 
 is injured. 
 
 Do not allow the water to be all converted into steam, as the 
 steam would then become superheated, and a dangerous condition 
 ensue or the plate be ruined, while the safety-valve would not indi- 
 cate it. Always have plenty of water in the boiler, and if steam 
 should cease to issue on raising the valve, the heat should be at 
 once withdrawn. 
 
 It lias been demonstrated by experimental tests, and is now very 
 generally conceded, that the best results are obtained in the use of 
 
CELLULOID BASE. 
 
 343 
 
 celluloid by subjecting it to dry heat in the process of molding, 
 the material, when exposed to a high temperature under such a 
 condition, retaining most perfectly its form, color, and consistency. 
 Hence the celluloid presses of more recent introduction, while 
 they are also equally well adapted to vulcanizing by the same 
 means, are provided with a distinct chamber in which hot air, of a 
 higher temperature than can be safely employed with glycerin or 
 steam, is utilized to secure the greatest practicable plasticity of the 
 
 Fig. 147. 
 
 Open. 
 
 Closed. 
 
 celluloid. Approved appliances of this kind are those devised by 
 Drs. Seabury and Evans. 
 
 Molding by Dry Heat. — When the investment is thoroughly 
 dried, insert and carefully adjust the selected blank; place the 
 flask in the oven (see Fig. 147) immediately under the screws; see 
 that the two sections are so placed that the guide-pins will enter 
 properly into the lugs ; turn down the screws until they bear lightly 
 upon the top of the flask, and close the machine. In less than 
 
344 MECHANICAL DENTISTRY. 
 
 five minutes the material will be sufficiently softened to permit the 
 commencement of the molding. The screws will turn readily 
 with the thumb and finger (using the smaller key-wrench), when 
 the blank is properly softened. Close the flask gradually, stopping 
 occasionally if the resistance is very material. Usually, if the 
 temperature is about 300 , the flask can be closed in ten minutes; 
 but if a very thick blank is used, the molding must proceed 
 slowly. As soon as the flask is closed — unless a lock flask is used 
 — the flame should be extinguished, the door opened, and the 
 machine allowed to cool. If a lock flask is used, it may be re- 
 moved and thoroughly cooled before opening it, the oven being 
 meanwhile ready for another case. The cooling may be accom- 
 plished rapidly, if necessary, by placing the flask in water. When 
 perfectly cold, remove the plate from the investment ; it will be 
 found enveloped in the tin-foil which had been burnished to the 
 wax plate. Peel off the foil. The celluloid will present a hard, 
 brightly-polished surface, received from its contact with the foil, 
 and will need no further finishing than cutting off the excess of 
 material and smoothing down the edges. 
 
 In the use of material, as a base for dentures, possessing prop- 
 erties so extremely sensitive to heat as that of celluloid, and so 
 liable to suffer changes of color and structure materially affecting 
 its usefulness by a misapplication of heat and faulty manipulation, 
 everything that contributes to a better understanding of its be- 
 havior in the process of molding must be of interest and practical 
 value. The following experiments of Dr. J. Stewart Spence, of 
 San Francisco, Cal., throw some additional light upon the subject. 
 He says : 
 
 " Having just made more than 30 experiments with celluloid 
 and the New Mode Heater, I have met with some interesting facts, 
 of which, during two years' previous use of the apparatus, I was 
 ignorant. The main results I will now give before relating the 
 experiments, thus inverting the usual order of placing results last, 
 for the sake of perspicuity. 
 
 " 1. Plaster investments require one and a half hours to dry in 
 the oven of the heater, with the thermometer at 400 , and half an 
 hour more to raise their heat to 320 . Drying them over a gas- 
 burner takes nearly as long, and loosens the plaster from the flask. 
 A thermometer placed between the slightly separated halves of 
 
CELLULOID BASE. 345 
 
 the flask in the oven indicates when this heat is reached, at which 
 time a blank previously prepared, should be expeditiously in- 
 serted. 
 
 " 2. Celluloid may be molded in from five to ten minutes at 320 ; 
 in about twenty to twenty-five minutes it degenerates, becoming 
 brown, hard, brittle, and porous, and in twenty-five to thirty min- 
 utes it burns up. 
 
 " 3. Celluloid will burn at either high or low temperatures, ac- 
 cording to the length of time it is exposed to them, as well as 
 their degree of heat. Thus it is unsafe to leave it at even a low 
 heat for a long time, as in slow cooling. 
 
 " 4. Celluloid is more liable to spoil if not under pressure, and 
 those parts of the blank least subject to pressure are most liable to 
 come out damaged. Therefore flasks should be closed with all 
 expedition. 
 
 " 5. Celluloid, unless worked at a high temperature, so as to flow 
 readily, and with well-hardened plaster, will press the model out of 
 shape and teeth out of position. 
 
 " 6. Steam brought in contact with heated celluloid makes it puff 
 up and degenerate. 
 
 " 7. Plaster retains heat longer than metal, and therefore plates 
 left in the oven to cool may spoil or burn up even when the tem- 
 perature of the heater has fallen to a low degree. 
 
 " 8. Tin-foil discolors celluloid at a high heat, making it 
 browner. 
 
 " 9. Celluloid after molding is hardest at the surface, as may be 
 clearly seen in a plate that has been slightly overheated, it being 
 porous internally, but very hard on its surface. 
 
 " Instead of giving a copy of my record of these experiments, 
 which would be unnecessarily prolix, I will give a condensed ac- 
 count of them by series. 
 
 " 1st Series. To test the heat of the oven. I placed in the dry 
 oven a separate thermometer, which, with the door closed, regis- 
 tered the same as that outside ; then reversed them with similar 
 results. Removing the central screw from the top did not reduce 
 the temperature perceptibly. Removing the door reduced it a few 
 degrees. Removing both door and screw caused a rapid decrease 
 from 320 ° to 290°. 
 
 " 2d Series. To test the heat of oven with plaster in it. I filled a 
 
346 MECHANICAL DENTISTRY. 
 
 half flask with plaster and placed it in the oven with a ther- 
 mometer on the floor beside it, of course closing the door, the 
 outer thermometer standing" at 320 . After twenty minutes the 
 inner thermometer had reached only 300 , showing the cooling 
 effects of the plaster on the air of the oven. Moved the ther- 
 mometer on to the plaster ; the thermometer fell considerably, 
 and while the outer thermometer rose in thirty minutes to 440 , 
 the inner reached only 290 ; steam was then admitted to the oven, 
 and it ran instantly up to 340 ° ; steam was then shut off, and the 
 outer thermometer maintained at about 360 for thirty minutes 
 longer, by which time the inner reached 320 . At this point 
 some steam was let off, which ran the outer thermometer 20 be- 
 low the inner, showing that plaster is slow to part with its heat as 
 well as to receive it. 
 
 " Further experiments were made in drying plaster, both in the 
 oven, with steam and without it, and out of the oven over a gas- 
 burner ; also with plaster mixed with pulverized pumice and mixed 
 with marble-dust. It was found that in the oven with either steam 
 or dry heat, and the outer thermometer at 400 , about thirty min- 
 utes were required to dry and heat a small half flask of plaster to 
 320 , and about two hours for a full flask. Done over a gas- 
 burner, under an inverted flower-pot, a little less time was con- 
 sumed, but the investments loosened from the flasks ; under higher 
 heats they become burnt and badly checked. Those mixed with 
 pumice and marble-dust took nearly as long to heat and became 
 softer than the plaster alone, and so were thereafter abandoned. 
 
 " 3d Series. Testing celluloid in the oven without the presence of 
 plaster, steam, or pressure. A piece of celluloid placed in the oven 
 at 320 , the heat rising, burned, after slight swelling, at 360 . A 
 second piece remained in thirty minutes with the heat at 320 , 
 swelled slightly, and crumbled to powder on being taken out. A 
 third piece left in three minutes at 320 was taken out a little 
 swollen and somewhat brittle and porous. 
 
 " 4th Series. Testing celluloid in the oven with plaster and with 
 moisture. A half flask of moist plaster was placed in the oven, 
 and on it a piece of celluloid and a thermometer. The outer ther- 
 mometer, starting from 320 , rose to 440 , and then fell to 360 in 
 about sixty minutes, by which time the inner thermometer reached 
 320 , and the celluloid, after great swelling, ignited. (In the 
 
CELLULOID BASE. 347 
 
 previous series of experiments the celluloid had swollen but about 
 one-tenth as much as it did in these.) Next a half flask of 
 previously dried plaster was inserted, and the inner thermometer 
 raised to 340 , when a piece of celluloid was dropped in, and 
 burned in five minutes. A second piece at about 330 puffed up 
 in ten minutes, and would probably have exploded in five more if 
 I had not varied the experiment by admitting steam to test its 
 effects, which were a greatly increased swelling and then gradual 
 shriveling to a thin wafer. (That steam does not produce ignition 
 was also demonstrated elsewhere, when its admission ran the inner 
 thermometer up to 340 , and yet afterward, when the steam was 
 shut off, the celluloid burned at 320 .) In the next test the dry half 
 flask was again used, but the outer thermometer was lowered to 320 , 
 which ran the inner one down much lower, but in forty minutes 
 they tallied, during which forty minutes the celluloid after the first 
 fifteen minutes began to puff, and in ten minutes more had reached 
 full size, and then for fifteen minutes slowly shrank, then exploded. 
 
 " Both thermometers being now at 320 , a piece of blank was 
 left in fifteen minutes, and on being taken out crumbled to powder 
 under the slightest pressure. A second blank, in twenty-five 
 minutes, at 300 °, came out not crumbling so badly. A third at 
 280 , for thirty minutes, was slightly swelled and somewhat brittle 
 and porous. 
 
 " 5th Series. Testing celluloid in the oven with pressure and plas- 
 ter. A full flask of plaster was placed in the oven, and its tempera- 
 ture raised to that of the outer thermometer, 320 ; then a piece of 
 celluloid was placed in the flask, which was closed down in three 
 minutes, and in five more the piece was removed from the flask in 
 perfect condition. A second piece was then inserted, closed in 
 ten minutes, and removed from the oven, and in five minutes more 
 opened in perfect condition. A third piece was left in twenty 
 minutes, and in five more opened in perfect condition, not even 
 discolored. A fourth piece was given twenty-five minutes in the 
 oven and ten more before opening the flask, with disastrous results ; 
 it had crumbled to a brown powder. 
 
 " This fifth series of tests show that the material in question 
 remains perfect under pressure longer than without it. But it is to 
 be remembered that the investment here used must have lost some 
 of its heat while out of the oven. Later trials seem to indicate 
 
348 MECHANICAL DENTISTRY. 
 
 twenty minutes as the longest time that celluloid can safely be left at 
 320 . As a side issue, the cohesion of the material was tested 
 during this series ; freshly-filed surfaces were placed together, and 
 apparently joined, but they separated under a strong strain. 
 
 "6th Series. Testing the effect of steam on the celluloid at 320 . 
 The same investment was used as in Series 5, and the flask closed 
 in ten minutes, when steam was admitted. In ten minutes more 
 the blank came out spoiled, being disintegrated, whitish, and sticky- 
 I have seen celluloid take on this soft and white condition when 
 heated in water above 270 . 
 
 "7th Series. Testing the flowing qualities of celluloid at 320 . 
 A piece of celluloid was placed in a flask heated to 320 , no cavity 
 being left in the plaster to receive the celluloid. Closed in ten 
 minutes. It sunk a bed for itself in the hard plaster, flowing but 
 little. This is a hint as to the cause of misfits, raised bites, and 
 thickened palates, of plates molded with soft plaster and low 
 heats. 
 
 " 8th Series. Testing the effects of quick closing. A full blank 
 was placed in a full flask of plaster heated to 320 , and closed so 
 that the halves of the flask came together on one side consider- 
 ably sooner than on the other. Gave it over fifteen minutes in the 
 oven. When opened it showed, as expected, the side of the plate 
 which had been the latest closed porous and brittle. As a side 
 issue in this experiment, tin-foil of two thicknesses, 18 and 60, were 
 placed side by side on the blank, and when peeled off the surface 
 below was of a browner color than the adjacent celluloid. 
 
 " I would hint at the possibility of the celluloid which oozes 
 from the flask, and touches the wall of the oven, being ignited 
 thereby in some instances. A deep excess-chamber should be 
 cut around the model to prevent this. Moreover, this escaped 
 celluloid, not being under pressure, is doubtless more liable to 
 burn. 
 
 " Celluloid hardens on being subjected to dry heat, but much 
 of this is not desirable, as its hardness is external, while inside- 
 it becomes porous, and when thus hardened is very brittle. Cel- 
 luloid will burn under water, as demonstrated in a vulcanizer, at 
 320 . 
 
 ' Thin edges of celluloid will soften in hot drinks in the mouth. 
 Thus, the festoons of gum left thin will shrink from the tooth, pro- 
 
CELLULOID BASE. 
 
 349 
 
 ducing what may be termed a free edge of celluloid gum, under 
 which dirt deposits, and shows through the semi-translucent cellu- 
 loid. This is prevented by making the edges of the festoons of 
 proper thickness. Another error frequently seen is that of cutting 
 away the interdental celluloid gum (contrary to nature), thus form- 
 ing cavities difficult to cleanse by the brush, producing unsightly 
 discoloration at those points. 
 
 " The principal objection to celluloid is that after a year or two 
 in the mouth it loses its beautiful color, and becomes of a dull 
 vermilion shade, or even black. This will probably remain the chief 
 objection to it. That it is not so tough nor so elastic as vulcanite, 
 and that in consequence it wears away and loses its smooth surface 
 in the mouth, and is unfitted for clasps, and that it is a little more 
 difficult to work than rubber, would not prevent its popularity, if 
 it were not for this discoloration. However, the loss of color does 
 not always extend far into the plate, and much of it may be quickly 
 removed with a brush wheel and pumice." 
 
 Finishing. — This is accomplished with the use of the same 
 instruments used in rubber cases. The final polish may be given 
 first with pumice-stone, and afterward with whiting or Vienna lime. 
 Dr. H. D. Knight recommends a polish obtained by rubbing with 
 an old cloth wet with camphor. This may be valuable between 
 teeth and in places inaccessible to the brush wheel. In finishing, 
 care should be taken not to heat the plate by friction, as by so 
 doing the surface may be injured or the plate sprung out of shape. 
 
 VULCANITE BASE-PLATE FACED WITH CELLULOID. 
 
 The above method of constructing an artificial denture, desig- 
 nated by the inventor as the " new mode continuous-gum " proc- 
 ess, provides for the use of single porcelain teeth without artificial 
 gums, the latter being represented by the celluloid facing. This 
 expedient is most esteemed by those who regard rubber as a more 
 suitable material for a base than celluloid, and who, in the use of 
 the former, are unable to meet the requirements of a certain class 
 of cases with either single gum teeth or sectional blocks. 
 
 In this combination work, which admits of an optional arrange- 
 ment of each individual tooth, the conditions are secured which 
 better enable the operator to effect such arrangement of the teeth 
 as will best serve the purposes of mastication and aid in restoring 
 
■?-0 MECHANICAL DENTISTRY. 
 
 the customary facial contour and expression of the individual. 
 Still other advantages are claimed for this method, namely, that 
 the rubber is stronger and more elastic, and, being harder, the pins 
 are less liable to draw or loosen, while the same property diminishes 
 the liability to mechanical abrasion of the palatal surface in masti- 
 cation, and. lastly, that in case of accident to the teeth they may 
 be replaced with the use of celluloid, thus obviating entirely the 
 necessitv of revulcanizing, a process which always impairs the 
 structural integrity of the rubber. 
 
 The first step in the process of constructing this kind of work 
 consists in molding the rubber base-plate, with the teeth attached. 
 All the preliminary processes, including the arrangement of the 
 teeth, are the same as those practised when rubber alone is used. 
 The teeth employed are those manufactured expressly for continu- 
 
 FlG. 148. 
 
 ous-gum work and celluloid, as shown in Fig. 148. In waxing up 
 the case, all the exterior surfaces of the teeth and marginal portions 
 of the trial-plate are left uncovered, and a strip of wax arranged 
 all along the external border of the wax plate to form a groove for 
 the celluloid, as shown in Fig. 148. The excavation thus formed 
 exteriorly should extend inwardly into the interdental spaces far 
 enough to secure anchorage for the celluloid in connection with 
 that obtained by the grooved border. The space or spaces for the 
 celluloid facing being thus provided for, the palatal portion is 
 properly contoured, the case flashed, packed, and vulcanized in the 
 usual manner. The piece, when removed from the flask, will ex- 
 hibit an undercut groove along the border, and the external portions 
 of the crowns and roots exposed in the manner shown in the illus- 
 tration. 
 
 The second step in the operation consists in molding the cellu- 
 
CELLULOID BASE. 
 
 351 
 
 loid facing. The following is the method of forming the matrix 
 and molding the celluloid : Fill up all the space between the 
 rimmed border of the plate and crowns of the teeth with wax and 
 paraffin, as being preferable to wax alone, and then contour it 
 exactly as required in the finished piece; cover with tin-foil, and 
 stipple the surface in the manner heretofore described. The case 
 thus prepared is ready to be invested for the purpose of obtaining 
 the matrix in which to mold the celluloid. In so doing, fill the 
 lower section of the flask partly with plaster, and also the palatal 
 
 Fig. 149. 
 
 portion of the plate, and then place the latter in the flask with the 
 teeth upward, raising the front part of the plate somewhat, giving 
 it a downward inclination posteriorly, in order that the upper sec- 
 tion, when the investment is completed, may be detached without 
 dragging. The plate should not be imbedded in the plaster 
 beyond the grooved margin, making the line of separation on the 
 outside along the border from heel to heel of the plate. Additional 
 plaster is now poured in, covering the entire palatal face of the 
 plate and crowns of the teeth, leaving only the outer portions of the 
 
y^ 
 
 MECHANICAL DENTISTRY. 
 
 latter and the plate exposed. When the plaster sets somewhat, 
 pour in more plaster around the inner edge of the flask ring, form- 
 ing a ridge, and also a corresponding groove or space between it 
 and the plate. The piece thus invested will present the appearance 
 shown in Fig. 149. The surface of the plaster is now varnished, 
 and thin oil applied to all the surfaces. When the wax facing is 
 covered with tin-foil, the latter should not be oiled, as it is intended 
 that this shall adhere to the plaster when the flask is separated. 
 The investment is now completed by adjusting the upper section of 
 the flask and filling it with plaster. When sufficiently hard, the 
 sections are carefully separated and the wax thoroughly removed 
 
 Fig. 150. 
 
 with boiling water. The tin-foil will remain adherent to the plaster 
 in the upper section. 
 
 Select a celluloid blank of suitable size and saw off the outer rim, 
 as shown in Fig. 150. Dress and carve this to near the size and 
 form of the space to be filled, having some excess of material. 
 Having first softened the rim thus prepared by immersing it in 
 boiling water for a few moments, press it well into the space 
 provided for it, and hold there until rigid. Place the two sec- 
 tions of the flask together in their proper relation, introduce into 
 the oven previously heated, and close the flask in the usual 
 way. When the piece is removed from the flask, and the tin-foil 
 removed by peeling it from the surface, to which it will adhere, 
 little will be required in the way of finishing except to remove 
 surplus material at the necks of the teeth and borders of the plate, 
 
CELLULOID BASE. 353 
 
 and final smoothing and polishing at these points. If the facing 
 material has been stippled, the finished piece will present the appear- 
 ance shown in Fig. 151. 
 
 The above process is also applicable to gold and cast metallic 
 plates. 
 
 ZYLONITE.* 
 
 " A modified form of celluloid has been introduced under the 
 name of zylonite, the working results of which appear to show some 
 difference in quality. Zylonite, like celluloid, is composed of 
 pyroxylin and camphor, but in different proportions, being, it is 
 
 Fig. 151. 
 
 claimed, a chemical combination, while celluloid is a mechanical 
 mixture. 
 
 " Possessing translucency, the effect of zylonite in the mouth is 
 very pleasing, and, so far as it has been tested, promises to be more 
 durable than celluloid, without the tendency to warp or to change 
 color when ordinary care is taken in its manipulation, which is the 
 same as for celluloid. The zylonite blanks are uniform in color, 
 and although this material requires the same amount of pressure to 
 mold, it flows with a more perfect sharpness of outline than cellu- 
 loid, and apparently does not disintegrate." 
 
 * Harris' " Principles and Practice of Dentistry." 
 
 23 
 
CHAPTER XXV. 
 
 ATTACHING PORCELAIN TEETH TO A METALLIC BASE WITH 
 RUBBER OR CELLULOID. 
 
 The following method of attaching porcelain teeth to a metallic 
 plate by means of rubber or celluloid, though but little practised 
 heretofore, is attracting more attention than formerly, and is 
 eminently deserving of more favorable consideration and general 
 adoption, by reason of its conspicuous and acknowledged merits, 
 than it has ever yet received. The credit of its first introduction 
 to the notice of the profession is due to Dr. P. G. C. Hunt, of 
 Indianapolis, Ind., who practised the method as early as 1859, anc ^ 
 whose published descriptions of the manner of preparing the plate- 
 base, substantially the same as that for which Mr. S. D. Engle, of 
 Hazleton, Pa., obtained letters-patent some years later, were given 
 in the first edition of this work. 
 
 That it possesses marked advantages over the method of attach- 
 ing teeth to a metallic plate-base by soldering is unquestionable. 
 The waste and consequent change in the form of the plate incident 
 to soldering, so inseparable from the older method of attachment 
 by means of stays or backings, is wholly avoided ; the strain upon 
 the platina pins is greatly lessened by reason of the perfectly 
 adapted rubber or celluloid socket in which each tooth or block 
 securely rests ; the liability to fracture of the teeth from concus- 
 sion or violence is materially diminished on account of the pliable 
 nature of the attaching material used ; a near approximation to the 
 natural form of the ridge or gum on the lingual side of the plate 
 is secured ; the rubber or celluloid, penetrating all the joints and 
 openings between and beneath the teeth, renders the piece wholly 
 impervious to the oral secretions, making it, in point of cleanliness 
 and purity, equal to continuous-gum work ; the facility with which 
 injury to the teeth may be repaired; the practicability of remodel- 
 ing the piece without impairment of the teeth or plate ; its suscep- 
 tibility of receiving a final finish excelled by no other method in 
 point of artistic beauty; — these are among the qualities which 
 
 354 
 
METALLIC BASE WITH RUBBER ATTACHMENT. 355 
 
 commend this method of substitution as one of peculiar merit 
 and excellence. 
 
 In mounting teeth by this method, preference should be given to 
 either gold, platinum, aluminium, or cast metal as a base. When 
 silver is used, the plate should be made from refined silver alloyed 
 with platinum, with the additional precaution of interposing a 
 layer of tin-foil between the rubber and plate, an expedient not 
 necessary when celluloid is employed. Aluminium has a limited 
 adaptability to this mode of substitution, but requires special treat- 
 ment in its preparation for the purpose, a description of which will 
 be given in connection with the manner of preparing the plate. 
 
 The manipulative details concerned in the construction of an 
 artificial denture by the method under consideration are thus de- 
 scribed by Dr. Hunt : 
 
 " Take the impression, make metallic dies, and form the plate 
 as for work in the ordinary way. After fitting the plate in the 
 mouth, get the articulation, the fullness and length of the teeth, 
 remove the wax and plate from the mouth, and make the plaster 
 articulation. If a full set, after separating the articulation, and 
 before removing the wax from the plate, take a small, light pair of 
 dividers, set them say one inch apart, and with one point following 
 the margin of the wax, representing the cutting edge of the teeth, 
 and the other point marking permanently the plaster, you have 
 always in the dividers so set a gage for the length of any par- 
 ticular tooth. A convenient substitute for the dividers may be 
 formed from a piece of wire of convenient length, one-half the 
 diameter of a common excavator, by suitably twisting its middle 
 for a handle, and its ends being sharpened, and pointing in the same 
 direction, I or \}A inches apart. 
 
 " Thus far we proceed as we do for ordinary gold work. We 
 will now suppose the teeth ground and jointed, leaving as much 
 space between the teeth and plate as the plate will admit of. We 
 next mark with a sharp-pointed instrument on the labial surface of 
 the plate each point where it is necessary to place a loop for pur- 
 poses hereinafter described. Then apply wax to the external or 
 labial parts of the teeth and plate in any manner sufficient to retain 
 the teeth in position, remove the wax from the lingual parts of 
 the teeth and plate, and mark the position on the metal where it 
 is desirable to insert loops ; remove the teeth and wax, and with a 
 
356 
 
 MECHANICAL DENTISTRY, 
 
 small bow-drill make holes through the plate at the several points 
 previously determined on for the attachments, about the size of the 
 ordinary plate punch-hole ; take a wire, or ordinary gold plate, cut 
 in strips, say from a half to one line in width, being governed by 
 the amount of room there is under the base of the teeth, and 
 with small, round-nosed pliers, bend the strip around ; grasp both 
 ends with square-nosed pliers, draw the round-nosed pliers from 
 the loop, still grasping the square-nosed pliers with the left hand, 
 and with a hammer strike the top of the loop a sufficient blow to 
 keep the ends from springing apart. Cut off the ends, and dress 
 down to fit the holes in the plate, after which solder on charcoal or 
 other suitable substance without investment." 
 
 By reference to Fig. 152, which illustrates Mr. Engle's method 
 of providing attachment for the rubber to the plate by means of 
 bent wires soldered to the base, the substantial identity of Dr. 
 Hunt's mode of forming loops for the same purpose will be apparent. 
 With this digression, we return to Dr. Hunt's instructions : 
 "Pickle, dress, and polish that portion of the plate to be exposed 
 to view. Bend and flatten the pins, arrange the teeth according to 
 the articulation, waxing so as to cover up the loops if practicable; 
 the loops should be placed as near the base of the teeth as possible, 
 the rubber forming when finished a part of that general concave 
 shape which is desirable in upper dentures, and which it is not pos- 
 sible to obtain with the ordinary soldered work. Then with silicate 
 of soda paint the joints, to keep the rubber from forcing in where 
 
METALLIC BASE WITH RUBBER ATTACHMENT. 357 
 
 it would show after vulcanizing. Flask, vulcanize, and finish up 
 as usual. The advantages of this style of work are obvious. 
 With this you have work as cleanly as the continuous gum, de- 
 cidedly more so than the very best single gum or block-work sol- 
 dered in the usual way; again, it is very much stronger, less liable 
 to breakage, both in and out of the mouth, as the rubber gives a 
 perfect base and support for the teeth to set upon. By this method 
 there is no springing of plates. As your plate fits the mouth when 
 the articulation was taken, so will be the fit when the case is com- 
 pleted. 
 
 " On the labial edge of the upper plate, the rubber may be al- 
 lowed to project beyond the edge, if desirable, and it will be found 
 in many cases exceedingly satisfactory to do so, and allow the rub- 
 ber to be of considerable thickness near the alse of the nose, where 
 the loss of the cuspidati may leave a want of support to the soft 
 parts adjacent, and which in this manner can be readily corrected. 
 If the rubber extends upward so far as to irritate the muscular 
 structure, a few minutes will be sufficient to make the necessary 
 alterations. In all such cases where we have control of our patients, 
 we place the denture in the mouth before finally polishing, so as to 
 determine as accurately as possible the limit to which extension 
 upward may be carried. 
 
 " The neatest work on this principle is made by carving blocks, 
 giving to the lingual surface that regular concave form which is 
 desirable. In this no platinum pins or loops are necessary, but in 
 that half of the matrix on which the blocks are carved, large 
 metallic pins are so arranged as to be hid from view in the tooth 
 body. Different-sized pins may be used, as large as the nature of 
 the case will admit. In short, we make the holes in the block 
 similar to those in pivot teeth, where there is not sufficient room 
 in the block above the tooth (or below if an under) to allow the 
 pins to run into the body of the teeth. After burning, grinding,, 
 and fitting, get the position of the holes in the blocks relative to 
 the plate, and drill through the plate as before, and instead of 
 loops, solder gold wire of suitable size and length, sav a very 
 little shorter than the depth of the hole in the blocks, and two- 
 thirds the diameter thereof ; the wire should have a screw-thread 
 cut on it, or, that which is just as good and more expeditious, barb 
 or cut with a sharp knife. At this point of the manipulation, if it 
 
3^8 MECHANICAL DENTISTRY. 
 
 is desired that the rubber should extend beyond the labial or 
 buccal edge of the metallic plate, place as many loops at different 
 points as are sufficient to retain it with firmness, after which 
 polish the plate, wax, and proceed as before described. If you 
 desire no rubber beyond the blocks, the roughness of the holes in 
 the same, and the barbed points on the gold wire, when properly 
 packed and vulcanized, will give ample strength and firmness to 
 the case, and if care has been used in the entire manipulation, 
 you will have, when finished, but a thin line of rubber exposed to 
 view. 
 
 " In partial cases, if of gold base, solder on loops, as before, for 
 the retention of the teeth; and if there are to be any clasps, make 
 them of rubber, uniting them, as the teeth, with loops. If the 
 ordinary plate teeth are used, it is frequently necessary to back 
 them to give better retaining-points for the rubber. If blocks are 
 to be burned, insert loops of platinum plate in the shape of the letter 
 U in place of the platinum wire pins. In consequence of the affinity 
 of the sulphur in the vulcanite for silver, plates of that metal should 
 not be used." 
 
 Another method of increasing the attachment between the metal- 
 lic base and the rubber, is that of spurring the plate over the ridge 
 with a sharp-pointed chisel, as shown in Fig. 153. 
 
 When aluminium is employed as the base, the strongest and alto- 
 gether the best means of increasing the attachment is that of cutting 
 or punching loops from the plate itself, as shown in Fig. 154. Prob- 
 ably the best instrument for this purpose is that devised by Dr. J. 
 H. Gaskill, which is illustrated in Fig. 155. 
 
 When a cast metal plate is employed, loops or pins are not 
 needed, as sufficient anchorage is secured by cutting out the wax 
 on the labial surface and from between the teeth (in fact, from every 
 point where it is desirable to have the rubber) before Hashing for the 
 casting process. After the plate has been cast and finished, the rub- 
 ber may be packed and the case reflasked, vulcanized, and finished 
 in the usual manner. 
 
 The following unique and original method of casting a metal 
 base-plate, fastenings, and hooks, in a single piece, is thus described 
 by Dr. Xorman W. Kingsley : " The plate is formed of a thin sheet 
 of wax sel up on the plaster model, but before it is Masked for cast- 
 ing I take a dozen small gimp tacks, with half round heads, and set 
 
METALLIC BASE WITH RUBBER ATTACHMENT. 
 
 359 
 
 them in a row upon the ridge of the lower jaw, with their heads 
 just imbedded in the wax, and then flask the piece. In flasking it, 
 I use plaster and sand, in the proportions of about three parts of 
 sand to one of plaster. This gives a fine surface when it comes in 
 contact with the wax in making the mold, and it is sufficiently 
 porous to dry out quickly. When the flask is opened, the wax is 
 readily removed ; ' the tacks are pulled out, and when the casting 
 
 Fig. 153. 
 
 Fig. 155. 
 
 Fig. 154. 
 
 is made, the spaces that were occupied by the tacks are filled with 
 the metal, so that we have a plate with a row of tacks of the same 
 metal, which can be easily bent for attachments, standing around 
 upon it." 
 
 If gum sections are used in connection with a plate formed in 
 the manner just described, vulcanite may be employed as a means 
 of attachment, but plain, single teeth are equally admissible in the 
 
360 MECHANICAL DENTISTRY. 
 
 use of either rubber or celluloid. The particular alloy used by Dr. 
 Kingsley in casting plates, and of which he speaks in terms of high 
 commendation, consists of pure tin and bismuth, in the proportion 
 of one pound of the former to one ounce of the latter. 
 
 The following method of preparing aluminium plates for the at- 
 tachment of the rubber was communicated to the author by Dr. J. 
 W. Hollingsworth, of Greencastle, Indiana, an intelligent practi- 
 tioner who has had long and extended practical experience in the 
 various modes of working this metal for dental purposes, and who 
 says of the following mode of procedure that " it is the most prac- 
 ticable and the most easily manipulated method that I have yet 
 seen." 
 
 The following is the manner of preparing the plate as described 
 by Dr. Hollingsworth : " Perforate the ridge of the plate at proper 
 points and intervals ; then pass through these perforations, from the 
 inner surface of the plate, headed pins made of aluminium, which, 
 after replacing the plate with the pins back upon the die, we shrink 
 down to permanency with a hollow punch. The punch must be 
 made with the hole not quite equal in depth to the length of the ex- 
 truding portion of the pins and slightly bell-mouthed. The riveting 
 process forms seriate studs or pins, which may be bent or flattened 
 with pliers in any way to suit the requirements of the case." 
 
 When celluloid is used for purposes of attachment in the case of 
 full upper dentures, the palatal portion of the blank should be cut 
 or sawed away, leaving only the ridge portion to be used, and this 
 should be trimmed, if necessary, so as to have but little excess of 
 material. The ordinary full blank may be used for lower cases, 
 observing the same precautions in regard to quantity of material. 
 When the blank is thus prepared, the subsequent manipulations are 
 the same as those described in connection with the celluloid base. 
 
 It may be observed that, when rubber or celluloid is used, it is 
 better to dispense with the plaster model in forming the mold or 
 matrix, and proceed as follows: When the teeth are arranged, and 
 the required contour and fullness given to the wax drafts, fill the 
 lower section of the flask with plaster, and, having also filled the 
 plate with the same, imbed the plate in it, making the dividing line 
 on the external rim of wax. When the plaster has hardened, and 
 the other section formed, and the two afterward separated, the 
 
METALLIC BASE WITH RUBBER ATTACHMENT. 361 
 
 metallic plate will remain in the lower section and the teeth in the 
 upper. 
 
 When using celluloid, plain teeth may be advantageously em- 
 ployed, the former representing the gum ; this gives perfect freedom 
 
 in the arrangement of each separate tooth in the denture, an 
 
 optional disposition the importance of which cannot be over-esti- 
 mated. 
 
CHAPTER XXVI. 
 CAST METAL BASE. 
 
 Cheoplastic Process. — The method of mounting artificial den- 
 tures by what is familiarly known as the " cheoplastic process," in 
 which the base consists of certain metallic compounds or alloys in 
 cast form, has comparatively but limited application in prosthetic 
 practice. The method, as commonly practised, is rarely applied to 
 full upper cases, occasionally to partial upper pieces, but chiefly to 
 lower dentures in cases of unusual absorption of the alveolar ridge, 
 requiring increased weight to secure adequate stability of the sub- 
 stitute. The alloys in most general use for this purpose are those 
 compounded by Drs. Wood, Weston, and Watt, whose names are 
 a sufficient guarantee of the suitableness of those several alloys 
 for the purpose. 
 
 The construction of a denture by this method is readily accom- 
 plished by any one familiar with the working of vulcanite or cel- 
 luloid. The manipulations concerned in the formation of a mold 
 or matrix are, in general, the same as those employed in forming a 
 matrix for rubber or celluloid. The model and investing material, 
 however, must.be of such substances as maintain their integrity of 
 form perfectly under the heat necessarily applied in thorough 
 drying of the case and contact of molten metals. Simple plaster, 
 on this account, is unsuitable, either for the model or investment, 
 and it is customary, therefore, to add to it, in relatively large pro- 
 portions, such substances as undergo but little, if any change of 
 form when exposed to the necessary heat. Those most commonly 
 employed are finely-pulverized pumice-stone, marble-dust, soap- 
 stone powder, or clean white sand. Tn the use of any of these 
 substances, only enough plaster should be added to give to the mold- 
 ing material sufficient body or strength necessary to provide against 
 defacement in handling; say one part plaster to three of sand, which 
 is the mixture generally employed. 
 
 One of the best adapted flasks for molding and casting purposes, 
 
 362 
 
CAST METAL BASE. 
 
 363 
 
 contrived by Prof. George Watt, is exhibited in Fig. 156. The 
 piece, properly prepared by careful contouring of the wax or 
 paraffin, is then flasked in the same manner as when preparing a 
 mold for vulcanite. When the sections of the flask are separated, 
 grooves or gateways should be cut, extending from the posterior 
 and lateral margins of the mold to the openings on either side, 
 shown in the figure, thus providing for the ingress and egress of 
 the melted metal when poured ; after which all traces of wax should 
 be thoroughly washed out with boiling water. 
 
 The sections of the flask are now adjusted to each other, and 
 tightly clamped, to prevent the escape of metal when poured. 
 
 Fig. 156. 
 
 Before casting, the mold should be thoroughly dried by exposing 
 it for two or three hours to an oven heat, and the temperature, at 
 the moment of pouring, should be raised to about that required to 
 fuse the alloys mentioned, or about 400 ° to 440 ° F. 
 
 In pouring the metal into the mold through one of the lateral 
 openings, the metal should rise freely and quickly into the opposite 
 one, and if bubbling occurs, which will never happen if the plaster 
 has been sufficiently dried, the flask should be lightly tapped on 
 some hard surface until the ebullition ceases, thus insuring a more 
 certain intrusion of the metal into all parts of the mold before 
 solidification takes place. 
 
364 
 
 MECHANICAL DENTISTRY. 
 
 Dr. Weston has devised a casting flask (Fig. 157), the two sec- 
 tions of which form an encircling band with the sides, or top and 
 bottom, open, and which are closed securely with screw-bolts. 
 This form facilitates the escape of moisture from the plaster invest- 
 ment in the process of drying. 
 
 When the piece is quite cold, it may be readily removed from 
 
 Fig. 157. 
 
 tin- flask by soaking the investing material for a few minutes in 
 water. 
 
 All superfluous metal is removed with suitable instruments, and 
 ;ill surfaces except the palatal face smoothed and polished, first with 
 Scotch stone or fine emery cloth, and finally with chalk used upon 
 a brush wheel. 
 
CAST METAL BASE. 365 
 
 If there are any narrow spaces or interstices, not affecting the 
 integrity of the plate, that are not completely filled at the time of 
 casting, such imperfections, Dr. Kingsley suggests, may be readily 
 and perfectly repaired with amalgam. 
 
 There are other practicable methods by which cast metallic plates 
 may be utilized to advantage, and their application to the needs of 
 the practitioner greatly extended. There are many cases of ab- 
 sorption in which a lower denture constructed entirely of cast 
 metal would be objectionable on account of excessive weight. 
 In such cases, a plate of sufficient thickness to secure the required 
 stability may be cast, and the teeth subsequently attached with 
 rubber or celluloid, as described in connection with swaged plates ; 
 or the base-plate may be cast in the form of the rubber base 
 described in connection with the new mode continuous gum, and 
 faced in the same manner with celluloid — either method, while 
 securing the requisite weight, admitting also of the use of single 
 plain teeth. 
 
 GOLD ALLOY CAST BASE. 
 
 The compound of gold, silver, and tin, in varied proportions, in 
 connection with specific and original methods of casting dental 
 plates, devised and patented by Dr. George F. Reese, of Brooklyn. 
 N. Y., has attracted attention as a possible substitute for the plastic 
 vegetable substances so commonly employed as a base for artificial 
 dentures. 
 
 After premising that the methods in common use for casting 
 alloys were not applicable to one having the molecular properties 
 of Reese's compound, the inventor says he was led, after multi- 
 plied experiments, to adopt the plan of which the following is a 
 description : 
 
 The impression is taken with plaster, to which salt or sulphate 
 of potassa has been added, and the model obtained from this with 
 pure plaster. Upon this the teeth are arranged. For the trial 
 plate, gutta-percha, paraffin, and wax, or modeling compound, may 
 ~be used. When satisfaction in the occlusion is obtained, then the 
 case is returned to the model, and the waxing around the labial 
 and buccal borders of the teeth completed. That portion of the 
 trial plate which covers the palatine surface is now removed, so 
 that the pins of the teeth will be nearly exposed, allowing the wax 
 
366 MECHANICAL DENTISTRY. 
 
 which is under the gum to remain. That the plate, after casting,. 
 shall not be too cumbrous, the trial plate, which has been removed, 
 must be substituted with two thicknesses of French flower wax, 
 cut carefully to the model, and pressed down closely with the 
 finger in such a manner that no wrinkles will appear to mar the 
 beauty of the work. 
 
 Fig. 158 represents a case thus prepared. The dotted lines show 
 the borders of the thin wax. B, A, and C, represent nipples of 
 solid wax, fixed to the posterior border and to the tuberosities, A 
 and C being the places of exit for the molten metal into the waste 
 
 Fig. 158. 
 
 pockets, and B the place of entrance of the metal from the pouring- 
 gain. 
 
 The case is now transferred to the small brass flask, r, Fig. 159,. 
 the sections of which have been welj oiled upon the inner surface,, 
 to facilitate their removal from the investment. Either section is 
 then placed upon a plate of glass and plaster poured into it until 
 half filled. The model, as prepared, after being well saturated 
 with water, is imbedded in this single section, allowing the teeth 
 and gums to remain uncovered. Set on the counterpart of the- 
 flask and add more plaster along the posterior border until the 
 nipples are reached or slightly covered. After this has set, the 
 upper section may be removed and the surface of the plaster 
 covered with a thin varnish or soapy water. Return the section. 
 
CAST METAL BASE. 
 
 367 
 
 and complete the investment. Fig. 159 shows the case thus made 
 ready. 
 
 After a proper time place the flask in hot water, that it may be 
 separated without injury. When separated, wash away all the wax, 
 and, by means of gentle tapping, remove the flask rings from the 
 investment and set them aside. The depressions formed by the 
 nipples may now be extended through the plaster to the external 
 edge; or, if the circumstances of the case make this impossible, 
 the channels may be made at the line of division between the two 
 
 Fig. 159. 
 
 Case Ready for the Completion of Investment. 
 
 sections, as shown by the dotted lines in Figs. 160 and 161. 
 Externally, the channels, D, E, F, Fig. 161, should be neatly 
 countersunk and varnished with shellac to receive the pockets. 
 The latter are made of the French wax by warming and wrapping 
 the same around a cone-shaped stick and the base and apex of the 
 cone neatly trimmed of all inequalities. These pockets should be 
 about i J / 2 inches long, and about ]/ 2 of an inch in diameter at the 
 base, and % of an inch at the apex. The pouring-gain is made 
 in the same manner, but should be smaller in diameter at the base 
 
3 68 
 
 MECHANICAL DENTISTRY. 
 
 and about two inches long. After removing these wax covers from 
 the molding sticks, the larger ends of each should receive a thin 
 wax cover secured to its place, and made water-tight by flowing 
 hot wax along the line of junction, after the manner of soldering. 
 Trim the covers, then place the smallest ends of the large cones 
 
 Fig. 160. 
 
 in the countersunk channels at the tuberosities and the small cone 
 in the middle hole, and secure them with melted wax. Fig. 160, 
 d' , e', f , shows the pockets thus attached. 
 
 Should the channels have been made through the solid plaster 
 of the lower section, as in Fig. 160, then the upper section, Fig. 
 161, need not be joined to it until after the pockets are secured to 
 
CAST METAL BASE. 
 
 369 
 
 their places. Should, however, the channels have been made upon 
 the line of division, then the sections must be joined before the 
 pockets can be attached. 
 
 The case is now ready for a second investment, which is done in 
 a flask sufficiently large to embrace the case as it now presents. 
 Fig. 162 represents the construction of the large flask. One section 
 of the same is placed upon glass and about half filled with plaster. 
 The case, having been well soaked with cold water, is laid carefully 
 upon the plaster, allowing the long cone to rest in the notch at the 
 
 Fig. 161. 
 
 Upper or Counter Section corresponding to Fig. 160. 
 for entrance and exit of metal. 
 
 D, E, F, channels 
 
 heel of the flask, and the waste pockets to become imbedded in the 
 plaster. Immediately put the other section of the flask in place 
 and complete the investment by filling with plaster the uppermost 
 section to fullness. Of course, there will be no division of the sec- 
 tions, as was the case in the former flasking. After solidification, 
 the pouring-gain must be neatly trimmed and countersunk, and 
 great care must be exercised that no dirt be allowed to enter the 
 channel. 
 
 The wax, which is imbedded in the plaster, and which forms 
 the waste pockets, will be entirely absorbed, and no trace of it will 
 be seen upon opening the flask. 
 24 
 
370 
 
 MECHANICAL DENTISTRY. 
 Fig. 162. 
 
 Fig. 163. 
 
 — S 
 
CAST METAL BASE. 37 1 
 
 All is now ready for drying. This is done in an oven specially 
 prepared for the purpose, but it may be accomplished in any way 
 to be chosen by the manipulator. An ice-cold mouth mirror 
 placed over the opening of the pouring-gain will detect the 
 slightest moisture which may remain, and until this is entirely 
 dispelled the casting should not be attempted. 
 
 There are several grades of the gold alloy, as compounded by 
 Dr. Reese, to melt which require a heat registering from 6oo° to 
 700 F., but a higher temperature than this must be attained before 
 pouring, in order to secure a satisfactory flow. At 900 rapid oxida- 
 tion takes place. This, of course, should be avoided. The alloy 
 may be melted in an ordinary iron ladle or crucible, over a gas or 
 other flame, and should be poured while the mold is hot. 
 
 Fig. 164. 
 
 After the lapse of an hour or two, or until the cast is sufficiently 
 cooled to insure the integrity of the teeth, it may be placed in warm 
 water, when the investment can be easily removed. 
 
 Fig. 163 represents the cast after removal. The surplus metal 
 may be separated along the dotted line S, with a ribbon saw, after 
 which the denture is ready for the pumice wheel and brush. Fig. 
 164 represents the finished case. 
 
 Repairing. — The process of repairing broken plates is, in prin- 
 ciple, the same as above. A flask, specially constructed by the 
 inventor, is used for this purpose, whereby a single investment 
 suffices. Suppose, for example, a plate is broken, from the labial to 
 the posterior border, along the median line; the broken edges are 
 scraped clean, and a separation made of about ^ of an inch. The 
 parts are then adjusted upon the model, and the space between the 
 
37^ 
 
 MECHANICAL DENTISTRY. 
 
 approximate edges filled with wax. At each extremity of the 
 fissure a pencil of wax, ]/§ of an inch in diameter, and l}4 inches 
 long-, is securely attached, perpendicularly, to the palatal surface, 
 and the whole surrounded with plaster to the depth of one inch. 
 Thus will be constituted two sections, which are separated, and the 
 wax washed out. The external ends of the channels, formed by 
 the pencils, are then countersunk, and into each is inserted a wax 
 cone, the one forming a pouring-gain and the other a waste 
 pocket. The latter should be entirely covered by the plaster. 
 The whole is now invested in the repair flask, and subsequently 
 submitted to the process of drying. 
 
 Dr. W. S. Elliott, of New York, has taken advantage of the 
 method above described to overcome the difficulties attending the 
 construction of continuous-gum work. 
 
 To maintain a perfect adaptation of a swaged plate seems 
 almost impossible, in consequence of the springing of the plate 
 in the furnace. To avoid this difficulty, the following plan is 
 suggested: The plaster model is first covered with two thick- 
 nesses of French flower wax, carefully adjusted. From this a 
 metallic die and counter-die are made, and a very thin (No. 32) 
 platina plate is swaged to fit the waxed model. The labial border 
 need not be returned, as in ordinary cases. Upon this the teeth 
 are arranged, and the case is transferred to the furnace for biscuiting 
 and enameling. After proper annealing, it is replaced upon the 
 model and waxed up, on the labial and buccal borders, over the 
 edge of the plate, then flashed, the wax removed, and the metal 
 cast upon it in the manner heretofore described. 
 
 Danger of checking the enamel is associated with the process ; 
 but success has attended the effort, and it is hoped that further 
 experiments will insure perfect and uniform results. 
 
CHAPTER XXVII. 
 
 DEFECTS OF THE PALATAL ORGANS AND THEIR TREATMENT 
 BY ARTIFICIAL MEANS. 
 
 Palatine Defects. — Defects of the palatine organs may be divided 
 into two classes, viz., accidental and congenital. The first includes 
 all loss of substance in either hard or soft palate by disease or other- 
 wise. Such defects are not uniform in locality or extent, being 
 sometimes but a simple perforation of the palate, and at others in- 
 volving the destruction of the entire soft palate, a considerable por- 
 tion of the hard palate, the vomer and turbinated bones, and the loss 
 of the teeth. 
 
 The second class includes all malformations, from the simple 
 division of the uvula to an opening through the velum, palatine 
 and maxillary bones, and a division of the upper lip, thus uniting 
 throughout their entire extent the nasal passages with the oral 
 cavity. 
 
 These malformations are quite similar in character, but not uni- 
 form in extent. They may be said to begin with the uvula, and in 
 the uvula and velum always occupy the median line; but as the 
 defect progresses anteriorly, it may deflect to one side or the other 
 of the vomer, and follow the nasal passage through the lips, leav- 
 ing the vomer articulated with the palate bone on one side; while 
 in other cases the deformity seems to follow the median line, and 
 thus involves both nasal passages and terminates in a double fissure 
 of the lip. 
 
 In both cases, accidental and congenital, the faculty of distinct 
 articulate speech is seriously impaired by defects of any extent. 
 In ordinary cases of congenital deformity, deglutition is not 
 materially interfered with. The patient, having never known 
 any other method of swallowing, is not conscious of any diffi- 
 culty. Accidental lesions, however, coming generally in adult life, 
 produce, in this respect, very great inconvenience. The remedy 
 for these evils must be the closing of the abnormal passage by 
 
 373 
 
374 
 
 MECHANICAL DENTISTRY. 
 
 some means which will restore the functions to the deformed 
 organs. In perforations of the hard palate, unless of extraordinary 
 extent, the method is very simple. In the loss of the soft palate 
 by disease the remedy is more difficult, and in extensive congenital 
 deformity still more complicated appliances will be required. 
 
 As we have classified the defects, we shall also classify the ap- 
 pliances used for their remedy. 
 
 The term obturator will be used for all appliances intended to 
 stop a passage, or all openings in the hard or soft palate which 
 have a complete boundary. Appliances made to supply the loss of 
 the posterior soft palate, whether accidental or congenital, will be 
 called artificial vela, or palates. 
 
 Obturators. — Any unnatural opening from the oral cavity into 
 the nasal cavity, which will permit the free passage of the breath, 
 will impair articulation. Any appliance which will close such pas- 
 sage, and can be worn without inconvenience, will restore articula- 
 tion.* Obturators were formerly made of metallic plate, gold or 
 silver being most commonly employed, and many very ingenious 
 pieces of mechanism were the result of such efforts, but latterly 
 vulcanized rubber has almost entirely superseded the use of metals. 
 Vulcanite has been found preferable to metals, being much lighter 
 and much more easily formed and adapted, particularly when of 
 peculiar shape. 
 
 The steps to be taken in the formation of an obturator are not 
 unlike those used in making a base for artificial teeth. It is essen- 
 tial that an accurate model be obtained of the opening, the adjacent 
 palatal surface, and the teeth, if any remain in the jaw. For this 
 purpose an impression in plaster is the only reliable means for such 
 an end. Care must be used that a surplus of plaster is not forced 
 through the opening, thus preventing the withdrawal of the im- 
 pression by an accumulated and hardened mass larger than the 
 opening through which it passed. To avoid this, beginners or 
 timid operators had better take an impression in the usual manner 
 with wax ; if this is forced through, it can be easily removed, 
 
 * The student will bear in mind that no cognizance is here taken of openings 
 similar to those described in cases of congenital fissure, where the surgeon has 
 united the soft palate, and left an opening through the hard palate, to be covered 
 by an obturator. In such cases, neither the surgeon's operation nor the obturator 
 will prove of much advantage. 
 
ARTIFICIAL TREATMENT OF PALATAL DEFECTS. 
 
 375 
 
 without injury to the patient. From this wax impression make a 
 plaster model, and upon this form an impression-cup of sheet 
 gutta-percha, with a stick, piece of wire, strip of metal, or any other 
 convenient thing for a handle. This extemporized impression-cup 
 must not impinge upon the borders of the opening, neither should 
 it enter to any extent. With a uniform film of soft plaster, of from 
 jL to x /% of an inch in thickness, laid over this cup, a correct impres- 
 sion can be made without any surplus to give anxiety. Upon a 
 correct plaster cast, taken from such an impression, make a model 
 of the obturator out of gutta-percha, thin sheets of modeling com- 
 pound, or other plastic substance; the subsequent steps being in 
 principle the same as in making any other piece of vulcanite. It 
 is desirable that it should enter the perforation and restore as far 
 as possible the lost portion of the palate, but it must not protrude 
 into or in any way obstruct the nasal passage. 
 
 The entire freedom of the nasal passage is essential to the purity 
 of articulation. 
 
 That portion of the obturator which occupies the oral cavity 
 should be made as delicate as possible, consistent with its strength 
 and durability. 
 
 A clumsy contrivance will interfere with articulation almost as 
 much as it is improved by stopping the opening; therefore, if the 
 obturator could be confined entirely to the opening, like a cork in 
 a bottle, it would be all the more desirable, but as it cannot, resort 
 must be made to clasping to the contiguous teeth, if there are any, 
 and if not, the obturator must spread out over the whole jaw, and 
 receive its support in the same manner as would a set of artificial 
 teeth. In fact, this is just what it would become in such a case, 
 viz., an upper set of teeth bridging over and filling up an opening 
 in the palate, thus combining an obturator with a set of teeth. 
 
 Kingsley's Obturators and Methods of Procedure. — The 
 following descriptions, with accompanying illustrations, were con- 
 tributed to this work by Professor Norman W. Kingsley, who 
 excels in the practice of this difficult and important specialty of the 
 dental art. 
 
 Fig. 165 represents an obturator without teeth and without 
 clasps, for a perforation of the hard palate, being sustained in situ 
 by impinging upon the natural teeth with which it comes in con- 
 tact. Accuracy of adaptation and delicacy in form are all that is 
 
3/6 
 
 MECHANICAL DENTISTRY. 
 
 essential in such cases, and the restoration of the speech will follow 
 immediately. 
 
 Fig. 1 66 represents a more complicated obturator, adapted to an 
 opening- in the soft palate. 
 
 The necessity for a variation in the plan will be found in the 
 anatomical fact of the constant muscular action of the soft palate, 
 which would not permit, without irritation, the presence of an im- 
 movable fixture. 
 
 This is contrived, therefore, with a joint that will permit the part 
 attached to the teeth to remain stationary, while the obturator 
 proper is carried up or down as moved by the muscles. The 
 joint, A, should occupy the position of the junction of the hard 
 and soft palates. The joint and principal part of the appliance is 
 
 Fig. 166. 
 
 made of gold, the obturator of vulcanite. The projection, B, lies 
 like a flange upon the superior surface of the palate and sustains 
 it; otherwise the mobility of the joint would allow it to drop out 
 of the opening. This flange is better seen in the side view marked 
 C. It is readily placed in position by entering the obturator first, 
 and carrying the clasps to the teeth subsequently. 
 
 Figs. 165 and 166 will illustrate the essential principles involved 
 in all obturators. The ingenuity of the dentist will often be taxed 
 in their application, as the cases requiring such appliances all vary 
 in form and magnitude. 
 
 Artificial Palates. — Before proceeding to a description of 
 appliances, a brief reference to the anatomical relations and func- 
 tions of the palate will be necessary. The palate exercises quite 
 
ARTIFICIAL TREATMENT OF PALATAL DEFECTS. 
 
 377 
 
 as important an office in the articulation of the voice as does the 
 tongue or lips. Being a muscular and movable partition to sep- 
 arate the nasal and oral cavities, one edge is attached to the border 
 of the hard palate, while the other vibrates between the pharynx 
 and the tongue. The voice, therefore, as it issues from the larynx, 
 is directed by the palate entirely into the mouth, or through the nose, 
 or permitted to pass both ways. 
 
 A very slight deviation in this organ from its natural form will 
 make the voice give a different sound. So will, also, the presence 
 of anything that clogs the natural passages, either oral or nasal. 
 
 Place any obstruction in the nasal passages, paralyze the soft 
 
 Fig. 167. 
 
 palate, or let it be deficient in size, and the power of distinct articu- 
 lation is wanting. 
 
 The evidence of this statement is frequently found after the 
 surgeon has successfully performed the operation of staphylor- 
 rhaphy in cases of congenital fissure. 
 
 In such instances, with rare exceptions, the newly formed palate 
 is so deficient in length, and so tense, as to be deprived of its func- 
 tion. It cannot be raised so as to meet the pharynx and shut off 
 the nasal passage, but hangs like an immovable septum to divide the 
 column of sound. 
 
 Fig. 167 represents a defective palate belonging to the first class, 
 the uvula and a portion of the soft palate contiguous being de- 
 
3/8 MECHANICAL DENTISTRY. 
 
 stroyed by disease. In such a case an obturator would be useless ; 
 the constant activity and the surrounding parts would not tolerate 
 it. The material used for a substitute must be soft, flexible, and 
 elastic, and the elastic vulcanite is admirably adapted to this pur- 
 pose. 
 
 By observing the cut (Fig. 167) it will be seen that a portion of 
 the soft palate along the median line remains, and consequently 
 there will be considerable muscular movement which must be 
 provided for, and which may be taken advantage of. It is desir- 
 able to make this movement available in using an artificial palate, 
 as thereby more delicate sounds are produced than otherwise. 
 
 This case presents some extraordinary difficulties in the fact 
 that all the teeth of the upper jaw have been extracted, and it was 
 
 Fig. 168. 
 
 necessary, therefore, to adopt a plate which should not only sustain 
 teeth for mastication, but bear the additional responsibility of 
 supporting the artificial palate. In the choice of material best 
 adapted for the base for the teeth in such instances, it is preferable 
 to adopt that which will prove the most durable. There are too 
 many interests involved to risk the adoption of anything but the 
 best. In the case under description, the patient desired duplicates, 
 and two sets of teeth were made, one on gold and the other on 
 platina, with continuous gum. 
 
 The plates were made like other sets of teeth, with the excep- 
 tion of a groove located on the median line at the posterior edge 
 to receive the attachment for the palate (marked C, in Fig. 168). 
 
 Fig. 168 will indicate the set of teeth with palate attached. The 
 wings marked letters A and B are made of soft rubber; the frame 
 
ARTIFICIAL TREATMENT OF PALATAL DEFECTS. 379 
 
 to support them is made of gold, with a joint to provide for the 
 perpendicular motion of the natural palate, as in the case of the 
 obturator represented in Fig. 166. 
 
 When the artificial palate is in use, the joint and frame imme- 
 diately contiguous lie close to the roof of the mouth ; the rubber 
 wing, letter A, bridges across the opening on the inferior surface, or 
 side next the tongue ; the wing, letter B, bridges across the opening 
 on the superior or nasal surface, and is also prolonged backward until 
 it nearly touches the muscles of the pharynx when they are in repose. 
 
 Both these wings reach beyond the boundary of the opening 
 and rest on the surface of the soft palate for a distance of from y% 
 to 54 of an mcn > thus embracing the entire free edge of the soft 
 palate. This last provision enables the natural palate to carry the 
 artificial palate up or down, as articulation may require. 
 
 When the organs of speech are in repose, there is an opening 
 behind the palate sufficient for respiration through the nares. 
 When these organs are in action, a slight elevation of the palate, 
 •or a contraction of the pharynx, will entirely close the nasal pas- 
 sage and direct all the voice through the mouth. The palate thus 
 becomes a valve to open or close the nares, and to be tolerated 
 must be made with thin and delicate edges which will yield upon 
 pressure. An instrument thus made will restore, as far as is pos- 
 sible by mechanism, the functions of the natural organ. 
 
 In the case under description the patient was a lady; the defect 
 had existed for seven years before remedy. Articulation was very 
 defective; distinct and perfect articulation followed within one 
 month. 
 
 Fig. 169 represents the artificial palate separated into its con- 
 stituent parts. The frame is bent at the joint, in the engraving, to 
 show a stop, marked D, which prevents the appliance from drop- 
 ping out of position. Letter C shows the tongue, which enters the 
 groove in the plate of teeth and connects them. Letters A and B 
 are the rubber flaps, which are secured to the frame by the hooks, as 
 seen in the engraving. 
 
 The process for making the rubber wings will be found described 
 on page 385. 
 
 Fig. 170 shows a more extensive palatine defect of the first class. 
 In this case the entire soft palate is gone, together with a small 
 portion of the hard palate at the median line. 
 
3 8o 
 
 MECHANICAL DENTISTRY. 
 
 Although this defect is greater in extent, the means for its remedy 
 are more simple. The muscles of the palate are entirely gone, and 
 consequently no perpendicular movement need be provided for. 
 
 Fig. 169. 
 
 The appliance in this case will resemble an elastic obturator 
 more than the valve-like palate of the preceding one. The 
 principle here adopted will be substantially that recommended 
 by Mr. Sercombe, of London, and consists of a plate with a set 
 
 Fig. 170. 
 
 of teeth in the usual form, and attached to its posterior edge an 
 apron of soft rubber, which shall bridge the opening on its in- 
 ferior surface, extending nearly to the pharynx. Fig. 171 repre- 
 
ARTIFICIAL TREATMENT OF PALATAL DEFECTS. 
 
 33l 
 
 sents the set of teeth with the palate attached. In Mr. Sercombe's 
 appliance this apron was made of the common sheet rubber in 
 the market, prepared for other uses, and is objectionable for two 
 reasons : First, a want of purity in the materials of which it is com- 
 pounded, in many instances substances being used in its manufacture 
 which would prove deleterious to the health of the patient; and, 
 second, its uniformity of thickness. It is far preferable, therefore. 
 to make a mold which will produce a palate of pure and harmless 
 materials, and which shall be of sufficient thickness in the central part, 
 and at its anterior edge, to give it stability, and shall have a thin 
 and delicate boundary wherever it comes in contact with movable 
 
 Fig. 171. 
 
 tissue. Such a palate may be made in a mold by substantially 
 the same process as hereinafter described. (See page 386.) It 
 may be secured to the plate by a variety of simple means. One, 
 which will give as little trouble to the patient as any other, 
 is to make a series of small holes along the edge of the plate 
 and stitch it on with silk; or fine platina, gold, or silver wire may 
 be used. 
 
 It is desirable to have the plate and palate present a uniform 
 surface on the lingual side. In fitting the plate, therefore, it mav 
 be raised along the posterior edge from Jg to -^ of an inch, 
 according to the thickness of palate desired. The rubber will thus 
 
382 MECHANICAL DENTISTRY. 
 
 be placed on the palatine surface of the plate and present uniformity 
 on the lingual surface. 
 
 A little thought will show that in this case the patient must edu- 
 cate the muscles of the pharynx alone to do the work of shutting off 
 the nares, which in the former case was performed by them in con- 
 junction with the muscles of the palate. Perfection of articulation 
 will therefore depend upon the success of the patient in this new 
 use of these muscles. 
 
 In cases of accidental lesions of the palate, such as are under 
 consideration, this education of the muscles to a new work will 
 not be difficult. The patient at some former time has had the 
 power of distinct articulation; his ear has recognized in his own 
 voice the contrast between his present and former condition ; the 
 ear will therefore direct and criticize the practice until the result 
 is attained. 
 
 In the case illustrated by Figs. 170 and 171, the defect had ex- 
 isted for twenty-eight years, the patient at the time of the intro- 
 duction of the artificial palate being nearly fifty years of age. The 
 effect upon the speech was instantaneous. Articulation was im- 
 mediately nearly as distinct as in youth, and this remarkable dis- 
 tinctness can only be accounted for upon the assumption that the 
 pharyngeal muscles had undergone a thorough training in the vain 
 effort to articulate without any palate.* 
 
 The two cases chosen to illustrate the application of artificial 
 palates in accidental lesion have required, as will have been per- 
 ceived, entire upper sets of artificial teeth in connection with the 
 palates. This selection was purposely made, because the difficul- 
 ties to be overcome are much greater. In cases where there are 
 natural teeth remaining in the upper jaw, the palate and its connec- 
 tion with a plate would be substantially the same, and the plate 
 might easily be secured to the teeth by clasps, in the same manner 
 as a partial denture. 
 
 Artificial Palates for Congenital Fissure. — Congenital fissure 
 of the palate presents far greater difficulties to be overcome than 
 cases of accidental lesion. The opening is commonly more exten- 
 sive, the appliance more complicated, and the result more prob- 
 
 * An account of this case appears in the Argus, of Bainbridge, Georgia, August 
 1, 1868, written by the patient himself, the editor of that paper. 
 
ARTIFICIAL TREATMENT OF PALATAL DEFECTS. 383 
 
 lematic. Nevertheless, appliances have been made in a large number 
 of cases which have enabled the wearer to articulate with entire 
 distinctness, so much so as not in the least to betray the defect. 
 The first efforts in this direction were of the character of obturators, 
 simply plugs to close the posterior nares, and the results were far 
 from satisfactory. It was not until it was recognized that the two 
 classes of cases, accidental and congenital, were entirely distinct that 
 much progress was made. 
 
 Nearly every case of accidental lesion can be treated with an 
 obturator with considerable success; very rarely will an obturator 
 be of any benefit in congenital fissure, even if the congenital and 
 accidental case present substantially the same form of opening. 
 For this reason so much mystification has been thrown around 
 these appliances within a few years past. The character of the 
 different classes has been confounded, and an instrument admirably 
 adapted to one class has had claimed for it an equal application to 
 the other class. Let it be understood, therefore, as a rule to which 
 there will be but few exceptions, that congenital fissure of the soft 
 palate requires for its successful remedy a soft, elastic, and mov- 
 able appliance, and that when the most skilfully made and adapted 
 instrument is worn, articulation must be learned, like any other 
 accomplishment. Various inventions have been made for this 
 purpose within the last twenty-five years, from the most compli- 
 cated one of Mr. Stearns, described in the first edition of this work, 
 to the extreme of simplicity of bridging the gap with a simple flap 
 of rubber. The Stearns instrument, with all its complexity, em- 
 bodied the only true principle, viz., the rendering available the 
 muscles of the natural palate to control the movements of the arti- 
 ficial palate. 
 
 The essential requisites of an artificial palate will be to restore, 
 as far as possible, the natural form to the defective organs with such 
 material as shall restore their functions. Muscular power, certainly, 
 cannot be given to a piece of mechanism, but the material and form 
 may be such that it will yield to and be under the control of the 
 muscles surrounding it, and thus measurably bestow upon it the 
 function of the organ which it represents. 
 
 Fig. 161 represents a model of a fissured palate, complicated 
 with harelip on the left side of the mesial line. There is a divi- 
 sion, also, of the maxilla and the alveolar process, the sides being 
 
3§4 
 
 MECHANICAL DENTISTRY. 
 
 covered with mucous membrane, which come in contact with each 
 other but are not united. The left lateral incisor and left canine 
 tooth are not developed. 
 
 Fig. 173 represents the artificial velum, as viewed from its supe- 
 
 Fig. 172. 
 
 rior surface, together with the attachment and two artificial teeth 
 to fill the vacancy. 
 
 The lettered portion of this appliance is made of soft vulcanized 
 
 Fig. 173. 
 
 rubber; its attachment to the teeth of hard vulcanized rubber, to 
 which the velum is connected by a stout gold pin, firmly imbedded 
 at one end in the hard rubber plate. The other end has a head, 
 marked C, which, being considerably larger than the pin, and also 
 
ARTIFICIAL TREATMENT OF PALATAL DEFECTS. 
 
 385 
 
 than the corresponding hole in the velum, is forced through — the 
 elasticity of the velum permitting — and the two are securely con- 
 nected. 
 
 The process, B, laps over the superior surface of the maxilla 
 (the floor of the naris), and effectually prevents all inclination to 
 droop. 
 
 The wings, A A, reach across the pharynx, at the base of the 
 chamber of the pharynx, behind the remnant of the natural velum. 
 
 The wings, D D, rest upon the opposite or anterior surface of 
 the soft palate. 
 
 Fig. 174. 
 
 Fig. 174 represents a model, the same as Fig. 172, with the ap- 
 pliance, Fig. 173, in situ. 
 
 The wing, D D, in Fig. 173, and the posterior end of the arti- 
 ficial velum only in this cut being visible. 
 
 Method of Making an Artificial Palate. — The success of these 
 appliances depends very much upon the accuracy of the model 
 obtained to work by. 
 
 It is essential that the entire border of the fissure, from the apex 
 to the uvula, should be perfectly represented in the model, as the 
 parts are when in repose. It is also necessary that the model show 
 definitely the form of the cavity above, and on either side of the 
 opening through the hard palate, being that part of the cavity which 
 
 25 
 
386 MECHANICAL DENTISTRY. 
 
 is hidden from the eye. It is desirable, also, that the posterior sur- 
 face of the remains of the soft palate be shown, but this is not 
 essential ; but it is especially important that the anterior or under 
 surface be represented with relaxed muscles and in perfect repose. 
 The impression for such a model must be taken in plaster; it is 
 the only material now in use adapted to the purpose. An ordinary 
 Britannia impression-cup may be used, selecting one in size and 
 form corresponding to the general contour of the jaw. This cup 
 will be found too short at the posterior edge to receive the soft 
 palate, but it may be extended by the addition of a piece of sheet 
 gutta-percha, which must be molded into such form as not to im- 
 pinge upon the soft palate, but which will reach under and beyond 
 the uvula, and thus protect the throat from the droppings of plaster. 
 Before using the plaster the posterior edge of the gutta-percha 
 extension may be softened by heat and introduced into the mouth ; 
 contact with the soft palate will cause it to yield, so that there is 
 no danger of its forcing away the soft tissues when the plaster is 
 used. With the precaution not to use too much plaster, the first 
 effort will be to get only the lingual surface. After trial, if the 
 impression show definitely the entire border of the fissure, and the 
 soft palate has not been pushed up by contact with the cup, nor 
 pulled up by the spasmodic action of the levator muscles, it is all 
 that is thus far desired. If, however, the soft parts have been dis- 
 turbed (which on close comparison a little experience will decide), 
 it is better to cast a model into the impression, and upon this 
 model extemporize an impression-cup. This temporary cup will 
 have the advantage of the former, insomuch that it will require 
 but a film of plaster to accomplish the result, thus lessening the 
 danger of disturbing the soft tissues. After the removal, if it is 
 seen that any surplus has projected through the fissure and lapped 
 out to the floor of the nares, it may be pared off. 
 
 The next step will be to obtain, in conjunction with this impres- 
 sion of the under surface, which we will call the palatal impression, 
 an impression of the upper or nasal surface of the hard palate. 
 
 This can be done by filling the cavity above the roof of the 
 mouth with soft plaster down to the border of the fissure, and 
 while yet very soft carrying immediately the palatal impression 
 against it, and retaining it in that position until the plaster is hard, 
 which can easily be ascertained by the remains in the vessel from 
 
ARTIFICIAL TREATMENT OF PALATAL DEFECTS. 387 
 
 which it was taken. With the precaution to paint the surface of 
 the palatal impression with a solution of soap, to prevent the two 
 masses from adhering when brought in contact, there will be no 
 difficulty in removing it from the mouth, leaving the mass which 
 forms the nasal portion in situ. With a suitable pair of tweezers 
 this mass is easily carried backward and withdrawn from the 
 mouth, and the irregular surface of contact indicates its relation to 
 its fellow when brought together. 
 
 The method of obtaining the model of the jaw from the im- 
 pression does not require any particular description. The process 
 is similar to the making of a cast in any other mouth impression. 
 
 The model represented in Fig. 172 shows a convenient form for 
 such a cast. 
 
 When the nasal portion of the impression does not indicate the 
 superior surface of the soft palate, the part may be represented in 
 the cast by carving. It is not essential to the success of the instru- 
 ment to be made that the posterior surface of the soft palate should 
 be represented with the same accuracy that is required of the 
 inferior surface, or of both surfaces of the hard palate. By the aid 
 of a small mirror and a blunt probe, the thickness of the velum 
 and the depth behind the fissure can be ascertained, and the model 
 carved accordingly. 
 
 The portion of the artificial palate coming in contact with it is 
 so elastic that it easily adapts itself to a slight inequality, rendering 
 absolute accuracy less important. 
 
 The next step will be the formation of a model or pattern of the 
 palate. Sheet gutta-percha is preferable for this purpose, although 
 wax, or many other plastic substances, might answer. 
 
 The form which should be given it is better indicated by the 
 drawing, Figs. 173 and 177, than a written description would give. 
 The complicated provision for the contraction of the fissure found 
 in older forms of instruments is entirely superseded in these by 
 making the appliance somewhat in the form of two leaves, one to lie 
 on the inferior and the other upon the superior surface of the palate, 
 and joined together along the median line. When the fissure con- 
 tracts, the halves of the divided uvula slide toward each other be- 
 tween these two leaves. The posterior portion, marked A in Fig. 
 173, is made very thin and delicate on all its edges, as it occupies 
 
3 88 MECHANICAL DENTISTRY. 
 
 the chamber of the pharynx and is subject to constant muscular 
 movement. 
 
 The sides are rolled slightly upward, while the posterior end is 
 curved downward. The inferior portion, marked D D, in Fig. 173, 
 should reach only to the base of the uvula, and bridge directly 
 across the chasm at this point, and no effort to imitate the uvula 
 should be made. The extreme posterior end should not reach the 
 posterior wall of the pharynx when all the muscles are relaxed by 
 54 of an inch, although subsequent use must determine whether 
 this space be increased or diminished, thus leaving abundant room 
 for respiration and the passage of nasal sounds. In cases where it 
 is desirable to make the instrument independent of the teeth, so 
 far as possible, in its support, the anterior part, which occupies the 
 apex of the fissure in the hard palate may lap over on to the floor 
 of one or both nares. Such a projection is seen in Fig. 173, 
 marked B, and a like process is seen in Fig. 177, but not lettered. 
 Were it not for this process in this case, the palate would drop out 
 of the fissure into the mouth, the single clasp at the extreme an- 
 terior end not being sufficient to keep the whole appliance in place 
 throughout its entire length. Caution must be exercised that this 
 projection entering the nares be not too large,, or it will obstruct 
 the passage and give a disagreeable nasal tone to the voice. 
 
 All these described peculiarities must be provided for in the 
 gutta-percha model, which, after having been carefully formed to 
 the cast, may be tried in the mouth to ascertain its length or 
 necessary variations. When its ultimate form has been decided 
 upon, provision must be made to duplicate it in soft rubber. 
 
 A parallel process, and one which will be a familiar illustration, 
 is used when a set of teeth is made on vulcanite base. A model or 
 pattern form is made of gutta-percha, bearing the teeth, and in all 
 its prominent characteristics is shaped as the completed denture 
 is desired, the rubber duplicate being vulcanized in a plaster mold. 
 In like manner the rubber duplicate of the palate, as before de- 
 scribed, may be made in a plaster mold. 
 
 If plaster is used it must be worked with much care, so that the 
 surface shall be free from air-bubbles, or the rubber palate will be 
 covered with excrescences that cannot be readily removed. By 
 covering the surface of the mold with collodion or liquid silex, 
 
ARTIFICIAL TREATMENT OF PALATAL DEFECTS. 
 
 389 
 
 it will be much improved. But ordinarily plaster molds will be 
 found too troublesome for general use. They may be put to a 
 most excellent use, however, by using one to make a duplicate of 
 the gutta-percha in hard rubber. 
 
 This is not necessary with those who have had much experience, 
 but with beginners it will be difficult to work up the gutta-percha 
 as nicely as may be desired ; a duplicate of vulcanite will enable 
 the operator to make a more artistic model of the palate, and one 
 which can be handled with greater freedom. 
 
 As in the course of a lifetime a considerable number of elastic 
 palates will be required, the mold which produces them should be 
 made of some durable material. The type-metal of commerce is 
 admirably adapted to this use. The most complete mold is one- 
 made of four pieces, which will produce a palate of one continuous, 
 
 Fig. 175. 
 
 piece. Such a mold requires very nice mechanical skill in fitting 
 all the parts accurately, and unless the operator has had experience 
 in such a direction, it is better to simplify the matter. By making 
 the palate in two pieces, to be joined after vulcanizing, the mold 
 may be made in two pieces, and with very little trouble. 
 
 Fig. 175 shows a palate divided. 
 
 Fig. 176 shows the mold or flask in which it is vulcanized. These 
 flasks were made expressly for this purpose, but they are not so 
 unlike the flasks in common use in dentists' laboratories that the 
 latter will not answer. The common flask is simply unnecessarily 
 thick or deep. 
 
 The mold is really produced in the following manner: Imbed 
 the two pieces of the palate in plaster, in one-half of the flask; 
 when the plaster is set and trimmed into form, duplicate it in type- 
 metal by removing the palate, varnishing the surface, molding in 
 
39o 
 
 MECHANICAL DENTISTRY. 
 
 sand, and casting. In making the sand mold, take a ring of sheet- 
 iron of the same diameter as the flask and three or four inches 
 high; slip it over the flask and pack full of sand. Separate them, 
 remove the plaster, return the flask to the sand mold, and fill with 
 the melted metal through a hole made in the side or bottom of the 
 
 Fig. 176. 
 
 flask. With one-half thus made, substantially the same process 
 will produce the counterpart. 
 
 Fig. 177 shows the palate complete, with its attachment to the 
 teeth. The palate is secured to the plate by a pin of gold passing 
 through a hole in the palate of the same size; the head on the pin, 
 
 Fig. 177. 
 
 being larger than the hole, is forced through, and thus the two 
 halves of the palate are bound together and joined to the plate. 
 
 Fig. 178 shows a mold in four pieces. The blocks, C C, are 
 accurately adapted to the body of the mold, marked A, and are 
 prevented from coming improperly in contact with each other by 
 the flanges, D D, which overlap the rest upon the sides of the 
 
ARTIFICIAL TREATMENT OF PALATAL DEFECTS. 
 
 391 
 
 main piece. B shows the top of the mold, and the groove, E, 
 provides for the surplus rubber in packing - . 
 
 Such a mold makes the most perfect appliance that can be pro- 
 duced. The palate is one homogeneous and inseparable piece. 
 
 Fig. 178. 
 
 The cut will sufficiently indicate the forms of the several parts. 
 Each of these pieces is first made in plaster of exactly the form of 
 which the type-metal is desired. They are then molded in sand 
 and the type-metal cast as in making an ordinary die for swaging. 
 
 Fig. 179. 
 
 When in use, a clamp similar to Fig. 179 is placed around the mold 
 to keep the several parts firm in their position. 
 
 The packing of the mold with rubber will be done in the same 
 manner as when hard rubber is used for teeth bases, with which 
 
392 
 
 MECHANICAL DENTISTRY. 
 
 process it is assumed that the operator is familiar. By washing 
 the surface of the mold with a thick solution of soap previous to 
 packing, the palate will be more easily removed after vulcanizing. 
 
 The rubber used for this purpose must be a more elastic com- 
 pound than that used as a base for teeth. The composition used 
 for the elastic fabrics of commerce will answer if made of selected 
 materials. 
 
 Suersen's Obturator. — Dr. Wilhelm Suersen, of Berlin, intro- 
 duced an obturator, the principle of which has seemed to many 
 the best for obtaining correct articulation. In describing it in 
 The American Journal of Dental Science, he says : 
 
 " In order to be able to pronounce all letters distinctly, it is 
 accordingly necessary besides other conditions, which are far away 
 from our present subject, to separate the cavity of the mouth 
 from the cavity of the nose by means of muscular motion. That 
 separation is, under normal conditions, effected, on the one hand, 
 by the velum palati, which strains itself (consequently by the leva- 
 tor and tensor palati) ; but, on the other hand, also, by a muscle 
 which, to my knowledge, has, in connection with these operations, 
 not yet received a sufficient amount of attention — I mean the con- 
 strictor pharyngeus superior. This muscle contracts itself during 
 the utterance of every letter pronounced without a nasal sound, 
 just as the levator palati does. The constrictor muscle contracts 
 the cavum pharyngopalatinum, the pharynx wall bulging out; 
 and it is chiefly on the action of this muscle that I base the system 
 of my artificial palates. 
 
 " These palates, which in all their parts are made of hard caout- 
 chouc, consist of a teeth-plate suitably attached to existing teeth, 
 and which, at the same time, covers the fissure in the hard palate, 
 if such a fissure exists. Where the fissure commences in the velum, 
 that plates terminates in an apophysis broad enough for filling up 
 the defect. This apophysis is at the same time of such thick- 
 ness as to keep up a contact between the high edges forming the 
 sides of the apophysis and the two halves of the velum, even 
 when the levator palati is in activity. To bring about this contact 
 the more surely, the high edges forming the sides do not rise 
 straight, but obliquely, toward the outside. The lower surface of 
 the apophysis, turned toward the mouth, lies on about an equal 
 level with the velum if the latter is raised by the levator palati. But 
 
ARTIFICIAL TREATMENT OF PALATAL DEFECTS. 
 
 393 
 
 when the velum hangs loosely downward, the back part of the 
 artificial palate is lying over it. This back part, accordingly, fills 
 up the cavum pharyngopalatinum, and in such a manner as not 
 to impede the entrance of the air into the cavity of the nose when 
 the constrictor pharyngeus superior is inactive. Thus the patient 
 can without any impediment breathe through the nose. But as 
 soon as the constrictor contracts the cavum pharyngopalati (this 
 happens, as I will repeat for the sake of clearness, in the utterance 
 of every letter with the exception of m and n), the muscle already 
 named reclines against the vertical back surfaces of the obturator. 
 By this operation the air-current is prevented from entering the 
 cavity of the nose, and is compelled to take its way through the 
 
 Fig. 180. 
 
 mouth, and thus the utterance loses its nasal sound. To the ex- 
 istence of those vertical surfaces, and consequently to the thick- 
 ness of that part of my palates which fills up the fissure in the 
 soft palate and the cavum pharyngopalatinum, I must attach 
 special importance. But for that thickness the levator palati, 
 when it rises upward, would not remain in contact with the side 
 edges of the obturator, nor would the constrictor pharyngeus be 
 able to effect a sufficient termination if the portion of the obtura- 
 tor nearest to it consisted only of a thin plate." 
 
 Fig. 180 represents the mouth without the apparatus. 
 
 Fig. 181 shows the apparatus in position ; Fig. 182 gives a view 
 of the appliance out of the mouth. 
 
394 
 
 MECHANICAL DENTISTRY. 
 
 Dr. Henry Baker, in writing of this appliance in the "American 
 System of Dentistry," says : 
 
 " The plate, a, and its narrow and thin apophysis, i, which ex- 
 
 Fig. 181. 
 
 tends from the boundary, b, of the hard palate to the commence- 
 ment of the defect, c, in the soft palate, serve also as supporters to 
 the real thick obturator, d. The latter lies in the pharyngopalatine 
 
 Fig. 182. 
 
 hollow, so that the lower surface of the obturator turned toward 
 the mouth, is about on the same level as the rest of the velum 
 palati, e. Against the vertical side, /, and back edges, g, of the 
 
ARTIFICIAL TREATMENT OF PALATAL DEFECTS. 395 
 
 obturator the walls of the pharynx lean if the latter is contracted 
 by a contraction of the superior constrictor of the pharynx. But 
 if the muscle just mentioned is not in activity, the obturator does 
 not touch the pharyngeal wall. The contraction of the constrictor 
 superior, therefore, closes the valve formed, with the help of the 
 obturator, between the cavity of the mouth and that of the nasal 
 bone, while any relaxation of the above-mentioned muscle imme- 
 diately reopens that valve. The thickness of the obturator begins 
 where the fissure in the soft palate commences. With the high 
 side edges of the fore part of the thick obturator, which edges 
 ascend, not straight but obliquely, toward the outside, the side 
 halves of the fissured velum palati, e, are in constant contact, even 
 when the latter are raised by the action of the muscular levator 
 palati. The proportions of the back part, which, in the same 
 manner as in the case of an acquired defect, fill up the cavum 
 pharyngopalati, k k, are the two halves of the fissured uvula." 
 
 Dr. Suersen admits the importance of the part taken by the 
 levator palati muscles in the formation of articulate speech ; yet he 
 makes no provision for utilizing them as such, and provides only 
 for the contact of the superior constrictor muscle with the distal 
 surface of the appliance to shut off the nasal passage. For the 
 patient afflicted with congenital cleft, to acquire perfect articulation 
 with such an appliance, even if it be possible, years of application 
 and training of this muscle would be necessary ; and a little 
 reflection will show that this muscle, besides performing its own 
 functions, must be trained to fulfil those of the velum palati, 
 levator palati, and tensor palati. But in an accidental lesion this 
 may be all that is necessary, as the patient having previously 
 learned to articulate distinctly, and having this deformity come 
 upon him afterward, the superior constrictor muscle would no 
 doubt be sufficiently developed to perform that function. Sir 
 William Ferguson, in his report of a dissection made by him of a 
 cleft palate, in 1844, states distinctly that the constrictor was very 
 full, and he also claimed for that muscle very decided forward ac- 
 tion in deglutition. 
 
 Dr. Kingsley, in speaking of Suersen's appliance, says : " First, 
 that of all obturators this is the best form for congenital fissure, 
 but while the wearer is enabled to articulate with such an instru- 
 ment, it is only after he has learned articulation with another ap- 
 
396 
 
 MECHANICAL DENTISTRY. 
 
 paratus. Second, that a soft, elastic, artificial velum is much better 
 adapted to the acquirement of articulation than any unyielding, 
 non-elastic substance, but when acquired an obturator may be sub- 
 stituted. Third, that in very rare cases articulation may be acquired 
 with an obturator only, but it is the extra activity of the pharyngeal 
 muscles, while with the elastic velum the levators of the palate 
 contribute largely." 
 
 Baker's Velum. — Dr. Henry Baker describes his appliance as 
 follows : " Numerous experiments to provide an artificial appliance 
 
 Fig. 183. 
 
 The cleft, extending a little beyond the soft into the hard palate. 
 
 with hard rubber, utilizing the levator muscles to control the 
 movement of the appliance, and with which articulation could be 
 learned as well as with the perishable soft-rubber velum, resulted in 
 my adoption of the following device in cases where the cleft extends 
 a little beyond the soft into the hard palate, as shown in Fig. 183. 
 The appliance consists of a gold or hard-rubber plate (A, Fig. 184), 
 covering the roof of the mouth down to the junction of the hard 
 and soft palates. From this point the movable portion, F, extends 
 back and downward, restoring symmetry of the palatal surface by 
 
ARTIFICIAL TREATMENT OF PALATAL DEFECTS. 
 
 397 
 
 bridging across and lying upon the muscles of each side. C E is 
 a spring controlling the upward movement of F. The distal sur- 
 
 FlG. 
 
 face, G, or that portion coming in contact with the pharyngeal 
 wall, is quite broad, and so constructed as to articulate perfectly 
 
 Fig. 185. 
 
 ■with this surface, while the constrictor muscle contracts and closes 
 around it on a semicircle." This is the Suersen principle, and the 
 main ideas are taken from that appliance. 
 
39§ 
 
 MECHANICAL DENTISTRY, 
 
 The velum is of polished hard rubber, gold, or platinum, and 
 much resembles a chestnut in form. 
 
 It is attached to the plate with a hinge-joint, B B, thus giving 
 
 Fig. i 
 
 free movement at the junction of the hard and soft palates. At the 
 junction of the hard and soft palates there is a stop, which prevents 
 any downward pressure upon the muscles when in a relaxed con- 
 dition. 
 
 Fig. 187. 
 
 The muscles relaxed, the appliance descended, thus giving a free passage for 
 nasal sounds and respiration. 
 
 Fig. 185 shows the appliance in position, the dotted lines show- 
 ing the part of the appliance resting on the muscles. 
 
 The main advantages of this appliance are that it is made of a 
 durable material, is easily constructed, and that articulation can be 
 
ARTIFICIAL TREATMENT OF PALATAL DEFECTS. 399 
 
 learned with it more readily than with any other appliance. In 
 addition, it is so easily movable as to be acted upon by, and be 
 under perfect control of the muscles by which it is surrounded. 
 In studying the mechanism of speech, we learn that more than 
 three-fourths of the sounds of articulate language depend upon the 
 integrity of the soft palate for their perfect enunciation. This being 
 the fact, articulation with a rigid obturator must be extremely 
 difficult to acquire. If three-fourths of the sounds depend on the 
 free movement of the natural palate, it seems a sufficient reason why 
 provision should be made for the same movement in an artificial 
 one. 
 
 Dr. Kingsley says that with a yielding appliance the levators of 
 the palate contribute largely to correct speech. The surrounding 
 muscles have control over the appliance here described in the 
 following way : The artificial velum bridges across the opening 
 and lies upon the muscles of either side. (See Fig. 185, D D.) 
 With all sounds requiring the closure of the nasal passage it is 
 thrown up by the levator muscles, as shown at D in the sectional 
 Fig. 186, there being no resistance. The thickness of the velum 
 brings its posterior surface in close apposition with the superior 
 constrictor muscle, F, affording in the pronunciation of the gutturals 
 a firmer resistance to the pressure of the tongue, G, than can be 
 obtained with a thin obturator. By the presence of the hinge, B, 
 the above movements are rendered so free and facile that there is 
 no tendency to displacement of the plate, such as occurs with a 
 rigid appliance. If a nasal sound immediately follows a guttural, 
 the descent of the velum is rendered certain by its own weight, even 
 if not aided by the spring. 
 
CHAPTER XXVIII. 
 
 APPLIANCES FOR THE CORRECTION OF FRACTURED 
 
 MAXILLA. 
 
 (Interdental Splints.) 
 
 Dentists are peculiarly fitted to overcome the mechanical diffi- 
 culties in the treatment of fractures of the maxillae ; while the 
 general surgeon, whose services are usually first sought, encounters 
 many annoyances, and seldom secures a correct adaptation and 
 retention of the fragments in their normal position. In fact, all 
 of the approved appliances and methods have emanated from 
 dentists. 
 
 Fractures of the jaw are unmistakable, the prominent symptoms 
 being pain, swelling, drooling, mobility of the fragments, crepitus, 
 and displacement of the teeth. If there is any doubt as to the 
 location of the fracture of the lower jaw, the operator should be 
 seated in front of the patient, and gently but firmly grasp the bone 
 on either side, allowing the forefinger to extend into the mouth and 
 rest upon the teeth, when the false point of motion or crepitus will 
 be readily recognized. 
 
 The Division of Fractures. — Fractures are divided into simple, 
 compound, and comminuted. Simple, when the bone only is broken 
 without piercing the integuments ; compound, when the fracture is 
 accompanied by laceration of the tissues through to the surface, so 
 as to establish communication with the air; comminuted, when the 
 bone is broken or crushed into several pieces. If the body of the 
 bone is involved, fractures of the lower jaw are usually compound 
 in the direction of the mouth ; but when the ramus, condyle, or 
 coronoid process are fractured this is not the case (on account of 
 their being so deeply seated) unless the wound is caused by a gun- 
 shot or missile. Several cases of fractured maxillae have been sent 
 to the writer for treatment, at the clinics of the Pennsylvania Col- 
 lege of Dental Surgery. These operations have been carried out 
 according to the principles herein described, and with entirely satis- 
 factory results. 
 
 400 
 
APPLIANCES FOR THE CORRECTION OF FRACTURED MAXILLAE. 40I 
 
 Securing the Impression. — The fundamental principles of tak- 
 ing the impressions of both jaws and reconstructing the model of 
 the fractured jaw by articulating the teeth to the cast of the 
 unbroken jaw, and upon this making the appliance, or splint, were 
 inculcated by Drs. Gunning and Bean. 
 
 The impression of both jaws should be taken, either in wax or 
 modeling compound, using as small a quantity as will insure a 
 good impression of the teeth and gums. That of the uninjured 
 jaw should be taken first, thus gaining the confidence of the patient, 
 and deferring the most painful operation until the last. 
 
 As it is impossible to keep the fragments of a fractured inferior 
 jaw in perfect apposition while taking an impression, no attempt 
 should be made to entirely reduce the fracture at this time. The sec- 
 
 FlG. I 
 
 tions, however, should be brought as nearly to position as possible 
 without causing much pain to the patient. 
 
 An assistant should stand behind the patient and support the 
 broken jaw, keeping it steady while the impression is being taken. 
 This is more important, however, when the fracture is double. 
 
 The impression material being ready, it should be introduced 
 into the mouth and carefully brought to position, and much care 
 should be exercised to prevent the pieces of bone and loosened 
 teeth from moving when this material is being molded about their 
 necks. 
 
 Preparing the Models. — After the impression has been secured, 
 mix plaster and pour cast in the usual manner. Figs. 188 and 189 
 represent casts showing double fractures. 
 
 The casts or models of both jaws being obtained, they should 
 be carefully articulated. This is done by cutting, with a small saw, 
 26 
 
402 
 
 MECHANICAL DENTISTRY, 
 
 the lower cast at the point, or points, of fracture, and rearranging 
 the sections thus made so as to bring the teeth of the two models 
 into correct articulation. This is represented in Fig. 189. 
 
 The pieces should then be secured in this position with plaster 
 and the two models placed in an articulator. 
 
 Forming the Splint in Wax. — Any interdental dovetail spaces 
 should be filled with soft plaster, so that the splint when finished 
 can be readily adjusted and removed. 
 
 The articulator should now be arranged (by the set screw in the 
 back) so as to open the bite about y 2 of an inch. Carefully cover 
 teeth' and gums of both casts with No. 60 tin-foil. Over this 
 covering of tin-foil build up the splint in wax. This is best done 
 
 Fig. 189. 
 
 as directed by the late Dr. Alonzo Beak* First, place two layers 
 of thin base-plate wax over the teeth of both models, allowing it 
 to extend just beyond the necks of the teeth upon the gums, but 
 not quite to the edge of the tin-foil. Then make a strip of wax 
 about yV °f an mcn thick and wide enough to fit between the 
 pieces of wax on the models, and long enough to extend as far 
 back as they do, joining the three pieces together with melted wax. 
 Pass a hot spatula all around the edge of the wax, where it joins 
 the tin-foil, to make a perfect joint. The object of the tin-foil is to 
 make the rubber smooth, and to have the splint, when finished, a 
 trifle larger than the natural teeth, so that it will pass into position 
 without binding at any point. 
 
 * " American System of Dentistry," Vol. ii. 
 
APPLIANCES FOR THE CORRECTION OF FRACTURED MAXILLJE. 403 
 
 Flasking. — The wax splint and tin-foil covering, now being one 
 piece, should be removed from the models and the models care- 
 fully taken from the articulator. Trimming their bases and sides is 
 necessary, so that when the splint is in position on them the whole 
 will fit in the vulcanizing flask. The lower model, with the splint 
 upon it, should be flasked first and the investment allowed to ex- 
 tend half way up the splint. Trim, varnish, and oil. Place the 
 upper model in position in the splint and finish flasking. By allow- 
 ing the tin-foil to extend beyond the wax (as at T, Fig. 190) the 
 investment holds it in position when the wax is removed. Fig. 
 190 gives a sectional view of the flask with the splint invested. F 
 represents the flask ; M, the models ; P, plaster investment ; T, tin- 
 
 Fig. 190. 
 
 foil coverings of the teeth extending beyond the wax splint; W, 
 wax model of splint. Before opening the flask place it in hot water 
 to soften the wax. Separate the sections carefully. Wash the wax 
 out by pouring boiling water upon it, instruments not being used, 
 as they are liable to injure the tin-foil. 
 
 Packing and Vulcanizing. — Liberal outlets for the rubber 
 should be made in both sections. Cut the rubber into thin strips 
 and soften over boiling water. It is also advisable to cut up a piece 
 of previously vulcanized rubber, small pieces of which may be packed 
 in between the other rubber at the thickest points, making it less 
 liable to become porous in vulcanizing. Pack each section care- 
 fully and thoroughly a little more than full. Place the sections 
 together, boil, and close them in the usual way. In vulcanizing 
 
404 
 
 MECHANICAL DENTISTRY, 
 
 allow the mercury one hour to rise to 320 F. When this point is 
 reached the temperature should be kept uniform for one hour or 
 
 more. 
 
 Fig. 191. 
 
 Finishing. — When the flask is taken from the vulcanizer and 
 has become cold, carefully remove the plaster and tin-foil from the 
 rubber. In trimming - , the rubber should be cut away nearly to the 
 necks of the teeth and the edges all nicely rounded. The opening 
 
 Fig. 192. 
 
 made in the splint for feeding purposes should be in front, if pos- 
 sible, and large enough to allow for the free passage of a feeding 
 tube, and should have the edges well rounded. The splint should 
 now be immersed in dilute muriatic acid to dissolve the tin, after 
 
APPLIANCES FOR THE CORRECTION OF FRACTURED MAXILLAE. 405 
 
 which it should be carefully finished and polished. Fig. 191 repre- 
 sents the completed splint. It is often advisable to make openings 
 through the top or side of the splint against each tooth adjoining 
 the fracture, so that it can be determined when the fractures are in 
 place. This plan is represented in Fig. 192. 
 
 Securing Splint in the Mouth. — The splint is now ready to be 
 adjusted in the mouth, and if the foregoing instructions have been 
 closely followed the teeth of the superior jaw will readily slip into 
 place. After so placing it, carefully manipulate the lower jaw, 
 reducing the fracture and bringing the teeth to position in the splint. 
 The jaw should then be firmly secured by external bandages. 
 
 The Kingsley Splint. — A splint devised by Dr. Norman W. 
 
 Kingsley consists of a vulcanite covering to the lower teeth, having 
 two steel wires attached extending out of the corners of the mouth 
 and then backward along the cheek on a line with the teeth. It 
 is held in position by having the wires bound to a sub-metal splint 
 of padded wood. The upper teeth must articulate with the upper 
 surface of the rubber, so that the patient can use it for mastica- 
 tion. Take upper and lower impressions ; pour models and articulate 
 them, as before described, and place them in an articulator. Upon 
 the lower model carefully press a piece of wax about one line in 
 thickness over the teeth, allowing it to encroach a little upon the 
 gums. Close the articulator to make the imprints of the upper 
 teeth in the wax. The best method to make the arms is to use a 
 couple of old dental excavators. Flatten the ends which are to be 
 
406 
 
 MECHANICAL DENTISTRY. 
 
 imbedded and curve them carefully, so that they will pass out of the 
 mouth and extend backward without pressing hard on the corners 
 of the mouth, and terminate near the angle of the jaw. The flat- 
 tened ends should be made quite broad and be thoroughly imbedded 
 
 Fig. 194. 
 
 in the splint, as much strain comes upon them. Fig. 193 represents 
 this form of splint. 
 
 The following cases, taken from the practice of Dr. Kasson C. 
 Gibson, of New York, are of especial interest in this connection. 
 Fig. 194 represents a fracture at the symphysis; Figs. 195 and 196 
 the displaced fragments sawed from the casts. 
 
 Fig. 195. 
 
 Fig. 196. 
 
 The occluding or grinding surfaces of antagonistic teeth are 
 unmistakable, and tbere is no excuse for making an error in reset- 
 ting the plaster model. Should any discrepancy occur, it will be 
 fatal to the success of the appliance. In all cases where there are 
 
APPLIANCES FOR THE CORRECTION OF FRACTURED MAXILLAE. 407 
 
 teeth which occluded with those of the opposite jaw (previous to 
 the fracture) a mistake is impossible, if care be exercised. 
 
 Fig. 197 shows the plaster fragments placed in their normal posi- 
 tion and cemented together, ready for the articulator. 
 
 If fractures where the teeth are missing, take an impression of 
 the alveolar ridge in the same manner as for artificial teeth, and 
 there will be no difficulty in correcting the model. The splint should 
 be molded with wax on the reconstructed plaster cast, and must 
 embrace each fragment of the jaw. If to be used for mastication, 
 the splint should cover all the teeth. 
 
 After modeling the splint in wax, and just before removing the 
 cast for flashing, soften the wax with dry heat. (The grinding 
 surface of the teeth should have been previously oiled to prevent 
 their adhering.) Then close the articulator, forcing the grinding 
 
 Fig. 197. 
 
 surface of the upper teeth into the wax, thus giving a uniform grind- 
 ing surface. Before packing the rubber, cover the teeth and model 
 with two or three thicknesses of tin-foil. There are two reasons for 
 doing this : first, it makes the splint a trifle larger ; second, it gives 
 a clean surface. After vulcanizing, immerse the splint in diluted 
 muriatic acid to dissolve the tin. Interdental splints ought to be so 
 adjusted that mastication can be performed. 
 
 In many fractures of the lower jaw it will be impossible to hold 
 the fragments in the splint, in their normal relations, by merely 
 attaching them to the splint. In these cases the appliance must be 
 supplemented by an external metal compress, so attached to it that 
 the jaw will be held as in a vise. The tightening of this compress 
 forces the fragments into the splint and securely holds them. 
 
 Fractures of the upper jaw require but little treatment compared 
 
408 MECHANICAL DENTISTRY. 
 
 with those of the lower, since the bones are naturally immovable, 
 and there is little difficulty in keeping the fragments in position. 
 
 The length of time necessary for wearing an interdental splint is 
 variable ; the shortest time, however, being about three weeks. 
 
 Brief histories of the following cases are furnished as illustrating 
 the different methods and appliances used in the treatment. 
 
 Case i. — Male, aged fifty. Treated at Bellevue Hospital. Lower 
 jaw fractured on the left side, the line extending through the body 
 between the cuspid and first bicuspid. The displacement of the 
 posterior fragment was downward and outward. No displacement 
 of the right side. 
 
 The splint used for this patient was made of vulcanite, covering 
 all the teeth, and held in position by first tying ligatures to the teeth 
 and afterward to the splint. The holes on the grinding surface were 
 for two purposes : first, to ascertain if the teeth were in proper posi- 
 tion ; second, to introduce the nozzle of the syringe for cleansing. 
 After reducing the fracture and adjusting the splint, the patient was 
 enabled to masticate without any difficulty. The splint was worn 
 about four weeks, and on its removal occlusion of the teeth was 
 found to be correct. 
 
 Case 2. — Male, aged thirty-five. Treated in Bellevue Hospital. 
 Lower jaw fractured in two places; on the right side between the 
 lateral incisor and cuspid, and on the left of the symphysis, between 
 the central and lateral incisors. Two incisors on the right side and 
 one on the left side had been knocked out at the time of the injury. 
 The anterior fragment was forced back and downward under the 
 tongue; the left side of jaw displaced downward and inward. (See 
 Fig. 198.) 
 
 A splint similar to the one just described was applied, except that 
 after inserting the splint and reducing the fracture a chin piece of 
 gutta-percha (the impression material now used by dentists is much 
 better), padded with cotton, held in position with a four-tailed band- 
 age, was added. Nourishment was taken through a space left in 
 the splint. (See Fig. 199.) 
 
 After a few days it became necessary to remove the chin piece, 
 as the patient complained of soreness and pain. It was then dis- 
 covered that an abscess had formed on the left side of the symphy- 
 sis. This, on being opened and probed, was found to contain a 
 small piece of bone, which was removed. The parts were cleansed 
 
APPLIANCES FOR THE CORRECTION OF FRACTURED MAXILLAE. 
 
 409 
 
 with a solution of carbolic acid and glycerin, the cotton padding 
 renewed, and the chin piece reapplied. This was frequently re- 
 moved for renewing the cotton and for treatment of the abscess, 
 
 Fig. 
 
 which healed in a few days. About this time a second abscess 
 formed under the splint, near the symphysis. This, on being 
 opened, contained a piece of alveolar process, which was removed. 
 
 Fig. 199. 
 
 A. Space through which nourishment was taken. B, B. Holes and slots for tying 
 the ligatures to the splint, these having been previously tied around the teeth. 
 These holes were also used for introducing the nozzle of a syringe for clean- 
 sing. C, C. Ligatures. D. Ligature tied. 
 
 Later several other pieces of alveolar process presented themselves 
 at or near this opening, and were removed. At the end of three 
 weeks the union of the fragments was sufficiently firm to permit 
 
410 MECHANICAL DENTISTRY. 
 
 of the removal of the chin piece, allowing the use of the jaw for 
 mastication. The bandage, however, was retained, except when 
 nourishment was being taken. The splint was removed after being 
 worn about six weeks, when occlusion of the teeth was found to be 
 correct. 
 
 Case j. — The patient, a miner, aged twenty-seven. Three days 
 before admission to the hospital, May 2, 1872, he was injured by a 
 splinter of wood from an explosion of nitroglycerin. Examination 
 revealed a compound comminuted fracture of right half of inferior 
 maxilla. There were three points of fracture : first, between the 
 left lateral incisor and the cuspid ; second, between the bicuspids ; 
 third, at or near the angle of the jaw ; considerable displacement 
 of all the fragments. 
 
 The anterior fragment, containing three incisors, the cuspid, and 
 first bicuspid, was depressed y 2 of an inch and displaced backward. 
 The middle fragment, including the second bicuspid and three 
 molars, was carried up nearly to the median line and slightly back- 
 ward. The posterior fragment was slightly elevated. 
 
 A splinter of wood about 3^2 of an inch long had been extracted 
 from an external wound which extended inward from the symphy- 
 sis for iy 2 inches along the line of the jaw. A clot of blood occu- 
 pied the left side of the floor of the mouth ; there was also consider- 
 able swelling about the face. The patient swallowed with difficulty, 
 fluids escaping through the nose ; articulation very indistinct. 
 
 May 3. Patient partook of milk through a glass tube with less dis- 
 comfort than the day before. 
 
 May 4. Patient still unable to swallow with ease, although the 
 swelling had greatly subsided. An attempt was made to introduce 
 the stomach-pump, but patient would not submit. In the afternoon 
 Prof. Stephen Smith saw him and advised wiring the anterior frag- 
 ments in order to draw and retain the tongue forward. This was 
 accomplished, though not without some difficulty, and the patient 
 drank two glasses of milk. About two hours later the wire broke, 
 but the patient was able to swallow as well as before, although com- 
 plaining of pain during the act. 
 
 May 5. Patient took three cups of coffee. Fragments again 
 wired in position. 
 
 May 6. Patienl swallowed all the food he wished. Wire failed to 
 hold fragments in place. 
 
APPLIANCES FOR TPIE CORRECTION OF FRACTURED MAXILLA. 4H 
 
 May 7. Swelling had almost disappeared. Odor from the mouth 
 was very offensive. 
 
 May 9. Large fragment of the jaw, containing one bicuspid and 
 two molars, became detached during the night, and the third molar 
 also came away (Fig. 200). Treatment up to this time consisted of 
 
 Fig. 200. Fig. 201. 
 
 Model showing displacement. 
 
 •disinfecting the mouth with a solution of carbolic acid and glycerin. 
 The wound was also dressed with the same, and the jaw supported 
 with a four-tailed bandage. 
 
 May 15. Impressions were taken in plaster-of- Paris preparatory 
 "to making an interdental splint (Fig. 201). This was constructed 
 
 Fig. 202. 
 
 •similar to those already described, with the addition of two steel 
 wires (old excavators) vulcanized in the splint and curved upward 
 as they emerged from the corners of the mouth, thus avoiding 
 pressure on the lip, and extending backward nearly to the angle of 
 /the jaw (Fig. 202). A rubber band was substituted for the bandage, 
 
4i: 
 
 MECHANICAL DENTISTRY. 
 
 and extended from one steel wire under the jaw to the other, out- 
 side of the gutta-percha chin piece. 
 
 May 19. Interdental splint adjusted (Fig. 203). Patient removed 
 this five hours later, on account of considerable pain on the right 
 side of the symphysis. 
 
 May 20. A very tender induration appeared posterior to and below 
 the cuspid and first bicuspid of the right side. On opening this, a 
 small piece of bone was found and removed. 
 
 May 21. Splint readjusted. Patient ate and slept well. 
 
 May 23. Splint again removed by patient, as he could not endure 
 
 Fig. 203. 
 
 the pressure. Bandage applied, which imperfectly held the frag- 
 ments. 
 
 May 28. Interdental splint readjusted and fragments placed in 
 position. Wound under the chin nearly healed. 
 
 During a period of ten days after the readjustment of the appli- 
 ance, it was found necessary occasionally to remove the chin piece 
 for some hours, owing to extreme pain and tenderness of the ex- 
 ternal surface. Cotton and a bandage were temporarily substituted 
 for the chin piece and rubber band. Both pain and tenderness were 
 partly caused by the pressure requisite to retain the fragments and 
 splint in position. The splint was constantly worn, except at such 
 times as were necessary to remove it for cleansing. After two 
 
APPLIANCES FOR THE CORRECTION OF FRACTURED MAXILLAE. 413 
 
 months, firm union was found to have taken place, and occlusion 
 of the teeth correct. This case appears in an article written by Dr. 
 N. W. Kingsley, published in Johnston's Miscellany, in January, 
 1874, wherein Dr. Kingsley gives Dr. Gibson (who was at that time 
 his assistant) credit for making and adjusting the splint. 
 
 Case 4. — Male, aged about sixty. Lower jaw fractured on the 
 right side, between the bicuspids. Previous to admission to hospital 
 he had been treated with gutta-percha covering the teeth, and a four- 
 tailed bandage. About four weeks after the accident these were 
 removed, as union had taken place, but upon examination all the 
 teeth to the left of the fracture, back to the wisdom tooth, were 
 found to be displaced downward from V2. to %. of an inch (Fig. 204). 
 
 Impressions were taken, and a splint made similar to that de- 
 scribed in Case 3. The patient was etherized and the jaw refractured 
 
 Fig. 204. 
 
 at the same point. The splint was adjusted and held in position as 
 in Case 3. About twenty-four hours after the adjustment of the 
 appliance, the patient complained of numbness extending from the 
 point of fracture to the symphysis. On examination, after the re- 
 moval of the chin piece, it was thought that this was due to an 
 injury of the nerve at or near the mental foramen. It remained for 
 some weeks, but eventually normal sensation was regained. 
 
 The splint was worn with comfort for six weeks, the chin piece 
 being occasionally removed for the purpose of cleansing. Occlu- 
 sion of teeth was found correct at this time. 
 
 Case 5. — Male, aged thirty. Lower jaw fractured at the symphy- 
 sis. The left central incisor, being loose, was removed. The right 
 fragment was displaced downward and inward; the left inward. 
 
 The splint used in this case was similar to the one last described, 
 
414 
 
 MECHANICAL DENTISTRY. 
 
 except that for the steel wire, gutta-percha chin piece, and rubber 
 band, an external metal compress was substituted. This was con- 
 structed from a saw-frame such as is used by mechanical dentists 
 (Fig. 205). To this was attached a revolving brass chin piece (Figs. 
 206 and 207) ; this was padded with spongiopilin covered with oiled 
 silk (Fig. 208). The splint was worn four weeks, when occlusion 
 of the teeth was found to be correct. 
 
 This external metal compress was found to be simpler in its con- 
 struction, more readily applied, and more effective. The chin piece 
 
 Fig. 205. 
 
 The handle and the 
 parts marked A, 
 B, were re- 
 moved. 
 
 C, revolving brass chin piece. The 
 rod at D, the point of contact 
 with the lips, is made round to 
 avoid irritation, and at E is split 
 and bent to nearly conform to 
 the contour of the jaw and teeth. 
 To this (E) is attached the vul- 
 
 Vulcanite attached. 
 The top holes 
 serve for ascer- 
 taining if splint 
 and fragment are 
 in position ; the 
 side holes are for 
 cleansing. 
 
 should be made of any size or form the case may require. If there 
 are external wounds or abscesses, holes should be cut in the chin 
 piece corresponding with these, thus permitting drainage and treat- 
 ment. 
 
 For the reduction or retention of any fracture of the lower jaw, 
 with much displacement, and where external pressure is required, 
 this form of splint will prove as effective as any appliance that may 
 be employed. When used, it is not always necessary completely to 
 reduce the fracture at the time of introduction. The use of the jaw 
 
APPLIANCES FOR THE CORRECTION OF FRACTURED MAXILLAE. 415 
 
 for masticating will gradually cause a proper adjustment of the 
 teeth to the splint. 
 
 Case 6. — Male, aged about forty. Lower jaw fractured at the 
 symphysis. Left side displaced downward about % of an inch and 
 carried inward. Appliance similar to that last described. Frac- 
 ture reduced without any difficulty. After wearing the splint four 
 weeks, occlusion of the teeth was found to be normal. 
 
 Case 7. — Male, fifty-two years of age ; while assisting in launch- 
 
 Fig. 208. 
 
 Appliance in position (from photograph of patient). 
 
 ing a ship, was struck by a heavy bar across the left side of the face. 
 Admitted as a patient to Bellevue Hospital. 
 
 Examination revealed a lacerated wound an inch long, situated 
 Ya, of an inch above the right angle of the mouth. The lower 
 jaw was fractured in three places : First, at the end of the sym- 
 physis, between the central and lateral incisors ; second, at the 
 right of the symphysis, between the central and lateral incisors; 
 third, at the angle back of the last molars, right side. The anterior 
 
416 MECHANICAL DENTISTRY. 
 
 fragment was displaced downward and backward, and the large 
 fragment on the right, containing six teeth, was depressed at the 
 anterior end, much elevated at the posterior. No displacement of 
 the left side of the jaw. 
 
 The wound in the lip was closed with silk sutures, and a four- 
 tailed bandage applied to the jaw, but a few days' trial proved its 
 inefficiency. Impressions were then taken for an interdental 
 splint. Upon removing impression of the upper jaw, this also was 
 found to be fractured as follows : first, from behind the second 
 bicuspid on the right side across the roof of the mouth, through 
 the alveolar process on the left side, where the first molar had been 
 extracted, then around in front, above the teeth, to the right side; 
 second, between the central and lateral incisors of the right side, 
 
 Fig. 209. 
 
 running along the median line and intersecting the fracture before 
 described (Fig. 209). The two fragments containing all the teeth 
 anterior to the molars were slightly displaced. These fractures 
 were readily readjusted and held with ligatures. 
 
 For the lower jaw the splint similar to that used for Case 5 was 
 applied March 9th, with the exception that the tongue-holder or 
 duct compressor (used by dentists) was substituted for the saw- 
 frame; the chin piece padded with spongiopilin covered with 
 oiled silk. From that date the patient experienced no discomfort, 
 and ate the ordinary hospital food without difficulty (Figs. 210 and 
 211). On March 20th he was discharged from the hospital, and on 
 April 10th the splint was removed. No deformity remained. 
 
 This case appears in Dr. N. W. Kingsley's article published in 
 Johnstons Miscellany, February, 1874; also in his work on "Oral 
 
APPLIANCES FOR THE CORRECTION OF FRACTURED MAXILLAE. 417 
 
 Deformities." From the former we quote : " The impressions, cast, 
 and adaptation of this instrument were made by my assistants, 
 Messrs. Gibson and W. H. Kingsley." 
 
 Fig. 210. 
 
 Case 8. — Patient, a policeman, aged thirty-five. Lower jaw 
 fractured on right side, between second bicuspid and second 
 
 Fig. 
 
 Appliance in position (from photograph of patient). 
 
 molar; the first molar having been extracted, third molar missing. 
 An attempt had been made to reduce and hold the fracture by cov- 
 
 27 
 
41 8 MECHANICAL DENTISTRY. 
 
 ering the teeth with gutta-percha and supporting the jaw with a 
 four-tailed bandage. 
 
 Twenty days after the injury was received, on taking impressions 
 for an interdental splint, it was discovered that there was no actual 
 displacement of the anterior fragment, but the posterior one, in- 
 cluding the second molar, was elevated about ^4 0I an inch, the 
 tooth coming in contact with the third molar on the upper jaw. 
 The treatment was similar to that used in Case 7, and the fracture 
 was reduced without any difficulty. The splint was worn with 
 comfort for thirty clays. On removal,- the teeth occluded correctly. 
 
 Case p. — Male, aged about twenty-five, subject to epileptic con- 
 vulsions. Fracture due to a fall during one of these attacks. The 
 lower jaw was fractured at the symphysis; right side displaced 
 downward about y^ of an inch ; anterior end of fragment outward ; 
 posterior portion of jaw inward about *4 OI an inch. No displace- 
 ment of left side of the jaw. An attempt had been made to reduce 
 and hold the fragments in position with gutta-percha covering the 
 teeth, and a four-tailed bandage. 
 
 Two weeks after the accident impressions were taken for an inter- 
 dental splint, which was applied, the fracture being reduced with- 
 out any difficulty. The splint was worn with comfort for five weeks, 
 when it was removed, occlusion of the teeth being correct. A few 
 minutes after the removal of the splint the patient had an epileptic 
 seizure, although he had been free from these attacks during the 
 treatment for fracture. Appliance similar to Case 8. 
 
 Case 10. — Patient, a boy, aged six. Two fractures of the lower 
 jaw. First, between the lateral incisor and cuspid, left side; sec- 
 ond, back of last temporary molar on right side. Displacement of 
 anterior fragment downward and inward, each about % of an 
 inch ; slight displacement of posterior fragment ; no displace- 
 ment of left side (Fig. 212). The splint used was similar to the one 
 in Case 7, with necessary alterations (Fig. 213). 
 
 Attempts had been made to reduce and hold the fragments, first, 
 with ligatures about the teeth ; second, with gutta-percha covering 
 the teeth and a bandage, neither of which proved effectual. 
 
 Three weeks after the accident an interdental splint was adjusted. 
 Great difficulty was encountered in reducing this fracture. A few days 
 later, the reduction not being satisfactory, the splint was removed, 
 nitrous oxid administered, fracture reduced, and splint replaced. 
 
APPLIANCES FOR THE CORRECTION OF FRACTURED MAXILLAE. 
 
 419 
 
 The following form of appliance has been adopted as best meet- 
 ing the requirements of cases needing an external metal compress. 
 It consists of three parts : First, a compressor ; second, a chin piece ; 
 third, an inner steel band or the wire splint, as shown in Fig. 214. 
 
 First, the compressor (used without alteration for all cases), con- 
 
 FlG. 
 
 Fig. 213. 
 
 Fig. 214. 
 
 sisting of a horizontal rod (A) and a vertical rod (B), each about 
 two inches in length, meeting at right angles. Rod B is hollow, 
 and at its upper end is fitted a thumb-screw so adjusted as to hold 
 at any point in it a movable rod (C), thus regulating pressure. 
 Passing horizontally through a bulb at top of rod C is a rod (D) 
 three inches in length, bent downward at right angles for about an 
 inch. One-half of this lower end is smaller 
 in diameter than the other half, leaving a 
 shoulder. A thumb-screw in the bulb admits 
 of the adjustment of rod D at any angle. 
 
 Second. The chin piece is attached to the 
 compressor by a thumb-screw, so adjusted 
 that it may be pushed backward and forward 
 on the rod A, and at the same time affording 
 a double rotary movement. The chin piece 
 is made in different forms, each peculiarly 
 
 adapted to the location of fracture, (a) If fracture is at or near 
 the symphysis, the chin piece consists simply of a flat piece of 
 brass placed directly under the chin; (b) if back of the cuspid 
 teeth involving the molars, it should fit the chin extending back to 
 the angle of the jaw; (c) if involving both the angle and the con- 
 dyle, it must include the entire lower jaw, and extend to the line 
 
420 MECHANICAL DENTISTRY. 
 
 of the ear. A metal button (E) should be attached on each side of the 
 chin piece for use in attaching any necessary support. For support 
 nothing surpasses a skull-cap, to each side of which can be attached 
 a piece of elastic reaching to the chin piece ; this in turn can be 
 fastened to the metal button by a ring sewed in the end of the elastic. 
 
 Third. The inner steel bands are made of various sizes and shapes 
 to conform as nearly as possible to the contour of the jaw and teeth, 
 and are vulcanized in the splint. 
 
 This appliance has been so constructed that the external compress 
 may be removed independent of the splint proper ; temporarily where 
 external wounds or abscesses need treatment; permanently where 
 there is sufficient union to retain fragments. 
 
 Any irritation of the lips caused by the adjustment of the rod at 
 the median line may be remedied by removing (the patient having 
 previously closed the jaws firmly) the external compress and read- 
 justing it at any point to the right or left. 
 
 Splintage for Section of Inferior Maxilla. — In certain opera- 
 tions designed to reach the zygomatic fossa and in external pharyn- 
 gectomy an interdental splint has been employed with much satis- 
 faction. A very interesting case in point* is that treated by George 
 R. Fowler, M.D., Professor of Surgery in the New York Polyclinic, 
 and Rodriguez Ottolengui, M.D.S., of New York. After some 
 preliminary remarks upon different methods of procedure, or forms 
 of operations, Dr. Fowler says that section of the maxilla, as hereto- 
 fore accomplished, has consisted in dividing the bone either just 
 above, or in front of the angle, i. c, either through the ramus, in 
 which case the saw-cut runs in a horizontal direction, or through 
 the body of the bone, the section being made vertically. These 
 sections were first proposed by Mikulicz, to which he added, in cases 
 of external pharyngectomy, removal of a portion or the whole of 
 the ascending process, or ramus of the jaw. The latter is usually 
 an unnecessary mutilation and seriously interferes with the func- 
 tions of the jaw, as well as leading to an unsightly appearance of 
 the parts. If the section is made in front of the angle and in a 
 vertical direction, the angle itself is in the way of complete access 
 to the parts above the • latter, an important consideration both in 
 neurectomy at the foramen ovale, and in external pharyngectomy. 
 
 * Reported in the Items of Interest, January, 1897. 
 
APPLIANCES FOR THE CORRECTION OF FRACTURED MAXILLAE. 42 1 
 
 In order to overcome these objections, Dr. Fowler makes an 
 oblique section directly across the angle itself. This is done with 
 a chain saw, the attachments of the masseter upon the external, 
 and those of the internal pterygoid upon the internal surface of the 
 jaw, being first detached. The soft parts are raised, together with 
 the periosteum, which is stripped from the outer and inner surface 
 of the bone by means of the rugine or raspatory. The chain saw 
 is passed beneath the periosteum, and the cut commenced just pos- 
 terior to the site of the wisdom tooth. The jaw is steadied by an 
 assistant, and the chain saw so directed that the cut shall terminate 
 at the point of the angle. By this means an oblique section is 
 made across the angle, and a result produced, when readjustment 
 of the divided bony parts is effected, not unlike what is known 
 among mechanics as a " miter." The advantages gained, in the 
 way of access to the deeper parts, are beyond question, and are 
 illustrated in Fig. 215. 
 
 In the case of a young lady, operated on for the removal of a 
 sarcoma of the tonsil and its neighborhood, it was determined to 
 overcome, if possible, the disadvantages which constituted the ob- 
 jectionable features of the older methods of bone section, and re- 
 adjustment of the fragments and the maintaining of the same in 
 their proper relations. In furtherance of this desire, Dr. Fowler 
 conceived the idea of having a proper interdental splint made pre- 
 liminarily, which could be applied immediately after the completion 
 of the operation, and which should automatically adjust the divided 
 parts and maintain them in their proper relations, thus assuring a 
 perfect restitution of their physiological functions. 
 
 Accordingly, a few days prior to the operation he called into 
 requisition Dr. Ottolengui, whose ready appreciation of the neces- 
 sities of the case proved to be invaluable in carrying the latter to a 
 most successful termination, so far as the mechanical difficulties to 
 be overcome were concerned. The necessary casts were obtained 
 and an interdental splint constructed. 
 
 All being in readiness, the operation of external pharyngectomy, 
 with oblique section of the jaw at the angle, was performed. Upon 
 the completion of the operation, the bony parts were readjusted. 
 It was found that the two halves of the obliquely divided ramus 
 and body of the jaw fitted together like the united corners of a 
 
4^2 
 
 MECHANICAL DENTISTRY. 
 
 picture frame, the comparatively long cut and the broad bony 
 surfaces aiding this materially. 
 
 Fig. 215. 
 
 1. Hyoglossus muscle. 2. Retracted posterior belly of the digastric. 3- Stylo- 
 hyoid muscle divided at its lower and anterior attachment at 4. 5- Mylo- 
 hyoid muscle, retracted anteriorly. 6. Body of inferior maxilla. 
 
 But as it was subsequently discovered that the slight separation 
 of the jaws which the interdental splint produced displaced the 
 body of the bone in a forward and downward direction, and sepa- 
 
APPLIANCES FOR THE CORRECTION OF FRACTURED MAXILUE. 423 
 
 rated the fragments, it at once became evident that a splint was 
 needed which would admit of adjustment of the tooth surfaces to 
 each other with the minimum amount of intervening space. This 
 was undertaken and successfully accomplished by Dr. Ottolengui. 
 
 The patient was fed at first by a tube led through the external 
 wound and into the pharynx. Through this tube, also, frequent 
 irrigations of the parts with potassium permanganate, as well as 
 the application of peroxid of hydrogen solution, were carried on. 
 Subsequently the feeding and irrigation were effected by means of 
 a soft rubber catheter passed between the metal splint and cheek, 
 and into the pharynx. 
 
 The splint was dispensed with in the third week and movements 
 of the jaw permitted. The healing was uneventful, and the masti- 
 catory function of the jaw, despite the fact that the callus thrown 
 out in the reparative process was at the site of the attachments of 
 the internal pterygoid and masseter muscles, was complete. A 
 point worthy of note in the case is the fact that almost perfect 
 restoration of phonation finally took place, despite the fact that in 
 the operation for the removal of the diseased parts it became neces- 
 sary to remove, in addition to the tonsil and underlying parts, all 
 of the faucial pillar and at least three-fourths of the velum. The 
 cicatricial contraction which followed the healing process upon the 
 diseased side, displaced toward the median line the remains of the 
 velum. The effect of this, as well as the control over the move- 
 ments which the patient obtained, was finally sufficient to produce 
 occlusion of the postnasal space, and overcome to a great extent 
 the nasal sound of the voice which at first was quite marked. 
 
 After constructing and inserting a modified form of the Gunning 
 splint, which seemed to fit accurately and comfortably, the divided 
 jaw was held in position by a series of bandages which covered the 
 head, as well as the dressings over the wound in the neck, and 
 passing around and under the chin. This, however, as has 
 been stated, proved ineffectual, and Dr. Ottolengui describes 
 the peculiarities of the case from this stage, as follows : " Two 
 days later I was called to visit the patient, as she was suffering 
 considerably from the splint. With some chagrin I visited the 
 hospital, and upon examination discovered that in the region of the 
 wound all the soft parts had become so much swollen that the 
 splint, which at first did not touch the gum tissue at any point, was 
 
424 
 
 MECHANICAL DENTISTRY. 
 
 now in contact with it, and had already caused a most painful 
 abrasion. Had this been the only fault in the splint it would have 
 been trivial in importance, easily remedied by cutting away all of 
 that part of the splint which engaged the lower molars of that side, 
 which I did, the splint being perfectly comfortable when replaced. 
 Nevertheless I record this fact, as worthy to be remembered by all 
 who may choose to make an interdental splint of rubber, especially 
 when through neglect an operation shall have become necessary in 
 order to bring the ends of the bones together, in order to introduce 
 the splint. After all such surgical interference it is well to remem- 
 ber that swellings may occur immediately in the region of the frac- 
 ture, and special caution should be taken to avoid impingement of 
 the splint in this vicinity. 
 
 " But an examination of the parts, while I had the splint out, sud- 
 denly aroused a suspicion in my mind, which, if true, would prove 
 that the splint was inherently wrong in principle. This visit being 
 at night, I allowed the house surgeon to replace the splint and 
 bandages, and arranged for a consultation with Dr. Fowler for the 
 following morning, which fortunately was Sunday, so that I had the 
 whole day at my disposal. At this examination we found to our 
 regret that my suspicion was well founded, and that the splint 
 would prove harmful ; consequently a splint of an entirely new de- 
 sign was decided upon. 
 
 " The fault in the splint lay in the opening of the jaws. The main 
 object of a splint, aside from obviating the necessity of wire suture, 
 is to hold the jaws during the processes of union in such position 
 that subsequently the occlusion will be correct. The double in- 
 terdental splint was specially designed to this end, and has un- 
 questionably accomplished the purpose in hundreds of cases, but 
 these cases have been fractures of the bodies of the bones, the rami 
 being unaffected. / have little doubt now, that in cases where the 
 ramus has been involved, perfect occlusion has not resulted, and 
 moreover that it has remained unsuspected that the splint actually pre- 
 vented such occlusion. In the case of our patient, we found that the 
 interposition of the splint caused a V-shaped gaping of the divided 
 parts, and it was an unavoidable deduction from the premises that 
 union would result from the deposition of new bone to fill this gap, 
 so that after healing, while the jaws would accurately occlude with 
 the interdental splint, the splint being removed, the additional bone 
 
APPLIANCES FOR THE CORRECTION OF FRACTURED MAXILLAE. 425 
 
 deposited in the ramus would preclude the possibility of perfect occlu- 
 sion of the teeth, each set with the other." 
 
 Ottolengui's Splint. — " Under these circumstances I obtained 
 new impressions of the jaws, and hurried from the hospital in Brook- 
 lyn to my office in New York, arriving in the laboratory at one 
 o'clock. I started again for the hospital at five o'clock, carrying the 
 completed splint with me. I mention this as an indication of what 
 may be done in an emergency. Models, dies, and counter-dies are 
 then made. Using 20-carat gold, 29 gage, I struck up a continuous 
 cap to cover all of the teeth in each jaw, in the incisive region, how- 
 ever, extending only over the cutting edges. The plaster models, 
 with the gold covering the teeth, were then occluded, and the two 
 caps fastened together with hard wax. They were then invested and 
 
 Fig. 216. 
 
 permanently united with solder. It may be useful to record a little 
 trick in connection with the soldering, which saved a great deal of 
 time. Of course the teeth of two jaws do not occlude like cog- 
 wheels, consequently these gold caps were found to be in contact 
 at some points, while spaces appeared at others. I took a piece of 
 platinum wire and cut it into small bits, which I bent into suitable 
 curves and dropped into the spaces. These bits of wire served as 
 leaders for the solder, which flowed like water, closing the seam 
 throughout its entire extent. Fig. 216 shows the form of this 
 double interdental splint, made of gold. 
 
 " I mentioned that in the incisive region the splint extended only 
 slightly over the cutting edges. There was a useful purpose in 
 this, which is comprehensively shown in Fig. 217 where the splint 
 
426 MECHANICAL DENTISTRY. 
 
 is seen as it appeared in the mouth. Had the labial surfaces of the 
 anterior teeth been covered as well as the buccal surfaces of the 
 posterior teeth, it would have been impossible to know positively 
 that the jaws were properly in place within the splint; whereas by 
 cutting away the gold from the faces of the anterior teeth, so that 
 no gold whatever covered those surfaces, it could be determined 
 readily, and at all times, whether the jaws were properly in position. 
 In this respect the illustration is not perfect, as the artist has de- 
 picted the gold extending somewhat upon the labial surfaces, 
 whereas in this region no gold whatever was visible, except that 
 actually between the cutting edges of the teeth of the opposite 
 jaws. This feature was shown to be of considerable value, as the 
 tendency of the tired jaws will be to open, and these frequent efforts 
 may stretch the bandages, thus allowing play to the mouth, which, 
 
 Fig. 217. 
 
 however, is readily detected by the attendant, who may ask the 
 patient occasionally to endeavor to open the mouth, whereupon it 
 can be observed whether the teeth move from their places in the 
 splint, in which case the bandages can be tightened. 
 
 " This splint, when placed in position, caused absolutely no 
 discomfort to the patient, was clean, free from odor at all times 
 and proved to be all that could be desired. The long advo- 
 cated feeding space was not missed, because at first the patient 
 was fed through the tube which entered the mouth through the 
 wound, and subsequently through a catheter which passed back 
 between the cheek and jaws, entering the mouth behind the molars, 
 the patient finding no difficulty to draw it in with the tongue, and 
 to obtain liquids by suction." 
 
 So far as the records show this was the first use of a double 
 
APPLIANCES FOR THE CORRECTION OF FRACTURED MAXILLAE. 427 
 
 interdental splint, bringing the jaws into close occlusion, and 
 abandoning the theory of the feeding space. As a division of the 
 jaw at the ramus offers more difficulties than a fracture in the body 
 of the bone, and as this form of splint is here shown to be ade- 
 quate in such cases, there can be no necessity hereafter for open- 
 ing the jaws and thus stretching and tiring the muscles, which by 
 the method here advocated are all at rest. 
 
 Angle's Method of Fixation. — A comparatively recent and ex- 
 cellent method for treatment of fractures of the maxillae is that de- 
 vised by Dr. E. H. Angle, of Minneapolis, and through the doctor's 
 courtesy I am enabled to give a full description of his methods and 
 appliances here. He says : " The methods used by myself in treat- 
 ing fractures of the maxillae have been so successful and so gratify- 
 ing that it would seem they approach for efficiency and simplicity 
 more nearly the ideal than any yet devised." 
 
 In order that this system of treating fractures of the maxillary 
 bones may be more easily understood, we will divide them into 
 three classes. The first class comprises all simple fractures in 
 which the teeth are good and sufficiently firm in their attachments 
 (especially on each side of the fracture) to afford anchorage for the 
 appliance. 
 
 The second class comprises all fractures where the teeth are un- 
 suited, from disease or any other cause, for anchorage, but yet suffi- 
 cient to give the correct articulation of the jaws. 
 
 The third class comprises all fractures where the jaws are edentu- 
 lous. The following cases, treated by Dr. Angle, will enable the 
 reader to comprehend the method peculiar to each class : 
 
 Case No. i will illustrate class No. I. A young man fell from 
 a pile of lumber, a distance of 15 or 20 feet, and, besides severe 
 bruises, suffered a simple fracture through the symphysis, termi- 
 nating, however, in front between the central and lateral on the 
 left side, as shown by the line in the engraving (Fig. 218). 
 
 Upon examination, it was found that the fractured bone was quite 
 widely separated at the top, and the left central incisor was loosened. 
 The treatment practised was as follows : The ends of the fractured 
 bones were placed in their proper position and temporarily fastened 
 by lacing the teeth with silk ligatures. Bands of very thin German 
 silver were made to encircle and accurately fit the cuspid teeth. A 
 small tube of German silver, y 2 of an inch in length, was soldered 
 
428 
 
 MECHANICAL DENTISTRY. 
 
 to each band and in exact alignment; a piece of wire accurately 
 fitting the bore of these tubes, bent at right angles at one end and 
 having a screw cut upon the other end, was slipped through each 
 tube and secured therein by adjusting a nut on the screw. The 
 bands were cemented in position upon the teeth by means of oxy- 
 phosphate cement, as shown in Fig. 218. 
 
 After the cement had become thoroughly set, the nut was then 
 tightened until the fractured ends of the bone were drawn snugly 
 together. 
 
 The appliance was worn without displacement or trouble for 
 twenty-one days, when it was removed, the bone having become 
 firmly united. I may add, that during the time the appliance was 
 worn, so firmly was the jaw supported, the patient suffered little if 
 any inconvenience, and after the third day partook regularly of his 
 
 Fig. 218. 
 
 meals, using his jaws freely, but, of course, avoided the hardest 
 particles of food. After removing the appliance a careful impres- 
 sion of the jaw was taken, a model made, and the appliance trans- 
 ferred to the model, exactly as shown in the engraving. The 
 lower part of the jaw is, of course, diagrammatic, and was added 
 by the engraver to show the line of fracture. 
 
 It should be borne in mind that the principle upon which this 
 appliance is based is not the same as where the teeth are simply 
 wired together, but very different ; for in wiring, the upper parts of 
 the fracture only are tipped or drawn together, and no pressure or 
 support is given to the lower parts, while in the method here shown 
 it will be seen that, by reason of the bands and pipes being rigidly 
 attached to the anchor teeth, tipping is impossible, and pressure is 
 exerted equally upon both parts (upper and lower) of the fracture 
 as they are drawn together by the screw. 
 
APPLIANCES FOR THE CORRECTION OF FRACTURED MAXILLAE. 429 
 
 This device may be applied in any locality in either jaw, provided 
 suitable teeth for anchorage be not too far remote from line of 
 fracture. The screw may be bent to accommodate the curve of 
 the arch, should the fracture occur in the region of the cuspid. 
 
 These bands, tubes, wires, screws, and nuts are some of the ap- 
 pliances known as " Angle's Regulating and Retaining Appliances," 
 devised and used for the purpose of correcting irregularities of 
 the teeth. They may be procured of dealers in dental goods. (See 
 Fig. 219.) 
 
 The treatment for cases of the second class is illustrated in the 
 following instance : On July 4, 1889, a man aged forty-five was ad- 
 mitted to the Minneapolis City Hospital. A blow from a police- 
 
 Fig. 219. 
 
 man's club had produced two simple fractures of the inferior max- 
 illa. The first was an oblique fracture of the right side, beginning 
 with the socket of the second bicuspid, extending downward and 
 backward, involving the socket of the first molar, breaking out the 
 second bicuspid, and greatly loosening the first molar. The second 
 molar had been lost years before, while the third, as well as the re- 
 maining teeth, were much abraded and loosened by salivary cal- 
 culus, thus making the application of the appliance described in 
 Case No. 1 impossible. The second fracture was situated on the 
 opposite side high up in the ramus. 
 
 Because of swollen condition of the parts, the exact line of frac- 
 ture could not be detected, but the grinding of the ends of the bone 
 and the great pain occasioned thereby were unmistakable evidences 
 
43° 
 
 MECHANICAL DENTISTRY. 
 
 of a fracture. The patient, as in all such cases, was unable to close 
 the jaws. The fracture on the right side was widely separated, 
 and the anterior piece much depressed by reason of the contraction 
 of the depressor muscles, while the posterior bone was drawn firmly 
 up, the molar teeth occluding. (See Fig. 220.) 
 
 The following is the treatment used : Bands were made to encir- 
 cle all four of the cuspid teeth, they being the most firmly attached 
 in their sockets. The fractured ends of the bones were placed in 
 apposition, the lower jaw closed carefully. The occlusion of the 
 lower teeth upon the upper required so much force and occasioned 
 such intense pain that it became necessary to anesthetize the 
 patient. Points on the bands for the necessary attachments were- 
 carefully noted. The bands were then slipped off the teeth, and. 
 
 Fig. 220. 
 
 little pipes (shown at Fig. 219) soldered at the necessary points,, 
 after which the bands were cemented in their proper position upon 
 the teeth, and two small traction screw-wires, the same as shown at 
 Fig. 219, were slipped into the pipes. The jaws were closed and the 
 nuts tightened on the screws, until the jaws were drawn firmly to- 
 gether, and each tooth occupied its exact position in occluding upon 
 its fellow of the opposite jaw. Both fractures were then carefully 
 examined and found to be in perfect apposition, and presented the- 
 appearance shown in Fig. 220. The most natural position for the 
 jaw and the muscles had been secured, thus placing the parts in 
 their natural positions of relaxation and rest. 
 
 During an attack of coughing during the night following, one of 
 the bands was wrenched loose, but was replaced the next day with- 
 
APPLIANCES FOR THE CORRECTION OF FRACTURED MAXILLAE. 
 
 431 
 
 out trouble. No further accidents occurred. The patient readily 
 took nourishment through the spaces between the teeth. Thus 
 the fractured jaw was firmly supported without the least motion for 
 twenty-two days, when the appliance was removed, showing most 
 excellent results. 
 
 The following case possesses several points of special interest; 
 the fractures were in regions similar to the case just described, and 
 the appliances, though involving similar mechanical principles, will 
 be found to be greatly simplified. 
 
 Thomas B. was admitted to the Dental Infirmary of the Univer- 
 sity of Minnesota, suffering from the effects of a blow received on 
 the left side of the jaw from a cant-hook while working in a lum- 
 ber camp in Wisconsin, which produced fracture of the jaw in two 
 places. The first fracture was on the left side, beginning between 
 the first and second bicuspids and extending downward and back- 
 ward, and involving the lower part of the anterior root of the first 
 molar. The second fracture was on the right side, directly through 
 the angle of the jaw. The fractures had occurred thirty-two days pre- 
 vious to his admission to the infirmary, during which time nothing 
 had been done to reduce them. He reported that he had called upon 
 a physician, who supposed the trouble was merely an abscessed 
 tooth, and had lanced the gum with the view of reducing the swell- 
 ing. Later the patient had called upon a dentist in one of the 
 smaller towns, who also failed to diagnosticate the fracture, and ex- 
 tracted both bicuspids, in the hope of giving relief. Upon exami- 
 nation I found considerable swelling in the region of this fracture, 
 with the usual result ; the patient being unable to close his mouth 
 by reason of the anterior piece of the fractured bone being drawn 
 down by the contraction of the depressor muscles. A false joint 
 had also become established, and the bones could be easily worked 
 without causing pain. 
 
 At the point of fracture on the right side there was little or no 
 displacement; the swelling was also slight. 
 
 The patient was anesthetized. The ends of the bone were 
 then rubbed forcibly together with the view of breaking up the 
 false attachments and stimulating activity in repair. 
 
 The ends of the bones were now placed in perfect apposition, 
 and the mouth closed, great care being taken to articulate the teeth 
 in their correct position against the upper ones. 
 
43 2 
 
 MECHANICAL DEXTISTRY. 
 
 Fig. 221. 
 
 The jaw was now firmly bound in this position to the upper 
 teeth, in the same manner as described in Case No. 2, with this 
 difference, that the method was improved upon and simplified by 
 using clasp bands, as shown in Fig. 221. No cement was used, and 
 instead of the screws small metallic buttons were soldered to the 
 sides of the bands (as shown in the 
 cut), around which fine binding wire was 
 wrapped in the form of a figure 8. (See 
 Fig. 222.) 
 
 The bands seen upon the molar teeth in 
 the engraving were not used in this case, 
 but are shown for the purpose of illustrating how they may be used 
 in case of comminuted fracture. At the end of seventeen days the 
 bands were removed and the patient discharged, the bone having 
 been firmly united. 
 
 Dr. Angle suggests that it might be urged as an argument against 
 this method that, the teeth being closed and the jaws being firmly 
 bound together, the patient would be unable to take sufficient 
 
 Fig. 
 
 nourishment. It, however, rarely happens that a patient is found 
 without some teeth missing, thereby leaving abundance of space 
 for the passage of liquid foods, and even if all the teeth were sound 
 and in perfect position, it has been proved that there is plenty of 
 space between the teeth and behind the molars and between the 
 upper and lower incisors for taking all nourishment necessary. In 
 
APPLIANCES FOR THE CORRECTION OF FRACTURED MAXILLAE. 433 
 
 such cases more time would be consumed in taking nourishment, 
 but this obstacle is compensated for by the main points of advantage 
 in its favor, such as cleanliness and greater comfort to the patient, 
 as compared with the many bulky and awkward appliances in use. 
 
 Thirdly, its extreme simplicity enables any one with ordinary 
 mechanical ability, when provided with a set of clamp bands, to 
 easily and quickly set all ordinary cases of fracture. 
 
 And, lastly, the certainty of correct results will be sufficient rea- 
 son for all those who are interested in this branch of surgery to give 
 it a trial. Class No. 3, comprising fractures of edentulous jaws, are 
 fortunately very rare. The method of treatment is similar in prin- 
 ciple to that already described in class No. 1, only that in place of 
 the teeth small bone hooks are used, drilling for their reception a 
 suitable cavity on each side of the fracture, comparing in position 
 to the original sockets of the teeth, the same as if the operation of 
 implanting teeth were intended; the cavities thus made need not 
 be nearly so large or deep. They should also be drilled obliquely, 
 to correspond to the course taken by the hooks. The hooks before 
 insertion should, of course, be made antiseptic. While Dr. Angle 
 has confidence in this means of treatment for edentulous jaws, it 
 seems evident to the writer that the interdental splint already de- 
 scribed would be more practicable. 
 
 28 
 
CHAPTER XXIX. 
 
 APPLIANCES FOR THE CORRECTION OF DENTAL IRREGU- 
 LARITIES. 
 
 Orthodontia, which pertains to the correction of irregularity in 
 the position of the human teeth, and which was given little or no 
 attention by the earlier teachers, is now recognized as a distinct 
 branch or specialty of dental science. To practice this field along 
 the advanced lines requires special study, investigation, and training 
 and it is our purpose, in the present chapter, to introduce the most 
 important methods and principles involved, with the manner of con- 
 structing and adjusting the appliances. 
 
 Mechanical Forces. — The operator in orthodontia has an 
 opportunity to utilize his knowledge of physics, and the laws of 
 mechanics. As a very able writer, Dr. Eugene Talbot, says : 
 These laws are founded upon the action of simple elements which 
 are interposed between the moving power and the resistance, for 
 the purpose of changing the direction of the force. These are 
 called mechanical powers, and are divided into two primary ele- 
 ments, the lever and the inclined plane. The principle of the lever 
 is the basis of the pulley, the wheel, and axle. That of the inclined 
 plane is the basis of the wedge and screw. 
 
 Elasticity, as shown in India-rubber and the spring of metals, 
 although not classified with the primary forces in mechanics, plays 
 an important part in the application of force in regulating teeth. 
 When these laws and their applications are firmly fixed in the mind 
 of the operator, he can readily take advantage of the one which 
 should properly be applied, or, when necessary to apply more than 
 one, can combine them in such a manner as will best accomplish 
 the desired result. 
 
 The most frequent forms of irregularity arc protrusion of the 
 cuspid teeth, misplaced bicuspids, contraction of the arch, protru- 
 sion of the upper jaw, protrusion of the lower jaw, torsion, and lack 
 of anterior occlusion. 
 
 434 
 
CORRECTION OF DENTAL IRREGULARITIES. 4^ 
 
 Protrusion of Cuspid Teeth. — In correcting this form of irreg- 
 ularity, which is possibly the most frequently met with, we have 
 to decide from other existing circumstances whether the enlarge- 
 ment of the arch is indicated or the extraction of one or more 
 teeth. If the upper arch is large enough, the simple extraction of 
 certain teeth, in a young person, will allow nature to correct the 
 deformity; which she will do unaided usually, by bringing the cus- 
 pids down, and back into position. In extracting teeth for regulating 
 purposes, a mistake is frequently made in the selection of the tooth 
 or teeth to be removed ; we have, in our practice and clinical experi- 
 ence, met with several cases where practitioners have, at times, ex- 
 tracted the lateral incisors, allowing the cuspids to come forward and 
 down, and on other occasions the cuspids have been removed. The 
 result, in each case, has been an almost hopeless deformity. The 
 cuspid teeth brought next to the central incisors oftentimes gives the 
 face a canine expression, while if the cuspids are removed the coun- 
 tenance is robbed of that prominence near the angles of the mouth 
 which is very necessary to harmonious expression ; in fact the cus- 
 pids contribute more than any of the teeth, unless it is the central 
 incisors, to the beauty of the mouth. In consideration of these 
 facts it is readily seen that the practice of removing the projecting 
 teeth is most injudicious. 
 
 It is a disputed point as to which of the teeth, posterior to the 
 cuspids, can be best spared from the mouth, and for these cases no 
 rule could be universally adopted. One must be guided entirely 
 by the circumstances existing in each individual case. For in- 
 stance, when the space between the lateral incisor and the first 
 bicuspid is equal to, or more than one-half the width of the crown 
 of the cuspid, and all the teeth are sound, the second bicuspid 
 should be removed ; when there is practically no space, or less than 
 that mentioned between these teeth, the first bicuspids are the teeth 
 to be extracted. If, however, the bicuspids are all sound, and the 
 first molars are badly broken down by caries, the removal of the 
 latter would be indicated, after which the bicuspids could be brought 
 back by suitable appliances. 
 
 Numerous forms of appliances are employed in correcting an 
 irregular arrangement of the teeth, as every case presents its own 
 peculiarities. Those which, in the experience of the writer and 
 
436 
 
 MECHANICAL DENTISTRY. 
 
 others, have proven most simple in construction and effectual in 
 treatment, will be described in detail. 
 
 When teeth have been removed for the correction of irregular 
 cuspids, and it is desired to hurry the operation, or where the bone 
 is too hard to permit nature to move the tooth sufficiently, appliances 
 such as are illustrated in Figs. 223 and 224 are usually employed. 
 The first, Fig. 223, was originally described by Dr. S. H. Guilford. 
 
 A platinum band, with short gold wires soldered to the buccal 
 and lingual surfaces, is cemented to the tooth to be moved, while 
 a similar one is attached to a molar or other anchor tooth. The 
 wires on the anterior band are bent forward, and those on the 
 posterior one are curved backward. Two rubber rings, caught 
 
 Fig. 223. 
 
 over the gold hooks, connect the two bands and yield the tractile 
 power required. These rubber rings can be removed and replaced 
 for cleansing the teeth, or can be renewed at will by the patient. 
 Two rings can be attached to each pair of hooks, if greater power 
 be required; or the same object can be attained by cutting wider 
 rings from thicker tubing. 
 
 The second method, introduced by Dr. E. H. Angle, and illus- 
 trated in Fig. 224, is a part of what is known as the " Angle system 
 of regulating " — one of the best, most complete, and simplest sys- 
 tems extant. 
 
 The first molar, or, when considered necessary, two teeth, may 
 be encircled by a metallic band, to which is soldered a piece of 
 tubing to accommodate the traction bar or screw. A band is also 
 
CORRECTION OF DENTAL IRREGULARITIES. 
 
 437 
 
 fitted to the cuspid ; to this a short tube is soldered on the palato- 
 distal portion, into which the bent end of the traction screw-bar is 
 
 engaged. The nut, which is operated against the distal end of the 
 tube, will readily move the tooth into position. 
 
 We sometimes meet with obstinate cuspid teeth, which refuse to 
 drop into line after the necessary room has been secured for them. 
 
 Fig. 225. 
 
 When this is the case, an appliance, such as is illustrated in Fig. 
 225, — the pull-back jack-screw devised by Dr. F. H. Lee. — 
 answers the purpose admirably. 
 
43§ 
 
 MECHANICAL DENTISTRY. 
 
 The post or nut shown in the side cut is set in position and held 
 by vulcanizing into a rubber plate as shown in the illustration ; 
 the screw-bolt is then placed through the post and a wire is passed 
 around the tooth, the ends being secured to the holes in the cross- 
 head or swivel-block. The wire is then taken up and tightened as 
 the tooth is brought into place. To prevent the plate from being 
 moved out of position by the strain upon it, it should be secured 
 to the teeth of the arch by ligatures. 
 
 Correction where the Cuspid Tooth is Inside the Arch. 
 — The power usually necessary to move an inlying cuspid is very 
 great. The jack-screw is, therefore, one of the forms of appli- 
 ances; this, however, may sometimes be aided by what is known 
 as the inclined plane. Dr. Angle's method is shown in Fig. 226. 
 
 Fig. 226. 
 
 Fig. 22j. 
 
 The base of the tube containing the screw-liar, or jack-screw, is 
 soldered to a band encircling the opposite cuspid and reinforced 
 by a spur resting against the first bicuspid (see illustration), and 
 also by the large traction screw, which is hooked into a pipe 
 soldered to the labial surface of the band and passing in front of 
 the incisors through a tube soldered to a band on the labial surface of 
 the incisors, against which the nut works. In this case, the left 
 central and lateral were moved forward in the line of the arch, 
 thereby closing the space between the centrals, and, at the same 
 time, providing space for the out-moving cuspid. The large screw 
 was beaten flat and polished before insertion. 
 
 The Inclined Plane. — One of the earliest methods employed 
 in correcting, or aiding to do so, where the superior cuspid or in- 
 
CORRECTION OF DENTAL IRREGULARITIES. 
 
 439 
 
 cisor teeth were interlocked, was what is known as the inclined 
 plane. This is formed of metal, by first striking up a saddle to 
 cover two or more of the lower incisors. To this, at the desired 
 point, is soldered an inclined piece of heavy metal, so directed that 
 when the appliance is cemented in position the inlocked tooth will 
 strike upon it in mastication and be forced outward into line. Fig. 
 227 shows a form of this appliance. 
 
 Fig. 228. 
 
 No, 2 
 
 No. 1. 
 
 Another device for the same purpose is that of Dr. T. Stanton 
 Holmes, wherein is combined the screw and spring methods. Fig. 
 228 shows the appliance in position. It is operated by the nut-fitting 
 ends of the wrench ; the turning of the screw causes a forceful 
 spring action to the extent only of the screw thrust, and so avoids 
 the common danger of spring action, which, if neglected, may carry 
 
44Q 
 
 MECHANICAL DENTISTRY. 
 
 the tooth too far. The screw is made by the substitution of a long 
 head No. 2, for the short head of No. 1. 
 
 Misplaced Bicuspids. — A simple method of moving bicuspids 
 into position when they are inside the arch is the simple jack- 
 screw of the Angle system. Another very ingenious method is the 
 Jackson crib and spring appliance.* Fig. 229 shows such an appli- 
 ance in position. A base wire is shaped to the lingual side of the 
 anterior teeth and anchored to the bicuspids by means of a single 
 " crib " appliance. To each of these latter is attached a hook or 
 eyelet to sustain a straight bar of spring wire that is sprung over 
 the anterior teeth. 
 
 Dr. Jackson gives another very simple fixture for the purpose of 
 
 Fig. 229. 
 
 Fig. 230. 
 
 moving a single bicuspid either inward or outward. It is shown 
 in Fig. 230. 
 
 A spring wire is bent in the form of a crib surrounding the mis- 
 placed tooth and an adjoining one on each side, passing well up 
 toward the gum on the labial and lingual sides, with the ends of 
 the spring wire terminating and overlapping upon the tooth to be 
 moved. The elasticity of the spring will exert enough force to 
 move the tooth. 
 
 Contraction of the Arch. — The enlargement of the arch by 
 lateral expansion may be accomplished by a number of methods. 
 Older practitioners usually make use of the Coffin split plate, but 
 
 * Devised by Dr. V. H. Jackson, of New York. 
 
CORRECTION OF DENTAL IRREGULARITIES. 
 
 441 
 
 it is the author's opinion that heavy, cumbersome appliances 
 should be discarded as far as possible. Among' the neatest and 
 most effective for this purpose are those devised by Dr. Eugene 
 Talbot and Dr. Angle. Dr. Talbot's method is as follows : 
 
 A vulcanite plate is made to fit the teeth and alveolar process, 
 and cut away so that the anterior parts extend far enough forward 
 to inclose the teeth to be moved. (See Fig. 231.) A piece of piano- 
 wire is bent into either of the forms shown in Fig. 232, wherein a 
 is the coil and fixed point ; b b, movable arms extending from a, 
 and c c, movable arms extending from b b. Grooves are cut into 
 the anterior and posterior parts of the plate to correspond with and 
 receive the points b b and c c. Holes are drilled at these points, 
 
 Fig. 231. 
 
 and the wires tied to the rubber plates. In order that the anterior 
 teeth may be moved with the greatest force, the arms are so ad- 
 justed that the greatest pressure is exerted on the anterior parts of 
 the plate. This appliance is readily removed for cleansing and 
 returned to place by the patient. 
 
 Dr. Angle's method utilizes the principle of the Coffin spring 
 without the objectionable features of the rubber plate. It can be 
 used either in the upper or lower arch ; and where no greater power 
 than the spring affords is needed will prove very efficient. As seen 
 in Fig. 233 a rubber ligature may be attached to the center of the 
 spring and be connected with any cross-bar appliance upon the 
 incisors for drawing them inward when such additional movement 
 is desired. 
 
442 
 
 MECHANICAL DENTISTRY. 
 
 A very excellent method of spreading the arch is that practised 
 by Dr. C. Heydenhauss, Dentist to the Court of H. R. M., the 
 Grand Duke of Sachsen-Weimar. 
 
 In a recent interview with Dr. Heydenhauss, he explained his 
 
 Fig. 233. 
 
 methods to the editor as given below. The Doctor has made use 
 of the continuous gold-caps in this work, as illustrated in Figs. 234- 
 237, for several years, and presented the same to the Odontological 
 Society of Geneva, Switzerland. It consists, first, of capping the 
 teeth on both sides of the mouth, from the cuspids back to 
 
 Fig. 234. 
 
 ^ WMMWMMMWm 
 
 the second molars, with continuous shell-crowns. These crowns 
 are constructed of one continuous piece of gold plate, 22-carat. 
 The cuspid teeth, however, if they are to be forced outward, 
 only need covering on the palatine surface. This is all clearly 
 shown in Fig. 234. After the crowns are well fitted and fin- 
 
CORRECTION OF DENTAL IRREGULARITIES. 
 
 443 
 
 ished, two platinized gold bars are soldered to their palatal surface 
 and shaped according to the form of the palatine vault. To 
 one side a heavy screw-bar is soldered, while to the other a short 
 hollow tube, to receive the free end of the screw-bar, is attached. 
 The screw-bar is provided with a nut, which, after the crowns 
 have been securely set with cement, is turned up on the bar until 
 moderate pressure is exerted. This nut is then given two or three 
 turns, three or four times a week, according to the case in hand. 
 The appliance in position is shown in Fig. 235. 
 
 When it is desirable to expand the lower maxilla, continuous 
 •crowns are made as has been directed, but to each of these an open 
 
 Fig. 235. 
 
 'Cylinder is soldered to the lingual surface. This is done by fit- 
 ting and soldering a gold tube over a piece of piano-wire of the 
 same size as the wire which is to exercise the traction. After this 
 is done, the gold tube is cut in its long axis, by which we get the 
 open cylinders. The posterior ends of these tubes are closed so 
 as to receive the ends of the traction wire when in position. When 
 the crowns are secured in position with cement, a piece of piano- 
 wire, previously shaped from the cast or die, is sprung into the open 
 tubes. To exercise the necessary traction, the wire must be slightly 
 spread before placing it in the mouth. 
 
 The placing of this wire requires some skill, but is, however, 
 easily understood. To prevent oxidation the wire can be gold 
 
444 
 
 MECHANICAL DENTISTRY. 
 
 plated. The wire should be taken out every two or three days 
 and slightly expanded, then replaced. This appliance is shown in 
 
 Figs. 236 and 237. 
 
 Protrusion of the Upper Jaw. — One of the most efficient meth- 
 ods of reduction in superior protrusion is that given by Dr. Angle*. 
 
 Fig. 236. 
 
 It consists of anchor bands (D, Fig. 238) for the molar teeth,, 
 with long tubes soldered to their buccal surfaces to receive the 
 wire bow-spring, which rests in front in notched projections upon 
 the bands cemented to the central incisors. At the center of the 
 bow-spring is soldered a short tube, having upon its labial sur- 
 face a rounded projection to receive the standard (cupped at its free 
 
 Fig. 237. 
 
 end) of the long traction bar, Fig. 239. In use, the clamp bands 
 (D) are attached to the anchor teeth, and the plain bands (A, A) 
 cemented to the central incisors. The bow-spring is now placed in 
 position. 
 
 Occipital resistance is obtained by means of a netted cap, fas- 
 
CORRECTION OF DENTAL IRREGULARITIES. 
 
 445 
 
 tened to a circle of wire fitted to the head, to which are attached 
 rubber bands. When the cupped standard of the traction bar has 
 been placed over the central spur of the bow-spring, the rubber 
 bands of the cap are drawn forward and looped over the curved 
 ends of the traction bar, as shown in Fig. 240. This cap, traction 
 bar, and rubber bands, are worn only at night, on account of their 
 
 Fig. 238. 
 
 conspicuousness. During the day, rubber rings (B, Fig. 238) are 
 caught over the tubes on the molar bands and secured by ligatures 
 to projections on the bow-spring in the region of the cuspid teeth. 
 The appliance in position, as worn during the day, is illustrated by 
 Fig. 241. 
 
 After reduction of anterior protrusion we are met with the diffi- 
 culty of retaining the results gained. Although the posterior teeth 
 
 Fig. 239. 
 
 in many cases will not furnish the resistance necessary for drawing 
 the anterior teeth inward, they will usually answer perfectly for 
 retaining them afterward. Attachment can be made to them either 
 by means of a rubber plate covering the roof of the mouth and 
 extending around their distal surfaces in the form of a clasp, or by 
 means of metal bands or caps cemented to them. In the former 
 
446 
 
 MECHANICAL DENTISTRY. 
 
 case, a small round, or half round, gold wire may be made to pass 
 around the arch, touching the regulated teeth on their labial sur- 
 
 Fig. 240. 
 
 Night appliance. 
 
 faces, and be attached at each end to the rubber plate at convenient 
 points — as where teeth have been extracted. In the latter case, a 
 
 similar retaining wire may be soldered to the molar bands, or the 
 
CORRECTION OF DENTAL IRREGULARITIES. 
 
 447 
 
 bands may have tubes soldered to their buccal surfaces and the 
 wire, threaded at the extremities, passed through these and re- 
 tained by means of nuts operating upon them. In either case, the 
 retaining wire should have short gold clips attached to it in front 
 to engage with the cutting edges of at least two of the incisor teeth. 
 
 When it is desired to avoid having a retaining wire pass entirely 
 around the front of the arch, a rubber retaining plate may be made 
 with a gold T passing between the centrals, and long enough to rest 
 upon all four of the incisors. Holding these teeth firmly in place 
 will also keep the cuspids in line through lateral pressure. 
 
 The principal appliances of the Angle system are manufactured 
 and kept in stock at the dental depots. There are certain portions, 
 however, which have to be united or soldered to suit the case in 
 
 Fig. 242. 
 
 Fig. 243. 
 
 hand, and as these fixtures are made as light and delicate as pos- 
 sible, some care is required in handling them. 
 
 In uniting the parts of the appliance with solder, a fine, sharp 
 flame from a Bunsen burner is most desirable, as both the hands 
 are free and can be used in holding the pieces. Notwithstanding 
 many ingenious spring clamps and devices have been invented for 
 holding such small work while soldering, yet the method of hold- 
 ing them with the fingers is greatly to be preferred, as it is much 
 easier and simpler, steadying the hands by touching the fingers 
 together, as shown in Figs. 242 and 243. 
 
 In writing of this subject, Dr. Angle says: 
 
 "The small tubes are best held by slipping them on to the end 
 of an excavator shank, or, what is just the ideal, one of Gates' 
 
448 MECHANICAL DENTISTRY. 
 
 nerve drills after the cutting point has been broken off. It is so 
 slender that but little of the heat is absorbed. Two of these 
 handles may be employed when a couple of the small tubes are 
 soldered, or the pliers may be used for holding one of them. (See 
 Fig. 243.) 
 
 " I should judge it not difficult to learn this method of soldering; 
 the only point which at all may perplex the beginner is to hold the 
 pieces immovable just at the time solder is congealing, but this can be 
 done by touching the fingers of the opposite hand in order to steady 
 and prevent all motion at the point of union, and at the same time 
 holding the pieces gently, not rigidly, just as a good penman holds 
 a pen. After a little, any of the combinations may be easily made 
 in a very few minutes. Where the ends of small tubes are to be 
 secured, it is best to first fuse the solder upon the band, and then 
 hold the small tubes, by means of the soldering pliers, in con- 
 tact with the solder and again apply heat, otherwise the solder will 
 be drawn into the tube. The solder best adapted in uniting the 
 different parts of these appliances is the ordinary jeweler's silver 
 solder, although 18-carat gold solder may be used. Plenty of 
 borax should always be used as a flux. Scrape bright the silver 
 solder and the points to be soldered, and borax both. Never use 
 more solder than is necessary, especially in attaching the small 
 tubes; use just sufficient to make the union. 
 
 " Always avoid overheating; just enough heat from a small flame 
 to thoroughly fuse the solder is all that should ever be employed. 
 In every instance avoid heating the screws or nuts. This is to be 
 especially observed with the jack and traction screws, as great care is 
 observed in their manufacture to produce the greatest stiffness and 
 strength, and this fine temper is ruined by heating." 
 
 Protrusion of the Lower Jaw. — When this deformity is slight, 
 it may usually be corrected by drawing the lower incisors in and 
 the upper ones outward. Where the case is a pronounced one, 
 there is no remedy except the retraction of the entire lower jaw. 
 In many cases, however, the two measures can be combined to 
 advantage. 
 
 Method of Retraction. — It was for many years supposed that 
 the retraction of the inferior maxilla was brought about entirely 
 by a change effected at the angle of the jaw ; but some years ago 
 it was noticed by Prof. C. N. Peirce that where sufficient pressure 
 
CORRECTION OF DENTAL IRREGULARITIES. 
 
 449 
 
 was brought to bear a change was brought about in the temporo- 
 maxillary articulation. That is, if pressure was continued at the 
 mental region, it would cause resorption of the posterior wall of 
 the glenoid cavity, thus permitting the condyles to recede, and ar- 
 ticulate somewhat posteriorly to their former positions. 
 
 Through this fact, and the change that is brought about at the 
 angle of the jaw, we are enabled to correct one of the most 
 unsightly of dental deformities. The method of procedure is well 
 illustrated by a case brought before the Odontological Society of 
 
 Fig. 244. 
 
 
 l 
 
 New York by Dr. Geo. S. Allen. He says, in part : " As will be 
 seen from the photograph (Fig. 244), taken at the time the patient 
 was wearing this apparatus, it consists of two parts. For the lower 
 part I made a brass plate to fit the chin, having arms with hooked 
 ends reaching to a point just below the point of the chin. 
 These arms were arranged in such a way that the distance between 
 them could be altered at will by simply pressing them apart or to- 
 gether. The upper part consisted of a simple network, going over 
 the head and having two hooks on each side, one hook being 
 above and the other below the ear. When this apparatus was 
 29 
 
45° 
 
 MECHANICAL DENTISTRY. 
 
 completed and in use, there were four ligatures of ordinary elastic 
 rubber pulling in such a way as to force the lower jaw almost di- 
 rectly backward. The work proceeded very rapidly, so that at the 
 end of two months the irregularity was almost entirely cured." 
 
 A very good method of making the chin piece is that described 
 by Dr. Guilford. Take impression of the chin and from this make 
 a model. The model is then overlaid with a piece of trial-plate 
 wax, from which, after being varnished, a mold in sand is obtained 
 and a die and counter-die made. Between these a piece of soft and 
 heavy brass plate is struck up and drilled full of holes. After 
 fashioning heavy piano wires to cross the plate and extend suffi- 
 ciently beyond to form hooks, they are soft-soldered to the brass 
 plate and the latter covered with black silk, with a thick layer of 
 cotton batting laid between the two. 
 
 The enlarged size of the chin piece will admit of this. The piece 
 
 Fig. 245. Fig. 246. 
 
 thus padded will fit the chin and be soft enough to prevent pain 
 when pressure is brought to bear upon it. 
 
 Torsion. — The term torsion, when applied to the teeth, sig- 
 nifies that condition in which a tooth is found to be turned upon its 
 axis. Rotation refers to the act of turning a tooth so as to bring it 
 into normal position. Torsion, therefore, describes the condition, 
 while rotation refers to the operation. 
 
 Rotation by Rubber Rings. — In the accompanying illustra- 
 tions, Figs. 245 and 246, Dr. Guilford's method of employing bands 
 and rubber rings for rotation is given. Platinum bands were fitted 
 to the centrals, with a gold hook soldered to each at points that would 
 furnish the greatest amount of tractile power. After the bands 
 were cemented in place a rubber ring was stretched from tooth to 
 tooth, in the manner shown in Fig. 245. The malposed tooth was 
 thus readily brought into contact with its fellow, and at the same 
 time considerably straightened. After which it was retained by 
 the retainer shown in Fig. 246. 
 
CORRECTION OF DENTAL IRREGULARITIES. 45 1 
 
 Rotation by Spring Bar. — When the mesial angles protrude, 
 double rotation can be accomplished by the very simple and effec- 
 tual method recommended by Dr. Angle. 
 
 Upon each of the teeth to be rotated place bands with tubes sol- 
 dered to their labial faces near the distal angles. One tube is set 
 vertically and the other horizontally. A soft piece of piano or 
 German silver wire, bent to a right angle at one end, is inserted in 
 these tubes, and rotation is effected by the elasticity of the wire (Fig. 
 247). Once in position, the teeth are retained by inserting in the 
 tubes a suitably shaped piece of non-elastic gold wire, as shown in 
 Fig. 248. 
 
 Lack of Anterior Occlusion. — This form of irregularity is for- 
 tunately rare, as it is one of the least amenable to treatment. The 
 cause is usually the lack of alveolar development in the anterior 
 portion of the mouth, sometimes accompanied with an excessive 
 growth in the molar region. 
 
 Fig. 247. Fig. 248. 
 
 Treatment. — When the deformity is slight it may be corrected 
 by grinding off all the antagonizing points from the posterior teeth, 
 which will shorten the bite, bringing the anterior teeth closer to- 
 gether. If the third molars were in position and adding to the 
 trouble they should be extracted. Then, if necessary, one or more 
 of the remaining molar teeth upon either side of the mouth (those 
 in the poorest condition to be selected) may be devitalized, ground 
 down beyond the point necessary, and then covered with gold 
 crowns. 
 
 Where considerable grinding upon vital teeth is done and the 
 exposed dentine becomes quite sensitive, it may be obtunded by a 
 repeated application of either chlorid of zinc or nitrate of silver. 
 
 Unusual Forms of Irregularities. — The following cases of un- 
 usual forms of irregularities, illustrated in Figs. 249, 250, 251, and 
 252, were treated and described by Dr. Angle. The first, Fig. 249, 
 shows the manner of bringing a cuspid tooth out into line, that is, 
 
452 
 
 MECHANICAL DENTISTRY. 
 
 aiding it to erupt. The clamp band was fixed on the lower second 
 bicuspid. A very small hole was drilled into the cuspid, and a 
 short pin was set with thin cement. A common pin answers the 
 purpose, and the hole need not be deeper than the enamel if the 
 pin is accurately fitted to it. A rubber ligature was given the 
 patient, with instructions to slip it over the pins, as shown in the 
 
 Fig. 249. 
 
 engraving. The anchor tooth in this case is directly opposed by 
 the superior bicuspid. The anchorage is simple and efficient. 
 The ligature may be worn at night only, so as to interfere as little 
 as possible with speech and mastication, although some patients wear 
 it almost continuously. Too strong a ligature should not be worn, 
 as it might endanger the life of the pulp, but gentle traction should 
 be used, gradually directing the tooth into its proper position. 
 
 Fig. 250. 
 
 The direction of force to be exerted upon the tooth to be moved 
 will, of course, indicate which tooth in the inferior arch should be 
 selected for anchorage. Should the anchorage fall upon a tooth 
 with no antagonist there would, of course, be danger of loosen- 
 ing it. 
 
 Fig. 250 shows a case in which the anchorage was modified to 
 suit the conditions. A deciduous cuspid had been retained too 
 
CORRECTION OF DENTAL IRREGULARITIES. 
 
 453 
 
 long, causing the permanent cuspid to remain in the alveolar 
 process on the palatal side of the lateral incisor, necessitating a 
 complex movement of the tooth backward, outward, and down- 
 ward, requiring a very firm anchorage and a strong ligature. On 
 the inferior cuspid and- second bicuspid were fixed bands, having 
 
 Fig. 251. 
 
 pipes attached to their labial surfaces. A piece of the wire of suit- 
 able length was bent at right angles and hooked into the pipes, as 
 shown. The wire fits the bore of the pipe so accurately that in 
 cutting off the ends which emerge through them, each end spreads 
 sufficiently to prevent its coming out. A pin was soldered to the 
 
 Fig. 252. 
 
 wire about midway between the pipes. The ligature was stretched 
 from pin to pin, as seen in the engraving. 
 
 Fig. 251 shows a modification of this method of anchorage. The 
 anchor wire was made detachable and the pin dispensed with, the 
 patient slipping the wire through the ligature and into the pipes 
 upon retiring, and removing it during the day. A delicate band, 
 to which was soldered the pin, was fixed on the moving tooth. 
 
454 
 
 MECHANICAL DENTISTRY. 
 
 Fig. 252 illustrates a case in which the appliances used were 
 similar to those before described, but the wire anchorage was at- 
 tached to teeth in the same arch in which was located the malposed 
 tooth. The first bicuspid was banded and a pipe soldered to the 
 labial surface of the band, in which was hooked a piece of the wire, 
 the other end of the wire being bent so as to rest on the cutting 
 edge of the lateral incisor. A pin was soldered to this wire, as in 
 the case before described, and a rubber ligature stretched from pin 
 to pin. 
 
 Regulating Supplemented by Crown-work. — An interesting 
 case treated, and reported in the Dental Cosmos, by Dr. F. M. 
 Willis, is that of a young lady who, several years previous to 
 treatment, had the left superior lateral incisor and right first bi- 
 
 Fig. 253. 
 
 cuspid extracted by a dentist to correct a slight irregularity. The 
 result was that instead of remedying the condition, there was a 
 general settling in of the entire upper jaw, resulting in a much 
 worse condition than the first. The right superior central incisor 
 was the only one of the upper teeth that touched the lower. There 
 was a space of *4 °f an mcn between the upper and lower bicuspids 
 and molars when her jaws were brought together. (See Fig. 253.) 
 
 The patient was unable to masticate her food properly, and as a 
 natural consequence she was suffering from indigestion so badly 
 that she was unable to attend school, and her system was very much 
 run down. 
 
 A split plate, with a piano wire spring, was made to spread the 
 upper bicuspids and molars. The patient wore this appliance for 
 
CORRECTION OF DENTAL IRREGULARITIES. 455 
 
 six weeks, calling once a week to have the spring opened as the 
 case progressed. The upper molars and bicuspids were now di- 
 rectly over the corresponding teeth of the lower jaw, having been 
 spread about 34 oi an inch. 
 
 The cuspids occupied about the right position, so the next step 
 was to move forward the centrals and lateral incisor. A gold band 
 was fitted around the right central, with a spud resting behind the 
 other central and the lateral incisor. The left central and the lateral 
 incisor were somewhat twisted on their axes, so the spuds resting 
 behind them were bent so as to twist these teeth as they moved 
 forward. A plate was made, covering the molars and bicuspids, 
 with a piano wire spring resting in a notch in the gold band 
 behind the right central. This appliance was worn for a month. 
 The incisors were now straight on their axes, and were far 
 enough forward to allow them to shut outside the lower teeth. 
 Now when her jaws were closed there was less than -Jg of an inch 
 space between the bicuspids and molars of the upper and lower 
 jaws. 
 
 The lower molars and bicuspids were badly broken down from 
 decay, some of them having been filled half a dozen times. To 
 put them in good condition and raise their grinding surfaces 
 to articulate with the upper teeth, it was decided to crown them 
 with gold. The molars were capped in the usual way with gold 
 crowns. 
 
 In order to avoid too much show of gold on the bicuspids, 
 a new method was resorted to in crowning them. A gold band 
 was fitted around the tooth, extending about Jg of an inch above 
 the end of the tooth. An impression and bite were taken at the 
 same time by covering the tooth and band with plaster and closing 
 the jaws while the plaster was soft. The band and plaster were 
 removed intact, and Melotte's fusible metal poured into the band 
 and a pin stuck into the metal to hold in the plaster. The crown 
 was placed on the articulator, and the bite completed with Melotte's 
 metal and plaster. The plaster was now removed from the band, 
 leaving a metallic surface Jg of an inch below the top of the band, 
 against which to fit a porcelain top for the crown. In this case 
 an ordinary plain tooth, such as is used in vulcanite work, was 
 selected and ground to fit into the gold band and the right length 
 to articulate with the upper teeth. This porcelain tip was cemented 
 
456 
 
 MECHANICAL DENTISTRY. 
 
 into the gold band, and the whole removed from the articulator. 
 The fusible metal was heated a little, and readily came away from 
 the crown. Fig. 254 represents the finished crown. 
 
 These crowns were cemented on in the mouth and produced a 
 nice appearance, as nothing but the porcelain showed when the 
 mouth was opened, the lip and tongue entirely hiding the gold 
 
 Fig. 255. 
 
 A. Porce- 
 lain tip. 
 B. Gold 
 band. 
 
 band. A crown of this description is particularly advantageous 
 for the lower molars and bicuspids, especially where they need to 
 be brought up some distance above the natural tooth. 
 
 Such a crown can be made, with absolute accuracy, in one 
 hour, and there is no risk of a fractured porcelain, as no heat 
 is used. 
 
 Fig. 255 represents the case completed. 
 
 Reposing the Features in Orthodontia. — The science of ortho- 
 dontia, under the influence of modern methods of practice and 
 improved appliances, is now claiming a distinct field in dental art 
 and mechanics, embracing the esthetic contours of the face as 
 well as the movement and rearrangement of individual teeth. In 
 the ordinary practice of this branch of dentistry, not enough atten- 
 tion has been given to facial effects; the aim usually being simply 
 to bring the teeth to a more perfect occlusion, with little regard 
 to the movement of the roots, and the surrounding bony struc- 
 ture. In examining dental literature, little is found in regard to the 
 movement of roots, and methods by which it may be accomplished; 
 and it was not until Dr. Calvin S. Case presented his paper at the 
 World's Columbian Dental Congress that much of practical value 
 in the development of esthetic facial contours was established. 
 
CORRECTION OF DENTAL IRREGULARITIES. 
 
 457 
 
 To illustrate the possibilities in the treatment of dental irregu- 
 larities, we present an interesting case from among those we have 
 recently treated. It is that of a young man of eighteen, whose 
 mouth presented a very homely appearance. The upper jaw was 
 contracted upon the sides and very prominent in front, with very 
 large, protruding incisors and cuspid teeth. The median line of 
 the face, too, was nearly the width of a central tooth to the left, 
 giving the jaw a twisted appearance, as though the teeth had been 
 forced over in a body to the right. Fig. 256 gives a fair idea of 
 the appearance of the mouth when the work was commenced. A 
 bicuspid was extracted upon either side. The left cuspid was then 
 drawn back to the position formerly occupied by the first bicuspid 
 
 Fig. 256. 
 
 by an appliance similar to that illustrated in Fig. 223, page 436 ; 
 then the lateral incisor was brought over to the left, which was 
 followed by the centrals ; in this way the center of the teeth was 
 brought nearly to the median line of the face. The next procedure 
 was to band the molars and bicuspids upon either side, upon the 
 buccal surface of which a hook was soldered, directed backward; a 
 gold cap was then made with hooks directed forward, and cemented 
 upon the central incisors. Rubber bands were then brought from 
 the posterior hooks to those in the front of the mouth. Very light 
 bands were employed at first, which were gradually increased in 
 width and strength as the teeth moved inward and backward. 
 While this was being done a light jack-screw (of the Angle system) 
 was worn in the mouth, bringing pressure upon the second bicus- 
 
458 
 
 MECHANICAL DENTISTRY. 
 
 pids and molars, which gradually enlarged the arch, helping 
 to fill out the face upon the sides and giving the anterior teeth 
 more of an opportunity to move backward. After the anterior 
 teeth were drawn back as near to the normal position as we could 
 bring them, the pressure was relaxed by substituting much lighter 
 bands, which, with the jack-screw across the palate, were worn for 
 several months. When these fixtures had been removed, the lat- 
 eral incisors, which were turned slightly upon their axes, were 
 rotated by the means of ligatures, and a gold cap, covering the 
 lower half of the six anterior teeth, was made and cemented in 
 position. This was worn as a retaining appliance for six months. 
 The results, which were most gratifying, may be seen by compar- 
 ing Figs. 256 and 257. One of the most interesting points in rela- 
 tion to this case is that the work was completed without destroying 
 
 Fig. 257. 
 
 the vitality of any of the teeth, which is too often the case where 
 heavy, cumbersome appliances are employed and the teeth moved 
 too rapidly. While the retaining appliances were being worn, the 
 third molars were erupted as can be seen by referring to the illus- 
 trations. 
 
 Dr. Case's Methods. — From the paper referred to above we 
 have selected three of the most interesting and pronounced cases. 
 In this connection Dr. Case states that he is now able to correct, 
 with perfect certainty of success, any marked depression or pro- 
 trusion of the upper lip which is mainly due to a malposition of 
 the roots of the incisor teeth ; and further says : 
 
 " Instances are often observed among the youth who demand our 
 professional services which show a comparatively perfect alignment 
 and occlusion of the teeth, and yet because of the position of the 
 
CORRECTION OF DENTAL IRREGULARITIES. 459 
 
 roots, with a consequent abnormal depression or protrusion of the 
 adjoining bone, considerable imperfection of features and external 
 contour of the face is produced. These deformities are peculiar 
 and not common, but have rarely engaged attention with a view 
 of orthopedic treatment directed to the development of a more 
 esthetic facial form. In the instance of a marked depression of 
 the upper lip, as in Cases I and 2, they are often mistaken for a 
 prognathous lower jaw, because of the lack of proper fullness in the 
 central features of the face, which frequently affects the shape of 
 the nose and deepens the lines on either side. For the same reason 
 the cheek bones will at times appear abnormally prominent, giving 
 to the face a broad and flattened appearance, especially if the cus- 
 pids, being retarded in their eruption for the want of room, take a 
 more lateral and prominent position. If the lower teeth are in 
 proper relative position and the deformity caused, as is most com- 
 mon, by the lower incisors occluding in front of the upper, every 
 change desirable may be effected by an appliance attached to the 
 superior teeth alone. As an illustration of this, I call attention 
 to the models in Case 2. 
 
 " On the other hand, if the entire superior dental arch is narrow 
 and contracted, with a high palatal dome, the teeth long, uncrowded, 
 and not materially affected in position by occlusion, the face will 
 usually be long and narrow, the nose prominent, thin, and of the 
 Roman type (see Fig. 264, Case 1). In these cases the entire 
 dental arch and alveolus should be expanded, and the force so ap- 
 plied and controlled as to retain the teeth in an upright position, 
 especially in the process of carrying the anterior teeth forward, 
 which is of vital importance in the restoration of the features of the 
 face. The principal force, therefore, should be exerted upon the 
 anterior superior teeth ; and this force may be reciprocated by rub- 
 ber bands extending from the posterior part of the upper appliance 
 to the anterior part of an appliance that is attached firmly to all the 
 lower teeth. These bands can be made to exert almost any desired 
 force, according to the heft of the tubing from which they are cut; 
 and their positions being such as not to interfere with mastication, 
 they can be worn continuously. 
 
 " If the inferior dental arch is large, with the teeth occluding 
 outside of the alignment of the superiors, it may be reduced in 
 
460 MECHANICAL DENTISTRY. 
 
 size by the extraction of a bicuspid on either side and the anterior 
 teeth forced back to fill the space (see Case 1, Figs. 264 and 265). 
 If, however, the chin is abnormally prominent below the incisive 
 fossa?, teeth should not be extracted from the lower jaw, the prin- 
 cipal change to correct the facial deformity should be accomplished 
 on the upper jaw. 
 
 " I have abandoned all attempts after early childhood to reduce a 
 prognathous lower jaw by external pressure upon the chin, never 
 having derived the same satisfaction from this operation that others 
 claim. I find, however, that the rubber bands before mentioned, 
 extending from the upper to the lower appliance, can be made to 
 exert all the force the patient can stand at the glenoid fossse, and 
 doubtless this influence tends to force the lower jaw to a more 
 posterior position. Examples of deformities of this character and 
 their treatment are shown by Cases I and 2, which were selected 
 for the purpose of showing the varieties of protruding lower jaw 
 and teeth. 
 
 " On the other hand, with equal facility, I am able now to reduce 
 a protrusion of the upper lip at that point where it merges into the 
 nasal septum and orifices, when due to a malposition of the roots 
 of incisor teeth alone, causing an abnormal prominence of the ante- 
 rior nasal spine and incisive fossse. (See Case 3.) This position 
 of the roots of the superior incisors is not uncommon, even when 
 the antagonizing ends are in perfect position ; and often with the 
 production of quite a marked facial deformity. 
 
 " In like manner I am able to force the anterior inferior teeth 
 bodily forward, with the entire alveolar ridge in which they are im- 
 bedded. Instances are not rare where the point of the chin, the 
 upper lip, and the anterior superior teeth are relatively in proper 
 position, but with inferior teeth, from various causes, so posteriorly 
 placed as to produce an abnormally deep depression or curve in 
 that portion of the lower lip along the line of the incisive fossse. 
 By forcing the anterior inferior teeth forward, with the alveolus in 
 which they are imbedded, a more esthetic shape will be given to 
 the chin ; and this change, though slight according to measure- 
 ment, will often produce an improvement in the general appearance 
 of the face that is quite remarkable. The same is true, also, in a 
 posterior movement of the inferior incisor teeth and alveolus, when 
 
CORRECTION OF DENTAL IRREGULARITIES. 46 1 
 
 they are so anteriorly placed in relation to the point of the chin as 
 to obliterate the graceful curve of the lower lip. This is shown in 
 Case 1. 
 
 ;Ji ^ >t< ^ >i= -'fi $< ;K $' H" ^ 
 
 " Before describing the peculiar construction of the contouring 
 apparatus I use in these cases, I wish to say that I endeavor to 
 have all regulating appliances made as substantially and finished as 
 perfectly as a piece of jewelry. The bands are fitted to the natural 
 teeth with as much perfection — especially where they extend under 
 the free margins of the gum — as a band for a crown. I use German 
 silver principally, and heavily gold-plate the apparatus before 
 attachment. 
 
 " The limited area upon which force can be applied to a tooth, 
 compared to that portion covered by the gum and imbedded in a 
 hony socket, has made it next to impossible, with all ordinary 
 methods, to move the apex of the root in the direction of the 
 applied force; nor could this ever be accomplished with force 
 exerted in the usual way at one point upon the crown, however 
 near the margin of the gum it be applied, for the opposing margin 
 ■of the alveolar socket must receive the magnitude of this direct 
 force, and in proportion to its resistance it will become a fulcrum 
 exerting a tendency to move the apex of the root in the opposite 
 direction. 
 
 " But if, in the construction of the apparatus, a static fulcrum is 
 created independent of the alveolus at a point near the occluding 
 portion of the crown, while the power is applied at a point as far upon 
 the root as the mechanical and other opportunities of the case will 
 permit, the apparatus becomes a lever of the third kind, the power 
 being directed to a movement of the entire root in the direction of 
 the applied force." 
 
 This proposition is made plain by reference to the diagrams. 
 In Fig. 258 let A be a point upon a central incisor at which force 
 is applied in the direction indicated by the arrow, then will the 
 opposing wall, B, of the alveolar socket near its margin receive 
 nearly all of the direct force ; and in proportion to its resistance 
 will there be a tendency to move the root in the opposite direc- 
 tion. This proposition will also hold good even if we apply the 
 force at A, Fig. 259, or as far upon the root as may be permitted 
 "by attaching a rigid upright bar, C, to the anterior surface of the 
 
462 
 
 MECHANICAL DENTISTRY. 
 
 crown; the only difference being that we distribute the direct 
 force over a greater area. But if, as in Fig. 260, we attach to the 
 lower end of C a traction wire or bar, F, and further enforce the 
 mechanical principles of our machine by uniting its posterior 
 attachment to the anchorage of the power bar, P, we will have 
 neutralized our anchorage force materially and created an inde- 
 pendent static fulcrum at D. Our apparatus now will distribute: 
 
 Fig. 258. 
 
 Fig. 259. 
 
 its force over the entire root, and give us complete direction and 
 control of whatever power we put into it. The entire tooth can- 
 be carried forward bodily, or either end can be made to move the 
 more rapidly. The force thus directed to the ends of the roots 
 will have an increased tendency to move the more or less yielding 
 and cartilaginous bone in which they are imbedded. 
 
 Fig. 260. 
 
 An apparatus for moving the roots of the anterior teeth in a 
 posterior direction, as in Case 2, is constructed quite similarly, the 
 direction of the two forces being reversed. See Fig. 261. 
 
 Protruding Apparatus. — In constructing an apparatus for forc- 
 ing the roots and adjoining bone of the anterior teeth forward, 
 wide German silver banding material for the teeth should be 
 selected, that is, T7 . 5 f . f . or - 6 . -- of an inch in thickness. This. 
 
CORRECTION OF DENTAL IRREGULARITIES. 
 
 463 
 
 should be fitted to the crowns of the anterior teeth near the mar- 
 gins of the gum, perhaps extending beneath the margins on the 
 proximal sides. Then bars of No. 15 B. and S. G. wire, slightly 
 flattened, should be soldered to each of the bands in an upright 
 position, and bent so as to lie along the anterior surface of the 
 crowns from the apex to where the bars join the band; here they 
 should take a direction somewhat parallel to the gum, but free 
 from the surface to about y ] g of an inch above its margin, at which 
 point they should be flattened or thinned, so as to be more easily 
 
 Fig. 261. 
 
 Protruding apparatus in position. 
 
 bent forward, and firmly clasped around a rigid bar which is made 
 to extend from anchorage tubes attached to the posterior teeth. 
 See Fig. 261. 
 
 The upright bars are now made of slightly heavier material, and 
 made to rest in front of the power bar, and cut off even with its top 
 edge, when they are thinned and rounded, as shown in the illustration. 
 
 This bar, which should be very rigid, is drawn without anneal- 
 ing from a No. 9 extra hard German silver wire to No. 15 B. and S. 
 G. The ends are threaded in the No. 4 hole of the Martin screw- 
 plate, and the central portion is slightly flattened in the rollers. 
 
464 MECHANICAL DENTISTRY. 
 
 Then it should be bent so as to rest when in proper position in 
 the unclasped ends of the upright bars that have been left open 
 to receive it. Before placing it in position, the nuts should be 
 screwed on to work at the anterior ends of the tubes. 
 
 This apparatus can be made to exert an exceedingly powerful 
 force, but if put into practical use as it now stands, the ends of the 
 roots and the adjoining bony structure would not be forced forward, 
 notwithstanding the fact that the power is applied directly to the roots 
 somewhat above the crevices. The crowns and the body of the 
 roots, with a portion of the alveolus only, would be moved forward. 
 
 To complete the apparatus, therefore, the fulcrum should be 
 removed from the anterior alveolar plate and placed so that the 
 power can be applied between it and the ends of the roots to be 
 moved. In other words, the crowns should be restricted or con- 
 trolled in movement so that the applied force may be directed to 
 the roots alone. 
 
 This is accomplished by a second bar much smaller and thinner 
 than the first, but proportionately rigid, which rests in depressions 
 in the upright pieces along the occluding ends of the teeth. The 
 ends of the fulcrum bar are threaded and passed through tubes that 
 are soldered to the anchorage bands on each side below the power 
 bar tubes, with nuts which work posteriorly to the tubes. 
 
 Retruding Apparatus. — An apparatus for reducing a promi- 
 nence of the features by exerting a posterior force upon the roots 
 and alveolus of the anterior teeth, is constructed in a similar man- 
 ner to the one just described, with the following exceptions: 
 (1) The bands should be fitted to the crowns of the incisors near 
 their occluding ends, for the purpose of obtaining a more rigid 
 bearing in the changed application of force. (2) The lower ends 
 also of the upright pieces should be made to clasp the fulcrum bar. 
 (3) The nuts should be reversed in their relative positions to the 
 tubes. (4) The most difficult and equally important part of our 
 task will now consist in moving the roots of the cuspids, if they 
 are prominent, but their position is such if much force is applied 
 with the present arrangement of the apparatus, the bars will slip 
 through the clasps at the ends of the upright pieces. Therefore 
 some provision should be made to prevent this, which may be 
 accomplished by short sections of pipe clasped around and soft 
 soldered to the bars. 
 
CORRECTION OF DENTAL IRREGULARITIES. 
 
 46; 
 
 The most modern method of constructing the retruding appara- 
 tus is well shown in Figs. 262 and 263. 
 
 In considering the mechanical qualities of the contouring ap- 
 
 Fic. 262. 
 
 paratus outlined, we wish to direct attention to the fact that 
 the force expended at the anchorage attachments is largely neu- 
 tralized by the reciprocating influence of the two forces, and this 
 
 Fig. 263. 
 
 Retruding apparatus in position. 
 
 reciprocation is always equal to the power used on the fulcrum 
 bar in preventing a movement of the occluding ends of the 
 crowns. The balance of the power, which may be considerable 
 30 
 
Fig. 264. 
 
 November, 1892. 
 Fig. 265. 
 
 April, 1893. 
 Case i. — Half-tone copies of photographs of plaster casts, made before and after 
 (466; completion. 
 
Fig. 266. 
 
 Fig. 267. 
 
 November, 1892. April, 1893. 
 
 Model from occlusion impression. 
 
 Fig. 268. 
 
 Fig. 269. 
 
 After extraction of inferior bicuspids. 
 
 Fig. 
 
 270. 
 
 Fig. 271. 
 
 
 
 
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 flSS- 
 
 
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 m v 
 
 
 
 fe' 
 
 5k 
 
 Srv* 
 
 11 
 
 ■£# 
 
 
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 w "** 
 
 *^ ■■" 
 
 V %»<s 
 
 
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 v£I 
 
 Case i. — Notice the upright position of the superior teeth in Figs. 267 and 269, 
 notwithstanding the expansion and extension of the arch as shown in com- 
 paring Figs. 270 and 271. 
 
 (467) 
 
Fig. 272. 
 
 November, 1892. 
 Fig. 273. 
 
 June, 1893. 
 Case 2. — The entire operation in this case was accomplished with appliances at- 
 (468) 
 
 tached to the superior teeth alone. 
 
Fig. 274. 
 
 Fig. 275. 
 
 November, 1892. 
 
 June, 1893. 
 
 Fig. 278 
 
 Fig. 
 
 Case 2. — Notice the deep incisive fossre and the posterior position of the superior 
 incisors and alveolus, as shown in Figs. 274, 276, and 278, and compare with 
 Figs. 275, 277, and 279 ; the upright position of the incisors ; the forward 
 movement of adjoining bone. 
 
 Notice also, in this and other cases, the occlusion of the posterior teeth, before 
 and after treatment, showing that nearly all change has been produced ante- 
 rior to the bicuspids. (469) 
 
Fig. 280. 
 
 (470) 
 
 August, 1893. 
 Case 3. 
 
CORRECTION OF DENTAL IRREGULARITIES. 
 
 471 
 
 in the general movement of the parts, must be sustained by the 
 anchorage teeth, if not further neutralized by other auxiliaries. 
 
 When the central features of the face are depressed, with anterior 
 superior teeth occluding posteriorly to the lowers, accompanied 
 with the usual real or apparent prognathous lower jaw, great re- 
 ciprocating force may be beneficially obtained from the rubber 
 bands before mentioned. Rubber rings are cut from a ^ of an 
 inch rubber regulating tube of good heft, and passed over the pro- 
 jecting ends of the anchorage tubes on the upper appliance to 
 buttons on a lower appliance, opposite the first bicuspids. The 
 
 Fig. 282. 
 
 Fig. 283. 
 
 April, 1893. August, 1893. 
 
 Case 3. — In this case the roots, as well as the crowns, of the superior incisors 
 have been forced to a more posterior position, reducing the prominence of the 
 nasal spine of the superior maxillary and an exceedingly unpleasant fullness 
 of the upper lip where it merges into the nasal septum. See Figs. 280 and 
 281. 
 
 latter appliance may be so constructed that the force will be dis- 
 tributed to all the inferior teeth, and indirectly to the jaw, forcing 
 it to a more posterior position. Or it may be that the first bicus- 
 pids have been extracted, as in Case I, for the purpose of forcing 
 the six anterior teeth back. In either case the elastic force of the 
 rubber bands can be made to do effective work to the full extent 
 of their power on both the upper and lower jaws, neutralizing force 
 which otherwise would be expended upon a static anchorage. In 
 writing of this apparatus, Dr. Case says : 
 
 " They are useful also as an auxiliary to the reduction of a prog- 
 
472 
 
 MECHANICAL DENTISTRY. 
 
 nathous upper jaw by reversing their attachments. In these cases I 
 also make use of the occipital force, largely for the advantage I ob- 
 tain in forcing the anterior teeth further into their sockets. Cases 
 of prognathous upper jaw with protruding teeth are rare in which 
 there is not an abnormal prominence at the base of the nose of the 
 bones that sustain the septum and wings of the nose. When force 
 is applied to the crowns alone of the anterior teeth, this prominence 
 may become more pronounced, even though the position and appear- 
 ance of the teeth and the face are improved by the operation. 
 
 " In these cases, therefore, I consider it quite as important to 
 move the roots as well as the crowns of the anterior teeth, when 
 by so doing I find I am able to remove the entire deformity, and 
 greatly improve the general form of the face, as seen in Case 3. 
 
 " In giving a history of the cases I shall not enter into a specific 
 description of the methods employed in each particular case, but 
 will allow them ' to speak for themselves.' 
 
 " Case 1. — Ruby S., aged fourteen, commenced treatment Novem- 
 ber 22, 1892. Final models made April 25, 1893. Correction com- 
 pleted. 
 
 " Case 2. — Phcebe B., aged thirteen, commenced treatment No- 
 vember 29, 1892. Final models made June 3, 1893. Correction 
 completed. 
 
 " The entire change in this case was accomplished with the con- 
 touring apparatus on the upper teeth alone without auxiliaries. 
 
 " Case 3. — Helen S., aged thirteen, commenced treatment April 5, 
 1893. Final models August 13, 1893. Correction incomplete. 
 
 " In this case the masticating occlusion of the teeth permitted the 
 inferior incisors to strike the gums considerably posterior to the 
 superior incisors, making it necessary to lengthen the bite of the 
 posterior teeth and shorten the anterior. This was accomplished 
 by a plate covering the roof of the mouth, which received the bite 
 of the anterior inferior teeth, and by temporary crowns upon the 
 first inferior molars. A small but very flexible German silver wire, 
 with the ends resting in tubes in the buccal sides of the crowns, was 
 sprung down under hooks on the sides of the bicuspids and then 
 up over similar hooks attached to the incisors near their occluding 
 ends. This raised the bicuspids and tended to force the incisors 
 further into their sockets. 
 
 " A simple traction bar encircled the upper teeth with anchorage 
 
CORRECTION OF DENTAL IRREGULARITIES. 473 
 
 tubes and screws on the molars. At the same time a rubber piece 
 was fitted to the anterior superior teeth with occipital pressure, 
 which forced them and. the alveolus up and back. I soon found 
 that this apparatus forced the crowns of the teeth back only, with 
 an apparent tipping of the roots forward, increasing the facial 
 prominence at the base of the nose, since which time the con- 
 touring apparatus has been worn, with all the force directed to the 
 posterior movement of the roots alone. The case now promises a 
 perfect result, as may be seen by the models. (Figs. 280 and 281.)" 
 
CHAPTER XXX. 
 ARTIFICIAL CROWNS. 
 
 Introductory Remarks. — Though the proper construction of a 
 modern collar crown or bridge denture requires much scientific in- 
 formation, unusual skill, and sound judgment, a great portion of the 
 work entailed is necessarily done in the laboratory. It should, 
 therefore, have a place in every work embracing the subject of 
 dental prosthesis ; it demands, in fact, a distinctive place, as it 
 is one of the most important and exacting branches of dental 
 practice. 
 
 As Dr. George Evans has well said, modern crown- and bridge- 
 work, properly understood and properly performed, takes high 
 rank in dental art, and offers wide scope for versatility of talent 
 and inventive genius. The varied and complicated cases presented 
 for treatment frequently suggest to the expert novel contrivances 
 and methods of construction and application. Successful practice 
 of crown- and bridge-work depends upon a thorough mastery of 
 the underlying principles and expertness in the processes involved, 
 governed by sound judgment and perfect candor. When practised 
 by dentists possessing the requisite attainments and governed by 
 correct ethical principles, it gives results which are gradually 
 establishing its value, removing erroneous impressions, and insur- 
 ing a wide professional and public endorsement. 
 
 There are, however, limits to the utilization of these means of 
 support. There are many roots wholly unsuitable for the purpose. 
 The operation may be said to be valuable in proportion as the 
 artificially crowned root can be made comfortable, serviceable, and 
 durable. A pulpless root that is extensively disintegrated, or that 
 is greatly denuded from excessive absorption of the surrounding 
 alveolus, or very loose in consequence of extended destruction of 
 the investing membranes, cannot, in any sufficient degree, meet 
 these requirements. Between these extreme conditions on the one 
 hand, and those associated with partially crownless roots with the 
 
 474 
 
ARTIFICIAL CROWNS. 475 
 
 pulp intact, the investing membranes free from disease, the cervical 
 portions of the bony structure unimpaired by decay, and a firm 
 attachment to the socket, conditions representing, on the other 
 hand, an opposite extreme, there are graduations of normal and 
 abnormal states, which, while they may not exclude the operation, 
 must in some degree impair its value. Any estimate of the ab- 
 solute value of this method of substitution that excludes a recog- 
 nition of this fundamental truth is a false and unwarranted one, 
 and there can be no rational prognostication in these cases that 
 does not admit this truth as an essential element in forecasting 
 results. 
 
 Not only will results be modified by conditions immediately 
 associated with the root to be operated on, but also, to some extent, 
 by the general health of the mouth. Any abnormal states of either 
 the hard or soft tissues, or the presence of foreign deposits, will act 
 as predisposing causes in the development of unfavorable conditions 
 whenever the root operated on has, previous to curative treatment, 
 been morbidly affected, and especially if such diseased conditions 
 have been somewhat virulent and of long standing. It is best, there- 
 fore, in all cases to inspect the mouth carefully before attaching the 
 crown, and if any of the remaining teeth are found carious or in- 
 crusted with tartar, or the mucous membrane and gums are in- 
 flamed or otherwise diseased, appropriate treatment should be 
 directed to the correction of such abnormal conditions as may be 
 present. 
 
 In the less favorable class of cases, or where the root has been 
 previously diseased, though subsequently restored to a healthy con- 
 dition, any diathesis or constitutional tendency predisposing to in- 
 flammation or suppuration may become a factor in the develop- 
 ment of unfavorable results. Whenever this predisposition exists 
 in any marked degree, the operation should be performed in the 
 most careful manner, avoiding, as far as possible, all sources of 
 irritation in the use of stones, saws, drills, and in tapping and 
 malleting, and especially in the use of excising forceps for the re- 
 moval of any remaining portions of the crown. Should any ten- 
 derness or loosening of the root supervene after its necessary 
 preparation, and before setting the crown, it will be prudent to 
 defer the completion of the operation until there is a subsidence of 
 the morbid conditions, for if, by reason of such irritation or in- 
 
476 
 
 MECHANICAL DENTISTRY. 
 
 Fig. 284. 
 
 flammation, suppuration should be reestablished, it may be neces- 
 sary to free the pulp canal and renew treatment through the apical 
 foramen. 
 
 The success of the operation may also be greatly impaired by 
 careless, hurried, and injudicious manipulation; as where the re- 
 maining portions of the natural crowns of the tooth are violently 
 removed with excising forceps, by the unskilful use of instruments 
 in dressing the root, by drills in enlarging the central cavity, by 
 undue or misapplied force in the final adjustment of the artificial 
 crown, or, finally, by a faulty position of the tooth of replacement, 
 by which the root is subjected to injurious strain, either by lateral 
 pressure or premature closure against those of the opposite jaw. 
 By the operation of either or all of these causes, disease of a more 
 or less intractable character may be induced 
 which will impair the usefulness of the arti- 
 ficial organ and subject the patient to much 
 annoyance. 
 
 Preparation of the Root. — In the process 
 of preparing the root for the attachment of an 
 artificial tooth, all remaining portions of the 
 natural crown should first be removed with 
 suitable instruments. If the cervical portion 
 of the tooth is comparatively sound and un- 
 broken, this may be most expeditiously ac- 
 complished, and with less risk of injury to 
 the root, by cutting two parallel grooves, opposite each other, on 
 the labial and palatal surfaces, with a small circular saw, or a hard 
 rubber or rubber and corundum disc. These grooves should be 
 cut through the enamel deep into the dentine. Then, with the excis- 
 ing forceps, the cutting edges of which are placed in the grooves,, 
 the crown is readily severed from the root. 
 
 After the use of the disc and excising forceps, any remaining 
 portions projecting beyond the free margins of the gum should be 
 removed, and proper shape given to the end of the root. A flat- 
 edged corundum stone or what are known as the Ottolengui root 
 facers (Fig. 284) are the best for the purpose, and when in use the 
 stones should be kept constantly wet and free from clogging par- 
 ticles of tooth substance. The end of the root should be dressed 
 down, anteriorly, a little below the free margin of the gum, care 
 
ARTIFICIAL CROWNS. 477 
 
 being taken not to cause unnecessary laceration ; in this way 
 the artificial crown, when adjusted to the root, will unite so 
 intimately with the gum in front, in ordinary cases, as to render 
 exposure unnecessary. The surface of the root prepared in this 
 manner will present a concavity corresponding with the festoon of 
 the gum. 
 
 If a living pulp remains in the root, it will not ordinarily be 
 practicable — unless there is partial obliteration and consequent 
 recession of the pulp cavity as the result of ossific deposits — either 
 to cut off the tooth on a line with the gum, or even transversely, or 
 to dress the root even with the gum, without inflicting insufferable 
 pain. It will be necessary, therefore, under such circumstances, 
 either to devitalize and extirpate the pulp through the carious 
 opening in the crown before the latter is removed, or, if not ex- 
 posed by excising the tooth, through an opening into the pulp, made 
 with a drill revolved by the dental engine, after excision. 
 
 Devitalization of the Pulp. — There are several ways of extir- 
 pating a dental pulp. One of the older and still not uncommon 
 methods of operating consists, first, in devitalizing it with arsenious 
 acid and then removing it with a broach. Another method prac- 
 ticed by some is to thoroughly expose the pulp, apply cocain, and 
 then extract the pulp with a broach. 
 
 Excision of Crown and Instantaneous Extirpation of the Pulp. 
 — A somewhat heroic method, though one with which some opera- 
 tors have much satisfaction, by which a living pulp may be quickly 
 and successfully removed, with comparatively little pain, consists 
 in cutting the labial and palatal grooves as has been directed, mak- 
 ing them as deep as possible, without inflicting too much pain; 
 then, with the excising forceps, the cutting edges of which are 
 inserted in these grooves, the crown is quickly severed from the 
 root. This usually leaves the pulp fully exposed and paralyzed, 
 when a piece of orange wood — previously cut and shaped to about 
 the size of the canal, not larger, and the point saturated with 
 carbolic acid — is carefully placed against the exposed point of the 
 pulp and quickly driven, with one light blow from the mal- 
 let, into the pulp canal. When the wood is withdrawn, the 
 pulp often adheres to it ; if not, it may be quickly and painlessly 
 removed with a broach. In this operation the immediate paralysis 
 induced renders it comparatively painless. Still another method, 
 
478 
 
 MECHANICAL DENTISTRY 
 
 Fig. 285. 
 
 and a very satisfactory one, is to remove the pulp while the patient 
 is under the influence of a general anesthetic. 
 
 Preparation of the Pulp Canal. — After the removal of the pulp 
 the apical foramen should be thoroughly closed by any method 
 usually employed in root filling. A neglect of this impor- 
 tant measure will greatly endanger the success of the opera- 
 tion. 
 
 The proper treatment and preparation of the root having been 
 thus far accomplished, the canal of the latter should next be en- 
 larged for the reception of a dowel-pin. This is effected with an 
 ordinary fissure drill or root reamers (Fig. 285). 
 
 The natural opening in the root should be enlarged to the depth 
 of two or more lines, according to the length of the 
 root; and the orifice should be made large enough 
 to admit a support of sufficient size to secure the 
 crown firmly in position. The direction of the drill 
 in cutting should follow closely that of the natural 
 canal in the root, since but a slight deviation in this 
 respect may endanger the integrity of the latter by 
 too great a thinning, or actual perforation, of its walls. 
 The face of the root should then be given a suitable 
 shape for the reception of the form of crown to be 
 attached, the methods of fitting and inserting which 
 will now be considered, the simple or all porcelain 
 system being first taken up. 
 
 Porcelain Crowns. — The system of using all por- 
 celain crowns has a number of advantages, and at the 
 same time there are strong reasons, we think, for using another 
 system — known as the ferrule or collar crown — in all favorable 
 cases. 
 
 The porcelain crown is especially useful where an inexpensive 
 and quickly adjusted crown is necessary; or where some patho- 
 logical condition would seem to limit the probable permanency of 
 an operation, or, again, where a temporary crown is desired to 
 serve, as is sometimes necessary, until the patient or operator can 
 make suitable engagements for more permanent work. 
 
 The objections made to the use of this class of crowns for per- 
 manent work are that the pin or post upon which almost the entire 
 support of the crown is thrown acts as a lever in the root canal, 
 
ARTIFICIAL CROWNS. 479 
 
 and sooner or later many of the weaker roots are fractured, thus 
 ending their usefulness as a support; and again, the pin or post, 
 entering, as it does, deeply into the body of the porcelain, weakens 
 it at this point, and not infrequently do patients return with the 
 crowns fractured through the center from the force of mastication. 
 Then, again, when the crowns are set with amalgam, which is the 
 practice of many, the discoloration at the line of union with the 
 root, if subsequently exposed, is very objectionable. 
 
 The all-porcelain crowns may be divided into two classes : First, 
 those having one end of the pin or post baked in the porcelain 
 when the crown is made, such as the Logan, Brown, and new Rich- 
 mond; second, those attached to the root by a pin, post, or screw, 
 one end of which is first cemented in the root and the other after- 
 ward to the crown. Of this class we have the Bonwill, How, Gates, 
 Foster, and Howland. 
 
 After deciding upon the form of crown to be used, one should 
 be selected to correspond as nearly as possible in size and general 
 configuration with its fellow on the opposite side, and to harmonize 
 in color with those immediately adjoining. The manner of prepar- 
 ing and adjusting each of the crowns named will be taken up in 
 the order given. 
 
 The Logan Crown. — The Logan crown, invented by Dr. M. 
 L. Logan, is probably of all these the one most extensively used. 
 The method of adjusting and mounting is given in all its details in 
 the following article by Dr. W. S. How : 
 
 " Fig. 290 shows a superior right central root, an end appearance 
 of the same, and a Logan crown, front view. Fig. 185 exhibits, at 
 a right angle to the plane of the first figure, the same root, its end, 
 and the Logan crown, side view. In both figures the root canal 
 is supposed to have been first drilled to a gaged depth with an 
 engine twist-drill, No. 154, and then enlarged by means of a fissure- 
 bur, No. 70, to the tapering form shown; the walls being subse- 
 quently grooved with an oval bur, No. 90. The enlarged section 
 (Fig. 292) shows the crown adjusted on the root by means of 
 cement or gutta-percha, which surrounds the post and fills all the 
 spaces in the root and crown. Fig. 293 shows the completed 
 crown. Fig. 294 exhibits a bifurcated bicuspid root, its end appear- 
 ance, and a Logan crown adjusted to the root. Fig. 295 illustrates 
 the best manner of bending the post. Fig. 296 shows a split post, 
 
480 
 
 MECHANICAL DENTISTRY. 
 
 and its adaptation to a bifurcated bicuspid root is seen in Fig. 297. 
 Figs. 298 and 299 exhibit the mode of mounting the Logan crown 
 
 Fig. 286. Fig. 287. Fig. 288. 
 
 Fig. 2i 
 
 Fig. 290. Fig. 291. 
 
 Fig. 292. 
 
 Fig. 293. 
 
 Fig. 294. 
 
 Fig. 295. 
 
 Fig. 296. Fig. 297. 
 
 on a superior molar root, and Figs. 300 and 301 the same crown 
 in its relation to an inferior molar root. 
 
ARTIFICIAL CROWNS. 
 
 481 
 
 " The preceding - figures clearly present to the mind's eye of the 
 expert dentist the essential features of the Logan crown and the 
 method of mounting it. 
 
 " The details are as follows : In every instance where a root is 
 deemed ready to receive its filling, it should first be measured 
 through its canal from the cervical opening to the apical foramen, 
 and this may be accurately done with a gage adjustable on a deli- 
 cate canal explorer. The same device serves to measure the 
 distance from the apex to which the canal should then be filled 
 (Fig. 286). It also gages the depth to which the drill may be 
 carried. The proper degree of enlargement from the bottom of 
 the drilled hole will, of course, depend on the observed size and 
 character of the root. Every dentist should familiarize himself 
 with generic tooth forms, so that when the length of an incisor, 
 cuspid, or other tooth root is known, he can so nearly determine. 
 
 Fig. 298. 
 
 Fig. 299. 
 
 Fig. 300. 
 
 Fig. 301. 
 
 its hidden outlines as to form with precision a corresponding en- 
 largement of the root canal, such as is shown by the several cuts. 
 For preparing the roots, the Ottolengui root reamers and facers 
 (see pages 476 and 478) are very desirable instruments. The 
 reamers are made in three sizes to correspond with the Logan 
 pins. With a root reamer of the appropriate size, the root canal 
 is enlarged to fit the pin along its whole length, and so hold 
 the crown firmly, independent of the cement. With a root facer 
 a labial slope is given to the root end, so that the crown neck 
 shall fit under the edge of the gum. Fig. 302 shows the method 
 and its result, and the cross-section shows how the cement in- 
 cases the pin. The suitable preparation of the bifurcated roots 
 of some bicuspids and of all the molars is a matter involving 
 difficulties of an unusual character and requiring good judgment. 
 The feasibility of splitting the post of a Logan crown to adapt it to 
 31 
 
482 
 
 MECHANICAL DENTISTRY. 
 
 the bifurcated root of a bicuspid is shown in Figs. 296 and 297. 
 This example directs attention to the peculiar shape of the post, in 
 which there is effected such a distribution of the metal that its 
 greatest strength is in the line of the greatest stress that will in use 
 be brought to bear on the crown, while the least metal is found at 
 
 Fig. 302. 
 
 the point of the least strain; the applied part of the post being in 
 outline nearly correspondent to that of the root itself. The root 
 canal is likewise conformably enlarged to receive the largest and 
 stiffest post which the size and shape of the root will permit. 
 
 " The fitting of a Logan crown to a root may be done with a 
 
 Fig. 303. 
 
 Fig. 304. 
 
 wet stump wheel in the engine hand-piece. A safe-side crown 
 corundum wheel (Fig. 303) can be used in the same manner. It 
 also affords the greatest facility for the slight touches required to 
 abrade the thin cervical borders of the crown, which may by this 
 means be done without encroachment on the post. 
 
ARTIFICIAL CROWNS. 483 
 
 " By the old method of adapting pivot teeth to roots, the close 
 fitting of the crown precluded the use of a plastic packing, because 
 its thinness over the surface of the joint made the packing liable to 
 break loose under the shock and strain of use. The recess in the 
 Logan crown obviates this defect by providing a receptacle for a 
 considerable interior body of cement that will be deep enough to 
 be self-sustaining internally, and yet allow the peripheral portions 
 of the root and crown to approach each other so closely that, though 
 only a film of packing remain, it will still be strong enough to insure 
 the persistent tightness of the joint. The annular boss, if formed 
 of amalgam, also adds strength in some cases to the mount. 
 
 " When enough of the natural crown remains, it is well to leave 
 standing some of the palatal portion, and cut the root under the 
 gum margin at only the labial part, as shown by Fig. 287. The 
 safe-side crown wheel is especially useful in such cases (Fig. 304). 
 Thus the labial joining of the root and crown will be concealed, and 
 the other parts of the joint will be accessible for finishing and keep- 
 ing clean (Fig. 288). The Logan crown may be ground until a 
 large part shall have been removed for adaptation to the occluding 
 tooth or teeth without seriously impairing its strength (Fig. 289). 
 This crown also in such cases maintains the translucency, which is 
 one of its peculiar excellences, owing to its solid porcelain body 
 and the absence of a metallic backing or an interior largely filled 
 with cement or amalgam. 
 
 " The distal buccal root of the natural superior molar is nearly 
 always too small to receive a post of any useful diameter, and there- 
 fore the Logan superior molar crown has but two posts, which, 
 like those of the inferior molar crown, are square, and thus may be 
 easily barbed, as may also the ribbed posts of the crowns from the 
 anterior tooth roots. These posts are large enough in all the 
 Logan crowns to answer in any given case, and can, of course, be 
 easily reduced to suit thin or short roots. 
 
 " Any of the cements or amalgams may be used in fixing these 
 crowns, but good gutta-percha, softened at a low heat and quickly 
 wrapped around the heated crown-post, which is at once seated in 
 the root, forms the best mounting medium, and has the great 
 advantage of permitting a readjustment, or, if need be, the ready 
 removal of the crown by grasping it with a pair of hot pliers or for- 
 ceps, and holding it until the gutta-percha is sufficiently softened." 
 
484 
 
 MECHANICAL DENTISTRY. 
 
 The Brown Crown. — This crown, invented by Dr. E. Parmley 
 Brown, is shown in Figs. 305 to 308. Fig. 305 gives a lateral view 
 of a porcelain crown, with an iridioplatinum pin baked in position. 
 The pin has great strength at the neck of the tooth, where the 
 strain is heaviest, and this strength is further increased by extend- 
 ing the porcelain up on to it, as shown in the accompanying illustra- 
 tions. 
 
 A front view of the same crown is illustrated in Fig. 306. The 
 dotted lines show the shape of the pin and the position which it 
 occupies in the crown. 
 
 The pin is flattened laterally, affording a strong hold in the porce- 
 lain without bringing it too near the surface in thin teeth, while it 
 also permits alteration of the palatal surface of the crown in a close 
 bite without risk of weakening: the bodv. 
 
 Fig. 305. 
 
 Fig. 306. 
 
 Fig. 307. 
 
 Fig. 308. 
 
 Fig. 307 is a view of the bicuspid crown, in which two pins are 
 provided, one for each root of two-rooted bicuspids. 
 
 Fig. 308 is a view of the same crown with the two pins pressed 
 together, forming a single pin of great strength for a single-rooted 
 bicuspid. 
 
 The double pin in the bicuspids prevents the gradual loosening 
 of the crown by the rotary movement of the jaws in mastication, 
 which, acting on the two cusps, exerts such leverage as to some- 
 times turn and break down ordinary crowns where only one pin is 
 used. 
 
 The roots are ground concave, to fit the crowns, with corundum 
 points or a Willard countersink bur, and close joints are made 
 well under the gum, the pins being set with oxyphosphate cement. 
 The canal should be enlarged just enough to admit the pin, which 
 should fit snugly throughout its entire length, the better to dis- 
 tribute the leverage exerted by the crown, and thus directly to in- 
 crease the strength of the attachment. 
 
ARTIFICIAL CROWNS. 
 
 485 
 
 The New Richmond Crown. — Dr. George Evans, in his treatise 
 on " Crown and Bridge Work," describes the new Richmond 
 crown as follows : " To illustrate and describe the method of 
 mounting this crown, a superior left central incisor root will serve 
 as a typical case, and its projecting end is to be shaped as seen in 
 Figs. 309 and 310. This can be rapidly done with a narrow, safe- 
 
 Fig. 309. 
 
 Fig. 310. 
 
 Fig. 311. 
 
 sided flat or square file, the angles of the slopes being such that 
 the gum on the labial and palatal aspects will not interfere with 
 nor be disturbed by this preliminary work, as the root end is not, 
 in this operation, to be cut quite down to the gum. An Otto- 
 lengui root reamer No. 2 is then employed to bore out the root to 
 receive the crown-post, which is of the same size and shape as the 
 Logan crown-post for a central incisor. 
 
 Fig. 312. 
 
 Fig. 313. 
 
 Fig. 315. 
 
 " The sectional view (Fig. 311) shows the relation of the reamer 
 to the root. The new Richmond crown (Fig. 312) is then tried on 
 the root (Fig. 313), and its position relative to the adjacent and 
 occluding teeth noted. If the cutting edge of the crown is to be 
 brought out for alignment with its neighbors, the root can be 
 drilled a little deeper, and the reamer pressed outward as it revolves, 
 
486 
 
 MECHANICAL DENTISTRY. 
 
 to cut the labial wall of the cavity. The palatal root slope must 
 then be filed to make the V correspond to the changed inclination 
 of the crown. 
 
 " Thus, by alternate trial and reaming and filing, the crown may 
 be fitted to the root and adjusted in its relations until the post has 
 a close, solid bearing against the labial and palatal walls of the 
 enlarged pulp chamber, and the crown slopes are separated from 
 the root slopes by the thickness of a sheet of heavy writing-paper. 
 This space can be accurately gaged, and the root slopes con- 
 formed to the crown slopes by warming the crown and putting on 
 its slopes a little gutta-percha, so that an impression of the root 
 end may be taken, and the root slopes dressed with a file until 
 the film of gutta-percha proves to be of equal thinness on both 
 slopes. 
 
 " To permanently attach the crown, Dr. Richmond usually takes 
 
 Fig. 317. 
 
 Fig. 31! 
 
 a thin, perforated disc of gutta-percha, pushes the post through it, 
 warms the crown, presses it into place, and when cooled removes 
 it, and with a sharp knife trims away the gutta-percha close to the 
 crown neck. He then warms the crown, puts a very little oxy- 
 phosphate cement on the post, and presses the crown home. Fig. 
 314 shows the completed crown." 
 
 The obvious advantages of the device are the readiness with 
 which the slopes of the root end may be shaped with a file ; the 
 facility with which these slopes may be given any angle to set the 
 crown out or in at the base, or at the cutting edge, or to give it a 
 twist on its axis; the certainty that, once adjusted, the final setting 
 will exactly reproduce the adjustment; the assurance that in use 
 the crown will not be turned on its axis, a most common cause of 
 the loosening of artificial crowns ; the firmness of its resistance 
 to outward thrust in the act of biting. This is made apparent by 
 
ARTIFICIAL CROWNS. 487 
 
 Fig. 315, wherein it will be seen that in an outward movement the 
 crown B would rock upon A as a pivot. The dotted line D shows 
 how the crown slope is resisted by the root slope, which extends 
 so far toward the incisive edge that a much firmer support is given 
 to the crown than if the resistance should be, as it usually is, on 
 the line of the gingival margin C. 
 
 For roots that have become wasted below the gum surface it is 
 not suitable, except in such cases as are decayed under the labial 
 or palatal gum margin only, but have yet projecting the approximal 
 portions of the crown (Fig. 316). 
 
 The sectional view (Fig. 317), and the perspective plan views 
 (Fig. 318) illustrate the manner of mounting these crowns on this 
 class of roots. The finished crown appears as in Fig. 318. 
 
 The cases for which this crown seems specially adapted are 
 such as have some considerable portion of the natural crown remain- 
 ing. 
 
 The Bonwill Crown. — This was one of the first crowns intro- 
 duced in improved porcelain crown-work. The process of its 
 adjustment and insertion is explained in a lengthy article by its 
 inventor, Dr. W. G. A. Bonwill, from which the following is pre- 
 sented : 
 
 " These all-porcelain crowns have three distinctive features : A 
 concave or countersunk base; a triangular opening from the base 
 to a point at or near the cutting edge of the incisors, the base pre- 
 senting to the labial surface (at its upper portion this groove is 
 enlarged) ; a peripheral margin or border resting perfectly flat on 
 the root, the concavity of the base on the palatal side being at a 
 much more acute angle than on the approximal sides. An 
 anchorage is made in the incisors by a depression or undercut 
 between the labial and palatal surfaces, opening on the latter. In 
 the bicuspids and molars the retaining pits are nearer the grinding 
 surface. 
 
 " The concave base of the crown prevents the amalgam from 
 escaping under the heavy pressure exerted to force it into position, 
 and in impacting the amalgam and expressing the mercury. It 
 allows of a dense body of material around the metallic pin, giving 
 the equivalent of a pin the whole diameter of the base of the 
 crown. It leaves no joint, the crown and root being continuous. 
 The amalgam is so thoroughly hardened at once by impaction in 
 
488 
 
 MECHANICAL DENTISTRY. 
 
 the double concave of crown and root as to make a very firm 
 operation. It prevents any possibility of the crown's twisting upon 
 the pin and root. In the event of fracture of the crown, the con- 
 vex surface of the amalgam on the root makes the substitution of 
 a new crown an easy operation. It enables the operator to fit the 
 crown in much less time ; it allows a proper position to be given 
 to the pin, with less danger of fracture therefrom ; it permits of a 
 larger quantity of amalgam in the crown, and is capable of bear- 
 ing greater strain ; it makes the permanent success of the operation 
 
 Fig. 319. Fig. 320. Fig. 321. 
 
 Fig. 322. Fig. 323. Fig. 324. Fig. 325. 
 
 " Fig. 319. — Sectional view of an incisor crown from mesial side, showing the 
 undercut at the point opening on palatal surface, the conical base, and the open- 
 ing of the same to the retaining grooves, with the exact relations. 
 
 " Fig. 320. — Palatal view of same tooth ; a is the external opening for egress of 
 alloy and for packing around the pin. The dotted lines show the recess or under- 
 cut on the mesial and distal sides and near the point for retaining the crown, and 
 its relation with the conical base. 
 
 " Fig. 321. — Grinding surface view of a superior molar with the countersunk 
 pin-holes on the buccal and palatal sides. 
 
 " Fig. 322. — Same view of an inferior molar with the pin-holes on the mesial 
 and distal sides. 
 
 " Figs. 323 and 324. — Sectional views of a molar and a bicuspid crown, show- 
 ing the countersinks and their relations with the conical base. 
 
 " Fig. 325. — Sectional view of an incisor root, showing the retaining cuts made 
 by the wheel-bur shown in Fig. 332. 
 
 probable, from the fact that it is absolutely jointless, and secures 
 immediate solidity, even while the amalgam is semi-plastic. These 
 crowns are capable of resisting the force of biting or mastication, 
 because they are supported nearly to the cutting edge or grinding 
 surface, the triangular opening from the concave base nearly to the 
 cutting edge allowing the pin to be imbedded in the labial face of 
 the crown where there is the greatest amount of porcelain. 
 
 " The amalgam to be used as the medium of union must set 
 quickly and be very hard. Thus far I have found nothing better 
 than the alloys I have specially prepared for this line of work, and, 
 
ARTIFICIAL CROWNS. 
 
 489 
 
 though they are costly, the superior results obtained by their use 
 amply repay the cost. I use No. 1 generally. If mixed thick, it 
 will set so quickly that the operator must work rapidly to prevent 
 its being wasted. In incisor cases I use No. 3 at the gum line and 
 make a close joint. 
 
 Fig. 326. Fig. 328. Fig. 329. 
 
 © 
 
 Fig. 327. 
 
 Fig. 330. 
 
 Fig. 331. 
 
 Fig. 
 332. 
 
 " Fig. 326. — End view of a canal prepared for the improved combination-metal 
 pin. 
 
 " Fig. 327. — End view of same canal as in Fig. 326, prepared for a triangular 
 pin, showing how much more of the mesial and distal surfaces have been cut 
 away from it than in Fig. 326 for the improved pin. 
 
 " Fig. 328. — Sectional view of an incisor crown and root, with the improved 
 pin in its relative position to each,* with the depressions made by wheel-bur. 
 
 " Fig. 329. — Sectional view of a superior molar, with the large angular pin in 
 palatal root and two square pins in the buccal roots, one being shorter and not 
 passing through the crown. 
 
 " Fig. 330. — Block of a molar and bicuspid, showing the countersunk holes for 
 pins in the molar, and the hole in the mesial side of the second bicuspid where a 
 pin is alloyed in and set into a decayed cavity in the distal surface of the first 
 bicuspid, being held upon the molar roots and attached to the bicuspid by the 
 alloy. 
 
 " Fig. 331. — Side and end view of the largest sized angular combination-metal 
 pin with the stamped serrations. f The square pins are without serrations and 
 double-pointed, made of the same metal and of equal thickness throughout. 
 
 " Fig. 332. — The smallest sized wheel-bur for grooving the canal for anchoring 
 the pin and alloy. 
 
 * The sectional views of the incisor and molar, giving the relative position of 
 the pins in the crowns and roots, should show pins of larger size. The pins as 
 furnished should be filed down but little. It is not absolutely necessary that so 
 many serrations should be made in the canals by the wheel-bur for retaining the 
 amalgam and pin as are shown in the sectional view of the root of an incisor. 
 While no serrations are shown in the roots of the molars, it is understood that all 
 the canals must have the serrations. The square pins in the canals need no ser- 
 rations. At the point where they occupy the countersink in the crowns, make 
 two or three very slight cuts on the edges with a sharp file. The ends can be 
 left blunt. 
 
 t These pins are now made without serrations. When amalgam is used for 
 securing them, they become amalgamated and firmly united. 
 
49Q 
 
 MECHANICAL DENTISTRY. 
 
 " In preparing the canal, use first a small-sized, spear-shaped 
 drill, carefully following the natural channel. Then follow with a 
 larger one, taking care not to cut through the root near the apex. 
 On the mesial and distal sides cut away but little, as there is where 
 fractures are most liable to occur. The canal can be very tapering 
 and yet hold the pin. There need be but very little space around 
 the pin. By all means save all the walls of the root possible. The 
 smallest sized wheel-bur may be used to make a thread at various 
 points along the canal to hold the amalgam. 
 
 " If the patient exposes the gums much in speaking or smiling, 
 the root may be cut down with the bur or corundum wheel beyond 
 the free edge, to conceal the joint. With bicuspids and molars it 
 is not necessary to go below the gum; a joint well made will not 
 be observed, and the strength of the root will be preserved. If 
 the root is decayed below the gum, after removing the softened 
 parts fill it with alloy. 
 
 " It is not necessary that the face of the root should be flat ; it 
 may be either concave or convex, according to indications. 
 
 "It is advantageous to take an impression and bite of the root, 
 and make a model and articulation in plaster. 
 
 " The crown to be inserted should be inspected closely, as the 
 retaining undercut in the incisors and the depressions in the bicus- 
 pids and molars may not be well defined. If not, the crowns are 
 liable to work loose. If the base has been ground off in fitting, the 
 edges should be beveled again to a fine margin with a corundum 
 point. The crown should be fitted to the root in the mouth, not 
 to the plaster cast. The articulation should be clear, to avoid dis- 
 placement. The pin should be as large as the previously prepared 
 canal will admit. The pin must in every case be fitted, and in fit- 
 ting it file only on the plain sides. Leave the end sharp, to offer 
 the least resistance in passing through the amalgam. The end of 
 the pin to be passed into the crown needs very little alteration. 
 The crown, being open on the palatal surface of the incisors, per- 
 mits a blunt-pointed pin to go up to its place. The middle of 
 the pin should not be interfered with if it can be avoided. It is 
 well to cut the pin a little short for incisors, as it may not get 
 pushed entirely up in the root through the amalgam. Small square 
 pins arc used in the bifurcated roots of bicuspids and in the buccal 
 roots of molars. They can be sharpened at both ends, but the 
 
ARTIFICIAL CROWNS. 49 1 
 
 outer end will not require so much sharpening. The palatal roots 
 of molars will generally take one of the largest thick pins, with one 
 square pin in the largest and most accessible buccal root. Each 
 canal should have a pin, if the canal can be reached and properly 
 prepared to receive it, even though the pin has to be so short as 
 not to pass through the hole in the crown. If it enters the counter- 
 sunk base it will support the root. The lower molars will require 
 two of the largest sized pins. As the support of the root is depend- 
 ent upon the size of the pin and the depth to which it is inserted, 
 single-rooted teeth should have the very largest thick pin. If the 
 root is thin on the mesial and distal sides, the thin, angular pin is 
 to be preferred. Ordinarily, these large pins do not have to be bent. 
 If necessary, it had better be done with a hammer and before the 
 mercury touches them. The pin should have free movement in 
 both root and crown. Should it be discovered that the pin is too 
 long after it has been packed in the root, it can be cut off with 
 sharp forceps, pressing them up against the pin to prevent displace- 
 ment. The pin can be sharpened subsequently with the corundum 
 wheel. 
 
 " To insure an amalgamation of the pin with the filling, brighten 
 the surface of the former before inserting. 
 
 " The roots, crown, and pins being in readiness and arranged on 
 the table, so that no mistake may occur from getting the pin in the 
 wrong position, and the appliances necessary for the operation 
 being at hand, the alloy preferred should be mixed a little thinner 
 than if intended for a filling, especially where the root has a long 
 canal. The shorter the canal, the thicker the amalgam may be 
 mixed. Mix only enough at one time for one root. Put enough 
 amalgam in the canal to nearly fill it, but do not pack it ; force into 
 it a steel pin made for the purpose, of about the same size as the 
 pin, to make way for the easier insertion of the latter. Then grasp 
 the pin with suitable forceps, and carefully but steadily press it up 
 to its destination. If you cannot succeed in doing so, remove it, 
 and again use the steel pin. When in place, use an instrument with 
 a point small enough to pass between the pin and the root, and 
 pack by tamping the amalgam around it. A piece of bibulous 
 paper placed over the point of the instrument will assist materially 
 in carrying the amalgam before it. Before the amalgam has be- 
 come too hard, replace the crown to determine that the pin is in 
 
492 
 
 MECHANICAL DENTISTRY. 
 
 proper position ; if not, it can be crowded to one side or the other 
 with the tamping tool. Should the pin be found to be rather long, 
 it can be ground off with the corundum wheel, holding it meanwhile 
 with the forceps. No attempt should be made to bend the pin 
 after it has been amalgamated, for fear of breaking it. If any 
 amalgam has been left, and it is still plastic, it may be packed 
 around the pin at the base of the root, using the bibulous paper 
 as before directed. If not, mix again to complete the operation. 
 Bank up the amalgam on the root high enough to fill the base of 
 the crown. The crown should now be tried on, and forced home 
 with an adjuster adapted to the case, removing the surplus amalgam 
 if too much, or adding if not enough. Remove and dry the crownj 
 and fill up simply the undercut cavity near the cutting edge if an 
 incisor, or the depressions in the crowns of bicuspids or molars, 
 allowing a very little to extend into the cervical base. Now force 
 it home with the adjuster. It requires considerable force to set one 
 of these crowns according to directions — a force which cannot be 
 applied with a mallet without danger of loosening or displacing the 
 crown. Steady pressure with slight rotation will carry the crown 
 into place, if the amalgam is not too hard or there is not too much 
 of it. I would advise you not to attempt to set a crown without 
 an adjuster or its equivalent. Free mercury will be squeezed out 
 on the palatal surface, which should be wiped off. Now hold the 
 crown in place with the fingers, with the bibulous paper under the 
 tamping instrument, and consolidate the amalgam around the point 
 of the pin in the crown, absorbing any free mercury which appears 
 there. The excess of alloy at the joint must now be removed, 
 care being taken to press the crown up while this is being done. 
 The amalgam packed around the pin in the crown on the palatal 
 side should be as stiff as may be to work readily. It is well to 
 leave over some of the first mixing for holding the pin, and this 
 will be about right for consolidating about this point. 
 
 " If, in a bicuspid or molar crown, the pin should come so far 
 through as to interfere with articulation, it may be ground off with 
 the corundum wheel while the crown is firmly held. 
 
 ' The case can now be dismissed, with directions for the patient 
 to return the next day, in order to make sure that the articulation 
 is correct and to dress off the joint between the crown and root, 
 which may be done with a small, round-headed bur. 
 
ARTIFICIAL CROWNS. 
 
 493 
 
 " There are some cases in which the root cannot be filled with 
 anything; if in a molar, the pulp-chamber can be relied upon to 
 hold a headed pin or pins. When a tap-hole is required in the 
 root it can be made low down and at an acute angle, and the amal- 
 gam packed around the root canal above the tap. 
 
 " Should an artificial crown be broken, another can easily be 
 substituted by burring off any excess of amalgam, and using fresh 
 amalgam, mixed thin, to allow of ready adjustment. 
 
 " Two crowns can be inserted on the root of one large molar with 
 the assistance of the decayed approximal surface of an adjacent 
 tooth (see Fig. 330)." 
 
 The Porcelain Dovetail Tooth Crown. — These crowns are 
 designed for the roots of bicuspids and molars only, and the process 
 of mounting them may be very briefly described : 
 
 " Fig. 333 shows the roots of an inferior molar after the apical 
 
 Fig. 333. Fig. 334. Fig. 335. 
 
 Fig. 336. Fig. 337. 
 
 Fig. 338. 
 
 portions have been filled, the neck recessed, the canals drilled and 
 tapped, and two How screw-posts firmly fixed therein, the ends of 
 the posts having been pinched toward each other by means of a 
 pair of pliers, so that they will go through the central opening in 
 the crown (Fig. 334). This opening is of a dovetail form, as 
 shown in cross-section by Fig. 335, where the crown is seen in 
 place over the posts on the root. It is thus made obvious that the 
 crown may be easily put on and off the root in the process of 
 fitting the crown-neck to the root-^ieck, and also that, for occlusion, 
 the crown may be ground low on any or all sides without destroy- 
 ing the dovetail function of the central cavity. When the fitting 
 is completed, and the crown cut so short as to be J~ of an inch 
 distant from the occluding tooth, amalgam is packed into the 
 neck recess, around the posts, and thinly over the cervical margin 
 of the root, the crown put in place, and, with thumb pressure, 
 firmly seated. Then test the occlusion, and complete the opera- 
 
494 
 
 MECHANICAL DENTISTRY. 
 
 tion by packing amalgam into the crown opening, which will 
 permit the forcing of the amalgam in all directions, to insure a firm 
 base for the crown and its secure dovetail attachment to the posts, 
 as shown by Fig. 335. 
 
 " The bicuspid crown (Figs. 336 and 337) is similarly mounted, 
 as may be seen in Fig. 338, cross-section ; the same crown and 
 root being shown in contour by Fig. 339. In some instances this 
 bicuspid crown may, like the Foster crown, be secured by a headed 
 screw, as shown in Fig. 340. The root having been drilled and 
 tapped and recessed, and the crown properly fitted and articulated, 
 the screw is put through the crown, amalgam packed in the crown 
 groove and around the screw, which is then inserted in the root, 
 and the crown pressed hard into its place. The screw is then 
 turned into the position shown in Fig. 340, thus compressing the 
 amalgam or cement in both recess and groove, after which the 
 
 Fig. 339. 
 
 Fig. 340. 
 
 Fig. 341. 
 
 Fig. 342. 
 
 screw-head may be covered with amalgam, cement, or gold, as 
 desired. 
 
 " As a preferable mode, however, the screw-post may first be 
 fixed in the root, the crown adjusted over the post, amalgam 
 packed on the root and around the post, the crown seated firmly, 
 more amalgam packed in the crown cavity around the post, and 
 then a nut screwed on the post, as shown in Fig. 341. In all the 
 sectional cuts cement, amalgam, or gutta-percha is to be understood 
 as filling the cavities in the conjoined roots and crowns. 
 
 " Fig. 342 shows in contour a dovetailed crown mounted on a 
 superior molar root in the manner shown by Fig. 335. It is 
 obvious that the crown of Fig. 335 might be ground quite down 
 to the post ends, and yet be firmly held by the dovetail sides of 
 the central cavity." 
 
 The Gates Crown. — The Gates crown is quite similar to the 
 
ARTIFICIAL CROWNS. 
 
 495 
 
 Bonwill crown. It is usually attached to the root, however, by a 
 metallic screw manufactured for the purpose, such as is illustrated 
 
 Fig. 343. 
 
 Fig. 344. 
 
 in Fig. 344, instead of the Bonwill pin. The screw is first inserted 
 in the root and the amalgam packed around it. In nearly all roots, 
 at a reasonable distance up the canal, a suitable place for fastening 
 the end of the screw can be found. Too much force 
 must not be applied in its insertion, as a root is easily 
 split. In bicuspid and molar crowns nuts are used on 
 the screws, which fit slots in the grinding surface of 
 the porcelain. They are screwed into the amalgam or 
 cement, and covered with it in the process of cementa- 
 tion of the crown. 
 
 The Foster Crown. — The Foster crown also resem- 
 bles the Bonwill, but has less concavity at the base. The crown is 
 attached to the root by a headed screw (Fig. 346) or a screw with 
 a nut, instead of the Bonwill pin. 
 
 Fig. 345. 
 
 Fig. 346. 
 
 The How screws and instruments (Fig. 347) are best adapted for 
 use with these crowns. 
 
496 
 
 MECHANICAL DENTISTRY. 
 
 Fig. 348. Fig. 349. Fig. 350. 
 
 The Howland Crown. — This crown is attached like the How 
 dovetail crown, with screws that are first inserted in the root. 
 It is used mostly on bicuspid and molar roots, and consists of a 
 hollow porcelain crown, with a cavity in the crown sufficiently 
 large to admit the screws or pins (Fig. 348) and, when necessary, 
 a small portion of the root. 
 
 The method of setting this crown, as described by Dr. S. E. 
 Howland, the inventor, is to trim the root even with the gum, with 
 
 a stump file (a corundum stone or the Ottolengui root- 
 Fig. 347. facer on the dental engine, however, is more suitable) ; 
 
 fit the crown to the root; enlarge the root canal so that 
 
 a threaded pin of proper size will pass in easily, partially 
 
 fill the canal with zinc 
 
 phosphate, and press the 
 
 pin to its place with pliers. 
 
 The crown should then 
 
 be filled with zinc phos- 
 phate and pressed to its 
 
 place, care being taken to 
 
 hold it in position until 
 
 the cement sets (Fig. 349). 
 
 If any operator distrust the ability of zinc phosphate to 
 
 make a perfect joint, a small quantity of silver amalgam 
 
 or gutta-percha can be used to advantage. 
 
 The mode of fastening is strong and simple, and 
 
 when set, if a good joint has been made, none of the 
 phosphate or other setting material is visible. It is a perfect imi- 
 tation of the natural tooth (Fig. 350). 
 
 PORCELAIN CROWNS WITH GOLD COLLAR ATTACHMENT. 
 
 A very good combination for some cases is to use a gold collar, 
 either seamless or soldered, in combination with any of the porce- 
 lain crowns. 
 
 The root having been properly prepared to receive a collar, it is 
 adjusted and adapted the same as for the Richmond crown (see 
 p. 503). The porcelain crown, the base of which should be fully 
 as large as the end of the root, is then ground even with the cer- 
 vical walls, and fitted into the collar, which should be trimmed 
 and burnished to the form of the crown. Dr. Townsend's fusible 
 
ARTIFICIAL CROWNS. 
 
 497 
 
 Fig. 351. 
 
 metal die, used in the following manner, facilitates the application 
 of a collar to a Logan crown (Fig. 351). Prepare the root canal 
 to receive the pin. Grind a suitable Logan crown to fit, and 
 articulate it. Construct a band of No. 30 gold (for instructions 
 see p. 505), which should be wide enough to project beyond 
 the end of the root %% of an inch. Cut a wooden peg about an 
 inch long and taper one end of it to the general size and shape of 
 the pin in the Logan crown. Place the band 
 on the root, insert the peg in the canal, and fill 
 up the band with Melotte's moldine, pressing it 
 closely about the peg. Remove all together, 
 and, holding the die over the flame of an alcohol 
 lamp to melt the fusible metal, place them alto- 
 gether on the die, with the pin in the socket, 
 and press down until the moldine rests on the 
 surface of the molten metal. Then carefully 
 chill the tooth; in cooling, the fusible metal take's a firm hold on 
 the lower edge of the gold band, holding it securely in place during 
 the remainder of the operation. Now remove the peg and the 
 moldine, and with a wooden mallet drive the Logan crown into 
 the band until the porcelain rests upon the fusible metal. Burnish the 
 band smoothly about the crown. When it is perfectly adjusted to 
 the porcelain, melt the fusible metal to release the band and crown. 
 
 Socket. 2. Fusible 
 Metal. 
 
 Fig. 352. 
 
 Fig. 353. 
 
 Fig. 354. 
 
 Fig. 355. 
 
 If the work has been carefully done, the crown will then be ready 
 to be adjusted in the mouth. 
 
 Enough of the labial portion of the band should be trimmed 
 away to prevent too conspicuous exposure of the gold (Fig. 
 352). 
 
 This collar combination is available in very difficult cases, as, for 
 32 
 
498 MECHANICAL DENTISTRY. 
 
 instance, when a root is decayed upon one side beneath the gum 
 margin, as seen in Fig. 353. 
 
 This operation, when completed, would appear in vertical sec- 
 tion like Fig. 354, and a view in perspective would resemble Fig. 
 
 355- 
 
 Dr. E. C. Kirk's method of combining the porcelain crowns 
 with a band or collar, is shown in Figs. 356 and 357. Here the 
 Foster crown is employed. First a collar is made and fitted to 
 the root; it is cut narrow on the labial side, and left wide on the 
 lingual, so that it shall extend nearly to the cusp of the crown when 
 finished (Fig. 357). The seamless gold collars are well suited for 
 application to this style of crown. 
 
 The crown selected should have a somewhat greater circumfer- 
 ence at the base than the collar, so that when ground down some- 
 
 Fig. 356. Fig. 357. 
 
 what conically on its lingual and approximal surfaces it can be 
 tightly adjusted to the collar, which would be impossible if a 
 crown smaller than the collar is used. The screw is fitted so that 
 it will hold the crown in proper relations with the root. It is then 
 removed with the crown, the parts dried, and the root canal filled 
 with a slow-setting oxyphosphate cement. The crown is then 
 pressed home, the surplus cement flowing through the opening in 
 the porcelain and filling up any interstices around or between the 
 band, the root, and the crown. The screw is then forced to posi- 
 tion, and, when the cement is set perfectly hard, the head of the 
 screw or the nut on it is notched to form a retaining pit, and the 
 countersink of the crown filled with gold. 
 
 Dr. C. S. W. Baldwin's method is to cap the root and attach a 
 Logan crown in the following manner : 
 
 First, the root is shaped for the proper adaptation of the band. 
 
ARTIFICIAL CROWNS. 
 
 499 
 
 The band and cap are then made as directed for the Richmond 
 crown on page 503. The edges are then trimmed to fit the fes- 
 toon of the gum ; a hole drilled from the inner side for the pin, 
 leaving the raggedness made by drilling to catch in the cement. 
 Place the cap on the root and fit the porcelain crown accurately to 
 it in the desired occlusion and position. Fig. 358 shows a root, 
 cap, and a Logan crown. A crown having the H-shaped pin, but 
 square on the edge, like some of the early patterns of Logan or 
 Bonwill crowns, would reduce the time of setting and give best 
 results. Having polished the edges of the cap, the crown may be 
 conveniently adjusted as follows : Place oxyphosphate cement in 
 the countersunk portion of the porcelain, and in the canal only 
 
 Fig. 358. 
 
 Fig- 359- 
 
 Fig. 360. 
 
 Fig. 361. 
 
 enough cement, of creamy consistency, to fill it, as the pressure 
 required to force out the surplus under the edges of the cap destroys 
 many nicely adjusted crowns, leaving bulging irritants instead of 
 smooth supports. If proper attention has been given to fitting the 
 crown and root, all will come nicely to place; but in some cases of 
 difficult adjustment it may be necessary to cement the crown to the 
 cap before fastening the pin in the root (Fig. 359). 
 
 In most cases the gold band will be invisible and below the free 
 margin of the gum. There are instances, where the anterior teeth 
 are prominent, in which it will be necessary to cut away the top of 
 the cap in front, allowing the porcelain to come directly in contact 
 with the root, the band going deeper than in ordinary cases, which 
 prevents the appearance of gold (Fig. 360). 
 
500 
 
 MECHANICAL DENTISTRY. 
 
 Dr. Bomvill's plan is to cap the tooth with a platinum or gold 
 cap having a slot, into which the pin passes as it is slipped on the 
 root (Fig. 361). The crown is then secured with amalgam in the 
 usual way. 
 
 Dr. Sidney S. Stowell's method is as follows : Make a closed 
 cap, using the combination crown metal, and place it upon the root. 
 The cap is then perforated and the root reamed for the dowels. 
 The bite in wax is now taken, after which the cap is burnished into 
 the countersunk end of the root (Fig. 363). The dowels of plati- 
 num and iridium wire are now set in their places, being allowed to 
 project ]/\ of an inch so that they may adhere to the impression 
 of plaster which is then taken. From this a cast is made of invest- 
 ing material ; calcined marble-dust and plaster is preferable, though 
 fine molding sand will do. The dowels are now cut off even with 
 the top of the cap (Fig. 364). 
 
 Fig. 362. Fig. 363. Fig. 364. Fig. 365. Fig. 366. Fig. 367. Fig. 368. Fig. 369. 
 
 The tooth to be used may be a Logan or Brown crown, or a 
 common countersunk tooth. As the case in question is a bicuspid, 
 we have selected for it a Logan crown. First, cut off the pin, and 
 then the tooth is ground into position on the cap ; grinding the 
 stump of the pin and porcelain alike evenly and smoothly. The 
 stump of the pin is now ground with a small wheel below the sur- 
 face of the porcelain (Fig. 365). The tooth is invested (Fig. 366), 
 and pure gold fused on to the platinum pin, and while in a fluid state 
 it is, with a wax spatula, spatted down flat (Fig. 367). The gold is 
 filed or ground down even with the porcelain, and at the palatal bor- 
 der the tooth is ground to bevel back until the gold is reached (Fig. 
 368. The tooth is now fastened in place on the cap with wax 
 cement (Fig. 369), the cast cut away, and the case invested in 
 asbestos and plaster (Fig. 370). This is used because of the fiber 
 of the asbestos, which prevents the separation of the crown and 
 cap. The wax is removed with boiling water, or is burned out, the 
 
ARTIFICIAL CROWNS. 
 
 50I 
 
 case thoroughly heated up, then a small clipping of thin platinum: 
 plate is crowded into the opening (see Fig. 370) caused by the 
 grinding of the bevel on the crown. The clipping of platinum 
 serves as a lead for the solder, which follows it down into the 
 countersunk cap, around the ends of the dowels, and finally 
 attaches itself to the pure gold already firmly attached to the stump 
 of the platinum pin. When cool the case is removed from the in- 
 vestment, dressed and polished (Fig. 371). A sectional view of a 
 like tooth (Fig. 372) shows the organization in detail. 
 
 Fig. 373 shows a central incisor root on which a Logan crown is 
 used after this method. Fig. 374 shows how delicately an operation 
 of this kind may be performed upon an inferior central incisor, by 
 the use of the countersunk tooth crown, which is shown as it 
 appears before gold has been melted in its cup around the pin; 
 when the cup has been filled with gold, and after the crown has 
 
 Fig. 370. 
 
 Fig. 371. Fig. 37; 
 
 Fig. 373. 
 
 Fig. 374- 
 
 Fig. 375. 
 
 been ground and beveled. A countersunk molar. crown is shown 
 as likewise mounted on the roots of a superior left second molar 
 
 (Fig- 375)- 
 The cuts are made from photographs of prepared specimens, the 
 
 natural roots of which vary in the several figures; and in the sec- 
 tion (Fig. 371) the continuation of the pulp canal does not appear, 
 because obliterated in preparing the section. 
 
 The claims for this method of crown-work are as follows : The 
 combination of an all-porcelain crown with a closed cap and dowels; 
 the adaptation of which crown and its final attachment to the root 
 can be made perfect. 
 
 The dowels may be set at any angle that the direction of the root 
 canal may indicate, using one or more dowels as the case may re- 
 quire, and when the root has to be cut off much below the gum, 
 and a collar cannot be placed, a platinum disc floor on the root 
 
502 
 
 MECHANICAL DENTISTRY. 
 
 end is the preferable plan. The well known and easily detected 
 plate tooth having a gold backing which renders the tooth dull in 
 appearance is thus made obsolete, for this crown possesses the trans- 
 lucent appearance of the natural organ. Best of all, the glaring 
 gold of which some so-called beautiful crowns are almost entirely 
 composed is by this means superseded. We here refer to gold 
 bicuspids and molars, more especially to the former; it was the 
 unsightly appearance of these which first led us to try and improve 
 on them. 
 
 While recognizing the unquestioned value of the closed cap and 
 dowel, we respectfully present a supplemental method which results 
 in a crown possessing all the merits of the former with additional 
 embodiment of strength, beauty, and practicability. 
 
 Dr. Shulze's Method. — Another method of crowning, by using 
 a plain rubber porcelain tooth in combination with a gold collar is 
 that described by Dr. Wm. H. Shulze, Atchison, Kansas. The 
 
 Fig. 376. Fig. 377. Fig. 378. Fig. 379. Fig. 380. Fig. 381. Fig. 382. Fig. 383. 
 
 doctor says : " My mode of utilizing the plain rubber porcelain tooth 
 for a bicuspid crown will be found to be both simple and practical. 
 After preparing a tooth root as for an all-gold crown by fitting 
 over the root neck a gold collar of the proper width, as in Fig. 
 376, remove and cut away the front of the collar (Fig. 377). Bevel 
 the labial edge of the root so that the tooth can set well into the 
 collar (Fig. 378). Replace the collar on the root, dry out, and 
 place a little softened wax on the end of the root. Select a suitable 
 plain rubber tooth, nip off the heads of the pins, grind so that it 
 will enter the collar, adjust, and articulate, pressing the tooth 
 against the wax. Carefully remove the collar and tooth (Fig. 379). 
 Invest in plaster and asbestos fiber (Fig. 380). Fit a thin piece of 
 platinum into the collar, burnishing it down on the tooth, and 
 bending it down to the pins. If it is desired to use a post, remove 
 and punch the platinum plate at the proper place, and solder in a 
 post ; replace within the collar, and secure with a piece of binding 
 
ARTIFICIAL CROWNS. 5O3 
 
 wire imbedded in the investment (Fig. 380). A little 18-carat solder 
 will join together the collar, platinum plate, and tooth pins (Fig. 
 381). If there are any places where the collar does not fit the tooth 
 closely, pack in gold-foil before soldering. If the inner cusp does 
 not fill the collar, or it needs lengthening for occluding purposes, 
 get the desired shape with wax when fitting the tooth. Remove 
 the wax after investment, pack in gold-foil pellets, and add enough 
 20-carat solder to flow through it, and the desired addition will ap- 
 pear as in Fig. 382. The completed crown, mounted as usual with 
 cement, is shown in Fig. 383. 
 
 The advantages of this method are its simplicity, ease of adapta- 
 tion and articulation, the short time required to fit and make the 
 crown, its strength, security, and natural appearance, and the con- 
 venience of using a plain rubber or saddle-back tooth. 
 
 FERRULE OR COLLAR CROWNS. 
 
 The Richmond Crown. — This crown was originally brought 
 to the notice of the profession by Dr. C. M. Richmond, of New 
 York. Numerous modifications have been made, however, which 
 enhance its value. The process of constructing the 
 improved crown is as follows : FlG - 384- 
 
 1. The root must be trimmed down to about the Stj f=^\ 
 gum line, except the labial portion, which should be , j ' 
 cut nearly ^ of an inch below the gum margin. For I | I / 
 this purpose, corundum stones or the Ottolengui root \ I | / 
 facers are employed, as shown in the preparation of ^ W 
 roots for the Logan crown. (See pp. 476 and 478.) 
 
 2. The ring of enamel remaining upon the root should be care- 
 fully and thoroughly removed (see Fig. 384), making the sides of the 
 root parallel, so that the band, when applied, may fit closely its entire 
 width. If this is not done, the band, even if a narrow one, instead of 
 fitting closely will form a pocket beneath the gum margin, and will, 
 in consequence of its irritating effect upon the surrounding tissues, 
 cause more or less inflammation and possibly the loss of the root. 
 
 Numerous instruments have been devised for the removal of this 
 enamel ; among the most efficient are those invented by Dr. Calvin 
 S. Case and Dr. Geo. M. Weirich. Fig. 385 illustrates Dr. Case's 
 enamel cleavers. These are so shaped that they can be partially 
 rotated under the margin of the gum, presenting a sharp point 
 
504 MECHANICAL DENTISTRY. 
 
 toward portions of the enamel that will not easily clean off, with a 
 
 Fig. 385. 
 
 Fig. 386. 
 
 view to fracturing it as the 
 diamond cuts glass, breaking 
 it up into small pieces which 
 can readily be detached and 
 the sides straightened and 
 smoothed by the broad blade. 
 The peculiarities of shape are shown in the enlarged 
 cuts. 
 
 The Wei rich cleaver or chisel is shown in Fig. 
 386. With this instrument and a few gentle blows 
 from the mallet the enamel is readily broken up and 
 detached. The rubber cushion in the center of the 
 chisel takes up the blow, thus relieving the root 
 from unnecessary shock. In the accompanying 
 illustration the instrument is shown in place ready 
 to receive the blow from the mallet. It is a well- 
 known fact that with most of the appliances on 
 sale it is difficult to properly remove the enamel 
 from the approximal surfaces of roots, especially 
 where they are very close. With this instrument, to be 
 followed with the ordinary cervical wall chisel or the Chase 
 cleavers, the root upon all sides can be readily and properly 
 prepared for the reception of a band or collar with very little 
 discomfort to the patient or trouble to the operator. 
 
 3. After the enamel has been thoroughly removed, an 
 accurate measurement of the neck of the root should be 
 secured. For this purpose Dr. A. I. F. Buxbaum, of Cin- 
 cinnati, has devised an instrument known as Buxbaum's 
 dentimeter, with which the work can be very satisfactorily per- 
 
ARTIFICIAL CROWNS. 
 
 505 
 
 formed. It is illustrated in Fig. 387. It is very simple to adjust 
 and operate, and has the advantage over other instruments of this 
 kind, that, as you do not have to twist the entire instrument, the 
 wire does not incline to slip off the root or lacerate the gum. 
 
 Dr. Buxbaum gives instructions for using his dentimeter as 
 follows : " Pass one end of a soft wire through tube at C, as shown 
 in Fig. 2 of accompanying illustration, and wrap once around knob 
 D. Pass the other end of wire through tube at E, as shown in 
 Fig. 2, and wrap around knob F. Place the loop H around the 
 tooth or root. While unscrewing the screw, by holding milled nut 
 B between the thumb and forefinger of right hand, you must make 
 constant traction on loop around the tooth by gently pulling on 
 
 Fig. 387. 
 
 barrel A, held between thumb and finger of left hand ; this will give 
 a perfect twist, as shown in Fig. 3. Unfasten ends of wire from the 
 knobs D and F and withdraw from dentimeter. The result is 
 shown in Fig. 4." 
 
 Other and simpler instruments for taking measurements of teeth 
 or roots have been devised, notably those by Dr. Edward C. Kirk, 
 and Dr. Geo. M. Weirich, of Philadelphia, which are shown in 
 Fig. 388. 
 
 4. In order to transfer this measurement accurately to the band- 
 ing material, cut the wire loop in the center and spread the ends 
 in opposite directions, as shown in Fig. 389. It is then laid on 
 the piece of gold to be used for the band (which should be 22-carat 
 and about 30 gage) ; this should be cut the exact length of the ivire, 
 
5o6 
 
 MECHANICAL DENTISTRY. 
 
 \u 
 
 and about }i of an inch in width, unless for special reasons it is 
 necessary to have it wider. This small strip of 
 Fig. 388. g^ s h ou icl now be annealed over a lamp or 
 
 Bunsen burner, then with round-nosed pliers it 
 should be brought into a circular form, and with 
 the fingers the ends should be carefully pressed 
 by each other. This will form a slight kink in 
 the band, so that the ends, if now gently drawn 
 apart and let go, will spring accurately together 
 ready for soldering. 
 
 5. In soldering the band, a corner of the two 
 edges should be grasped with the soldering pliers, 
 the joint slightly coated with borax, and a small 
 piece of 20-carat solder placed over it, on the out- 
 side of the band (see Fig. 390). It 
 should then be held in the flame of a FlG - 389< 
 Bunsen burner until the solder flows, 
 at which time it should be instantly 
 removed. With a little experience 
 and care in soldering in this way 
 (over a Bunsen burner), it can be 
 done more conveniently, in less time, 
 and with much less danger of burn- 
 ing the band, than with the blowpipe. 
 
 6. The band is now ready to be fitted or ad- 
 justed to the root. If the end of the root is not 
 round, as is usually the case, the sides of the 
 band can be flattened or otherwise shaped with 
 slight pressure from the thumb and finger or 
 with suitable pliers. The upper border should 
 then be trimmed to conform to the shape of the 
 process or the line of the gum attachment; in 
 many cases, unless the band is greatly depressed 
 or cut out on the sides, it will be found that the 
 gum will be detached from the sides of the root, 
 and that the process will be reached before the 
 root is covered high enough on the labial and 
 palatal surfaces. Place the band thus shaped 
 
 ii] >i m the root, and if the measurement and each progressive stage 
 
ARTIFICIAL CROWNS. 
 
 507 
 
 have been accurately performed, it will be found to fit perfectly. 
 Now press or drive it up carefully, until the point of attachment 
 between the soft tissues and the root is reached (about Jg of an 
 inch bevond the gum margin), which is shown by the slight 
 whitening of the gum. When this is very marked upon any 
 side, the band should be removed and relieved by cutting it away 
 at that point, and then readjusted. A corundum wheel is now 
 gently passed over the labial portion of the lower edge of the band, 
 to level it with the face of the root and to render the band invisi- 
 
 Fig. 390. 
 
 Fig. 391. 
 
 ble when the crown is finished. In doing this the wheel used 
 should be revolved toward the root, to prevent irritation of the soft 
 tissues, and at the same time it will turn the feather edge of metal 
 •over the end of the root. 
 
 7. The base-plate is more easily and quickly formed. Cut a 
 piece of gold (34 gage) of suitable length and width, anneal, and 
 then press it against the lower edge of the band with the fingers 
 until it is nicely adapted ; secure it in this position for soldering by 
 three or four strands of wire, as shown in Fig. 391. 
 
 Now paint the joint with borax dissolved in water, lay 
 a small piece of 20-carat solder against the back or 
 palatal portion of the band, on the outside, and hold it 
 in the flame of a Bunsen burner until the solder flows, 
 which will be seen to run entirely around the band, uniting it with 
 the base-plate at every point. The surplus of the base-plate material 
 should, with shears (see Fig. 392) and corundum stone, be trimmed 
 •off flush with the band, the two now forming a complete cap for the 
 face and sides of the root. 
 
 8. The next step is the preparation and adjustment of a pin 
 through the cap into the root canal. The canal should be enlarged 
 toward the palatal side of the root; this will give more room for 
 grinding and adjusting the tooth, and at the same time secure the 
 greatest attainable strength when the crown is completed. 
 
 The base-plate of the cap is perforated at a point directly over 
 the opening into the canal. This may be done either with a bur 
 
;o8 
 
 MECHANICAL DENTISTRY. 
 
 on the dental engine or with the plate punch. A pin of platinum 
 wire., Xo. 16 or 17, standard gage, should now be slightly 
 
 Fig. 392. 
 
 Fig. 393. 
 
 tapered at the end and passed through the aperture, and up into 
 the root canal. The end of the pin projecting below the cap may 
 be marked, withdrawn, and bent at a right angle, so that 
 it will point away from the tooth, that is, toward the palatal 
 surface ; it may then be waxed in, invested, and soldered 
 with the tooth, or, invested and soldered at this stage, and 
 the surplus of pin and solder brought down flush with a 
 file or stone. 
 
 9. The cap and pin should be readjusted to the root. A 
 plain plate tooth,* of suitable form and color, is now ground and 
 fitted to the cap. The labio-cervical edge of the tooth (a, Fig. 393), 
 
 * Many writers advise using cross-pin teeth ; it is self-evident, however, that in 
 this work straight-pin teeth should be employed and the cross-pins avoided 
 wherever possible, for the following reasons: (1) The position of the pins weak- 
 ens the body of the tooth. (2) Their position makes the strain upon the tooth 
 greater, as it gives increased leverage between the pins and the cutting edge. (3) 
 There is more liability of cracking the teeth in soldering, on account of so much 
 metal being brought at one point. 
 
ARTIFICIAL CROWNS. 509 
 
 should be so ground that it will be flush with the edge of the band 
 and meet the margin of the gum. It should also be ground out 
 at the center of the base (&), so as to form a slight space just over 
 the base of the pin. 
 
 The tooth is then backed with either thin platinum or gold plate 
 (gold will give a slight yellow shade to the tooth, while platinum 
 will give a bluish tint). The upper edge of the backing, brought 
 down thin with a file or stone, should extend as far as possible 
 under and between the tooth and the cap, so that the solder will 
 more readily flow in and fill what space there may be. The incisive 
 edge of the backing should also be brought slightly over the edge 
 of the porcelain (though it is not so shown in the accompanying 
 illustrations), this portion of the tooth being previously beveled 
 with a fine corundum stone. In this, the possibility of breaking the 
 tooth from the force of mastication is much diminished. 
 
 10. A perfect joint and the proper length and angle of the tooth 
 having been secured, the pieces, that is, the tooth, cap, and pin, 
 should now be thoroughly dried and then held together in the 
 proper relationship, and secured in this position by running warm 
 adhesive (resin) wax over the palatal portion of the tooth, attaching 
 the backing to the cap. It should then, before the wax gets very 
 hard, be carefully carried to position upon the root, when any cor- 
 rection in the position of the tooth can readily be made. Now apply 
 a little cold water from the syringe or on a pledget of cotton; this 
 will harden the wax, so that the crown may be removed without 
 changing the position of the tooth upon the cap. It will then be 
 ready to be invested for soldering. 
 
 A most suitable investment for crown-work is marble-dust and 
 plaster, equal parts, with a small' quantity of fine asbestos fiber 
 thoroughly incorporated. After the investment has thoroughly 
 set, the wax may be removed and the surface of the backing and 
 cap cleansed by directing upon it a small stream of boiling water. 
 The investment should be cut away so as to expose the sides of the 
 backing and the lower border of the band, as illustrated in Fig. 394. 
 but every portion of the porcelain should be protected. The case 
 should then be at first gently heated up, to drive off the moisture, 
 then transferred to the soldering block, when, with the blowpipe, 
 more heat should be applied, continuously at first, until the in- 
 vestment and tooth are thoroughlv and evenlv heated throughout. 
 
IO 
 
 MECHANICAL DENTISTRY. 
 
 Gold solder, 18-carat, is then cut in small pieces and placed, with a 
 little borax, over the aperture between the backing of the tooth 
 and the cap. The investment being now uniformly heated, the 
 flame from the blowpipe should be directed upon the solder, 
 mostly in the direction indicated in Fig. 394, when, if the entire 
 case has been previously brought to a red heat, the solder will 
 readily melt and flow betwen the tooth and cap. Additional solder 
 should now be added and melted until the proper contour of the 
 tooth is insured. 
 
 The tooth and investment should then be placed in and covered 
 with sand, plaster, or some other suitable substance to keep the 
 heat from radiating too rapidly and thus cracking the tooth. It 
 should be left so covered until it is thoroughly cool. We might 
 add here, that it is well to direct the flame from the blowpipe into 
 the sand or other material for a moment before placing the tooth 
 
 Fig. 394. 
 
 Fig. 395. 
 
 in. After the tooth is thoroughly cool, the investment may be 
 broken away, and all oxidation and borax removed by placing it 
 for a few minutes in the acid bath. The crown is then ready to be 
 finished and polished. The shaping of the solder can best be done 
 with corundum stones, followed with hard-rubber discs, and then 
 fine sandpaper or cuttlefish discs, while the polishing is accom- 
 plished with brush and buff wheels, pumice-stone, whiting, and 
 rouge. The completed crown in position is shown in Fig. 395. 
 
 The Richmond Method Applied to Bicuspid Roots. — The 
 capping of the root is similar to that already described ; the crown 
 will have greater strength, however, if a portion of the palatal 
 section of the natural crown, when strong enough, is retained, and 
 the band made deep enough to cover it. One pin is all that is 
 usually required, and where there are two distinct canals, the 
 palatal should be used to receive the pin ; thus greater strength is 
 
ARTIFICIAL CROWNS. 
 
 511 
 
 secured at the point where it is most needed, and the pin is so 
 located that it will not interfere with the grinding and adjustment of 
 the tooth. The cap and pin being in position, a suitable cuspid 
 tooth or bicuspid facing is then ground, backed, and adjusted to 
 represent the labial aspect, and then properly secured to the cap 
 with adhesive wax. The tooth, cap, and pin are then carefully 
 removed, invested, and soldered; after which they are again 
 placed upon the root, and the occluding edge of the tooth is 
 ground clear of the antagonizing teeth at about the angle shown 
 at A, Fig. 396. 
 
 From a suitable die or die-plate the cusps or occluding surface 
 of the tooth are swaged from 22-carat gold plate. These cusps 
 should then be filled in with 18- or 20-carat plate or solder. 
 This is done by cutting the gold into small pieces, and placing 
 them, with a little borax, in the depressions of the cusps, all of 
 
 Fig. 396. 
 
 Fig. 397. 
 
 Fig. 398. 
 
 which is held over a Bunsen burner until the small pieces are 
 melted, when they will flow into these depressions and fill them 
 level full. The surplus is trimmed away, the cusps ground and 
 fitted to the edge of the porcelain front, in position to secure 
 proper occlusion (Fig. 397), and secured with wax as shown at A. 
 
 A piece of thin, pure gold plate or mica is then adjusted on 
 each side of the crown (B, Fig. 397), the surfaces of which, if dry 
 and slightly warm, will be held in position temporarily by pressing 
 them gently against the side of the wax. This is all now invested 
 together (Fig. 398). 
 
 The long ends of these side pieces, after being invested, hold 
 them in position, as the investment should be cut away so as to 
 expose the sides of the crown as shown at A, Fig. 398. In the 
 process of soldering, after the case has been properly heated, the 
 small pieces of solder and borax are placed in the aperture formed 
 
512 MECHANICAL DENTISTRY. 
 
 by these sides of gold or mica (the place formerly filled with wax), 
 and the flame from the blowpipe directed cautiously against these 
 exposed sides (A). The solder will then flow, uniting the several 
 parts, when more should be added until the proper contour, with 
 perfect continuity of structure, is secured. The crown can be made 
 without the gold or mica sides if great care is exercised in flowing 
 the solder. There will be more surplus solder, however, to be fin- 
 ished off. 
 
 In finishing, the solder is brought to the contour of a bicuspid 
 tooth with corundum stones and sandpaper discs, when it is ready 
 for the polishing process. The finished crown is represented in 
 place upon the root in Fig. 399. 
 
 There are other methods practised, and though some of them 
 may not be as artistic as the one just described, they are much 
 simpler and quicker. For instance, the palatal cusp may be built 
 up with several pieces of gold plate — previously melted 
 _ 399 ' into the form of balls and flattened out with a hammer. 
 The backing is brought down and closely burnished over 
 the cutting edge of the tooth, which is then waxed in 
 position, tried in the mouth, and invested, and when ready 
 to be soldered these flattened pieces of gold are laid in 
 position, united, and filled in with 18-carat solder, which 
 is also brought over the backing to the tip of the tooth. 
 This plate and solder are afterward brought to the proper shape 
 and contour with the stones and discs. 
 
 Then, again, the palatal portion of the band is extended down 
 so as to nearly touch the antagonizing tooth. This leaves only a 
 comparatively small space to be filled in with solder, which is 
 afterward trimmed and finished to the form of the crown. 
 
 Or, a method that the writer often employs is to back the tooth, 
 grind off or bevel the occluding surface, and then joint and adjust 
 the prepared gold cusps ; wax them in position, invest, and flow 
 in sufficient 20-carat solder to hold them securely in position, after 
 which the tooth may be ground, adjusted, and soldered to the cap, 
 as has been directed. One advantage of this method is that differ- 
 ent forms and shades of bicuspid facings may be so prepared — 
 with gold occluding surfaces — and kept in stock ; and, again, in 
 the latter three methods, as may be seen, it is only necessary to 
 invest the cap once after adjusting the tooth. 
 
ARTIFICIAL CROWNS. 
 
 513 
 
 Fig. 401. 
 
 Dr. Litch's Method. — The method devised by Prof. Wilbur F. 
 Litch for forming collar crowns was first published in the Dental 
 Cosmos (Vol. xxv, p. 449), and was afterward revised and repro- 
 duced in the " American System of Dentistry." In this Prof. Litch 
 describes his method as follows : 
 
 " The processes to be described reduce destruction of tooth 
 substance to the minimum. Instead of cutting the palatine wall of 
 the tooth down to the gum margin, the greater portion of it is care- 
 fully- conserved, its presence, while not indispensable to a success- 
 ful result, being in the highest degree desirable. How much of this 
 portion of the tooth can be retained will depend upon the nature of 
 the occlusion. 
 
 " In Fig. 400 the dotted line from C to D represents the point to 
 which the tooth is cut away in the older methods of pivoting; the 
 dotted line from A to B, the line of abscission practised by the writer. 
 
 " As will be seen by reference to 
 Fig. 401, the face of the tooth thus 
 prepared presents a gradual slope 
 from the palatal surface to the labio- 
 cervical margin. At the latter mar- 
 gin the root should be cut down with 
 suitable instruments to a point a little 
 beneath the edge of the gum, in order 
 that the porcelain tooth in front may 
 pass up under the gum margin, and 
 
 the joint between the tooth and root be concealed. At this point 
 tooth substance may be sacrificed, as it does not materially diminish 
 the strength of the root. 
 
 " The several parts employed in making the collar crown are a 
 plain plate porcelain tooth or facing, a platinum-iridium retaining 
 pin, and a backing, base-plate, and collar, made either of platinum, 
 pure gold, or 22-carat gold, either metal being made in thickness 
 about No. 30, American gage. When platinum is used, coin gold 
 or 20-carat gold, alloyed with copper or silver only, should be em- 
 ployed as a solder and covering. Twenty-carat gold may be used 
 as a solder when pure gold is employed, while 18-carat gold will- 
 solder the 22-carat plate. 
 
 " In shaping the pulp canal for the reception of the retaining 
 pin care should be taken not to weaken the root by an unnecessary 
 
 33 
 
 A-' 
 
5 J 4 
 
 MECHANICAL DENTISTRY. 
 
 enlargement of the caliber of the canal. The platinuni-iridium 
 pin need not be more than No. 14 American gage in thickness at 
 its point of greatest diameter, near the free surface of the root, 
 where all the strain, if any, falls ; from this point it should be made 
 a gentle taper corresponding to the natural shape of the space it is 
 to occupy. Half an inch in length is ample ; even less will serve. 
 
 " The retaining pin being shaped and adjusted on the root, care 
 being taken to leave an excess in length at the free end for con- 
 venience in subsequent manipulations, the next step in the process 
 is the making of the base-plate and its attachment to the pin. 
 A strip of platinum or gold of suitable size is pressed upon the face 
 of the root with broad-pointed, serrated instruments until it is in 
 close adaptation to the surface at every point. This base-plate is 
 allowed to project beyond and overhang the palatine portion of the 
 root, but should not come quite to the labial edge. 
 
 " Adaptation being secured, an opening is made in the base-plate 
 where it covers the pulp canal, through which opening the retain- 
 ing pin may be pressed up into position in the root. Pin and base- 
 plate are then removed from the mouth, dried, and cemented with 
 a brittle resinous cement, and then, while the cement is still plastic 
 and yielding from heat, placed again in position in and upon 
 the tooth, and perfect adaptation secured. While still in position 
 in the mouth, throw upon the cement a stream of very cold water, 
 so that it may be made brittle and incapable of bending. Then 
 remove from the mouth and invest in a mixture of equal parts of 
 plaster and pulverized marble, with enough water to make a thick 
 paste. After the investment has set, solder the retaining pin and 
 the base-plate together. 
 
 '' To make the collar, a somewhat crescent-shaped piece of 
 platinum or gold of suitable size is prepared and pressed into 
 shape upon the palatine and palatoproximal face of the tooth; 
 little slits may be cut in the collar with a delicate pair of scissors, 
 to make easier this adaptation. Care should be taken not to push 
 the collar up under the gum at any point, provided the palatine 
 wall of the tooth, which had been allowed to remain standing, is at 
 all ample in height — say X of an inch ; if less than this the collar 
 may pass under the gum for a short distance, as will be shown 
 subsequently. In the average case this collar will not quite en- 
 circle one-half the tooth. 
 
ARTIFICIAL CROWNS. 5 I 5> 
 
 i " Fig. 402 shows the collar curved to the outline of the gum 
 margin and shaped to the contour of the palatoproximal wall of 
 the tooth. At G the slits are cut in the platinum to allow over- 
 lapping in shaping to contour. 
 
 " In order to strengthen the collar and facilitate its attachment to 
 the base-plate cut a series of slits in -that portion of the base-plate 
 which has been made to project beyond the palatine wall of the 
 tooth, and the base-plate, with its now attached pin, 
 being placed with the collar in position in and upon 
 the tooth, the little strips of metal into which the 
 overhanging edge of the base-plate has been cut are 
 pressed, one after the other, down upon the collar 
 and carefully molded to its surface, so that the collar 
 will no longer consist of a single thickness of metal, but will be 
 reinforced by these additional thicknesses of base-plate thus pressed 
 upon it. 
 
 " Fig. 403 shows this quite perfectly : H is the free end of the 
 retaining pin, which is to be cut off when the porcelain tooth is 
 mounted. I is the base-plate, with its overhanging palatine 
 margin cut into strips, J, which are being pressed down upon the 
 
 collar, F, by the broad-surfaced and serrated 
 Fig. 403. . 
 
 instrument, K. This being accomplished, re- 
 move the several pieces from the mouth, care- 
 fully cement the collar in its proper position 
 relative to the base-plate, which will now form 
 a sort of matrix for it, again place in the mouth, 
 readjust, harden the cement, remove from the 
 mouth, invest as before, and solder the collar 
 and base-plate together, using a considerable 
 Pressing the base-plate f w f covering, so that the collar 
 
 over the collar. fe 
 
 may be still further strengthened and its 
 surface be made uniform. 
 
 " In cementing the collar to the base-plate one precaution is 
 imperative — namely, not to allow a film of cement to get between 
 the collar and the tooth. If this is done and the investment poured 
 in upon this film of cement, the latter will immediately burn out as 
 soon as heat is applied, leaving a space between the collar and the 
 investment into which the gold solder will flow, and thus interfere 
 
5 l6 MECHANICAL DENTISTRY. 
 
 with that perfect adaptation of the appliance to the tooth which is 
 necessary to a successful result. 
 
 " The mounting of the facing next demands attention. As 
 already stated, a plain plate porcelain tooth is used. This must 
 have what are technically known as cross-pins; that is, pins placed 
 at right angles with the long axis of the tooth. They must also 
 be placed well up toward the cutting edge. If they are too near 
 the neck they will inevitably be cut out in fitting the tooth to the 
 slope of the base-plate on which it must be mounted. 
 
 " Fig. 404 shows the form of the facing and indicates the slope 
 given it in fitting. The fitting process does not differ from that 
 ordinarily employed with porcelain teeth ; an impression may be 
 taken and the work done on a cast, or the facing may be fitted to 
 the mouth. In either case it is in the mouth that the finer and final 
 adjustments as to height, contour, alignment, etc., must be perfected. 
 " This being done and the facing backed, tooth 
 and base-plate are cemented together, restored to the 
 mouth, finally adjusted, removed, and soldered as be- 
 fore, as much gold being flowed into the angle be- 
 tween the backing and the base-plate as occlusion 
 
 Shape of porce- ^ ^ 
 
 lain facing. , . . . . . 
 
 ' This artificial crown, being properly finished 
 
 and cemented into position in and upon the tooth, makes what 
 the writer, from several years' experience in its use in a large 
 number of cases, has found to be an appliance which will remain 
 for an indefinite period without the slightest deviation from posi- 
 tion and alignment, and which in many respects is almost as 
 strong as the natural tooth, because its point of greatest resist- 
 ance to pressure is placed where Nature anchors her enamel 
 walls — namely, upon the outside and not upon the inside of the 
 walls of dentine; so that in the act of occlusion the force applied 
 by the lower incisors as they come up in position inside the upper 
 incisors falls upon the whole thickness of the root through the collar, 
 and not upon less than half its thickness through a centrally 
 anchored pin — a pin, too, prolonged into a lever of enormous power 
 by its attachment to the porcelain tooth. 
 
 " In this respect there is a manifest weakness in all methods of 
 mounting artificial crowns which depend for their stability solely 
 upon the central pin. Ultimate failure through splitting of the 
 
ARTIFICIAL CROWNS. 
 
 517 
 
 Fig. 405. 
 
 F 1 lMh-H 
 
 root is the frequent result, and the larger and stronger and more 
 deeply anchored the pin the more certain this result, because a 
 large pin necessitates a large opening for its reception, and a 
 corresponding weakening of the root, upon which the strain must 
 ultimately fall : the lever is strengthened and the point of resistance 
 weakened. 
 
 " The only safety for the usual form of pivot tooth is, either 
 that the occlusion shall be slight, the root very strong, or the 
 pivot very flexible or elastic. This elasticity of the old hickory 
 pivot was one of its chief excellences : roots were much less 
 likely to split than with a rigid, unyielding metallic 
 pin. In cuspids or incisors, however, metallic pins, 
 unless enormously large, or thickly packed around 
 the amalgam, will very often bend outward, thus 
 allowing a slight displacement forward of the arti- 
 ficial crown, and to that extent relieving the root 
 from strain. 
 
 " Fig. 405 gives a sectional view of the collar 
 crown in position, the lower incisor being in occlu- 
 sion. L is the porcelain facing. H is the pin at- 
 tached to I, the base-plate. M is the backing and 
 solder. N is the lower incisor, and F the collar. 
 It is clearly evident that here the force of occlusion 
 falls upon the palatine wall of the natural tooth at 
 O through the collar F, and not upon the pin at the 
 point of its attachment to the base-plate H, and 
 through the pin upon the thin outer shell of the 
 root. 
 
 " In cases frequently met with, where the entire 
 crown of the tooth has been removed, the collar, as before described, 
 can be adapted to the palatine face of the root, provided the latter 
 be not decayed away up to the alveolar margin. Usually, however, 
 there is a considerable space between the free edge of the root and 
 the alveolus, and here, running up to the alveolus, the collar must 
 be placed. 
 
 " The dotted line E in Fig. 401 indicates a collar so placed. 
 All the steps in the process are essentially the same as before 
 described. Adapting the collar to the surface of the root beneath 
 the gum is somewhat painful, but not excessively so, and in the 
 
 Sectional view of 
 collar crown in 
 position, the 
 lower incisor 
 in occlusion. 
 
518 MECHANICAL DENTISTRY. 
 
 wearing the irritation caused by its presence is very slight and 
 transient in character, assuming, of course, that care has been taken 
 to leave upon it a smooth, thin, and well-polished edge. 
 
 " The objection may be urged that this form of crown resists 
 pressure only in one direction, from within outward, and does not 
 provide for lateral pressure or pressure from the front. As a rule, 
 the latter can occur with any force only as the result of accident, 
 while if the crowned tooth is in normal relation with its fellows, 
 and the artificial crown be closely fitted between them, they will 
 fully sustain lateral force. 
 
 " Where such lateral support is wanting through isolation of the 
 tooth, the collar must be extended into a ring or ferrule completely 
 encircling and grasping the root, and thus affording support on all 
 sides. The ring, however, is more troublesome to make and more 
 painful to apply, and generally shows a line of gold in front. In 
 the average case the simple collar gives all requisite strength. 
 
 " In mounting crowns upon bicuspid and molar roots, however, 
 the ferrule principle is often essential to stability; especially is this 
 true of lower bicuspids and molars, as here the forces applied in 
 mastication are as erratic in direction as they are powerful in char- 
 acter, and the root must be guarded at every point against their 
 violence. 
 
 In fixing in position the artificial crowns just described, the 
 writer prefers to use a gutta-percha cement adhesive in character, 
 which will not strip from the pin when the crown is forced into 
 position. 
 
 " The apical foramen is closed, the pulp canal grooved and 
 thoroughly dried, the central pin is barbed, and the pin and inside 
 of the collar and under surface of the base-plate are thickly coated 
 with the gutta-percha ; the entire appliance is then heated to a 
 temperature sufficient to thoroughly soften the gutta-percha, and 
 firmly pressed up into position ; the excess of gutta-percha will 
 ooze out at all free margins, and may be subsequently removed 
 with suitable instruments. 
 
 " A good gutta-percha cement will hold firmly in a great majority 
 of cases, but when, as in a small lateral incisor, the retaining pin 
 is necessarily small and short and the collar not as ample as could 
 be desired, an oxyphosphate cement, mixed thin, will be found to 
 give greater stability. When this cement is used, however, it will 
 
ARTIFICIAL CROWNS. 
 
 519 
 
 be found very difficult to detach the artificial crown from the root, 
 should it for any reason become necessary to do so; whereas a 
 little heat will quickly soften a gutta-percha packing and permit 
 the entire appliance to be withdrawn without difficulty." 
 
 As a modification of the manner of constructing the collar, Dr. 
 Theodore F. Chupein contributes the following to the Dental Cos- 
 mos: 
 
 " After the root face has been dressed down as shown in Fig. 
 401, a piece of pure gold plate of No. 30 gage is cut as shown in 
 Fig. 406. This is bent around the root, as shown in Fig. 407, the 
 wide part resting against its palatal aspect, while the ends are seized 
 with a pair of narrow-beaked, flat-nosed pliers at the labial aspect. 
 While thus held, the band may be burnished to fit accurately 
 against the approximal and palatal parts of the root. This done, it 
 is removed and the ends soldered together, as shown in Fig. 408. 
 
 Fig. 406. 
 
 Fig. 407. Fig. 
 
 Fig. 409. Fig. 410. Fig. 411. 
 
 This band is then replaced on the root, and, as it hugs the root 
 snugly, any of the edges which may be higher than the face of the 
 root may be ground down even with a corundum stump wheel. 
 It is again removed from the root and laid on a piece of pure gold 
 plate of the same thickness, to which it is soldered, as in Fig. 409. 
 The overhanging edges of the plate, as soldered to the collar, are 
 now dressed down even with the collar, and the forward part of 
 the collar filed or ground away from the plate, as shown in Fig. 
 410. A hole is now drilled or punched through the face-plate to 
 receive the dowel, which passes through it into the root. The 
 under part of the face-plate at the hole should be well countersunk, 
 so that the solder that binds the dowel to the face-plate may creep 
 through and hold the dowel on its under surface. The face-plate 
 and collar, as shown at Fig. 410, are placed on the root and bur- 
 nished down to fit accurately at all points. A slight smearing of 
 
520 MECHANICAL DENTISTRY. 
 
 cement is placed over the dowel hole, so as to fill the countersink, 
 and the dowel passed through and secured to the face-plate with 
 more cement. Before this hardens it is placed on the root in its 
 proper position, after which the cement is chilled by a stream of 
 cold water, when it is removed, invested, and soldered. Fig. 411 
 shows the collar, face-plate, and dowel complete. This being accom- 
 plished, the face-plate is slightly reduced on its labial aspect, so as 
 to expose the root against which the porcelain facing is to rest. The 
 protruding part of the dowel is now cut off level with the face-plate, 
 and the porcelain tooth fitted to it. This part of the operation does 
 not differ from that indicated by Prof. Litch, and therefore need not 
 be repeated here. 
 
 " The operation as set forth consumes much less time, is less 
 tedious, does not demand the nice manipulative ability of the other, 
 and is more certain in its results." 
 
 Dr. Knapp's Process. — No individual method has, perhaps, 
 more immediately and generally commanded the approval and 
 commendation of expert and discriminating operators than the one 
 brought to the notice of the profession by Dr. J. Rollo Knapp, of 
 New Orleans, La. Omitting some judicious and pertinent general 
 reflections on the subject (see Dental Cosmos, of February, 1887), 
 all that relates to practical details in his methods of procedure is 
 here reproduced : 
 
 " The collar being removed, its gingival border must be carefully 
 filed so as to adjust it exactly to the various inequalities existing 
 in the borders of the alveolar process and its investing gum. The 
 other border should then be evenly filed down so as to reduce the 
 collar to the requisite narrowness. A piece of pure gold plate, gage 
 34, is now to be soldered upon this latter border so as to convert 
 the collar into a cap for the root. This cap must have pierced in 
 it such an aperture as will conform to the configuration of the pin 
 or dowel best suited to the particular case in hand. Cap and pin 
 waxed together, should then be tried in the mouth, carefully removed, 
 invested in calcined marble-dust and plaster, and soldered. Being 
 again placed upon the root, an impression of it should be taken, as 
 well as of the two approximal teeth." 
 
 Small trays especially made for the purpose (Figs. 412 and 413), 
 will be found very convenient for taking impressions for crown- 
 work. Plaster or modeling composition can be used in doing this. 
 
ARTIFICIAL CROWNS. 
 
 521 
 
 Upon its being ascertained that the cap, with pin attached, is in its 
 proper position in the impression, a plaster cast can be obtained, 
 which, with a cast of the occluding teeth, should be placed in an 
 articulator. 
 
 While the writer believes it to be the most accurate, when 
 making single crowns, to grind and adjust the tooth in the mouth, 
 
 Fig. 412. 
 
 it frequently happens, from lack of time or other -reasons, that it is 
 not practicable; then the impression should be taken as directed. 
 
 From this point succeeding steps will differ according to the 
 character of crown to be inserted. If it be an incisor, which is to 
 have a porcelain front, a plain plate tooth of suitable size, shape, 
 and shade should be backed with pure gold, ground to position 
 upon the anterior portion of the cap, and united to it by adhesive 
 
 Fig. 413. 
 
 wax. Sufficient wax should be used to perfectly restore the con- 
 tour and to produce the most accurate knuckling or adjustment of 
 the approximal surfaces of the teeth. Too much stress cannot 
 be laid upon this latter point — one not usually attended to. Yet 
 all the reasons for observing it in all other kinds of contour work 
 are no less potent here. In this procedure pure gold of 34 gage 
 
522 MECHANICAL DENTISTRY. 
 
 should be made to completely envelop the sides and incisive 
 portion of the wax, including the edges of the backing and con- 
 tiguous portions of the cap. All should now be invested, the wax 
 removed by boiling water, drying effected by a gentle heat, and 
 the resulting golden pocket filled with 20-carat solder. The solder, 
 previously cut in small squares, is to be dropped into the mouth 
 of the mold, and sprinkled with a very little powdered borax — re- 
 peating this process with the left hand as fast as the solder is 
 melted under the blowpipe while held in the right hand until the 
 mold is quite filled. To accomplish this in the best manner the 
 flame of the blowpipe should be quite intense, but at the same time 
 exceedingly small. 
 
 The small and deep mold formed by the gold shell enveloped in 
 the marble and plaster matrix has a very narrow opening, which 
 renders necessary an intense heat, capable of concentration upon 
 and easy application to the innermost recesses of the mold, which 
 is to be filled with molten gold. An oxyhydrogen blowpipe* was 
 therefore constructed to utilize the condensed nitrous oxid gas in 
 combination with common illuminating gas for the production of a 
 mixture which is conducted through a thin rubber tube of }i of an 
 inch bore to a very small blowpipe, which emits a steady flow of 
 constantly ignited gas in the form of a pointed pencil about ]/ 2 
 of an inch in length by ]/\ of an inch at its greatest diameter. 
 With this blowpipe in hand, the plaster matrix may be speedily 
 heated by playing the stream of fire over its surface until the mass 
 is aglow, when the point of the flame is thrown into the mold by 
 rapid thrusts until the solder melts like wax and fills every part of 
 the mold with liquid gold. From the first application of the flame 
 to the previously dried and warmed matrix, there is usually no 
 more than ten minutes consumed in bringing the solder to the fus- 
 ing-point and completing the cast of gold in the little mold. It 
 would seem that by such means only can the requisite heat be 
 obtained, directed, and controlled with the sensitiveness of adjust- 
 ment that admits of the 20-carat solder being melted in, yet with- 
 out destruction of, the thin gold crucible within the matrix. After 
 cooling, removing investient, and boiling in acid, superfluous solder 
 can best and most expeditiously be removed by corundum wheels 
 
 * See page 45, Fig. 20. 
 
ARTIFICIAL CROWNS. 
 
 523 
 
 on the engine. Care should be taken not to cut away the gold 
 forming the approximal knuckling, and to artistically carve the 
 palatal portion. 
 
 Fig. 414 represents a band of collar gold, 22 carats fine, 28 gage; 
 Fig. 415, a soldered collar or ferrule made from it; Fig. 416, a 
 square gold pin, 20 carats fine; Fig. 417, a plate of pure gold, 34 
 gage, for a cap; Fig. 418, the collar, cap, and pin duly invested. 
 Fig. 419 represents the collar, cap, and pin soldered together with 
 20-carat solder; Fig. 420, a lateral incisor plate tooth, backed with 
 pure gold, 28 gage, ground to the anterior portion of the cap, 
 fastened to it with wax, contoured to represent a natural incisor, 
 the approximal sides as well as incisive portion of which, together 
 with the edges of the gold backing and contiguous parts of the 
 cap, all enveloped in pure gold, 34 gage. Fig. 421 represents the 
 
 Fig. 414. 
 
 Fig. 415. 
 
 Fig. 416. 
 
 Fig. 417. 
 
 Fig. 418. 
 
 Fig. 419. 
 
 same, invested in calcined marble-dust and plaster, the wax removed, 
 disclosing the golden pocket ready for the reception of the solder. 
 Fig. 422 shows the crown after the soldering has been effected ; Fig. 
 423, the lateral incisor crown divested of superfluous solder and 
 completely finished. 
 
 In constructing a cuspid, its natural palatal characteristics should 
 be as accurately reproduced as practicable, Figs. 424, 425, 426, 427, 
 and 428. The formation of a porcelain-faced bicuspid is similar to 
 that which has just been detailed, up to the soldering of the backed 
 tooth to the cap, Fig. 429. The subsequent stages, however, are 
 very different. The perfect configuration of a bicuspid should be 
 reproduced in wax, aptness of occlusion and knuckling being care- 
 fully attended to," Fig. 430. In this condition the crown should be 
 placed in a small ring, such as is shown in Fig. 431, first set with 
 wax in the desired position, and then secured there by plaster. 
 
5^4 
 
 MECHANICAL DENTISTRY. 
 
 The exposed portion of the crown and surrounding - plaster should 
 then be coated with sandarac varnish and molded in marble-dust 
 and glycerin, contained in a corresponding annular section, Fig. 
 432. Over this is to be placed a conical tube, such as is repre- 
 sented in Fig. 433, and into which molten zinc is to be poured. 
 
 Fig. 420. Fig. 421. 
 
 Fig. 422. 
 
 Fig. 423. 
 
 Fig. 424. 
 
 Fig. 425. 
 
 Fig. 426. Fig. 427. Fig. 428. Fig. 429. Fig. 430. Fig. 431. 
 
 Fig. 432. 
 
 Fig. 433. 
 
 Fig. 434. 
 
 Fig. 43S- 
 
 Fig. 436. 
 
 Fig. 437. 
 
 With the die, Fig. 434, thus cast, in accurately reproducing the 
 natural cusps and sulci, there can be obtained with pure gold plate, 
 34 gage, a perfect counterpart of the grinding surface of a bicuspid 
 crown, Fig. 435. The palatal cavity of the impression thus made 
 in the plate must now be filled with gold solder, 20 carats fine, 
 
ARTIFICIAL CROWNS. 
 
 525 
 
 after which the piece must be finished up by any requisite trim- 
 ming-. Care should be taken to leave the palatal cusp entire, and 
 just enough of the buccal or external cusp to combine with the 
 porcelain face in the formation of a proper occluding surface, Fig. 
 436. From the model, as represented in Fig. 430, sufficient wax 
 
 Fig. 438. Fig. 439. Fig. 440. Fig. 441. 
 
 Fig. 442. Fig. 444. 
 
 must now be displaced to permit of the prepared gold cusps assum- 
 ing their proper position, and the approximal surfaces remaining 
 in the wax then enveloped with pure gold, 34 gage. The palatal 
 portion of the collar must be protected with a strip of pure gold, 
 28 gage, Jg of an inch in width. All is now ready to be invested, 
 Fig. 437. After removal of the wax, through the palatal aperture 
 
 Fig. 445. 
 
 Fig. 446. 
 
 Fig. 447. 
 
 Fig. 449. 
 
 Fig. 450. 
 
 remaining, the internal walls of gold will be disclosed, Fig. 438. 
 By careful manipulation with the small and intense blowpipe flame 
 before mentioned, 20-carat solder can be so flowed in as to make a 
 solid golden mass, from which can be readily shaped a perfect bicus- 
 pid, Fig. 439. 
 
526 MECHANICAL DENTISTRY. 
 
 In the construction of an all-gold bicuspid crown some of the 
 steps differ from those just described. Upon the cap are dropped 
 several beads of wax. From this shapeless mass is carved a per- 
 fect bicuspid. Fig-. 440. A die is then obtained, Fig. 441. after the 
 manner just detailed. A grinding surface is swaged in pure gold, 
 Fig. 442. and the cusps are filled with 20-carat solder, Fig. 443, and 
 placed in proper position upon the wax tooth. A piece of pure 
 gold plate, slit at the edges for facilitating adjustment, should now 
 be made to cover about two-thirds of the yet exposed border of 
 wax. Fig. 444. After being invested, and the wax removed by hot 
 water, a suitable aperture is left for soldering, Fig. 445. The result- 
 ing completed bicuspid, true to nature, is seen in Fig. 446. The 
 descriptions just given answer for all-gold molars, Figs. 447, 448, 
 449, and 450. 
 
 In carving the cusps and sulci, and in otherwise modeling the 
 gold parts of the crowns, small engine corundum wheels and 
 points, varying from coarse to fine, and barely moistened, to insure 
 accuracy and delicacy of touch, are preferable to files or any form 
 of steel instruments. The smoothing and polishing is done with 
 wet felt wheels, fine pumice, pulverized silex, moose-hide points with 
 chalk, brush wheels and whiting, and finally with rouge. It is a 
 matter of much importance that great care should be exercised in 
 the preparation of the gold used. The solder should be uniform,, 
 flow easily, and conform well in color to the work in hand. 
 
 Dr. Shields' System. — The following methods, first published 
 in the Dental Cosmos, are contributed by Drs. N. T. and L. N. 
 Shields. " The points in this work to which we desire to direct atten- 
 tion are its permanency, absolute cleanliness, and artistic beauty 
 By the methods herein described the crowns are constructed upon 
 anatomical lines, larger at the grinding and cutting surfaces, so as 
 to admit of thorough mastication of food without injury to the 
 gums. The ordinary shell crowns are positively wrong in shape 
 and construction, because the normal crown has a larger diameter 
 than the neck of the tooth, therefore a band made to fit the crown 
 of a tooth tightly will be tod large at the neck. This will neces- 
 sarily leave a space for the lodging for food debris, although it may 
 go under the gum, will make the gum present a very unnatural', 
 appearance, will make the gold tooth altogether unnatural in con- 
 struction, and the result, after a very few years, will be a mass of 
 
ARTIFICIAL CROWNS. 
 
 527 
 
 Fig. 451. Fig. 452. Fig. 453. 
 
 decay under the shell crown, which makes it not only a temporary 
 operation, but a constitutionally as well as a locally injurious one. 
 
 " The enamel widens or becomes thicker the nearer it approaches 
 the grinding and cutting surfaces, and in order to get a perfect 
 junction of the collar crown and the neck of the tooth we must 
 remove all enamel." Their procedure is as follows : First destroy 
 the vitality of the pulp, then extract all of it with Donaldson's 
 nerve canal cleansers. With a little patience and using No. 5 all 
 fine, and for every sitting a new cleanser, every particle should be 
 removed from the roots, when they should be perfectly filled to 
 their respective apices. This done, the whole crown is cut off 
 almost even with the gum; there will still be a thin portion of the 
 enamel left surrounding the root, and this can easily be removed 
 by using the No. 2 and No. 3 scalers made by the S. S. White 
 Dental Mfg. Co. (See Figs. 451 and 
 452.) This done, shape the root for a 
 solid all-gold crown, as shown in Fig. 
 453. The procedure in the case of por- 
 celain faced crowns will be described 
 later. 
 
 Around this conically shaped root 
 (the removal of the enamel alone will 
 generally shape it sufficiently) fit a 
 22-carat gold band so as to come in 
 contact with all parts of the conical 
 
 portion of the root, which, when made, naturally gives a conical 
 band. To make this band, first make a tin-foil model, as seen in 
 Fig. 454; this causes less pain to the patient. From this an absolute 
 shape in gold is obtained more quickly, and a saving of gold results. 
 This band is soldered with 22-carat solder, then placed in position, 
 and its free margins ground down even with the root end. 
 
 Next prepare the band for a pure gold floor by taking a Butler 
 corundum point and hollowing out the upper or small end by 
 beveling from the inside edge so as to allow room for the solder. 
 Although only an infinitesimal amount of solder runs inside, still 
 there must be a place for that little to flow ; otherwise the band 
 could not go back into place, on account of the solder flowing in- 
 side, and we must have the solder to flow inside in order to make 
 a complete cone externally. Now take a piece of pure gold (No. 
 
5 28 
 
 MECHANICAL DENTISTRY. 
 
 34 American gage) and cut just a little larger than the band, 
 anneal it and adapt it perfectly, then place the two in a No. 7 
 Melotte soldering clamp (Fig. 455), and be sure they do not move; 
 place borax, mixed with water to a thin cream, all around the over- 
 lapping edge of pure gold, place a small piece of 22-carat gold 
 solder at the junction of the band and floor, and with a broad, 
 gentle flame solder the entire floor with the one piece of solder and 
 at the same moment. The clamp holds them firmly together, and 
 
 Fig. 455. 
 
 the work can be placed back on the tooth without rocking. (Fig. 
 
 456.) 
 
 Now make the pivots or dowels (of platinum and iridium wire), 
 and roughen them before placing in position. Drill holes corre- 
 sponding with the root canals, place the pivots in position, and 
 fasten them to the floor with prepared hard wax. Now remove 
 carefully, and invest pivots, floor, and band in equal parts of plas- 
 ter and marble-dust, and, after removing the wax with boiling 
 water, unite them with 22-carat gold. Now cut down the over- 
 
 Fig. 456. Fig. 457. Fig. 458. Fig. 459. 
 
 Fig. 460. 
 
 lapping pure gold floor exactly even with the band, also cut down 
 the projecting ends of the pivots. This constitutes the foundation 
 for a solid gold crown. Never make pivots for canals which cannot 
 be thoroughly filled with cement. It is better to shorten the pivot 
 somewhat and make it thicker, and depend for anchorage only 
 upon the lower part of the canal, as shown in Fig. 457. 
 
 Now put the foundation in its position in the mouth (upper jaw, 
 for example), and take an impression of the whole upper jaw in 
 
ARTIFICIAL CROWNS. 529 
 
 modeling- compound, also take an impression of the whole lower 
 jaw. Remove the foundation, and place it with great care exactly 
 in its proper matrix in the impression just taken, then stay it to the 
 modeling compound with wax in two or three places ; be careful 
 not to move it with the wax knife, dry the pivots and band on the 
 inside, and cover the pivots with a film of wax, also run a film of 
 wax around the band on the inside, but be sure to remove all wax 
 from the edge of the band, because we want that to rest firmly 
 upon the plaster. Now fill the impression with plaster to make a 
 model. 
 
 After separating the model, remove the crown foundation from 
 the model by making a hole, usually on the palatal surface, with a 
 pocket-knife, through the plaster to the apical end of the pivot. 
 Now place the model and foundation in hot water, and with a little 
 pressure on the end of the pivot the whole foundation is easily 
 removed. Syringe out all wax from the model and foundation; the 
 latter should then be replaced upon the model. 
 
 Next make the stamp for a grinding surface; use for this pure 
 gold, 34 American gage, and fill in the cusps with 22-carat solder. 
 Melotte makes a very fine set of steel stamps that one can generally 
 make use of, but a zinc cast can be made in a few minutes by simply 
 placing White's prepared molding sand, always ready for use, in a 
 ring and gently imbedding the grinding surface of a suitable tooth, 
 and in a minute by the watch a small quantity of zinc can be melted 
 and poured into the impression in the sand. The molar or bicuspid 
 stamp is made in the usual way by placing the pure gold, always 
 well annealed, on a piece of lead and striking a few light blows on 
 the die, which gives a perfect grinding surface, as seen in Fig. 458. 
 This is the reverse side of a stamp of a superior left first molar. 
 
 Next trim off all surplus gold, leaving the grinding surface as 
 represented in the cut. The cusps are next filled with 22-carat 
 solder. The reason 22-carat solder is used is, when the whole 
 space between the grinding surface and the foundation is filled in 
 with 20-carat solder there is no danger of the 22-carat being melted 
 out of the cusps, and consequently no danger of having an air- 
 bubble just under the grinding surface which, of course, would 
 make itself visible after a few days' use. 
 
 Having taken a full impression of both upper and lower jaws, 
 an absolutely correct articulation is secured. Now add wax to the 
 34 
 
530 MECHANICAL DENTISTRY. 
 
 foundation, which can be removed from the plaster, until an exact 
 articulation with the pure gold grinding surface is produced. 
 After having gotten this with hard wax so that it may be manipu- 
 lated without disturbing its position, continue to build out the 
 tooth to its anatomically correct contour with wax, frequently 
 trying it into place. After the foundation is removed from the 
 plaster, the plaster is cut away from between the foundation and 
 the adjoining teeth without disturbing the plaster upon which the 
 band rests. When this plaster is removed, wax is added up to the 
 very edge of the band, so that the entire anatomical contour can 
 be restored with gold, including even that of the enamel chipped 
 off at the cervical margin. The wax tooth should always be tried 
 in the mouth, to be sure that 'everything pertaining to form, con-* 
 tour, and position is just right. This was the object of removing 
 the foundation from the plaster model at the outset, as it is a great 
 advantage, and particularly so with facings, to always 
 Fig. 461. j ust at f^-g t - me tr y tne j-QQth i n the mouth. 
 
 Now from a piece of tin-foil (No. 60) a model is cut 
 so as to fit the wax exactly. We cut the gold on the 
 palatal surface from the height of foundation (see A, 
 Fig. 459), thereby enabling us to join the free ends at 
 the cervicopalatal surface. The large ends of the gold 
 we turn out and back, to stay it in the investment of 
 plaster and marble-dust. The gold can be cut a little long, to allow 
 of bringing the cervical ends together. This cervical margin is very 
 important, as shown in Fig. 460. Sometimes three pieces of gold 
 are used instead of one, but if so the pieces of gold should always 
 be cut with projections (as seen in Fig. 459) to retain the exact 
 shape of the tooth and not pull it from the instrument when sol- 
 dered. This gold band must fit just under the edge of the grind- 
 ing surface stamp, and be in perfect contact with it, so as not to 
 allow the grinding surface to move. This little thickness of pure 
 gold (No. 34 American gage) must be allowed for waxing up the 
 tooth. 
 
 Now we have the wax tooth' thoroughly boxed in, excepting the 
 palatal surface. Before taking the next step, be sure that the pure 
 gold band for boxing is in contact with the cervical margin of the 
 foundation band. At the point of junction here and at the grinding 
 surface place a little wax, and then cut all possible surplus away, 
 
ARTIFICIAL CROWNS. 
 
 531 
 
 leaving - only the very junction filled; also be sure no wax gets on 
 the inside of the cervical margin of the foundation band. Now 
 place the tooth in water and invest it in plaster and marble-dust, 
 covering the whole tooth except the palatal surface of the crown ; 
 the plaster must just cover the narrow gold joined at the cervical 
 margin. After the plaster sets, boil out the wax and cut the in- 
 vestment as small as possible, leaving the plaster only about l /§ of 
 an inch all around. Now dry thoroughly, but not in contact with 
 a flame ; ' have something — a top of a tin box, for instance — be- 
 tween the flame and the tooth. After it is dry, place it in the flame 
 of a small Bunsen burner. To hasten the heating up process, a 
 foot blowpipe may be used to get it red-hot very quickly, but 
 nevertheless the heating up is to be done cautiously, and during 
 this time we still have the little Bunsen flame under it. Now, by 
 applying the flame of the Knapp blowpipe, the gold flows with the 
 greatest ease in all parts and in all directions. Here use 20-carat 
 solder. Fill the molar about half full with gold, using borax as a 
 flux, before using the Knapp blowpipe. 
 
 It should be observed that we have the solder almost to the 
 melting-point, everything is .red-hot, and a hot flame beneath the 
 investment, so that when we gently apply the blowpipe flame 
 the gold simply drops, and while in this molten condition add the 
 rest of the solder, never allowing it to cool for one moment, for 
 if it does air-bubbles will result. Here the gold boxing band at 
 the cervicopalatal margin does its work beautifully; the gold flows 
 freely all around, with no danger of solder running inside the 
 foundation from the palatal side. The plaster and marble-dust 
 should always be worked as stiff as possible, so as to always have 
 the gold in contact with plaster, which will not be the case if the 
 investment is mixed thin. The necessity of having everything firmly 
 held, so that the gold solder will not pull it in and change the entire 
 shape of the crown, becomes evident when the large amount of solder 
 used is considered. This being a solid crown, we put it in water to 
 cool, and next in very dilute sulphuric acid, and gently heat it to re- 
 move adhering borax and oxidation. Now we can shape the gold to 
 anatomically correct contour lines and bring the cervical margin 
 down to a feather edge, so that when again placed on the root we 
 have an absolute junction without a lodging place for acids, and the 
 whole tooth restored to a state of perfection. (See Fig. 461.) 
 
MECHANICAL DENTISTRY. 
 
 In the construction of a crown with a porcelain face, the root is 
 shaped just as for a solid crown, excepting that it is cut under the 
 gum on the labial surface, and also lower on the palatal surface, 
 so as to remove all enamel (Fig. 462). After cutting under the 
 gum hold the gum back by anchoring premium gutta-percha in 
 the root canal and press it over the labial surface. After the crown 
 has been set, the gum comes down beautifully over the gold band 
 and prevents its being visible. Prepare and complete the founda- 
 tion the same as for the solid crown, taking impressions, bite, etc., 
 
 Fig. 462. 
 
 Fig. 463. 
 
 Fig. 464. 
 
 as before, and select the shade. Now prepare the facing 
 carefully as follows : Grind the facing shorter than you 
 desire by the thickness of No. 34 gold plate; grind off 
 both angles left at the cervical portion, and also grind 
 the cutting edge on the palatal side from pins to cutting 
 edge, leaving a feather edge at the cutting surface ; like- 
 wise grind the cervical portion from pins to cervical 
 margin, leaving this margin also a feather edge ; also 
 remove angles from pins to approximal margins, the 
 object being to give a perfectly convex contour to the 
 palatal side of the facing. 
 
 After grinding off the heavy angles with the lathe, 
 use discs in the engine, and be sure that all angles are 
 removed. Sometimes it is even necessary to go be- 
 tween the pins with a disc. Now take Scotch stone and make 
 the surface perfectly smooth, edges particularly, or the gold 
 cannot be brought in absolute contact. Three different views 
 of a facing so prepared are shown in Fig. 463. The surface 
 where the pins arc being the highest part, the grinding of the 
 palatal surface is done so as to fill in with 20-carat solder and 
 give all the strength that would be obtained if we ground the 
 cutting edge off square, for when the tooth is finished we have a 
 slightly beveled surface of gold at the cutting edge, the facing hav- 
 
ARTIFICIAL CROWNS. 533 
 
 ing only a feather edge; but that edge is well protected, so we get 
 great strength. We secure, besides, artistic beauty by having the 
 facing exactly the shape of the natural tooth on the whole labial 
 surface. By this method of shaping the facing we never have a 
 tooth to crack, because there are no angles, and, finally, the solder 
 will flow perfectly around the cervicolabial surface. 
 
 Now take this facing (being sure that the palatal surface is clean) 
 and back it with pure gold, No. 34, allowing the gold to project a 
 little at both cervical and cutting edges. In order to back this facing 
 so that the pure gold is in absolute contact with the facing, 
 anneal several times, each time pressing it in contact with the fac- 
 ing with a broad instrument like a plastic spatula No. 20 (Fig. 464). 
 Never stop annealing and working to place until the tooth can be 
 held in contact with the backing at the cutting edge and permits 
 no motion of gold at the cervical margin. The same with the 
 
 Fig. 465. Fig. 466. Fig. 467. 
 
 approximal surfaces. Now hold the tooth and backing tightly 
 between the thumb and middle forefinger, and with the point of a 
 pocket-knife' push the gold into hard contact with the pins all 
 around, using the very point of the knife, and there will be no occa- 
 sion to bend the pins ; besides, it makes a perfect gold surface. 
 
 Place the facing with its backing on the foundation, wax up with 
 hard wax, and try it in position in the mouth. If doubt exists as 
 to the correctness of the position, stay it well with hard wax, then 
 try again for position. After obtaining it, finish waxing up until 
 the contour is anatomically correct, leaving a little margin all around 
 the backing so as to be perfectly boxed in. This is done, just as in 
 the case of the molar, by making a tin-foil model (Fig. 465) and 
 bringing the gold into absolute contact with the backing, because 
 if a small space is left borax will run through and crack the tooth. 
 Great care must be exercised with regard to this contact. 
 
 This cuspid box may be made in two pieces, joined at the cervico- 
 
534 MECHANICAL DENTISTRY. 
 
 labial surface the same as seen at the cervicopalatal and cutting 
 edges. When we bring the gold across the cutting edge, which 
 has the gold projecting a little, not bent over the edge but project- 
 ing in perfect contact, make the pure gold go just a little lower than 
 the cutting edge, so as to have a little bevel of 20-carat gold, 
 so slight that it cannot be seen (Fig. 466). For exceedingly heavy 
 use leave the bevel a little thicker, but even that is scarcely notice- 
 able. Xow fill in the junction of the boxing with the backing, and 
 also of the cervical margin of the foundation with wax, and invest 
 the same as for a solid crown, allowing the plaster and marble-dust 
 to come over the cervicopalatal boxing, etc. 
 
 To solder this crown, place but a few pieces of 20-carat 
 solder and borax in before using the blowpipe, because we 
 want the first gold to flow perfectly at the cervicolabial sur- 
 face and so avoid air-bubbles, after which the course is clear. 
 After the soldering is completed, place the 
 crown under a little box, so that it may 
 cool off slowly and no draft can reach 
 it. When cold, boil in dilute sulphuric 
 acid. This gold will cut down absolutely 
 in contact with the tooth, and when the 
 cutting edge is finished with a slight bevel, 
 it will be seen and understood what great 
 strength has been secured, with, at the same time, a beautiful 
 labial facing of porcelain. When the cervical surface, in fact the 
 whole crown, is finished up in the thorough and artistic manner of 
 which it is capable, it becomes a piece of perfection. (See Fig. 
 467.) 
 
 A bicuspid is made exactly the same as a cuspid, with the ex- 
 ception of the stamp. Make the stamp, and fill the cusps with 
 22-carat solder, then hollow out the buccal cusp to fit the cusp of 
 the facing, and place a very narrow piece of pure gold at the junc- 
 tion on the buccal surface, and continue as in the cuspid. (See 
 Fig, 468. ) 1 f the bicuspid is a short one, do not be afraid of crack- 
 ing die facing; grind and make it exactly as directed, and it will 
 not crack. Notice the curve in the bicuspid cut. 
 
 For a bridge tootb, take a superior right cuspid. Now, when 
 grinding a tooth to fit the gum we necessarily expose the small 
 porosities in the body of the tootb, winch always have a tendency 
 
ARTIFICIAL CROWNS. 535 
 
 to lodge food, thus producing an offensive breath. To correct this 
 defect, shape up this cuspid exactly the same as if we were making 
 a crown, and back it up the same way. Now flow wax over the 
 whole surface, and regulate the thickness of the wax according to 
 the required fullness of the tooth, boxing in with pure gold the 
 height of the wax and restoring the shape of the lost tooth ; then 
 invest to the top of the boxing, and after the proper steps of invest- 
 ing fill in with gold. Here there are two great points to observe. 
 First, this gold can be finished absolutely smooth, so that nothing 
 can collect in the way of food, hence nothing but perfect cleanliness 
 can exist. Secondly, any amount of absorption of gum can be coun- 
 teracted by building out with gold exactly the amount of absorp- 
 tion. This will give the tooth a natural position, a perfectly smooth 
 palatal surface, and restore the lip to its normal, or, in case of a 
 cuspid, almost normal, expression. 
 
 Dr. Mason's System. — It has long been the desire of the pro- 
 fession to overcome the annoyance caused by the breakage of the 
 porcelain facings in crown- and bridge-work. Many efforts have 
 been made to produce detachable facings, but prior to the intro- 
 duction of the *Mason crown none has been designed that could 
 be manufactured and sold to the dentist for his immediate use. 
 Through the efforts of Dr. W. L. Mason, a system of corresponding 
 dovetail and groove, and a process of manufacturing whereby a por- 
 celain facing is made independent of its backing, has been devised. 
 Figs. 469, 470, and 471 represent the manner of constructing a 
 superior cuspid crown. Fig. 469 shows the root, prepared in the 
 usual way for the reception of a collar crown, with the Mason 
 metallic backing adjusted to same ; also the back face of a cuspid 
 facing, showing the dovetail attachment, which is baked in the 
 body of the tooth. Fig. 470 shows the same tooth being adjusted 
 to the backing, while in Fig. 471 we have the crown complete, the 
 same principle being carried out in any other tooth and in bridge- 
 work. 
 
 The tooth, with its dovetail, is fitted to the band by grinding out 
 where necessary. Then the gold backing is waxed to the band, 
 and, after wax is hard, the porcelain is removed from its backing, 
 by taking hold of extended portion of dovetail, and drawn from 
 same. The crown without the porcelain, is now ready to invest for 
 soldering. First the dovetail groove is filled up with Mason's invest- 
 
536 
 
 MECHANICAL DENTISTRY. 
 
 ment material, to keep out the solder, which it will do perfectly, 
 then the piece is invested as usual, letting the plaster come well 
 over the cutting point of backing. It is now ready for soldering, 
 and can be heated up, soldered, and cooled off as quickly as desired. 
 After removing from investment, the groove should be thoroughly 
 cleansed and dried; also the dovetail in porcelain. Now take 
 some chlora-percha, quite thick, fill up groove, and press porcelain 
 home. Saw off (never cut) the extended portion of metal dovetail 
 and finish as usual. Porcelain can also be cemented on with cement 
 or sulphur. For use as a dummy, articulate to position, remove, 
 and solder " stop " to neck of backing to prevent porcelain from 
 slipping upward ; replace on model, join parts with wax, then with- 
 draw the porcelain and invest. 
 
 The advantages gained by this method can only be appreciated 
 
 Fig. 469. 
 
 Fig. 470. 
 
 Fig. 471. 
 
 by practice. The first is that we do not, at any time, have to place 
 the teeth under the flame of the blowpipe ; second, we are not 
 annoyed by the changing of color which takes place in soldering; 
 third, a solid backing, without bubbles; fourth, the invested piece 
 can be quickly heated, soldered, and cooled ; fifth, the small 
 amount of solder necessary — just enough to join parts together; 
 sixth, saving the porcelain from being etched by borax; seventh, 
 we are able to fit a bridge releasing the strain by cutting and 
 resoldering and not have the porcelain interfered with ; eighth, 
 the most important of all, the amount of time saved to the busy 
 dentist in making repairs, it being accomplished in a few minutes. 
 
ARTIFICIAL CROWNS. 537 
 
 THE ALL-GOLD CROWN OR CAP. 
 
 In the construction of the all-gold crown, the sides of the natural 
 crown and neck of the tooth are brought down to, or a little 
 smaller than, the size of the root. This is best accomplished by 
 the use of diamond discs and small corundum stones on the dental 
 engine. From the occluding surface, if any of it remains, a suffi- 
 cient amount should be ground away, and the edges slightly 
 rounded, to allow the introduction of the gold cusps. The meas- 
 urement and making of the band is the same as described in con- 
 nection with the Richmond collar crown (see p. 503), excepting 
 in the width of the ferrule. This should extend from the root, 
 below the gum-margin, to within a line of the occlusion with the 
 antagonizing teeth. After soldering and adjusting, the band should 
 be shaped and contoured with burnishers and suitable pliers, the 
 smooth, round-nosed, answers very nicely. The surface of the band 
 to which the cusps are to be attached should then be brought down 
 perfectly smooth and flat with a fine file; readjusted carefully to the 
 root, to make sure that it has not been so distorted by the different 
 manipulations that it will not pass readily to place and fit the root 
 perfectly at every point. Finding all correct, the next step is mak- 
 ing the cusp. 
 
 A number of methods have been put forward for making gold 
 cusps. The two that have proven most satisfactory are the use of 
 the die, such as described in connection with the Knapp system of 
 making crowns, and by means of the die plate as described by Dr. 
 E. T. Starr, in the Dental Cosmos, as follows: 
 
 In the construction of metal cap crowns to cover natural" teeth 
 or roots there are many methods which result in good work, but in 
 most cases the caps do not articulate as well as they might, for the 
 reason that means for embossing the bicuspid and molar cusps are 
 not at hand, or available within the short time at the disposal of 
 either the patient or the dentist. With the object of providing an 
 easy and quick way of working under such circumstances, I have 
 made a single plate, Fig. 472, in which are four groups of intaglio 
 dies, representing with distinctive correctness the peculiar cusps of 
 the upper and lower right and left bicuspids and molars. These 
 are indicated by the Hillischer notation, so that each form may be 
 easily identified in practice. 
 
538 
 
 MECHANICAL DENTISTRY. 
 
 The hubs A B, Fig. 473, are of the sizes shown, and are made of an 
 alloy composed of tin one part, lead four parts, melted together. The 
 
 Fig. 472. 
 
 Fig. 473. 
 
 mold C should be warmed, the melted alloy poured in every hole, 
 and the overflow wiped off just before the metal stiffens. This will 
 
ARTIFICIAL CROWNS. 
 
 539 
 
 make the butts of the hubs smooth and flat. After a minute or two 
 the mold may be reversed, the hubs shaken out, and the casting 
 process continued until a considerable number of hubs shall have 
 been cast. 
 
 In Fig. 474 a molar hub is shown in place on a piece of Xo. 32 
 
 Fig. 474. 
 
 gold plate, which lies over the upper right first molar die. A suc- 
 cession of blows on the hub, with a four-pound smooth-faced ham- 
 mer, will drive the plate into the, die, and at the same time spread 
 the hub metal from the center to its circumference in such a man- 
 
 Fig. 475. 
 
 ner that the plate will be perfectly struck up with the least possible 
 risk of being cracked. The flattened hub is seen in Fig. 475, which 
 also shows at D the obverse of the struck up hub, and at E the 
 cameo of the struck up plate, having every cusp and depression 
 sharply defined. 
 
540 
 
 MECHANICAL DENTISTRY. 
 
 The counter-die plate. Fig. 472, is made of a very hard cast 
 metal, which will admit of the striking up of many crown-plates by 
 the means and methods described, if the crown-plates be not too 
 thick and stiff. Of course, they should be annealed before they 
 are placed over the die. In careful hands the die-plate should give 
 clear cusp definitions after years of use. 
 
 The peculiar action of the hub in forming first the center of the 
 crown-plate, and spreading from the center outward, as the hub is 
 shortened under the hammer, until the die is overspread by the plate 
 and hub, with the result shown in Fig. 475, is an essential feature 
 of this process for obtaining easily and quickly the superior styles 
 of coronal cameos shown. If a cusp or fissure should chance to 
 crack in hubbing, a small piece of plate may be struck over it, 
 
 Fig. 476. 
 
 or another crown-plate be struck over the first and the two soldered' 
 together. 
 
 The depressions in the struck plate can be partly or wholly filled 
 with scraps of plate or solder, and the surplus plate cut away from 
 the cameo. 
 
 The fact is noteworthy that, by means of a Bunsen burner on 
 blowpipe, these swaged cusps may even be filled with melted scraps 
 cut from the identical plate out of which the cameo was struck. 
 The better way, however, is to fill, say, a 22-carat cameo with 20- 
 carat plate scraps. The fitting and soldering of the doubled or filled 
 cameos to suitable collars is a simple matter, and need not be 
 described. 
 
 It only remains to arid the statement that, by this counter-die and 
 hub process, gold, platinum, silver, or other metallic cap crowns,, 
 
ARTIFICIAL CROWNS. 
 
 541 
 
 having finely formed and solid cusps for proper occlusion and 
 resistance to wear, can be made with little trouble and in a very 
 short time. 
 
 After securing a well-defined occluding surface or cameo for the 
 case in hand, it should be filled with gold plate scraps or solder of 
 a lower carat, with a little borax. This is all held over a Bunsen 
 burner until the small pieces of gold come to the fusing-point and 
 settle down into the depressions of the shell. More small pieces 
 should then be added until it is level full. The surplus gold should 
 then be trimmed away, and a file 
 
 passed several times over the sur- Fig. 477. Fig. 479. 
 
 face of the solder to bring it down 
 perfectly level and smooth. (See Figs. 
 477 and 478.) 
 
 Before removing the band from its 
 position in the mouth, a small mark 
 should be made with an excavator to 
 indicate the center of the buccal sur- 
 face, which will serve as a guide for 
 the correct placement of the cusps. 
 The band should then be contoured 
 with suitable pliers (see Fig. 476), to 
 suit the requirements of the case in 
 hand ; a smooth surface is then given 
 to the end which is to receive the 
 cusps, and it will be found that an 
 accurate joint between them can 
 readily be secured. 
 
 Having carefully noted the line of occlusion and marked the band 
 to indicate the point where the center of the buccal surface of the 
 cusps or crown-plate should be placed and soldered, the two — the 
 band and the crown-plate — should be carefully brought together and 
 secured with a few strands of small binding wire. The joint should 
 now be coated with borax dissolved in water, when it is readv for 
 the final soldering. If solder has been used in filling the cusps, 
 no additional solder will be needed at this time, as bv simply hold- 
 ing the crown over the flame of a small Bunsen burner, as shown 
 in Fig. 479, until the solder is seen' to come to the fusing-point, 
 
54- MECHANICAL DENTISTRY. 
 
 then instantly withdrawing it, the crown-plate and band will be 
 united perfectly. If, however, gold plate has been used entirely 
 in forming the crown-plate, a small piece of solder will be needed 
 to unite them. The crown is then ready for the finishing proc- 
 esses, which consist in filing or grinding off the projecting edges 
 of the crown-plate flush with the face of the crown, and smoothing 
 and beveling the free edge of the band or ferrule ; the crown 
 should then be adjusted to the root and the occlusion noted. If, 
 as is frequently the case, a little of the gold needs to be removed 
 at one or more points, in order to have a perfect occlusion, it should 
 be done with a small, flat-faced corundum stone. The crown should 
 then be removed and polished at the lathe. 
 
 Gold Seamless Contour Crowns. — The manner of construct- 
 ing what is known upon the market as the " Evans Gold Crowns " 
 we here present, through the courtesy of Dr. George Evans, who 
 says : 
 
 " The artistic requirement of all-gold crown-work is, that it shall 
 reproduce the anatomical contour of the natural teeth. This is 
 usually accomplished by melting solder on the collar and then trim- 
 ming it to the form of the crown. A preferable method is to shape 
 the metal forming the sides of the crown by swaging. This is 
 easily done in a crown formed in sections, but a special process 
 is required in the construction of seamless crowns." 
 
 A contour crown can be made by placing a seamless cap on a 
 sectional die or mandrel of the shape of the tooth, first swaging 
 the grinding surface on the mandrel and then stamping downward 
 on the straight sides of the crown with a cap fitted to the shank 
 part of the mandrel. But such a process, like many others, is too 
 complicated to be of any use to the dental practitioner. The sec- 
 tional mold method here presented is simple, practical, and general 
 in its application. 
 
 To describe and illustrate the process, we will take one of the 
 most difficult crowns to construct — a superior molar (Fig. 480). 
 A natural tooth, or one made of plaster, is used as a model. From 
 this a sectional mold is made, as illustrated in Figs. 481 and 482, 
 in Babbitt metal, zinc, or fusible alloy. Into the mold a cap of 
 gold (Fig, 483) 23 to 24 carats fine, 30 to 32 gage, is adjusted, 
 fitting tightly the orifice of the closed mold. The mold is placed 
 
ARTIFICIAL CROWNS. 
 
 543 
 
 in a vise, the cap expanded to the general form of the mold by 
 hammering - into it a mass of cotton, and then swaged more in de- 
 tail to the form, and with a wood point or a burnisher revolved by 
 the dental engine burnished into every part of the mold (Fig. 484). 
 To facilitate the process, the mold should be frequently opened 
 
 Fig. 480. 
 
 Fig. 482. 
 
 ^ii> 
 
 and the gold annealed. Fig. 485 represents the completed crown. 
 These results can be secured by other styles of molds. 
 
 Another method is to form a fusible metal die of the tooth to be 
 crowned, and, after having stamped the grinding surface of the 
 crown, to reverse and swage the sides close to the die; the crown 
 
 Fig. 484. 
 
 Fig. 485. 
 
 w 
 
 Fig. 486. 
 
 is then relieved of the core (die) by heating to the melting-point of 
 the fusible metal and pouring it out. 
 
 For practical use a variety of molds is required, made from 
 natural teeth of different sizes and average forms to serve in cor- 
 responding cases. The crowns can be contracted at the neck more 
 than their size and contour call for, so that the gold will act as a 
 tight-fitting band, which will expand to the form of the root as the 
 crown is pressed up in the process of adjustment. 
 
544 MECHANICAL DENTISTRY. 
 
 Caps of metal can be made in different sizes and kept on hand 
 for use in this and other styles of crown-work by means of a 
 machine, which in principle is such as is used by jewelers for form- 
 ing cap-shaped pieces of gold, and in factories for making copper 
 cartridges. The gold plate, cut into circular pieces, is pressed 
 through a steel die-plate, with punches gaged to the holes; at 
 each punch a small portion of the gold is turned over, thus pre- 
 venting its lapping or creasing. Repeated annealing of the metal 
 is very necessary in this process. 
 
 Methods of Contouring Crowns Constructed in Sections. — 
 In constructing a crown in sections, the collar can be first formed 
 on a mandrel, then placed in a mold, and burnished to the shape 
 of the sides. The process of its adjustment to the neck of the root 
 is then continued in the usual manner. 
 
 Another method is to stamp or burnish up the collar on a die 
 representing the upper sections of a tooth, designated as the mid- 
 dle and cervical third (Fig. 486). After contouring the collar, the 
 cap is adjusted and soldered on. With a metallic stamping plate 
 (see page 538) these caps are quickly made. 
 
 The Selection and Adjustment of Seamless Contour Crowns. 
 — A superior molar — one of the most difficult teeth to operate 
 on — will serve as a typical case to illustrate 
 this process. The crown or root is first 
 shaped, and if necessary built down with 
 amalgam, straight, or tapering slightly on 
 its sides toward the occluding surface. 
 
 The width of the crown required from the 
 anterior to the posterior sides of the occlud- 
 ing surface is first obtained by measurement with a piece of card- 
 board or thin copper plate, as shown at A, Fig. 487. The measure- 
 ment can be taken direct from the mouth, or more conveniently 
 from a small plaster cast made from a correct impression of the 
 prepared crown or root and the two approximal teeth. This meas- 
 urement can also be taken by means of tweezers with a set-screw 
 (Fig. 488). With this measurement as a guide, the proper-sized 
 occluding surface is readily found by comparison with the dimen- 
 sions of the various crowns as shown on the printed chart of the 
 crowns (( ', Figs. 489 and 490). 
 
 The size of the neck can be calculated by the eye, or by taking 
 
ARTIFICIAL CROWNS. 
 
 545 
 
 the dimensions with a piece of fine wire (Fig. 493), pressing the 
 wire on the surface of a piece of sheet-wax, and then comparing 
 with the impression the necks of the gold crowns. 
 
 In making a selection, it should be borne in mind that the cervix 
 of the gold crown should preferably be smaller than larger, as it 
 
 Fig. 488. 
 
 Tweezers with set-screw to use as calipers. 
 
 can always be easily expanded, while its contraction is difficult. 
 It is not essential that the curve of the collar shall correspond with 
 that of the tooth, as the gold will readily take the proper shape as 
 the crown is adjusted. 
 
 Method of Adjusting the Crown. — 1. Anneal the crown se- 
 
 Fig. 489. 
 
 lected, and slip it over the end of the natural crown or root and 
 gently press or work it upward — the gold of the collar will expand 
 to the form of the root in the operation — until the edge meets the 
 margin of the gum (A, Fig. 491). 
 
 2. Mark a line (B) on the gold parallel with the margin of the gum. 
 
 35 
 
546 
 
 MECHANICAL DENTISTRY. 
 
 3. Remove and trim to this line (A, Fig. 494). If necessary- 
 repeat the marking and trimming until the edge meets the gum 
 evenly. 
 
 4. Bevel the edge of the gold, readjust the crown, and press it 
 up until the edge of the collar passes under the margin of the 
 
 Fig. 493. 
 
 Fig. 494. 
 
 gum, and, if the occlusion is correct, burnish the gold to the cer- 
 vix. 
 
 To Expand the Collar and Crown. — If the collar of the crown 
 needs enlargement, it is easily and most properly accomplished with 
 crown expanders shown in Fig. 495, the points of which should be 
 introduced at first just within the edge of the neck, and the gold 
 
 Fig. 495. 
 
 spread sufficiently to allow it to fit over the end of the natural crown 
 or root, the process of expansion being gradually continued as the 
 crown is brought into position. By proceeding in this manner too 
 great expansion is avoided. 
 
 If the entire crown needs enlargement, it is best done by soften- 
 ing a mass of gutta-percha of about the same size as the crown 
 
ARTIFICIAL CROWNS. 
 
 547 
 
 Fig. 496. 
 
 upon the closed ends of a pair of expanding or clamp forceps, 
 which are heated for the purpose. The forceps points with the 
 gutta-percha are then introduced inside the collar of the crown, 
 which should be moistened to prevent adhesion. The gutta-percha 
 is next withdrawn, hardened in cold water, and cut through the 
 center between the points of the forceps. This makes practically 
 an expanding sectional mandrel with which the crown 
 can be enlarged according to the position in which the 
 forceps were introduced (Fig. 496). 
 
 To expand the crown without enlarging the neck, 
 trim off the gutta-percha on the forceps at the neck. 
 
 The naked points of an ordinary lamp forceps can 
 sometimes be used to advantage in expanding a portion 
 of the coronal section of the crown. 
 
 To Alter a Side. — The contour of one or both sides can be 
 depressed and the crown thus narrowed by introducing the 
 points of a crown expander or some tool that will fit loosely inside 
 the crown, then steadying the crown with the fingers, as shown in 
 Fig. 393, and tapping the sides to be reduced with the flat end of a 
 riveting: hammer. This is necessarv when the contour or the side of 
 
 Fig. 497. 
 
 a crown presses on an adjoining tooth, and the crown is thus pre- 
 vented from coming in proper position. 
 
 To Alter the Shape of a Portion of the Collar or Side of a 
 Crown. — Slip the crown over the point of an anvil, the end of a 
 pair of expanders, or a small round-handled instrument held in a 
 vise; then tap the part to be altered with the flat end of a riveting 
 hammer to the form desired. 
 
 To Alter the Occluding Surface. — Before the crown is pressed 
 
548 
 
 MECHANICAL DENTISTRY, 
 
 up to its apparently proper position, the occlusion should be ex- 
 amined, and calculations carefully made to obviate any defects of 
 articulation, which can be readily corrected at this stage by proper 
 manipulation of the crown. Any necessary change in the form of 
 the occluding surface can be made with the crown in position on 
 the tooth, by means of an instrument tapped by the mallet; by 
 removing the crown, placing it over the closed points of an ex- 
 pander, and tapping and burnishing the part ; or by holding the 
 crown between the thumb and forefinger with the edge of the collar 
 resting on the side of the next finger, which when necessary can 
 be protected with a napkin, and then tapping the gold with the point 
 of a riveting hammer (Fig. 498). 
 
 The occluding of the antagonizing teeth on the crown by the 
 patient will assist and complete the process of articulation. 
 
 Fig. 498. 
 
 Fig. 499. 
 
 To Contract the Neck. — Slightly bend in the edge of the gold 
 at the neck with narrow-beaked pliers, and, holding the crown evenly 
 and firmly between the fingers, as shown in Fig. 499, burnish the 
 sides of the neck section inward around the entire circumference of 
 the crown. 
 
 To Considerably Contract a Crown. — Slit the gold longitudin- 
 ally at the palatal side, nearly its full length to the grinding sur- 
 face, bevel off the edge to lap under, contract the crown, readjust 
 to the tooth, remove, place the smallest quantity of dampened fluxed 
 solder filings in the seam on the inside of the crown only, and solder 
 by holding in an alcohol flame. Then proceed with the further 
 adjustment of the crown. 
 
 The outside line of the seam can be stoned off and polished after 
 
ARTIFICIAL CROWNS. 
 
 549 
 
 the crown has been fitted, and additionally soldered to strengthen 
 the sides or grinding surface. 
 
 Strengthening Seamless Gold Contour Crowns. — Additional 
 strength and stiffness can be given to seamless gold crowns, when 
 desired, in several ways. The liability of melting the gold which 
 forms the sides of the crown in the operation has, with some, been 
 the principal objection to their use. This, however, can be avoided. 
 
 When the crown has been properly adjusted, dampen the inner 
 surface with a piece of wet cotton on the point of an instrument; 
 place in the interior a quantity of fluxed solder filings (solder filings 
 mixed with Parr's flux or pulverized vitrified borax) ; place the 
 finger over the open end of the crown, invert, and shake well. A 
 portion of the solder filings will adhere evenly all over the wet sur- 
 face. The surplus is allowed to drop out by removing the finger. 
 Then gradually and uniformly heat the crown by holding it with 
 tweezers in an alcohol flame (not gas) until the solder fuses, when it 
 will flow evenly over the surface of the gold without materially 
 altering the general form. The crown should be held in such a 
 position that a full view of the interior is presented and the melting 
 of the solder rendered visible, which will occur at a red heat. 
 
 An extra quantity of the solder filings can be placed in the inte- 
 rior of the cusps with a spoon-shaped excavator to additionally fill 
 or strengthen them if found necessary. 
 
 When a Bunsen gas flame is used instead of an alcohol flame, the 
 grinding surface and sides of the crown should be first coated' with 
 whiting. This is easily done by dipping the crown into a cream- 
 like mixture of whiting just before inserting it in the flame. The 
 moisture in the whiting should be first slowly evaporated by heat- 
 ing up gradually. Great care must be exercised in the use of a 
 gas flame to avoid melting the crown. The crown should be 
 watched, and instantly removed as soon as the solder fuses and 
 flows. 
 
 If too much solder has been applied at any point, it can be 
 trimmed and smoothed with corundum melted on to an old engine 
 bur point. Always boil the crown in acid to remove the flux. The 
 removal of flux from the inner surface of the crown is absolutely 
 necessary if you intend to use it in bridge-work, as solder will have 
 to be melted on the outside. 
 
 To Repair a Gold Crown. — When a hole is cut or melted in 
 
55Q 
 
 MECHANICAL DENTISTRY. 
 
 Fig. 500. 
 
 any kind of a gold crown, place a piece of soft wax in the aperture 
 on the outside of the crown, adapt on the inside close against the 
 gold a piece of platinum foil, somewhat larger than the aperture, so 
 that it will adhere to the wax. Fill the interior of the crown with 
 investing material, and flow a little solder over the surface of the 
 platinum and gold on the outside of the crown. 
 
 Gold seamless crowns can also be strengthened 
 or filled with solder, or even 18- or 20-carat gold 
 plate, by investing the outside surface in plaster 
 and marble-dust (Fig. 500), and then with a small 
 flame of the carbo-oxyhydrogen blowpipe, not over 
 Yz of an inch in length, introduced inside of the 
 crown, melt and flow the solder or gold plate over 
 any portion or even all of the surface of the gold. 
 The crown, if formed of gold with a thin lining of 
 platinum, can be soldered by either method with 
 little danger of being melted. 
 Supporting the Crown. — In crowning teeth with living pulps 
 there is sufficient of the natural crown present to afford a secure 
 foundation and attachment for the artificial crown, as is also the 
 case with many teeth that are pulpless ; but in badly broken-down 
 crowns, or where only the root is present, a metallic pin or post 
 should be inserted in the root, and the part built down with amal- 
 gam to a form which will afford secure support and 
 attachment to the artificial crown and facilitate its ad- 
 justment. 
 
 In many cases the required support for the crown can 
 be secured by means of a screw (Fig. 501). A How 
 screw or a post of silver wire is inserted in the root 
 canal A. Amalgam is then packed in the lower 
 section of the artificial crown C to the line B, and 
 the screw is pressed into the amalgam. Amalgam 
 which has been put in a piece of chamois and the mer- 
 cury pressed out with a pair of pliers until it is in the condition 
 termed " dry " will adhere to the gold without affecting it. The 
 amalgam is first placed in the crown slightly in excess of the 
 amount required, and the crown adjusted, removed, and the 
 surplus scraped out. This process is continued until the screw or 
 the crown section of the natural tooth forms an indentation in the 
 
 Fig. 'soi. 
 
ARTIFICIAL CROWNS. 
 
 551 
 
 amalgam, which it will fit when the crown is cemented on. The 
 vent for the escape of air and surplus cement — which should always 
 be put in perfect-fitting crowns and afterward filled with gold or 
 amalgam — should be in the line of the indentation in the amalgam, 
 with which it must connect (D). 
 
 These crowns can be inserted in an easy and inexpensive manner 
 by filling in the lower section of the crown with amalgam instead 
 of gold, and allowing the head of the screw or the natural crown to 
 indent the amalgam as above described, and then cementing on the 
 crown with oxyphosphate in the usual manner. 
 
 In a case so inserted, with no antagonizing teeth, the result is the 
 same as though the inside of the occluding surface of the crown was 
 filled with gold ; but if antagonizing teeth are present, the gold of the 
 crown is apt to wear through in places and expose the amalgam. 
 
 To Securely Attach a Crown. — If the tooth is short, and the 
 occlusion of a character requiring the reduction of the collar to 
 such a degree as to suggest insecurity when the crown is cemented, 
 a barbed or headed pin, which will anchor in the natural crown or 
 root, should be soldered in the center of the gold crown. This is 
 done by passing the pin through a hole drilled in the occluding 
 surface of the crown, which is then adjusted in the mouth, removed, 
 invested, and the pin soldered from the outside. If the pin is 
 tapered and fitted tightly to the hole, the soldering can be accom- 
 plished without investing, by holding the crown and pin with sol- 
 der in position in an alcohol flame. 
 
 To Alter a Gold Crown to the Exact Form of any Corres- 
 ponding Natural One. — In a case having nearly all the natural 
 teeth present, in which the occluding surface and sides differ in 
 shape from the form of the gold crown, to such an extent as to in- 
 terfere with its adjustment, a die of the natural crown should be 
 made of fusible metal (Melotte's fusible alloy), and with it the in- 
 terior of the gold crown should be altered in shape sufficiently to 
 receive the natural crown, by resting the occluding surface of the 
 gold crown on a folded napkin and gently tapping the die into it. 
 
 The advantages of seamless contour crowns are, that they represent 
 perfectly the tooth in its anatomical contour, present a uniform sur- 
 face of pure gold, which preserves its color without tarnishing, and are 
 quickly and easily adjusted. Their defects are inability to meet the re- 
 quirements of abnormally-shaped roots and anomalous articulations. 
 
CHAPTER XXXI. 
 BRIDGE DENTURES. 
 
 To the skilled dentist, well versed in crown-work, bridge-work 
 does not present any great difficulty, inasmuch as crowns are the 
 beginning and the end; it is practically continuous crown-work, 
 though many of the crowns — those rilling or bridging the space 
 where the roots have been removed — have neither collars nor posts. 
 In constructing these teeth, the matter of cleanliness should espe- 
 cially be considered ; where it is admissible to allow them to come 
 in contact with the gum tissue (as in the anterior part of the 
 mouth), only the cervical porcelain tips should touch. The metallic 
 backing and solder should recede, leaving self-cleansing spaces. 
 
 Some diversity of opinion exists, however, as to the advisability 
 of permanently fixing such appliances in the mouth. Prominent 
 among the objections urged is, that, in the event of accident to the 
 porcelain facing of the crown, there is no sufficient remedy without 
 detaching the entire piece, of which the teeth are a part. It is 
 further objected that a stationary fixture of this kind in the mouth 
 must become not only offensive from the accumulation and reten- 
 tion of oral debris incapable of adequate dislodgment, but a source 
 of injury to the remaining natural teeth, which necessarily follows 
 the prolonged retention of alimentary substances exposed to con- 
 ditions so favorable to fermentation and putrefactive decomposi- 
 tion. 
 
 On the other hand, the writer entirely agrees with many compe- 
 tent, intelligent, and conscientious operators, who, from observa- 
 tion and experience, are qualified to form a just estimate of the 
 merits or demerits of bridge dentures, and who bear testimony in 
 unqualified commendation of its superior excellence when skilfully 
 performed under conditions that justify the operation, and claim for 
 it as complete exemption from the alleged objections as is obtained 
 in the use of any other mode of replacement in similar cases. 
 
 In fact, herein, we think, lies the secret of either success or 
 
 552 
 
BRIDGE DENTURES. 553 
 
 failure in connection with bridge dentures, for it is in the construc- 
 tion of this class of dentures, more than any other, that unusual 
 mechanical skill is required, and professional judgment needed for 
 determining where they are admissible. 
 
 Limitations. — For the support of bridge dentures, strong, 
 healthy roots are required, and the width of the space to be spanned 
 must be governed by the size and strength of these points of anchor- 
 age. Whether a full upper or lower denture can be supported by 
 four points of attachment depends upon the relative smallness of 
 the jaw, the size and strength of the roots and teeth, and the occlu- 
 sion, the operator always being governed by the exact condition of 
 individual cases. 
 
 Before entering upon a more general consideration of the subject, 
 it may be helpful to give a few reflections or suggestions in the way 
 of typical cases, as follows : 
 
 One strong central root will support two teeth, that is, the crown 
 and either the adjoining central or lateral. Two central roots will 
 support the four incisors. Two strong cuspid roots alone, or with 
 the aid of a central root, will support the six anterior teeth. A 
 cuspid root and a strong, healthy second or third molar on the 
 same side will support the intervening teeth. One molar or 
 bicuspid on one side, and a bicuspid or molar on the other, with 
 one or two central roots, will support a bridge between them. One 
 right and one left molar, with the assistance of the two cuspid 
 roots, when the conditions are favorable, as spoken of above, will 
 support a bridge comprising the entire arch. 
 
 It should be remembered that the preparation of the teeth and 
 roots for the support of a bridge is the same as in ordinary crown- 
 work, except that the trimming of the sides and the drilling of the 
 root canals should be, as far as possible, in parallel lines,, so that in 
 the adjustment of the finished piece the crowns will move readily 
 to their places. 
 
 STATIONARY BRIDGE DENTURES. 
 
 Among the simpler forms of substitution which may be properly 
 classed under the head of " bridge-work,'" is the one in which a 
 single artificial crown derives support from attachments made to 
 one or more of the adjoining natural teeth, originally by a process 
 of cavity filling. The original conception and practical application 
 
554 MECHANICAL DENTISTRY. 
 
 of such a method of supplying' an edentulous space is attributed 
 to Dr. B. J. Bing, of Paris, France, whose method of operating has 
 since been greatly modified. 
 
 Dr. Webb's Method. — One of the earlier experimenters in this 
 mode of replacement was the late Dr. Marshall H. Webb, who 
 thus describes his method of operating in these cases : 
 
 " The insertion of a crown without plate or clasps, where no 
 root remains, is a difficult operation, but when well performed, and 
 the crown attached to teeth that are firm in their sockets, it is both 
 satisfactory and permanent. 
 
 " The first such operation performed by the writer was com- 
 pleted February 12, 1873, and the crown now remains as firm as 
 when inserted. The operation was performed in the following 
 manner : After suitably forming the cavities in the proximate wall 
 of each tooth next the space left by the loss of the one that had 
 been extracted (unnecessarily) some years before, an impression of 
 the parts was taken, and a plain porcelain crown was selected, 
 fitted to place, and backed with gold plate (18 carat). A por- 
 tion of the backing extended about i 1 /* lines from each side of 
 the crown for insertion in the cavities prepared in the adjoining 
 teeth, and to these parts a gold wire was soldered to fit into the 
 pulp chamber of the central and lateral incisors. A small gold 
 plate was then formed to fit upon the gum, covering as much space 
 as was taken up by the neck of the natural tooth. The backing 
 was riveted to the pins in the porcelain, and this placed in position, 
 and while the whole rested on the small plate upon the gum, the 
 backing and plate were so secured by wax that they could be removed 
 intact, and, after being placed in a matrix, soldered. Each extended 
 side of the backing and the surface of the wire was barbed with an 
 engraver's bossing tool, so that the gold-foil would the better secure 
 the crown when filled into every part. 
 
 " The porcelain, with the gold attachments, being ready for in- 
 sertion, a piece of light, medium rubber dam was put in place on 
 two teeth each side of the space to be filled, and over the gum 
 upon which the crown was to rest. (The rubber takes up but lit- 
 tle space, and this is more than compensated for, when the liga- 
 ture — waxed floss-silk — is pressed to or near the neck of each 
 adjoining tooth.) Oxychlorid of zinc was then placed in the pulp 
 chamber of the central incisors and the crown at once pressed to 
 
BRIDGE DEXTURES. 
 
 555 
 
 place. When the cement had hardened sufficiently to safely admit 
 of further progress in the work, a portion of it was cut away from 
 around the wire so as to make proper anchorage for the gold. 
 Small pieces of light cohesive gold-foil were then impacted around 
 part of the wire and that portion of the plate extending into the 
 cavities, and the crown was thus secured. The porcelain and gold 
 attachments as prepared for insertion, and the crown in position, 
 are illustrated in Fig. 502. 
 
 " The cavity in the central incisor was extended to the cutting 
 edge of the tooth, that access might be had to the wire and both 
 sides of the plate; foil could not otherwise have been put in place, 
 unless a portion of the labial margin of enamel were cut away, and 
 this would have been objectionable because of the exposure of gold. 
 
 Fig. 502. 
 
 A small part of the labial instead of the cutting edge of the enamel 
 of the lateral was removed, for the reason that there is not such a 
 body of tissue as to safely allow it to be cut away to the same 
 extent as in a central incisor. The margin of enamel was so formed, 
 and the foil so inserted and finished, however, that, though the gold 
 can be seen, it is not conspicuous. 
 
 " While the operation just described has thus far proved success- 
 ful, yet there is a possibility of the porcelain being broken from the 
 platinum pins which hold it to the gold plate. To avoid such an 
 accident, a groove should be cut on each side, and along the cutting 
 edge of the porcelain (Fig. 503, b), that gold-foil may be impacted 
 into it, after a heavy backing of gold plate and the wire have been 
 fixed in place and soldered. When the groove has been cut in the 
 
556 
 
 MECHANICAL DENTISTRY. 
 
 porcelain with a fine-edged corundum disc, one with an edge of the 
 diameter of the gold wire selected for the case should be used to 
 make a groove across the porcelain between the pins (Fig. 503, a), 
 into which the wire to connect the artificial crown with the natural 
 teeth is to be placed (Fig. 503, b), either beneath the plate, or so 
 that the edges of the latter may be joined to it, as the necessities 
 of the case may require. 
 
 " A starting-point should be made either between the gold 
 backing and porcelain, or between this and the wire, and the latter 
 firmly fixed in a hand-vise while the gold-foil is being impacted 
 with the electromagnetic mallet. When the gold is properly and 
 solidly placed in the groove and over the backing and wire, it not 
 only aids in securing the porcelain, but the contour of the crown 
 
 Fig. 503. 
 
 Fig. 504. 
 
 can be nicely filled out, and the operation made durable and beau- 
 tiful (Fig. 504). 
 
 " The surface of the gold placed along the base of the crown to 
 the edge of the porcelain, and which is to rest against the gum, 
 together with the palatal portion, ought to be properly formed and 
 finished before the crown is put in place, and this should be done 
 in the manner before described. There should be a little space 
 between the wire and cervical wall in each tooth to which the 
 crown is to be attached, and narrow pieces of light gold-foil care- 
 fully placed in this part, between the wire and enamel, with small 
 curved instruments and the aid of the mallet; the surface of the 
 gold at this part at least should be smoothly finished with very 
 narrow (yV of an inch) strips of fine emery cloth before the rubber 
 dam is removed. 
 
 " One of the most satisfactory operations the writer ever per- 
 formed was the insertion of a crown where a cuspid root had been 
 
BRIDGE DENTURES. 
 
 557 
 
 extracted (unnecessarily), and the lady subjected to the wearing of a 
 gold plate for some time. This crown was prepared and the con- 
 tour filled out with foil as described and as illustrated in Fig. 504, 
 but gold wire. No. 13, was attached to and built in with the porce- 
 lain, placed into the pulp chamber of the adjoining lateral incisor 
 (which had been filled), and this same wire extended from the 
 anterior to near the posterior proximate surface of the first bicuspid 
 tooth, the pulp of which remained in normal condition. The 
 crown was placed in position with oxychlorid of zinc, and cohesive 
 gold-foil was then impacted with the electromagnetic mallet 
 around a portion of the wire in the root and info the cavity in the 
 crown of the incisor, also into the cavity in each proximate wall of 
 the bicuspid tooth, as well as around and over the wire, joining the 
 two fillings through the enlarged fissure. 
 
 " An extensive operation of attaching a crown to adjoining teeth 
 was performed by the writer before the Pennsylvania State Dental 
 Society, in July, 1879. ^ n this case disintegration had taken place 
 in many of the teeth, and cavities of decay had been prepared and 
 filled from time to time. The teeth were abraded and the dentine 
 was exposed along the entire cutting edge of each tooth that oc- 
 cluded with another. The right upper lateral incisor had been 
 lost twelve years before. The crown of the left cuspid tooth was 
 missing, and but a small portion of the enamel and dentine of the 
 first bicuspid upon either side remained. These last were, of 
 course, pulpless, as also were the right cuspid and central and left 
 lateral incisor teeth, and the pulp chamber of each of these had 
 been filled. All the operations were performed previous to the 
 insertion of the crown in the space left by the loss of the lateral 
 incisor, and, as this crown and each cavity and pulp chamber was 
 prepared for the gold, all appeared as here illustrated (Fig. 505).* 
 
 "Gold wire (No. 13), with a sharp thread cut upon it, was 
 screwed into the dentine, and, at the same time, all the interstices 
 between the tissue and the gold were filled with oxychlorid of zinc. 
 When crystallization had taken place, some of the cement and den- 
 tine was removed from around the wire with a small bur, and a 
 groove was cut in the dentine near the margin of the root so as to 
 
 * The cut (Fig. 505) illustrates the case well, though there are parts and 
 grooves in which to anchor the gold that are not distinctly shown. — M. H. W. 
 
558 
 
 MECHANICAL DENTISTRY, 
 
 secure proper and sufficient anchorage for gold ; cohesive foil (prin- 
 cipally Xo. 30) was impacted into these parts, and the entire con- 
 tour of the crown was restored with the electromagnetic mallet. 
 This crown was not faced with porcelain, because the teeth of the 
 gentleman for whom these operations were performed are but 
 slightly exposed to view ; and then, too, the gold had to be placed 
 over the enamel to support and protect it along the cutting edges 
 of all the incisor, the cuspid, and bicuspid teeth. A gold screw 
 was placed in the pulp chamber and extended into the crown of 
 each bicuspid tooth (Fig. 505). The apical foramen of each pulp- 
 less tooth was closed, and the whole of each pulp chamber into- 
 
 Fig. 505. 
 
 which a wire was not placed was filled with gold. With a properly 
 adjusted electromagnetic mallet, carefully guided, and operated 
 with a full current of electricity from a freshly charged four-cell 
 Bunsen battery, the contour of each crown was restored with gold, 
 made solid and perfect throughout ; the foil was placed in the same 
 manner over the finely prepared margins of enamel, which were 
 not marred in the least (Fig. 506). 
 
 " The lower incisor teeth had so changed after the loss of the 
 upper lateral that they almost closed upon the gum. This was 
 partly owing to the abrasion of the remaining teeth, and in part 
 due to the lower incisors gradually rising in the alveolar process. 
 Because of such occlusions of the teeth a porcelain crown (plain 
 
BRIDGE DENTURES. 
 
 559 
 
 ' plate tooth ') with ' cross-pins ' was used, and fitted .and soldered to 
 the gold wire, there being- no space for a backing of plate. When the 
 wire was prepared, the porcelain grooved and fitted to it, and ready 
 for the placing on of the gold-foil, the whole appeared as illustrated 
 (Fig. 505), the wire extending into each adjoining root about four 
 lines. The cutting edge of the porcelain was removed to the same 
 extent as that of the abraded and prepared incisors, so as to present 
 the same appearance and have the gold support and protect the re- 
 maining part. The wire of the crown was held in a hand-vise, 
 while cohesive gold-foil was placed solidly in the grooves, around 
 the wire, over the cutting edge of the porcelain, and the entire con- 
 tour restored with the electromagnetic mallet. During the final 
 fitting of the crown, it was made to so rest against the gum that 
 the blood was pressed from the capillaries of the part. When 
 
 Fig. 506. 
 
 ready for insertion, a medium rubber dam was applied to two teeth 
 each side of and across the space which was to receive the crown ; 
 small barbs were made all around the wire with a sharp knife, and 
 oxychlorid of zinc was then placed in the pulp chamber of the cen- 
 tral incisor and cuspid, and the crown at once pressed to place. 
 After it had been in position an hour, to allow of complete crystal- 
 lization of the cement, portions of this and of the dentine were re- 
 moved with a small bur so as to better secure the crown and ob- 
 tain anchorage for the gold-foil then to be put in place around the 
 wire, into each cavity, and over the prepared margins of the enamel. 
 Principally No. 30 gold (% of an ounce cohesive foil) was used 
 in this case, and all was impacted with the electromagnetic mallet, 
 except a few pieces of light foil placed in the space between the 
 wire and cervical wall, and even these pieces were gone over with 
 this very valuable instrument after they were in place. With this 
 
560 
 
 MECHANICAL DENTISTRY, 
 
 and all the operations completed, the case appears as illustrated in 
 Figs. 506 and 507. 
 
 " All those who have the ability" and who will work earnestly 
 and conscientiously to properly perform the various operations 
 described, and .do their very best in every case, can so manage their 
 practice as not to make it necessary for any of the patients they have 
 charge of to wear artificial teeth mounted upon plates." 
 
 Dr. W ebb's method of operating in these cases was, to some ex- 
 tent, subsequently modified as follows : 
 
 " The method, modified and followed by the writer since per- 
 
 a, b, d, f, g, and h. Pulpless teeth, g. Whole crown restored with gold, a, f, and 
 h. Almost entire gold crowns. The teeth, b and d, support the gold crown 
 faced with porcelain, c, and fully one-fourth of the crown of each of these is 
 restored with gold, as is also that of e, the pulp of which is living. 
 
 forming his first operation, is quite different from the mode adopted 
 in inserting the first crown, which was prepared somewhat accord- 
 ing to Dr. Bing's plan, and, though the work is more difficult, yet 
 the improved crown is stronger, and more complete, cleanly, and 
 beautiful than when gold plate is simply riveted and soldered to the 
 porcelain. It was to avoid such an accident as the breaking of the 
 porcelain from the pins that the writer modified the method of pre- 
 paring and inserting crowns. Among the changes made were 
 those of making a groove (though not cutting it too deeply) in 
 
BRIDGE DENTURES. 
 
 501 
 
 each side and along the cutting edge of the porcelain, and placing 
 gold-foil solidly in the groove and slightly over the cutting edge, 
 to make the porcelain more secure than when the platinum pins 
 alone hold it, and to protect the edge from the occlusion of the 
 lower teeth; also, to build the crown into the approximal surfaces 
 only. After the wire has been fitted to the adjoining tooth or teeth, 
 or properly placed in a root, and a heavy but rather narrow back- 
 ing of gold plate has been riveted to the porcelain, and the parts 
 are fixed together and soldered, the greater part of the preparation of 
 a crown which remains to be made, and the whole of the building 
 of gold-foil about it, is done out of the mouth at whatever time 
 may best suit the operator; but the work requires care, and must 
 be skilfully and well done. A starting-point should be made 
 either between the gold backing and porcelain or between this and 
 the wire, and the latter must be firmly fixed in a hand-vise while 
 the gold- foil is being put in place and made compact with the electro- 
 magnetic mallet. All crowns should be prepared and finished in 
 the manner described, with such change or additional work as is 
 necessary to place them on roots, or to attach them to single or to 
 the two adjoining teeth where roots are missing. 
 
 " Methods have been devised or adopted with the object of les- 
 sening the time necessary to perform such operations, and making 
 them easy and cheap, by the use of amalgam or some other plastic 
 material; but sufficient time must be taken, excellent judgment and 
 ability are required, and the use of gold is necessary for the doing 
 of really fine, beautiful, and permanent work. 
 
 " When a crown is to be attached to one tooth alone, the opera- 
 tion is not likely to be successful (excepting where a bicuspid 
 crown is built into a molar tooth), unless the tooth which is to 
 support the crown be a pulpless one, and then such an operation 
 can be made both durable and beautiful. To secure sufficient an- 
 chorage for the insertion of a crown in such a manner, therefore, 
 it may sometimes be necessary to destroy a pulp; but this ought 
 to be the last resort, and should be done only when calcification 
 of the enamel and dentine is complete or apparently so. The end, 
 if well attained, justifies the destruction of a pulp for the insertion 
 of a crown, mainly because of the beneficial results which follow. 
 
 " Where a crown is to be built on to one tooth only, a gold wire 
 no lighter than No. 12 should be used. It should be fitted as far 
 36 
 
562 MECHANICAL DENTISTRY. 
 
 up the root as it is safe to enlarge the pulp chamber for it; but 
 
 the drilling may be properly done only after every part of the pulp 
 
 has been removed and the apical foramen has been carefully 
 
 closed with small, narrow pieces of light gold-foil, which must not 
 
 be put in place so long as there is any irritation about the end of 
 
 the root. 
 
 " In the case here illustrated (Fig. 508), the wire is fitted in the 
 
 root and bent to receive the crown, and the cavity is prepared 
 
 for the filling in of gold. The cuspid, as well as the other teeth 
 
 remaining in the mouth, became so abraded as to expose the 
 
 dentine, so that the margins of enamel had to be prepared for the 
 
 placing of gold over them, and when the crown was built in place, 
 
 they were carefully covered with and are thus protected by the 
 
 solid metal. After the porcelain part of the crown of the lateral 
 
 incisor had been fitted to the model and 
 Fig. 508. 
 
 soldered to the wire — this portion of 
 
 the wire should be flattened somewhat 
 
 in some cases — the groove was made 
 
 around the porcelain ; the foil was solidly 
 
 built in place, and finished in the manner 
 
 hereinbefore described ; the crown was 
 
 then inserted, and the contour of the 
 
 cuspid tooth was restored with gold. 
 
 The root of the left central incisor remains, and the crown which is 
 
 fitted upon it is prepared for the building on of gold-foil; after 
 
 which it will be ready for insertion. When this crown is put in 
 
 place, the gold wire is to be surrounded with gutta-percha; but 
 
 little of which is, or should be, needed in the pulp chamber, because 
 
 of the close fitting of the wire in, and of the crown upon, the root. 
 
 During this preparation, a plain pivot crown is kept upon the root, 
 
 held by wood and gutta-percha. 
 
 " When the lateral incisor crown, in the case illustrated, was 
 
 ready for insertion, and the gold at the base, which was to rest 
 
 upon the gum, had been nicely fitted to it, and the whole of the 
 
 gold was smoothly finished, a good-sized piece of medium rubber 
 
 dam was applied to the teeth (the cuspid and the central and 
 
 lateral incisors) on each side of the space to be filled, and arranged 
 
 so as to cover the gum and the ropt between these teeth. The 
 
 crown was made to so rest upon the gum as to press the blood 
 
BRIDGE DENTURES. 563 
 
 from the capillaries of the part, and thus prevent particles of food 
 from getting under it. (While the thickness of the rubber dam 
 might, to some extent, prevent the placing of such a crown against 
 the gum as firmly as it should be pressed, yet this thickness is 
 compensated for by the pressing up of the gum when the floss-silk 
 ligatures are placed about the neck of each adjoining tooth.) 
 After all this had been done, and fine barbs were cut around the 
 gold wire with a sharp knife-blade, oxychlorid of zinc was placed 
 in the pulp chamber of the cuspid tooth, and, while the cement 
 was still plastic, the crown was at once pressed into place, and held 
 there for a few moments. 
 
 " After the cement had hardened sufficiently to safely admit of 
 it, it was cut away from around the wire at such parts as would 
 make proper anchorage for the gold. There was, and in every 
 case should be, a little space left between the wire and cervical wall 
 to be filled with gold for the protection of the enamel at this part. 
 Narrow pieces of light cohesive foil were first placed in this space 
 with small, suitably curved instruments, and afterward solidified 
 with the mallet; after which a little larger, though still narrow, and 
 heavier (none over No. 32) pieces of folded foil were used for 
 placing around and about the wire in the root, filling the cavity, 
 restoring the contour, covering and protecting the prepared mar- 
 gins of the enamel, each piece of the gold being thoroughly cohesive 
 and made compact with the electromagnetic mallet. The surface 
 of the gold placed around the wire between it and the cervical wall, 
 as well as all that part near the gum, was smoothly finished with 
 small files and very narrow (Jg of an inch wide) strips of emery 
 cloth before the removal of the rubber dam; after which the re- 
 mainder of the gold was made smooth and so trimmed down as to 
 be sure of the proper occlusion of the teeth. The crown attached 
 to the cuspid tooth was made just short enough to be free from the 
 striking of the lower teeth. The operation was finished at another 
 time with Hindustan stones, together with pumice upon fine wood 
 made into suitable shape. 
 
 " When a crown can be securely attached to one instead of two 
 teeth, the time of building-in is lessened about one-half. The 
 slight movement which takes place in the socket of the tooth 
 supporting the crown is not so interfered with as when two teeth 
 are fixed together by the gold wire holding the porcelain. If it 
 
564 
 
 MECHANICAL DENTISTRY. 
 
 should afterward become necessary to perform operations upon 
 the adjoining teeth, the rubber dam can as readily be applied as 
 before attaching the crown." 
 
 Dr. Darby's Method. — Professor E. T. Darby, in commenting 
 on the method just described, says : " Dr. B. J. Bing was the first to 
 call my attention to a method of building one tooth into the adjoin- 
 ing teeth by means of gold wires running from the artificial into 
 the natural teeth. I have never seen any of Dr. Bing's operations, 
 but Dr. Marshall H. Webb has called my attention to one or more 
 in the mouths of his patients, which have done good service for 
 years. I also have in my own practice several of which have proved 
 most satisfactory. 
 
 "The cuts, Figs. 509 and 510, represent two cases where arti- 
 
 Fig. 509. 
 
 Fig. 510. 
 
 ficial crowns have received their support from the adjoining teeth. 
 It is desirable to have a pulpless tooth for a neighbor, though I 
 question if one would be justified in devitalizing a pulp to secure 
 this end. In the cases presented, a piece of gold wire was soldered 
 to the backing of the porcelain tooth, and allowed to extend well 
 up the pulp canal of one of the adjoining teeth. After it had been 
 nicely fitted to its place, the rubber clam was applied and drawn 
 tightly over the gum between the two natural teeth ; the canal of 
 the devitalized tooth was then filled with oxychlorid of zinc and the 
 tooth, with its gold support, pressed into position. When the cement 
 had hardened, the bulk of it was cut out and the space filled thor- 
 oughly with gold. The other end of the bar was packed around 
 with gold-foil, and the cavity of decay or cavity of convenience was 
 filled in the ordinary way. 
 
BRIDGE DENTURES. 
 
 565 
 
 " It is always better to take an impression of the space and 
 adjoining teeth at the outset, and then do the major part of the 
 work in the laboratory. The gold wire which enters the root can 
 be bent or shaped with the pliers when the crown is adjusted for 
 final insertion. 
 
 " I would not be understood as saying that these operations can 
 only be performed successfully where there is a devitalized tooth 
 for a neighbor; on the contrary, I have seen teeth inserted in this 
 way where both teeth were living, but the support which is to be 
 derived from the long right angle of gold in the root is certainly a 
 great security against accident, adding, as it must, much strength 
 to the operation." 
 
 The Plate and Pin Bridge. — Professor Wilbur F. Litch has 
 greatly improved and simplified the method of attaching a single 
 
 Fig. 51 1. 
 
 crown to the adjoining teeth in the class of cases under considera- 
 tion. The following is his description of the process : 
 
 "Fig. 511 represents a typical case, in which a lateral incisor 
 (crown and root) has been lost, the cuspid and front incisor, fully 
 vitalized and without approximal carious cavities, remaining in posi- 
 tion. 
 
 " 1. Take in plaster an accurate impression of the cuspid and 
 incisor and the interspace. From this obtain a plaster model of 
 the parts. 
 
 " 2. Make from pure gold, rolled to the thinness of 26, standard 
 gage, base-plates, to be carefully adjusted to the palato-approxi- 
 mal surfaces of the cuspid and incisor. These can be made by 
 swaging on dies and counter-dies obtained from the model, but more 
 conveniently by bending the gold into shape upon the plaster model 
 and pressing and burnishing it into perfect adaptation upon the 
 natural teeth. 
 
5 66 MECHANICAL DENTISTRY. 
 
 " 3. Select a plain plate porcelain tooth of suitable length, shape, 
 and shade, and wide enough to fit easily into the interspace. Let 
 the neck of the tooth rest lightly upon the gum. 
 
 " 4. With pure gold or platinum make a backing for the porce- 
 lain tooth. 
 
 " 5. Place the tooth thus prepared and the base-plates already 
 made upon the cast, and accurately adjust the approximal edges of 
 the base-plates to the backing of the porcelain tooth in situ upon the 
 cast. 
 
 " 6. When this adjustment is made, cement together the base- 
 plates and backing with a brittle, resinous cement (resin, two 
 parts; wax, one part; or sealing-wax will answer), and before the 
 cement has fully hardened remove from the cast to position in the 
 mouth, perfecting the final adjustment there. By this method much 
 greater accuracy of adaptation is obtained, as the lines of length, 
 width, and contour are too fine to be reproduced with absolute 
 fidelity in a plaster model. In this part of the process too much 
 care cannot be taken to have each piece of the appliance fitted with 
 absolute accuracy to the surface for which it is designed. When 
 this has been accomplished, throw upon the yet more or less plastic 
 cement a stream of ice-cold water from an office syringe; this ren- 
 ders the cement perfectly brittle and incapable of bending. Imme- 
 diately remove from the mouth and invest in a mixture of equal 
 parts of marble-dust and plaster-of-Paris. 
 
 " 7. After the investment has firmly set, solder the base-plates 
 to the backing, and the backing to the platinum pins of the porce- 
 lain tooth, using as a solder 20-carat gold. Thus joined, the appli- 
 ance will present the appearance shown in Fig. 515. A represent- 
 ing the base-plate for the cuspid ; B, the base-plate for the incisor ; 
 C, the porcelain tooth with its platinum backing; D, the points of 
 union between the base-plates and backing. At these points the 
 greatest strength is required, and it is important that here a large 
 amount of the solder should be placed. The porcelain tooth being 
 usually thinner than the natural teeth, there is nearly always an 
 angle or depression at the points indicated, in which the thickness 
 of the gold can be considerably increased without interfering with 
 occlusion. 
 
 " 8. For the purpose of attaching the denture as thus far con- 
 structed, drill a small cylindrical opening through the palatal stir- 
 
BRIDGE DENTURES. 567 
 
 face of the enamel of the cuspid and incisor respectively. These 
 openings should usually be placed about as indicated in Fig. 514, 
 at C, D. Sometimes, owing to a close occlusion, or to the con- 
 tour of the tooth, it is desirable that they should be located a trifle 
 nearer the neck of the tooth. Each opening should be well under- 
 cut, but must not encroach upon the dentine far enough to endanger 
 the pulp. In size the openings need not be larger than will admit 
 a platinum pinhead, in diameter corresponding to 13, standard gage, 
 with a shank of 18, standard gage. Into each of these openings 
 must be fitted a platinum pin of the size indicated. The head of 
 each pin must be made thin and perfectly flat both upon its upper 
 and under surfaces. 
 
 " 9. In each of the base-plates make an opening corresponding 
 in position to those in the natural teeth. Pass through these open- 
 ings and cement in them the free ends of the platinum pins. 
 
 Fig. 512. Fig. 513. 
 
 While the cement is yet plastic, place the denture in position in 
 the mouth, carefully pressing the pinheads into the openings made 
 for them and burnishing the base-plates into perfect contact with 
 the palatal surfaces of the teeth; chill the cement, remove and 
 invest as before, and with 20-carat gold solder the pins to the base- 
 plates, flowing upon them and the backing as much of the solder 
 as may be necessary to give them the desired thickness and rigidity ; 
 the amount admissible largely depending upon the nature of the 
 occlusion, a central thickness of about 21, standard gage, being all 
 that is really requisite for strength, while the edges can be made 
 much thinner. 
 
 "Fig. 512 represents the appliance without the pin. A is the 
 porcelain tooth and backing ; E, the base-plates ; C and F, the open- 
 ings for the pins. 
 
 "Fig. 513 represents the appliance completed, with the pins in 
 position. 
 
5 68 
 
 MECHANICAL DENTISTRY. 
 
 " Fig. 514 represents the natural teeth and interspace B, with 
 openings for retaining pins, C, D. 
 
 "Fig. 515, already described, represents the appearance presented 
 when the bridge is cemented in position. 
 
 " To Attach the Bridge. — To attach the bridge the best attainable 
 oxyphosphate cement should be used. It is desirable that it should 
 set slowly. Thoroughly dry the teeth and denture; mix the cement 
 to as thick a consistency as is compatible with perfect plasticity. 
 A thick, viscid, semi-fluid mass is what is required. With suitable 
 instruments, swiftly but carefully place the cement around the head 
 and shank of each platinum pin, and also in the openings in the 
 natural teeth. This care is necessary in order to exclude all the 
 air-bubbles and thoroughly engage the pinheads in the cement. 
 They furnish ample retaining surface, but none to spare. In pack- 
 
 Fig. 514. 
 
 ing the cement around the pins, the under surface of the base-plates 
 should at the same time be covered. 
 
 " The above details being perfected, the denture is at once car- 
 ried to position, and with broad-pointed, serrated instruments 
 pressed firmly into place, the excess of cement, if of the proper con- 
 sistency, freely oozing at all margins. 
 
 " Too much care cannot be exercised in the cementing process. 
 As every second of time is of value, all instruments required must 
 be selected and conveniently placed before the oxyphosphate is 
 mixed. To secure the most rapid, and at the same time thorough, 
 admixture of the phosphoric acid and zinc oxid, a thick plate-glass 
 slab, four inches square, with a flat (not a concave) surface should 
 be used. The spatula should be of steel, thin and elastic, and ^ of 
 an inch wide. With these implements the whole mass of cement, 
 acid, and oxid can almost instantly be brought into union, the 
 
BRIDGE DENTURES. 569 
 
 spatula being used as a muller. When a narrow and rigid spatula 
 is used in mixing any considerable amount of oxyphosphate, the 
 process can be accomplished only in detail, portion by portion, much 
 valuable time being thus lost, during which the setting process is 
 every moment hastening to its completion- and rendering the cement 
 unfit for use in this or any other form of bridge-work. A large 
 excess of acid will, of course, make a thinner and more slowly 
 setting mass, but a cement thus mixed is deficient in strength and 
 too unstable to give good results. 
 
 " A very troublesome obstacle to success in the use of the 
 oxyphosphate cements will often be found in the temperature of 
 the air, an elevated temperature so hastening those chemical 
 changes upon which the hardening of these cements depends as 
 to render their use almost impracticable. This difficulty is likely 
 to occur only in the hotter seasons of the year, and can readily be 
 overcome by placing the mixing slab, as well as the acid and oxid 
 bottles, in cold water until their temperature has been considerably 
 reduced. 
 
 " During severe winter weather too low a temperature also gives 
 trouble, the acid and oxid, even when the former is in some excess, 
 forming a powdery mass utterly unworkable, but which melts down 
 into an almost fluid condition when brought into contact with the 
 warmth of a tooth in situ. A temperature between 6o° and 65 ° F. 
 secures the best results in mixing oxyphosphate cements. 
 
 " Application to Piilpless Teeth. — In the above description the 
 vitality of the cuspid and incisor has been assumed; but, as can 
 readily be understood, the pin and plate bridge can be even more 
 readily and securely placed when one or both pulps are devitalized, 
 for the reason that, the pulp chamber being empty, the pinholes 
 in that tooth can be made as much larger and deeper as may be 
 deemed desirable, the size of the pin being, of course, correspond- 
 ingly increased. In a devitalized tooth, too, the base-plate can be 
 sunk into the palatine surfaces when they interfere with occlusion, 
 as sometimes happens when the antagonism of the lower teeth is 
 very close and the overlap is considerable. 
 
 " Ordinarily, however, such interference is considerable, and the 
 difficulty can always be overcome either in devitalized teeth by the 
 expedient just suggested, or by carrying the base-plates as far 
 away from the cutting edge as practicable, at the same time mak- 
 
5/0 
 
 MECHANICAL DENTISTRY. 
 
 ing them at the point of contact as thin as is consistent with strength ; 
 finally, if necessary, removing a slight portion of the cutting edge 
 of the occluding lower tooth. 
 
 " As experience with this as well as other forms of bridge- work 
 has fully demonstrated, a slight mutilation of a natural tooth is far 
 less destructive in its ultimate results than is the wearing of partial 
 plates, in the use of which pressure falls upon the gum tissue, with 
 the ultimate effect of stripping it from around the necks of the 
 natural teeth, thus denuding them of that protective covering, and 
 exposing them to the ravages of decay, and it may be safely 
 affirmed that in all applicable cases the pin and plate bridge ac- 
 complishes its purpose with the minimum of injury to the natural 
 organs. 
 
 " The small size of the retaining pins may excite doubts as to 
 the strength of the denture ; but pins smaller in size are constantly 
 used for attaching porcelain teeth to plates, and in the upper in- 
 cisors these pins are much less advantageously placed for resist- 
 ance to pressure than are those imbedded in the natural teeth in the 
 process above described. 
 
 " The weakest point in the bridge is not the pins, but the cement ; 
 this, while not so. strong as the fused porcelain which surrounds the 
 pins in artificial teeth, is, as experience has demonstrated, just strong 
 enough to resist all ordinary wear and tear, without being so in- 
 tractable as to render the removal of the denture for purposes of 
 repair a practical impossibility by any method short of its destruc- 
 tion. 
 
 " Even with a good oxyphosphate cement, the work of removal 
 is one of no slight difficulty, and requires the exercise of so con- 
 siderable an amount of force that no one who has had occasion to 
 perform that operation will question the security of any well- 
 constructed specimen of this form of bridge. During an experi- 
 ence of some seven or eight years in their use, the writer has had 
 but one or two cases in which the appliance became loosened, and 
 only one in which it was detached outright. In the latter case 
 the bridge (constructed with the natural tooth of the wearer in- 
 stead of a porcelain substitute) had been firmly in position for 
 more than a year, when the sudden wrench, consequent upon 
 biting into a very hard peach, detached it. Being immediately 
 replaced, it has since then done good service. In such cases it is 
 
BRIDGE DENTURES. 57I 
 
 usually advisable to slightly deepen the undercuts in the pinholes 
 before replacing. 
 
 " Repairing. — As in all other forms of bridge-work in which 
 porcelain teeth are used, the accident most likely to happen is the 
 fracture of this brittle material. As the bridge does not yield 
 under pressure as does a detached plate, resting upon the compres- 
 sible gum tissue, this form of breakage is one to which bridge- 
 work is more than usually liable. For the pin and plate bridge, 
 the least difficult method of repair is to separate the tooth and 
 backing from the base-plates by means of a watch-spring saw, and 
 then force off the base-plates singly, this being much more easily 
 accomplished than their removal when united to the backing. 
 Another tooth is then selected, fitted, backed, and soldered as 
 before. 
 
 " As a rule, the writer has confined the use of this form of 
 bridge to cases in which only a single incisor is missing, but he 
 lias successfully attached a front and lateral incisor to a cuspid 
 and the remaining front incisor. When an unusual strain is to be 
 expected, the retaining pins and pinholes should, when practicable, 
 1}e made correspondingly large, or two smaller pins may be an- 
 chored in one tooth, which latter plan gives very great resisting 
 power, and renders removal in the highest degree difficult and 
 laborious." Prof. Litch informs us that, for his more recent opera- 
 tions of this class, he has adopted the method of using one plate 
 only; that is, making the attachment to one of the adjoining teeth, 
 iDUt uses in this two small retaining pins, one of them being placed, 
 say, near the cutting edge on the mesial side and the other on the 
 distal side near the palatal edge of the plate. (See Fig. 511.) 
 
 Under this head, plate and pin bridges, may properly be classed a 
 process of replacement described by Prof. Litch in connection with 
 the " pin and plate attachments " as a means of support for single 
 front teeth, a method of attachment which, he says, although chiefly 
 applicable to the incisors, may be combined with crown or bar 
 bridges for molars and bicuspids. 
 
 "Fig. 516 represents a practical case in which the upper third 
 molar and first bicuspid (both without antagonizing teeth) were 
 utilized for the attachment of a bridge made of gold crowns with 
 porcelain facings, to supply the loss of the intervening teeth. 
 
 " Fig. 517 represents the case as prepared for the bridge. A, 
 
572 
 
 MECHANICAL DENTISTRY. 
 
 the inner cusp of the bicuspid cut down to allow the placing of a 
 sufficiently thick crown-plate ; B, a cylindrical undercut opening 
 between the cusps for a retaining pin ; C, the third molar made 
 uniform in size from neck to grinding surface, the latter also being 
 considerably retrenched ; D, the crown-plate of a partial cap, made 
 of pure gold, soldered with 20-carat gold, and so constructed as 
 
 Fig. 516. 
 
 to cover every portion of the tooth except its buccal surface, the 
 free edge passing up under the gum; E, a retaining pin adapted to> 
 the opening, B ; F, the gold cap for the molar. 
 
 " Fig. 518 represents the bridge anchored in position with oxy- 
 phosphate cement. 
 
 " In the above case it will be observed that there is a cons.ider- 
 
 Fig. 517. 
 
 able space between the bicuspid and cuspid. This made it readily 
 practicable to give so considerable a thickness to the mesial waif 
 of the partial cap as to hold it securely against the side of the tooth. 
 Had the space been less, contact with the cuspid would have afforded 
 the desired security. 
 
 " Fig- 5 T 9 represents another case in which a bridge was at- 
 
BRIDGE DENTURES. 
 
 573 
 
 tached by a bar, partial cap, and retaining pin. A is an upper sec- 
 ond bicuspid, without antagonist; B, its inner cusp cut down; C, 
 opening for retaining pin ; D, second molar, with slot for bar ; E, 
 cuspid; F represents the partial facing; G, the retaining pin; H, 
 a molar crown of gold, with porcelain front; I, a platinum bar at- 
 
 Fig. 518. 
 
 Fig. 519. 
 
 Fig. 520. 
 
 ,; : :___... _ 
 
 tached to the crown (H) and made to fit into a slot (at D) ; J, a 
 plain plate cuspid, heavily backed and strongly soldered to the 
 partial cap, but left without attachment to or contact with the 
 cuspid. 
 
 " Fig. 520 shows the bridge anchored in position. 
 
574 MECHANICAL DENTISTRY. 
 
 " This case, after two years of wear, is still in perfect condition 
 and doing good service. As it was possible to keep the gold at- 
 tachments, backings, etc., out of sight, the appearance presented 
 is very natural. 
 
 "The bridge shown in Fig. 518 has been in use but a few 
 months. 
 
 " The absence of antagonizing teeth for the bicuspids in each of 
 these cases was a favorable condition, as a considerable thickness 
 could be given to the crown-plate without any interference with 
 occlusion. When the conditions are not so favorable, cutting 
 down the inner cusp to the required extent and sinking the open- 
 ing for the retaining pin to the necessary depth are processes cer- 
 tainly to be, as a rule, preferred to the entire removal of the crown 
 for the purpose of ferruling the root for the mounting of a crown 
 of gold and porcelain — a procedure, however, not by any means to 
 be indiscriminately denounced, for in many cases it is in the high- 
 est degree advisable. 
 
 " There is this fact to be considered in regard to the use of the 
 partial caps here figured — that many patients can be induced to 
 consent to their employment who would refuse to submit to more 
 radical measures, and thus, even when the latter would be advis- 
 able, the former may be employed as a compromise, or even as a 
 temporary expedient. Having once tested the advantage of a well 
 fitting bridge, the wearer is much more likely to consent to what- 
 ever measures are necessary to give it security and permanence. 
 
 " In the cases figured, however, as well as in analogous cases,- 
 these qualities seem to be amply secured. In every instance in 
 which the removal of a pin and plate bridge has been necessary, 
 the film of oxyphosphate cement has been found intact, and the 
 surface of the tooth upon which it rested perfectly protected from 
 decay. The only exceptions to this rule have been the very few 
 cases in which one or the other of the retaining pins has become 
 loosened, the bridge being for some weeks still worn in the 
 loosened condition. Under such circumstances the cement will, of 
 course, become detached and wash out, admitting food and secre- 
 tions; but so long as the appliance remains immobile — and that is 
 its normal state — the cement rests undisturbed. It need hardly 
 be claimed that its durability is without limit, although under a 
 metallic covering it appears to be practically so; but under the 
 
BRIDGE DENTURES. 
 
 575 
 
 conditions represented in the processes as above described, it is 
 certainly good for many years of satisfactory service, and when it 
 fails, through chemical abrasion, it will fail first at the free margins, 
 where defects are most easily seen and remedied." 
 
 Dr. Register's Method. — The following is a condensed ac- 
 
 Fig. 521. 
 
 Fig. 522. 
 
 count, by Dr. Dexter, of a method of bridging devised by Dr. H. 
 C. Register, one of the earliest experimenters in this method of 
 replacement. The distinctive feature, as also the special merit, of 
 Dr. Register's appliance consists in the provision made for the 
 
576 MECHANICAL DENTISTRY. 
 
 ready replacement of broken crowns. The process is thus de- 
 scribed : 
 
 "Taking a typical case (Fig. 521), a rim or saddle of gold, 
 platinum, or iridinized platinum is struck to fit the spaces between 
 the teeth A and B. To this are attached bars X (Fig. 523), to 
 enter the fillings at Z Z (Fig. 522). Posts or pivots (D, Fig. 523) 
 are soldered upon this saddle where the artificial teeth are to be 
 placed, their free ends being threaded to carry the nut E. Hollow 
 crowns, countersunk for the nut at G, and having the necks 
 ground to reach over the saddle and press upon the gum, are fitted 
 over each post. Amalgam is used to fill in the space between the 
 post and the tooth wall, as in a Bonwill setting, and the crowns are 
 drawn to place and held with the nut. The saddle is fixed in its 
 place in the mouth, before the crowns are finally attached, by filling 
 into the cavities Z, the bars X X." 
 
 Dr. Williams' Method. — Dr. J. L. Williams has given to the 
 profession a number of important communications relating to 
 bridge-work, to which space is given to such portions only as 
 relate more especially to practical details. The initial portion of 
 the following, reproduced from the Dental Cosmos, treats also of 
 single crown replacement, and is embodied in this connection as 
 having immediate and necessary relation to subsequent descrip- 
 tions. 
 
 The following are Dr. Williams' descriptions of his methods of 
 crown and bridge replacement : 
 
 After the end of the root has been properly shaped and a gold 
 ferrule or band fitted to it, a suitable tooth is selected and backed 
 with pure platinum, or pure gold. The cervical end of the tooth 
 is ground to the proper position on the front bevel of the cap; all 
 of the fitting being done while the cap is in position on the root. For 
 detailed directions see Richmond ferrule or band crown, page 503. 
 
 After the fitting is completed, the cap is removed and the tooth 
 
BRIDGE DENTURES. 
 
 577 
 
 attached by strong resin wax and again placed in position while 
 the wax is warm. Any slight change in position which is neces- 
 sary can then be easily made. The tooth and cap are now removed 
 together, invested, and united at the back by solder. It is well to 
 use a solder for the cap with a higher melting-point than that 
 used for the backing, as it obviates the danger of unsoldering the 
 band when the backing is flowed on. After finishing and polishing 
 the work, the end of the root is made perfectly dry, a sufficient 
 quantity of oxyphosphate cement, mixed somewhat thinner than 
 for filling purposes, is placed in the enlarged pulp canal and also 
 in the cap. The crown is then carried to the place with firm, 
 steady pressure, and held a few minutes until the cement is 
 sufficiently hard to prevent displacement. The surplus cement 
 which has oozed out around the band should be carefully removed, 
 and the work is then completed. This is all illustrated in Fig. 524. 
 
 Fig. 524. 
 
 The bridge-work is simply an extension of the crowns over spaces 
 where the natural teeth have been lost. 
 
 Fig. 525 was drawn from a model of a case in practice. In this 
 the roots of the centrals are shown prepared for the fitting of the 
 bands, the laterals having been extracted. Single crowns are 
 made for these roots precisely as described. They are then 
 temporarily placed in position. Laterals are selected, backed, 
 ground, and fitted to position. The laterals are then attached by 
 means of strong wax to the centrals, carefully adjusted in the 
 position which we wish them to occupy, and the whole removed 
 in an impression of investing material. An additional quantity of 
 investment is mixed and poured over the exposed ends of the caps, 
 and the whole allowed to harden, after which the investing material 
 is cut away from the backs of the teeth and crowns, when they 
 should all be united by soldering. 
 
 37 
 
5/3 
 
 MECHANICAL DENTISTRY. 
 
 Fig. 526 shows the work completed, and Fig. 527 is from a 
 model of the mouth as restored with the crowns. 
 
 In cases where the space is occasioned by the loss of more than 
 one tooth a somewhat different method of procedure is necessary. 
 
 Fig. 528 shows a model of a mouth in which the superior 
 
 laterals and centrals had been extracted. The canines were badly 
 decayed, with exposure of the pulp. The first step is the removal 
 of the pulps from the canine roots. The crowns are then fitted as 
 already described and placed in position. An impression is taken 
 in plaster, the crowns remaining imbedded on its removal. The 
 
 Fig. 526. 
 
 Fig. 527. 
 
 impression is varnished and oiled, and a model of investing 
 material poured. After this has hardened, the impression is 
 carefully cut away, and we have a model of the mouth with the 
 crowns in position. A bite is taken and the articulation se- 
 cured in the usual manner. The remaining crowns, having been 
 
BRIDGE DENTURES. 
 
 579 
 
 backed, are fitted, and the face of the work imbedded in investing 
 material. 
 
 The whole piece is now united at the back by soldering, and when 
 finished presents the appearance shown at Fig. 529. 
 
 Fig. 528. 
 
 Fig. 529. 
 
 Fig. 530 shows a model of the mouth after the bridge has been 
 cemented in place. 
 
 Fig. 531 is an illustration of a piece of this work for which there 
 
 Fig. 530. 
 
 is a very frequent demand. It is for supplying the loss of the first 
 molar and bicuspids. If the cuspid is intact, the anterior end of 
 the bridge may be attached by a strong band of clasp metal passing 
 
5 8o 
 
 MECHANICAL DENTISTRY. 
 
 around this tooth, partly beneath the margin of the gum, so as to 
 present the least possible exposure. If, as is frequently the case, 
 there is extensive decay, it will be best to excise the remaining por- 
 tion of the tooth and replace it with an artificial crown as shown in 
 the illustration. The latter method the editor believes to be the 
 better practice, even where the cuspid is a vital tooth. A gold cap 
 is then made for the second molar. If this tooth is decayed it will 
 only be necessary to remove the decay, and the cement which is used 
 for setting the bridge will make the most perfect filling material be- 
 neath the gold cap. The intervening molar and bicuspid crowns are 
 made in the following manner : The porcelain faces are backed with 
 
 Fig. 531. 
 
 gold or platinum and the tips ground squarely off. Zinc pattern dies, 
 an assortment of which should be made from the grinding surfaces of 
 molars and bicuspids, are used for swaging from pure gold a tip or 
 cap for the protection of the porcelain face ; for without this protec- 
 tion the porcelain would be almost certain to be broken. The con- 
 cave surface of these tips is filled by melting coin-gold into them. 
 This surface is then ground smooth and fitted to the squared surface 
 of the porcelain face and waxed in position. Triangular pieces of 
 platinum are then cut of the proper size to fit the sides of the tooth, 
 waxed in position, and the whole invested, leaving the back open, 
 which is filled with coin-gold. The several surfaces of a tooth thus 
 prepared are shown in Fig. 532. 
 
BRIDGE DENTURES. 
 
 581 
 
 These teeth are then fitted into position in the bridge, as previ- 
 ously described. 
 
 Fig. 534 shows the completed work in the mouth. 
 
 Where only one molar or bicuspid is lost, sufficient support may 
 be gained by the cap, which is made to pass over the adjoining 
 molar. If the first molar and second bicuspid are lost, the ante- 
 
 Fig. 532. 
 
 Fig. 533- 
 
 rior end of the bridge may receive sufficient support from a strong 
 spur (Fig. 533), which may rest in the groove or sulcus between 
 the cusps of the first bicuspid ; or this groove may be deepened into 
 a cavity, into which the spur projects and around which a filling is 
 placed. 
 
 The most extensive pieces of this work which have been at- 
 
 tempted are cases of 12 and 14 teeth upon three and four roots. 
 Several of these have been worn for a year or more, and none of 
 which we have any knowledge shows any signs of failure. 
 
 Perhaps we cannot better close this paper than with the descrip- 
 tion of the restoration of a mouth where any attempt to remedy 
 
5§^ 
 
 MECHANICAL DENTISTRY. 
 
 the ruin save by extraction would have been considered madness ; 
 and yet the lady for whom this work was accomplished is, to-day, 
 so far as appearance, utility, and comfort are concerned, enjoying 
 as perfect a denture as any person who has the same number of nat- 
 ural teeth intact. 
 
 Fig. 535 was drawn from a model of the mouth as presented. 
 Only one tooth remained the pulp of which was not exposed — 
 the left second superior molar. In the first bicuspid, cuspid, and 
 central of the left side the pulps were exposed and in a partially 
 putrescent condition. Abscesses had formed about the roots of 
 the second left bicuspid, right central, cuspid, and second bicuspid. 
 
 Fig. 535. 
 
 The pulp was slightly exposed and inflamed in the right first supe- 
 rior molar. The second bicuspid on the right side and both bi- 
 cuspids on the left were extracted at once as worthless. The ex- 
 posed pulp in the right molar was treated and capped. The par- 
 tially living pulps were removed from the teeth above mentioned, 
 the fistulous openings were healed, and all of the roots thor- 
 oughly cleansed, and plugged with orange- wood saturated with 
 carbolic acid and glycerin. The greatest difficulty was encoun- 
 tered in the treatment of the right cuspid root, which had two 
 large openings through the side of it, and through which pro- 
 jected into the enlarged pulp canal a tumefied growth of the peri- 
 
BRIDGE DENTURES. 
 
 533 
 
 cementum. For several weeks the tissues around this root were 
 highly inflamed, and the face was several times badly swollen. 
 The difficulty was finally overcome by covering these openings 
 with No. 30 gold-foil and filling the root with amalgam. Crowns 
 were then fitted over all of the roots. A bridge was then extended 
 
 Fig. 536. 
 
 from the left cuspid to the first molar to restore the lost bicuspids. 
 The missing bicuspid on the right side was restored by attaching 
 the crown to the cap which was placed over the molar containing 
 the exposed pulp. 
 
 Fig. 536 was drawn from a model of the mouth as restored. 
 
 Fig. 537 shows a piece of work made for a case of quite fre- 
 
 Fig. 537- 
 
 quent occurrence. It represents the restoration of the inferior 
 bicuspids and first molar of the right side. A gold crown is made 
 for the second molar, and then the three intervening teeth, or 
 " dummies " are made as has been previously described. For the 
 support of the anterior end of the bridge the method hitherto 
 practised has been to excise the crown of the cuspid and fit a 
 
5§4 
 
 MECHANICAL DENTISTRY. 
 
 porcelain crown with gold backing to the root, and to this the 
 anterior end of the bridge is soldered. We have, however, 
 in Fig. 538 illustrated a device which obviates the necessity for 
 removing the cuspid crown. A gold band is fitted around the 
 cuspid. At the front, shown at a, this band is allowed to pass a 
 little beneath the margin of the gum so as to make the smallest 
 possible exhibition of gold. On the lingual aspect of the tooth 
 this band is allowed to be nearly the length of the crown. It will 
 be seen that when this band is fitted as perfectly as possible there 
 must necessarily be quite a vacancy between the upper part of the 
 lingual surface of the tooth and the band. It is important that 
 this portion of the band fit the tooth perfectly, and an accurate 
 adaptation is obtained as follows : A piece of pure gold, rolled to 
 No. 35 American gage, is fitted over that portion of the lingual 
 
 Fig. 538. 
 
 surface of the tooth which it is desired to cover, d, in Fig. 538, 
 shows the shape that this little pure gold plate usually assumes. 
 It can easily be fitted perfectly by the use of a burnisher, and 
 then, with the band in position, a drop of melted resin wax is 
 flowed into the space between the pure gold and the band. It is 
 now removed from the tooth, invested, and, after melting out the 
 wax, solder is flowed into the vacancy, filling completely the space 
 occupied by the wax. The top of the lingual portion will now be 
 thicker than is necessary, but can be easily ground or filed down to 
 the proper thickness. We now have a band which fits all portions of 
 the tooth perfectly. The anterior end of the bridge is soldered to 
 this band, and after work is properly finished it is cemented in 
 place in the usual manner ; /; and c show side and lingual views 
 of this band after the fitting is completed. 
 
 Another device for obviating the necessity for removing the 
 
BRIDGE DENTURES. 
 
 585 
 
 crowns of natural teeth in preparing the mouth for bridge-work is 
 illustrated in Fig. 539. Crowns are fitted in the mouth to the points 
 of attachment in the usual manner. An impression is taken, bring- 
 ing the crowns away in their proper positions. From this the cast or 
 
 Fig. 539. 
 
 model is obtained. Heavy bands of half-round gold or platinum bars 
 are now fitted around the necks of the natural teeth on their lingual 
 surfaces. These bands being waxed in position, serve to connect 
 the different parts of the bridge, uniting them in one piece without 
 
 Fig. 540. 
 
 the loss of any of the natural crowns. This has been found a highly 
 satisfactory method of inserting extensive pieces of bridge-work. 
 Fig. 540 shows the mouth as presented for which the piece shown 
 was constructed. Fig. 541 shows the piece in position. 
 
;86 
 
 MECHANICAL DENTISTRY. 
 
 Fig. 542 illustrates a case which is a type of a class of frequent 
 occurrence. Alternate molars and bicuspids in the upper and 
 lower jaws are lost, until the occlusion is somewhat changed, and 
 
 Fig. 541. 
 
 Fig. 542. 
 
 Fig. 543. 
 
 Fig. 544. 
 
 the force of mastication is gradually brought upon the front teeth. 
 Rapid wearing of these teeth results. The cases are among the 
 most difficult that the operator is called upon to treat by the 
 
BRIDGE DENTURES. 
 
 587 
 
 ordinary methods. In the case herewith illustrated, the lower 
 bicuspids, with a molar on one side, were in good condition, but 
 the loss of the upper bicuspids and molars made them useless. 
 As usually happens, the upper incisors had suffered most. The 
 lower incisors were restored by capping them with cohesive foil. 
 The bridge shown in Fig. 543 was constructed for the right side 
 of the upper jaw, while the teeth on the left side were restored by 
 contour work, as shown in Fig. 544. 
 
 The superiority of the condition of this patient's mouth, which 
 resulted from this work, over anything which could have been ac- 
 complished by plate-work, is almost inconceivable to one not familiar 
 with these methods. 
 
 Dr. Knapp's Method. — After constructing the crowns as di- 
 rected on page 420, suitable plain plate teeth should be backed 
 
 Fig. 545. 
 
 Fig. 547. 
 
 Fig. 548. 
 
 Fig. 550. 
 
 Fig. 551. 
 
 with pure gold and built up to the desired shape with wax, Fig. 
 
 545, which should be incased in pure gold as before described, Figs. 
 
 546, 547, and 548. After investing and subsequent removal of the 
 wax, the resulting receptacle can readily be filled with 20-carat sol- 
 der, Fig. 549. 
 
 In the preparation and in the drilling of the roots, great care 
 should be exercised to have the caps and the pins as nearly paral- 
 lel as possible. Here, as well as elsewhere, sound judgment is 
 essential to the accomplishment of the best results. For the at- 
 tainment of accuracy, it is essential that an impression should be 
 taken, preferably in plaster, of the caps in their proper positions 
 upon their several roots. An impression should likewise be taken 
 of the occluding teeth. The models obtained from these impres- 
 sions should then be placed in an articulator, as for plate-work, 
 
;SS 
 
 MECHANICAL DENTISTRY. 
 
 and the articulating surfaces of the porcelain crowns should be 
 carved in wax to a nicety. By the methods just mentioned these 
 occluding surfaces are reproduced in gold. The requisite exercise 
 of the dental organs and immunity from breakage of porcelain 
 faces are in this way secured. The porcelains should not press 
 upon the gums except in the anterior portion of the mouth, where 
 the formation of the alveolar process permits and the perfection of 
 speech demands it. The gold from the grinding surfaces should 
 form a gradual slope until it reaches the porcelain, and should be 
 entirely free from pits and other irregularities. When they occur, 
 it becomes necessary to remedy these as well as other defects. 
 This is to be done by the refiring of either a single crown or an 
 
 Fig. 552. 
 
 entire piece of bridge-work. At times gold, where needed, may 
 be added by the use of the electric mallet, and a beautiful finish 
 obtained with it. Under all circumstances, both porcelain and gold 
 should present a perfect continuity of surface. With diligent at- 
 tention given to the important details of construction which are 
 here pointed out, the great bugbear of uncleanliness, suggested as 
 an objection to this method of substitution, is entirely removed. 
 Of course, food and salivary deposits will accumulate around ar- 
 tificial crowns as well as about natural teeth, and the personal 
 cleanliness of the wearer is the greatest and indeed sole safeguard 
 against such injurious accretions with any denture. A philosophy 
 that would condemn the insertion of bridge-work, artistically con- 
 
BRIDGE DENTURES. 
 
 539 
 
 stracted on scientific principles, on the score of uncleanliness, would 
 as consistently advise the extraction of the natural organs for the 
 reason that their possessor was a sloven. " Cleanliness is next to 
 godliness," says Wesley, and he who expects to wear a " crown," 
 here or hereafter, must heed this maxim. 
 
 Fig. 550 shows an upper central and lateral incisor mounted upon 
 a central root with spud attachment. Fig. 551 represents the four 
 tipper front teeth held in position by the two lateral roots. Fig. 552 
 the six upper front teeth mounted upon the two cuspid roots. Fig. 
 553 represents a full upper denture with the two cuspid roots and 
 two molars as anchorages. 
 
 For the attachment of crown- and bridge-work the best obtain- 
 able oxyphosphate cement should be used. With the pins notched, 
 and the roots perfectly free from moisture, sufficient oxyphosphate 
 should be placed around each pin and inside of the collar to com- 
 pletely fill all the space between the pin and the canal, the collar 
 and the root. Firm, well-directed pressure should then be exerted 
 to carry the piece to its proper position, where it should be held 
 for a few minutes to permit of the hardening of the cement, all 
 excess of which oozing through at the edge of the collar should 
 "be carefully removed. Before being dismissed, the patient should 
 be instructed to be a little cautious in regard to subjecting the 
 •crown or bridge to any force for a short time. 
 
 Dr. Low's Method. — The following illustrated account, de- 
 scriptive of Dr. J. E. Low's methods of procedure in the cases 
 under consideration, was especially prepared by him for this work. 
 His definition of " bridge-work " has special application to his 
 distinctive method of construction. It is as follows : 
 
 " Bridge-work consists of supplying vacancies between teeth or 
 roots with artificial teeth, attached to the adjoining natural teeth or 
 roots by means of bands or crowns, and held in such a position that 
 there is no contact with or pressure on the gums beneath, and thus 
 no opportunity for secretions or other foreign matter to be held 
 there, and thereby become offensive. 
 
 " There is really but one kind of bridge-work, and but one way 
 to make bridge-work to insure success. There are many ways of 
 making teeth without plates, but this is not bridge-work. 
 
 "" For the first illustration, as seen in Fig. 554, we have a case 
 
590 
 
 MECHANICAL DENTISTRY. 
 
 where all the teeth have been extracted except the two cuspids and' 
 two second molar roots. 
 
 " First proceed to prepare the roots by crowning. I use gold 
 crowns on the molar teeth, and what is known as the Low crown 
 on the cuspids. The preparation of the two cuspids consists in 
 making the crown ready for adjustment, the process of which is 
 about the same as for the Richmond crown. I always measure 
 the tooth to be crowned with gold with a strip of block tin, No. 
 35 thick Stub gage or thereabouts. Place the tin around the tooth,, 
 and with pliers carefully measure the full size of the same. 
 
 " Should you be measuring a tooth, or part of a tooth, on which; 
 
 Fig. 554. 
 
 there are projections, take the engine, and with a stone grind off' 
 the same, making a smooth surface, so there will be nothing to 
 interfere with the fitting of the bands properly. After cutting the 
 tin measures by the marks made by the pliers, you have the 
 measures ready to make the gold bands by. Cut the bands and 
 bevel the edges and solder together, and you are ready to fit. 
 After fitting all the bands and finishing the crowns in the usual 
 way, place each in position in the mouth, having previously reg- 
 ulated the articulation of each crown as desired, in the process of 
 making. We now take a deep articulation in wax, and impression 
 in plaster-of-Paris ; remove before it gets too hard, and place all 
 the crowns in their positions in the impression; varnish, oil, and'. 
 
BRIDGE DENTURES. 59 1 
 
 pour in the usual way; separate the cast from the impression and 
 place in the articulator. Then pour with plaster. After the 
 plaster has hardened, remove the wax, and we have the articulation 
 proper, and are ready to select and grind the teeth, having- pre- 
 viously selected the shade. My experience has long ago taught 
 me that no porcelain tooth can stand the pressure for bridge-work, 
 the strain on them being twice as great as with teeth on plates which 
 rest on the gums, that give to pressure. In order to prevent break- 
 age of teeth and give strength, we must supply the teeth with gold 
 cusps. I will here describe my manner of doing so. 
 
 " For the first step, use No. 28 gage platinum for a covering of 
 the inside of the tooth, or just where you wish gold to flow. Then 
 bend the pins down to hold the platinum in position, and with a 
 file remove all overlapping platinum to prevent breaking of the 
 tooth in heating. The tooth is made flat on the crown surface 
 with the express intention of restoring with a gold crown. This 
 crown need not be very thick, but should perfectly resemble the 
 cusps on the natural tooth, for the purpose of mastication. As 
 these cusps are not on the market, and every dentist making 
 bridge-work cannot make it in a way to stand without putting 
 gold cusps on the grinding surface of the bicuspids and molars, 
 I will here describe how they can be made with very little trouble. 
 Pick out a natural tooth with cusps the exact shape you wish to 
 have your gold cusps resemble; mix up some fire clay in a thick 
 paste; then press your tooth into it a little deeper than you wish 
 the cusps. Having made the proper impression remove the tooth, 
 and set the impression over the gas-stove to dry. After it is 
 dried and reasonably hot, lay your pieces of gold in the impres- 
 sion and with a blowpipe melt them. When melted, press with a 
 piece of steel on the gold till cool. This mold will do to make 
 many from. If you have not the fire clay, and can get charcoal 
 that is burned from fine-grained wood and is soft, you can simply 
 press your tooth into the charcoal and melt in the same way, or 
 you can carve your teeth as you desire in a block of carbon. Of 
 course, the little steel die-plates are handier, as we can swage up our 
 gold cusps in them, either solid or thin. 
 
 " Having described our manner of making the cusps, we will 
 now return to the finishing of the tooth. We left off by say- 
 ing we covered the inside and bent down the pins and filed off 
 
59^ 
 
 MECHANICAL DENTISTRY. 
 
 Fig. si 
 
 the overlapping platinum. Now place the cusp on the top of 
 the tooth, and place in the position desired, holding it there with 
 wax, and with a spatula trim the wax the exact shape we wish 
 our tooth to be, V-shaped, tapering from the crown down. We 
 now incase in plaster and sand, which gives us a box. When 
 hard, remove the wax and place over the stove, and when suf- 
 ficiently dry fill in with coin-gold, using the blowpipe to melt it in 
 
 a solid mass, and our tooth is ready to file up and place 
 
 in position on the articulator. Fig. 555 shows the tooth 
 
 in this condition. 
 
 " After our teeth are arranged, we hold the same in 
 
 position with wax, remove from the articulator, incase 
 with plaster and sand or asbestos in the usual way. That we may 
 have a strong case, I always place platinum wire between each 
 tooth, and then proceed to heat and solder. Be sure that all the 
 gold cusps are so arranged that you can get it all soldered together, 
 as this gives great strength. My formula for solder, which will 
 be found very easy-flowing, and almost the exact color of the gold 
 you are using, is as follows : Always figure from the carat of gold 
 you are working. Take one dwt. coin-gold, two grains of copper, 
 and four of silver. We now have our case soldered ; after filling as 
 
 Fig. 556. 
 
 desired, commence to finish with felt wheels and pumice-stone, after 
 which use rouge on buff wheels. It is now ready to be placed in 
 the mouth. In Fig. 556 we see the case ready for adjustment. 
 
 " Have the assistant dry all the teeth or roots to be operated 
 upon while you are mixing the cement. Be sure and use a kind 
 which will not harden very rapidly, or your cement will set before 
 you get your teeth home. Use sufficient cement to fill all the 
 gold crowns perfectly when the case is driven to place. Moisten 
 the step-plugs and cap with cement, touching every portion, and 
 
BRIDGE DENTURES. 
 
 593 
 
 with an instrument place a little cement in the bottom of the cavity. 
 We now adjust our case, using a wooden plug for driving on the 
 crowns. Fig. 557 represents the case when in position. 
 
 " It will be seen by looking at the previous cut (Fig. 556), that 
 the teeth, after having been soldered, are all spaced fully one-third 
 of the distance from the place of contact with the gums and the 
 
 Fig. 557. 
 
 grinding surface of the teeth, so that secretions could not possibly 
 lodge there." 
 
 Dr. Melotte's Method.— Dr. G. W. Melotte, of Ithaca, N. Y., 
 contributed to the Dental Cosmos an account of his method of 
 bridging in a given case, the manipulative details of which are here 
 reproduced : 
 
 " Fig. 558 illustrates a case for the supply of a lateral and a 
 bicuspid. In this instance the cuspid should be cut off, and the 
 
 Fig. 558. 
 
 root collared and capped in combination with a pin entering the 
 enlarged pulp canal; but, as there may be grounds for objecting to 
 cutting off sound teeth, I obviate the necessity by cutting a shoulder 
 on the lingual portion of the cuspid, and suitably shaping its sides 
 to permit a close fitting of the collar just under the free margin of 
 the gum. A narrow strip of pure pattern tin, bent tight around 
 the tooth neck, and cut through with a knife at the lap on the 
 labial surface, will serve as a measure for the length of a strip 
 38 
 
594 MECHANICAL DENTISTRY. 
 
 of 22-carat gold plate, No. 29, thick, and as wide as the length 
 of the distal side of the cuspid. The ends of the gold are 
 then squared, and with round-nosed pliers brought evenly together, 
 to be held in flush contact with suitable pliers. The soldered 
 collar, with its joint side inward, is then adjusted on the tooth as 
 accurately as possible, giving slight blows with a mallet until the 
 collar touches the gum, when it should be marked to indicate the 
 necessary trimming to conform it to the gum contour. After it 
 has been thus trimmed, the edges beveled, the labial part swelled 
 with contouring pliers, and the lingual part cut down to about J^ 
 of an inch in width, the collar is again driven on, and will appear 
 as seen in Fig. 558. A stump corundum wheel is then used to 
 grind a shoulder on the lingual surface of the tooth, grinding also 
 the edges of the collar flush with the shoulder. The collar is 
 again removed, and a piece of thin platinum plate, about No. 32, 
 
 Fig. 559. Fig. 560. Fig. 561. 
 
 sufficient to cover the lingual surface of the tooth, is caught on the 
 lingual edge of the collar by the least bit of solder, and all put in 
 place on the cuspid (see Fig. 559). The platinum should now be 
 burnished on to the shoulder, and over the tooth and collar to the 
 extent shown by the lines in Fig. 559. After trimming to those 
 lines, and carefully replacing and burnishing to the tooth, the collar 
 and half cap are removed, filled with wet plaster and sand, and the 
 platinum soldered to the gold. It is then placed on the tooth, bur- 
 nished into all the inequalities of the tooth, very carefully removed, 
 invested, and enough solder flowed over the platinum to cover and 
 give it strength. Fig. 560 shows it complete on the cuspid. I have 
 often made such collars in less than an hour, and in any case time 
 must be made subservient to exactness of fit and adaptation to the 
 end in view. 
 
 " In the preparation for fitting a collar on the first molar (Fig. 
 558) I should have wedged or otherwise separated it from the 
 
BRIDGE DENTURES. 595 
 
 second molar, so that a piece of sheet-brass might be put in place, 
 as shown in Fig. 561, and an impression taken in plaster, which, if 
 allowed to get hard, would bring away the metal. If not, it could 
 be replaced in the plaster. Melted fusible metal, when near the 
 cooling-point, is then poured into the impression, and when cold 
 will allow the safe removal of both the plaster and the metal strip. 
 On this metal model a collar can be formed that will accurately- 
 fit the molar, as seen in Fig. 558. If the molar has no antagonist, 
 a cap may at once be struck up on the model; but if there be an 
 antagonist, the cusps of the natural molar should be removed by 
 grinding at points where the occluded tooth will admit of sufficient 
 thickness of the gold cap. An exact copy of the ground cusps 
 can then be made in less than five minutes by the use of moldine 
 with its accessories, see page 138, and the process is as follows: 
 Make the tooth perfectly dry. Put the collar on it. Nearly fill 
 the cup with moldine, and coat it with soapstone powder. Press 
 the compound on the tooth and collar firmly to about one-fourth the 
 depth of the tooth. Carefully remove the cup ; trim off any over- 
 hanging material, and place the rubber ring over the cup to about 
 one-half the depth of the ring. Melt the fusible metal and pour it 
 as cool as it will run from the iron ladle. As soon as the metal is 
 hard, remove it with the ring, taking care not to impair the im- 
 pression, which can be used again if the die is found imperfect or 
 gets injured in use. Place the die and ring in cold water, to remain 
 until quite cooled. While the die is wet and held over a basin of 
 water, pour into the ring fusible metal which has been stirred until 
 it begins to granulate, and quickly immerse all in the water. The 
 die and counter-die should separate readily by tapping them with a 
 hammer, but if they stick, others can be quickly made from the 
 same impression, by the same method, using more care. With this 
 die and its counter-die, a piece of No. 29 or 30 gold plate is swaged 
 to fit perfectly the cusps and collar, which, when removed, can be 
 held to its place on the cap by the soldering clamp, using spring 
 pressure enough merely to hold them together for careful soldering 
 with the pointed flame so as not to unsolder the collar. The seam- 
 less collars are excellent when care is used in selecting the proper 
 size, as directed on the diagram. 
 
 " The caps being in place on the cuspid and molar, an impression 
 is taken with plaster, the caps accurately set in the impression, and 
 
596 MECHANICAL DENTISTRY. 
 
 hard wax melted with a hot spatula around the edges of the caps. 
 The impression is then thoroughly coated with sandarac varnish, 
 after which it is dipped for a moment in water and filled with a wet 
 mixture of one part marble-dust with two parts of plaster, using 
 great care to perfectly fill the caps and molds of the teeth. Wait 
 until this mixture has become quite hard, remove the cup, and with 
 a suitable knife clip off the plaster without marring the cast ; secure 
 a good articulating impression, and transfer it to the cast to obtain 
 an exact reproduction of the relative occlusions of all the teeth 
 involved. With such an articulation in hand, and with the means 
 already described for swaging gold or platinum plate to fit the 
 cusps and articulating surfaces of either the natural or artificial 
 teeth, it should be within the capacity of any competent dentist to 
 complete a suitable bridge, although there are practical points that 
 can only be imparted by clinical instruction and actual demonstra- 
 tion in the mouth. Such a bridge is shown in position in Fig. 562." 
 
 Fig. 562. 
 
 The Mandrel System.— The following description of " A Sys- 
 tem of Crown- and Bridge-work " is given by the experts of the 
 S. S. White Manufacturing Co., who have designated it as " The 
 Mandrel System " : 
 
 " An examination of a large number of human teeth shows that, 
 no matter how great differences may exist in the apparent shapes 
 of the crowns of individual teeth of a given class, there is a remark- 
 able uniformity in the configuration of their necks. That is, the 
 necks of upper cuspids, for instance, were found to have a fixed 
 type, from which the variations were very slight as to shape, though 
 there appeared to be no exact standard of size. So of the other 
 classes, with the single exception of the superior molars, in which 
 two distinct forms were found, the first being those in which 
 the buccal roots were wider than the palatal ; the second, those in 
 which the reverse condition was found, the single palatal root being 
 wider at its junction with the crown than the two buccal roots. 
 
Fig. 563. 
 
 =q 
 
 No. 1. 
 
 No. 2. No. 8. 
 
 Mandrels for shaping 
 
 No, 4. Ho. 6. No. fl. 
 
 seamless tooth-root collars. 
 
 a, 
 3 
 02 
 
 'a, 
 
 3 
 
 o 
 M 
 t3 
 
 No. 7. 
 
 597 
 
593 
 
 MECHANICAL DENTISTRY, 
 
 The occurrence of roots of the second class being rather excep- 
 tional, the first class was accepted as the type. 
 
 " The configuration of the necks of all the teeth having been 
 determined, a set of mandrels for shaping collars to fit them was 
 devised. The set (Fig. 563) consists of seven mandrels, six of which 
 are double end. Their shapes are modeled upon the general typal 
 
 Fig. 564. 
 
 forms of the necks of the teeth which they represent, and they are 
 made tapering to provide for all required variations in size. The 
 illustrations are about two-thirds actual size, the longest instruments 
 being nine inches in length. The cross-sections show the shapes and 
 proportionate sizes at the greatest and least diameters. The long 
 taper permits the most minutely accurate adjustment of the collars. 
 
BRIDGE DENTURES. 
 
 599 
 
 " No. i is a double-end mandrel, for superior molars, right and 
 left ; No. 2 is a single mandrel, for superior bicuspids, right and 
 left ; No. 3 is a double-end, for superior cuspids, right and left ; No. 
 4, double-end, for superior centrals, right and left; No. 5, double- 
 end, for inferior molars, right and left; No. 6, double-end, for the 
 inferior centrals, laterals, cuspids, and first bicuspids, right and left; 
 No. 7, double-end, one end for the superior lateral incisors, the 
 other for those bicuspids in which a bifurcation of the roots, or a 
 tendency in that direction, extends across the neck to the crown in 
 the form of a depression on one or both approximal surfaces. The 
 foregoing scheme comprehends all the teeth of the permanent set 
 except the second inferior bicuspids. The necks of these approxi- 
 mate those of the superior central incisors so closely in shape that 
 it was deemed inexpedient to make a separate mandrel, as the No. 
 4 mandrel will serve for both. 
 
 " The collars or bands are made seamless, of No. 30 (American 
 gage) gold plate, 22 carats fine. Fifteen sizes, each of three widths 
 (iV> To' an ^ to" °f an mc h) are made (Fig. 565), which it is be- 
 lieved will cover all requirements. These collars, although devised 
 as a part of the system, can be used in all methods of crown- and 
 bridge-work which require bands, and possess many advantages 
 over any others. They are really labor-saving devices, as their use 
 saves the time and' trouble of making, and there is no danger of 
 their coming unsoldered when the pins or the backing of the crown 
 are being soldered; and there are no hard spots to give trouble in 
 burnishing, as, for instance, close to the root, after the collar has 
 been shaped and placed in position, the whole surface being uni- 
 formly soft. 
 
 " The seamless collars are also especially adapted to removable 
 or detachable bridge-work. They are so constructed that Nos. 1, 
 16, and 31 exactly fit into or telescope with Nos. 2, 17, and 32, and 
 so on through the entire set, each collar fits into the series next 
 higher ; so that a root may be banded with one size and the size 
 next larger used to form the tube for the telescoping crown. When 
 desirable, the ' seamless ' collar can be strengthened, after it has 
 been adapted to the conformation of the crown so as to slide freely 
 over it, by investing and flowing solder over the outer surface; or, 
 still better, by adapting the next larger size of collar to exactly fit 
 around the first, and then investing the two and soldering them 
 
( 
 
 o 
 
 o 
 o 
 
 o 
 o 
 o 
 o 
 
 Fig. 565. 
 
 ft 
 
 S> 
 
 X 
 
 » 
 
 e 
 
 88 
 
 «(D 
 -(D 
 
 ?« 
 
 VZ. 
 
 §D 
 
 2D 
 2D 
 BD 
 
 20 
 
 
 O 
 
 J 
 
 M li. / 
 
 S O 
 
BRIDGE DENTURES. 
 
 60 1 
 
 together. The advantages of these collars for this kind of work, and 
 also for the construction of cap crowns, are obvious. 
 
 " The other appliances specially devised for this system are, a re- 
 ducing plate or contractor, a pair of collar pliers, and a hammer. 
 
 Fig. 566. 
 
 " The contractor (Fig. 564) contains holes which are comple- 
 mentary in shape to the mandrels. The mandrels being applied to 
 the inner circumferences of the collars, while the contractor must 
 admit the collars themselves, the short taper of the holes in the 
 contractor necessarilv covers a somewhat greater range of size than 
 
602 
 
 MECHANICAL DENTISTRY. 
 
 Fig. 567. 
 
 is shown in the mandrels. With this appliance collars can be evenly 
 and accurately reduced in size at the edges, without burring or 
 buckling. The illustration is actual size. 
 
 " The collar pliers (Fig. 566) are for contouring 
 the collars to shape, one beak being made convex 
 and the other concave to correspond. With this 
 appliance the slightest changes required in the 
 contour of the collars are easily made. About 
 */2 of an inch from the extremity of the concave 
 beak a small bar of flat steel is attached to it by 
 means of a screw. The free end of the bar has 
 a minute projection upon one face, the other be- 
 ing reinforced to fit into the concavity of the beak. 
 In the center of the face of the convex beak is a 
 depression, into which the projection on the steel 
 bar strikes, making a very efficient punch for 
 forming guards or stops to prevent the collars 
 from being forced too far under the gum. The 
 depression in the convex beak being slightly 
 larger than the projection or punch, the metal is 
 not cut through, but merely raised on the side 
 opposite to the punch. The punch attachment 
 being pivoted can be swung to one side when not 
 in use. 
 
 " The mallet or hammer, with steel face and 
 horn peen, is shown in Fig. 567. 
 
 " One of the appliances required is a lead anvil, 
 which, being only a piece of soft lead, say two by 
 three inches, and an inch thick, is not illustrated. 
 The counter-die of an ordinary case will answer 
 very well. 
 
 " To illustrate the uses of these appliances, take 
 a case in which the two inferior bicuspids of the 
 left side are missing, and the crowns of the cuspid 
 and first molar so badly decayed that the prob- 
 abilities arc that they will soon fall victims to 
 the forceps. The old-time way would have been to extract the 
 molar and cuspid, and make a partial plate. Examination, how- 
 ever, shows that the roots of these two teeth are in good con- 
 
BRIDGE DENTURES. 
 
 603 
 
 dition, affording an excellent opportunity for the construction of a 
 piece of bridge-work. 
 
 " With a corundum stone, cut off the remaining portions of the 
 crowns level with the gum margins. Prepare the roots in any of 
 the well-known ways, thoroughly cleansing the apical portions 
 and filling them with whatever material is desired, being careful 
 only that the work is well done. For the better retention of the 
 filling material to be placed in the pulp chamber, retaining grooves 
 can be made or retaining posts inserted. Take a piece of binding 
 wire (No. 26, American gage), say 2^ inches long, pass it around 
 the neck of the molar stump, cross the free ends, and, holding 
 
 Fig. s< 
 
 Fig. 569. 
 
 Fig. 570. 
 
 the wire in place with one finger, twist the ends with a pair of 
 flat-nosed pliers until the wire clasps the tooth closely at every 
 point (Fig. 568). When there are any irregularities in the con- 
 tour of the tooth, it is necessary to press the wire into them 
 with an approximal burnisher. It is obvious that the ring thus 
 formed will show the exact size and shape of the neck of the 
 tooth. Remove the ring carefully, lay it on the lead anvil, put over 
 it a piece of flat metal, and with a smart blow from a hammer 
 drive the wire into the lead (Fig. 569). Upon removing the wire 
 an exact impression of the ring will be left in the lead anvil, as 
 shown in Fig. 570. (This part of the work, as indeed all others, 
 should be done carefullv as described. The wire ring mav be driven 
 
604 MECHANICAL DENTISTRY. 
 
 into the lead by a direct blow of the hammer face, but the blow- 
 might not strike equally, and the interposition of the flat metal 
 held level insures an even impression. A piece of an old file is 
 best, as the file-cuts keep the wire from slipping.) 
 
 " Next, cut the wire ring at the lap, straighten out the wire, and 
 select a suitable collar by comparing the length of the wire with 
 the straight lines in the diagram, which show the inside diameters 
 of the various sizes. Should none of these correspond exactly, 
 take preferably the next size smaller. It will be remembered that 
 the collars are No. 30 in thickness, while the wire with which the 
 conformation is secured is No. 26. This difference permits the 
 collar, when contoured to shape, to enter the lead impression 
 readily, a decided advantage in fitting. Having selected the collar, 
 fit it to mandrel No. 5, with the peen of the hammer, holding it 
 upon the lead anvil, and using a slight pushing force to help in 
 stretching and forming it (Fig. 569). Having driven the collar to 
 form, remove it from the mandrel and try in the lead impression. 
 If it does not fit exactly return it to the mandrel and stretch it a 
 little, when it will usually fit perfectly, as the mandrels have been 
 designed carefully to the average shapes which obtain in the 
 great majority of tooth necks. In the exceptional cases where 
 the collar does not fit, it can readily be contoured to the exact 
 shape with a pair of flat-nosed pliers. Of course, if it fits the im- 
 pression in the lead, it will fit the neck of the tooth, always pro- 
 vided the measurement and the impression have been carefully 
 made. 
 
 " If the collar or band has been accidentally stretched too much, 
 or if, for any reason, when brought to shape, it is too large, its- 
 root end can easily be reduced to the proper size by the use of the 
 contractor. Place the edge of the collar which is to fit in the root 
 in the proper hole; hold it level with a piece of file as in taking 
 the lead impression of the ring, and tapping lightly on the file 
 drive the collar into the plate (Fig. 564) until the proper reduction 
 is made. The collar is next ' festooned ' to correspond to the 
 shape of the maxillary ridge. Lay it, gum edge up, on the lead 
 anvil, and with the piece of flat file and the hammer drive it into' 
 the lead. A few cuts with a fine half-round file across the approxi- 
 mal diameter will conform the edges to the surface of the ridge 
 (Fig. 571). Then place the collar in position, and, having ascer- 
 
BRIDGE DENTURES. 
 
 605 
 
 tained just how far it should go down on the root, remove it, and 
 with the small spring punch in the collar pliers (Fig. 566) form 
 projections on the inside of the band at the proper points to serve 
 as stops, which, resting on the top of the root, will prevent the 
 collar from being forced further down upon it than is desirable 
 (Fig. 572). 
 " A collar for the cuspid is then fitted in the same manner, 
 
 Fig. 571. Fig. 572. 
 
 . Hi 
 
 using mandrel No. 6 for shaping, after which the case is ready for 
 the building of the bridge. 
 
 " Place both collars in position and take an impression of the 
 parts, including the interiors of the excavated pulp chambers, from 
 which make a cast in the usual way. Bend a short piece of half- 
 round gold or platinum wire into the form of a horseshoe, the 
 two extremities of which shall fit into the roots of the molar. 
 
 Fig. 573. 
 
 Then take a longer piece of the same wire, somewhat more than 
 enough to extend from the toe of the horseshoe when in position 
 to the cuspid root; bend one end of it at a right angle, or nearly 
 so, to fit the root of the cuspid, and, cutting off any excess of 
 length, solder the other end to the toe of the horseshoe. The 
 bar extending between the two roots is the truss of the bridge. 
 Next, place the appliance on the cast (Fig. 573), holding it in 
 
6o6 
 
 MECHANICAL DENTISTRY, 
 
 position with wax, and select the teeth to take the place of the 
 missing bicuspids and molar. The best form for this purpose is 
 a tooth having holes extending through it vertically from the 
 neck to the grinding surface, similar to the well-known Bonwill 
 crown. 
 
 " The crowns used should be large enough to fill the space rather 
 tightly, even if their sides have to be flattened to let them in. If 
 the teeth do not fill the space perfectly, a small portion of plastic 
 filling material crowded between them, as mortar between the 
 granite blocks in the arch of a railway bridge, will greatly increase 
 the strength of the work. 
 
 " After the teeth are ground to fit, and the proper length for 
 occlusion ascertained, the truss is covered with a film of wax, upon 
 which the crowns are again pressed to their positions. Upon the 
 
 Fig. 574. 
 
 removal of the crowns the impression of the holes running through 
 them will be found in the wax. At these points drill holes through 
 the bar with a small twist drill run by the dental engine, and into 
 these fit and solder the pins for the support of the crowns, as shown 
 in Fig. 574. 
 
 " The bridge is now ready to be attached permanently. Set the 
 crowns in position upon their supporting pins, to secure the proper 
 alignment. (If the operation were upon the upper jaw they would 
 have to be held with wax.) Put into the canals of the supporting 
 roots (the cuspid and first molar) a sufficient quantity of some 
 quick setting plastic, as oxyphosphate, to about half fill the pulp 
 chamber, but not enough to prevent the supports of the truss 
 from being forced home. Force the bridge supports to place, and 
 after allowing the filling material to become set remove the crowns. 
 
BRIDGE DENTURES. 
 
 607 
 
 Fill the remainder of the pulp chamber and the whole of the 
 collar with gold, amalgam, gutta-percha, oxyphosphate, or other 
 suitable plastic (Fig. 574). Set the crowns permanently, the 
 molar and cuspid first, as this affords greater facility for the 
 trimming off of any excess of the filling material used in the at- 
 tachment. For attachment of the crowns gutta-percha is probably 
 the best material, as crowns set with it are readily removed for the 
 correction of any inaccuracies of occlusion or alignment by grasp- 
 ing them between the beaks, previously warmed, of a pair of uni- 
 versal lower molar forceps. The heat warms the gutta-percha and 
 releases the tooth, which can then be reset properly. In attaching 
 crowns with gutta-percha, the holes in the crowns are first filled 
 with the material, after which the crown is wanned and forced to 
 place. Any of the other plastics ordinarily used can be employed, 
 
 at the discretion of the operator. Fig. 575 shows the case com- 
 pleted. 
 
 " In securing the occlusion of a piece of bridge-work it is well 
 to make the artificial teeth a little short, so that the natural teeth 
 on both sides will meet the first shock of mastication. Nature 
 will correct the occlusion in time by slightly elongating the roots 
 supporting the bridge. If the artificial crowns are permitted to 
 strike the natural teeth from the first, the undue strain upon the 
 two supporting roots will cause soreness and, perhaps, more serious 
 consequences. 
 
 " When a sound tooth is to be used as one of the supports of the 
 bridge, a modification of the method just described is necessary. 
 Take a case where it is desired to bridge the space caused by the 
 loss of the right inferior bicuspids and first molar. The crown of 
 
6o8 
 
 MECHANICAL DENTISTRY. 
 
 the right cuspid is nearly gone, but the root is sound and capable 
 of supporting one end of the bridge. The other end will be attached 
 to the second molar, which is a sound tooth. Prepare and band 
 the cuspid root as before, dress off the second molar crown until it 
 is slightly smaller than the neck, so as to permit a cap to be tele- 
 scoped over it, and take the measure of the crown with the binding 
 wire. Select a suitable seamless collar of sufficient width to extend 
 from the neck to a little beyond the grinding surface and drive it up 
 on the pro.per mandrel to get the general shape, but not the full size 
 required to fit the tooth, leaving it so that the edge having the 
 larger circumference will just pass over the end of the crown; 
 place the collar on the tooth and with a block of wood and the 
 mallet tap it to place just beyond the free margin of the gum. 
 This method will make a close fit, as the collar will readily stretch 
 
 Fig. 576. 
 
 all that is necessary. With a sharp-pointed instrument mark the 
 length of the crown, remove the collar, and cut it to the proper 
 width as indicated. Then in a piece of gold plate of the thickness 
 used for caps form four little depressions of the general character 
 of an impression of the molar cusps. An easy way to do this is 
 to lay the plate on the lead anvil; then with the ball on the end of 
 an ordinary socket handle and the hammer the depressions are 
 made in a moment. Set the collar on the plate, borax it, charge 
 with solder, and heat until the solder flows. Cut off the surplus 
 plate, and a perfect cap for the molar is made. Place it on the 
 tooth and take an impression, and thereafter proceed as before 
 directed to make the truss of the bridge and mount the teeth, 
 except that in this case the posterior end of the truss is to be sol- 
 dered to the molar cap. For the final attachment place a little 
 
BRIDGE DENTURES. 
 
 609 
 
 oxyphosphate or other plastic filling material in the cap to secure 
 it firmly in position." 
 
 The Hollingsworth System. — This system supplies, in the first 
 place, a variety of forms for the various teeth great enough to cover 
 almost any case, and for the rare cases which cannot be suited direct 
 it affords a ready means of making the exact form required. They 
 are made of metal, and are used as patterns from which to make 
 dies or molds, as may be required, for the swaging of gold cusps 
 or crowns. There is, therefore, no wear upon them, and they re- 
 tain their shapes and sizes unaltered. 
 
 The outfit for working these forms consists of a molding-plate, 
 three rubber rings, a sheet of asbestos, 10 X 7 inches, and a carbon 
 stick for use in casting. 
 
 Fig. 577. 
 
 Fig. 579. 
 
 Fig. 578. 
 
 This system permits cusps to be made either hollow or solid. 
 Scrap gold can be used for casting solid cusps, and porcelain fac- 
 ings can be quickly inserted in crowns without investing; but per- 
 haps its most important advantage is the exactness with which the 
 fit and articulation of bridges are obtained and maintained. 
 
 The features which Dr. Hollingsworth claims for his methods 
 are illustrated in the following directions : 
 
 After making a band to fit the root in the ordinary way, place it 
 in the mouth (see Fig. 577), and cut off on a line where the adjoin- 
 ing teeth begin to turn to form the cusp (see c, Fig. 577). Place a 
 small piece of wax inside the band to assist in holding the cusp 
 button, which should be selected to fit the circumference of the 
 band, to articulate properly, and to correspond in shape with the 
 other teeth (see b, Fig. 577). Remove the button, and place it on 
 39 
 
Fig. 580. 
 
 
 
 am 
 
 m 
 
 ' r "■'. ". ."""■- '■'^::..^-7:~:^ 7r :-'.'.^vl ~: 4Z^4-~ :r 4 : - : ^wy^S^ 
 
BRIDGE DENTURES. 
 
 611 
 
 the molding-plate with the grinding surface up (see Fig. 578). 
 Place the small rubber ring d around it, with the button as near 
 the center as possible, and pour in a sufficient quantity of Melotte's 
 metal to nearly fill the ring (Fig. 579). Start to pour the metal 
 directly on top of the cusp, otherwise the flow of metal may force 
 the cusp to one side and make an imperfect die. As soon as the 
 metal sets, chill the surface by dipping in water for a moment, and 
 then remove the rubber ring. When the heat begins to return to 
 the surface, a quick rap of the die on the bench will cause the cusp 
 button to drop out and leave the mold ready to form the gold cusp. 
 Xow take a small piece of lead, and with a few taps of the ham- 
 
 Fig. 581. 
 
 Fig. 58; 
 
 Fig. 583. 
 
 Fig. 584. 
 
 mer drive it into the Melotte metal die (Fig. 581) to form the 
 counter-die (Fig. 581, d). 
 
 Anneal the gold plate, and start the swaging process by coaxing 
 the plate into the die by hand pressure (Fig. 582), using a piece of 
 wood, which makes a depression for the lead counter-die to rest in. 
 Then place the counter-die on the gold plate (Fig. 583), and drive 
 to a partial fit. Remove the partially formed cusp, pickle it to re- 
 move traces of lead, and again anneal it. Place the counter-die on 
 the die without the gold plate and drive it in with a smart blow ; 
 this will resharpen all the lines of the counter-die. Next replace 
 the partly formed gold cusp in the die, and again drive the counter- 
 die into it for a perfect fit. Again pickle the cusp and proceed 
 to cut the surplus metal from it with shears (Fig. 584), filing up the 
 
6l2 
 
 MECHANICAL DENTISTRY, 
 
 edges when necessary, and rub down the under surface on a smooth 
 file until it fits the band made for it (Fig. 577). Wire the cusp and 
 crown together (Fig. 585), place flux and solder in the cap, and 
 hold over a lamp until soldered. Then finish in the usual way. 
 
 If the forms of cusp buttons do not afford one which articulates 
 perfectly, the difficulty is easily remedied by taking the button 
 which most nearly answers, and building up the cusps with Mel- 
 otte's moldine (Fig. 586). If necessary to make an absolutely per- 
 fect articulation, and the forms as supplied do not permit of it, 
 select a cusp that will otherwise suit the case, set it on the band 
 on the crown, cover the face of the cusp with moldine, coating the 
 
 Fig. 5S5. 
 
 Fig. 
 
 Fig. 587. 
 
 L_ 
 
 3 
 
 surface with collodion to prevent the saliva from 
 crumbling it, and direct the patient to bite upon it, or, 
 if a perfect plaster model has been made, articulate the 
 opposing teeth with the cusp placed on the band, 
 omitting the coating with collodion. Remove the 
 cusp with the moldine, trim off the surplus, and pro- 
 ceed to cast as shown in Fig. 579. If a band is acci- 
 dentally cut too short, it can still be utilized. Place 
 moldine upon the molding-plate, put the cusp but- 
 ton upon it, press down and adjust to make up the deficiency of the 
 band, cutting away the surplus moldine. This will, of course, throw 
 the soldering line a little further up on the crown (Fig. 587). 
 
 Solid Cusps. — Scrap gold can be utilized for making a solid 
 gold cusp by casting in asbestos by the following method : 
 
 After selecting the desired cusp button, instead of making a mold 
 in Melotte's metal, as before described, take a piece of asbestos 
 board about one inch square and 34 °f an mcn thick, moisten it, 
 and with a hammer drive the cusp button into it, flush with the sur- 
 face of the button. (See Fig. 589.) Remove the button, and dry 
 
BRIDGE DENTURES. 
 
 6l3 
 
 the asbestos in a flame (Fig. 588). When perfectly dry, place a 
 sufficient quantity of gold scraps in the die made in the asbestos, 
 and direct the blowpipe flame upon it until melted, inclining the 
 carbon stick, as shown, against the die for the double purpose of 
 confining the heat and warming up the carbon stick. When the 
 gold is fused into a button, press it into the die with the carbon 
 stick (Fig. 590). Avoid the use of Hux when working with asbestos. 
 To build up a cusp to make a perfect articulation in this manner, 
 sealing-wax must be used instead of moldine, as in the method of 
 swaging the cusp. Warm the button before applying the wax, and 
 with a warm instrument shape the cusp as desired. 
 
 Fig. 588. 
 
 Fig. 590. 
 
 Gold Central, Lateral, and Cuspid Crowns. — Select from the 
 40 different forms in the set that which is most suitable to the 
 case in hand (Fig. 591). (The forms are in pairs, showing labial 
 and lingual surfaces.) Take the measurement of the root to be 
 crowned with one of the annealed copper strips, binding the strip 
 around the tooth with pliers and pinching the joint firmly together. 
 Trim off the surplus ends, and cut the measure (Fig. 592, a) through 
 the center (Fig. 592, b), then bend the respective halves over the 
 lingual and labial forms selected, at the necks, with the cut ends of 
 the strips resting on the flat of the plate (Fig. 593). If the meas- 
 ure is larger than the form selected, build the latter up with mold- 
 ine until the space between the form and strip is filled (Fig. 593, b). 
 Avoid getting moldine on the approximal surface. Remove the 
 strips, dry out the moldine by passing through a flame a few times, 
 then place the form on the molding-plate with a rubber ring around 
 it. Pour Melotte's metal into the ring as in forming the molar or 
 
614 
 
 MECHANICAL DENTISTRY. 
 
 bicuspid cusp, which makes a die of the two sections, lingual and 
 labial. Make a lead counter-die and proceed as directed in the 
 making of a molar cusp, swaging the sections separately (Fig- 594-)- 
 Trim off the surplus plate (Fig. 596), and square the opposing 
 
 Fig. 591. 
 
 Fig. 592. 
 
 Fig. 594. 
 
 /b 
 
 Fig. 593. 
 
 edges of the two sections by rubbing them over a dead smooth 
 file. Bind the two sections together with wire with sufficient solder 
 and flux inside (Figs. 597 and 598), and proceed as in soldering 
 an ordinary band. With a small mechanical saw cut off the upper 
 
 Fig. 595. 
 
 Fig. 598. 
 
 Fig. 596. 
 
 Fig. 597. 
 
 portion where the tooth begins to slope back (about the dotted lines 
 in Fig. 598). This leaves the crown as shown in Fig. 595, approxi- 
 mal and labial views. Drive on the root. If too small, place on 
 the horn of an anvil and enlarge by hammering; if too large, band 
 
BRIDGE DENTURES. 
 
 615 
 
 the root in the same manner as for a Richmond crown, grinding 
 the tooth to fit. 
 
 Porcelain Facings. — First make the gold crown as described. 
 Select a porcelain facing suitable for the case (Fig. 600). Place the 
 crown on the root in the mouth, and with an excavator mark on 
 the face where the porcelain is to appear. Remove the crown and 
 saw out, so that the facing will fit loosely. With a knife bevel the 
 inner edge or seat for the facing (Fig. 603). Grind the facing to 
 fit (Fig. 605). Back up the facing with No. 34 or 36 gage pure 
 gold, punching holes in the backing for pins, annealing as required 
 
 Fig. 599. 
 
 Fig. 600. 
 
 Fig. 603. 
 
 Fig. 605. 
 
 Fig. 607. 
 
 Fig. 608. 
 
 to readily conform it to the tooth (Figs. 601 and 602). With a 
 sharp knife cut a barb on each side of the pins in the facing, and 
 press the barbs against the backing (Fig. 604), to keep the backing 
 in place. Burnish down the edges well, being careful not to let 
 the backing overlap the facing. 
 
 Place the facing in the space prepared for it in the crown (Fig. 
 606), and bind the two together (not too tight) with wire, wrapping 
 the wire directly over the facing with asbestos to prevent discolora- 
 tion of the porcelain. Flux and solder by holding over a lamp as 
 in the case of a band (Fig. 599). Then finish in the usual way. 
 
 If it is desired to use a platinum pin for anchorage, as, for in- 
 
6i6 
 
 MECHANICAL DENTISTRY, 
 
 stance, a Logan pin, bend the pins in the facing- sufficiently 
 to clamp the anchorage pin, and insert the pin through the gold 
 crown (Fig. 607), finishing as before described. Fig. 608 shows 
 a finished crown so made. 
 
 The Grinding Surface of a Bridge in One Continuous Piece. 
 — After having crowned the teeth for the attachment of the bridge, 
 take a bite in modeling compound, remove the compound, place 
 the crowns in their impressions, make a cast of sand and plaster, 
 
 Fig. 609. 
 
 and place on an articulator; now put moldine between the abut- 
 ments instead of wax, and get the articulation with cusp buttons 
 the same as you would for plate teeth (Fig. 609). Then to 
 remove the buttons without destroying the articulation, make a 
 cup by pouring Melotte's metal, as cool as it will flow, on the face 
 of the cusp buttons. Heat the pouring lip of the ladle and use it 
 to smooth out the half congealed metal, much as you would a 
 soldering iron (Fig. 610). Then place a thin coating of moldine 
 
 Fig. 610. 
 
 upon the molding-plate. Remove the cup from the articulator 
 with the cusp buttons in place (Fig. 610, a). Transfer the cusps 
 by inverting the molding-plate (Fig. 611), and turn the cusp but- 
 tons out upon the moldine on the plate with the grinding surface 
 up (Fig. 611, a), and they will occupy the same relative positions 
 as when on the articulator. 
 
 Now place the large rubber ring around the buttons on the 
 plate, and proceed to make a die with Melotte's metal. When cool, 
 
BRIDGE DENTURES. 
 
 6l7 
 
 remove the buttons, and coat the face of the die with whiting. 
 Invert the die and raise the rubber ring sufficiently high on it, and 
 make a counter-die with the same metal by pouring as cool as pos- 
 sible (Fig. 613). 
 
 This gives the male and female dies with which to swage the 
 continuous grinding surfaces. Then proceed to swage the gold 
 plate in one piece (Fig. 614), annealing as often as necessary. 
 
 Fig. 612. 
 
 Fig. 
 
 6n. 
 
 1 
 
 = — =J 
 
 a 
 
 l 
 
 %^~^<^^ 1 
 
 s^^~*^~~>s~^~*n v. ^y 
 
 
 
 Trim off the surplus plate (Fig. 614, a), and place in position on 
 the articulator. Cut the cusps out on the buccal face to avoid 
 showing the gold (Fig. 615), grind the porcelain facings to fit the 
 cusps, and back with gold, No. 34 or 36, letting the gold come 
 to the cutting edge, the same as in a single crown, as before 
 described. 
 
 If there is a space between the cutting edge and the porcelain, 
 
 Fig. 613. 
 
 Fig. 614. 
 
 Fig. 615. 
 
 place a little wax in the joint to keep out the plaster investment, 
 invest, remove the wax from between the joints, flux, and solder. 
 
 Facings for an All-gold Bridge. — If it is desired to make 
 an all-gold bridge, select the proper facings from the set, make a 
 die of Melotte's metal, and swage up, the same as in the continu- 
 ous bridge before described, and mount gold facings in place of 
 porcelain. 
 
6l8 MECHANICAL DENTISTRY. 
 
 Dr. Parmly Brown's Method. — Dr. E. Parmly Brown de- 
 scribes a process of bridging which is characterized as " all-porce- 
 lain." This is true only in the sense that no metal is visible, all 
 parts of the metal framework being concealed within the body of 
 the porcelain. The method is as follows : 
 
 A lateral view of a porcelain crown, with a platino-iridium pin 
 baked in position, is shown in Fig. 616. The pin has great strength 
 at the neck of the tooth, where the strain is greatest, the porcelain 
 of the tooth extending up on to it, to increase the strength ; a front 
 view of the same crown is seen in Fig. 617, showing by dotted lines 
 the form which the metal occupies in the crown to increase the 
 strength of the attachment, and prevent the pin from approaching 
 the surface in thin teeth. 
 
 Fig. 618 is a view of the two-pin bicuspid crown, which affords 
 
 Fig. 616. Fig. 617. Fig. 618. Fig. 619. 
 
 a pin for each root of a two-rooted bicuspid, the staple form of 
 the pin, shown by dotted lines, being a feature of strength. 
 
 Fig. 619 is a view of a bicuspid crown with the two pins pressed 
 together, making a single pin for the one root. 
 
 The double pin in the bicuspid crowns prevents the loosening 
 of these teeth by the rotary movements of mastication, which by 
 means of the two cusps exert such leverage as to turn and break 
 down the ordinary crown where only one pin is used. 
 
 This bridge-work system has the metal baked invisibly through 
 the body of the teeth. No metal shows either inside or outside 
 of the dental arch. The six anterior teeth are riveted to the 
 platino-iridium bar by the ordinary pins of plate teeth, which are 
 the teeth used for this work. The bicuspids and molars are pre- 
 pared by grinding a slot on the palatal surfaces of the teeth. The 
 bar, which is squared for these teeth, instead of being flattened, as 
 for tbe front teeth, is inserted into this groove or slot, which 
 should be ground with a thin corundum wheel to fit the bar, 
 
BRIDGE DENTURES. 
 
 6l9 
 
 which can be barbed to make proper impingement. It is then 
 ready to receive the creamy tooth body, which at this juncture is 
 applied to the palatal surface of all the teeth, completely covering 
 the metal and giving the natural contour to the inner surfaces. A 
 little of the tooth-body is allowed to run between the teeth, unit- 
 ing their approximal surfaces. 
 
 In this work, when cross-pin teeth are used, the pins will be 
 ground out in most cases; but if straight-pin teeth are used the 
 pins will be bent over the bar. We will give a few illustrations of 
 the many ways in which this work can be done. 
 
 Fig. 620* is a view of a platino-iridium bar baked on to a plain 
 plate tooth, by first riveting the flattened bar on the pins, then 
 applying tooth body to the back, completely covering bar and pins, 
 and then baking in continuous-gum furnace. The body, mixed to 
 
 Pig. 620. 
 
 Fig. 621. 
 
 Fig. 622. 
 
 ! : .' 
 
 a creamy consistency, can readily be applied, and after being held a 
 moment over a spirit lamp is ready to be put on the slide and baked. 
 
 Cavities or fillings are usually found on either side of a space 
 made by the loss of a tooth or teeth that will allow the insertion of 
 the ends of the metal bar and the thorough impacting of gold 
 around them. Amalgam can be used in posterior teeth in many 
 cases, or gold crowns penetrated by the bar, as in Figs. 621 and 
 622. 
 
 In Fig. 621, No. 1 is a third molar, pulp alive, with large filling; 
 No. 2 is a porcelain bridge ; No. 3 is a first molar, pulp dead, with 
 a metal bar entering the pulp cavity. 
 
 * Fig. 620 is incorrect in two respects. The palatine aspect of the completed 
 bicuspid should be a curved line from the palatine cusp to the cervicolabial por- 
 tion, and not make a saddle over the ridge, as shown in the cut, which would be 
 non-cleansible. The other cut, with a bar riveted on to a bicuspid, should have 
 the bar placed in a groove ground into the center of the teeth, riveting being 
 done to incisors and cuspids only. 
 
620 
 
 MECHANICAL DENTISTRY. 
 
 In Fig. 622. No. I is a second molar, pulp alive, with the crown 
 filling of gold or amalgam retaining the bar; No. 2 is a porcelain 
 bridge ; No. 3 is a gold crown with bar passing through crown into 
 root. 
 
 Fig. 623 is a view of a bridge of two teeth — a central porce- 
 lain crown with a lateral baked into it, the bar and pin being of the 
 same piece, bent at right angles. 
 
 In Fig. 623, No. 1 is a porcelain crown forming part of the 
 bridge ; No. 2, a bridged lateral with metal bar baked through it ; 
 No. 3, a living cuspid with a metal bar running in the center of a 
 solid gold filling. 
 
 Fig. 624 is a view of a central incisor bridged on to two teeth 
 whose pulps have been lost. 
 
 Fig. 623. 
 
 Fig. 624. 
 
 Fig. 625. 
 
 As many as six teeth have been inserted in this way on two 
 central roots, and the posterior end of the invisible metal bar run- 
 ning through the six teeth worked firmly into a gold filling in a 
 molar — the six teeth being united on their approximal surfaces by 
 the porcelain running between them at the baking. The backs of 
 such teeth must be given a curved form to insure a cleanly condi- 
 tion. 
 
 Fig. 625 is a view of the attachment of the bridge to a tooth 
 standing alone, where the tooth has a gold crown attached, or the 
 bar is worked into a filling. Nos. 1 and 3 are teeth on a porcelain 
 bridge ; No. 2 the natural tooth over which the bridge is saddled. 
 
 All teeth for this bridge-work should be ground so that no con- 
 siderable portion of gum would be covered, the teeth just touching 
 the gum by a point only at the cervicolabial portion. 
 
BRIDGE DENTURES. 
 
 621 
 
 REMOVABLE BRIDGE DENTURES. 
 
 As has been intimated, there are operators who prefer bridge 
 dentures that are readily removed from the mouth to any form of 
 stationary fixture. These devices may be made so that the dentist 
 may readily remove them if required either for therapeutic treat- 
 ment, or for repair; or they may be constructed in such a manner 
 that the patient may remove them for hygienic reasons. We will 
 first consider the system introduced by Dr. R. Walter Starr, whose 
 description is about as follows : 
 
 " The case of Mr. W. presented difficulties of an unusual charac- 
 
 Fig. 626. 
 
 ter, as may be seen by inspecting the illustration, Fig. 626, which 
 renders detailed description unnecessary. 
 
 " It will be observed that the molars and the left second bicuspid 
 overhang to a degree that would make the taking of an accurate im- 
 pression by ordinary methods well-nigh impossible. After a careful 
 study of the case, it was decided that two separate pieces of remov- 
 able bridge-work should be attempted, and, as an essential prelimin- 
 ary step, the overhanging sides of the molars and bicuspids were 
 ground with engine corundum wheels and points until those sides 
 were made much less inclined, when plaster impressions were 
 
622 
 
 MECHANICAL DENTISTRY. 
 
 taken, first of one half, and then of the other half of the jaw. 
 Gold cap crowns were closely fitted over the molars, left second 
 bicuspid, right first bicuspid, and cuspid stump. Gold crowns 
 were made to telescope over all the caps, which were then, by 
 means of oxyphosphate cement, fixed firmly on the teeth. Suit- 
 able plate teeth were selected, fitted, backed, and waxed in place 
 between the telescoping crowns. After hardening the wax with 
 cold water from a tooth syringe, the pieces were carefully removed,, 
 invested, and soldered. The two completed bridges were easily 
 
 Fig. 627. 
 
 replaced on or removed from the supporting capped teeth, and 
 their appearance when detached is correctly shown by the illus- 
 tration, Fig. 627, which also shows the capped teeth and stumps.. 
 This figure likewise shows the results of the novel method em- 
 ployed in crowning the incisors. Gold collars were fitted tight on 
 the necks of the incisor stumps, and the new style porcelain caps 
 adjusted in the collars, and set in the oxyphosphate cement which 
 had been packed into the collars; thus at the same time fastening 
 the collars on the stumps and the caps in the collars. 
 
BRIDGE DENTURES. 
 
 623 
 
 " Fig. 628 illustrates the finished crowns and bridges, which latter 
 were secured in position by placing a small piece of gutta-percha 
 in each of the telescoping cap crowns, which were then warmed 
 and carefully pressed in place — the gutta-percha filling only the 
 spaces between the flat tops of the caps of the natural teeth and 
 cuspid caps of the bridges. 
 
 " Whenever, for repair or for any other purpose, it shall become 
 desirable to remove one of the bridges, that may readily be done 
 by applying a hot instrument or hot air to the caps to soften the 
 
 Fig. 628. 
 
 gutta-percha sufficiently to permit the telescoping bridge to be taken 
 off. 
 
 " A full upper vulcanite denture was made to replace the old 
 one, which, by improper occlusion, had thrown the full force of 
 mastication on the anterior teeth of the lower jaw, and produced 
 the destructive action that resulted in the deplorable loss of tooth 
 substance shown in Fig. 626.* 
 
 " The next case also presented unusual difficulties. The forward 
 overhang of the inferior right second molar was so excessive that 
 an impression could hardly be taken, until with corundum wheels 
 
 * Dental Cosmos, vol. xxviii. 
 
624 
 
 MECHANICAL DENTISTRY. 
 
 and points the sides of the tooth had been made parallel, or, rather, 
 slightly tapering, to form a truncated cone, with the neck as a base. 
 The molar was alive and sound, but the crown was gone from the 
 pulpless cuspid, which I suitably shaped by means of my root trim- 
 mers (Fig. 629). 
 
 " An impression was then taken, the cast from which is illus- 
 trated by Fig. 630. A seamless gold collar was, by means of a 
 slightly tapering mandrel, made to exactly fit the tapered natural 
 molar, the lower edge of the collar cut to conform to the gingival 
 margin, a cap piece of gold plate soldered to the top edge of the 
 collar, and a hole drilled through the center of the completed cap 
 
 Fig. 629. 
 
 (A). Care was taken to so fit and proportion the cap that it would 
 require finally pretty hard driving to send it home on the tooth; 
 but first there was fitted to the cap a telescoping seamless collar, 
 on which was soldered a gold plate, with cusps, to form a molar 
 crown as shown. The molar was then thoroughly dried, slightly 
 painted with agate cement, and the cap, A, driven hard down with 
 a flat pine stick held upon it and struck with a mallet, the hole in 
 the cap enabling me to see when the cap was quite down. The 
 cuspid was then likewise fitted with a seamless gold collar, the top 
 edge of which was given a roof shape, as seen above the root in 
 Fig. 630. A piece of gold received a corresponding roof shape, 
 
BRIDGE DENTURES. 
 
 62: 
 
 had a short section of gold tubing soldered into it, and was trimmed 
 to the outline of the collar, beside which, B, its form is seen, and 
 to which it was subsequently soldered, after suitable investment to 
 keep the parts in proper place. The root canal had been pre- 
 viously prepared to receive the tube, which, with its roofed cap, 
 was with stick and mallet driven hard down over the root. A 
 piece of gold wire exactly fitting the tube had a roof-shaped 
 piece of properly perforated gold plate slipped over it into posi- 
 tion on the root; became fixed in such relation by a drop of melted 
 hard wax; was removed, invested, soldered, and finished in such 
 shape that, excepting the hollowness, it looked like the tube and 
 cap B. 
 
 " The relations of the occluding teeth had, of course, been de- 
 
 Fig. 631. 
 
 termined by an articulating model, and by means of it a series of 
 seamless gold collars and cusp crowns were adjusted on a thin 
 platinum plate fitted on the cast between the cuspid and second 
 molar, and the collars soldered to the plate after investment. The 
 truss thus formed received an appropriate finish by the rounding 
 and smoothing of its basal borders. A plain plate cuspid was 
 backed with gold plate and fitted on the roof-plate, to which, after 
 determining its proper occlusion, it was secured by hard wax, re- 
 moved, invested, and soldered. It was then put into the tube on 
 the root, the telescoping cap put over the molar, the truss put in 
 position in the mouth, and the whole covered with plaster and 
 marble-dust, contained in a suitable sectional impression-tray, 
 which enabled me to hold the mass steadily in place until the mix- 
 ture was sufficiently hard to bring away cap and truss and roof- 
 40 
 
626 MECHANICAL DENTISTRY. 
 
 plate all in proper position. A second mixture of plaster and 
 marble-dust, and a suitable trimming of the first mixture after all 
 was hard, sufficed for the soldering process that resulted in the 
 denture which, when finished, appeared as shown detached at C, 
 Fig. 630, and mounted on the cast in Fig. 631. It went firmly to 
 place in the mouth, and yet was removable in the possible event of 
 accident to the denture, or for readjustment of the cusp crowns, 
 which latter could easily be done by warming the piece sufficiently 
 to soften the gutta-percha, replacing the denture on its anchorages, 
 and directing the proper closure of the occluding teeth." 
 
 Dr. Parr's Method. — The following is a method of construct- 
 ing removable bridge dentures, first described by Dr. H. A. Parr, 
 in the Dental Cosmos, vol. xxxi. 
 
 In the construction, adjustment, and placing of a dental substi- 
 tute, one of the first considerations is its immovability in position,, 
 and next its removability for cleansing or repair. The old styles 
 of clasp dentures met these two essential requirements when the 
 forms and relations of the supporting teeth were such that the 
 clasps would firmly embrace those natural teeth and hold the close- 
 fitting plates in position. But the clasped teeth soon became worn 
 or wasted, and in consequence the loose denture lost its efficiency. 
 Even in favorable cases the inverted cone shape of nearly every 
 natural tooth made it a matter of difficulty to secure at the neck 
 near the gum a tight fit of the springy clasp, which, in every in- 
 stance, must have been large enough to go over the crown of the 
 supporting tooth. Then, too, there was the tendency of the plate 
 to press into the gum and so become loose by carrying the clasp 
 to a yet narrower place on the tooth. In many cases, moreover, 
 the supporting teeth inclined toward or away from one another, and 
 made it well-nigh impossible to construct a plate which could be 
 sprung into place and yet so tightly clasp the teeth as to firmly hold 
 the denture in position. 
 
 The object in devising the method of attachment and organiza- 
 tion of dental substitutes now to be explained was, as Dr. Parr 
 explains, to avoid the difficulties mentioned, which will be made 
 evident in the following description of two practical cases. 
 
 Fig. 632 is from the plaster cast of a lower jaw in which only 
 the lower left second molar, cuspid, and right first bicuspid re- 
 mained. The molar and bicuspid were fitted with gold cap crowns. 
 
BRIDGE DENTURES. 
 
 627 
 
 Gold sockets were prepared, and gold tongues, made of strips of 
 spring gold plate having their ends folded upon themselves to 
 form spring catches, were fitted to the sockets. The cap crowns 
 were placed on the plaster teeth, the boxes or sockets hard waxed 
 
 Fig. 632. 
 
 to the sides of the crowns, and the tongues hard waxed to a piece 
 of stiff wire so that the two tongues could be lifted out of their 
 sockets without breaking either the tongues from the wire or the 
 sockets from the crowns. When by repeated trials this could be 
 done, the crowns and sockets were taken from the cast, invested in 
 
 Fig. 633. 
 
 plaster and marble-dust, and the sockets soldered to the crowns. 
 These were replaced upon the cast and appeared as seen in Fig. 
 632. 
 
 The tongues were then placed in the sockets, the artificial teeth 
 
628 
 
 MECHANICAL DENTISTRY, 
 
 arranged on the cast and waxed up as usual for vulcanite work, 
 taking care that the projecting ends of the tongues were so im- 
 bedded in the wax that they would be held firmly when the piece 
 should be removed to be flashed. It is, in fact, best that at the 
 outset the tongues should be soldered to a stout gold wire bent 
 
 Fig. 634. 
 
 to fit the cast, so that the wire will stiffen the waxed-up piece, and 
 also hold the tongues more securely in the piece during and after 
 vulcanization. 
 
 Fig. 633 shows the vulcanized denture in place on the cast. 
 
 The under side of the denture is shown in Fig. 634, which also 
 makes evident the forms and relations of the tongues which hold 
 
 Fig. 635. 
 
 Fig. 636. 
 
 
 the denture in place. The parallelism of the tongues permits 
 their ready removal from their sockets, no matter how much awry 
 the supporting teeth may be. The bearing of the denture upon 
 the cap crowns admits of the contact of the denture with the 
 gum on which it rests but cannot be pressed into because of the 
 
BRIDGE DENTURES. 62CJ 
 
 cap crown supports. The original denture, of which this is a dupli- 
 cate, is now in satisfactory use. 
 
 Fig. 635 represents the articulated cast of a case for which a 
 similar tongue and clasp vulcanite denture was made. This is illus- 
 trated in Fig. 636, which needs no description. Fig. 637 shows 
 the denture in place, the original having been made for and placed 
 in the mouth of a patient exhibited at the clinic of the Odontolog- 
 ical Society of Pennsylvania, at Philadelphia, in December, 1888. 
 
 These are simple examples of a class of work having a wide range 
 of application and capable of construction without the trouble and 
 cost of all-gold plate-work. 
 
 The sockets and spring tongues require some skill and nicety of 
 workmanship to insure a close fit of the one in the other so that 
 the attachment shall be firm, yet capable of easy-designed detach- 
 ment for cleansing or repair. 
 
 Fig. 637. 
 
 A notable advantage of this mode of constructing dentures for 
 the upper jaw is manifest in the fact that the surface of the plate 
 which rests upon the gums need only be wide enough to cover the 
 ridge, and thus avoid the common interference of artificial dentures 
 with the function of speech. 
 
 Dr. Davenport's Method. — The following method of construct- 
 ing partial dentures, described by Dr. J. L. Davenport in the Den- 
 tal Cosmos is an amplification of the principle of attachment in- 
 volved in the process just considered. 
 
 The case treated was one where the only teeth remaining in the 
 upper jaw were the six front teeth, the three molars on the right 
 side, and the first bicuspid on the left. The crowns of the front 
 teeth were wholly obliterated from excessive attrition consequent 
 on the loss of the occluding back teeth, necessitating the exclusive 
 use of the former in mastication, as shown in Fig. 638. The shorten- 
 
630 
 
 MECHANICAL DENTISTRY. 
 
 ing of the lower teeth, resulting from the same cause, was remedied 
 by building them up to a uniform height with crystal gold, Fig. 642, 
 the vacuities in the lower jaw resulting from the loss of the left 
 central incisor and several of the back teeth being supplied with 
 substitutes in the manner hereinafter described. 
 
 For this case, what is termed a " combination plate and movable 
 bridge " was constructed, and is thus described : 
 
 " The two superior cuspid roots were dressed down nearly to the 
 gum and fitted with 22-carat gold cap crowns, similar to those de- 
 scribed by Dr. J. Rollo Knapp. After these had been placed in 
 position, a hole was drilled through each cap of a size suited to 
 that of the pulp canal, and a tube of iridium and platinum was ad- 
 
 Fig. 638. 
 
 justed in the root cap and waxed in position. The cap and tube 
 were then taken off and soldered, great care being taken to have 
 the tubes enter both roots perfectly parallel. These were perma- 
 nently secured in the roots with gutta-percha, and to prevent the 
 caps being pulled off, the top of each tube was slit down a trifle, 
 and after insertion was bent back into the gutta-percha with a warm 
 instrument. 
 
 ' The incisor roots having been dressed down even with the 
 gum and filled, a plaster cast was taken and a narrow 20-carat gold 
 plate was swaged to fit over the ends of the incisors and the capped 
 cuspids, making it a little broader where it had to rest on the gum 
 back of the first left bicuspid root. A hole in the plate was then 
 made to expose the root of the first left bicuspid. This was fitted 
 
BRIDGE DENTURES. 
 
 63I 
 
 with a bifurcated iridioplatinum pin, having notched sides, and a 
 hammered head upon its lowered end, which came down below the 
 root about }i of an inch. 
 
 " A thin iridioplatinum band was then made to encircle the root, 
 passing just under the gum and being slightly longer than the 
 headed pin. This band was perforated with two rows of holes, 
 from without inward, giving the inner surface a roughness similar 
 to that of a nutmeg grater. The band and pin were then made 
 secure to the root with a non-shrinkable copper amalgam. 
 
 " Fig. 639 shows the upper jaw ready for the plate. 
 
 " I must mention here that this method of lengthening the bi- 
 
 Fig. 639. 
 
 cuspid is not original with me, but has been previously described 
 by Dr. E. Parmly Brown. I have, however, used this method 
 several times on very frail roots, and cemented over it a gold cap 
 crown. 
 
 " In the present case, after the amalgam had become hard and 
 the end and sides had been polished, a gold crown was fitted over 
 all just up to the margin of the gum, and in close contact with the 
 end of the band and amalgam. This crown was loose enough to 
 admit of its sliding on and off, though with just enough friction to 
 hold it in place when at rest. This gold crown was then placed in 
 position, the plate also inserted, and hard wax used to firmly join 
 the two in the mouth. They were then removed and soldered. 
 
6.^2 
 
 MECHANICAL DENTISTRY. 
 
 " Gold pins were then placed through holes drilled in the plate 
 into the tubed cuspids; then soldered to the plate, the pins being 
 of a size to fit the tubes accurately. The plate was also provided 
 with a wide clasp encircling the first molar on the right. 
 
 " The plate was then provided with a gold bar about % of 
 
 Fig. 640. 
 
 an inch wide, occluding perfectly with the lower teeth, and 
 plain teeth soldered in place, hiding the bar, and just meeting 
 the gum in front of the incisor roots. The plate rested squarely 
 against the capped cuspids, each of which showed a narrow band 
 of gold when the plate was in position. As finally completed (see 
 Fig. 640) this was the most perfectly fitting piece I ever inserted, 
 
 Fig. 641. 
 
 requiring great care in its removal, and yet by a little practice the 
 gentleman was able to remove and replace it quite easily. It was 
 also as firm as any permanent bridge could have been, though it 
 had no support on the left side back of the first bicuspid. 
 
 " The lower jaw was supplied with a double 20-carat gold plate, 
 having a wide clasp on the first right bicuspid, which, after being 
 
BRIDGE DENTURES. 
 
 633 
 
 built up, presented a cone-shaped top, about which the clasp fitted 
 so as to rest firmly upon the end of the tooth, thus preventing in- 
 jury to the gums during mastication. 
 
 " The only peculiarity was that the second left inferior molar, 
 being abnormally short, though well-formed and standing upright, 
 was fitted with a wide clasp, extending about ]/§ of an inch 
 about the tooth, and a piece of gold plate with gold cusps was 
 soldered into its clasp, covering the molar crown and occluding 
 with the molar on the upper plate. (See Fig. 641.) This not only 
 prevented the plate from being bitten down unpleasantly on the 
 gums during mastication, but enabled me to use a shorter molar 
 upon the upper than I otherwise could have done, and better al- 
 
 FlG. 642. 
 
 lowed the antero-posterior and lateral movements of the jaws. The 
 case as completed is shown in Fig. 642." 
 
 Detachable Bridge by the Mandrel System. — A description 
 of two or three methods of constructing detachable bridges by the 
 mandrel system will suffice to indicate the general principles in- 
 volved. Having these, each operator will find it an easy task to 
 devise the modifications necessary to adapt a method to individual 
 cases. 
 
 The first method is especially applicable to cases where both ends 
 of the bridge are attached to roots, as, for example, the inferior 
 cuspid and second molar roots of the left side, the intervening 
 teeth having been lost. The operation is conducted as described 
 in the first case of fixed bridge-work down to the construction of 
 
634 
 
 MECHANICAL DENTISTRY. 
 
 the truss, for which in this method square gold wire is used. Hav- 
 ing cut the wire to the proper length, lav it upon a piece of gold 
 plate (about No. 26, American gage) of the same length and full 
 three times as wide, and, placing the two upon the lead anvil, with 
 a hammer and the piece of file before used drive them into the 
 lead. This will form the plate into what we may call an open trunk, 
 which fits the square wire. Remove the two from the lead together, 
 and, without separating them, curve to the proper shape to form 
 the truss. Grind crowns having vertical holes, like the Bonwill, to 
 fit, and having determined the proper points for the supporting pins, 
 drill through both trunk and bar at these points. Separate the bar 
 from the trunk, and fit and solder pins to the bar. Construct small 
 tubes to fit the pins, ream out the holes through the trunk to admit 
 
 Fig. 643. 
 
 them, and set the tubes with solder in the enlarged holes (Fig. 643). 
 Fix the crowns permanently upon the tubes. They may be 
 mounted in any of the approved ways, by vulcanizing or by the 
 use of a plastic filling material. Wben they are firmly set, place 
 the trunk with the teeth upon the bar and anchor it permanently 
 as already described. Fig. 644 shows the completed work. 
 
 " In this method the truss consists of the bar and the open trunk 
 which covers three sides of it. The bar is, of course, permanently 
 attached to the roots of the molar and cuspid, but the trunk with 
 the teeth can be removed at any time. 
 
 " The second method of constructing a detachable bridge is 
 applicable to cases where one or both of the supports or piers are 
 sound teeth. In the case adduced for illustration, the right inferior 
 
BRIDGE DENTURES. 
 
 ^\ 
 
 •cuspid crown was decayed, and both of the bicuspids and the first 
 molar were absent. The supports for the bridge were the sound 
 second molar and the cuspid root. After the cuspid root was 
 prepared and banded, the crown of the molar was reduced very 
 slightly, not sufficient to destroy the enamel, but just enough to 
 permit a collar properly fitted to pass over it. A collar somewhat 
 wider than the length of the crown from grinding surface to neck 
 was fitted and cut to the proper width. Two lugs were then soldered 
 upon the anterior and posterior sides and bent to fit into the ap- 
 proximal fissures, which were slightly cut out to admit them. An 
 impression was taken, the collar coming away in the plaster, and a 
 cast was made with the collar in position. A coned tube was then 
 made for the root of the cuspid and a coned pin fitted into it. A 
 
 Fig. 644. 
 
 truss of half round wire was made, to which the collar, coned pin, 
 and the molar were next soldered (Fig. 645). A half-clasp to grasp 
 the lateral was next soldered to the end of the truss, to be supported 
 by the cuspid. The object of this clasp was to guard ^ against the 
 teeth being thrown out of proper alignment by the force of masti- 
 cation. Bonwill crowns were then vulcanized to the truss, after 
 their supporting pins had been fitted and soldered to it. (Counter- 
 sunk crowns can be used as well in the same way. Plain plate 
 teeth may also be used in this style of work, in which event they 
 are to be soldered to the truss.) The bridge was then ready to be 
 set, which was accomplished in the following manner : The cuspid 
 root was nearly filled with oxyphosphate, and the coned tube was 
 placed upon the pin. The band was put on the molar, and the 
 - coned pin, with the tube upon it, was forced into the plastic in the 
 
6 3 6 
 
 MECHANICAL DENTISTRY. 
 
 cuspid root. As soon as this became set, the tube was held perma- 
 nently, while the bridge itself could be removed whenever desired 
 (Fig. 646). 
 
 " This method of fixing the tube allows considerable range in its 
 adjustment. In soldering the coned pin to the truss, care should 
 be taken to set it at an angle exactly parallel to the axis of the- 
 molar; otherwise there will be difficulty in removing the bridge. 
 
 Fig. 645. 
 
 Fig. 646. 
 
 " The third style of detachable bridge-work to be described in- 
 volves the use of cusp crowns (Fig. 647) for supporting posts or 
 piers. Suppose a case similar to that just described, where a 
 bridge is required to extend from the right inferior cuspid to the 
 right inferior second molar, with only the roots of the two teeth 
 named as supports. Prepare the roots and pulp chamber. Set 
 screw-posts into the dentine for anchorage, or as retaining pins, and 
 
 Fig. 647. 
 
 fit the collars, using sizes wide enough to form the walls of the- 
 crowns. Fill the pulp chamber and about two-thirds of the depth 
 of the collars with a plastic filling material, packing it well around 
 the retaining posts. Select suitable cusp crowns for the molar and 
 cuspid and place them in the ends of the bands to ascertain the 
 occlusion. If too long, shorten the cusps or reduce the bands with 
 engine corundum wheels, and when the correct articulation is found 
 
BRIDGE DENTURES. 
 
 637 
 
 form a small square shoulder in the lingual edge of the cuspid and 
 in the posterior grinding surface of the molar. Fill the remaining 
 portion of the collars with plastic mixed somewhat thinner than 
 the first lot, and set the cusp crowns in position. If there are an- 
 tagonizing teeth, the mere closing of the patient's jaws will force 
 the crowns to place. If there are no antagonizing teeth, the crowns 
 •can be readily tapped to place with the mallet, using a piece of 
 wood as a driver. Allow the filling material to set firmly, trimming 
 off any excess which may exude around the collars. Bridge sup- 
 ports or piers constructed on this plan are strong and durable, and 
 likely to withstand any strain. Take an impression and proceed 
 to fit seamless collars to telescope over those already set upon 
 
 Fig. 648. 
 
 Fig. 649. 
 
 the cuspid and second molar roots. It will be remembered that 
 these collars are so made that each size telescopes into the next 
 higher series. If the proper sizes are selected for the outside bands, 
 the work of fitting is readily and quickly accomplished, forming 
 tubes which slide easily over the supporting piers, and at the same 
 time fit closely. It is only necessary to take care in shaping the 
 tubes not to drive them too far up on the mandrels, and thus stretch 
 them so as to destroy the fit. To the outer end of each of the tubes 
 solder a small piece of gold plate, forming partial caps so placed 
 as to rest when in position upon the shoulders previously cut in the 
 cusp crowns. Adjust a truss bar of half round gold wire, to the 
 ends of which solder the tubes (Fig. 648). The truss is now ready 
 
638' MECHANICAL DENTISTRY. 
 
 for the teeth, which may be of any of the forms used for this pur- 
 pose, and they may be attached to the bar in any way desired. 
 One of the strongest attachments is vulcanite. 
 
 '* An easy modification of this plan is readily adapted to cases 
 where only a small space is to be filled and one end of the bridge 
 is to be supported by a sound tooth. Thus, suppose it is desired to 
 bridge a space formerly occupied by the two inferior left bicuspids, 
 the crown of the first molar being a mere shell. The operation would 
 be essentially the same as in the previous case, except that the sound 
 cuspid would be utilized for one of the piers, as follows : Fit a seam- 
 less collar, cut out a portion of it so that it will embrace only about 
 two-thirds of the cuspid crown, and solder a partial cap or cover to 
 it (Fig. 649). Or, the cuspid crown may be separated from the lat- 
 eral incisor with a diamond disc and the collar allowed to embrace 
 the whole crown. 
 
 " The great desideratum in constructing a piece of bridge-work 
 is, of course, the securing of perfect usefulness in mastication and 
 speech, combined with absolute comfort and cleanliness. The 
 closer a bridge approaches that condition where its wearer loses 
 consciousness of its presence in his mouth, the nearer perfection it 
 is. Scarcely less important, however, is the necessity of providing 
 for repair. Accidents will occur, and the system which superadds 
 to usefulness, comfort, and beauty, ready facility for repairing "break- 
 ages, is by so much superior to those which make no such provision. 
 The place of a crown broken from a bridge constructed by any of 
 the methods above described can be easily supplied, and the piece 
 when repaired will be as strong and serviceable as it was originally." 
 
 Dr. Condit's System. — The method devised by Dr. A. S. 
 Condit is the combination of removable plate with gold or 
 Richmond crowns, which are cemented upon the natural teeth or 
 roots, contiguous to the space to be filled with the artificial sub- 
 stitute. The plate is made to rest upon the gums, and held firmly 
 in place by means of an attachment, part of which is placed upon 
 the crowns and a part in the plate. 
 
 The construction of the attachment is such that when the work 
 i^ in place it cannot be detached except by a straight up or down 
 pull, nor can there be any lateral movement. It is also claimed to 
 have sufficient tension to hold the work securely in place, yet not 
 so firmly but that it can be easily removed by the patient. 
 
BRIDGE DENTURES. 
 
 639 
 
 By the use of this method the natural teeth are sealed up and 
 protected from the attrition of the plate, and they are held firmly 
 in their normal position and, Dr. Condit says, are not moved out of 
 line during mastication. 
 
 A prominent feature of this work is that the bearing is supposed 
 to be equally divided between the teeth attached to, and the ridge. 
 
 Figs. 650 and 651 represent the loss of the lower incisors. The 
 advantage in using the method for such cases is that the cuspids 
 are held firmly in their normal position and undue pressure is re- 
 leased from the gums. 
 
 If the ridge had to bear the entire weight of the plate, the gums 
 would soon be pressed away from the cuspids, and the teeth would 
 move out of line. 
 
 In upper cases, where bicuspids and molars have been lost on 
 
 Fig. 650. 
 
 Fig. 651. 
 
 both sides, as shown in Figs. 652 and 653, the work can be con- 
 structed by connecting the sides with a narrow plate across the 
 center of the palate, or by skirting the anterior teeth with a narrow 
 strip of plate, and the same object be accomplished as when the 
 entire palate is covered. 
 
 This method is considered by Dr. Condit to be applicable in 
 one-attachment cases, such as are shown in Figs. 654 and 655. He 
 suggests, however, that in making this appliance a small, soft-rub- 
 ber washer should be placed over the pin in the attachment, so that 
 the greatest strain should be brought upon the ridge, the attach- 
 ment merely giving it stability. 
 
 The directions given by Dr. Condit for the construction of this 
 class of denture are about as follows : 
 
 One-attachment Case. — First fit a gold cap crown to the tooth, 
 
640 
 
 MECHANICAL DENTISTRY, 
 
 contiguous to the space to be occupied by the piece, with the same 
 accuracy as for an ordinary bridge. When in place, mark with a 
 
 Fig. 652. 
 
 Fig. 653. 
 
 sharp instrument the position for the tube (1, Fig. 656), which 
 should be at the posterior lingual side, far enough from the buccal 
 to avoid interference with the artificial teeth, and yet not so far as 
 
BRIDGE DENTURES. 
 
 64I 
 
 to make an undue prominence on the lingual side. The crown or 
 band is now removed from the mouth and the tube (1, Fig. 656) 
 attached with 18-carat gold solder, using no more than just suf- 
 ficient solder to hold it securely. To properly do this the tube 
 should be placed on one point of a pair of soldering pliers, with the 
 open side out, as shown in Figs. 658 and 659, and held as nearly 
 vertical in its relation to the crown as possible. If the crowned 
 tooth leans to the one side or the other, so that it is necessary in 
 giving the tube its vertical position to stand it away from the crown 
 at either the coronal or gingival ends, it may easily be accom- 
 plished by bending the points of the pliers out or in, as is clearly 
 shown in Figs. 658 and 659. The tube now being soldered in 
 
 Fig. 654. 
 
 Fig. 655. 
 
 place, should be spread very slightly by passing a round instru- 
 ment through it — to allow the pin and shield (Fig. 656) to slip 
 easily on and off — and the crown or band returned to the tooth with 
 the pin and shield in position. 
 
 If the articulation is interfered with, the tube may be dressed 
 down from the coronal end, and the pin and shield correspondingly 
 ground off from the gingival end, repointing the pin by carefully 
 running a small pear-shaped bur around between it and the shield. 
 
 The crown or band should now be cemented to the tooth and the 
 cement allowed to thoroughly harden, when the pin and shield are 
 again placed in position and the bite and impression taken. Be 
 sure to take the bite before taking the impression. 
 41 
 
6-12 
 
 MECHANICAL DENTISTRY. 
 
 If the pin and shield do not come away with the impression they 
 must be removed from the tube and carefully placed in proper 
 position in the impression, which should be varnished or otherwise 
 prepared for pouring the model. Before pouring - , however, the 
 long tube (Fig. 657) is filled with plaster and slipped over the pin 
 in the shield, the lug (A) projecting from the open side of the shield. 
 This long tube prevents any possible displacement of the shield 
 after the model is poured, and the filling with plaster prevents the 
 vulcanite from filling the shield. 
 
 The model is now poured in the usual manner and placed on the 
 articulator; teeth arranged, flasked, and finished as in any ordinary 
 denture — except before packing the vulcanite, the point of the lug 
 (A) attached to the shield (Fig. 656) may be bent slightly, in such 
 wise as to give it firmer hold in the plate. After vulcanizing, the tube 
 
 Fig. 656. 
 
 Fig. 658. 
 
 Fig. 659. 
 
 (Fig. 657) is removed from the shield and the piece finished. Pinch 
 tube (1, Fig. 656) on the crown very slightly and adjust the work. 
 
 Tzvo-attachmcnt Case. — The proceedings are identical, except in 
 the matter of attaching the tubes to the crowns or bands. In these 
 cases the crowns are properly fitted and placed upon the teeth 
 selected for attachments. Then an impression must be taken and 
 the crowns removed from the teeth and placed in their relative posi- 
 tions in the impression and a model made. (Wooden cores about 
 y 2 of an inch in length may be fitted rather loosely in the crowns 
 before pouring, to permit their easy removal from the model.) 
 
 After the model is secured, crowns in place thereon, the guide 
 (Fig. 660) is adjusted with reference to the proper placing of the 
 tubes (1, Fig. 656), as directed in the one-attachment case, and 
 fixed with the set-screws. (One post of the guide is adjustable 
 to allow for any variation in the height of the crown.) The tubes 
 are now placed upon the ends of the guide posts, with the open 
 
BRIDGE DENTURES. 
 
 643 
 
 side away from the crowns. The screw (B), Fig. 660, is run down 
 until the point touches the model, when a little melted beeswax 
 dropped at the point will hold the whole in position until the tubes 
 (1, Fig. 656) are waxed with hard wax to the crowns. After which 
 the center screw (B), Fig. 660, may be carefully turned to the left, 
 releasing it from the wax, and the guide may be removed from the 
 tubes. The crowns are then removed from the model, invested in 
 plaster and sand, and tubes soldered. 
 
 In cementing the crowns on the teeth, in the mouth, before the 
 cement hardens, it is well to remove the center screw from the 
 guide and test the tubes to be sure that the crowns have gone back 
 ^exactly to their proper places on the teeth. 
 
 Attachments for Porcelain Work. — The crowns and attachments 
 
 Fig. 660. 
 
 are made and adjusted in the manner just described. After cement- 
 ing them to the teeth, platinum shields, the same as Fig. 656, lacking 
 the lug A, are placed over the tubes and impression taken. If the 
 shields do not come away with the impression they must be re- 
 moved and placed in their proper places therein. 
 
 Pour your model now with the view to making metal dies 
 for swaging. 
 
 The plate must be swaged to fit with the utmost nicety around 
 the shields and teeth. 
 
 If several teeth must be skirted, to give the requisite strength an 
 extra piece of 28 gage platinum should be swaged and soldered to 
 the plate with pure gold. 
 
 After swaging, remove the shields from the model and place 
 
644 MECHANICAL DENTISTRY. 
 
 them in position in the mouth ; then try in the plate ; if swaged to a 
 proper fit, take impression with plate and shields in position. If 
 they come out with the impression, a platinum tube, the same as 
 Fig. 651, is placed in the shield and a plaster and sand model is 
 poured. When separated, solder the shields to the plate, using pure 
 gold solder, and again try in the mouth. If care has been exercised 
 in every detail, the plate must fit snugly, when wax may be inserted 
 and the bite secured. Remove the wax and plate together ; tack 
 asbestos fiber, soaked in water, into the shield until filled ; then place 
 on the articulator, and proceed as in the case of any ordinary con- 
 tinuous-gum piece. 
 
 Attachments for gold work are made identically as described for 
 porcelain above. The shields for gold work are made of 20-carat 
 gold, soldered with 20-carat solder. Thus the gold attachments 
 made for vulcanite work cannot be used in connection with gold 
 plates, as the shields are of 18-carat gold, the pins 16-carat, and 
 soldered with 14-carat solder. 
 
 Attachments for cast aluminium are made exactly as for vulcanite, 
 described above, using, however, the platinum shields. 
 
 Dr. Carr's Method. — A system of making anchored, adjustable, 
 and removable dentures was devised about six years ago by Dr. C. 
 M. Carr, of Salt Lake City, Utah. In describing his work he says : 
 " I have adopted the name ' anchored, adjustable, and removable den- 
 ture,' because it better fits the work than either ' plate ' or ' bridge.' 
 While the method partakes partially of both bridge- and plate-work, 
 yet it is neither of them, the palate never being covered and the 
 teeth or roots used for anchorage having no excessive pressure or 
 lateral strain placed on them. There is, however, a light and yield- 
 ing pressure placed upon the roots during mastication — an inter- 
 mittent pressure, which nature seems to require to sustain a healthy 
 union between any root and the alveoli. This intermittent pressure 
 is imparted by the little spiral spring, which is the secret of my 
 method, everything else being employed to accommodate it." 
 
 In illustrating this form of denture we have selected an extreme 
 case, one where other forms seem almost barred out. It is a fac- 
 simile of a case now being worn by a lady in California. The 
 mouth was such that an adhesive plate was not very successful, and 
 it was a great desire of the patient to have the palate free and un- 
 encumbered, as is frequently the case with speakers and singers. 
 
BRIDGE DENTURES. 645 
 
 All the teeth having been lost, the first thing done was to implant 
 two roots, one on either side, in about the center of the ridge. 
 These roots, however, were prepared for the reception of the 
 posts, and filled with gutta-percha before being implanted. After 
 the roots became thoroughly attached, an impression was taken ; 
 the imprints of the roots were enlarged about T \ of an inch in 
 same before the cast was run. This is done so that the roots 
 will appear larger on the cast and die, both in height and breadth, 
 and when the saddle or base (Fig. 662) is swaged and placed 
 upon the ridge in the mouth there will be a space between 
 the chambers on the roots and the roots themselves. This being 
 accomplished, a little warm wax was placed in these chambers 
 and the saddle pressed firmly into position against the gum tissue. 
 In this way the exact location (by impression of the end of root in 
 wax) of the tube in the root is secured. Then, with a plate punch, 
 a hole is made in the exact center of the impression of the end of 
 tube, after which two other holes are punched, one on either side 
 of the first, or center one; then with a fissure drill on the dental 
 engine cut the three together, making a slot, as shown on the left 
 side of Fig. 662, through which the T head of the anchorage stud 
 (A) will pass. Then, as it is necessary to prevent the T head of 
 stud A from rotating or moving during mastication, and thus re- 
 leasing the denture, a segment of a disc is soldered on each side of 
 the slot, as shown at H in Fig. 662, and a cross-cut filed, with a 
 very small round file, directly across these two segments at right 
 angles with the slot. It is in this small cross-cut that the T head, 
 the under portion of which is half-round, will rest when the denture 
 is in position. 
 
 The next step is to secure the outer tube, with lid at top for 
 closing same (F, Figs. 662 and 670), in the exact location for the 
 free working of the adjusting stud (A). After this is located cor- 
 rectly and soldered in position, the saddle is ready to receive the 
 teeth. 
 
 For this purpose place the saddle (Fig. 662) in the mouth, and with 
 a key (Fig. 672) rotate stud A one-quarter turn in tube (F), and the 
 T head will stand directly across slot and rest in cross-cut H (Fig. 
 662), thus locking denture securely against the gum so far as any 
 liability of being thrown out of position is concerned. And yet these 
 roots beneath are not in actual contact with the saddle, the counter- 
 
646 
 
 MECHANICAL DENTISTRY 
 
 Fig. 661. 
 
 Fig. 662. 
 
 Cast of upper jaw ready to receive 
 the denture. 
 
 Saddle formed to receive teeth 
 for upper denture. 
 
 Fig. 663. 
 
 Upper denture in position. 
 
 Fig. 664. 
 
 Straight root 
 attachment 
 in position. 
 
 Fig. 665. 
 
 Transverse section of 
 molar root attach- 
 ment in position. 
 
 Fig. 666. 
 
 'fi^ 
 
 Third molar attached 
 where there is no 
 occluding tooth. 
 
BRIDGE DENTURES. 
 
 647 
 
 sunk chambers leaving a space over and around hem. The saddle 
 is now between the little washer B and the T head A, Fig. 667 ; the 
 spring C is under the washer B and encircles the shaft of the stud 
 in the root down to the threaded portion (see Fig. 668) and rests on 
 a shoulder in tube between E and D. Now, during mastication the 
 gum still admits of some motion of the denture, it being of a soft and 
 
 Fig. 667. 
 
 Single straight 
 root attachment. 
 
 Fig. 668. 
 
 Adjusting stud, spiral 
 spring and washer. 
 
 Fig. 669. 
 
 Molar root 
 attachment. 
 
 Fig. 670. 
 
 Tube with 
 spring lid. 
 
 Fig. 6; 
 
 yielding nature, so that when there is any pressure placed on the piece 
 the spring beneath is compressed slightly, imparting a light and yield- 
 ing pressure to the root or roots beneath. This intermittent pres- 
 sure seems to be what nature requires to sustain a healthy union be- 
 tween the roots and the process. Without the spring there would 
 not be any pressure on the roots at any time, and the weight of the 
 denture would eventually draw the roots from 
 their sockets, until the denture would come in 
 contact with them during mastication, after which 
 the pressure of mastication of the whole case 
 would be on the roots, which nature would never 
 tolerate. 
 
 The case completed and in position is shown 
 in Fig. 663. 
 
 In attaching this system to a first molar root, 
 Dr. Carr describes his process as follows : " In 
 this case we must utilize breadth in place of depth 
 to accommodate the attachment. The spring is 
 what we wish to accommodate. Now, the root 
 being found in position and the second molar 
 missing, we grind the root down until it just 
 stands flush with the gum ; then chamber out to near the bifurcation 
 of the roots, making the chamber of considerably larger diameter 
 
 Posterior end 
 saddle, held in 
 position against 
 ■ gum by means of 
 platinized gold 
 pin set into the 
 tooth or filling. 
 
648 
 
 MECHANICAL DENTISTRY. 
 
 Fig. 672. 
 
 than for the other form (compare Figs. 664 and 665). A piece of 
 gold plate covers the end of the root the same as in the other case, 
 with larger hole through same. In this hole is placed an internally 
 threaded tube, adapted to engage another externally threaded tube 
 or cup ; for one end of this second tube is closed, and in the center 
 of this closed end is soldered the adjusting stud with washer 
 encircling same next to T head, A. The spring interposed between 
 washer and bottom of cup (Fig. 669) imparts the intermittent 
 pressure as in the other form of attachment. 
 Now this same form is used for wisdom teeth 
 attachments where there is no occluding mate 
 and it becomes necessary to impart an artificial 
 pressure to overcome gravity. In this case it is 
 either anchored in a large approximal filling or 
 soldered to a gold crown. (See Fig. 666.) The 
 most common case to be met with is the pin in 
 a molar left protruding to engage the posterior 
 end of the saddle; this is the form that is appli- 
 cable to all molar cases except as stated above, 
 viz., no occluding mate, or sixth year molar root 
 found in position with twelfth year molar miss- 
 ing. In all molar cases of the attachment where 
 it does not become necessary to impart any arti- 
 ficial pressure, a simple pin attachment is all that 
 is necessary." The washer, B, is used to com- 
 press the spring or to prevent the spring from 
 working through the oblong slot in saddle, 
 through which the T head of stud passes in 
 removing and replacing the case, which is done 
 daily by the patient wearing the case. To ad- 
 just it to any desired pressure against the ridge the adjusting stud 
 is simply rotated one way or the other until the desired position 
 is secured. The key, Fig. 672, is to be given to the patient for 
 manipulating adjusting stud at will. Dr. W. J. Younger of Cali- 
 fornia, who has had personal experience with this form of denture, 
 says of it : "I could not for a long time believe it was of such 
 broad and universal utility." 
 
 Key for manipulating 
 adjusting stud. 
 
BRIDGE DENTURES. 649 
 
 METHODS OF CONSTRUCTING CROWNS AND BRIDGES IN CASE 
 OF IRREGULARITY. 
 
 A young lady of about twenty-two years called upon the writer 
 for services. Her mouth presented a very homely appearance, 
 which was largely due to the ignorance or lack of judgment upon 
 the part of her dentist in former years. The history of her case 
 can be given in a few words. It is a characteristic of her family to 
 have large, strong teeth, with the cuspids quite prominent; but in 
 her mouth these teeth were so prominent as to disfigure her, and 
 when she commenced to grow into womanhood her mother took 
 her to their dentist to have the irregularity corrected. This gentle- 
 man, as I have said, through bad judgment extracted the two lateral 
 incisors, and allowed the cuspids to come down and forward to 
 
 Fig. 673. 
 
 partially take their place. Then the mischief was done. The 
 mouth was given a very coarse appearance by the large teeth being 
 brought so near the center, and as they did not entirely fill the 
 space, an ugly opening was left between these teeth and the central 
 incisors. (See Fig. 673.) When the lady consulted me, it was with 
 the idea of having the cuspids extracted and two smaller teeth 
 inserted upon either side; it was her wish at the same time to have 
 it done, if possible, in some way, so that she would not have to wear a 
 plate. After studying her case it was, therefore, decided to extract, 
 not the cuspids, but those teeth which should have been removed in 
 the first place — the first bicuspids. Then with suitable regulating 
 appliances the angle of the cuspids was corrected and they were 
 drawn back so as to partially fill the space formerly occupied by the 
 first bicuspids ; at the same time the second bicuspids were brought 
 into line, and all secured with retaining appliances, which were 
 
650 
 
 MECHANICAL DENTISTRY. 
 
 worn for several weeks. A lateral incisor was then prepared for 
 either side, and inserted by means of plate and pin bridges. 
 Described by Professor Litch on page 565. 
 
 The result obtained was exceedingly gratifying, a fair idea of 
 which is shown in Fig. 674. 
 
 Another case is one treated by Dr. I. N. Broomell, who con- 
 tributes the following description : 
 
 " The superior cuspid was fully Y\ of an inch out of line ; stand- 
 ing inside the arch to such a degree that a casual glance at the pa- 
 tient would lead one to suppose the tooth was missing. It was 
 also imperfectly developed, so that, had age and other circum- 
 stances favored its restoration to the proper position in the arch, 
 its malformation made it inadvisable to attempt such an operation 
 (Fig. 675). The patient being desirous of having the deformity 
 
 Fig. 674. 
 
 remedied, at least so far as appearances were concerned, I pro- 
 ceeded to do so in the following manner : Grinding off the irregu- 
 lar prominences of the tooth, I made it more perfectly conical in 
 shape. After securing an impression of the deformed tooth and 
 casting zinc dies, I swaged a hollow gold cap to accurately cover 
 the whole surface and extend slightly under the gum. This added 
 thickness of gold, when placed over the tooth, extended the labial 
 surface to about what should have been the palatal line ; thus per- 
 mitting me to adjust, by grinding and filing, a porcelain tooth with 
 its backing to the cap. These were soldered together and the ap- 
 pliance secured on the cuspid by oxyphosphate cement. In this 
 case no pins were used, the cap alone being sufficient to hold the 
 denture in position, (a, Fig. 675.) It has now been in the mouth 
 some three or four years, during which time I have removed it 
 several times in order to be satisfied that all was right under the 
 
BRIDGE DENTURES. 
 
 6« 
 
 cap. In fact, I consider that, when it* is at all possible to do so, all 
 appliances of this order, including small pieces of bridge-work, 
 should be so constructed that they may be removed from time to 
 time, thus affording an opportunity to detect any carious condi- 
 tions. 
 
 " Another case which I will briefly present was somewhat similar 
 in construction to the one just described, but was inserted under 
 different circumstances. For some reason unknown to the patient, 
 lie had lost from a lower incisor the entire labial surface, extending 
 from the cutting edge to the gum margin, and somewhat below it. 
 The lingual half of the crown remained, and fortunately the pulp 
 was not exposed (Fig. 676). With a corundum wheel I ground 
 
 Fig. 675. 
 
 Fig. 676. 
 
 off the cutting edge of the tooth, to the horizontal dotted line seen 
 in the illustration, until it was below the line of the pins in the porce- 
 lain tooth, which had been selected because its cross-pins were near 
 its cutting edge, and ground the porcelain tooth to fit the inclined 
 surface of the natural organ. I then fitted a backing of very thin 
 platinum, allowing it to extend over the whole back of the porce- 
 lain tooth, including the inclined surface. After making a cap to 
 perfectly fit the lingual surface of the incisor, I pressed it around 
 the sides until it could be soldered to the backing, thus making a 
 cap (a, Fig. 676) which completely covered the abraded tooth, oxy- 
 phosphate cement being used in setting the denture." 
 
65^ 
 
 MECHANICAL DENTISTRY 
 
 BRIDGE-REPAIR. 
 
 The greatest annoyance which bridge-work is likely to cause 
 patient or operator is the occasional breaking of a porcelain facing. 
 One of the most secure and artistic methods of repairing such a 
 break is that devised by Dr. E. A. Bryant, and is illustrated in Figs. 
 6yy, 678, 679, and 680. 
 
 His method is as follows : Select the facing to be attached, 
 color, size, and shape to suit, grind or clip off the pins extending 
 out from the space from which the original facing was broken from 
 the bridge, and smooth this space so as to present a flat surface. 
 Drill two holes through the backing of the bridge for the reception 
 of the pins of the new facing to be attached, and as near the size 
 of the pins as possible. With the countersink bur in the right- 
 angle hand-piece, countersink from the inside until the bur comes 
 
 Fig. 677. 
 
 Fig. 678. 
 
 Fig. 679. 
 
 Fig. 680. 
 
 through to the front, but not far enough to enlarge the holes (Fig. 
 677 J. Now try on and fit the facing, grinding the backing or the 
 tooth to accomplish this result. When fitted to suit, cut the threads 
 on the pins of the facing to be used, first with the larger sized die, 
 then with the smaller, the latter being the perfect thread and cor- 
 responding to the nuts. In cutting this thread, care should be 
 taken not to force it too fast, and a little oil should be used, other- 
 wise you will twist off the pins in the die, and it is difficult to re- 
 move them, besides losing the use of the facing. 
 
 Now select two nuts, and try them to see that they will go to 
 place on the pins of the facing before putting the facing in place, 
 laving the nuts selected in such position that you will be able to 
 place them upon the same pin which you tried them on. Place the 
 facing in position, holding same close and tight with the thumb of 
 the left hand, pick up one of the nuts by inserting one of the legs 
 
BRIDGE DENTURES. 
 
 653 
 
 of the screw-driver into the open- 
 ing (Fig. 678), carrying the nut 
 to the pin in this manner, and 
 starting it upon the thread, then 
 change to the cut in the nut for 
 the reception of the screw-driver, 
 and screw to place, not using any 
 force to do so, doing likewise 
 with the other nut. When the 
 two are in place, if they are not 
 quite down, hold the facing 
 firmly with the thumb of the 
 left hand, then screw up first 
 one nut, then the other, until 
 entirely home. If you undertake to 
 screw up one entirely at first, and there 
 happens to be the least tipping upon the 
 other side, when you screw the other 
 nut down tight it will break the facing. 
 Therefore you must understand it is 
 essential to screw each down equally. 
 Do not use undue force with the screw- 
 driver after the tooth is home, with the 
 idea of making it extra tight, for you are 
 liable to pull the pins out of the facing. 
 The strength of the threads being 
 stronger than that of the porcelain, the 
 latter will give first. 
 
 When the nuts are down tight, grind 
 off the extending parts with the corun- 
 dum wheel and smooth up with cuttle- 
 fish or sandpaper discs. This whole 
 operation consumes about fifteen to 
 twenty-five minutes' time. With these 
 instruments you are enabled to arrange 
 new facings where the gum happens to 
 have receded, or where they encroach 
 upon the gum. By baking a little gum 
 npon the facings to be used, you can fill 
 
 Fig. 681. 
 
654 MECHANICAL DENTISTRY. 
 
 any irregularities at the junction of the gum and facing, thus doings 
 away with the open spaces usually seen in bridges consisting of the 
 six anterior teeth. In fact, these instruments are indispensable to 
 any dentist who does bridge-work or ever contemplates doing it. 
 They can be used to great advantage in many other operations in 
 dentistry, covering more ground than any other set of instruments 
 ever devised for the use of the profession. 
 
 If the pins are bent and the nut strikes the edge, as at A, Fig. 
 679, straighten by pulling the nut and pin toward the side it does 
 not strike, until it goes home (Fig. 680). 
 
 When it is found necessary for any reason to remove a crown 
 or bridge from the mouth, it is usually desirable to do so with as 
 little damage to the fixture as possible. The old method of 
 mutilating the bands or caps with burs or discs is now unnecessary, 
 since we have in the "crown-slitter" — an invention of Dr. J. B. 
 Monfort — an instrument with which we may neatly and quickly cut 
 the cap; then by introducing a thin chisel-shaped instrument, the 
 edges may be so pried apart as to break up the cement and readily 
 admit of its removal. After this has been accomplished and the 
 fixture thoroughly cleansed, the edges, where cut, may be carefully 
 brought together and soldered, so as to admit of subsequent re- 
 placement. This instrument and the method of using it is illus- 
 trated in Fig. 681. 
 
CHAPTER XXXII. 
 
 ELECTRICITY, AND ITS APPLICATION IN DENTAL MECHANICS. 
 
 Historical. — Observations of electrical phenomena were made 
 at a very early date. Thales, one of the seven sages of Greece (born 
 640 b. c.) is supposed to have been the first to observe that amber, 
 when rubbed, had the power of attracting small bodies. The 
 Greeks knew amber, when rubbed, as " elektron," from which the 
 word " electricity " has been derived. These ancient people, how- 
 ever, had but little knowledge of the subject, and were quite unable 
 to explain the few phenomena they observed. 
 
 The knowledge of electricity remained in this condition for about 
 two thousand years, when William Gilbert, physician to Queen 
 Elizabeth, made a series of experiments and discoveries in electri- 
 cal phenomena, which won him the title of the founder of the 
 science. "He was born at Colchester in 1540, studied at Oxford 
 and Cambridge, afterward establishing himself as a physician in 
 London, where he died in 1603. Considering the period in which 
 Gilbert lived, his scientific knowledge must have been remarkable. 
 It gained for him the favor of the queen, who gave him the means 
 of carrying out his scientific experiments, and also appointed him 
 her private physician. The principles and theories of Lord Bacon, 
 who frequented Queen Elizabeth's court, probably greatly in- 
 fluenced Gilbert. It is, however, certain that he did not adopt the 
 plan previously followed by schoolmen of making daring hypo- 
 theses to explain natural phenomena, but formed his ideas from 
 direct experiment. This is exactly the plan adopted by Bacon. 
 Gilbert discovered that other bodies besides amber could be electri- 
 fied by friction. He also ascertained that the production of elec- 
 tricity was affected by moisture ; that hot or burning bodies lost all 
 electricity; and that an electrified body attracts a variety of other 
 bodies, whereas a magnet only attracts steel or iron. The latter 
 fact shows that he was acquainted with the difference between elec- 
 tricity and magnetism." * 
 
 * " Electricity," R. Wormell. 
 655 
 
656 MECHANICAL DENTISTRY. 
 
 Then followed (about 1670) an important electrical discovery by 
 Otto von Guericke. Up to this time electricity had been produced 
 by taking larger or smaller pieces of various substances in one 
 hand and rubbing them with the other. This, of course, produces 
 very small quantities. Guericke now added, in a crude form, the 
 electric machine. He cast a globe of sulphur and supplied it with 
 a wooden axle, then mounted it on a frame, the hand being employed 
 as the rubber. By means of this discovery it was learned that the 
 production of electricity in large quantities was accompanied by 
 light and sound. It was further noticed that the electrified sulphur 
 globe attracted light bodies, which it afterward repelled, until they 
 had touched some other body. At about the same time Picard ob- 
 served the luminosity of greatly rarefied gases. While agitating 
 the mercury in an imperfectly exhausted barometer tube, he pro- 
 duced electricity, which caused the mercurious vapor and the re- 
 maining air to glow. 
 
 Further discoveries were made by Robert Boyle and Dr. Wall 
 — the former discovered that substances are attracted by an electri- 
 fied body in a vacuum, while the latter was the first to produce the 
 electric spark. 
 
 .Stephen Gray, a Fellow of the Royal Society, and about whom 
 little is known, discovered, early in the seventeenth century, that 
 certain bodies were capable of conveying, or, as we now express it, 
 conducting, electricity from one body to another. Contemporane- 
 ously with Gray, Charles F. C. DuFay, of the Academy of Sciences, 
 was working, in France, along the same lines. He found that 
 electrified bodies attracted the unelectrified, electrifying them in 
 turn, and then repelling them. He also discovered the insulating 
 properties of glass. 
 
 From this time on, through the seventeenth century, new dis- 
 coveries and advances were made in electrical science. We have 
 the work of Newton, substituting the glass ball for the sulphur 
 globe employed by Guericke; of Gordon, who substituted a glass 
 cylinder for Newton's glass ball ; of Morrison, who devised and 
 constructed an electric telegraph ; of Kleist, who first discov- 
 ered the means of accumulating and storing up large quantities of 
 electricity. This discovery was also independently made by Mus- 
 chenbroeck, of Leyden, and the name " Leyden jar," was given it. 
 The apparatus was soon perfected, receiving its present form of a 
 
ELECTRICITY : ITS APPLICATION IN DENTAL MECHANICS. 657 
 
 jar coated with tin-foil, inside and out, at the hands of Sir William 
 Watson. 
 
 One of the greatest names in the early development of electrical 
 science is that of Dr. Benjamin Franklin, of Philadelphia. His 
 first labors (about 1750) were in the elucidation of the theory of 
 positive and negative electricity, which, however, was first pro- 
 pounded by Sir William Watson. 
 
 Franklin claimed that electricity was not created by friction, but 
 was only transferred from one body to another. That is, " a body 
 which becomes positively electrified receives its charge of electri- 
 city from one or more other bodies which will be found to be neg- 
 atively electrified. In other words, positive electrification is due to 
 an excess of electricity, and negative electrification to a deficiency." 
 Franklin also set forth the analogies between lightning and the 
 electric spark, and in some of his earliest writings he enumerates 
 the electrical effects which were manifested by lightning. His later 
 experiments with his kite and iron key are a matter of familiar 
 history. A few years later (1759) Robert Symmer advanced the 
 idea, in opposition to Franklin's theory, that there were two kinds 
 of electricity, not, however, independent of each other, but coex- 
 istent. 
 
 Then followed, at the close of the eighteenth century, many 
 interesting experiments by Coulomb, Galvani, and Volta. The 
 new century opened with the accumulated evidence of the past, 
 and soon presented Sir Humphrey Davy, Oersted, Ampere, 
 Seebeck, and Faraday. Davy was the first to offer an explanation 
 of the chemical action of the electric current in decomposing water, 
 and in 18 10 he produced the arc light for the first time, at the Royal 
 Institution. He used carbon points as his electrodes, and a bat- 
 tery, it is said, of 2000 cells. 
 
 The discovery of the connecting link between the phenomena of 
 electricity and magnetism was made by Oersted, of Copenhagen, 
 who, in 1820, observed that a current of electricity flowing along 
 a conductor deflected a magnetic needle placed near it, and his ex- 
 periments were eagerly followed by Ampere, in France, who built 
 up a wonderful mathematical theory of the magnetic action of linear 
 conductors carrying currents. Seebeck, in 1822, opened up a most 
 interesting department of electricity by the discovery of a method 
 of converting heat energy into electrical energy, and he founded 
 42 
 
658 MECHANICAL DENTISTRY. 
 
 the science of thermo-electricity. The last of this group is 
 Michael Faraday, the pupil of Sir Humphrey Davy, and we owe 
 to him the further working out of many of Davy's ideas. Fara- 
 day's name is chiefly associated with the laws of electrostatics and 
 magneto-electric induction. The great importance of this discov- 
 ery of induction may be seen by looking to the present condition 
 of electro-technics — the telegraph, telephone, dynamo machine, etc. 
 Faraday also substituted electrode for pole, calling the positive elec- 
 trode the anode, and the negative the cathode. 
 
 From the period of Davy and Faraday on to the present time 
 may be considered modern history in electric science, and among the 
 names most cherished in this domain are Samuel Morse, Alexander 
 Bell, Thomas Edison, Elihu Thompson, and Sir William Thomp- 
 son, Cyrus W. Field, Edwin J. Houston, and Nikola Tesla. 
 While we must not forget to do honor to the earliest investigators 
 — as their labors helped to bring the science to its present posi- 
 tion — yet the discoveries and developments which have been and 
 are being made by our present brilliant scientists, are, in the closing 
 years of the nineteenth century, resulting in a great social revolu- 
 tion. Electricity is now used and depended upon in countless de- 
 partments of science, and in the arts of peace and war; in fact, no 
 other element ministering to the good of mankind has ever proved 
 such a versatile servant. 
 
 Electric Energy. — The fundamental principle with which we 
 have to deal — though it was not so accepted by physicists until the 
 middle of the nineteenth century — is the conservation of energy. 
 For the study of dynamics, we learn that an agent that is capable 
 of doing work possesses a certain amount of energy, and it is only 
 due to, and so far as it possesses, this energy that it is capable of 
 doing work. Examples of what is known as actual energy are the 
 energy of sensible motion, as in a cannon ball, of sound-waves, of 
 heat, etc. ; of potential energy, that of position of a weight raised 
 above the earth, of elasticity in a bent bow ; of electricity,, chemical 
 combination, etc. Potential or positional energy and actual energy 
 are in incessant interconversion ; for potential energy implies force, 
 or a tendency to motion, as much as actual energy implies motion 
 or change of position. 
 
 From the above we learn that electricity in motion, or the electric 
 current, is a form of energy. And this can only be procured by 
 
ELECTRICITY : ITS APPLICATION IN DENTAL MECHANICS. 659 
 
 the continuous expenditure of energy — as through the steam-engine 
 and dynamo, for instance — while through or from electricity in 
 motion various forms of energy can be procured, as in heat, 
 light, and power. Thus, we observe the wonderful correlation of 
 energies or forces ; that is, the transformability of one form into 
 another. 
 
 Electrical Terms. — Before going further into the subject, the 
 student should fix in his mind a few of the most important terms 
 adopted for designating certain principles in the management and 
 application of the electric current. The ampere is the unit of current 
 strength ; that is, it is the flow produced by the pressure of one 
 volt in a circuit whose resistance is one ohm. An anode is the 
 positive terminal or electrode, cathode being the name given to the 
 negative terminal. The ohm is the unit of electrical resistance. A 
 rheostat is an apparatus for throwing a variable resistance, or num- 
 ber of ohms, into a circuit at will. The volt is the unit of electro- 
 motive force or pressure, while a watt is the unit of activity or rate 
 of doing work. The activity of a circuit expressed in watts is the 
 product of the volts multiplied by the amperes. Seven hundred and 
 forty-six watts represent one horse-power. 
 
 Electric Dental Apparatus. — The advent of the incandescent 
 lamp, in 1880, made electricity in dentistry practicable; it brought 
 with it other benefits, besides the convenience and superiority of the 
 light in the office and laboratory. It solved the problem of supply, 
 and has done as much as any other agent to place the practice of 
 dentistry upon its present advanced plane, and through it the dentist 
 has the power to do more work, and to do it more conveniently, and 
 with less discomfort and fatigue to himself and clients. 
 
 The principal electric dental apparatus may be summarized as the 
 motor for running the laboratory lathe and office engine, the mouth 
 lamp, root-dryer, hot-water heater, gold annealer, apparatus for 
 producing cataphoresis, the electric oven or furnace for porcelain 
 crown- and bridge-work, etc. 
 
 The Electric Motor. — An electric motor may be defined as a 
 machine for converting the energy of an electric current into me- 
 chanical energy. These are manufactured in various forms and 
 sizes according to the amount and form of energy required. 
 
 Electric Engine. — The most useful of all the electric dental ap- 
 paratus is the motor-driven engine and lathe. A simple form of 
 
66o 
 
 MECHANICAL DENTISTRY. 
 
 motor for this purpose is shown in Fig. 682. The electro-dental 
 engine should be as simple and light as possible, thus reducing the 
 
 Fig. 68; 
 
 moving parts to a minimum, making the bearings few and easily 
 accessible. The motor also should be carefully mounted, so as to 
 
electricity: its application in dental mechanics. 66i 
 
 minimize the vibrations. If it is fastened to the floor or a wooden 
 stand it is advisable to insert a felt or rubber pad between the feet 
 of the motor and the woodwork. Electric motors are supplied with 
 rheostats, through which the power is controlled. For dental pur- 
 poses these are made so as to be controlled by the foot of the 
 operator. The later forms of these devices are so arranged that the 
 dental engine can be stopped, started, or reversed instantly. They 
 also give the operator the advantage of half a dozen different speeds. 
 
 The apparatus represented in Fig. 682 consists of the S. S. White 
 dental motor No. 2, an iron stand with a mahogany top, on which 
 it sits, a fire-proof speed-regulating resistance in an iron case sup- 
 ported by the stand, an electromagnetic clutch on a countershaft 
 supported on front of stand, and a governing treadle, or rheostat, 
 connected to it by a cable. The motor is inclosed in a glass vase 
 to protect it from dust, and the stand is mounted upon rubber 
 rimmed wheels to facilitate its movement from one position to 
 another. The several speeds given to the engine-bit through this 
 apparatus may vary from 500 to 5000 revolutions per minute. The 
 entire control of the running of the engine is in the treadle, as 
 previously explained. 
 
 Laboratory Lathe. — AVhen the motor is employed for driving a 
 laboratory lathe a different form of rheostat is used, as it is not 
 necessary to have this machine so thoroughly under control. A 
 rheostat and motor similar to those shown in Fig. 683 are -generally 
 employed. 
 
 The motor shown at a, is of about ]/% horse-power, which, with 
 the 1 10- volt incandescent current, will run a dental lathe with more 
 satisfaction than any other power at present known to us. The 
 rheostat (b) is so arranged that the different speeds can be governed 
 by the slight raising or lowering of the foot-pedal. The wires at- 
 tached to the binding posts, a, b, are for connection with the in- 
 candescent current. 
 
 The Electric Oven or Furnace. — The utility of the electric 
 furnace depends upon the fact that the electric current can convey 
 energy from the outside into a closed space, and liberate it there in 
 the form of heat. The electric furnace is available, not only for 
 metallurgical operations, but for some of the finest of the dental 
 laboratory procedures, as well as for chemical experiments. 
 
 A very complete furnace for metallurgical purposes in which the 
 
662 
 
 MECHANICAL DENTISTRY. 
 
 electric arc is produced is shown in Fig. 684.* Ordinary electric 
 light carbons, c c', slide through the clamping cylinders p p', and 
 are brought together just over the crucible cr, at right angles to 
 one another. For many reasons this position is found to be, for 
 general work, more convenient than the vertical position used in 
 
 Fig. 683. 
 
 the Siemens furnace. The crucible, according to the operation 
 that has to be performed, consists of carbon, plumbago, lime, mag- 
 nesia, etc. It is in a closed refractory chamber k, with an aperture 
 Bo at the top through which the materials to be smelted can be 
 introduced. When large currents are used, the carbon holders p p' 
 
 * Described by Professor R. M. Wamsley, Edinburgh. 
 
ELECTRICITY : ITS APPLICATION IN DENTAL MECHANICS. 
 
 66 3 
 
 have to be kept cool by currents of water circulating through them. 
 The front side of the furnace chamber is closed by the removable 
 screen k, which for many purposes can be made of deep ruby-red 
 glass, through which the operations in the crucible can be watched; 
 but when the highest temperatures are developed it has to be made 
 of a more refractory material. There are apertures not shown in 
 the figure, by which, if required, gases can be introduced into the 
 furnace. The magnet a 1 controls the play of the electric arc on 
 
 Fig. 684. 
 
 the materials in the crucible, converting the arc, if need be, into a 
 long flame which acts as a veritable electric blowpipe. The maxi- 
 mum temperature attainable is about 6332 F., the temperature, 
 according to M. Violle, at which carbon volatilizes. With a current 
 of about 12 amperes at 55 volts the most refractory ores can be 
 reduced in a few minutes, and pure metals can be obtained in suffi- 
 cient quantities for chemical analysis. In this way, at the Ecole 
 Normale Superieure, specimens of metallic ruthenium and osmium 
 have been obtained. 
 
664 MECHANICAL DENTISTRY. 
 
 The writer has had a more simple device constructed for experi- 
 mental metallurgical work at the Pennsylvania College of Dental 
 Surgery, consisting of a carbon crucible for the cathode and a car- 
 bon point for the anode. The carbon crucible is constructed so 
 as to act both as a crucible in which metal may be fused and as 
 a conductor for the current employed for that purpose. The 
 carbon pencil has a small screw attachment at the upper end for 
 the connection of the positive wire, while a similar screw, con- 
 nected with the crucible, is for the negative wire. After the current 
 has been turned on, the point of the pencil is carefully brought in 
 contact with the bottom of the crucible, or the metal which it may 
 contain, thus establishing the current. After this is done the 
 pencil may be slowly withdrawn two or three inches from the 
 metal, which will form an electric or voltaic arc. The heat of the 
 voltaic arc is intense, and hence can be employed for fusing the 
 most refractory substances. Platinum, for instance, can be brought 
 to the molten condition in a few seconds. 
 
 The electric oven for fusing porcelain in crown-, bridge-, and con- 
 tinuous-gum-work is quite a different and more recent apparatus. 
 In 1890 Mr. J. O'Meara devised an electric heater, consisting of a 
 muffle of fire-clay, with wires imbedded in the same, and patented 
 the combination of a furnace with a rheostat. This patent was pur- 
 chased by Dr. H. C. McBrair, and is incorporated in what is now 
 known as the " McBrair furnace," evidently the first to be devised 
 and employed for fusing porcelain, and is very complete and satis- 
 factory for dental laboratory work. This furnace is shown, with 
 the rheostat to control the current, in Fig. 685. The electric furnace 
 has several advantages over every other form of apparatus for sim- 
 ilar purposes : 
 
 First. — The heat, not being the direct product of combustion, is 
 pure, and is radiated equally from all directions within the oven; 
 and what is known in porcelain work as " gassing " is therefore an 
 impossibility. The ease and accuracy with which this heat can be 
 secured and controlled is also a great desideratum. 
 
 Second. — The piece to be fused can be placed in the oven with- 
 out previous heating, and remain there after fusing until entirely 
 cool. That is, the invested piece may be placed in the oven, the 
 lid closed, and current turned on gradually by the rheostat, and 
 when properly fused the button is turned and the work done. 
 
ELECTRICITY : ITS APPLICATION IN DENTAL MECHANICS. 665 
 
 Third. — The oven is small, clean, and noiseless, and can therefore 
 be used as conveniently in the office as in the laboratory. 
 
 Fourth. — The cost of operating, compared with other methods, 
 is reduced to a minimum. 
 
 Minor Apparatus.- — The motors usually employed in the dental 
 office are furnished with an extra pair of brushes and collecting 
 
 Fig. 685. 
 
 rings, and supply an alternating current, which is sent through a 
 transformer, where, by induction, it generates a secondary current 
 to operate the smaller apparatus, such as the electric mallet, mouth 
 lamp, hot-air syringe, cautery, etc. These appliances, however, can 
 be operated quite as satisfactorily from an electric battery. 
 
 The Electric Mallet. — This piece of apparatus combines the 
 work of Drs. Bonwill and Webb in this direction. It has favor 
 with many of the most skilful operators in the world, and by some 
 
666 
 
 MECHANICAL DENTISTRY. 
 
 Fig. 686. 
 
 is thought to approach more 
 nearly to the ideal condensing 
 instrument than any other ever 
 offered to the profession. This 
 instrument is illustrated in Fig. 
 686. 
 
 A later form of electric dental 
 mallet is that designed by Dr. 
 Perry Skinner, and shown in Fig. 
 687. In this instrument there is 
 no friction connected with the 
 armature, as it stands directly 
 over its field of magnetism, 
 guided by the tool holder passing 
 through its center to a point 
 where it strikes the tool. Owing 
 to this arrangement, as free a 
 blow is struck as that given by 
 a hand mallet. Previously all 
 mallets of sufficient power were made with two 
 or more magnets, but by using a magnet of 
 special design one is found to meet all require- 
 ments, and to condense gold thoroughly. This 
 mallet works by pressure on the point or side 
 of point, thereby removing all complicated slid- 
 ing connections from the hand-piece of the in- 
 strument. It also enables the operator to have 
 free access to the electric contacts at the other 
 extremity. Owing to the simplicity of construc- 
 tion and arrangement of these contacts they can 
 be removed and replaced by any person having 
 a limited knowledge of electricity. This mallet 
 also has a specially designed connection (a) for 
 the electric cable, which gives the instrument a 
 perfectly free motion. The adjustment regulat- 
 ing the blow is very simple and under the control 
 of the operator. 
 
 Electric Mouth Lamp. — With this miniature 
 electric lamp (shown in Fig. 688) the dentist has 
 
ELECTRICITY I ITS APPLICATION IN DENTAL MECHANICS. 667 
 
 a means for exact diagnosis in certain pathological conditions of 
 the teeth, which, with ordinary means, are difficult to locate. It 
 lights up the mouth so effectively that a hidden cavity of decay, 
 
 Fig. 687. 
 
 Fig. 688. 
 
 :» 
 
 ■an unsuspected devitalized pulp, or any deviation from normality 
 in the body of the teeth will be readily discernible. With the 
 electric lamp placed back of the teeth, those that are sound will 
 appear translucent, without variations in structure, while a devital- 
 
668 MECHANICAL DENTISTRY. 
 
 ized tooth will appear opaque, even when to ordinary observation 
 its color gives no such indication. 
 
 Electric Hot-air Syringe. — The value of the hot-air blast in 
 dental operations is recognized by all intelligent operators, and 
 when the manufacturers produced an apparatus for generating this 
 through the agency of the electric current, they gave us a neat, 
 convenient, and time-saving instrument. The appearance of the 
 appliance can be seen by referring to Fig. 689. 
 
 A switch under the thumb makes the circuit and gives the dentist,, 
 on compressing the rubber bulb, an instant current of heated air, 
 which can be regulated from slightly warm to the hottest blast. 
 
 Different sized nozzles can be screwed on, giving fine or diffused 
 jets of air; and as glass is a poor conductor of heat, the handle 
 remains cool while the air loses none of its heat. 
 
 Fig. 689. 
 
 Cataphoric Apparatus. — The medication of tooth structure by 
 electric osmosis, or, as it is generally known, " cataphoresis," has 
 taken a very important place in dental therapeutics, and we believe, 
 that in the hands of intelligent and careful operators it will prove 
 one of the most important discoveries ever made in the field of 
 dental science. We say in the hands of " intelligent and careful 
 operators " for the reason that to practise it intelligently requires 
 as great a breadth of knowledge as any other process in dental or 
 medical practice. It requires a knowledge of the principles under 
 which electricity operates, and the conditions necessary for its suc- 
 cessful application ; a knowledge of the control of the agent, of 
 resistance, and of electrolysis. 
 
 Through the employment of electric osmosis, the most sensitive 
 
ELECTRICITY : ITS APPLICATION IN DENTAL MECHANICS. 669 
 
 Fig. 690. 
 
 dentine may be obtunded, living pulps be painlessly removed, or 
 discolored teeth may be readily bleached. Numerous forms of 
 apparatus have been devised for the application of this process, 
 which have proven more or less successful. It will answer our 
 purpose here, however, to illustrate two of the most simple and 
 effective, yet offered to the profession. Fig. 690 shows an excellent 
 instrument for the utilization of the street current. 
 
 The resistance board (A) is hung on the wall, in a convenient 
 position for operating — the controller (B) 
 being placed either on the office bracket, 
 or, if preferred, in the patient's lap, and can 
 be operated by either party. By pushing 
 the lever forward on the resistance board 
 to point of first contact, seven volts are 
 conducted to the controller — by turning 
 handle (D) you increase the voltage from 
 nothing to a maximum of seven volts by 
 gradations of one to ten volts. Should 
 stronger current be required, the handle 
 on controller must first be brought back 
 to zero; the lever (C) can then be pushed 
 forward to point of second contact, when 
 12 volts will be conducted to controller, 
 and so on to 
 30 volts. The 
 simple move- 
 ment of han- 
 dle (D) will 
 then be all 
 that is neces- 
 sary. 
 
 The Dry Cell Battery System. — In the next illustration, Fig. 
 691, is shown the ideal instrument for the employment of the battery 
 system. Some of the advantages of this apparatus are compact- 
 ness, cleanliness, constancy of current, and durability ; the weight of 
 each cell, too, being only about two ounces, 25 or 50 of them, with 
 the case, meter, current controller, electrodes, etc., make it perfectlv 
 portable. These cells being hermetically sealed admit of no leak- 
 age; and should one of the batteries be tipped over, an accident 
 
6jo 
 
 MECHANICAL DENTISTRY. 
 
 likely to happen to any instrument of the kind, it can remain in a 
 reversed position for an indefinite period of time without being 
 injured in the slightest. Then, again, as caustic and corrosive 
 liquids do not enter into the composition of the cells, the batteries 
 remain clean at all times, and connections cannot become corroded 
 so as to interfere with the circuit. The simplicity of mechanism 
 and absence of parts likely to wear prevents any necessity for 
 repairs, so that the life of this battery is only limited by the actual 
 amount of work done. The strength of the chlorid of silver cell is 
 
 Fig. 691. 
 
 fixed and constant, each cell representing one volt. They are also 
 very readily removed, so that any one can readily fit out a 50-cell 
 battery with an entire new set of cells, or replace any one cell in 
 a series with a fresh one in a few minutes without disturbing the 
 balance. Other features of this outfit are its meter for measuring 
 the current and the rheostat for controlling the same. The latter 
 permits of administering the current smoothly and with the greatest 
 minuteness of dosage. With these two adjuncts the current is 
 manipulated to a nicety, the patient not being used as a meter, as 
 is too often the case. 
 
INDEX. 
 
 ADJUSTING clasps to the plate, 192 
 Air-chambers, 151, 199, 200 
 All-gold crown or cap, artificial, 537 
 Alloys, aluminium, 109 
 
 bismuth, 116 
 
 compounding, 117 
 
 copper, in 
 
 fusible, 175 
 
 general properties of, 117 
 
 gold, determining the carat of, 85 
 formulas for, 81 
 reducing, to required carat, 80 
 
 platinum, 105 
 
 silver, 98 
 
 tin, 115 
 Aluminium, 107 
 
 alloys of, 109 
 
 annealing, 108 
 
 casting, 109 
 
 corrodibility of, 108 
 
 dental uses of, no 
 
 derivation of, 107 
 
 fusing-point of, 108 
 
 general properties of, 107 
 
 melting, manner of, 109 
 
 polishing, 109 
 
 soldering, 109 
 
 solubility of, 108 
 Antagonizing dentures, 206, 238, 242 
 
 models, manner of securing, 203 
 Anthracite coal as a fuel, 26 
 Antimony, 115 
 
 fusing-point of, 115 
 
 general properties of, 115 
 Appliances for the correction of dental 
 irregularities, 434 
 
 for the correction of fractured 
 maxilla?, 400 
 
 used in the generation and applica- 
 tion of heat, 31 
 Arranging teeth, 220, 228, 249, 284 
 for temporary plates, 248 
 Articulators, 243 
 
 Artificial all-gold crown or cap, 537 
 repairing, 549 
 
 crown, Bonwill's, 487 
 Brown's, 448 
 devitalization of pulp for, 477 
 
 Artificial crown, excision of vital tooth- 
 pulp in preparation for, 477 
 Foster's, 495 
 Gates', 494 
 
 gold seamless contour, 542 
 Howland's, 496 
 introductory remarks on, 474 
 Logan's, 479 
 
 porcelain, with gold collar at- 
 tachment, 496 
 dovetail, 493 
 Baldwin's method for 
 
 making, 498 
 Kirk's method for mak- 
 ing, 498 
 Shulze's method for mak- 
 ing, 502 
 Stowell's method for 
 making, 500 
 preparation of pulp canal for, 
 478 
 
 of the root for, 476 
 Richmond's, new, 485 
 dentures, beaded or grooved, 325 
 continuous-gum, 264 
 entire, 213 
 
 on celluloid base, 327 
 rubber base, 281 
 partial, constructed on a base 
 of rubber, 317 
 
 retained in the mouth by 
 
 means of clasps, 178 
 supported by atmospheric 
 pressure or adhesion, 
 198 
 treatment of the mouth pre- 
 paratory to the insertion of, 
 120 
 ferrule or collar crown, Knapp's 
 process for making, 520 
 
 as applied to bicuspid 
 
 roots, 510 
 Litch's method for 
 
 making, 5 1 3 
 Mason's method for 
 
 making. 535 
 Richmond's method 
 for making, 503 
 
 671 
 
6 7 2 
 
 INDEX. 
 
 Artificial ferrule or collar crown, 
 Shield's method for making, 526 
 palates, 376 
 
 for congenital fissure, 382 
 method of making, 385-399 
 Asbestos molds, 90 
 
 Atmospheric pressure or adhesion, 198, 
 213, 214, 215 
 
 BABBITT metal, 112, 174 
 
 Backing the teeth, manner of, 208, 256 
 
 Baker's velum, 396 
 
 Baking furnaces, 51 
 
 Basal temperaments and their general 
 
 indications, 225, 226 
 Beaded or grooved dentures, 325 
 Beeswax as an impression material, 129 
 Bellows blowpipe, 37 
 Bismuth, 116 
 
 alloys of, 116 
 fusing-point of, 116 
 general properties of, 116 
 Bite, manner of taking the, 202 
 Bituminous coal as a fuel, 24 
 Blowpipes, 34 
 bellows, 37 
 gasolene, 42 
 mouth, 34 
 oxycarbon, 42 
 oxyhydrogen, 44 
 Bonwill's articulator, 243 
 Brass solder, 112 
 Bridge dentures, 552 
 
 in case of irregularity, 649 
 limitations of, 553 
 removable, 621 
 
 Carr's method of making, 
 
 644 
 Condit's method of mak- 
 ing, 638 
 Davenport's method of 
 
 making, 629 
 Parr's method of making, 
 
 626 
 Mandrel system of mak- 
 ing, 633 
 stationary, 553 
 
 Darby's method of mak- 
 ing, 564 
 Knapp's method of mak- 
 ing. 587 
 Litch's method of mak- 
 ing, 565 
 Low's method of making, 
 
 589 
 
 Melotte's method of mak- 
 ing. 593 
 
 T'armly Brown's method 
 of making, 618 
 
 Bridge dentures, stationary, Register's 
 method of making, 575 
 
 Webb's method of making, 
 
 554 
 Williams' method of mak- 
 ing, 576 
 Hollingsworth's system of 
 
 making, 609 
 Mandrel system of mak- 
 ing, 596 
 Brown's clamp flask, 297 
 Burners, 32 
 
 CARBON molds, 91 
 Cast base, gold alloy, 365 
 metal, 362 
 
 repairing, 371 
 Casting aluminium, 109 
 Cataphoric apparatus, 668 
 Celluloid, 327 
 
 as a base for artificial dentures, 
 
 327 
 attachment for metallic base, 354 
 composition and manufacture of, 
 
 328 
 finishing, 349 
 hot moist-air machine for molding, 
 
 337 
 investing, 331 
 metal casts for, 330 
 modeling, 337 
 molding, by dry heat, 343 
 
 in steam, 340 
 plaster model in molding, 329 
 processes preliminary to molding, 
 
 329 
 selection and preparation of, 334 
 vulcanite faced with, 349 
 waxing or modeling, 331 
 zylonite compared with, 353 
 
 Charcoal as a fuel, 23 
 molds, 90 
 
 Clasps, adjusting, to plate, 193 
 
 metallic, attached to rubber plate, 
 
 318 
 modifications in form of, 183 
 observations on use of, 178 
 partial or stay, 186 
 scalloped, 186 
 securing, to plate, 193 
 separation of teeth for, 182 
 standard, 185 
 
 teeth for application of, 180 
 with spurs, 196 
 
 Coal as a fuel, anthracite, 26 
 bituminous, 24 
 
 Coke as a fuel, 24 
 
 Components of dental norcelain, 258 
 
 Composition and manufacture of cellu- 
 loid, 328 
 
INDEX. 
 
 6/3 
 
 Compounding and general properties of 
 alloys, 117 
 
 rubber for dental purposes, 282 
 Constructing and attaching spiral 
 
 springs, 252 
 " Continuous-gum " dentures, 264 
 
 Allen's methods of making, 
 
 266 
 Haskell's methods of making, 
 
 Tees' methods of making, 276 
 Converting gold alloys into the required 
 
 forms, 89 
 Copper, in 
 
 alloy, Babbitt metal as a, 112 
 
 German silver as a, 112 
 alloys of, in 
 general properties of, in 
 Correction of dental irregularities, 
 
 appliances for the, 434 
 Corrodibility of aluminium, 108 
 Counter-dies, 156, 168 
 
 progressive, 169 
 Crowns, artificial, 474 
 Crucibles, 65 
 
 DEFECTS of the palatal organs, 373 
 
 artificial palates for, 376 
 for congenital, 
 
 382 
 method of mak- 
 ing, 385 
 Baker's velum for, 396 
 Kingsley's appliance and 
 methods of procedure 
 for, 375 
 Suersen's appliance for, 
 392 
 Dental irregularities, appliances for the 
 correction of, 434 
 
 Case's methods of treating, 458 
 contraction of the arch in, 440 
 lack of anterior occlusion in, . 
 
 45i 
 mechanical forces in. 434 
 method of retraction in, 448 
 misplaced bicuspids in, 440 
 most frequent forms of, 434 
 protruding apparatus for cor- 
 recting. 462 
 cuspids in, 435 
 protrusion of lower jaw in, 
 448 
 
 of upper jaw in. 444 
 regulating, supplemented by 
 
 crown-work, _i."4 
 re-nosing the features in, 456 
 retruding apparatus for cor- 
 recting, s6i 
 
 cuspids in. 438 
 
 43 
 
 Dental irregularities, rotation by rubber 
 rings in, 450 
 
 by spring bar in, 451 
 the inclined plane for correct- 
 ing, 438 
 tortion in, 450 
 unusual forms of, 451 
 porcelain, components of, 258 
 uses of aluminium, no 
 of platinum, 105 
 Dentures, beaded or grooved, 325 
 bridge, 552 
 continuous-gum, 264 
 entire, 213 
 
 on celluloid base, 327 
 rubber base, 281 
 partial, on rubber base, 317 
 
 retained in mouth by means of 
 
 clasps, 17S 
 supported by atmospheric pres- 
 sure or adhesion, 198 
 Derivation of aluminium, 107 
 Determining the carat of any given 
 
 alloy, 85 
 Dies, metallic, 156 
 
 Babbitt metal, 174 
 counter-, 156, 168 
 
 progressive, 169 
 essential properties of, 170 
 fusible alloys for, 175 
 manner of obtaining metallic, 156 
 materials used in molding metallic, 
 
 156 
 molding, where undercuts are pres- 
 ent, 158 
 
 with cores, 158 
 preparing and pouring metal for, 
 
 165 
 
 cast for molding, 165 
 model previous to molding, 156 
 securing mold for, 157 
 type-metal for, 174 
 withdrawing the cast, 157 
 Draft or wind furnace, 49 
 Dry method of refining gold, 75 
 of refining silver, 99 
 
 ELECTRICAL terms, 659 
 
 cataphoric apparatus, 668 
 dental apparatus, 659 
 dry-cell battery system, 669 
 energy, 658 
 engine, 659 
 hot-air syringe, 668 
 laboratory lathe, 661 
 mallet, 665 
 motor, 659 
 mouth lamp, 666 
 oven or furnace. 661 
 vulcanizer. 665 
 
674 
 
 INDEX. 
 
 Electricity, and its application in dental 
 mechanics, 655 
 history of, 655 
 Elements employed in refining gold, 74 
 Entire dentures, 213 
 
 adhesion of, 213 
 antagonizing model for, 238, 
 
 243 
 arranging for temporary, 248 
 
 teeth for, 249 
 articulators for, 242 
 atmospheric pressure for, 214 
 application of atmospheric 
 
 pressure for, 215 
 backing or lining teeth in, 256 
 constructing and attaching 
 
 spiral springs to, 252 
 forming a rim to the plates in, 
 
 251 
 forming the borders of the 
 
 plate for, 236 
 four basal temperaments and 
 
 their general indications in 
 
 making, 225, 226 
 grinding and adjusting single 
 
 gum teeth in, 247 
 investing, 253 
 method of constructing, 233, 
 
 237 
 
 modifications in the form of 
 plates for, 235 
 
 on celluloid base, 327 
 rubber base, 281 
 
 overcoming tendency to change 
 in form of plates for, 255 
 
 preliminary observations on, 
 213 
 
 projection of lower jaw in se- 
 curing bite for, 241 
 
 re-posing of the features for, 
 
 239 
 selection and arrangement of 
 
 the teeth of replacement for, 
 
 220, 228, 249, 842 
 soldering and finishing, 257 
 swaged metallic plate-base for, 
 
 233 
 trying plate for, in mouth 236 
 warping or springing of, 254 
 lower dentures, impressions for, 
 
 137. 146 
 upper dentures, impressions for, 
 136, 144 
 Extraction of teeth, surgical treatment 
 of the mouth after the, 123 
 
 FELDSPAR, 259 
 
 Forming an air-chamber, 199 
 Formulas for gold plate, 8t, 82 
 for gold solder, 83 
 
 Formulas for silver solder, 102 
 Fractured maxillae, 400 
 
 Angle's method of fixation for, 
 
 427 
 appliances for the correction 
 
 of, 400 
 finishing appliances for the 
 
 correction of, 404 
 flasking for, 403 
 forming splint in wax for, 402 
 Kingsley splint for, 405 
 Ottolengui's splint for, 425 
 packing and vulcanizing splints 
 
 for, 403 
 preparing the methods for, 401 
 securing splint in the mouth 
 in, 405 
 
 the impression in, 401 
 splintage for section of in- 
 ferior, 420 
 Fractures of the maxillae, division of, 
 
 400 
 Franklin's mold, 166 
 Fuels employed, gaseous, 28 
 liquid, 22 
 solid, 2.2 
 Furnaces, 49 
 baking, 51 
 draft or wind, 49 
 electric, 661 
 gas crucible, with blast, 61 
 
 without blast, 60 
 Land's, 56 
 Sharpe's, 58 
 wind, 49 
 Fusible alloys of lead, 114 
 Fusing-point of aluminium, 108 
 of antimony, 115 
 of bismuth, 116 
 of gold, 70 
 of lead, 114 
 of platinum, 103 
 of silver, 98 
 of tin, 115 
 of zinc, 113 
 
 GAGE plate, standard, 94 
 Gas crucible furnaces, 60, 61 
 illuminating, 28 
 olefiant, 55 
 Gaseous fuels, 28 
 
 illuminating gas as, 28 
 oxyhydrogen gas as, 30 
 Gasolene, 55 
 
 blowpipe, 42 
 Gassing the body and enamel, 53 
 General properties of alloys, 117 
 of aluminium, 107 
 of antimony, 115 
 of bismuth, 116 
 
INDEX. 
 
 675 
 
 General properties of copper, 111 
 of gold, 69 
 of lead, 114 
 of platinum, 103 
 of rubber, 281 
 of silver, 98 
 of tin, 115 
 of zinc, 113 
 Generation and application of heat, 31 
 Geographical distribution of gold, 69 
 Geological situations of gold, 68 
 German silver, 112 
 Gold alloy cast base, 365 
 fusing-point of, 70 
 geographical distribution of, 69 
 geological situations of, 68 
 influence of alloying and the prop- 
 erties of, 70 
 ingots of, 89 
 
 manner of making, 89 
 laminating or rolling, 92 
 malleability of, 70 
 plate, formulas for, 81 
 
 laminating or rolling, 92 
 required fineness of, 80 
 thickness of, required for arti- 
 ficial dentures, 94 
 thickness of, required for 
 clasps, backings, etc., 94 
 properties of, 69 
 
 of particular alloys of, 71 
 raised to a higher carat, 87 
 reduced to a required carat, 86 
 refining, 74 
 solders, 83 
 wire, method of obtaining, 95 
 
 HAWES flask, 159 
 
 Heat, appliances used in the generation 
 
 and application of, 31 
 Humid method of refining gold, 78 
 
 ILLUMINATING gas as a fuel, 28 
 Impressions, beeswax for, 129-137 
 entire lower, 137, 146 
 
 upper, 136, 144 
 for interdental splints, 401 
 manner of obtaining, 126 
 modeling composition for, 138 
 moldine for, 138 
 partial lower, 134 
 
 upper, 130 
 plaster-of-Paris for, 139-146 
 of the mouth, materials, etc., em- 
 ployed in obtaining, 126 
 India-rubber, general properties of, 281 
 Influence of alloying on the prorerties 
 
 of gold, 70 
 Ingot, manner of procuring, 89 
 Interdental splints, 400 
 
 Introduction, 17 
 Iridium, 106 
 
 KAOLIN, 259 
 
 Kingsley's obturators, 375 
 splint, 405 
 
 LABORATORY uses of lead, 114 
 
 Laminating or rolling gold plate, 92 
 
 Lamps, 32 
 
 Land's furnace, 56 
 
 Lead, 114 
 
 fusible alloys of, 114 
 
 fusing-point of, 114 
 
 laboratory uses of, 114 
 
 properties of, 114 
 
 soft, solder, 114 
 Lewis's molding-flask, 160 
 Liquid fuels, 22 
 Lower jaw, projection of, 241 
 
 MALLEABILITY of gold, 70 
 Materials, etc., employed in obtaining 
 
 impressions of the mouth, 126 
 Maxillae, appliances for the correction 
 
 of fractured, 400 
 Melotte's clamp for soldering, 48 
 Mesial line, the, 203 
 Melting aluminium, 109 
 Metallic base with rubber or celluloid 
 
 attachment, 354 
 Metals employed in laboratory opera- 
 tions, 68 
 Modeling composition as an impression 
 
 material, 138 
 Models, plaster, 148 
 Moldine as an impression material, 138 
 Molding by dry heat, 343 
 
 in steam, 340 
 
 materials used in, 156 
 
 when undercuts are present, 158 
 
 with coves, 158 
 Molds, asbestos, 90 
 
 carbon, 91 
 
 charcoal, 90 
 Mouth blowpipe, 34 
 
 OBTURATORS, 375 
 
 Olefiant gas, 55 
 Orthodontia, 434 
 Ottolengui's splint, 425 
 Oxycarbon blowpipe. 42 
 Oxyhydrogen blowpipe, 44 
 
 PALLADIUM, 106 
 Parker swaging device, 176 
 Partial dentures, adjusting clasps to, 192 
 annealing, 191 
 
6;6 
 
 INDEX. 
 
 Partial dentures, constructed on a base 
 of rubber, 317 
 
 lower impressions for, 134, 140 
 manner of forming an air- 
 chamber for, 199 
 modifications in form of, 187 
 reinforcement of, 189 
 retained in the mouth by means 
 
 of clasps, 178 
 soldered air-chamber in, 200 
 supported by atmospheric pres- 
 sure or adhesion, 198 
 swaging, 190 
 
 the form of the base for, 198 
 upper impressions of, 130, 140 
 use of a tracer in the swaging 
 process for, 200 
 or stay clasps, 186 
 Pearsall molding-flask, 162 
 Plaster models, 148 
 
 forming an air-chamber on, 151 
 manner of obtaining, 148, 150, 
 
 152, 154 
 
 Plaster-of-Paris, 139 
 derivation of, 139 
 manner of preparing, 140 
 to hasten the setting of, 140 
 
 Platinoid metals, 105 
 
 Platinum, 103 
 
 alloys of, 105 
 
 fusing-point of, 103 
 
 general properties of, 103 
 
 solder for, 105 
 
 use of, for dental purposes, 105 
 
 Polishing aluminium, 109 
 
 Porcelain teeth, 258 
 
 coloring materials for, 260 
 manufacture of, 261 
 components of dental, 258 
 
 Preparing and pouring metal for dies, 
 
 16s 
 
 casts for molding, 165 
 model previous to molding, 156 
 Principles of soldering, 65 
 Projection of the lower jaw, 241 
 Properties' of a die, 170 
 
 of particular alloys of gold, 71 
 
 RAISING gold to a higher carat, 87 
 Reducing gold to a required carat, 86 
 metals, 80 
 
 silver to the required forms for 
 dental purposes, 101 
 Reduction of gold solder into proper 
 
 form for use, 95 
 Refining gold, 74 
 
 elements employed in, 74 
 dry method of, 75 
 humid method of, 78 
 
 Refining gold, separation of foreign 
 metals in, 75 
 silver, 99 
 Regulating supplemented by crown- 
 work, 454 
 Reinforcement of partial dentures, 189 
 Removal of flask after vulcanizing, 315 
 Replacement of the inferior teeth, 182 
 Re-posing the features, 239, 456 
 Required fineness of gold plate, 80 
 
 thickness of gold plate, 94 
 Rubber or vulcanite base, 281 
 
 arranging teeth for, 
 
 284 
 finishing process for, 
 
 3i5 
 flaskiag for, 288-298 
 grinding and jointing 
 
 teeth on, 286 
 packing the mold for 
 
 a, 292 
 partial dentures con- 
 structed on a, 317 
 vulcanizing, 298-315 
 celluloid attachment for metal- 
 lic base, 354 
 compounding for dental purposes, 
 
 282 
 general properties of, 281 
 metallic clasps attached to, plates, 
 
 318 _ 
 repairing, plates, 319 
 substitution of plate for, teeth, 319 
 
 SCALLOPED clasp, 186 
 Securing clasps to the plate, 193 
 
 mold, 157 
 Selecting and arranging artificial teeth, 
 
 204, 220, 228, 249, 284 
 Separation of foreign metals from gold, 
 75 
 of teeth for the reception of clasps, 
 J82 
 Sharpe's furnace, 58 
 Silex, 259 
 Silver, 98 
 
 alloys of, 98 
 
 formulas for, solders, 102 
 
 fusing-point of, 98 
 
 general properties of, 98 
 
 reduction of, to required forms for 
 
 dental purposes, 101 
 refining, 99 
 Soft solder, 114 
 Solder, brass, 112 
 
 formulas for silver, 103 
 
 for platinum, 105 
 gold, 83 
 
 reduction of, 95 
 
INDEX. 
 
 677 
 
 Solder, gold, reduction of, into proper 
 form for use, 95 
 soft, 114 
 Soldered air-chamber, 200 
 Soldering aluminium, 109 
 principles of, 65 
 supports for, 46 
 Solid fuel, 22 
 
 anthracite coal as, 26 
 bituminous coal as, 24 
 charcoal as, 23 
 coke as, 24 
 Solubility of aluminium, 108 
 Spiral springs, constructing and at- 
 taching, 252 
 
 method of constructing, 96 
 Springing or warping of dentures, 254 
 Standard clasp, 185 
 
 gage plate, 94 
 Steam-gage for vulcanizer, 314 
 Suersen's obturator, 392 
 Supplying the loss of the inferior in- 
 cisors, 182 
 Supports for soldering, 46 
 
 Melotte's clamp-, 48 
 Surgical treatment of the mouth after 
 
 the extraction of teeth, 123 
 Swaging the plate, 190 
 
 TEETH, manner of backing, 208, 256 
 for the attachment of clasps, 180 
 grinding, 204, 286 
 investing, 208, 253 
 manufacture of porcelain, 258 
 replacement of the inferior, 182 
 securing harmony of color of, 204, 
 
 247 
 selecting, arranging, and antagon- 
 izing the, 204, 220, .228, 249, 284 
 separation of, for reception of 
 
 clasps, 182 
 soldering and finishing, 211 
 substitution of plate for rubber, 319 
 surgical treatment of mouth after 
 extraction of, 123 
 
 Temperaments, the four basal, and their 
 
 general indications, 225, 226 
 Temporary plates, arranging for, 248 
 Thermometers as indicators of heat, 313 
 Tin, 115 
 
 alloys of, 115 
 fusing-point of, 115 
 properties of 115 
 Treatment of defects of the palatal or- 
 gans, 373 
 of the mouth preparatory to the in- 
 sertion of artificial dentures, 120 
 Trying the plate in the mouth, 236 
 Type-metal, 174 
 
 Use of a tracer in the swaging process, 
 200 
 
 clasps, 178 
 
 VACUUM chamber, 151, 199, 200 
 Vulcanite base-plate faced with cellu- 
 loid, 349 
 Vulcanizers, Boston, 309 
 
 electric, 665 
 
 Mann, 307 
 
 Philadelphia, 310 
 
 steam-gage for, 314 
 
 Whitney, 307 
 Vulcanizing, 298-315 
 
 time and temperature necessary 
 for, 305 
 
 WARPING or springing of dentures, 
 
 254 
 Wet method of refining silver, 99 
 Wind or draft furnace, 49 
 Wire, method of obtaining gold, 95 
 Withdrawing the cast, 157 
 Wood as a fuel, 23 
 
 ZINC. 113 
 
 dental uses of, 113 
 fusing-point of, 113 
 sreneral properties of. 113 
 Zylonite, 353 
 
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 3-5o 
 3-5o 
 
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 4.50 
 4.50 
 4.50 
 
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 of Hearing — Brain — Female Perineum — Male Perineum. 
 Volume III. — Abdominal Wall — Abdominal Cavity — Pelvic Cavity — Chest — 
 
 Lower Extremity. 
 
 fi^F* See next page for Reviews. 
 
MEDICAL AND SCIENTIFIC PUBLICATIONS. 13 
 
 Deaver's Surgical Anatomy 
 
 The illustrations, which at the first glance appear as the prominent feature of 
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 From The Journal of the American Medical Association. 
 
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MEDICAL AND SCIENTIFIC PUBLICATIONS. 15 
 
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 Gould and Pyle. Cyclopedia of Practical Medicine and Surgery. 
 72 Special Contributors. Illustrated. One Volume. 
 
 A Concise Reference Handbook, Alphabetically Arranged, of Medicine, Surgery, 
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 *„* The great success of Dr. Gould's "Illustrated Dictionary of Medicine" sug- 
 gested the preparation of this companion volume, which should be to the physician the 
 same trustworthy handbook in the broad field of general information that the Dictionary 
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 aim has been to provide in a one-volume book all the material usually contained in the 
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 ing the latest methods of diagnosis, treatment, and operating — a working book in which 
 the editors and their collaborators have condensed all that is essential from a vast 
 amount of literature and personal experience. 
 
 The seventy-two special contributors have been selected from all parts of the 
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 may be considered expert authorities. They are all men of prominence, teachers, 
 investigators, and writers of experience, who give to the book a character unequaled by 
 any other work of the kind. 
 
 "The book is a companion volume to Gould's 'Illustrated Dictionary of Medicine,' which 
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 a vast amount of time in having at hand an instant reference cyclopedia covering every subject in 
 surgery and medicine." — Chicago Medical Recorder. 
 
 Pocket Cyclopedia of Medicine and Surgery. 
 
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 Full Limp Leather, Gilt Edges, $1.00 ; With Thumb Index, $1.25 
 $&&" See next page for List of Contributors. 
 
MEDICAL AND SCIENTIFIC PUBLICATIONS. 
 
 17 
 
 Gould and Pyle's Cyclopedia of Medicine 
 LIST OF CONTRIBUTORS 
 
 Samuel W. Abbott, A.M., M.D., Boston. 
 
 James M. Anders, M.D., LL.D., Phila. 
 
 Joseph D. Bryant, M.D., New York. 
 
 James B. Bullitt, M.D., Louisville. 
 
 Charles H. Burnett, A.M., M.D., Phila. 
 
 J. Abbott Cantrell, M.D., Philadelphia. 
 
 Archibald Church, M.D., Chicago. 
 
 L. Pierce Clark, M.D., Sonyea, N. Y. 
 
 Solomon Solis-Cohen, M.D., Philadelphia. 
 
 Nathan S. Davis, Jr., M.D., Chicago. 
 
 Theodore Diller, M.D., Pittsburg. 
 
 Augustus A. Eshner, M.D., Philadelphia. 
 
 J. T. Eskridge, M.D., Denver, Col. 
 
 J. McFadden Gaston, A. B., M.D., Atlanta, 
 Ga. 
 
 J. McFadden Gaston, Jr., A.M., M.D., At- 
 lanta, Ga. 
 
 Virgil P. Gibney, M.D., New York. 
 
 George M. Gould, A.M., M.D., Phila. 
 
 W. A. Hardaway, A.M., M.D., St. Louis. 
 
 John C. Hemmeter, M.B., M.D., Baltimore. 
 
 Barton Cooke Hirst, M.D., Philadelphia. 
 
 Bayard Holmes, M.D., Chicago. 
 
 Orville Horwitz, B.S., M.D., Philadelphia. 
 
 Daniel E. Hughes, M.D., Philadelphia. 
 
 James Nevins Hyde, A.M., M.D., Chicago. 
 
 E. Fletcher Ingals, A.M., M.D., Chicago. 
 
 Abraham Jacobi, M.D., New York. 
 
 William W. Johnston, M.D., Washington, 
 D. C. 
 
 Wyatt Johnston, M.D., Montreal. 
 
 Allen A. Jones, M.D., Buffalo. 
 
 William W. Keen, M.D., LL.D., Phila. 
 
 Howard S. Kinne, M.D., Philadelphia. 
 
 Ernest Laplace, M.D., Philadelphia. 
 
 Benjamin Lee, M.D., Philadelphia. 
 
 Charles L. Leonard, M.D., Philadelphia. 
 
 James Hendrie Lloyd, A.M., M.D., Phila. 
 
 J. W. MacDonald, M.D. (Edin.), F.R.C.S. 
 Ed., Minneapolis. 
 
 L. S. McMurtry, M.D., Louisville. 
 
 G. Hudson Makuen, Philadelphia. 
 
 Matthew D. Mann, M.D., Buffalo. 
 
 Henry O. Marcy, A.M., M.D., LL.D., 
 
 Boston. 
 Rudolph Matas, M.D., New Orleans. 
 Joseph M. Mathews, M.D., Louisville. 
 John K. Mitchell, M.D., Philadelphia. 
 Harold N. Moyer, M.D., Chicago. 
 John H. Musser, M.D., Philadelphia. 
 A. G. Nicholls, M.D., Montreal. 
 
 A. H. Ohmann-Dusmesnil, M.D., St. 
 Louis. 
 
 William Osier, M.D., Baltimore. 
 
 Samuel O. L. Potter, A.M., M.D., M.R. 
 
 C.P. (London), San Francisco. 
 Walter L. Pyle, A.M., M.D., Philadelphia. 
 
 B. Alexander Randall, A.M., M.D., Phila. 
 Joseph Ransohoff, M.D., F.R.C.S. (Eng.), 
 
 Cincinnati. 
 Jay F. Schamberg, A.M., M.D., Phila. 
 Nicholas Senn, M.D., LL.D., Chicago. 
 Richard Slee, M.D., Swiftwater, Pa. 
 S. E. Solly, M.D., M.R.C.S., Colorado 
 
 Springs, Col. 
 Edmond Souchon, M.D., New Orleans. 
 Ward F. Sprenkel, M.D., Philadelphia. 
 Charles G. Stockton, M.D., Buffalo. 
 John Madison Taylor, A.M., M.D., Phila. 
 William S. Thayer, M.D., Baltimore. 
 James Thorington, A.M., M.D., Phila. 
 Martin B. Tinker, M.D., Philadelphia. 
 James Tyson, M.D., Philadelphia. 
 J. Hilton Waterman, M.D., New York. 
 H. A. West, M.D., Galveston, Texas. 
 J. William White, M.D., PH.D., Phila. 
 Reynold W. Wilcox, M.A., M.D., LL.D., 
 
 New York. 
 
 George Wilkins, M.D., Montreal. 
 DeForest Willard, M.D., Philadelphia. 
 Alfred C. Wood, M.D., Philadelphia. 
 Horatio C. Wood, M.D., LL.D., Phila. 
 Albert Woldert, PH.G., M.D., Phila. 
 James K. Young, M.D., Philadelphia. 
 
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MEDICAL AND SCIENTIFIC PUBLICATIONS. 19 
 
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MEDICAL AND SCIENTIFIC PUBLICATIONS. 21 
 
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MEDICAL AND SCIENTIFIC PUBLICATIONS. 23 
 
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MEDICAL AND SCIENTIFIC PUBLICATIONS. 25 
 
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MEDICAL AND SCIENTIFIC PUBLICATIONS. 27 
 
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MEDICAL AND SCIENTIFIC PUBLICATIONS. 29 
 
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MEDICAL AND SCIENTIFIC PLBLICATIONS. 31 
 
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MEDICAL AND SCIENTIFIC PUBLICATIONS. 33 
 
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34 P. B LA KIS TON'S SOA T <S- CO.' S 
 
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MEDICAL AND SCIENTIFIC PUBLICATIONS. 35 
 
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 No. 10. MEDICAL CHEMISTRY. Fourth Edition. Including Urinalysis, Chemistry of 
 Milk, Blood, etc. By Henry Leffmann, m.d., Professor of Chemistry in Pennsylvania 
 College of Dental Surgery and in the Woman's Medical College, Philadelphia. 
 
 No. n. PHARMACY. Fifth Edition. Based upon Professor Remington's Text-Book of 
 Pharmacy. By F. E. Stewart, m.d., ph.g., late Quiz-Master in Pharmacy and Chemistry, 
 Philadelphia College of Pharmacy ; Lecturer at Jefferson Medical College. 
 
 No. 12. VETERINARY ANATOMY AND PHYSIOLOGY. Illustrated. By Wm. 
 R. Ballou, m.d., Professor of Equine Anatomy at New York College of Veterinary Sur- 
 geons ; Physician to Bellevue Dispensary, etc. With 29 graphic Illustrations. 
 
 No. 13. DENTAL PATHOLOGY AND DENTAL MEDICINE. Third Edition, 
 Illustrated. By George W. Warren, d.d.s., Pennsylvania College of Dental Surgery. 
 
 No. 14. DISEASES OF CHILDREN. Colored Plate. By Marcus P. Hatfield, 
 Professor of Diseases of Children, Chicago Medical College. Third Edition. Just Ready. 
 
 No. 15. GENERAL PATHOLOGY. Illustrated. By A. E. Thayer, m.d., etc. 
 
 No. 16. DISEASES OF THE SKIN. By Jay F. Schamberg, m.d., Professor of Skin 
 Diseases, Philadelphia Polyclinic. Third Edition, Revised. Ic6 Illustrations. 
 
 No. 17. HISTOLOGY. Illustrated. By H. H. Cushing, m.d. Preparing. 
 
 No. 18. SPECIAL PATHOLOGY. Illustrated. By same author as No. 15. Jusl Ready. 
 
 No. 19. KYLE— EAR, NOSE, AND THROAT. Illustrated. In Press. 
 
 43 
 
PRACTICAL GYNECOLOGY 
 
 A Modern Comprehensive Text-Book 
 By E. E. MONTGOMERY, MX). 
 
 Professor of Gynecology, Jefferson Medical College? Gynecologist to the Jefferson Medical 
 
 College and St. Joseph's Hospitals ; Consulting Gynecologist to 
 
 the Philadelphia Lying-in Charity 
 
 WITH FIVE HUNDRED AND TWENTY-SEVEN 
 ILLUSTRATIONS 
 
 Nearly all of which have been Drawn and Engraved Specially for this 
 Work, for the most part from Original Sources 
 
 OCTAVO. 819 PAGES. CLOTH, $5.00 j LEATHER, $6.00 
 
 From THE JOURNAL OF THE AMERICAN MEDICAL ASSOCIATION. 
 
 " Fashion in medical book-making seems to be running to the composite, which 
 may be advantageous and the means of producing a better book than one written by 
 an individual. It may be the old-fashioned notions of the reviewer, but he belives in 
 the old idea of one book, one author, and he should have all the responsibility, all the 
 criticism, and all the glory that attach to it. The composite is likely to be written 
 under a ' rush ' order — so much space, in so much time, for so much money. The work 
 before us is the work of one individual, and the personality of that individual is evident 
 through the whole book. . . . The result shows painstaking effort in every detail, 
 in conciseness of statements, in arrangement of subjects, and in the systematic order 
 and completeness in which each is considered. . . . The author is neither too 
 radical nor too conservative in his consideration of the conditions that may need radical 
 operations. In the introduction he tells us that the true gynecologist must be ' so con 
 servative that he will sacrifice no organ whose physiologic integrity is capable of being 
 restored; so bold and courageous that his patient shall not forfeit her opportunity for 
 life or restored health through his failure to assume the responsibility of any operative 
 procedure necessary to secure the object.' This is the basal idea that permeates the 
 book : the ultra-radical operator will find no endorsement, and the 'tinkering' gynecologist- 
 he who treats all diseases of women by means of a pledget of cotton and a speculum — 
 no encouragement in its pages. 
 
 "The book is one that can be recommended to the student, to the general practi- 
 tioner — who must sometimes be a gynecologist to a certain extent whether he will or not 
 — and to the specialist, as an ideal and in every way complete work on the gynecology of 
 to-day — a practical work for practical workers." 
 
 DESCRIPTIVE CIRCULAR UPON APPLICATION. 
 
 44 
 
NOW READY 
 
 DISEASES OF THE 
 
 SKIN 
 
 Their Description, Pathology, Diagnosis, and Treatment, with 
 Special Reference to the Skin Eruptions of Children. 
 
 By H. RADCLIFFE CROCKER, M.D. 
 
 'Physician to the Department of Skin Diseases, University College Hospital, London 
 
 MESSRS. P. Blakiston's Son & Co. take pleasure in announcing the 
 publication of the new third revised edition of Diseases of the Skin, by 
 Dr. H. Radcliffe Crocker. This announcement, coming at a time when 
 recent progress in dermatology makes an authoritative work upon the subject a 
 positive necessity, is considered of special importance by the publishers, and it is 
 believed the same view will be taken by the profession. Crocker on the Skin is 
 a book built entirely upon superior merit. It has been acknowledged by the 
 American medical press as "the best text-book in the English language." The 
 new third edition maintains this high standard of excellence. 
 
 It is a safe, accurate, eminently practical and strictly modern treatise, well 
 and clearly written by a man of large experience and most excellent judgment. 
 Though completely scientific, it is written in such a happy manner that the tyro 
 may follow the writer almost as readily as the expert on diseases of the skin. It 
 will be seen, therefore, that it appeals to general practitioners as well as specialists, 
 while to the student it will serve as a valuable guide when he enters upon the 
 more arduous task of practice. 
 
 The etiology, symptomatology, pathology and minute anatomy, constitutional 
 conditions, diagnosis and treatment of each disease mentioned is fully entered 
 upon, the therapeutics, dietetics, and general regimen coming in also for their 
 due share of attention, great strength in the accuracy of statement and method 
 and clearness of definition and differentiation being shown. The newer remedies 
 and bacteriological researches, in their bearing upon dermatology, are carefully 
 noted ; and particular attention is paid to eruptions as they occur in childhood. 
 This latter feature is one usually much neglected in general text-books, and its 
 value is the greater from the known practical and extensive experience which the 
 author has had in this field. 
 
 The book proves Dr. Crocker to be closely in touch with the work and 
 teachings of modern dermatology ; and he has sifted from the vast accumulations 
 of recent literature the facts and opinions which have a definite value and are 
 worthy of permanent record. The illustrations, too, showing as they do the 
 morbid conditions of the different structures affected in diseases of the skin, are 
 a not unimportant feature. 
 
 Many valuable additions to the text are noted in the new third edition of 
 this standard work. The whole book has been systematically gone over and 
 numerous changes made where recent progress in dermatology and a more exact 
 knowledge of the subject has dictated. The result is a work every page of which 
 bears the impress of honesty, thoroughness, and large personal experience. 
 
 Third Edition, Thoroughly Revised, with New Illustrations. Octavo ; 1400 pages. 
 Cloth, $5.00 ; Leather, $6.00. 
 
 45 
 
Carpenter on THE MICROSCOPE 
 
 AND ITS REVELATIONS 
 
 EIGHTH ETHTIOff 
 
 Edited by W. H. Daliinger, D.Sc, D.C.L, F.R.S. 
 
 With 23 Plates and nearly 900 Engravings 
 
 OCTAVO. 1181 PAGES. CLOTH, $8.00; HALF MOROCCO, $9.00 
 
 *#* Eight of the chapters have been entirely rewritten and the text 
 throughout reconstructed, enlarged, and revised with the aid and advice 
 of E. M. Nelson, ex-President of The Royal Microscopical Society; 
 Arthur Bolles Lee, author of "The Microtomist's Vade Mecum"; Dr. E. 
 Crookshank, the well-known Bacteriologist; Prof. T. Bonney, F.R.S.; 
 "W. J. Pope, F.I.C., F.C.S., etc., Chemist to the Goldsmith's Technical 
 Institute ; Prof. A. W. Bennett, Lecturer on Botany at St. Thomas' Hos- 
 pital ; and F. Jeffrey Bell, Professor of Comparative Anatomy and Zoology, 
 King's College, London. 
 
 *** A thorough and complete revision of the entire text has 
 been made ; eight chapters have been entirely reconstructed, and 
 everything of importance to Microscopy which has transpired in 
 the interval has been noted. This applies to the theory of the 
 Microscope as well as to its use. Many new illustrations have 
 been included and it has been very materially increased in size. 
 
 CARPENTER" is the only complete and exhaustive modern work on 
 
 the Science of Microscopy 
 
 46 
 
Diseases of ike Digestive Tract 
 
 Their Special Pathologfy, Dia gnosis, and Treatment* With 
 Sections on Anatomy and Physiology, Analysis of Stomach 
 and Intestinal Contents, Secretions, Feces, Urine, Bacteria, 
 Parasites, etc., S urgery, Dietetics, Diseases of the Rectum, etc* 
 
 AN EXHAUSTIVE SYSTEMATIC TREATISE 
 
 By JOHN C. HEMMETEK, M.D. 
 
 Professor in the Medical Department of the University of Maryland j Consultant to the University Hospital and 
 
 Director of the Clinical Laboratory, etc.; formerly Clinical Professor of Medicine 
 
 at the Baltimore Medical College, etc. 
 
 DISEASES OF THE STOMACH. Third Edition. 
 
 With 15 Plates and 41 other Illustrations, some of which 
 are printed in Colors. Octavo. 894 pages. 
 
 Cloth, $6.00 ; Sheep, $7.00 
 
 DISEASES OF THE INTESTINES. Two Volumes. 
 
 With 19 Plates and no other Illustrations, some of which 
 are printed in Colors. Octavo. 1421 pages. 
 
 Vol. I. Anatomy, Physiology, Pathology, Diagnosis, Thera- 
 peutics, Intestinal Clinic, etc. Cloth, $5.00; Sheep, $6.00 
 
 Vol. II. Appendicitis, Occlusions, Intestinal Surgery, En- 
 teroptosis, Infectious Granulomata, Neuroses, Parasites, Dis- 
 eases of the Rectum, etc. Cloth, $5.00 ; Sheep, $6.00 
 
 *^* These books form a complete treatise on Diseases of the Digestive Tract. 
 The subject is covered thoroughly and systematically by an author of well-known 
 reputation and ability. The results of recent investigation, by which so much 
 progress has been made in the Pathology, Diagnosis, and Medical and Surgical 
 Treatment of disorders of the intestinal tract, make their issue at this time of 
 special importance. They are handsomely illustrated, exhaustive, and written 
 for the general practitioner, taking into special consideration American habits of 
 living, diet, and climate. 
 
 " We wish to express unqualified approval of the tendency which is shown to emphasize the 
 simple and more practical methods of diagnosis." — New York Medical Journal, Review of " Dis- 
 eases of the Stomach." 
 
 DESCRIPTIVE CIRCULAR UPON APPLICATION 
 
 47 
 
NEARLY READY 
 
 Edgar's Obstetrics 
 
 A NEW TEXT-BOOK 
 
 By J. CLIFTON EDGAR, M.D. 
 
 Professor of Obstetrics, Medical Department of Cornell University, New York Cityj Physician to Mothers' and 
 Babies' Hospital and to the Emergency Hospital, etc. 
 
 Octavo, about J 000 Pages; 900 Illustrations 
 
 The Illustrations in Edgar's Obstetrics surpass in number, in artistic 
 beauty and in practical worth those in any book of similar character. They are 
 largely from original sources. Those which follow other works have been 
 redrawn with modifications so that the entire series is new. All have been drawn 
 by artists of long experience in this department of medical illustration, and 
 whenever of advantage to do so are reproduced at a stated scale. 
 
 No attempt has been made at display. When a small cut serves every pur- 
 pose drawings are not reproduced to occupy a large space; when black and white 
 are equally expressive an elaborate colored plate has not been used. So far 
 as possible, cuts have been inserted in the text where they are wanted and where 
 the eye catches them at the place the text explains them. Relative importance 
 has determined the selection, the size, and the character of each figure. There 
 are many explanatory diagrams which add greatly to the teaching values of the 
 pictures. The aim of author, artist, and publisher has been to make a series of 
 pictures useful to the student and reader, and no time, labor, or money has 
 been spared to gain this end. The lack of uniformity in quality and failure to 
 observe scale — the great faults in books on this subject — have been kept constantly 
 in mind, and every endeavor has been made to avoid similar defects. 
 
 The Text has been prepared with great care. The author's extensive 
 experience in hospital and private practice and as a teacher, his cosmopolitan 
 knowledge of literature and methods, and an excellent judgment based upon all 
 these fit him specially to prepare what must be a standard work for both students 
 and physicians. 
 
 In the text as in the illustrating, uniformity and consistency have been kept 
 constantly in view. The subjects of monstrosities and malformations, for example, 
 do not take up space which could be better used for more practical and useful 
 matters, though these topics like others of their class receive due consideration 
 and are illustrated by a very complete series of small figures. Nothing of 
 importance remains unsaid, and the relative value of each subject has been care- 
 fully planned out and fixed by deliberate thought. The author's reputation is 
 sufficient guarantee of the merit of this book; the publishers, however, ask a 
 comparison with other works, with confidence that this will be found the most 
 useful. 
 
 4?> 
 

 COLUMBIA UNIVERSITY LIBRARY 
 
 This book is due on the date indicated below, or at the 
 expiration of a definite period after the date of borrowing, 
 I as provided by the rules of the Library or by special ar- 
 I rangement with the Librarian in charge. 
 
 DATE BORROWED 
 
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 DATE DUE 
 
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 1897 
 
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