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A PRACTICAL TREATISE 
 
 MECHANICAL DENTISTRY. 
 
Valuable Works Connected with Dentistry 
 
 PUBLISHED BY 
 
 LINDSAY & BLAKISTON, 
 
 PHILADELPHIA. 
 
 HARRIS (CHAPIN A.), M.D., D.D.S. 
 
 The Principles and Practice of Dentistry. Tenth Eevised 
 Edition. In great part Eevvritten, Rearranged, and with many new 
 and important Illustrations. Edited by P. H. Austen, M.D., Professor 
 of Dental Science and Meclianism in the Baltimore College of Dental 
 Surgery. With nearly 400 Illustrations. Royal octavo. 
 
 Price, in cloth, 6.50 ; in leather, 7.50 
 
 HARRIS (CHAPIN A.), M.D., D.D.S. 
 
 A Dictionary of Medical Terminology, Dental Sur- 
 gery, and the Collateral Sciences. Fourth Edition, 
 Carefully Revised and Enlarged. By Ferdinand J. S. Gorgas, M.D., 
 D.D.S., Professor of Dental Surgery in the Baltimore College, etc. 
 Royal octavo. Price, in cloth, 6.50 ; in leather, 7.50 
 
 RICHARDSON (JOSEPH), D.D.S. 
 
 A Practical Treatise on Mechanical Dentistry. Third 
 Edition, much Enlarged. With 185 Illustrations. Octavo. 
 
 Price, in cloth, 4.00; in leather, 4.75 
 
 TAFT (JONATHAN), D.D.S. 
 
 A Practical Treatise on Operative Dentistry. Third 
 Edition, thoroughly Revised, with Additions. Over 100 Illustrations. 
 Octavo. Price, in cloth, 4.25 ; in leather, 5.00 
 
 WEDL (CARL), M.D. 
 
 Dental Pathology. With Special Reference to the Anatomy and 
 Physiology of the teeth, and notes by Thos. B. Hitchcock, M.D., 
 Prof, of Dental Pathology, Harvard University. 105 Illustrations. 
 
 Price, in cloth, 3.50 ; in leather, 4.50 
 
 HANDY (WASHINGTON R.), M.D. 
 
 Handy's Text-Book of Anatomy and Guide to Dis- 
 sections. For the use of Students. 312 Illustrations. Octavo. 
 
 Price, cloth, 3.00 
 
 LEBER AND ROTTBNSTEIN (Drs.) 
 
 Dental Caries and Its Causes. An Investigation into the 
 Inlluaice of Fungi in the destruction of the Teeth. With Illustra- 
 tions. Price, cloth, 1.25 
 
 SEWILL (H. E.), M.R.C.S., Eng., L.D.S. 
 
 The Student's Guide to Dental Anatomy and Sur- 
 gery. With 77 Illustrations. Price, cloth, 1.50 
 
 SANSOM (ARTHUR ERNEST), M.B. 
 
 Chloroform. Its Action and Administration. Price, cloth, 1.50 
 
 TURNBULL (LAURENCE), M.D. 
 
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 thesia. A Manual of Ansesthetic Agents, Modes of Administration, 
 etc. Second Edition, Enlarged. 25 Illustrations. Price, cloth, 1.50 
 
A 
 
 PRACTICAL TREATISE 
 
 MECHANICAL DENTISTRY. 
 
 JOSEPH RICHARDSON, D.D.S., M.D., 
 
 PROFESSOR OF THE PRIXCIPLES OF PROSTHETIC DENTISTRY K THE INDIANA DENTAL 
 
 COLLEGE; FORMERLY PROFESSOR OF MECHANICAL DENTISTRY AND 
 
 METALLURGY IN THE OHIO COLLEGE OF 
 
 DENTAL SURGERY. 
 
 THIRD EDITION, 
 REVISED AND ENLARGED, 
 
 WITH 
 
 ONE HUNDRED AND EIGHTY-FIVE ILLUSTRATIONS. 
 
 PHILADELPHIA: 
 
 LINDSAY & BLAKISTON. 
 
 18 80. 
 
Entered according to Act of Congress, in the year 1880, 
 
 By LINDSAY & BLAKISTON, 
 
 lu the Office of the Librarian of Congress, at Washington, D. C. 
 
€n 
 
 JAMES TAYLOR, M.D., D.D.S., 
 
 KMEBITUS PEOFESSOR OF THE INSTITUTES OF DENTAL SCIENCE IN THE OHIO 
 COLLEGE OF DENTAL SURGERY, 
 
 ACKNOWLEDGMENT OF PROFESSIONAL EMINENCE 
 AND PRIVATE WORTH, 
 
 €^u Mmu is grntrfnllt[ instrih^^; 
 
 HIS FEIEND AND FORMER PUPIL, 
 
 THE AUTHOR. 
 
PREFACE TO THIRD EDITION. 
 
 In responding to the demand made for a third edition of 
 the presf nt work, the author has subjected the preceding one 
 to a careful and thorough revision, and has endeavored to 
 make it, as nearly as practicable, a faithful reflex of the ad- 
 vanced thought and experience of the profession in all essen- 
 tial matters relating to the facts, appliances, methods, and 
 principles appertaining to the department of prosthetic dent- 
 istry. 
 
 In this endeavor no attempt has been made to incorporate 
 the almost limitless shades of opinion which prevail among 
 members of the profession concerning methods and appliances, 
 or the almost equal diversity of the latter themselves. Much, 
 therefore, of individual thought, experience, and modes of 
 operating, differing chiefly in the manipulative details by 
 which similar objects and results are sought to be obtained by 
 different practitioners, are necessarily excluded. While there 
 are undoubtedly many appliances and methods of procedure 
 which are approved and meritorious, the limits of the work 
 can admit only those which, in the judgment of the author, 
 are esteemed typical of the best. 
 
 In addition to the consideration of new and improved meth- 
 ods and ai)pliances of more recent introduction, as well, also, 
 as conspicuous supplementary matters in connection with the 
 older on(!S, the reader will find throughout the body of the 
 present work not only interpolations of important facts relat- 
 ing to the minor details of practice, but also careful elimination 
 of Biicli ])ortions of the original text as are believed, on more 
 matured reflection, to be at variance with accepted facts and 
 
Vlll PEEFACE. 
 
 theories. This is done under the conviction that it is the 
 province of a work like the present to preserve and perpetu- 
 ate only that which survives the ordeal of experience, and to 
 teach only that which has the sanction and approval of the en- 
 lightened judgment of the profession. 
 
 As still occupying somewhat middle ground between con- 
 demnation and approval, the chapter on Vulcanite Base, with 
 some modifications, has been retained in deference to many 
 who continue to claim for it important advantages as a cheap 
 and convenient base. The growing distrust of its fitness, how- 
 ever, for this purpose, points to . the conclusion that, at no 
 distant day, it will be classified among the obsolete processes. 
 
 While the reader will share the author's regret that nothing 
 additional appears from the pen of Dr. John Allen in connec- 
 tion with the subject of Continuous Gum Work, by reason of 
 afflictive surroundings which rendered it impossible for him to 
 farther enrich this chapter with the results of his added ex- 
 perience, yet, with the additional practical details relating to 
 this unequalled process obtained from other sources, it is be- 
 lieved the descriptions found embodied in the present volume 
 are exceptionally full and complete. 
 
 An additional chapter relating to Celluloid as a base has been 
 introduced, embracing a full and particular account of the most 
 approved appliances and methods of manipulating this ma- 
 terial. 
 
 A new chapter is also introduced relating to an approved 
 method of recent introduction entitled " Gold Alloy Cast 
 Base," of which Dr. Reese, of Brooklyn, N. Y., is the inven- 
 tor, and to whom the author is indebted for detailed descrip- 
 tions and illustrative models. 
 
 A distinct chapter has also been assigned to the subject of 
 Porcelain Teeth in connection with Carved Block-work, em- 
 bracing an interesting account of their composition and manu- 
 facture, with reflections upon the aesthetic requirements of 
 prosthetic practice. 
 
 A separate chapter has also been given to an account of the 
 method of attaching teeth to a metallic plate base by means of 
 
PREFACE. IX 
 
 rubber or celluloid, a process of constructing dentures scarcely- 
 inferior to that of continuous gum work itself. 
 
 The author would especially direct attention to the chapter 
 on Pivoting Artificial Crowns. The conceded importance and 
 superior excellence of this method of substitution will fully 
 justify, it is believed, the large space devoted to its considera- 
 tion. To the members of the profession whose names appear 
 in connection with the several methods, the author is under 
 peculiar obligations for personal courtesies and indispensable 
 aid in the preparation of descriptive material and accompany- 
 ing illustrations. 
 
 While much valuable matter has thus been added to the 
 present volume, the author has not hesitated to exclude what- 
 ever, in his judgment, the common experience of the profession 
 has demonstrated to be impracticable, and therefore useless. 
 Among the omitted matter is the consideration of cast alumi- 
 num plate base and other forms of this metal requiring the use 
 of solder as a uniting medium for the attachment of teeth. 
 Long-continued, patient, and intelligent experimentation with 
 this metal as a base has demonstrated its practical inutility, 
 its only exceptional use as such being confined to the process 
 in which the attachment is secured in the manner described 
 in Chapter XVI. 
 
 For fuller information on the subject treated of in the con- 
 cluding chapter, and which could not be extended consistently 
 with the proper limits of a work like the present, the reader is 
 referred to a recently publislied treatise by Professor Norman 
 W. Kingsley, entitled Oral Deformities, a comprehensive work, 
 embracing, among other important matters, an exhaustive con- 
 sideration of Palatal Defects and their Treatment. The au- 
 thor would commend this invaluable work as the embodied 
 thought and experience of the foremost and most successful 
 practitioner in this department of prosthetic dental surgery in 
 this country or elsewhere ; a work which not only enriches, in 
 an eminent degree, the special literature of the dental profes- 
 sion, but adds fame and lustre to American authorship. 
 
 In closing, the author desires to express his sense of obliga- 
 
X PREFACE. 
 
 tion to those members of the profession who have freely and 
 generously assisted in placing their special methods of operat- 
 ing before the profession through the medium of this work, 
 and also to the representatives of the late Dr. S. S. White, the 
 members of the Celluloid and Buffalo Dental Manufacturing 
 Companies, and others, for needful illustrations and essential 
 information respecting appliances, etc. ,, 
 
 Remembering gratefully the many valuable suggestions 
 received .during a somewhat extended correspondence with 
 representative members of the profession, and cordially appre- 
 ciating the many substantial and essential favors voluntarily 
 proffered by individual practitioners, the author, in conclusion, 
 trusts that the present volume, thus enhanced in value by the 
 friendly and helpful assistance of others, will continue to merit 
 the same consideration and approval that have been accorded 
 to former editions. 
 
 Teree Haute, Ind., September, 18S0. 
 
PREFACE TO FIRST EDITION. 
 
 In the preparatioD of the following treatise, the author has 
 endeavored to present, in as concise and methodical a form as 
 possible, the material facts and principles which relate to the 
 Mechanical Department of Dental Practice in its present ad- 
 vanced condition. In the accomplishment of this undertaking, 
 the primary and leading purpose has been to furnish the stu- 
 dent and more inexperienced practitioner with a practical guide 
 to the manipulations of the laboratory, with accompanying 
 elucidations of the elementary principles which underlie the 
 practice of this important specialty. In furtherance of this 
 design, all matters, discussions, and commentaries, not strictly 
 material, have been carefully excluded. 
 
 The arrangement and treatment of the various subjects em- 
 braced are such, it is believed, as will best facilitate the student 
 in the acquisition of a knowledge of the department alluded 
 to, and the practitioner in the intelligent and successful con- 
 duction of the manipulations which appertain to this branch of 
 Practical Dentistry. 
 
 In the belief that these objects have been mainly accom- 
 plished, the work is respectfully submitted to the profession. 
 
 J. Richardson. 
 
 Cincinnati. 
 
CONTENTS. 
 
 PAGE 
 
 Dedication, 5 
 
 Preface, 7 
 
 PAKT FIKST. 
 
 METALS EMPLOYED IN DENTAL LABORATORY OPERATIONS, WITH PRE- 
 LIMINARY OBSERVATIONS ON THE DIFFERENT MODES OF 
 APPLYING HEAT. 
 
 • CHAPTER I. 
 
 DiFFEREXT Modes of Applying Heat, 17-40 
 
 Blowpipes 17 
 
 Mouth Blowpipe, 18 
 
 Bellows Blowpipe 22 
 
 Lamps 26 
 
 Oil Lamp 26 
 
 Spirit Lamp, 27 
 
 Furnaces, 28 
 
 Draft or Wind Furnace, 28 
 
 Baking Furnace 29 
 
 Gas Furnace without Blast, . . • 31 
 
 Blast Furnace, 32 
 
 Fuel 35 
 
 Supports 38 
 
 Crucibles, 40 
 
 CHAPTER 11. 
 
 Gold, 41-47 
 
 Geological Situations 41 
 
 Geographical Distribution, 42 
 
 Properties of Gold, 42 
 
 Influence of Alloying on the Properties of Gold, 43 
 
 ProperticH of Particular Alloys of Gold 45 
 
XIV CONTENTS. 
 
 CHAPTEE III. 
 
 PAGE 
 
 Repining Gold, . 48-53 
 
 EJements Employed, 48 
 
 Separation of Foreign Metals from Gold 49 
 
 CHAPTEE IV. 
 
 Alloys of Gold for Dental Purposes 54-67 
 
 Reducing Metals, 54 
 
 Required fineness of Gold Plate,- 54 
 
 Formulas for Gold Plate used as a Base for Artificial Dentures, .... 55 
 
 Formulas for Gold Plate used for Clasps, Wire, Stays, Metallic Pivots, etc., . 57 
 
 Gold Solders 57 
 
 Method of reducing Gold to a Lower or Higher Standard of Fineness, and of 
 
 Determining the Carat of any given Alloy, 59 
 
 Table of Gold Coinage of Difi'erent Nations 63 
 
 CHAPTEE V. 
 
 Method of Converting Gold Alloys into the Required Forms for Dental 
 
 Purposes 68-75 
 
 Manner of Procuring an Ingot, 68 
 
 Forging, ' 70 
 
 Laminating or Rolling, '. . 70 
 
 Thickness of Gold Plate required as a Base for Artificial Dentures, ... 72 
 
 Thickness of Plate for Clasps, Stays, etc., 73 
 
 Reduction of Gold Solders into Proper Forms for Use, 73 
 
 Method of obtaining Gold Wire, 73 
 
 Method of constructing Spiral Springs 74 
 
 CHAPTEE VI. 
 
 Silver, 76-78 
 
 General Properties of Silver, 76 
 
 Alloys of Silver 76 
 
 Reduction of Silver to the required forms for Dental Purposes, .... 77 
 Formulas for Silver Solders, 78 
 
 CHAPTEE VII. 
 
 Platinum and the Platinoid Metals 79-82 
 
 Alloys of Platinum, 81 
 
 Platinoid Metals, . 81 
 
 CHAPTEE VIII. 
 
 Aluminum, 83-86 
 
 General Properties of Aluminum, • . 83 
 
 Alloys, ■ . 85 
 
CONTENTS. XV 
 
 CHAPTER IX. 
 
 PAGE 
 
 Copper, Zinc, Lead, Tin, Aktimoxy, and Bismuth, 87-92 
 
 Copper, 87 
 
 Alloys of Copper, 87 
 
 Zinc, 88 
 
 Lead, 89 
 
 Alloys of Lead, 89 
 
 Tin, 90 
 
 Antimony, 91 
 
 Bismuth 91 
 
 CHAPTER X. 
 
 General Propertiesof Alloys, and their Treatment and Behavior in the 
 
 Process of Compounding 93-96 
 
 PART SECOND. 
 
 ARTIFICIAL DEKTURES. 
 
 CHAPTER I. 
 
 Treatment of the Mouth Preparatory to the Insertion of Artificial 
 
 Dentures, 97-104 
 
 Useless and Diseased Remains of Teeth 98 
 
 Removal of Salivary Calculus or Tartar, 101 
 
 Diseased Conditions of the Mucous Membrane and Gums, .... 102 
 
 Caries or Decay of the Remaiuing Teeth, 102 
 
 Surgical Treatment of the Mouth after the Extraction of Teeth, . . . 102 
 Time Necessary to Elapse after the Extraction of Teeth before Inserting 
 
 Artificial Dentures, 103 
 
 CHAPTER 11. 
 
 Materials and Methods Employed in Obtaininu Impressions of the 
 
 Mouth 105-1'20 
 
 Wax, 105 
 
 Manner of Obtaining an Impression of the Mouth in Wax for Partial 
 
 Upper Dentures, 106 
 
 Manner of Obtaining an Impression of tlie Lower Jaw in Wax for Partial 
 
 Dentures, 109 
 
 Manner of Obtaining an Impression of the Mouth in Wax for Entire 
 
 Upper Dentures, 110 
 
 Manner of Obtaitiing an Impression of the Lower Jaw in Wax for Entire 
 
 I^entures, 112 
 
 Gutta-percha, 112 
 
 Plaster of Paris, 113 
 
 Manner of Obtaining an Impression of the Mouth in Plaster for Partial 
 
 Upper Dentures, 115 
 
 Manner of Obtaining an Impression of the Mouth in Plaster for Entire 
 
 Upper Dentures 118 
 
 Manner of Obtaining an Impression of the Mouth in Plaster for ICutire Lower 
 
 Dentures 120 
 
XVI CONTENTS. 
 
 CHAPTER III. 
 
 PAGK 
 
 Plaster Models, 121-127 
 
 Manner of Obtaining a Plaster Model from an Impression in Wax for Par- 
 tial Dentures, 121 
 
 Manner of Obtaining a Plaster Model from an Impression in Wax for En- 
 tire Dentures, 123 
 
 Manner of Obtaining a Plaster Model from an Impression in Plaster for 
 Partial Dentures, 125 
 
 Manner of Obtaining a Plaster Model from an Impression in Plaster for En- 
 tire Dentures, 127 
 
 CHAPTER IV. 
 
 Metallic Dies and Counter-dies, 128-144 
 
 Manner of Obtaining a Metallic Die, 128 
 
 Moulding, 128 
 
 Dipping, . „ 134 
 
 Counter-die, 135 
 
 Essential Properties of a Die, 136 
 
 Table of Fusible Alloys, 143 
 
 CHAPTER V. 
 
 Partial Dentures 145-199 
 
 Means Employed in Retaining Partial Sets of Teeth in the Mouth, . . 145 
 
 Pivoting Artificial Crowns 145 
 
 Circumstances Modifying the Success of the Operation, 146 
 
 The Condition of the Roots, etc., . 146 
 
 Diathesis of the Patient, 147 
 
 Manner of Performing the Operation, 147 
 
 Preparation of the Root 147 
 
 Fitting the Crown, 151 
 
 Attaching Crowns with Wood Pivots, 152 
 
 Pivots of Metal and Wood, 155 
 
 Pivot Plate, 158 
 
 Dr. E. T. Darby's Method, 159 
 
 Dr. M. H. Webb's Method, 161 ' 
 
 Gold Crown faced with Porcelain, 164 
 
 Dr. M. H. Webb's Method .164 
 
 Attaching Porcelain Crowns with Steel Screws, 166 
 
 Dr. E. W. Foster's Method, 166 
 
 Substituting an All-porcelain Crown upon any Root in either Denture, . 172 
 
 Dr. Bonwill's Method, 172 
 
 Dr. Richmond's Method of Attaching Artificial Crowns, 185 
 
 Dr. M. H. Chappell's Method 187 
 
 Substitution of an Artificial Crown by Pivoting in the Absence of the Nat- 
 ural Root, 189 
 
 Dr. M..H. Webb's Method, 189 
 
 Dr. E. T. Darby's Method, , . . . 197 
 
205 
 209 
 
 CONTENTS. XVll 
 
 CHAPTER VI. 
 
 PAGE 
 
 Partial Dentures Retained in the Mouth by means of Clasps attached 
 
 TO THE Natural Teeth 200-220 
 
 Eeinarks on the Use of Clasps 200 
 
 The Teeth to which it is Most Proper to Attach Clasps, 202 
 
 Separation of the Teeth, by Filing, for the Reception of Clasps, ... 204 
 
 Modifications in the Form of Clasps 
 
 Modifications in the Form of Plates for Partial Dentures Supported in the 
 
 Mouth by Clasps, 
 
 Swaging or Stamping the Plate 214 
 
 Uniting the Plate and Clasps, ^^^ 
 
 CHAPTER VII. 
 
 Partial Dentures Supported in the Mouth by means of Cylinders of 
 
 Wood attached to Tubed Plates, 221-223 
 
 CHAPTER VIII. 
 
 Partial Dentures Supported in the Mouth by Pivoting the Plate to 
 
 THE Roots of the Natural Teeth, 224-226 
 
 CHAPTER IX. 
 
 Partial Dentures Supported in the Mouth by Atmospheric Pressure, . 227-230 
 
 Modifications in the Form of the Base, 227 
 
 Manner of Forming an Air-chamber 229 
 
 CHAPTER X. 
 
 Method OF Obtaining an Antagonizing Model for Partial Dentures; 
 Selecting, Arranging, and Antagonizing the Teeth; Investing, 
 Adjusting Stays, Soldering, Etc. 231-245 
 
 CHAPTER XI. 
 
 Entire Dentures 246-275 
 
 Method of Constructing a Plate Base for an Entire Denture for the Upper 
 
 Jaw 246 
 
 . Mfxlifications in the Form of Plates for Entire Upper Dentures, ... 249 
 Method of Constructing a Plate Base for an Entire Denture for the Under 
 
 Jaw, , 
 
 253 
 
 Antagonizing Model for an Entire Upper and Lower Denture, . . . 255 
 Antagonizing Model for an Entire Upper Denture with the Natural Teeth 
 
 of the Ixjwer Jaw Ri-maiiiiiig, 258 
 
 Dr. Bonwill's Anatomical Articulator 260 
 
 Selecting, Arranging, and Antagonizing the Teeth ; Rimming the Plate; At- 
 taching Spiral .Springs ; Investing, Ivining, Soldering, and Finishing, . 265 
 
XVlll CONTENTS. 
 
 CHAPTER XII. 
 
 PAGE 
 
 Porcelain Teeth, 27G-306 
 
 Components of Dental Porcelain, 277 
 
 Manufacture of Porcelain Teeth 279 
 
 Comments on the iEsthetic Requirements of Prosthetic Practice, . . . 282 
 
 Carved Block-Teeth, 285 
 
 Composition and Preparation of the Body, 285 
 
 Composition and Preparation of Crown Enamels, ..,.., 287 
 
 Composition and Preparation of Gum Enamels, 288 
 
 Antagonizing Model for an Entire Upper and Lower Denture, . . . 292 
 
 Antagonizing Model for an Entire Upper Denture, 292 
 
 Forming a Matrix for Moulding the Body preparatory to Carving the 
 
 Teeth, 294 
 
 Moulding the Porcelain Paste preparatory to Carving the Teeth, . . . 296 
 
 Carving the Teeth, 298 
 
 Crucing, or Bisciiiting, 298 
 
 Application of the Crown and Gum Enamels, 300 
 
 Final Bating, 301 
 
 Fitting and Attaching the Blocks to the Metallic Base 301 
 
 Dr. Calvert's Method, 303 
 
 CHAPTER XIII. 
 
 Uniting Single Porcelain Teeth to Each Other and to a Metallic Base 
 WITH A Fusible Silicious Compound, Forming a Continuous Artifi- 
 cial Gum, 307-335 
 
 Introductory Remarks 307 
 
 Dr. Allen's Methods, • . . . . 311 
 
 Dr. Hunter's Formulas and Methods, 318 
 
 Dr. Haskell's Methods, 325 
 
 Dr. Field's Methods, 330 
 
 Application of Continuous Gum to Partial Sets, 333 
 
 CHAPTER XIV. 
 
 Vulcanite Base, . 336-376 
 
 General Properties of India-rubber, 336 
 
 Compounding Rubber for Dental Purposes, 338 
 
 Method of Constructing an Entire Denture in a Base of Rubber, . . . 338 
 
 Arranging the Teeth, 339 
 
 Formation of the Mould or Matrix, 342 
 
 Packing the Mould, 347 
 
 Vulcanizing, 354 
 
 Finishing 367 
 
 Partial Dentures constructed in a Base of Rubber, 368 
 
 Metallic Clasps attached to Rubber Plates, 369 
 
 Substitution of Plate for Rubber Teeth 370 
 
 Repairing 371 
 
 Reiitting Gold or Rubber Plates with Rubber Lining 372 
 
 Manner of Obtaining an Exact Duplicate of a Set of Teeth on Rubber, . .374 
 
CONTENTS. xix 
 CHAPTER XV. 
 
 PAGE 
 
 Celluloid Base, 377-399 
 
 Introductory Remarks 377 
 
 Composition and Manufacture, 378 
 
 Processes Preliminary to Moulding, 380 
 
 Selection and Preparation of the Celluloid Blank, 384 
 
 Moulding, 386 
 
 Hot Moist Air (so-called "Dry Heat ") Machines, 387 
 
 Moulding in Glycerin, 39O 
 
 Moulding in Steam, 392 
 
 Repairing 396 
 
 Finishing, 399 
 
 CHAPTER XVI. 
 
 Attaching Porcelain Teeth to a Metallic Base with Rubber or Cellu- 
 loid 400-406 
 
 CHAPTER XVII. 
 
 Gold Alloy Cast Base, 407-415 
 
 CHAPTER XVIII. 
 
 Defects op the Palatal Organs and their Treatment by Artificial 
 
 Means 416-438 
 
 Dr. Kingsley's Artificial Velum and Palate 416 
 
 Palatine Defects, 416 
 
 Obturators, 417 
 
 Artificial Palates 420 
 
 Artificial Palates for Congenital Fissure, 426 
 
 Method of Making an Artificial Palate 429 
 
MECHANICAL DENTISTRY. 
 
 PART FIRST. 
 
 METALS EMPLOYED IX DENTAL LABOKATORY OPERATIONS, 
 WITH PRELIMINARY OBSERVATIONS ON THE DIF- 
 FERENT MODES OF APPLYING HEAT. 
 
 CHAPTER I. 
 
 Different Modes of Applying Heat. 
 
 The application of heat to the various mechanical processes 
 of the dental laboratory would seem to require a brief descrip- 
 tion of some of the agencies employed for the purpose. As 
 full a description of the appliances used will be introduced as 
 is compatible with the scope of the present work. 
 
 BLOWPIPES. 
 
 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-OAitinr/ or spirit, and hydrostatic 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 " oxy-hydrogen blowpipe." The latter is 
 
 2 
 
18 MECHANICAL DENTISTRY. , 
 
 capable of producing a heat that immediately fuses the most 
 refractory substances^ 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 one hundred ounces by means of this 
 powerful instrument. As, however, these blowpipes are of no 
 special practical utility in the dental laboratory, any further 
 reference to them will be omitted. Nor is it deemed neces- 
 sary to embrace descriptions of either spirit or hydrostatic 
 blowpipes, as they have fallen of late years almost wholly 
 into disuse. 
 
 Month 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 conve- 
 nient and economical. Those 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. 1. It consists usually of a plain tube of brass, larger at 
 
 Fig. 1. 
 
 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 calibre of the instrument 
 terminates here in a very small orifice. The point of the in- 
 strument, as well as that part of it received into the mouth, is 
 sometimes plated with a less oxidable metal than brass, as 
 silver or platinum. The stem is generally from twelve to 
 
BLOWPIPES, 19 
 
 twentv inches in length, and the mouth extremity from one- 
 half to three-fourths of an inch in diameter. 
 
 In operations requiring protracted blowing, a somewhat dif- 
 ferent form of the instrument will be required, owing to the 
 accumulation of moisture within the tube, which, being forcibly 
 expelled from the orifice, spirts 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 meas- 
 ure, by applying the form of blowpipe represented in Fig. 2. 
 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 spherical or 
 
 Fig. 2. 
 
 cylindrical 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 thecham- 
 Vx;r, a basin is formed at the depending portion of the latter, 
 which, by collecting the fluids, will eifectually prevent them 
 from overflowing and passing into the tube beyond. 
 
 Thoma.s Fletcher, of Warrington, England, has introduced 
 modifications in the construction of mouth blowpipes, which 
 are unquestionably improvements upon the simpler forms just 
 described.* One form, styled the hot-blast mouth blowpipe. 
 
 * The several appliances embraced in the above chapter, and designated 
 by the FiKnres 3,4, 5, 6,8, 9, 11, lo, 16, 17, 18, 19, are such jwrtions of 
 Flet'her's heating apparatus as are more especially adapted to the work of 
 the dental lalK)ratory, and are l)elieved to possess peculiar and unequalled 
 advantages in the application of heat for <lenta] j)iirpo!5c.';. For the illus- 
 
20 
 
 MECHANICAL DENTISTRY. 
 
 is shown in Fig. 3. The improvement in this instance con- 
 sists in coiling the air-tube into a light spiral over the point 
 of the jet. This coil takes up the heat which would other- 
 wise be wasted, and utilizes it by heating the air in its passage. 
 It is claimed that with the use of this instrument much higher 
 temperatures ^re reached than is possible with the ordinary- 
 blowpipe, and that with the same amount of blowing nearly 
 double the work is accomplished, while, if a high heat is not 
 
 Fig. 3. 
 
 Fig. 4. 
 
 -°^=^iH^' 
 
 required, the labor of blowing is reduced in proportion. A 
 similar form of instrument (Fig. 4) is made with a hard-rubber 
 mouth-piece. 
 
 Another form of mouth blowpipe by the same inventor is 
 
 Fig. 5. 
 
 exhibited in Fig. 5. It will be seen to be wholly unlike any 
 mouth blowpipe yet devised, and admits of great latitude of 
 
 trative cuts above alluded to, the author is indebted to the Buffalo Dental 
 Manufacturing Company, sole manufacturers of Fletcher's heating appa- 
 ratus in this country. 
 
BLOWPIPES. 2X 
 
 movements in the application of heat. The form of the mouth- 
 piece 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 preventing the passage of 
 heat up to the end. The instrument can be readily changed 
 from a cold to a hot-blast blowpipe by substituting 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 analyses, and as they possess no advantages for dental purposes 
 over those already mentioned, a description of them is not 
 deemed necessary. 
 
 In the production of heat by the use of the mouth blow- 
 pipe, either an oil or alcohol lamp, or the gas flame may be em- 
 ployed, and these will generally be found sufficient when only 
 moderate degrees of heat are required. When gas is used, the 
 ordinary gas-jet should be inclosed within a tube of copper, 
 or other metal not easily oxidized, two or three inches in length 
 and extending some distance above the point of the jet. This 
 tube or funnel should be perforated near its base at a number 
 of points for the free admission of air, which will insure more 
 perfect combustion of the gas,, augment the heat, and provide 
 against carbonaceous deposits upon the substances submitted to 
 the action of the flame. 
 
 Mechanism Involved in the Act of Prodacuig a Continuous 
 Blast with the Mouth Blovrpipe. — 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 stead- 
 ily 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. 
 
 " 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 compress- 
 ing the muscles of the cheeks, while he breathes through the 
 nostrils, and uses the palate as a valve. When tlie mouth 
 
22 MECHANICAL DENTISTRY. 
 
 becomes nearly empty, it is replenished by the lungs in an 
 instant, while the tongue is momentarily 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 injSating 
 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 process, 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 stand- 
 ing or by dirt, dirty cotton-wick, or an untrimmed one, or a 
 dirty wickholder, or a want of steadiness of the hand that holds 
 the blowpipe, will prevent a steady jet of flame. But, fre- 
 quently, the fault lies in the orifice of the jet, or too small a 
 hole, or its partial stoppage by dirt, which will prevent a steady 
 jet of air and lead to difficulty. With a good blowpipe, 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 envelop- 
 ing it, and terminating at a point beyond that of the blue 
 flame."* 
 
 Bellows Bloivpipe. — There are many processes of the dental 
 laboratory requiring the application of a higher temperature 
 than is obtainable with the mouth blowpipe. A more power- 
 ful and persistent air-blast is readily produced with a bellows 
 or foot blower, used commonly in connection with a burner of 
 suitable form attached to the common gas pipes, by means of 
 
 * The Practical Use of the Blowpipe. — Anon. 
 
BLOWPIPES. 
 
 23 
 
 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. 6. The pressure obtainable with this instru- 
 ment is continuous, equable, and completely under the control 
 
 Fig. G. 
 
 of the operator, but the current may be greatly increased in 
 power after the rubber disc is distended until forced against the 
 net. 
 
 A contrivance, essentially d liferent in its construction from the 
 ordinary bellows, employed to produce the air-jet, is shown in 
 Fig. 7, 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. When operating, place the entire foot upon the 
 treadle, so that an easy rocking motion is obtained ; by pressing 
 the toe downwards air is drawn into the cylinder, and in revers- 
 ing the motion it is driven into the air-chamber above. The 
 pipe outlet is much smaller than in the mouth blowpipe, to en- 
 able a pressure to be obtained, which is increased or diminished 
 by a quick or slow motion of the treadle. The air-chamber 
 is easily tilled, and when so a constant supply of pure air is at 
 the control of the operator. 
 
24 
 
 MECHANICAL DENTISTRY. 
 
 The blowpipes used in connection with the bellows are of 
 various forms. Fig. 8 represents one form of apparatus em- 
 ployed in the application of the air-blast to the gas-flame. 
 
 A movable gas-jet attached to two short arms of an ordinary 
 gas-pipe is made to receive within it the blowpipe point con- 
 nected 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 pas- 
 
 FiG. 7. 
 
 Fig. S. 
 
 sage of gas. The gas, being admitted by turning the tap con- 
 nected with the gas-pipe, is ignited, when the current of air 
 from the bellows will strike the centre of the flame and pro- 
 ject 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 downward motion, while the volume 
 of gas and air is readily graduated by the stop-cocks attached 
 to the air and gas tubes. 
 
BLOAVPIPES. 
 
 25 
 
 A bellows blowpipe, cbnstructed on similar principles, but 
 admitting of greater latitude of movements, is exhibited in 
 Fig. 9. 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 
 tor raising, lowering, or adjusting work 
 before it. 
 
 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. 1 0. It 
 is capable of producing very high degrees of heat, but the in- 
 tensity of the latter may be graduated at the will of the opera- 
 
 FiG. 10. 
 
 tor, as the stop-cocks, which are both under perfect control of 
 the thumb of the hand which holds the blowpipe, regulates the 
 supply of gas, and controls the volume of air. The air-jet is 
 one-eighth inch bore, and requires a supply from a bellows. 
 
 The several forms of bellows blowpipes introduced here are 
 the most complete and efficient yet devised for dental pur- 
 poses. The jet may be elevated or depressed at will, while 
 the force of the air-current and the volume of 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 considerable quantities is almost 
 immediately fused in the flame. They are, therefore, well 
 
26 
 
 MECHANICAL DENTISTEY. 
 
 adapted to all operations in the laboratory, but will be found 
 of special utility in the construction of work requiring pure 
 gold as a solder. 
 
 LAMPS. 
 
 The lamps most commonly used by dentists in blowpipe 
 manipulations are oil and spirit lamps. 
 
 Oil Lamp. — When oil is burned, the form of lamp repre- 
 sented in Fig. 11 may be used. It should hold from one to 
 
 two pints, and should have a spout one inch or more where it 
 joins the body of the lamp, tapering gradually to three-fourths 
 
 WICK HOLDER TURNED 
 HAL" A REVOLUTION. 
 
 of an inch at the top. The spout should be well filled with 
 wick, but not so tightly as to prevent it from being freely sat- 
 
LAMPS. 
 
 27 
 
 urated. The best combustible is pure sweet oil, but common 
 lamp or lard oil is generally employed and answers every prac- 
 tical purpose. The wick should be kept well cleaned and 
 trimmed, and fresh oil should be substituted whenever that in 
 use becomes thickened by dirt or otherwise deteriorated. 
 
 A somewhat novel form of oil lamp is shown in Fig. 12. 
 The wick-holder is not only of unique design, but can be ad- 
 justed to any desired angle by simply revolving it in the fixed 
 collar. The wick-holder lifts out for refilling. 
 
 Spirit Lamp. — Alcohol is preferred by many on account of 
 its greater cleanliness, although it does not afford so great 
 a heat as oil. When spirit is employed, a somewhat different 
 form of lamp should be used. With one like that described 
 
 Fi(i. 13. 
 
 for oil, there is danger of explosion in the event of the flame, 
 mixed with air, communicating with the alcohol contained in 
 the lamp, and which is more liable to happen when the spout 
 is but loosely filled with wick. To provide against such 
 ca.sualty, it is not unusual to pack the wick too closely, which, 
 by obstructing the flow of alcohol into the spout, lessens the 
 heat of the flame. The proximity of the flame, also, to the 
 body of the lamp, produces undue waste of alcohol by evapo- 
 ration. 
 
 The objections stated may be obviated by employing a lamp 
 of the form shown in Fig. 13. With a lamp like that 
 represented, the spirit is entirely uninfluenced by the heat of 
 the flame, while explosion is rendered impossible. The centre 
 of the upright portion of the spout is traversed by a small 
 
28 MECHANICAL DENTISTRY. 
 
 tube extending throughout, and open at both ends to admit of 
 the application of a jet of air to the lower orifice, impelling 
 the flame from the centre and thereby intensifying the heat. 
 Around this central tube the wick is arranged ; the space occu- 
 pied by the latter communicating with the body of the lamp 
 through the horizontal arm of the spout. 
 
 FURNACES. 
 
 It would be inconsistent with the design of the present work 
 to introduce a description of any forms of furnace other than 
 those of practical use to the dentist. Many of those, used in 
 the arts, or for chemical and pharmaceutical purposes, em- 
 brace almost endless varieties, and have no special adaptation 
 to the uses required of them in the dental laboratory. 
 
 Draught or Wind Furnaee. — 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 
 cylindrical 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 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 surmounting this simple appa- 
 ratus with a pipe, or connecting it with 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 sol- 
 dering, annealing, etc. 
 
 A more durable and serviceable draught furnace, however, 
 may be built of masonry, a convenient form of which is repre- 
 sented in Fig. 14. The construction of this stationary fixture 
 is so plainly exhibited in the cut that any extended description 
 of it is deemed 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 chambers. Two fire apartments are here 
 shown ; one for melting and refining the more precious metals, 
 
FURNACES. 
 
 29 
 
 heating up operations for soldering, etc. ; the other being used 
 exclusively for fusing the baser metals, as zinc, antimony, lead, 
 
 Fig. 14. 
 
 etc. These furnaces are sometimes constructed with a single 
 fire-chamber, but the one exhibited is in every way preferable. 
 
 Baking Furnace. — The chief purposes to which these fur- 
 naces are applied are the manufacture of porcelain teeth, single 
 and in sectional blocks, the preparation of silicious compounds, 
 and the construction of what is known as " continuous gum 
 work." The most recent and approved form of this furnace 
 is exhibited in Fig. 15. 
 
 The body of the furnace rests upon a cast-iron framework 
 or basement, which serves the purpose of an ash-pit. The grate 
 immediately over this inclines from eacii side of the furnace 
 toward the bottom and the centre of the ash-pit, to aiford more 
 ample room for fuel directly underneath tlie lower muffle. 
 
30 
 
 MECHANICAL DENTISTRY. 
 
 The upper portion or body of the furnace is made of fire-clay, 
 and contains three muffles arranged horizontally ; the upper 
 two, termed " annealing muffles," are designed more especially 
 for drying substances, partial heating preparatory to final 
 baking, and to receive substances from the lower muffle to be 
 gradually cooled. The lower or main muffle is for general 
 baking purposes requiring the employment of extreme degrees 
 of heat. Each muffle is provided with fire-clay slabs or slides, 
 on which substances to be heated are placed and introduced 
 
 Fig. 15. 
 
 inlT) the muffles ; and also plugs of the same material to close 
 the openings to the former. Openings are made on each side 
 of the furnace, intermediate between the muffles, for the intro- 
 duction of fuel, and to afibrd ready access to the latter with 
 tongs or other implements. These entrances are also provided 
 with plugs, which are applied during the process of heating. 
 This furnace should be connected with a flue having a strong 
 and unobstructed draught. 
 
FURNACES. 
 
 31 
 
 Gas Furnace without Blast. — Fig. 16 represents a small cru- 
 cible furnace, that will be found very convenient for melting and 
 refining the precious and more infusible metals employed by 
 the dentist. It takes crucibles up to 2i 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. 
 
 Fig. 16. 
 
 Fig. 17. 
 
 The construction of the burner usisl with this furnace is 
 illustrated by the sectional diagram, Fiii;. 17, and is thus 
 described. "The gas enters a chamber at tiic bottom of the 
 burner through a device similar to a Bun.sen burner, mixing 
 witii uir as it enters, and is burned at the upper ends of a 
 series of concentric tubes, furnishing air-spaces alternately 
 with those supplying the mixture of gas and air. The whole 
 burner is constructed of iron, and will be found better able to 
 withstand an intense heat, more durable and quicker in its 
 operation tlian the old pattern, with gun-metal tubes. In 
 
32 MECHANICAL DENTISTRY. 
 
 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 acci- 
 dent, it 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 
 efficient and economical yet devised for furnace purposes." 
 
 The following instructions in the use of this furnace should 
 be observed : 
 
 " A chimney or stovepipe 8 or 10 feet high may be used as 
 a fixture, and the draught partially stopped with a damper or 
 slide when lower temperatures are required, the gas being 
 turned down in proportion ; the guide for the proper adjust- 
 ment 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 gas is doing its extreme 
 duty under the most favorable circumstances, 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 temperature much 
 exceeding the fusing-point of cast iron. Plumbago fittings and 
 crucibles 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." 
 
 Blast Furnace. — A small, compact, and convenient crucible 
 furnace is shown in Fig. 18. Of this simple but powerful 
 heating apparatus, which will be found especially adapted to 
 the necessities of the dental laboratory, the manufacturers* 
 observe : 
 
 Owing to the discovery by Mr. Fletcher of a singularly 
 perfect non-conducting furnace casing, we are enabled to pro- 
 
 * Buffalo Dental Manufacturing Company. 
 
FURNACES. 
 
 33 
 
 duce the first really simple gas furnace ever constructerl. 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- 
 tor}' substances can be fused with ease, using a common foot 
 blower. Half a pound of cast iron requires from 7 to 12 
 minutes for perfect fusion ; the time depending on the gas 
 supj»ly and pressure of air from the blower. 
 
 Fig. 18. 
 
 The power which can be obtained is far beyond what is re- 
 quired for most purjjoses, 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 ^\ or f will work it efficiently. 
 It requires a much smaller supply of gas than any other fur- 
 nace known. About ten cubic feet per hour is sufficient for 
 most purposes. 
 
 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 bel- 
 
 3 
 
34 
 
 MECHANICAL DENTISTRY. 
 
 lows aud 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 thumbscrew on the side of the 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. 
 
 A modified pattern of the foregoing furnace (Fig. 19) has 
 been designed, retaining all the peculiar advantages of the one 
 
 Fig. 19. 
 
 fecv;^t^"<~> — - 
 
 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 for this furnace is constructed upon the prin- 
 ciple of an atomizer ; and this of course dispenses with a wick. 
 This method has proved the most efficient of any that has been 
 experimented 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 burner is so made that it can be taken apart and 
 cleansed, in case there should be any obstruction to its proper 
 working. Remove the burner from the reservoir, by unscrew- 
 ing the small screws ; draw out the oil tube, which is operated 
 by the milled nut A, take off the sleeve B, and remove the 
 inside tube. 
 
FUEL. 35 
 
 The same furnace and stand are used for either gas or petro- 
 leum, the lamp being fitted for adjustment in place of the gas 
 burner, so that the same apparatus can be furnished for burn- 
 ing either gas or refined petroleum. 
 
 There is no doubt that these furnaces in one or both forms 
 will become a necessity in every workshop, as they fill a place 
 intermediate between a blowpipe and a large furnace — which 
 has never yet been filled ; whilst their strength, cheapness, 
 simplicity, and general usefulness recommend them to all. 
 
 A very useful and almost indispensable heating apparatus 
 in the dental laboratory, suitable for drying, boiling, melting 
 metals requiring: a moderate tempera- 
 
 , , . Fig. 20. 
 
 ture, as zinc, tin, lead, etc., heating ^ 
 
 flasks preparatory to packing with rub- ^i^fel" vZj^ 
 ber, and a variety of other purposes, ■SSHHSfflSH 
 
 is exhibited in Fig. 20. ll,.,a^JII9lliB^^^ 
 
 The burner, consisting, as will be ^i^^^^«'|l 
 seen, of a circular perforated gas tube, '^tIi^^^'— s--[iil| ^ ,i.. 
 with a central air-jet, gives a complete ^^^^^^I^^^^kW 
 range of temperature, from a gentle ^^^^far^ "-^^^s^ 
 current of warm air to a clear red heat, 
 
 and is so perfectly under control, that a common glass bottle 
 may be placed on the tripod and heated to any required tem- 
 perature without the slightest risk of fracture. For veiy 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, melting, 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 blast-pipe 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. 
 
 FUEL. 
 
 Under this head are comprehended such combustible sub- 
 stances as are used for fires or furnaces, as v)ood, coal, charcoal, 
 
36 MECHANICAL, DENTISTRY. 
 
 and Gohe. For dental furnace operations only the latter two 
 are, as a general thing, admissible. 
 
 Bituminous, or pit coal, is unfit for the uses required of fuel 
 by the dentist, and is therefore seldom used. 
 
 Anthracite coal, if carefully selected, may be employed, pro- 
 vided it is clean, free from slate, and does not yield a fusible 
 ash. As charcoal and coke are the fuels chiefly used in the 
 processes of the laboratory, these substances will be more par- 
 ticularly described. 
 
 Charcoal. — Charcoal 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. When com- 
 bustion has proceeded slowly for a certain length of time, the 
 openings to the bed or mound are closed, and the wood 
 allowed to char. 
 
 When it is desired to maintain a high heat in a small com- 
 pass, the charcoal best adapted to the purpose is that obtained 
 from what is termed hard wood, as the beech, the oak, the 
 alder, the birch, the elm, etc. A cubic foot of charcoal derived 
 from these woods weighs, upon an average, from twelve to 
 thirteen 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 for- 
 mer when purchased by the bulk ; and of this class the beech- 
 wood charcoal is the best, on account of its greater specific 
 gravity. The more heavy charcoals require a stronger draught 
 than those of a lighter character, as a more generous supply of 
 oxygen is necessary to their perfect combustion. Charcoal 
 should be kept as dry as practicable, since it rapidly absorbs 
 moisture from the atmosphere, by which its calorific energy is 
 materially impaired. 
 
 Cohe. — This substance, like charcoal, is a carbonaceous resi- 
 duum obtained from pit coal that has been exposed to ignition 
 for some time, excluded from the contact of air, the volatile 
 
 * Ure. 
 
FUEL. 37 
 
 products of the coal, like those of wood, having been driven 
 off bv the heat. Coke differs in appearance as well as in 
 quality. The principal part of that obtained from gas houses 
 is of a dull, iron-black color, very spongy and friable, and is 
 more rapidly consumed, and produces less heat than the harder 
 and more compact kinds. The best coke for furnace use is 
 that used by brassfounders, and has a steel-gray color, with a 
 somewhat metallic lustre ; is compact in its structure, and splits 
 into pieces having a longitudinal fracture. 
 
 Coke does not readily ignite, and at first generally requires 
 the admixture of charcoal to effect its combustion ; it also re- 
 quires a strong draught to burn it, but when thoroughly 
 ignited it produces an intense and persistent heat. It is the 
 principal fuel used in baking mineral teeth, porcelain blocks, 
 and the silicious compounds employed in the fabrication of 
 continuous gum work. 
 
 Professor Piggot, in his remarks on the comparative value of 
 fuels, observes: "Practically, for the purposes 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 exce&s it corrodes the bricks, by forming with them a 
 silicate of potash, which runs down the walls and chokes the 
 bars. In small quantities this action is beneficial, as it fur- 
 nishes 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 
 composed chiefly of oxide of iron and clay. The latter is not 
 fusible by itself, but may soften. When pure it forms a harm- 
 less slag, which injures neither the furnace nor the crucibles. 
 Usually, however, the oxide of iron predominates. In this 
 case the ash is very injurious, for it is reduced to a protoxide, 
 which is not only fusible, but powerfully corrosive to all 
 argillaceous matters, so that both the crucibles and furnaces 
 suffer." * 
 
 * Dental Chemistry and Metallurgy, p. 274. 
 
38 MECHANICAL DENTISTRY. 
 
 In order that the greatest amount of heat may be evolved 
 from these fuels, it is necessary that the conditions necessary 
 to secure their perfect ignition should be strictly observed ; 
 these have reference to an unobstructed circulation of air, that 
 oxygen may be freely supplied to them. To this end the fur- 
 nace should be kept clean, the bars of the grate unbroken, and 
 a good draught 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 Avill be too rapidly consumed. It is 
 essential, also, to have the fuel as free as possible from dust and 
 dirt, as these fine particles, in any considerable quantities, ob- 
 struct the draught, and prevent a thorough ignition of the 
 mass. Coke, especially, should be preserved clean, and should 
 be broken into fragments 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 the air. 
 
 SUPPORTS. 
 
 There are many processes in the dental laboratory requiring 
 the application of heat, for which a suitable holder or support 
 should be provided. A very convenient form of holder, used 
 in soldering, may be made of a circular or semi-el iptical piece of 
 heavy sheet iron, the margin being serrated and turned at right 
 angles, forming a cup. To the under side and centre of this 
 an iron rod, ten or twelve inches long, may be 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. 21) is sometimes used, and will 
 be found a very convenient and useful apparatus, not only for 
 soldering, but for preparatory heating. It consists of a funnel- 
 shaped receptacle made of sheet iron, with a light grate or per- 
 forated plate of the same material adjusted near the bottom, 
 and an opening on one side, underneath the grate, for the ad- 
 mission of air. The upper part of the holder is surmounted 
 
SUPPORTS. 
 
 39 
 
 by a cone-shaped top, whicli 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 to be placed 
 inside on a bed of charcoal, the top adjusted to its place, and 
 the fuel ignited ; when the operation is sufficiently heated the 
 top may be lifted off, and the piece remaining in the furnace 
 
 Fig. 21, 
 
 soldered with the blowpipe in the usual manner, the furnace 
 thus serving the purpose of a holder. 
 
 A support in very common use consists simply of a large 
 close-grained piece of charcoal, invested in plaster one-half or 
 three-fourths of an inch thick, one end or side being left open 
 and scooped out to receive whatever is being heated. Or a 
 plaster cup two or three inches deep may be made, and its 
 interior partly filled with a mixture of plaster, sand, asbestos, 
 and pulverized cliarcf)al. Carbon blocks, suitably moulded, 
 may also be used. They are cleanly, perfect non-conductors, 
 and imperishable. 
 
40 MECHANICAL DENTISTRY. 
 
 CRUCIBLES. 
 
 Crucibles are small conical -shaped vessels used by the dent- 
 ist principally for the purposes of melting and refining metals 
 used for plates, compounding metallic alloys, preparing and 
 compounding the various ingredients employed in the manu- 
 facture of porcelain teeth and 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 oxide of iron. Plumbago crucibles are 
 also made from special patterns, and expressly designed for 
 Fletcher's furnaces. For a more particular description of the 
 various components entering into the structure of crucibles, as 
 well as the manner of manufacturing them, the reader is refer- 
 red to Piggot's Dental Chemistry and Metallurgy, and other 
 works treating more fully of the subject. 
 
GOLD. 41 
 
 CHAPTER 11. 
 
 Gold. 
 
 Gold has been known from a period of great, antiquity? 
 has'ing, according to the writings of Moses, been wrought 
 into articles of jewelry more than three thousand years ago. 
 As a base or support 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, notwithstanding the more recent in- 
 troduction of approved processes in which, as a base, this 
 metal is wholly discarded. 
 
 Gold is found only 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 
 octahedral crystals; also in spangles or roundish grains. 
 Ihese latter, 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 
 twenty-eight 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 Ame- 
 rica, as a contribution to the World's Exhibition in London. 
 New Granada, California, Russia, and Australia, have each 
 produced pepitas or masses of gold Aveighing respectively 
 twenty-seven and a half, twenty-eight, seventy, and one hun- 
 dred and six pounds. 
 
 Geological Situations. — The crystalline primitive rocks, the 
 compact transition rocks, the trachytic and trap rocks, and 
 alluvial grounds, are the formation in which gold occurs. 
 Unlike many other metals, it is never in such large quantities 
 
42 MECHANICAL DENTISTEY, 
 
 as to constitute veins by itself, but is either disseminated 
 through the rocky masses, or spread out in thin plates or 
 grains on their surface, or confined in their cavities in the 
 shape of filaments or crystallized twigs. The minerals com- 
 posing 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 
 re-entering angles, at the season of low water, and after 
 storms and temporary floods. Sufficient reasons have been 
 advanced in sup2)ort of the belief that gold, found in alluvial 
 situations, belongs to the grounds traversed by these rivers, 
 instead of being washed, as was formerly supposed, from the 
 mountains in which their waters have their origin. 
 
 Geographical Distribution. — The European mines, more 
 particularly distinguished for their richness, are in Hungary 
 and Transylvania, especially the former. Gold also occurs, 
 but more sparingly, in Ireland, Sweden, Siberia, Germany, 
 Russia, and Spain. In Asia and Africa, the mines which 
 yield most abundantly, are situated in the southern portions 
 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 quanti- 
 ties. Washings are also common in several States of the 
 Union, but California stands unrivalled, except by Australia, 
 in the immense productiveness of its mines, and its resources 
 in respect to this rare and valuable metal are reckoned inex- 
 haustible. 
 
 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 of a high polish, but is inferior in brilliancy to 
 steel, silver, or mercury. Its specific gravity varies some- 
 what, according as it is fused or hammered; the former 
 having a density of 19.26; the latter ranging from 19.4 to 
 
GOLD. 43 
 
 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 aver- 
 age thickness of ordinary gold leaf is ^go'ij??^ of an inch, but 
 the ultimate degree of attenuation of 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 500 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 i-jf-Q of an inch in diameter will sustain a weight of 150 
 pounds. Gold fuses at 2016° with considerable 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 oxidized in any heat that may be applied to it, and is 
 only volatilized with great difficulty in the resistless heat of 
 the oxy-hydrogen blowpipe. It is unaffected by the most 
 concentrated of the simple acids, but is readily soluble in 
 aqua ref/ia 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 al/oy signifies a compound of any two or more metals, 
 as brass, which is an alloy of copper and zinc. 
 
 Alloys, in respect to their uses, are practically new metals, 
 and <lifler 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 u[)on the general properties of metals, 
 and their management and behavior in the process of com- 
 pounding, will be given under the head of alloys of the baser 
 metals. As gold combines readily with most metals, some of 
 
44 MECHANICAL DENTISTRY. 
 
 the more prominent conditions which distinguish its alloys 
 will be given. 
 
 The malleability of gold is, strictly speaking, always im- 
 paired by its union with other metals. This effect is emi- 
 nently characteristic of certain contaminations, as those with 
 arsenic, tin, antimony, bismuth, lead, etc.; while with certain 
 other metals, as silver, 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 dimin- 
 ished by its incorporation with foreign metals ; sometimes in 
 a remarkable degree. Gold is always rendered harder, and 
 its tenacity is generally increased, by alloying, while its density 
 varies with the particular metal or metals 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 having 
 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 uncom- 
 bined 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, composed 
 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 oxidable 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 1 atom of silver, united to 4, 5, 6, 
 
GOLD. 45 
 
 12 atoms of gold, but never with a fractional part of an atom. 
 The same circumstance is noticed in connection with the amal- 
 gam of silver and mercury. But as alloys are generally 
 soluble in each other, the definiteness of this atomic combina- 
 tion is obscured and disappears in most cases. 
 
 Propei'ties of Particular Alloys of Gold. — The metals with 
 which gold is liable to be contaminated in the dental labora- 
 tory are zinc, tin, lead, antimony, bismuth, iron or steel, mer- 
 cury, and arsenic ; as also excess of silver, copper, and platinum. 
 As several of these metals when alloyed with gold, even in 
 very minute quantities, are highly destructive in their influ- 
 ence upon those properties which adaj)t this metal to the 
 various wants of the mechanical operator, and as their separa- 
 tion is often attended with considerable difficulty, annoyance, 
 and lo&s of time, it is practically important that care should be 
 taken to prevent, as far as practicable, the admixture of any 
 one or more of them with the gold scrap, filings, or sweepings, 
 which are to be re-converted into proper forms 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 de- 
 scription 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- 
 ing gold intractable. 
 
 One part of antimony with nine parts of gold, forms 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 oi' arsenic with gold containing ^\^ of the former 
 is a gray brittle metal, while in the proportion of g,Ljj, the 
 malleability of the gold is seriously impaired without suffering 
 any change of color. So energetic is the influence of this 
 
46 MECHANICAL DENTISTRY. 
 
 i' 
 
 metal on gold that the latter is rendered brittle when sub- 
 jected 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 
 almost inappreciable quantities, rendering the latter metal 
 unmanageable 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. 
 
 Zine 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 unfrequently 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 preponderates, Mdiile remaining portions of the 
 plate retain a moderate degree of softness and pliability. 
 
 The working properties of gold are not sensibly affected by 
 the 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, \b. as before 
 stated, rendered fusible in combination with other metals. 
 When combined with gold in small proportions, the latter is 
 rendered harder and more elastic without having its mallea- 
 bility practically impaired. Platinum very readily affects the 
 color of gold, the smallest 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 mallea- 
 bility. The alloy is light-colored in proportion to the amount 
 of silver introduced. 
 
 Copper, like silver, is usually combined with gold in the 
 
GOLD. 47 
 
 formation 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 propor- 
 tions of any one of the base metals mentioned, and possess 
 certain physical characteristics that indicate, with toleraljle 
 certainty, the particular alloying component. Thus, for ex- 
 ample, if the alloy is light-colored and very brittle, the pres- 
 ence of tin may be suspected ; 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 
 metals in varying proportions, are sometimes accidentally 
 formed, in which case the more distinctive features which 
 characterize the binary compounds are lost or obscured. 
 
48 MECHANICAL DENTISTEY. 
 
 CHAPTEE III. 
 
 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, chlorine, 
 or sulphur, converting them into oxides, chlorides, or sulphu- 
 rets. Certain compound 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 (nitre, or salt- 
 petre), which yields oxygen ; chloride of mercury (corrosive 
 sublimate), which yields chlorine ; and sidphuret of antimony, 
 (crude antimony), which yields sulphur. Other compounds 
 contain these elements, but those mentioned are generally 
 preferred, because iihey 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 refin- 
 ing alloys of gold, it will be convenient to classify the differ- 
 ent forms of gold as they occur in working this metal in the 
 laboratory. 
 
 1. 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, plati- 
 num, etc. These, when melted alone, produce an alloy more 
 or less impoverished in proportion to the quantity and quality 
 
REFINING GOLD. 49 
 
 of the foreign metals introduced in finishing pieces constructed 
 of gold, and should be either separately refined by roasting, 
 or reduced to pure gold by the " humid method," to be de- 
 scribed hereafter. 
 
 3. Sweepings. This form embraces many impurities, earthy 
 and metallic, and should first be thoroughly washed to remove 
 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 follow- 
 ing proportions : Of sweepings, eight parts; chloride 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 complete 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 shop. Separate lapskins 
 or receptacles, therefore, should be appropriated to the working 
 of gold, one to receive scrap and unmixed plate-filings, which 
 may be re-converted into plate without refining ; another to 
 collect the solder-filings, and such impure fragments as require 
 purification. 
 
 Sepamtion 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 re- 
 agent is employed, inasmuch 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 oxygen will, by virtue of the 
 affinity of the latter for these metals, effect their separation by 
 converting them into oxides, hence, when these metals arc to 
 be got rid of, nitrate of potassa is employed. But oxygen has 
 
 4 
 
50 MECHANICAL DENTISTRY. 
 
 but a feeble affinity for tin, and when this metal is present, its 
 separation is better effected by some compound which parts 
 with chlorine in the act of decomposition ; chloride 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 powerful 
 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." 
 
 After all traces of iron or steel have been removed from the 
 gold fragments and filings by passing a magnet 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 
 of roasting is likely to be protracted, 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 fragments of 
 fuel are permitted to fall in upon the fused metals. Small 
 portions of borax may first be added, and when the metals are 
 fluid, the refining agents may be introduced in small quanti- 
 ties from time to time, and the roasting continued from half 
 an hour to an hour, according to the coarseness of the alloy. 
 The roasting may be conducted first with borax and nitre to 
 effect partial separation, when the crucible may be removed 
 from the fire, and the metals allowed to cool gradually. The 
 crucible may then be broken, and the button of gold at the 
 bottom removed and separated from the slag that covers it 
 with a hammer. The button is then put into a fresh crucible 
 and re-melted. If there is any known base metal present 
 
REFINING GOLD. 51' 
 
 likely to render the gold brittle, the particular reagent which 
 will most readily attack it may now be used. If, however, as 
 is generally the case, the alloy is of uncertain composition, or 
 contains various metals having distinct affinities, the process 
 becomes, to some extent, experimental, and it may become 
 necessary to use first one refining agent and then another, 
 until sufficient separation is eiFected. Generally, it will be 
 sufficient to use the nitrate of potassa alone, as most metals are 
 oxidable. After roasting with nitre for half or three-fourtjjs 
 of an hour, adding small portions at a time, the melted metals 
 may be poured into ingot moulds previously warmed and 
 oiled. If, after hammering, annealing, and rolling the ingot, 
 it should still be found brittle, it must be re-melted, and chlo- 
 ride of mercury used as the refining agent. This will remove 
 any traces of tin which may be present. 
 
 If the alloy, however, is greatly impoverished, it may be 
 more advantageously treated with sulphuret of antimony ; in 
 which case the metal should be melted in a large crucible with 
 about twice or three times their weight of the native sulphuret, 
 which should be added in small quantities at a time. Tlie 
 heat decomposes the sulphuret of antimony; the sulphur unit- 
 ing with the base metals forming sulphurets, and the antimony 
 uniting with the gold forming a leaden-colored alloy. The 
 antimony may be parted from the gold alloy in the following 
 manner : Place the mixture in a clean crucible, and when 
 melted, force a current of air with a pair of bellows upon its 
 surface; this oxidizes the antimony, which passes off in the 
 form of vapor. The current should be mild at first, as too 
 great a draught is apt to carry off portions of gold by a too 
 hurried volatilization of the antimony. A current strong 
 enough to produce visible fumes will be sufficient. When 
 these cease, the crucil)le may be covered, and as the melting- 
 point of the gold rises with the escape of antimony, the fire 
 should be urged to a stronger heat, and before pouring, a for- 
 cible current of air should again ])c thrown upon the surface 
 of the melted metals to effectually dissipate any remaining por- 
 tions of the antimony. 
 
62 MECHANICAL DENTISTRY. 
 
 If, after treatment with the reagents enumerated, the alloy 
 should be found malleable, but stiif or elastic, and dull-col- 
 ored, it is probably due to the presence of platinum; and any 
 further attempts to reduce it by roasting will prove unavail- 
 ing. It must then be subjected to the process which will be 
 hereafter described for the separation of gold and platinum. 
 
 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 containing large 
 quantities of solder, linings with platinum pins attached, par- 
 ticles of base metals, etc., the "humid process," as it is called, 
 should be employed. The solvents in common use for this 
 purpose are the nitric, sulphuric, and nitro-muriatic or hydro- 
 chloric acid ; but as the desired results can be more conveni- 
 ently and directly obtained by the use of the latter, or hydro- 
 chloric acid, this most available method alone will be given. 
 The following practical remarks on the process are copied 
 from an article on the " Management of Gold,"* by Professor 
 George Watt. 
 
 " When the alloy is composed of metals differing but little 
 in their affinities for oxygen, chlorine, 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 con- 
 taminated with platinum to such extent that the color and 
 elasticity of the plate is 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 textbooks, is, that when the solution 
 is completed, there is but little, if any, excess of nitric acid. 
 
 * Dental Register of the West, vol. xii, p. 251. 
 
REFINING GOLD. 53 
 
 If the acids be ^chemically pure/ four parts of the hydro- 
 chloric to one of the nitric, produces still better results. 
 
 " By this process the metals are all converted into chlorides ; 
 and, as the chloride of silver is insoluble, and has a greater 
 specific gravity than the liquid, it is found as a grayish-white 
 powder at the bottom of the vessel. The chlorides of the 
 other metals, being soluble, remain in solution. By washing 
 and pouring off, allowing the chloride 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 
 remain in solution. This precipitation may be effected by 
 any one of several different agents, but we will mention only 
 the protosulphate 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 
 farther. It should be dissolved in clean rain-water, and the 
 solution should be filtered, and allowed to settle till perfectly 
 clear. Then it is to be added gradually to the gold solution 
 as long as a precipitate is found, and even longer, as an ex- 
 cess 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 pre- 
 cipitated. These can be removed by digesting the gold in 
 dilute sulphuric acid; and, when the process is properly con- 
 ducted, thus far, the result is jyare gold, which may be melted, 
 under carbonate of potash, in a crucible lined with borax, and 
 reduced to the required carat." 
 
54 MECHANICAL DENTISTRY. 
 
 CHAPTER IV. 
 
 Alloys of Gold for Dental Purposes. 
 
 • Gold, in its pure state, is rarely employed by the dentist 
 in laboratory processes on account of its softness and flexi- 
 bility; it is, therefore, usually alloyed with such metals as 
 impart to it — without practically impairing either its mallea- 
 bility, pliancy or purity — the degree of hardness, strength 
 and elasticity necessary to resist 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 sup- 
 posed to be more readily tarnished and to communicate to the 
 mouth a disagreeable metallic taste. This is unquestionably 
 true, if, as is sometimes the case, the copper used is in excess ; 
 when, in addition 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 propor- 
 tions of copper usually employed in forming gold plate, how- 
 ever, are not likely to produce, in any objectionable degree, 
 the consequences complained of, unless the fluids of the mouth 
 are greatly perverted. If gold coin is used in the formation 
 of plate, it may be sufficient to add silver alone, inasmuch as 
 copper is already present; though, usually, additional quan- 
 tities 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 com- 
 
ALLOYS OF GOLD FOR DENTAL PURPOSES. 55 
 
 promise either the comfort or health of the patient. Evils of 
 no inconsiderable magnitude are sometimes inflicted, either 
 through ignorance, carelessness or cupidity, by disregard of 
 this important requirement. If the general health of the pa- 
 tient remained always uniformly unimpaired, with the secre- 
 tions of the mouth in their normal state, gold degraded to 
 eighteen or even sixteen carats fine, would undergo no mate- 
 rial 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, 
 become more or less acidulated. Indigestion, with acid eruc- 
 tations ; gastro-enteritis ; ague ; inflammatory and typhoid fe- 
 vers ; 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. These readily attack the impoverished gold 
 too frequently employed as a base for artificial teeth ; and as 
 a natural sequence to such practice we find supervening, in- 
 flammation of the mucous membrane and gums, with chronic 
 periodontitis and loosening of the teeth ; aphthous ulcers ; gas- 
 tric irritation ; general nervous disorders ; decay of the teeth ; 
 foetid breath ; disagreeable metallic taste in the mouth, etc. 
 Gold plate intended to be introduced into the mouth, should 
 not, therefore, as a general thing, be of a less standard of fine- 
 ness than twenty 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 pres- 
 ent American coin, which is 21.6 carats fine. 
 
 Fonnulasfor Gold Plate used as cr. 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 
 artificial dentures. The relative proportions of the alloying 
 components may be varied to suit the peculiar views or neces- 
 sities of the manipulator. The estimated carat of the ap- 
 
56 MECHANICAL DENTISTEY. 
 
 pended formulas are based on the fineness of the American 
 gold pieces coined in 1837 and thereafter. 
 
 GOLD PLATE EIGHTKEN CARATS FINE. 
 
 Formula No. 1. Fm~)nula 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. S. Formula No. 4. 
 
 19 dwts. pure gold, 20 dwts. gold coin, 
 
 3 dwts. copper, 25 grs. copper, 
 2 dwts. silver. 40+ grs. silver. 
 
 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. 
 
 21 dwts. pure gold, 20 dwts. gold coin, 
 2 dwts. copper, 13+ grs. silver. 
 
 1 dwt. silver. 
 
 Formula No. 9. 
 20 dwts. gold coin, 
 
 6 grs. copper, 
 7^ 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 Avith gold, as in Formula No. 10, 
 furnishes an alloy rich in gold, while it imparts to the plate 
 derived from it a reasonable degree of stiffness and elasticity ; 
 
ALLOYS OF GOLD FOR DENTAL PURPOSES. 57 
 
 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 
 Linings, MetalUe Pivots, etc. — Gold used in the formation of 
 clasps, stays, etc., is improved for these purposes by the addi- 
 tion 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 w'ill be required ; the elasticity of 
 these supports, also, will not only lessen the chances of acci- 
 dent 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 
 mentioned are obtained from this property in the use of metal- 
 lic 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 gi-s. platinum. 
 
 The alloy derived from either of these formulas will be 
 twenty carats fine. 
 
 Gold Solders. — Solders are a class of alloys by means of 
 which the several pieces of the same or of difi'erent metals are 
 
58 , MECHANICAL DENTISTEY. 
 
 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 pro- 
 vided, from which the one most suitable for any given case 
 may be selected. 
 
 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 664, recipe No. 3, may be used in con- 
 nection with eighteen or twenty carat gold plate, and is six- 
 teen carats fine : 
 
 6 dwts. pure gold, 
 2 dwts. roset 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 fourteen carats, while the latter is still more 
 objectionable, exceeding but little, twelve and one-half carats. 
 
 Formula No. 1 of the following recipes is a fraction over 
 fifteen carats fine; and No. 2 furnishes a solder eighteen 
 carats fine : 
 
 Formula No. 1. Formula No. 2. 
 
 6 dwts. gold coin, Gold coin, 30 parts. 
 
 30 grs. silver, Silver, 4 " 
 
 20 grs. copper, Copper, 1 " 
 
 10 grs. brass. Brass, 1 " 
 
 ■ Zinc, as will be observed by the incorporation of brass in 
 the above formulas, is sometimes employed, principally with a 
 view of rendering the alloy more fusible. Its employment 
 under any circumstances is objected to by many on the 
 ground that it more readily tarnishes in the mouth, is more 
 brittle, and furnishes more favorable conditions for galvanic 
 
ALLOYS OF GOLD FOR DENTAL PURPOSES. 59 
 
 action. These objections only hold good when zinc is nsed 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 equal, or nearly so, in fineness to the plate. If such is 
 the case, they are desirable alloys for soldering purposes, inas- 
 much as the importance of having the various parts of a piece 
 of dental mechanism differ as little as possible in their affinity 
 for the acids of the mouth is generally recognized. 
 
 3Iethod of reducing Gold to a loivei' or 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 employs. Gold alloys are too often arbitrarily com- 
 pounded, and used without any adequate knowleflge of their 
 qualities or properties ; and formulas, taken on trust, are em- 
 ployed 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, whether higher or lower, and the method of ascer- 
 taining 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 copied from an article 
 on " Alloying Gold,"* by Professor G. Watt. 
 
 " 1 . To ascertain the carat of any given alloy. — The propor- 
 tion may be expressed as follows : 
 
 * Dental RegiHter of tlie West, vol. x, p. 396. 
 
60 MECHANICAL DENTISTRY. 
 
 " As the weight of the alloyed mass is to the weight of gold 
 it contains, so is 24 to the standard sought. Take, for exam- 
 ple, Harris No. 3 gold solder: 
 
 Pure gold, 6 parts. 
 
 " silver, 2 " 
 
 " copper, ' . 1 " 
 
 Total, 9 
 
 " The 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 
 
 " Now, as the gold used is but 22 carats fine, one-twelfth of 
 it is alloy. The one-twelfth 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 6 ounces of pure gold to 16 carats. 
 
ALLOYS OF GOLD FOR DENTAL PURPOSES. 61 
 
 ," The statement is expressed thus : 
 16 : 24 : : 6 : 9. 
 
 " Six subtracted from 9 leaves 3, 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. 
 
 " As another example under the same rule, reduce 1 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 
 
 twenty-two grains of pure gold. The statement is, therefore, 
 
 thus expressed : 
 
 18 : 24 : : 22 : 291 
 
 "Twenty-two subtracted from 29 J leaves 7^. Therefore, 
 each pennyweight of 22 carat gold requires 7^ grains of alloy 
 to reduce it to 18 carats. 
 
 " 3. To reduce gold from a lower 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 expression : 
 
 " 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 applied 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 propor- 
 tion of alloy 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: 
 
 " Reduce 1 pennyweight of 16 carat gold to 18 carats. 
 
 "The numbers representing the proportions of alloy in this 
 
62 MECHANICAL DENTISTRY. 
 
 example are found by respectively subtracting 18 and 16 from 
 24. The statement is, therefore : 
 
 6 : 8 : : 1 : li-, 
 
 from which it follows that to reduce one pennyweight of 16 
 carat gold to 18 carats, there must be one-third of a penny- 
 weight of pure gold added to it. 
 
 " But suppose that, instead of pure gold, we wish to eifect 
 the change by adding 22 carat gold. The numbers, then, 
 respectively representing the proportions of the alloy would 
 be found by subtracting, in the above example, 16 and 18 from 
 22, and the statement would be : 
 
 4 : 6 : : 1 : 11. 
 
 " It follows, then, that to each j^enny weight of 16 carat gold, 
 a half 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." 
 
 To facilitate the student in accurately compounding gold 
 alloys from coins of that metal, the following table, giving the 
 weight in grains, fineness, and the value of the gold coins of 
 different nations, is given in this connection. 
 
ALLOYS OF GOLD FOR DENTAL PURPOSES. 
 
 63 
 
 TABLE OF COINAGE OF DIFFERENT NATIONS. 
 
 ARGENTINE EEPUBLIC. 
 
 Doubloon, Province of Rio de la Plata., 
 Doubloon, Province of Rio dt la Plata., 
 
 The same variation of fineness and weight 
 in coins of the same date are to be found 
 in the silver coinage of this republic. 
 
 AUSTRIA. 
 
 Ducat of Maria Theresa 
 
 Sovereign of Maria Theresa 
 
 Ducat of Leopold II 
 
 Ducat of Francis I 
 
 Quadruple of Francis I 
 
 Sovereign of Francis I 
 
 Sovereign of Ferdinaud I 
 
 Half-sovereign of Ferdinand I 
 
 Ducat of Ferdinand I 
 
 Quadruple of Ferdinand I 
 
 Hungary ducat of Ferdinand I 
 
 BADEN. 
 
 Ten guilder (five guilder same quality) of 
 Louis, Grand Duke 
 
 BAVARIA. 
 
 Ducat of Maximilian Joseph and Charles 
 
 Theodore 
 
 Ducat of Maximilian Joseph II 
 
 Ducat of Louis 
 
 BELGIUM. 
 
 Forty francs 
 
 Twenty francs in proportion, same fine- 
 ness. Sovereigns same as Austrian coin- 
 age. 
 
 BOLIVIA. 
 
 Doubloon 
 
 BRAZIL. 
 
 Moidore of Maria I, and John III 
 
 Half-Joe of Peter II 
 
 The other moidores and half-joes are of the 
 same fineness with the moidore of 1779, 
 varying slightly in weight. 
 
 BRITAIN. 
 
 The gold coins of this kingdom are of the 
 uniform finene.ss of Sl.'j,.'?, but below the 
 legal standard about one thousandth. The 
 par value of the pound sterling is about 
 84.84. Sterling gold is worth 94.6 cents 
 per pennyweight. 
 
 BRUNSWICK. 
 
 X. Thaler of Charles 
 
 X. Thaler of Charles William Ferdinand... 
 X. Thaler of Win. Fred, and George Regent. 
 
 X. Thaler of Charles „ 
 
 X. Thaler of William 
 
 V. Thaler of Charles 
 
 Year. 
 
 :828-32 
 1813-32 
 
 1762 
 1778 
 1790 
 1809-34 
 1830 
 1831 
 1838 
 1839 
 1838 
 1840 
 1839 
 
 1819 
 
 1764-97 
 1800 
 1832 
 
 1779 
 1833-38 
 
 174.') 
 1805 
 18l:i-19 
 1824-30 
 1831-38 
 1748-64 
 
 Weight. Fineness, 
 
 Grains. 
 
 418 
 415 
 
 53.5 
 170 
 
 53.5 
 
 53.7 
 215.5 
 174.5 
 174.5 
 
 87 
 
 53.7 
 215.5 
 
 53.7 
 
 53 
 53 
 53.5 
 
 125.5 
 221.5 
 
 202 
 
 204 
 
 204.5 
 
 205 
 
 205 
 
 102 
 
 Thous. 
 815 
 
 965 
 917 
 986 
 983 
 983 
 898 
 901 
 902 
 985 
 985 
 986 
 
 984 
 987 
 
 914 
 915 
 
 898 
 896 
 896 
 896 
 894 
 903 
 
 14 66 
 
 15 51 
 
 2 23 
 
 2 24 
 2 27 
 
 15 58 
 
 4 94 
 
 8 72 7 
 
64 
 
 MECHANICAL DENTISTRY. 
 
 TABLE OF COINAGE OF DIFFERENT NATIONS {continued). 
 
 CENTKAL AMERICA. 
 
 Doubloons 
 
 CHfLI. 
 
 Doubloons 
 
 Doubloons 
 
 COLOMBIA. 
 
 Doubloon of eight escudos, Colombia, Bogo- 
 
 tan Mint 
 
 Doubloon of eight escudos, Popayan Mint. 
 
 Doubloon of New Granada, Bogota 
 
 Half-doubloon of Ecuador, Quito 
 
 Quarter-doubloon of Colombia, Bogota 
 
 Quarter-doubloon of Ecuador, Quito 
 
 Eighth-doubloon of Colombia, Bogota 
 
 Eighth-doubloon of Colombia, Popayan 
 
 These last coins vary in fineness from 849 
 to 854, and in weight from 44^4 to 613^. 
 The sixteenth-doubloons are of the same 
 quality. 
 
 DENMARK. 
 
 Specie ducat of Frederick V 
 
 Specie ducat of Christian VII 
 
 Current ducat of Christian VII 
 
 Christian d'or of Christian VII 
 
 Double Frederick d'or of Frederick VI 
 
 EGYPT. 
 
 Sequin fundoukli of Achmet III 
 
 .Sequin fundoukli of Malimoud I 
 
 Sequin fundoukli of Mahmoud I 
 
 Sequin fundoukli of Mustapha III 
 
 Sequin fundoukli of Abdul Hamed 
 
 Sequin fundoukli of Abdul Hamed 
 
 Sequin fundoukli of Selim III 
 
 Half-sequin fundoukli of Mahmoud II 
 
 Bedidlik, 100 piastres, of Abdul Majeed 
 
 Nusflix, 50 piastres, of Abdul Majeed 
 
 Kairia Hastreen, 10 piastres, of Abdul 
 Majeed •. 
 
 The first date given above is the year of 
 the Hegira, the second, the Christian era. 
 
 FRANCE. 
 
 Louis d'or of Louis XV 
 
 Louis d'or of Louis XVI 
 
 Double Louis d'or of Louis XV 
 
 Double Louis d'or of Louis XVI 
 
 Napoleon, 20 francs, of Napoleon 
 
 The subsequent gold coinage of France is 
 of the uniform fineness of 899, except 
 the twenty franc pieces of Louis Phil- 
 ippe, coined in 1840-41, which are 900. 
 
 GREECE. 
 
 Twenty drachms of Otho 
 
 Year. 
 
 Weight. 
 
 HANOVER. 
 
 Ducat of George III 
 
 1819-24 
 1835 &seq. 
 
 1823-36 
 
 1823-36 
 1837 
 18.36 
 
 1823-35 
 1835 
 
 1823-36 
 
 1749 
 
 1795-1802 
 
 1783 
 
 1775 
 
 1813-39 
 
 1115(1703) 
 1143(17.30) 
 1143(1730) 
 1171(1757) 
 1187(1773) 
 1187(1773) 
 1203(1789) 
 1233(1818) 
 1255(1839) 
 1255(1839) 
 
 1255 (1889) 
 
 1726-73 
 1786-92 
 1744 
 1786-92 
 1803-14 
 
 1833 
 1776 
 
 Grains. 
 417 
 
 417 
 417 
 
 416.8 
 
 416.5 
 
 416.8 
 
 209 
 
 104 
 
 104 
 
 51 
 
 51 
 
 53.5 
 53.7 
 48 
 
 103 
 
 204.5 
 
 53 
 39 
 39 
 39 
 39 
 39 
 39 
 18 
 
 132.2 
 66.1 
 
 27 
 
 124 
 116.5 
 250 
 235 
 99.2 
 
 Fineness. Value. 
 
 Thous. 
 833 
 
 867 
 872 
 
 870 
 844 
 865 
 844 
 865 
 852 
 
 979 
 876 
 905 
 895 
 
 958 
 940 
 
 848 
 781 
 7H6 
 645 
 690 
 670 
 874 
 875 
 
 897 
 900 
 902 
 901 
 899 
 
 900 
 993 
 
 d. c. m. 
 14 96 
 
 15 57 
 15 66 
 
 15 61 
 15 39 
 15 61 
 
 2 27 
 
 2 26 
 
 1 81 
 
 4 01 
 
 7 88 
 
 1 01 
 
 4 79 
 
 4 51 
 
 9 71 
 
 9 11 
 
 3 84 
 
 3 45 
 
 2 28 8 
 
ALLOYS OF GOLD FOR DENTAL PURPOSES. 
 
 65 
 
 TABLE OF COINAGE OF DIFFERENT NATIONS [continued). 
 
 HANOVER (continued). 
 
 Pistole or five tlialer of George III 
 
 Pistole or five thaler of (ieorge III 
 
 Ten thaler of (ieor^e Id 
 
 Ten thaler of William IV, and Ernst. 
 August 
 
 HESSE. 
 
 Ten thaler of Frederick II 
 
 Five thaler of Frederick II 
 
 Five thaler of William IX 
 
 Five thaler of William I 
 
 HINDOSTAN. 
 
 Mohurof B'Tigal 
 
 Mohur of Bengal 
 
 Mohur of Bengal 
 
 Mohurof Bengal 
 
 Mohur of Madras 
 
 Mohur of Bombay 
 
 Half-raohiir of Bengal 
 
 Star pagoda of Madras 
 
 Pondiclierry pagoda of Pondicherry 
 
 Porto Novo pagoda of Portuguese Company. 
 
 MECKLENBURG SCHWERIN. 
 
 Ten thaler of Frederick Francis.... 
 
 MEXICO. 
 
 Doubloon of Mexico, Augustin, Emperor... 
 Doubloon of Mexico, Mexican Republic 
 
 Other doubloons minted at Mexico weigh 
 417 grains, and are from 867 to 869 ihou- 
 sandthsfioe. The doubloon of Guanaxu- 
 ato varies from 860 to 867 in fineness. 
 
 Doubloon of Durango 
 
 Doubloon of Durango 
 
 Doubloon of Durango 
 
 Doubloon of Guadalaxara. 
 
 MILAN. 
 
 I Zecchino, or Sequin, of Maria Theresa and 
 
 Joseph II 
 
 I Doppia, or Pi.slole, of Joseph II 
 
 j Forty lire of Napoleon 
 
 Sovereign of Francis I 
 
 Sovereign of Ferdinand I 
 
 Half-sovereign 
 
 NAPLE.S AND SICILY. 
 
 Six ducat, of Ferdinand IV 
 
 Onzia of .'^icily of Charles 
 
 Onzia of Ferdinand I 
 
 Twenty lire of Joachim Napoleon. 
 
 NKTHEBLAKDS. 
 
 Ducat I 1770-1810 
 
 Ducat of Williiim 1 
 
 Ten guilders of William I 
 
 Year. 
 
 Weight. 
 
 
 Grains. 
 
 1803 
 
 102 
 
 1813-14 
 
 102 
 
 181H-14 
 
 204.5 
 
 1835 &seq. 
 
 205 
 
 1773-8.5 
 
 202 
 
 1771-84 
 
 101 
 
 1788-89 
 
 101.5 
 
 1815-17 
 
 101.5 
 
 1770 
 
 190 
 
 1787 
 
 191 
 
 1793 
 
 191 
 
 1818 
 
 204.7 
 
 1818 
 
 180 
 
 181H 
 
 179 
 
 1787 
 
 9.5 
 
 
 52.5 
 
 
 52.5 
 
 
 52.5 
 
 1831 
 
 204.5 
 
 1822 
 
 416.5 
 
 1824-30 
 
 416.5 
 
 1 
 
 1 
 
 
 1 
 417 1 
 
 
 417 j 
 
 1833-36 
 
 417.5 
 
 
 416 ! 
 
 i 
 
 1770-84 
 
 53 5 
 
 1783 
 
 97.5 
 
 180.5-14 
 
 199 
 
 1831 
 
 174 5 
 
 1838 
 
 174.5 
 
 1839 
 
 87 
 
 1783 
 
 135 
 
 1751 
 
 68 
 
 1K18 
 
 68 
 
 . 1813 
 
 99 i 
 
 1770-1810 
 
 1 
 53.5 ' 
 
 183:i-39 
 
 53.7 
 
 1816-b9 
 
 103.5 
 
 Fineness. 
 
 Thous. 
 
 896 
 
 . 890 
 
 890 
 
 895 
 
 890 
 893 
 892 
 894 
 
 982 
 989 
 993 
 917 
 917 
 920 
 984 
 800 
 708 
 740 
 
 864 
 
 865 
 
 872 
 805 
 
 990 
 908 
 S99 
 898 
 901 
 902 
 
 893 
 9.59 
 995 
 900 
 
 980 
 981 
 899 
 
 Value. 
 
 d. c. m. 
 
 3 93 6 
 
 3 91 
 
 7 83 8 
 
 7 74 2 
 
 3 88 4 
 
 3 89 9 
 
 3 90 8 
 
 8 03 
 8 13 
 8 16 
 
 2 28 
 
 3 81 
 
 6 74 
 6 77 
 
 15 49 8 
 15 51 6 
 
 15 58 8 
 
 15 53 4 
 
 15 67 9 
 
 15 49 7 
 
66 
 
 MECHANICAL DEKTISTEY. 
 
 TABLE OF COINAGE OF DIFFERENT NATIONS (continued). 
 
 PERSIA. 
 
 Toman of Fatha Ali Shah, Eajar \ 
 
 Toman of Mohammed Shah, Shakinshah... 
 Half-toman of Mohammed Shah 
 
 POLAND. 
 
 Ducat of Stanislaus Augustus 
 
 PORTUGAL. 
 
 Moidore of Peter II 
 
 Moidore of Peter II 
 
 Moidore of John V 
 
 Half-joe 
 
 Half-joe of Maria I, and Peter III 
 
 Half-joe of Maria I 
 
 Half-joe of John VI 
 
 Joannese of John V 
 
 Crown of Maria II 
 
 PRUSSIA. 
 
 Frederick d'or of Frederick II 
 
 Frederick d'or of Fi-ederiek William II 
 
 Frederick d'or of Frederick Wilhelm III... 
 Double Frederick d'or of Fred.Wilhelm III. 
 Double Frederick d'or of Fred.Wilhelm III. 
 Ducat of Frederick William II 
 
 ROME. 
 
 Sequin of Pius VI 
 
 Doppia of Pius VI 
 
 Doppia of Pius VII 
 
 Gold scudo of Republic 
 
 Ten scudi of Gregory XVI 
 
 RUSSIA. 
 
 Imperial of Elizabeth 
 
 The gold coins of Russia, though irregular 
 in weight, are of the same standard fine- 
 ness during the reigns of Elizabeth and 
 Catharine II. 
 
 Ducat of Paul I 
 
 Three roubles of Nicholas 
 
 Half-imperial of Nicholas 
 
 SARDINIA. 
 
 Pistole of Victor Amadeus, etc 
 
 Carlino (island) of Victor Amadeus, etc 
 
 Marengo of Republic 
 
 Eighty lire 
 
 Genovine of Ligurian republic (Genoa) 
 
 SAXONY. 
 
 Double August d'or of Fred. August. III... 
 Double August d'or of Fred. August. HI... 
 
 Double Anton d'or of Anthony 
 
 Ducat of Anthony 
 
 Year. 
 
 Weight. 
 
 
 Grains. 
 
 1230-40 
 
 (1814-24) 
 
 1255(1839) 
 
 1252(18.37) 
 
 71.2 
 53.7 
 27 
 
 1791 
 
 53.5 
 
 1689 
 
 1705 
 
 1714-26 
 
 1727-77 
 
 1778-85 
 
 1787-1804 
 
 1822-24 
 
 1730 
 
 1838 
 
 165 
 165 
 165 
 217 
 220 
 221 
 221 
 439 
 148 
 
 1752-82 
 
 1795-96 
 
 1799-1812 
 
 1800-11 
 
 1831 
 
 1787 
 
 102 
 102 
 102 
 205 
 205 
 53.5 
 
 1775-83 
 1777-86 
 
 1799 
 1836 
 
 525 
 
 84 
 
 84.5 
 910 
 267.5 
 
 1756 
 
 253 
 
 1798 
 1838 
 1839 
 
 66 
 60.5 
 100.5 
 
 1773 
 1800 
 
 1798 
 
 148 
 247 
 98 
 398 
 888 
 
 1784-1817 
 
 1826 
 
 1830-36 
 
 1830 
 
 204.5 
 205 
 205 
 53.7 
 
 Fineness. 
 
 Thous. 
 
 991 
 966 
 9ii8 
 
 928 
 913 
 914 
 913 
 914 
 909 
 912 
 912 
 
 901 
 897 
 91)1 
 898 
 903 
 979 
 
 996 
 906 
 901 
 833 
 900 
 
 915 
 
 969 
 
 917 
 917 
 
 905 
 890 
 
 900 
 979 
 
 Value. 
 
 6 45 
 
 6 59 
 
 6 48 
 
 8 62 
 
 8 65 
 
 8 69 
 
 8 65 
 
 17 24 
 
 5 81 
 
 2 25 
 
 3 27 
 3 27 
 
 32 64 
 
 10 36 
 
 9 97 
 
 2 75 4 
 
 2 38 9 
 
 3 96 9 
 
 5 76 
 
 9 46 
 
 3 79 
 
 15 39 
 
 15 17 
 
 7 89 1 
 
 7 92 8 
 
 7 94 6 
 
 2 26 4 
 
AI LOYS OF GOLD FOR DENTAL PURPOSES. 
 
 67 
 
 TABLE OF COINAGE OF DIFFERENT NATIONS (continued). 
 
 Cob doubloon of Philip V, American 
 
 Doubloon of Ferdinand VI, American 
 
 Doubloon of Charles III, AiuericaD 
 
 Doubloon of Charles III, Spanish 
 
 DoublooQ of Charles IV, and Ferdinand 
 
 VII, American 
 
 Pistole of Philip V, Spanish 
 
 Pistole of Charles III, American 
 
 Pistole of Ferdinand VII, American 
 
 Escudo of Charles III, Spanish 
 
 Escudo of Charles IV 
 
 Escudo of Ferdinand VII, American 
 
 Half-doubloon of Charles III, Spanish 
 
 Half-doubloon of Charles IV, American.... 
 Ualf-doubloon of Ferdinand VII, Spanish. 
 
 SWEDEN. 
 
 Ducat of Gustavus III, and Gustavus IV... 
 Ducat of Charles John XIV 
 
 SWITZERLAND. 
 
 Pistole of Berne 
 
 Pistole of Basle 
 
 Pistole of Soleure 
 
 Pistole of Helvetian Republic 
 
 Ducat of Berne 
 
 Ducat of Basle 
 
 TUNIS. 
 
 Half-sequin of Abdul Hamed 
 
 TURKEY. 
 
 Sequin fondouk of Selim III 
 
 Sequin zermahboub of Selim III 
 
 Obikilik of Mahmoud II 
 
 Twenty piastres, of Mahmoud II 
 
 Yirmilik, 20 piastres of Abdul Medjid 
 
 TUSCANY. 
 
 Ruspone of Francis III, to Leopold III 
 
 Ruspone of Louis I, and Charles I 
 
 Ruspone of Leopold II 
 
 Sequin of Leopold 
 
 Sequin of Leopold II 
 
 UNITED STATES. 
 
 Eagle 
 
 Eagle 
 
 Eagie 
 
 WURTEMBERO. 
 
 Ducat of Charles 
 
 17.3.3-44 
 
 17.51 
 1772-84 
 1786-88 
 
 1789-1821 
 
 174.5 
 
 1774-82 
 
 1813-24 
 
 17S6-88 
 
 1789-1808 
 1809-20 
 1780-82 
 
 1789-1808 
 1810-24 
 
 1777-1800 
 1838 
 
 Weight, 
 
 Grains, 
 
 416 
 416 
 416 
 416 
 
 416.5 
 103 
 103 
 104 
 
 52 
 
 52 
 
 52 
 206 
 208 
 208 
 
 17961 116 
 1795 118 
 
 1798, 
 1800 
 1794 
 
 1789 
 1789 
 1822-24 
 1827 
 1840 
 
 1738-1800 
 1801-07 
 1824-34 
 1765-79 
 1824-34 
 
 1792-18341 
 
 1834-371 
 
 1837 &seq. 
 
 116 
 116 
 
 52.5 
 
 53 
 
 1773 19 
 
 52.5 
 
 36 
 
 25 
 
 27.5 
 
 24.5 
 
 160 
 161 
 161 
 
 53 
 
 53.5 
 
 270 
 258 
 258 
 
 53 
 
 Fineness, 
 
 Thous. 
 
 895* 
 908 
 843t 
 890 
 
 909 
 895 
 872 
 874 
 868 
 851 
 896 
 870 
 865 
 
 977 
 975 
 
 901 
 891 
 898 
 897 
 974 
 943 
 
 800 
 800 
 833 
 875 
 832 
 
 997 
 998 
 999 
 997 
 999 
 
 916.7 
 899.2 
 900 
 
 980 
 
 Value, 
 
 d. c. m. 
 
 16 03 4 
 
 16 26 5 
 
 16 00 
 
 15 58 7 
 
 15 57 
 
 10 67 
 9 99 
 10 
 
 1 80 9 
 1 24 
 
 89 7 
 
 1 03- 7 
 
 87 7 
 
 * Varies from 893 to 898. t Varies from 883 to 893, the oldest pieces being the best. 
 
MECHANICAL, DENTISTRY. 
 
 CHAPTER V. 
 
 Method of Converting Gold Alloys into the Re- 
 quired Forms for Dental Purposes, 
 
 Manner ofProeuring an Ingot. — The gold, with its alloying 
 constituents, 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 moulds ; 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 moulds, if made of iron, should be 
 moderately heated and oiled, or coated with lamp-smoke by 
 
 Fig. 22. 
 
 holding their inner surfaces over the flame of an oil-lamp or 
 gas-jet. 
 
 Ingot-moulds are constructed of various substances, but 
 those in most common use, and, at the same time, most conve- 
 nient, are formed of iron, and, for gold, are generally about 
 two inches square and from one-eighth to one-sixth of an inch 
 thick. (Fig. 22.) They should be slightly concave on their 
 
CONVERTING GOLD ALLOYS INTO REQUIRED FORMS. 69 
 
 inner surfaces to compensate for the greater shrinkage of the 
 gold in the centre than at the margins of the ingot. 
 
 A very ingenious, convenient, and useful contrivance, com- 
 bining crucible and ingot-mould, and by the use of which in- 
 gots of gold, silver, etc., may be quickly 
 obtained without the use of a furnace, is fig. 23. 
 
 shown in Fig. 23. The crucible (A) is of 
 moulded carbon, and is supported in position 
 by an iron side-plate. The ingot mould is 
 indicated by the letter C. The letter D 
 shows clamp holding crucible and ingot 
 mould in position, and swivelling on the cast-iron stand, B. 
 
 The metal to be melted is placed in the crucible, and the 
 flame of a blowpipe is directed on it until it is perfectly fused. 
 The waste heat serves to make the ingot mould hot, and the 
 whole is tilted over by means of the upright handle at the 
 back of the mould. With this simple instrument a sound 
 ingot may be obtained at any time in about two minutes. 
 
 Soapstone is sometimes employed for the same purpose, and 
 is preferred by many. It should also be warmed and oiled 
 before pouring the metals. Moulds made from charcoal are 
 also sometimes used, but, as they require to be frequently 
 renewed, are not generally employed. Moulds are formed 
 from this latter substance by selecting two pieces with even 
 surfaces or dividing a single piece with a saw, when either the 
 required size and shape of the mould may be cut out in one 
 half, or a strip of sheet-iron a little broader than the required 
 thickneas of the iugot, being bent into proper form, is placed 
 between, and the edges partially iml>edded in the two pieces of 
 charcoal, and the latter secured by binding them together with 
 wire. Moulds made from this material do not require to be 
 either heated or oiled. 
 
 It not unfrequently 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 remain- 
 ing above. Whenever this occurs the ingot must be broken 
 
70 
 
 MECHANICAL DENTISTEY. 
 
 into pieces and remelted ; this should be repeated, if necessary, 
 until the alloy assumes a perfectly homogeneous appearance. 
 It should then be annealed in hot ashes, which softens the 
 gold and removes the adhering grease. 
 
 Forging. — Before laminating the ingot it 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 
 frequently annealed, and the process of forging continued, 
 alternately 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 
 thinness by passing it repeatedly between two strong, highly- 
 
 Fltt. 25. 
 
 polished, cylindrical steel rollers. The mills used for the pur- 
 pose are variously constructed, the plainest forms (Fig. 24) be- 
 ing very simple in their mechanism, while others, or geared 
 mills, are more complicated, and are constructed with a view 
 to a greater augmentation of power, and precision, and cer- 
 tainty of action. The latter (Figs. 25, 26), if of approved pat- 
 tern, materials, and manufacture, are, upon the whole, more 
 economical and reliable than the cheaper varieties. The rollers, 
 for the purposes of the dentist, should be from three to four 
 inches in length. 
 
COXVERTING GOLD ALLOYS INTO REQUIRED FORMS. 71 
 
 In laminating, the rollers should first be adjusted equidis- 
 tant at both ends, and this uniformity, as they are approxi- 
 mated from time to time, should be preserved throughout. 
 At every passage of the gold bar between the rollers the dis- 
 tance between the latter should be diminished, care being taken 
 that the approximation be not sufficient to clog or impede the 
 
 Fig. 26. 
 
 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 opera- 
 tion in the press. 
 
 When the ingot has been extended in one direction as far 
 as may be desired, it should always be re-annealcd before 
 
72 
 
 MECHAlvICAL PENTTIBTEY. 
 
 FiG- 27. 
 
 tamino:: it in the mills ; a neglect of this precaution will seri- 
 ously interfere with the working of the gold by twisting or 
 doubling the plate upon itself; and in some instances, pro- 
 vided the gold has not been well annealed throughout the 
 operation, or is in any considerable degree unmalleable, the 
 plate wiD be torn across and rendered unfit for use. 
 
 A thin or retreating edge may be given to the plate at any 
 desired point or points by passing such portions part way 
 between the rollers and withdrawing ; repeating this, with the 
 rolleis brought a little nearer to each other every time the plate 
 is introduced between them, and decreasing the distance the 
 plate passes each time until it is reduced to as thin an edge as 
 may be d^ired. 
 
 The degree of attenuation obtained by rolling is determined 
 
 by what is called a gauge-plate, 
 (Fig. 27.) Tills instrument is 
 usually circular or oblong in form, 
 and is marked at intervals on its 
 edge by cross-cut grooves or fis- 
 '^-i sures, which successively dimin- 
 ish in size and are indexed by 
 numbers ranging from 6 to 40. 
 The size of the grooves diminish 
 with the ascending numbers. 
 During the operation of rolling, 
 the plate should be tested, from time to time, by the gauge, to 
 determine when it has undergone sufficient attenuation. 
 
 Thichiess of Gold Plate required as a Base for Artificial 
 BaitureB. — ^In prescribing the thickness of plate proper for 
 the puq>ose indicated, no estimate can be given that will 
 apply to all cases, as certain conditions of the mouth, to be 
 mentioned hereafter, will suggest some modifications in this 
 lespect. Usually, however, plate for entire upper sets should 
 correspond in thickness with number 26 of the gauge-plate ; 
 for the under jaw, number 24 may be used ; while for partial 
 upper pieces, an intermediate number may be chosen, unless 
 
CONVERTING GOLD ALLOYS INTO REQUIRED FORMS. 73 
 
 atmospheric-pressure plates are used, when the number recom- 
 mended for full upper sets may be employed. 
 
 Thickness of Plate for Clasps, Stays, etc. — Plate for these 
 purposes should correspond with from 20 to 22 of the gauge ; 
 a less amount of substance, as before stated, being required 
 when the alloy has incorporated with it a small proportion of 
 platinum. 
 
 lied action 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 com- 
 pletely fused, and then instantly poured to prevent undue 
 wasting of the base metals by a too protracted heat. 
 
 The solder should be reduced to plate somewhat thinner 
 than that used for upper sets, 28 of the gauge-plate. It is 
 customary sometimes to roll the solder into very thin rib- 
 bons, but this is objectionable for the reason that a greater 
 amount of the alloying metals being exposed in a given sur- 
 face to the action of the heat in soldering, are burnt out or 
 oxidated, whicli interrupts the flow and weakens the attach- 
 ment between the solder and plate. / 
 
 Method of Obtaining Gold Wire. — To convert gold or its 
 alloys into the form of wire, the operator should be provided 
 with a draw-plate, a vice, and a pair of hand-pincers. A 
 draw-plate (Fig. 28) is an oblong piece of steel pierced with a 
 regular gradation of holes, or a series of progressively dimin- 
 ishing 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 is last drawn. The holes are 
 formed with a steel punch, and are enlarged on the side 
 where tlie wire enters and diminish with a gradual taper to 
 the other side. A draw-bench is sometimes employed in ex- 
 tending the wire, the power being applied by a toothed wheel, 
 pini<;n, and rack-worK, and is moved by the hands of one or 
 two persons. For the purposes of tlie dentist, however, it 
 will be sufficient to fix the draw-plate securely between the 
 
74 MECHANICAL, DENTISTRY. 
 
 jaws of a bench-vice, and, by seizing hold of one end of the 
 gold rod with a strong pair of clamps or hand-pincers, serrated 
 or cut like a file on the inside of the jaws, the wire may be 
 drawn steadily through the plate, passing from the larger to 
 the smaller holes until a wire of the required size is obtained. 
 
 
 
 
 Fig. 28. 
 
 
 
 
 
 6'.v 
 
 5^ 
 
 VV 
 
 fc-^^ 
 
 
 
 ^,^ 
 
 .) 
 
 
 
 c) 
 
 Cv 
 
 0O 
 
 • 
 
 ^) 
 
 '<.•) 
 
 I • 
 
 k)© 
 
 <^ 
 
 ^ 
 
 (!J>C 
 
 '^^ 
 
 «® 
 
 ■d^gss- 
 
 In drawing the wire, the motion should be steady and uni- 
 form, 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 re- 
 ducing 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 
 the mouth, and as all the principal dental furnishing houses 
 are suppled with these appliances already prepared for use, 
 the author does not deem it necessary to enter into a descrip- 
 tion of the various apparatuses used in making them. 
 
 The following simple contrivance will meet the limited re- 
 quirements of those who are obliged or prefer to manufacture 
 
CONVERTING GOLD ALLOYS INTO REQUIRED FORMS. 75 
 
 their own springs. The wire, obtained as already described, 
 is held between two blocks of wood fastened between the jaws 
 of a bench-vice. By means of a small hand-vice, one end of 
 the wire is clamjied to a uniformly cylindrical and well-tem- 
 pered steel rod or wire four or six inches long, and about the 
 size of a small knitting needle, and which being made to re- 
 volve while resting on the blocks of wood, the wire is wound 
 firmly and compactly around it, producing a uniform coil. 
 
76 MECHANICAL DENTISTRY. 
 
 CHAPTER yi. 
 
 Silver. 
 
 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 ; but when hammered or condensed 
 in the coining press, its density is increased, and its specific 
 gravity becomes 10.6. It fuses at an extreme red heat, gener- 
 ally estimated at 1.873° Fahrenheit. It is remarkably lamin- 
 able and ductile; yielding leaves not more than _-j_'__^ 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 respect. 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 ex- 
 posure to sulphuretted hydrogen. The sulphuret of silver 
 thus formed may be easily removed by rubbing the metal with 
 a solution of cameleon mineral, prepared by calcining equal 
 parts of black or peroxide of manganese and nitre. Unlike 
 gold and platinum, it is readily soluble in nitric acid ; this and 
 sulphuric acid being the only simple ones that dissolve it. 
 Silver becomes very brilliant when heated ; boils and vaporizes 
 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, duc- 
 tility, 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, 
 
SILVER. 77 
 
 platinum, iridium, steel, manganese, and mercury, also form 
 alloys with silver. 
 
 An alloy of nine parts of silver and one of copper is the 
 Government standard of the United States coinage since 1837. 
 To this, three-cent pieces form an exception; these being com- 
 posed of three parts silver and two of copper. The coins of 
 silver having a greater average fineness than those of <Hir own 
 country, are Brazil, Britain, Chili, France, Greece, Hindostan, 
 Persia, Portugal, Rome, and Tuscany. A common impression 
 prevails that the Mexican silver coin contains more than an 
 average percentage of silver, and is therefore sought after on 
 account of its supposed purity. This is true of some pieces 
 coined at different periods, but the average fineness of the 
 Mexican, as well as Spanish coins, is exceeded by those of the 
 United States mints. 
 
 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 debased, 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 entertainerl but 
 that, under the favoring conditions which usually exist in the 
 mouth, the evils accruing, 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 practicable 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 tendency 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 
 chloride of soda, or common salt, or by scrubbing it with aqua 
 
78 MECHANICAL DENTISTEY. 
 
 ammonia, which removes the superficial particles of copper, and 
 exposes a surface of fine silver. When platinum 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 sufficiently inflexible 
 and elastic. From three to five grains of platinum 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. 
 
 Formulas for Silver Solders. — Silver solders are usually 
 composed 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 also be used for the same 
 purpose. 
 
 Formula No. 1. Formula No. 2. 
 
 Silver, . . 66 parts. Silver, . . 6 parts. 
 
 Copper, . . 30 " Copper, . . 2 " 
 
 Zinc, . . 10 " Brass, . . 1 " 
 
 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 afterwards added, when 
 they should be quickly poured to prevent undue waste, by 
 oxidation, of the more fusible com23onent. The ingot when 
 cold, should be rolled into a plate a little thicker than that 
 recommended for gold solder. 
 
PLATINUM AXD THE PLATINOID METALS. 
 
 CHAPTER VII. 
 
 Platinum and the Platinoid Metals. 
 
 Platinum is a grayish-white metal, resembling in some 
 measure polished steel. It is harder than silver, and has a 
 density greater than any other known metal, its specific gravity 
 beino- 21.25. It remains unaltered in the highest heat of a 
 smith's forge, and can only be fused by means of the oxy- 
 hydrogen blow-pipe 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 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 
 the two-thousandth 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. 
 
 Platinum is very soft and flexible, and when rolled into 
 thin sheets, say 28 or 30 of the gauge-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 following interesting and practical observations on the 
 method of melting and welding platinum scraps are taken 
 from a recent dental publication,* by E. A. L. Roberts. By 
 this process, the operator will be enabled to re-convert his 
 wa-ste scraps of platinum into convenient forms for use, and 
 which he could not otherwise avail himself of 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 
 
 * Dental Instructor, vol. i, p. 10. 
 
80 MECHANICAL DENTISTRY. 
 
 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 delicacy of this process, and the uncer- 
 tainty of success, has led some writers to declare that platinum 
 is incapable of being welded. The platinum must be per- 
 fectly 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 ham- 
 mer. 
 
 "The scraps or sponge should be condensed in a square 
 mould, very compactly, two pieces of which, weighing from ten 
 to twenty ounces, may be put into 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 manner, and thus alternately till both 
 are thoroughly welded. 
 
 " We use one of our improved tooth -furnaces of the largest 
 size, fourteen by ten inches, inside measure. 
 
 " Platinum should never be thrown into water while hot, 
 as that tends to make it crystallize. It should be thoroughly 
 hammered, as it 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 mould. Lay the con- 
 densed mass on a concave tire-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 the globules and 
 other loose particles of the metal. Place it under the jet of 
 the oxy-hydrogen blowpipe, in the following manner : 
 
PLATINUM AND THE PLATIXOID METALS. 81 
 
 " The pan is provided with a handle, opposite to which is a 
 ring, which is to be attached to an iron hook and rod, sus- 
 l^ended from the ceiling by a slip of india-rubber, which en- 
 ables the operator to hold the pan conveniently at any distance 
 from the jet of the burning gases. The hydrogen is first 
 lighted, and gives a powerful flame, but as the oxygen com- 
 bines 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 towards 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 
 continuatior; of this process renders it soft, tough, and fibrous. 
 When reduced to the width desired, and to the thickness of 
 one-fourth of an inch, it should be made very hot, and passed 
 instantly through the rollers." 
 
 Platinum, in mechanical practice, is chiefly employed as a 
 base for continuous gum work ; it is also used as a coloring 
 ingredient of porcelain, and for pins in the manufacture of 
 mineral teeth ; and, to a limited extent, in some of the minor 
 operations of the shop. 
 
 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 
 depending on the quantity of gold added. Silver hardens it, 
 the resulting alloy being unaffected by sulphur. 
 
 Platinoid 3fetals. — 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 is the only one that 
 has been used for dental purposes, and that only to a limited 
 extent. It is of a steel-gray color, and when planished, is a 
 
82 MECHANICAL DENTISTEY. 
 
 brilliant steel- white metal not liable to tarnish in the air. 
 Though closely resembling platinum, it may be readily distin- 
 guished from the latter metal, by the following tests: 1. It 
 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 resumes its original lustre. 3. When a drop of the 
 tincture of iodine is let fall upon its surface and evaporated 
 over the flame of a lamjD, a black spot remains, which does 
 not occur with platinum. Palladium melts at about 9500° 
 Fahrenheit, and does not oxidize at a white heat. Its specific 
 gravity is from 11.8 to 12.14. 
 
ALUMINUM. 83 
 
 CHxlPTER YIII. 
 
 Aluminum. 
 
 Aluminum is the metallic basis of alumina, the latter being 
 the characteristic ingredient of common clay. It is only within 
 the past few years that the attention of chemists has been di- 
 rected to the production of this remarkable 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 quantities produced and the corresponding exorbitant 
 prices it commanded, rendered it entirely unavailable for other 
 purposes than merely scientific experiment. The improve- 
 ments in the methods of obtaining it, however, which have 
 been recently introduced, cannot fail, by rendering its produc- 
 tion more economical, to supply it in much larger quantities 
 and at a corresponding reduction in the cost of the metal. 
 
 The following account of the properties of this metal is 
 taken from a paper read before the Society of Arts, London, 
 by its Secretary, P. Le Xeve Foster. It embodies the most 
 authentic and complete description of the properties of alu- 
 minum that has yet been published. 
 
 "One of the most striking properties of aluminum is its ex- 
 treme lightness, its specific gravity being 2.6, nearly that of glass, 
 whilst that of platinum is 21.5, gold 19.5, silver 10.5, copper 
 8.96, zinc 7.2, tin 7.3. 
 
 "The metal is malleable, ductile, almost without limit; it 
 can be reduced to very thin sheets, or drawn into very fine 
 threads. Its tenacity, though su])erior to that of silver, is less 
 than that of copper ; but no very accurate experiments have 
 been made in this respect. 
 
84 MECHANICAL DENTISTRY. 
 
 "When pure it is about as hard as silver. Its elasticity is 
 not great. It files readily, and is said not to injure the file. 
 It conducts electricity with great facilty, so that it may be con- 
 sidered as one of the best conductors known, almost equal in 
 this respect to silver, and more than eight times a better con- 
 ductor than iron. It melts at a temperature a little above that 
 of zinc, between zinc and silver. In its chemical qualities it 
 would seem to take an intermediate rank between whatjare 
 termed the noble metals and the common metals, being, as 
 Deville states, one of the most unalterable of metals. 
 
 "It might be imagined that it would as readily reassume 
 its oxygen as it parted with it with difficulty when in its state 
 of oxide. This, however, is not the case; it appears to be as 
 indifferent to oxygen as either platinum or gold. In air and 
 in oxygen it undergoes no sensible alteration, and it even re- 
 sists it at the highest temperature which Deville could produce 
 in a cupelling furnace, a temperature higher than that em- 
 ployed in assaying gold. Water has no action, according to 
 Deville, on aluminum, neither at its ordinary temperature, nor 
 when boiling, nor even upon the metal at a low red heat, near 
 its melting-point. J^ccording to Professor Grace 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 affected by sulphur or 
 sulphuretted hydrogen, like silver, nor is it acted upon to any 
 considerable degree by any of the oxy-acids 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 aluminum, plunged in sulphuric acid for three 
 months, remained apparently unaltered. The vegetable acids, 
 such as acetic, oxalic, and. tartaric acids, have scarcely any 
 efiect on it at all. The true solvent of the metal is hydro- 
 chloric acid, which attacks it rapidly. It appears to resemble 
 tin when brought into contact with hydrochloric acid and the 
 chlorides. Its absolute harmlessness permits of its being em- 
 ployed in a vast number of cases where the use of tin would 
 
ALUMINUM. 85 
 
 not be desirable on account of the extreme facility with which 
 that metal is dissolved in the organic acids. 
 
 "Figuier, in his scientific Year Book for 1858, just pub- 
 lished, states that the caustic alkalies, potash, and soda, and 
 even ammonia, dissolve aluminum sensiljly. He also states 
 that common salt and acetic acid (vinegar), especially when 
 mixed, attack and dissolve aluminum. He adds, that the mix- 
 ture of salt and vinegar for seasoning a salad, made in a spoon 
 of aluminum, feebly but inevitably attacks it. 
 
 "All these points, however, deserve to be inquired into, as 
 there seems some discrepancy between different writers on 
 them." 
 
 Alloys. — " Aluminum, like iron, does not unite with mer- 
 cury, and scarcely at all with lead. It, however, forms a 
 variety of alloys with other metals. It can be alloyed with 
 iron, and when aluminum becomes clieaper, it will be curious 
 to see what effect mixtures of this metal with iron will have 
 upon its quality, whether for good or for evil. It seems to 
 unite readily with zinc, and these have been found to give the 
 best promise as solders for aluminum; but, unfortunately, 
 when melted, neither of them are sufficiently liquid, and does 
 not run readily. The joints will not bear a blow. A variety 
 of alloys with nickel have been made, and that consisting of 
 100 parts of aluminum and 3 of nickel, is found to work 
 readily, and to have gained hardness 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 aluminun), 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 [tah gold. Alloys of copper with five and 
 ten per cent, of aluminum, resemble gold perhaps more than 
 any other metallic alloy hitherto employed. They do not tar- 
 nish sensibly by exposure to the air. xVluminum can be de- 
 
86 MECHANICAL DENTISTEY. 
 
 posited by the battery, and by the same agent it can be gilt 
 or silvered." 
 
 Some attempts have been made to render aluminum availa- 
 ble as a base for artificial teeth, but with only partial success. 
 When in the form of plate, no suitable solder has yet been dis- 
 covered by which the several parts of a dental appliance may 
 be securely united to each other ; and experiments in casting 
 this metal have practically failed, owing to its extreme lightness 
 and consequent want of fluidity, and great contraction. More 
 experience in its proper management, and a further acquaint- 
 ance with its capabilities in yet unknown forms of combina- 
 tion with other metals, may ultimately demonstrate its general 
 applicability to dental purposes. 
 
 At the present time, its use is rarely attempted except as a 
 base in connection with rubber or celluloid, the latter sub- 
 stances being employed as a means of attaching teeth by a 
 method similar to that described in another place when gold or 
 silver plate is used. 
 
COPPER. 87 
 
 CHAPTER IX. 
 
 Copper, Zixc, Lead, Tin, Antimony, and Bismuth. 
 
 COPPER. 
 
 Copper is one of the metals most anciently known ; is of a 
 brownish-red color, with a tinge of yellow ; has a faint but 
 nauseous and disagreeable taste, and imparts, Avhen 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. Cop- 
 per melts at 1996° Fahrenheit. 
 
 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 
 distinctive 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 propor- 
 tion to form speculum metal (9 C — 1 T), forms an alloy dis- 
 tinguished for its extreme 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 or ductile, be- 
 comes eminently tough and rigid. Other prominent examples 
 might be given, showing how completely this combining influ- 
 ence defies all calculations in regard to ultimate results. The 
 following summary embraces the names and composition of 
 the more familiar alloys of copi)er, omitting, as unnecessary in 
 this connection, a description of their individul properties. 
 
88 MECHANICAL, DEJSTTISTEY. 
 
 Alloys of. Copper with Zinc. — Brass is an alloy of uncertain 
 and variable composition, consisting usually, however, of 2 to 
 5 parts of copper and one of zinc. Brass melts at 1869° 
 Fahr. Prince's metal, and its allied compounds. Pinchbeck, 
 Similor, and Ifanheim gold, consist 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 obtained, is formed of 11 parts of 
 copper with 2 of zinc. Bath metal is composed of 32 parts of 
 brass and 9 of zinc. 
 
 Brass solder consists of 2 parts of brass and 1 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 10 of tin. 
 Cymbals and gongs contain 100 parts of copper and 25 of tin. 
 Speculum metal consists of two parts of copper and 1 of tin. 
 
 Copper and arsenic form a white-colored alloy, and in the 
 proportion of 9 parts of copper and 1 of arsenic, is white, 
 slightly ductile, and is denser and more fusible than copper. 
 
 Genuine German silver is composed of copper, 40.4 ; Jiickel, 
 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. 
 
 Chinese pachfong consists of 5 parts of copper alloyed with 
 7 parts of nickel and 7 parts of zinc. 
 
 A very useful alloy, employed in making plummer blocks, 
 bushes, and steps for the steel and iron gudgeons and pivots of 
 machinery to run in, is said to consist of 90 parts of copper, 5 
 of zinc, and 5 of antimony. 
 
 ZINC. 
 
 Zinc is a bluish-white metal, possessing considerable lustre 
 when broken across. The commercial variety is always im- 
 pure, containing traces of iron, lead, cadmium, arsenic, carbon, 
 etc. It does not easily tarnish in dry air, but soon becomes 
 dull on exposure to moisture. In the condition in which it 
 
LEAD. 89 
 
 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°, at which temperature it may be rolled into 
 sheets, and retain its malleability when cold. The best anneal- 
 ing temperature for zinc is about 245°. 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 specific gravity of zinc varies from 6.9 to 7.2. It 
 melts at about 773°, and Avhen heated much above this point 
 with contact of air, it burns with a brilliant greenish-white 
 flame, while woolly-looking flocculi rise from the vessel in 
 which it is being heated and float in the air. 
 
 Zinc has been long and almost exclusively employed in the 
 formation of dies used in swaging metallic plates employed 
 in mounting artificial teeth, and experience has very justly 
 accorded to it undisputed pre-eminence above all other unal- 
 loyed 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. 
 
 LEAD. 
 
 Lead has a grayish-blue color, with a bright metallic lustre 
 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. It fuses at 612°. Exposed to a high heat, 
 it absorbs oxygen rapidly, forming on its surface a gray film 
 of protoxide and metallic lead. It is both malleable and duc- 
 tile, but soft and perfectly inelastic. 
 
 Lead, either in its pure state or when alloyed with certain 
 other metals, serves important purposes in the laboratory. In 
 its simple or uncombined state it is useful only in forming 
 counter-dies. Alloyed with antimony in the proportion of 
 from ^ to J of the latter, with the addition sometimes of very 
 
90 MECHANICAL DENTISTRY. 
 
 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 used as a counter 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. 
 
 The alloy known as Rose's fusible metal is composed of 2 
 parts of bismuth to 1 of lead, and 1 of tin, and melts at about 
 200°. A still more fusible alloy is composed of lead 3 parts, 
 tin 2 parts, and bismuth 5 parts, which fuses at 197°. There 
 are other alloys of lead, to be mentioned 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 adap- 
 tation to the mouth. 
 
 Soft solder is an alloy composed of lead and tin in the pro- 
 portion of two parts of the former to one of the latter. 
 
 TIN. 
 
 Tin is a brilliant, silver-white metal, the lustre of which is 
 not sensibly aifected by exposure to the air, but is easily oxi- 
 dized 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 mal- 
 leable, and may be beaten into leaves the 2¥o¥ ^^ ^^ ^^^^ ^^ 
 thickness ; ordinary tin foil being about y ^^q-^ of an inch 
 thick. It fuses at 442° ; boils at a white heat, and burns 
 with a blue flame to binoxide. 
 
 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 
 
BISMUTH. 91 
 
 counter-dies, and occasionally for dies. When employed for 
 the latter purpose in connection with a lead counter, the latter 
 should not be obtained directly from the die, as the high tem- 
 perature of melted lead would produce, when poured upon tin, 
 partial fusion of the latter and consequent adhesion of the two 
 pieces. When tin is used in the formation of a die, therefore, 
 either a counter previously obtained from a zinc die should be 
 used, or the "dipping" method employed, by which the 
 counter-die is first obtained from the plaster model, and a die 
 from the counter. 
 
 ANTIMONY. 
 
 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. The specific gravity of the purest variety 
 is 6.715. It fuses at about 810°, and when heated at the 
 blowpipe, it melts with great readiness, and diffuses white 
 vapors, possessing somewhat of a garlic smell. 
 
 Antimony 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. 
 
 BISMUTH. 
 
 Bismuth is a white-colored metal resembling, in some de- 
 gree, antimony. It is soft, but so brittle as to be easily pul- 
 verized. Its specific gravity is 9.83, which may be increased 
 somewhat by hammering. It melts at 480° Fah., and may 
 be cooled six or seven degrees below this point without fixing; 
 but the moment it begins to solidify the temperature rises to 
 480°, and continues stationary till the whole mass is congealed. 
 When the temperature of the metal is raised from 32° to 212° ' 
 it expands ^i^ in length. 
 
 Bismuth has the property, in a high degree, of increasing 
 the fusibility of the metals with which it is incorporated, and 
 
92 . MECHANICAL DENTISTRY. 
 
 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 besides 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 on account 
 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 produced on it by exposure 
 to the air ; potassium, on account of its extreme sensitiveness 
 to the influence of low temperature, being semi-fluid at 60° 
 Fah., nearly liquid at 92°, and entirely so at 120° ; arsenic, 
 because it volatilizes before fusing; cadmium, with no ad- 
 vantages above tin, on account of its scarcity and costliness ; 
 etc. 
 
GENERAL PROPERTIES OF ALLOYS. 93 
 
 CHAPTER X. 
 
 General Properties of Alloys, and their Treat- 
 ment AND Behavior in the Process of 
 Compounding. 
 
 All alloys possess metallic lustre, 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 focility ; thus it is difficult 
 to unite silver and iron, but the former combines readily with 
 gold, copper, or lead. 
 
 The ductility of an alloy is, in general, less than that of its 
 constituent metals, and this diffiirence is, in some instances, 
 reraarkaljly prominent, as in the case of certain alloys of cop- 
 per 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 
 formation of dies for stamping purposes. To the rule stated, 
 amalgams, or mercurial alloys, are cited as exceptions. 
 
 The density of an alloy varies with the particular metals 
 composing it, being generally either greater or less than the 
 mean density of its several components. 
 
94 MECHANICAL DENTISTRY. 
 
 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 
 remarkable degree. The alloy of 5 parts of bismuth, 3 of 
 lead, and 2 of tin is a striking example of this fact, this com- 
 pound melting at 197°, while the mean melting-point of its 
 constituents is 514°. Silver solder is also a familiar illustra- 
 tion of the influence of alloying on the fusibility of metals, 
 copper melting at 1996°, and silver at 1873°, when com- 
 bined, 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 latter. 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 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 considerable quantities, but the fallacy of such an in- 
 ference 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, composed each of nearly equal parts 
 of copper and zinc ; and manheim gold, compounded of 3 parts 
 copper and 1 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 ten- 
 dency of one of the oxides to combine with the other; by others 
 it is attributed to galvanic action. According to Faraday, 100 
 parts of steel, alloyed with one of platinum, is dissolved with 
 eflPervescence, in dilute sulphuric acid too weak to act with 
 perceptible energy on common steel. It is offered, in explana- 
 tion of this fact, that the steel is rendered positive by the pres- 
 ence of platinum. A similar illustration is afforded by the 
 
GENERAL PROPERTIES OF ALLOYS. 95 
 
 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 
 separate metals composing them. To this, however, there 
 are exceptions, as the alloy of 3 parts of lead and 1 of 
 tin, which, when heated to redness, burns briskly into a red 
 oxide. 
 
 Some points of practical interest suggest themselves in con- 
 nection 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 that this tendency, which is incompatible with the 
 proportional accurateness of the compound, should be, as far as 
 practicable, guarded against. Hence, various substances hav- 
 ing 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 
 affijrding a protective covering, preserves, with little change, 
 the proportions of the alloy. 
 
 Some difficulty is occasionally experienced in obtaining a 
 perfectly 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 silver, provided they have not been adequately 
 stirred before pouring. This result is not so likely to occur 
 when the metals employed are in small quantities and are sud- 
 denly 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 ofder of their separate densities. Hence, 
 whenever a notable difference in the specific gravity of the 
 metals exists, the fused mass should be briskly stirred imme- 
 diately before the instant of pouring it, and should be made to 
 solidify quickly. If uniformity be not obtained in this man- 
 ner, it will be necessary to rcmelt, and repeat the process, if 
 necessary, until the alloy is rendered sufficiently homogeneous. 
 
96 MECHANICAL DENTISTRY. 
 
 In alloying three or more metals diiFering greatly in fusi- 
 bility, 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. 
 
PART SECOND. 
 
 AKTIFICIAL DENTURES. 
 
 Before considering particularly the distinct and sj^ecial 
 methods employed in the construction of artificial dentures, 
 such preliminary processes as are common, in some degree, to 
 all, will, for the sake of convenient arrangement, and the 
 avoidance of unnecessary repetition hereafter, be first consid- 
 ered. These processes relate: 1. To the treatment of the 
 mouth preparatory to the insertion of artificial teeth. 2. The 
 manner of obtaining impressions of the mouth. 3. The 
 manner of procuring and forming plaster models of tlie mouth. 
 4. Metallic dies and counter-dies. 
 
 CHAPTER I. 
 
 Treatment of the Mouth preparatory to the Inser- 
 tion OF Artificial Dentures. 
 
 It rarely occurs that all the structures of the mouth arc in 
 such condition as will render it proper to insert an artificial 
 appliance without some pixiparatory treatment. This impor- 
 tant requirement cannot, in any material respect, be disre- 
 garded by the practitioner without endangering the utility 
 and permanence of the substitute, and inflicting upon the 
 patient a train of consequences alike distressing and perni- 
 cious. Every experienced dentist is familiar with the fact 
 that an artificial substitute resting upon diseased roots of 
 teeth and impinging continually upon gums ah'cady irritable 
 
 7 
 
98 MECHANICAL DENTISTRY. 
 
 and inflamed^ soon becomes a source not only of annoyance 
 and discomfort to the patient, but is rendered, in a great de- 
 gree, inefficient in the performance of some of its more impor- 
 tant offices. There is, besides, a perpetual and cumulative 
 aggravation of the morbid conditions, and, sooner or later, 
 irretrievable destruction of the remaining natural organs will 
 be induced. These consequences cannot be wholly averted by 
 the most skilful manipulation, but they may be greatly mag- 
 nified by a defective execution of the work or by a faulty 
 adaptation of the appliance to the parts in the mouth. 
 
 Patients not unfrequently attempt, by every artifice or pre- 
 text that caprice or timidity may suggest, to persuade the 
 operator to violate his own clear convictions of duty, but, un- 
 less under circumstances of peculiar exigency, he should be 
 careful to guard himself against the imputation of incom- 
 petency 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 neces- 
 sary to direct attention in the treatment of the mouth, are, the 
 presence of useless and diseased remains of teeth; accumula- 
 tions of tartar ; diseased states of the gums and mucous mem- 
 brane ; and caries. 
 
 Useless and Diseased Remains of Teeth. — It may be stated, 
 as a general rule of practice, that . all the remaining natural 
 teeth that are not susceptible of being restored to a state of 
 comparative health and usefulness, should be removed before 
 inserting an artificial substitute. Especially should this course 
 be pursued whenever the remaining roots are found partially 
 or wholly necrosed, and the peridental membranes and sur- 
 rounding tissues inflamed and suppurating. Such should be 
 extracted if for no other reason than that they are offensive in 
 the mouth, and tend, in a greater or less degree, to compromise 
 the general health. 
 
 In respect to the utility, comfort, and permanence of a 
 
TREATMENT OF THE MOUTH. 99 
 
 dental appliance, the expediency of removing the roots of teeth 
 prior to the introduction of the former, is apparent. If a 
 dental substitute is adapted with necessary accuracy to all the 
 parts which it covers, it will be plainly seen that the forces 
 applied to the base at every occlusion of the jaws in the act of 
 mastication, instead of being equalized or diffused, will be ex- 
 pended mainly on the roots, inasmuch as they afford so many 
 fixed points of resistance, whilst the adjacent soft tissues, yield- 
 ing to the pressure, permit the artificial piece to bear with un- 
 due and unequal force upon the former. The consequences of 
 this action are inevitably pernicious. In a comparatively short 
 time, inflammation and suppuration are induced about the 
 roots, which ultimately become loosened and painfully sensitive 
 to the slightest pressure; the secretions of the mouth, becom- 
 ing more and more acrimonious, act persistently and with in- 
 creasing energy on oxidable materials present in the mouth, 
 as well as upon the remaining natural teeth, inducing rapid 
 and general decay ; contiguous parts, through their immediate 
 connection or sympathetic relations with the structures of the 
 mouth, respond to the local disturbances, and the case, in time, 
 becomes complicated with those various distressing maladies 
 about the head and face so commonly associated with diseased 
 conditions of the buccal cavity. At last, the patient, no longer 
 able to endure the offensiveness and distress arising from the 
 presence of the substitute in the mouth, or to properly masti- 
 cate his food, is compelled to have the offending organs re- 
 moved. The absorption of the gums and processes which 
 follow this operation, and the corresponding changes which 
 occur therefrom in the form of the alveolar ridge, make it im- 
 perative in all cases either to reconstruct the same piece or to 
 supply the ])atient with an entirely new substitute ; whereas, if 
 due regard is had to the proper preparation of the mouth in 
 the first instance, the patient may be spared such inflictions, 
 and the o])erator the discredit which almost invariably attaches 
 to the neglect of the measures recommended. 
 
 An additional reason why roots of teeth should be extracted 
 Is, that their presence prevents, in some degree, an accurate 
 
100 MECHANICAL DENTISTEY. 
 
 and uniform adaptation of the appliance to all the parts on 
 which it is designed to rest, and this is particularly true of 
 those cases where atmospheric pressure is made available in 
 the retention of the substitute. Any condition of the mouth 
 that prominently modifies the natural and uniform pliancy of 
 the soft parts will, just to that extent, weaken the attach- 
 ment of the plate. This fact is made obvious when we reflect 
 that it is only the soft and yielding condition of the mucous 
 membrane and gums that permits the adhesion of the artificial 
 appliance for a single moment by atmospheric pressure ; for it 
 will be readily comprehended that, if the tissues on which it 
 rests were as hard and unyielding as bone, a dental substitute, 
 though it were moulded directly to the parts, would not be 
 sustained for an instant by the external pressure of the air. 
 
 The retention of every root that may, by treatment or other- 
 wise, be secured in good condition, has been insisted on by a 
 few in the profession, on the ground that they aiford a fixed 
 and permanent basis for the dental appliance, and preserve, 
 without change, the customary fulness and contour of the 
 mouth. Individual instances doubtless occur that render this 
 course admissible, but as a rule of practice, it is exposed, though 
 in a less degree perhaps, to the same objections which have 
 been adverted to in connection with diseased roots. However 
 carefully or skilfully such roots may be treated and prepared, 
 or the substitute applied, entire success and permanent benefit 
 to the patient cannot be reasonably anticipated. It rarely hap- 
 pens that the roots of teeth, whose crowns have been destroyed 
 by caries or accident, are found without having suffered, at 
 some time and in some degree, from disease of the investing 
 membranes and surrounding structures, and although these 
 conditions may have apparently subsided, or may have been 
 temporarily subdued by . treatment, yet observation of such 
 cases leads to the conclusion that, however free from indica- 
 tions of active disease they may appear at the time, the latent 
 predisposition favoring a recurrence of the morbid action 
 usually exists in such cases, and it will require no greater prov- 
 ocation than the continued and unequal action of an artificial 
 
TREATMENT OF THE MOUTH. 101 
 
 fixture on them to awaken this predisposition into active de- 
 velopment. 
 
 From the views here expressed, we are convinced that as a 
 principle of practice, the roots of teeth, however apparently 
 free from disease, should be extracted in the first instance. 
 There are, nevertheless, circumstances which clearly justify a 
 departure from the rule we have endeavored to enforce; as in 
 the process of engrafting an artificial crown upon a well-con- 
 ditioned root ; or supplying the loss of one or more of the front 
 teeth by attaching the artificial organs to a plate and fixing the 
 latter in the mouth by pivoting to one or more of the natural 
 roots. Either of these methods may, under certain circum- 
 stances and within certain limitations, be preferable to extract- 
 ing the roots of such teeth and supplying the vacuities by other 
 means. 
 
 JRemoral of Salivary Cak-idiis or Tartar: — The deposits of 
 tartar which so frequently collect at the necks of the teeth and 
 under the free margins of the gum, not only promote inflam- 
 mation and absorption of the investing membrane and contigu- 
 ous soft ])arts, but involve, by degrees, the alveolar processes 
 in the destructive action ; so that teeth originally firm become 
 loosened in their sockets, and thus, in their turn, become addi- 
 tional sources of diseased action in the surrounding structures. 
 Hence it becomes absolutely necessary, as it relates to the gen- 
 eral health of the mouth, to thoroughly remove, with suitable 
 instruments, all traces of this concretion from the teeth. 
 
 If any considerable number of the teeth are found coated 
 with tartar, and it is deposited in large quantities, it will be 
 impracticable, as a general thing, to remove thoroughly all 
 remains of it at a single sitting. The operation should be 
 repeated, therefore, from time to time, until every portion of 
 it is completely separated from the teetii ; the latter should 
 then be well polished with suitably shaped burnishers, and 
 the gums, if highly inflamed and turgid, may be either freely 
 scarified at those points where they dij) between the teeth, or 
 clejmsed and treated with appropriate detergent and remedial 
 agents. 
 
102 MECHANICAL DENTISTRY. 
 
 Diseased Conditions of the 3'Iucous Membrane and Gums. — 
 It will seldom be necessary to institute treatment for the reduc- 
 tion of inflammation and ulceration of the soft tissues of the 
 mouth after the 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, there are other morbid 
 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 
 otherwise treat, such as may be affected by caries. This opera- 
 tion will be attended with more satisfactory results and be 
 accompanied 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 irrita- 
 bility of the general system, and reduced sensitiveness of the 
 teeth operated on. 
 
 Siirgieal Treatment of the Moidh after the Extraction of 
 Teeth. — In the preparation of the mouth for entire sets of arti- 
 ficial teeth, it frequently becomes necessary to extract the re- 
 mains of all or nearly all of the teeth of one or both jaws. In 
 such cases, the ridge is left ragged and broken, with flaps of 
 gum lying in loose folds along the border, and the exposed 
 margins of the alveolar processes projecting from underneath. 
 These parts, if left in this condition, will be productive of more 
 or less inconvenience to the patient ; for as the gums close over 
 and contract upon the cutting edges of the processes, irritation 
 and inflammation will be induced at those points where they 
 are most prominent. Immediately after the extraction of the 
 teeth, therefore, any flaps of gum hanging loosely around the 
 sockets should be clipped off, and sharp and protruding portions 
 of processes cut away with excising forceps. If^ in the course 
 
TREATMENT OF THE MOUTH. 103 
 
 of a few weeks, prominences still remain, over which the mucous 
 membrane is stretched and irritated or inflamed, as is more fre- 
 quently the case around the sockets of the cuspidati, the mem- 
 brane should be divided over such points with a lancet, and the 
 sharp points of bone underneath broken down with suitable cut- 
 ting instruments. 
 
 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 arti- 
 ficial substitutes, will depend upon various circumstances. If 
 the appliance is only intended to meet the wants of the indi- 
 vidual 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 mouth 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 con- 
 dition, 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, and which will render the wearing of an artificial piece 
 uncomfortable to the patient, and in some degree mischievous, 
 by aggravating the morbid conditions already existing. An- 
 other objection to the too early introduction of artificial sub- 
 stitutes into the mouth arises from the fact that the changes 
 wliicii occur in the ridge are much more rapid within the first 
 few weeks after the extraction of the teeth than at any subse- 
 quent period, so that the plate, if inserted immediately or 
 within a few days after such operation, will soon lose its bear- 
 ing upon the ridge and become inefficient for masticating pur- 
 poses, or may even fiiil to be retained in the mouth without 
 much annoyance to the patient. Two or more weeks, therefore, 
 should elapse before applying the substitute. In the meantime, 
 
104 MECHANICAL DENTISTRY. 
 
 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 compldion of those changes which 
 occur in the alveolar border after the extraction of all or any 
 considerable number of the teeth, cannot be definitely stated, 
 but will range from five to eighteen months or more, accord- 
 ing 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; 
 
OBTAINING IMPRESSIONS OF THE MOUTH. 105 
 
 CHAPTER II, 
 
 Materials and Methods Employed in Obtaining 
 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 appliance is in any way connected. If this important pre- 
 liminary step is, in any essential respect, imperfectly performed, 
 the ultimate utility of the artificial fixture will either be greatly 
 impaired or wholly destroyed, notwithstanding all the subse- 
 quent manipulations may be most carefully and skilfully per- 
 formed. The operator, therefore, should avail himself of every 
 appliance and facility that will enable him to attain, in this 
 respect, the most perfect results. 
 
 The materials ordinarily employed for this purpose are, 
 wax; combinations of wax and paraffin and gutta-percha; 
 modelling composition; gutta-percha; and plaster of Paris. 
 
 Wax. — There are two varieties of this substance in common 
 use, the yellow and tchite wax. The yellow variety is es- 
 teemed preferable to the white on account of its superior tough- 
 ness ; the latter being, to some extent, disintegrated, or ren- 
 dered less tenacious in the process of bleaching, but is fre- 
 quently used and is preferred by many on account of its color. 
 The more desirable properties of the yellow wax are often im- 
 paired by the admixture with it of tallow, with which it is, 
 for mercenary purposes, frequently contaminated. The pres- 
 ence of tallow may be detected by its characteristic 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. 
 
 Wax used for impressions should always be kept in con- 
 venient form for immediate use, and may be prepared either 
 
106 MECHANICAL DENTISTRY. 
 
 by warming it until sufficiently soft and then rolling; or press- 
 ing 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 suc- 
 cessive layers cool, until a coating of sufficient thickness is ob- 
 tained. 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 
 modelling composition. 
 
 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 ob- 
 taining an impression of the mouth 
 in those cases where any number 
 of the natural teeth remain in 
 either or both jaws, and, for this 
 purpose, is ordinarily more con- 
 venient and manageable than plas- 
 ter, and, if carefully manipulated, 
 will secure in most cases a sufficiently accurate impression of 
 the parts. 
 
 Before preparing the wax, a suitable cup or holder should 
 be selected for the particular case in hand. These appliances 
 are usually constructed either of plate or block-tin, Britannia 
 metal, or silver, and a sufficient number of the various forms 
 required should be provided to meet perfectly every require- 
 ment in respect to the size and form of the jaws of individual 
 cases. 
 
 For upper partial or broken sets, the form of cup repre- 
 sented in Fig. 29 may be used. It should be large enough to 
 embrace the alveolar ridge, leaving a space of nearly a fourth 
 of an inch between its outer rim and the external border of the 
 gum. If it is designed to employ an atmospheric pressure plate 
 covering nearly or quite all of the hard palate, a cup of the same 
 general form, but with its central portion extended posteriorly, 
 
OBTAINING IMPRESSIONS OF THE MOUTH. 107 
 
 niav be used; or a full cup, like that represented in Fig. 31, 
 may be employed. Having selected a cup of the proper form 
 and size, the wax should be warmed in a spirit flame until it 
 acquires about the consistence of freshly made putty. AVax 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 continuity. In taking the impression the oper- 
 ator should place himself behind and to the right of the patient, 
 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. The cup with the wax ar- 
 ranged 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 unyielding, the introduction of a cup of suffi- 
 cient size may be attended with some little difficulty and em- 
 barrassment. This impediment, however, may be readily 
 overcome in most cases by presenting the cup obliquely to the 
 mouth, one side resting against, and pressing outv/ard, the cor- 
 ner 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 
 adjusted over the ridge before pressing it up, so that no por- 
 tions of the rim may cut into the soft tissues of tlie mouth, an 
 accident liable to happen without care, and which will make it 
 necessary, in most cases, to withdraw the cup before the im- 
 pression is complete. The jiroper position of the cup in the 
 mouth sef;ured, it should be held firmly with the thumb rest- 
 ing on the handle above, and two or more of the fingers on the 
 under surface, when it is slowly but steadily and forcibly })ressed 
 against the j)arts above until the ridge is completely imbedded, 
 
108 MECHANICAL DENTISTRY. 
 
 and the wax carried closely against the roof of the mouth. 
 The cup should then be held stationary with one hand, while 
 with the fingers of the other the wax around the margins of 
 the cup should be pressed closely into all the depressions oc- 
 curring on the outside of the ridge between the remaining 
 teeth, or wherever irregularities may present themselves on the 
 external border of the jaw. The finger should also be passed 
 to the roof of the mouth at the central and posterior edge of 
 the cup, making pressure against the protruding wax upward 
 and forward into the anterior and deeper portions of the palatal 
 arch. When the operation has been conducted thus far, and 
 before removing the cup, gentle upward pressure upon the lat- 
 ter may again be made — not enough to move the entire body 
 of wax, but only sufficient to correct any partial displacement 
 that may have happened from accidental tilting or lateral 
 movement of the cup during the concluding manipulations. 
 
 After the wax has remained in the mouth long enough to 
 become in some degree hardened, it should be carefully de- 
 tached 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 im- 
 pression. More or less dragging of the wax, however, will 
 unavoidably occur in proportion as the teeth are irregularly 
 arranged in the arch, or have contracted necks. Imperfections 
 occurring from these sources may be remedied with tolerable 
 accuracy by subsequent carving of the plaster model, but the 
 better plan, where these conditions prevail to any considerable 
 extent, is to substitute gutta-percha for wax, the elasticity of 
 this substance enabling it to regain the form it acquires in the 
 mouth after having been temporarily disturbed or changed in 
 the act of detaching it from the teeth. 
 
 Inasmuch as it is necessary, in constructing partial sets of teeth, 
 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. 
 
OBTAINING IMPRESSIONS OF THE MOUTH. 109 
 
 Manner of Obtaining an Imj)ression of the Loicer Jaw in 
 Wax for Partial Dentures. — If the case is one where teeth at 
 intervals are to be supplied, the form of cup used in taking 
 an impression for an entire 
 lower denture (Fig. 33) may 
 be employed ; or if the vacuity 
 exists in the front part of the 
 ridge only, then one like that 
 represented in Fig. 29 will 
 answer the purpose. If, how- 
 ever, as is more generally the 
 case, the front teeth remain, 
 
 and those posterior to the cuspids or bicuspids are to be 
 replaced, the form of cup exhibited in Fig. 30 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 prematurely in contact with the floor of the cup in 
 front. Instead of the ojjcning represented in the cup, how- 
 ever, it will be sufficient in most cases to have it formed with 
 a depression in front of adequate depth to receive the points of 
 the anterior teeth. 
 
 In taking an impression of the lower jaw, after having pre- 
 pared and arranged the wax by softening and filling the 
 groove of the cup flush with the margins, the oj)erat()r may 
 first take a position to the right and back of the patient, and 
 introduce the cup into the mouth in the manner heretofore 
 described, when he should pass to the front of the patient, 
 and having adjusted the cup properly over the ridge, the first 
 two or three fingers of each hand should be placed upon the 
 top of each side of the cup, and a thumb upon each side and 
 underneath the jaw, and firm and steady pressure made until 
 the ridge is wholly imbedded. The wax may then be pressed 
 in around the margins of the cup, and the impression carefully 
 removed froin the mouth in the manner before indicated. 
 
110 MECHANICAL DENTISTEY. 
 
 ■ Manner of Obtaining an Impression of the Mouth in Wax 
 for Entire Tlpj^er Dentwes. — Tlie form of cup emplojed in 
 taking an impression of the upper jaw in the absence of all the 
 natural teeth, is seen in Fig. 31. ' A number of these, corre- 
 sponding as nearly as possible in 
 form and size to the various modi- 
 fications in the configuration and 
 dimensions of the maxillary arch, 
 should be kept conveniently at 
 hand. If the teeth have been re- 
 cently extracted, the wax should 
 be prepared somewhat softer than usual to prevent displace- 
 ment of the gums, which, in their unabsorbed condition, pos- 
 sess more or less mobility. The cup should be filled flush 
 with the edges, and built up in the centre 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 ulti- 
 mately 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, filling up any depressions or fosses 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 extrac- 
 tion of the teeth. 
 
 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 atmospheric 
 pressure ; 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 centre of the arch and 
 upward, dragging the mucous membrane somewhat from the 
 
OBTAINING IMPRESSIONS OF THE MOUTH. 
 
 Ill 
 
 edo-e of tlie 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, and thereby 
 prevent it from dragging at those points where the ridge over- 
 hangs, or to prevent any change of form on the application of 
 sufficient force to detach it from the mouth when it adheres 
 Avith great tenacity, a cup has been constructed with a cham- 
 ber underneath into which a stream of cold water is admitted. 
 Two short pipes, as will be seen by .reference to Fig. 32, com- 
 municate with the chamber, and these again connect with a 
 
 Fig. 32. 
 
 double tube fitting them closely, and united at the other end 
 with two gum-elastic tubes — one communicating with a vessel 
 of water conveniently placed and provided with a stop-cock, 
 the other leading to a spittoon or other waste place. The two 
 portions of pipe may be disconnected when not in use. After 
 taking an impression with this cup, and before removing the 
 wax from the mouth, the two portions of pipe are connected 
 and a continuous current of cold water passed through the 
 chaml)er by turning the faucet connected with the tank ; when 
 sufficiently hard, the wax is removed from the mouth before 
 disjointing the pipes, to prevent the water from flowing upon 
 the patient. 
 
 To provide more ])erfectly against failure of the wax being 
 carried closely against the roof of the mouth in cases where 
 the palatal vault is very deep, a piece may be cut from the 
 central part of the cup, the wax being pressed at this point 
 upward and forward into the deeper portions of the palatal 
 fowia. 
 
112 MECHANICAL DENTISTEY. 
 
 The author would express, in this connection, his convic- 
 tion that it is impracticable, in most cases, to obtain a fault- 
 less impression of the mouth in wax for full upper dentures. 
 There are points, not readily accessible to the fingers, where 
 the wax departs from the external 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 assurance that in pressing the wax in at one point we 
 are not displacing it at another. For this reason, we invaria- 
 bly use plaster in these cases, and we have sufficient reason to 
 believe that the results are more uniformly successful. 
 
 Manner of Obtaining an Impression of the Lower Jaw in 
 Wax for Entire Dentures. — The method pursued in securing 
 an impression of the lower jaw in wax for an entire denture 
 
 differs in no essential respect from 
 
 Fig 33 
 
 that described when taking an 
 impression for lower partial 
 pieces, the form of cup being 
 represented in Fig. 33. When 
 the parts are imbedded in the 
 wax, the latter 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 be- 
 fore removing it, to correct any partial deformity that may 
 have occurred during the previous manipulations. 
 
 Gutta-percha. — This material is rarely used except in ob- 
 taining impressions for partial pieces, and is more particularly 
 indispensable whenever a perfect representation of the parts in 
 plaster is essential to the success of any method in which the 
 base is moulded or cast upon the model, as in the use of rub- 
 ber, celluloid, etc. It takes the form and position of the teeth 
 readily, and preserves them unchanged, by virtue of its elas- 
 ticity, when removed from the mouth. 
 
OBTAIXING IMPRESSIONS OF THE MOUTH. 113 
 
 The general management of tliis substance in the process of 
 obtaining an impression Avith it, is in most respects similar to 
 that of wax, when used for the same purpose. It should, 
 however, be prepared by softening it in hot water, but as the 
 heat required to render it sufficiently plastic is greater than 
 could be well endured without inflicting injury upon the soft 
 tissues of the mouth, and subjecting the patient to pain in its 
 application, it is customary, after having heated it sufficiently 
 and packed the cup, to chill the surface by plunging it into 
 cold water, and then introduce it quickly into the mouth. 
 When the impression is secured, and the gutta-percha has be- 
 come somewhat rigid in the mouth, it should be removed and 
 filled immediately with plaster, as it contracts rapidly in cool- 
 ing. 
 
 Plaster of Paris, or gypsum, or technically, calcium sul- 
 phate, has been long employed in taking impressions of the 
 mouth for entire dentures, and more recently and to a limited 
 extent, for partial or broken sets. For entire pieces, it has 
 almost wholly suj^erseded the use of wax, and is better adapted 
 for receiving an accurate impression of the mouth, whenever 
 it is desired to secure a copy of all its parts in their undis- 
 turbed relation to each other, than any material that has yet 
 been employed. 
 
 When used for this purpose, it should be of the best quality, 
 finely pulverized and well sifted, and should always be kept 
 in a closed vessel, as the moisture which it attracts from the 
 atmosphere impairs its property of hardening quickly when 
 prepared for use. If impregnated with moisture, it should be 
 first dried in a shallow vessel over a moderate heat before 
 being used. 
 
 It is prepared for use by mixing with it a sufficient quantity 
 of water to form a batter of about the consistence of very 
 thick molasses, in which condition it hardens by a species of 
 crystallization in from three to five minutes. The condensation 
 of the plaster mixture is hastened somewhat by the admixture 
 of a small (piantity of sodium chloride or common salt. The 
 best method of preparing plaster, however, for the purpose 
 
 8 
 
114 MECHANICAL DENTISTRY. 
 
 under consideration, is to combine water with it in sufficient 
 quantity to form, in the first place, a very thin batter, and 
 then to stir or beat it constantly with a small spatula until it 
 becomes sufficiently thickened to admit of its adhering in a 
 body to the vessel in which it is mixed when the latter is in- 
 verted, and when one portion will retain nearly its form when 
 heaped upon another. By this process of protracted beating, 
 calling sometimes "tempering," it is made tough and pasty, 
 without having its plasticity impaired, and when introduced 
 into the mouth in this condition, it adapts itself readily to the 
 parts, hardens quickly, and is not liable, with ordinary care, to 
 incommode the patient by running back into the fauces. So 
 quickly, indeed, does it condense, that unless expeditiously in- 
 troduced into the mouth, it will begin to "set" before the 
 parts are fairly imbedded. When preparing it for use, there- 
 fore, 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 operation. 
 
 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, pro- 
 ducing nausea and involuntary retching, and which is very 
 liable to occur whenever the mixture is too thin or is im- 
 properly manipulated, it is recommended to instruct the patient 
 to avoid swallowing while the plaster is in the mouth. Patients 
 are also advised to breathe through the nostrils, but we see no 
 good reason for this injunction. It should be remembered 
 that, in the act of breathing through the nose, the velum palati or 
 soft palate is depressed to cut off the passage of air through the 
 mouth, and that it is thus brought more immediately in contact 
 with any portions of plaster that may be protruding from the 
 heel of the cup. The stimulus of contact will tend to produce 
 involuntary contractions of the muscles of the soft palate and 
 fauces, and thus portions of soft, or fragments of hard, plaster 
 will be worked or drawn back into the fauces, producing the 
 very evils it is designed to avoid. If, therefore, patients are 
 instructed at all in this respect, they should be advised to 
 breathe naturally through the mouth, this channel affording 
 
OBTAINING IMPRESSIONS OF THE MOUTH. 115 
 
 less obstruction to respiration than that through the nostrils in 
 the act of taking an impression. 
 
 Manner of Obtaining an Impression of the Movih in Plaster 
 for Partial Upper Dentures. — There are conditions of the 
 mouth, incident to the presence of natural teeth within it, 
 which would seem to preclude the use of plaster in taking an 
 impression of the parts. Thus, if any number of the teeth 
 remaining are small at the necks with enlarging crowns, or if 
 they are irregularly arranged in the circle, having' either an 
 anterior, posterior, or lateral obliquity, it would not only be 
 difficult to detach hardened plaster from teeth so circum- 
 stanced, but the force necessary to remove it would inevitably 
 break away portions of plaster from around the teeth. Another 
 apparent objection to the use of plaster in these cases consists 
 in the difficulty with which the impression is separated from 
 the plaster model, it being necessary to cut away the former 
 by piecemeal, as it would be impossible to separate the two in 
 the ordinary Avay. 
 
 The difficulties incident to the detachment of the plaster 
 from the teeth in the mouth may be obviated in either of the 
 following Avays: 1. Take an impression first in wax, and with 
 a metallic die and counter, obtained from a model of the parts, 
 swage a plate of tin, brass, zinc, or silver, of the size and form 
 of the intended base ; coat the palatal surface of this temporary 
 holder with a thin coating of plaster mixture, and apply it to 
 the mouth in the manner usually employed in obtaining an 
 impression. 
 
 2. Take an impression of the parts in wax and cut away 
 from tlie latter all those portions indented by the teeth, leaving 
 only so much of the wax surface as corresponds with the palate 
 and interspaces in the ridge ; use this as a holder, and secure 
 the impression by coating its surface, as before, with a thin 
 layer of |)la'^ter batter. By either of the above methods an 
 impression of those parts, only, on which the substitute is 
 designed to rest, can be taken ; the form and position of the 
 teeth must be scr;ured in a separate impression either with wax 
 or gutta-percha. 
 
116 
 
 MECHANICAL DENTISTRY. 
 
 Notwithstanding the obvious objections already stated, many- 
 operators prefer, in taking impressions for partial cases, to 
 imbed all the parts in plaster in the same manner as when 
 wax is used, being careful to remove the plaster from the 
 mouth before it has acquired the usual hardness. If the re- 
 maining teeth have contracted necks, or are placed irregularly 
 in the arch, they may be partially encased in wax before apply- 
 ing the plaster; this will facilitate the withdrawal of the im- 
 pression and preserve the form of the teeth ; the wax, receiving 
 the impress of the teeth, coming away with the plaster. The 
 form of the cup used in these cases is the same as that repre- 
 sented in Fig. 31, the edge of which may be turned in a little 
 at points to prevent the plaster from being dragged from the 
 cup. The cup being filled with the plaster mixture is intro- 
 duced into the mouth and carefully pressed up until all the 
 
 Fig. 34. 
 
 parts are fully imbedded. When partial hardening of the 
 plaster has occurred, sufficient tractive force should be judici- 
 ously appKed to the cup to separate the plaster from the teeth 
 and soft parts, when it should be carefully removed from the 
 mouth. If any portion of the plaster, essential to the form of 
 the impression, should break away, the fragment or fragments 
 may be secured and afterwards applied to the fractured surfaces. 
 Considerable force is sometimes necessary to separate the 
 plaster from the teeth, and in the effort to remove the former, 
 it is liable to part from the cup and remain fixed in the mouth ; 
 in which case it will be necessary to cut it away by piecemeal. 
 
OBTAINING IMPRESSIONS OF THE MOUTH. 1 1 7 
 
 This casualty may be eifectually prevented by employing the 
 form of cup shown in Fig. 34, contrived by Dr. Samuel War- 
 die, of Cincinnati, and used by him with entire success. It 
 will be seen to consist of an ordinary holder, the cup portion 
 perforated in the centre, through which a small rod passes with 
 a screw cut on one end, and the other surmounted with a con- 
 cave flange, around and underneath which the plaster collects. 
 The rod is formed with a shoulder resting on the palatal face 
 of the cup, and is fixed in position by screwing the tap against 
 the lower surface of the holder. A number of these centre- 
 pieces, with shafts of various lengths, should be provided, in 
 order that any desired elevation may be given to the cap or 
 flange ; for the latter is designed not only to confine the plaster, 
 but also to carry it up into the roof of the mouth where the 
 latter is very deep. 
 
 An admirable expedient for securing an impression with 
 plaster for partial cases is thus described by Professor Charles 
 J. Essig: 
 
 " An impression cup should first be selected of the proper 
 size and shape, — those with the flat floor are best for partial 
 cases ; the plaster should be mixed thin, almost as thin as water, 
 adding chloride of soda to facilitate setting. Plaster mixed in 
 this manner does not become as hard and unyielding as that 
 mixed merely to saturation. Now oil the cup so that it will 
 readily separate from the impression when hard, fill the cup 
 as soon as the plaster thickens sufiiciently, then, with a small 
 spatula, place a layer of the soft plaster in upon the palatine 
 surface, otherwise by inclosing the air in the deep portion of 
 the arch the accuracy of the impression 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 sufiiciently 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 cover- 
 ing the j)alatine 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 
 fijund to articulate with perfect accuracy. 
 
318 MECHANICAL, DENTISTRY. 
 
 "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 gargle, which will in nearly every case, prove an effec- 
 tual remedy." 
 
 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. If the external border of the alve- 
 olar ridge is very deep, or there is considerable space interven- 
 ing between the heel of the cup and the floor of the palate, a 
 rim of wax may be placed along the outer margin of the cup, 
 and extended across its posterior border, in order more effectu- 
 ally 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 very deep, with a marked excava- 
 tion in its central and anterior portion, or if it presents some- 
 what the form of a deep fissure, the plaster may fail to be car- 
 ried 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 corre- 
 sponding 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 trim- 
 ming 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. 
 
 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 until the parts 
 are completely encased and portions of plaster are seen to pro- 
 trude from all parts of the margins of the cup, otherwise the 
 impression is liable to be imperfect either on its outer borders 
 
OBTAIXIXG IMPRESSIONS OF THE MOUTH. 119 
 
 or on its palatal face. Immediately after introducing and press- 
 ing up the cup, the lip in front should be extended and drawn 
 down over the cup, when gentle pressure, as the plaster is hard- 
 ening, may be made upon the outside of the lip in front and at 
 either side of the mesial line to force the plaster more perfectly 
 into the fosses which exist at these points. 
 
 It is essential to perfect success in this operation, that the 
 cup, after the parts are once imbedded, should be held perfectly 
 stationary until the plaster becomes fixed, as the slightest move- 
 ment, when the plaster is in the act of consolidating, will de- 
 range the impression and render it faulty. Again, if after the 
 parts are imbedded, the operator discovers that they are not 
 sufficiently encased, 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 impression may be fractured or otherwise impaired. In 
 addition to the means already adverted to in connection with 
 the method of separating wax impressions from the mouth, re- 
 sort is sometimes had to the following expedient: The central 
 portion of the cup being pierced with two or three small holes, 
 a blunt-pointed ])robe is passed at these points through the 
 plaster, before tlie 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 author 
 has succeeded best in detaching impressions in such cases, by 
 upward and interrupted traction u])()n the handle of the cup, 
 which, by depressing the heel of the same, more readily permits 
 the introduction of air than by either of the methods commonly 
 cnij)loyed. 
 
 Manner of Obtaining an Impression of the Mouth in Plaster 
 
120 MECHANICAL DENTISTRY. 
 
 for Entire Lower Dentures. — Until recently, wax has been al- 
 most invariably used in taking impressions of the lower jaw. 
 Plaster, however, may be used for the same purpose, and, by 
 some, is esteemed superior to the former. The ordinary wax- 
 holder as shown in Fig, 32 may be used, and which, being 
 filled with the plaster batter thoroughly beaten until quite 
 tough and pasty, is inverted and quickly introduced into the 
 mouth and pressed down upon the ridge until the latter is 
 completely imbedded; when sufficiently hard it should be re- 
 moved in the ordinary way. 
 
 In securing an impression of the lower ridge in plaster, 
 better results can, in many cases, be obtained by first taking 
 the impression in wax, enlarging the impression thus secured 
 with suitable instruments, and using this as a tray for plaster. 
 
 A form of tray, contrived expressly for the use of plaster 
 by Dr. B. W. Franklin, is exhibited in Fig. 35. It consists 
 of two chambers, or a double groove, communicating with each 
 
 other by a fissure running from heel to heel of the cup. The 
 groove corresponding with the curvature of the lower jaw is 
 filled with plaster properly prepared, inverted, passed into the 
 mouth, and pressed down upon the parts. As the cup is pressed 
 down, portions of plaster will be forced through the fissure into 
 the upper chamber, — this should be pressed down at all points 
 along the groove with the finger, securing more perfectly, in 
 this manner, the intrusion of the plaster into any irregularities 
 or depressions that may occur in the ridge. Or, the empty 
 cup may be placed in its proper position over the jaw and the 
 plaster introduced into the upper groove and pressed down 
 with the fingers through the fissure on to the ridge, filling the 
 depending chamber. 
 
PLASTER MODELS. 121 
 
 CHAPTER III. 
 
 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, and, if cor- 
 rectly obtained, is a true counterpart or fac-simile of all parts 
 of the mouth represented in the impression. 
 
 Planner of Obtaining a Plaster Model from an Impression in 
 Wax for Partial Dentures. — The impression in wax should be 
 first trimmed by cutting away superfluous portions that over- 
 hang the borders of the cup, care being taken not to mar any 
 essential })art of the impression. The surface of the wax im- 
 printe<l should then be uniformly smeared with a thin coating 
 of oil applied with a carael's-hair brush. The oil should not 
 be of too thick a consistence, nor applied in too large quan- 
 tities, as it will collect in the more depending portions of the 
 impression, and failing to be displaced by the plaster, will 
 leave the model imperfect at these points, especially at the 
 coronal extremities of the plaster teeth. The cup is now sur- 
 rounded by some substance that will confine the plaster and 
 give ])roper 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, stri|:>s 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 Vxi im))arte<l to them by placing short pieces of stiff wire 
 verti(;ally in the depressions made in the wax by the teeth, and 
 
122 MECHANICAL DENTISTRY. 
 
 which may be supported in an upright position by imbedding 
 one end in the wax in the centre of the bottom of each cavity. 
 
 When the cup is properly inclosed a batter of plaster, of some- 
 what thinner consistence 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, ac- 
 cording to the particular requirements of the case. The plaster 
 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 depressions, 
 expelling the contained oil or air, and filling them perfectly. 
 When the plaster has become sufficiently hard, any portions 
 overlapping the borders of the wax, and not essential to the 
 form of the model, should be cut away, and the two separated 
 either by immersion in warm water, or by placing the model 
 over the flame of a spirit-lamp or upon a heated surface, until 
 the warmth imparted to the model renders the wax sufficiently 
 soft to allow the former to be removed without fracturing the 
 plaster teeth. The latter methods should be adopted whenever 
 it is desired to obtain duplicate copies from the same impres- 
 sion, as by the use of hot water the impression is destroyed, 
 the latter, however, being generally used when gutta-percha is 
 employed. When separated from the impression, the model 
 should be properly trimmed and shaped with a knife-blade. 
 
 The general form of the body of a model is shown in Fig. 
 36. The walls, as it 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 moulding; for if made too flar- 
 ing 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 
 
PLA8TER MODEI.8. 
 
 123 
 
 prevented by cutting away all of the plaster teeth from the 
 model, leaving, however, encjugh of them remaining where 
 they unite with the body of the model to form a shoulder to 
 each tooth, as in Fig. 30. In this 
 «ise the plate should besufficiently i-'k;. ■%. 
 
 ample in its dimensions to parti- 
 ally overlap the border, when, as 
 it is forced into adaj)tation, distinct 
 indentations will be made in it, 
 corresponding exactly with the pa- 
 latal curvaturfiS 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, li', however, the plate is of the exact size re- 
 quired before stamping, one f)r two plaster teeth upon f;ac-h side 
 of the model maybe allowed to remain, against the anterior 
 face of which the plate is made to rest holding it stationary. 
 
 Manner of Ohtainiru/ a Pluder Model frcmi an Imjjression 
 in Wax for Entire Denturea. — Tlie same general method is 
 pursued in obtaining a plaster model from an imjiression in 
 
 Fk;.;57. 
 
 wax of cither the up[)er or lower jaw for entire denturcis, as 
 that employed in [>artial f^s^-s. The general form of thfise 
 p'lecjiH is represented in Figs. 37 and 38. 
 
 li' it is desired to swage a rim to the plate, forming a groove 
 
124 MECHANICAL. DENTISTRY. 
 
 or socket into which the plate extremities of the teeth are 
 received, the model should be formed in the manner repre- 
 sented in the annexed 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. 37), but which on the lower (Fig. 
 38), 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 fii"«t instance and afterwards 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 bor- 
 der 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, and which should be in- 
 dicated upon the model with a pencil-mark before applying 
 the roll of wax. Plaster may be substituted for wax, and 
 should always be used whenever heat is applied to the model 
 in the process of obtaining a metallic swage, as by the " dip- 
 ping" method. 
 
 If the model is to be used in moulding, the groove should 
 be sufficiently open to permit the ready withdrawal of the 
 sand, otherwise the die at this part will be imperfect ; if, how- 
 ever, the face of the model is to be immersed in molten metal, 
 securing first the counter-die, any form may be given to the 
 groove that will best facilitate the operation of overturning 
 the margins of the plate. 
 
 Rimmed plates 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. 
 
 Whenever an air-chamber is to be stamped in the base, the 
 model should be prepared for the purpose before casting the 
 metallic swages. The general form and position of the central 
 cavity or chamber in the arch is represented in Fig. 37. The 
 model may be prepared in either 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 cor- 
 responding point or points upon the model, and will have ex- 
 actly the same form and depth as the cavity in the impression. 
 
PLASTER MODELvS. 125 
 
 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 portion to the proper form. 3. Cut a pat- 
 tern chamber, of the required form and thickness, 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 con- 
 fining it with a small piece of wire or tack driven through it 
 into the plaster, or by interposing softened wax or other adhe- 
 sive material between the chamber and model. A small brush 
 loaded with a varnish mixture passed round the edge of the 
 chamber will insure sufficient adhesion of the latter. 
 
 The same general method as that when central chambers 
 are formed is pursued in the preparation of the model when it 
 is desired to construct lateral cavities in the plate. The form 
 and position of these on the model will be indicated by inspec- 
 tion 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, and will be described in a 
 subsequent chapter, but does not require a model differing in 
 form from the one described in connection with full dentures 
 wdth central chambers. 
 
 Manner of Obtaining a Plaster 3Iodel from an Impression 
 in Plaster for Partial Dentures. — The surface of the impres- 
 sion in plaster should first be rendered hard 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 transparent and colored. Tlie former is pre- 
 ferred for the reason that it penetrates the plaster more thor- 
 oughly, giving to it a greater depth of surface hardness, while 
 the latter, if not sufficiently fluid, forms a somewhat sui)erticial 
 incrustation, which is liable to peel off in handling, leaving 
 
126 MECHANICAL DENTISTRY. 
 
 portions of the model unprotected. Either, however, if prop- 
 erly prepared and applied, may be employed. 
 
 Formula No. 1, Formula No. 2. 
 
 Transparent Varnish. Colored Varnish. 
 
 Gum sandarach, . 5 oz. Gum shellac, . . 5 oz. 
 
 Alcohol, . . .1 quart. Alcohol, . . .1 quart. 
 
 The sandarach and shellac should first be freed from all 
 impurities by careful jjicking and washing ; they are then 
 added to the alcohol and digested over a moderate heat until 
 thoroughly dissolved. Other substances, as gum elemi, Ve- 
 nice turpentine, etc., have been recommended as additional 
 ingredients, but they are not indispensable, and may be 'omitted 
 without sensibly impairing the properties of the varnish. 
 
 After glazing the surface of the plaster impression with var- 
 nish a thin and uniform coat of oil should be applied ; it is 
 then enveloped, and the model procured in the same manner 
 as when wax is used. 
 
 The following method of preparing the plaster impression 
 before it is filled in for the model is recommended by Dr. C. 
 W. Spalding : " After the impression has become hard, coat 
 the surface with a lather of soap and water ; wash this off and 
 immerse the model in water. This expels air and avoids lia- 
 bility to porosity 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 this method to varnishing for the reason 
 that the varnish used is not always of uniform consistenc.e." 
 
 In separating the model from a plaster impression, for par- 
 tial cases, it will be necessary to cut the latter away in pieces, 
 as any attempt to separate the two in the ordinary manner 
 would inevitably break away the plaster teeth from the model. 
 The impression should be chipped away with great care, to 
 avoid defacing the model. To provide more perfectly against 
 this accident, it is better to coat the impression with colored 
 
PLASTER MODELS. 127 
 
 varnish,* as this will indicate with greater certainty the line of 
 contact or union between the two pieces. When separated, 
 the model should be trimmed and formed in the manner here- 
 tofore described. 
 
 Manner of Obtaining a Plaster 3Iodel from an Impression 
 in Plaster for Entire Dentures. — -The preparation of a plaster 
 impression 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 impression has been taken in 
 plaster for partial pieces. A model can, ordinarily, be readily 
 detached from an impression of the lower jaw, but is not always 
 so easily effected in the case of the upper. To accomplish this 
 in the latter case, the model may be taken in the hand and the 
 back of the handle of the cup tapped lightly with an instru- 
 ment; or, a small, wedge-shaped instrument may be carefully 
 forced between the model and impression at the posterior bor- 
 der of the latter until they part slightly, when they may be 
 easily detached ; before doing which, however, any overlap- 
 ping portions of the model which may tend to bind the two 
 pieces together should be trimmed away. If any portion of 
 the heel of the model is defaced by the introduction of the 
 wedge, it may be afterwards remedied by restoring the con- 
 tour of the parts with either wax or plaster. 
 
 After obtaining a model in either of the ways mentioned, 
 the entire body of it should be glazed and hardened by apply- 
 ing to it a uniform coat of varnish. 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 mould. A model may be better prepared for 
 permanent preservation by immersing it for a short time in 
 a solution of carbonate of soda, by which its surface is con- 
 verted into carbonate of lime, and thereby rendered hard and 
 durable; care must be taken not to introduce any of the bicar- 
 bonate of soda into the solution. 
 
 * The author is indebted to Dr. Spalding for a simple and admirable de- 
 vice for the Hame purjjoso, wliicli consists in coloring the water used to mix 
 plas'er for the impression with aniline red. 
 
128 MECHANICAL DENTISTRY. 
 
 CHAPTER ly. 
 
 Metallic Dies and Counter-Dies.' 
 
 A metallic die is a fae simile 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 moulding; secondly, by a process termed "dipping." 
 
 Moulding. — For this purpose the best material is marble- 
 dust, though other substances — as sand, Spanish whiting, etc. 
 — have been recommended. Marble-dust has the advantage 
 of being always ready for use, as it absorbs sufficient 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 brassfounders. It is prepared by mixing 
 with it sufficient water to render its particles somewhat adhe- 
 rent, 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 dis- 
 place 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 has 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 immediate readiness for use. 
 
 The moulding material properly prepared, the model is next 
 placed with its face uppermost, on the moulding-board, and 
 
METALLIC DIES AND COUNTER-DIES. 129 
 
 surrounded with a metallic ring. A common " wagon-box," 
 of which two or three sizes should be had, will answer every 
 purpose. 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 moulding 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 form imperfections in the face of the 
 die; or, if too loosely packed, the fluid metal, when poured 
 into the mould, will, to some extent, permeate the pores of the 
 sand or other material, and render the face of the die rough 
 and imperfect. 
 
 The box, with the model encased, is then lifted above the 
 board and the model dislodged by tapping it gently under- 
 neath Avith a small mallet or hammer until it parts from the 
 mould. The uncertain and hazardous method, sometimes re- 
 sorted to, of detacliing the model by pressing it alternately 
 backward and forward until loosened, and then lifting it out, 
 should never be practiced, as more or less deformity of the 
 mould is unavoidably produced thereby. 
 
 It not unfrequently happens that the ridge on the plaster 
 model of the upper jaw overhangs, forming corresponding 
 depressioas above, the excavations occurring more commonly 
 in front and on each side of the mesial line. Whenever this 
 form of the model exists, it will be impracticable to obtain a 
 correct mould in the manner just described, since the sand 
 becoming impacted in these excavations will be broken away 
 and remain with the model when the latter is dislodged. 
 
 The difficulty mentioned, however, may be readily over- 
 come in all cases by employing the sectional moulding flask 
 iiivented by Dr. G. W. Hawes, the several parts of which are 
 represent<id in the accompanying cuts. 
 
 Fig. 30 represents the lower ring, composed of three mov- 
 able pieces with flange extensions, which project in toward the 
 centre, ^\l^en used, this portion of the flask is closed and the 
 
130 
 
 MECHANICAL DENTISTEY. 
 
 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 indi- 
 cated by the dotted line in Fig. 41. 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 break- 
 ing away when the model is withdrawn. Very finely pulver- 
 ized charcoal contained in a loose muslin bag is now sifted 
 
 Fig. 39. 
 
 Fig. 40. 
 
 Fig. 41. 
 
 over the exposed surface of the sand, to prevent the next por- 
 tion contained in the upper ring from adhering. ^ The plain 
 ring (Fig. 40) is then placed over the one containing 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 sections 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 
 
METALLIC DIES AND COUXTER-DIES. 131 
 
 its proper relation to the lower one, and the flask inverted ; 
 when the mould, if the process has been accurately conducted, 
 will be found perfect. 
 
 In the absence of the " Hawes" flask, the same results may 
 be attained by employing the following simple method, re- 
 commended by Dr. Berhard, and substantially described as t 
 follows : " The plaster model being prepared in the usual man- 
 ner for moulding, varnish the front (or the whole) with a thin 
 solution of shellac. When dry, apply a mixture of plaster of 
 proper consistence to the front of the model from the bottom 
 up to the edge of the alveolar line, spreading it on both sides 
 so as to entirely fill up the depression around, making the 
 bottom half an inch thick, and sloping off toward the alveolar 
 ridge. When this has hardened, separate it from the model, 
 and draw the top of it over sandpaper to obtain a flat edge, and 
 let it dry. Readjust this front piece to the model ; procure a 
 mould in sand or other material in the usual way; place the 
 extra piece back in its proper position in the mould, and pro- 
 ceed to cast for the die," 
 
 In obtaining a mould from the model of a lower jaw, but 
 little difficulty will ordinarily be experienced in obtaining it 
 perfect in the manner first described. The depressions at the 
 posterior and inner border of the ridge are the points most 
 liable to drag or displace the sand, and when the latter occurs, 
 the surplus metal in the die at such points must be cut away 
 with suitable instruments ; or the cavities in the model may be 
 so filled out with wax before moulding as to permit the ready 
 separation of the model without displacing the sand, in which 
 case, also, it will be necessary, afterward, to trim the redun- 
 dant metal from the die. 
 
 A die is more readily and accurately ol)tained from a model 
 for partial dentures by cutting away the plaster teeth as before 
 described. The displacement of sand where the ridge over- 
 hangs will, as a general thing, be unimportant in these cases, 
 as the base but rarely more than partially overlaps the border. 
 
 When whiting or marble-dust is used in moulding, it is un- 
 necessary to mix water with them, as the moisture which they 
 
132 MECHANICAL DENTISTEY. 
 
 absorb from the atmosphere will give to them the proper con- 
 sistence. 
 
 Having obtained a mould in either of the ways mentioned, 
 the metal designed for the die shonld 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 mould. 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 protect the 
 sand from the overaction of heat, prevent ebullition of the 
 fused metal from the too rapid decomposition of the water of 
 the sand, and 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 consequence of contraction, can only occur in the 
 metal between its 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 more de- 
 pending portions of the mould ; 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 
 (773°), after which, and not until then, the zinc begins to part 
 from the face of the mould by contracting 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. 
 
METALLIC DIES AND COUNTER-DIES. 133 
 
 The author is indebted to Dr. B. W. Franklin for the fol- 
 lowing method of securing metallic dies and counters by a pro- 
 cess which greatly facilitates the operation and insures accurate 
 and satisfactory results : " I take all impressions, full and par- 
 tial, in plaster. A small hole, less than tV inch, is drilled 
 through the highest point of the palatal surface of the impres- 
 sion through cup and all ; into this place two or three broom 
 splints, cutting them oft' even with the surface of the plaster, 
 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 consistent with the mobility 
 required for sharp castings, the bismuth alloy known as Sir 
 Isaac Newton metal, or, which is better in some respects, 8 
 parts bismuth and 4 parts each of tin and lead — the latter 
 composition being a little harder. If a little judgment is ex- 
 ercised in pouring either of the above alloys, a perfect die will 
 be secured from moist plaster impressions without any drying. 
 As the bismuth is expansive and the alloy is hard and some- 
 what brittle, I run only a thin casting, not more than | inch 
 in thickness, over the highest portion of the impression, I 
 have cast-iron or brass heads made 3^ inches in length, 3 
 inches in diameter at 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 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 spread- 
 ing of the face of the die or liability of breaking in the process" 
 of swaging. 
 
 " I now tjikc sheet-lead of the thicknc&s of about No. 24, 
 standard gauge, and adapt it to the face of the die by means 
 of a wooden mullet or burnisher, or other convenient means. 
 Trim the lead plate to the size required for the plate to be 
 
134 MECHANICAL DENTISTEY. 
 
 stamped; when the lead plate is nicely fitted^ remove it care- 
 fully from the die and place it in a ring or narrow moulding- 
 flask, the palatal side up ; now gently stamp moulding-sand 
 into the plate and flask up level with the edges of the flask ; 
 then reverse the flask and cut the sand away dean for J inch 
 or more down to the edge of the lead plate all around. 
 Around the plate place a common moulding-ring sufiiciently 
 large to form the counter, which is made by pouring melted 
 tin or lead (or any alloys of these metals) 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 adher- 
 ing sand is brushed or Avashed 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 or 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 impres- 
 sion, with the aid of an assistant, 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 
 ofiice." 
 
 Dipping. — By this process the counter-die is first obtained, 
 and from this the die. For the purpose, two or three sheet- 
 iron pans, varying in size, should be provided, measuring from 
 three to five inches in diameter and from two to three inches 
 in depth, the open ends of which should be somewhat larger 
 than the bottoms. The metal for the counter is melted and 
 poured into the pan, and, immediately before " setting," the 
 model, being unvarnished and previously well dried, is im- 
 mersed, face downward, until all parts of the palatal arch and 
 ridge are imbedded in the metal. The chamber, as well as the 
 groove around the outside of the ridge concerned in the forma- 
 
METALLIC DIES AND COUNTER-DIES. 135 
 
 tion of a rim to the plate, should, in this ease, be formed in 
 plaster. 
 
 Ordinarily, the conformation of the ridge above and below 
 is such as to render it impracticable to remove the model from 
 the metallic matrix without injury; hence two or more models 
 will be required whenever this method is practiced. 
 
 After the counter-die and model are separated, all traces of 
 plaster should be carefully washed from the matrix and the 
 latter surrounded with a sheet-iron ring; forced slie-htlv into 
 the counter immediately outside of the cavity formed by the 
 model ; into this the metal for the die is poured, filling the 
 matrix and ring. 
 
 If the metal or alloy forming the die fuses at the same or a 
 higher heat than that composing the counter, the matrix should 
 be protected from adhering to the die by coating its surface 
 uniformly either with lamp-smoke or a thin mixture of whiting 
 and water or alcohol. 
 
 Counter-die. — A counter to the die is generally obtained 
 directly from the latter, and may be procured in either of two 
 ways. 1. The die is placed, face upward, upon the moulding- 
 board, and sand, prepared as in moulding, 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. 2. The metal for the counter may 
 first be j)6ured into a sheet-iron vessel of proper size, and, im- 
 mediately before setting, the face of the die is immersed in the 
 liquid mass and held perfectly stationary until solidification of 
 the counter takes place. The method of procuring a counter- 
 die directly from the plaster model, as in the process of dipping, 
 has already been described. 
 
 The metal commonly employed for the counter is lead, 
 although other substances, as tin, type-metal, some of the more 
 fusible alloys hereafter to be mentioned, etc., are sometimes 
 employed. When the counter is taken by pouring the metal 
 or metals composing it upon a die fusing at a low heat, some 
 
136 MECHANICAL DENTISTRY. 
 
 caution should be observed lest the two pieces adhere by par- 
 tial 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 practicable temperature, 
 and the conduction of heat facilitated by surrounding the die 
 with a heavy cast-iron box or ring. To avoid incurring any 
 risk, however, the counter-die, if composed of a less fusible 
 metal or compound than the die, may be first obtained directly 
 from the model, and the die obtained from this, as in the pro- 
 cess of dipping ; or, a counter of lead, previously taken from 
 a zinc or other more infusible die, may be used. 
 
 During the process of forcing a plate into adaptation to the 
 form of the mouth with swages, it not unfrequently happens 
 that the marginal portions of the former become wedged or 
 immovably fixed between the outer border of the die and cor- 
 responding portions of the counter before its central portion is 
 forced into contact with the palatal surface of the former, thus 
 rendering it difficult to conform the plate accurately to the 
 parts without the application 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. After forcing the central part of 
 the plate into adaptation with the partial counter, the process 
 may afterwards be completed with a full counter after having 
 turned the edges of the plate down upon the outer border of 
 the ridge with a mallet and pliers. 
 
 As before remarked, preference is usually given to lead in 
 the formation of a counter-die, mainly on account of its greater 
 softness. 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 neces- 
 sary 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 
 
METALLIC DIES AND COUXTER-DIES. 137 
 
 which it is indispensable that a metallic die should possess 
 more or less perfectly 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 suifering 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 
 into contact. This property is most indispensable in those 
 cases where the arch of the mouth is very deep, the ruga promi- 
 nent and sharply defined, 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 coaptation to the mouth, to that extent, 
 rendered faulty. The cases in which a less degree of hardness 
 is admissible is where the arch of the mouth is broad and shal- 
 low, the ruga imperfectly defined, and the ridge regular and 
 symmetrical. The conformation of the mouth, therefore, will, 
 in respect to the property of hardness, admit 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- 
 cojitraction, so far, at least, as this is attainable. Inasmuch as 
 the successful 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 essential requisites being secured, should be com- 
 posed of some metal or metals having the least possible con- 
 traction 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 faultless co])y of the 
 mouth in metal. Fortunately, as well for the expert as the 
 unskilled manipulator, the unavoidable shrinkage incurred is 
 partially or wholly compensated for by the expansion of the 
 plaster and the yielding condition of the soft tissues of the 
 month, but under no circumstances should the accommodation 
 
138 MECHANICAL DENTISTEY. 
 
 aiforded by the condition last mentioned encourage 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 practicable 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 prop- 
 erty of more practical importance. It is well known that all 
 metals expand by heat and contract by cold. In obedience to 
 this law, metals fusing at a high heat suffer a greater aggregate 
 contraction than those melting at a lower temperature, and, as 
 between two metallic bodies of equal dimensions, liquefying at 
 different temperatures, the difference in contraction will corre- 
 spond 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 contraction. Two dies, one com- 
 posed of copper and the other of zinc, will serve to illustrate. 
 Fused copper solidifies at 1900°. lu cooling, therefore, it 
 contracts through over 1800° to reach a working temperature, 
 while zinc, fusing at 773°, contracts through only about 700° 
 to reach the same temperature. As before stated, the difference 
 in the contraction of metals 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 
 
METALLIC DIES AND COUNTER-DIES. 139 
 
 repeated blows of a heavy hammer without parting or crack- 
 ing. Many metals, as aiitimony, bismuth, etc., in other re- 
 spects suitable for dies, are objectionable on account of brittle- 
 ness. But it must not, therefore, be inferred that all metals 
 that are denominated 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, provided 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 
 compression ; that fuses at a low temperature ; that does not, 
 in any material degree, contract in the act of cooling; and 
 whose particles adhere with sufficient cohesive force to main- 
 tain perfectly its integrity 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 per- 
 fectly. Thus either cast iron, brass, bronze, or cannon-metal 
 Avould form an excellent material in respect to surface hardness, 
 and in the compact form of a die, would be sufficiently cohe- 
 sive, but few enjoy convenient facilities for melting them ; be- 
 sides, their great contraction consequent upon their high fusing- 
 point would render their employment entirely inadmissible. 
 Again, certain alloys, as those composed of lead, tin, and anti- 
 mony or bismuth, are eminently suitable on account of their 
 extreme fusibility and comparative exemption from shrinkage, 
 but they gain these properties at the expense of that degree of 
 hardness necessary to resist compression. Tin in its uncom- 
 bined state is ordinarily sufficiently fusible, tenacious, and non- 
 contraetile, but is too soft and yielding when forcibly com- 
 pressed. Antimony and bismuth are sufficiently hard, fusible, 
 and non-contractile, but are objectionable on the score of ex- 
 treme brittleness. 
 
 Any metallic substance that combines most perfectly the 
 several properties referred to is, therefore, best adapted to the 
 
140 MECHANICAL DENTISTEY. 
 
 necessities of the mechanical operator, and experience has uni- 
 versally accorded pre-eminence in this respect to zinc. It pre- 
 sents a more resistant surface to the blow of a hammer than 
 either copper 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 an- 
 nealed it is tough and malleable. It melts at a heat (773°) 
 which may be readily commanded, and contracts but little in 
 cooling. The late Professor Austen demonstrated by actual 
 experiments that an average-sized zinc die, measuring two 
 inches transversely, contracts 27-lOOOths of an inch from out- 
 vside to outside of the alveolar ridge, being equivalent in thick- 
 ness to three ordinary leaves of a journal. Professor Austen 
 remarks : " In the first case (upper jaw) the plate would ' bind,' 
 and if the ridge were covered by an unyielding mucous mem- 
 brane, it would prevent accuracy of adaptation. In the second 
 case (under jaw) the plate would have too much lateral ^play,' 
 and consequently lack stability. Again, in a moderately deep 
 arch, say a half inch in depth, the shrinkage between the level 
 of the ridge and the floor of the palate will be nearly 7-lOOOths 
 — rather more than one leaf of the journal. In the deepest 
 arches this shrinkage becomes a serious difficulty ; in the shal- 
 lower cases it is not of much moment, as there is no mouth so 
 hard as not to yield the 1 or 2-lOOOths of an inch." 
 
 As before stated, a moderate degree of shrinkage in the die 
 may, in certain conditions of the mouth, practically favor the 
 adhesion 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 comparatively 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, however, a space equal to one or two thick- 
 
METALLIC DIES AND COUXTER-DIES. 141 
 
 nesses 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 resistant basis along the border, 
 and providing more certainly against displacement of the base 
 on the application of forces brought to bear upon it in masti- 
 cation. 
 
 The extent to which the shrinkage of a die may be admitted 
 in any given case, will depend partly upon difference in the 
 conditions heretofore mentioned in the soft parts of the mouth, 
 and in part, also, upon the general configuration of the jaw. 
 In a medium-sized mouth, with a depth of say half 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 advantageous. 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 
 palate. Again, as an extreme case, if the ridge and palate are 
 somewhat uniformly unyielding, and the palatal vault is, at 
 the same time, very deep, a zinc die can only be made avail- 
 able in bringing the base as nearly into adaptation as possible, 
 after which the operation may be completed with a swage hav- 
 ing a less degree of shrinkage, and which, as a mere finishing 
 die, need not necessarily 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 extremi- 
 ties of the ridge, giving too much lateral play to the plate ; in 
 addition to which the posterior and inner edge of the base, 
 
142 MECHANICAL, DENTISTRY. 
 
 projecting out from the ridge, will obstruct the free action of 
 the tongue, Avhile the latter will tend to lift it from the ridge 
 and render it unstable. These conditions may be partially- 
 remedied by turning the eclgQ 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 adapta- 
 tion 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, 5 parts ; antimony, 1 part. Fuses at 
 500° ; contraction less than one-half that of zinc ; more com- 
 pressible than the latter, and very brittle. 
 
 Babbitt, or Anti-fridion 3Ietal. — Copper, 3 parts ; antimony, 
 1 part ; tin, 3 parts. First fuse the copper, and then add the 
 antimony and tin. Melts at a moderately low heat; contracts 
 but little ; is brittle, but may be rendered less so by adding 
 tin. 
 
 Zinc, 4 parts ; tin, 1 part. Fuses at a lower heat, contracts 
 less in cooling, and has a less surface hardness than zinc. 
 
 Tin, 5 parts ; antimony, 1 part. Melts at a lower heat than 
 either of the preceding alloys; contracts but slightly in cool- 
 ing ; is harder than tin, and sufficiently cohesive. It is readily 
 oxidized, and should be poured as soon as melted. 
 
 Fusible Alloys. — The following tabular view of the more 
 fusible 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 purpose of comparison. 
 
 * American Journal of Dental Science, vol. vi, p. 367. 
 
METALLIC DIES AXD COUNTEE-DIES. 
 
 143 
 
 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,o, Tin, 3, Bismuth, 8 
 
 9. Lead, 2. Tin, 1, Bismuth, 3 
 
 Melting 
 
 Contrac- 
 
 Hard- 
 
 Brittle- 
 
 point. 
 
 tility. 
 
 ness. 
 
 ness. 
 
 770° 
 
 .013fi6 
 
 .018 
 
 5 
 
 440° 
 
 .00033 
 
 .050 
 
 3 
 
 340" 
 
 .OOSOO 
 
 .040 
 
 3 
 
 420° 
 
 .00433 
 
 .026 
 
 7 
 
 320° 
 
 .00566 
 
 .035 
 
 6 
 
 300° 
 
 .00266 
 
 .030 
 
 9 
 
 250° 
 
 .00066 
 
 .042 
 
 7 
 
 200° 
 
 .00200 
 
 .045 
 
 8 
 
 200° 
 
 .00133 
 
 .048 
 
 7 
 
 Professor A., in commenting on the preceding table, ob- 
 serves : " The last column contains an approximate estimate of 
 the relative brittleness of the samples given. As in the other 
 columns, the low numbers represent the metals, so far as this 
 property is concerned, most desirable. Those marked below 
 5 are malleable metals ; those above 5 are brittle ; zinc, 
 marked 5, separates these two classes, and belongs to one or 
 the other, according to the way in which it is managed." Allu- 
 sion is here made to the process of annealing zinc, and which 
 has already been adverted 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 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° (100° 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 crmnter, would be apt to raise the 
 zinc at least to 400°, and so impair its malleability, whilst, if 
 
144 MECHANICAL DENTISTRY. 
 
 poured as hot as many are in the habit of doing, the zinc will 
 remain as brittle as when first cast."* 
 
 * To Professor P. H. Austen, whose various contributions relating to the 
 mechanical department of practical dentistry have done much to unfold and 
 elucidate the principles involved in the practice of this important specialty, 
 the author would acknowledge his indebtedness for many of the valuable 
 data and practical suggestions that may be found embodied in the foregoing 
 chapter ; and, had not the limited space assigned us compelled a condensa- 
 tion of his views on the subject of metallic dies and counters, we might 
 have done the reader an essential service by transferring to our pages many 
 of his eminently practical observations on the subject entire. 
 
PIVOTING ARTIFICIAL CROWNS. 145 
 
 CHAPTER Y. 
 
 Partial Dentures. 
 
 The almost unlimited modifications in the form of substi- 
 tutes designed to supply the loss of a portion only of the 
 natural teeth, and the difficulties oftentimes incident to a har- 
 monious arrangement of the teeth of replacement, as well, 
 also, as the impracticability of always securing a perfectly 
 satisfactory 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 discrimination than are usually required of him 
 in the construction and application of entire dentures. 
 
 The various means employed in fixing or retaining partial 
 sets of teeth in the mouth will be first considered. Either of 
 the following methods may be adopted according to the pref- 
 erences of the operator, or the requirements of individual cases. 
 
 1. 'Pivoting an ariifieial crown to the root of a natural tooth. 
 
 2. Clamping to the natural teeth. 3. Wood pivots adjusted to 
 tubed plates. 4. Pivoting plate to the 7'oots of the natural teeth. 
 5. Atmospheric pressure. 
 
 PIVOTING artificial CROWNS. 
 
 The process of pivoting or grafting an artificial crown upon 
 the root of a natural tooth has been long practiced, and, when 
 skilfully performed with intelligent views of the various con- 
 ditions which recommend and justify the operation, affi)rds 
 a valuable and unobjectionable means of substitution. The 
 success of the operation will be greatly modified by the follow- 
 ing circumstances : 
 
 10 
 
146 MECHANICAL DENTISTRY. 
 
 1. The Condition of the Root, its Appendages, and Sur- 
 rounding Structures. — If the root to be pivoted is strong, well 
 formed and securely attached to the jaw, a living, healthy- 
 pulp present, and the peridental membrane free from disease, 
 the operation will be attended, in a large preponderance of 
 cases, with the happiest results, and in respect to utility, com- 
 fort, and appearance, is superior to any other mode of substi- 
 tution. If, however, the pulp of the tooth has been previously 
 destroyed by disease, and inflammation and suppuration of the 
 adjacent tissues have supervened, the probabilities of complete 
 success will be somewhat modified ; for although these latter 
 conditions may ordinarily be subdued by appropriate treat- 
 ment, yet that a latent predisposition favoring their recurrence 
 exists is manifested by the unfavorable results which sometimes 
 follow the operation of pivoting under apparently favorable 
 circumstances. 
 
 In no case, we are convinced, unless under circumstances of 
 peculiar exigency, should an artificial crown be attached to a 
 root whenever the latter is complicated with incurable disease 
 of the investing membrane or alveolar abscess. It may be 
 safely affirmed that the failures so common to this method, and 
 the consequent disrepute into which it has deservedly fallen, as 
 ordinarily performed, is fairly chargeable not so much to un- 
 skilful manipulation as to a want of proper appreciation of 
 the pathological conditions which clearly contraindicate its em- 
 ployment. The facilities enjoyed by the dentist of the present 
 day in the employment of the various approved methods of 
 replacement, other than the one under consideration, no longer 
 make it either necessary or pardonable to subject the patient to 
 a course of treatment which unavoidably necessitates a per- 
 petual drainage of depraved and offensive pus either through 
 fistulous openings in the gum or through channels provided by 
 art. 
 
 As respects the surrounding structures, it is well, with a 
 view of removing any disturbing causes, to institute a careful 
 examination of the mouth before inserting pivot teeth, and if 
 any of the remaining teeth are found carious or incrusted with 
 
PIVOTING ARTIFICIAL CROWNS. 147 
 
 tartar, or the mucous membrane and gums are inflamed or 
 otherwise diseased, they should be treated in accordance with 
 the indications furnished by the particular morbid conditions 
 present. 
 
 2. Dic(the8is of the Patient. — Cases frequently occur where 
 there exists a marked constitutional predisposition to inflam- 
 mation, and where, from the operation of very slight causes, 
 injuries inflicted upon any portion of the body tend to termi- 
 nate in suppuration of the tissues involved. Whenever this 
 predisposition exists in any marked degree, the operation, 
 though other conditions may favor success, is liable at all times 
 to terminate unfavorably, and, therefore, if performed at all, it 
 should be done in the most careful manner and only under 
 circumstances that promise the best chances of success. In 
 such cases not more than one tooth should be inserted at a 
 single sitting, and it will be prudent, in many cases, after hav- 
 ing prepared the root, to defer the completion of the operation 
 for a few days, or to adjust a tooth temporarily with a pivot 
 loosely fitted, until the irritation, unavoidably produced by 
 filing, drilling, etc., has completely subsided. 
 
 3. Manner of Performing the Operation. — The healthy con- 
 dition of the root and contiguous parts, and the ultimate utility 
 of the substitute, may be very materially prejudiced by care- 
 less, hurried, or injudicious manipulation; as where the re- 
 maining portions of the natural crowns of the tooth are vio- 
 lently removed with excising forceps, or by the unskilful use 
 of files in dressing- the root, or drills in enlarg-ino; the central 
 cavity, or 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 present and future 
 distress and annoyance. 
 
 Preparation of the Root. — In the process of preparing the 
 
148 
 
 MECHANICAL DENTISTEY. 
 
 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 unbroken this may be most expedi- 
 tiously accomplished, and with less risk of injury to the root, 
 by employing a very fine saw attached to a steel frame or car- 
 rier, as shown in Fig. 42. The saw should be narrow enough 
 
 Fig. 42. 
 
 to enable it to take a curvilinear direction in cutting;, as this 
 will enable the operator to separate the crown nearly or quite 
 on a line with the arched margin of the gum, thus dispensing, 
 in a great measure, with the use of other instruments in the final 
 dressing of the cut end of the root. 
 
 The saw should be passed along the side of the tooth to the 
 gum, and the crown separated either by cutting directly across 
 to the opposite side, or as nearly on a line with the curvature 
 of the anterior and posterior margins of the gum as possible 
 without wounding the latter. During the operation the saw 
 should be kept constantly wet, and the crown should be sup- 
 ported by the fingers. 
 
 If the remains of the crown are friable, or if they consist of 
 but fragmentary portions of enamel, they may be readily cut 
 
 Fig. 43. 
 
 ^^ -"'"^vr^ 
 
 away with excising forceps, two forms of wmS^re exhibited 
 in Fig. 43. The one having square, transverse cutting-edges, 
 
PIVOTING ARTIFICIAL CROWXS. 149 
 
 closing at right angles with the shaft is generally employed. 
 Serious, if not irreparable, injury may be inflicted by the care- 
 less or unskilful use of this instrument, either by producing so 
 violent a concussion as to induce, in some instances, incurable 
 disease or absolute necrosis of the root; or by fracturing the 
 latter in such a way as to unfit it for the reception of the pivot- 
 crown. The forceps, therefore, should never be used to excise 
 the crown with a single cut whenever any considerable portion 
 of the root at the gum remains unaffected by disease, and even 
 when the latter is friable or partially destroyed by decay, they 
 should be used with great caution, cutting or chipping away 
 small portions at a time until as much of its substance is re- 
 moved as is practicable with the forceps. 
 
 After the use of the saw or excising forceps, any remaining 
 portions projecting beyond the free margins of the gum should 
 then be removed and proper shape given to the end of the 
 root. A half-oval file, with a sharp and tolerably fine cut 
 running obliquely across its convex surface, or suitably formed 
 corundum burrs or disks are the best for the purpose, and, when 
 in use, should be kept constantly wet and free from clogging 
 particles of bone. The end of the root should be dressed down, 
 anteriorly, at least, a little below the free margin of the gum, 
 care being taken not to lacerate its peridental attachment ; in 
 this way the artificial crown, when adjusted to the root, will 
 unite so intimately with the gum in front as to render exposure 
 impossible. 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 j)racticable, unless there is partial obliteration and conse- 
 quent recession of the pulp-cavity as the result of ossific de- 
 posits, either to saw off the root on a line with the gum, or 
 even transversely, or to dress the root even with the gum, with- 
 out inflicting insuflerablepain. It will be necessary, therefore, 
 either to extirpate the ])ulp through the carious opening in the 
 crown before the latter is removed, or, if not exposed by the 
 
150 
 
 MECHANICAL DENTISTEY. 
 
 operation of sawing or filing, through an opening into the pulp 
 made with a drill or cutting instrument after excision. 
 
 Arsenic may be employed for the purpose of devitalizing 
 the pulp preparatory to its removal, or its extirpation may be 
 effected by direct operation with suitable instruments. By 
 the latter method the vitality of the root, through its peri- 
 dental circulation, will be better preserved. Its extirpation 
 may generally be readily effected with the use of a three or 
 four-sided, barbed, untempered broach, which, being small 
 enough to penetrate freely to the apex of the root, is thrust 
 quickly to the bottom of the canal, rotated, and withdrawn ; 
 when, if the entire pulp does not come away adherent to the 
 broach, the operation may be repeated, with comparatively 
 little pain, until all portions of it are removed. 
 
 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 important measure will greatly en- 
 danger the success of the operation. 
 
 The proper treatment and preparation of the root having 
 been thus far accomplished, the canal of the latter should next 
 
 Fig. 44. 
 
 4 
 
 be enlarged for the reception of a pivot. This is effected with 
 a suitable broach or with drills of various forms. When the 
 canal presents the form of a cleft or fissure, a spherical or cone- 
 shaped burr-drill should be used ; if, however, the pulp-cavity 
 approaches a cylindrical form, the operation will be more 
 speedily performed with a four-sided broach, or, what is still 
 better, a spear-pointed or spiral drill, all of which are exhibited 
 in Fig. 44. The natural opening in the root should be en- 
 
PIVOTING ARTIFICIAL CROWNS. 151 
 
 Jarged to the depth of from one and a half to two or more 
 lines, according to the length of the root ; and the orifice should 
 be made large enough to admit a pivot of sufficient size to 
 secure the crown firndy 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 en- 
 danger the integrity ot the latter by too great a thinning, or 
 actual perforation, of its walls. In all cases, however, where 
 the direction of the canal will admit of it, the shaft of the in- 
 strument should be held steadily on a line with the circle 
 formed by the cutting edges of the adjoining teeth, and either 
 equidistant between the latter or with such a lateral inclina- 
 tion as will give to the tooth of replacement a symmetrical 
 arrangement in the arch. During the operation, the drill 
 should be kept constantly wet, and loose particles of bone 
 should be washed from the cavity by occasional injections of 
 water. 
 
 Fitting the Crown. — The pivot crown selected for any given 
 case should correspond, as nearly as possible, in size and gen- 
 eral configuration with its fellow of the opposite side, or, where 
 sev^eral are inserted, with the form and size of the natural 
 organs which they represent. The tooth or teeth of replace- 
 ment should also harmonize in color with those immediately 
 adjoining. The cervical portion of the crown applied to the 
 root should correspond, as nearly as possible, in dimensions 
 with the filed surface of the root, and the adaptation of the 
 two surfaces should be sufficiently accurate at all points to affijrd 
 a firm basis for the crown, and, at the same time, to exclude 
 perfectly all particles of alimentary or other solid substances, 
 the decomposition of which would tend to the decay or disease 
 of the root, or become oifensive in the mouth. To secure such 
 a coaptation of the articulating surfaces, more or less dressing 
 of the root and grinding from the base of the crown will be 
 required, so that while uniform contact of the surfaces is se- 
 cured, the artificial crown will be made to occupy its proper 
 relative position in the arch. 
 
 The articulation of the crown and root may be very accu- 
 
154 MECHANICAL DENTISTRY. 
 
 the rod, and thus indicate with certainty the depth of the canal. 
 The pivot being cut oif at a point distant from the crown equal 
 to the length of the uncovered end of the wire, is then dressed 
 to the size of the orifice in the root. The pivot should be 
 accurately fitted to the canal in the root, but not so tightly as 
 to require any greater force in adjusting the crown to the root 
 than may be readily applied with the fingers. A pivot thus 
 easily applied will, when enlarged by the absorption of fluids, 
 be so firmly retained as to render its removal difficult ; and 
 even when moisture is excluded, adequate stability will be 
 imparted to the attachment, provided sufficient depth is given 
 to the cavity in the root. 
 
 It may be observed, however, that any method of pivoting 
 which does not effectually exclude the secretions of the mouth 
 is objectionable. The too frequent method of fixing artificial 
 crowns with pivots of wood, without providing for the exclu- 
 sion of the oral secretions and pulpy portions of food, not only 
 hastens the destruction of the root, but, in addition to being 
 positively harmful, cannot fail to bring a desirable method of 
 replacement into general and merited disrepute by reason of 
 the offensive odors accompanying the animal decomposition in- 
 separably associated with such a mode of procedure. 
 
 To provide against the intrusion of the secretions or portions 
 of alimentary substances, either of the following expedients 
 may be adopted : 
 
 If the coaptation of the prepared surfaces of crown and 
 root in contact is accurate and uniform, one or two thicknesses 
 of No. 4 or 6 gold foil, or corresponding thickness of tin foil, 
 interposed when the crown is forced to its place, will exclude 
 the secretions with tolerable certainty. 
 
 Such plastic substances, however, as are impervious and in- 
 soluble will more certainly accomplish the object in view, and 
 among these. Hill's stopping is generally esteemed the best. 
 
 Amalgam may also be used for the same purpose, in which 
 case the central portion of the articulating surface of the root 
 should be somewhat countersunk. 
 
 It not unfrequently happens that a cone or funnel-shaped 
 
PIVOTING ARTIFICIAL CROWNS. 155 
 
 enlargement exists at the orifice of the root-canal as the result 
 of decay. In such cases it will be difficult and often imprac- 
 ticable to adjust a pivot crown securely without preliminary 
 treatment of the root. 
 
 Firmness of attachment, in these cases, may be secured in 
 either of the following ways: 1. Having removed all softened 
 or decayed material from around the orifice of the canal and 
 enlarged the latter to the required depth for a pivot of ordi- 
 nary length, the canal so prepared, together with the carious 
 excavation, may be filled compactly with gold flush with the 
 margins of the dressed end of the root. Through this a cen- 
 tral passage is made with suitable drills for the admission of a 
 pivot. 2. A highly polished and uniformly cylindrical steel 
 wire, somewhat smaller than the prepared opening in the root, 
 may be introduced into the latter and gold packed around it 
 and into the excavation, flush, as in the former case, with the 
 margins of the root, after which the steel wire is carefully 
 withdrawn. In either of the above cases the gold should be 
 securely fixed in place in the first instance by forming small 
 pits or circular grooves in the walls of the enlarged canal, and 
 by retaining-points in the sides of the excavation. 
 
 Pivots of Metal and Wood. — Pivots are sometimes formed 
 of gold wire encased in wood. These impart additional strength 
 to the attachment, and, at the same time, enable the operator 
 to change the direction of the crown by bending the pivot 
 whenever the root stands irregularly in the arch. A hole, 
 somewhat smaller than that in the root, is drilled into a block 
 of pivot wood, and into this is forced a gold wire — that formed 
 of gold and platinum being the best, as it possesses greater 
 stiifness and elasticity. The wood is then dressed down to a 
 size a little larger than the canal in the root, and then coni- 
 jM-essed. One end being fitted to the hole in the crown, the 
 projecting portion of the pivot, cut to the proper length, is 
 trimmed to fit tlie opening in the root, and applied in the man- 
 ner before described. 
 
 Another method is to close the hole in the crown with a 
 cylinder of j)ivot wood, trim it even with the base of the crown, 
 
152 MECHANICAL DENTISTRY. 
 
 rately obtained in the following manner : Attach to the crown 
 a temporary pivot of wood that may be easily applied and 
 removed ; coat the surface of the root uniformly with some 
 pigment, as carmine, rouge, or rose pink, and apply the crown, 
 with pivot attached, to the root ; the points of contact will be 
 indicated upon the base of the crown by the adherent coloring 
 matter ; the colored portions are then ground down somewhat 
 on an emery wheel, and this process is repeated until the entire 
 surface of the base of the crown exposed to the pigment becomes 
 uniformly coated. Whenever it is thought important to pre- 
 serve the form of the porcelain crown unchanged, the operation 
 may be reversed by coloring the base of the latter and filing 
 from the extremity of the root until a perfect adjustment of 
 the parts is secured. 
 
 Another method, sometimes employed, may be adopted, and 
 will secure an equally accurate bearing of the crown without 
 subjecting the patient to the annoyance of repeated trials of 
 the pivot tooth in the mouth. After having prepared the root 
 in the manner already described, an impression of the root and 
 contiguous teeth is taken, and from this a plaster model is ob- 
 tained. The drilled cavity in the root will be indicated on the 
 model by a corresponding depression ; this may be extended 
 into the body of the latter with an instrument fitting the ori- 
 fice and held in the exact position as when enlarging the canal 
 in the fang. The model is then varnished, and a pivot being 
 temporarily attached to the crown, the base of the latter may 
 be ground, with or without the use of coloring matter applied 
 to the model, until the articulating surfaces close uniformly, 
 and the crown occupies the required position indicated by the 
 adjoining teeth represented on the model. If the impression 
 is correct, and the manipulations are accurately conducted, a 
 pivot tooth prepared in this manner will be found to fit the 
 root and occupy a proper position in the circle with but little, 
 if any, additional filing or grinding. 
 
 Attaching the Oroivn by Means of Wood Pivots. — The older 
 and less expensive method of fixing artificial crowns to the 
 roots of teeth is by means of pivots of wood. Thoroughly 
 
PIVOTING ARTIFICIAL CROAVNS. 153 
 
 seasoned white hickory of small growth, fine-grained, and 
 straight, compact fibres, is esteemed the best for the purpose. 
 This substance is often used in its natural condition, but it will 
 be much improved, both in respect to strength and durability, 
 if previously well condensed by forcing it through the hol(!S of 
 an ordinary draw-plate, or, what is better, through aj)ertures 
 of various sizes formed with smooth bevelled edges in a piece 
 of ivory, steel, or porcelain of sufficient thickness. Cylinders 
 of wood, of uniform thickness throughout, are most conve- 
 niently formed by splitting the timber into rods five or six 
 inches in length, and from one-eighth to a quarter of an inch 
 in diameter, trimming them with suitable instruments to a size 
 one-third larger than required when condensed, and then pass- 
 ing them through the holes of a draw-plate, on the side where 
 they form a cutting edge, commencing with the larger and 
 passing to those of diminished calibre, until a cylinder of the 
 
 Fio. 45. 
 
 size mentioned is obtained. These are then compressed in the 
 manner V)efore mentioned. When the draw-i)late is used to 
 compress the pivot, the latter should be passed through from 
 the side opposite to the one used in forming the pivot. 
 
 One end of the pivot, dressed to the proper size, is maxle to 
 fit accurately the hole in the crown, care being taken not to 
 fracture the latter when forcing the pivot into place. The 
 depth of the enlarged opening in the root will determine the 
 length to be given to the end of the pivot ]»rojecting from the 
 crown, and the former may be readily determined Ijy means of 
 a gauge (Fig. 45), cf)nsisting of a rod of wire of a size to enter 
 freely the canal in the root, with a movable slide, to the end of 
 which is attached a circular collar or flange. The end of" tiie 
 wire being pressed to the bottom of the canal, the flange, rest- 
 ing against the end of the root, will force the slide l>a<'k upon 
 
154 MECHANICAL DENTISTEY. 
 
 the rod, and thus ijidicate with certainty the depth of the canal. 
 The pivot being cut off at a point distant from the crown equal 
 to the length of the uncovered end of the wire, is then dressed 
 to the size of the orifice in the root. The pivot should be 
 accurately fitted to the canal in the root, but not so tightly as 
 to require any greater force in adjusting the crown to the root 
 than may be readily applied with the fingers. A pivot thus 
 easily applied will, when enlarged by the absorption of fluids, 
 be so firmly retained as to render its removal difficult ; and 
 even when moisture is excluded, adequate stability will be 
 imparted to the attachment, provided sufficient depth is given 
 to the cavity in the root. 
 
 It may be observed, however, that any method of pivoting 
 which does not effectually exclude the secretions of the mouth 
 is objectionable. The too frequent method of fixing artificial 
 crowns Avith pivots of wood, without providing for the exclu- 
 sion of the oral secretions and pulpy portions of food, not only 
 hastens the destruction of the root, but, in addition to being 
 positively harmful, cannot fail to bring a desirable method of 
 replacement into general and merited disrepute by reason of 
 the offensive odors accompanying the animal decomposition in- 
 separably associated with such a mode of procedure. 
 
 To provide against the intrusion of the secretions or portions 
 of alimentary substances, either of the following expedients 
 may be adopted : 
 
 If the coaptation of the prepared surfaces of crown and 
 root in contact is accurate and uniform, one or two thicknesses 
 of No. 4 or 6 gold foil, or corresponding thickness of tin foil, 
 interposed when the crown is forced to its place, will exclude 
 the secretions with tolerable certainty. 
 
 Such plastic substances, however, as are impervious and in- 
 soluble will more certainly accomplish the object in view, and 
 among these, Hill's stopping is generally esteemed the best. 
 
 Amalgam may also be used for the same purpose, in which 
 case the central portion of the articulating surface of the root 
 should be somewhat countersunk. 
 
 It not unfrequently happens that a cone or funnel-shaped 
 
PIVOTIXG ARTIFICIAL CROWNS. 155 
 
 enlargement exists at the orifice of the root-canal as the result 
 of decay. In such cases it will be difficult and often imprac- 
 ticable to adjust a pivot crown securely without preliminary 
 treatment of the root. 
 
 Firmness of attachment, in these cases, may be secured in 
 either of the following ways : 1. Having removed all softened 
 or decayed material from around the orifice of the canal and 
 enlarged the latter to the required depth for a ])ivot of ordi- 
 nary length, the canal so prepared, together with the carious 
 excavation, may be filled compactly with gold flush with the 
 margins of the dressed end of the root. Through this a cen- 
 tral passage is made with suitable drills for the admission of a 
 pivot. 2. A highly polished and uniformly cylindrical steel 
 wire, somewhat smaller than the prepared opening in the root, 
 may be introduced into the latter and gold packed around it 
 and into the excavation, flush, as in the former case, with the 
 margins of the root, after which the steel wire is carefully 
 withdrawn. In either of the above cases the gold should be 
 securely fixed in place in the first instance by forming small 
 pits or circular grooves in the walls of the enlarged canal, and 
 by retaining-points in the sides of the excavation. 
 
 Pivots of Metal and Wood. — Pivots are sometimes formed 
 of gold wire encased in wood. These impart additional strength 
 to the attachment, and, at the same time, enable the operator 
 to change the direction of the crown by bending the pivot 
 whenever the root stands irregularly in the arch. A hole, 
 somewhat smaller than that in the root, is drilled into a block 
 of pivot wood, and into this is forced a gold wire — that formed 
 of gold and platinum being the best, as it possesses greater 
 stiffness and elasticity. The wood is then dressed down to a 
 size a little larger than the canal in the root, and then com- 
 pressed. One end being fitted to the hole in the crown, the 
 projecting portion of the pivot, cut to the jtroper length, is 
 trimme<l to fit the opening in the root, and applied in the man- 
 ner before dc^scribed. 
 
 Anotlier method is to close the hole in the crown with a 
 cylinder of pivot wood, trim it even with the base of the crown, 
 
156 MECHANICAL DENTISTRY. 
 
 perforate its centre with a drill^ and introduce into this one 
 end of the wire, the surface of which is cut up into small barbs, 
 or otherwise roughened to prevent it from drawing. A similar 
 piece of wood is fitted to the orifice in the fang, and trimmed 
 and drilled in like manner for the reception of the wire pivot 
 — the latter being barbed and filed square to render it station- 
 ary when forced into place. 
 
 The author, in a number of cases, has adopted the following 
 methods of inserting pivot teeth, in connection with the use of 
 rubber, with gratifying results. 
 
 Having prepared the root in the ordinary manner, select 
 and fit the pivot crown to the vacuity, leaving something of a 
 space posteriorly between the base of the crown and the root. 
 Fit a temporary wood pivot to the enlarged opening in the 
 root, accurately, but in such manner that it may be easily with- 
 drawn ; the end projecting from the root should be trimmed 
 down to say half the diameter of the hole in the crown, so that 
 when the latter is applied in the manner to be mentioned 
 directly, some latitude of movement will be provided, admit- 
 ting of a proper adjustment of the crown when applied to the 
 space. With the wood pivot in the root, fill the hole in the 
 crown with stiffened wax, warm the pivot crown sufficiently to 
 soften the wax, and apply it to the root in the desired position 
 with respect to the other teeth. When the wax has hardened 
 somewhat, withdraw the crown carefully on a line with the 
 pivot, bringing the latter with it; then add sufficient softened 
 wax to the base of the crown to fill in the gap or space between 
 the croM^n and root ; replace the tooth with the pivot attached, 
 and press up until the crown again takes its proper position 
 in the vacuity. By this means we get an impression of the 
 filed extremity of the root, and, at the same time, secure an 
 accurate relation of all the parts. The crown and pivot are 
 then carefully removed. Now take plaster and pour a small 
 quantity on a piece of paper or card and sink the pivot into it 
 until the surface of the wax at the base of the crown rests 
 upon the plaster, and then build the latter up upon the front 
 part of the crown to the cutting edge, thus forming a shallow 
 
PIVOTING ARTIFICIAL CROWNS. 157 
 
 bed for its anterior face. When the plaster has hardened, 
 warm the model to soften the wax, and then remove the crown 
 and wax ; the pivot will be found remaining in the model, but 
 which, if previously oiled, can be readily drawn. We have 
 now in the model an accurate representation of the end of the 
 root, the size and direction of the root-canal, and, when the 
 crown is replaced in its shallow bed, also the space between 
 the crown and root to be filled in with rubber. The hole in 
 the model, corresponding with that in the root, should be en- 
 larged somewhat, and this may be done with the same drill 
 used in enlarging the orifice of the root. After varnishing the 
 hole in the model, pack in softened rubber until full, and in- 
 sert into this the gold wire previously heated, the crown end 
 of the wire projecting a line or so. Next fill the hole in the 
 crow^n with rubber, heat the crown, and press it down upon 
 the model and over the gold wire until the crown goes accu- 
 rately into the depression made for it in the model. Then pack 
 softened rubber into the space between the base of the crown 
 and the model until it is filled in compactly. The whole is 
 then encased in plaster, confined in a flask, and vulcanized. 
 If the foregoing manipulations are carefully conducted, the 
 crown will go to its place in the mouth with unerring accuracy, 
 and, by placing one or two thicknesses of gold foil between 
 the rubber and root, or some plastic material, as Hill's stop- 
 ping, the joint will be rendered impervious. There is still an 
 additional advantage in this method. All are aware of the 
 liability of a wood pivot drawing from the crown where the 
 latter is short and tiie hole in it shallow. The wired rubber 
 pivot, vulcanized in the crown, cannot be drawn from the 
 most shallow cavity without fracturing the crown. In very 
 many cases this circumstance is of great value. 
 
 In sul>stituting a porcelain plate tooth for the pivot crown 
 in connection with the use of rubber the following method may 
 be j)ursued : Fit a metallic pivot, composed of gold and pla- 
 tinum, accurately to the enlarged opening in the root, but not 
 HO tiglitly but that it may be readily withdrawn. Select and 
 fit a suitable plate tooth, and solder to this a moderately thin 
 
158 MECHANICAL DENTISTRY. 
 
 gold backing. If, on reapplying the crown, with the pivot in 
 place, the former is crowded forward out of proper position by 
 the pivot, cut a slot in the latter, and, if necessary, groove the 
 gold backing and crown at the base of the latter until the 
 crown will take its required place, and the projecting portion 
 of the. pivot lies in close contact with the gold backing for a 
 distance sufficient to insure adequate strength of attachment 
 when the two are united by solder. When the crown is thus 
 adjusted to the pivot, secure them in this relation with wax or 
 plaster and remove them carefully ; imbed in plaster and unite 
 them securely with solder, and then proceed to take an accurate 
 impression of the end of the root in connection with the united 
 crown and pivot. This may be done by first filling in over 
 the dressed end of the root with a sufficient quantity of soft- 
 ened wax, forcing the crown and pivot into place, and then 
 moulding the wax with the finger to the end of the root and 
 over the backing. Trim away superfluous portions of wax, 
 remove carefully, imbed in plaster in the same manner as de- 
 scribed in connection with pivot crown, form matrix in plaster, 
 pack with rubber, vulcanize, dress down to the form of adjoin- 
 ing crowns, and polish. 
 
 To secure more perfectly the attachment of the rubber, the 
 porcelain crown may be sufficiently undercut with a corundum 
 disk along the sides of the gold backing, to bind the rubber, 
 and this should be done either before or immediately after 
 soldering the pivot to the crown. 
 
 AVhen employing either of the foregoing methods, the wire 
 pivot should be well barbed, and the joint between the crown 
 and root sealed either by interposing folds of soft foil, or by 
 some durable and impervious plastic material when the crown 
 is finally and permanently adjusted. 
 
 Pivot Plate. — The following methods of pivoting an arti- 
 ficial crown are applicable to all cases admitting of this mode 
 of substitution, but will be found of especial utility under 
 certain circumstances or conditions which exclude the use of 
 the simple pivot crown, or which at least render their employ- 
 ment difficult and unsatisfactorv. 
 
PIVOTING ARTIFICIAL CROAVNS. 159 
 
 It frequently occurs that the root to be used occupies a posi- 
 tion in the arch inconsistent with a harmonious arrangement of 
 the tooth of replacement by the usual method of attaching an 
 ordinary pivot-crown. Thus it may lie closely against one or 
 other of the adjoining teeth, distant from the centre of the 
 space ; or it may have too great an anterior or posterior ob- 
 liquity, or too great a lateral inclination; or, again, it may 
 range with the other teeth with respect to its direction, but may 
 occupy a position entirely within the circle ; in either case it 
 will be difficult or impracticable to give a proper relative posi- 
 tion to the crown in the usual way. It is true that any slight 
 deviation from a just position or inclination of the root may 
 be compensated for by a corresponding inflection of the pivot, 
 or by forming an abrupt angle to it where the crown and root 
 unite, or by placing the pivot on one side of the hole in the 
 crown ; but when the irregularities spoken of exist to any con- 
 siderable extent, it will become necessary to adjust a pivot-plate 
 to the root, and attach to the base an ordinary plate tooth, to 
 which any desired position may be assigned. 
 
 One of the simplest and most practicable methods of per- 
 forming this operation is thus described by Professor Edwin 
 T. Darby: 
 
 " After this (the proper preparation of the root) has been 
 thoroughly done, select a piece of gold or platinum wire («), 
 Fig. 40, of the diameter of the opening in root, and fit nicely 
 
 Fig. 4G 
 
 I © 
 
 tt 
 
 to the opening, letting it project one-eighth inch beyond the 
 end of the root, that it may be readily removed and inserted 
 in the root during the operation. Next select a thin piece of 
 platinum, of which make a cap with hole to fit around the 
 wire pivot snugly, and over the whole end of the root (6). 
 
162 
 
 MECHANICAL DENTISTEY. 
 
 is here given (Fig. 47, o). When this is done and the wire 
 and plate taken from the root and put in place in the impres- 
 sion, a correct model of the teeth and parts adjoining can be 
 made with the gold in the same relative position as when in 
 the mouth. After the model is made, the gold removed from 
 it, the end of the wire which extended outside the root to aid 
 in marking the position of the wire and plate in the impres- 
 sion cut off and filed down to the surface of the plate, a thick, 
 narrow gold backing should be fitted and riveted to a suitable 
 crown (plain 'plate tooth' with 'straight pins') and a groove 
 be cut along each side, and, in some cases, near the cutting 
 edge of the porcelain, as illustrated in Figs. 47 6, and 48. 
 This is done that the parts may then be built out and the por- 
 celain more perfectly secured, and the contour of the palatal 
 
 Fig. 47. 
 
 Fig. 48. 
 
 portion restored with pure gold, as shown in the cut with 
 crown in place (Fig. 48). After the backing is placed upon 
 the porcelain, it should be attached to the plate with wax and 
 the whole carefully removed from the model, encased in plas- 
 ter and sand, gradually heated, and soldered. The parts, pre- 
 pared as described and illustrated, may be held by screwing 
 the wire in a hand-vice while the gold foil is being built in 
 place. This can be nicely done with the electro-magnetic 
 mallet, and the crown made ready for insertion by the time of 
 the next appointment with the patient. 
 
 " A very good and less difficult method of preparing crowns 
 is to back the whole of the porcelain and restore the contour 
 of the palatal portion with fine gold plate (18 to 22 k.), 
 united with correspondingly fine solder. 
 
 " The apical foramen should be closed with gold. If gutta- 
 percha or oxychloride of zinc be used for this purpose, some of 
 
PIVOTING ARTIFICIAL CROWNS. 163 
 
 the material may be pressed through the foramen, but with 
 gold the operation can be made more certain and satisfactory. 
 To avoid any exposure of gold should recession of the gum 
 take place, the edge of the plate ought to be so cut away that 
 the porcelain may be accurately fitted upon the labial portion 
 of the root. 
 
 " When all is in readiness for placing the crown upon the 
 root, fine barbs should be made with a knife or lancet along 
 the entire surface of the gold wire, a thin layer of white gutta- 
 percha (such as requires little heat) placed around the wires 
 and against the plate ; the metallic parts should be heated suf- 
 ficiently to just soften the gutta-percha, and, with the root 
 dried, the whole must be immediately pressed and carefully 
 malleted to place. The surplus stopping should be trimmed 
 oif with a lancet a few hours or the day after the crown is 
 placed upon the root, or when the gutta-percha shall be thor- 
 oughly cooled ; the gum will then have been so pressed away 
 that the boundary-line between the crown and root can be seen 
 and the edge of the gutta-percha smoothly finished with pellets 
 of Japanese bibulous paper, lint, or cotton saturated with chlo- 
 roform. 
 
 " There is a still less difficult and yet good method of plac- 
 ing crowns upon roots of teeth, and one, too, that does not re- 
 quire so much time as that just described ; but the root should 
 be prepared and a gold wire fitted in it in the same manner. 
 A suitable plain 'pivot' crown, having a hole in it a little 
 larger than the gold wire, should be selected and fitted to the 
 surface of the root as perfectly as possible, and the opening in 
 the porcelain filled with fine, well-seasoned hickory wood, 
 which must then be cut off even with the base of the crown, 
 and a hole drilled in the centre and entirely through it large 
 enough to insert one end of the wire. The surface of the wire 
 should l)c roughened or finely barbed along its whole length, 
 one end })]aced (not malleted) tightly in the opening made for 
 it in the wood in the crown, and the whole then placed upon 
 the root and finished Jis above descril)ed. 
 
 "An artificial crown, l)y whatever method mounted, can be 
 
164 
 
 MECHANICAL DENTISTEY. 
 
 ■ more successfully placed upon a root, and all operations better 
 performed, when the rubber dam is applied than where it is 
 not used, and it should, therefore, be secured, if the operator 
 can apply it, to the adjoiniug teeth, and then to the root, be- 
 fore the final fitting and mounting of the crown." 
 
 Gold Crown Faced with Porcelain. — The subjoined method 
 of attaching an artificial crown to a root was originally intro- 
 duced to the notice of the profession, in 1872, by Dr. Marshall 
 H. Webb. The following is a description of his more recent 
 and perfected method of operating, which, while it necessitates 
 great care, dexterity, and delicacy of manipulation, unquestion- 
 ably possesses, in aa exceptional degree, the important advan- 
 tages not only of security of attachment, but of indestructi- 
 bility, the union with the prepared surface of the root being 
 effected by direct contact of impacted gold. 
 
 " Building crowns of gold upon roots of teeth and facing 
 them with porcelain makes the most secure and satisfactory 
 
 though difficult operation. After preparing the root, closing 
 the foramen with gold, and cutting away the irregular or pro- 
 jecting edges to within about a half line of the margin of the 
 gum (leaving this much to aid in applying the rubber dam), a 
 gold wire, No. 13 or 14, with a fine, sharp thread cut upon it, 
 should be accurately fitted in the pulp-chamber to near the 
 apical foramen. To the platinum pins of the porcelain selected 
 for the case a cylinder or tube made of gold plate should be 
 fitted, and, after it is opened (Fig. 49), riveted and then closed, 
 placed in plaster and fine sand, and carefully heated and sol- 
 dered. A thread must then be cut in the cylinder correspond- 
 
PIVOTIXG ARTIFICIAL CROWNS. 165 
 
 ing to that upon the wire to which it is to be attached. This 
 is done that the crown may be more securely placed upon the 
 root than by the method described by the writer in the Dental 
 Cosmos, June, 1873. The end of the gold tube next the cut- 
 ting edge of the crown may be bevelled and a slot made in the 
 wire at that part, so that the cylinder will be prevented from 
 turning, while still greater strength is added by impacting gold 
 into the open part, thus spreading the end of the wire. A 
 groove should be cut with a corundum disk in each side (6), 
 and sometimes along the cutting edge of the porcelain, into 
 which gold foil is to be placed, to secure greater strength and 
 permanency. 
 
 " When all is in readiness for the operation, the rubber dam 
 should be applied to two teeth each side of the root and to the 
 root itself. The ligature of waxed floss silk should be placed 
 twice around the root, tightened, and pressed well to place with 
 a burnisher, the ends of the silk wrapped twice, as in tying a 
 surgeon's knot, and the ligature then attached to the ring at 
 the end of an elastic rubber dam holder and held just below 
 the edge of the slightly upraised lip, so that, when the holder 
 is fixed to a tie put around the patient's neck, there shall be 
 constant tension upon the ligature. After this has been done 
 the root should be trimmed down with corundum wheels or 
 cones to the ligature, although not close enough to displace it. 
 The porcelain should then be so fitted as to leave a half line 
 of space to be filled with gold (as at c) between it and the root, 
 after the wire has been placed in the cylinder and screwed into 
 the root. In placing the parts in position a little oxychloride 
 of zinc, nearly the consistency of cream, should be placed in 
 the root next the gold that closes the foramen, and the gold 
 wire at once put in this and screwed securely to place. After 
 the oxychloride of zinc has crystallized, sufficient of it and of 
 the dentine should be cut away with small burs to secure good 
 anchorage for the gold now to be placed as perfectly and solidly 
 as possible around the wire, to and over the margin of the root, 
 along the gold tube, into the grooves made in the porcelain, 
 and betwficn it and the labial margin of the root (c). This 
 
166 MECHANICAL DENTISTEY. 
 
 narrow line of gold need not be made visible when the oper- 
 ation is completed. The gum should cover it. While the 
 gold is being placed around the wire in the root the porcelain 
 can be turned a little to one side upon the gold wire till the 
 cylinder is reached and restoration of the contour of the parts 
 commenced. All the gold should be cohesive and impacted by 
 the aid of the electro-magnetic mallet, with which the surplus 
 foil can easily be trimmed away from the margin of the root 
 as placed upon it, and the form of the crown so nicely carried 
 forward that but little dressing is afterwards necessary. The 
 gold should be filed even with the margin of the root, and 
 finished with narrow strips of fine emery cloth at and near that 
 point, while the rubber dam is yet in place; after this is re- 
 moved the gold should be so cut away as to allow proper occlu- 
 sion of the teeth, and a little space should afterwards be gained 
 by very careful wedging for the trimming and finishing of the 
 gold along each proximate surface separately." 
 
 The form and relations of the several parts entering into the 
 construction of a crown by Dr. Webb's method are shown in 
 Fig. 49. 
 
 A process of attaching porcelain crowns to the roots of teeth 
 by the use of steel screws, originally introduced to the notice 
 of the profession by Dr. George T. Moffat, of Boston, Mass., 
 but more recently and particularly described by Dr. E. W. 
 Foster of the same city, is worthy of a place among the best 
 operations of this kind by reason of its simplicity, security of 
 attachment, comparative inexpensiveness, and its practicable 
 application to other than the single-rooted teeth. Dr. F. thus 
 describes the method : 
 
 " Among the principal features of this method is the steel 
 screw in place of the steel pin, as first applied, and which 
 unites the crown to the root in the most perfect and absolute 
 manner. The inner head of the screw (Fig. 50 a) is a concave 
 or half globular, and completes the principle of a ball-and- 
 socket joint between itself and the circular cavity in the poste- 
 rior part of the crown, seen at b, in a vertical section of the 
 same. This, it will be observed, permits of an automatic ad- 
 
PIVOTING ARTIFICIAL CROWNS. 167 
 
 justment to the root, but more so in lateral directions, a fact of 
 great importance and convenience where the root is out of its 
 normal position, as is frequently the case, especially as regards 
 the anterior teeth. Where the root is sound and the joint close, 
 a few layers of soft gold foil are placed between the crown and 
 the root. After a careful and final setting of the screw, an 
 impervious joint is thereby obtained — one perfectly odorless 
 and highly antiseptic to the root for an indefinite period of 
 time. 
 
 " The prejudice against the old and odorous varieties of 
 crowns is well sustained by all persons of intelligence and re- 
 finement. 
 
 " The front view of an incisor crown thus set is shown at a 
 (Fig. 51). The posterior cavity in the crown, over the screw- 
 
 FiG. 50. Fig. 51. 
 
 head at 6, is filled with gold, or other material, and finished 
 flush and smooth with the surfaee. Where gold is u.sed, which 
 is generally preferable, the retention of the first pellets is 
 greatly facilitated by the previous arrangement of a few layers 
 of adhesive gold foil under the head of the screw, whose over- 
 lapping edges serve admirably the purpose intended. 
 
 " Oxychloride of zinc or gutta-percha would be indicated in 
 cases where the root was hypersensitive. In the place of the 
 layer or layers of foil in the joint, a drop of gum sandarac 
 varnish — quite thick — will often be all that is required to ac- 
 complish the same results. Where the end of the root is ex- 
 tensively decayed, the jagged interval in adjustment may be 
 filled with gold or gutta-percha according to the judgment of 
 the operator. The screws should be made of the best watch- 
 
168 MECHANICAL DENTISTRY. 
 
 steel wire, and in the main shaft do not require to be larger in 
 diameter than a small knitting or common-sized darning-needle. 
 The screws may be also slightly washed in a nickel bath to suit a 
 whim or fancy, but practically they have no advantage what- 
 ever over plain screws, for the obvious reasons of their seclu- 
 sion and dryness when in position. Most of the anterior roots 
 will, for a sufficient distance, permit the use of a drill which 
 is three or four, or even five times the diameter of the screw. 
 A plug of hickory in such cases is firmly set in the hole thus 
 drilled in the root, and the end of the wood neatly finished with 
 the outer surface. The tooth crown, now firmly held in the 
 desired position on the end of the prepared root, will act as a 
 guide in drilling for the screw, the drill passing up through 
 the posterior cavity of the crown. Presuming, of course, that 
 the nerve cavity is filled to the screw with gold, a vertical half 
 section of the root and crown with the inserted wood for the 
 attachment of the screw would appear as in Fig. 52. At a 
 
 Fig. 52. Fig. 53. 
 
 appears the wood, and at b the external gold plug. The final 
 attachment is facilitated by having previously run the screw 
 once through the wood before the crown is put on. A tap for 
 the screw is easily made from a broken excavator or other in- 
 strument of like dimensions by drawing the temper and cutting 
 the same thread as the screw for a suitable distance upon the 
 end. After the end is slightly rounded, three grooves, equi- 
 distant from each other, should be filed rather deeply, length- 
 wise of the tap, then the whole tempered and drawn back to 
 straw color. The screws themselves will run better by being 
 grooved likewise, but should not be tempered. However, if a 
 
PIVOTING ARTIFICIAL CROWNS. 169 
 
 tap is necessary, and a regular one is not at hand, from acci- 
 dent or otherwise, the screw, already grooved, needs simply to 
 be tempered to act admirably in a double capacity. 
 
 "We have spoken principally of the anterior teeth. We 
 will now refer to this method as applied to those teeth, in either 
 arch, that are posterior to the canines. 
 
 " It will be evident from the principles involved, that bicus- 
 pid and molar crowns can be applied with the same facility, 
 especially whenever their situation in the arch will permit the 
 use of the drill. Bicuspids are treated in the same manner as 
 the anterior teeth, save that in the strong, broad, and frequently 
 bifid roots of second bicuspids, two screws may attach the 
 crown, especially where extra strength will be required from 
 their situation in mastication. 
 
 "Fig. 53 will illustrate a second upper bicuspid, in part sec- 
 tion vv-ith two screW'S. Upper and lower molars will require 
 two, three, or more screws as the operator may determine, 
 ]Many more layers of foil will be required for molar crowns than 
 for others, in order to secure an equal perfection of their joints. 
 Where many crowns may be called for in a case, the carver is 
 indispensable. In cities, and in offices, even, where good 
 carvers may be had, nearly, if not every tooth may be carved 
 by him to suit each place precisely, and little or no fitting will 
 be required. More diversified and desirable results are thus 
 obtained. In the country, and places too remote for such ad- 
 vantages, the anterior and bicuspid crowns may be furnished 
 in various colors and shapes after the ordinary patterns. Excel- 
 lent crowns of the above description have been furnished us by 
 the enterprise and accommodation of S. S. White from moulds 
 made expressly for such. 
 
 " In the matter of screws we will merely remark that, as no 
 town furnishes a dentist without at the same time furnishing 
 him with a neighbor equally constant, omnipresent, and inde- 
 fatigable, — the jeweller, — the facility of obtaining screws made 
 to a desirable j)attorn will be abundant and satisfactory. 
 Where it is decided to give the carver an opportunity to dis- 
 play his skill, whether it be upon one crown or a dozen, an 
 
170 MECHANICAL DENTISTEY. 
 
 impression in plaster will be necessary. Preceding this, all the 
 crown-bearing roots should be prepared, dressed, and drilled 
 the same as for setting, but not tapped. Bits of wire of any- 
 kind, the diameter of the drill, are now set in each place in- 
 tended for a screw, and rising to the height of the future crown. 
 These pins should sit in their places easily enough to come 
 away readily with the impression when it is withdrawn. The 
 removal of the impression from about the other teeth may be 
 facilitated by the use of a slight portion of glycerin applied 
 with a small camel's-hair brush about their necks and crowns. 
 Glycerin, though agreeable of itself to most people, may be 
 rendered quite so by perfuming it with some generally accept- 
 able odor. The impression being now removed is carefully 
 varnished and oiled, the pin or pins remaining in situ. From 
 this the true cast is made, the pins now being transferred to 
 this one in turn. By careful manipulation and cutting the 
 pins will part with the old cast or impression with little or no 
 difficulty. The purpose of these pins is to serve the carver 
 for attachment of the ' body ' in its first moulding, and give, 
 at the same time, the direction and diameter of the screws in 
 the crown, the heads of which should finally occupy the posi- 
 tion of about a sixteenth of an inch from the joint. A plaster 
 bite of the antagonizing teeth should also accompany the final 
 cast. If shrinkage in baking of the crown will not permit 
 the passage of the screw freely, a small, soft steel mandril in 
 the lathe, with the use of oil and the flour of emery, will be 
 efficient. 
 
 " Fig. 54 represents a case where eight crowns have been set 
 by this method. The black dots represent the gold fillings 
 over the screws — two in the second bicuspid and three in each 
 of the two molars. 
 
 " In conclusion, with regard to the above method of crowning 
 roots, and its application, we may be permitted to offer for 
 consideration a summary of its characteristics ; 
 
 " 1st. Its simplicity, neatness, and permanency. 
 
 " 2d. The impervious and antiseptic character of the union of 
 crown and root. 
 
PIVOTING ARTIFICIAL CROWNS. 
 
 171 
 
 " 3d. The practical application of these crowns to bicuspids 
 and molars, as well as to the anterior teeth, which have been 
 chiefly concerned in this matter hitherto. 
 
 "4th. The use of the screw, which is one of the most pow- 
 erful adjuncts in mechanics; and this screw of steel, uniting 
 the minimum of size with the maximum of strength. 
 
 " 5th. The application of an entire crown of porcelain, ivory, 
 or gold and porcelain, as set forth. 
 
 Fig. 54. 
 
 "6th. The ball-and-socket principle of the screw-head and 
 its cavity of reception in the crown, permitting of automatic 
 adjustment to the root, whether in its normal position or other- 
 wise. 
 
 " 7th. The facility with which the carver may adapt one or 
 many crowns in cither dental arch. 
 
 " 8th. The final filling and finish of gold or other material 
 in the posterior cavity over the screw, sealing the whole imper- 
 viou.sly, and at the same time permitting of the speedy and safe 
 removal of the crown, when necessary from its fracture, or 
 from other causes. 
 
 " *Jth. The many objections it refutes witii regard to the 
 
172 MECHANICAL DENTISTEY. 
 
 popular notion of 'pivoting' teeth in general. Among the 
 raost j)rominent of which are not only the oifensive odor and 
 other imperfections of the older forms, but the costliness and 
 tediousness of some of the later ones." 
 
 The author is indebted to the obliging courtesy of Dr. W. 
 G. A. Bonwill, of Philadelphia, Pennsylvania, for advance 
 proof-sheets of an article descriptive of a " New Method of 
 Substituting an All-poecelain Crown upon any Koot 
 IN Either Denture/' prepared for August number (1880) 
 of the Dental Cosmos. Dr. Bonwill's long-continued, intelli- 
 gent, and successful experimentation in this sj)ecial department 
 of practice is well known to the profession, and the following 
 may be accepted as embodying his best and latest experiences. 
 He writes : 
 
 "No argument is needed to convince the advanced practi- 
 tioner that some method is demanded whereby the thousands 
 of good roots now sacrificed can be made permanently useful. 
 Notwithstanding the great revolution wrought by machinery 
 and improved appliances for filling teeth, so few are the suc- 
 cesses that, unless some plan is brought to our aid to save the 
 remaining roots from the ravages of decay and from a want of 
 skill and judgment by three-fourths of the dentists, we shall 
 have little else than plates with which to meet the issue. Teeth 
 can be saved without filling as well as by filling by some 
 operators, but by a few only. Most of the dilemmas which all 
 of us encounter every day are the results of bad dentistry. The 
 plan to meet the difficulty must be one which is founded on 
 such mechanical and physical laws that it can be safely relied 
 upon for resisting both time and the various surrounding cir- 
 cumstances; one which any ordinary operator can follow, and 
 which will be so cheap as to bring it within the reach of all; 
 one which, if by accident the porcelain crown has been frac- 
 tured, will allow of easy substitution in a few minutes without 
 interfering again with the operation performed on the root. A 
 crown is needed which can be obtained by every operator as 
 easily as porcelain teeth for plate work, and kept in stock by 
 him ready for any emergency, and costing but a trifle to replace; 
 
PIYOTIXG ARTIFICIAL CROWXS. 173 
 
 a method by which we can take any case of great irregularity, 
 of any age and standing, and, without disturbing the root, cut 
 oiF the crown and place the porcelain one in the proper curve 
 in the arch ; a result which is absolutely clean, and which will 
 make the patient feel safer from accident than any other pro- 
 cess of restoration. 
 
 " Has any such plan been generally practiced? A few have 
 been successful by certain elaborate methods which only the 
 exceptionally skilful could perform, and even then, when a 
 ' break-do^v•n ' came, there was no alternative but to do it all 
 over again, either at the cost of patient or operator. 
 
 " Since 1871 I have been experimenting in this direction. 
 The grand object in view was to give to the dentist at large 
 such a made-up all-porcelain tooth as would meet almost any 
 requirement. 
 
 "My first jilan (see Dental Cosmos, September, 1877) of a 
 bolt and nut planted in the root by gold foil did not succeed, 
 as the safety of the whole depended on the perfect rigidity 
 of the bolt. Gold could not be so packed, save in a few cases. 
 Amalgam overcame this difficulty, a platinum bolt being used 
 instead of a gold one ; but this operation was practicable only 
 to skilled mechanicians ; the average dentist was unable to per- 
 form it. 
 
 " To meet this issue, the all-porcelain crown, without nut, 
 was devised. In looking at the incisor crowns, superior and 
 inferior, one might suppose that with so much cut away from 
 their base, and with the pin-hole running entirely through the 
 crown, the strength would be impaired. So I feared when the 
 idea was first suggested to my mind. But upon trial the 
 strength was found entirely sufficient. The experiments were 
 made Ijy drilling out old-style pivot teeth with a diamond. 
 They are now made by the Trustees of S. S. White in special 
 moulds. With these still greater strength is attained. The in- 
 cisors are so shaped as to form a dovetail, which allows the 
 strain outward t<j come high up near the cutting edge, and not 
 to depend upon the palatal base for support. The bicuspids 
 
174 MECHANICAL DENTISTEY. 
 
 and molars are cut out at the base, leaving a little more than a 
 shell, with undercuts for the amalgam to act as dovetails. 
 
 " This method leaves no joint on the natural root, and none 
 in the crown, the operation being really an amalgam filling 
 capped with porcelain. The hollow crown enables the opera- 
 tor to fit it in a very brief time, there being but little material 
 to grind oif. 
 
 " If a fracture occurs, a new crown can be placed with but 
 little fitting on to the old amalgam base, first burring oif any 
 excess. When a case is presented where the pulp is not ex- 
 posed, the hollow-base crown permits of so shaping the root as 
 not to endanger the pulp, and to place the pins on either side of 
 the same into solid dentine. At this time I cannot conceive of 
 a single case occurring that cannot be met by one or the other 
 of the plans herein described and shown clearly in the cuts, — 
 equally adaptable where a number of roots are in continuous 
 circle, or at intervals, or even for a full denture, as the teeth 
 one by one give way ; or in making the root of a lateral bear 
 the crown of a central, or vice versa ; or one or two adjoining 
 crowns where no roots are left. Where more than one crown 
 is needed, the nut and bolt are called for, as in case of accident, 
 or the necessity for readjustment, they can be unscrewed, the 
 fixture removed, repaired in the laboratory, and again screwed 
 in place. 
 
 " Let me say just here that this plan of nut and bolt is ap- 
 plicable where no roots are present, for fastening one or more 
 plate-teeth on a plate instead of by the method of Dr. Bing, in 
 which, if the teeth are broken, they cannot again be readjusted. 
 Such bolts with threads cut upon them can be inserted in any 
 part of a perfect crown or a filled one by the use of amalgam, 
 or gold, if one will use it in such cases. 
 
 " Next in importance to a crown that will meet all cases are, 
 the bolt which is intended to attach it to the root or roots, and 
 the cement for securing it. 
 
 " In such cases as are outlined in Figs. 59 and 60, see that 
 the platinum pin is secure, and so placed where occasion de- 
 mands that the lower part of the root need not be filled with 
 
PIVOTING ARTIFICIAL CROWNS. 175 
 
 cement, but that space be left for gases to escape through the 
 tap-hole, which should be made obliquely from near the margin 
 of the gum down below the cement, guarding against the liability 
 of decay again occurring at the cervical margin by bevelling 
 well the mouth of the cavity in the root. This once done cor- 
 rectly, there will be no need of again disturbing it. (Before 
 setting the pin in any case the root should be temporarily filled 
 at the apex to insure against abscess.) Cases will present, 
 however, where gases will form and escape. Here perfect se- 
 curitv can be obtained by the tap-hole, as before described. 
 This left open a useful root is retained, and without any ap- 
 parent unpleasant odor. Do not condemn an abscessed root. 
 Such can be made equally successful where the periosteum can 
 be restored to health. Save every old root that has any length, 
 and in which the pin can be well anchored high up, even if 
 the walls are fractured for an eighth of an inch below the gum, 
 or even where the root is split. In such cases dovetailed holes 
 can be made in each fractured part, and the amalgam will 
 hold them together. Even without this if the pin have a good 
 quarter-inch anchorage at the very apex it will be hard to dis- 
 lodge. 
 
 " To make doubly sure, when a tap-hole has to be made, 
 that it is open from the apex, pass a fine thread of silk or 
 cotton down alongside of the pin, build up the amalgam 
 around it, withdrawing it after the crown is on and before the 
 amalgam has set, holding the crown firmly while doing it. 
 Or the thread can be introduced through the tap-hole and then 
 passed up to the apex, withdrawing it when the crown is in 
 place. This practice is perfectly justifiable rather than to lose 
 a serviceable root. To a conscientious operator it needs no 
 argument. In a very important root I go so far as to allow or 
 even to force an abscess to form, and then treat it through the 
 pulp-canal and fistula. I save seventy-five per cent, of such 
 cases rather than abandon them. 
 
 " Do not cut away the root very much, as a trifling space around 
 the three-cornered pointed pin will permit enough cement for 
 strength. Roughen the inner walls of the pulp-canal, and 
 
176 MECHANICAL DENTISTEY. 
 
 they may be left conical without clanger of the pin being with- 
 drawn. One very great satisfaction to the patient, as well as 
 to the operator, is that the rubber-dam need never be used. 
 The base of the root can be so prepared with, a sharp bur that 
 but little injury is done to the gum, and if it bleeds creasote or 
 chloride of zinc will stop it ; or, pressure of the thumb and 
 index-finger against the buccal and palatal walls will stop it 
 or any serous discharge while the root is being filled with ce- 
 ment. After that there is nothing to hinder the placing on of 
 the crown. Be sure before forcing in the amalgam or cement 
 that the apical foramen is closed. For this purpose I use fine 
 zephyr saturated with creasote, except in cases were a tap-hole 
 has to be made. 
 
 " Only in cases of fracture of the shaft of a root would I 
 use a band, and that should be placed on separately from the 
 crown, not with it. Not a half dozen times in nine years have I 
 had occasion to use such a band. The use of the platinum pin in 
 the pulp-canal and passed high up obviates any necessity for 
 such band, which is at best unsightly, and, for many, other 
 reasons, objectionable. Such a plan admits of no readjust- 
 ment, and has been used by others only to assist the cement in 
 setting. Cases occur where each root of a molar or bicuspid 
 stand separated. One small pin in each well pressed up gives 
 equally good results. 
 
 " Never depend upon cutting a female thread in the dentine 
 and placing a screw therein. This can be done, but it is so 
 easy to be deceived that the plan as shown in Fig. 58 is much 
 more desirable because more reliable. It is preferable in such 
 cases to place in the pins and wait until the next visit of the 
 patient, and, before placing on the crown, to try the pins to 
 see if they are well anchored. When more than one crown is 
 to be placed on in a continuous circle or line., cut off all the 
 natural crowns at one sitting instead of finishing one at a time 
 as I once advised. As many as four incisors can be inserted 
 at one sitting, though two is as much as one generally cares to 
 adjust at one time. Where the crowns have been well fitted 
 to a plaster model there will be little difficulty in getting a 
 
PIVOTING ARTIFICIAL CROWNS. 177 
 
 good arch in the month, though a model is not necessary ex- 
 cept for the superior or inferior incisors. If you liave a large 
 stock of bicuspid and molar crowns on hand the fitting can be 
 done at once. For special cases of very short teeth it would 
 be well to have a plaster model. The only objection ever 
 urged against using amalgam in the roots to secure tlie pins is 
 that the gums soon look purple or blue. This can only occur 
 where the joint is not high enough above the margin of the 
 gum and where poor amalgam is used. Oxyphosphate or 
 oxychloride of zinc can be used, but I prefer a special quick- 
 setting amalgam such as I am using. Gutta-percha for such an 
 operation is no better than putty. Some cases have succeeded 
 with its use, but it does not at all meet the requirements. 
 
 " As to the oljjection against amalgam that it is too plastic 
 and too long in hardening, let me say that in fact such is not 
 the case, unless the ordinary amalgam is used. I have never 
 had to replace in a single case from such cause, where the 
 amalgam I have adopted is used in the crown. For the roots, 
 any first-class amalgam will do that does not take too long to 
 set. The safety is in having it not too soft in the crown when 
 it is pushed home. AVhen the platinum pin is pressed up into 
 the root with forceps, with the pin resting against the palatal 
 wall of the tooth in incisors, there is no displacement. The 
 pressure made on the crown 'squeezes' out all surplus mer- 
 cury and impacts the amalgam well around the pin, and with 
 a lump of it well pressed or pounded with small points 
 around tiic pin in the crown from the outside orifice, it holds 
 securely. 
 
 " When amalgam is used, the shade of the crown should be 
 rather lighter than if a white cement were to be used, as the 
 opacity of the amalgam adds a blue tinge to it, just as in 
 plate teeth the shade is made darker by the stay-plate, after 
 soldering. 
 
 " Fig. 55 shows the crown of a superior central from the 
 palatal surface, the base cut out high, and with another coun- 
 tersunk hole near the cutting edge, and undercut on the mesial 
 and distal walls, to allow the amalgam to grasp the body of 
 
 12 
 
178 MECHANICAL DENTISTRY. 
 
 the tooth well up, so that it shall not depend for support at 
 the base only. The base may be cut away after the amalgam 
 has hardened and the crown would not fall off. The base is 
 countersunk to admit of easy and free adjustment of the pin, 
 and to allow of a large body of amalgam around it, making 
 one continuous amalgam filling from the root through the 
 crown, with no joint for retention of food, the material being 
 stronger tlian the porcelain. The opening on the palatal sur- 
 face is convenient as a safety outlet for the amalgam, and per- 
 mitting the crown to go up to its place without obstruction. 
 When the crown is well pressed up, the amalgam can be 
 packed in around the pins, and the amalgam will act as a me- 
 tallic base or backing for the palatal surface, thereby strength- 
 ening it. The thumb or index finger on this orifice prevents 
 the too free escape of amalgam when pressing up the crown. 
 
 These crowns have no platinum lining or tubes as the English 
 teeth have. They are stronger without them. A sectional 
 view of a central is also shown in Fig. 55, with barbed pin 
 bent at the proper angle, the dark part showing the amalgam. 
 
 "Fig. 56 shows a bicuspid with double pulp-canal, the 
 cross-section of a crown with countersunk base, and the open- 
 ing on the grinding surface for the escape of surplus amalgam. 
 
 " Fig. 57 embraces sectional views of a superior and inferior 
 molar, showing arrangement of pins, with a magnified view of 
 the platinum pin, pointed at each end, made triangular and 
 well barbed, the barbs looking towards the angle of the pin 
 where bent. The perfected crown on the root shows the line 
 of amalgam. When two or more pins are used they need not 
 
PIVOTING ARTIFICIAL CROWNS. 
 
 179 
 
 be placed so far up in the roots or be so large in diameter as 
 when a single pin is used. In cases where the root has to be 
 tapped, then the pins can be placed in the mouth of each pulp- 
 canal and the tap-hole made below, which should always be 
 done before the pins are inserted, similar to Fig. 58, where 
 there is a living pulp. Indeed, were it not for the fear of 
 displacement before the hardening is complete, pins could be 
 dispensed with in molars, as the body of amalgam is so great 
 
 Fig. 56. 
 
 Fig. 57. 
 
 ^ 
 
 that when set it will hold sufficiently. The pins when set 
 like a tripod at the base offer greater security than one alone. 
 
 " Fig. 58 shows an all-porcelain crown, sectional view, where 
 the pulp is still living. A hole is made on the buccal and 
 lingual sides of the root as far away from the pulp-canal as 
 possible, and of size very little larger than the three-cornered 
 pin, with an enlargement near the opening made with a barrel- 
 shaped bur. The side of the under-cut next to the crown 
 should be as square as possible, not rounded, as in Fig. 58. 
 In such a case the amalgam should l)e used quite dry, as the 
 pins do not have to be pushed far, and can be well tamped in 
 with narrow steel blunt points, so as to make sure that the 
 amalgam is solid. The crown can be placed on at once, or 
 you can wait until the next day to see that the pins are all 
 secure. 
 
 " Fig. 59 is a sectional view of a case that requires tapping. 
 The pin shows its thin flattened edge, with space on either side 
 
180 
 
 MECHANICAL DENTISTRY. 
 
 for gas to escape from the foramen. It is pressed up about 
 three-fourths of the length of the canal. 
 
 " Fig. 60 illustrates the same case as Fig. 59, giving a view 
 of the flat side of the pin and showing its bearing on either 
 side of the canal, by which it is prevented from lateral move- 
 ment, the same as if the amalgam encased it all the way. The 
 gas escapes at the opening at A. (This opening should extend 
 obliquely up to near the free margin of gum, and not as shown 
 
 Fig. 58. 
 
 Fig. 59. 
 
 in the cut.) The amalgam extends no further into the root 
 than A. This plan holds good in any tooth of one or more 
 roots. 
 
 "Fig. 61 shows views of a superior central incisor crown as 
 made from a plate tooth (pins crosswise), backed up with 
 heavy gold plate entirely to the cutting edge and down to the 
 base where it rests on the root. The .shape is given to the 
 palatal surface by an extra plate, struck up concave with a 
 round tool on lead and nicely fitted up to the backing on the 
 buccal side, extending as high up as the angle or about up to 
 the cross-pins, and filled in with scraps of gold plate and then 
 soldered. The drilling of the hole through the base and the 
 countersinking on the palatal side are done with the engine. 
 
PIVOTING ARTIFICIAL CROWXS. 
 
 181 
 
 The base of the plate tooth should be cut off from the pins 
 down to the cervix to leave more room for the nut. The nut 
 ordinarilv goes nuich closer to the backing than is shown in 
 the sectional view of Fig. 61. The pin is barbed on its three 
 sides and thread-cut on the end passing through the crown. 
 This is done -with the ordinary screw-plate before inserting. 
 For central incisors the pin of platinum wire should be No. 
 16, and for small lateral No. 18. The nut is made of half- 
 round or oval gold wire, about three thirty-seconds of an inch in 
 thickness. The hole should be drilled before cutting it off 
 from the main piece, and a female thread cut in it by a tap 
 
 made of an old excavator filed down and run through the 
 hole in a screw-plate of the size of the wire to be used in the 
 root. The slots in the head of the nut should be crucial, to 
 admit of the screw-driver (Fig. 63) being used at each quarter 
 of a circle. The nut should be tried upon the threaded part 
 of the pin before being finally inserted, to see that no mistake 
 has been made in the size of either the nut or pin. Such 
 mistakes will sometimes occur. The pin is bent slightly, to 
 allow it to pass through the hole in the crown and stand in 
 the countersink equidistant from all sides, so that when the 
 nut is placed on it it will bear on all sides of the countersink 
 alike, and the cn)wn will not be tipped to one side. The pin, 
 after the amalgam lias hardened, can be bent with forceps to 
 suit the countersink, tidving care not to bruise the thread. The 
 nut cannot be placed on at tlie same sitting, as the amalgam 
 will not be hard enough to justify it. 
 
182 
 
 MECHANICAL DEJVTISTEY. 
 
 " If SO unfortunate as to injure the thread, repair it with a 
 little screw-plate, as shown in Fig. 62. This may be made 
 from a piece of steel dividing-file, cut down to about the size 
 shown in cut, and bent at right angles after heating it to a 
 cherry red, and afterwards drilling a smaller-sized hole than 
 the pin, through the short angle, and tapping it with the same 
 tap used in making the gold nut, then tempering it to a 
 dark straw color. This screw plate can be run up on the pin 
 in the root, and recut it its full length to the base. This ob- 
 viates the removal of the pin after the amalgam has set. Taps 
 and plates of various sizes should be kept on hand in dupli- 
 cates. 
 
 " Fig. 63 is a forked screw-driver, bent at right angles to 
 admit of getting into the palatal surface to put on the nut. It 
 
 Fig. 63. 
 
 should straddle the pin and be only wide enough to cover the 
 diameter of the nut. 
 
 " Fig. 64 shows a case of irregularity which was beyond 
 correction, on account of the poor character of teeth, their very 
 
 Fig. 64. 
 
 ugly shape, their position in the palatal arch, and the age of 
 the patient. In such cases I do not hesitate to cut off the 
 crown, destroy the pulp, and place one of the plate-tooth 
 
PIVOTING ARTIFICIAL CROWNS. 183 
 
 crowns with a nut. To do so, the crown must be connected 
 to the root by a strip of heavy gold plate, extending for a 
 quarter of an inch or more, to bring the artificial crown into 
 the circle. For such cases the all-porcelain crown will not do. 
 The teeth can be separate or connected. I prefer the former. 
 
 " The nut and bolt is best where a crown has to be very 
 long and there is a close ana deep underbite, with little room 
 for the crown, without being too full in front. The gold back- 
 ing gives greater security, and should cover the whole palatal 
 surface of the tooth. There are other special cases in which 
 this plan is to be preferred, but only for superior incisors or 
 cuspidati. 
 
 '' This plan, as before suggested, I should use in attaching 
 one or more teeth on a small plate, where the roots have been 
 lost, securing the bolt with amalgam to either decayed or sound 
 crowns. 
 
 *•' In this plan (Fig. 61) the pin is placed in the same as for 
 all-porcelain crowns, and adjusted before it is set to suit the hole 
 in the base of the crown, placing gutta-percha over the pin in 
 the countersink until the next visit of the patient, when it is 
 removed and the gold nut placed on. All excess of amalgam 
 around the margin of the gum should be removed, and before 
 placing on the crown finally it should be warmed and a piece 
 of gutta-percha stuck on to the base and pressed up, making 
 a water-tight joint when the nut is screwed up. 
 
 " The illustrations are so accurate that it seems almost un- 
 necessary to enter into any detailed direction as to the manner 
 of procedure ; but as it may help to perfect operations, I will 
 do so in few words. 
 
 " The root or roots having been prepared, and in readiness 
 for the crowns, the canals enlarged, and the foramina closed, 
 the platinum pin is cut off rather shorter than the length of 
 the root, as it cannot be pressed up quite its full length through 
 the amalgam. It is made three-cornered, and pointed at either 
 end — more so at the root end — and well barbed with a sharp 
 knife, as shown in cut, to and from the line between the crown 
 and root, and bciiding tlie pin so that it shall impinge upon 
 
184 MECHANICAL DENTISTEY. 
 
 the palatal wall if for an incisor, which will hold the crown 
 firm while the amalgam is setting. 
 
 " The crown having been adjusted to its place on the root, 
 and all being in readiness, the canals dry, place soft amalgam 
 entirely up to the end of the canal, and when full, take a 
 pointed, three-cornered excavator and run it up through the 
 amalgam, to force a way for the platinum pin. This latter is 
 placed by grasping the pin with a pair of forceps, and gradu- 
 ally pressing it up as far as it will go. A thin, flat-pointed 
 tool can now be used to condense the amalgam about the pin. 
 Before this is done the crown should be placed on to see 
 whether the pin will permit it to assume its proper place. If 
 not, the crown can be forced either way, and the pin will fol- 
 low. The tamping around the pin can now be completed, and 
 an excess of amalgam placed around it. The crown is now 
 filled with amalgam and grasped between the thumb and in- 
 dex-finger, and pressed hard home. The opening on the pal- 
 atal side of the crown can be filled with hard amalgam and 
 well driven up about the pin, leaving a surplus for dressing 
 when it is fully hardened. The excess of mercury is pressed 
 out by the force used in driving it into place. When more 
 than one pin is used, they can be filled in between on the 
 grinding surface, and wedged apart against the wall of the 
 porcelain tooth, which will very much assist in retaining them. 
 
 " This can be done all at one operation, although the pin 
 can be placed in at one visit and the crown at the next. Where 
 a crown has to be replaced from fracture, cut off the surplus 
 amalgam around the pin with the engine and cutting-pliers 
 until the new crown fits nicely. Fresh amalgam having been 
 laid over the old amalgam, and the crown pressed up as be- 
 fore, the repair is complete. The crowns are not made to 
 allow of their being pressed up over the end of the root, as in 
 the Richmond plan of a gold band, as there is no necessity for 
 the band, save in the few instances named in a former part of 
 this article. 
 
 " As to many little details, the practitioner can improvise to 
 suit every case. I am of opinion that platinum wire is the 
 
PIVOTING ARTIFICIAL CROWNS. 185 
 
 best for the pins, although steel well softened will do if entirely 
 covered with amalgam. The cost of platinum is but a trifle 
 more than the steel, and with it there is no danger of oxida- 
 tion or of injury from the mercury. 
 
 " I give this plan to the profession with the assurance that 
 there is no other operation in dentistry which will so delight 
 patients. Instead of crowns patched up with gold, amalgam, 
 gutta-percha, etc., you have in this plan 'art concealing art,' 
 recommending itself to the common sense of the patron and 
 enabling the operator to get well paid for his labor, and suit- 
 ing itself to the purse of eyery class of society, — a plan which 
 will enable us to blot from our practice in a great measure the 
 necessity for dental plates." 
 
 What is known as Richmond's method of attaching artificial 
 crowns to the roots of teeth is applicable to bicuspids and 
 molars as well as to single-rooted teeth. The latter, or incisors 
 and cuspidati, however, are porcelain-faced, and are constructed 
 and fixed in the following manner : 
 
 Prepare the root in all respects as in the case of an ordinary 
 pivot tooth. Bevel the sides of the dressed end of the root 
 with chisels or other suitable instruments one-half or three- 
 fourths of a line in depth, forming parallel walls for the recep- 
 tion of a narrow gold band, which is subsequently to be forced 
 over the end of the root Take then a narrow strip of gold 
 plate (that made from the gold pieces coined since 1860 being 
 the best adapted to the purpose) about 24 gauge, and three 
 lines or more in width. AVith round-nosed pliers, bend this 
 strip so as to encircle the end of the root ; mark the point of 
 junction and cut off. From this again cut off from one-six- 
 teenth to one-eighth of an inch according to the size of the 
 root, and unite the ends with solder composed of gold coin 
 same as band five parts, and one ))art of fine brass wire. With 
 files or corundum disks fashion this band so that, while it is of 
 equal width, it will conform to the marginal contour of the 
 dressed end of the root, the edge of the band underlying the 
 gum, presenting, when finished, an antero-posterior convexity 
 
186 MECHANICAL DENTISTRY. 
 
 and lateral concavity corresponding with the marginal inequal- 
 ities of the alveolar processes. 
 
 Bevel the outer and upper edge of this band, and force it 
 over the end of the root. Fit a gold or platinum wire pivot to 
 the enlarged opening in the root accurately, but not so tightly 
 as to prevent its ready withdrawal on gentle traction, and long 
 enough to j)roject a line or more from the orifice. With the 
 metal pivot in place, take an accurate impression of the parts, 
 including the adjoining teeth, and remove carefully, when the 
 metal pivot will be found imbedded in the wax impression, or 
 if not, it may be afterwards removed from the root and ad- 
 justed in its proper place in the impression. The gold band 
 should also be forced from the root and placed in the impres- 
 sion. The latter should then be filled in with plaster to secure 
 a» model of the parts, with the pivot and band secured in their 
 proper relations. Then cut and fit a cap of thin platinum 
 plate, perforated to pass over the pivot and down upon the 
 end of the root, or within a little distance of it, leaving some 
 space underneath for plastic material on final adjustment. 
 This platinum cap should fit into the gold band accurately. 
 JSText, select and adjust a suitable plain plate tooth to the space 
 to be supplied ; remove and back it with a thin plate of pla- 
 tinum, and rivet or bend the pins to secure it in place. Then 
 readjust it in its i3roper place on the model, and secure it by 
 adding fresh portions of plaster and sand, building it up over 
 the front face of the tooth and around the model. 
 
 The several parts are thus secured in their proper relations 
 to each other. When the investient is sufficiently hard, heat 
 up the piece slowly, and with the blowpipe flow in upon the 
 parts exposed to view successive portions of gold solder, com- 
 pounded as before mentioned, until sufficient has been added to 
 form the desired posterior contour of crown. 
 
 The piece, when properly dressed and polished, is now ready 
 for final and permanent adjustment to the root, previous to 
 which, however, the walls of the root-canal should be rough- 
 ened or grooved somewhat, and the wire pivot or tube barbed 
 or serrated. 
 
PIVOTING ARTIFICIAL CROWNS. 187 
 
 Before forcing the band, with tooth now attached, over the 
 root, introduce into the enlarged canal of the root, and ai'ound 
 the base of the crown, sufficient os-artificial, phosphate of zinc, 
 German cement, or other allied plastic material, to fill completely 
 all vacuities that may exist around the wire pivot and under- 
 neath the platinum base plate, securing by this means increased 
 attachment and stability to the substitute. To permit the es- 
 cape of surplus material a small opening may be made with 
 a drill through the posterior face of the crown near the band, 
 and which may afterwards be closed with gold foil. When in 
 place and firmly fixed, the lower edges of the gold band under- 
 neath the gum should be forced in closely upon the root with 
 burnishers. 
 
 In attaching artificial crowns to the roots of bicuspids and 
 molars by this method, the operation is simplified some- 
 what by constructing the crown, superficially, exclusively of 
 gold plate. A band, of the quality of gold before mentioned 
 in connection with the front teeth, equal in width to the re- 
 quired length of crown, is employed, and is prepared in the 
 same manner as the narrow band. The end of this gold tube 
 or band antagonizing with the teeth of the opposite jaw is then 
 closed with a platinum cap fitting into it, and solder flowed over 
 this until sufficient thickness is provided for purposes of mas- 
 tication, while cusps are raised by adding and flowing addi- 
 tional pieces of solder at appropriate points. A small open- 
 ing having been previously made for the escape of surplus, the 
 hollow crown is filled with some one of the plastic materials 
 heretofore mentioned, and the crown forced over the root and 
 into proper position. Increased stability and firmness of at- 
 tachment may be secured by fixing serrated gold wires in the 
 roots before placing the crown. 
 
 The following method of substitution, contributed at the so- 
 licitation of the author, by Professor M. H. Chappell, of the 
 Indiana Dental College, though similar in some respects to that 
 practice<l l^y Dr. Richmond, is sufficiently original and dis- 
 tinctive in its main features to warrant its introduction in this 
 connection. 
 
188 MECHANICAL DENTISTRY. 
 
 Having formed and fitted a gold band to the root in the 
 manner heretofore described, the writer continues : " Fit the 
 crown to the root, and to the ferule or band ; bevel the tooth 
 at the gum edge ; dress the inside of the band to a sharp edge, 
 so as to form a lap joint with the tooth ; or, if preferred, use 
 diamond disk and cut shoulder in crown to receive the un- 
 trimmed edge of band. 
 
 "The pulp or pivot canal must be drilled in a line with the 
 palatine surface, so that the plate will not have to be forged 
 back under the tooth. The canal is made the usual size and 
 depth for pivot teeth. 
 
 " A backing, of the same quality of gold as the band, 
 soldered to a thin plate of platinum, is the best. Punch or 
 drill holes to attach the tooth pins ; countersink and rivet solid. 
 Have sufficient plate of backing to form the pivot. With a 
 fine saw or separating file cut in each side at base of tooth one- 
 third way off", and bend in the edges forming a tube for pivot. 
 Solder the rivets and upper part of tube to make firm. 
 
 " The tooth and ferule are now ready to be attached. Dry 
 the mouth and root, using napkins and saliva ejector. Force 
 the band over the root, firm and perfect, to the exclusion of 
 moisture. Line the inside of band and end of root with gutta- 
 percha, extending it down the canal. Etch the tube or pivot 
 so that the beards of etching touch the walls of pivot canal. 
 Fill the tube of plate with gutta-percha, and line the etched 
 surface and end of crown. Heat the artificial crown and 
 gutta-percha on water-bath pan, and with warm pliers place 
 the tooth in position, forcing the pivot to its place. When 
 cool burnish the band or ferule to root and crown. 
 
 "Have retaining-points in root and tube; build up with 
 gold from root and ferule, to give the proper contour of the 
 palatine surface of the natural teeth. After polishing the 
 ferule or band and palatine filling, the case is complete." 
 
 Though differing very materially from the ordinary methods 
 of pivoting an artificial crown, the following novel manner of 
 supplying the loss of a natural tooth, in the absence of the root, 
 and without the intervention of a plate or clasps, may properly 
 
PIVOTING ARTIFICIAL CROAVXS. 189 
 
 be classed under the same general head. The original concep- 
 tion and practical application of the process is ascribed to Dr. 
 B. J. Bing, of Paris, France. Space will only permit the in- 
 troduction of descriptions which relate to the- more recent 
 modifications of the method. 
 
 Dr. Marshall H. AVebb thus describes his method of oper- 
 ating 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 12th, 1873, and the crown now remains as firm 
 as when inserted. The operation Avas performed in the follow- 
 ing manner : After suitabh' forming the cavities in the proxi- 
 mate wall of each tooth next the space left by the loss of the 
 one tliat 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-k.). A portion of the backing extended about one and a 
 half lines from each side of the crown for insertion in the cav- 
 ities 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. When 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 ex- 
 tended side of the backing and the surface of the wire was 
 barbed with an engraver's lossing tool, so that the gold foil 
 would the better secure the crown when filled into every part. 
 
 " The porcelaiU) with the gold attachments, being ready for 
 insertion, a piece of light nicdiuni rubber-dam was put in [)lace 
 on two teeth each side of the space to be filled, and over the 
 gum upon which the crowii was to rest. (The rubber takes up 
 
190 MECHANICAL DENTISTRY. 
 
 but little space, and this is more than compensated for when 
 the ligature — waxed floss-silk — is pressed to or near the neck 
 of each adjoining tooth.) Oxychloride of zinc was then placed 
 in the pulp-chamber of the central and lateral incisors and the 
 crown at once pressed to place. When the cement had hard- 
 ened 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 aiichorage 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 pre- 
 pared for insertion and the crown in position are illustrated in 
 Fig. 65. 
 
 " The cavity in the central incisor was extended to the cut- 
 ting edge of the toothy that access might be had to the wire and 
 
 Fig. 65. 
 
 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. 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 
 
PIVOTING ARTIFICIAL, CROWNS. 
 
 191 
 
 and finished, however, that, though the gold can be seen, it is 
 not conspicuous. 
 
 "AMiilethe operation just described has thus far proved 
 successful, 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. 49, 6), 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. 
 After the groove has been cut in the porcelain with a fine- 
 edged corundum disk, 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. 66, «), into which 
 the wire to connect the artificial crown with the natural teeth 
 is to be placed (Fig. 66, h), either beneath the plate or so that 
 
 Fig. 66. 
 
 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 electro-magnetic mallet. When the gold is 
 properly and solidly placed in the groove and over the back- 
 ing and wire, it not only aids in securing the porcelain, but 
 the contour of the crown can be nicely filled out, and the op- 
 eration made durable and beautiful (Fig. 67). 
 
 "The surface of the gold |)laccd 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 prop- 
 
192 • MECHANICAL. DENTISTEY. 
 
 erly 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 carefully placed in this part, between 
 the wire and enamel, with small curved instruments, and with 
 the aid of the mallet ; the surface of the gold at this part at 
 least should be smoothly finished with very narrow (,'g in.) 
 strips of fine emery-cloth before the rubber-dam is removed. 
 
 " In cases where the pulp is living in one or both of the 
 teeth to which an artificial crown is to be attached, the heavy 
 gold plate or the wnre must be so arranged as to fit as accurately 
 and to be made as secure as possible in the cavities prepared 
 for them. In some cases, and where the form of the cavity 
 admits of it, it is better to adjust and solder a small gold plate 
 to the end of and at right angles with the wire attached to the 
 crown. This plate should be so formed and bevelled that gold 
 foil can be solidly placed over the surface of it next to the 
 artificial crown, and into the groove made around the cavity 
 in the dentine along the boundary-line between this tissue and 
 the enamel. When all is in readiness for the operation, oxy- 
 chloride of zinc should be placed in each cavity and the crown 
 immediately put in place, and very carefully held there till the 
 cement has so crystallized as to secure the ends of the wire 
 and plate ; about an hour is necessary to such perfect crystal- 
 lization as to safely admit of the preparation for and the pack- 
 ing of the gold foil. The oxychloride of zinc should be left 
 between the little plate or end of the wire and bottom of the 
 cavity, and all parts where gold cannot well be placed ; this 
 preparation also protects the dentinal fibres from thermal 
 changes. 
 
 " One of the most satisfactory operations the writer ever 
 performed was the insertion of a crown where a cuspid root 
 had been extracted (unnecessarily), and the lady subjected to 
 the wearing of a gold plate for some time. This crown was 
 prepared and the contour filled out with foil as described (and 
 as illustrated, Fig. 67), but gold wire, No. 13, was attached to 
 
PIVOTING ARTIFICIAL CROWNS. 
 
 193 
 
 and built in with the porcelain, and 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 pos- 
 terior proximate surface of the first bicuspid tooth, the pulp of 
 which remained in normal condition. The crown was placed 
 in position with oxychloride of zinc, and cohesive gold foil 
 was then impacted with the electro-magnetic mallet around a 
 portion of the wire in the root and into the cavity in the crown 
 of the incisor, and also into the cavity in each proximate wall 
 of the bicuspid tooth, as well as around and over the ware, 
 joining the two fillings through the enlarged fissure. 
 
 Fig 68 
 
 " The most extensive operation of attaching a crown to ad- 
 joining teeth was performed bv the writer before the Pennsyl- 
 vania State Dental Society, at Delaware Water Gap, in July, 
 1879. In 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 
 occluded with another. The right upper lateral incisor had 
 Ijeen hjst 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 
 
 13 
 
194 MECHANICAL DENTISTEY. 
 
 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 made neces- 
 sary by the abrasion and fracture of enamel from time to time, 
 and because of imperfection in the fillings before introduced, 
 were performed previous to the insertion of tlie crown in the 
 space left by the loss of the lateral incisor, and as this crown 
 and each cavity and pulp-chamber Avas prepared for the gold, 
 all appeared as here illustrated (Fig. 68).* 
 
 "Gold wire (No. 13), with a sharp thread cut upon it, was 
 screwed into the dentine, and, at the same time, all the inter- 
 stices between the tissue and the gold were filled with oxychlo- 
 ride of zinc. When crystallization had taken place some of 
 the cement and dentine was removed from around the wire 
 with a small burr, and a groove was cut in the dentine near the 
 margin of the root so as to secure proper and sufficient anchor- 
 age for gold ; cohesive foil (principally No. 30) was impacted 
 into these parts, and the entire contour of the crown was 
 restored with the electro-magnetic 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 and the cuspid and bicuspid teeth. A gold screw 
 was placed in the pulp-chamber and extended into the crown of 
 each bicuspid tooth (Fig. 68). The apical foramen of each 
 pulpless tooth was closed, and the whole of each pulp-chamber 
 into which a wire was not placed was filled with gold. With 
 a properly adjusted electro-magnetic 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 g.nd perfect throughout; 
 the foil was placed in the same manner over the finely prepared 
 
 * The cut (Fig. 68) illustrates the case well, though there are parts and 
 grooves in which to anchor the gold that are not distinctly shown. — M. W. H. 
 
PIVOTING ARTIFICIAI^ CROWNS. 
 
 195 
 
 margins of enamel, and these were not marred in the least 
 (Fig. 69). 
 
 " 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 occlusion of the teeth a porcelain 
 crown (plain 'plate tooth') with 'cross pins' was used, and 
 
 Fig. 69. 
 
 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. 68) ; the wire 
 extending into each root about four lines. The cutting edge 
 of the porcelain was removed to the same extent as that of the 
 abraded and j)repared incisors, so as to present the same ap- 
 pearance and have the gold support and protect the remaining 
 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 
 contour restored with the electro- magnetic 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 ready for insertion, a light medium rubber dam was ap- 
 plied 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 oxychloricle of zinc was then 
 placed in tlic pulp-chamber of the central incisor and cuspid, 
 and the crown at once pressed to place. After it had been in 
 
196 
 
 MECHANICAL DENTISTEY. 
 
 position an hour to allow of complete crystallization of the ce- 
 ment, portions of this and of the dentine were removed with a 
 small burr so as to better secure the crown and obtain anchorage 
 for the gold foil then to be put in place around the wire, into 
 each cavity, and over the prepared margins of enamel. Prin- 
 cipally No. 30 gold (one-quarter ounce cohesive foil) was used 
 in this case, and all was impacted with the electro-magnetic 
 mallet, except a few pieces of light foil placed in the space be- 
 tween the wire and cervical wall, and even these pieces were 
 
 Finisbt'd Case. 
 
 a, 6, 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. 
 
 gone over with this very valuable instrument after they were 
 in place. With this and all the operations completed, the case 
 appears as here illustrated (Fig. 70). 
 
 " All those who have the ability and who will work ear- 
 nestly and conscientiously to properly perform the various oper- 
 ations described, and do their very best in every ease, can so 
 manage their practice as not to make it necessary for any of the 
 patients they have charge of to wear artificial crowns mounted 
 upon plates." 
 
PIVOTING ARTIFICIAL CROWNS. 
 
 197 
 
 Professor Darby, in commenting on this method, says : 
 " Dr. B. J. Bing was the first to call my attention to a 
 method of building one tooth into the adjoining 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. Mar- 
 shall 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 ])ractice one or more which 
 have proved most satisfactory. 
 
 "The cuts, Figs. 71 and 72, represent two cases where arti- 
 ficial crowns have received their support from the adjoining 
 
 Fio. 71. 
 
 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, 
 
 Fio. 72. 
 
 and allowed to extend well up the pulp-canal of one of the ad- 
 joining teeth. After it had been nicely fitted to its place, the 
 rubber dam was applied and drawn tightly over the gum be- 
 tween the two natural teeth ; the canal of the devitalized tooth 
 was then filled with oxychloride of zinc, and the tooth with its 
 
198 MECHANICAL DENTISTRY. 
 
 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 con- 
 venience was filled in the ordinary way. 
 
 " 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 patient 
 presents 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 in- 
 serted in this way where both teeth were living, but the sup- 
 port which is to be derived from the long right angle of gold 
 in the root is certainly a great security against accident, add- 
 ing, as it must, great strength to the operation." 
 
 If, after the operation of ingrafting an artificial crown, in- 
 flammation of the peridental membrane and surrounding struc- 
 tures ensues, active measures should be immediately instituted 
 for its reduction. In a majority of cases, active suppurative 
 inflammation is induced either by shutting up an habitual dis- 
 charge from secreting surfaces at the apex of the root, or by a 
 forcible injection of the air contained in the nerve canal into 
 the sensitive tissues beyond the apex in the act of pressing up 
 a tightly fitting pivot. These two circumstances, in conjunc- 
 tion, sometimes, with rough and unskilful manipulation, af- 
 ford a rational explanation of the needless failures so common 
 to this method, and enforce the necessity of first radically treat- 
 ing any existing disease in the appendages of the root, and of 
 afterward filling to the apex before introducing a pivot. 
 Where inflammation results from the injudicious application 
 of the pivot as just stated, it will ordinarily be sufficient to re- 
 move the latter if timely application is made by the patient for 
 relief ; and it is important in all cases to instruct the latter in 
 reference to the necessity of early attention to any disturbance 
 that may accrue from the operation. Unavoidable inflamma- 
 
PIVOTING ARTIFICIAL CEOWNS. 199 
 
 tion may generally be aborted by the timely application of 
 some active connter-irritant to the gum directly over the af- 
 fected root, or by local bloodletting, until resolution is eifected. 
 The topical remedies will sometimes be rendered more effective, 
 especially when the local trouble is associated with an inflam- 
 matory diathesis or febrile condition of the system, by such 
 constitutional treatment as will tend to diminish or equalize 
 the force of the circulation. 
 
200 MECHANICAL DENTISTRY. 
 
 CHAPTER VI. 
 
 Partial Dentures retained in the Mouth by Means 
 OF Clasps attached to the Natural Teeth. 
 
 Remarhs on the Use of Clasps. — Clasps, or metallic bands, 
 have been long and very generally employed as a means of re- 
 taining parts of sets of teeth in the mouth, and are still used 
 for that purpose by many practitioners. When these appli- 
 ances are skilfully adjusted, and all the conditions pertaining 
 to the mouth and remaining natural teeth are favorable to 
 their application, they afford a certain, permanent, and satis- 
 factory 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, 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 unlimited extent this method is subject to 
 abuses. In fact, no other special process in mechanical prac- 
 tice has been so fruitful of evil as that under consideration, 
 and the opprobrium which but too justly attaches to it in pro- 
 fessional as well as popular estimation, is chargeable more 
 properly to bad faith and unskilfulness on the part of the 
 operator, and to want of attention in respect 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 
 
CLASPS. 201 
 
 renders it the more Imperative that the process should be sur- 
 rounded 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 concerned in its production are chiefly of chemical 
 origin. Thus, the secretions of the mouth with j)articles of 
 alimentary and other substances being retained between the 
 clasp and tooth for a sufficient period of time, and exposed to 
 the favoring conditions of Avarmth and immobility, suffer a 
 process of putrefactive decomposition by which acids are elimi- 
 nated, and which, in their nascent state, act with perceptible 
 energy upon the bone constituents of the tooth, producing 
 decay. The rapidity and extent of this action will depend 
 much upon the nature and quantity of the acids liberated ; 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 cleanli- 
 ness. 
 
 The most usual seat of decay 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- 
 tants. With a continuance of the cause, the superficial por- 
 tions of the affected parts become more and more thoroughly 
 disintegrated, and sooner or later assume the open form and 
 characteristics of ordinary decay. If, as was formerly sup- 
 posed, decay or solution of tooth-bone in these cases resulted 
 from mechanical attrition, or wearing away of the enamel, the 
 injury would Fjc inflicted at points distant from the neck of the 
 tooth, wliere the clasp lies in more direct and immediate con- 
 tact with the protuberant portions of the crown ; but we find 
 that decjiy, from this cause, is not only of infrequent occur- 
 
202 MECHANICAL DENTISTEY. 
 
 rence at such points, but, on the contrary, the enamel here is 
 frequently found condensed and polished by the mechanical 
 action of the clasp. Certain conditions of the plate and clasp 
 undoubtedly favor mechanical action and accelerate the de- 
 struction 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, admitting, by its 
 mobility, of irregular traction or pressure upon the organs 
 of support. Whenever the artificial appliance is thus unskil- 
 fully 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 respect 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 per- 
 manent preservation 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 upper set. The application 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. Besides, such teeth can be 
 retained in the mouth only for a short time, and when they give 
 way, the artificial appliance becomes 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 careless ob- 
 server."* 
 
 Teeth, also, that are too short to admit of sufficient breadth 
 
 * Principles and Practice of Dental Surgery, p. 717. 
 
CLASPS. 203 
 
 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 unsuit- 
 able as organs of support. 
 
 In respect to the individual classes of teeth, it may l>e ob- 
 served that the incisors, lx)th as regards form and situation, 
 are inadmissible for clasping, and are, therefore, never used 
 for this purpose. The cuspidati, likewise, being placed con- 
 spicuously in the front part of the mouth, cannot be securely 
 embraced without manifest exposure of the clasp ; besides, the 
 conical form of these teeth makes the use of a very slender 
 clasp indispensable ; henc-e, 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 Ijeing s^-em to require it. 
 
 Either the anterior or the posterior molars, when sound and 
 firm, offer, in respect to their general conformation and posi- 
 tion 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 attach- 
 ments to the Jaw, the greatest security' to the artificial appli- 
 ance. The anterior molars are preferable where these are 
 remaining in good condition, or are sasc-eptible of being prop- 
 erly restored and preserved if diseased or carioiK. 
 
 Of the bicuspids, the posterior are to be selected, if practi- 
 cable, 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 denies sapientite, 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 ; Ix-sides, the retractive forces applied to 
 the anterior teeth of the substitute, would, on account of the 
 increased leverage consequent upon the extension of the plate 
 back to these teeth, tend either to disengage the clasps or pro- 
 duce displacement of the teeth to which they are applied. 
 
204 MECHANICAL DENTISTRY. 
 
 In supplying the loss of one or more 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, are 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 edentated 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 elevation at the base of 
 the coronoid process, it may become necessary 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 dentes sapientise 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 entirely 
 the necessity of clasps in front. 
 
 Separation of the Teeth, by Filing, for the reception of 
 Clasps. — The practice of separating the teeth with the file to 
 provide for the application of clasps should always be avoided 
 if practicable, 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 sub- 
 jects, especially, where the teeth are but imperfectly consoli- 
 dated, and in adults whose teeth are defectively organized, pre- 
 senting but a feeble resistance to the disorganizing agents 
 usually present in the mouth, the use of the file, for the pur- 
 pose indicated, is eminently pernicious, and should never be 
 resorted to until every other means of supporting the artificial 
 appliance have been fairly and patiently tried. 
 
 Whenever a plain necessity for this operation exists, a care- 
 
CLASPS. 205 
 
 ful examination of all the teeth to which it is proper to ap- 
 ply clasps should be made, and if decay is found upon their 
 proximate surfaces, the separation should be made between the 
 teeth so affected ; and this circumstance should, in most cases, 
 determine the selection, though the affected tooth or the one ad- 
 joining 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 file should 
 be employed, and the filing confined entirely to the carious 
 tooth, leaving the enamel of the one adjoining unbroken. The 
 cavity of decay should be well filled, and the filed surface 
 thoroughly condensed and polished with a burnisher. 
 
 Modifications in the Form of Clasps. — 1. Plain Band. The 
 most usual form of clasp is that shown in Fig. 73. It consists 
 
 of a plain metallic band of greater or less width and thickness, 
 and is made to embrace the larger portion of the circumfer- 
 ence of tiie tooth. In respect to the general properties of metal- 
 lic clitsi)s, it may be said that they should be, as nearly as prac- 
 ticable, 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, say twice the thickness of 
 the base, and exceeding this in some cases; 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 constructing a 
 plain band or clasp, a strip of sheet lead or other pliable sub- 
 stance may first be fitted accurately to the plaster tooth, mak- 
 ing it of tiie rerpiired width, and shaj)ing the edge next the 
 gum in conformity with the irregularities in the latter around 
 
206 
 
 MECHANICAL DENTISTRY. 
 
 the neck of the tooth ; the exact counterpart of the pattern 
 thus obtained is then cut from the plate to be used in the 
 formation of the clasp. The strip thus obtained is then bent 
 with round-nosed or grooved pliers (Fig. 74), until conformed 
 as perfectly as possible to every portion of the surface of the 
 tooth embraced 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 secured in the following manner : First secure a 
 pattern, as before described, and by this cut from a thin strip 
 of platinum, say ISTo. 30 or 32 of the gauge-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 condi- 
 
 FlG. 74. 
 
 tion of this metal will admit of its being easily adapted to any 
 irregularities upon the lateral walls of the tooth. The band 
 thus moulded to the tooth is then carefully removed from the 
 model, or the mouth, if fitted to the tooth in the latter, and its 
 central portion filled with a mixture of plaster and sand with 
 a small metallic wire or bar passing through the centre to sup- 
 port it while soldering. The outer or exposed surface is then 
 smeared with a mixture of borax, and small scraps or frag- 
 ments of gold plate of equal fineness with the main plate, are 
 placed at intervals and fused with the blowpipe until diffiised 
 uniformly over the surface. Small pieces may be added from 
 
CLASPS. 207 
 
 time to time, until the required thickness of the clasp is ol> 
 tained. The piece should be heated uniformly throughout to 
 induce an even flow of the gold over the exterior surface of 
 the 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 sta- 
 bility to the plate, and does not endanger the tooth clasped in 
 any greater degree than a narrow one. 
 
 2. Standard Clasp. — To guard more perfectly against the 
 retention 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 i>rofession by Dr. 
 
 Fig. 75. 
 
 C W. Spalding, which, by leaving the cervical portion of 
 the tooth in a great degree uncovered, permits the action of 
 the tongue and the natural circulation of the fluids of the 
 mouth to wjish or cleanse that portion of the tooth most 
 liable to be injuriously aflected. In commenting on this 
 method, Dr. S. remarks : " The writer has for many years 
 been in the habit of employing narrow clasps for the pur- 
 poses 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 tlie removal of 
 accumulations between the clasp and tooth, by the circulation 
 of the saliva (Fig. 75). The use of one or more standards 
 as a means of attachment, also provides, by a variation of their 
 lengtli, for the grasping of the tooth at any desired point. If 
 the tooth Ls long, and particularly if it is at the same time bell- 
 
208 MECHANICAL DENTISTEY. 
 
 crowned, the point selected should be toward the grinding sur- 
 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 one or one and a half lines from the tooth, 
 and standards introduced for the purpuse of promoting circu- 
 lation, by affording a free passage for the ingress and egress of 
 fluids. These standards should also be narroto, no wider than 
 the clasp itself, and should constitute the only point of union 
 between the clasp and plate. Haf-round wire will be found 
 to be a very convenient article for making clasps. The par- 
 ticular form of the clasp is, however, immaterial, 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 portion of it next the gum on the lingual side of 
 the tooth is scalloped 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 applied to the base 
 will present very nearly the appearance of the standard clasp 
 as represented in Fig. 75. 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 
 embracing 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. (Fig. 76.) They should be so connected 
 to the plate that when pressed over the enlarged portions of the 
 
 * American Dental Review, vol. i, p. 12. 
 
CLASPS. 
 
 209 
 
 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 
 
 Fig. 76. 
 
 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 insecure in the 
 mouth. The result alluded to should be particularly guarded 
 against in the case of young subjects, whose teeth are easily 
 moved by the application of very slight forces. 
 
 Modification in the Form of Plates for Partial Dentures 
 supported in the 3fouth by Clasps. — The particular form and 
 dimensions of a plate, when clasps are used, will be mainly 
 
 determined by the number and position of the teeth to be 
 replaa;d, and by tiie 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 
 
 14 
 
210 
 
 MECHANICAL DENTISTRY. 
 
 of the several classes of teeth. In supplying the loss of a 
 superior central or lateral incisior, it will be sufficient in many 
 cases to attach the plate to either a bicuspid or molar on the 
 same side, as in Fig. 77. 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. 78. 
 
 Fig. 79. 
 
 Ij>r— £|^> 
 
 (Fig. 78) ; or to a bicuspid on one side, and a molar on the 
 other; unless two firm and well-formed teeth on the same or 
 the opposite side can be commanded (Fig. 79), while those upon 
 the other could hot be employed without a separation. 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 pos- 
 teriorly in the arch, the former should be strengthened by 
 soldering a narrow rim of plate or half-round wire along the 
 
CLASPS. 
 
 211 
 
 border next the teeth, and the clasp should, Avhenever 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 (Fig. 80, right side), or if 
 both are absent, then to the first molar (Fig. 80, left side), 
 or the clasp may embrace both of the latter if remaining and 
 no separation between them exists. Fig. 81 represents the 
 form of a plate supplying the loss of teeth at intervals; the 
 clasp on one side embracing the posterior bicuspid in front 
 and extending round the back part of the adjoining molar. 
 
 Fig. 82 represents the form of plate supplying the loss of 
 the two bicuspids on one side, and the anterior bicuspid and 
 
 Fig. 82. 
 
 Fig. 83. 
 
 molar on the opposite, the plate being attached to an anterior 
 molar and second bicuspid. The antero-posterior extension 
 of the plate, as exhibited in connection with the bicuspid 
 tooth, greatly favors the stability of the substitute, and, pro- 
 vided 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 firm and well-formed 
 molar clasped as shown on the opposite side. A base so sup- 
 ported may be made to sustain any number of teeth with the 
 greatest security. 
 
 Either the anterior or posterior molars, if firm and securely 
 attached to the jaw, will afford adequate support to a ])late 
 replacing all of tlie teeth anterior to them. (Fig. 83.) Even 
 
212 
 
 MECHANICAL DENTISTRY. 
 
 a single molar situated on either side of the arch, if similarly 
 circumstanced, may be made to sustain, with tolerable firm- 
 ness, a base supplying the loss of all the remaining teeth, — 
 though, ordinarily, it is better to extract such a tooth and 
 substitute an entire upper denture. In 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. 84), the latter affording a counter-point of resist- 
 ance when traction is made upon the anterior teeth, thus di- 
 recting the forces 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. 84. 
 
 Fig. 85 is generally employed. The parts of the plate over- 
 lapping and resting upon the ridge behind, are connected with 
 each other by a narrow strip of plate extending round the 
 ridge in front on 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 beneath the tongue or the frse- 
 nura linguae. To avoid wounding these parts, and to allow 
 them unobstructed play, it will be necessary to make this por- 
 tion of the plate quite narrow ; and as a single thickness of 
 
CLASPS. 213 
 
 plate would not impart adequate strength, it is customary to 
 double this connecting baud — the duplicate band extending 
 back to the lateral wings of the plate, and crossing them ob- 
 liquely, as indicated by the dotted lines in Fig. 85. Addi- 
 tional 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 half 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 iu 
 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 iu the groove with solder, or by soldering a narrow 
 
 Fig. 86. 
 
 strip of plate or half-round ware along the border. The cir- 
 cumstances or conditions which make the use of clas2>s neces- 
 sary in these cases, as well as those, also, which contraindicate 
 their employment, have already been noticed. The practice 
 of extending 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 irritation and tenderness of tlie mucous membrane 
 immediately over the roots of the anterior teeth, and should, 
 therefore, never be resorted to, unless there are no teeth re- 
 maining to which clasps may be applied. 
 
 If tiie appliance is designed to restore the loss of teeth re- 
 cently extracted, and where but little or no change has occurred 
 from ab.sorj)tion of the parts, the portions of the j^late which 
 
214 MECHANICAL, DENTISTRY. 
 
 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 fes- 
 toons of the gum, as seen in Fig. S6. In such cases, plain or 
 plate teeth, by which is meant those which represent only the 
 crowns of the natural organs, should be employed ; these, rest- 
 ing 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 ex- 
 traction 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 or Stcimping the Plate. — Haying 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 partially overlap the cut extremities 
 of the teeth when the latter are not represented upon the die, 
 having been previously cut from the model. The outlines of 
 the pattern are then traced upon the plate of gold or other 
 metal to be 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 
 where it describes the palatal curvature of the teeth, is a plate 
 forceps, as exhibited in Fig. 87. 
 
 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 resist- 
 ing surface, when the two metallic pieces are brought forcibly 
 
CLASPS. 
 
 215 
 
 together with a few stearly 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 equalized and concentrated more 
 directly over the die. The metallic swages should at first 
 be brought cautiously 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 part- 
 ing, its further extension at that point may be prevented by 
 
 Fig. 87. 
 
 flowing a little solder at the termination of the fissure. Dur- 
 ing the progress of swaging, the plate should be frequently 
 annealed, which is done by bringing it to a full red heat under 
 the blowpipe, or by j)lacing it in the furnace; the plate is 
 thus rendered more pliant and can be more readily and per- 
 fectly 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 
 counter should be substituted for that in use; and, indeed, it 
 is better in all cases to have duj)licate copies both of the die 
 and counter in reserve with whit^h to complete the swaging, 
 inasmuch as more or less deformity of both swages unavoid- 
 ably occurs before the plate is brouglit into very accurate 
 
216 MECHANICAL DENTISTRY. 
 
 coaptation with the die. The stamping conducted thus far, the 
 plate may be applied to the plaster model, and if found too 
 full at any points, 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 nar- 
 row 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. 
 
 If the portion of the plate which passes in between the re- 
 maining 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 point. It is also advisable in many 
 cases, in order to provide more perfectly against fracture or 
 distortion 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 soldered to the edge of the plate next the teeth ; but 
 unless the substitute is frequently removed from the mouth 
 and cleansed, as well, also, as the teeth to which they are ap- 
 plied, serious injury is likely to be inflicted upon the teeth im- 
 plicated. 
 
 The edges of those parts of the plate occupying the vacuities 
 on the ridge should be filed thin to admit of a more accurate 
 adaptation 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, however, the concavity between and above 
 the teeth on the external border of the ridge is considerable, 
 the interdentinal portions of plate should overlap the border 
 completely and underlie the porcelain gum. 
 
 Uniting the Plate and Clasps. — Having proceeded thus far 
 
CLASPS. 217 
 
 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 support, will depend, in a great measure, upon the 
 accurateness of the relation of the several parts of the appli- 
 ance 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, Avhile 
 at the same time it should be so fitted as to be easily removed 
 and applied by the patient. 
 
 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 im- 
 pression 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 im- 
 pression, 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 bound to the 
 model with annealed wire, and united to each other with 
 solder ; V)ut the better way is to attach them to each other tem- 
 porarily, with adhesive wax, in the relation they occupy on the 
 model, and then remove them carefully and imbed the clasps 
 and i)alatal face of the plate 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 straightened out or spread apart, in order that they 
 may part readily from the plaster teeth, without, in any de- 
 gree, changing their exact relation to the plate ; in doing 
 which, it should be observed that all parts of the clasps which 
 are to be united to the })late should remain in close contact 
 with the plaster teeth. After the plaster mixture, in which 
 the plate and clasps are imbedded, has become sufficiently 
 
218 MECHANICAL DENTISTRY. 
 
 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, smeared with borax ground 
 in water to the consistence of cream ; small pieces of solder 
 are then placed along the lines of contact, the investient heated 
 in the furnace until the plate acquires a full 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 
 are not fairly represented on the model, owing to dragging or 
 displacement of the wax in withdrawing the impression, the 
 difficulties of securing a proper relative adjustment of the sev- 
 eral parts of the appliance will be increased ; but either of the 
 following methods, if carefully and accurately manipulated, 
 will secure accurate results. 
 
 1. Gutta-percha may be substituted for wax when taking 
 an impression with the plate in the mouth. With the proper 
 use of this material, the exact form and inclination of the 
 teeth will be preserved ; and when employed, it should be 
 filled in Avith plaster for the model immediately after removing 
 it 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 to be 
 easily removed from the tooth ; place this upon the tooth in 
 the mouth to be clasped ; then adjust the plate in the mouth, 
 and attacli the two to each other by pressing a piece of stiif, 
 adhesive wax in against the clasp and plate where they unite ; 
 harden the wax by placing against it, for a few minutes, 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 
 
CLASPS. 219 
 
 to; this is tlien temporarily fastened to the plate and other- 
 wise treated in like manner as the one first described. If the 
 teeth to be clasped are favorably formed and regularly ar- 
 ranged in the arch, both clasps may, at the same time, be tem- 
 porarily attached to the plate in the fii*st 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, Avill, in 
 proportion as they secure better results, amply reward the op- 
 erator for his painstaking. 
 
 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 por- 
 tions of the plate and clasp, and allowed to remain until suf- 
 ficiently 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 re- 
 moved from the mouth. A separation of the plaster from the 
 clasp or plate, or both, may occur 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 sticking them to- 
 gether with a little softened wax, when they are invested, the 
 temporary fastenings of plaster removed, and the pieces united 
 l)y soldering. The use of plaster in these cases is due to Dr. 
 Lester Xoble, and unquestionably possesses many advantages 
 over wax for the purpose, as the latter is liable even with the 
 most skilful manipulation, to become displaced in removing it 
 from the mouth; and this change, when it occurs, not being 
 indicated by inspection of the m ax, is incapable of timely cor- 
 rection. 
 
 3. Still another method is that contrived by Dr. Fogle and 
 describc<J Ijy Dr. Cusihman in the tenth volume of the American 
 Journal of Denial Science. It consists in securing the proper 
 
^20 MECHANICAL DENTISTEY. 
 
 relation of the clasps to the teeth in the mouth by the use, in 
 the first instance, of what are termed " temporary fastenings." 
 The plate 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. The pieces thus tempo- 
 rarily 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. 
 
CYLINDEES OF WOOD ATTACHED TO TUBED PLATES. 221 
 
 CHAPTER YII. 
 
 Partial Dentures supported in the Mouth by means 
 OF Cylinders of Wood attached to Tubed Plates. 
 
 The following description of a method of supporting partial 
 sets of teeth in the mouth by means of wood cylinders attached 
 to the plate is copied from an article contributed by Dr. W. M. 
 Hunter to the fourth volume of the American Journal of Dental 
 Science. The same principle has long been made available in 
 Europe in attaching artificial substitutes constructed of the hip- 
 popotamus ivory, but the credit of its application to metallic 
 plates is alike due to Drs. Hunter and Charles Stokes of London. 
 
 ."After swaging, the plate, as usual, is tried in the mouth, 
 and an accurate impression of the teeth to be used is taken over 
 the plate, as recommended by Dr. Arthur, in the American 
 Journal, which will show the exact position of the tooth in its 
 relation to the plate; after which the edge of the plate sur- 
 rounding the teeth to be made use of, should be doubled or 
 wired, wlien the tubes may be soldered at their proper points, 
 taking care never to apply pressure to one side of a tooth with- 
 out some means of counteracting the effect ; the means being 
 either a .sufficient number of natural teeth contiguous to the tooth 
 to be used, a counter tube, an arm of metal, or an artificial 
 tooth, depending entirely upon the nature of the case. 
 
 " At times, it is well to tube but one side of the plate and 
 clasp the other ; in cases where the crown of the tooth is much 
 larger than the neck, a beautiful application may be thus made. 
 
 " 'J'lie tubes should be from one-eighth of an inch to one 
 line in diameter, and should be filled with whiting before ap- 
 plying heat, to j)revent them from filling with solder at the time 
 of soldering to the plate. They should be placed upon the 
 plate so carefully, that the mouth of the tube Avill come in con- 
 
222 MECHANICAL DENTISTRY. 
 
 tact with the natural tooth, as it is desirable to have the wood 
 protrude but very slightly beyond the orifice. 
 
 " When it can be properly done, the tubes are soldered at 
 the same time the teeth are, as it saves much trouble in fitting ; 
 it cannot, however, be very well done where it is designed to 
 fit a tooth over a tube, but can very readily be done where 
 the tooth is designed to fill the angle caused by the meeting of 
 the stay and plate, in the incisors and canine teeth, and where 
 a canine is used for a bicuspid, building over the tube with 
 metal to form the inner cusp." 
 
 The accompanying cuts show clearly the form and applica- 
 tion of the tubes referred to. In Fig. 88, showing on one 
 side but a single tube, the counter-force is obtained by the 
 
 artificial tooth which rests against the anterior face of the one 
 to which the wood cylinder is applied. Fig. 89 exhibits 
 tubes arranged on one side, and a clasp on the other; and 
 shows the substitution of a canine for a bicuspid, with an 
 inner cusp built up over the tube, practically converting a 
 cuspid into a bicuspid tooth. 
 
 In commenting on the application of this principle to partial 
 sets of teeth, Dr. H. remarks : " The advantages in many cases 
 must be apparent to the thinking dentist, but, perhaps, it 
 might not be amiss to enumerate a few. 
 
 " The fixture is held in place with greater firmness than by 
 means of clasps. 
 
 " In some instances where I have used clasps, I have also 
 used the tube in combination, to give stability for masticating 
 purposes. 
 
CYLIXDEES OF "WOOD ATTACHED TO TUBED PLATES. 223 
 
 "The injury to the natural teeth must be much less, owing 
 to the smaller amount of surface in contact. 
 
 " If decay should take place, it would require but an ordi- 
 nary filling to restore the tooth. 
 
 " It prevents that peculiarly disagreeable sensation experi- 
 enced, particularly in fruit season, upon removing and replac- 
 ing artificial teeth. 
 
 " After having tested it for more than a year, I am satisfied 
 that it greatly lessens the chances of decay in those cases where 
 it can be applied, and I have removed the clasps in some old 
 cases with great satisfaction to my patients." 
 
224 MECHANICAL DENTISTEY. 
 
 CHAPTER yill. 
 
 Partial Dentuees supported in the Mouth by Piv- 
 oting THE Plate to the Roots of the Natural 
 Teeth. 
 
 A limited number of teeth may be mounted on a plate 
 pivoted to the roots of two or more of the front teeth ; and 
 provided the latter are firm, well formed, and in a healthy 
 condition at the time of the operation, an appliance so adjusted 
 may be worn by the patient with comparative comfort and 
 efficiency for from five to eight years. 
 
 Ordinarily, the roots of the cuspidati afford the most secure 
 means of attachment, and will furnish adequate support to a 
 
 Fig. 90. Fig. 91. 
 
 substitute supplying the loss of a part or all of the teeth 
 anterior to the bicuspids (Fig. 90), and, in some cases, one or 
 two of the latter on each side. The roots of the incisors, also, 
 may be used, or one of the latter and a cuspidatus. In some 
 cases the plate may be secured in the mouth by pivoting to a 
 root on one side, or in front, and clasping to a tooth on the 
 opposite side (Fig. 91), provided the crown of the latter and 
 the pivot root stand nearly or quite parallel with each other, 
 as any considerable deviation from this relation will render it 
 difficult or impossible to apply and remove the substitute. 
 The roots of the teeth to be used as a means of support 
 
PIVOTING TO THE ROOTS OF THE NATURAL TEETH. 225 
 
 should be prepared in the manner described under the head of 
 " Pivoting Artificial Crowns," In all cases, the enlarged canal 
 of the root should be jirovided with a gold tube, as this 
 method is the only one which will protect the root from the 
 mechanical action of the pivot, or permit a ready or frequent 
 removal of the appliance for the purpose of cleansing it and 
 the parts associated with it in the mouth. 
 
 The roots being prepared in the manner indicated, an im- 
 pression of the mouth is taken, and with a die and counter 
 obtained from a plaster model of the ])arts, a plate of the 
 required form is swaged covering the filed extremities of the 
 roots to be pivoted, and extending anteriorly very nearly or 
 quite to the free margins of the gum in front. The plate, at 
 those points corresponding with the openings into the roots, 
 is then perforated and enlarged sufficiently to admit of the 
 passage of the metallic pivots; tire form and position of the 
 orifices in the roots being transferred to the metallic die, the 
 corresponding de])ressions in the plate at these points, w'hen 
 the latter is swaged, will serve as a sufficient guide in perfo- 
 rating the plate for the pivots. The plate is now applied to 
 the mouth, and the metallic pivot, one-half longer than that 
 ultimately required and formed to fit the tube accurately but 
 not tigiitly, is passed through the opening in the plate and 
 pressed to the bottom of the tube, leaving the surplus portion 
 of the pivot projecting on the lingual side of the plate. The 
 plate and pivot are now secured in this precise relatixDu by im- 
 bedding the projecting portion of the latter and the parts of 
 the plate immediately surrounding it, in a batter of plaster. 
 When the plaster has hardened, the plate and pivot, with the 
 plaster attached, are removed in their undisturbed relation 
 from the mouth. To ]>rcscrve the several pieces in situ more 
 perfectly, the projecting end of the pivot may be flexed, or a 
 head formed on it with the file before applying the plaster; the 
 pivot thus secured will bring all f)arts together if traction is 
 made on the plate in the act of withdrawing the pivot. 
 
 The plate being removed from the mouth, its palatal por- 
 tion is imbedded in the plaster mixture, and when the latter 
 
 15 
 
226 MECHANICAL DENTISTEY. 
 
 is hard, the plaster is removed from around the pivot on the 
 opposite side of the plate, and the pivot permanently united 
 by flowing solder at its point of contact with the plate. The 
 redundant portion of the pivot on the lingual side of the base 
 is then cut and filed away even with the surface of the latter. 
 If the manipulations have been accurately conducted, the plate 
 and pivot, on being reapplied to the parts in the mouth, will 
 be found to adapt themselves perfectly to the palatal arch and 
 roots. 
 
 It is better, unless the roots to be pivoted stand nearly or 
 quite parallel, to adjust and solder but a single pivot at a 
 time, as but a very slight variation in the direction of the 
 roots would render the withdrawal of both pivots at the same 
 time difficult or impracticable without more or less change of 
 relation. The same may be remarked of those cases where a 
 clasp is used in conjunction with the pivot. 
 
 The most efficient method of rendering the appliance sta- 
 tionary when applied to the roots, and at the same time of 
 enabling the patient to readily apply and remove it at will, is 
 that recommended by Dr. Dwindle, and which consists in 
 splitting the pivot with a fine saw, and spreading the sections 
 apart somewhat, thus giving them an increased lateral bearing. 
 
 Gold used for pivots in these cases should be alloyed with 
 platinum, as that ordinarily employed for plate is too inelastic 
 for the purpose. 
 
ATMOSPHERIC PRESSURE. 
 
 227 
 
 CHAPTER IX. 
 
 Partial Dentures Supported in the Mouth by 
 Atmospheric Pressure. 
 
 The method of attaching partial sets of teeth to the superior 
 jaw by means of atmospheric pressure, is much more generally 
 practiced now than formerly, and whenever the condition of 
 the soft parts of the mouth, the general configuration of tlie 
 palatal arcli, and the antagonism or occlusion of the artificial 
 witli the natural teeth favor its adoption, there are good and 
 sufficient reasons why it should be preferred, in all practicable 
 cases, to either of the other methods heretofore described. 
 
 Modifications in the Form of the Base. — If vacuities exist at 
 various points on the ridge, the plate on which the teeth of re- 
 placement are mounted, should be ample in its dimensions, 
 covering nearly or quite all Fig. 92. 
 
 of the hard palate. The gen- 
 eral form of the base wher- 
 several teeth scattered through- 
 out the arch are required, is 
 shown in Fig. 92. In most 
 cases, whether but one or a 
 greater number of teeth are to 
 be replaced, increased adhe- 
 rence and stability of the sub- 
 stitute 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 diminished surface may be given to the base with 
 cfjually 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 
 
228 
 
 MECHANICAL DENTISTRY. 
 
 wall of the palate. (Fig. 93.) lu the latter case, the plate 
 used may be very thin, say No. 30 of the gauge ; it will thus 
 impede the movements of the tongue less, and may be swaged 
 more accurately to the parts. If constructed with an air-cham- 
 ber, 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 
 
 Fig. 94. 
 
 is to secure, in such cases, increased stability of the substitute, 
 while much of the palatal arch is left uncovered. It consists, 
 as will be seen by reference to Fig. 94, of two lateral 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 
 connected 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 sepa- 
 rately swaged and secured in their proper relation to each 
 other in the mouth with wax or plaster, when they are care- 
 
 * Dental Register of the West, vol. xiii, p. 112. 
 
ATMOSPHERIC PEESSUEE. 229 
 
 fullv removed, invested, and soldered together; it should then 
 be re-swaged to correct any change of relation that may have 
 happened during the concluding manipulations. The liability 
 of the plate to ride upon the central and raised portion of the 
 palate, when pressure is made upon one side, throwing 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 pres- 
 sure plates for partial cases are usually constructed with a 
 central air-chamber; in which case, the part of the model 
 representing the chamber 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 redundant por- 
 tions are then cut away with plate-shears and forceps. The 
 plate is now placed on the die, and brought as nearly as possi- 
 ble into adaptation to the latter with the mallet and pliers ; it 
 is tlien interposed between the die and 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. Unless the plate used is purer and thin- 
 ner than is generally employed, or than is consistent with the 
 required strength, it will fail to be forced perfectly into the 
 groove around the chamber by the process of swaging alone ; 
 a more definite border, ho\v'ever, may be formed by forcing 
 the j)late in at this place with a small, smooth-faced stamp, 
 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 abru])t angle is 
 obtained to the palatal edge of the chamber. After the cham- 
 ber is as perfectly formed as possible in this way, the plate 
 should l>e well annealed and again swaged to correct any par- 
 tial deformity occasioned by stamping the chamber. 
 
 A still more perfectly defined angle may be given to the 
 
230 MECHANICAL DENTISTRY. 
 
 borders of the chamber in the following manner : After SM^ao;- 
 ing 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 small, sharp, chisel-shaped instrument, cutting on a line with 
 the groove around the chamber until the latter is entirely sepa- 
 rated. 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 until the overlapping portions of 
 the central piece are forced down upon the plate around the 
 margins of the chamber. It is not, however, always necessary 
 to employ a separate piece of gold for the chamber, as the cen- 
 tral portion cut from the plate in the first instance may be suf- 
 ficiently enlarged for the purpose. This is accomplished by 
 first flattening out the detached portion, annealing it, and then 
 passing successive portions of its edges a sixteenth 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 
 attenuated and extended, it will be found so much enlarged 
 that when adjusted to the die and swaged in connection with 
 the main plate, its borders will overlap and rest upon the mar- 
 gins of the opening in the base, as in the other case. 
 
 The portions of the plate and cut chamber lying in contact 
 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 permanently 
 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. 
 
SELECTIXG AND AERAXGIXG THE TEETH. 231 
 
 CHAPTER X. 
 
 Method of Obtaining an Antagonizing Model for 
 Partial Dentures; Selecting, Arranging, and 
 Antagonizing the Teeth ; Investing, Adjusting 
 Stays, Soldering, Etc. 
 
 Haying constructed the plate or base to be used as a sup- 
 port 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, pre- 
 serving accurately the relation which these organs bear to 
 each other in the mouth. This is effected by what is called 
 an antagonizing model, and may be secured in the following 
 manner : 
 
 . A roll or strip of adhesive wax is first attached to the lin- 
 gual border of the plate, and its adhesion secured by holding 
 the opposite side of the plate for a moment over the flame of a 
 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, 1 pound 
 
 Guru inastich, 2 ounces 
 
 Spanish wliiting, 1 ounce 
 
 The wax is first melted in a shallow vessel, and the mastich, 
 finely pulverized, gradually added, and then the whiting, stir- 
 ring constantly until thoroughly incorporated. The rim of wax 
 being arranged on the plate, all superfluous portions over- 
 hanging 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 
 
232 MECHANICAL DENTISTRY. 
 
 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 crowais of the 
 opposing teeth opposite the spaces will 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. If a series of anterior 
 teeth are to be replaced, 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 
 
 Fig. 95. 
 
 central incisors and adjoining teeth. The plate and wax are 
 then carefully removed from the mouth and again placed upon 
 the plaster model, the latter having been previously obtained 
 from an impression of the parts with the plate in the mouth. 
 The model is then placed 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 half or 
 
SELECTING AND ARRANGING THE TEETH. 
 
 233 
 
 thrcc-fonrths of an inch. When hard, the edges and upper 
 surface of the added phister should be trimmed smooth, and a 
 crucial groove, or two or three conicaI-shai)ed holes, cut in the 
 surface of tiie 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 })iaster from 
 adhering ; the imprints of the teeth in the wax are also oiled. 
 This portion of the antagonizing model, with the plate and 
 wax attached, is exhibited in Fig. 95. The open sj)ace look- 
 ing into the ])alatal vault should be closed with a sheet of 
 softened wax to prevent the next portion of plaster from flow- 
 ing 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 
 
 Fig. 96. 
 
 the heel of the model until it acquires a depth of half an inch 
 or more. When sufficiently hard, the two sections of the 
 model are sejjarated, superfluous portions triuinied away, 
 and the entire surface of both pieces glazed with varnish. The 
 model complete, with the plate in place, and the wax (retained 
 as a tem^jorary support, whilst adju.sting the artificial teeth) 
 trimmed as required, are shown in Fig. 96, and if the manip- 
 ulations have been accurate this simple contrivance will ex- 
 hibit all the parts represented in plaster in precisely the same 
 relative position which they occupy in the mouth when the 
 teeth are closed upon each other. It will be seen, by reference 
 to Fig. 9o, that only those teeth of the opposing jaw which 
 
234 
 
 MECHANICAL DEXTISTEY. 
 
 Fig. 97. 
 
 present to the spaces, are represented in plaster, as these are 
 all that are required in arranging the teeth of replacement. 
 
 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 require- 
 ment, by comparison, in respect to the 
 various tints or delicate shades of color 
 characteristic of the natural teeth and 
 gums. The required size and form of 
 the artificial teeth may be determined 
 with tolerable accuracy by a compari- 
 son with those on the plaster model, 
 but the form or figure more certainly 
 by a careful inspection of those in the 
 mouth. 
 
 A greater or less change in the form 
 of porcelain teeth will be required, in 
 nearly all cases, in arranging and fit- 
 ting 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 is effected by grind- 
 ing away portions of the tooth upon an emery or corundum 
 wheel, attached, as will be seen in Fig. 97, to a foot-lathe. If 
 the edentated portions of the ridge have suffered but little 
 change of form by absorption, as w^here the teeth have been 
 recently extracted, and plate 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, grinding sufficiently to give to them the 
 proper length and relative position, while their anterior cer- 
 vical portion is permitted to overlap the edge of the plate and 
 rest directly upon the gum in front on a line with the adjoin- 
 
SELECTING AXD ARRANGING THE TEETH. 235 
 
 ing teeth. AVhen, however, a considerable concavity exists in 
 the ridge and external border, and single gum teeth are em- 
 ployed 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 rela- 
 tive position of the artificial crown ; while those portions of 
 the porcelain gum terminating at, and adjoining the remain- 
 ing teeth, next the spaces, should be formed with a thin, re- 
 treating edge, where it laps upon the natural gum, giving to 
 the parts, when the substitute is adjusted 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 comparatively 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. 
 
 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 op- 
 posing teeth will permit. A changed or abnormal relation 
 of the teeth of both jaws, however, frequently renders it diffi- 
 cult tf» effect a satisfactory adjustment of the teeth of replace- 
 ment. 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 ujjon these, in the ordinary manner, would 
 be impracticable without a corresponding shortening of the 
 porcelain teeth, enforcing, in such cases, an inharmonious 
 
236 MECHANICAL DENTISTRY. 
 
 arrangement, entirely inconsistent with the just requirements 
 of the case. The difficulty cited, Or any of the various modi- 
 fications of it, may be overcome wholly or in part in one of 
 two or three ways. If the teeth encroaching upon the opposite 
 space are very loose, as is frequently the case with those that 
 have become elongated from 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 in- 
 ward inclination in the arch, the vacuity opposite may be filled 
 with non-masticating teeth, as a canine, on the lingual side of 
 which an antagonizing cusp of gold may be constructed, 
 allowing the point of the cuspid to lap over upon the labial 
 face of the encroaching tooth or teeth ; or a bicsupid, manufac- 
 tured for the purpose, with the inner cusp near the base of the 
 tooth, may be used instead. Additional room may be pro- 
 vided, in such cases, for the overlapping portion by filing 
 away from a corresponding point on the opposing tooth. If, 
 however, taking the most impracticable case, the intruding 
 teeth are sound and firm, and stand vertically in the arch, 
 closing between the opposing teeth on a line with, or some- 
 what 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 an- 
 tagonizing teeth and a corresponding approximation 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 grinding surfaces to permit an unob- 
 structed closure of the natural organs, or decline the operation 
 altogether. 
 
 The undue projection of the teeth of one jaw into a vacuity 
 occurring in the one opposite more frequently happens, how- 
 ever, in connection with tlie loss of the superior incisors. In 
 such cases, the points of the lower incisors very frequently 
 encroach upon the circle of the upper teeth, so that when the 
 artificial teeth are arranged above in correspondence with the 
 
SELECTING AND ARRANGING THE TEETH. 237 
 
 circle of the adjoining teeth, antl the jaws are approximated, 
 the points of the inferior teeth will strike prematurely either 
 upon the cutting edges of those above or will close upon their 
 inner surfaces, — impeding thereby, or entirely preventing, the 
 Qi^clusion of the teeth posterior to them. For such cases thin 
 teeth should be selected, and whenever necessary the lower 
 teeth may be filed away sufficiently, while those of replacement 
 should, at the same time, be arranged as prominently as the 
 circle will admit of. If these expedients fail, and a sufficient 
 number of teeth posterior to the incisors require to be substi- 
 tuted in connection with the same appliance, it will be better, 
 in cases not susceptible of satisfactory correction by the means 
 already suggested, to change the bite by substituting an entirely 
 new antagonism with the artificial teeth, — spreading the jaws 
 sufficiently apart to relieve the artificial incisors in front. 
 
 In no case, except that last described, should the artificial 
 teeth come in contact with the oi)posing teeth before the occlu- 
 sion of the remaining natural organs when the jaws are closed. 
 The contact of all the teeth of one jaw, artificial and natural, 
 with those of the opposite, should either be simultaneous, or 
 the natural teeth should be permitted to strike first. 
 
 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 
 essential to the natural and agreeable expression of the indi- 
 vidual 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 re- 
 spect to the comfort and utility of the appliance or the safety 
 of the natural organs, demand it ; — to what extent appearances 
 should he sacrificed to these considerations will dejjend upon 
 the ])eculiar exigencies of the case, and cannot, therefore, be 
 specifically stated. On the other hand, it may be observed that, 
 if a sufficient numl)cr of the natural teeth are remaininjj in 
 both jaws to enable th(! patient to ]X'rform, with tolerable effi- 
 ciency, the act of mastication, the mere utility of the substitute 
 in regard to the performance of this function may l)e partly or 
 
238 MECHANICAL DENTISTEY. 
 
 wholly disregarded whenever there is sufficient reason to appre- 
 hend that the substituted organs cannot be antagonized with a 
 view to the comminution of food without endangering the per- 
 manency and usefulness of the appliance by necessitating the 
 application of forces unfavorably directed. 
 
 Investing, Adjusting Stays, Soldei^ing, and Finishing. — Hav- 
 ing 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 mixture 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 investient may be surrounded by a copper or sheet-iron 
 band to prevent the plaster from breaking away whilst adjust- 
 ing the stays or linings 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 in plaster to the depth of half 
 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. 
 
 The piece is now ready for the adjustment of stays or back- 
 ings, which, when permamently united by soldering to the 
 base and teeth, are designed to sustain the latter in position. 
 These supports are formed from plate somewhat thicker than 
 that used for the base; a heavier and stronger stay being 
 necessary when they are not united laterally, as 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, ordi- 
 narily, impart adequate security to the attachment. A plain 
 strip, corresponding in width with the tooth to be lined, is cut, 
 and the end resting on the main plate conformed accurately 
 with the file to the irregularities on the surface of the latter, 
 and in such a manner as to permit the strip to take the direc- 
 tion 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 
 
SELECTING AND AERANGING THE TEETH. 
 
 239 
 
 with a pair of plate forceps. (Fig. 98.) 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 
 
 Fig 98 
 
 softened in the flame of a spirit-lamp, and pressing it first 
 against the lower pin, the point of which will be indicated by 
 an indentation of the wax. The backing is then perforated 
 
 Fig. 99. 
 
 at this point with a plate punch, two forms of which are ex- 
 hibited in Fig. 99, one armed with a tongue, which, when the 
 plate is pierced, forces the latter from the punch. The strip 
 
240 
 
 MECHANICAL DENTISTRY. 
 
 is then reapplied 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 lining. 
 
 Fig. 100 represents an ingeniously contrived instrumentj 
 invented by Dr. Samuel Mallet, and designed to secure an 
 accurate relation of the two holes. After straightening the 
 pins, one is placed in the hole i, at the head of the punch, 
 the other pin pressing out the movable punch e (which works 
 
 Fig. KO. 
 
 by the spring g), until it slips into the slot h ; the two punches, 
 /, e, then make the holes at the exact distances apart to receive 
 the pins. 
 
 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 then shaped with a file to 
 the general form of the crown. When the stays are to be 
 united they should be formed with a shoulder at a point cor- 
 responding with the neck of the tooth, and the proximate 
 edges below united closely by square edges, or the latter may 
 be bevelled and made to lap upon each other. The process of 
 soldering will be greatly facilitated and the piece will be more 
 easily and artistically finished, by securing, in the first in- 
 stance, a perfect coaptation of all the parts which are ulti- 
 mately to be united. The sides of the holes in the stays facing 
 the plate should now be enlarged or countersunk with a spear- 
 shaped or conical burr drill, and when applied to the teeth the 
 
SELECTING AND ARRANGING THE TEETH. 241 
 
 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, and which will prevent them 
 from drawing from the linings. All the lines of union between 
 the several pieces should next be well scraped, exposing a 
 clean, bright, metallic surface to the solder ; the seams are then 
 smeared with borax, ground or rubbed in clean, soft water to 
 about the consistence of cream ;* after which small j^ieces 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 
 throughout 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 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 investient, 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 evolution of vapor, and the in- 
 tegrity of the porcelain teeth will be endangered. The piece 
 may be allowed to remain in the fire until the plate acquires a 
 visible red heat, when it should be removed, placed ou a suit- 
 able holder, and the solder fused with the blowpipe. A broad, 
 spreading flame should first be thrown over the entire surface 
 of the plate and border of the plaster until the temperature of 
 the entire mass is nearly that required to fuse the solder, and 
 which is indicated by the latter settling and contracting upon 
 itself; the flame may then be concentrated upon a particular 
 point, as at the heel of the plate on one side, passing round 
 
 * 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. 
 
 16 
 
242 
 
 MECHANICAL DENTISTRY. 
 
 from tooth to tooth until all 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 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 
 soldering, are removed ; or it may be put into a small copper 
 vessel, partly filled with the same solution and boiled for a few 
 
 Fig. 101. 
 
 minutes. After removing the plate from the acid, it should 
 be boiled for five or ten minutes in a solution of chloride of 
 soda or common salt and water to remove thoroughly all traces 
 of the former. Superfluous portions of solder are now to be 
 removed, and this at first may be more quickly accomplished 
 by the use of burrs of various forms and sizes attached to a 
 lathe. After the rougher and more redundant parts are thus 
 cut away, any remaining irregularities upon the surface may 
 be further reduced with properly formed files, scrapers, and 
 cutting instruments. Flat and half-round curved files, and 
 scrapers having a right and left curvature to their cutting 
 edges, and chisel-shaped cutting instruments for paring or 
 chipping away (Fig. 101), are the implements usually employed 
 for this purpose, and with which a comparatively smooth sur- 
 
SELECTING AND ARRANGING THE TEETH. 243 
 
 face may be obtained ; after whicli, the filed portions should 
 be well rubbed with Scotch stone until all traces of file-marks 
 or other scratches are completely removed. With a rapidly 
 revolving brush attached to a foot-lathe, the final polish or 
 lustre may be imparted by the use, first, of Spanish whiting, 
 or prepared chalk, and then rouge mixed with water or 
 alcohol. 
 
 The following method of finishing plate-work communi- 
 cated by Professor J. L. Suesserott,* embodies some practical 
 suggestions in reference to this process : " The first step is to 
 procure and attach to the lathe a three- or four-pronged fork, 
 or a screw such as is used for withdrawing a load from a gun ; 
 upon this a good smooth cork is fixed, and, with a sharp knife, 
 turned to any desired shape. The cork is saturated with water 
 as well as it can be, and powdered pumice placed upon it. If 
 we have been careful to remove all excess of solder from our 
 work, which can easily be done by a burr attached to the lathe, 
 we can, with the cork and pumice, make a very smooth sur- 
 face, and this can be still more perfectly accomplished by sub- 
 stituting a very finely powdered spar for the pumice, after we 
 have removed the largest scratches with tlie latter. By con- 
 tinuing the cork for a little while after the above-named pow- 
 ders have been used oif, we avoid the use of the Scotch stone ; 
 and finally we dispense with the burnisher, by taking a new 
 cork with a piece of chamois or buckskin stretched upon it, 
 and going over the plate in the same manner as before, with 
 the lathe revolving very rapidly. 
 
 " A higher color can be given to the plate by the use of the 
 burnisher after the above proceeding, but we can certainly not 
 produce a smoother surface. 
 
 " Some precaution is necessary by those who have never 
 used the lathe in finishing the j)late ; in the first place the 
 careless use of the burr, in removing the excess of solder, might 
 result in the weakening of the piece by removing more than 
 neces.sary, or, what would .be still worse, holes might be cut 
 
 * Erroneously aHcribod in tlie fii-st edition to Professor T. L. Buck- 
 ingham. 
 
244 MECHANICAL DENTISTRY. 
 
 entirely through the plate. Again, in polishing, if a little 
 care is not taken, the fork or screw, whichever is used, may 
 pass through the cork, and before the operator is aware he 
 will have inflicted an injury that will be difficult to repair. 
 A small amount of experience — that which is essential in the 
 proper performance of every nice operation — will enable almost 
 any one, even those, to use a common expression, ' whose fingers 
 are all thumbs,' to finish their work in about one-eighth of the 
 time that the most expert workman would require for the 
 accomplishment of the same by the old method."* 
 
 In the final adjustment of the finished piece to the mouth, 
 and after any additional change in the form of the teeth neces- 
 sary 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 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 four to six weeks ; 
 and this estimate of time, in a majority of cases, will be fully 
 justified by experience in the cases under consideration. 
 
 * Dental Cosmos, vol. i, p. 330. 
 
SELECTING AND ARRANGING THE TEETH. 245 
 
 The importance of thorough and absolute cleanliness of the 
 substitute and 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, or any of the means usually recommended for 
 the purpose. 
 
246 MECHANICAL DENTISTRY. 
 
 CHAPTER XI. 
 Entiee Dentures. 
 
 Method of Constructing a Plate Base for a,n Entire Denture 
 for the Upper Jaio. — The general form and dimensions 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 
 to serve as a guide in securing the form of the plate to be 
 swaged. Whenever the substitute for the upper jaw is de- 
 signed to be retained in situ by the external pressure of the 
 atmosphere, and especially where a central air-chamber is 
 employed, the plate should be made sufficiently ample in its 
 dimensions to cover all the hard palate, the alveolar ridge, and 
 all portions of the external borders of the latter not directly 
 encroached upon by the muscles and reflected portions of the 
 mucous membrane of the lips and cheeks. 
 
 Before swaging, the plate should be well annealed, and its 
 central portion brought as nearly as possible to the form of 
 the palatal face of the die with the mallet, forcing the heel of 
 the plate down in advance of the portion covering the more 
 anterior concavity of the arch, preventing thereby a doubling 
 of the posterior edge of the plate upon itself. This central 
 portion may also be forced more perfectly into adaptation 
 with a partial counter before swaging in the ordinary manner, 
 and this is advisable in all cases when the palatal arch is very 
 deep ; but as this is very liable to be drawn from the arch in 
 the process of turning the borders of the plate over upon the 
 ridge, a useful contrivance has been invented by Dr. Rurras, 
 of Xew York, to prevent the displacement. Fig. 102 shows 
 the form of this instrument. The die and plate are placed near 
 the edge of the bench, and the upper part of the clamp adjusted 
 
ENTIRE DENTURES. 247 
 
 over the central portion of the plate ; the two pieces are then 
 bound firmly to the bench by tightening the screw underneath. 
 A protective piece of buckskin, cloth, or paper, should be 
 placed between the plate and clamp, to prevent the former from 
 being bruised or indented. The margins of the plate are now 
 turned over upon the ridge, and if the external borders of the 
 latter are undercut or stand even verti- 
 cally, the edges of the former will tend to 
 double upon themselves at such points, 
 and hence it will be necessary, before 
 swaging, to split the plate in front, and, 
 in some cases, on each side, and wherever 
 divided, a V-shaped piece may be cut out 
 of sufficient "svidth to allow the divided 
 edges to overlap slightly when approxi- 
 mated in the process of swaging. The 
 proximate edges of the divided sections 
 should be filed to a thin edge before 
 swaging, so that when brought together 
 and soldered there will be but little additional thickness of the 
 plate at such points. The cut portions should not be soldered 
 until after a partial or complete swaging. 
 
 Having conformed the plate as nearly as practicable to the 
 die with the mallet and pliers (Fig. 103), or with plate forceps 
 constructed for the purpose (Fig. 104), it should be placed 
 between the die and counter, and the latter 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 stam])ing to render it more pliable. At 
 first considerable yielding and consequent deformity of the 
 counter-die will occur ; hence, after partial swaging, another 
 should be substituted and the process continued until the 
 greatest possible accuracy of adaptation is secured. If the face 
 of the die is marked by prominent and sharply defined rugie, 
 or other irregularities, such points will, to some extent, be 
 bruised or flattened; it will therefore be expedient in such 
 cases, and better perhaps in all, to finish the swaging with a 
 
248 
 
 MECHANICAL DENTISTEY. 
 
 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 
 
 Fig. 103. 
 
 of its adaptation out of the mouth. In no case will the swaged 
 plate fit the plaster model perfectly, inasmuch as the unavoid- 
 able contraction of the die, however slight, will, especially in 
 deep-arched mouths, cause the plate to bind on the posterior 
 
 Fig. 104. 
 
 and external borders of the ridge, preventing it from touching 
 the floor of the palate ; while the bruising, though inconsider- 
 able, of the more prominent points upon the die, and a corre- 
 sponding flattening of the plate at such points, will prevent 
 uniform contact of the latter with the unchanged surface of 
 the plaster model. 
 
EXTIRE DENTURES. 249 
 
 After final swaging, the plate should be again annealed with 
 a heat nearly or quite equal to that which will be ultimately 
 required in soldering ; after this any additional swaging should 
 be avoided, unless the plate warps in the heat, and which may 
 be determined by applying it to the die; if any change has 
 occurred, it should be re-swaged 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 Den- 
 tures. — Whenever a central air-chamber is employed, it may 
 be constructed in either of the ways described when treating of 
 
 Fig. 105. Fig. 106. 
 
 partial atmospheric pressure plates. The general form of a 
 plate for an entire upper denture, with a central chamber, is 
 exhibited in Fig. 105. 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 bicuspids on each side, as seen in 
 Fig. 106, called " Lateral Cavity Plates." Dr. M. Levett, of 
 New York, has recently introduced another modification of 
 cavity plate, consisting of a number of small air-chambers 
 arranged directly over the ridge and placed at short intervals 
 througiiout the entire border. It is claimed that plates con- 
 structed in either of the ways last mentioned cohere with equal 
 
250 MECHANICAL DENTISTRY. 
 
 firmness to the jaw, and are less liable to " rock " in the mouth, 
 than when formed with a central chamber. Whatever their 
 general utility may be, cases doubtless occur where they may 
 be advantageously employed, as when any great inequality 
 exists in the hardness of the ridge and palate, and a plate con- 
 structed in the ordinary manner is dislodged by "riding" upon 
 the hard palate when forces are applied to the ridge on either side. 
 
 It has been recommended, after having constructed a base of 
 the form represented in Fig. 105, to cut through the plate im- 
 mediately in front of the central chamber, making an opening 
 of a semilunar form. It is claimed that, by the more ready 
 application of the tongue to this part, the air contained in the 
 chamber, when the plate is applied to the mouth, may be 
 more easily and thoroughly exhausted. There is great danger, 
 however, of the soft tissues being drawn into the opening, in 
 which case it can scarcely fail to produce injury to the parts 
 implicated ; the expedient, therefore, is seldom resorted to. 
 
 There is still another form of cavity plate known as Cleve- 
 land's modification of air-cliamber, and which is constructed in 
 the following manner : A plate like that exhibited in Fig. 105 
 is first struck up and the chamber cut out. A thin sheet of 
 wax^ or a layer of plaster, is then placed upon the lingual side 
 of the plate, extending from two to three or four lines from the 
 edges of the orifice in the main plate ; a thin, retreating edge is 
 given to the wax or plaster at the outer borders, making it con- 
 tinuous with the surface of the plate. The plate with the wax 
 attached may now either be tacked to the model with softened 
 wax along its outer borders, and shaped in such a way as to 
 permit the model and plate to be withdrawn from the sand, and 
 a mould of the parts taken in the ordinary way, and from this 
 a die and counter ; or an impression in wax or plaster may be 
 taken of the lingual face of the plate and wax, and afterwards 
 a model, die, and counter. With the latter, a second plate, 
 covering nearly or quite all of the palatal concavity, is swaged, 
 and when this is applied to the main plate over the cut cham- 
 ber, and united by soldering, a space, equal to the thickness of 
 the wax or plaster placed on the primary plate, will be found 
 
ENTIRE DENTURES. 251 
 
 to exist between the two laminse. Fig. 107 exhibits a trans- 
 verse section of the two plates, disclosing the space between 
 them, and also the opening through the gum plate into the 
 cavity. Before soldering on the duplicate plate, a half-round 
 wire should be soldered around the opening in the palatal 
 plate on its lingual side, to protect the soft tissues of the mouth 
 from injury when drawn in as the air is exhausted from the 
 chamber ; or, what is preferable, this form of cavity may be 
 converted, practically, into what is known as " Gilbert's cham- 
 ber" (which is the central swaged chamber before described), 
 by filling in the space between the two plates with some im- 
 pervious substance, as Hill's filling, or an amalgam of gold, 
 the excess of mercury being driven off by heat. In the con- 
 struction of continuous gum work, the interspace may be filled 
 in with gum body. The advantages of these double plates are, 
 
 a greatly increased strength imparted to the base, a diminished 
 liability of warping in the process of soldering, a smoother sur- 
 face presented to the tongue, and a more decidedly angular 
 form of tlie chamber. 
 
 In whatever way the plate is formed, a notch or fissure of 
 sufficient depth to receive and permit an unobstructed play 
 of the frtenum 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 pre- 
 vent un<]ue contact of its edges with the folds of the mucous 
 membrane stretching obliquely across from the cheeks to the 
 jaw. Care should also be taken to trim away from the heel 
 of tlie i)late any portions that might otherwise encroach upon 
 the soft palate. 
 
252 MECHANICAL DENTISTRY. 
 
 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 
 reception 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 neces- 
 sitating, in some degree, a departure from a just arrange- 
 ment and antagonism 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 to the plate along the plate 
 ends of the teeth after the arrangement of the latter on the 
 base is completed. 
 
 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 adapta- 
 tion 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 re -swaged; in the 
 latter, a less contractile metal or compound should be employed 
 in the formation of the die. To determine the practical effi- 
 ciency of the adaptation and adherence of an atmospheric pres- 
 sure 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 its adjust- 
 ment 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 be 
 readily 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 pressure applied in the manner indi- 
 cated, the adaptation may be safely relied on ; if it slides upon 
 
ENTIRE DEXTURES. 253 
 
 the palate or is easily disengaged from the mouth, the insta- 
 bility 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. Thus, for example, if the 
 ridge along the mesial line of the palatal vault is more than 
 usually prominent and incompressible, and the alveolar ridge 
 relatively soft and yielding, the plate, meeting with a fixed 
 point of resistance at the floor of the palate, will prevent the 
 ridge from being sufficiently compressed when the atmosphere 
 is exhausted from underneath the plate ; and hence, when 
 forcible pressure is made on one side over the ridge, the plate, 
 riding upon the resistant surfoce of the arch, will be thrown 
 off from the opposite side. Whenever, therefore, the condi- 
 tions alluded to prevail to any considerable extent, a perfect 
 coaptation of the plate to the parts, instead of favoring the 
 retention of the former, will impair its stability for all practi- 
 cal purposes. The remedy is found in so constructing the 
 plate that, when adjusted to the mouth, and before the air is 
 exhausted, a greater or less s])ace will exist between the central 
 portion of the plate and palate, but which, when a vacuum 
 is formed, will be carried up into contact with the roof of the 
 mouth, and at the same time compress the ridge sufficiently to 
 afford a firm and resisting basis for the plate in mastication. 
 This peculiar adaptation of the plate may be obtained by ad- 
 justing a piece of sheet-lead or wax plate over the central ridge 
 on the plaster model, by means of which the corresponding 
 portion of the plate, when swaged with a die obtained from the 
 model so prepared, will be thrown far enough from the roof 
 of the mouth to answer the purpose before indicated. This 
 will be more particularly necessary in shallow arches ; while, 
 if the arch is very deep, or even moderately so, the unavoidable 
 contraction of the die may render the expedient unnecessary. 
 
 Method of Construdinrj a Plate Bern; for an Entire Devture 
 for the Under Jav\ — 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 essen- 
 
254 MECHANICAL DENTISTRY. 
 
 tially 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 addi- 
 tional thickness of the plate and the peculiar form of the in- 
 ferior maxilla renders a greater degree of pliancy necessary in 
 swaging it to the form of the ridge. The general form of a 
 base for an entire lower denture is exhibited in Fig. 108. 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. 
 
 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 
 
 Fig. 108. Fig. 109. 
 
 which case a thin basement plate, not exceeding No. 30 of the 
 gauge, 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 con- 
 formed 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 dou- 
 bling the entire plate, it will be sufficient, in most cases, to adapt 
 the second plate only to the lingual surface of the first, extend- 
 ing it up from the lower edge to a point corresponding as 
 nearly as possible with the posterior portions of the base of the 
 
ENTIRE DENTURES. 255 
 
 teeth when the latter are adjusted to the plate (Fig. 109). A 
 moderately thhi plate may, in this manner, be used for the 
 primary base, while the duplicate band will impart the requi- 
 site strength to the plate, and, at the same time, obviate the 
 necessity of wiring its inner edges. 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. 
 
 Antagonizing Ilodel for an Entire Upper and Lower Den- 
 ture. — Either of the following methods may be adopted in se- 
 curing an antagonizing model for complete dentures : 
 
 1. Attach to the ridge of each plate a roll or strip of adhesive 
 wax corresponding in widtli 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 asso- 
 ciated with the lips and mouth are secured. The approxima- 
 tion of the two jaws, when the finished substitutes are ulti- 
 mately 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 closure of the jaws secured at this time should be such as 
 will most perfectly fulfil the requirements of the case in respect 
 to the utility and comfort of the appliance, and the proper 
 restoration of the required facial proportions. If there is any 
 considerable change produced in the relation of the jaws habit- 
 ual to them })rior to the loss of the natural teeth, the charac- 
 teristic expression of the individual will, in some degree, be 
 changed or marred ; an unaccustomed and restrained action 
 will be imposed ui)on the muscles concerned in the movements 
 of the lower jaw, which will render the use of the appliances 
 at least temporarily, if not permanently, uncomfortable and 
 fatiguing, or even j)ainrid ; while the utility of the fixtures 
 may be impaired or wholly destroyed, by compelling a partic- 
 
256 MECHANICAL DENTISTRY. 
 
 ular 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 approxinating surfaces until the jaws close suffi- 
 ciently to permit the edges of the lips to rest easily and natu- 
 rally upon each other when in a relaxed condition, or the 
 upper rim may extend somewhat below the margin of the 
 up2)er lip, while the lower section of the 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 required; as where the 
 alveolar ridge is very deep, and the lip covering it either abso- 
 lutely or relatively short, or where the latter is retracted, 
 exposing, even when in a state of repose, a greater portion or 
 all of the crowns of the teeth, and in extreme cases the mar- 
 gins of the gum. Between the latter extreme and an inordi- 
 nate extension of the upper lip below the ridge all intermediate 
 conditions occur, and the practitioner, aiming to produce an 
 agreeable, harmonious, and truthful expression of all the parts, 
 must rely wholly upon his judgment in reference to the neces- 
 sary approximation of the jaws, the restoration of the natural 
 fulness and contour of the mouth, and the relative length to be 
 given to the upper and lower teeth. 
 
 Patients, when requested to close the mouth naturally, are 
 very liable to j)roject the under jaw ; hence it is well to have 
 them open and close the jaws frequently, 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, the patient should be directed to 
 relax and abandon for the moment all control over the muscles 
 of the lower jaw ; the operator should then grasp the chin and 
 press the jaw first directly backward and then upward until 
 the opposing surfaces of the wax meet, in which po&ition it 
 should be steadily held by the patient until the two portions of 
 wax are attached to each other in that particular relation. 
 The latter may be done by drawing lines vertically across the 
 
ENTIRE DENTURES. 257 
 
 rims of wax at various points "wliicli will serve to indicate their 
 relation to each other when out of the mouth ; or a heated 
 knifeblade may be passed between the two sections, the melted 
 wax temporarily uniting them. A very convenient and secure 
 method is to attach them together by means of two strips of 
 metal bent in the form of a stajile; 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. 
 Before removing the plates, the mesial line of the mouth 
 should be indicated upon the wax by drawing a line vertically 
 across the latter in front to serve as a ffuide in the arrano-ement 
 of the central incisors. 
 
 2. Another method is to attach to either the upper or lower 
 plate a single rim of wax somewdiat wider than will be required 
 for both the upper and lower teeth. The plates are then placed 
 in the mouth, and the jaws brought together, imbedding the 
 opposite plate in the wax. When this method is adopted, the 
 proper closure of the jaws is best determined by a gauge or 
 guide consisting of .a strip of plate or other substance encased 
 in the wax and interposed edgewise between the borders of the 
 two plates in front in such manner that, when the latter are 
 approximated, they will close upon the guide, the desired rela- 
 tion of the jaws to each other having been previously ascer- 
 tained by trial of the guide with the plates in the mouth before 
 adjusting the wax. The exterior surface of the wax rim is 
 then trinmied away, or additional portions added to it, until 
 the proper fulness and contour are given to the lips; after 
 which the medium line of the mouth should be traced upon 
 the wax in front, as before described. 
 
 The plates, attached to each other in either of the ways 
 mentioned, having been removed from the mouth, a batter of 
 plaster may be poured upon a piece of paper or other substance, 
 forming a layer a fourth or a half an inch thick and two or 
 three inches long, when the under surface of the lower plate 
 may be imbedded in one end of the plaster, and the remaining 
 portion of the latter projecting from the heel of the plate 
 trinnned and formed for articulating with the second piece of 
 
 ]7 
 
258 MECHANICAL DENTISTRY. 
 
 the antagonizing model in the same manner as described when 
 considering partial dentures. The entrance to the cavity be- 
 tween the two plates is now closed up with a sheet of softened 
 wax or otherwise, and the whole surrounded by a piece of oil- 
 cloth, wax, or other substance, and the second part of the model 
 obtained by pouring plaster in upon the exposed surface of the 
 upper plate and the plaster posteriorly to the depth of half an 
 inch or more. When the plaster is sufficiently condensed, the 
 line across the wax in front 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 cut away, and without 
 this precaution the mesial point of the mouth may be lost. 
 The form of an antagonizing model for an entire upper and 
 
 Fig. 110. 
 
 lower denture, with the plates and wax attached, the latter 
 being cut away somewhat preparatory to adjusting the teeth, 
 is shown in Fig;. 110. 
 
 Antagonizing 3Iodel for an Mitire Upper Denture with the 
 Natural Teeth of the Lower Jaw Remaining. — In forming an 
 antagonizing model to be used as a guide in arranging and ar- 
 ticulating 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 j)laced in the mouth, the exterior surface of the wax 
 draft should be cut away or added to, until the proper fulness 
 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 of the 
 opposing teeth. If a fuller impression of the exterior faces of 
 
ENTIRE DENTURES. 
 
 259 
 
 the lower teeth are required, it may be obtained by pressing in 
 a small strip of softened wax against them and the lower edge 
 of the rim of wax upon the plate ; or the projecting borders 
 of the latter may be forced down upon the crowns with the 
 fingers. The median line of the mouth is then indicated upon 
 the wax, the plate removed, and its palatal surface imbedded 
 
 FiCx. 111. 
 
 in one end of a layer of plaster spread upon a strip of paper; 
 the portion of plaster extending from the heel of the plate 
 trimmed, grooved, varnished and oiled; the entire piece in- 
 closed, and plaster ])oured in upon the exposed surfaces of the 
 wax and plaster to the depth of one-fourth or one-half of an 
 inch. The two sections of the model, with the plate and wax 
 
 Fig. 112. 
 
 attached, the latter being cut away somewhat to receive the 
 porcelain teeth, is exhibit(;d in Fig. 111. 
 
 Various articulators, or antagonizing frames, have been de- 
 vised, and may be substituted for the plaster articulator just 
 described. A very excellent adjustable contrivance of the kind, 
 invented by Dr. Hayes, is exhibited in Fig. 112. Witii this 
 
260 MECHANICAL DENTISTRY. 
 
 appliance, all the motions of the jaws can be represented, and 
 the relative positions again brought back at pleasure at the 
 starting-point. The screw hinge admits lateral motion. The 
 set screv/ on the side plays into a slot, securing one central 
 position, to which it can at all times, when desired, be brought 
 back. The long screw in the foot produces back and forward 
 motion, the main hinge up and down motion, and the large 
 nut on the bottom renders all the parts taut and unyielding. 
 
 Considerable space is here devoted to the consideration of an 
 ingenious and novel device, introduced to the notice of the pro- 
 fession by Dr. W. G. A. Bonwill, of Philadelphia, Pa., and 
 characterized by him as the 
 
 " Anatomical Articulator." 
 
 As to the character of this instrument, the author cannot 
 speak personally. Dr. B., whose name is inse])arably connected 
 with the electric mallet, dental engine, original methods of 
 attaching pivot crowns described elsewhere, and various other 
 practical devices, says that it holds the same positive relation or 
 position in his laboratory as do the electric mallet and engine 
 in his operating room. In other words, it is indispensable to 
 the perfect articulation of all artificial dentures from one to a 
 full set, — that it is a sine qua non. He says : 
 
 " It is modelled on the same geometrical system as the hu- 
 man jaw. 
 
 " I found by measurement that the average width of the lower 
 jaw from centre to centre of each condyle was four (4) inches, and 
 from the same centre of each condyloid process to the median 
 line of the lower jaw, where the cutting edges of the lower in- 
 cisors meet, was also four (4) inches, making of the human jaw 
 an equilateral triangle. This holds good in all jaws, and the 
 difference of a quarter of an inch in this radius of a circle of 
 four inches would make but little practical difference as to the 
 results. 
 
 " This beautiful law enables us to have the fullest benefit of 
 mastication at the least expense of power and motion in the 
 arc of the circle of four inches as a radius. 
 
ENTIRE DENTURES. 261 
 
 " This being an absolute law, I have so made this articula- 
 tor, and the cast of every case is set therein with tiie median 
 line at the lower centrals just four (4) inches, by the dividers, 
 from each condyloid process. 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. 
 
 "I found that there is a further positive law in the mechan- 
 ism of the human jaw that should be regarded in every sub- 
 stitute 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 upwards . and 
 backwards at the ramus is due solely to the depth of closure 
 of the ujiper over the lower jaw. That where there is occlu- 
 sion or closing of the cutting surfaces of the incisors directly 
 upon each other, then a straight line, directly backwards, is 
 the consequence. 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. 
 
 " Where there is an eighth of inch depth of bite, then, as 
 you go back to the centre of motion — the condyloid processes — 
 the cusps in the bicuspids and molars grow less deep, and the 
 curvature at the ramus is an eighth of an inch out of line. 
 
 " When there is an overbite of an eighth of an inch, then, in 
 opening the lower jaw and carrying it forward to use the in- 
 cisors for cutting, the back teeth of lower jaw are brought for- 
 ward ; 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 u])ward, 
 and is the highest out of line in the superior jaw, and they 
 meet at same time that the incisors do. And the same law holds 
 good when the lower j-aw 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 recog- 
 
262 MECHANICAL DENTISTRY. 
 
 nizing 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 artificial dentures, most of their articulating sur- 
 faces being utilized at every position of the lower jaw. Any 
 human jaw will show this 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 advanced civilization. 
 
 " When a set is commenced in this articulator with the up- 
 per overbiting the lower an eighth of an inch, as you set each 
 tooth backward towards the condyloid processes, they will 
 assume the exact angle and depth of cusps, as well as the cur- 
 vature at the ramus, as found in nature. If both jaws are in 
 
 Fig. 113. 
 
 direct apposition at the incisors, 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. 114 shows, there is a sep- 
 arate 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 year if necessary, and then articulated. A pair of 
 bows can be used for as many separate cases, while only one 
 base is required, which should be made absolutely and geomet- 
 rically exact — approximately so. 
 
 " There is no need for set screws to hold the bows, as they 
 
ENTIRE DENTURES. 
 
 263 
 
 go up just so far and remain so. Nor is there any set screw and 
 prop to hold the jaws or casts apart. This is 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. It would interfere 
 with the lateral movement if a rigid prop were there. The 
 dividers make each case 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 gauged 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. 
 
 " Make 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, tlie uj)j)er 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 
 
264 MECHANICAL DENTISTRY. 
 
 be done with the dividers set just four (4) 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 centre of jaw equidistant from the 
 condyles. The study of this principle will make one fully 
 realize the beautiful workings of Divinity, which is only gov- 
 erned by positive law in every department of the universe. 
 With this plan, understand one will never again attempt to 
 articulate a set of teeth on the unwritten law, as now univer- 
 sally made and recognized by every dentist in the land. 
 
 " Until this system is taught in the schools, and by private 
 practitioners, no truly artistic and fully natural set of teeth 
 can ever be made, for we have been without law in this de- 
 partment. To describe it is not enough. It must be seen and 
 demonstrated, one tooth at a time, until the whole set is made. 
 Only in this way can it be understood. 
 
 "The Figs. 113 and 114 show clearly the simple construc- 
 tion. It is made of brass wire (one-eighth 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 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, 'svhich is 
 easily done at first by asking the patient to swallow, when the 
 jaws will automatically 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 unartistic work when 
 this instrument is once understood, and the law controlling the 
 
ENTIEE DENTURES. 265 
 
 human jaw. As we may forever have to resort to artificial 
 dentures, we should demand of the colleges that such an instru- 
 ment be used, and it alone, as furnishing the only hope now 
 offered of an approach to high-toned, artistic, mechanical den- 
 tistry. 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." 
 
 Selecting, Arranging, and Antagonizing the Teeth; Rimming 
 the Plate; Attaching Spiral Springs ; Investing, Lining, Sold- 
 ering, and Finishing. — In selecting teeth for an entire upper 
 and lower denture, the special requirements in respect to size, 
 form, and color, will depend, in a great measure, upon the 
 complexion, age, sex, general configuration of the face, etc., 
 of the patient. Every separate denture, therefore, that is con- 
 structed in strict conformity with a faithful interpretation of 
 the special requirements of each individual case, will be char- 
 acterized by shades of differences in the color, form, size, and 
 arrangement of the teeth of replacement. It will be sufficient 
 in this connection to observe that such selection of the teeth 
 should be made as will most perfectly reproduce the lost pro- 
 portions of the facial contour, and impart to the individual a 
 natural, harmonious, and agreeable expression. 
 
 In arranging or adjusting single gum teeth to the plate in 
 those cases where the changes in the form of the alveolar rido-e 
 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 sur- 
 faces to the base should be accurate enough to exclude perfectly 
 particles of food, an<l to furnish such a basis to each tooth as 
 will provide most effectually against fracture when acted upon 
 by the forces api)Hed to them in the mouth. The gum extremi- 
 ties of the teeth should also be accurately united to each other 
 laterally by 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 
 
266 MECHANICAL DENTISTRY. 
 
 of the adjoining surfaces is uniform, for if confined to the outer 
 edge alone, portions of the gum enamel may be broken away 
 iu the process of soldering. 
 
 In the construction of substitutes designed to fulfil only a 
 temporary purpose, and where the alveolar processes remain in 
 a great measure unabsorbed, and plain teeth (those represent- 
 ing 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 
 recently 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 scolloped (Fig. 115), permitting the 
 anterior cervical portions of the artificial incisors and canines, 
 and, in some cases, the anterior bicuspids, to overlap the edge 
 of the plate and rest directly upon the gum in front. This 
 abridgment of the plate will not ordinarily materially aflPect 
 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 absorption alternate with other points 
 upon the ridge in a comparatively unchanged condition. To 
 give uniformity to the denture by restoring perfectly the re- 
 quired circle of the arch in such cases will necessitate the em- 
 ployment of plain and single gum teeth conjointly. When- 
 ever 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 de- 
 scribed. 
 
 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, keeping the upper ones in advance of those 
 
EXTIRE DENTURES. 
 
 267 
 
 of the lower jaw. The central incisors above, should be placed 
 parallel with each other, but tlie cutting edges of the laterals, 
 and the points of the canines, should incline slightly toward 
 the medium line of the mouth. lu arranging 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 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 de- 
 
 Fin. Hi. 
 
 Fig. 116. 
 
 scribed, the peripheral outline of the arch will exhibit some- 
 what the form ])resented in the above diagram (Fig. 116). 
 
 In regard to the practical efficiency of an upper denture re- 
 tained in the mouth by atmospheric pressure, it is important 
 that the teeth engaged in the comminution of food, as the bi- 
 cuspids and molai's, should occupy a position directly over the 
 central line of the ridge, and should either be arranged verti- 
 cally or with a slight inclination toward the centre of the 
 mouth. The liability to displacement of the substitute in 
 mastication will thus be greatly diminished, wherea.'!, if placed 
 outside of the line indicated, and especially with a diverging 
 inclination, the stability of the appliance will be endangered, 
 
268 MECHANICAL DENTISTRY. 
 
 and the functions of mastication impeded, notwithstanding 
 other conditions necessary to complete success hav^e been fully 
 secured. In arranging the upper and posterior teeth as de- 
 scribed, it will sometimes be necessary to give to the opposing 
 under teeth a decided inward inclination in order to effect a 
 satisfactory 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 associated with an expanded ridge 
 below. 
 
 In articulating the upper and lower teeth, the closure or re- 
 lation of the natural organs should be imitated as nearly as the 
 other essential requirements of the case will admit of. Hence 
 the upi^er front teeth, describing the segment of a larger circle 
 than the corresponding 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 laterally 
 beyond the opposing teeth, covering one-third of the crowns of 
 those next adjoining, so that when the canines of the upper jaw 
 are reached, they will close between the lower canines 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 an- 
 terior 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 remaining posterior half of the second 
 molars above extending posteriorly beyond those of the lower 
 jaw. The outer cusps of the superior 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 external cusps, 
 and the external cusps of the inferior teeth will, in like man- 
 ner, be received into the corresponding excavations of the upper 
 teeth. The relative position and antagonism of the teeth, as 
 
ENTIRE DENTURES. 269 
 
 they a})pear in a regularly arranged denture for both jaws, are 
 shown in Fig. 117. An abnormal relation of the jaws, as 
 where undue projection, 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 teeth are remaining below, or vice versa, the 
 color, size, and form of the latter, w'ill serve as a guide in the 
 
 choice of teeth appropriate for the opposite jaw. In fitting 
 and arranging the teeth ui)on the base, and in antagonizing 
 them with the opposing natural teeth, the same general prin- 
 ciples aj)ply as those already adverted to in connection with full 
 upj)er 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 either in re- 
 spect to prominence, position, hiclination, length, or antago- 
 nism. 
 
 Forming a Rira to the Plate. — If the case is one where sin- 
 gle gum or block teeth are employed, and it is intended to 
 form a socket or groove upon the borders of the plate lor the 
 reception of the plate extremities of the teeth, the rim forming 
 the gro<Jve should be fitted and soldered to the l)ase before in- 
 
270 MECHANICAL DENTISTRY. 
 
 vesting 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 be 
 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 
 consist of one entire strip extending from heel to heel of the 
 plate, and passing round the posterior molars to unite with 
 the stays; but it may be more conveniently adjusted by em- 
 ploying two pieces, extending from each heel of the plate, and 
 uniting in front. 
 
 2. A half-round wire with the edge bevelled 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 extremities of the teeth. A narrow strij) of plate, 
 about the thickness of a heavy clasp material, may be sub- 
 stituted 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 ; re- 
 move 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 re-enter the rivet-holes in the wax, thus 
 restoring them to their proper position 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 impossible to detach either wax or plaster in per- 
 
ENTIRE DENTURES. 271 
 
 feet condition, when encircling the entire arch, or to swage 
 perfectly with a die so unfavorably formed for stamping, sepa- 
 rate impressions of the two lateral halves of the piece should 
 be taken, — from these plaster models ; and from the latter, dies 
 and counters; — 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 embra- 
 cing 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. An upper denture rimmed in 
 the manner last described is exhibited in Fig:. 118. In what- 
 ever way the rim is formed, when it has been fitted to the plate 
 and teeth, it may be held temporarily in place with clamps 
 adjusted at two or three 'points around the plate, and then 
 
 Fig. 118. 
 
 transferred to a piece of charcoal, 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 alcohol, to pre- 
 vent 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 through- 
 out with the blowpipe; after which the wax and teeth are re- 
 applied to the plate. 
 
 (Jondruetincj and Attaching Spiral Springs. — The success 
 which has been attained in the use of atmospheric pressure 
 plates has almost entirely superseded the necessity of employ- 
 ing spiral sj)rings as a means of support; nor should the latter 
 be resorted to except under circumstances that preclude the use 
 of the former. When api)licd, they should be attached to the 
 base on each side between the posterior bicusj)id and first molar 
 
272 MECHANICAL DENTISTEY. 
 
 below, and opposite the posterior bicuspid above. To the 
 border of the plate near the base of the teeth a narrow 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 con- 
 nected with the standard by a small wire on which the looped 
 extremity of the spring plays. To each end of the spring is 
 
 B 
 
 attached a gold wire, doubled iipon itself in such a way as to 
 form a loop, the closed ends being soldered together and filed 
 to enter the hollow in the wire. A, Fig. 119. B, Fig. 119, 
 copied from Professor Harris's work on dental surgery, repre- 
 sents another method of attaching springs, but the former is 
 more readily constructed and will answer every practical pur- 
 
 FlG. 120. 
 
 pose. Fig. 120, exhibits the application of springs to an upper 
 and lower denture. 
 
 Investing, Lining, Soldering and Finishing the Plate. — The 
 plate, with the wax and teeth in place, is next encased in a 
 mixture of plaster preparatory to lining the teeth and uniting 
 them with solder to the base. For this purpose, plaster and 
 
ENTIRE DENTURES. 273 
 
 sand may be employed, using as little of the former as will 
 serve to hold the investment together during the subsequent 
 manipulations. Asbestos may be added, and is a useful ingre- 
 dient. Burnt plaster, or that which has been previously used 
 for investing, may be substituted for the sand and asbestos, 
 adding a sufficient quantity of unused plaster to eifect consoli- 
 dation. Either of the combinations mentioned will suffer but 
 little change in the fire, if properly managed. It is customary 
 to incase the piece in the plaster mixture to the depth of from 
 one-half to three-fourths of an inch, leaving only the lingual 
 surfaces of the plate and teeth uncovered. However compara- 
 tively free from change of form the best combinations of plaster 
 may be, yet some slight contraction of the body of the invest- 
 ient doubtless ensues on the application of heat, and it is 
 probable that so large and resistant a mass must tend, in 
 some degree, to produce deformity of the plate in soldering ; 
 for, as the investient 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 
 plaster exceeds the expansive force of the metal ; and when 
 the peculiar form of the upper plate is considered we can read- 
 ily conceive how a slight contraction of the plaster of the thick- 
 ness 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 author's observations, be found, in an 
 upj)er plate, to exist on each side of the sloping walls of the 
 palate, em1>racing the posterior half or two-thirds of the plate 
 at these two points, — the change manifesting itself in an in- 
 ward displacement of the lateral walls of the plate midway 
 between the summit of the palatal arch and the most depending 
 ])ortion of the ridge. We would suggest in explanation of this 
 result that, as the ])liister contracts with sufficient force to carry 
 the j)late with it, the sides (^f 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 
 
 18 
 
274 MECHANICAL DENTISTRY. 
 
 the ridge is incased in and" embraced by the plaster, and as 
 the palatal portion is arched in form with its convexity pre- 
 senting 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 centre of the mass, their relation to 
 each other is also changed, and this changed relation must 
 necessarily eventuate 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 necessity, the sides of the plate 
 along the sloping walls of the palate, which from their form 
 are neither resistant nor self-sustaining under pressure, and 
 whose inward displacement is unopposed by any counter-force, 
 is projected in toward the centre of the palatal excavation in 
 proportion as the borders and central portions are approxi- 
 mated ot" converged in the direction of the centre of the piece. 
 The practical effect of this approximation of the lateral and 
 posterior borders, and internal displacement of the plate, is to 
 make the latter " bind " upon the outer and posterior borders 
 of the alveolar ridge, and to tlirow the central portion of the 
 plate from the roof of the mouth. To obviate, as far as prac- 
 ticable, any change in the form of the plate which may result 
 from the contraction of the plaster investient, various expedi- 
 ents have been suggested, but the following will sufficiently 
 counteract the influence of the plaster by permitting an unob- 
 structed 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 half an inch between it and 
 the teeth, the ends being united to each other back of the plate 
 by riveting or otherwise. Holes are then made in the band 
 at numerous points throughout 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 
 
ENTIRE DENTURES. 275 
 
 of the latter ; the palatal surface of the plate is also covered 
 with plaster and may be connected with the outer portion by 
 a very tliin 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 ap- 
 plied, 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 interruption. On cooling, the 
 entire mass will contract together and assume its original form, 
 unless warping is induced by other agencies acting indepen- 
 dently of the enveloping plaster, as excess or unequal distribu- 
 tion of solder, irregular heating, etc. 
 
 It is not, ordinarily, necessary to provide by any special ex- 
 l^edient 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 whilst lining and soldering them to the 
 base. 
 
 The plate being properly invested, all portions of the wax 
 attached to the inner surface of the teeth and plate should be 
 thoroughly removed with suitable instruments; after which 
 stays are to be adjusted to the teeth. In reference to the 
 method of forming and adjusting stays, little need be added to 
 what has already been' said when treating of partial dentures. 
 One method, not there specified, consists in first fitting to each 
 tooth separately, in the usual manner, a thin stay formed of plati- 
 num, which is temporarily fastened to the tooth by splitting and 
 spreafling apart the ends of the rivets with a small chisel-sha])ed 
 instrument. The teeth are then removed from the investicnt 
 and partially imbedded side by side in plaster, tlie i)latinum 
 strips remaining uncovered. The plaster and teeth may then 
 
276 MECHANICAL DENTISTEY. 
 
 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 
 stays and thoroughly fused with the blowpipe until they flow 
 perfectly in around the rivets, and uniformly over the surface 
 of the linings. 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 to the linings. 
 The backings are then trimmed smoothly and burnished, when 
 they may be placed back in the investient in their appropriate 
 places. The linings which support the teeth may be united to 
 each other laterally in sections or continuously. When the 
 teeth are joined to each other throughout, a very small quan- 
 tity of solder will be sufficient to support the teeth, provided 
 it is well diffused along the joints uniting them perfectly at all 
 points. 
 
 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, and need not, therefore, be re- 
 capitulated. 
 
 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 per- 
 formed, such instructions 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 absolute necessity of early and 
 prompt attention to any injuries inflicted upon the soft tissues 
 of the mouth by the substitutes, as much future 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, 
 
ENTIRE DENTURES. 277 
 
 when dividing food with the front teeth, to press the substance 
 back.ward 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 completely the substance seized. 
 In reference to the mastication of food, it has been sug-o-ested 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 
 substitute. 
 
278 MECHANICAL DENTISTRY. 
 
 CHAPTER XII. 
 
 Porcelain Teeth — Carved Block-Teeth. 
 
 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, un- 
 distinguishable from the latter when applied in obedience to the 
 aesthetic requirements of individual cases, is one of the marvels 
 of ceramic art. Nowhere, perhaps, have the conceptions of 
 genius been embodied in porcelain 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 ordinary 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 demanded of the general practitioner except in ex- 
 treme cases resulting either from accident or disease. Thus, 
 as aptly remarked by the late Professor Austen, " The depot 
 not only renders service by the superior excellence of the sur- 
 gical instruments and prosthetic materials which it supplies, 
 but it directly benefits the science and art of dentistry by re- 
 leasing the practitioner from manufacturing toil, and giving 
 time for the acquirement of increased knowledge and skill. 
 Thus, if the time heretofore given to block-making were de- 
 voted to the study of dental aesthetics, patients would have the 
 
PORCELAIN TEETH. 279 
 
 benefit of an artistic selection from a far larger variety of 
 porcelain dentures than could otherwise be possibly made." 
 
 As affording some curious as well as practical information 
 in regard 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 
 material, etc., are composed of two distinct portions, — the 
 body or base, and enamel. The chief mineral substances 
 which compose the body, are, silcx, felsjjar, and kaolin. The 
 enamel, both crown and gum, consists principally o^ felspar. 
 
 The various tints or shades of color are imparted to the 
 porcelain by certain metals in a state of minute division or 
 their oxides. The Jiiore general properties of the mineral in- 
 gredients will be first described. 
 
 Sile.r. — Silex, silica, or silicic acid, is a white powder, in- 
 odorous, and insipid. It forms the chief part of many familiar 
 mineral formations, as quartz, rock crystal, flint, agate, calce- 
 don, 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 manu- 
 facture of porcelain teeth. It is prepared for use by subject- 
 ing 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. 
 
 Felspar. — This mineral substance occurs crystallized in ob- 
 lique rhomboidal prisms, and is a constant ingredient of gran- 
 ite, trachyte, porphyry, and many of the volcanic rocks. The 
 felspathic mineral formations present either a pearly or vitreous 
 lustre, and vary in color, being red, green, gray, yellow, brown, 
 flesh-colored, pure white, milky, transparent, or translucent. 
 Felspar yields no water when calcined ; melts at the blowpipe 
 into a white enamel, and is unaflected by acids. It is composed, 
 
280 MECHANICAL, DENTISTRY. 
 
 according to Rose, of silica, 66.75; alumina, 17.50; potash, 
 12; lime, 1.25; oxide of iron, 0.75. It is found in various 
 localities throughout the United States, the purest and whitest 
 kinds being employed in the manufacture of mineral teeth. It 
 is prepared for use in the same manner as silex. 
 
 Felspar, from its ready fusibility, serves to agglutinate the 
 particles of the more refractory ingredients, silex and kaolin ; 
 and when diffused throughout the mass imparts to the porce- 
 lain a semi-translucent appearance. 
 
 Kaolin. — Kaolin, or decomposed felspar, is a fine white 
 variety of clay, and is composed chiefly of silica and alumina, 
 the latter being the characteristic ingredient of common clay. 
 It is found in various localities throughout the Eastern States, 
 and in parts of Asia and Europe. Kaolin is refractory or 
 fireproof, but is rendered more or less fusible by the contami- 
 nations of iron and lime with which it is usually combined. 
 The opaque and lifeless appearance 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 present 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, felspar. 
 
 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 oflP, and the remaining kaolin dried in 
 the sun. 
 
 Coloring Materials. — The following metals and oxides are 
 employed in coloring mineral teeth ; titanium, platina sponge 
 and oxide of gold being those chiefly used in producing the 
 more positive tints, and by combining which in varying pro- 
 portions, any desired shade of color may be obtained. 
 
PORCELAIN TEETH. 281 
 
 Metals and Oxides. Colors produced. 
 
 Grold in a state of minute division, . . Rose red. 
 Oxide of gold, .... 
 Platina sponge and filings, 
 Oxide of titanium. 
 Purple of Cassius, 
 Oxide of uranium. 
 Oxide of manganese, . 
 Oxide of cobalt, 
 
 Oxide of silver, .... 
 Oxide of zinc, .... 
 
 Bright rose red. 
 Grayish-blue. 
 Bright yellow. 
 Rose purple. 
 Greenish-yellow. 
 Purple. 
 Bright blue. 
 Lemon yellow. 
 Lemon yellow. 
 
 As the preparation of most of the above colors requires 
 great care, and a soraewliat intimate knowledge of chemistry, 
 and as the most delicate manipulations are necessary to secure 
 accurate and satisfactory results, it is better for the "mechanical 
 operator to procure the coloring ingredients already prepared 
 from some competent chemist, rather than attempt their pro- 
 duction himself. For a particular description of the various 
 modes of preparing them, the reader is referred to Piggot's 
 Dental Chemistry and Metallurgy, and other works treating 
 fully of the subject. 
 
 3Iamifaeiure of Porcelain Teeth. — The subjoined account of 
 the processes concerned in the manufacture of porcelain teeth 
 is descriptive of those at present employed in the manufactory 
 of the late S. S. White, and which, in the main, are doubtless 
 the same as those of other leading establishments. 
 
 The felspar is first calained by throwing it in large masses 
 into a furnace, and subjecting it to a red heat and then plung- 
 ing 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 Hint .stones, and when fine enough 
 is afterwards ground under water in a mill in which heavy 
 blfx;ks of French burr stone revolve upon a nether millstone 
 of the same material, until sufficiently pulverized, when it is 
 floated off and aHowed 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. 
 
282 MECHANICAT. DENTISTRY. 
 
 The kaolin, already of the desired consistence as found in 
 nature, 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 
 consistence for moulding. The degree of plasticity of the body 
 and enamel pastes differ with the methods of manufacture. 
 Formerly, the teeth, when moulded, were first exposed to a 
 heat just sufficient to produce partial baking of the body, and 
 this was called cruising or biscuiting, after which a thin paste 
 of enamel material was applied with a camePs-hair brush, and 
 the whole subjected to a second heat for complete and final 
 fusion. This preliminary process of biscuiting is essential in 
 carved block and continuous gum work, but in the S. S. White 
 factory, and probably others, this partial baking is dispensed 
 with, and the body and enamel pastes of the uniform consis- 
 tency of putty are introduced into the moulds in the first in- 
 stance, properly distributed, and final fusion effected by a single 
 exposure to heat. 
 
 The moulds 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 or teeth is carved out with great care 
 and precision, and must be anatomically correct and mechani- 
 cally perfect, while the matrix, is made about one-fifth larger 
 than the required size to compensate for shrinkage of the ma- 
 terials in baking. Holes are drilled in each half of the mould 
 to receive the platinum pins, and the exact closure of the two 
 pieces of the mould secured by guiding pins. 
 
 The moulds having been previously greased, and the plati- 
 num 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 posi- 
 
PORCELAIN TEETH. 283 
 
 tion. The body is then added, in quantity exceeding some- 
 what the capacity of the mould, when the sections of the 
 mould are closed upon each other and subjected to a pressure 
 sufficient to insure compactness of the inclosed mass. When 
 thoroughly dried by a shnv heat, to which the moulds are ex- 
 posed, 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 moulding to the trimmer's room, 
 where, after critical inspection, all defe(!tive ones are either 
 repaired or condemned, all excess of material filed 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 in- 
 telligent observer writes : 
 
 " Beyond this, no tool can follow them. Imperfections here- 
 tofore could be repaired, but in the future, beyond the fire, the 
 tooth is either perfect or a failure irremediable. The furnace 
 is an institution entitled to respect for its intensity. In its 
 centre is a muffle of fire-clay, entirely surrounded by the glow- 
 ing 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 done and finished. The dull 
 enamel has become as glass. The lustreless oxides have yielded 
 their color, and the tooth that went in friable and brittle has 
 come out adamant. But there is an intermediate skill, the ac- 
 quisition of which is one of the marvels of the mechanic arts. 
 A little too long in that heat and the teeth are ruined, and the 
 evils of 'underdone' are equally to be guarded against as in 
 the housekeeper's baking. It is a trained judgment, a skill of 
 eye and handling that enables the burner to lend success to the 
 
284 MECHANICAL DENTISTRY. 
 
 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 curious, charac- 
 teristic red wax cards, on which they go to the trade." 
 
 We cannot close this account of the composition and manu- 
 facture of porcelain teeth more appropriately than by quoting 
 from an excellent popular treatise, entitled The Teeth, by Dr. 
 J. W. White, the present accomplished editor of the Dental 
 Cosmos : 
 
 " If it is true of any pursuit, it is emphatically true of the 
 attempt to imitate natural dentures, that ' the beauty of the 
 result well repays the highest exercise of art.' The manufac- 
 turer should furnish teeth in accordance with nature's types, 
 and each tooth in a set should harmonize with the rest ; for though 
 each may be an exact representation of a natural tooth, the 
 general effect is spoiled unless they are, in all their distinguish- 
 ing features, of the same family or class of teeth. No two 
 teeth in a natural set are alike ; every one has its distinctive 
 contour, and besides possessing individuality, indicates the 
 character of the adjoining teeth. In an artificial set, unless 
 these distinctive differences and resemblances have been faith- 
 fully studied and copied, their artificial character is apparent. 
 
 " The observant dentist will take into the account complexion* 
 age, sex, height, the color of hair and eyes, and other charac- 
 teristics of the individual when selecting teeth to replace lost 
 ones ; and the manufacturer should be skilled in the observance 
 of the varied classes of dentures required. To inattention in 
 this direction on the part of the dentist, or to dictation on the 
 part of the patient, is to be charged the unseemly incongruities 
 constantly staring the observer in the face from mouths whose 
 lost organs have been replaced in disregard of this universal 
 law. 
 
 "No matter how anatomically correct, or how skilfully 
 adapted for speech and mastication, an artificial denture may 
 be, yet if it bear not the relation demanded by age, tempera- 
 ment, facial contour, etc., it cannot be otherwise than that its 
 artificiality will be apparent to every beholder. 
 
PORCELAIN TEETH. 285 
 
 "This law of correlation, harmony, running through nature, 
 attracts and enchants us by an infinite diversity of manifestations; 
 the failure to recognize its demands by art is correspondingly 
 abhorrent to our sensibilities. 
 
 "In the social gathering, a lady who appreciates the law of 
 harmony delights the eye by the taste displayed in her attire ; 
 another, though more elaborately and expensively adorned, yet 
 failing to harmonize the details of her costume, attracts atten- 
 tion only by the impression of incongruity. We hear fre- 
 quently from a lady who is selecting a bonnet, or from a gen- 
 tleman pnrehasing 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 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 association, to be fair, 
 or sandy, and if otherwise, a wig or a dye is instantly sug- 
 gested. 
 
 " 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, 
 ^his 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 ra^atron of fifty ; a l)runettc or a blonde, — these 
 and other varieties present as many diifering types, with teeth, 
 in size, shape, color, density, etc., corresponding. If, then, teeth 
 correlated 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 displeasing to the eye, whether the observer be 
 skilled in perf;ej)tion, or intuitively recognizes inharmony 
 without understanding the cause. 
 
286 MECHANICAL DENTISTRY. 
 
 "Artificial teeth should be natural as to shape, color, and 
 vital appearance ; there should be a nice blending of the colors 
 of the body and enamel, not an abrupt union of the two ; there 
 should be the precise amount of translucency, and the peculiar 
 texture of the surface, and these characteristics should be main- 
 tained by artificial light as well as by daylight ; for many teeth 
 which in daylight look reasonably well have a very artificial 
 appearance when exposed in the mouth to an artificial light. 
 They should also possess strength sufficient for the uses for 
 which they are designed. This strength should come from the 
 quality of their composition, the skilful distribution of bulk 
 to parts most requiring it, and the due form, position, and pro- 
 portion of the pins, rather than from any increase in bulk and 
 weight beyond that of the natural organs. Besides all this, 
 there must be taken into the account the varying forms of the 
 jaw or maxillary ridge, so that the dentist may be enabled to 
 select teeth which are adapted to each particular case, and 
 which can be made to articulate nicely with each other or with 
 the natural teeth, if there are any remaining in the mouth ; 
 otherwise his best efforts will not secure a good appearance, 
 comfort to the wearer, or usefulness in mastication. 
 
 "To meet all these requirements, the reader can easily per- 
 ceive, is no easy task, and cannot be accomplished without an 
 amount of care and attention to every detail which effectually 
 excludes artificial teeth from the list of cheap manufactures. 
 The difference in all the essential characteristics which they 
 should possess, appears when what are called cheap teeth are 
 compared with the best. First upon the skill of the manu- 
 facturer, and then upon the judgment of the dentist, depends 
 whether an artificial set of teeth shall be pleasing or disagree- 
 able to the observer; whether they shall disarm the suspicion 
 of artificiality, or proclaim it to every beholder. 
 
 " Those who desire the result of experience, skill, and culture 
 in manufacture and application, who seek the advantages of 
 artistic taste and faithful service, should ponder the signifi- 
 cance of the following remarks by one who, in his time, con- 
 tributed largely to the development of the art to which he was 
 devoted : 
 
CARVED BI.OCK-TEETH. 287 
 
 "'All works of taste must bear a price in proportion to the 
 skill, taste, time, expense, and risk attending their invention and 
 manufacture. Those things called dear are, when justly esti- 
 mated, the cheapest ; they are attended with much less profit 
 to the artist than those which everybody calls cheap. Beau- 
 tiful forms and compositions are not made by chance, nor can 
 they ever, in any material, be made at small expense. A com- 
 petition for cheapness, and not for excellence of workmanship, 
 is the most frequent and certain cause of the rapid decay and 
 entire destruction in arts and manufactures.' " 
 
 CARVED BLOCK-TEETH. 
 
 The fabrication of porcelain block-teeth constitutes a some- 
 what distinctive branch of practical dentistry, and from the 
 delicate nature of the manipulations and long experience neces- 
 sary to attain to any considerable degree of excellence in the 
 various processes connected with their manufacture, their con- 
 struction is seldom attempted by those engaged in general 
 practice. Cases occasionally present themselves, however, 
 which, bv reason of unusual or unequal absorption, or exten- 
 sive and irregular loss of tissue as the result of accident or 
 disease, demand, for their successful treatment, specific forms 
 of dental substitutes not obtainable from any collection of 
 ready-made teeth, single or in sections, however large or varied. 
 To meet properly such possible exigencies of practice, either 
 the services of an experienced block-workman must be ob- 
 tained, or the demands of the case must be supplied by such 
 skill as the general practitioner can bring to the work. To 
 the latter, the following descriptions of the process may prove 
 helpful. 
 
 A descri[)tion of the general properties of the several in- 
 gredients, earthy and metallic, used in the formation of block- 
 teeth, has already been given in the preceding part of the 
 present chapter. The method of compounding and preparing 
 the materials will next be given, with various approved recipes 
 for body and enamel. 
 
 CornponUion and Preparation of the Body. — The porcelain 
 
288 MECHANICAL DENTISTEY. 
 
 paste for the body of block-teeth may be compounded from 
 either of the following formulas. There are a great variety 
 of recipes, differing more or less in the proportion of the com- 
 ponent ingredients, but the following will be found to answer 
 every practical purpose, and are such as are generally employai' 
 at this time by experienced block-workmen. 
 
 NO. I. 
 
 
 NO. 
 
 III. 
 
 Delaware spar, 
 
 12 oz. 
 
 Spar, 
 
 . 12 oz. 
 
 Silex, 
 
 2 oz. 8 dwts. 
 
 Silex, 
 
 . 2 oz. 8 dwts. 
 
 Kaolin, 
 
 11 dwts. 
 
 Kaolin, 
 
 . 12 dwts. 
 
 Titanium, . 
 
 18 to 36 grs. 
 
 Titanium, . 
 
 . 24 grs. 
 
 NO. II. 
 
 
 NO, 
 
 . IV. 
 
 Delaware spar, 
 
 16 oz. 
 
 Spar, 
 
 . 8oz. 
 
 Silex, 
 
 3Joz. 
 
 Silex, 
 
 . I5 oz. 
 
 Kaolin, 
 
 J oz. 
 
 Kaolin, 
 
 . 4 dwts. 
 
 Titanium, . 
 
 20 to 60 grs. 
 
 Titanium, . 
 
 . 22 grs. 
 
 
 NO. 
 
 V. 
 
 
 
 Spar, 
 
 . 2oz, 
 
 
 
 Silex, 
 
 . 8 dwts. 
 
 
 
 Kaolin, . 
 
 . 2 dwts. 
 
 
 
 Titanium, 
 
 . 4 grs. 
 
 
 The titanium is first ground in a mortar until reduced to an 
 impalpable powder ; the silex is then added and ground from 
 one to three hours, or until there is no perceptible grit ; after 
 which the kaolin is added and thoroughly ground ; and lastly 
 the spar, adding small portions at a time, and grinding the 
 whole until perfect comminution and intermixture of the 
 several ingredients are effected, say from half an hour to an 
 hour. The ingredients may be ground dry or in water, — in 
 the latter case a sufficient quantity of clean rain-water should 
 be added, from time to time, to form a mixture of about the 
 consistence of thick cream. After sufficient comminution is 
 effected, the surplus water may be abstracted by pouring the 
 mixture upon a clean, dry slab of plaster of Paris. When it 
 acquires about the consistence of thick dough, it should be 
 beaten with a wooden mallet, or thrown repeatedly and forcibly 
 upon a marble slab, and, if prepared in quantities for future 
 use, it should be preserved in its plastic state by confining it 
 
CARVED BLOCK-TEETH. 289 
 
 in a closely-stopped earthen jar. When ground dry, the 
 materials are prepared for immediate use by adding to the 
 powder clean rain-water in sufficient quantity to form a thick 
 paste ; it is then well beaten on a porcelain or marble slab, 
 and pressed, just before using, between folds of cloth, to expel 
 perfectly all particles of air that may be confined in the body 
 of the paste. 
 
 Composition and Preparation of Crown Enamels. — The 
 enamel, which forms the external covering to the crowns of 
 porcelain teeth, is composed wholly of felspar, with such color- 
 ing matters as serve to communicate to it the various tints or 
 shades of complexion characteristic of the natural organs. The 
 more positive tints, grayish-blue and yellow, are produced by 
 titanium, platinum sponge, and oxide of gold; intermediate 
 colors being produced by varying the special combinations of 
 these ingredients. 
 
 The following recipes will furnish various tinted enamels, 
 the varieties of grayish-blue being applied to the points or 
 coronal extremities of the teeth — the yellow to the necks: the 
 two colors being so blended when applied as to run imper- 
 ceptibly into each other. 
 
 Grayish-blue Enamel. 
 
 NO. I. 
 
 
 NO. III. 
 
 
 Spar* 
 
 . 2 oz. 
 
 Spar, . 
 
 . 2oz. 
 
 Platina sponge, . 
 
 • ig'-- 
 
 Platina sponge, . 
 
 • f gr. 
 
 Oxide of gold, . 
 
 • \ gr- 
 
 Oxide of gold, . 
 
 . ^gr. 
 
 NO. II. 
 
 
 NO. IV. 
 
 
 Spar, . 
 
 . 2oz. 
 
 Spar, . 
 
 . 2 oz. 
 
 Platina sponge, . 
 
 . ^gr. 
 
 Fli]x,t 
 
 . 24 gr. 
 
 Oxide of gold, 
 
 • I gr- 
 
 Platina sponge, . 
 
 • i gr- 
 
 * The Boston spar is preferred on account of its greater fusibility. 
 
 t Flux is composed of silex, 4 oz. ; borax, 1 oz. ; sal tartar, 1 oz. ; these 
 are ground to an impalpable powder and packed in the bottom of a clean, 
 light-colored crucible. A piece of fire-clay slab is then fitted into the top 
 of the crucible and luted with kaolin clay. It is then exposed to the heat 
 of a furnace until con)pletely fused, when it is removed, and when cold the 
 crucible is broken, all foreign particles or discolored portions thoroughly 
 removed, and the remainder well pulverized. 
 
 19 
 
290 
 
 MECHANICAL DENTISTRY. 
 
 
 Yellow L 
 
 Enamel. 
 
 
 NO. I. 
 
 
 NO. III. 
 
 
 Spar, . 
 
 2 oz. 
 
 Spar, . 
 
 . 2 oz. 
 
 Titanium, 
 
 . 10 grs. 
 
 Titanium, 
 
 , 16 grs 
 
 Platina sponge, 
 
 *gr. 
 
 Platina sponge, 
 
 • igr- 
 
 Oxide of gold. 
 
 . ^gr. 
 
 Oxide of gold, 
 
 • i gr- 
 
 NO. II. 
 
 
 NO. IV. 
 
 
 Spar, . 
 
 . 2oz. 
 
 Spar, 
 
 . 2 oz. 
 
 Titanium, 
 
 . 14 grs. 
 
 Flux, . 
 
 . 20 grs 
 
 Platina sponge, . 
 
 . 2gr. 
 
 Titanium, 
 
 . 10 grs 
 
 Oxide of gold, 
 
 . Jgr. 
 
 
 
 In compounding enamels from the foregoing recipes, the 
 coloring ingredients should first be ground to a very fine 
 powder, with five or six dwts. of the spar; the remaining 
 portions of the latter should then be added, a little at a time, 
 and ground for half an hour or more. The shades of color 
 may be varied almost indefinitely by changing the propor- 
 tions of the coloring matter. 
 
 Grayish-Blue Enamel. 
 
 NO. I. 
 
 
 NO. II. 
 
 
 Spar, 
 
 . 1 oz. 
 
 Spar, 
 
 . 1 oz. 
 
 Blue frit,* . 
 
 . 5 grs. 
 
 Yellow frit, f 
 
 . 4 grs 
 
 
 
 Gold mixture,! 
 
 . 20 grs 
 
 Composition and Preparation of Gum Enam,els. — Either of 
 the following recipes will furnish a good gum enamel, and 
 may be used in connection with any of the compositions for 
 body heretofore enumerated. 
 
 NO. I. 
 
 Gum frit, No. 1, . 
 Spar, . 
 
 NO. II. 
 3 dwts. Gum frit, No. 2, . 3 dwts. 
 
 9 to 12 dwts. Spar,. . . 3 to 18 dwts. 
 
 * Blue frit is composed of spar, 5^ oz. ; platina sponge, 4 dwts. ; powder 
 finely, make up into a ball with water, and fuse very slightly upon a slide 
 in a furnace. It is then plunged into water while hot, and when dry, finely 
 pulverized. 
 
 f Yellow frit is made by mixing intimately J oz. of spar with two dwts. of 
 titanium, and heating as above. 
 
 X Gold mixture is prepared by dissolving 8 grs. of pure gold in aqua regia, 
 and then stirring in 12^ dwts. of very finely pulverized spar. When nearly 
 dry, it is formed into a ball fused upon a slide, and then coarsely pulverized. 
 
CARVED BLOCK-TEETH. 291 
 
 It IS recommended, in order to impart a granular appear- 
 ance to the gum, to grind the spar somewhat coarsely; any 
 required shade or depth of gum color being obtained by vary- 
 ing the proportions of the frit, — the latter containing the color- 
 ing; ino;redients. 
 
 Gum frit, No. 1, is composed of felspar, 700 grs. ; flux, 175 
 grs. ; oxide of gold, or metallic gold in a state of minute divi- 
 sion, 16 grs. 
 
 The above are ground in a mortar for five or eight hours, 
 or until they are reduced to an impalpable powder; they are 
 then packed in the bottom of a clean Hessian crucible, coated 
 on the inside with a thin mixture of pulverized silex, and on 
 the outside with kaolin. A piece of tile or slab is then luted 
 with kaolin to the top of the crucible, when it is placed in the 
 furnace for from one to two hours, or until complete vitrifi- 
 cation is effected. It is then removed, and when cold, the crn- 
 cible is broken and all traces of adhering silex ground off; it 
 is then broken in pieces and ground until it will pass through 
 a sieve, No. 9, bolting cloth. 
 
 Gum frit, No. 2, is composed of spar, 700 grs. ; flux, 175 
 grs. ; purple cassius, 8 grs. 
 
 The purple cassius is first thoroughly ground in a mortar, 
 after which the flux is added in small quantities at a time, 
 then the spar in the same manner, grinding until perfect com- 
 minution and intermixture of the several ingredients are 
 effected. It is then packed tightly in the bottom of a clean 
 white crucible, the inside lined with silex, and a slab luted to 
 the top, as before, and the whole exposed to a heat suflicient to 
 fuse perfectly. It is then removed from the fire, and when 
 cold, all foreign substances are ground off" and the remaining 
 portions pulverized until it will pass through a sieve of No. 9 
 bolting cloth. 
 
 Having given the composition and mode of preparation of 
 tlie various compounds which enter into the formation of the 
 body and crown and gum enamels, it only remains to describe 
 the different processes, concerned in the construction of porce- 
 
292 MECHANICAL DENTISTRY. 
 
 lain blocks from the several compositions given, and first of 
 the method of procuring an antagonizing model. 
 
 Antagonizing Model for an Entire Upper and Lower Den- 
 ture Constructed of Block-teeth. — The first step in the process 
 of constructing block-teeth, for either a full upper set with the 
 natural teeth of the opposite jaw remaining, or for entire den- 
 tures for both jaws, is to secure an antagonizing model." For 
 the latter, or complete dentures, above and below, the method 
 does not differ from that employed when single gum teeth are 
 used. A rim of wax is adjusted to each plate in the manner 
 heretofore described, and the plates placed in their proper posi- 
 tions in the mouth ; the wax drafts are then trimmed until the 
 exact fulness and contour of the lips and cheeks are secured and 
 proper relative width is given to the wax rims. Great exactness 
 should be observed in these latter manipulations, inasmuch as 
 the wax drafts are the only guides in the formation of the blocks, 
 both as respects the form and fulness of the arch and the 
 length of the teeth. The proper relation of the two pieces in 
 the mouth is now secured, the wax rims attached to each other, 
 and the median line of the mouth indicated on the wax, and 
 being removed from the mouth, an antagonizing model pro- 
 cured in the same manner as described in a former chapter. 
 
 Antagonizing Model for an Entire Upper Denture with the 
 Natural Teeth of the Opposing Jaw Remaining. — A rim of wax, 
 half an inch or more in width, is attached to the ridge of the 
 plate and the latter placed in the mouth. The patient is then 
 directed to close the jaws until the cutting edges and grinding 
 surfaces of the teeth of the opposing jaw are fairly imbedded 
 in the wax. The piece is then removed from the mouth and 
 the wax rim detached from the plate by holding the latter for 
 a moment over a spirit-flame. The wax is then placed upon 
 a strip of paper with the side indented by the teeth looking 
 upward, the surface of the wax oiled and a batter of plaster 
 poured upon it, filling the imprints of the teeth and running 
 back an inch and a half or more behind the wax, raising 
 the plaster to a level of half an inch above the wax. When 
 the plaster is sufficiently condensed, it is turned over, the wax 
 
CARVED BLOCK-TEETH. 
 
 293 
 
 removed without fracturing the plaster teeth, and a crucial 
 groove made in the surface of the model posterior to the teeth. 
 This constitutes the lower section of the antagonizing model, 
 and is a representation of the teeth of the lower jaw. The 
 upper section is next obtained in the following manner : A 
 second rim of wax, in width equal to the required length of 
 the teeth, is adjusted to the plate as before and placed in the 
 mouth. The exact contour and fulness of the arch required 
 is then given to the external or labial surface of the wax draft, 
 and the lower edge cut away until the required approximation 
 
 of the jaws is secured, and the points of all the teeth remaining 
 below touch the wax at the same instant. The patient is now 
 required to close the jaws gently upon each other until a slight 
 indentation is made in the Avax by the opposing teeth ; the 
 median line of the mouth is then marked upon the wax and 
 the plate removed. The plate and wax are now adjusted to 
 the lower section of the model, the points of the plaster teeth 
 being received into the indentations in the wax made by the 
 natural teeth. The upper and posterior surface of the lower 
 section of the model having been varnished and oiled, and the 
 
294 
 
 MECHANICAL, DENTISTRY. 
 
 exposed surface of the plate also oiled, a mixture of plaster is 
 poured in upon the latter and back upon the model, raising 
 the whole to a level of half an inch above the plate. The two 
 sections, when the latter portion of plaster has consolidated, 
 are then separated, reserving the lower part of the antagonizing 
 model for future use. 
 
 Forming a Matrix for Moulding the Body Preparatory to 
 Carving the Teeth. — As the process of forming a matrix in 
 which to mould the porcelain paste, giving the general form and 
 
 Fig. 122. 
 
 outlines to the blocks before carving the teeth, is the same 
 for an upper and lower denture, it will be sufficient to describe 
 the method as it relates to the superior arch. A matrix for 
 an entire denture above or below, whether consisting of three, 
 four, or six blocks, is ordinarily made to consist of three dis- 
 tinct pieces independently of the plate and model, and is con- 
 structed in the following manner : Three conical shaped holes 
 are made in the sides of the model, one in front and one on 
 each side, to furnish a fixed articulation for the three sections 
 
CARVED BLOCK-TEETH. 
 
 295 
 
 forming the external walls of the matrix. The appearance of 
 the model when thus prepared with the plate and wax run m 
 place is exhibited in Fig. 121. The sides of the model and 
 external face of the wax are now oiled, and both surfaces 
 covered with a batter of plaster to the depth of a fourth or a 
 half of an inch, extending from the base of the model to the 
 lower edge of the wax, and posteriorly about half way on each 
 side of the model to form a matrix for the front block, "or the 
 
 two anterior bl(»cks, if the arch is made to consist of more than 
 three sections. Supposing the wax removed from the plate 
 and this front piece in place, the several parts will j)resent the 
 apiiearance shown in Fig. 122. The plaster rim forming the 
 external wall of the front block being removed, plaster is again 
 adde^l, as before, to the outer surfaces of the model and wax, 
 extending it from the heel of the idate on each side forward an 
 eighth or a fourth of an inch in advance of the posterior ex- 
 tremities of the plaster rim first formed. Wiicn hard the 
 plaster is trimmed even with the edge of the wax draft, and 
 the two pieces removed from the model. The matrices ibrmed 
 
296 MECHANICAL DENTISTEY. 
 
 by these lateral sections when readjusted to the model with the 
 wax removed are shown in Fig. 123. Having thus provided 
 a matrix determining the general outline and length of the 
 teeth for the entire arch, the wax draft is removed and the 
 plate thoroughly cleansed preparatory to moulding the paste, — 
 before doing which, however, the line upon the wax indicating 
 the median point of the mouth should be extended across the 
 model' 
 
 Moulding the Porcelain Paste Preparatory to Carving the 
 Teeth. — In the process of constructing an entire denture, it is 
 impracticable, owing to the shrinkage of the body, to form a 
 single continuous block or full arch without materially chang- 
 ing its relation and adaptation to the metallic base, and also to 
 the natural organs in cases where the latter are remaining in 
 the opposite jaw ; hence it is customary, as before intimated, 
 to divide the arch into sections, — usually three; a central front 
 block embracing the incisors and cuspidati, and two lateral 
 blocks including the bicuspids and molars on each side ; or the 
 denture may consist of four blocks, dividing the arch between the 
 central incisors, and also between the first and second bicuspids 
 on each side ; making the two anterior blocks to consist each of a 
 central and lateral incisor, a cuspidatus, and anterior bicuspid, 
 and the posterior blocks of the second bicuspid and the two 
 molars. Again, the arch is sometimes divided into six blocks, 
 — an anterior embracing the central and lateral incisor and 
 cuspidatus, a central comprising the bicuspids, and a p6sterior 
 including the molars. If constructed in three sections, as is 
 ordinarily the case, the front block should be moulded and 
 carved first. The material for the body, if in a dry state, is 
 mixed with a sufficient quantity of clean rain-water to form a 
 thick batter, and mixed thoroughly in a mortar. It should 
 then be poured upon a dry slab of plaster of Paris, and when the 
 excess of water is absorbed, removed, and well beaten with a 
 spatula on a marble or porcelain slab until it assumes a some- 
 w^hat pasty form ; it may then be well pressed between folds of 
 cloth to force out any remaining portions of confined air. The 
 plaster rim forming the matrix for the front block is now ad- 
 
CARVED BLOCK-TEETH, 297 
 
 justed in its proper position to the model, and its inner surface, 
 as well as that of the plate, oiled; the porcelain paste is then 
 packed into the matrix as compactly as possible, filling it even 
 with the upper edge of the plaster rim. When the paste has 
 been worked in as solidly as possible, patting it with the fin- 
 gers or suitably formed instruments as successive portions are 
 added, it should be trimmed even with the edge of the plaster 
 rim and the palatal surface cut away to near the thickness re- 
 quired for the teeth included in the block, leaving it somewhat 
 thicker, however, to compensate for the shrinkage of the body, 
 and to allow for small portions which will be cut away in 
 carving the teeth. The plaster rim forming the external bor- 
 der of the matrix is now loosened by tapping gently upon the 
 model and then carefully removed. The mark upon the 
 model, showing the mesial line of the mouth and indicating 
 the proper position of the central incisors, is then extended 
 across the block, after which the width of each adjoining tooth 
 is lined off, making each one as much broader than will be re- 
 quired in the finished piece as the porcelain composition will 
 shrink in baking, — this, in a block embracing the six anterior 
 teeth, will be equivalent to about one-third or one-half the 
 width of a bicuspid on each side. If the case is one requiring 
 a full denture above and below, the operator should next pro- 
 ceed to mould the front block for the lower arch in the same 
 manner as described for the upper. The two sections of the 
 antagonizing model are then placed together, and the proper 
 relative width for the lower teeth indicated upon the inferior 
 block, — the drawn lines upon the upper block serving as a 
 guide. Tlie points to which the posterior extremities of the 
 front block extend on each side of the ))late should be marked 
 upon corresponding points of the model above and below, to 
 enable the manipulator to determine how far the side blocks 
 should be extended anteriorly when moulding the paste for the 
 latter, — the marks upon the model being subsequently trans- 
 ferred to the lower edges of the lateral sections of plaster con- 
 cerned in the formation of the side matrices. Before njmoving 
 the front blocks from the plates preparatory to carving the 
 
298 MECHANICAL DENTISTRY, 
 
 teeth, the surface of the paste may be dried somewhat by 
 throwing upon it, with a blowpipe, a broad spreading flame 
 from a spirit-lamp. The blocks are then carefully detached 
 by rapping lightly upon the model, assisted by gentle traction 
 with the fingers. The front blocks being removed from the 
 upper and lower plates, the side sections of plaster concerned 
 in the formation of the posterior matrices are adjusted to the 
 model, and, being oiled, the paste filled in as before described, 
 extending each block forward beyond the point occupied by 
 the cuspidatus of the front block a distance equal to about one- 
 third or one-half of the width of the latter. These are then 
 cut away even with the edges of the plaster rims and trimmed 
 on the palatal sides, leaving them somewhat thicker than will 
 be required for the bicuspids and molars. The plaster walls 
 of the matrices are then removed ; the two parts of the articu- 
 lating model placed together, and the relative width and posi- 
 tion assigned to the upper and lower teeth by drawing lines 
 across the external surface of the blocks. They are then sepa- 
 rately removed from the plates in the manner before described, 
 and the necessary additional portions of paste added to the 
 grinding surfaces to compensate for the contraction of the body 
 in baking. In constructing a full upper denture with all or a 
 portion of the natural organs remaining below, the proper 
 width to be given to the upper teeth, as well, also, as the re- 
 quired relation or antagonism of the artificial with the oppos- 
 ing natural teeth, may be readily determined by applying the 
 lower portions of the antagonizing model representing the 
 teeth of the under jaw, and marking upon each block, as it is 
 being moulded, the necessary width and position of each tooth 
 above, — being careful to make allowance for shrinkage by 
 adding to the length, width and thickness of each block as 
 much as will compensate for the contraction of the body. In 
 every other particular, the process is conducted in the same 
 manner as heretofore described. 
 
 Carving the Teeth. — The teeth are first separated by drawing 
 between them a thread attached to a small bow, and it may be 
 observed in this connection that the most careful and delicate 
 
CARVED BLOCK-TEETH. 299 
 
 manipulation is required in handling the blocks while carving 
 to prevent portions of the paste from crumbling away, a ten- 
 dency that may be counteracted, in some measure, by moisten- 
 ing the paste occasionally with a little water taken up on the 
 point of the carving knife. The general outline of each tooth 
 having been traced upon the exterior surface of the block with 
 the point of the instrument, the operator proceeds next to give 
 the distinct and characteristic form to the crowns, and the har- 
 monious and agreeable effects produced will depend upon the 
 fidelity with which the manipulator copies nature in the form 
 and arrangement of the teeth. The requirements of individual 
 cases are too varied in their nature to admit of specific direc- 
 tions in respect to their formation, — a careful study of the 
 modified forms of the natural organs, combined with some de- 
 gree of manipulative tact, will enable any one, after sufficient 
 experience, to attain to satisfactory results in this particular. 
 
 After the teeth are I'ormcd, and the body of the block is re- 
 duced to the required thickness, superfluous portions extending 
 from the ends of the block should be cut away, leaving enough, 
 however, projecting to allow for grinding when jointing and 
 adjusting the several blocks to the metallic base. Fig. 124 
 exhibits the general form of the blocks when carved, showing 
 also the platinum pins, but which are not usually attached to 
 the blocks until after the latter are first biscuited. 
 
 Q-uoinfj, or Bbieaitiny — The blocks being carved, are next 
 placed on a fire-clay slab with their palatal surfaces resting on 
 a bed of silex. As soon as the paste has become thoroughly 
 dry, the slab may be gradually introduced into the muffle of a 
 baking furnace (Fig. 15), and exposed to a full red heat until 
 semi-fusion of the body takes place. This partial vitrification 
 of the body serves to agglutinate the particles of the compound, 
 
300 MECHANICAL DENTISTRY. 
 
 and is termed Gruoing or biscuiting. When removed from the 
 furnace, and cool, the platina pins should be introduced into 
 the blocks before applying the gum and crown enamels, and 
 is accomplished in the following manner. One or two small 
 holes, as the case may require, are drilled into the body of the 
 blorik immediately behind and below the crown of each tooth, 
 extending about half way through the block ; into these, plati- 
 num pins or wires are introduced, a head being formed to the 
 end of the pin entering the block. A small portion of the 
 body composition, mixed with water to the consistence of thin 
 cream, is then worked into the hole around the pin with a 
 sharp-pointed carving knife or camel's-hair brush, its intro- 
 duction being facilitated by first immersing the block in water 
 immediately before inserting the ]>ins. 
 
 AppliGation of the Crown and Gum Enamels. — The gum 
 enamel is applied first, the material being first prepared by 
 mixing the gum composition with sufficient clean rain-water 
 to form a batter of about the consistence of thin cream. This 
 is then taken up with a camel's-hair brush and applied uni- 
 formly to all parts of the external surface of the block repre- 
 senting the natural gum. It should be applied very carefully 
 to the necks of the teeth, forming a neat and well-defined fes- 
 toon at these points. In applying the crown enamel to the 
 labial surfaces of the teeth, it is customary, in imitation of the 
 natural organs, to so distribute the more positive tints as to 
 give to that portion of the crown representing the neck of the 
 tooth a somewhat yellowish hue, and to the points, a grayish-blue 
 tint. To effect this, the material for the yellow enamel, re- 
 duced to the consistence before mentioned, is first applied to 
 the necks, uniting it carefully with the gum enamel ; and after- 
 wards the grayish-blue to the points, extending it a little be- 
 low the cutting edges of the incisors, and the cusps of the 
 cuspidati, bicuspids, and molars, giving to the teeth, at these 
 points, a translucent appearance. It is only the external and 
 lateral surfaces of the teeth that are enamelled, the palatal 
 surfaces remaining unglazed. The yellow and blue enamels 
 
CARVED BLOCK-TEETH. 301 
 
 should be so blended when applying them to the crowns that 
 the one shall fade away imperceptibly into the other. 
 
 Final Baking. — The enamelling completed, the blocks are 
 placed upon a bed of silex on a slide, and the latter carefully 
 and slowly introduced into the mouth of the furnace. The 
 fire should then be urged to a clear white heat, and when per- 
 fectly dry, the blocks should be carried with the slide into 
 the body of the muffle, and the mouth of the latter closed 
 tightly with a fire-clay plug. Some knowledge of the requi- 
 site degree of heat and time necessary to effect perfect fusion 
 of the ingredients composing the blocks is required, and these 
 are ordinarily well known to experienced block-workmen, but 
 those unaccustomed to the process will better determine the 
 completion of the baking by introducing into the muffle along 
 with the blocks a small portion of the body covered with 
 enamel attached to one end of a platinum wire, the other pass- 
 ing through a small stopper fitted to the centre of the plug 
 closing the end of the muffle, and which may be removed and 
 the wire withdrawn from time to time to observe the effect of 
 the heat upon the test-piece. When this is seen to be per- 
 fectly fused, as evidenced by a uniform glossiness of the sur- 
 face, the slab should be drawn to the mouth of the muffle, the 
 draft cut off, and the blocks allowed to cool gradually with the 
 furnace. In place of using a test-piece, however, it will an- 
 swer the purpose to withdraw the slide to the mouth of the 
 muffle occasionally, where it may be readily inspected and the 
 progress of baking noted. When sufficiently cool to be taken 
 in the hand, the blocks are removed from the furnace. 
 
 Fitting and Attaching the Blocks to the Metallic Base. — On 
 applying the blocks to the plate, it will be found that a greater 
 or less change of relation between the two has occurred in the 
 process of baking, so that the base of the former will not fit 
 the portion of the plate on which they rest as accurately as when 
 first moulded. It will, therefore, be necessary, when adjusting 
 each block, to grind away somewhat from the base of the latter 
 until the coaptation of the two surfaces is as perfect as practi- 
 cable. The «('V(;rul blocks should also at the same time be 
 
302 MECHANICAL DENTISTRY. 
 
 accurately united to each other laterally, grinding away from 
 the ends, and approximating the sections as the articulation of 
 the opposing dentures may require to eifect a proper and efficient 
 antagonism, and which may be determined by the use of the 
 antagonizing model employed in moulding the blocks. After 
 the blocks are fitted, and the teeth antagonized, and before unit- 
 ing the former permanently to the plate, a rim should be formed 
 and attached to the borders of the metallic base to form a socket 
 for the plate extremities of the blocks, and which, extending 
 around the margins of the plate, should be continued across the 
 heel of the latter on each side and made continuous with the 
 band of lining on the palatal sides of the teeth. The manner 
 of forming and attaching the rim does not differ from the method 
 heretofore described in connection with full dentures constructed 
 of single gum teeth, and to which the reader is referred. The 
 rim fitted, and the blocks replaced, the whole is invested in the 
 usual way, the wax removed from the plate, and a continuous 
 band or lining adjusted to each block. The latter is accom- 
 plished by first cutting a pattern of the band from sheet lead 
 of the length of the block, and of the required width, trimming 
 the edge applied to the plate in such a manner that when ad- 
 justed to the backs of the teeth it will lie in uniform contact 
 with the base; this is then pressed against the pins with suffi- 
 cient force to perforate it. The lead pattern is then placed upon 
 a strip of gold of the required thickness, and the counterpart 
 of the pattern cut from the gold plate, marking at the same 
 time the points to be perforated for the platinum rivets. This 
 is then pierced with a plate-punch, and the strip bent to the 
 proper curve and applied to the block, when it is bound to the 
 latter by splitting and spreading apart the ends of the rivets. 
 A band is thus applied to each block. Solder is then applied 
 along the joints, and over the pins, and all parts united with 
 the blowpipe in the usual manner. The piece is then finished 
 up the same as ordinary gold Avork. Fig. 125, exhibits a 
 palatal view of an upper set of block- teeth mounted on a metallic 
 base. When skilfully executed, the finished work presents a 
 beautiful and highly artistic appearance. The application of 
 
CARVED BLOCK-TEETH. 
 
 303 
 
 sectional porcelain blocks to the necessities of mechanical prac- 
 tice has been greatly extended in connection with the vulcan- 
 ite and celluloid bases, and, to a limited extent, with other 
 processes. Their construction, however, is modified some- 
 what by the requirements of these special processes, and as 
 made for the latter are of such approved manufacture, and 
 are supplied in such abundance and at so reasonable a cost 
 by all the principal dental furnishing establishments, that 
 the general practitioner, we apprehend, will ordinarily find it 
 more convenient and economical to purchase rather than manu- 
 facture them himself. 
 
 Fig. 125. 
 
 The subjoined account, descriptive of a new method of making 
 block-teeth, by Dr. William Calvert, Avas inadvertently omitted 
 in the former edition of this work. The process has received 
 marked commendation by competent persons who have investi- 
 gated its merits, and will be highly esteemed by those who 
 desire to excel in this beautiful but difficult art. 
 
 " The first pre})aratory step to be taken, after having correct 
 articulating models, is to select single teeth so defined as may 
 eithersuit the taste of the operator or the peculiarity of the case, 
 and supposing the case to be an upper denture, it will be neces- 
 sary to have hvo front and two lateral incisors, two canine or 
 cuspids, two bicuspids (or if more convenient the cuspids), and 
 four molars, all of which should be sufficiently large to com- 
 pensate for shrinkage, in the material of which the teeth are to 
 be corn[)Osed. 
 
 " The plate upon which the blocks arc to be made, and to 
 
304 MECHANICAL DENTISTRY. 
 
 which they are to be subsequently fitted, being upon its cor- 
 responding model, a rim of wax may be placed upon it, and 
 the teeth arranged upon the wax, articulating with the antago- 
 nizing model, allowing sufficient in the length of the teeth for 
 shrinkage. Beginning with the front incisors, the teeth should 
 be set to the wax (as above) as far back on each side as the 
 first bicuspids, inclusive; then leaving a space equal to the 
 width of half a tooth, the arch may be completed by the addi- 
 tion of the molars, two on each side. The teeth having been 
 thus arranged upon the wax, with reference to regularity or 
 irregularity, height, etc., the desired outline of gum may be 
 filled up with wax. 
 
 " Special care is requisite in so trimming the wax where 
 joints are contemplated, that no subsequent alteration will be 
 needed during the further manipulations. 
 
 " It will be necessary, previous to making the moulds, to 
 make some provision for replacing them, after they have been 
 once removed, so that they shall occupy the same position as 
 they did previous to their first removal. For this, it will be 
 only necessary to make some conical holes in the face of the 
 cast, say two on each side, between the centre and the first bi- 
 cuspid teeth, and two opposite the molar teeth of each side. 
 These holes need not be more than about a quarter of an inch 
 deep, and should be but a short distance below the edge or 
 line of the plate. The face of the cast, including said holes, 
 should now be varnished, when the case is ready for making 
 the moulds. 
 
 " The first mould to be made should be that including the 
 four incisors, two canine, and two first bicuspids, eight teeth 
 in all. This may be done by simply oiling the face of the 
 teeth, outline of gum, and plaster cast, and pouring plaster of 
 Paris of a proper consistency over the surface of the same, 
 allowing it to fall slightly over the cutting edges, so as to form 
 a more perfect mould. This mould should be divided in the 
 centre, making two sections, which can be done by cutting 
 through the plaster while in the state of hardening ; or, what 
 is perhaps better, before applying the plaster, make an incision 
 
CAEVED BLOCK-TEETH. 305 
 
 in the wax outline of gum, in which place a thin slip of sheet 
 lead, letting it extend a little above the cutting edges of the 
 teeth, and as far down the face of the cast as is desired to ex- 
 tend the mould. When hard, remove from the cast and teeth, 
 and we have the untrimmed mould for said eight teeth. Pre- 
 vious to making the moulds for the back teeth, it is necessary 
 to remove the first bicuspids, or the cuspids representing them, 
 from the position they occupied in making the mould just de- 
 scribed, and placing them beside the first molars so as to 
 represent the second bicuspids. Care is to be taken in re- 
 moving and replacing them, so that the original form of the 
 wax may be preserved, otherwise the end thereby intended to 
 be secured will be defeated, and the joints at these points will 
 be irregular and unsightly. 
 
 " For the purpose of rendering clear a point necessarily left 
 somewhat obscure in the foregoing description, it may be well 
 here to state that the space of half a tooth, left between the 
 first bicuspids and the first molars, is to compensate for shrink- 
 age in the length of the arch, for after the first bicuspids are 
 removed and set adjacent to the first molars, thereby repre- 
 senting the second bicuspids, they occupy the entire vacancy 
 first left and one-half the space formerly occupied by said first 
 bicuspids ; hence the extension of the back moulds toward the 
 centre is equivalent to the shrinkage of the entire arch. 
 
 " As the foregoing is applicable where the case of fourteen 
 teeth is to be divided into four blocks, as is usual in soldering, 
 I would say that when the intention is to make pin-holes for 
 riveting, the space of Jut/fa tooth must be left between tlie canine 
 and bicuspids, instead of between the bicuspids and molars. 
 
 "The moulds for the back teeth may now be made in the 
 
 same manner as those of the front ones. After the moulds have 
 
 been made as already described, they should be so trimmed 
 
 that in the process of moulding the blocks there would be no 
 
 liability of removing portions of the enamel oif the teeth in 
 
 withdrawing the moulds. The moulds should now be varnished 
 
 with some spirit varnish, and after it becomes dry are ready 
 
 for use. 
 
 20 
 
306 MECHANICAL, DENTISTEY. 
 
 " The moulds being prepared, the next step is the enamelling 
 of the teeth in the moulds. The enamels should be moistened 
 with a little clean water, and having previously oiled the sec- 
 tion or sections of the mould, the blue or point enamel may be 
 first applied (as stiff as it will work) with a very small spatula 
 made for the purpose. This enamel should be thin at the base, 
 and gradually thickening with the concavity of the mould to 
 the cutting edges of the teeth. The yellow or base enamel is 
 next applied heavy at the base, and gradually terminating near 
 the point. 
 
 " After the enamelling has been completed so far as is de- 
 signed to be moulded at one time, a small quantity of the body 
 about the consistency of a thick paste may be spread over the 
 surface of the moulds and of the enamels, the moulds replaced 
 upon the model, and the body carefully filled in, at first rather 
 soft, but subsequently harder and harder, until the mould is 
 sufficiently full. Then applying the flame of a spirit-lamp 
 for a few minutes with the blowpipe, the body will be tough- 
 ened enough to work well, when the moulds may be removed. 
 The teeth may then be separated and trimmed, the blocks di- 
 vided as desired, the gum enamel applied, etc., and so com- 
 pleted. \ 
 
 " The process of enamelling and moulding being precisely the 
 same with all the blocks, it needs not that I should go into 
 further detail. 
 
 " I have already said, that when the blocks are intended to 
 be riveted upon the plate, the moulds are required to be some- 
 what different. There is also another difference ; that is, the 
 moulding of the pin or rivet holes, which may be done by re- 
 moving the plate from the model, placing the moulds upon 
 the model, and drilling a small hole upon the prominence of 
 the ridge opposite the centre of each tooth, in which insert a 
 piece of wire of a desired size. The enamelling, etc., may 
 then be done as before described, and after the body has been 
 hardened sufficiently, the pins may be removed, leaving the 
 holes neatly moulded, perfectly smooth, and straight. The 
 blocks may then be finished at once, before removing from 
 the cast." 
 
DENTURES WITH CONTINUOUS GUMS. 307 
 
 CHAPTER XIII. 
 
 Uniting Single Porcelain Teeth to Each Other and 
 TO A INIetallic Base with a Fusible Silicious Com- 
 pound, FORMING A Continuous Artificial Gum.* 
 
 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 imperfect 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 
 ])ractice both in the preparation and combination of materials, 
 and the modes of manipulating them; and after an extended 
 series of experiments, commencing in 1844, succeeded in ob- 
 taining 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 platina base 
 
 * The attentive reader of the first edition of this work will not fail to 
 note that the statements involving the question of priority, contained in the 
 introductory portion of the above chapter, are at variance with those originally 
 published. A more extended examination and careful analysis of tlie evi- 
 dences as they appear upon record — evidences not fully accessible to the 
 author at the time of the publication of the first edition — establish 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 t(> the plate is effected liy direct fusion of the gum material. Dr. Hun- 
 ter's earliest and contemporaneous experiments contemjilated simply a union 
 of all the teeth, by means of a fusible cement, forming a single, continuous 
 block, which was afterwards united to the l)ase by riveting or soldering. 
 
 This brief explanation is here introduced as an act of simple justice to 
 Dr. Allen, who has devoted the best energies of his life to the successful de- 
 velopment of a process which stand* unrivalled in all tlie chief rcciuisites 
 of an artificial denture. 
 
308 MECHANICAL DENTISTRY. 
 
 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 compounds, made to represent the natural gums, roof, 
 etc., are applied 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 compounds, which are called the body and 
 the gum enamel, are fused, thus producing a continuous gum, 
 roof, and ruga of the mouth, without seam or crevice. 
 
 The compounds at present employed in this process, as well 
 as the more fusible preparations used for repairing purposes, 
 are manufactured in quantities sufficient to meet the wants of 
 the profession, and may be procured at all the dental furnish- 
 ing; 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 prac- 
 tice has contributed to its development in a modified form. 
 Dr. Hunter's formulas, and modes of manipulating his com- 
 pounds, will be introduced hereafter. 
 
 Following Dr. Hunter's descriptions, the reader will find 
 practical and valuable instructions in this method of substitu- 
 tion, contributed for this edition, at the solicitation of the 
 author, by Dr. S. P. Haskell, of Chicago, Ills., and Professor 
 George S. Field, of Detroit, Mich., both of whom are recog- 
 nized experts, and whose long experience and intimate famil- 
 iarity with the most approved methods of constructing continu- 
 ous gum dentures impart special value to the subject-matter of 
 their communications. 
 
 Before introducing an account of Dr. Allen's modes of pro- 
 cedure, the author 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 witli the formation of plaster models and metallic 
 
DE]>,TURES WITH CO^'TINUOUS GUMS. 309 
 
 swages, these processes being essentially the same as in the 
 construction of ordinary gold work. Whenever a rira is to be 
 formed to the border of the plate extending from heel to heel 
 of the latter, and this is to be accomplished by swaging, the 
 model should be shaped as described in connection with Fig. 37. 
 If it is designed to enamel the entire lingual surface of the 
 plate (a method now commonly practiced), the shoulder upon 
 the model should be extended across tlie heel of the latter from 
 each extremity of the ridge on a line with the posterior border 
 of the hard palate, to form a groove in swaging similar to, and 
 continuous with, that on the outside of the ridge. The edges 
 thus turned in swaging will flare more than is required, — the 
 operation must, therefore, be completed by carefully turning 
 them over sufficiently with the pliers. In place of swaging 
 the rim, however, it may be formed by fitting and soldering 
 along the border a narrow plain strip of platinum, extending 
 it as before, if desired, across the posterior edge of the plate. 
 Or a triangular piece of wire may be soldered on, bevelled 
 somewhat so as to overhang the base slightly, thus forming a 
 shallow groov^e. The border to the palatal portion of the gum 
 at the heel of the plate is sometimes formed in swaging by ad- 
 justing a wire across the heel of the model, which will be 
 transferred to the plate in the form of a ridge. The latter 
 should be raised a line or more from the posterior border of 
 the plate, and should incline gradually to the edge, while the 
 anterior surface should present an abrupt shoulder to the mar- 
 gins of the gum enamel. 
 
 The process of forming the rim is sometimes deferred until 
 after the first portion of the body is baked, and before the gum 
 enamel is applied. In this case, the borders of the plate, to 
 the depth of from a line to a line and a half, are left uncovered 
 by the base ; after the latter has been baked, the uncovered 
 margins are turned over uj)on the ])ody with pliers and })ur- 
 nisher, and the gum enamel afterwards applied flush witli the 
 edge or surface of the rim. 
 
 In wJiat(!ver way the rim or socket is formed, it is j)racti- 
 cally of the first importance that the exact dimensions of the 
 
310 MECHANICAL DENTISTRY. 
 
 plate required should be ascertained before the groove is 
 formed, as it will be impossible to subsequently diminish the 
 extent of the borders without, to some extent, impairing the 
 integrit}' of the finished work. The mouth, therefore, should 
 be carefnlly examined, and the precise location, extent, and 
 fulness of the muscles and integuments along the external 
 borders of the ridge above and below, the glands underneath 
 the tongue, and the extreme boundaries of the hard palate 
 carefully noted and accurately traced upon the plaster model, 
 to serve as a guide in determining the dimensions of the plate. 
 
 Additional strength will be imparted to the metallic base by 
 doubling the central portion of the plate as described in Chap- 
 ter XI. The following additional remarks on the method by 
 Dr. Hunter are introduced : 
 
 " Platina as usually applied I think objectionable, wanting 
 stiffness; my method of using it is similar to that proposed by 
 Delabarre, but possessing greater strength than even his method, 
 and by it can be made as light as a good gold plate got up in 
 the ordinary way. I first strike a very thin plate to the cast, 
 and cut out a piece the size of the desired chamber, taking care 
 not to extend it forward to embrace the palatal artery. Add 
 wax to the plate for the depth of the cavity, diminishing it neatly 
 as it approaches the alveolar ridge. Cement this plate to the 
 cast and take another metallic cast, strike another thin plate 
 over the whole, and solder throughout with an alloy — of gold 
 twenty-two parts, platina two parts — or with pure gold. The 
 chamber thus formed is precisely the same as 'Cleveland's 
 Patent Plate,' but the space between the plates, for which he 
 obtained his patent, is subsequently filled up, leaving a cavity 
 resembling Gilbert's, but with a sharper edge when so desired. 
 This space is filled up with base and enamel, and gives great 
 stiffness without the ugly protrusion of the struck chamber. 
 The plate thus formed assimilates much more closely to the 
 palatal dome, not interfering with pronunciation ; another 
 great advantage gained by it is the impossibility of warping. 
 I say impossibility, because I have submitted plates so con- 
 structed to the severest tests, and never had them to warp. 
 
DENTURES AVITH CONTINUOUS GUMS. 311 
 
 It is well to rivet the two plates together before proceeding to 
 solder, especially gold plates, and to bring the heat carefully 
 upon them ; once prepared there is no danger of change in the 
 succeeding manipulations." 
 
 Dr. Allen's Methods. 
 
 The following descriptions, contributed by Dr. Allen, embrace 
 a clear and concise account of the manipulations at present 
 practiced by him 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 require- 
 ments of the case. Tliey are then covered with a thin coating 
 of plaster mixed with water to the consistence 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 outside of the previous covering 
 and the plate. A convenient way of aj)iilying the second cover- 
 ing is to turn the mixture out of the vessel upon a piece of tin, 
 say four or five inches square, thus forming a cone, upon which 
 tlie 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 investient that 
 will not crack in the process of soldering. Sand may be used 
 with the plaster for this purpose, but I think asbestos preferable. 
 
 " When the covering has become sufficiently 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 sold- 
 ered 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 tfie lining for the teeth, is usually about the thickness of 
 tlie plate upon which they are set, say twenty-eight to thirty ; 
 but should the case require more than ordinary strength, a 
 double or triple thickness of rim should be used. This may 
 
312 MECHANICAL DENTISTEY. 
 
 become necessary in cases where the natural rnolar 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 circum- 
 stances or conditions of each particular case, and then exercise 
 his best judgment in executing the work. 
 
 " In soldering platinum with pure gold, flat surfaces of this 
 metal should be brought in 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 an eighth to a fourth 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 to- 
 gether 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 may be asked. Why not use 
 common gold solder for this style of work? Answer, Because 
 the alloy in the solder will greatly injure the color of the gum 
 enamel in baking. Copper alloy will turn it to a greenish shade, 
 and silver Avill give it a yellow tinge. Although pure gold 
 requires more intense heat to melt it (being about two thousand 
 degrees) 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 introduce the piece with the investient into a heated 
 muffle, and bring the whole mass up to a red heat ; then with- 
 draw it from the furnace, and bring it quickly under the blow- 
 pipe to flow the gold. In this way the teeth do not become 
 
DENTURES WITH COXTINUOUS GUMS. 313 
 
 etched, as they are liable to be if the soldering is done in the 
 furnace. 
 
 " The piece being soldered and cooled, the covering is re- 
 moved from the teeth, taking care to preserve the base un- 
 broken for the plate to sit upon during the subsequent bakings 
 of the body and gum enamel. 
 
 "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 
 instruments for the purpose) to the teeth and plate. It is then 
 carved to represent the gum, roof, and rugae of the mouth, 
 taking care to keep the crowns of the teeth well defined. 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 eight or ten minutes 
 it should be moved forward into the muffle, say two or four 
 inches each time, until the piece shall have passed the centre 
 of the same, which should be at a red heat. It is then with- 
 drawn and passed into a lower muffle, where the heat is greater, 
 in which the body soon becomes semivitrified, which is suffi- 
 cient for the first bake. It is then taken out and (together 
 with the slide on which it was baked) placed in a cooling muf- 
 fle, the mouth of which should be closed to prevent the change 
 of t(!mperature from being too rapid, and causing the teeth to 
 become brittle. When the piece is sufficiently cool to handle, 
 a second a))plication of body is made for the purpose of re- 
 pairing any defects that may have occurred in the baking; this 
 done, the piece is again introduced as before into the upper 
 muffle, then in the lower, allowing the second bake to be(!omc 
 a little harder than the first, but not so much as to appear 
 glossy. It is then withdrawn, and cooled as described above. 
 
 "A flesh-colored compound is then applied, which is called 
 the gum enamel. This is also made j)lastic with water, and 
 a thin coating is put over the body, and closely packed and 
 
314 MECHANICAL DENTISTRY. 
 
 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. 
 
 " 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 bakings 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 the 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, several 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. 
 
 " The finishing process consists simply in smoothing and 
 polishing the plate, and burnishing the rim. It is then ready 
 to be adjusted to the mouth. In baking, great care is necessary 
 to prev-ent the piece from becoming gassed. This can be avoided 
 by allowing the gas to escape entirely from the burning coal 
 or coke i;i the furnace 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 pur- 
 pose, as it maintains a longer and stronger heat than coke. 
 
DENTUEES WITH CONTINUOUS GUMS. 315 
 
 Bituminous coal is not good for this kind of work unless first 
 converted into coke. 
 
 " It often occurs that the natural gums will change more or 
 less after the teeth are inserted. In such cases a new impres- 
 sion 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 maybe 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])urpose. A new coat 
 of body is then applied where the plate has been refitted, and 
 then baked, cooled, enamelled, and baked again, — still observ- 
 mgr the same directions as detailed in the management of new 
 pieces. 
 
 " If the tooth gets broken (a mishap which seldom occurs by 
 use in the mouth), it can be replaced with another, by grind- 
 ing out the remaining portion of the broken tooth, and the 
 gum which covers the fang, and then fitting a new one in the 
 place. This tooth need not be soldered to the inside rim; it is 
 sufficient to o;rind a small notch or g-roove 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 number 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 this additional 
 precaution, which is simply 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 den- 
 ture. The wax soon becomes hard, and is readily removed as 
 each sucrcssive tooth is ground and adjusted in its proper place. 
 
 " When the teeth are thus fitted with each pin accurately 
 
316 MECHANICAL DENTISTRY. 
 
 pressed into the groove prepared for it, and the wax being 
 placed upon the inside to support the teeth in proper posi- 
 tion, — 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 care- 
 fully 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 before, to give it the de- 
 sired form. This done, if the teeth are set a little apart, and 
 it is desired to keep them in that position, take a small piece 
 of asbestos and gently press it in between the teeth at the cut- 
 ting edges ; this will prevent them from being drawn together 
 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 beino; done, it is then withdrawn from the furnace 
 and transferred 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 bleaching or becoming lighter colored in 
 consequence of repeated bakings, a very thin coating of fresh 
 gum enamel should be lightly brushed over the entire en- 
 amelled 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 requi- 
 sites in order to produce good practical results. For example, 
 if the carving of the body is not properly done, 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 be- 
 comes gassed in baking it will be porous and of a bluish color. 
 Again, the teeth of different persons vary as much as any fea- 
 
DENTURES WITH CONTINUOUS GUMS. 817 
 
 ture of the face, and present as great a variety of expressions. 
 Therefore, in the construction of artificial dentures, the dentist 
 should select and arrange the teeth with special reference to 
 each individual case. The length, size, form, shade, and posi- 
 tion of the teeth should be varied to meet all the different 
 physiognomical requirements tliat occur in dental practice. 
 
 " This system also combines with great advantage the restora- 
 tion of the face in cases where the muscles have become sunken 
 or fallen in from the loss of the teeth and consequent absorp- 
 tion of the alveolar processes. Here, again, the artistic skill 
 of the dentist is brought into requisition. He should study the 
 face of his patient as the artist studies his picture, for he dis- 
 jjlays his genius not upon canvas but ui)on the living features 
 of the face ; and of how much more importance is the living 
 picture, that reflects even the emotions of the heart, than the 
 lifeless form upon canvas. He should know the origin and 
 insertion of every muscle of which the face is formed, and what 
 ones he is to raise, otherwise he will be liable to produce dis- 
 tortion instead of restoration. This improvement consists of 
 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. There are four points of 
 the face (of many persons) which the mei-e insertion of the teeth 
 does not restore, viz., one upon each side beneath the malar or 
 cheek-bone, and also a jwiut 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, 
 according to their temperaments. If the ]ym[)hatic tempera- 
 ment predominates, the diange will be slight. If nervous or 
 sanguine, it may be very great. .The muscles situated upon the 
 sides of the face, and which rest upon the molar or back teeth, 
 are tlie zygomaticus major, masseter, and buccinator. The loss 
 of the above teeth cause these muscles to fall in. The princi- 
 pal muscles which form the front portion of the face and lips 
 are the zygomaticus minor, hivator labii superioris alaeque nasi, 
 and orbicularis oris. 
 
318 MECHANICAL DENTISTEY. 
 
 " These rest upon the front, eye, 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 por- 
 tion 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 uj^jper 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 infraorbitar 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 narrowness and sunken expression about the upper lip and 
 cheeks to the same breadth and fulness which they formerly 
 displayed. If skill and judgment have presided over all parts 
 of the operation, the result will be highly pleasing, and of 
 practical utility."* 
 
 Dr, Hunter^ Formulas and 3Iodes of Practice. — The fol- 
 lowing methods of compounding and applying the continuous 
 gum materials, as practiced by Dr. W. M. Hunter, are repro- 
 duced from his latest published descriptions in 1852. 
 
 The following is a description of the materials and com- 
 pounds employed : 
 
 " Silex should be of the finest and clearest description, and 
 kept on hand ready ground, the finer the better. 
 
 ^' Fused spar should be the clearest felspar, such as is used 
 
 * Inasmuch as the improvement for restoring the face has been claimed 
 by others, the reader is referred for the evidences establishing the claim of 
 Dr. Allen to priority of invention to the historical record which appears in 
 the old American Journal of Dental Science of 1845. In the published pro- 
 ceedings of the American Society of Dental Surgeons of that year, it will be 
 seen that a medal was awarded to one of its members, inscribed, " Awarded 
 to Dr. John Allen, for his invention for restoring the contour of the face, 
 August, 1845." This, in connection with the fact that no other record upon 
 this subject is found in our dental literature, fixes the date of this improve- 
 ment. 
 
DENTURES WITH CONTINUOUS GUMS. 319 
 
 by tooth manufacturers for enamels, completely fused in a 
 porcelain furnace, and ground fine. 
 
 " Calcined borax'is prepared by driving off the water of crys- 
 tallization from the borax of commerce, by heating in a covered 
 iron vessel over a slow tire, and it is better to use immediately 
 after its preparation, as it attracts moisture. It should be 
 perfectly clean and white, and free from lumps. 
 
 " Caustic Potas.'ta Optimus. — Known also as potassa fusa. 
 
 " Asbestos. — Take the ordinary clean asbestos, free it from 
 all fragments of talc or other foreign substances, and grind fine, 
 taking care to remove any hard fragments that may occur. 
 
 " Granulated Body. — Take any hard tooth material (I use 
 the following formula: spar 3 ozs., silex 1| ozs., kaolin ^ oz.) 
 and fuse completely. Any very hard porcelain, wedge wood 
 ware, or fine ciiina will answer the same purpose. Break and 
 grind so that it will pass through a wire sieve, No. 50, and 
 again sift off the fine particles which will pass through No. 10 
 bolting cloth. It is then in grains about as fine as the finest 
 gunpowder. 
 
 ^' Flux. — Upon this depends the whole of the future opera- 
 tions, and too much care cannot be taken in its preparation. 
 It is composed of silex 8 oz., calcined borax 4 oz,, caustic po- 
 tassa 1 oz. Grind the potassa fine in a wedgewood mortar ; 
 gradually add the other materials until they are thoroughly 
 incorporated. Line a Hessian crucible (as white as can be got) 
 with pure kaolin, fill with the mass, and lute on as a cover 
 a piece of fire-clay slab with the same. Expose to a clear 
 strong fire in a furnace with coke fuel for about half an hour, 
 or until it is fused into a transparent glass, which should be 
 clear and free from stain of any kind, more especially when 
 it is used for gum enamels. Break this down, and grind until 
 fine enough to pass through a bolting cloth, when it will be 
 ready for use. 
 
 " JJase. — Take flux 1 oz., asbestos 2 oz., grind together very 
 fine, completely intermixing. Add granulated body 1^ oz., 
 and mix with a spatula to prevent grinding the granules of 
 IxxJy any finer. 
 
320 MECHANICAL DENTISTEY. 
 
 " Gum Enamels. — No. 1. Flux 1 oz., fused spar 1 oz., English 
 rose 40 grains. Grind the English rose extremely fine in a 
 wedgewood mortar, and gradually add the flux and then the 
 fused spar, grinding until the ingredients are thoroughly in- 
 corporated. Cut down a large Hessian crucible so that it will 
 slide into the muffle of a furnace, line with silex and kaolin 
 each one part, put in the material, and draw up the heat on 
 it in a muffle to the point of vitr if action, not fusion, and with- 
 draw from the muffle. The result will be a red cake of enamel, 
 which will easily leave the crucible, which, after removing any 
 adhering kaolin, is to be broken down and ground tolerably 
 fine. It may now be tested, and then (if of too strong a color) 
 tempered by the addition of covering. This is the gum which 
 flows at the lowest heat, and is never used when it is expected 
 to solder. 
 
 " No. 2. Flux 1 oz., fused spar 2 oz., English rose 60 grains. 
 Treat the same as No. 1. This is a gum intermediate, and is 
 used upon platina plates. 
 
 " No. 3. Flux 1 oz., fused spar 3 oz., English rose 80 grains. 
 Treat as the above. This gum is used in making pieces in- 
 tended to be soldered on, either in full arches or in the sections 
 known as hloch-ioork. It is not necessary to grind very fine in 
 preparing the above formulas for application. 
 
 "■ Covering. — What is termed covering is the same as the 
 formulas for gum, minus the English rose, and is made without 
 any coloring whatever when it is used for tempering the above 
 gums which are too highly colored, and which may be done 
 by adding, according to circumstances, from 1 part of covering 
 to 2 of gum, to 3 of covering to 1 of gum, thus procuring the 
 desired shade. When it is to be used for covering the base 
 prior to applying the gum it may be colored with titanium, 
 using from two to five grains to the ounce. 
 
 " Investient — Take two measures of white quartz sand, mix 
 with one measure of plaster of Paris, mixing with just enough 
 water to make the mass plastic, and apply quickly. The slab 
 on which the piece is set should be saturated with water, to 
 
DENTURES WITH CONTINUOUS GUMS. 321 
 
 keep the material from setting too soon, and that it may unite 
 with it. 
 
 " Cement. — Wax 1 oz., rosin 2 oz. The proportions of this 
 will vary according to the weather ; it should be strong enough 
 to hold the teeth firmly, and yet brittle enough to chip away 
 freely when cold. A little exjjerience will enable any one to 
 prepare it properly." 
 
 (Inasmuch as the method of constructing the platinum base, 
 with Cleveland's modification of chamber as described by Dr. 
 H., has already been introduced, this portion of the descrip- 
 tion is omitted in this connection.) 
 
 " After the plates are perfectly adapted to the mouth, place 
 wax upon each, which trim to the proper outline as regards 
 length and contour of countenance, marking the proper occlusion 
 of the jaws and the median line. These waxen outlines are 
 CJalled the drafts, and are carefully removed from the mouth, 
 and an articulator taken bv which to arrange the teeth. 
 
 " When the absorption is considerable and the plate in con- 
 sequence is rather flat, it is necessary to solder a band or rim 
 along the line where the upper draft meets the plate, about 
 one-sixteenth or one-eighth of an inch wide, and fitting up 
 against the outline of the draft. When the ridge is still prom- 
 inent, the block will not of course be brought out against the 
 lip so much, and a wire may be soldered on instead of the 
 wider band. I think one or the other necessary, as it gives a 
 thick edge to the block, rendering it far less liable to crack off 
 than if it were reduced to a sharp angle; it also allows the 
 edge of the plate to be bent in against the gum, or away from 
 it, as circumstances may require, and affords in many cases a 
 far iK'ttr-r support for the plates than can be given to one in 
 which the band is druck up, or the edge turned over witli pliers, 
 where the block must extend to the edge of the plate. Some 
 few cases do occur when the band may be struck as far back 
 as tlic bicuspids with advantage, and some in the lower jaw 
 where it is nece-ssary to solder on the band, but the general 
 practi(;c is not so. 
 
 "The upper teeth are first arranged on the plate uiitago- 
 
 21 
 
322 MECHANICAL DENTISTRY. 
 
 nizing with the lower draft, supported by wax or cement, or 
 both. Then remove the lower draft and arrange the lower 
 teeth so that the coaptation of the cutting edges of the teeth 
 shall be perfect as desired. The patient may now be called in 
 again, and any change in the arrangement made to gratify his 
 or her taste or whim. Now place the plates with the teeth 
 thereon, on their respective casts, oil the cast below the plate 
 and apply plaster of Paris over the edge and face of the teeth 
 and down on the cast, say an inch below the edge of the plate. 
 This will hold them- firmly in their place while you remove 
 the wax and cement from the inside, and fit and rivet backs to 
 the teeth. When backed, cut the plaster through in two or 
 more places, and remove. Clean the plate by heating. Cut 
 the plaster so that while it will enable you to give each tooth 
 its proper position, you can readily remove it from the teeth 
 when they are cemented to the plate. Adjust the sections of 
 plaster and the teeth in their proper positions. The plaster 
 may be held by a piece of soft wire. Cement the teeth to the 
 plate and strengthen the cement by laying slips of wood half 
 an inch long along the joint and against the teeth. (I gene- 
 rally use the matches which are so plenty about the laboratory.) 
 Remove the sections of plaster, being careful not to displace 
 any of the teeth. If it be intended to cover the strap with 
 enamel, you should solder a wire after backing, and previous 
 to replacing the teeth, along the plate parallel with the bottom 
 of the straps, and about ^ or J of an inch from them. 
 
 " The teeth are now backed and cemented to the plate, and 
 present an open space between the plate and the teeth, which is 
 to be filled up with the base, using it quite wet to fill up the 
 small interstices, filling in the rest as hard and dry as possible. 
 Fill the cavity between the plates in the same manner, and oil 
 the edge. Oil the surface of the base, envelop in the investient 
 (precisely as you Avould put an ordinary job into plaster and 
 sand for soldering), and set on a fire-clay slab pr-eviously satu- 
 rated with water. When hard chip away the cement, cooling 
 it if necessary with ice, until it is perfectly clean. Along the 
 joints place scraps and filings of platina very freely, and cover 
 
DENTURES WITH CONTINUOUS GUMS. 323 
 
 all the surface you wish to enamel with coarse filings, holding 
 them to their place by borax ground fine with water. Apply 
 pure gold as a solder quite freely, say two dwt. or more to a 
 single set. Put in a muffle and bring up a gradual heat until 
 the gold Rows freely, which heat is all that will be needed for 
 the base ; withdraw and cool in a muffle. Remove the invest- 
 ient and fill up all crevices and interstices not already filled, 
 with covering No. 2 ; cover the straps and base with the same, 
 about as thick as a dime, and cover this with gum No. 2 about 
 half that thickness. At the same time enamel the base in the 
 chamber, and cover with thick soft paper. Set the plate down 
 on the investient on a slab, with the edges of the teeth up. 
 Fuse in a muffle, and the work is completed. Blemishes may 
 occur in the gum from a want of skill in the manipulation; 
 should such occur, remedy by applying gum No. 1. 
 
 " Should the patient object to the use of platina as a base, the 
 work can be made as above on an alloy of gold and platina 
 20 carats fine, and soldered with pure gold, etc., as above. In 
 all cases, however, where it is used, the upper plate should be 
 made as I have described above, but with platina any kind of 
 plate can be used. 
 
 "Ordinary Alloy. — Blocks may be made and soldered to the 
 ordinary plate if the absorption is sufficient to require much 
 gum, without any platina. Arrange the teeth on wax on the 
 plate, fill out the desired outline of gum, and apply plaster one- 
 fourth of an inch thick over the face of the teeth, wax and cast. 
 When hard, cut it into sections (cutting between the canines 
 and bicuspids), remove the wax from the plate and teeth, bind 
 the .sections of the plaster mould thus made to their places with 
 a wire, oil its surface and that of the plate, fill in the space 
 beneath the teeth with the base, wet at first, but towards the last 
 as hard and dry as possible, and thoroughly compacted. Trim 
 to the desired outline on the inside, oil the base, and fill the whole 
 palatal spa(;e with investient, supporting the block on its lingual 
 side. Remove the plaster mould, and cut through the block 
 with a very thin blade between the canines and bicuspids. 
 Take the whole job off of the plate, and set on a fire-clay slab 
 
324 MECHANICAL DENTISTRY. 
 
 with investient, the edges of the teeth clown ; bring up the heat 
 in a muffle to the melting-point of pure gold. When cold, 
 cover and gum with No. 3 gum and covering. 
 
 " Another mode is to back the sections with a continuous 
 strap (using only the lower pin), fill in the base from the front, 
 use covering and gum No. 3, finish at one heat. When the 
 blocks are placed upon the plate, the other pin is used to fasten 
 the gold back, which is soldered to it and the platina half-back ; 
 neither of these backs need be very heavy, as soldering the two 
 together gives great strength and stiffness. Very delicate block- 
 work can be made in this way, and it is applicable also, where 
 a few teeth only are needed. 
 
 " A very pretty method, where a section of two or four teeth 
 (incisors) is needed, and only a thin flange of gum, is to fit gum 
 teeth into the space, unite by the lower platina with the con- 
 tinuous back, and unite the joint with gum No. 3. A tooth left 
 ungummed by the manufacturer would be best for the pur- 
 pose. The same may be applied to blocks for a full arch, 
 remembering not to depend entirely upon platina backs. 
 
 " The method I prefer for full arches on ordinary plate, is 
 to take a ribbon of platina, a little Avider than the intended 
 base, and of the length of the arch, cut it nearly through in 
 five places, viz., between the front incisors, between the lateral 
 incisors and canines, and between the bicuspids. Adapt it to 
 the form of the alveolar ridge with a hammer and pliers, and 
 swage on the plate along where the teeth are to be set. Solder 
 up the joints with pure gold, and proceed to back the teeth, 
 etc., as before ; making preparations for fastening, and remov- 
 ing the slip of platina from the gold plate before enveloping 
 in the investient, when proceed as before. 
 
 " When the teeth are arranged, insert four platina tubes, 
 about one line in diameter, two between the molars, and two 
 between the cuspidati and bicuspids, and solder to the platina 
 base. These are designed, after the teeth are finished, to be 
 the means of fastening to the gold plate, either by riveting in 
 the usual way, or by soldering pins to the gold plate passing up 
 through the tubes, fastening with sulphur or wooden dowels. 
 
DENTURES AYITH CONTINUOUS GUMS. 325 
 
 Bv these methods we are enabled to readily remove the block 
 and repair it, should it meet with any accident, and also, in 
 case absorption should go on, to restrike the plate, or to 
 lengthen the teeth. The rim should be put on the gold plate 
 after the block is finished ; it gives great additional strength 
 and a beautiful finish. 
 
 " Memoranda. — In preparing material always grind dry, 
 and the most scrupulous cleanliness should attend all of the 
 manipulations. In all cases where heat is applied to an article 
 in this system, it should be raised gradually from the bottom 
 of the muffle and never run into a heat. Where it is desired 
 to lengthen any of the teeth, either incisors or masticators, or 
 to mend a broken tooth, it may be done with covering, properly 
 colored with platina, cobalt, or titanium. 
 
 " In preparing a piece of work, wash it with great care, 
 using a stiff brush and pulverized pumice-stone. Bake over a 
 slow fire to expel all moisture, and wash again, when it will be 
 ready for any new application of the enamel. Absorption, 
 occurring after a case has been some time worn, by allowing 
 the jaws to close nearer, causes the lower jaw to come forward 
 and drive the upper set out of the mouth. By putting the 
 covering on the grinding surface of the back teeth in sufficient 
 quantities to make up the desix'ed length, the coaptation of the 
 denture will be restored, and with it the original usefulness. 
 
 " Any alloy containing copper or silver should not be used 
 for solder or j)late, if it is intended to fuse a gum over the 
 lingual side of the teeth, as it will surely stain the gum. 
 Simple platina backs alone do not possess the requisite stiff- 
 ness, and should always be covered on platina with the enamel, 
 and on gold with another gold back. In backing the teeth, 
 lap the backs or neatly join them up as far as the lower pin in 
 the tooth, and higher if admissible, and in soldering, be sure 
 to have the joint so made perfectly .soldered." 
 
 Dr. IlaakelVs Methods. 
 
 "It should be borne in mind that the strength of this work 
 depends mainly upon the vietaf, and not upon the porcelain, 
 
326 MECHANICAL DENTISTEY. 
 
 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 porce- 
 lain, can be made very stiff and strong, therefore everything 
 that can be done to secure a strong foundation should be care- 
 fully 'observed. 
 
 " The plate should be of the best French material (not re- 
 melted scraps and old plates), 29 to 30 gauge 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 articulating model. 
 
 " The back of the plate should be doubled, for the following 
 reasons : 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 three-sixteenths of an 
 inch wide, with the edge turned up slightly to receive the 
 porcelain. Around the outer edge, solder a flattened wire, 
 one-sixteenth, or less, of an inch wide, and 22 gauge, 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 wevy little) to give direction to the flow of solder. 
 
 " Then comes the arrangement of the teeth, and this should 
 always be done in the mouth, the articulating model being 
 only a preliminary guide ; for by the mouth alone can one de- 
 termine the correct expression and arrangement desired ; and 
 it is just here that three-fourths or more of the artificial den- 
 tures fail in an utter lack of artistic skill. In this work there 
 is ample opportunity for the display 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 
 
DENTURES AVITH CONTINUOUS GUMS. 327 
 
 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 latter to two of the former. Let the portion 
 under the plate extend at least one inch back of the latter, as 
 this bottom portion is to be retained to bake the case on ; in- 
 vest the whole one-half 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 back- 
 ings should be continuous, and be lapped on to the plate, for 
 in this is the main stay 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 eye-teeth ; the foot-piece should 
 lap on to the plate about three-sixteenths 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 slitting 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 not 
 material, as the ' body ' will hold it. 
 
 " After cooling, remove the plaster, and save the base. If 
 any teeth are etched, sandpaper them and remove every par- 
 ticle of plaster ; with a sharp instrument scarify the surface 
 of the plate. Place the plate on the articulating model, and if 
 it is sprung, press it into place, which is very readily done. 
 
 "The ' body,' and enamel or gum color, as prepared by S. 
 L. Close, is the only reliable material to be had, as Dr. Allen 
 no longer furnishes it for the trade. Apply the ' body ' mixed 
 with water, quite thin, by means of an oval-pointed knife, oc- 
 casionally 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, apj)ly it thicker, jarring, absorbing, and 
 j)acking hard, until enough is on the outside to produce the 
 proper shape and contour of the lips. Then ap})ly, with the 
 curved point of knife, the body to the lingual side of the plate, 
 
328 MECHANICAL DENTISTRY. 
 
 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 toothpick, and brush all particles off the 
 surface of the teeth and exposed portions of plate, and the case 
 is ready for baking. 
 
 " The Philadelphia furnace, sold by all dealers in dental 
 goods, we prefer. It is always best to use the largest size, No. 
 1, yet No. 2 will do if the larger size cannot be had. Be sure 
 of a good draught. The furnace can be used as it comes ; a 
 better plan is to knock the bottom out of the lower section, 
 get longer bars, that will extend some distance through the 
 front, the two centre ones at least 18 inches. Build a hearth, 
 two bricks thick and three feet square ; build an inclosure of 
 brick, about 12 inches high, large enough to set the furnace on, 
 and line with fire-brick. Provide a sheet-iron cover for the 
 front to close the draught. 
 
 " 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. 
 
 " The fuel to be used must be anthracite coal, or else coke ; 
 Lehigh, range size, is the best. 
 
 " A sheet-iron shelf, the edge bent into the space between 
 the furnace and cover, and with a leg riveted to it and resting 
 on the long bars, is needed to set the case on, to heat up and 
 run into the muffle gradually. Set the case ten or twelve 
 inches from the opening, move forward, every ten or fifteen 
 minutes, a couple of inches, until it is in the muffle ; ])lace it 
 within two inches of the back, and close the door. If the heat 
 is right, 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. Remove 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 fulness are secured, trimming around the teeth, and 
 
DENTURES WITH CONTINUOUS GUMS. 329 
 
 doing as previously described, and bake as before, only more 
 so ; it should be ghssy. 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 remove 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. Use plate No. 8, or 
 even thicker, and solder on the edge a narrow strip, ^«^ 
 
 " 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 
 chamber, 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 centre, according to the softness of the palate. 
 
 "This work is not advisable for partial sets, except in some 
 partial 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. 
 
 " Very few seem to know how to prepare a case for repair- 
 ing. Invest it in plaster and asbestos at least one-half of an 
 inch deep entirely ; place in the muffle before lighting the fire, 
 and allow it to remain witii the door open, as the fire comes 
 up, until it is red hot ; then remove, cool, and clean off the 
 plaster thoroughly, 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 tliis work, filing off the pins; hold with 
 wax until a little })la.ster and asbestos can be placed over it 
 and the adjoining teeth ; remove the wax thoroughly and put 
 
330 MECHANICAL DENTISTRY. 
 
 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 ease, and put on just a little new, and bake as at first. 
 
 " If blisters occur, grind into them and fi:ll with body and 
 gum, three to one, press hard, and enamel." 
 
 Dr. Field's Methods. 
 
 " When the platinum has once touched the metal dies, never 
 place it under the blowpipe without its having been thoroughly 
 pickled. This is often neglected, and the consequence is that 
 the plate will become more or less discolored from the absorp- 
 tion, under heat, of the baser metal into the platinum. When 
 the teeth are properly arranged with wax on the plate, as di- 
 rected by Dr. Allen, invest, but use no sand, simply plaster 
 and asbestos. My reason for this I will give further on. 
 
 "After the investment has become sufficiently hard to han- 
 dle, the backings may be adjusted, and here I shall differ some- 
 what with Dr. Allen, for, instead of the continuous backing, I 
 back each tooth separately, and for two reasons, one of which 
 is, that I think my job will be stronger when completed, by 
 allowing the body to be well worked in between, below, and 
 completely around the teeth without a platinum wall, as it 
 were, separating the body on a line running completely around 
 the alveolar ridge, and only just touching over the top of this 
 platinum. 
 
 "My second reason is that, should the teeth be drawn 
 out of place any, as they are sometimes by the investings 
 cracking and pulling away from the plate, the single backing 
 of each tooth admits of a much easier and more perfect re- 
 adjustment than when the backing is continuous. Make the 
 backings of a somewhat V shape, that is, let them be a little 
 narrower at the top than where they come in contact with the 
 plate ; bend up the lower part of the backing to the extent of 
 about one-sixteenth of an inch, and at such an angle that when 
 placed in position behind the platinum pin, to which it is to 
 be soldered, it shall fit fairly and squarely on the plate ; put 
 in position and press down your pin on it, first having placed 
 
DENTURES WITH CONTINUOUS GUMS. 331 
 
 a piece of, say number 20, gold foil, folded two or three times 
 on itself, one-sixteenth of an inch square, against the backing, 
 so that when the pin is bent down upon it, it shall hold it 
 from slipping away; then with a pair of ordinary plugging 
 pliers squeeze the foil up to and around the pin; then place 
 one or two pieces of solder (pure gold) just behind, and close 
 against, the heel of the foot-shaped backing. By placing it 
 here, the danger of it slipping away when the borax calcines 
 under heat is a%'oided. The less solder you use, and still have 
 your teeth fastened, the better, for the reason that the gold 
 flowing at a less heat than that required for the fusing of the 
 body, the gold is in a state of fusion ichen the body has set, and 
 there will be no adhesion between the gold and the body. Now 
 solder as most convenient. I find the Fletcher furnace an ad- 
 mirable contrivance for this purpose, ten minutes being all the 
 time necessary to complete the work. Remove the investing 
 carefully, and presei've it all for future use. The plate is then 
 tried in the mouth, and the teeth nicely adjusted to those with 
 which they are to antagonize. 
 
 '' Everything is now ready for the first baking. Pour out 
 upon a clean butter plate the amount of body required, into 
 which pour sufficient pure water to make a thin paste, and then 
 begin the work of moulding and carving your job by filling 
 in between and under all the teeth, tapping your plate gently 
 from time to time ; this will bring the water to the surface and 
 settle the body into every nook and crevice. After each tap- 
 ping, absorb the surface water with a clean napkin ; by so 
 doing, you will the better hold the body to its place, and pre- 
 vent its running where not wanted. Build over the roots of 
 the incisors and cuspids boldly, leaving a corresponding de- 
 pression between the teeth; thus, when the piece is completed, 
 you will have that natural and lifelike appearance as of the 
 roots of the teeth showing slightly through the gum. 
 
 " Xow take that part of your investing material that cov- 
 ered the teeth when the piece was soldered, and grind up fine, 
 and with it make a cushion on the slab that is to hold the case 
 in the furnace. This cushion should be about one-fourth of 
 
332 MECHANICAL DENTISTRY. 
 
 an inch thick ; then place your piece on this base, teeth down- 
 wards, and take a small spatula and work the powdered ma- 
 terial well up against the teeth, so that the bearing shall be 
 equal under every tooth ; this, if properly done, will prevent 
 any dravnng aioay of the teeth from their proper position, as 
 is frequently the case when the plate is placed in the muiSe 
 with the teeth upwards, the cause being the shrinkage of the 
 body ; and now comes my reason for not using sand in this in- 
 vesting material, viz., the sand acting as a flux would attach 
 itself more or less to the teeth themselves, and I have seen this 
 thing carried so far, when the heat was a little too high, as to 
 solidly fuse teeth and slab together. 
 
 " The piece is now ready for the first baking, and this should 
 be carried no farther than to shrink the body as much as pos- 
 sible, not going beyond a semi-fuse. After this is completed, 
 and the case cooled, proceed to fill up all cracks and shrinkage 
 by the application of more body, when the case is ready for 
 the second baking. This should be done with the plate re- 
 versed, teeth upwards, using for a support that part of the 
 investing which came in contact with the platinum, and which 
 should be preserved unbroken. In this second baking of the 
 body, care should be taken that it be not overdone. A piece 
 properly baked will present a beautifully granulated appear- 
 ance, the tips of the granules sparkling like little dewdrops. 
 Carrying the heat beyond the stage necessary to produce this 
 effect, vitrifies the body, thereby very much lessening the 
 strength of the work when completed. 
 
 " If now it is found that a third body is not required (and 
 it rarely is if proper care has 1 een taken with the work so far, 
 although occasionally it may be necessary) proceed with the 
 enamelling as directed by Dr. Allen. Should there be any 
 little rough spots on the teeth, caused by overheating when 
 soldering, paint them over with a little clean pulverized borax 
 mixed with water ; this will flow the tooth enamel, and cause 
 them to come out from the mufile as bright and smooth as 
 when they first left the factory. 
 
 "The work is now ready for its third and final baking, 
 
DENTURES WITH CONTINUOUS GUMS. 333 
 
 which should be with a quick, sharp fire. When fused, draw 
 to the front part of the muffle; put in the muffle pUig, and 
 then dump the fire, and leave until tlie furnace is cold ; by so 
 doing, the case is well annealed, and all danger of checking 
 the enamel avoided. Twenty or thirty minutes now are all 
 that are necessary for what little finishing the plate will require, 
 when it will be ready for the mouth. 
 
 " Let it be remembered by the beginner tliat on the carving 
 of the first body largely depends the artistic beauty of the work. 
 Keep your patient's face well before you in your mind's-eye, 
 and reproduce in the porcelain all those little minor details 
 which, when properly arranged and blended together, shall so 
 counterfeit nature's handiwork that that of man's can hardly 
 be detected." 
 
 Application of Continuous Gum to Partial Sets. — The fol- 
 lowing method of constructing partial sets of artificial teeth 
 with continuous gum is taken from a practical and well-written 
 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 neces- 
 sarily depend much upon his own judgment. Difficult cases 
 will constantly present themselves, that will require the exer- 
 cise of much study and ingenuity ; in which the general instruc- 
 tion 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 
 motion between the teeth, so that they could be adjusted as 
 desired. I then placed a bit of tissue-paper on the plaster 
 mcxlel, covering the spot to be occupied by the teeth and gum, 
 to i)revent the adhesion of the body to the plaster, and holding 
 the two incisors in their j)laces, I worked the body into all 
 the depressions of the gtim and around the roots of the teeth. 
 I then removed the whole from the model, and pUu-ctl the 
 
334 MECHANICAL DENTISTEY. 
 
 piece 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 
 somewhat ; 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 around the roots of the teeth, and 
 rebaked. 
 
 " After enamelling, if the work has been carefully and skil- 
 fully done upon this plan, it will be as fine a piece in appear- 
 ance 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 often encountered from discoloration of the 
 gum, or from other injuries incurred in soldering. But with 
 Roberts's material, these are easily avoided, and the piece can 
 be treated the same as a block or single gum teeth. In par- 
 tial sets on entire plates of platinum, I have sometimes found 
 trouble, from the enamel giving way upon the small narrow 
 points that connect the teeth with the plate, by the shock occa- 
 sioned in biting. I have consequently left these points un- 
 covered, 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 one-eighth 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 
 case of imperfections caused by the difficulty of obtaining exact 
 impressions in these places. In such cases I have sometimes 
 formed a strong standard of several thicknesses of platinum 
 fitting closely against one or more natural teeth, leaving a 
 
DENTURES WITH CONTINUOUS GUMS. 335 
 
 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 
 platinum, and sometimes by two or three gold screws, not pro- 
 viding, 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 subr 
 stance ; 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 communicate a yellowish tinge 
 to the gum, spoiling the whole work. Many operators in their 
 early practice, I doubt not, experienced this result ; and learned 
 that no alloys, especially of silver or copper, can be admissible 
 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 in enamelling, the piece is 
 sometimes changed in its texture and color, as is supposed by 
 tlie gases present, and the phenomenon is called gassing the 
 piece. The body becomes porous like honeycomb, 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 
 tlie heated air and gases," 
 
336 MECHANICAL DENTISTRY. 
 
 CHAPTER XIV. 
 Vulcanite Base. 
 
 While there are undoubtedly many important uses to which 
 vulcanized india-rubber may be applied in the practical depart- 
 ments of dentistry, and for which it would be difficult to find 
 an adequate substitute, yet there are accumulating evidences 
 leading to the conclusion that its total abandonment, as a base 
 for artificial dentures, by intelligent and conscientious prac- 
 titioners everywhere is an event of the near future. 
 
 This anticipated result, in respect to a material which has 
 been almost universally employed as a base for the past twenty 
 years, is assured by the confirmed and steadily increasing dis- 
 trust of its suitableness for the purpose indicated, and the grow- 
 ing tendency in the profession to return to higher and less 
 objectionable forms of substitution as respects both material and 
 construction. 
 
 While what has heretofore been stated in regard to rubber 
 as a base in former editions of this work reflected, as the author 
 then believed, the estimate of its fitness by the profession gen- 
 erally, so, it is believed, does what is now written embody the 
 present judgment of the mass of enlightened practitioners in 
 reference to its unsuitableness and the necessity of its abandon- 
 ment as a base. That the latter is a consummation " devoutly to 
 be wished," and that it would be in the interests not only of the 
 profession but of all concerned, is scarcel}^any longer a disputed 
 question, and should the present work ever reach another edition, 
 the author hopes to find in a still more advanced professional 
 and public sentiment authority for classifying it, as a base, 
 among the obsolete methods of substitution. 
 
 General Properties of India-rubber. — Caoutchouc, gum-elastic 
 or india-rubber, exists as a milky juice in several plants, but 
 
VULCANITE BASE, 337 
 
 is extracted chiefly from the Siphonia cahuca, which grows in 
 South America and Java. It is discharged through numerous 
 incisions made in the tree through the bark, and is spread upon 
 clay moulds, and dried in the sun, or with the smoke of a fire, 
 which blackens it. The juice when first obtained is of a pale 
 yellow color, of about the consistence 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 albumen, on the application of heat, 
 the elastic gum rising to the surface. The specific gravity of 
 the juice is diminished by inspissation, becoming 0.925 when 
 hard, and cannot be permanently increased by any degree of 
 pressure. When once stiffened by cold, or continued quies- 
 cence, it cannot be restored to its original condition of juiciness. 
 The inspissated juice, or crude rubber of commerce, is alto- 
 gether insoluble in water or alcohol, but is readily soluble in 
 ether deprived of its alcohol by washing, affording a colorless 
 solution. On evaporation 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 solul)le in the fixed oils, but is not readily 
 decomposed by cold sulphuric acid or diluted nitric acid, and is 
 unaffected by either muriatic acid gas, sulphurous acid gas, fluo- 
 silicic acid, ammonia or chlorine, nor is it dissolved by the 
 strongest caustic potash lye, even at a boiling heat, and is there- 
 fore highly esteemed as an appliance of the chemical laboratory. 
 According to the experiments of Ure, Faraday, and others, caout- 
 chouc contains no oxygen, as almost all other solid vegetable 
 products do, but is a mere compound of carbon and hydrogen, 
 in the proportion of three atoms of the former to two of the 
 latter. From its proi)crty of resisting the corrosive action of 
 ar-id vapjrs, and its tenacity of adhesion to glass, caoutchouc, 
 whea melte<l, forms a very excellent lute for chemical apjiarata. 
 Such are some of the properties of this remarkable product, 
 the uses of which have been almost immeasurably extended 
 
 22 
 
338 MECHANICAL DENTISTRY. 
 
 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 vary- 
 ing proportions, 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 substances, properly combined, are sub- 
 jected to artificial heat for a specified time,, producing a hard, 
 elastic, hornlike substance, possessing the qualities of lightness, 
 strength, durability, imperviousness to fluids, insolubility in the 
 oral secretions, unchangeableness in exposure to ordinary tem- 
 peratures, 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 modifi- 
 cations of practice which will readily suggest themselves, it 
 will be sufficient to describe the method of constructing an en- 
 tire denture for the upper jaw. 
 
 An impression of the mouth is first secured in the usual 
 manner, and, for full sets, plaster of Paris is preferable to any 
 other material for the purpose. In all practicable cases the 
 same substance may be employed in cases of partial pieces. 
 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. F04' the 
 latter purpose, lead is often used, but sheet tin, cut to the re- 
 
VULCANITE BASE. 339 
 
 quired form, is preferable, as the former leaves a tenacious coat- 
 ing of oxide adhering to the plate. 
 
 A temporary or model base plate is next conformed as ac- 
 curately as possible to the face of the model, and for this pur- 
 pose the prepared gutta-percha is the best, though sheet wax 
 may be used. The former may be softened either by sub- 
 jecting it to a dry heat until sufficiently plastic, or by im- 
 mersing it in hot water. The face of the model being pre- 
 viously well saturated with cold water to prevent the wax 
 or gutta-percha from adhering, the latter is pressed or moulded 
 accurately to the model with the fingers moistened 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 di- 
 mensions. 
 
 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, fulness, and contour, 
 and the " bite " of the under teeth secured ; it is then removed 
 and placed in its proper position on the model, and the heel of 
 the latter extended an inch or more posteriorly to form an 
 articulating; surface for the remaining; section of the antagoniz- 
 ing model, the latter being obtained in the manner described 
 in connection with metallic plate base. The mode of proced- 
 ure in case of entire dentures for the upper and lower jaws 
 differs in no respect from that practiced 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 
 gutta-percha plate in the usual manner. The porcelain teeth 
 used in this process are more commonly in the form of blocks 
 or sections, although either single gum or plate teeth may be 
 employed. Preference is given to the former, because a fewer 
 number of seams or joints arc presented for the intrusion of 
 rubber, which, though forming ever so minute a line of sepa- 
 ration, mars the beauty of the finished work by an unsightly 
 contrast in color with the porcelain gum, and which is not 
 
340 MECHANICAL DENTISTEY. 
 
 always possible entirely to exclude. The increased strength 
 of attachment formed by the greater number of pins also ren- 
 ders them more permanent and enduring than single teeth. 
 Teeth made expressly for rubber base were originally manu- 
 factured with plain platina pins, longer and heavier than those 
 used in connection with metallic plates (Fig. 126); these, 
 when used, were curved and pressed together, forming loops 
 or hooks to prevent them withdrawing from the rubber. Sub- 
 sequently, however, the detachment of the teeth was more 
 securely and certainly provided against by the substitution of 
 headed pins (Fig. 127), which rendered their withdrawal from 
 the rubber impossible. For this valuable improvement the 
 
 Fig. 126. Fig. 127. 
 
 profession is indebted to the late Dr. S. S. White, whose genius, 
 enterprise, and intelligence Avere so long and unceasingly tribu- 
 tary to the needs of the dental practitioner. 
 
 In arranging the teeth, portions 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 proxi- 
 mate edges until the proper position is assigned to the teeth, 
 and the required antagonism is secured. The teeth, whether 
 single or in the form of blocks, 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 felspar 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 
 
VULCANITE BASE. 341 
 
 substances mentioned, Professor Wildman very justly ob- 
 serves :* " 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 flask together, there is little danger of the rubber insinuat- 
 ing 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 uniform coaptation of the ground sur- 
 faces where they unite in front, and the " enveloping 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 impercepti- 
 ble in the finished work, and wholly so in the mouth. To 
 better eifect the object stated, the author has been accustomed, 
 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 de- 
 signed for that purpose, until the required form and fulness 
 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 considerable excess of material should be 
 avoided, since it will not only materially increase the labor of 
 dressing the vulcanized plate, but tend to induce sponginess of 
 the rubber 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. 
 
 * Instructions in Vulcanite, p. 19. 
 
842 
 
 MECHANICAL DENTISTRY. 
 
 Wax used for the purposes indicated should be of the cleanest 
 and purest varieties. A model set prepared in the manner de- 
 scribed will present the appearance represented in Fig. 129. 
 
 Formation of the Mould or Matrix. — 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 for- 
 mation of a mould or matrix in which the gum material is 
 packed and pressed preparatory to being indurated or vulcan- 
 ized. In forming a matrix, a vulcanizing flask is used, the 
 various parts of which are separately represented in Fig. 128. 
 
 Fig. 128. 
 
 The lower section of the flask A, is first filled one-half or two- 
 thirds full of plaster mixed with water to the consistence of 
 cream. Into this the base 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 ex- 
 tending 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 
 
VULCANITE BASE. 343 
 
 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 several parts will now present the ap- 
 pearance represented in Fig. 129. The upper section of the 
 flask J5, is next placed in its proper position over the lower,* — 
 the slides formed in one, and corresponding grooves in the 
 other, determining an accurate relation of the two pieces. 
 Into the upper rim of the flask, plaster, mixed to the consist- 
 ence before mentioned, is now poured, filling it completely. 
 The lid or cap D, also filled in with plaster, is then applied to 
 
 Fig. 129. 
 
 the opening above, and the several parte of the flask com- 
 pressed by placing them within the clamp C, and forcing them 
 together with the screw, impacting the plaster and driving out 
 the excess through the jointe of the flask. As soon as conden- 
 sation of the plaster takes place, the flask should be placed in 
 a hot-air chamber or on a stove, and heated throughout suffi- 
 ciently to soften, but not melt, the wax. The clamp is tlien 
 removed and the two sections of the flask carefully separated by 
 forcing a small chiscl-shajjed instrument in at different points 
 between them, tiie 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 
 
344 MECHANICAL DENTISTRY. 
 
 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 towards the matrix, as seen in 
 Fig. 130. The gutta-percha plate and wax should now be 
 carefully detached %vith such instruments as will best enable 
 the operator to work out confined portions around the plati- 
 num pins and from the interstices between the teeth, being 
 careful at the same time not to deface the plaster surface of the 
 mould. 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 heat sufficient to induce its com- 
 plete absorption by the plaster. The flask should be heated 
 gradually, otherwise the contents may be suddenly and forcibly 
 ejected in consequence of the too rapid evolution of vapor. 
 
 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 between the surfaces of the plaster around 
 the matrix, the vulcanized 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 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 applica- 
 tion of full sets of teeth, but it is far different in the construc- 
 tion 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 replace- 
 ment in the several vacuities on the ridge. If, for example, 
 in replacing the superior incisors, the approximation of the 
 two sections forming the mould is obstructed by the intrusion 
 of the gum material between the plaster surfaces, the teeth, 
 whether plate or gum, will be relatively elongated in propor- 
 tion to the increased thickness imparted to the base consequent 
 upon the incomplete closure of the fl.ask, and however accu- 
 
VULCANITE BASE. 
 
 345 
 
 rately 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 will 
 be displaced and projected below those of the contiguous natural 
 organs. Such displacement in the cases last referred to, how- 
 ever small in degree, cannot fail either to impair or destroy 
 the value, both as respects appearance and utility, of the sub- 
 
 stitute. The usual method of furnishing an exit to redundant 
 material, is to form a series of conduits or grooves in the sur- 
 face of the plaster containing the teeth, extending them from 
 the edge of the matrix to the rim of the cup. The escape of 
 the gum will be facilitated by filing notches at intervals around 
 the rim of the flask, making the grooves in the plaster continu- 
 ous with them, the grooves being an eighth or a fourth of an 
 inch apart. To still more efFectually j)revent the intrusion of 
 the vulcanite material between the surfaces of the opposing 
 sections of plaster, a circular groove may be cut in the plaster 
 
346 
 
 MECHANICAL DENTISTEY. 
 
 within a line or two of the margins of the matrix, into which 
 narrow channels at short distances are made leading from the 
 mould ; others, again, are made at wider intervals from the 
 circular groove to the outer margins of the flask, terminating 
 as before in small notches formed in the rim of the cup. 
 Fig. 130 exhibits the section of the flask containing the teeth 
 with the channels formed as described ; the remaining section 
 containing the model is shown in Fig. 131 ; the two pieces 
 when closed upon each other forming the matrix. Into the 
 grooved section of the mould, the vulcanizable substance is 
 
 Fig. 131. 
 
 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. Barker's ethereal 
 solution, or the collodion of the shops, may be used for the 
 purpose. Preference is given by Professor Wildman to solu- 
 ble glass or liquid silex, as being more readily detached from 
 the surface in finishing than the preparation mentioned. The 
 
VULCANITE BASE. 347 
 
 latter should be allowed to dry perfectly before packing. 
 Either of these substances is best applied with a small brush, 
 coating the face of the model uniformly. 
 
 Packing the Mould. — 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 vulcanizable gum soft and pliable as 
 successive portions are applied and pressed into the mould, and 
 to retain it in that condition until the operation of packing is 
 completed. Narrow strips of the gum material should first be 
 worked carefully into the contracted groove underneath the 
 platinum pins with small curved or straight-pointed spear- 
 shaped steel instruments (Fig. 132), adding on small pieces at 
 
 Fig, 132, 
 
 a time after each successive portion is thoroughly impacted, 
 until the main groove of the matrix over the base of the teeth 
 is partially filled. The palatal convexity of the mould may 
 then be covered with a single piece cut to the form of the un- 
 covered space ; a smaller piece of the same general form as the 
 latter may then be added, giving to the central portion a double 
 thickness of the gum plate material, so that when the two sec- 
 tions of the flask are brought together, the excess of gum in 
 the centre will be forced gradually to the margins of the mould, 
 diminishing, thereby, the liability of the grooves becoming 
 prematurely clogged with the material before the opposing sec- 
 tions of the flask close upon each other. Especial care should 
 be taken in the process of packing to avoid contact of the in- 
 struments with the surface of the mould, 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 to fill the 
 matrix perfectly, experience in its use will enable the operator 
 
348 
 
 MECHANICAL DENTISTEY. 
 
 to estimate the capacity of the mould with tolerable accuracy. 
 Some small excess of rubber should always be provided. The 
 required quantity, however, can be more certainly determined 
 by measurement or weight. A very simple instrument (Fig. 1 33), 
 contrived by Mr. E. T. Starr, may be used to determine the 
 
 Fig. 133. 
 
 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 model plate 
 is immersed, and the rise of water indicated in the same man- 
 ner by the upper point. The vessel is then emptied and well 
 cleansed, clean water filled into the level of the lower point, 
 
VULCANITE BASE. 349 
 
 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. 
 
 The following method of determining the quantity of rubber 
 by weight is given by Professor Wildman : 
 
 " The specific gravity of wax is .96. I have found that of 
 the American Hard Rubber Company's prepared gutta-percha 
 to be 2.454, and the same company's red rubber to be 1.572. 
 Hence, to fill the mould, when pure wax is used for a model 
 plate, it will require to one part of wax, by weight, 1.6 of the 
 Company's red rubber ; and when the plate is made of prepared 
 gutta-percha, it will require to one part of it, by weight, .6 of 
 red rubber. When the wax is colored, the disparity in weight 
 will not be so great as with pure wax, 
 
 " Of the two methods to ascertain the quantity of rubber, 
 that by measure offers an advantage over that by weighing, in 
 the facility Avith which it can be arrived at, especially when 
 Starr's instrument is used, the calculation being based upon 
 bulk only ; whilst by weight, when the model plate is composed 
 of more than one substance, as it frequently is, of gutta-percha, 
 wax, and sometimes wires introduced to give stiffness, quite 
 an intricate calculation must be made to ascertain the exact 
 quantity." 
 
 Having completed the packing of the mould, the two por- 
 tions of the fla.sk are reapplied to each other in exactly their 
 original relation, 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 often 
 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. Those 
 manufactured by L)rs. Hayes and Whitney enjoy deserved 
 po[)ularity, and are, perhaps, in most general use. Fig. 134 
 represents one of Hayes's flasks, with improved clamps. The 
 lug-joint is so constructed that the strain all comes upon the 
 
350 
 
 MECHAXICAL DEXTISTEY. 
 
 casting. The pin only serves to keep the lug in place while 
 not in use. The several pieces all being attached together, are 
 
 Fig. 134. 
 
 not liable to get lost or mislaid. Whitney's flasks, original 
 and improved forms, are shown in Fig. 135. The improve- 
 ment in construction consists in reversing the position of the 
 
 Fig. 135. 
 
 bolts, fitting the head into the hole in the lower part of the 
 flask, and using a nut on top. 
 
 What is known as the *' Starr Flask " is highly commended 
 as fulfilling very perfectly the requirements of practice. An 
 
 Fig. 136. 
 
 admirable flask, happily meeting some important indications, 
 is represented in Fig. 136. Every operator of experience is 
 
VULCANITE BASE. 351 
 
 familiar with the annoyance and difficulty sometimes attend- 
 ing 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 Flasks/' invented by 
 Mr. E. T. Starr, the different parts of which are represented 
 in the accompanying cuts, provides very perfectly for any exi- 
 gency that may arise in the class of cases mentioned. The 
 following description of this flask is taken from the advertising 
 columns of the Dental Cosmos: 
 
 " The rings of this flask 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 deep cases and partial sets, or where the 
 artificial gum rests on the natural. The narrov; 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 trou- 
 ble. The cuts represent the flask in different positions." 
 
 The author has, for the past several years, used exclu- 
 sively, and with the greatest 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. 137. The closure of tlie sections 
 by this arrangement, with the bolts in place, is unerring, and 
 is accomplished with the greatest facility. It is called the 
 '^Anchor " flask, furnished by the Philadelphia Dental Manu- 
 facturing Company, but the author is unadvised of the name 
 of the inventor. 
 
 AVhatever flask is used, the entire mass of inclosed rubber 
 should be rendered uniformly plastic, after packing, by sub- 
 
352 
 
 MECHANICAL DENTISTRY. 
 
 jecting it to either a dry heat, such as may be obtained with a 
 conveniently constructed sheet-iron furnace, the baking apart- 
 ment 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 water for a time 
 sufficient to soften the rubber. The approximation of the sec- 
 tions of the flask should be effected interruptedly, — alternately 
 heating the entire mass and tightening by means of the screw- 
 bolts until all the redundant material is expelled by degrees 
 
 Fig. 137. 
 
 through the outlets provided for it, and the sections of the 
 flask close accurately upon each other. 
 
 A somewhat novel and ingenious device employed in pack- 
 ing the mould is exhibited in Fig. 138, known as "Hayes's 
 Condensing Flask." 
 
 To form the mould, first smear over the plunger with soap, 
 put into the flask and secure it in place by a turn of the set-screw. 
 Pour in the plaster and place the model in the usual way, 
 allowing the plaster to flow up and take the imprint of the 
 lower half of the plunger. When the teeth are in place the 
 back edge of the plate must be connected with the plunger by 
 a broad strip of wax reaching across its entire face, to form a 
 gateway, or, if an under set, two strips connecting the plunger 
 
VrLCANITE BASE. 
 
 353 
 
 with the mould on each side opposite the molar teeth. These 
 strips may be thickened a little where they connect with the 
 plunger, to allow a free flow of rubber into the mould. Also 
 lay a narrow strip of wax from the mould to the notch in the 
 front edge of the flask, from which the rubber will protrude 
 and show when the mould is full. Then put on the upper 
 section, fill with plaster, and drive on the cover before the 
 plaster sets. 
 
 AVhen hard, first withdraw the plunger, then open the flask 
 and remove the wax in the usual way. Take once and a half 
 as much rubber by measure, or three times as much by weight, 
 as there was of the wax. There is no occasion to warm either 
 
 Fig. 138. 
 
 the mould or the rubber. Cut into strips, lay as much into the 
 mould as may be without preventing the flask from closing, and 
 place the balance within the cavity formed by the plunger. 
 Now close tlie flask, again smear the plunger with soap and 
 press it into the flask as far as it will go. Then connect the 
 flask with the screw- press, turn down the set-screw firmly 
 upon the flask, and place the whole in the open vulcanizer two- 
 thirds filled with water. When it boils freely, turn down the 
 screw — not faster than one revolution a minute — till rubber 
 appears at the opening in front left for that purpose. 
 
 Sliould there be a surplus of rubber, it may be withdrawn 
 with the plunger, by leaving the end without soap; or it may 
 be left in and removed with the plaster after the piece is vul- 
 canized. In either ca.se there is no need of closing the cylin- 
 der while vulcanizing, as the rubber in the mould will not be 
 
 23 
 
354 MECHANICAL DENTISTRY. 
 
 displaced. If desired, however, the cylinder may be filled 
 with plaster or a cork. Should the plunger be used without 
 soap, the rubber will adhere somewhat, but will do no harm, 
 as it is easily removed by a cloth moistened with kerosene or 
 naphtha. In driving on the cover, or removing it from the 
 flask, a few light blows with a small mallet serves the purpose 
 best, and will not batter the metal. 
 
 The packing accomplished, the piece is ready for the vulcan- 
 izing process. 
 
 Vulcanizing. — The process of vulcanizing or hardening the 
 various rubber compounds employed for dental purposes is 
 eifected by subjecting them for variable periods of time to the 
 action of heat, the substances to be acted on being confined 
 within a steam-chamber constructed for the purpose. The 
 
 Fig. 139. 
 
 time and temperature necessary to produce the requisite in- 
 duration differ with the various compounds in use, and, to 
 some extent, are influenced by the kind of vulcanizing ap- 
 paratuses employed and which present various modifications of 
 form and mechanism, being constructed, in part, with refer- 
 ence to the source and mode of application of the heat, the 
 former being derived either from coal or charcoal, or other 
 solid combustible substances, or from the flame of a spirit- 
 lamp, gas, or coal oil or some of its products. 
 
 As fuel is no longer employed in vulcanizing, any descrip- 
 tion of the apparatuses specially adapted to this mode of pro- 
 ducing heat is deemed unnecessary. They have been entirely 
 
VULCANITE BASE. 
 
 355 
 
 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. Fig. 139 represents one of Dr. Hayes's 
 Single Flask Iron-clad Ovens, convenient and compact in 
 form, and capable, it is claimed, of vulcanizing in 40 minutes 
 at a temperature of 320°, with one ounce of alcohol. Instru- 
 ments of similar construction are produced by the same manu- 
 
 Fm. 140. 
 
 Fig. 141. 
 
 facturer with a larger boiler capacity for from one to three 
 cases. Figs. 140, 141. 
 
 The iron-clad improvement in these machines is designed 
 as a protection from the dangers of explosion consequent upon 
 a gradual thinning of the copper boiler from corrosion, a safe- 
 guard 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, J 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 perfect safety, even when the copper has 
 become as thin as paper, and then, when an opening has been 
 fairly cat through, steam will escape from between it and the 
 
356 
 
 MECHANICAL DENTISTRY. 
 
 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 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 
 
 Fig. 142. 
 
 t^^tv/' 
 
 to happen when it is exposed to the steam itself, necessitating 
 its frequent replacement. 
 
 A not less convenient, safe, and reliable vulcanizer is that 
 known as Dr. Whitney's, represented in Fig. 142, having a 
 steam-chamber capacity for from one to three flasks. The 
 boiler is made of wrought copper ; the top or cap, which is 
 screwed on, being provided with a thermometer, and an aper- 
 ture filled with fusible metal, which renders explosion of the 
 boiler, unless materially weakened by corrosion, impossible. 
 The author has had one in constant use for many years with- 
 out any perceptible deterioration. 
 
 A well-approved instrument, called the " Buckeye Vulcan- 
 izer," invented by Dr. C. H. James, of Cincinnati, Ohio, is 
 
VULCANITE BASE. 
 
 357 
 
 exhibited in Fig. 143. The mechanism of this instrument is 
 remarkably simple and ingenious, the relation of the diiferent 
 parts being plainly exhibited in the accompanying cuts. The 
 top is very quickly and readily adjusted, and is clamped and 
 held securely in place, making a steam-tight joint, by a single 
 set-screw acting upon the centre of the cover. 
 
 The application of heat derived from coal oil and its prod- 
 ucts, for the purpose of vulcanizing, is shown by the accom- 
 
 FlG. 143. 
 
 panying cut (Fig. 144), which represents what is advertised 
 a.s "JIuWn Petroleum Gas Burner/^ and which the inventor 
 claims is "a lamp by which coal oil and its products can be 
 substituted for gas or alcohol for heating purposes. This ap- 
 paratus will burn Benzine with perfect safety, and with 
 greater heat than either gas or alcohol, and free from smoke. 
 The cut will show its adaptation for vulcanizing, and can be 
 
358 
 
 MECHANICAL DENTISTRY. 
 
 used for any other purpose. There is an attachment for a 
 compound blowpipe." 
 
 Whatever form of vulcanizing apparatus is used, or means 
 of heating adopted, the flasks are introduced and sufficient 
 water poured in to cover them. If the flasks are hot when 
 placed in the boiler, water of nearly the same temperature 
 should be added to avoid fracturing the teeth. Before screw- 
 ing on the cap, the rubber packing should be dusted with 
 whiting or pulverized soapstone to prevent adhesion. As it is 
 very important to secure a steam-tight joint, the packing should 
 be of uniform thickness, firm, and securely fixed. The webbed 
 rubber is the best for the purpose. In arranging a new pack- 
 ing, cleanse w^ell the groove in the boiler which receives the 
 rim of the cap, and fit the packing accurately. Before screw- 
 ing on the top, dust the surface of the packing as before recom- 
 mended, and as the heat rises tighten the screw from time to 
 time until the rubber no longer yields. If the latter precau- 
 
VULCANITE BASE. 359 
 
 tion is not observed, the packing is either liable to blow out or 
 the joint leak steam. To insure uniform results it is necessary 
 that there should be absolutely no leakage. 
 
 When the flasks are properly secured within the steam- 
 chamber, heat is applied and continued until the requisite in- 
 duration of the gum is effected. The time and degrees of heat 
 necessary to effect this result differ somewhat with the rubber 
 compounds and kind of vulcanizer employed. The heat should 
 be raised gradually until the thermometer indicates the proper 
 vulcanizing temperature, when the flame should be lowered, aud 
 the heat maintained at this point until vulcanization is com- 
 pleted. In all cases it is best to raise the heat slowly until it 
 reaches 320°, which temperature should not be attained in less 
 than from one-half to three-quarters of an hour. Where there 
 is any considerable or unusual body of rubber, the time taken 
 to raise the heat to that point should be extended to one hour 
 or longer, for if the mass is heated too rapidly, porosity or 
 sponginess of the thicker portions of the rubber will almost 
 certainly ensue. This result would seem to be due to the en- 
 ergetic evolution of sulphuretted hydrogen gas under a quick 
 heat, the proper elimination of which is checked and the gas 
 confined within the body of the mass by a too rapid surface 
 induration of the rubber. The evolution of this gas is demon- 
 strated by Professor Wildman in the following experiment : 
 
 " To ascertain if sulphuretted hydrogen is given off during 
 vulcanization, a bulb was blown at the end of a glass tube; 
 this was filled with red rubber; the tube was then drawn out 
 very small from immediately above the bulb, and curved so 
 that the small part when the bulb was in the paraffin bath 
 could be inserted into a vessel beside it. 
 
 "The bulb was then placed in a paraffin bath, and the curved 
 end of the tube inserted in a vessel containin"; a solution of 
 acetate of lead. The heat was raised to 320° F., and retained 
 at that point for one hour and a quarter. 
 
 "The mean result of several experiments conducted in this 
 manner was, that during the first thirty or forty minutes after 
 the heat had attained to 320°, bul)bles of sulphuretted hydro- 
 gen came over at short intervals, and at the expiration of 
 
360 MECHANICAL DENTISTEY. 
 
 this time it was evolved in a continuous stream, which con- 
 tinued for a few minutes, causing a copious precipitate of sul- 
 phide of lead. After this, until the expiration of the hour and 
 a quarter, the gas was only given ofiP sparingly at intervals. 
 This experiment gives us ocular demonstration that this gas 
 is evolved during vulcanization, and in large quantities, and 
 conclusively shows that in thick pieces, especially, the heat 
 should be slowly raised, and the rubber should be under strong 
 pressure to insure a successful result." 
 
 When the American Hard Rubber Company's red rubber 
 is used, the heat should be maintained at 320° for about one 
 hour and ten or twenty minutes. Induration may be effected 
 at a lower heat, but the time must be proportionally extended ; 
 or a higher heat being employed, a less time will be required 
 to vulcanize. With the use of the rubber mentioned, the 
 author has obtained good results by vulcanizing for 45 min- 
 utes at 340°. Care, however, should be taken not to over- 
 heat, as the rubber is thereby rendered dark and brittle, and 
 the important property of elasticity impaired. The time and 
 degrees of heat first mentioned, therefore, may be regarded as 
 the safest, and as yielding the best results, though with other 
 rubber compounds, and the use of modified forms of vulcanizers, 
 corresponding differences in time and temperature may be re- 
 quired, and which can only be accurately determined by vul- 
 canizing test-pieces of rubber. 
 
 In this connection the reader's attention is called to some 
 practical observations on the subject of steam pressure in vul- 
 canizing, 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. Professor 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 his end. It is perfectly safe ; 
 
 but the following will show him that it must be used with 
 
 * Instructions in Vulcanite, p. 26. 
 
VULCAXITE BASE. 3G1 
 
 discretion and judgment. Numerous experiments have been 
 made bv scientific men to ascertain the elastic force of steam 
 at diflerent temperatures. The results of their investigations 
 are not uniform ; although they all agree in showing the im- 
 mense force exerted by this agent at high temperatures. Has- 
 well's tables are looked upon as good authority. The results 
 of the investigations of the Franklin Institute Committee, in 
 the higher degrees, give a greater elastic force than the table 
 below quoted. I shall, however, quote the results of the ex- 
 periments 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 atmospheric 
 pressure as unity. 
 1 
 
 Temperature F. 
 212° 
 
 Pressure per square 
 inch, pounds. 
 14.7 
 
 u 
 
 233.96° 
 
 22.05 
 
 2 
 
 250.52° 
 
 29.4 
 
 2h 
 
 263.84° 
 
 36.75 
 
 3 
 
 275.18° 
 
 44.1 
 
 3} 
 
 285.08° 
 
 51.45 
 
 4 
 
 293.72° 
 
 58.8 
 
 4} 
 
 300.28° 
 
 66.15 
 
 5 
 
 307.05° 
 
 73.5 
 
 ol- 
 
 314.24° 
 
 80.85 
 
 6 
 
 320.36° 
 
 88.2 
 
 6} 
 
 326.26° 
 
 95.55 
 
 7 
 
 331.70° 
 
 102.9 
 
 7h 
 
 336.86° 
 
 110.85 
 
 8 
 
 341.78° 
 
 117.6 
 
 9 
 
 350.78° 
 
 132.3 
 
 10 
 
 358.88° 
 
 147 
 
 11 
 
 366.85° 
 
 161.7 
 
 12 
 
 374.00° 
 
 176.4 
 
 13 
 
 380.00° 
 
 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 
 
 418.40° 
 
 294 
 
362 MECHANICAL DENTISTRY. 
 
 " 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 
 taking steps as near fifty degrees as is given in the ascending 
 scale, we find this exemplified. Thus : 
 
 Increase of tempera- Increase of force per Giving a force per 
 
 ture. square inch. square inch. 
 
 From 212° to 263.84° = 51.85° 22.05 lbs. 36.75 lbs. 
 
 " 336.84 to 314.24° = 50.40° 44.10 lbs. 80.85 lbs. 
 
 " 314.24 to 366.85° = 52.61° 80.85 lbs. 161.85 lbs. 
 
 " 366.85 to 418.46° = 51.61° 132.15 lbs. 294 lbs. 
 
 " This comparison shows clearly how rapidly the pressure 
 increases 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 in- 
 crease of pressure, it must be borne in mind that at high tem- 
 peratures, 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 Associa- 
 tion, January, 1865, Dr. A. Lawrence affirms that "most 
 vulcanizers are now made of sheet copper one-sixteenth of an 
 inch in thickness, and, agreeably to the foregoing facts, have a 
 tensile strength of 1875 pounds; and one four inches in diame- 
 ter 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 pres- 
 sure 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 gauge connected with my own vulcan- 
 izer, and which I now use in preference to the thermometer, as 
 I consider it more convenient, safer, and less liable to accidents. 
 
VULCANITE BASE. 363 
 
 " Practical engineers concur in the opinion that a force of 
 not over one-half the sustaining capacity of the boiler can be 
 safely applied." 
 
 The logical deduction from these statements is plain. If a 
 boiler four inches in diameter, constructed of sheet copper one- 
 sixteenth of an inch thick, will not sustain a pressure of more 
 than 1 50 pounds per square inch, and, accepting as true what 
 is affirmed by practical engineers, " that a force of not over one- 
 half the sustaining capacity of the boiler can be safely applied," 
 then every operator who, with the use of such an instrument, 
 vulcanizes at a heat of 320° is in hourly jeopardy of life and 
 limb. 
 
 Intimately 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 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 indi- 
 cate 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 conclusion 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 
 bull), and the mystery was solval. But what force of steam 
 was produced during these almost despondent trials? 
 
 "Although my vulcanizer would safely bear a pressure of 
 one hundred pounds per square inch, I concluded to use a 
 steam gauge for the future, and now feel a security in its use 
 positi vely refresh i ng." 
 
 Tlie unreliability of thermometers, in connection with vul- 
 canizers, has been recognized by many in the profession who 
 liave testified to their uncertainty and insecurity as a means of 
 
364 MECHANICAL DENTISTRY. 
 
 determinins: with exactness at all times the amount of steam- 
 pressure employed in the process of vulcanizing at a high heat. 
 The steam gauge (Fig. 145), spoken of by Dr. L., seems very 
 perfectly to fulfil the requirements of the dentist, and may 
 justly claim favorable consideration from the commendation 
 bestowed upon it by tlie distinguished gentleman who has 
 brought it to the notice of the profession. The following is 
 the author's own account of the instrument : " The gauge most 
 suitable for the purpose in question, somewhat resembles a 
 small circular clock ; is about six inches in diameter and 
 marked to register one hundred and forty or one hundred and 
 eighty 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. The price of such a gauge, at this time, is |18 ; 
 and, though more expensive ones can unquestionably be made, 
 they are no more reliable, the difference consisting in mere 
 ' outward show and adorning.' 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 under the 
 gauge to receive the condensed steam, as water alone should 
 enter that instrument. 
 
 " The following table exhibits a range of pressure sufficient 
 for vulcanizing purposes, with the temperature necessary to 
 produce the same. 
 
 Pressure 
 
 Tempera- 
 
 Pressure 
 
 Tempera- 
 
 Pressure Tempcra- 
 
 Pressure 
 
 Tempera- 
 
 in lbs. 
 
 ture. 
 
 in lbs. 
 
 ture. 
 
 in lbs. 
 
 ture. 
 
 in lbs. 
 
 ture. 
 
 60 
 
 295° 
 
 69 
 
 305° 
 
 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° 
 
 110 
 
 339° 
 
 64 
 
 300° 
 
 73 
 
 309° 
 
 82 
 
 317° 
 
 115 
 
 342° 
 
 65 
 
 301° 
 
 74 
 
 310° 
 
 83 
 
 318° 
 
 120 
 
 345° 
 
 66 
 
 302° 
 
 75 
 
 311° 
 
 84 
 
 319° 
 
 125 
 
 349° 
 
 67 
 
 303° 
 
 76 
 
 312° 
 
 85 
 
 320° 
 
 130 
 
 352° 
 
 68 
 
 304° 
 
 77 
 
 313° 
 
 90 
 
 324° 
 
 
 
VULCANITE BASE. 
 
 365 
 
 " It will readily be seen by the above, that a pressure of 
 sixty pounds requires a temperature of two hundred and ninety- 
 five degrees by Fahrenheit's scale to produce it, and eighty- 
 five pounds three hundred and twenty degrees, at which latter 
 pressure I vulcanize, running one hour, and with the most 
 satisfactory results. 
 
 " The manner of putting up and using the gauge is very 
 simple. All that is required is to secure it, by screws passing 
 through the flange on the back, in some conspicuous and con- 
 venient place, attach a pipe and carry it down ten or twelve 
 inches, give it a bend or curve upward about half its length, 
 or five or six inches, thence at right angles or otherwise, and 
 in any convenient length not less than three feet, to the vul- 
 canizer. 
 
 " The annexed cut is from a photograph of a Whitney vul- 
 canizer with the gauge attached, but is by no means the only 
 
 Fig. 145. 
 
 arrangement which can be made, as, in some cases, convenience 
 may require more pipe, or a different distribution. 
 
 "A, table or work-bench; B, vulcanizer; C, side outlet 
 pendant cock screwed on in [)lace of the thermometer scale ; 
 D, cou[)ling joint; K, angle in the pipe; F, iron pipe, three- 
 sixtcentlis in.side; G, U-shaj)ed curve, five or six inches in 
 depth ; J I, cock to the gauge ; I, gauge. 
 
366 MECHANICAL DENTISTEY. 
 
 " The fitting, putting up and arranging the entire apparatus 
 can be done in an hour's time by any gasfitter, or^ to those 
 residing away from cities or towns where such mechanics are 
 employed, can be furnished to order by them, or by the parties 
 furnishing the gauge. 
 
 " All the joints, from the vulcanizer to the gauge, except 
 the coupling, should be ' leaded ' with very thick lead paint, 
 and screw together steam tig-ht. 
 
 " In using the apparatus, the cocks C and H must be turned 
 straight with the pipe, for if shut oif at either point, the gauge 
 cannot be acted upon by the steam. I generally heat the water 
 in the vulcanizer nearly or quite to the boiling-point, and let 
 oif the heated air by turning, or allowing to remain open, the 
 cock C, then connect at the coupling D, turning the nut tight 
 (not too tight) with a wrench. 
 
 " So soon as steam begins to form, it is condensed by con- 
 tact with the cold part of the pipe, and falls into and fills the 
 curve or coil with water, which is then forced into the gauge 
 with a power indicated by the pointer«on the dial. The pipe 
 should descend a trifle from the angle E to the commencement 
 of the curve, to facilitate the passage of the condensed steam to 
 that point. 
 
 " Although vulcanizing one hour at eighty-five pounds af- 
 fords results satisfactory to me, others may prefer a diiferent 
 time with more or less heat. 
 
 " The table will be found a guide in such cases. 
 
 " When the time is up, discontinue the fire, and shut oif 
 the steam by turning the cock C. Turn the cock H in the 
 same manner, to prevent a too sudden reverse movement of 
 the machinery of the gauge, the pressure on which should be 
 gradually relieved at any convenient time. 
 
 " Now disconnect by unscrewing the coupling and dispose 
 of the steam in the vulcanizer by blowing oif, or any other 
 means preferred. Further remarks would seem unnecessary 
 to a full understanding of the subject. Having used the gaiige 
 almost every day for about six months, I am fully satisfied 
 that it is a decided improvement in vulcanizing, and am so de- 
 
VULCANITE BASE. 
 
 367 
 
 liglited with it that no reasonable sum would induce me to 
 substitute the thermometer." 
 
 AVhen the process of vulcanizing has been conducted a suffi- 
 cient length of time, the flame is turned oif and the steam dis- 
 charged 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 vul- 
 canizer 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 temperature. Neither should the flask be opened while hot, 
 for the plate being pliable when heated, would be liable to suf- 
 fer 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 brueh. 
 
 Finishing. — The rougher and more redundant portions of 
 the indurated material are first removed with coarse files or 
 
 Fig. 146. 
 
 rasps, following with those of a finer cut until all parts of the 
 piece accessible to such instruments arc reduced to nearly the 
 thickness required. The excess of material on tiie lingual side 
 of the plate and other points not admitting of the use of the 
 
368 MECHANICAL 'dENTISTEY. 
 
 file, is removed with scrapers of various forms, some of which 
 are shown in Fig. 146. 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 
 sandpaper, using first the coarser and finishing with the finer 
 kinds. The final polish is then given to the surface, first with 
 the use of finely pulverized pumicestone, and afterwards with 
 either prepared chalk or whiting. The best method of apply- 
 ing 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 satu- 
 rated with cold water throughout the operation. 
 
 Partial Dentures Constructed in a Base of Rubber. — The 
 foregoing description of the method of forming entire dentures 
 in a base of indurated gums, together with a knowledge of the 
 manner of constructing 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 
 gutta-percha plate of the required thickness and dimensions is 
 accurately moulded to a model of the parts, the narrower por- 
 tions passing into the spaces between the teeth being stiffened 
 by doubling the plate at these points with an additional strip 
 of gutta-percha warmed at the lamp and made to adhere to 
 the primary plate. The central portion of the plate may also 
 be temporarily supported, and its form preserved, by filling 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 articu- 
 lating 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 man- 
 
VULCANITE BASE. 369 
 
 ner as when metallic plates are used, and the wax trimmed to 
 the required fulness. The plate, with the teeth attached, is 
 then placed in the mouth and any necessary 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- 
 portance, when forming the mould, 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 mould 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 
 fulness, 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 mould, 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- 
 mospheric pressure should be made available in all practicable 
 cases as a means of retaining parts of sets of teeth in the mouth, 
 yet cases occasionally present themselves necessitating the 
 employment of clasps. These may be of rubber, but those 
 formed of gold, or gold alloyed with platina, are more reliable, 
 and better adapted to those cases where the spaces between the 
 teeth are contracted. The following description of the method 
 of constructing them is given by Professor Wild man.* 
 
 "First bend the clasp to fit the tooth accurately; 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 platina 
 
 * Instructions in Vulcanite, p. 3G. 
 24 
 
370 MECHANICAL DENTISTRY. 
 
 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. 147). This 
 plate entering the base, the rubber tilling the holes forms pins 
 which rivet the clasp securely to the rubber plate. 
 
 " Or the attachment may be made in this manner : On the 
 parts 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. 148) ; 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 perfo- 
 rated plate of being more easily manipulated, and less liable to 
 become displaced in packing the mould. The clasp is to be 
 
 Fig. 147. Fig. 148. 
 
 attached to the model plate, and will remain secured in the 
 mould when it is opened." 
 
 A metallic clasp may also be very securely attached to the 
 rubber by drilling a number of holes in that part of the clasp 
 Avhich lies in contact with the rubber, and countersinking them 
 well on the inside of the clasp. 
 
 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 platina pins, forming a loop or staple (Fig. 149), 
 and which imbedded in the rubber, renders the attachment 
 very secure. A narrow arm of rubber extending to a single 
 tooth may be materially strengthened by permitting the gold 
 strip, perforated with holes or roughened on its edges, to pass 
 some distance into the rubber as seen in Fig. 150. 
 
VITLCAXITE BASE. 371 
 
 Instead of forming a loop or staple as mentioned, it will be 
 preferable in many cases to solder to the tooth a somewhat 
 wider strip than that represented, in the same manner as ordi- 
 narily practiced in backing for gold work, the strip being 
 strengthened by flowing solder at the angle of divergence from 
 the heel of the tooth, and extending thence into the body of 
 the rubber, perforated or roughened on the edges as before 
 recommended. The rubber in this case may be cut away, when 
 finishing, to the angle, leaving nothing but the strip of gold and 
 sub-linino; of rubber at the base of the tooth. This method 
 may be resorted to with signal advantage in those cases where, 
 
 Fig. 149. Fig. 150. 
 
 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 as thinly formed 
 throughout 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 fulness to compensate for 
 waste in finishing. All portions of the piece except the lin- 
 gual face of the plate and teetli are then imbedded in plaster 
 in the lower section of the flask. The upper section of the 
 mould is obtained in the usual way. AV^hen separated and all 
 traces of wax removed, the gum is packed into the cavity 
 around the tooth or teeth. Grooves are then cut extending 
 out from the mould ; the two sections heated and forced to- 
 gether, and the process of vulcanizing conducted in the usual 
 manner, the same time and degrees of heat being required as 
 
372 MECHANICAL DENTISTRY. 
 
 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. 
 
 Refitting Gold or Rubber Plates with Rubber Lining. — Gold 
 or rubber plates, whose adaptation to the mouth has become 
 impaired, in a greater or less degree, by subsequent absorption 
 of the alveolar ridge, may be easily refitted and the adaptation 
 restored by either of the following methods : 
 
 First Method. — Take, for example, a full upper set on 
 either gold or vulcanite. Secure, in the first place, an accu- 
 rate impression of the mouth, in its changed condition, in 
 plaster, and from this a plaster model in the manner usually 
 practiced. Perforate the palatal portion of the plate with 
 from eight to twelve holes at different points, and also the ex- 
 ternal borders, from heel to heel of the plate, at intervals of 
 from one-eighth to half an inch apart, and near the edges. 
 These holes may be enlarged to the dimensions of a medium- 
 sized knitting-needle;, or if the piece is of vulcanite, to twice 
 or three times that size. On the lingual and buccal surfaces 
 the holes are well countersunk with a burr drill. The plaster 
 model, with the central portion raised to form a chamber (and 
 which should be made to correspond, as nearly as possible, in 
 position, form, and thickness, with the chamber in the plate, 
 if one exists), is next heated throughout by placing it over a 
 spirit-flame, or in the baking furnace of an ordinary cooking 
 stove, or the muffle of a furnace, and when of a temperature 
 that will barely admit of being taken in the hand, remove and 
 cover the face of it with a sheet of india-rubber or gutta- 
 percha as prepared for vulcanite work, and press it down upon 
 the face of the model with the fingers. Apply the perforated 
 plate to the model, being careful to secure a proper relation of 
 
VULCANITE BASE. 373 
 
 the two ; then press the former down firmly upon the model. 
 To render the vulcanite material still more plastic and com- 
 pressible, the whole may now be returned to the furnace, and 
 subjected to a uniform heat throughout, when it may be re- 
 moved, and firm and steady pressure made upon the plate and 
 teeth, until forced, as nearly as practicable, into contact with 
 the face of the model. Portions of gum will be forced through 
 the apertures and out at the borders of the plate ; these should 
 be well packed into the countersinks and under the edges of 
 the plate, when the model, with the rubber and plate adherent, 
 may be placed in a vulcanizing flask and incased bodily in 
 plaster. It is tlien placed in a heater and vulcanized. If all 
 the steps in the process have been carefully conducted, the fit 
 of the plate will be perfectly restored, with no material change 
 in the antagonism, or none, at least, that is not susceptible of 
 ready correction. The union between the vulcanite lining and 
 the plate will be strong and lasting, and altogether imperme- 
 able to the fluids of the mouth. 
 
 In the case of lower pieces, the holes should be made along 
 the external and internal borders of the plate near the margins. 
 In all other respects the manipulations are the same as those 
 described above. 
 
 It is scarcely necessary to observe that, in the use of gold 
 plates, the method is inapplicable whenever it is designed to 
 re-swage the same plate for the permanent piece. 
 
 Second Method. — Perforate the plate, whether of gold, silver, 
 or vulcanite, as before directed ; and employing this as a cup 
 or holder, take an impression of the mouth in plaster, pressing 
 the plate up closely to the parts. The plaster forced through 
 the holes, and filling the countersinks on the opposite side of 
 the plate, will serve to bind the plaster to the plate,' and pre- 
 vent, with cautious manipulation, the two from separating as 
 they are being detached from the mouth. When removed, the 
 piaster impression lining the plate is trimmed even with the 
 borders of the latter, and then varnished and oiled. The lower 
 section of a vulcanizing flask is now filled with a batter of 
 plafiter on a level with its upper surface, and the impression, 
 
374 MECHANICAL, DENTISTRY. 
 
 filled with the same, is turned over and placed in the centre of 
 the flask, with the edges of the plate touching the surface of the 
 plaster. The plate and adhering plaster are now carefully 
 separated from the model. After cutting out the plaster from 
 the holes and countersinks in the plate, the plaster forming the 
 impression is detached from the plate, and the holes and coun- 
 tersinks filled with wax. The plate is then readjusted over 
 the model, and (the surrounding surface of the plaster in tlie 
 flask liaving been varnished and oiled) plaster is poured in 
 upon the upper surface of the plate and teeth, filling the upper 
 ring. When the plaster is sufliciently hard, the two sections 
 of the flask are separated, and grooves formed, running out 
 from the matrix to the margins of the flask. A sufficient 
 quantity of vulcanizable rubber is now either placed upon the 
 model or packed in upon the palatal surface of the plate — 
 before doing which, however, the Avax filling the holes and 
 countersinks in the plate (and which was placed there to pre- 
 vent portions of plaster last poured, in forming the matrix, 
 from running in and filling them up) should be worked out 
 with a small instrument. The whole being sufficiently heated, 
 the two sections of the flask are forced together, expelling re- 
 dundant material. The piece is then vulcanized as in the 
 former case. 
 
 The above method, though somewhat more complicated than 
 the former, is quite simple in its details, and will occupy but 
 little more time, and is, withal, more certain in its results. 
 
 Manner of Duplicating Sets of Teeth Mounted on Rubber. — 
 When from accident, or other causes, a rubber set becomes 
 broken, or its integrity otherwise impaired, necessitating an 
 entirely ilew plate with an exact reproduction of the arrange- 
 ment and* articulation of the teeth, the following method, de- 
 scribed by Professor Wildman, may be pursued with an absolute 
 certainty of success. " Roughen the palatal surface of the rubber, 
 to cause the plaster to adhere to it ; then use it as an impression- 
 cup to take a plaster impression, being careful when it is in the 
 mouth to preserve the articulation. In this impression, cast the 
 model, trim, cut keys or conical holes at several points in its outer 
 
VULCANITE :base. 375 
 
 face, Xow, before separating the impression from the model, 
 make a cast of the face of the teeth in two or three perpendicular 
 section?, extending to the base of the model, using a solution of 
 soap or other parting substance on the plaster mould. Remove 
 this mould of the face of the teeth, which indicates their true 
 position relative to the model ; then take the impression from 
 the model. By the aid of heat sufficient to soften the rubber, 
 remove the teeth from it. Next make a model plate with pre- 
 pared gutta-perclia. Now secure the section of the mould of 
 the face of the teeth to the model (their place will be indicated 
 by the keys); adjust the teeth to their proper positions in the 
 plaster mould of them, and build up with gutta-percha or wax 
 to the proper form of the model set. This being done, test its 
 accuracy of contour and articulation by placing it in the mouth. 
 Then, using the model, proceed as for making a new set." 
 
 It will be observed that the above process contemplates the 
 necessity of the patient's presence to secure, in the first instance, 
 an impression of the mouth, and again for a trial of the teeth 
 in the mouth to test the accuracy of arrangement, etc. This 
 procedure is rendered necessary in all cases of faulty adapta- 
 tion of the primary plate, but where the adaptation is satisfac- 
 tory, and it is desired to construct a duplicate set in all respects 
 precisely like the original, the following method, in the main 
 the same as the one just described, may be adopted in the 
 absence of the patient. Oil, or coat with a solution of soap, 
 the palatal surface of the plate to be duplicated ; into this pour 
 plaster for the model ; trim to the edges of the plate, and give 
 the usual form to the body of the model; form conical holes 
 in the same and secure sectional moulds of the outer faces of 
 the teeth in the manner described by Professor Wildman. 
 When hard, remove these se( tlons and detach the model from 
 the plate. Many cases will admit of a ready separation ; in 
 others it will be found impossible to force them apart without 
 fracturing the model. To avoid such an accident, the model 
 may Ijc ciust in sections, the latter being bound together after- 
 wards in their proper relation to each other. But a better 
 ])lan is to heat the model and plate sufficiently to render 
 
376 MECHANICAL DENTISTRY. 
 
 the rubber soft and pliant enough to be removed without 
 injury to the model. Cases not admitting of the successful 
 application of either of these expedients must be treated in the 
 manner described by Professor Wildman, that is, by securing 
 an impression of the mouth. After the separation of the 
 model and plate, the manner of conducting the subsequent 
 steps of the operation is precisely the same as that described in 
 the preceding method. The author has adopted the above pro- 
 cess in a number of instances with the most gratifying success 
 in cases of defects or accidents to the original plate, and where 
 the presence of the patient could not be conveniently com- 
 manded. 
 
CELLULOID BASE. 377 
 
 CHAPTER XV. 
 Celluloid Base. 
 
 The employment of celluloid in prosthetic dentistry, though 
 of recent date, and notwithstanding the very general failure 
 ■which attended its first introduction into practice, is rapidly 
 acquiring very general professional favor as a cheap, conve- 
 nient, and serviceable base for artificial dentures. With the 
 more recent improvements in the manufacture and seasoning 
 of blanks, more perfectly adapted appliances for moulding, 
 and a more extended acquaintance with the peculiar and dis- 
 tinctive characteristics of this material, it promises, in the 
 near future, to supersede in a great measure all other known 
 plastic substances for the purpose indicated. 
 
 That celluloid possesses many important qualities M'hich 
 commend its employment as a base in preference to rubber can 
 hardly be questioned. It is more in harmony w^th the soft 
 tissues of the mouth, more cohesive in texture, fig- i^i 
 
 approximates more nearly the natural gum 
 color, contains far less vermilion pigment in 
 its composition, and is less objectionable by 
 reason of the comparative cleanliness accom- 
 panying its manipulation. 
 
 The chief objection urged against celluloid as a base is its 
 low ])Ower of transmitting caloric, but it is believed to be less 
 objectionable in this respect than rubber. Both are poor con- 
 ductors, and the soft tissues of the mouth in contact with either 
 suffer, in some degree, as a consequence of this property. To 
 obviate, to some extent at least, this objectionable feature of 
 both rubber and celluloid, Dr. S. C. Carter has devised and 
 recommended what is termed " palate coolers," consisting of a 
 
378 MECHANICAL DENTISTEY. 
 
 central plate of either gold, platinum, or aluminum, dove- 
 tailed into the rubber or celluloid, and represented in Fig. 151. 
 
 Celluloid, as at present produced, and when properly ma- 
 nipulated, does not, in any appreciable degree, undergo change 
 of form after moulding by warping either in or out of the 
 mouth, as was formerly the case, nor, it is believed, does it 
 absorb the oral secretions. It loses somewhat the freshness 
 and clearness of its original pink color after having been in 
 use for some time, but not in any very marked degree. 
 
 Though not bearing so perfect a resemblance to the com- 
 plexion 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 connection with rubber has, it may be 
 safely affirmed, 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 requirements 
 of special cases in respect to expression, articulation, and an- 
 tagonism is one of the absolute and indispensable requirements 
 of a perfect artificial denture. A more general recognition of 
 this important fact must, sooner or later, lead to the entire 
 abandonment of rubber in connection with " ready-made " 
 sectional gum teeth. " Taking into view all its qualities," says 
 a well-known writer, " and leaving out the question of freedom 
 from monopolies, the conclusion is that celluloid has the 
 potentialities which should dethrone rubber, and establish itself 
 as the best of the cheap bases." 
 
 Composition and Manufacture. — The following is the sub- 
 stance of Professor Charles J. Essig's account of the composition 
 and manufacture of celluloid : 
 
 Celluloid is derived from cellulose, a woody fibre, constitut- 
 ing the framework or foundation of j)lants. 
 
 Linen, cotton-wool, hemp, etc., are examples of cellulose. 
 For the manufacture of celluloid, the cellulose is first converted 
 
CELLULOID BASE. 379 
 
 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 
 undergoes a physical change only, while chemically it remains 
 the same, viz., nearly pure cellulose, and has a formula of 
 CgHioOj. The cellulose, now in the form of hemp-paper, is 
 converted into pyroxylin by a process technically known as 
 "conversion," this change being effected by immersing the 
 hemppaper 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 its weight will be 
 found to have increased about seventy 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, 100 parts 
 
 Camphor, . . . ' 40 " 
 
 Oxide of zinc, 2 ' 
 
 Vermilion, .' 0.6 
 
 Some alcohol is used to soften the camphor. The mass is 
 now put under a hydraulic pressure of two thousand 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 cellu- 
 loid, and as it is forced out it is cut off in pieces of the proper 
 size, and moulded 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 ai)out two months, during- which 
 time they are kept in a room at a temperature of 1G0° F. 
 
380 MECHANICAL DENTISTEY. 
 
 Processes Preliminary to Moulding. 
 
 While many of the processes entering into the construction 
 of artificial dentures, with celluloid as a base, are essentially 
 the same as those required when rubber is used, yet there are, 
 in many important respects, modifications of practice made 
 necessary by the peculiar nature and behavior of the material 
 employed. 
 
 When the distinctive characteristics of celluloid are well 
 understood, and the operator is familiar with the approved 
 methods of working it, no unusual difficulties attend its success- 
 ful manipulation. To attain uniform and satisfactory results, 
 however, it is absolutely necessary that there should be a faith- 
 ful compliance with every manipulative detail, however seem- 
 ingly unimportant, which experience in the use of this substalice 
 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 mould it into, 
 any given form, makes it necessary to give to the plaster model 
 the greatest practicable hardness and strength. To secure these 
 important 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. In- 
 creased hardness will be secured by adding to the plaster mix- 
 ture 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 
 air-bubbles by tapping or shaking the impression-tray as the 
 plaster flows in. 
 
 In cases where there is any considerable anterior projection 
 
CELLULOID BASE. 381 
 
 of the alveolar ridge in front, above or below, the correspond- 
 ing portion of tlie plaster model is liable to be crushed under 
 the pressure necessary to mould 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 im- 
 pression a curved piece of brass plate punched full of holes, 
 one-half or three-fourths 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. 
 
 In extreme cases, where the ridge is very thin and the pro- 
 jection spoken of excessive, it may be necessary 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. 
 
 Waxing. — After having arranged the teeth for any given 
 case, place them with the trial plate on the model, and build 
 out with wax to the required form, but a little in excess of the 
 fulness necessary in the finished piece. Care should be taken 
 that the palatal portion should be somewhat thinner than the 
 blank to be used. Clean, pure wax should always be used in 
 preparing a case for flasking, as it will be necessary some- 
 times to free the mould of adhering and inaccessible portions 
 with boiling water, in which case, if there are impurities in 
 the wax, sedimentary particles will be left in the mould and 
 become incorporated with the celluloid in the process of 
 moulding. 
 
 Investing. — The piece prepared as above is then placed in a 
 flask especially designed for ceHuloid, invested in plaster, and 
 the mould or matrix formed in the same manner as practiced 
 when rubber is used. In case the ridge overhangs, to which 
 the term " under-cut " is applied, the model, before being 
 incased in the flask, should be cut across diagonally with the 
 slope towards the heel of the model, thus depressing the latter 
 
382 
 
 MECHANICAL DENTISTRY. 
 
 posteriorly, as exhibited in Fig. 152. By this means the pro- 
 jecting portion of the ridge will be brought more directly in a 
 line Avith 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 model for the want of adequate lateral sup- 
 port, but of displacement of the teeth by being forced into the 
 plaster. So important is the right condition and manipula- 
 tion of plaster in the use of celluloid that the author feels war- 
 
 FlG. 152. 
 
 ranted in adding, to what has already been said in this connec- 
 tion, 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 convenient, 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 under- 
 stand how to mix plaster so as to get the greatest strength and 
 resistance to pressure. The proper way to mix plaster for 
 both models and filling flasks is as follows: First, stir up 
 some 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 
 
CELLULOID BASE. 383 
 
 much plaster can be stirred in after the first is poured out, and 
 also how a thick 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 afterwards added, 
 into all the crevices, and most of it will escajie from the flask, 
 leaving a body of solid, resisting plaster that cannot be ob- 
 tained by the ordinary method of mixing." 
 
 AVhen the piece is incased, and the plaster has sufficiently 
 hardened, the two sections 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 wxix by too great or 
 long-coiitinued heat. 
 
 When the flask is separated, all portions of wax or other 
 material should be carefully and thoroughly removed from 
 the mould, 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 wel^ 
 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 celluloid in 
 moulding. AVhen this is done, put the flask together and see 
 if there is ample room for the " jiose" of the model to pass the 
 edge of the matrix. 
 
 To permit the escape of surplus material in moulding, either 
 of the following plans may be adopted : 1. Cut two concen- 
 tric grooves in tlie plaster of the upper or lower section com- 
 pletely encircling the matrix, the inner one not less than one- 
 fourth or one-sixth of an inch from the mary-in of the mould, 
 and the other at the border of the flask, the inner side of the 
 latter forming a part of the outer groove. 2, Bevel the plaster 
 around the jnould, commencing about one-fourth of an inch 
 from the margins of the latter and extending it to the sides of 
 the flask. 3. (Jut cone-shaped cross or radiating grooves from 
 
384 MECHANICAL DENTISTEY. 
 
 the inner circular gutter to the margins of the flask, — shallow 
 where they connect with the circular groove, and deepening 
 and widening towards the edges of the flask. 
 
 In no case should cross grooves be made communicating 
 with the matrix, as these aiford too ready an exit for surplus 
 material, and prevent that " back pressure " so essential to a 
 complete and compact filling of the mould. The grooves 
 should be deep and ample enough to receive all surplus, other- 
 wise it will be diflicult if not impossible to close the flask per- 
 fectly. In the use of gum teeth, holes may be drilled in the 
 matrix inside tlie teeth, opposite each joint, not over an eighth 
 of an inch in diameter, and as deep as it may be deemed neces- 
 sary. These act as waste gates, and relieve the blocks from 
 pressure. 
 
 Selection and Preparation of the Celluloid Plate or Blank. — 
 The mould having been prepared in the manner described, a 
 suitable blank should be selected, and, as it is important that 
 this should be, as nearly as possible, the size and general form 
 of the mould, 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 intermix 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 pres- 
 sure, 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 mould perfectly, with some 
 slight excess, and the central portion should always be some- 
 what thicker than the corresponding part of the trial or pattern 
 plate. 
 
 As celluloid cannot be depended on to flow from one part of 
 the mould to another, it is important that there should not only 
 be an excess of material, but that this excess should be, as 
 
CELLULOID BASE. 385 
 
 nearly as practicable, distributed throughout all portions of the 
 matrix. A neglect of this precaution will result either in an 
 imperfect filling of the mould in some places, and consequent 
 defect of the plate, or a porous condition of the celluloid will 
 be found wherever the material, though apparently filling the 
 mould, has not been impacted with sufficient force. 
 
 The selected blank should be conformed as nearly as pos- 
 sible to the shape of the mould 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 fulness 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 neces- 
 sary in any given case may be obtained by measurement, the 
 simplest method being by the use of the Starr instrument, 
 illustrated in the chapter on Vulcanite. It must be remembered, 
 however, that this device onlv determines the ago-regate 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 correspond with the capacity of the mould. 
 
 A more reliable, though somewhat tedious, method of secur- 
 ing exactness in the quantity and distribution of material nec- 
 essary, and which acquires special value in cases where there 
 Ls unusual danger of fracture of the model or teeth, and espe- 
 cially of the latter when gum teeth are used and these are 
 ground very thin, is the following, given by a correspondent 
 of the Cosmos : " After preparing the case ready to flask, 
 remove the teeth from the pattern ; stop the pin-holes, then 
 remove the pattern and carefully flask it. When the mould is 
 ready, remove all the wax or material of the pattern; place 
 the celluloid ' blank ;' api)]y heat, and cast the same as if for 
 final case. Remove the flask from the heater; ])]ace 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 
 
 25 
 
386 MECHANICAL DENTISTRY. 
 
 comes out thicker). Now you have a blank with but little ex- 
 cess; only what the vacuum and pins displace, or slightly 
 more, and exactly the shape of the pattern, minus the teeth. 
 Now 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 mould 
 slightly, which will be all that is needed. Replace the blank ; 
 apply heat, when but moderate pressure will be found neces- 
 sary to bring the flask entirely together. If dry heat is pre- 
 ferred, dip the edges of the blank to come in contact with the 
 pins in spirit of camphor for a few minutes before casting." 
 
 Before the blank is placed in the flask preparatory to mould- 
 ing, some provision should be made against adhesion of the plas- 
 ter 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 collodion or liquid silex, or by rubbing the surfaces well 
 with French chalk, or powdered soapstone ; or a layer of tin 
 foil may be interposed between the model and blank. The fol- 
 lowing novel method of coating the surface of the model with 
 tin is recommended by Charles P. Alker, of Bordeaux, France : 
 " Reduce ordinary collodion with about three times its bulk of 
 ether, and add powdered tin until the solution is well impreg- 
 nated with the metal. The tin is the same that is sometimes 
 used for coating plaster images. When properly mixed and ap- 
 plied 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 read- 
 ily cleansed with a coarse brush, and presents the appearance 
 of having been made in a metallic mould." 
 
 The case, as thus described, is now ready for moulding. 
 
 Moulding. — The various machines or heaters now generally 
 employed in moulding celluloid into dental plates contemplate 
 the use of either hot moist air, glycerin, or steam for the pur- 
 pose of producing the requisite plasticity of the material sub- 
 jected to pressure. There is considerable diversity in the form 
 and construction of heaters designed to utilize these several 
 sources of heat, as well as differences in the modes of applying 
 
CELLULOID BASE. 
 
 387 
 
 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 2Ioist Air (so-called "Dry Heat") Maekines.—ln the 
 use of these heaters, the water with which the plaster is im- 
 
 pregnated is relied upon to produce the steam necessary to carry 
 off all excess of camphor from the celluloid in the process of 
 moulding. An easential point by this method is to have the 
 plaster in the flask thoroughly wet, and this may be better at- 
 tained 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 sn)all quantity of water may be introduced 
 into the tank before applying lieat. 
 
 Fig. 153 represents a moulding or packing machine of the 
 
388 MECHANICAL DENTISTRY. 
 
 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 are pierced with holes, to allow 
 a circulation through the chamber, for the purpose of carry- 
 ing 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 flask. 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. 153, which gives a pure, blue flame without 
 smoke, may be used. If gas cannot be commanded, however, 
 any of the alcohol or kerosene 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. 154, and its construction in 
 detail shown in sectional diagram. Fig. 155, will be found 
 convenient and efficient. 
 
 Having applied the heat, it is of the first importance that 
 unremitting attention should be given to the process of mould- 
 ing until it is completed. If pressure is applied before the 
 celluloid is rendered somewhat plastic, or too great force is ex- 
 erted during the earlier stages of the process, and without suf- 
 
 * Among other approved machines, applicable to the so-called " dry heat " 
 process, may be mentioned " Brown's " and " Hays's " celluloid apparatus, 
 provided with screw-bolts similar to the " Best," the Hays heater being 
 used in connection with the Hays or Whitney boiler ; the " Hindsman 
 Heater ;" a " Celluloid Press " manufactured by Spencer and Crocker, of 
 Cincinnati, and doubtless others with which the author is unacquainted. 
 All of these, except the "Hindsman" Heater, are adapted to either dry 
 heat or glycerin. 
 
CELLULOID BASE. 
 
 389 
 
 fiolent intervals of rest, there is danger of crushing or fractur- 
 ino" the model, and of impairing the articulation by displace- 
 ment of the teeth. On the other hand, the nature of celluloid 
 is such that if it is exposed to a temperature of 270°, without 
 beino- under pressure, the camphor evaporates, and the material, 
 besides being rendered hard and intractable, is puiFed 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 
 
 Fig. 154, 
 
 Fig. 1.55. 
 
 /i^iCiO^ 
 
 A. Reservoir, made of gal- 
 vanized Iron. B. Top of reser- 
 voir. C. Chimneys. D. Drum. 
 E, Hanging panilion, which 
 keeps the radiated heat from 
 reservoir. F. Principal air 
 deflectors. H. Supplementary 
 air deflectors. T. Tank sur- 
 rounding VFick tube. R. Per- 
 forated ring through which 
 all the air that supplies the . 
 stove passes. W. Wick cham. 
 bar. X. Wick tubes. 
 
 first, with no more force than can be readily exerted with the 
 thumb and finger. As the heat increases, and the celluloid be- 
 comes more and more phistic and yielding, the pressure should be 
 correspondingly 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 require<J in any case untilnearthecloseof the operation, 
 
390 MECHANICAL, DENTISTEY. 
 
 when the mould 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. 
 
 During the progress of the moulding, the flask should be 
 withdrawn 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 cor- 
 rect the faulty approximation. No difficulty will be experi- 
 enced 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 
 instance should the flask be removed from the clamp (unless 
 securely locked, as is practicable with the "standard" flask),* 
 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 seasoning is advisable, and the flask should be placed 
 near a stove or over a register (keeping it closed by a clamp, or 
 by an instrument or j)iece 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 warp- 
 ing plates will be experienced. 
 
 Moulding in Glycerin. — Glycerin, as a medium of impart- 
 ing heat in the process of moulding celluloid, has almost 
 entirely superseded the use of oil, paraffin, and other allied 
 substances originally employed. It is a favorite method with 
 many leading practitioners, and is recommended by the manu- 
 facturers of celluloid as superior to any other. The long and 
 familiar acquaintance of these parties with the composition, 
 nature, behavior, and treatment of the material they produce, 
 entitles their opinions and preferences to more than ordinary 
 consideration. 
 
 * Manufactured by the Celluloid Company, and represented in Fig. 156. 
 
CELLULOID BASE. 
 
 391 
 
 The improved glycerin apparatus manufactured by them is 
 exhibited in Fig. 156 ; consisting of a tank A for containing 
 the glycerin ; a stand S with detachable legs L, which slip into 
 slots as shown at S ; an alcohol cup shown at K in sectional 
 diagram of steam machine, Fig. 158 ; a screw clamp B ; a flask 
 C ; and a thermometer D to indicate the heat. 
 
 Either alcoliol or gas may be used with this machine. When 
 kerosene is employed, the manufacturers recommend the use of 
 the " leader " oil stove, which will be seen attached to the 
 "steam" apparatus, Fig. 157. When this stove is used, the 
 
 Fig. 156. 
 
 lono- lef'S of the steam machine must be substituted for the 
 shorter ones represented in Fig. 156. 
 
 Having placed the blank in the flask, put the latter into the 
 screw clamp and turn down the screw until it touciics the flask 
 lightly; set the whole into the tank and pour enough glycerin 
 into the latter to come up to about the top of the flask. Apply 
 heat, aii<l prof;eed with the moulding in the same manner as 
 described in coiniection with the " dry heat" method. The heat 
 should not be permitted to rise much above 280°. If the flask 
 
392 
 
 MECHANICAL, DENTISTEY. 
 
 is not closed when that heat is reached, reduce the flame, and do 
 not hasten the closing. A little practice will enable the operator 
 to graduate the pressure exactly, without reference to the 
 thermometer. 
 
 Moulding in Steam. — The best adapted apparatus where 
 steam is used in moulding is that manufactured by the Celluloid 
 
 Fig. 15.7 
 
 Steam Apparatus, with Improved Stand and Long Legs, adapted to "Leader" Oil Stove 
 
 Company, and represented in Fig. 157. A sectional diagram of 
 the same is shown in Fig. 158. It consists of the following 
 parts: (The same letters represent the same parts in both cuts) ; 
 the base, or standard, J (now made with detachable legs, as in 
 cut of glycerin machine) ; the boiler B ; the cover D, to which 
 is attached the safety valve, H ; the plunger, E, and alcohol 
 
CELLtTLdlD BASE. 
 
 393 
 
 cup, Iv (shown only in the sectional diagram below) ; the 
 screw, F, for closing the flask, operated by the handle, L; 
 the gland or packing ring, G, the object of which is simply to 
 prevent the steam from leaking around the screw ; and the 
 wrench or spanner, S. 
 
 Fig. 158. 
 
 SecUoual Diagram. 
 M and N, in the sectional drawing, represent steam packing, to make the boiler tight. 
 
 The stand is the same as that for the glycerin machine shown 
 in Fig. 156, and is furnished with short legs, as shown in that 
 cut (for alcohol or gas), or long legs as above, as desired. To 
 u.se the old .steam machine with the "Leader " stove, it is neces- 
 sary to order only the improved stand with long legs. The 
 company send always the short legs unless otiierwise ordered. 
 
 In using the steam machine, care should be taken to keep it 
 
394 MECHANICAL DEJSTTISTEY. 
 
 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 tightened. Bear in mind that turning 
 this gland merely prevents the escape of steam, and does not affect 
 the p)ressure on the flash. 
 
 The safety-valve should be kept free from gum, and if either 
 it or the screw is fouled, it should be well cleansed with kero- 
 sene. This valve, in the machine now sold, is so constructed 
 that it blows oif 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 poiut, it is impossible to hum 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 at once reduced by 
 blowing oif steam as soon as the moulding is completed. The 
 first machines were constructed with the safety-valve much 
 heavier, and all in one piece, and were adjusted to a tempera- 
 ture of nearly 300°, which was higher than necessary or ad- 
 visable. 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 be easily done by removing a little 
 wire which passes through the stem and weight. A modern 
 valve will be furnished when ordered. When moulding, 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. 
 
CELLULOID BASE. 395 
 
 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 flask in position, turn down the screw verij 
 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 ofl" 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 moulding. 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 
 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 carefully, stopping when you feel the resistance in- 
 crease ; as soon as it yields again, turn it more, going slowly 
 and carefully at first, but increasing the pressure somewhat as 
 the steam gets u]), which you will know by occasionally rais- 
 ing the valve. It is just here that judgment is required, to 
 avoid, on the one hand, too mu(;h pressure before the material 
 is suHificntly 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. 
 
39g MECHANICAL DENTISTRY. 
 
 which would result in injuring the quality of the material. 
 The pressure should be followed up as the heat rises and the 
 sci'ew yields, the object being to get the whole of the plate 
 under pressure, in every part of the mould, by the time the 
 steam blows oif 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 flow- 
 ing celluloid to escape from under the pressure. Toward the 
 close of the process, the pressure should be considerable ; in 
 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 steam will blow off 
 at the safety-valve at about the time the moulding is completed, 
 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 moulding, 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 condi- 
 tion ensue or the plate be ruined, while the safety-valve would 
 not indicate 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. 
 
 Repairing. — This is very easily and satisfactorily accom- 
 plished. Cut away the plate, and fit in the new teeth or 
 block. Dovetails or holes may be made, but they are unnec- 
 essary. Always, if possible, before flasking, fit a new piece, 
 much larger than the portion cut away, to the plate as closely 
 as possible, and let it come as close as possible to the added 
 te»th ; then, having the surfaces clean, cement it fast with 
 spirits of camphor, or a solution of celluloid and camphor. 
 Allow it to dry, after which the new teeth should be waxed 
 into place. Invest the piece in the flask, covering the whole 
 
CELLULOID BASE. 
 
 397 
 
 plate and teeth in the plaster, except the added piece, Avhich 
 should be left at the bottom of a well or depression in the 
 plaster. 
 
 The above cut will show the manner of repairing, and make 
 it as plain as can be done in print. No. 1 shows the first step 
 in the process, the plate being cut away and the new piece 
 (shown at "a") fitted and cemented in place. After drying a 
 short time (allowing it to stand a few hours or over night if 
 convenient), fit the new block to its place, leaving as little 
 space as possible between the plate and block ; this space is to 
 be waxed up to keep out plaster when investing. Fig. 1 59 
 shows the piece invested, the whole plate and teeth, except the 
 new piece " a," being covered deep in the plaster, which is 
 trimmed as shown. The upper part of the flask is now put in 
 place, and filled in the usual manner. On opening the flask 
 Vjoil out the wax. Then lay another piece of celluloid, or a 
 ball of tin foil, or moistened blotting-pad — in fact anything 
 that will produce pressure, upon the piece "o," and heat up 
 and press as usual. In this way the new piece becomes a par^ 
 of the plate })y the cementing process, before the pressing is 
 done, and will not scale or separate. If neatly done, the line 
 of junction will be scarcely observable. The sharp edge of the 
 plaster at the bottom of the well or depression should be 
 trimmed out and well rounded, as otherwise these edges are 
 
398 MECHANICAL DENTTSTEY. 
 
 liable to fracture and get into the plate. If the new block or 
 tooth is separated from the plate, so that it has no support, and 
 is liable to be pushed down, it should be supported by crowd- 
 ing a small, bit of celluloid under it before beginning. The 
 new piece may be placed in position after opening the flask, a 
 few drops of spirits of camphor added, and the case pressed as 
 before ; but union by this means is not nearly as certain. There 
 is no certainty about uniting pieces in the machine. It may be 
 done, or it may not. But by cementing well-fitting or freshly 
 filed surfaces together outside the flask, perfect union may 
 always be had, and pieces added wherever desired. In invest- 
 ing, the plate should always be placed in a position the reverse 
 of that indicated by the cut on page 382, in order that a direct 
 downward and not a side pressure may be had. Care should 
 be taken to avoid air-bubbles in the plaster, and to pour it 
 smoothly. 
 
 If the plate is of sufficient thickness, the repair may be very 
 nicely made without adding any new material. Fit the new 
 block without cutting away more of the plate than absolutely 
 necessary. Invest the plate, leaving the tongue side exposed, 
 but covering the teeth ; on opening the flask, lay over the ex- 
 posed plate one or more thicknesses of wet thick brown paper, 
 blotting-pad, or unvulcanized rubber, fitting closely to the 
 teeth and having it thickest in the centre, and press as usual. 
 By this means the plate will be spread up to the new teeth, 
 which will be firmly united. Loose teeth, if any, on the plate 
 may be tightened by the same means, having been waxed in 
 place, and the wax afterwards thoroughly boiled out. Some 
 dentists attempt to mend in this way, without using anything 
 to produce pressure, depending upon the swelling of the plate 
 to fill the vacancy. This would be certain to injure the density 
 of the plate. 
 
 To remove teeth, heat the plate in boiling water or glyc- 
 erin, when they will easily come oif. 
 
 Rubber plates may be very nicely repaired with celluloid, 
 but as there is no union, dovetailing or drilling holes is 
 necessary. 
 
CELLULOID BASE. 399 
 
 Finishing. — This is accomplished in one-half the time nec- 
 essary with rubber. Use files, sandpaper, and scrapers, but 
 do not use too coarse materials. Polish with pumicestone, and 
 finish with a soft brush at high speed, and whiting or Vienna 
 lime. Dr. H. D. Knight, of Lancaster, Pa., recommends a 
 polish obtained by rubbing with an old cloth wet with cam- 
 phor. This may be valuable between teeth, and in places in- 
 accessible with the brush-wheel. In finishing, care should be 
 taken not to heat the plate by friction, as by so doing the sur- 
 face may be injured, or the plate sprung out of shape. 
 
400 MECHANICAL DENTISTEY. 
 
 CHAPTER Xyi. 
 
 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 practiced heretofore, is attracting more attention than for- 
 merly, and is eminently deserving of more favorable considera- 
 tion 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 prac- 
 ticed the method as early as 1859, and whose published de- 
 scriptions of the manner of preparing the plate base, substan- 
 tially the same as that for which Mr. S. D. Engle, of Hazle- 
 ton, Pa., obtained letters patent some years later, were given 
 in the first edition of this work. 
 
 In commenting on this method. Professor Charles J. Essig 
 very justly remarks that, by the means here indicated, we are 
 " able to produce an artificial denture embracing all that is 
 good in metallic and vulcanite work, at the same time avoid- 
 ing the great defects of each." 
 
 That it possesses marked advantages over the method of 
 attaching teeth to a metallic plate base by soldering is unques- 
 tionable. The warping 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 concussion or violence is materially 
 diminished on account of the pliable nature of the attaching 
 
METALLIC BASE WITH RUBBER ATTACHMENT. 401 
 
 material used ; a nearer approximation to the natural form of 
 the ridge or guiu on the lingual side of the plate is secured ; 
 the rubber or celluloid, penetrating all the joints and openings 
 between and underneath the teeth, renders the piece wholly im- 
 jjervious to the oral secretions, making it, in point of cleanli- 
 ness and purity, equal to continuous gum work ; the facility 
 with which injury to the teeth may be repaired ; the practica- 
 bility of remodelling the piece without impairment of the 
 teeth or plate ; its susceptibility of receiving a final finish ex- 
 celled by no other method in point of artistic beauty ; — these 
 are among the qualities which commend this method of sub- 
 stitution as one of peculiar merit and excellence. 
 
 In mounting teeth by this method, preference should be 
 given to either gold or platinum 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. Aluminum has a 
 limited adaptability to this mode of substitution, but requires 
 special treatment in its preparation for the purpose, a descrip- 
 tion 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 described 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 fulness 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 articula- 
 tion, and before removing the wax from the plate, take a small 
 light pair of dividers, set tliem say one inch apart, and with one 
 point following the margin of the wax representing the cutting 
 edge of the teeth, and tlie other point marking permanently 
 the plaster, you liave always in the dividers so set a gauge 
 for the length of any particular tooth. A convenient substi- 
 tute for the dividers may be formed from a i)iece of wire 
 
 26 
 
402 
 
 MECHANICAL DENTISTEY. 
 
 of convenient length, one-half the diameter of a common ex- 
 cavator, by suitably twisting its middle for a handle, and its 
 ends being sharpened, and pointing in the same direction, one 
 or one and a half 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 purposes hereinafter described. Then apply wax to 
 the external or labial parts of the teeth and plate in any man- 
 ner 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, re- 
 move the teeth and wax, and with a small bow-drill make 
 holes through the plate at the several points previously deter- 
 mined 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 
 
METALLIC BASE WITH RUBBER ATTACHMENT. 403 
 
 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. 160, wliich illustrates ]\Ir. Engle's 
 method of providing attachment for the rubber to the plate by 
 means of bent or hooked wires soldered to the base, the sub- 
 stantial 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 possible to obtain with the ordi- 
 nary soldered work. Then with silicate of soda paint the joints, 
 to keep the rubber from forcing in where 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, decidedly more 
 so than the very best single gum or block-work soldered in the 
 usual way ; again it is very much stronger, less liable to break- 
 age, both in and out of the mouth, as the rubber gives a jyer- 
 fect 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 completed. 
 
 " On the labial edge of the upper plate the rubber may be 
 allowed to project beyond the edge, if desirable, and it will be 
 found in many cases exceedingly satisfactory to do so, and 
 allow the rui)ber to be of considerable thickness near the alas 
 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 upwards 
 
404 MECHANICAL, DENTISTEY. 
 
 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 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. DiiFerent-sized pins maybe 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 suit- 
 able size and length, say 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 is desired that 
 the rubber should extend beyond the labial or buccal edge of 
 the metallic j)late, 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 manipula- 
 tion, 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. 
 
MKTALLIC BASE WITH RUBBER ATTACHMENT. 405 
 
 If the ordinary plate teeth are used, it is frequently necessary 
 to back them, to give better retain ing-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." 
 
 The following method of preparing aluminum plates for the 
 attachment of the rubber, was communicated to the author by 
 Dr. J. W. Hollingsworth, of Greencastle, Indiana, an intelli- 
 gent practitioner, who has had long and extended practical ex- 
 perience 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 practicable and the most easily manipu- 
 lated method that I have yet seen." 
 
 The following is the manner of preparing the plate as de- 
 scribed 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 aluminum, 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 extruding portion of 
 the pins, and slightly bell-mouthed. This 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 upper entire 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 ca.ses, 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 l>etter to dispense with the plaster model in forming the 
 mould or matrix, and proceed as follows : When the teeth are 
 
406 MECHANICAL, DENTISTRY. 
 
 arranged, and the required contour and fulness 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 afterwards separated, the metallic plate will remain 
 in the lower section, and the teeth in the upper. 
 
 When using celluloid, plain teeth may be advantageously- 
 employed, the former representing the gum ; this gives perfect 
 freedom in the arrangement of each separate tooth in the den- 
 ture, an optional disposition the importance of which cannot 
 be over-estimated. 
 
GOLD ALLOY CAST BASE. 407 
 
 CHAPTER XYII. 
 Gold Alloy Cast Base. 
 
 The compound of gold, silver, and tin, in varied propor- 
 tions, in connection with specific and original methods of cast- 
 ing dental plates, recently devised and patented by Dr. George 
 F. Reese, of Brooklyn, N. Y., is attracting attention as a pos- 
 sible substitute for the plastic materials so commonly employed 
 as a base for artificial dentures. 
 
 The properties and capabilities attributed to this alloy, and 
 which are deemed essential in a base, having been practically 
 tested by many representative and responsible practititioners 
 who have unreservedly indorsed its claims upon the confi- 
 dence of the profession, the author feels warranted in substi- 
 tuting Dr. Reese's materials and processes for the older alloys, 
 appliances, and modes of manipulation described in former 
 editions under the head of " Cheoplastic Method of Mounting 
 Artificial Teeth," and which, for many years past, have been 
 wholly abandoned except in the case of lower dentures where 
 extreme and exceptional absorption of the alveolar processes 
 make greatly increased weight necessary to provide against 
 mobility and displacement of the substitute. 
 
 After premising that the methods in common use for cast- 
 ing alloys were not applicable to one having the molecular 
 properties of Reese's compound, the inventor says he was led, 
 after multiplied experiments, to adopt the plan of which the 
 following is a description : 
 
 Th(; impression is taken with plaster, to which salt or sul- 
 phate of potassa has been added, and the model obtained from 
 this with pure j)laster. Upon this the teeth are arranged. For 
 the trial plate, gutta-percha, paraffin, and wax, or modelling 
 compound, may be used. When satisfaction in the occlusion 
 
408 
 
 MECHA]SriCAL DENTISTEY. 
 
 is attained, then the case is returned to the model, and the 
 waxing around the labial and buccal borders of the teeth com- 
 pleted. That portion of the trial plate which covers the pal- 
 atine surface is now removed, so that the pins of the teeth will 
 be nearly exposed ; allowing the wax which is under the gums 
 to remain. That the plate, after casting, shall not be too 
 cumbrous, the trial plate, which has been removed, must be sub- 
 stituted with two thicknesses of French flower wax, cut care- 
 fully to the model, and pressed down closely with the finger 
 
 in a manner that no wrinkles will appear to mar the beauty 
 of the work. 
 
 Fig, 161 represents a case thus prepared. The dotted lines 
 show the borders of the thin wax. B, A, and C, represent nip- 
 ples 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 pockets, and B the place of entrance of 
 the metal from the pouring-gaine. 
 
 The case is now transferred to the small brass flask, r. 
 Fig. 162, the sections of which having been well oiled, upon 
 the inner surface, to facilitate their removal from the invest- 
 ment. Either section is then placed upon a plate of glass and 
 
GOLD ALLOY CAST BASE. 
 
 409 
 
 plaster poured into it until half filled. The model, as pre- 
 pared, after being well saturated with water, is imbedded in 
 this single section, allowing the teeth and gums to remain un- 
 covered. Set on the counter-part 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 
 solution of shellac^ Elliott's parting fluid or vaselin. Return 
 
 Fig. 162. 
 
 Case ready for the completion of Investment. 
 
 the section and complete the investment. Fig. 162 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 i>y the nipples may now be extended tiirough the plas- 
 ter to the external edge ; or, if the circumstances of the case 
 
410 
 
 MECHANICAL DENTISTRY. 
 
 make this impossible, the channels may be made at the line of 
 division between the two sections, as shown by the dotted lines 
 m figures 163 and 164. Externally, the channels, D, E, F, 
 Fig. 164, should be neatly countersunk and varnished with 
 
 Fig. 163. 
 
 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 
 one and a half inches long, and about half an inch diameter at 
 
GOLD ALLOY CAST BASE. 
 
 411 
 
 the base, and an eighth of an inch at the apex. The pouring- 
 gaine is made in the same manner, but should be smaller in 
 diameter at the base, and about two inches long. After re- 
 moving these wax covers from the moulding-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 in the 
 counter-sunk channels at the tuberosities and the small cone 
 in the middle hole, and secure them with melted wax. Fig. 
 163, d', e',/', shows the pockets thus attached. 
 
 Upper or counter section corresponding to Fig. 163. D, E, F, channels for 
 entrance and exit of metal. 
 
 Should the channels have been made through the solid 
 plaster of the lower section, as in Fig. 163, then the upper 
 section, P'ig. 164, need not be joined to it until after the pockets 
 are secured to their places. Should, however, tiie channels 
 have been made uj)on the line of division, then the sections 
 must l>e joined before the pockets can be attached. 
 
 The case is now ready for a second investment, which is 
 
412 
 
 MECHANICAL DENTISTRY. 
 
 done in a flask sufficiently large to embrace the case as it now 
 presents. Fig. 165 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 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 invest- 
 
 FiG. 165. 
 
 ment by filling with plaster the uppermost section to fulness. 
 Of course there will be no division of the sections as was the 
 case in the former flashing. After solidification, the pouring- 
 gaine 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. 
 
GOLD ALLOY CAST BASE. 
 
 413 
 
 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-gaine 
 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, which require a heat registering from 600° to 
 
 Fig. 166. 
 
 - S 
 
 700° Fah. to melt, but a higher temperature than this must be 
 attaine<^l before pouring, in order to secure a satisfactory flow. 
 At 900° rapid oxidation takes place. This, of course, should 
 be avoided. The alhjy may be melted in an ordinary iron 
 ladle or crucible over a gas or other flame, and should be 
 poured while the mould is hot. 
 
 After the lapse of an hour or two, or until tiic cast is suffi- 
 ciently cooled to insure the integrity of the teeth, it may be 
 
414 MECHANICAl. DENTISTRY. 
 
 placed in warm water, when the investment can be easily 
 removed. 
 
 Fig. 166 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. 167 represents the finished case. 
 
 Fig. 167, 
 
 Repairing. — The process of repairing broken plates is, in 
 principle, the same as above. A flask, specially constructed 
 by the inventor, is used for this purpose, whereby a single in- 
 vestment 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 an eighth of an inch. The parts are then ad- 
 justed upon the model, and the space between the approximate 
 edges filled with wax. At each extremity of the fissure a pen- 
 cil of wax, an eighth of an inch in diameter, and one and 
 a half inches long, is securely attached, perpendicularly, to the 
 palatine 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 pour- 
 ing-gaine, and the other a waste-pocket. The latter should be 
 entirely covered by the plaster. The whole is now invested in 
 
GOLD ALLOY CAST BASE. 415 
 
 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 attend- 
 ing the construction of continuous-gum work. 
 
 To maintain a perfect adaptation of a swaged plate seems 
 often impossible, in consequenc^e 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 fur- 
 nace for biscuiting and enamelling. After proper annealing, it 
 is ref)laced upon the model and waxed up, on the labial and 
 buccal borders, over the edge of the j)late ; then flashed, the 
 wax removed, and the metal cast upon it in the manner hereto- 
 fore described. 
 
 Danger of checking the enamel is associated with the pro- 
 cess ; but success has attended the effort, and it is hoped that 
 present experiments will insure perfect and uniform results. 
 
416 MECHANICAL DENTISTEY. 
 
 CHAPTER Xyill. 
 
 Defects of the Palatal Oegans, and their Treat- 
 ment BY Artificial Means. 
 
 • DR. KINGSLEY's artificial VELUM AND PALATE.* 
 
 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 otherwise. Such defects are not uniform in 
 locality or extent, being sometimes but a simple perforation of 
 the palate, and at others involving the destruction of the entire 
 soft palate, a considerable portion 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, pala- 
 tine, 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 
 uniform 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, leaving the vomer articulated with the pala- 
 tine bone on one side ; while in other cases the deformity seems 
 to follow the median line, and thus involves both nasal pas- 
 sages, and terminates in a double fissure of the lip. 
 
 * The descriptions, with accompanying illustrations, embraced in the 
 above chapter were contributed, at the solicitation of the author, by Profes- 
 sor Norman W. Kingsley, and may therefore be relied upon as an authori- 
 tative exposition of the most approved manipulation and appliances involved 
 in the practice of that difficult and important specialty of the Dental Art in 
 which the writer excels. 
 
PE. kingsley's aetifictal velum and palate. 417 
 
 In both classes (accidental and congenital) the faculty of dis- 
 tinct 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 difficulty. 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 abnor- 
 mal passage by 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 diffi- 
 cult, and in extensive congenital deformity still more compli- 
 cated appliances will be required. 
 
 As we have classified the defects, we shall also classify the 
 appliances used for their remedy. 
 
 The term obturator will be used for all appliances intended 
 to stop a passage, as 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 con- 
 genital, 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 passage, and can be worn without inconvenience, will 
 restore articulation.* Obturators were formerly made of me- 
 tallic 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 pref- 
 erable to metals, being much lighter and much more easily 
 formed and adapted, particularly when of peculiar shape. 
 
 * The Htudent will hear in mind that no cognizance is here taken of open- 
 ings similar to tliose descrlhed in cases of congenital fissure, where the sur- 
 geon has united the soft palate, and left an opening through the hard palate, 
 to be covered hy an obturator. In such cases, neither tlie surgeon's opera- 
 tion nor the obturator will prove of any material advantage. 
 
 27 
 
418 MECHAlSriCAL DENTISTRY. 
 
 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 essential 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 pre- 
 venting the withdrawal of the impression 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, without injury to the 
 patient. From this wax impression make a plaster model, 
 and upon this plaster model 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 im- 
 pression-cup must not impinge upon the borders of the open- 
 ing, neither should it enter to any extent. With a uniform 
 film of soft plaster of from one-sixteenth to one-eighth of an 
 inch in thickness laid over this cup, a correct impression 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, or any other plastic sub- 
 stance, 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 
 
DR. KIXGSLEY's artificial VELUM AND PALATE. 419 
 
 cannot, resort must be had 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 bridg- 
 ing over and filling up an opening in the palate, thus combin- 
 ing an obturator with a set of teeth. 
 
 Fig. 168 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 contact. Accuracy of adaptation and delicacy in form are 
 
 Fig. 168. 
 
 Fig. 169. 
 
 all that is essential in such cases, and the restoration of the 
 speech will follow immediately. 
 
 Fig. 1G9 rei)resents 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 constaut muscular action of the soft 
 palate, which would not permit, without irritation, the presence 
 of an immovable fixture. 
 
 This is contrived, therefore, with a joint, that will permit 
 the part attached to the teeth to remain stationary, while the 
 obturat(jr proper is carried up or down as moved by the mus- 
 cles. The joint A should occupy tiie position of the junction of 
 the hard and soft palates. The joint and principal part of the 
 applian(;e is made of gold, the obturator of vulcanite. The 
 projection /> lies like a flange upon tlie superior surface of the 
 palate, and sustains it; otherwise the mobility of the joint 
 
420 MECHANICAL DENTISTRY. 
 
 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. 
 
 Figures 168 and 169 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 
 functions of the palate will be necessary. The palate exercises 
 quite as important an office in the articulation of the voice as 
 does the tongue or lips. Being a muscular and movable par- 
 tition to separate the nasal and oral cavities, one edge is attached 
 to the border of the hard jjalate, while the other vibrates be- 
 tween 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 palate, or let it be deficient in size, and the power of dis- 
 tinct articulation is wanting. 
 
 The evidence of this statement is frequently found after the 
 surgeon has successfully performed the operation of staphylor- 
 raphy 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 function. 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. 170 represents a defective palate belonging to the first 
 class ; the uvula and a portion of the soft palate contiguous 
 being destroyed by disease. In such a case an obturator would 
 
DE. KINGSLEY's artificial VELUM AXD PALATE. 
 
 421 
 
 be useless ; the constant activity of 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 purpose. 
 
 ^ By observing the cut (Fig. 170) it will be seen that a por- 
 tion of the soft palate along the median line remains, and con- 
 sequently there will be considerable muscular movement which 
 must be provided for, and which may be taken advantage of. 
 It is desirable to make this movement available in usine: an 
 
 Fig. 170. 
 
 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 neces.sary, therefore, to adapt a plate which should not 
 only sustain teeth for mastication but bear the additional re- 
 6ponsil)ility of supporting the artificial palate. In the choice 
 of material best adapted for the base for the teeth in such in- 
 stances, it is preferable to adopt that which will prove the most 
 durable. Tliere are too many interests involved to risk the 
 adoption of anything but the best. In the case under descrip- 
 tion, the patient desired duplicates, and two sets of teeth were 
 
422 
 
 MECHANICAL DENTISTEY. 
 
 made, one on gold and the other on platina with continuous 
 gum. 
 
 The plates were made like other sets of teeth, with the ex- 
 ception of a groove located on the median line at the posterior 
 edge to receive the attachment for the palate (marked C, in 
 Fig. 171). 
 
 Fig. 171 will indicate the set of teeth with palate attached. 
 The wings marked letters A and B are made of soft rubber; 
 
 Fig. 171. 
 
 the frame to support them is made of gold, with a joint to pro- 
 vide for the perpendicular motion of the natural palate, as in 
 the case of the obturator represented in Fig. 169. 
 
 When the artificial palate is in use, the joint and frame 
 immediately contiguous lie close to the roof of the mouth ; the 
 rubber wing, letter A, bridges across the opening on the infe- 
 rior 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 
 one-eighth to one-quarter of an inch, 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 articu- 
 lation may require. 
 
 When the organs of speech are in repose, there is an opening 
 
DR. KIXGSLEY's artificial VELUM AND PALATE. 423 
 
 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 
 passage and direct all the voice through the mouth. The palate 
 thus becomes a valve to open or close the nares, and to be tol- 
 erated must be made with thin and delicate edges which will 
 yield upon pressure. An instrument thus made will restore, 
 as for as is possible 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 
 
 Fig. 172. 
 
 was very defective ; distinct and perfect articulation followed 
 within one month. 
 
 Fig. 172 represents the artificial i^alate separated into its 
 constituent parts. The frame is bent at the joint, in the en- 
 graving, to show a stop, marked D, which prevents the appli- 
 ance from dropping out of position. Letter C shows the tongue, 
 which enters the groove in tlie 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 de- 
 scribed on page 429. 
 
 Fig. 173 shows a more extensive i)alatine defect of the first 
 cla.s.s. in this ca.se the entire soft palate is gone, together with 
 a small portion of the hard palate at the median line. 
 
424 
 
 MECHANICAL DENTISTEY. 
 
 Although this defect is greater in extent, the means for its 
 remedy are more simple. The muscles of the palate are en- 
 tirely gone, and consequently no perpendicular movement need 
 be provided for. 
 
 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 recomended 
 by Mr. Sercombe, of London, some ten years since, and con- 
 
 FiG. 173. 
 
 sists of a plate with a set of teeth in the usual form, and 
 attached to its posterior edge an apron of soft rubber, which 
 shall bridge the opening on its inferior surface, extending 
 nearly to the pharynx. Fig. 174 represents the set of teeth 
 with the palate attached. In Mr. Sercdmbe's appliance this 
 apron was made of the common sheet rubber in the market, 
 prepared for other uses, and is objectionable for two reasons: 
 1st, a want of purity in the materials of which it is compounded, 
 in many instances substances being used in its manufacture 
 which would prove deleterious to the health of the patient ; 
 and, 2d, its uniformity of thickness. It is far preferable, there- 
 
DR. KIXGSLEY's artificial VELUM AND PALATE. 425 
 
 fore to make a mould 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 tissue. Such a palate may be made 
 in a mould by substantially the same process as hereinafter 
 
 Fig. 174. 
 
 described. (See page 429.) 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 
 may be raised along the posterior edge from the sixteenth to 
 the tenth of an inch, according to the thickness of palate de- 
 sired. The rul>ber will thus 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 educate the ramdcH of the pJiarynx alone to do the work 
 of shutting off the nares, which in the former case was per- 
 formed by them in conjunction with the muscles of the palate. 
 
426 MECHANICAL DENTISTRY. 
 
 Perfection of articulation will therefore depend upon the suc- 
 cess 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 condi- 
 tion, the ear will therefore direct and criticise the practice until 
 the result is attained. 
 
 In the case illustrated by Figs. 173 and 174, the defect had 
 existed for twenty-eight years, the patient at the time of the 
 introduction of the artificial palate being nearly fifty years of 
 age. The effect upon the speech was instantaneous. Articu- 
 lation was immediately nearly as distinct as in youth, and this 
 remarkable distinctness can only be accounted for upon the 
 assumption that the pharyngeal muscles had undergone a thor- 
 ough training in the vain eifort 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 
 perceived, entire upper sets of artificial teeth in connection 
 with the palates. This selection was purposely made because 
 the difficulties to be overcome are much greater. In cases 
 where there are natural teeth remaining in the upper jaw, the 
 palate and its connection 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 extensive, the appliance more complicated, and the result 
 more problematical. 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 
 
 * An account of this case appears in the Argus, of Bainbridge, Georgia, 
 August 1st, 1868, written by the patient himself, who is the editor of that 
 paper. 
 
DR. KINGSLEY's artificial VELUM AND PALATE. 427 
 
 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 re- 
 quires for its successful remedy a soft, elastic, and movable 
 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 complicated 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 instru- 
 ment, with all its complexity, embodied the only true principle, 
 viz., the rendering available the muscles of the natural palate 
 to control the movements of the artificial 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 mecha- 
 nism, 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. 175 represents a model of a fissured i)alate, complicated 
 
428 
 
 MECHANICAL DENTISTEY. 
 
 with harelip on the left of the mesial line. There is a division 
 also of the maxilla and the alveolar process, the sides being 
 covered with mucons membrane which come in contact with 
 
 Fig. 175. 
 
 each other, but are not united. The left lateral incisor and 
 left canine tooth are not developed. 
 
 Fig. 176 represents the artificial velum, as viewed from its 
 superior surface, together with the attachment and two artifi- 
 cial teeth to fill the vacancy. 
 
 Fig. 176. 
 
 The lettered portion of this appliance is made of elastic vul- 
 canized 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 
 
DR. KI^'GSLEY'S ARTIFICIAL VELUM AND PALATE. 429 
 
 other end has a head, marked C, which being considerably 
 larger than the pin, and also the corresponding hole in the 
 velum, it is forced through, — the elasticity of the velum per- 
 mitting, — and the two are securely connected. 
 
 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 thQ remnant of the natural 
 velum. 
 
 The wings D D, rest upon the opposite or anterior surface 
 of the soft palate. 
 
 Fig. 177 represents a model, the same as Fig. 175, with the 
 appliance, Fig. 176, in situ. 
 
 Fig. 177. 
 
 ,,-j,^;^^ 
 
 The wing D D, in Fig. 176, and the posterior end of the 
 artificial velum only in this cut being visible. 
 
 Method of Making an Artificial Palate. — The success of 
 these ap})liances dej)ends 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, 
 
430 MECHANICAL DENTISTEY. 
 
 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 is hidden from the eye. It is desir- 
 able, also, that the posterior surface 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 ma- 
 terial now in use adapted to the purpose. An ordinary bri- 
 tannia 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 moulded into such form 
 as not to impinge 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 pre- 
 caution 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 disturbed (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 as de- 
 scribed on page 418. 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. 
 
DE. KINGSLEy's artificial VELUM AND PALATE. 431 
 
 The next step will be to obtain, in conjunction with tliis 
 impression 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 wnth soft plaster down to the border of the fissure, and 
 while yet very soft carrying immediately the palatal impres- 
 sion 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 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 con- 
 tact, there will be no difficulty in removing it from the mouth. 
 
 Fig. 178. 
 
 leaving the mass which forms the nasal portion in situ. AYith 
 a suitable pair of tweezers this mass is easily carried backward 
 and withdrawn from the mouth, and the irregular surface of con- 
 tact indicates its relation to its fellow when brouglit together. 
 
 Fig. 178 will show such an impression. The portion marked 
 A, B, C, will readily be distinguished as that which entered 
 the nasal cavity. The line of separation from the palatal im- 
 pression is plainly indicated in the engraving. The groove, 
 marked D, shows clearly the impression made by the delicate 
 uvula in the soft plaster. The nasal portion is relatively large, 
 showing an unusually large nasal cavity. 
 
 The vomer lies between the projections marked A A ; these 
 projections entering the nasal passages. The surfaces marked 
 B B, came in contact witli the middle turbinated bones; the 
 
432 
 
 MECHANICAL DENTISTRY. 
 
 surface marked C in contact with the inferior turbinated bone. 
 In many instances these turbinated bones are so large as to 
 nearly fill the nasal passages. 
 
 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 into any other mouth 
 impression. 
 
 The model represented in Fig. 175 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 repre- 
 
 FlG. 179. 
 
 sented in the cast by carving. It is not essential to the success 
 of the instrument 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. 
 
DE. KINGSLEY's artificial VELUM AND PALATE. 433 
 
 The next step will be the formation of a model or pattern 
 of the palate. Sheet gutta-percha is preferable for this pur- 
 pose, although wax, or many other plastic substances, might 
 answer. 
 
 The form which should be given it is better indicated by 
 the drawings. Figs. 176 and 183, than a written description 
 would give. The Stearns instrument, of which a cut is here 
 
 Fig. 180. 
 
 given (Figs. 179, 180), was made to embrace the edges of the 
 fissure, and was slit up through the middle, so that when the 
 edges of the fissure approach each other, as they always do in 
 swallowing, the two halves of the instrument would slide by 
 each other, and a third flap or tongue was made and supported 
 by a gold spring to cover and keep closed this central slit. 
 This complicated provision for the contraction of the fissure 
 is entirely superseded in Figs. 176 and 183, by making the 
 instrument somewhat in the form of two leaves, one to lie on 
 the inferior and the other upon the superior surface of the pal- 
 ate, and joined together along tiie median line. When the 
 fissure contracts the halves of the divided uvula slide toward 
 
 28 
 
434 MECHANICAL DENTISTRY. 
 
 each other between these two leaves. The posterior portion, 
 marked A in Fig. 176, is made very thin and delicate on all 
 its edges, as it occupies 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. 176, 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 a quarter of an inch, although sub- 
 sequent 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, as far as possi- 
 ble, 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. 176, 
 marked B, and a like process is seen in Fig. 183, but not let- 
 tered. 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 anterior 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 de- 
 cided upon, provision must be made to duplicate it in soft 
 rubber. 
 
 A parallel process, and one which will be a familiar illus- 
 tration, is used when a set of teeth is made on vulcanite base. 
 A model or patern 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 vul- 
 
DR. KINGSLEY'S AETIFICIAL VELUM AND PALATE. 435 
 
 canized in a plaster mould. In like manner the rubber dupli- 
 cate of the palate as before described may be made in a plaster 
 mould. 
 
 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 re- 
 moved. By covering the surfiice of the mould with collodion 
 or liquid silex, it will be much improved. But ordinarily 
 plaster moulds 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 expe- 
 rience, but w^ith beginners it will be difficult to work up the 
 gutta-percha as nicely as may be desired ; a duplicate of vul- 
 canite will enable the operator to make a more artistic model 
 of the palate, and one wliich can be handled wdth greater free- 
 dom. 
 
 Fig. 181. 
 
 As in the course of a lifetime a considerable number of 
 elastic palates will be required, the mould which produces them 
 should be made of some durable material. The type metal 
 of commerce is admirably adapted to this use. The most com- 
 plete mould is one made of four pieces, which will produce a 
 palate of one continuous piece. Such a mould requires very 
 nice mechanical skill in fitting all the parts accurately, and 
 unless the operator lias 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 mould may be made 
 in two pieces and with very little trouble. 
 
 Fig. 181 shows a palate divided. 
 
436 
 
 MECHAlSriCAL DENTISTRY. 
 
 Fig. 182 shows the mould 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' labora- 
 
 FlG. 182. 
 
 tories, that the latter will not answer. The common flask is 
 simply unnecessarily thick or deep. 
 
 The mould is readily 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, 
 
 Fig. 183. 
 
 duplicate it in type-metal by removing the palate, varnishing 
 the surface, moulding in sand, and casting. In making the sand 
 mould take a ring of sheet-iron of the same diameter of 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 mould, and fill with the melted metal through 
 a hole made in the side or bottom of the flask. With one- 
 
DE. KIXGSLEY's artificial VELUM AND PALATE. 437 
 
 half thus made, substantially the same process will produce 
 the counterpart. 
 
 Fig. 183 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 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. 184 shows a mould in four pieces. The blocks C C, 
 are accurately adapted to the body of the mould, marked A, 
 
 Fig. 184. 
 
 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 main piece. B shows the top of the mould, and 
 the groove E provides for the surplus rubber in packing. 
 
 Such a mould makes the most perfect appliance that can be 
 produced. The palate is one homogeneous and inseparable 
 piece. The cut will sufficiently indicate the forms of tlie 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 
 moulded in sand and the type-metal castas in making an ordi- 
 nary die for swaging. When in use, a clamp similar to Fig. 
 185 is placed around the mould to keep the several parts firm 
 in their position. 
 
438 
 
 MECHAlSriCAL DENTISTRY. 
 
 The packing of the mould with rubber will be done in the 
 same manner as when hard rubber is used for teeth bases; with 
 which process it is assumed that the operator is familiar. By- 
 washing the surface of the mould with a thick solution of soap 
 previous to packing, the palate will be more easily removed 
 after vulcanizing. 
 
 Fig. 185. 
 
 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. 
 
 The American Hard Rubber Company have recently placed 
 on sale at the dental depots a compound admirably adapted to 
 this purpose. The best results are obtained when the process 
 of vulcanizing is carried from a heat of 230° gradually during 
 four or five hours up to and terminating at 270°. 
 
INDEX. 
 
 PAGE 
 
 Air-chamber, manner of forming, 229 
 
 Alloys of gold for dental purposes, . . . '. . , .54 
 
 Alloys of copper, 88 
 
 silver, 76 
 
 platinum, 81 
 
 Aluminum, 83 
 
 alloys of, 85 
 
 Antagonizing model for partial dentures, 231 
 
 entire dentures, ...... 255 
 
 upper dentures, ...... 258 
 
 block-teeth, 292 
 
 Anatomical articulator, Bonwill's, 260 
 
 Antimony, 91 
 
 Application of heat, 17 
 
 Articulators, 259 
 
 Artificial dentures, 97 
 
 Artificial palates, 420 
 
 Artificial palates for congenital fissures, 426 
 
 Atmospheric pressure plates, ........ 227 
 
 Attaching teeth to metallic base with rubber or celluloid, . . . 400 
 
 Baking furnace, 29 
 
 Bismuth, 91 
 
 Block-teeth, 285 
 
 composition and preparation of body for, .... 285 
 
 crown enamel for, . . 287 
 
 gum enamel for, . . 290 
 
 Babbitt metal, 142 
 
 Blowpipe, 17 
 
 oxygen, .......... 17 
 
 oxy-iiydrogen, ......... 17 
 
 mouth, 18 
 
 Ijcllows, 22 
 
 Blank, celluloid, 384 
 
 Bla.st furnace, 32 
 
 Bonwill's method of attaching artificial crowns, 172 
 
 Brass, 88 
 
 Brass solder, 88 
 
 Carved l>lock-tecth, 298 
 
440 INDEX. 
 
 PAGE 
 
 Celluloid base, 377 
 
 processes pi-eliminary to moulding, . . . • • . 380 
 
 blank, selection and preparation of, 384 
 
 moulding in hot moist air (dry heat), 387 
 
 glycerin, ........ 390 
 
 steam, 392 
 
 Chappell's method of attaching artificial crowns, .... 187 
 
 Charcoal, 36 
 
 Clasps, 200 
 
 Cleveland's air-chamber, 250 
 
 Coke, , 36 
 
 Components of dental porcelain, 277 
 
 Continuous gum work, 307 
 
 Dr. Allen's methods, 311 
 
 Dr. Hunter's formulas and methods, . . 318 
 
 Dr. Haskell's methods, 325 
 
 Dr. Field's methods, 330 
 
 application to partial sets, . . . . 333 
 
 Congenital defects of the palate, 416 
 
 Converting gold alloys into required forms for dental purposes, . . 68 
 
 Counter-die, • 135 
 
 Copper, 87 
 
 alloys of, 87 
 
 Crucibles, . _ ,40 
 
 Crucirjg or biscuiting, . . 299 
 
 Darby's method of attaching artificial crowns, .... 159-197 
 
 Dental porcelain, components of, 277 
 
 Dentures, partial, . . 224 
 
 entire, . 246 
 
 Defects of the palatal organs, 134 
 
 Dipping, 134 
 
 Diseased conditions of the mucous membrane and gums, . . . 102 
 Diseased remains of teeth, . . . . . . . . .103 
 
 Dies, , ... 128 
 
 essential properties of, . . . 136 
 
 Draw-plate, 74 
 
 DraBght or wind furnace, .28 
 
 Duplicating a set of teeth on rubber, 374 
 
 Entire dentures, . . . 246 
 
 Essential properties of a die, 136 
 
 Elements employed in refining gold, 48 
 
 Felspar, 277 
 
 Fitting pivot crown, 151 
 
 Flasks, vulcanite, 350, 352, 353 
 
 Formulas for silver solder, 78 
 
 gold plate, 55 
 
 clasps, stays, etc., 57 
 
 Forging, . . ." . 70 
 
 Fuel, . . . . . 35 
 
 Foster's method of attaching artificial crowns, 166 
 
 Furnaces, 28 
 
 Fusible alloys, 142 
 
 table of, 143 
 
INDEX. 441 
 
 PAGE 
 
 Gas furnace without blast, ......... 31 
 
 General properties of alloys, and their treatment and behavior in the 
 
 process of compounding, 93 
 
 German silver, gg 
 
 Gold, 41 
 
 geological situations of, ........ 41 
 
 geographical distribution of, 42 
 
 properties of, 42 
 
 influence of alloying on the properties of, 43 
 
 properties of particular alloys of, .45 
 
 refining, ........... 48 
 
 separation of foreign metals from, 49 
 
 alloy cast base, . 407 
 
 crown faced with porcelain, 164 
 
 solders, 57 
 
 wire, 73 
 
 Gutta-percha, 112 
 
 Hand furnace, 38 
 
 Hawes's moulding flask, 129 
 
 Impression in wax for partial upper dentures, 106 
 
 partial lower dentures, 109 
 
 entire upper dentures, 110 
 
 entire lower dentures, 112 
 
 Impression in plaster for entire upper dentures, 118 
 
 entire lower dentures, 120 
 
 partial upper dentures, . . . ,11.5 
 
 India-rubber, 33(3 
 
 general properties of, 336 
 
 compounding, 338 
 
 method of constructing an entire denture in a base of, . 338 
 
 formation of the mould or matrix, 342 
 
 packing the mould, 347 
 
 Influence of alloying on the properties of gold, 43 
 
 Ingot moulds, 68 
 
 Kaolin, 278 
 
 Kingsley's artificial velum and palate, 416 
 
 Laminating or rolling, 70 
 
 Lampg, .26 
 
 oil, ! '. 26 
 
 spirit, 27 
 
 Lead, 89 
 
 Malleability of gold, 44 
 
 Manner of a.scertaining carat of gold alloys, 59 
 
 reducing gold to a re<piired carat, 60 
 
 reducing gold, 61 
 
 Manufacture of jjorcelain teeth, 279 
 
 Metallic dies anil counter-dies, 128 
 
 Manner of obtaining a die, 128 
 
 procuring an ingot, 68 
 
 Materials employed in obtaining impressions of the mouth, . . 105 
 
 Metallic clasps attached to rubber plates, 369 
 
442 INDEX. 
 
 PAGE 
 
 Method of constructing spiral springs, . . . . . . . 271 
 
 obtaining gold wire, 73 
 
 Models, 121 
 
 Modifications in the form of clasps, 205 
 
 plates for entire upper dentures, . . 249 
 
 entire lower dentures, . . 253 
 
 partial dentures, . . . 209 
 
 Moulding, 128 
 
 Moulding flask, Hawes's, 129 
 
 Moutli blowpipe, '18 
 
 Oil lamp, 26 
 
 Obturators, 417 
 
 Palatal defects, 416 
 
 Partial dentures, . 145 
 
 dentures in a base of rubber, . 368 
 
 or stay clasp, .......... 208 
 
 dentures secured by clasps, 200 
 
 dentures supported by cylinders of wood, .... 221 
 
 Pivoting artificial crowns, ......... 145 
 
 Pivot plate, 158 
 
 Pivots of metal and wood, ......... 155 
 
 Pivoting partial plates to the roots of the natural teeth, . . . 224 
 
 Platinum, 79 
 
 alloys of, 81 
 
 Platinoid metals, ........... 81 
 
 Plaster models, 121 
 
 of Paris, 113 
 
 Porcelain block-teeth, 285 
 
 Preparation of root for pivot tooth, ....... 147 
 
 Properties of particular alloys of gold, 45 
 
 gold, 42 
 
 Producing continuous blast with mouth blowpipe, .... 21 
 
 Pefining gold, 48 
 
 Removal of salivary calculus, 101 
 
 Reduction of silver to required forms for use, 77 
 
 Remarks on the use of clasps, 200 
 
 Reduction of gold solders to proper forms for use, .... 73 
 
 Reducing gold to a higher or lower standard of fineness, ... 59 
 
 Required fineness of gold plate, 54 
 
 Reducing metals, .54 
 
 Rei^airing vulcanite work, . . . . . . . . . 371 
 
 Refitting gold or rubber plates with rubber lining, .... 372 
 
 Richmond's method of attaching artificial crowns, .... 185 
 
 Rimming plate, . 269 
 
 Rose's fusible metal, 90 
 
 Rolling or laminating, . . . . . . . . .70 
 
 Rolling mills, . 70 
 
 Sand, for moulding, 128 
 
 Scalloped clasp, 208 
 
 Separation of foreign metals from gold, 49 
 
 Separation of teeth for clasps, 204 
 
 Sheet-iron furnace, 38 
 
INDEX. 443 
 
 PAGE 
 
 Silver, 76 
 
 general properties of, 76 
 
 alloys of, ........... 76 
 
 Silver solder, 78 
 
 Silex ! ". . 277 
 
 Soft solder, ............ 90 
 
 Spirit-lamp, ............ 27 
 
 Spiral springs, •••......,. 271 
 
 Standard clasp, 207 
 
 Stay chi-sp, ." ! ! 208 
 
 Steam gauge, 365 
 
 Substitution of plate for rubber teeth, 37O 
 
 Supports, .' .' 38 
 
 Surgical treatment of the mouth after the extraction of teeth, . . 102 
 
 Table of coinage of different nations, . 63 
 
 Teeth to which it is most proper to attach clasps, .... 202 
 
 Thickness of plate for clasps, stays, etc., 73 
 
 Tin, .' ." 90 
 
 Time necessary to elapse before insertion of artificial dentures, . . 103 
 Treatment of the mouth preparatory to tlie insertion of artificial den- 
 
 tures. 
 
 97 
 
 Type metal, J42 
 
 Uniting plate and clasps, 216 
 
 Varnish, •••••...... 126 
 
 Vulcanite base, •••....... 336 
 
 Vulcanizing, ........ ' 354 
 
 Vulcanizers, [ [ 354,355,356,307 
 
 Wax, ' .... 105 
 
 yellow, 105 
 
 white, 2Q5 
 
 Webb's method of attaching artificial crowns, .... 161-189 
 Wood pivots, ' * 152 
 
 Zinc, 00 
 
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 Geographical Distribution of Disease over the Globe, a Lithographic 
 Plate, and nearly 200 Illustrations on Wood. 
 
 Two volumes, royal octavo, bound in cloth, price, . . ^12.00 
 
 " " " " ■ leather, . . 14.00 
 
 For eighteen months Dr. Aitken has been engaged in again carefully revising this Greut 
 Work, and adding to it many valuable additions and improvements, amounting in the ag- 
 gregate almost to a volume of new matter, included iu which will be found the adoption and 
 incorporation in the text of the " New Nomenclature of the Royal College of Fhysicians of 
 London;" to which are added the Definitions and the Foreign Equivalents for their English 
 names ; the New Classification of Disease as adopted by the Koyal College of Physicians, &c. 
 
 The American editor, Meredith Clymer, M. D., has also added to it many 
 valuable articles, with special reference to the wants of the American Prac- 
 titioner. 
 
 The work is now, by almost universal consent, both in England and the United States, 
 acknowledged to he in advance of all other works on The Science and Practice of Medicine. 
 Jt is a most thorough and complete Text-BOOK for students of medicine, following such a 
 systematic arrangement as will give them a consistent view of the main facts, doctrines, and 
 practice of medicine, in accordance with accurate physiological and ]>athological principles 
 and the j>resent state of science. PVjr the practitioner it will be found equally acceptable as 
 a work of reference. 
 
 ALLINGHAM (william), F. R. C. S., 
 
 Surgeon to St. Mark's Hospital for Fistula, &.c, 
 
 FISTULA, IlyEMORRHOIDS, PAINFUL ULCER, STRICT- 
 URE, PROLAPSUS, and other Diseases of the Rectum, their Diagnosis 
 and Treatment. Third Edition, Revised and Enlarged by the Author. 
 Octavo. Price . . . . . . . . . $3- 00 
 
 This book has been well received by the Profession ; the first edition sold rap- 
 idly ; the present one lias been revised by the author, and some additions made 
 chiefly a.s to the mode of treatment. 
 
 The Medical J'regx and Circular, speaking of it, says: "No book on this special subjcci 
 can at all aj)f)roach Mr. Allingliam's in |»rccision, clearness, and jjractical good sense." 
 
 The London Lancet: "As a practical guide to the treatment of affections of the lower 
 bowel, this hook is worthy of all commendation." 
 
 The Edivhur'ih Monthly : " We cordially recommend it a.s well deserving the careful study 
 of PhyHiciau* and .Surgeons." 
 
ATTHILL (lombe), M. D., 
 
 Fellow and Examiner in JVlidwifery, King and Queen's College of Physicians, Dublin. 
 
 CMNICAL LECTURES ON DISEASES PECULIAR TO WO- 
 MEN. Fifth Edition, Revised and Enlarged, with numerous IHustra- 
 tions. Price . . . . . . . . . ^2.21; 
 
 The value and popularity of this book is proved by the rapid sale of the first edition, 
 which was exhausted ia less than a year from the time of its publication. It appears to 
 possess three great merits : First, It treats of the diseases very common to females. Second; 
 It treats of them in a thoroughly clinical and practical manner. Third, It is concise, orig- 
 inal, and illustrated by numerous cases from the author's own experience. His style is clear 
 and the volume is the result of the autlior's large and accurate clinical observation recorded" 
 in a remarkable, perspicuous, and terse manner, and is conspicuous for the best qualities 0^ 
 a practical guide to the student aad practitioner. — British Medical Journal. 
 
 ADAMS (WILLIAM), F.R. C.S., 
 
 Surgeon to the Royal Orthopedic and Great Northern Hospitals. 
 
 CLUB-FOOT: ITS CAUSES, PATHOLOGY, AND TREAT^ 
 MENT. Being the Jacksonian Prize Essay of the Royal College of 
 Surgeons. A New Revised and Enlarged Edition, with 106 Illustrations 
 engraved on Wood, and Six Lithographic Plates. A large Octavo 
 Volume. Price . . . . . . . . . ^q.oo 
 
 ADAMS (ROBERT), M.D., 
 
 Regius Professor of Surgery in the University of Dublin, &.C., &c. 
 
 RHEUMATIC GOUT, or CHRONIC RHEUMATIC ARTHRI- 
 TIS OF ALL THE JOINTS. The Second Edition. Illustrated by 
 numerous Woodcuts, and a quarto Atlas of Plates. 2 Volumes. 
 Price . ^7-5c> 
 
 ALTHAUS (JULIUS), M.D., 
 
 Physician to the infirmary of Epilepsy and Paralysis. 
 
 A TREATISE ON MEDICAL ELECTRICITY, Theoretical and 
 
 Practical, and its Use in the Treatment of Paralysis, Neuralgia, and other 
 Diseases. Third Edition, Enlarged and Revised, with One Hundred 
 and Forty-six Illustrations. In one volume octavo. Price . ^6.00 
 
 ALLEN (ALFRE^H.). F. C. S , 
 Lecturer on Chemistry at the Sheffield SchocI of Medicine. 
 
 AN INTRODUCTION TO THE PRACTICE OF COMMER- 
 CIAL ORGANIC ANALYSIS. Being a Treatise on the Properties, 
 Proximate Analytical Examination, and Modes of Assaying the various 
 Organic Chemicals and Preparations employed in the Arts, Manufac- 
 tures, Medicine, etc. ; with Concise Methods for the Detection and 
 Determination of their Impurities, Adulterations, and Products of De- 
 composition. Vol. I. — Cyanogen Compounds, Alcohols and their 
 Derivatives, Phenols, Acids, etc. Price . . . . ,$3 -50 
 
 AGNEW (d. HAYES), M.D.. 
 
 Professor of Surgery in the University of Pennsylvania. 
 
 THE LACERATIONS OF THE FEMALE PERINEUM. AND 
 VESICO-VAGINAL FISTULA, their History and Treatment, with 
 numerous Illustrations. Octavo. Price . . . . $1.50 
 
ACTON (WILLIAM), M.R.C.S., etc. 
 
 THE FUNCTIONS AND DISORDERS OF THE REPRODUC- 
 TIVE ORGANS. In Childhood, Youth, Adult Age, and Advanced 
 Life, considered in their Physiological, Social, and Moral Relations. 
 Fourth American from the Fifth London Edition. Carefully revised by 
 the Author, with additions. ....... $2.50 
 
 Mr. Actou has done good service to society hy grappling manfully with sexual vice, and 
 we trust that others, whose jxisition as men of science and teachers enable them to speak 
 witii authority, will assist in combating and arresting the evils which it entails. The spirit 
 which pervades his book is one which does credit equalfy to the head and to the heart of the 
 author. — British and Foreign JJtdico-Chirurf/ical Revieiv. 
 
 AVELING (j. H.), M. D., 
 
 Physician to Chelsea Hospital for Diseases of Women. 
 
 THE INFLUENCE OF POSTURE ON WOMEN IN GYNECIC 
 AND OBSTETRIC PRACTICE. Octavo. Cloth. Price . $2.00 
 
 ANSTIE (FRANCIS E.), M.D., 
 
 Lecturer on Materia Medica and Therapeutics, etc, 
 
 STIMULANTS AND NARCOTICS. Their Mutual Relations, with 
 Special Researches on the Action of Alcohol, Ether, and Chloroform 
 on the Vital Organism. Octavo. ..... ^3.00 
 
 ANDERSON (m'call), M.D., 
 
 Professor of Clinical Medicine in the University of Glasgow, &.c. 
 ECZEMA. The Pathology and Treatment of the various Pxzema- 
 tous Affections or Eruptions of the Skin. The Third Revised and En- 
 larged Edition. Octavo. Price . . . . . . $2.50 
 
 BUZZARD'S CLINICAL ASPECTS OF SYPHILITIC NER- 
 VOUS AFFECTIONS. i2mo. Cloth. Price . . . $1.75 
 
 BASHAM'S AIDS TO THE DIAGNOSIS OF DISEASES OF 
 THE KIDNEYS. Sixty Illustrations $1.75 
 
 BASHAM ON DROPSY, AND ITS CONNECTION WITH 
 DISEASES OF THE KIDNEYS, HEART, LUNGS, AND LIVER. 
 
 With Sixteen Plates. Third Edition. Octavo . ,. . 1^4.50 
 
 BARTH AND ROGERS MANUAL OF AUSCULTATION 
 AND PERCUSSION. From the Sixth French Edition $1.00 
 
 BRADLEY'S MANUAL OF COMPARATIVE ANATOMY 
 AND PHYSIOLOGY. Sixty Illustrations. Third Edition . $2.00 
 
 BERNAY'.S (ALBERT J.), Ph. D. 
 
 Professor of Chemistry at St. Thomas's Hospital. 
 
 N0TP:S I'OR STUDhLNTS IN CHEMLSTRY. Compiled from 
 Fowne's and other Manuals. The Sixth Edition. Cloth . $1.25 
 
 BY SAME AUTHOR. 
 
 THE STUDENTS GUIDE TO MEDICAL CHEMISTRY. 
 With Illustrations. Preparing. 
 
8 
 
 BEALE (LIONEL s.), M.D. 
 
 DISEASE GERMS: AND ON THE TREATMENT OF DIS- • 
 EASES CAUSED BY THEM. 
 
 Part L— SUPPOSED NATURE OF DISEASE GERMS. 
 Part II. — REAL NATURE OF DISEASE GERMS. 
 Part III. — THE DESTRUCTION OF DISEASE GERMS. 
 
 Second Edition, much enlarged, with Twenty-eight full-page Plates, 
 containing 117 Illustrations, many of them colored. Demy Octavo. 
 
 Price ^4-oo 
 
 LIFE THEORIES AND RELIGIOUS THOUGHT ON LIFE 
 AND VITAL ACTION IN HEALTH AND DISEASE. With 
 Plates. Price ^2.25 
 
 SAME AUTHOR. 
 
 BIOPLASM. A Contribution to the Physiology of Life, or an Intro- 
 duction to the Study of Physiology and Medicine, for Students. With 
 Numerous Illustrations. Price ^2.25 
 
 This volume is intended as a Text-Book for Students of Physiology, explaining the nature 
 of some of the most important changes which are characteristic of and peculiar to living 
 beings. 
 
 PROTOPLASM, OR MATTER AND LIFE. Third Edition, very 
 much Enlarged. Nearly 350 pages. Sixteen Colored Plates. One 
 volume. Price ......... $3-oo 
 
 Part I. DISSENTIENT. Part II. DEMONSTRATIVE. Part III. SUGGESTIVE. 
 
 HOW TO WORK WITH THE MICROSCOPE. Fifth Edition, 
 
 containing 400 Illustrations, many of them colored. Octavo. $7-5° 
 
 This work is a complete manual of microscopical manipulation, and contains a full descrip- 
 tion of many new processes of investigation, witli directions for examining objects under the 
 higliest powers, and for taking photogra^jhs of microscopic objects. 
 
 ON KIDNEY DISEASES, URINARY DEPOSITS, AND CAL- 
 CULOUS DISORDERS. Including the Symptoms, Diagnosis, and 
 Treatment of Urinary Diseases. With full Directions for the Chemical 
 and Microscopical Analysis of the Urine in Health and Disease. The 
 Third Edition. Seventy Plates, 415 figures, copied from Nature. 
 Octavo. Price . ^10.00 
 
 THE USE OF THE MICROSCOPE IN PRACTICAL MEDL 
 CINE. For Students and Practitioners, with full directions for exam- 
 ining the various secretions, &c., in the Microscope. Fourth Edition. 
 500 Illustrations. Octavo. Much enlarged. Price . . |7-5o 
 
 BLOXAM (c. L.), 
 
 Professor of Chemistry in King's College, London. 
 
 CHEMISTRY, INORGANIC AND ORGANIC. With Experi- 
 ments and a Comparison of Equivalent and Molecular Formulae. With 
 276 Engravings on Wood. Third London Edition, revised. Octavo. 
 Price, in cloth, $4.00; leather, ...... $5-oo 
 
 SAME AUTHOR. 
 LABORATORY TEACHING; OR PROGRESSIVE EXER- 
 CISES IN PRACTICAL CHEMISTRY. Fourth Edition. With 
 Eighty-nine Engravings. Crown Octavo. Price . . . ^1.75 
 
BENNETT (j. henry), M. D. 
 
 NUTRITION IN HEALTH AND DISEASE. A Contribution 
 to Hygiene and to Clinical Medicine. Third Edition, Revised and 
 Enlarged. Octavo. Cloth. Price $2.50 
 
 BY SAME AUTHOR. 
 THE TREATMENT OF PULMONARY CONSUMPTION BY 
 HYGIENE, CLIMATE, AND MEDICINE. With an Appendix on 
 the Sanitaria of the United States, Switzerland, and the Balearic Isl- 
 ands. The Third Edition, much Enlarged. Octavo. Price . $2.50 
 
 BUCKNILL(joHN CHARLES), M.D., & TUKE (daniel h.),M.D. 
 
 A MANUAL OF PSYCHOLOGICAL MEDICINE: containing the 
 Lunacy Laws, the Nosology, CEtiology, Statistics, Description, Diagno- 
 sis, Pathology (including Morbid Histology), and Treatment of Insanity. 
 Fourth Edition, much enlarged, with Twelve Lithographic Plates, and 
 numerous Illustrations. Octavo. Price .... ^8.00 
 
 This edition will contain a number of pages of additional matter, and, in consequence of 
 recent advances in Psychological Medicine, several chapters will be rewritten, bringing the 
 Classification, Pathology, and Treatment of Insanity up to the present time. 
 
 BURNETT (CHARLES h.), M. D., 
 
 Aurist to {he Presbyterian Hospital, &c, 
 
 HEARING, AND HOW TO KEEP IT. (Vol. I., American Health 
 Primers.) With Illustrations. Cloth. Price . . . $0.50 
 
 BIDDLE "(^S^B.), M. D., 
 
 Professor of Materia Medica and Therapeutics in the Jefferson Medical College, Phiiadelphia, &.c. 
 
 MATERIA MEDICA, FOR THE USE OF STUDENTS. With 
 Illustrations. Eighth Edition, Revised and Enlarged. Price $4.00 
 
 This new and thoroughly revised edition of Professor Biddle's work has incorporated in 
 it all the improvements as adopted by the New United States Pharmacopoeia just issued. It 
 is designed to present the leading facts and principles usually comprised under this head as 
 set forth by the standard authorities, and to fill a vacuum which seems to exist in the want 
 of an elementary work on the surjject. Tho larger works usually recommended as text-books 
 in our Medical schools are too voluminous for convenient use. This will be found to contaia, 
 in a condensed form, all that is most valuable, and will supply students with a reliable guide 
 to the course of lectures on Materia Medica as delivered at the various Medical schools in 
 the United States. 
 
 BALFOUrTgTw.), M.D., 
 
 Physician to the Royal Infirmary, Edinburgh; Lecturer on Clinical Medicine, &c. 
 
 CLINICAL LECTURP:S on diseases of the heart AND 
 AORTA. With Illustrations. Octavo. Price . . . $4.00 
 
 BYFORD (v^nryTA.M., M.D., 
 
 Professor of Obstetrics and Diseases of Women and Children in the Chicago Medical College, &c, 
 
 practice of medicine AND SURGERY. Applied to the 
 Diseases and Accidents incident to Women. Second Edition, Revised 
 and Enlarged. Octavo. Price 
 
 SAME AUTHOR. 
 
 ON THE CHRONIC INFLAMMATION AND DISPLACEMEN'I 
 
 OF THE UNIMPRKC;NATED uterus, a New, Enlarged, and 
 
 Thoroughly Revised P>lition, with Numerous Illustrations. 8vo. $2.50 
 
 Dr. Ryford writ^^s the exact present state of medical knowledge on the subjects presented ; 
 
 and does this so clearly, ko concisely, so truthfully, and so completely, that his book on the 
 
 ut<;ruH will always meet the approval of the profession, and be everywhere regarded as a 
 
 [xtpular standard work. — Jiujf'ulo Medical and Hur'jicul Journal. 
 
10 
 
 BLACK (d. CAMPBELL), M. D., 
 L. R. C. S. Edinburgh, Member of the General Council of the University of Glasgow-, Slc, &c, 
 
 THE FUNCTIONAL DISEASES OF THE RENAL, URINARY, 
 
 and Reproductive Organs, with a General View of Urinary Pathology. 
 
 Price . . . . . . . . . • . $2.00 
 
 The style of the author is clear, easy, and agreeable, . . . his work is a valuable contri- 
 bution to medical science, and being penned in that disposition of unprejudiced philosophical 
 inquiry which should always guide a true physician, admirably embodies the spirit of its 
 opening quotation from Professor Huxley. — Pkilada. 3Ied. Times. 
 
 BY SAME AUTHOR. 
 LECTURES ON BRIGHT'S DISEASE OF THE KIDNEYS. 
 
 Delivered at the Royal Infirmary of Glasgow. With 20 Illustrations, 
 engraved on Wood. One volume, octavo, in Cloth. Price . $1.50 
 
 BENTLEY and TRIMEN'S 
 
 MEDICINAL PLANTS. A New Illustrated Work, Complete in 
 
 Forty -two Parts. Eight Colored Plates in each Part. Price, each, 
 
 ^2.00 j or in Four Vols., One-Half Morocco, Gilt Heads . ^90.00 
 
 This work includes full botanical descriptions, and an account of the properties and uses 
 of the principal plants employed in medicine, especial attention being jsaid to those which 
 are ofiicinal in the British and United States Pharinacopffiias. The plants which supply 
 food and substances required by the sick and convalescent will be also included. Each spe- 
 cies will be illustrated by a colored plate drawn from nature. 
 
 BEASLEY (henry). 
 
 THE BOOK OF PRESCRIPTIONS. Containing over 3000 
 
 Prescriptions, collected from the Practice of the most Eminent Physi- 
 cians and Surgeons — English, French, and American ; comprising also 
 a Compendious History of the Materia Medica, Lists of the Doses of all 
 Officinal and Established Preparations, and an Index of Diseases and 
 their Remedies. Fifth Edition, Revised and Enlarged. Price ^2.25 
 
 BY SAME AUTHOR. 
 
 THE POCKET FORMULARY: A Synopsis of the British and 
 Foreign Pharmacopoeias. Tenth Revised Edition. Price . ^2.25 
 
 THE DRUGGIST'S GENERAL RECEIPT BOOK and VETERI- 
 NARY FORMULARY. Eighth Edition. Just Ready. Price, ^2.25 
 
 BIRCH (s, B.), M. D., 
 
 Member of the Royal College of Physicians, &Ci 
 CONSTIPATED BOWELS ; the Various Causes and the Different 
 Means of Cure. 
 
 BRAUNE— BELLAMY. 
 
 AN ATLAS OF TOPOGRAPHICAL ANATOMY. After Plane 
 Sections of Frozen Bodies, containing Thirty-four Full-page Photo- 
 graphic Plates and numerous other Illustrations on Wood. By Wilhelm 
 Braune, Professor of Anatomy in the University of Leipzig. Trans- 
 lated and Edited by Edward Bellamy, F. R. C. S., Senior Assistant Sur- 
 geon to, and Lecturer on Anatomy and Teacher of Operative Surgery 
 at, the Charing Cross Hospital, London. A large quarto volume. 
 Price in cloth, ^12.00 ; half morocco, ..... ^14.00 
 
11 "■ 
 
 COHEN (i. soLis), M.D. 
 
 Lecturer on Laryngoscopy and Diseases of the Throat and Chest in Jefferson Medical ColleEre. 
 
 ON INHALATION. ITS THERAPEUTICS AND PRACTICE 
 
 Including a Description of the Apparatus employed, &c. With Cases 
 and Illustrations. A New Enlarged Edition. Price . . $2.50 
 
 SAME AUTHOR. 
 CROUP. In its Relations to Tracheotomy. Price . . $l.oc 
 
 CARSON (JOSEPH), M.D., 
 
 Professor of Materia Medica and Pharmacy in the University. 
 
 A HISTORY OF THE MEDICAL DEPARTMENT OF THE 
 UNIVERSITY OF PENNSYLVANIA, from its Foundation in 1765: 
 with Sketches of Deceased Professors, &c. . . . . ^2.00 
 
 CHARTERIsTmTthew), M. D., 
 
 Member of Hospital Staff and Professor in University of Glasgow, 
 
 STUDENTS' HAND-BOOK OF THE PRACTICE OF MEDI- 
 CINE. With Microscopic and other Illustrations. Price . $2.00 
 
 This book forms oue volume of the Students' Guide Series, or Text-Books, now ia counse 
 of publicatioa. 
 
 CARPENTER (w. b.), M.D., F.R.S. 
 THE MICROSCOPE AND ITS REVELATIONS. The s.xth 
 London Edition, Revised and Enlarged, with more than 500 Illustra- 
 tions. ........... 
 
 CORR (l. h.), M.D. 
 
 OBSTETRIC CATECHISM, or Obstetrics reduced to Questions 
 
 and Answers. With Numerous Illustrations. Price . . ^2.00 
 
 CHAVASSE (p. henry), F.R.C.S., 
 
 Author of Advice to a Wife, Advice to a Mother, &c. 
 
 APHORISMS ON THE MENTAL CULTURE AND TRAIN- 
 ING OF A CHILD, and on various other subjects relating to Health 
 and Happiness. Addressed to Parents. Price . . . ^i.oo 
 
 Dr. Chavasse's works have been very favorably received and had a large circulation, the 
 value of his advice to WIVES and MOTHERS "having thus been very generally recognize<l. 
 This book is a sequel or companion to them, and it will be found both valuable and ini])or(anl 
 U> all who have the care of families, and wlio want to bring up their diildren to become useful 
 men aufl women. It is full of fresh thoughts and graceful illustrations. 
 
 CLARKE (w.fairlie), M.D., 
 
 Assistant Surgeon to Charing Cross Hospital. 
 
 CLARKE'S TREATISE ON DISEASES OF THE TONGUE. 
 
 With Lithograjihic and Wood-cut Illustrations. Octavo. Price ^4.50 
 
 It contains The Anatomy and Physiology of the Tongue, Importance of its Minute Exam- 
 ination, [tH Congenital Defects, Atroi)hy, "Hypertrophy, Parasitic Diseases, Intiammation, 
 Byphilis and ita effecte, Various Tumors to which it is subject. Accidents, Injuries, <fec., <tc. 
 
 COOPER (.s.). 
 
 A DICTIONARY OF PRACTICAL SURGERY AND ENGY- 
 
 CL0P^:DIA of SURC;ICAL science. New Edition, brought 
 
 down to the present time. By Samukl A. Lane, F.R.C.S., assisted by 
 
 other eminent Surgeons. In two vols., of over 1000 pages each. ;^ 1-2. 00 
 
CLAY (CHARLES), M. D. 
 
 Fellow of the London Obstetrical Society, &c. 
 
 THE COMPLETE HAND-BOOK OF OBSTETRIC SURGERY, 
 
 or, Short Rules of Practice in Every Emergency, from the Simplest to 
 the most Formidable Operations in the Practice of Surgery. First 
 American from the Third London Edition. With numerous Illustra- 
 tions. In one volume. ^2.00 
 
 CHAMBERS (thomas k.), M. D., 
 
 LECTURES, CHIEFLY CLINICAL. Illustrative of a Restorative 
 System of Medicine. 
 
 CORMACK (sir john ^J^^K. B., F. R. S. E., M. D. 
 
 Edinburgh and Paris, Fellow Royal College of Physicians, Physician to the Hertford British Hospital, Paris, &c. 
 
 CLINICAL STUDIES, Illustrated by Cases observed in Hospital and 
 Private Practice. With Illustrative Plates. 2 Volumes. Octavo. ^5.00 
 
 COBBOLD (t. spencer), M. D., F. R. S. 
 
 PARASITES : A Treatise on the Entozoa of Man and Animals ; 
 including some Account of the Ectozoa. With 85 Engravings. Oc- 
 tavo. Price .......... I5.00 
 
 CLEAVELAND (c. h.), M.D., 
 
 Member of the American Medical Association, &.c, 
 
 A PRONOUNCING MEDICAL LEXICON. Containing the Cor- 
 rect Pronunciation and Definition of Terms used in Medicine and the 
 Collateral Sciences. Improved Edition, Cloth, 75 cts. ; Tucks, $1.00 
 
 This work is not only a Lexicon of all the words in common use in Medicine, but it is 
 also a Pronouncing Dictionary, a feature of great value to Medical Students. To the Dis- 
 penser it will prove an excellent aid, and also to the Pharmaceutical Student. It has received 
 strong commendation both from the Medical Press and from the j)rofession. 
 
 COLES (oakley), D.D.S. 
 
 Dental Surgeon to the Hospital for Diseases of the Throat, Slc. 
 
 A MANUAL OF DENTAL MECHANICS. Containing much 
 information of a Practical Nature for Practitioners and Students. 
 
 INCLUDING . 
 
 . The Preparation of the Mouth for Artificial Teeth, on Taking Impressions, Various 
 
 Modes of Applying Heat in the Laboratory, Casting in Plaster of Paris and Metal, 
 Precious Metals used in Dentistry, Making Gold Plates, Various Forms of Porcelain 
 used in Mechanical Dentistry, Pivot Teeth, Choosing and Adjusting Mineral Teeth, the 
 Vulcanite Base, the Celluloid Base, Treatment of Deformities of the Mouth, Eeceipts 
 for Making Gold Plate and Solder, etc., etc. 
 With 140 Illustrations. Price ...... $2.00 
 
 SAME AUTHOR. 
 
 ON DEFORMITIES OF THE MOUTH, CONGENITAL AND 
 ACQUIRED, with their Mechanical Treatment. Second Edition, Re- 
 vised and Enlarged. With Illustrations. Price, . 
 
 DOMVILLE (EDWARD J.), M. D. 
 
 A MANUAL FOR HOSPITAL NURSES and Others engaged in 
 Attending the Sick. i2mo. Price . . . . . ^i.oo 
 
13 
 
 CLARK (f. le gros), F. R. S., 
 
 Senior Surgeon to St. Thomas's Hospital. 
 
 OUTLINES OF SURGERY AND SURGICAL PATHOLOGY, 
 including the Diagnosis and Treatment of Obscure and Urgent Cases, 
 and the Surgical Anatomy of some Important Structures and Regions. 
 Assisted by W. W. Wagstaffe, F. R. C. S., Resident Assistant-Surgeon 
 of, and Joint Lecturer on Anatomy at, St. Thomas's Hospital. Second 
 Edition, Revised and Enlarged. Price . . . . ^2.00 
 
 COTTLE (e. wyndham), M. A.. F. R. C. S., &c. 
 THE HAIR IN HEALTH AND DISEASE. Partly from Notes 
 by the late George Navler, F. R. C. S., Surgeon to the Hospital for 
 Diseases of the Skin, &c. i8mo. Cloth. Price . . $o-75 
 
 CURLING (t. b.), F.R.S., 
 
 Consulting Surgeon to the London Hospital, &,c. 
 
 A PRACTICAL TREATISE ON THE DISEASES OF THE 
 TESTIS AND OF THE SPERMATIC CORD AND SCROTUM. 
 
 Fourth Revised and Enlarged Edition. Octavo. Price. . $5-5o 
 
 BY SAME AUTHOR. 
 
 OBSERVATIONS ON DISEASES OF THE RECTUM. With 
 
 Illustrations. Fourth Edition, Revised and Enlarged. Octavo. Cloth. 
 
 Price . . . $2.75 
 
 CAZEAUX (p.). M. D., 
 
 Adjunct Professor of the Faculty of Medicine, Paris, etc. 
 
 A THEORETICAL AND PRACTICAL TREATISE ON MIDWIFERY, 
 including the Diseases of Pregnancy and Parturition. Translated from 
 the Seventh French Edition, ReA^sed, Greatly Enlarged, and Improved, 
 by S. Tarnier, Clinical Chief of the Lying-in Hospital, Paris, etc., 
 with numerous Lithographic and other Illustrations. Price, in Cloth, 
 $6.00; in Leather ........ $7-oo 
 
 M. Cazeaux's Great Work on Obstetrics has become classical in its character, and almost 
 an Encyclopie<iia in its fulness. Written expressly for the use of students of medicine, its 
 teachinsjs are ])lain and explicit, presenting a condensed summary of the leading principles 
 established by the masters of the obstetric art, and such clear, practical directions for the 
 management of the pregnant, parturient, and ))uerperal states, as have been sanctioned by 
 the moat authoritative practitioners, and confirmed by the author's own experience. 
 
 DOBELL (HORACE), M.D., 
 
 Senior Physician to the Hospital. 
 
 WINTER COUGH (CATARRH, BRONCHITIS, EMPHYSEMA, 
 ASTHMA). Lectures Delivered at the Royal Hospital for Diseases of 
 the Chest. The Third Enlarged Edition, with Colored Plates. Octavo. 
 Price $3.50 
 
 BY SAME AUTHOR. 
 
 ON LO.SS OF WEIGHT, BLOOD-SPITTING, AND LUNG 
 DISfc^ASE. With a Colored Frontispiece of the Lung, a Tabular Map, 
 &c., &c. Octavo. Cloth. Price . . . . • ?53-25 
 
14 
 DIXON (jAMEs), F.R. CS. 
 
 Surgeon to the Royal London Ophtha'mic Hospital, ic. 
 
 A GUIDE TO THE PRACTICAL STUDY OF DISEASES OF 
 
 THE EYE, with an Outline of their Medical and Operative Treatment, 
 
 with Test Types and Illustrations. Third Edition, thoroughly Revised, 
 
 and a great portion Rewritten. Price ..... ^2.00 
 
 Mr. Dixon's book is essentially a practical one, written by an observant author, who brings 
 to has special subject a sound knowledge of general Medicine and Unrgery. —Uubiin Quarteriy 
 
 DILLNBERGER (dr. emil). 
 
 A HANDY-BOOK OF THE TREATMENT OF WOMEN AND 
 
 CHILDREN'S DISEASES, according to the Vienna Medical School. 
 
 Part I. The Diseases of Women. Part II. The Diseases of Children. 
 
 Translated from the Second German Edition, by P. Nicol, M. D. 
 
 Price ^1-5° 
 
 Many practitioners will be glad to possess this little manual, which gives a large mass 
 (A practical hints on the treatment of diseases which probably make up tlie larger half oi 
 every-day practice. The translation is well made, and exjilanations of reference to German 
 medicinal preparations are given with proper fulness. — The Practitioner. 
 
 DUNGLISON (RICHARD j.), M. D. 
 
 THE PRACTITIONER'S REFERENCE BOOK. Containing 
 
 Therapeutic and Practical Hints, Dietetic Rules and Precepts, and 
 
 other General Information Useful to the Physician, Pharmacist, and 
 
 Student. Octavo. Cloth. Second Edition. Price . . $2fS^ 
 
 DUCHENNE (dr. g. b.). 
 LOCALIZED ELECTRIZATION AND ITS APPLICATION 
 TO PATPIOLOGY AND THERAPEUTICS. Translated by Her- 
 bert TiBBiTS, M.D. With Ninety-two Illustrations. Price . $3.00 
 Duchenne's great work is not only a well-nigh exhaustive treatise on the medical uses of 
 Electricity, but it is also an elaborate exposition of the diflferent diseases in which Electric- 
 ity has proved to be of value as a therapeutic and diagnostic agent. 
 
 Part II., illustrated by chromo-lithographs and numerous wood-cuts, is preparing. 
 
 DURKEE (siLAs), M.D., 
 
 Fellow of the Massachusetts Medical Society, &c, 
 
 GONORRHCEA AND SYPHILIS. The Sixth Edition, Revised 
 and Enlarged, with Portraits and Eight Colored Illustrations. Octavo. 
 Price ^3-5° 
 
 Dr. Durkee 
 thorough hon 
 
 ner in which the facts are cited, the clever way 
 
 in, the lucidity of the reasoning, and the care with which the therapeutics ot venereal com- 
 plaints are treated. — Lancet. 
 
 DRUITT (ROBERT), F.R.C.S. 
 THE SURGEON'S VADE-MECUM. A Manual of Modern Sur- 
 gery. The Eleventh Revised and Enlarged Edition, with 369 lUus- 
 trations. Price . . . ■ • • • • • $S-°° 
 
15 
 DALBY (w. B.), F. R. C. S., 
 
 Aural Surgeon to St. George's Hospital. 
 
 LECTURES ON THE DISEASES AND INJURIES OF THE 
 EAR. Delivered at St. George's Hospital. With Illustrations. 
 Price ^1-50 
 
 We eordiallv recommend this admirable volume hy Mr. Dalby as a trustworlliy tjiiide in 
 the treatment of tite ati'eetions of the ear. The bookis moderate in price, beautifully illus- 
 trated by wood cuts, and got up in the best style. — Glungoiv Medical Journal. 
 
 DAY (WILLIAM henry). M. D., 
 
 Physician to the Samaritan Hospital for Women and Children, die. 
 
 HEADACHES, THEIR NATURE. CAUSES, AND TREAT- 
 MENT. Third Edition. 121110. Cloth. Price . . $2.00 
 
 ELLIS (EDWARD). M. D., 
 Physician to the Victoria Hospital for Sick Children, &c. 
 
 A PRACTICAL MANUAL OF THE DISEASES OF CHIL- 
 DREN, with a Formulary. Third Enlarged Edition, Revised and 
 Improved. One volume ....... 
 
 The AlTTHOR, in issuing this new edition of his book, says : " I have very carefully revised 
 each chai)ter, adding several new sections, and making "considerable additions where the 
 subjects seemed to require fuller treatment, without, however, sacrificing conciseues.s or 
 uaduly increasing the bulk of the volume." 
 
 FENWICK (SAMUEL). 
 
 OUTLINES OF THE PRACTICE OF MEDICINE. With special 
 
 reference to the Prognosis and Treatment of Disease. With Formula 
 and Illustrations. Large i2mo. Price ^2.00 
 
 FOTHERGILL (j. milner), M. D.. 
 
 Assistant Physician to City of London Hospital for Diseases of the Chest, die. 
 
 THE HEART, ITS DISEASES AND THEIR TREATMENT, 
 
 including the Gouty Heart. Second Edition, Entirely Rewritten and 
 Enlarged, with Two Full-Page Lithographic Plates and Forty other 
 
 Illustrations. Octavo. Price ^3-5° 
 
 " Dr. FotherKill's remarks on rest, on j>roper blood nutrition in Heart Disease, in the 
 treatment of Se<iuela; of it, and on the action of special medicines, all indicate that in study- 
 ing the i)athology of Heart Disease, he has earnestly kept in view the best means of mitigat- 
 ing sufl'ering and of prolonging life." — Lancet. 
 
 FOX (CORNELIUS B.), M. 0. 
 SANITARY EXAMINATIONS of Water, Air, and Food. 94 En- 
 gravings. 8vo. Price . . . . . . • ^4.00 
 
 FOX (TiLiiUHY), M. D.. F. R. C. P. 
 
 Physician to the Department for Skin Diseases in University College Hosoital. 
 
 ATLAS OV SKIN DISEASE.S. Consi.sting of a Series of Colored 
 Iliii^trations, in Monthly Parts, togetiier witii Descri^jtive Text and 
 Notes ui>on Treatment ; each Part containing Four Plates, reproduced by 
 Chromo-Eithograpliy from the work of Willan & Pateman, or taken from 
 Original Sources. Now Complete in 18 Parts. Price, per Part, $2.00 ; 
 or in one large Folio volume, bound in cloth. Price . . ;^3o.oo 
 
16 
 
 FENNER (c. s.), M. D., &c. 
 
 VISION: ITS OPTICAL DEFECTS, and the Adaptation of Spec- 
 tacles ; embracing Physical Optics, Physiological Optics, Errors of Re- 
 fraction and Defects of Accommodation, or Optical Defects of the Eye. 
 With 74 Illustrations. Selections from the Test Types of Jaeger and 
 Snellen, etc. Octavo. Price . . . . . - ^3-5° 
 
 FOSTER (BALTHAZAR), M. D., 
 
 Professor of Medicine in Queen's College. 
 
 LECTURES AND ESSAYS ON CLINICAL MEDICINE. Re- 
 vised and Enlarged by the Author. With Engravings. Octavo. 
 Price ...... = .••• $3-°° 
 
 FRANKLAND (e.), M. D., F. R. S., &c. 
 
 HOW TO TEACH CHEMISTRY, being the substance of Six 
 Lectures to Science Teachers. Reported, with the Author's sanction, 
 by G. George Chaloner, F. C. S., 8z:c. With Illustrations . ^1.25 
 
 FULTON (j.), M. D., 
 
 Professor of Physiology, Trinity Medical College, TorontOi 
 
 A TEXT-BOOK OF PHYSIOLOGY. Second Edition, Revised 
 and Enlarged. With numerous Illusti-ations. Octavo. Price ^4.00 
 
 FLINT (AUSTIN), M.D., 
 
 Professor of the Principles and Practice of Medicine, &c., Bellevue Hospital College, New Ycrk. 
 
 CLINICAL REPORTS ON CONTINUED FEVER. Based on 
 an Analysis of One Hundred and Sixty-four Cases, with Remarks on 
 the Management of Continued Fever; the Identity of Typhus and 
 Typhoid Fever; Diagnosis, &c., &c. Octavo. Price . . ^2.00 
 
 GANT (FREDERICK J.), F. R. C. S., 
 Assisted by Drs. Morrell Mackenzie, Barnes, Erasmus Wilson, and other Specialists!' 
 
 THE SCIENCE AND PRACTICE OF SURGERY. Second 
 
 Edition. 1700 Pages. 1000 Illustrations. 2 Vols. Price, cloth, ^11.00 ; 
 sheep . . . . . . . . . . . ^13.00 
 
 DISEASES OF THE BLADDER, PROSTATE GLAND, AND 
 URETHRA, including a Practical View of Urinary Diseases, Deposits, 
 and Calculi. Fourth Edition, Revised and Enlarged. With New Il- 
 lustrations. Now Ready. Price ...... $3.00 
 
 GODLEE (r. J.), M.D., 
 
 Assistant-Surgeon University College Hospitali 
 
 AN ATLAS OF HUMAN ANATOMY. Illustrating the Anatomy 
 of the Human Body, in a Series of Dissections. Accompanied by 
 References and an Explanatory Text. To be completed in Twelve or 
 Thirteen Bi-monthly Parts, Folio Size, each Part containing Four large 
 Colored Plates, or Eight Figures. Ten Parts Now Ready. Price per 
 Part ^2.50 
 
17 
 GROSS (SAMUEL D.), M. D., 
 
 Professor of Surgery in the Jefferson Medical College, Philadelphia, etc. 
 
 AMERICAN MEDICAL BIOGRAPHY OF THE NINETEENTH 
 
 CENTURY. With a Portrait of Benjamin Rush, M.D. Octavo. $3.50 
 
 GREENHOW (e. headlam). M. D., 
 
 Fellow of the Royal Collego of Physicians, etc. 
 
 ON CHRONIC BRONCHITIS, Especially as Connected with Gout. 
 Emphysema, aijd Diseases of the Heart. Price . . . $1.50 
 
 ADDISON'S DISEASE. Illustrated by numerous Cases and 5 
 full-page Colored Engravings. Price . . . . . I3.00 
 
 GOWERS (w. R.), M. D., F. R. C. P., 
 
 Assistant Professor of Clinical Medicine in University College. 
 
 A MANUAL AND ATLAS OF MEDICAL OPHTHALMO- 
 SCOPY. With 16 Colored, Autotype, and Lithographic Plates, and 
 26 Woodcuts, comprising 112 original Illustrations of the Changes in 
 the Eye in Diseases of the Brain, Kidneys, etc. Octavo. . . $6.00 
 
 GALLABIN (alfred lewis), M. D., 
 
 Assistant Obstetric Physician and Joint Lecturer on Midwifery, Guy's Hospital, &c. 
 
 THE STUDENT'S GUIDE TO THE DISEASES OF WOMEN. 
 
 With Numerous Illustrations. i2mo. Cloth. Price . . ^2.00 
 
 HIGGINS (chX^s), F. R. C. S., 
 
 Ophthalmic Surgeon, Guy's Hospital, &c. 
 
 HINTS ON OPHTHALMIC OUT-PATIENT PRACTICE. Sec- 
 ond Edition. i6mo. Cloth. Price .... 60 cts. 
 
 HUNTErTcharles). 
 MECHANICAL DENTISTRY. A Practical Treatise on the Con- 
 struction of the Various Kinds of Artificial Dentures, with Formula, 
 Receipts, &c. 100 Illustrations. Price .... $2.. 2^ 
 
 HEATH (CHRISTOPHER), F. R. C. S., 
 
 Surgeon to University College Hospital and Holme Professor of Clinical Surgery in University College, 
 
 OPERATIVE SURGERY. Elegantly Illustrated by 20 Large Col- 
 ored Plates, Imperial Quarto Size, each Plate containing several Fig- 
 ures, drawn from Nature by M. Leveille', of Paris, and Colored by hand 
 under his direction. (Complete in Five Quarterly Parts. Price, per Part, 
 $2.50; or in one volume, handsomely bound ui cloth. Price $14.00 
 
 HEWITT (grah y), M. D., 
 
 Physician to the British Lying-in Hospital, and Lecturer on Diseases of Women and Children, &c, 
 
 THE DIAGNOSIS, PATHOLOGY, AND TREATMICNT OF 
 DISEA.SES OF WOMEN, including the Diagnosis of Pregnancy. 
 Founded on a Course of Lectures delivered at St. Mary's Hospital 
 Medical School. The Third Edition, Revised and Enlarged, with 
 new Illustrations. Octavo. Price in Cloth . . . j;4.oo 
 
 " Leather . . . 5.00 
 
 Tliis new edition of Dr. Ilcwitt'.sbook has been bo much modificil, that it may bo considered 
 subHtiintiuliy anf;w bv^k ; very much of the matter has been entirely rewritten, and tliewliole 
 ■work ha.H been rearrancfcd in hucIi a manner jw to present a most decided improvement over 
 previoiLS editions. \)t. Hewitt is tlie leadiiuj clinical teacher on Diseases of Women in London, 
 and the characteristic attention paid to Diagnrwia by him has given his work great j>opnlarity 
 
18 
 HILLIER (THOMAS), M.D., 
 
 Physician to the Hospitai for Sicl< Children, &.c 
 
 A CLINICAL TREATISE ON THE DISEASES OF CHILDREN. 
 Octavo. Price ......... ^2.00 
 
 HANDY'S TEXT-BOOK OF ANATOMY and Guide to Dissec- 
 tions for the Use of Students. 312 Illustrations. Octavo . $3.00 
 
 HOLDEN (luther), F.R.C.S. 
 HUMAN OSTEOLOGY, compri.sing a Description of the Bones 
 
 with Delineations of the Attachments of the Muscles, &c. With 
 
 numerous Illustrations. Fifth Edition, carefully Revised. Price, ^5.50 
 HOLDEN'S MANUAL OF DISSECTIONS OF THE HUMAN 
 
 BODY. Fourth London Edition. With Illustrations. Price $5.50 
 LANDMARKS, MEDICAL AND SURGICAL. Second Edition. 
 
 Revised and Enlarged. Price . . . . , .' $1.00 
 
 HARRIS (cHAPiN A.), M. D., D. D. S. 
 
 Late President of and Professor of the Principles and Practice of Dental Suri:ery in the Baltimore College, &.c, 
 
 THE PRINCIPLES AND PRACTICE OF DENTISTRY. Tenth 
 Revised Edition. In great part rewritten, rearranged, and with many- 
 new and important Illustrations. Including — i. Dental Anatomy and 
 Physiology. 2. Dental Pathology and Therapeutics. 3. Dental Sur- 
 gery. 4. Dental Mechanics. Edited by P. H. Austen, M.D., Pro- 
 fessor of Dental Science and Mechanism in the Baltimore College of 
 Dental Surgery. With nearly 400 Illustrations, including many new 
 ones made especially for this edition. Royal octavo. Price, in cloth, 
 ^6.50; in leather ........ ^7.50 
 
 This new edition of Dr. Harris's work has been thoroughly revised in all its parts — more 
 80 than any previous edition. So great have been the advances in many branches of dentistry, 
 that it was found necessary to rewrite the articles or subjects, and this has been done in the 
 most efficient raanuer by Professor Austen, for many years an associate and friend of Dr. 
 Harris, assisted by Professor Gorgas and Thomas S. Latimer, M. D. The publishers feel 
 assured that it will now be found the most complete text-book for the student and guide for 
 tlie practitioner in the English language. 
 
 SAME AUTHOR. 
 A DICTIONARY OF MEDICAL TERMINOLOGY, DENTAL 
 SURGERY, AND THE COLLATERAL SCIENCES. Fourth Edition, 
 Carefully Revised and Enlarged, by Ferdinand J. S. Gorgas, M. D., 
 D.D.S., Professor of Dental Surgery in the Baltimore College, &c., &c. 
 Royal octavo. Price, in cloth, ^6.50; in leather . . ^7-5° 
 
 The many advances in Dental Science rendered it necessary that this edition should be 
 thoroughly revised, which has been done in the most satisfactory manner by Professor Gorgas, 
 Dr. Harris's successor in the Baltimore Dental College, he having added nearly three thou- 
 sand new words, besides making many additions and corrections. The doses of the more 
 prominent medicinal agents have also been added, and in every way the book has been greatly 
 improved, and its value euhancetl as a work of reference. 
 
 HABERSHON (s. a), M. D., F. R. C. R, 
 
 Senior Physician, Guy's Hospital. 
 
 ON DISEASES OF THE ABDOMEN, STOMACH, and Other 
 
 Parts of the Alimentary Canal. Third London Edition. Price, $5.00 
 
 ON DISEASES OF THE STOMACH : The Varieties of Dyspepsia. 
 
 their Diagnosis and Treatment. Third Edition. Octavo . ^1.75 
 
19 
 
 HARDWICH AND DAWSON. 
 
 HARDWICH'S MANUAL OF PHOTOGRAPHIC CHEMISTRY. 
 
 With Engravings. Eighth Edition. Edited and Rearranged by G. 
 Dawson, Lecturer on Photography, &c., &c. i2mo . . $2.00 
 
 HARLAN (geTIrge c), M. D., 
 
 Su geon to Wills' Eye Hospital, &c. 
 
 P:YESIGHT. and how to care for it. (Vol. IV., Amer- 
 ican Health Primers.) Cloth. Price .... $0.50 
 
 HEADLAND (f. w.), M. D., 
 
 Fellow of the Royal College of Physicians, SiC, &c. 
 
 ON the action of medicines in the system. Sixth 
 American from the Fourth London Edition. Revised and Enlarged. 
 Octavo. Price . . . . . . . . . $3.00 
 
 Dr. Headland's work gives the only scientific and satisfactory view of the action of medi- 
 cine; and this not in the way of idle speculation, but by demonstration and experiments, 
 and inferences almost as indis|)utab]e as demonstration'!. It is truly a great scientific work 
 in a small compass, and deserves to be the hand-book of every lover of the Profession. It 
 has received the approbation of the Medical Press, both in this country and in Europe, and 
 is pronounced by them to be the most original and practically useful work that has been 
 issued for many years. 
 
 HOFF (o.), M.D. 
 
 on HiEMATURIA as a Symptom of Diseases of the Genito-Uri- 
 
 nary Organs. Illustrated. i2mo. Cloth. . . . . $0.75 
 
 HEATH (CHRISTOPHER), F.R.C.S.,, 
 
 Surgeon to University College Hospital, &c. 
 
 INJURIES AND DISEASES OF THE JAWS. The Jacksonian 
 Prize Essay of the Royal College of Surgeons of England, 1867. Sec- 
 ond Edition, Revised, with over 150 Illustrations. Octavo. Price, 
 
 ^4-25 
 
 SAME AUTHOR. 
 
 A MANUAL OF MINOR SURGERY AND BANDAGING, for 
 
 the Use of House Surgeons, Dressers, and Junior Practitioners. With 
 
 a Formulae and Numerous Illustrations. i6mo. Price .. ^2.00 
 
 A GUIDE TO SURGICAL DIAGNOSIS, for Practitioners and 
 Students, ismo. Cloth. Price . . . . . ^1.50 
 
 HAYDEN (THOMAS), M. D., 
 
 Fellow of the King and Queen's College of Physicians, &c., &.c. 
 
 THE DISEASES OF THE HEART AND AORTA. With 8r 
 Illustrations. In two volumes, Of:tavo, of over 1200 pages. Price, ^6.00 
 
 HUFELAND (c. w.), M.D. 
 
 THE ART OF PROLONGING LIFE. Edited by Erasmus Wil- 
 son, M. D., F. R.S., &c. i2mo. Cloth $1.00 
 
 HAY (iiioMAs). M. D., 
 
 HISTORY OF A CASE OF RECURRING SARCOMATOUS 
 TUMOUR OF THE ORlilT IN A CHILD. With Three Full Page 
 Illustrations, representing the Tumour in its Various Stages. Price, jSo.50 
 
20 
 HEWSON (addinell,) M. D. 
 
 Attending Surgeon Pennsylvania Hospital, &c. 
 
 EARTH AS A TOPICAL APPLICATION IN SURGERY. 
 Being a full Exposition of its use in all the Cases requiring Topical 
 Applications admitted in the Surgical Wards of the Pennsylvania Hospi- 
 tal during a period of Six Months. With Illustrations. Price ^2.50 
 
 HUTCHINSON (Jonathan), R R. C. S. 
 
 Senior Surgeon to tfie London Hospital. 
 
 ILLUSTRATIONS OF CLINICAL SURGERY. Consisting of 
 Plates, Photographs, Wood-cuts, Diagrams, etc., Illustrating Surgical 
 Diseases, Symptoms and Accidents, also Operations and other Methods 
 of Treatment. With Descriptive Letter-press. -10 Parts Bound, com- 
 plete in itself. Price, ^25.00. Parts 11 and 12 now ready. Price, ^2.50 
 
 HODGE (hughl.), M. D. 
 
 Emeritus Professor in tlie University of Pennsylvania. 
 
 HODGE ON FCETICIDE, OR CRIMINAL ABORTION. 
 Fourth Edition. Price, in paper, 30 cents; in cloth, . $0.50 
 
 HODGE'S (h. lenox) NOTE- BOOK FOR CASES OF OVARIAN 
 TUMORS. With Diagrams, etc. Price, . • . . . ^0.50 
 
 HOLDEN (edgar), A. M., M. D., 
 
 Of Newark, New Jersey. 
 CONTAINING THREE HUNDRED ILLUSTRATIONS. 
 THE SPHYGMOGRAPH. Its Physiological and Pathological In- 
 dications. The Essay to which was awarded the Stevens Triennial 
 Prize in the College of Physicians and Surgeons in New York, April, 
 38.73. Illustrated by Three Hundred Engravings on Wood. One vol- 
 lume octavo. Price. . . . . . . . . ^2.00 
 
 HOOD (p.), M.D. 
 
 A TREATISE ON GOUT, RHEUMATISM, AND THE ALLIED 
 AFFECTIONS. Crown octavo. ^3.50 
 
 JONES (h. macnaughton), M. D., M. Ch. 
 
 A PRACTICAL TREATISE ON AURAL SURGERY. Illus- 
 trated. i2mo. Price . . . . . . . .^1.50 
 
 JONES (t. WHARTON), F.R.S. 
 DEFECTS OF SIGHT AND HEARING. Their Nature, Causes, 
 Prevention, &c. Second Edition. Price ... - $°-5° 
 
 JONES, SIEVEKING, and PAYNE. 
 
 A MANUAL OF PATHOLOGICAL ANATOMY. By C. Hand- 
 field Jones,, M. D., F. R. S., Physician to St. Mary's Hospital; and 
 Edward H. Sieveking, M.D. , F.R.C.P., Physician to St. Mary's Hos- 
 pital. A New and Enlarged Edition. Edited by J. F. Payne, M.B., 
 F R.C.P., Assistant Physician and Lecturer on Morbid Anatomy at St. 
 Thomas's Hospital. With Numerous Illustrations. . . ^5.50 
 
21 
 JAMES (frosser), M. D., IvI. R. C. P., 
 
 Physician to Throat Hospital. 
 
 SORE THROAT: Its Nature.Varieties. and Treatment, and its Con- 
 nection with other Diseases. Fourth Edition. Colored Plates. i2mo. 
 Price ^2.25 
 
 JONES' AURAL ATLAS. 
 AN ATLAS OF DISEASES OF THE MEMBRANA TYMPANI. 
 
 Being a Series of Colored Plates, containing 62 Figures. With appro- 
 priate Letter-Press and Explanatory Text by H. McNaughton Jones. 
 M.D., Surgeon to the Cork Ophthalmic and Aural Hospital. 4to 
 Cloth'. Pnce ^^ °° 
 
 KIDD (josepioTmTd., M. R. C. S. 
 THE LAWS OF THERAPEUTICS, or The Science and Art of 
 Medicine. 121110. Cloth. Price ^^-^S 
 
 LONGLEy"(elias). 
 
 Author of a " Pronouncing Vocabul ry of Geographical f.nd Personal Names," Lc. 
 
 STUDENT'S POCKET MEDICAL LEXICON. Giving the Cor- 
 rect Pronunciation and Definition of all Words and Terms in general 
 use in Medicine and the Collateral Sciences. The Pronunciation being 
 plainly represented in the American Phonetic Alphabet. With an 
 Appendix, containing a Complete List of Poisons and their Antidotes, 
 Abbreviations used in Prescriptions, and a Metric Scale of Doses. 
 24nio. Cloth. Price, $1.00 ; in Leather, with Tucks and Pocket, $1.25 
 
 This is an entirely new Medical Pictionarv, containing sojiie 300 compactly printed 
 'Mmo pa«'-es very curefullv prepared bv the antlior, who has had much experience in the 
 preparation of si'inilar works, assisted bv the Professors of Chemistry and of Botany in one 
 ',f our leadinc' Medical Colleges. It contains all medical terms in common use, with their 
 pronunciation and definition, without i)eing encumbered with obsolete or useless words. 
 It is essentially new in many of its features, and fully brought up to the present state oi 
 medical science.- 
 
 LAWSON (^eo^e), F.R.C.S., 
 
 Surgeon to the Royal London Ophthalnnic Hospital. 
 
 DISEASES AND INJURIES OF THE EYE, THEIR MEDICAL 
 AND SURCICAL TREATMENT. Containing a Formulary, Test 
 Types, and Numerous Illustrations. Price .... 
 
 LEBER & ROTTENSTEIN (drs.). 
 
 DENTAL CARIES AND ITS CAUSES. An Investigation into 
 the Influence of Fungi in the destruction of the Teeth, translated by 
 'Ihomas H. Chandler, D.M.D , Professor of Mechanical Dentistry in 
 the Dental School of Harvard University. With Illustrations. Octavo. 
 Price ^1-25 
 
 LEARED (ARTHUR), M.D., F.R.C.P. 
 
 IMPERFECT DIGESTION: ITS CAUSES AND TREATMENT. 
 Tlie Sixth Edition, Revised and Enlarged. .... $1.50 
 
 KOLLMEYER (a. h.), A. M., M. D. 
 
 Professor of Materia Medica and Therapeutics, Montreal College, 
 
 CHEMIA COARTATA ; or, The Key to Modern Chemistry. With 
 Numerous Tables, Tests, &c., &c. Price, .... ^2.25 
 
22 
 
 LEWIN (dr. George). 
 
 Professor at the Fr,-Wilh. University, and Surgeon-in-Chief of tlie Syphilitic Wards and Skin Diseases of 
 
 the Charity Hospital, Berlin. 
 
 THE TREATMENT OF SYPHILIS by Subcutaneous Sublimate 
 
 Injections. With a Lithograpliic Plate illustrating the Mode and Proper 
 Place of administering the Injections, and of the Syringe used for the 
 purpose. Translated by Carl Prcegler, M.D., late Surgeon in the 
 Prussian Service, and E. H. Gale, M.D., late Surgeon in the United 
 States Army. Price . . . . . . . . ;gi.5o 
 
 MASON (FRANCIS), F.R.C.S., 
 
 Surgeon and Lecturer on Anatomy at St. Thonnas' Hospital, &c, 
 
 THE SURGERY OF THE FACE. With lOO Illustrations, En- 
 graved on Wood, of Various Operations Performed. Octavo. Cloth. 
 
 Price, $2.25 
 
 MORRIS ^ii^Y), F. R. C. S. 
 
 THE ANATOMY OF THE JOINTS OF MAN. Comprising a 
 Description of the Ligaments, Cartilages, and Synovial Membranes ; of 
 the Articular Parts of Bones, &c. Illustrated by 44 Large Plates and 
 Numerous Figures, many of which are Colored. Octavo. Price, ^^5.50 
 
 MACNAMARA (c). 
 
 Surgeon to the Ophthalmic Hospital, and Professor of Ophthalmic Medicine in the Medical College, Calcutta, 
 
 MANUAL OF THE DISEASES OF THE EYE. The Third 
 Edition, carefully Revised; with Additions, and numerous Colored 
 Plates, Diagrams of the Eye, many Illustrations on Wood, Snellen's 
 Test Types, &c., &c. Price . . . . . . ^4.00 
 
 MARSH (SYLVESTER). 
 
 SECTION-CUTTING. A Practical Guide to the Preparation and 
 Mounting of Sections for the Microscope — special prominence being 
 given to the subject of Animal Sections. With Illustrations. Cloth. 
 
 Price, $0.75 
 
 MACKENZIE (morell), M. D., 
 
 Physician to the Hospital for Diseases of the Throat, &c. 
 
 GROWTHS IN THE LARYNX. Their History, Causes, Symp- 
 toms, &c. With Reports and Analysis of One Hundred Cases. With 
 Colored and other Illustrations. Price ..... ^2.00 
 
 OTHER WORKS BY THE SAME AUTHOR. 
 
 THE LARYNGOSCOPE IN THROAT DISEASES. With an 
 
 Appendix on Rhinoscopy. Third Edition, Enlarged. With New Il- 
 lustrations. Price ........ 
 
 THE DISEASES OF THE THROAT AND NOSE. Including 
 The Pharynx, The Larynx, Trachea, CEsophagus, Nose, Neck, &c. 
 With numerous Illustrations. Preparing. 
 
 DIPHTHERIA. Its Nature, Varieties, and Treatment. Price, ^o 75 
 
 PHARMACOPGEIA OF THE HOSPITAL FOR DISEASES OF 
 THE THROAT. .With One Hundred and Fifty Formulae for Gar- 
 gles, &c., &c. Fourth Edition. Preparing. 
 
23 
 
 MEIGS AND PEPPER. 
 
 A PRACTICAL TREATISE ON THE DISEASES OF CHIL- 
 DREN. By J. Forsyth Meigs, M.D., Fellow of the College of Physi- 
 cians of Philadelphia, &c., &c., and William Pepper, M.D., Physician 
 to the Philadelphia Hospital, &c. Sixth Edition, thoroughly Revised 
 and greatly Enlarged, forming a Royal Octavo Volume of over looo 
 pages. Price, bound in cloth, ^6.00; leather . . . ^7.00 
 
 It is tiie most complete work ou the subject ia our language. It contains at once tlie re- 
 sults of personal, au<l tlie exjierience of others. Its quotations from the most recent authf)r- 
 ities, at liome and abroad, are ample, and we think tlie authors deserve congratulations for 
 having jiroduced a book unequalled for the use of the student and indispensable as a work 
 of reference for the practitioner. — American Jledical Journal. 
 
 MEARS (j. EwiNc;), M. D., 
 
 Demonstrator of Surgery in Jefferson Medical College, &c, 
 
 PRACTICAL SURGERY: Including Surgical Dressings. Bandag- 
 ing, Amputation, &c., <S:c. 227 Illustrations. For the use of Students. 
 
 Price, $2.00 
 
 MENDENHALL (george), M.D., 
 
 Professor of Obstetrics in the Medical College of Ohio, &.c. 
 
 MEDICAL STUDENT'S VADE MECUM. A Compendium of 
 Anatomy, Physiology, Chemistry, the Practice of Medicine, Surgery, 
 Obstetrics, Diseases of the Skin, Materia Medica, Pharmacy, Poisons, 
 &c., &c. Eleventh Edition, Revised and Enlarged, with 224 Illustra- 
 tions. In cloth $2.00 
 
 MAXSON (EDWIN R.), M.D., 
 
 Formerly Lecturer on the Practice of Medicine in the Geneva Medical College, &c. 
 
 THE PRACTICE OF MEDICINE ^^3.00 
 
 MARSHALL (john), F.R.S., 
 
 Professor of Surgery, University Colleffe, London. 
 
 PHYSIOLOGICAL DIAGRAMS. Life-size, and Beautifully Col- 
 ored. An Entirely New Edition, Revised and Improved, illustrating 
 the whole Human Body, each Map printed on a single sheet of paper, 
 seven feet long and three feet nine inches broad. ' 
 
 No. 1. The Skeleton and Ligaments. 
 
 No. 2. The Muscles, Joints, and Animal Me 
 chanics. 
 
 No. 7. The Brain and Nerves. 
 
 No. 8. The Organs of tlie Senses and Organs 
 
 of the Voice. Plate 1. 
 No. 9. The Organs of the Senses. Plate 2. 
 No. 10. The Jlicroscopic Structure ol' the 
 
 No. 11. The Microscopic Structure of tht 
 Texture-s. Plate 2. 
 
 No. 3. The Viscera in Position. — The Strut 
 
 ture of the Lungs. 
 No. 4. The Organs o.f Circulation. 
 No. 5. The Lymphatics or Absorbents. 
 No. 6. The Digestive Organs. 
 
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27 
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 11 
 
29 
 
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30 
 
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31 
 
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32 
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33 
 
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 COLUMBIA UNIVERSITY LIBRARIES (hsi.stx) 
 
 RK 651 R39 1880 C.1 
 
 A pracfeal treatise on mechanical denti 
 
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