HX64072614 RK666Ev11920 A practical treatise RECAP ^^mmi: 'mm^:. is^ Columbia ^nibersiitp ^^^ intijeCitpofi^etogorfe Cop* I College of Pfjpgicians anb ^urgtong Reference l^ibrarp Presented hy ILLIAM J. OIES^ enrich the library resources avaz/a6/e fo holders oi the FELLOWSHIP 'iolosicSil Chemistry % ^.'^v. /, ^/. '"^:^" ' ARTIFICIAL CROWN-, BRIDGE-, AND PORCELAIN-WORK EVANS A PRACTICAL TREATISE ON ARTIFICIAL CROWN-, BRIDGE-, AND PORCELAIN-WORK BY GEORGE EVANS, D.D.S., F.A.A.D.S. NEW YORK STATE BOARD DENTAL EXAMINER; FORMERLY CLINICAL PROFESSOR COLLEGE OF DENTAL AND ORAL SURGERY, NEW YORK; LECTURER BALTIMORE COLLEGE OF DENTAL SURGERY; POST-GRADUATES LECTURER ROYAL COLLEGE OF DENTISTRY, TORONTO, CANADA; MEMBER OF THE NATIONAL DENTAL ASSOCIATION: OF THE DENTAL SOCIETY OF THE STATE OF NEW YORK; OF THE FIRST DISTRICT DENTAL SOCIETY OF THE STATE OF NEW YORK; OF THE ODONTOLOGICAL society; OF THE AMERICAN ACADEMY OF DENTAL SURGERY; VICE-PRESIDENT OF THE NEW YORK DENTAL CLUB; ETC. EIGHTH EDITION, REVISED AND ENLARGED WITH 1143 ILLUSTRATIONS PHILADELPHIA P. BLAKISTON'S SON & CO. 1012 WALNUT STREET or) , Copyright, 1888, by George Evans. Copyright, 1889, by George Evans. Copyright, 1893, by George Evans. Copyright, 1893, by George Evans. Copyright, 1896, by George Evans. Copyright, 1900, by George Evans. Copyright, 1905, by George Evans. Copyright, 1920, by George Evans. TSE ai^PLE PKESS 'r O US. I»A To William Carr, M.D., D.D.S. in acknowledgment of his professional eminence and his services for dental legislation and its en- forcement in the State of New York, this volume is respectfully inscribed by THE AUTHOR. PREFACE TO THE EIGHTH EDITION Since the publication of the last edition of this treatise on crown-, bridge- and procelain-work, the evolution of the art has produced changes and modifications in the methods of its practice that require a revision for the present edition so extensive as to constitute practically a new book. As in former editions, the intention is to meet the require- ments of a treatise for college and post-graduate study, and as well a reference book for the practitioner. Like all text-books, it is largely a compilation of the most accepted methods in practice, including also those that are novel which in my opinion are worthy of consideration or adoption as tending to facilitate the performance of better opera- tions in a practical way. In presenting to the dental profession the subjects embraced in this treatise I have been guided by personal experience of nearly forty years specially devoted to their study and practice. The discussion of pathological conditions, surgical operations, and of therapeutic indications, metallurgy, and the mechanical processes involved in the construction of appliances, has been limited to their direct relationship to the work in hand. Dental students, and practi- tioners still more, are supposed to be generally informed respecting these topics with facilities for ready reference to works specially de- voted to them and to adjunct or collateral subjects. The endeavor in this treatise has always been to make the text comprehensive without bulkiness, concise without the sacrifice of clearness to brevity of statement, which latter is much assisted by reference to numerous illustrations, and to avoid repetition except when it conduced to better understanding. With the latter object in view the text is divided into seven sections, and a preliminary explana- tion and description of processes specially connected with the work is given in the first section, which is thereafter referred to only when necessary for the addition of supplementary descriptive matter con- nected with special operations. In the present edition the effort is made, even more seriously than in those that preceded it, to impress the importance from a physiological standpoint of the use of methods that permit the attainment of the desired results without the devitalization of pulps, and thus avoid viii PREFACE TO THE EIGHTH EDITION the chance of subsequent focal infection, and with the least mutilation of teeth, and the least exposure of metal. The subject of fixed and removable bridge- work is impartially discussed and the merits and dis- advantages of each clearly presented. The aim throughout the work has been to give to the dental profes- sion an up-to-date compilation of methods of practice. In this I have been guided by the writings and instructions and the opinions personally given me by specially qualified members of the profession, as well as my own experience. I desire particularly to acknowledge my indebted- ness for suggestions on removable crown- and bridge-work to Drs. Ralph B. Reitz, R. F. Getz, C. Barton Addie, Charles F. Ash, Herman E. S.* Chayes, George Evans Jr., and Mr. H. A. Gollobin, and to lec- tures by Dr. Frederick A. Peeso, and Mr. Louis J. Weinstein; on inlay work to Drs. Henry W. Gillett, William Dwight Tracy, Frank T, Van Woert, Alfred R. Starr, Herbert L. Wheeler, and William A. Capon; for courtesy in the use of illustrations or models, to Drs. F. T. Van Woert, F. R. Getz, Richard Blum, H. Schwitzer, F. E. Roach, H. E. S. Chayes and Messrs. Louis Weinstein, H. A. Gollobin and J. Zirikian. BOOKS OF REFERENCE American System of Dentistry. Johnson's Text-book of Operative Dentistry. Kirk's American Text-book of Operative Dentistry. Prothero's Prosthetic Dentistry. Turner's American Text-book on Prosthetic Dentistry. . Goslee's Principles and Practice of Crown- and Bridge-work. Peeso's Crown- and Bridge-work. Hovestad's Principles and Technique of Crowns and Bridges. Black's Descriptive Anatomy of the Human Teeth. Geokge Evans. 55 West 39th St., New York, May 1, 1920 CONTENTS PART I MATERIALS AND PROCESSES USED IN CROWN- AND BRIDGE-WORK CHAPTER I Page Preparatory Requirements 3 Instruments — Tools — Precious metals — Base metals — Materials and acces- sories. CHAPTER n Plates and Solders 7 Platinum — Platinum foil and wire — Platinum and gold for collars — Iri- dium — Gold — Gold alloys — Formulas for crown-work — Clasp gold — Gold platinum lined plate — Platinized gold — Melting and refining of gold scraps — Gold solders^ — Hard gold solder — Peeso formulas — Fluxed solder filings — Platinum solder — Silver solder — Flux — Jeweler's liquid flux. CHAPTER III Other Materials 14 Fusible alloys — Formulas — Impression compound — Dental lac — Moldine — Wax cement^ — To secure adhesion of wax to metal or porcelain — Por- celain teeth or facings — Essentials of porcelain teeth — Fractures in porce- lain teeth, causes of — Changes of shade in baking and soldering — Veneers — To change shape or contour of a porcelain tooth. CHAPTER IV Appliances and Methods 18 Impression trays — Articulators — Impressions — Sectional impressions — Roach sectional impression tray — Models — A hard surface — To harden plaster models — Artificial stone — Articulating impression or "bite" and model — Combination plaster and metal model — Copper amalgam models. CHAPTER V Molds and Dies 28 Tubes, caps and trays — How to make a tube quickly — Impression for ix X CONTENTS Page fusible metal die — Moldine — Casting the die^ — Counter-dies — Combina- tion lead and fusible-metal counter-die — Amalgam dies — Amalgam — The Swager-swaging. CHAPTER VI Investments and Soldering S3 Materials principally used for investments — Small investments — Large investments — Asbestos — ^Method of investing- — Preparation of investment for soldering — Heating the investment — Soldering blocks — A serviceable and lasting soldering block — The structure of flame — The bunsen flame — The blowpipe flame — -Blowpipe and method of using it — Preparation, application and fusing of solder — Solder-pointer — Soldering practice dummies for students — Open-flame soldering — Union by sweating — Soldering with a compound blowpipe flame— Annealing. CHAPTER VII The Casting Process 43 Inlay wax — Formation of the inlay wax model— Investment — Investment material — Heating of the investment — Gold — Expansion and contrac- tion of materials and metals — Casting machines — Casting process — ^Large castings — The Schweitzer wax sprue former — Exit vent — ^Large wax models — To insure against distortion of the wax model — To cast with a swager. CHAPTER VIII Finishing Process 55 Finishing and polishing — Electro-plating. PART II Preparatory Treatment or Teeth and Roots for Crown- and Bridge- work 59 General Consideration 61 CHAPTER I The Pulps op Teeth 63 Preparatory processes — Disinfection of vital dentin. CHAPTER II Devitalization of the Pulp 68 Instantaneous devitalization — -Use of cocain, cataphoresis and pressure CONTENTS xi Page anesthesia — Excision of the crown and instantaneous extirpation of the pulp — Devitalization with arsenic — When devitalization is necessary in preparation for crown-work two methods are practiced: the heroic — In- stantaneous devitalization — and gradual devitalization by arsenical treatment. CHAPTER III PuLPLESS Teeth 72 Requirements of treatment — Preparation of root-canals — Reaming — Treatment — Use of antiseptics — Closure of the apical foramen and fill- ing of the canal. CHAPTER IV Chronic Alveolar Abscess 89 The usual forms^ — Abscess of the first form — Abscess of the second form — Exostosis — Third form, blind abscess — Alveolarotomy — Granuloma — Apicoectomy, amputation of the apex of a root — Hydrogen peroxid — Prog- nosis of chronic alveolar abscess and apicoectomy — Perforation of a side wall of a root-canal or of the dentin at the bifurcation of the roots. PART III ARTIFICIAL CROWN- WORK CHAPTER I Artificial Crown-work loi First authentic account of artificial crowns or pivot teeth- — The first por- celain pivot teeth — Gold pivot teeth — First porcelain and gold pivot tooth or crown- — The Richmond porcelain and gold collar crown — The earlier operations — The Morrison and Beers gold crown — The Foster and Law- rence crowns — The Mack and Howland-Perry crowns — The Gates-Bonwill . crown — The How crown — The Weston crown — The Brown crown — The new Richmond porcelain crown — The Logan crown — Advantages conferred by improvements in cements — Classification of modern crown-work. CHAPTER II Principles Involved IN Crown-work . 108 Nomenclature of crown-work — The object of crowning operations — The subject of occlusion — Malformed occlusal surfaces — Median line of natural crown and root — The post in relation to canals and roots — The post in relation to post or Dowel crowns^ — Short and long crowns — Princi- ples governing the construction of root-caps without collars — Posts in re- lation to crowns — Selection of porcelain teeth^ — Dependence of crown-work operations on asepsis. xii CONTENTS CHAPTER III Page Shaping Teeth and Roots for Crown-work 119 Local anesthesia — Adrenalin and cocain — Instruments used — Crowns without collars and ready-made porcelain crowns — Collar crowns — Princi- ples involved — Preparation of teeth or roots for all-gold collar crowns — Collar crowns with porcelain facings — Partial collar crowns — Special prepa- ration of badly decayed teeth or roots — Restoration with gold. CHAPTER IV All-porcelain Post Crowns 132 All-porcelain detached-post crowns — Preparation of the root end — The S. S. White detached-post crown — Preparation of the root — Direct method of fitting the crown — Indirect method — The Davis crown — The Justi shoulder pin crown — Ash's tube teeth and crowns — Examination of the periphery of a porcelain post crown — Removal of excess of porcelain at the periphery^ — Cementation — Remarks on the use of ready-made por- celain crowns and crowns without collars. CHAPTER V Porcelain-post Crowns with Metallic Base 141 Porcelain detached post crown with cast base — Direct method — Indirect method — Porcelain faced gold post crown — Root end below gum margin. CHAPTER VI A Temporary Crown 145 CHAPTER VII Gold Collar Crowns 146 Construction and adaptation of collars — To measure the circumference of a root or tooth — The dentimeter — To determine the width of a collar — Cutting the plate for the collar — To solder the joint of the collar — Sweating method — Fitting a collar to root or tooth — Platinum collar — Reinforced thin platinum collar — Platinum-lined gold-plate collar — Application of a local anesthetic — Collar crowns hygienically considered. CHAPTER VIII -LL-GOLD Collar Crowns for Bicuspids and Molars Constructed in Sections 156 Methods of knuckling the collar and giving contour — Methods of forming the cusp-cap — Class A, dies — Method No. i — Swaging the cusp-cap — Stamping the cusp-cap in a swager — Reinforcement of the cusp-cap — Fit- CONTENTS xiii Page ting cusp-cap to collar — Soldering cusp-cap to collar — Swaged cusp-cap — Reinforced with 22-carat gold — Sweating — To unite by sweating — Method No. 2, hollow cusps^ — ^Class B, intaglio or depressed dies — Method No. 3 — Method No. 4, cusp buttons — Application — To enlarge a cusp button — Method No. s, intaglio die from wax model — Intaglio die-plate — Class C, casting — Method No. fr — Solid gold cusp-cap — Special method — Method No. 7 — Solid gold cusp-cap by soldering — Method No. 8 — All-gold crowns for — Incisors and cuspids — Cases of abrasion. CHAPTER IX Gold Collar Crowns with Porcelain Facings 174 Incisors and cuspids — Adaptation of the collar — To form floor of the collar - — Indirect method — Preparation of canal to receive post — Posts — Union of post and cap — Selection and adaptation of the porcelain facing — To pro- tect the incisal edge of the porcelain facing — Backing the porcelain facing — One piece backing — Pointed-pin facings — Use of swager — Preparation for investment — Investment — Soldering and finishing — Diversity of con- struction — Method of forming posts to fit canals accurately — Hollow posts — Construction — To separately back or veneer the base of a porcelain facing with platinum — Two-piece backing — Reinforced backing. CHAPTER X ^ Gold Collar Crowns with Porcelain Facings, Continued 188 Bicuspids and molars^ — To form a cusp-cap — Inlaying procelain facings in gold crowns — Application to a seamless gold crown — inlaying porcelain facings in sectional crowns — A faulty method — Crowning in cases of abrasion — Gold crowns with porcelain facings for teeth with vital pulps. CHAPTER XI The Gold Seamless Cap-crown System 194 Seamless root-caps for incisor, cuspid and bicuspid crowns with porcelain facings — Impressions and dies — Method of stamping seamless metal caps — All-gold seamless bicuspids and molars — All-gold seamless incisors and cuspids. CHAPTER XII Imparting Contour to Seamless Gold Crowns 199 Crowns swaged on dies — Method of slitting and contracting the neck — Use of contouring pliers — External application of contour — To contour on the die with a swager — Sectional mold method — Formation — Shaping the cap. CHAPTER XIII Adjustment of Seamless Gold Crowns . . . . ' 203 Expansion of the collar and crown — Alteration of a side or part of a crown XIV CONTENTS Page —Alteration of the occlusal surface — To deepen the cusps — To point, lengthen or narrow the buccal cusp in appearance — To lessen or remove the indentation between cusps — Strengthening and reinforcement of seam- less gold crowns^ — Method of forming a solid occlusal surface — External reinforcement v\'ith platinum and gold in close "bites" — Seamless solid gold dummies — Altering a seamless gold crown to the form of a corre- sponding natural crown^ — Comparative merits of the sectional and seam- less methods of constructing gold crowns. CHAPTER XIV Cast Gold Root-caps and Crowns 208 Cast root-cap— Cast gold crown with platinum collar — Cast gold crown on a sectional platinum or seamless gold cap. CHAPTER XV Various Forms of Porcelain-faced Gold Crowns 210 Cup-shaped cap — The V-shaped cap — Partial collar crowns — The Litch crown. CHAPTER XVI Porcelain Detached Post Collar Crowns 213 Porcelain detached post collar. S. S. White, Davis, Ash and Justi crowns — Attachment of a porcelain crown with a metallic base backing — The Goslee crown — Construction — Diatoric porcelain tooth crown-^Cast base for detached-post crown — Allow^ance for contraction. CHAPTER XVII Partial Crown-work 218 Restoration with inlays^ — History- — Merits — Criticism^ — Impartially con- sidered — Preparatory treatment in inlay work — Principles governing the preparation of cavities — Anchorage — Preparation of cavities — Gold inlays — ^Labial, buccal and occlusal cavities — -Approximal cavities — Compound cavities. CHAPTER XVIII Partial Crown-work, Continued 228 Gold inlay formation — Direct method — Pin anchorage for gold inlays — Hollowing of gold inlays — Matrix gold inlays — Process of formation — Solid gold tips for abraded pulpless anterior teeth — The cast- ingmethod — Cases of vital pulps. CHAPTER XIX Partial Crown-work, Continued . . : ! 236 Indirect method of formation of inlays — Comparative merits — Impression CONTENTS XV Page materials — Process — Impression tubes, caps and trays — Formation of tubes and caps — Method of forming trays and taking impressions — Inlay dies — Indirect inlay wax model formation — Metallic matrices, indirect method. CHAPTER XX Special Operations in Crown- work 249 Crowning molar roots decayed apart at the bifurcation — Cantilever crown — Method of construction — Methods of crowning in cases of irregularity. CHAPTER XXI Treatment by Cro'wn-work of Fractured Teeth and Roots 252 Fractured crowns and roots — Longitudinal fractures — Slanting fractures — Inlay casting method — Use of a cast of a fractured portion- — Amalgam — Post and amalgam. CHAPTER XXII Processes Connected with Crown- and Bridge- work 256 Correction of excess of solder — To securely attach a crown — Importance of removal of flux from interior of crowns — Correction of interfering points in adjustment and occlusion. CHAPTER XXIII Cementation of Crown- and Bridge- work 258 Zinc oxyphosphate- — Method of mixing — Application — Gutta-percha — Method of cementing with gutta-percha or gutta-percha cement — Method of measuring gutta-percha^ — To apply gutta-percha in the form of a film over a surface — To cement t!he crown or bridge — For temporary inser- tion — Requirements for success— Oxyphosphate in combination with gutta-percha or gutta-percha cement — Silicate cement — Amalgam. PART IV BRIDGE-WORK INTRODUCTION Scientific Mechanical Principles 269 Scientific mechanical principles — Dental bridge-work — Antiquity— Primi- tive methods^ — Modern literature — Modern methods — Advantages — Ob- jectionable features — Prophylaxis — Impartial consideration — Forms of bridge construction. CHAPTER I Construction of Bridge-work 274 Principles involved — Abutments, retentive and supporting — Occlusion — XVI CONTENTS Page The artistic and esthetic — Porcelain facings and teeth for dummies — Clas- sification of bridge-work — Preparation of the supporting teeth or abut- ments — Construction — Impressions and models — Selection and adjustment of artificial teeth — Backings — Occlusal cusp-caps — Investing the bridge — Soldering — Finishing — Variations in method of construction- — Construc- tion in sections — Soldering on the model — Correction of warping — Adjust- ment and insertion — Construction of bridge-woyk embracing both sides of the mouth — Construction of small pieces of bridge-work. CHAPTER II Replaceable Porcelain Facings and Teeth 299 Replaceable ordinary porcelain facings with cast box backing — A plate box backing — Manufactured replaceable facings and teeth — The Steele — The Ideal — The Evslin — The Stewart — The Dimelow — Impa]:tially considered. CHAPTER III Forms or Attachments for Bridge-work 305 Shoulders on superior incisor and cuspid crowns or dummies — Solid gold dummies — Casting method^ — Sectional method- — Seamless cap method — All-gold hollow dummies — Anchorage cavity in a solid gold crown — An- chorage cavity in a gold cap-crown. CHAPTER IV Attachments for Bridge- work Continued, 309 Open-face crowns — Preparation of the tooth — To form a die — Seamless open-face crown construction^ — Open face sectional crown- — Cementation of open-face crowns — Carmichael attachment — The Staple attachment — MOD and MODL or Tinker attachments — Shaping — Construction^ — Plate and pin attachments — Construction — Use with pulpless teeth — Inlay and bar bridge-attachments — Inlay attachments — Incisors and cuspids — Cavity formation — Bicuspid and molars — Another method- — Formation — Bar attachment — Construction — Connecting bars for bridges — Intervening roots. CHAPTER V Bridge Construction on Vital Tooth Abutments and Piers 321 CHAPTER VI Casting Method 323 Porcelain crown (detached-post) bridge-work — Cast sanitary bridge — Sanitary porcelain and gold bridge — Extension bridges — Mechanical principles governing construction — A lug support — Lug anchor with lock- pin. CONTENTS xvii CHAPTER VII Page Extension Bridges 328 Governing mechanical principles — Construction — A lug support — A lug anchor with lock-pin— Intervening roots. CHAPTER Vin Bridge-work and Splinting in Cases of Pyorrhea Alveolars 333 The plate and pin attachment — Use of connecting collars — Posterior teeth — Bicuspids and molars. CHAPTER IX Repair OF Crown- AND Bridge- WORK 337 The ordinary method — Dr. Bryant's method — Countersunk pinhole method — To repair with a Dimelow facing — Ash's repair facings — Inlay method — Repair of an incisor or cuspid gold-backed crown with a detached- post crown — Silicate cement — Advantages of detachable bridge-work — Re- moval of crowns or bridges cemented with zinc oxyphosphate — Removal of a post — A post puller — Difficult post removal — Removal of crowns or bridges cemented with gutta-percha, alone or combined with oxyphos- phate — Repair of a gold collar crown. CHAPTER X General Application of Fixed Crown- and Bridge-work 347 Central or lateral incisors, cuspids or bicuspids — Centrals, laterals or cus- pids combined — cuspids, bicuspids and molars combined — Bicuspids and molars combined— Use of partial cap — Incisors, cuspids, bicuspids and molars combined — Extensive application of fixed crown- and bridge- work — Criticism. CHAPTER XI Sectional and Detachable Bridge-work . ; 362 Construction in sections — Bar attachment- — Dovetail lug attachment — Detachable double-cap bicuspid and molar crowns — Detachable gold sertii- circular post crowns. CHAPTER XII Ti^E Hygienic Condition of the Mouth as Affected by Fixed Bridge- work 367 Consideration of the subject — Requirements — Method for cleanliness and health. xviii CONTENTS PART V CHAPTER I Page Removable Bridge-work 371 Limitations — Requirements — Examination models — Forms of crowns, at- tachments and supports — Removable retaining abutments — Removable supporting abutments — The tube and split-post attachment — Construction of the split post — Split-post swaging device — Split-post burnisher^ — Tele- scope crowns — The outer or telescoping cap — Contour — The cusp-cap — Telescope crown with tube and split-post — Removal of the cap from the die — Tube and split-post anterior crowns — Incisors, cuspids and bicuspids with porcelain facings — The outer cap — Converging teeth and roots — Retaining inlay abutments — Bicuspids and molars — The matrix or female inlay — Split-post and supplementary or male inlay — A pin bender — Va- riations in method — Incisors and cuspids — To take the impression — Inser- tion of the split post — The supplementary inlay — Use of swaged first or female matrix — Supporting abutments— Special forms of attachments — Collar and partial cap — Flanged collar attachment- — ^Lug collar support — Split-bar attachment — Construction — The split bar — The box — Paral- leling the box— The shield — Winged lug attachment — Split winged lug — Dove-tail flange and split-post attachment — Solid pin and tube attach- ment — Comparative values of the several forms of attachment — Reten- tive attachments — Retentive inlay attachments — Supporting attachments. CHAPTER II Construction of Removable Bridge-work 411 Method of construction — The paralleling staple — Removable bridge ex- tending on both sides of the mouth — Construction — Diversity of construc- tive details — Use of paralleling instruments — The Chayes parallelometer. CHAPTER III The Split Bar Bridge 425 CHAPTER IV Removable Saddle Bridge-work 428 Construction of saddles — Method of taking impressions for saddles — The articulation — The bridge teeth — Construction of porcelain-faced solid gold dummies for saddles — Solid gold teeth dummies — Vulcanite attach- ment — Extension saddle bridge — An adjustable saddle — Vulcanite exten- sion saddle. CHAPTER V Removable Plate Bridge-work 441 Merits — ^Limatations — Clasps with lugs — Preparation for clasp attachments CONTENTS XIX Page — Shaping clasps — Collar method — Cast clasps— Clasps and lugs — Forma- tion of inlay lugs — Lugs for natural crowns — Construction of a plate bridge — Uniting attachments to plate — To correct warping — A frequent cause of warping. CHAPTER VI General Application of Removable Bridge-work 456 Centrals, laterals and cuspids — Bicuspids and molars — Connecting bars to saddles — Cast saddles and plates. CHAPTER VII Manufactured Attachments 463 The roach attachment — Method of application — Construction of bridge — The Morgan attachment — ^Removable bar-bridge attachments — The Gil- more attachment — Split-bar bridge attachment — The Chayes method and attachments — The parallelometer — The parallelodrill — The attachments — The bucco-lingual attachment — The upright attachment — The distal extension attachment — Construction — Split-post and bar attachment. PART VI PORCELAIN DENTAL ART Introduction 481 CHAPTER I Porcelain Compounds or Bodies 482 Ingredients : Their chemical and physical character — ^Low- and high-fusing porcelain bodies — Coloring of porcelain compounds — Gum enamel — Foundation or basal body — Preparations of porcelain bodies — Selection of the color of the porcelain body — Sample shades — Variation in shade — Stability of shade in use — Spatula and brushes used — Preparation of porcelain body for use — Use of gum tragacanth or starch — Application of porcelain body. CHAPTER II Furnaces 488 Electric — Gasoline — Gas — Use of furnaces — Advantages of the electric furnaces — Dental furnace pyrometer. CHAPTER III Fusing of Porcelain 492 Importance of the operation of fusing — Shrinkage — Baking or fusing — Re- quirements in baking — First bake — Second bake — Final bake — Cooling XX CONTENTS Page and annealing or tempering of porcelain — Diiiiculty attending the proper fusion of small masses of porcelain body— Method used to indicate point of fusion — Merits of a pyrometer. CHAPTER IV Staining of Porcelain 496 Character and purpose of mineral stains — Use of the colors — -Application — Gradation of shade — Fusing. CHAPTER V Character and Suitability or Low- and High-fusing Porcelains for In- lay- AND Crown-work 499 Requirements — Comparative merits — -Fusing points of dental porcelains — Suitable application of each grade, CHAPTER VI Porcelain Inlays 501 The earlier methods — Modern inlays and their merits — Instruments and materials used in the adaptation of matrices — Preparation of cavities- Direct method — -Formation of matrices for low-fusing porcelains — Re- ■ moval of the matrix — Investing the matrix for low-fusing porcelain — Platinum matrix for high-fusing porcelain — To facilitate the shaping of a matrix — Indirect method — Process of shaping a matrix by a mold or die — Removal of the matrix — Application of porcelain body — The Jenkins low- fusing body — Use of electric furnace for baking^ — Method of fusing — The application of high-fusing porcelain body — First bake — Second bake — Final bake — Comparative heat of the final bake — Removal of a foil matrix — Preparation for cementation — Methods of etching with acid or a diamond — To aid adjustment in cementation — Cementation — Require- ments; effect on color of porcelain — Operation of cementation. CHAPTER VII Special Operations ■ 515 Large contour inlays — Use of pieces of porcelain teeth — Use of successive grades of bodies — Occlusion in close "bite" — Porcelain inlays in com- bination with gold or amalgam fillings — Atrophy and erosion^ — Porcelain tips — Porcelain shoulders preferable, to pins for retention — Wire loop — Small fractures — Preparation of the cavity — The rod inlay — Cementation and finishing — Points to bear in mind — To facihtate matrix adaptation — Tray to bake on — To overcome contraction of body— To aid removal and remedy tear of matrix — Advantages of the use of a foundation body in contour operations — The use of a lens — Porosity of porcelain — Edges of in- lays — Small inlays — Effect of cement on shade— Requirements in inlay- work — Conservative limitations of porcelain inlay-work. CONTENTS xxi « CHAPTER VIII Page Porcelain and Platinum Crown-work 523 Structural requirements — Platinum solder — Nature of adhesion of porce- lain fused on platinum — Application of porcelain body in cxown-work — Baking — Degrees of heat — Porcelain and platinum collar or partial collar crowns — Process of construction of collar crown — Partial collar-cap — Bi- cuspids and molars — Practical method to form occluding section — Crown without a collar — Limitations — Jacket crown — Incisors and cuspids with platinum jacket — Application of porcelain veneer — Protection of the in- cisal edge — Porcelain and platinum bicuspid cap-crown with porcelain occlusal surface — Porcelain and platinum tube crown — A porcelain and platinum bicuspid crown with metal occlusal surface— Porcelain and platinum tube crown — x\pplication to cases of fractured porcelain crowns — Ready-made crowns on capped roots — The S. S. White, Davis, Ash or Justi crown on a capped root — All-porcelain jacket crown — Application of veneer and porcelain to cone — To form a veneer — Formation of porcelain crown without a veneer — Removal of matrix or cone — Cementation — The overlap crown — Crowning of roots decayed apart at the bifurcation — Comments on grades of porcelain — Compounding artificial tooth body. PART VII CROWN-, BRIDGE- AND PORCELAIN-WORK COMBINED WITH OPERATIVE DENTISTRY IN DENTAL PROSTHESIS CHAPTER I Operations in Dental Prosthesis 545 Symmetrjr — Cases showing the results of combined operations — Gold and porcelain sanitary bridge — Combined root and crown replacement with porcelain — Inlay restoration in a close incisal occlusion. INTRODUCTION TO EIGHTH EDITION Or the origin of the art of dentistry no one can speak with certanity, as its early history is 'shrouded in the mists of antiquity; but dental operations are recorded in very remote times. References are made to the art in the writings of Hippocrates, in the fifth century B.C. Martial, the Latin poet, in the first century B.C., says of a Roman dentist, "Cascellius is in the habit of fastening as well as extracting the teeth." To Lelius he says, " You are not ashamed to purchase teeth and hair;" and adds that "the toothless mouth of Egle was repaired with bone and ivory;" also, that " Galla, more refined, removed her artificial teeth during the night." Horace, in the same century, cites the case of the "sorceresses Canidia and Sagana running through the city and losing the one her false hair, the other her false teeth." Galen, the celebrated physician, in the second century a.d., also speaks of the art of dentistry as being then practiced. These early operations were limited to the extraction of offending teeth and the replacement of those which had been lost with substitutes that were retained in position by means of narrow bands or ligatures attaching them to the adjoining natural teeth, and without the use of plates. Crude as they were, they formed the first expression of the art of dentistry, a beneficent art from the beginning, in that it sought to remedy pathological or accidental defects. Confined to the simplest operations, it existed for centuries, and then was apparently lost during the Dark Ages, to reappear when the more general diffusion of knowledge ushered in the modern era of science and invention. After its revival, dentistry, so much of it as was known, was in a measure a secret art, the practice of which even within the memory of men now living, was involved in mystery; but recent progress has lifted the veil, and dentistry, in the treatment of the teeth on correct, scien- tific, rational principles, has developed an art and a science which have given it honorable rank among the professions. In its twofold evolu- tion it has absorbed from every available source whatever would broaden its science or perfect its art. It calls to its aid anatomy, physiology, pathology, chemistry, therapeutics, metallurgy, sculpture, xxiv INTRODUCTION TO EIGHTH EDITION and mechanics, with each of which it stands in closer or more remote relation; and the practitioners of dentistry who have become the most eminent and useful have been men of broad attainments and great versatility of talent. In the history of all progress, movements apparently of a more or less reactionary character are recorded. In the useful arts especially it is not uncommon to find a return to forms and methods formerly used, but long since discarded and forgotten. So in dentistry we find methods of treatment and modes of practice once in vogue but long fallen into disuse, revived with improvements and modifications that stamp them as practically rediscoveries. These movements are not to be regarded as retrogressive, because the modifications which accompany the reintroduction of practical ideas and inventions attest them as real advances, and indicate clearly that the cycle of knowledge is ever widening with experience. This volume demonstrates how modern dentistry has utilized the principles of some of the simplest original oserations, and by "proving all things, holding fast that which is good," has attained its present honorable position in both its scientific and artistic departments. The history of dentistry of later years is, in brief, a recital of progress and improvement. The medical profession, recognizing the rela- tionship prophylaxis of the mouth bears to the general health and the important sphere in oral surgery and prosthesis dentistry filled in the late European war, accepts dentistry as a profession, an adjunct to their own. The United States Government so estimates the services of the dental profession in the Army and Navy as to commission members in the service. Such is the position which dentistry has attained. Much of the progress which has made its present elevation possible must be credited to the dental profession of the United States, which has been justly termed the cradle of modern dentistry. Here the validity of the idea that scientific knowledge should form the basis of training for prac- tice was first demonstrated by the successful establishment of dental schools; here the first journal for the interchange among dentists of thought and experience was founded; here the first association having for its object the uplifting and upholding of dentistry by the mutual helpfulness of its practitioners had its origin; here, in a word, dentistry was first divorced from mystery, here it first passed the narrow con- fines of a mere handicraft and earned for itself the right to be classed among the learned and liberal professions. ARTIFICIAL CROWN- AND BRIDGE-WORK Modern artificial crown- and bridge-work belongs to the depart- ment of dentistry formerly termed "mechanical;" but the judgment, skill, and scientific information required in the selection and treat- ment of teeth and roots, associates it with operative dentistry. Modern crown- and bridge- work, properly understood and properly performed, takes high rank in dental art, and offers wide scope for ver- satiHty of talent and inventive genius. The varied and complicated cases presenting for treatment frequently suggest to the expert novel contrivances and methods of construction and application. Successful practice of crown- and bridge-work depends upon a thorough mastery of the underlying principles and expertness in the processes involved, governed by sound judgment and perfect candor. The interests of the patient should be paramount to every other consideration, and after a careful examination he should be given an accurate statement of the applicability of the system to this case, in respect to usefulness, appear- ance, durability, and comfort, as compared with other processes and appliances in use. Surgical and mechanical operations of the most delicate nature are required. Nothing, indeed, in dentistry demands finer manipulation. A practical consideration of the subject will show that a knowledge of anatomy, pathology, and therapeutics, and as well mechanical and artistic skill, are necessary to the correct treatment of cases and the proper performance of the operations indicated. Among the principal steps in an operation may be named, first, the preparatory treatment of the natural roots and teeth for the final process, involving the diagnosis of present or probable lesions and the prescription of whatever remedial or prophylactic measures may be needful; second, in crown- work, the adaptation of the artificial crowns to the cervical portion of the natural roots and the contiguous membranes, and the restoration of the articu- lation and the anatomical contour; and, in bridge-work, the selection of suitable teeth or roots for foundation piers or abutments, and the choice and adaptation in constructive practice of the forms which will insure the highest degree of stability and best sustain the force of occlusion, thereby avoiding abnormal positions and conditions. XXVI ARTIFICIAL CROWN- AND BRIDGE-WORK In no branch of dentistry will lack of knowledge and skill or the exhibition of carelessness in constructive details be more plainly evi- denced or result in greater proportion of injury instead of benefit. Many failures are to be attributed to attempts to perform bridge-work operations with about the same expenditure of time on the part of the dentist and of money on the part of the patient as in plate- work. There is no such relationship between these two methods of procedure. The practice of crown- and bridge-work by dentists possessing the requisite attainments and governed by correct ethical principles gives results which have gradually estabHshed its value, removing erroneous impressions and insuring a wide professional and public indorsement of this important branch of prosthetic dentistry. Its extraordinary facilities for preserving and replacing teeth have made for it a high posi- tion in dental art. PART I MATERIALS AND PROCESSES USED IN CROWN- AND BRIDGE- WORK CHAPTER I PREPARATORY REQUIREMENTS INSTRUMENTS — TOOLS — PRECIOUS METALS — BASE METALS — MATERIALS AND ACCESSORIES A complete equipment for crown- and bridge- work, as will be seen from the list following, embraces, besides many instruments, materials and appliances both from the operative outfit of the practicing dentist and the dental laboratory. Not all of these are necessary for the beginner, but he will find, as he advances, that all of them will be required in the work itself or the preparatory surgical procedures. Instruments Swiss and Donaldson broaches. Kerr's Pulp-Canal Files and Reamers. Gates-Glidden drills — all sizes, straight and for right-angle attach- ment. Root-ca-roal probes and pluggers. Root-canal reamers, Peeso's. Enamel O. S. cleavers (Orton's). Root shapers — cross-cut cone-shaped trimmers (Evans) See Part III, Chapter III. Root facers, Nos. 7-8-9. Carborundum wheels, disks and points. See Part III, Chapter III. Tools Pliers for shaping collars — Peeso No. 118, Robinson No. 120, contouring No. 130. See part III, Chapters VI and VII. Pin roughening and bending pliers, No. 127. Cutting pliers. Small pointed shears, straight and curved, Nos. 10 and 11. See Part III, Chapter VIII. Plate burnisher No. i. Pin vise No. 4. Small anvil. See Part III, Chapter VI. Hammer-headed hand-vise — % inch jaw. Tweezers C, N, 0, L. Solder tongs. 4 CROWN-, BRIDGE-, AND PORCELAIN-WORK One round file, fine. Two half-round files, 3 in. No. 6 cut, and 5 in. No. 2 cut. Two flat files, 5 in. No. 2 cut, 5 in. No. 6 cut, one side smooth. Bunsen burner with spider — ^See Part I, Chapter VII. Asbestos soldering block — See Part I, Chapter VII. Charcoal soldering block — See Part I, Chapter VII. Blowpipe — ^Lee or Melotte. Ladle for melting fusible metal — See Part I, Chapter III. Small impression cups — See Part I, Chapter IV. Small articulators — See Part I, Chapter IV. Gage plate Standard Wire-gage (Brown and Sharpe). Crown swager with steel blank and rubber plunger (S. S. White) and Peeso's swaging device No. 2 for flattening plate. Die-plate for forming occlusal cusps. Cusp buttons, and assortment of. See Part III, Chapter VII. Precious Metals Pure gold plate, Nos. 28 to 34 gage, and No. 40 gage to form matrices for occlusal cusps. Gold plate, 22-carat, Nos. 28 to 30 gage. Gold clasp, No. 24 gage. Platinized gold wire, round, Nos. 12, 14, 16, 18, and 20. Platinized gold wire, half round, Nos. 12, 13, and 14. 18- and 20-carat solder; also hard-flowing solder. Platinum plate. Nos. 32 to 40 gage for collars and backings. Platinum foil, Kooo and ^^ooo- Iridio-platinum wire, Nos. 15 and 17 gage for posts and Nos. 19, 20 and 21 gage for pins in either gold tips, inlays or crowns. A few dwts. of silver solder for special purposes. Porcelain teeth; a small assortment of cross-pin plate teeth (fac- ings) of light, medium and dark shades, consisting of incisor, cuspid, bicuspid and molar forms, is very convenient to have on hand. Base Metals Fusible metal. Amalgam for models. Sheet copper, Nos. 30 to- 38 gage. Spool each of iron and copper wire No. 31 gage for measuring. Iron wire about No. 17 to 18 gage for encircHng investments and other purposes. German silver plate or platinoid, No 30 gage, and wire No. 12 to 20 gage. PREPARATORY REQUIREMENTS 5 Materials and Accessories Impression compound. Impression compound in sticks. Wax, stiff, in sheets. Sticky wax. Inlay wax. Finely ground silex or calcined marble-dust. Moldine.i A small rolling-mill for plate will be quite an acquisition, as gold scraps can be remelted and formed into plate, and plate on hand can be reduced to any desired gage. Fig. I. Pig. 2. For porcelain work an outfit of high or low-fusing porcelain body, or both, to be used for inlay or crown work. (See Part VI, Chapter I.) Six plug-finishing burs Nos. B, C, D, 200, 201, and 246. Two inlay burs Nos. i and 2. Three camePs-hair brushes — small, medium and large. One gem cavity trimmer No. 5. A double end spatula for porcelain work. (Capon.) Several fire-clay slabs for holding the work while baking. Pulverized silex. A set of suitable burnishers for adaptation of matrices, long handles, Nos. 25, 26, 27, and 28. Locking tweezers "K. " 1 Introduced by Dr. G. W. Mclotte. 6 CROWN-, BRIDGE-, AND PORCELAIN-WORK An electric furnace, preferably with a pyrometer. A bench on which the principal parts of the work are done should be especially designed and reserved for it. It may be in the same room, conveniently situated a little behind the dental chair out of view of the patient or located nearby in an adjoining room. Everything connected with the bench should be kept in order and ready for immediate use. Such a bench of oak or mahogany with a top that can be closed when not in use, making an unobjectionable piece of furniture, is represented in Figs. I and 2. The Bunsen flame in the center of the bench can be turned off and relighted instantly by a small jet at the side of the burner. The joint of the socket of the gas bracket is formed so that when the bracket is pushed to one side for the purpose of closing the cover of the bench, the gas supply is shut off. Large and small soldering with the regular gas blowpipe may be done at this bench; also soldering by the open flame; but the laboratory is a more suitable place for the former, as the smoke emanating from a blowpipe will gradually soil the adjacent walls and ceiling. A small electric lathe-head can be mounted on the bench. CHAPTER II PLATES AND SOLDERS' PLATINUM — PLATINUM FOIL AND WIRE — PLATINUM AND GOLD FOR COLLARS — IRIDIUM — GOLD — GOLD ALLOYS — FORMULAS FOR CROWN- WORK — CLASP GOLD — GOLD PLATINUM-LINED PLATE — PLATINIZED GOLD — MELTING AND REFINING OF GOLD SCRAPS — GOLD SOLDERS — HARD GOLD SOLDER — PEESO FORMULAS — FLUXED SOLDER FILINGS — PLATINUM SOLDER — SILVER SOLDER — FLUX — JEWELER's LIQUID FLUX In the construction of crown- and bridge-work, gold and platinum are used pure and alloyed with other metals of the platinum group, or with silver and copper as best suits the requirements of the work and the preference of the dentist. Platinum. — Platinum retains its color and resists the action of the secretions of the mouth better than pure gold. For this reason and also because of its physical properties respecting malleability and duc- tility, as well as its extremely high fusing-point when formed in any gage of plate or foil, it is a very useful material in many departments of the work. Platinum is also valuable as an alloy to raise the melting- point of gold plate and increase its tensility. Platinum plate gages Nos. 31 to 35 and when reinforced with pure gold as thin as No. 38 gage, is used for forming collars for crowns. Platinum FoU and Wire. — Platinum in the form of thin plate from No. 40 gage to that of foil, and of wire, gages No. 21 to No. 14, is used in various operations associated with the work. Platinum foil can be made exceedingly thin by first rolling it down to about i/iooo of an inch, annealing in an electric furnace, then oiling the surface, doubling over and again rolling down. Treated by this method the metal is less liable to crack. Platinum and Gold for Collars. — In some cases platinum can be utilized to advantage for making collars at from Nos. 36 to 38 gage. The collar, when fitted, is stiffened by the addition of pure gold melted over its outer surface. 1 The subject of plates and solders is here discussed only in relation to crown- and bridge-work operations. For an extensive consideration of their properties the reader is referred to works on Metallurgy. 7 8 CROWN-, BRIDGE-, AND PORCELAIN-WORK Iridium. — Iridium as an alloy for platinum imparts hardness and elasticity. The usual proportions are lo per cent, iridium and 90 per cent, platinum. Iridio-platinum wire of the same gages as plati- num wire for the same purposes is employed for posts and pins when greater rigidity is required than pure platinum affords. Palladium is also used as an alloy instead of iridium. Gold. — Gold plate, 24 carats, gages No. 28 to No. 36, is generally used for backing porcelain teeth and forming collars where great flexibility of metal is required; also, as thin as 4/1000 inch, cut in a strip five-eighths inch wide, when to be stamped up as a cusp-cap to act as a matrix for coin gold. The plate is slightly alloyed, about 23 carats fine, for crown-work when a less flexible metal is required; gold plate, 22 carats, gages Nos. 29 to 31, in constructing collars for crowns with porcelain facings, all-gold crowns made in sections and seamless crowns. Gold plate of 20 carats is also used in the construction of bridge-work. Gold for constructing collars should be of as high a carat as possible to better resist the action of acids. A large proportion of copper as an alloy is objectionable, owing to its tendency to cause tarnishing of the collar when an acid condition of the mouth exists. Gold Alloys. — United States gold coin is much used in crown- and bridge- work, owing to its flexibility, strength and the fine finish of which it admits. As it contains 10 per cent, of copper, it is not as well able to resist oxidation in the mouth as some other alloys that closely resemble it in commendable properties. Formulas for Crown-work The following is the author's formula for gold plate for crown- work: Pure gold 36 Platinum 3 Coin gold ,. 61 100 parts The platinum and pure gold should be melted together first, rolled out and cut into small pieces. The coin gold is next melted and the platinized gold added. The alloy closely resembles coin gold in color, flexibility and strength. It is much higher fusing, the joints of collars and crowns made of it can be soldered with coin gold and it will permit the use of high-grade solders with less risk of fusing the parts than when coin gold or ordinary 22-carat plate is used. PLATES AND SOLDERS 9 Clasp Gold. — The following alloy possesses resiliency and is of good color: Pure gold 20 dwt. Platinum 4 dwt. Silver 2 dwt. 20 grs. Copper I dwt. 18 grs. The above formula cannot be properly fused in less than one ounce lots. The platinum must be thoroughly alloyed with the pure gold before the addition of the other metals. Gold Platinum-Lined Plate. — Gold plate 24 carats, with a lining of platinum, can be used in any of the processes of crown- and bridge- work, and is recommended to the inexperienced because the melting of a part of the crown in the soldering process is less liable to occur by its use. It is formed by fusing a thick layer of pure gold over a piece of platinum about gage No. 30 and passing through a rolling mill. In soldering the seam of union of a collar made of this style of plate, the ends of the metal require to be clamped together until they are united by the solder, as otherwise the unequal expansion of the gold and platinum will spring them apart and open the seam. Platinized Gold. — An alloy of pure gold with from i to 3 per cent, platinum may be used to advantage in various operations. Gold so alloyed is but slightly affected in color and is very flexible. Plate of this alloy can be used exceedingly thin with much less liability of being melted than pure gold. Melting and Refining of Gold Scraps. — The conversion of gold scraps into plate is desirable from an economic standpoint. Passing a magnet through scraps or filings will remove particles of iron. A moderate quantity of clean scraps, using plenty of borax, can be melted with a gas blowpipe and allowed to cool in a depression of the soldering-block. For a large quantity use a small crucible well lined with borax, fuse in a gas or charcoal furnace and pour into a warm ingot-mold. The gold should be allowed to cool slowly and should never be removed from the ingot-mold and immersed in water while still hot. When cool the ingot should be boiled in acid, cleaned, hammered out, annealed and rolled in a mill to the desired gage. Filings and scraps containing particles of solder should be melted and refined by the ''dry process." This consists in placing the scraps in a crucible lined with borax, fusing at a high heat for a considerable time and applying potassium nitrate (saltpeter). Gold Solders. — The grade and character of solder are important in crown- and bridge-work operations. The solder should approach lO CROWN-, BRIDGE-, AND PORCELAIN -WORK the fineness of the plate used, exhibit strength and elasticity when in plate form and melt and flow smoothly under the properly applied heat of the blowpipe. The production of solder of uniform quahty requires a knowledge and skill only possessed by those constantly engaged in its manufacture. For this reason, although some operators alloy and make their plate and remelt their scraps, very few prepare their solder. When pur- chased, the name i8- or 20-carat solder does not imply that it will assay eighteen or twenty carats fine, respectively, but that the figure gives the grade of plate for which the particular solder is adapted. 18- and 20-carat solders are used for crowns and bridges, although some dentists consider i8-carat too low for the purpose. 22-carat solder is seldom used except to solder the joint of a collar or on the ex- posed outside surface of a gold crown. 14-carat solder is used only in filling the cusps of seamless crowns in single crowning operations and in some repairing operations. The following is the proportion for i8-carat solder generally given in text-books:^ Pure gold 18 grs. Silver 2 grs. Copper 3 grs. Zinc iH grs. The burning out of approximately one-half grain of zinc gives a solder close to 18 carats fine. Increase the copper slightly to darken the shade. Solder may be made by alloying the same grade of plate upon which the solder is to be melted. For such an alloy a soft quality of fine brass wire is the best. Spelter solder is also used. The following formula is an example: 22-carat plate 4 dwt. Fine brass wire 12 grs. Allowing for the alloy already present in the 22-carat plate, the result is a solder fully 19 carats fine. A smaller proportion of alloy added to the 22-carat plate will give a corresponding result; for example, 2 grs. to each dwt. will produce a solder about 20 carats fine. Dr. W. H. Dorrance many years ago supplied the following practi- cal formula^ for an alloy for the formation of different grades of gold ^ This is the formula generally asked for at State Board Examinations. 2 This formula is used by the author, and is convenient and reliable, and with it any grade of alloy is quickly formed. It is used by the author when he makes solder. PLATES AND SOLDERS li solder, the proportion of the alloy used determining the melting-point and fineness in carat of the solder: Pure silver i part Pure zinc 2 parts Pure copper 3 parts The silver and copper are first melted together in a crucible lined with borax and the zinc added quickly in small pieces, stirring the mass meantime with a clay pipe-stem. On the fumes of the zinc passing off, it is immediately poured into an ingot-mold or a large wooden pail filled with water. 4 grains of this alloy melted with 20 grains of pure gold will result in a solder fully 20 carats fine. Hard Gold Solder. — The term "hard solder" may be applied to any formula or carat of gold when used as a solder on one that is higher fusing. Thus, coin gold is so called when used to solder pure or platin- ized gold and pure gold when used to solder platinum or platinized gold. It is also applied to the successively higher grades in carat of the ordinary gold solders in which a gradually smaller percentage of zinc is used. An i8-carat grade of "hard solder" is conveniently made by melting together by weight, one- third i8-carat solder to two-thirds i8-carat gold plate; 20-carat solder and plate can be used in the same proportions to form a higher grade. The plate is first melted and the solder added and, when cool, rolled out to the desired gage.^ To form a lower flowing solder for use in successive stages of the work, melt together one part by weight, gold solder to one part of gold plate. Peeso Formulas^ No. I. — Coin Gold Solder No. 2. — Hard Flowing Solder Coin gold 8 dwt. Melt together equal parts of coin gold i8-carat solder 3 dwt. 8 grs. and Formula No. i solder. Pure copper 18 grs. No. 2 formula makes a solder 21 carats fine. These two alloys as solder flow freely and are excellent for use on coin gold. Fluxed Solder Filings. — Fluxed gold solder filings are made by filing with a clean flat plate-file a thick piece of solder held in a vise. The filings are allowed to fall into a box or on a sheet of paper placed to receive them. A magnet should be passed through the filings to remove any minute particles of steel from the file. To five parts of ^ Formula most used by the author. 2 Dr. F. A. Peeso. 12 CROWN-, BRIDGE-, AND PORCELAIN -WORK the filings so prepared is added and well mixed with them, one part of Parr's prepared flux or finely pulverized vitrified borax. As a vehicle with which to apply the filings in soldering, add enough vaselin to form a paste. Solder prepared in this form is useful for strengthening crowns and also in fine soldering operations, such as uniting the joints of a collar, as the particles of solder take the heat separately and fuse much more quickly than when the solder is cut in pieces. The flow of the solder is also more easily defined and limited. Platinum Solder. — Platinum solder is made by alloying pure gold with 15, 20, or 25 per cent, of platinum and fusing with a compound blowpipe. 30 per cent, platinum solder withstands the very highest heat ever used in the fusing of porcelain. Platinum solder is used to unite the platinum sectional frame- work of a crown for porcelain- work or for a casting operation. The grade of solder to be used is determined by the fusing point of the porcelain. 10 per cent, may be used to solder seams of platinum caps when pure gold is to be cast over it. Silver Solder. — Silver solder is frequently used by the student and practitioner in the construction of tubes for impressions and in the construction of experimental or specimen work made of coin silver, nickel or German silver. A reliable formula is: Coin silver 90 parts Zinc 10 parts Low fusing silver solder: Coin silver 50 parts Spring brass wire 50 parts Flux. — The object of flux is to prevent oxidation of the metal when heated and thus permit the portion which is fused to flow freely and unite with the surfaces of the higher fusing metal. The lower grades of alloys require more flux than the higher grades, as is evidenced in the soldering of platinum with pure gold. The quantity of flux applied to the work for soldering should be limited to that which will accomplish the desired object. An excess of flux affects the control of solder, forms pits and is liable to reach and check porcelain by fusing upon its surface. Borax is the preferred flux for soldering dental work. For small fine soldering and deeply invested sections it should be ground with water on a slab and applied with a fine camel 's-hair brush before heating the metal or investment. For application during soldering it should be first vitrified and then ground to a fine powder. Vitrification divests PLATES AND SOLDERS 13 borax of its water of crystallization and in this vitrified form, when powdered, it can be sprinkled on the metallic sectional parts of the work and fused without disturbing their position through expansion, which is liable to occur when ordinary pulverized borax is used. Preparations of borax should be kept perfectly clean, as the invasion of foreign matter will cause pits in the solder.^ Dental solder of a higher grade than that ordinarily used in the arts requires more heat. As borax melts at a comparatively low heat, its tendency is to flow off the prominent points of the metal and expose them. Consequently, as the addition of boric acid raises the fusing point of the flux, it tends to increase its efficiency. A formula^ for solder flux is: C. P. borax glass (fused) 55 parts C. P. boric acid (not fused) 35 parts C. P. silica 10 parts 100 parts The ingredients are fused at a red heat in fire-clay crucible and poured into cold water, then instantly removed, dried, pulverized and passed through an 80-mesh sieve. This £ux is applied in the powdered form, or mixed with vaselin to form a paste, or dissolved in boiling water and the saturated solution applied. Jewelers' Liquid Flux. — Jewelers' liquid flux may be used in some parts of the work in place of vitrified borax or flux. It is made of a saturated solution, equal parts borax and boric acid in water. It should be applied to the parts with a brush before heating and the heated point of a strip of solder dipped in it before application. ^ Dr. Parr's "Prepared Flux," a finely pulverized vitrified flux, can be used in this manner. It is also prepared in combination with wax cement. In the melting out of the wax when the case is invested and heated for soldering, the flux is carried into the interstices. 2 Mr. L. J. Weinstein's formula. CHAPTER III OTHER MATERIALS FUSIBLE ALLOYS — ^FORMULAS' — IMPRESSION COMPOUND — DENTAL LAC — MOLDINE — WAX CEMENT— TO SECURE ADHESION OP WAX TO METAL OR PORCELAIN — ^PORCELAIN TEETH OR FACINGS — ESSENTIALS- FRACTURES, CAUSES OF — CHANGE OF SHADE IN BAKING AND SOLDER- ING VENEERS — TO CHANGE SHAPE OR CONTOUR OF A PORCELAIN TOOTH Fusible Alloys. — Of the many fusible alloys of tin, the following — in parts by weight — will be found suitable for use in crown- and bridge-work. Formulas Tin Lead Bismuth Melting-point Deg. Fahr. 5^ 3 8 202 3 S 8 212 I Tin 2 Lead 2 Bismuth 236 Cadmium Melting-point Deg. Fahr. 3 4 8 2 150 22 3 5 2 180 Fusible metals should not^be heated beyond their melting points, a matter which is not as a rule carefully observed, and, after fusing, Fig. 3. should be allowed to cool moderately before pouring. A ladle, such as is illustrated in Fig. 3, with legs to prevent tipping while cooling, is a suitable form. Impression Compound. — Impression compound is for taking im- pressions of teeth for crown and inlay work. When an impression of the interproximal or other small space between the teeth, is desired, it is best obtained by first placing and pressing a small thin piece of the material used, into the space or spaces to be taken before pressing the main mass in the impression cup to position in the mouth. 1 Dr. G. W. Melotte's formula. 2 Dr. G. Molyneaux's formula. 14 OTHER MATERIALS 15 Impression compound is softened by warm water or dry heat, preferably the former. It should be partly or entirely hardened by chilling with cold water before removal. Dental Lac. — This is a preparation resembling sealing-wax. It is very hard and tough for a material of its kind, and softens and hardens very quickly under the application of heat and cold. It is softened for use by holding it in the heat above an alcohol or Bunsen flame. Den- tal Lac will maintain its form in the swager in stamping thin soft gold or platinum plate. Moldine. — This is a preparation compounded of potter's clay and glycerin. More glycerin may be added when the moldine becomes hard. It is of putty-like consistence and is useful in forming molds of teeth or occlusal surfaces from a model shaped either in wax or plaster, which is to be cast in fusible metal. Wax Cement. — Wax cement is used in two forms, adhesive and hard wax. Adhesive wax when moderately heated is quite flexible, adheres readily to metal and porcelain, and may be manipulated with the fingers without sticking to them. When chilled with cold water, it becomes quite hard. It is to be used during the adaptation of different parts of the work in and out of the mouth. Adhesive wax of a suitable quality can be made of pure yellow beeswax 4 parts, resin i part, and gum dammar i part, by weight. Hard wax requires more heat to soften it than the adhesive kinds. When sufficiently heated it is very soft and adhesive, but exceedingly brittle when cooled. It is best used as a support to adhesive wax; the adhesive wax having been first applied in the preliminary adaptation of the work, as much as possible of it is removed without disturbing the position of the parts and replaced with the hard wax for the final adjustment. Hard wax is made of yellow beeswax i part and resin 3 parts, by weight. Wax cement in the form of sticks is the most convenient for use. To Secure Adhesion of Wax to Metal or Porcelain. — Heated or melted wax when applied to a cold or wet surface does not adhere properly and is liable to loosen and cause displacement of sections of the fitted work. To prevent this, dry the metal or porcelain perfectly and heat it uniformly to a point that will fuse the wax when touched to its surface. Veneer the surface of the metal or porcelain with the wax and allow it to partly or entirely cool. Wax then applied will adhere firmly to the wax veneer. Porcelain Teeth or Facings. — The artificial teeth chiefly used in crown- and bridge- work operations are termed porcelain facings. 1 6 CROWN-, BRIDGE-, AND PORCELAIN-WORK Essentials of Porcelain Teeth. — The qualities requisite in porcelain tooth body for use in crown- and bridge- work are density, strength and the power to withstand unaltered in form or shade any degree of heat to which it may necessarily be subjected. In these respects the porcelain teeth of our best American manufacturers seem to excel. They afford at the same time those other essentials, artistic imitation of the natural teeth in form and shade, and practical location of the pins. Fractures in Porcelain Teeth, Causes of. — Porcelain facings are sometimes fractured in soldering by the contraction of the backing when adapted over the edges of the porcelain in an acute instead of an obtuse angle, or by the melting of solder on some part of the porcelain which is unprotected by a backing of metal. The cooling solder or borax contracting on the porcelain, or a very thin edge of the metal covering it, will usually cause a fracture. The porcelain tooth has yet to be made that will endure such extreme treatment without breaking. Porcelain facings set up for soldering with their sides touching aie very liable to fracture by expansion. An imperceptible space of at least 3^^00 inch should be left between them. Fractures are also caused by too rapid heating and, quite frequently, because the op- erator removes the work from the investment before it has become perfectly cool. Changes of Shade in Baking and Soldering. — The shade of porce- lain teeth is very slightly affected, if at all, by an ordinary soldering operation. Subjecting them to extremely high heat in a furnace tends to lighten the porcelain by burning out some of the metallic oxids or other compounds. To closely determine the shade developed by soldering, which may at times be necessary in the restoration of one of the six front teeth, back the facing with %ooo platinum, invest, heat slowly and reinforce the platinum substantially with pure gold. The shade thus developed will be very little affected subsequently, if at all, by the comparatively low heat required to fuse ordinary i8- or 20-carat solder, p Repeated soldering operations and the use of alloys composed largely of the base metals tend to darken the shade of porcelain. Veneers. — A veneer consists of a thin piece of porcelain represent- ing the labial aspect of a natural tooth. To form a veneer select a porcelain facing of the required shade and size. On the end of a piece of wood about the size of the facing, melt and attach a mass of shellac, heat the porcelain facing and imbed the OTHER MATERIALS 17 labial surface in the shellac, as shown in Fig. 4. Clip off the pins of the facing and with a carborundum wheel on the lathe grind down the porcelain uniformly to the required thickness. Heat the porcelain, release the veneer and remove all particles of shellac before the ap- plication of the veneer to the case. To Change Shape or Contour of a Porcelain Tooth. — Trim the surface of the porcelain to the desired form- and polish, first with coarse carborundum disks, then with finer grades, finishing with cuttlefish and oxid of tin (putty). If the restoration of the original glaze is desired after polishing, place the tooth on pulverized silex on a fire- clay slab and heat in the electric furnace up to over 2400° for American and about 2000° for English rnanufacture. The porcelain will then appear with its original glaze. CHAPTER IV APPLIANCES AND METHODS lAIPRESSION TRAYS — ARTICULATORS — IMPRESSIONS — SECTIONAL IMPRES- SIONS — ROACH SECTIONAL IMPRESSION TRAY — MODELS — A HARD SURFACE — TO HARDEN PLASTER MODELS — ARTIFICIAL STONE — ARTICULATING IMPRESSION OR "bITE" AND MODEL^ — COMBINA- TION PLASTER AND METAL MODEL — COPPER AMALGAM MODELS Impression Trays. — In crown- or bridge-work operations, as an impression of only a portion of the teeth is generally required, partial impression trays are mostly used. Trays suitable for the right and left sides and front of the mouth are illustrated in Figs. 5 and 6. They are of forms that favor the replacement of a plaster impression in the tray should it break or be disturbed in removal from the mouth. Fig. 7 is an adjustable partial impression tray. This device conveniently 18 APPLIANCES AND METHODS 19 takes the place of three trays. The tray proper rotates on a pivot, B, and is thus perfectly adapted for use in the front or on either side of the mouth, and is firmly held in position by the sliding guard A. Fig. 6. Pig. 7. Articulators. — The ordinary and anatomical forms of articulators are used in bridge- work, especially the latter for large operations em- bracing both sides of the mouth. For small bridges or single crowns the partial or an anatomical articulator with a graduating support, 20 CROWN-, BRIDGE-, AND PORCELAIN-WORK such as is illustrated in Fig. 8, is much used. Fig. 9 shows an anatom- ical articulator. (Kerr's). Impressions. — For the taking of impressions for bridge-work and for most operations in crown- work, plaster is most suitable. To sim- plify the separation of the impression from the model, a particle of carmine or other coloring material may be combined with the plaster in the mixing. Potassium sulfate, if added, wUl quicken the setting. The best method for the purpose is to dissolve a small teaspoonful Fig. 8. Pig. 9. of the potassium sulfate in a pint bottle of water and thus always have it ready for use in the proper proportions. The improved impression compound is serviceable for impressions and "bites" for crowns and small bridges. It is softened with a moderate heat and quickly becomes hard again on the apphcation of cold. It does not fracture as easily as plaster. This compound is much used for taking impressions for inlay work by the indirect method. Sectional Impressions. — When the exact form of the contour of a tooth is required or when teeth tip toward each other in such manner that in the taking of an impression the mass of plaster that sets around APPLIANCES AND METHODS or between them will not pull out, the best plan is to take the impres- sion one half at a time with a split tray which is jointed in the middle by a hinge. A brass hinge may be used to form a split impression tray, as shown in Fig. lo. An impression may also be taken in sections (Fig. Pig. 10. Fig. II. ii). Take the lingual and part of the incisal or occlusal surfaces first, remove that section, trim, varnish and oil; replace in position in the mouth and apply plaster to form the remaining section. Separate the sections for removal from the mouth, replace and run the model. Fig. 12. An impression of this character may also be obtained by taking the lingual side first with impression compound and then the labial with plaster, so that it will include the entire occlusal and incisal parts. This method will sometimes simplify the taking of a difficult impression for bridge-work. A method for use in contracted spaces for re- moval of abutment crowns in the impression, is to fit a piece of softened impression compound accurately in position between the overhanging teeth, so shaped that it will pull out of the plaster impression on re- moval, as shown in Fig. 12. The piece of compound is removed from its position in the mouth and replaced in the impression to complete the mold. When the line of the interproximal space between certain teeth is required, it is best obtained by inserting between the teeth, before taking the impression, a piece of separating file, as shown in Fig. 13, Fig. 13. 22 CROWN-, BRIDGE-, AND PORCELAIN-WORK or a strip of copper, single or doubled so that it fits the space closely, with the ends protruding, and removing it in the plaster. In this class of work the surfaces of all plaster impressions that are to be run with plaster require to be thoroughly varnished and oiled. Fig. 14. Roach Sectional Impression Tray. — Fig. 14 illustrates the Roach Sectional Impression Tray. A is intended for taking impressions of teeth standing alone. It is closed on both ends and has centrally located flanges to aid in splitting the plaster in two sections to permit its removal. B is for taking an impression of a space with teeth on one end and none on the other. Fig. 15. Fig. 15 shows the handle in position on the closed tray ready to use. The tray is filled with plaster and pressed to position in the mouth. When the plaster is set the handle is withdrawn, the impression parted in the center, which is aided by the flanges, and removed. The two sec- tions are then joined and the handle readjusted to lock them together. Fig. 16. Fig. 16 shows a separated and closed impression of a tooth, in a Roach Tray, also the plaster formed model of the tooth. APPLIANCES AND METHODS 23 Models Models. — Models on which bridge-work is to be constructed but not soldered, are made of plaster. To permit removal of the caps or crowns from the model^dunng^the construction of the bridge, the inside of the caps should be veneered with paraffin to fill in recesses; also the surfaces of posts or tubes to permit them to be easily withdrawn from the plaster. The exposed outer cervical surfaces of the collars in the impression should be coated with paraffin to prevent the edges of the collars scraping the plaster of the model in reinserting and pushing the scrapings into the grooves into which the edges of the collars fit (Fig. 17). The mere cervical edge of the collar should be left free of the paraffin to permit it to sit closely in the model. Fig. 17. — W. Paraffin or wax. Models on which bridge-work is to be formed and soldered should be made of a material as non-shrinkable when heated as is practicable. Plaster and finely ground calcined marble-dust or pulverized silex, mixed in the proportion of 3 parts marble-dust or silex to i part plaster for large models, and 3 parts marble-dust or silex to 2 parts of plaster, for small models, are suitable proportions. Slips of orange- wood, iron pins or small nails may be placed in the impressions of such teeth as are liable to be broken in the removal of the impression from the model. Should fracture occur, a thin mixture of oxyphosphate cement should be used to repair the parts, as this, when thoroughly set, makes them even stronger. A Hard Surface.' — A model of investment material for bridge-work can be given a hard pure plaster surface as follows : First place with a camel's-hair brush in the impression of the teeth and also the surface of the alveolar ridge a film of a thin mixture of pure plaster, and when it has partly set, fill the remainder of the impression with a mixture of plaster and marble-dust or silex. This to be effective must be skil- fully done. To Harden Plaster Models. — The surface of models of plaster or investing material can be hardened by first drying the plaster by placing it in the rays of the sun in the summer or over a radiator in the winter, thus drying it slowly. It should never be highly heated as that makes it chalky. Several coats of very thin sandarac varnish, diluted to about two-thirds the usual consistence, are then applied at intervals to the surface. Immersion of plaster models in melted 24 CROWN; BRIDGE-, AND PORCELAIN-WORK stearin is also recommended, but for a working model varnish is preferable. Artificial Stone.- — Weinstein's artificial stone, a calcium silicate compound, is used to some extent to form models. It is hard and durable, and models made of it when worked on are not distorted by friability. Wax or compound impressions for artificial stone models require no preparation, but plaster should be well varnished, first with shellac, and when thoroughly dry with sandarac. The impression is then soaked in water about five minutes, removed, and the water shaken and blown out, leaving the surface moist. The purpose is to avoid any absorption by the plaster of moisture from the slow-setting artificial stone, which would affect the setting. In the mixing of Weinstein's artificial stone the powder must be accurately proportioned to the water, one-half fluidounce of water to every four and one-half to four and five-eighths oz. avoirdupois, which is equivalent to 80 to 82 dwt. (Troy) of the powder. This makes a thick mix that requires to be thoroughly spatulated. As it cannot be poured it is inserted in deep places with a small stiff brush followed with pieces in the form of cones — ^proportioned to the size of the space ■ — which can be pressed on with the rubber eraser end of a pencil. The remainder of the impression is then filled with larger pieces until it is full, when a surplus is added. The impression and model are then reversed against the surface of a piece of glass and pressure exerted sufficient to uniformly condense the entire mass. While the model is pressed on it is leveled around the sides of the impression with the spatula. Healey^s artificial stone must be mixed with water that has been just brought to a boil, then treated and inserted in the impression or mold in the same manner as the Weinstein. It forms a pure white model. This artificial stone sets as hard as plaster in from five to six horns. When it is that hard, the model should be trimmed to the desired form and removed from the impression, unless it is a model considered preferable to leave in the impression a few hours longer until it becomes harder. It acquires its maximum hardness of form in one to two days and maintains it indefinitely. Articulating Impression or "Bite" and Model. — This impression is either taken separately or at the same time with the impression for the model; the last is the most accurate method. When taken separately it should be done with all the crowns or caps in position in the mouth previous to the impression for the model. Wax is more generally used APPLIANCES AND METHODS 25 for a separate "liite" than impression compound. Softened wax barely sufficient to cover the parts is pressed over the teeth and crowns to their form, and the antagonizing teeth then occluded. The finger or cheek is pressed against the outside of the wax and the patient is requested to press the tongue against it on the inside. The mouth is then opened, the wax chilled with cold water and removed. To secure accuracy it is often necessary to trim the impression of overhanging or superfluous parts and reinsert it a second time. Pieces of tin foil placed over the teeth which antagonize before inserting the wax will prevent their biting through the impression. Another method is to close the mouth so that the teeth and crowns do riot quite occlude, and mount the model and impression on a hinge articulator that will permit teeth and crowns to occlude after the mod- els are mounted and the impression material is removed. When the model with the crowns has been made, the articulating impression, if taken separately, is placed in position on it, an articulat- ing model run and both models mounted on an articulator. When impressions for both model and "bite" are to be taken together, plaster mixed moderately thick with the aid of a spoon or rolled in a mass with the fingers is used. The fingers should be pre- viously immersed in water to prevent adhesion of the plaster to them. The stiff plaster is placed around in the mouth, on the crowns, caps and parts to be included in the bridge and the antagonizmg teeth then occluded tightly and so held until the plaster sets. The mouth is then opened and the plaster carefully removed. If it breaks in re- moval, which is usually the case, all the pieces should be preserved, accurately fitted together and secured in position with small pieces of melted wax. The crowns or caps are generally removed in the im- pression; but if not, they should be transferred from the mouth to the plaster. The plaster is then varnished and oiled. On the side, of the impression containing the crowns, if they are to be removed from the model in the construction of the bridge, a plaster model is run, or, if not to be removed, plaster and marble-dust or silex in the proportions already mentioned is used. When the plaster has set, the model is mounted on an articulator and an articulating model of pure plaster run and the opposite section adjusted for the articulator. The im- pression plaster is next removed. (For further details see Part VI, Chapter I.) Combination Plaster and Metal Model. — A method of forming a model in which the parts representing the teeth are of amalgam is as follows: Take an impression in plaster or impression compound. Mix amalgam and pack it into each of the molds of the teeth or roots and 26 CROWN-, BRIDGE-, AND PORCELAIN-WORK run plaster into the remainder of the impression. The advantage of a model of this kind when gold attachments or clasps are to be shaped to teeth is obvious. Amalgam can also be used in abutment caps, there- by permitting them to be removed and accurately replaced on the model with a certainty not found in the use of plaster. Both the inside and the outside of the gold caps should be veneered with paraffin. The paraffin and all the exposed portions of the metal are then given one or two coats of collodion. When the collodion is dry, the entire impression is oiled in the usual manner. Amalgam from which all excess of mercury has been pressed is packed into the caps, using moderate pressure. A short cone of the amalgam is left extending from each cap, which may be slightly scratched or indented. The plaster is next run into the impression and the case is put aside until the next day before separation. In the case of a cap with a post or tube, if the amalgam is only placed around the point or sides of the post or tube it will aid proportionately in defining the position of the cap in replacing it when it has been removed from the model. The caps and crowns when removed from the model should be cleaned by boiling in water and sodium carbonate and next in nitric acid to remove any trace of the amalgam that might have adhered. Oxyphosphate of zinc or copper cement may be used quite effectively instead of amalgam as above described and the precautions required to avoid amalgamation of the mercury of the amalgam with the gold of the caps avoided. Another method of forming a combined metal and plaster model much practiced, especially for inlay work, is to first make amalgam or fusible dies with tapering shanks of the teeth or roots operated on, then take a wax impressiofi and "bite." Run plaster in the "bite" sec- tion and when set, fit the dies into the respective impressions in the wax and run the remainder of the impression with plaster, then mount on an articulator. To make a die easy to remove from the model, veneer the surface of the shank with paraffin. A hole made in the base of the model in a line with the end of the shank of a die can be used to introduce an instrument to push the die from position when it is desirable to remove it from the model and use it separately. Copper- Amalgam Models. — Models of this form are at present much used in the construction of bridge-work. The impression re- quires to be taken in plaster in a sectional impression cup so as to secure the exact contour of the teeth, or it may be taken in the form of an impression and "bite" if the fractured portions of the impression are skilfully replaced in position. APPLIANCES AND METHODS 27 Copper amalgam is manipulated by gently heating the tablets in a spoon to soften them. The mass is next transferred to the surface of a clean piece of thick paper, and spatulated with a stiff steel spatula until smooth and plastic. It should be carefully and thoroughly packed into the impression and then placed aside to set until the next day. The models are then mounted with plaster on an articulator and the plaster impression removed. It gives a hard, smooth model. Copper amalgam can be re-softened and used several times. For this reason it is much less expensive than the silver-tin amalgams. CHAPTER V MOLDS AND DIES TUBES, CAPS AND TRAYS — HOW TO MAKE A TUBE QUICKLY — ^IMPRESSION FOR FUSIBLE METAL DIE — MOLDINE — CASTING THE DIE — COUNTER- DIES COMBINATION LEAD AND FUSIBLE-METAL COUNTER-DIES AMALGAM DIES — AMALGAM — THE SWAGER^ — SWAGING Molds or impressions of single teeth; also cavities in teeth, are taken in metallic tubes, caps or small trays with some one of the im- pression materials used for the purpose. Stamped seamless caps or tubes can be used; also trays formed from seamless caps by trimming and shaping the caps. Copper plate not heavier than gage No. 32 is generally the most suitable for making tubes, but a much thinner plate may be used when it is required to be passed between the teeth. Tubes, Caps and Trays How to make a Tube Quickly. — Take a thin strip of copper plate about gage No. 35, anneal and bend it around the tooth in the mouth or its form on the plaster model. Both ends of the copper at the part lapped are next cut, as shown at A, Fig. 18, and turned over tight and close in the manner seen at B. This fastens the ends which, when trimmed off at C, form a tube. When one end requires extensive trimming to fit the curve of a gum margin, the seam should be soldered with a small piece of either silver or 14-carat gold solder. To take the mold of the end of the root or the whole or part of the natural crown, the end of the tube should be trimmed to the curve of the gum and inserted under the gum margin. Caps are fitted in a similar manner. Fig. 19. Trays are used to make the mold or impression of occlusal surfaces or cavities formed in teeth for inlays. A tube or cap when trimmed so that it encompasses only a portion of the crown, as shown in Fig. 19 28 MOLDS AND DIES 29 Fig. 20. at A, to take an occlusal surface, or at B for both occlusal and approxi- mal surfaces, is practically a small tray. The formation of trays and their use in inlay work together with tubes and caps is described in Part III, Chapter XVIII. Impression for Fusible-Metal Die. — Fill the fitted tube or cap with plaster mixed as for an impression, apply on root or tooth and press to position. In using a tube press the index finger on the open end of the tube and force the surplus plaster downward in the tube. Hold in position until the plaster is set. Moldine. — The application is similar in principle to plaster. The surface of the moldine should be dusted with pulverized soapstone to avoid adhesion. Casting the Die. — Closely encircle the tube or cap with a strip of paper. Place a rubber band around the paper to secure it, as shown in Fig. 20. Hold the paper and tube with a clamp; melt and pour the fusible metal, moderately cool, and immerse tube and metal in water. This gives a die with a long narrow shank, but which may require trimming at the neck. Plaster molds are generally more accurate then moldine and give better results in casting. Impression-compound or gutta-percha used as a mold for fusible metal is not reliable. Such a mold when used should be cooled in ice water and dried before pouring the fusible metal, which should be one that will melt at not higher than 150° F, Counter-Dies. — A counter-die to a small die of fusible metal is made by indenting a block of lead with a punch about the size of the die and then driving the cast or die into it. Its use in crown-work is described in Part III, Chapter VII. A counter-die of fusible metal to a fusible metal die may be made either by chilling the male die and oiling or vaselining its surface or coating it with moistened whiting with a brush, and after drying pouring the additional metal as it cools. Combination Lead and Fusible-Metal Counter-Die. — This is made as follows: Cut two disks of thick sheet pattern tin, such as is used to form patterns for gold plates, or of rolled sheet lead, which is pre- ferable, in sizes that will fully cover that section of the surface of the male die where the metal is to be swaged. Slit the disks from sides to center, as seen in Fig. 21, which shows disks and die. Place one disk. Fig. 21. 30 CROWN-, BRIDGE-, AND PORCELAIN-WORK on the die and lap it down on the sides. Press or hammer the occlud- ing surface against a tightly rolled ball of cotton; next shghtly vaselin the surface of the tin and fit over it in like manner the other disk. Imbed the die in moldine up to and slightly over the edge of the tin, place around it a metal ring and pour fusible metal. When cold, remov the disk next to the male die. This leaves a slight space for the metal plate which is to be swaged. Amalgam Dies.^ — Amalgam is given preference to fusible metal and all other materials to form small dies in crowning and inlay opera- tions, as it is certain to afford sufficient strength with great accuracy of details. Its use is principally confined to the formation of dies in impressions taken with compound. The compound is warmed, the impression taken in a tube, cap or tray, and cooled before removal. The amalgam is then packed in and compressed. If the shank requires lengthening, wind round the tube or cap a very thin strip of copper secured with a string. If the impression is taken in a tray, detach or cut off the handle, mix plaster to a thick creamy consistence, place a small quantity on a piece of paper and set the back of the tray on its surface, gently pressing the tray down into the plaster so as to form a cup-shaped cavity around the impression. This furnishes the means of packing and then compress- ing the amalgam into the impression (Fig. 22). IMP. ^-npUAilum/ p. Piaini' Pig. 22. Fig. 23. Amalgam. — ^The silver-tin amalgams^ are mostly used instead of copper amalgam for making small dies in molds of impression compound. The required quantity of the silver-tin alloy is placed in a mortar with a surplus of mercury and ground until the mercury incorporated. It is then rolled in a ball, inclosed in a piece of rubber dam, as shown in Fig. 23, and rubbed quickly in the palm of the hand. The amalgam ^ The Black Formula alloys are of this character. MOLDS AND DIES 31 mixture by this method will become very plastic and capable of adaptation to the finished margins of the mold. A small portion of the amalgam should be first inserted and burn- ished with a small ball burnisher without pressure to all parts of the impression, then more amalgam added until the surface is entirely covered and the impression is filled gradually but solidly. Amalgam dies should be allowed to stand over night. The impres- sion and die are separated by warming the compound slightly or by immersing the impression and die in warm, but not boiling water. The plaster, metal or paper matrix, when used, should be removed first. The base or shank of the die should be trimmed to the required form when necessary. Pig. 24. The Swager. — This is a tool in which pieces of foil or plate are shaped to the form of a die by compression, and which may be used as a counter-die to a die or vice versa. Fig. 24 illustrates a swager partly in section about three-fourths its actual size. A is the cylinder, B the plunger, C cavity in plunger D cup, E base. The die is mounted or cast in the cup D, placed in the base E, the cavity C in the plunger B is filled with some compressible substance like moldine, then placed in the cylinder A and the plunger struck down on the die in the cup. The pressure thus exerted by compression of the material in the plunger in the direction of the die gradually conforms the plate to its surface. 32 CRGWN-, BRIDGE-, AND PORCELAIN-WORK To mount a die for swaging a disk of plate or a gold cap in a swager, fill the cup with impression compound and insert the base or shank of the die in it, as shown in Fig. 25. A die for the same purpose may be cast directly in the cup by making an impression or mold of the model D Pig. 25. — I C, Impression Compound. in the center of the surface of a fiat piece of moldine, placing the cup over it, as shown in section in Fig. 26, and filling the cup through the aperture with the fusible metal. An intaglio die is made with a cusp button by placing the cup over it and then filling the cup with fusible metal (Fig. 27). Pig. 26. Pig. 27. — D, Cup; CB, cusp button. Swaging. — Cut the plate that is to form the matrix to the desired shape and with pressure by means of spunk or cotton approximately adapt it to the metal model and cover it with a rubber disk. Place in the cylinder a mass of moldine about three-quarters of an inch thick. Insert in the top of the cylinder the steel plunger and strike it lightly with a mallet. Remove cup and model from the cylinder, examine and burnish out any wrinkles or folds and reswage. CHAPTER VI INVESTMENTS AND SOLDERING MATERIALS PRINCIPALLY USED FOR INVESTMENTS — SMALL INVESTMENTS • — LARGE INVESTMENTS — ASBESTOS — METHOD OF INVESTING — PRE- PARATION OF INVESTMENT FOR SOLDERING — HEATING THE IN\^EST- MENT — SOLDERING BLOCKS — A SERVICEABLE AND LASTING SOLDER- ING BLOCK — THE STRUCTURE OF FLAME — THE BUNSEN FLAME — THE BLOWPIPE FLAME — BLOWPIPE AND METHOD OF USING IT — • PREPARATION, APPLICATION AND FUSING OF SOLDER — SOLDER- POINTER — SOLDERING PRACTICE DUMMIES FOR STUDENTS — OPEN- FLAME SOLDERING — UNION BY SWEATING — SOLDERING WITH A COMPOUND BLOWPIPE FLAME — ANNEALING Materials Principally Used for Investments. — Calcined marble- dust finely pulverized, silex, common white sand or ground asbestos, combined in proper proportions with plaster, are principally used to form investing materials for crown and bridge-work, as they give a small percentage of contraction. Small Investments. — For small investments like single crowns, the proportions generally used are 2 parts finely pulverized calcined marble- dust or silex to i part plaster. Large Investments. — For large investments, including pieces of bridge-work, i part finely pulverized calcined marble-dust or silex, i part sand and i part plaster. When used in this proportion the sand' prevents the excessive contraction that takes place in large masses of investing material composed entirely of fine marble-dust when sub- jected to great heat for considerable time. The fine marble-dust in combination with the plaster is more suitable to fill in interstices and the inside of caps than the sand alone. Asbestos. — Asbestos may be substituted for sand, the coarse being used in large investments. Trimming must be carefully done if coarse asbestos is used as it is not easily cut, and displacement of the investment material exposing some parts of the work is liable to occur. Method of Investing. — The ingredients should first be thoroughly mixed in the dry state. Water is then added in quantity sufficient to make a thick batter-like consistence. The thicker the mix can be 3 33 34 CROWN-, BRIDGE-, AND PORCELAIN-WORK made and be practical, the better. The mixture should be rapidly and thoroughly spatulated. Potassium sulfate may be used in very small proportion to cause the mixture to set quickly. To invest a model made of investing material on which bridge-work is being constructed the model should be trimmed as small as is safe without risk of fracture. It should then be soaked in water while the investing material is being mixed. The reduction of the model is for the purpose of securing the largest possible proportion of refractory investing material in the investment to that of the model; and its immersion in water is to prevent absorption of water from the investing material and to obtain a better adhesion of the investment to the model. In bridge-work, especially in cases of any great size, a loop of iron wire should encircle the piece in the investment. (See part IV, Chapter i.) Preparation of Investment for Soldering. — When it is desirable to remove the wax connecting sections of a crown or bridge in an invest- ment before heating, it should be done by pouring boiling water on the parts. The removal of wax with an instrument is not advisable, as parts delicately held in position are liable to become displaced. The removal of the wax exposes the metallic portions of the work to be soldered. All surplus and especially overhanging investing material should be removed, but parts already soldered should be left covered. The metallic parts to be soldered should bp exposed as much as possible to the direct flame of the blowpipe, as the greater their depression in the investment, the more difficulty will be experienced in guiding and controlling the solder at a particular point with the blowpipe. Care should be taken that all parts of the porcelain teeth are covered and all crevices between them filled with the investment ma- terial to prevent the invasion of borax or solder, either of which is very liable to cause their fracture. The filling-in with gold foil of small open seams between sections of metal to be united facilitates their union in soldering. The filling-in of large spaces under caps or tips to porcelain facings can also be much facilitated by packing into the spaces pellets of foil or by placing in them pieces of plate or wire. A moderate application of flux may now be made to the deeply invested parts, as directed under article on "Flux" Part I, Chapter II. Many prefer to trim the investment and let the wax burn out as the investment is heated. This is done when fluxed wax is used and the benefit of the flux is to be obtained. The objection to the burning-out of wax is that owing to the resultant debris pits are more liable to be found afterward in the solder. INVESTMENTS AND SOLDERING 35 Heating the Investment. — In soldering crowns and bridge-work or sections of it containing porcelain facings, the investment should be uniformly, gradually and thoroughly heated over a Bunsen flame until the bottom of the investment assumes a dull red tint. A piece of heavy iron wire, about gage No. 8, bent in the form of a scroll, as shown in Fig. 28, or a piece of sheet iron perforated with large holes placed across the top of a spider fitted to the burner, forms a good support. When heated, the investment should be removed to a soldering block. Soldering Blocks. — A large round piece of charcoal about 5 inches in diameter and 6 inches long, with a little concavity cut or burned out on one end, and with a thin covering of plaster on the sides to prevent soiling the hands, furnishes a good soldering support and one that will Pig. 29.. retain the heat. Seams or cracks in the charcoal should be filled in with a mixture of sand or asbestos and plaster, to retard the burning out of the block. Two or three iron nails inserted in the concavity of the block, a little to one side of the center, are useful at times to prop up an investment. Manufactured soldering blocks, such as are shown in Fig. 29, are preferred by many practitioners to those of charcoal. 36 CROWN-, BRIDGE; AND PORCELAIN-WORK Fig. 30. — P, Plaster; M, mixture; N, nails. A Serviceable and Lasting Soldering Elcck. — Take a porcelain bowl about six inches across the open end, vaselin the inside surface and place over it a half-inch coating of pure plaster. When set, remove the plaster coating, which may be facilitated by slightly warming the bowl. Next take equal pro- portions of coarsely pulverized charcoal, sand, asbestos and plaster, a sufficient quantity to fill the newly formed plaster howl, and mix together thoroughly with water. Place the mix- ture in the plaster cast of the bowl, slightly depress the center and insert in it four or five iron nails to tilt the investment during soldering and prevent it from sliding off the block. (In section, Fig. 30.) Place bowl and contents aside in a dry place to set and slowly dry out, which will take some time. Before using the first time, thoroughly heat the center of the surface of the block with the blowpipe flame. This will prove a very serviceable and durable soldering block and one that will hold the heat next to one entirely of charcoal. Fig. 31. The Structure of Flame A knowledge of the structure of flame will assist in its use in soldering. Fig. 3 1 shows a candle flame. A , central cone, consisting of unburned gases, termed non-luminous cone. B, yellow cone of partial combustion, which emits the light, termed the luminous cone. C, cone of nearly or complete combustion, which emits only a faint light and is termed the semi- luminous cone. D, blue section of the base, extending only a short distance upon the sides. A- Q Fig. 32. F.IG. 13. — B, Central cone; C, deoxidizing flame; D, oxidizing flame. INVESTMENTS AND SOLDERING 37 The Bunsen Flame. — The Bunsen flame consists of a gas flame, into the central cone of which oxygen is carried by draft through an aper- ture made in the base of the burner, as shown in Fig. 32. The air drawn by the draft of the flame enters the hole A and is carried into the central cone B, where the oxygen it contains causes complete combustion. C is the deoxidiz- ing or reducing flame; D the oxidizing. The Blowpipe Flame. — The blowpipe flame differs from the Bunsen flame in that the air is forced into the central cone of the flame through a central tube from a bellows or air- pressure tank, Fig. 7,7^. The heat is intensified by the complete combustion effected in the Bunsen and blowpipe flames. As shown in Figs. 32 and t^t^, the deoxidizing flame is the portion to be used for soldering, as it cuts off the oxygen from the air and prevents oxidization of the metal. When an oxidized sheet of copper is held in this part of either the Bunsen or blowpipe flame, its surface is bright- ened in the area of the flame. This is caused by the carbon, oxygen and copper uniting and forming carbonic dioxide, CO2, which is passed off. The use of the extremity of either of these flames should be avoided as it naturally oxidizes the surface of the metal. Blowpipe and Method of Using it. — A hand gas-blowpipe (Fig. 34) operated by a foot- bellows of medium size and so constructed as to be under perfect control, especially respect- ing diminution of the flame to a very small point, makes a satisfactory apparatus. Com- pressed air is much used at present in preference to the bellows. When heated and ready for soldering, place the investment in the center of the soldering block, using large tweezers for this purpose. The full flame of the blowpipe should be directed at first under and around the sides of the investment, which is slightly tipped or propped up at one side for the purpose. In this manner the invest- ment is uniformly heated to a point sufficient to melt the solder without pointing the flame. Fig. 34. 38 CROWN-, BRIDGE-, AND PORCELAIN-WORK When the heat of the surface of a piece of metal is lower than that required to fuse the applied solder, the solder if fused on it is liable to ball up and roll off. The tendency of melted solder is to flow to the hottest point. It is also affected by gravitation. By the application with the blowpipe of a greater -degree of heat under the investment than on the top, the solder can be drawn down into the deeply invested parts, but if after flowing solder to and in these parts a heat is still maintained sufficient to keep the solder in a molten condition, and a slightly greater heat is applied to the surface section of the investment, the solder is liable to be drawn upward. In the soldering of a collar crown in this manner, the solder that has been drawn down between the porcelain facing and cap and around the collar on a line with the porce- lain is liable to be largely drawn backward and absorbed in the final soldering of the backing and contouring of the crown. Therefore in soldering the work, especially crowns and dummies with porcelain facings, these points should be borne in mind. When certain parts of the work have been united and generally filled in with the solder under the effect of properly applied and moderate sized flame, the flame may then be reduced in volume and pointed for a moment to guide the solder to and better shape it at some special point. Proper position for the investment and correct application of the heat in soldering aid greatly in accomplishing the desired result. Preparation, Application and Fusing of Solder. — The solder should be cut in small square and oblong pieces and placed within convenient reach of the points of the tweezers. The pieces may be coated with borax finely ground in water or with liquid flux, and should be allowed to dry before application to the work. When the investment on the sold- ering block has been brought to a dull red heat, or approaching it, with the blowpipe, a little solder should be applied at the point where the soldering is to be begun. The portion placed in the investment is first melted and flowed into the insterstices of the work, using the large flame of the blowpipe under and around the in- vestment and alternately a moderately sized flame at the part being soldered, using the de- A oxidizing portion of the flame. More solder is ' ■■' then added by degrees and, as the parts become Fig. 35. filled, by the use of a smaller flame applied di- rectly to the part and the judicious use at times of a small-pointed flame and the gradual addition of more solder the parts can be given the desired form. Solder is also applied in strip form. The solder is cut in a long narrow strip and one end is held while the other, which has been fluxed, is applied to the part being INVESTMENTS AND SOLDERING 39 soldered. How to slit and form the ordinary form of solder into a strip is indicated in Fig. 35, The slit piece of solder bent out is shown in figure A. In large pieces of bridge-work with considerable curve it will be found necessary to solder a portion at a time. This is best done by placing each portion as it is to be soldered in the deepest part of the concavity of the soldering-block and, when soldered, slightly cooling and changing the position of the investment, as gravity tends to carry the melted solder to the lowest point. A pair of solder-tweezers with a long reach and small curved points, as illustrated in Fig. 36, should be used to pick up and place the small pieces of solder. Solder-pointer. — A small pointed instrument with a long handle, termed a solder-pointer, is useful at times to stir up, spread and draw the solder to a desired point. The point of the instrument should preferably be made of platinum instead of steel. When desirable to melt a very small piece of solder at a point where it is difficult to retain and fuse it in posi- tion, flux and melt the desired quantity of solder in a globule on the block, and touch it with the extreme tip of the ''pointer. " The globule will adhere to the "pointer" in the form of a little ball (Fig. 37). Heat the special r -zi Pig. 37. part to be soldered to the fusing heat of the solder and apply the globule with the "pointer. " When the soldering is completed, an investment that contains porcelain facings should be inverted on the soldering block and allowed to cool slowly. This tempers the porcelain and prevents checking. Soldering Practice Dummies for Students. — The use of practice dummy crowns and bridges affords an inex- pensive method of teaching students to solder. It con- sists in cutting and shaping small pieces of German silver or platinoid to represent the metallic parts of a Pig. 36. crown or bridge, then waxing the parts together, investing 40 CROWN-, BRIDGE-, AND PORCELAIN-WORK and soldering them with silver solder, as illustrated in Fig. 38 (slightly enlarged). A, shows a piece of the metal bent to represent the backing of a porcelain facing and the floor of the cap of a cuspid crown; B is a Pig. 38. side view of the same to indicate the angle at which the metal should be bent; C, the position of the wax, the dotted line indicating the surface of the wax; D, a ring of the plate to represent a molar crown; E is a side view of a piece of plate bent to represent the backing and cusp cap of a bicuspid dummy; F, a lingual view of the same; G, the line of the wax. Fig. 39 is a side view partly in section of a dummy cuspid crown Fig. 40. invested and ready for soldering practice. Fig. 40 represents a dummy bridge ready to solder, consisting of a cuspid and a molar crown as abutments supporting the bicuspids. Practicing soldering on these dummies involves only a trifling expense, and the student will readily acquire the technique and quickly be- come proficient without waiting for practical cases. Open-Flame Soldering. — Open- flame soldering is done in a Bunsen (gas) flame and is the method used for sold- ering small sections of the work such as the seams and floors of collars. A Bunsen burner of the form illustrated in Fig. 41 (one-half size) is most con- venient for general use, as it permits the supply of air to the center of the flame to be regulated. The metal is held by a clamp and heated in the flame. (See part III, Chapter VI.) The heat should be applied gradually, with the metal first held above the flame and then slowly brought downward Fig. 41. INVESTMENTS AND SOLDERING 41 into it to a point just above the deoxidizing or reducing flame, and held there as briefly or as long as is necessary to effect the desired fusion. Rouge in a very thin paste or a mixture of one part marble-dust and two parts whiting applied on the inner or cavo-surface of a col- lar or cap will obstruct intrusion of the solder. The marble-dust and whiting are easily washed out but are not as reliable a preventive as the rouge. The heat should be applied slowly at first to permit evapo- ration of the moisture. Union by Sweating. — This consists in uniting the edges or surfaces of two pieces of metal by heating them so closely to the fusing-point that union takes place without melting the main body of the metal. The process is much used to unite the seams of collars. The metal is first boiled in acid and washed; the clean edges are brought together, as in the case of a collar, so that they lap slightly, touching at every point. The edges are then fluxed and the collar is placed on a charcoal block. The whole of the collar is first brought to a bright red and then with a small pointed flame gently passed over the edges to be united the gold is fused at that point and no other. This is facilitated by applying the flux only to the parts to be united, which by preventing oxidation causes the surfaces to fuse together before the main body of the metal melts. Another method is to hold the collar with a soldering clamp, seam downward, in a Bunsen flame until it unites, when it should be instantly withdrawn (Fig. 42). Soldering with a Compound Blowpipe Flame. — Platinum solder requires a compound blowpipe flame to melt it. This can be impro- vised by connecting the air tube of an ordinary gas blowpipe to that of a cylinder of nitrous oxid gas. The flame of the blowpipe should be reduced to a very small jet and the volume of the nitrous oxid turned on very slowly until an amount of pressure is reached sufficient to point the flame and effect perfect combustion. A small compound blowpipe of the style illustrated in Fig. 43 is suitable for soldering and general use,^ but the fusing of platinum solder may be effected quite satisfactorily with the ordinary blowpipe, using nitious oxide instead of air as first described. Amiealing. — Annealing gold is done either with the open flame, the blowpipe, or in the muffle of a furnace. In the open flame by holding ^ The I.e Cron blowpipe. Fig. 42. 42 CROWN-, BRIDGE-, AND PORCELAIN-WORK the piece of plate with a clamp in the deoxidizing part of the flame — until as high a degree of heat is reached as the character or carat of the plate will permit without melting. Pure gold will permit a light yellow heat; i8- or 2 2 -carat plate from a dull to a bright red. Large pieces of gold require to be laid on a soldering block and heated with a blowpipe. Pig. 43. Platinum is best annealed in an alcohol flame or in the muffle of an electric furnace. It requires to be brought to a white heat and kept there for a short time. In a gas flame platinum suffers deterioration by the formation of carbide of platinum, which oxidizing later is liable to blister the metal. The best results in annealing are accomplished by allowing the metal to cool slowly, although much time is often gained by immersing in water. This, however, should not be practiced with ingots of gold or silver just melted and poured. Each time metal is bent, burnished, hammered, drawn or rolled, its softness, flexibility and ductility are impaired, but they are quickly restored by annealing. This fact should be always borne in mind in the manipulation of metal in the construction of all forms of work. CHAPTER VII THE CASTING PROCESS INLAY WAX^ — FORMATION OF THE INLAY WAX MODEL — INVESTMENT- INVESTMENT MATERIAL — HEATING OF THE INVESTMENT — GOLD — ■ EXPANSION AND CONTRACTION OF MATERIALS AND METALS — CAST- ING MACHINES — CASTING PROCESS — LARGE CASTINGS — SCHWEITZER WAX SPRUE FORMER — EXIT VENT — LARGE WAX MODELS — TO INSURE AGAINST DISTORTION OF THE WAX MODEL — TO CAST WITH A SWAGER The introduction in gold casting of the process of compression in the construction of dental appliances has simplified and improved the character of many operations. Because it has been comparatively recently introduced, like other innovations in dentistry, the sphere of its usefulness and whether it is to be preferred to other and longer established methods are not as yet definitely determined. Practical experience in time will alone decide. Many practitioners, for instance, who at first used the method extensively for plates, crowns and bridges have already gone back to swaged plates and soldering operations. For the formation of gold inlays and small pieces of bridge-work re- quiring accuracy in form and continuity of structure, the castmg process has decided advantages. But in the casting of large pieces the varying expansion and contraction of metal, wax and mold are diflacult to entirely control; and the cast plate and clasp lack the resiliency present in rolled gold plate or drawn wire attributable to the process by which they are made. Improvements in materials, and of details in methods of conducting operations may — indeed already are over- coming some of the objections above outlined to casting. The casting of gold from wax models requires great accuracy and care in all the details of the operation, as well as suitable materials and appurtenances. Inlay Wax. — Inlay wax for models is composed principally of wax and paraffin. Manufactured inlay waxes^ are supplied in sticks and in 1 Manufactured inlay wax is generally used for inlay and other casting opera- tions. The exact composition of the different inlay waxes is kept secret by those manufacturing them. Light-colored pink hard sheet wax is often preferred by many in forming casting models, especially of saddles in crown- and bridge-work construc- tion, as it can be more conveniently applied and manipulated than the regular inlay wax. 43 44 CROWN-, BRIDGE-, AND PORCELAIN-WORK cones or forms suitable for use in cavities by casting the wax in molds to regulate molecular tension. Formation of the Inlay Wax Model. — The wax model is made either in the mouth or on an anatomically articulated model. The former is termed the Direct Method and the latter the Indirect Method. When a casting is to form part of a crown or bridge, the shaping of the wax model is generally done on the model on which the work is being constructed. Wax to form a model for casting should be softened uniformly in warm water heated to a temperature comfortable to the fingers, which ranges from 120° F. to 135° F. It should be merely pressed to shape, but not rolled or balled with the fingers. The wax is first placed in position and then pressed with the finger, the pressure being so directed that the wax shall reach all parts to be reproduced, especially in the case of cavity walls and margins. The wax is then trimmed to the contour of the tooth with a small spatula. Every detail of form and finish desired in the gold must be effected in the wax. The wax model should be chilled before removal. For further details in inlay work see Part III, Chapters XVI, XVII, and XVIII. Adhesion of the wax to the tooth structure in the mouth is prevented by the saliva and on a plaster model by wetting the part to which the wax is applied. When oil or glycerin is used it should be only the smallest possible quantity. The warmth of the mouth prevents rapid hardening of the wax while it is being shaped. The same advantage may be obtained for a wax model in the indirect method by placing the entire case in tepid water for a short time at intervals. Investment. — The Taggart investment flask consists of a ring and cap termed a crucible former, as shown in section at A in Fig. 44 (three-fourths size) with the sprue wire B in position. The sprue wire forms the entrance to the mold of the wax. To invest the wax model remove the sprue wire from the cap, heat the point and veneer it with a particle of sticky wax, cool slightly and introduce the point into the outer surface of the wax model at the point of greatest bulk in the wax and as far as possible from all margins, and at an angle that will offer the most direct flow for the melted gold into the mold of the wax. This is shown Pig. 44. — A, Crucible former; B, sprue wire. Pig. 45. THE CASTING PROCESS 45 in Fig. 45 (three-fourths size), which illustrates the model of an occlusal surface of a crown mounted ready to receive the investment. It is always best to have the line of any part of the wax model below the point of entrance of the sprue wire into the wax so the molten gold on entering the mold will not be required to take an upward angle. A very small sprue should be used for extremely small castings. For such cases it is an advantage to fill the hole in the crucible former with wax, using a common pin with the head cut off for the sprue. The surface of the wax model should be cleansed before investment. This is especially required when oil has been used to prevent adhesion of the wax, as an oiled surface interferes with accuracy of investment. Spraying the surface of the wax with a mixture of equal parts alcohol and ether will effectively cleanse the wax. Glycerin being readily soluble in water is easily removed. Investment Material. Specially prepared in- Fig. 46. vestment material is used to invest in casting work.^ The material and water should be properly proportioned by weight and measure. Fig. 46 shows the Tag- gart device for measuring the proportion of water and powder. It is preferable to have the mixture a trifle thick rather than thin. A china bowl for mixing is pre- ferable to a rubber one, as a minute particle of rubber could be scraped off, and freedom from contamination is nec- essary. The material should be swiftly spatulated around the sides for at least a minute, occasionally jarring the bowl on the bench to remove air and insure a thorough mix (Fig. 47). A mixing apparatus has been introduced, but rapid continued manipulation with a spatula is effective. First spray or wash the surface of the wax with alcohol and ether, half and half, to cleanse it especially of oil, then dip in water. Care- ^ Prepared investment compounds variously contain plaster, graphite, whiting, silica, etc. The silica acts as a base, the graphite or whiting to fill interstices and the plaster as a binder. Mr. L. J. Weinstein gives his formula as plaster 29 parts, fine silex 71 parts to be mixed in the proportion of 21 dwt. (troy), of the powder to one-half fluidounce of water. Fig. 47. 46 CROWN; BRIDGE-, AND PORCELAIN-WORK fully place a thin layer of the investment on the wax model with a small camel's-hair brush, then larger portions until it is covered, as shown in Fig. 48. This is to avoid air-bubbles, which would fill with gold. Set the ring on the cap and carefully pour the remainder of the investment. Do not jar the flask to remove air-bubbles, for if they are present under- neath the wax model, they are liable to settle against its surface as they Fig. 48. Pig. 49. are forced upward. Take time, as the setting will not interfere with the investing for several minutes. Do not attempt to fill more than one investment at a time. Allow the investment to harden for at least twenty minutes but not for an indefinite time. If left until the next day the mold before heating should be placed in water until saturated, to compensate for the moisture that has dried out. When thoroughly set, remove the surplus investment, warm the flask slightly and remove the crucible former and sprue wire, also any loose particles of invest- ment material. The case is then ready to be heated for casting, as shown in Fig. 49. Heating the Investment. — This should be done so as to get rid of the wax model in a manner that will cause the least possible change in the shape or dimensions of the matrix, and leave the in- vestment in the best form to cast into. The flask is placed on a piece of sheet iron on a spider over a Bunsen flame, or a support such as is shown in Fig. 50. First the moisture of the investment should be evaporated slowly at a temperature that will melt the wax but not boil it. As the moisture is evaporated, the Pig. 50. THE CASTING PROCESS 47 ' investment gradually absorbs the wax, leaving a clean matrix of the model. • This takes twenty-five to thirty minutes, the heat being brought slowly up to 150° F., then gradually increased as the wax is absorbed. The heat is increased to a point that will volatilize and burn out the wax and carbonize any residue, which is about 350° F., and then to 450° F., allowing about fifteen minutes for the operation. In the last few minutes the flask may be placed on its side directly over the Bunsen flame. The investment is then ready for the casting. Conducted in the manner outlined, the injurious effect of sudden or excessive heat is avoided. • Whether a hot or a cool flask is preferable to cast into is disputed. The question is in a measure answered by the fact that the crucible section of the flask has to be heated to the fusing point of the gold in the operation of casting. The wax in the mold at the time it is burned out leaves a film or binder on the wall of the matrix that imparts to it a certain amount of firmness and a comparatively unyielding surface. This results in a smooth as well as a bright casting by carbonization of the wax film and exclusion of the oxygen of the air. As this film is greatly impaired by cooling and reheating the flask, the casting should be done immediately after the wax is burned out. Gold. — Pure gold sHghtly alloyed (i per cent, copper) is generally the best for inlays, platinized gold when toughness and hardness are required, and coin or 21-carat gold for special parts of crown- or bridge- work. (See Part I, Chapter II.) An ingot not over three or four dwts. more than is required for the casting is placed in the crucible. There is no waste of the surplus. Expansion and Contraction of Materials and Metals. — The ex- pansion and contraction of materials and metals when heated and cooled are difficult to determine and cannot be entirely overcome. Therefore all metallic castings, though approximately correct, are not absolutely so. Inlays or other gold castings are either expanded or contracted in part or all ,of their form. This is especially attributable to the expansion and contraction of the wax; also to the contraction of the investment material that forms the mold and that of the gold. It is also caused by the excessive expansion of the brass ring of the flask in large castings. Heat expands a wax model as it is molded to a given form, which contracts as it cools. Investment material of which a casting mold is made contracts from loss of moisture. "This contraction is largely counteracted^by; the expansion and non-shrinking properties of the 48 CROWN-, BRIDGE-, AND PORCELAIN-WORK other ingredients. Gold expands when fused and contracts when it cools (.001451 inch). To meet these conditions the wax model should be invested while it is warm, or if left to cool, its temperature should be raised by immersing it in water of a temperature of 90° F. The temperature of the invest- ment should also be brought to 90° F. by mixing with water of 110° F. The expansion of the wax and some expansion also effected by the use of an investment containing a proper proportion of silex will closely compensate for the contraction of the gold. Fig. 51. Casting Machines. — Various forms of machines are in use to per- form the operation of casting. The Taggart, Fig. 51, the style first introduced, melts the gold with the carbo-oxyhydrogen blowpipe and forces it into the mold by pressure of the same gas. It has two dial indicators, one of which registers the pressure of the gas in the cylinder and the other the pressure under which it is released; a pressure valve which can be set for the pressure desired; a carbo-oxyhydrogen blow- pipe; a compressing lever and a mold flask holder. The Jameson apparatus uses centrifugal force. The crucible is mounted on an arm which is swung in a circle when the gold is melted. THE CASTING PROCESS 49 The Price is a centrifugal machine which uses electricity to melt the gold. The temperature is maintained in the crucible while revolv- -J^^:^ Fig. 52. ing until the required pressure is reached so that the gold enters the mold at full heat. The Elgin, illustrated in Fig, 52, is a vacuum machine. When the gold has reached the molten condition, a vacuum is created under the flask which, by the porosity of the investment, sucks the metal into the mold. Casting machines are ex- tensively used for the compres- sion method. The gold when fused in the crucible is com- pressed with a wet asbestos packing that extends over the gold and flask disk. The steam, which is instantly generated, forces the molten metal into the mold. The Platschick, shown in Fig. 53, also the Seymour, are of this type. The S. S. White swager, (Fig. 24) with a specially designed casting outfit, is also used for the purpose. so CKUW^-, BRIDGE; AND PORCELAIN-WORK Casting Process. — In the operation of casting, the gold is placed in the crucible cavity of the mold and brought to a white heat, so that it appears to boil. The heat is then lessened momentarily sufficiently to allow the appearance of boiling to cease and the gold is ready to enter the mold. The blowpipe is instantly laid aside and the pressure applied and retained. A pinch of pulverized vitrified borax may be sprinkled over the gold or its surface painted with liquid flux before it is melted. In the use of a carbo-oxyhydrogen blowpipe a small intense flame is directed on the gold, which melts it quicker than an ordinary gas flame and without afifecting the mold proportionally. As pressure is applied on the molten gold, the residual air is driven off into and through the minute pores of the investment. Superheating the gold, or ex- cessive pressure in casting should be avoided. Superheated gold is liable to unite with the investment and excessive pressure tends to expand or distort the investment matrix. In the use of the carbo-oxyhydrogen blowpipe excessive heating is liable to occur, owing to the intense power of the flame. Excessive pressure can be avoided with the Taggart, as it can be controlled with the pressure valve. In other forms of casting machines there is no means of definitely regulating pressure. The pressure required for casting is from eight to ten pounds for large or moderate-sized castings and from ten to thirteen pounds for small ones. The smaller the cast- ing the greater the pressure required. The casting when cooled is removed from the flask and scrubbed with a stiff brush. Cut the casting from the ingot, heat to a dull red, drop into a strong solution of sulphuric acid or pure nitric acid, or both, then wash and place in hydrofluoric acid for a few hours or over night. This gives a clean surface to the gold. Large Castings. — ^Large castings and moderately small flat ones require one or more extensions of the sprue to better enable the molten gold to instantly reach all parts. Fig. 54 shows the model for a small plate so mounted. These extensions from the sprue are made of wax rolled to about the size of the sprue wire. The center of the roll is attached to the sprue wire and the ends of the wax placed in position on the wax model. The Schweitzer Wax Sprue Former In construction this is a telescoping syringe with a small hole at each end by which two sizes of wax sprues are quickly and easily formed. THE CASTING PROCESS SI To operate the syringe the inside is charged with inlay wax, the syringe moderately heated and pressure exerted on the end opposite to the one from which the required wax sprue is to be ejected (Fig. 55 in section). Exit Vent.* — In large castings, a vent that will allow free escape of vapor from the cavity of the mold as the molten metal is injected, facilitates and extends its distribution. Such a vent is best placed in the investment above the line of the cavity of the mold. The vent is made by covering an annealed piece of copper or iron wire about gage No. ^t,, with a veneer of wax, then passing it through a hole in the upper part of the flask and bring- ing it down to the wax model, as shown V H Fig. 55. — W, Reservoir of wax; VH, vent holes. Pig. 56. — SV, Sprue vent. in Fig. 56 (a Taggart flask); or, the waxed wire may be extended through the surface of the investment close to the rim of the flask down to the wax model. Large Wax Models. — To form wax saddle or plate models for cast- ing, mark on the plaster model the outline of the plate the same as for a swaging operation. To harden the surface of the plaster, slightly dry the model and give the surface one or two coats of shellac varnish well diluted with alcohol so that it will soak into the plaster, and allow it to dry. Next apply one or two coats of thin sandarac varnish and set the model aside until thoroughly dry. The shellac acts as a binder and the sandarac glosses the surface. Vaselin the surface with a piece of cotton and thoroughly wipe it off. This leaves a smooth and slippery but not a greasy surface to the model. During the formation of the wax model or pattern, ^ Method devised by Dr. H. Schweitzer. 5-2 CROWN-, BRIDGE-, AND PORCELAIN-WORK if a lubricant is desired, the use of glycerin is preferable to oil or vaselin as glycerin is miscible in water and consequently is easily washed ofl the surface of the wax. For the casting model use thin sheet wax, such as is prepared and sold for the purpose, or a piece of semi-transparent pinkish wax now used for base-plates. Soften the wax in tepid water; if too thick roll it out to the gage desired to cast the plate, transfer it to the plaster model and adapt the wax perfectly to its surface. Trim the surface to the required size as marked on the model and place a bead around the edge, if one is desired (Fig. 57). Fig. 57. Pig. 5f The sprue wire should be placed in position before removal from the model. It should form a canal in the investment through which the melted metal can flow directly and through short wax sprue branches to all parts of the mold. For casting a large saddle the sprue wire should be placed so as to allow the wax saddle to be set in the flask in a line perpendicular to the cavity of the crucible former, as shown in section in Fig. 58. When set as illustrated the sprue wire may be made of a piece of iron wire about gage No. 14. In this way a reliable viaduct is formed to carry the gold to the smaller channels. An extra long flask is used to furnish space. The end of the sprue wire is to be fastened in the hole in the crucible former with hard wax. The wax model is next thoroughly chilled and carefully removed without dis- tortion of the edges. If there is any apprehension that distortion has occurred, it is best to wet the plaster model and readjust the wax. Adhesion of the base of the wax to the model may be avoided by first adapting to the surface a layer of thin gold foil and placing the wax over it. THE CASTING PROCESS 53 To Insure Against Distortion of the Wax Model. — Cover the sur- face of the wax model with a thick coating of the investing material Fig. 59. — Three-fourths actuarsize. Pig. 60. A B A and allow it to set. Next lift the wax model and investing material together from the plaster model and invest in the flask. A saddle may also be made of inlay wax by melting it in a spoon, applying it on the model with a brush and smoothing the surface with a wax spatula. This is a suitable method when a model of investing material is used and the saddle is shaped and cast directly upon it. When rubber is to be vul- canized on the saddle or plate, to connect the artificial teeth, pieces of platinum wire as attachments should be inserted in the wax with the ends extended so that the wire shall be held in position by the investment in the casting. The ends of the cut-off sprues left after casting if properly located may also be used for the purpose. To Cast with a Swager. — A swager, such as the S. S. White Dental Swager, with the acces- sories that accompany it, can be used for casting. Wax models for inlays or small castings are invested in the small ring, Fig. 59, that comes with the outfit, the upper edge of which is tapered to facilitate quick adjustment of the swager. A piece of wire about gage No. 13 is used for a sprue. When the investment has set, cut with a sharp knife around the sprue to form a crucible for the casting (Fig. 60). Fig. 61. 54 CROWN; BRIDGE-, AND PORCELAIN-WORK Insert the plunger B of the swager about one inch from the lower end of the cylinder A, Fig. 6i. Fill the depression C in the plunger with moldine, extending it about three-fourths of an inch beyond the end of the plunger. With the thumb make an indentation I, in the center of the mass similar to the depression C in the end of the plunger. Fig. 62. — Bridge-work flask fourths actual size) . (three- FiG. 63. When the investment R has been dried out and heated and is ready for casting, set it in the base E. Melt the gold required for the inlay in the cup formed in the investment; heat to boiling point (white heat), set the cylinder over the ring and gently but firmly press the plunger down. The time consumed in adjusting the cylinder is just sufficient to let the boiling of the gold cease. Keep up the pressure for at least half a minute. The pressure of air by the plunger and the steam from the damp moldine combined, force the melted gold into the mold. For large castings the flask illustrated in Fig. 62 made in two sections as shown in Fig. 63 (three-fourths actual size) is used. The open cup section is of a size to ac- commodate the application of the swager. To invest the wax model, remove the upper cap and invest the model in the ring, then im- mediately place the removable cover over the ring, allowing the metal sprue to project through the center of the opening in the cover, and add enough investment to fill to this opening. When the investment has set, treat it exactly as an inlay imbedded in a small casting ring, only cupping up enough to provide fully for the larger quantity of gold to be melted. When the investment is dried out and heated, cast as previously directed. Fig. 64 shows an invested saddle for a bridge in the large flask. Fig. 64. CHAPTER VIII FINISHING PROCESS FINISHING AND POLISHING — ELECTRO-PLATING Finishing and Polishing. — The preparatory or preliminary dressing off of gold should be done with small carborundum wheels and points, first coarse and then fine, on the dental engine. This method is preferable for this part of the work to the use of files or the lathe. First trim and finish interdental spaces and fissures. Thin vulcan- ized rubber and carborundum wheels and sandpaper disks are service- able for the purpose. Narrow interdental and wash spaces are most effectively reached with pumice by applying it on a cotton cord. Fasten one end of the cord to the bench and holding the other end with the left hand draw the bridge back and forth Pig. 65. on the cord with the right hand (Fig. 65) . Next polish the easily reached surfaces with pointed or flat felt cones with pumice and water or some other preferred polishing material. Then go over the entire bridge with a brush wheel, using fine pumice and soap until the surfaces are rendered perfectly smooth. Apply the soap by holding a piece of it against the re- volving bristles for a moment. Wash off all the soap and pumice and for the final finish use, whiting or rouge applied with polishing wheels on the lathe. Then thoroughly wash the bridge with warm water. As a holder for an all-gold crown while polishing, trim a piece of wood, about four or five inches long and one-half inch wide and shape the end to fit closely into the crown for use as a handle. A piece of heated impression ss 56 CROWN-, BRIDGE-, AND PORCELAIN-WORK compound placed on the end of the stick and inserted in the crown will additionally secure it. Fig. 66 shows a crown holder that catches inside the crown. Electro-plating The surfaces of the different grades of gold composing a crown or bridge can be rendered uniform in color and more resistant to oxidation and discoloration by plating with pure gold. A plating outfit is readily constructed as described below. A plating solution to use with it consists of: CUoride of gold M oz. Cyanide of potassium i oz. Water 8 oz. Of Fig. 67. The plating outfit is illustrated in Fig. 67. The base (A) is a J;;^ in. board, i foot long by 8 inches wide. The upright piece (B) is 9 inches high by 6 inches wide. Two carbon globes (C) are placed at one end, and the jar (D) for the solution at the other. For a no-volt direct current use a no- volt i6-candle-power lamp and a 220- volt 32-candle- power lamp placed in series to reduce the current. The wires are first connected to the plugs (E). The positive current is passed through FINISHING PROCESS 57 the two lamps and the negative current transmitted direct to the so- lution. The wires pass through the two small holes (FF) in the upright board (B). Two hooks (GG) are inserted under the holes. The negative wire is connected to one and the positive to the other at the shanks of the hooks as they are screwed into the board. On the posi- tive side suspend in the solution a piece of pure gold plate (H) rolled very thin; the upper end of the plate is held by a clamp supported on the hook to which the negative wire is attached. The article to be plated (I) is held by a piece of copper wire looped over the hook con- nected with the positive wire. The positions of the positive and negative wires are distinguished the one from the other by first testing the current with the plating solution by the use of a two-piece plug and changing its position in the socket. When the position of the poles is determined the plug can be marked for future correct insertion. Before plating, the metal should be trimmed, smoothed and polished, using pumice and whiting or rouge, and then boiled in a solution of lye and washed in warm water. PART II PREPARATORY TREATMENT OF TEETH AND ROOTS FOR CROWN- AND BRIDGE-WORK PREPARATORY TREATMENT OF TEETH AND ROOTS FOR CROWN- AND BRIDGE-WORK GENERAL CONSIDERATIONS Preparatory to crown and bridge operations the mouth should be put in the healthiest possible condition. The teeth should be first scaled of any calculus present, then cleaned and polished. Roots or teeth incurably affected should be removed, pyorrhea and any existing lesions treated and cured; also, such measures should be adopted as will prevent the recurrence of old troubles or the inception of new. Notwithstanding all that advanced knowledge of therapeutic agents and skill in their use permit, there are many teeth and roots which cannot be rendered suitable for the successful apphcation of crown- and bridge-work. Roots which are permeated and softened by decay, exposed or loosened by absorption of the gingivae and alveoli, or affected by irremediable disease of the investing membranes should be thus classed. Cases in which abscess with necrosis has extensively impaired the walls of the alveoli are equally intractable. Experience shows that the results in this department of dentistry depend largely upon diathesis or constitutional tendency and upon the attention given to the preservation of the health of the mouth. These conditions should be carefully estimated in the selection of a system of treatment and the method of its application. CHAPTER I THE PULPS OF TEETH PREPARATORY PROCESSES — DISINFECTION OF VITAL DENTIN * The preservation of the vitality of the pulps of the teeth or their extirpation in crown- and bridge-work is a subject that requires careful consideration. The excision of natural crowns for the purpose of utilizing their roots for artificial crowns as abutments for bridge-work is extensively practiced, and is defended on the theory that the vitality of the dentin is to an extent maintained by the cementum after the extirpation of the pulp, or that the pulp, being the formative organ, is of no further value in a fully developed tooth when root-canal treatment is properly conducted. The pulp after going through the progressive changes which con- stitute its original function assumes a fixed anatomical character as the source of the vascular and nervous supply from which the dentin derives and maintains its vitality. The protoplasmic bodies of the pulp unite with the living matter of the tubuli, which anastomose to a limited extent with those of the cementum through the intervening protoplasmic bodies in the interzonal layer. This distribution and relative connection of living matter refers to an existing state of perfect vitality of all the parts. When the pulp loses its vitality, an entirely different condition results. The tubuli are then deprived of vital circulation, except along the lines of the outer portion of the dentin, where, in the interzonal layer, the fibrillse anastomose with the living matter of the cementum. The vitality supported by this anastomosis is insufficient to take over the functions of the pulp and maintain circulation in the main body of the dentin. (See Plate I.) When the pulp has been removed, the devitalized fibrillae still remain and, unless antiseptic root-canal treatment is thoroughly carried out, their disintegration generates septic gases capable of producing irritation of the cementum and pericementum.^ ^ The analysis of dentin by Dr. G. V. Black gives an average of — Lime-salts 63 . 54 Organic matter 25 . 36 Water 11 .06 Age slightly lessens the proportion of living matter and increases the percentage of lime-salts. 63 64 CROWN-, BRIDGE-, AND PORCELAIN -WORK An examination of the investing membranes of many pulpless teeth shows the existence through ineffective treatment of a percentage of abnormal conditions, by which their firmness is to an extent impaired, their susceptibility to acute imflammation increased, and their re- habihty as foundations for crown- and bridge-work greatly lessened a^ compared with teeth which have living pulps. Frequently such conditions, when found in evidence in connection with the work of some of our best operators, are attributable more to difficulties that interfered with the perfect performance of root treatment than to carelessness or lack of skill. Plate I. — L, Lacunae of the cementum; C, canaliculi of dentin; I, interzonal layer — X 210. Observation also has shown that the dentin of gold-capped pulpless natural teeth in the course of years gradually softens sufficiently to impair their strength. Again, on the other hand, the extirpation of pulps permits a better performance of details of operations, such as the shaping of natural crowns for crowning or for utilization as supports for bridges; and the advantages thus gained are in the opinion of many proportionately of greater consideration than that of pulp conservation. Additionally, as the dentin calcifies as years advance, the proportion of living matter in it becomes gradually less; therefore the older the patient the less pulp extirpation has to be seriously considered. THE PULPS OF TEETH 65 A general study of the subject will show many methods of practice that will properly permit pulp preservation and in contra-distinction also indicate where a preferable condition will be insured by pulp removal. Preparatory Processes That extirpation of the pulp and excision of the natural crown, especially of an incisor or cuspid, will at times simplify the work and permit better forms of construction is undeniable. Besides, the ques- tion of root-canal treatment is not to be as seriously considered in relation to anterior as to posterior teeth where its perfect performance is not so easy of accomplishment. When the removal of the entire enamel and a large portion of the dentin of, for instance, a bicuspid or molar tooth, is necessary to properly shape it for a collar or cap-crown, the removal of the pulp is usually demanded and should precede the operation; otherwise, irritation of the dentinal tubuli is liable to follow and consequent lesions of the pulp. In such cases, as the future of the Fig. 68. tooth depends on the effectiveness of the canal treatment that the circumstances will permit, it is advisable to take a radiograph that shows the form and condition of the roots and canals. Cases such as are illustrated in Fig. 68 present difficulties that suggest the advisa- bihty of resorting to the use of the most favorable method of bridge construction that will permit retention of the pulp in an abutment tooth; as a larger percentage of trouble results from ineffective root- canal treatment than from normal pulps degenerating under crown or inlay operations. Pulps which are in normal condition and still protected by a layer of partly decomposed dentin usually admit of successful treatment. In such cases the decayed dentin should be thoroughly excavated from the side-walls of the cavity, but that over the pulp need be only superficially removed. Extirpation is always demanded for pulps in a pathological condition or whose permanent preservation cannot be placed beyond doubt, as 66 CROWN-, BRIDGE-, AND PORCELAIN -WORK failure involves more serious consequences in crown- and bridge-work than in filling operations. The lesions of the pulp that require its extirpation are, all forms of exposure, congestion and pulpitis which does not yield promptly to remedial treatment. Disinfection of Vital Dentin. — When decay has extensively involved the dentin and closely approached the pulp, as a precaution against subsequent irritation, thorough disinfection of the dentin and any remaining decomposed portion which may have been left over the region of the pulp is advisable. The method of disinfection is to first thoroughly wash the cavity several times with tepid water thrown gently from a syringe around the sides of the cavity; then, taking measures to prevent the entrance of the saliva, wipe the cavity with absorbent cotton and pass over its surface a light current of hot air from a hot-air syringe. The heat should be suflScient to cause some discomfort to the patient but not enough to produce irritation of the pulp. The dried cavity is then immediately saturated with carbolic acid previously warmed to the normal tem- perature of the body by holding the pellet of cotton on which it is applied over the flame of a lamp for a moment.^ The carbolic acid relieves any pain caused by the evaporation of moisture and disinfects and sterilizes any decomposed matter in proximity to the pulp. The object of the application of the carbolic acid having been accomplished, the surplus may then be removed from the surface. To this end the cavity should first be wiped with absorbent cotton and hot air again introduced to evaporate the moisture sufficiently to give a dry appear- ance to the surface of the dentin. This second application of hot air, owing to the effect of the carbolic acid, will cause little or no pain. This method, if practiced early in the preparation of the cavity, will be found to considerably obtund sensation, and through the dryness secured, to materially facilitate the removal of the decomposed dentin. For excavating in the region of the pulp chamber, spoon-shaped excava- tors should invariably be used. For the thorough disinfection of dentin and the removal of hypersensitive conditions, the author prac- tices the method of previously placing and sealing in the cavity for from two days to a week a mixture of precipitated chalk, carbolic acid and oil of cloves in equal parts. A small quantity of aristol may also be added. ^ 1 Thermal shock to the pulp is as unwarranted from the application of cold carbolic acid as if produced in any other manner. 2 The chalk is placed in a mortar, and the carbolic acid and oil of cloves gradually introduced and thoroughly incorporated with the chalk by trituration until the mixture becomes a plastic mass. THE PULPS OF TEETH 67 The disinfected dentin over the pulp is next varnished with cloro- gutta-percha or some other preparation suitable for the purpose, and capped with oxyphosphate. When the capping is set, the remainder of the cavity is filled with the same cement as the capping or with an inlay or amalgam. The rubber-dam, when its use is practical, should always be applied in these operations. The shaping of the coronal section of a tooth for a crown or the preparation of the cavity for an inlay can then be proceeded with. In the latter case the cement can be trimmed as though it were dentin, leaving enough to fully protect the pulp. CHAPTER II DEVITALIZATION OF THE PULP INSTANTANEOUS DEVITALIZATION — USE OE COCAIN, CATAPHORESIS AND PRESSURE ANESTHESIA — EXCISION OF THE CROWN AND INSTANTANE- OUS EXTIRPATION OF THE PULP — DEVITALIZATION WITH ARSENIC When devitalization is necessary in preparation for crown- work two methods are practiced : the heroic — instantaneous devitalization — and gradual devitalization by arsenical treatment. Instantaneous Devitalization. — This is accomplished by first open- ing into the dentin or cavity in the direction of the pulp (Fig, 69), then administering to the patient sufiicient nitrous oxid to produce anesthesia and with a drill quickly exposing and lacerating the pulp well up the canal with a probe or smooth broach. In- stantly afterward a pellet of cotton saturated with carbolic acid is forced up the canal and, if possible, left until the next day, when the pulp will be found in a coagulated mass that is easily removed entire. Use of Cocain, Cataphoresis and Pressure Anesthesia. — In cases of actual exposure of the pulp and those in which the patient permits its exposure by removal of the decay or the use of a small spear-shaped drill, the rubber-dam is appHed, the exposed pulp obtunded with adrenahn and cocain (Parke, Davis & Co., Hypodermic Tablets No. 115) in tablets appHed in saturated solution. The diffusion may be hastened by electrolysis. Pressure anesthesia is effected by first removing a small portion of the enamel in the direct line of the pulp, then piercing the dentin with a fine spear-shape drill as deeply as possible without causing excessive pain. The cocain solution is then introduced on a few fibers of cotton placed in the hole drilled. Pressure is next exerted on the solution with a ball-shaped burnisher on a pellet of unvulcanized rubber inserted in the cavity. The pressure should be directed in the line of the pulp. 68 Pig. 69. DEVITALIZATION OF THE PULP 69 As soon as the action of the cocain is manifested the drilling should be continued and, if necessary, the solution again applied. The solution is to be gradually worked into the pulp as soon as it is exposed, with a fine smooth-pointed broach; or injected. After the lapse of two or three minutes the pulp can be painlessly extirpated. Excision of the Crown and Instantaneous Extirpation of the Pulp. — This is performed as follows: Two parallel grooves are cut through the enamel opposite to each other and deep into the dentin, one on the labial portion of the tooth and the other on the lingual wall, close to the gingiva, with a rapidly revolving carborundum or vulcarbo disk (Fig. 70). The crown is then severed from the root with excising forceps (Fig. Pig. 70. Pig. 71. Fig. 72. 71). The pulp either adheres to the excised crown, leaving the canal empty, or remains in the root fully exposed. In the latter case a pointed piece of orange wood, previously cut to fit the canal and saturated with carbolic acid, is driven with a quick blow into the pulp towards the apex of the root (Fig. 72), When the wood is withdrawn the pulp usually adheres to it, but, if not, the wood is instantly reinserted, cut off and drilled out with the pulp, using Gates-Glidden drills in the upper portion of the canal. Expertly performed this operation is advantageous. It should, however, be confined to teeth the pulps of which are in a normal condition. Practical experience shows that in such cases it is attended with the most satisfactory results. Only trifling pain is felt by the patient, as the pulp is paralyzed by shock in the excision of the crown or by being forced upward towards the foramen and against the walls 70 CROWN-, BRIDGE-, AND PORCELAIN-WORK oi the canal. This method however is seldom practiced since the in- troduction of the use of cocain. The subsequent vitality of the cementum is assured by the instan- taneous procedure in pulp extirpation, and discoloration of dentin and enamel is minimized as much as possible, but when the natural crown is utilized in bridge operations, the translucence of the teeth is usually impaired by pulp removal. Devitalization with Arsenic. — The methods of devitalization pre- viously described are most successfully applied to normal or only sHghtly calcified pulps. Pulps of teeth extensively calcified, molars especially, do not so well permit the instantaneous methods. Con- sequently recourse at times is had to arsenical treatment with highly nervous, sensitive patients, notwithstanding the.numerous objections to its use. Two theories as to the mode of its action in devitalizing are widely entertained: First, that its toxic effects produce hyperemia, which stops circulation; second, thrombosis. This theory of throm- bosis might account for the gradual devitalization of the pulp toward the foramen. Whatever the action of arsenic on the pulp may be, it causes some infiltration of the tubuli of the dentin with certain constituents of the blood, probably the liquor sanguinis. To an extent the residue of the infiltration, after the devitalization of the pulp, remains in the tubuli, increasing the difficulty of producing an aseptic condition of the dentin and proportionately causing its discoloration. This discoloration is most marked when arsenic is applied to dentin over an unexposed pulp. It is asserted that arsenic sometimes afifects the vitality of the cementum by its diffusion to the zone around the apex of the root. Arsenic when used, should be applied directly to the pulp in the smallest quantity possible to effect devitalization, and securely sealed in the cavity. In cases of non-exposure requiring its application, a small opening into the pulp-chamber if possible should be made. This can be accomplished, as already described, with but little pain to the patient. Arsenic may be combined with creosote or carbolic acid in the smallest possible proportion of the arsenic that will effect devitahzation, or with agents which are non-coagulants of albumin. Dr. Harlan's method to avoid using coagulants of- albumin is to apply an anodyne, such as wine of opium, for a minute or two, and then the following paste: I^. Arsenous acid, 3i Muriate of cocain, 3ij Lanolin in quantity sufficient to make a stiff paste. DEVITALIZATION OF THE PULP ^i No arsenical application should be kept in position longer than is necessary to effect devitalization of the pulp, twelve to forty-eight hours being sufficient. The short period refers to a case in which there is no calcification and application is made in direct contact with the pulp. The longer periods are where the application is not quite direct, or where the pulp is slightly or considerably calcified. The pulp- chamber is then opened, a saturated solution of tannin in glycerin applied and securely sealed in the cavity, and the patient dismissed for a day or two when, in favorable cases, the pulp can be removed entire. CHAPTER III PULPLESS TEETH REQUIREMENTS OF TREATMENT — PREPARATION OE ROOT-CANALS — REAM- ING — TREATMENT — USE OE ANTISEPTICS — CLOSURE OE THE APICAL FORAMEN AND FILLING OF THE CANAL Requirements of Treatment. — The treatment of pulpless teeth or roots consists in as thorough performance as possible of the following procedures: First: Proper opening up and enlargement of the canal to the fora- men and removal of the contents. Second: Antisepsis of the root-canal and dentin and the establish- ment of permanent aseptic conditions by mummification of the contents of the tubuli. Third: Closure of the apical foramen and prevention of future in- fection from the oral cavity by the hermetical closure of the entrance to the canal. Preparation of Root-Canals. — A knowledge of the usual form and position of the roots and of the different teeth and the orifices and lines of the root-canals (See Plate II and Figs. 130 to 138 inclusive) is essential for a generally successful performance of this operation. The proce- dure is greatly simplified since the introduction and use of radiographs that definitely show the length and form of the roots and canals to be operated on, as well as any abnormality present. The direct access in the line of the root-canals that is obtainable in crown operations greatly facilitates the work of effective treatment. In all cases, in the preliminary removal of tooth structure sufficient of the crown should be left to easily permit the application of the rubber-dam and the retention of dressings with gutta-percha seals. When teeth are broken down or extensivel}^ decayed beyond the gum margin and hypertrophied gum tissue invades the cavity, the diseased tissue should be removed, the cervical section of the margin of the cavity excavated and an antiseptic dressing applied. The cavity should then be packed with gutta-percha well anchored either against the adjoining tooth or in the orifice of the pulp cavity in 72. PULPLESS TEETU 73 a: / 74 CROWN-, BRIDGE-, AND PORCELAIN-WORK such a manner as to stop hemorrhage and press back the tissue slightly beyond the edge of the cavity and expose it for the next stage of the treatment, as shown in a case of approximal decay in Fig. 73 and decay on both sides in Fig. 74. In cases where the side wall of a tooth is so far decayed under the gum margin as to render application of the rubber-dam either extremely difficult or impracticable, a thin collar or matrix may be adapted to the peripheral sections and ce- FiG. 73. Pig. 74. Fig. 75. men ted in position with oxyphosphate cement, as shown in Fig. 75. D indicates the cervical line of decay. When the cement has set, the rubber-dam is applied and enough of the cement removed with a bur to expose the pulp cavity and permit the root-canals to be treated and filled. The collar may remain on during the treatment. When treatment and root-canal fillings are completed, the cavity inside the Pig. 76. Pig. 77. — Sectional view of an inferior molar decayed on the posterior approximal side. A. The line to which the crown should be removed to facilitate entrance to the pulp-chamber. collar can be filled vs-ith amalgam or first lined with oxyphosphate and the amalgam inserted while the oxyphosphate is still soft. When the amalgam has set the collar is removed. In the preliminary treatment of an infected pulpless tooth a fine probe should always be inserted in the root-canal, to be withdrawn when the temporary filHng is completed, to leave a vent for the escape «f gases. Pressure should be exerted with an instrument on the temporary filling to prevent its displacement as the probe is with- PULPLESS TEETH 75 drawn. First remove the tooth structure over the pulp-chamber in the direct line of the canal. Where the coronal section of a normal incisor or cuspid is to be preserved, operate from the lingual side, Fig. 76. The removal of the coronal section of teeth directly exposes the pulp- chamber. In bicuspids and molars for an all-gold crown, the occlusal surface and the side walls of the cavity should be removed, to give direct access to the canals (Fig. 77). The pulp-canal of an incisor or cuspid is easily reached; bicuspids and molars are more complicated. When the buccal roots of the superior molars join together, the canals incline to a similar condition, and in the third molars the buccal and lingual canals occasionally unite and form one large canal. These are conditions that are usually indicated to the operator by the radio- PlG. 78. • graph. In the case of the superior molars, the canal of the palatal root is the first that should be located, and in the inferior molars the canal of the distal root. By locating these canals in normal cases, the others can more easily be found. In cases of extensive calcification frequently the orifice of each canal must be separately located. If the orifice of a canal is not apparent, endeavor to locate it with a pulp- canal pick (Fig. 78) by prodding the dentin in the expected location. If calcification has only partly closed it, prodding with force will usually disclose it. If the orifice is entirely closed, remove some of the dentin, guided by a radiograph, and again apply the pick. When entrance to the canal has been effected, probe it with a fine sharp pointed broach to determine its direction and length. Next enlarge the orifice with a cone-shaped bur or a Gates-Glidden drill (Fig. 79) so as to give it a funnel shape to guide the points of instruments into the canal. For effective root-canal treatment the operator should be equipped with a full set of the most approved broaches, root-canal files, drills, 76 CROWN-, BRIDGE-, AND PORCELAIN-WORK and reamers for use both in hand and engine (Figs. 79, 80, 81. 82 and 83)- The orifice of the canal having been opened up, if a devitalized pulp is present, remove it with a fine Donaldson barbed broach by Pig. 79. 12 3 4 5 6 XIP XF F M XC Style B Pig. 82. i Pig. 80. Pig. 81. 1 2 3 4 5 6 7, 8 9 10 11 12 XXF XP P M C XC Fig. 83. — Root Canal Reamers. passing the broach as far up the canal as possible, then entangling the pulp on the barbs. This is best done by moving the broach a little upward and downward and twisting it slightly in the downward move- ment. Next, guided by frequent explorations with a fine pointed broach (Fig. 80), the canal is carefully enlarged with Kerr's root-canal PULPLESS TEETH 77 files (Fig. 82) and Donaldson broaches (Fig. 81). They should be used delicately with an up-and-down motion, beginning with the smallest first and then increasing in size. A 75-per cent, aqueous solution of sulfuric acid carried on a fine platinum probe to the canal, then pumped into it with a small broach, is most effective as an aid in opening up very small canals or those partly closed by calcification. In the former case the acid softens the dentin of the sides of the canal so that the friction of a smooth broach will materially enlarge it. In the latter, in addition to this effect, it de- composes the calcified contents of the canal. The enlargement of the canal with a smooth broach permits the introduction of root-canal files and Donaldson barbed broaches, first small and increasing in size, by Fig. 84. — Radiographs showing wires in root-canals. which the canal can almost invariably be safely opened and enlarged to the zone of the cementum and, when alveolar abscess exists, through the foramen. When so opened, they can be thoroughly divested of organic matter by the action of the acid and use of the broaches. The application of acid in root-canals of normal teeth should not be carried further than the zone of the cementum at the apex, for, should it penetrate the foramen and reach the pericementum, it is liable to cause irreparable injury to that membrane. When the acid has ac- compHshed its purpose it should be removed and its further action neutralized by sodium bicarbonate solution. A canal should be slightly enlarged to the foramen to facilitate root- canal filling, but not through to the apical space except when an ab- scess is present. The depth to which a canal is or has been penetrated can be determined by the insertion of a metallic wire into the canal and then taking a radiograph with the wire in position. This is re- peated as often as is deemed necessary during the operation (Fig. 84). 78 CROWN-, BRIDGE-, AND PORCELAIN-WORK It should, though, be borne in mind that divergence of a broach from the Hne of a canal is indicated according to the angle the radiographic rays have been cast. Accordingly, any divergence of a broach in a canal in either a lingual, labial or buccal direction is not always as certainly determined. When a canal has been penetrated and slightly enlarged with root-canal files or broaches, apply Gates-GHdden drills (Fig. 79) or reamers (Fig. 83) from a small to a large size, as the case requires. The distance a reamer should be used up a canal and the size of the reamer are regulated by the form and size of the root and whether or not the canal is to carry an anchorage post. Reaming, with hand reamers or with Gates-Glidden drills — which are practically reamers — and the engine, should be done with a slight up- and-down movement as they are revolved and with very little pressure apphed. Under too much pressure the instrument might be broken off, or in a straight root be forced through the foramen. Nor should reamers be forced into canals closed by calcification or into a curved root. A slight pain is usually experienced under normal conditions when they enter the zone of sensibility formed by the cementum which composes the end of the root, of the slightest symptom of which the patient should be instructed to instantly inform the operator. The probe-like points of the Gates-Glidden drills do not cut but simply guide the drills and confine them to the line of the canal. They should be frequently sharpened with an Arkansas stone of knife-blade form. An occasional quick withdrawal of the drill from the canal during the process of drilling will aid the removal of the debris. Moderate reaming of a root-canal, in addition to simplifying the operation of filling, opens up the ends of the tubuli and facilitates the permeation of antiseptic agents. Opening up root-canals evidences the skill of the operator and when effectively performed and associated with correct filling insures the success of the operation. Occasionally a root-canal is so small and the end of the root so shaped — as indicated by the radiograph — that enlargement of the canal to the extremity of the apex is hazardous, because liable to involve perforation of the root, especially when advanced or entire calcifica- tion is present. In such cases, especially in entire calcification of the canal showing no lesion of the apex, the canal should be opened up as far as practical and the remainder rendered inert by mummification with repeated dressings of antiseptics. The canal is then filled and the ori- fice hermetically closed. When a root is very small or the end curved — as indicated by a radiograph — in the former, reaming should be pro- portioned to the size of the root, and in the latter it should carry only as PULP LESS TEETH 79 far as the curve will safely permit. In both cases the remainder of the canal can then be enlarged with root-canal files and broaches. In a case of entire calcification and obliteration of the canal, the center of the root should be opened up in the line of the track formerly occupied by the pulp, with round burs proportioned in gage to the former canal and in depth as far as is safe without risk of penetration of the side of the root or apex. The dentin is then mummified by applications of a saturated solution of aristol in the essential oils, re- peated at intervals of three or four days, until the dentin is darkened in shade, indicating its thorough permeation. The canal is best entirely filled with zinc oxychlorid. Treatment. — Pulpless teeth are presented for treatment in one of the four following conditions: 1 . Where the normal pulps have just been extirpated from the canals. 2. Where on opening into the pulp-chamber, the pulp is found partly or entirely calcified in the canals with little or no vitality and the root externally in a healthy condition. 3. Where the pulp is found diseased or in a putrescent condition. 4. Where alveolar abscess is present and a septic condition of the canals and dentin exists. In the first and second classes the treatment should be directed to assuring a continuance of the existing aseptic condition and the filling of the canal; in the third and fourth classes, to bringing about an aseptic condition by disinfection and sterilization and making certain of its future maintenance, including incidentally the cure of any existing disease of the external membrane of the alveolus. In cases of the first and second classes, if possible, saliva should be excluded from the pulp-chamber and canals during their entire prepara- tion and filling. If necessary to syringe out the canal, alcohol can be used instead of water. The instruments should be sterilized and broaches, if serrated, had better be new. In the third and fourth classes, exclusion of saliva or water is not necessary in the preliminary work on the canal; and water may be freely used until the process of disinfection and sterilization is commenced, after which its entrance should be prevented. To this end the rubber-dam should be applied if practicable. When not, as frequently occurs with roots and teeth badly affected with cervical decay, they should be treated as shown in Fig. 75, or other means of keeping out moisture be resorted to. In such cases, when the rubber-dam is not applied and cotton rolls are used, during each interruption of the operation the entrance to the canal should be packed with absorbent cotton saturated with alcohol, the saliva being thus excluded. 8o CROWN-, BRIDGE-, AND PORCELAIN-WORK In cases of the third class in opening up the canal great care should be taken not to force any of the septic matter through the foramen and cause infection of the apical space. This is frequently difficult to avoid; so, as a precautionary measure, at first open up only the ori- fice of the canal, then introduce and inclose in it — leaving a vent — anti- septic agents until its contents are rendered inert. After the canal has been properly opened up and its contents removed, it is washed out with alcohol and wiped with absorbent cotton, and is then ready for further treatment. The use of sodium potassium is recommended by Dr. E. C. Kirk at this stage as a germicidal saponifier and to open up the ends of the tubuli, but, as in the use of sulfuric acid in normal cases it should not be allowed to reach the zone of the cementum. The next procedure is to secure as thorough a state of dryness in the pulp-chamber as is possible, by forcing into it hot air with a hot-air syringe, (hand or electric), at a temperature higher, as it leaves the nozzle, than is comfortable for the finger. A root-canal drier with a tapered point may then be introduced into the canal, preferably with the point of silver and the bulb of copper (Fig. 85). As silver possesses remarkable properties as a thermal conductor, the heat is trans- mitted to the point of the probe very rapidly. The probe being inserted as far as possible up the canal (Fig. 86), the patient is directed to raise the hand as a signal should the heat cause pain, in which case the probe must be moved up and down or withdrawn for a moment. This procedure, following the previous application of the hot air with the syringe, evaporates the moisture and aids the escape of any gases present in the root-canals and the open ends of the tubuli. The point of the root-canal drier acts as a sterilizer and may be applied so hot as to carbonize any organic matter which it reaches in the end of the canal, a portion of which may be removed each time on its point. As the silver point can be tapered as small as the finest broach, canal contents impossible to entirely remove may be reached and ren- dered inert. ^ 1 Use introduced by the author in 1887 and use of hot-air published in article in the Herald of Dentistry in 1 884. Fig. 85. PULP LESS TEETH 8i In cases of the third or fourth class, sepsis being present, the heat is very serviceable, as it aids the escape of gases from the canal and dentin and acts as a germicide. When in this dry and heated condition the dentin is in the best possible state for the application of antiseptic agents. Use of Antiseptics. — Great diversity of opinion exists as to the suitability of various antiseptics in treating tooth-structure, their effectiveness and permanency when so used, whether singly or in combination, and their adaptability to various conditions. Many of the antiseptics in common use, being coagulants of albumin, obstruct the dentinal tubuli and their diffusibility through the dentin is conse- quently retarded. To this class belong carbolic acid, creosote and the like. They are not entirely non-diffusible in devitalized dentin or ce- mentum, as decomposition effects elementary changes in the contents of the tubuli, but their action is slow and limited as compared with that of some other agents, as the essential oils. The former are also irritants and unsuitable in cases where an acute or chronic inflammation of the peridental membranes is to be treated. Formalin in the form of Formocresol is recommended by Drs. Kirk and Inghs. There is no question as to the efficiency of formalin, but on account of its irritant properties it should be used with great caution. It should not be introduced up the canal as far as the zone of cementum at the apex and a vent shoul dbe left in the filling placed over it suffi- ciently large to permit free escape of the formalin gas into the oral cavity instead of being forced up in an apical direction. The essential oils, which are non-coagulative in their action, have greater diffusibility and, according to Miller, Harlan and others, possess much greater antiseptic power than was formerly attributed to them. For this reason the essential oils in combination with preparations of iodin that exert a chemical action and retain their antiseptic properties for a great length of time, are the most approved. The selection of antiseptic agents is therefore important, and the choice is indicated by the conditions presented in a pulpless tooth. A tooth from which a healthy pulp has just been extracted with the canal in an aseptic condition differs in its requirements from a case in which sepsis of dentin or a diseased or putrescent pulp is present. In the first mentioned conditions favorable results usually follow root filling, with or without antiseptic treatment, the advantage of the antiseptic agent in the canal being to better assure the continuance of the state of asepsis. When a healthy pulp has just been extirpated and immediate root filling is practiced, the use of carbolic acid or creo- sote is indicated. The minute fibrous connections with the wall of the 82 CROWN-, BRIDGE-, AND PORCELAIN-WORK canal and the vessels at the apical foramen are severed and the action of an escharotic antiseptic agent is in fact required, as it acts as a coagu- lant and instantly seals up the ends of the tubuli. If immediate root filling is not to be practiced, then the prescription of such agents as the essential oils with aristol or iodoform seems suitable, as by their action a sort of mummification of the non- vital organic matters follows. More- over, the oils possess advantages over the coagulants in that they are not miscible in water and are less easily eliminated. Their use will tend better to perpetuate an aseptic condition. In the second class of cases, also in teeth of the third and fourth classes with sepsis of dentin, or diseased or putrescent pulps, we need the intervention of agents which will not only destroy ptomaines but which will exert a chemical action on sulfureted hydrogen and ethereal ammoniacal gases, the products of putrefaction, and entirely eliminate them. On this depends the successful treatment of such cases, for until disinfection of the dentin is absolutely accompHshed the canal is not in a suitable condition to be closed. Carbolic acid, creosote or the essential oils, under such circumstances, exert no chemical action on these gases, merely disguising their odor, though it is true that by repeated dressings of cotton saturated with one of these agents, the gases are absorbed by the cotton and slowly eliminated. What is required is the action of disinfecting agents whose elements possess an affinity for these gases and so will immediately decompose them, forming new combinations and entirely changing their character. In accordance with this principle, iodin is indicated as preferable to the other agents mentioned. Its effects are best obtained from some one of the preparations in use, preferably aristol (dithymolbiniodid) from which nascent iodin is liberated, the odor of which is not objectionable, in a strong or saturated solution in one of the essential oils. In practice the oils of cloves, cassia, myrtol and eucalyptol are favored for this purpose, the first named being reckoned more sedative in its action than the others. The canal should be flooded with the solution, thereby to some extent permeating the dentin, as well as the cementum at the apex. A more complete saturation can be accomplished by drying and heating the dentin and applying the solution several times, or by filling the canal with cotton saturated with it, hermetically closing it and letting it so remain for a day or two. As aristol in combination with oil of cloves or cassia has a tendency to slightly discolor dentin, its use should be confined to the extremity of the root-canal and plain oil of eucalyptol or myrtol used in the orifice and coronal section of the tooth where maintenance of the natural shade of the crown is to be considered in an operation. When PULP LESS TEETH 83 a normal pulp has been extirpated from an anterior tooth and the crown is to be preserved intact and its shade maintained, oil of myrtol should alone be used; and the foramen within a day or two, if not immediately, should be closed with gutta-percha and the canal filled with zinc oxychlorid. The disadvantage of immediate root filling is that should some minute fragment of the pulp remain in the extremity of the canal, it fails to receive the benefit accruing from the reapplication of antisep- tics, which would better assure its inertness by mummification. In the treatment of a root-canal from which a pulp has just been removed or when no pathological condition exists at the apex, an acute inflammation of the pericementum of that part is frequently produced from the applied antiseptic agent being pressed or pumped through the foramen and invading the apical space. Such cases are relieved by washing out the canal with alcohol, applying the alcohol as a dressing and tightly sealing the entrance to the canal with oxyphosphate cement for a few days. To avoid such an inflammation the author at first applies the essential oil diluted with alcohol or chloroform. The solution is applied on cotton, — 'from which all excess is removed, — gently packed in the canal and sealed with cement for a day or two. At the next treatment the foramen and only the extreme end of the canal are pj,, g closed with gutta-percha as shown at GP, in Fig. 87. The treatment can then be continued and the antiseptic be applied with safety in full strength. The dressing of root-canals is best performed with the aid of ordi- nary smooth flexible rectangular broaches, and with root-canal dress- ers. The form of these instruments permits fibers of cotton to be easily wound around them lengthwise and over the point in one con- nected mass. When the cotton is introduced in the canal, it is retained on and carried forward by the instrument which, when withdrawn, leaves the cotton in position in the canal in the form of a cone or tampon that in septic cases will favor the escape of gases and may still be easily removed at any time After one or several treatments in the manner described, between which, if intervals of time are to elapse, the antiseptic agents must be hermetically sealed in the cavity with gutta-percha or oxyphosphate or a small quantity of gutta-percha covered with oxyphosphate. When the treatment is completed the canal is dried and the foramen closed, if this has not already been done,'and the canal filled. 84 CROWN-, BRIDGE-, AND PORCELAIN-WORK Closure of the Apical Foramen and Filling of the Canal. — The object of root-canal filling is the maintenance of an aseptic condition in a sterilized root-canal by hermetically closing it at both the apical foramen and the orifice, thus preventing its infection by the entrance of either fluids or gases. Gutta-percha to close the foramen and fill the extremity of the canal and zinc oxychlorid to fill the remainder and the orifice are generally accepted as most suitable. The extreme end of the canal is first pumped full of chloro-gutta- percha with a broach or small probe, and any surplus towards the orifice of the canal absorbed with cotton. A cone of solid gutta- percha of suitable size to fill the upper third of the canal is then inserted and pressed into the chloro-gutta-percha. The cone is best carried to ^ position by heating the point of a small root-canal plugger and attaching the cone on the point, as shown at A, Fig. 88. The cone is then placed and gently pressed but not suddenly pushed into position in the canal and de- tached from the plugger by giving the plugger a sudden twist. The gage of the. point of the plugger used should always be larger than the foramen so as to avoid the risk of pushing the point through in packing the gutta- PiG 88 percha. A current of hot air is next thrown on the protruding end of the cone at a temperature sufficient to soften it and warm the dentin, when it should be again gently pressed up the canal. A slight twinge of pain to the patient will usually be the signal of its complete impactment in the end of the canal. The solid gutta-percha absorbs what little chloroform is present, the heat then evaporates the chloroform and the pressure condenses the gutta- percha. If the process of heating and condensing is repeated suffi- ciently, the gutta-percha can be solidly condensed. Its shrinkage is thus reduced to a minimum or entirely overcome. The advantages possessed by zinc oxychlorid over other materials are its antiseptic qualities and its density. Its disadvantages are its tendency to produce irritation when pumped into or through a foramen, and the difficulty attending its removal from the extremity of the canal, should conditions require that course. These objections are removed by filling the upper third of the canal, as described, with gutta-percha. The remainder of the canal and the pulp-chamber are filled with the oxychlorid. To effect this proportion of the oxychlorid, remove any excess of the gutta-percha present from the orifice and lower section of the canal with a round-headed bur as shown at B. The oxychlorid should be mixed very thin, carefully pumped up the canal and compressed with an instrument or cotton as it sets (C). . PULP LESS TEETH 85 The combination of gutta-percha and zinc oxychlorid forms an ideal root-canal filling, as the zinc oxychlorid hermetically closes the orifice of the canal and prevents its infection from the oral cavity. When metallic points of lead or copper, shaped to fit, are used to fill root-canals, unless a small quantity of chloro-gutta-percha is first placed in the extremity of the canal, the complete closure of the foramen is doubtful. The best method is to close the foramen with gutta- percha, pump up the canal a thin mixture of zinc oxychlorid and then insert the metallic point. The use of cotton as a filling in root-canals is to be condemned. A few fibers of iodoformized cotton' may be used as a vehicle to aid in carrying zinc chlorid to position in the canal, especially of an upper root. Asbestos is given preference to cotton by some. Tin or gold foil makes an effective root-canal filling, but is difficult to insert without leaving vacuoles. Paraffin combined with a small quantity of aristol as a material to fill root-canals has been suggested by Dr. Kirk, especially after the use of sodium potassium. This agent, being a most active solvent of albuminous matter, in a measure frees the ends of the tubuli of a canal of their organic contents, a favorable condition for the use of paraffin. Paraffin is aseptic, melts at a low temperature and, with a heated root-canal drier can be flowed into the ends of the tubuH or into a minute canal not considered safe to open up extensively. Re- cently, chloro-rosin has been recommended by Dr. Callahan as a root- canal filling that will penetrate the exposed ends of the tubuH in the dentin and adhere to the walls of the canal. I^ Rosin gr. xi Chloroform 3 iii Ordinary gutta-percha should be used to close a foramen when an abscess has just been treated by injecting through it. The rubber- dam is placed on the root or it is otherwise protected from the saliva, the canal washed with alcohol, and dried. The length of the canal should be measured with a hook-pointed broach and gaged with a small perforated disk of rubber-dam slipped upon the instrument, as shown at D, Fig. 89. The gutta-percha should then be carried to position on the point of a canal plugger, the point having been heated just enough to cause slight adhesion of the gutta-percha F. An allowance should be made for the displacement of the instrument by the cone on the point by comparing the length with the broach, E. The cone is then de- tached from the point and left in position in the apex by giving the ^ Cotton may be sterilized by immersing it for a time in a saturated solution of iodoform in ether, and then drying. It should be kept in a tightly-corked bottle. The odor of iodoform in the operating-room is thus avoided. 86 CROWN-, BRIDGR-, AND PORCELAIN-WORK instrument a twist, G. As oil of eucalyptus is a solvent of gutta- percha, the application of this oil to the surface of the gutta-percha is recommended in its final insertion as better adhesion to the walls of the canal is thus obtained. To properly fill and close an enlarged foramen, an accurately fit- ted plug of gutta-percha should be used. This can be obtained by rolling a strip of pink base-plate gutta-percha into the form of a long tapering cone, as shown at H, Fig. 90, with a slightly heated spatula on a glass E r i 1 H I J K L Pig. Fig. 90. slab which has been dipped in hot water. With the end of the cone held by the fingers, the point is inserted up the canal and pressed into the foramen, and the line of the surface of the end of the root marked on the cone, which is then withdrawn. The length of the cone in the canal is compared with the measure of the canal, as shown by the broach L and the surplus that protrudes through the foramen is cut off. The cone is again inserted up the canal, marked, then removed and trimmed until the cone fits closely in the apex of the root, as illustrated at I. It is then removed and about one-fourth of an inch of the section that fits into the foramen is cut off, J. The cut-off portion is next mounted on the point of a canal plugger which has been heated in an alcohol flame just enough to cause adhesion of the gutta-percha, as shown at K. A little of the point of the cone is then trimmed off, causing the remaining portion, which is slightly larger, to require pressure to place it in position in the foramen. The length of the canal is then gaged on the shank of the plugger from the point of the cone with the rubber-dam which has previously been placed there, as shown at K and L. The canal is next washed with alcohol and dried. The cone, having been PULP LESS TEETH 37 dipped in oil of eucalyptus, is inserted and pressed up the canal until the disk on the plugger meets the surface of the end of the root, which indicates that the cone is in correct position in the foramen. The plugger is then twisted around several times to disengage it from the Fig. 91. Pig. 91. — Radiograph of a fractured central incisor of a boy nine years old with the large foramen incident to his age closed with a measured gutta-percha cone and the remainder of the canal as yet unfilled. gutta-percha. Fig. 91 shows a case treated as described. If the plugger is pressed beyond the line at the disk, the gutta-percha will be proportionately protruded through and beyond the foramen. Fig. 92. Fig. 93. — G, Gutta-percha; O, oxychlorid; P, post. When two canals in a root terminate in the same foramen, it is best closed by first filling the canal through which the foramen is most easily reached (Fig. 92) after which the other canal is filled. Ample room should be left in any root-canal which is to receive the post of a crown, as any part of the canal not occupied by the post will later be filled with the cement. ,88 CROWN-, BRIDGE-, AND PORCELAIN-WORK When a post has been fitted to a canal previous to the closure of the foramen, the foramen should be closed with gutta-percha, the oxy- chlorid pumped up the canal and the post inserted. When the ce- ment is. about half set, the post is seized with pliers and withdrawn and not again inserted until the cement is perfectly set. In this man- ner an oxychlorid socket is formed into which the post will fit accurately (Fig. 93). The same can be done with the post of a finished crown, if the foramen has been previously closed with gutta-percha. A pulpless tooth presented for crowning, the roots of which have been treated and filled in some previous operation, should be carefully Fig. 94. examined. If the slightest doubt is entertained as to its hygienic condition, it should receive antiseptic treatment as previously de- scribed, as the ultimate success of crown- work depends primarily upon the thoroughness of the preliminary operations. Fig. 94 shows radio- graphs of properly filled root-canals, which are the superior cuspid and inferior bicuspid shown unfilled in Fig. 84. The approved method in practice is to take preliminary radiographs to determine the form and condition of roots and canals of teeth and then again other radiographs during stages of the treatment, and finally to determine the effective- ness of the operation. CHAPTER IV CHRONIC ALVEOLAR ABSCESS THE USUAL FORMS — ABSCESS OF THE FIRST FORM — ABSCESS OF THE SECOND FORM — EXOSTOSIS — THIRD FORM, BLIND ABSCESS — ALVEO- LAROTOMY — GRANULOMA — APICOECTOMY, AMPUTATION OF THE APEX OF A ROOT — HYDROGEN PEROXID — PROGNOSIS OF CHRONIC ALVEOLAR ABSCESS AND APICOECTOMY — PERFORATION OF A SIDE- WALL OF A ROOT-CANAL OR OF THE DENTIN AT THE BIFURCATION OF THE ROOTS Many teeth and roots presented for crown- work are affected with chronic alveolar abscess. A general description of an effective method of treatment is therefore properly associated with a discussion of the subject. The cause of chronic alveolar abscess will be found in a continuation of those conditions which originally produced the acute form. The tooth or roots being pulpless, pyogenic organisms and septic gases, generated by the decomposition of organic matter in the root-canal and in the tubuli of the dentin find an outlet through the foramen into the apical space, or by failure of root-canal filling present to effectually prevent infection from the oral cavity, causing pericementitis and forma- tion of pus. The general treatment consists in the removal of all septic matter and gases from the root-canal and dentinal tubuli, the destruction and removal of the pus-sac, the application of suitable therapeutic agents and the adoption of measures to prevent further formation of pus. The Usual Forms. — Chronic alveolar abscess is usually found in the following forms : First, abscess with fistulous opening through the alveolus and gum and accessible through the root-canal and foramen. Second, abscess with fistulous opening but not accessible through the apical foramen. Third, abscess without a fistula and from which pus discharges through the apical foramen and root-canal, or does so as soon as the foramen is opened, termed blind abscess. Abscess of the First Form. — In the treatment of an abscess of the first form, the canal should be enlarged, as described in the treatment of pulpless teeth, and the foramen opened with broaches without the use 89 90 CROWN-, BRIDGE-, AND FORCEL A IN-WORK of a drill. Aromatic sulfuric acid on cotton placed in the end of the canal for a day will usually open up the most minute foramen, A small quantity of 75 per cent, aqueous solution of sulphuric acid pumped into the extremity of the canal will often enable a broach to instantly effect a passage. The saline solution slightly colored with tincture of iodin is then forced through the foramen with a fine-pointed syringe (Fig. 95) introduced well up the canal and surrounded with a packing of gutta- percha; or it may be pumped up with cotton on a serrated broach until it passes into the abscess and out through the fistula. This is followed by pumping through with a broach carbolic acid 95 per cent, or some other preferred agent. Aromatic sulfuric acid may also be injected through the foramen or the fistulous opening into the abscess a few times in cases that do not quickly respond to other treatment. Abscess of the Second Form.^ — When calcification has caused the obstruction in the canal, enlarge the canal as far as possible with broaches and Gates-Glidden drills. Next, guided by the outline of the root and canal, as shown by a radiograph, with small-sized burs penetrate the cal- cified area. When the latter is accomplished, with a small, sharp-pointed round broach and sulfuric acid endeavor to make a passage to and directly through the foramen into the abscess, as the apical section of the canal is not always entirely calcified. Placing a little of the acid in the extremity of the root to remain for two or three days will sometimes aid the operation. Drilling directly through the end of a root should be practiced only when other treatment fails, as the opening made seldom follows the line of the canal through the foramen. Exostosis. — When exostosis closes the foramen, the root-canal should be sterilized and filled and the affected portion of the end of the root removed (see Apicoectomy) and the area of the sinus curetted. Third Form, Blind Abscess. — In these cases first open, clean and disinfect the canal and enlarge the foramen with broaches and root- canal files, if necessary aided by sulfuric acid, so that the largest size will pass freely into the abscess. Through the enlarged foramen, by aspirating and then gently injecting, wash out the abscess cavity at first daily with the saline solution or absolute alcohol or both, using a Pig. 95. CHRONIC ALVEOLAR ABSCESS 91 sub Q or similar syringe with ihe smallest size gold point, gage No. 22, or pumping with cotton on a broach. In some cases the point of the syringe may be introduced through the foramen directly into the ab- scess cavity. Another syringe of the same style may be used to with- draw the injections and contents of the abscess cavity by inserting the point with a packing up the root-canal and withdrawing the piston. In this way the injections may be repeated and withdrawn. The canals are next filled loosely with a dressing of saturated solution of aristol and oil of cloves, eucalyptus or, preferably, oil of myrtol, if tooth dis- coloration is to be avoided. Insert a small probe in the canal, pack the orifice and cavity with gutta-percha, press on the gutta-percha and withdraw the probe. The aperture left by the probe furnishes a small vent. Continue this line of treatment until evidence of suppuration ceases, then temporarily pack the canal closely with the medicated dressing and seal the cavity, first with and later without a vent. After the lapse of three or more weeks, should the indications appear favor- able on removal of the dressing, and as viewed in a radiograph, close the foramen with a cone of gutta-percha, carefully avoiding pressure of air or excessive protrusion of the gutta-percha into the apical space. If the abscess is only acute or small this method, if skilfully prac- ticed, will usually effect a cure. Should this treatment fail, an opening through the gum and alveolus into the abscess must be obtained (see Alveolar- otomy) and the same course pursued as described in the first form of abscess. Alveolarotomy. — For this operation the length of the root and position of the apex should first be accurately determined. This is best done by the aid of a radiograph and introducing a broach with a hook point through the canal and foramen — if it is open — into the abscess and then slowly withdrawing the broach. In the withdrawal the hook by catching on the apex indicates both the position and the length of the root (Fig. 96) . A small pellet of gutta-percha or a little disk of heavy rubber-dam placed on the broach, as shown at A, will form an accurate gage. After the withdrawal of the broach a straight line probe is passed up the canal through the foramen into the abscess and left there in position. The exposed portion (A, Fig. 97) will fairly indicate the direction in which the root points, and should Pig. 96. 92 CROWN-, BRIDGE-, AND PORCELAIN-WORK there be no considerable curve towards the apex, the line in which the abscess cavity is most likely to be found. The hook broach B is then placed externally with its shank exactly parallel with the probe A in the canal, and. the line of the broach and more especially the location of the hook point, marked on the gum with carbolic acid. A few shreds of cotton twisted around the broach, especially at the point, will aid in carrying and holding the acid. In the manner described, aided by a radiograph, the line of the root and the position of the apex can be located within a small fraction of an inch, and as well the cavity of the abscess, which may be a little to the right or left of the apex. The membrane at the spot marked is then punctured and entrance to the apex of the root and apical space and abscess effected through the bone with a small spear-shaped drill and spoon-shaped excavators. The fine probe protruding through the foramen into the abscess will additionally aid the operator in locating the abscess cavity and root apex. The membrane may be anesthet- ized, preferably by conductive anesthesia, previous to the operation, or the operation may be performed under analgesia. Local hypo- dermic injections dilate the tissue, which is an interference with the operation. An entrance into the apical space can be made almost painlessly in the following manner, as described by Dr. G. V. Black: "The mucous membrane is first dried at the point at which it is desired to make the opening, and napkins are so placed as to keep it dry. Then a plugging instrument with fairly sharp serrations and of convenient shape is selected, the point of this dipped into a 95 per cent, solution of carbolic acid, and a drop conveyed to the mucous membrane; this will at once produce a white eschar. Then a slight scratching motion with the serrated point is begun, with the view of removing the tissue that is whitened. This is continued until the carbolic acid is thick with debris of the tissue torn up, then it is dried out and another drop added, as before, and the process continued. This is repeated as often as may be necessary, going deeper and deeper into the tissue in the desired direc- tion until the bone is laid bare. Then a fresh drop of the acid is placed on the bone, and the periosteum carefully raised over a sufficient space; then with a sharp chisel or a coarse bur cut through to the peridental membrane. This will generally cause some pain and some hemorrhage, but after giving a little time for this to cease and adding more of the acid, the apical space can usually be reached without difficulty. No blood should be drawn at any time during the operation except in penetrating the walls of the alveolus. In doing this no tissue is re- moved until it is anesthetized by the carbolic acid. This is a little CHRONIC ALVEOLAR ABSCESS 93 tedious, but is almost painless, and the general affect is usually better than by other modes of penetrating the apical space. The carbolic acid has the effect of modifying the pain, and the opening left does not close so readily. ' ' A variation of this method is: after reaching the alveolus, instead of using more carbolic acid, press pellets of adrenalin and cocain into the tissue. In this manner anesthesia is produced, sufl&cient for the operation, without dilatation of the tissues by injecting. In these cases, curetting of the cavity of the abscess and apex of the root is most effective, but removal of healthy bone tissue should be avoided as much as possible, as the stability of the root and sometimes of the adjoining teeth is proportionately impaired thereby. A period of entire cessation of discharge of pus is to be considered the most favorable indication of successful treatment of alveolar abscess. Thorough disinfection and sterilization of the root-canals and dentin are included in the treatment of alveolar abscess. This is best ac- complished by saturating the dentin with a solution of oil of cloves and aristol until the dentin darkens in shade. As soon as the treatment is followed by favorable indications, the foramen should be closed with gutta-percha while the fistula is yet open, and the remainder of the canal filled with zinc oxychlorid as described in Chaper III. Any fur- ther treatment considered necessary can be conducted externally through the fistula. This may be facilitated by enlarging the orifice with tents of iodoform gauze and in very small places with iodoformized cotton or in cases of small abscesses cotton saturated with oil of cloves and aristol. Enlargement of the fistula tends to encourage the process of granulation in the region that has been occupied by the abscess, especially when a carious or necrosed condition of the bone required its removal. Aromatic sulfuric acid is a powerful astringent and germicide. It will be found most useful in cases where only a very slight carious state of the walls of the alveolus exists and does not indicate the necessity of curetting. Its use, however, should be limited and in subsequent external treatment through the fistula some of the other therapeutic agents may be employed, such as the essential oils or carbolic acid alone or combined with one of the preparations of iodin. Injections of sulfuric acid in the region of the mental foramen should be made cautiously and should not be applied to an abscess bordering on the antrum until the operator is positively assured that the abscess does not open into that cavity. 94 CROWN-, BRIDGE-, AND PORCELAIN-WORK Granuloma. — Granuloma is a tumorous growth around the apex or on the side of the root of a tooth. It is caused by inflammation and gradual hypertrophy of the pericementum, pus usually not being present. The treatment is removal of the tumor, curetting of the cavity in the alveolus and if indicated amputation of the affected por- tion of the apex of the root. Apicoectomy, Amputation of the Apex of a Root.— In chronic al- veolar abscess the pus cavity occasionally involves the alveolus in such a way as to destroy a considerable portion of the pericementum of the end of the root. The cementum of that part is consequently devitalized and the portion of the root affected becomes degenerated in structure and permeated with septic matter. In this condition it acquires the character of a foreign substance, proves a constant source of irritation and defies all efforts of the membrane to perfectly inclose or encyst it. y ^-N In such cases when curetting of the abscess cavity and end of the root has failed, amputation of the por- tion of the root which is denuded of pericementum is the best course to pursue. This also is the only treatment that can be resorted to in exostosis. An incision is made in the alveolar tissues sufficient to fully expose the affected part at least 3^^ to 3''^ inch in length. Any carious or necrosed bone in the territory is then curetted and the end of the root re- PiG. 98. moved to the line of the curetted bone (Fig. 98). The root-canal should be filled solidly with gutta- percha previous to the amputation so that when the end of the root is excised the stump will be left smooth and snugly filled. The end of the root is best removed by first locating the apex and then trimming off the required amount with a fissure or rose-shaped bur. The instrument should be held at a right-angle to the line of the root in an apical direction to avoid a slanting amputation. The ground- off particles of the root are to be removed by injections of the saline solution into the cavity during and after the operation. Gradual removal of the apex as described is preferable to cutting across the root with a bur, as the amputated part or parts are occasion- ally difficult to remove. When the required amount has been removed the ledge of the surface of . Pig. 159. Fig. 160. Pig. 161. 124 CROWN-, BRIDGE-, AND PORCELAIN-WORK the line of the periphery of the cervix. Such a form is necessary to admit of a perfect adaptation of the cervical section of the collar. Preparation of Teeth or Roots for All-Gold Collar Crowns. — The coronal section of a natural crown to be prepared is usually first Fig. 162. ground on the incisal or occlusal surface with as large a carborundum wheel as the case will conveniently admit and avoid injury to the adjoining teeth (Fig. 162). Sufficient tooth structure should be re- FiG. 163. moved from the occlusal surfaces to afford space for any applied inter- vening plate or occlusal cusps and reinforcements, which as a rule in teeth with vital pulps is one-sixteenth inch; and in pulpless bicuspids Pig. 164. Pig. 165. and molars is a little beyond the line of the points of the occlusal cusps of the antagonizing teeth when occluded, as indicated by the dotted line in Fig. 163. The approximal sides of the cervix should be removed sufficiently to allow a free space between the gold collar when adjusted and the cervices of approximal natural teeth or artificial crowns, to SHAPING TEETH AND ROOTS FOR CROWN -WORK 125 make room for the gum septa (Fig. 164). Teeth with vital pulps that will not admit of such preparation should have the pulps removed, or some other method besides crowning adopted. The removal of the approximal sides should be first started at the occlusal surface in a straight line to the cervix, as illustrated in Fig. 164, in a case of a molar, using vulcarbo disks straight-sided or cup-shaped to get the angle (Fig. 149). Occasionally thin safe-sided separating files are serviceable to avoid injury to the contour of an adjoining tooth in starting the trimming. Next, as the Fig. 166. Fig. 167. approximal teeth are then more easily avoided, the labial and lingual portions are reduced with small carborundum wheels (Fig. 165), and Fig. 168. vulcarbo points (Fig. 150) in the straight hand-piece and angle attachment. Pulpless teeth usually require complete removal of the enamel (Fig. 166). When a tooth contains a vital pulp and a portion of the 126 CROWN-, BRIDGE-, AND PORCELAIN-WORK, enamel is allowed to remain, the surface of the enamel should be leveled in parallel lines as far as the edge of the collar is to be extended (Figs. 167 to 169). In preparing incisors and cuspids for gold cap-crowns where the pulp is to be preserved, after trimming the approximal sides, the labial surface and incisal edge should be ground down as much as possible, without too closely approaching the pulp or subjecting it to irritation; then the lingual portion at an angle from the cervical border to the incisal edge, enough to level its prominence of contour and furnish ample space between it and the antagonizing teeth for the metal that will cover the surface (Fig. 167). Bicuspids and molars, with or without pulps, for all-gold cap-crowns should have as much of the natural crown left as may be without ob- structing the proper and accurate adaptation and adjustment of the Pig. 169. crown (Figs. 168 and 169). A shghtly tapering form is advisable: a thimble shape is unnecessary and undesirable. While the approximal sides may incline toward the occlusal surface, the other sides should be more nearly parallel. This form is preferable in the constructing of the crown and is more favorable for its attachment. The proportion of teeth with living pulps to which gold cap-crowns should be applied is small. The exceptions are cases in which extensive decay has involved considerable of the coronal section of the tooth and caused more or less calcification of the pulp. The preparation of these cases, of which Fig. 170, a bicuspid, and Fig. 171, a molar, are typical, consists in the trimming of the decomposed enamel at the approximal sides, a moderate reduction of the occlusal surface, and the removal of enough from the contour of the labial and lingual surfaces to allow the edge of the collar to pass over and be closely adjusted at the cervical section under the free margin of the gum. Trimming of the tooth for the purpose of deeply embedding the edge of the collar under the SHAPING TEETH AND ROOTS FOR CROWN-WORK 127 gingival margin, so that it will closely approach the pericementum, is unnecessary and not advisable unless some special condition suggests it. Irritation of the pericementum from impingement of the collar will result in recession of that membrane, also of the gingival margin and the exposure of the edge of the collar. Figs. 172 and 173 show a typical bicuspid and molar prepared for the adaptation of metallic cap-crowns, the natural teeth having been trimmed and the cavities sterilized and filled with amalgam or oxyphosphate covered with amalgam. Extremely short teeth and teeth slightly embedded in the t'ssues, as many third molars are, when capped without removal of their pulps, do not require as much shaping as long bicuspids and first molars. It should be borne in mind, however, that excessive or unneces- sary cutting away of the enamel and dentin of teeth with living pulps, leaves them in an extremely sensitive condition, and is likely to result subsequently in some serious lesion of the pulp. Slight sensitiveness, such as may be caused by excessive shaping, is relieved by drying the Fig. 170. Fig. 171. Fig. 172. Fig. 173. exposed dentin with hot air and applying carbolic acid two or three times as required. When this treatment is not suflEiciently effective, a temporary cap of pure gold about gage No. 34 can be quickly con- structed and cemented on with gutta-percha. A small quantity of a compound of oil of cloves, carbolic acid and chalk (Part II, Chapter I), placed in the center of the cap acts as a sedative agent. Collar Crowns with Porcelain Facings. — For collar crowns for the anterior teeth the end of the root is left projecting at the lingual side in removable bridge operations, and the surface of the end ground on an inclined plane towards the gum margin at the labial section, as shown in Fig. 174. For ordinary crowning operations the projecting end is usually preferably squared-off, as shown at Fig. 175. Bicuspids which are to have porcelain facings are given the same general form (Fig. 176). In preparing the roots of incisors, cuspids or bicuspids it is advisable to allow the labial section of the end of the root to project slightly beyond the gum-margin until the collar has been fitted, after which it can be reduced. 128 CROWN-, BRIDGE-, AND PORCELAIN-WORK Partial Collar Crowns. — Shape the approximal and lingual sides of the root, leaving the labio-cervical side intact (Figs. 177 and 178). The surface of the end of the root is shaped as for the full collar. Fig. 174- Fig. 175. Fig. 176. Fig. 177. When necessary, the incisal edges and occlusal cusps of antagoniz- ing teeth should be sufficiently reduced to furnish ample space for the artificial crowns, and to favor them in occlusion. Accord- ingly, when a tooth is to be crowned that is broken down and shortened by long-continued decay and the antagoniz- ing teeth have consequently become elongated, they should be reduced in length as much as they properly can be to proportion the space between them and the artificial crown Fig 178 '^ -^ '■ A, Cervico- ^nd improve the occlusion. When the approximal teeth. labial sec- are Crowded against and overhang the end of a root so that intact. the space for the artificial crown at the occlusal surface is narrower than at the cervical section measured from mesial to distal side, the approximal teeth should be pressed back to furnish space to permit the adjustment of a straightsided collar on the pre- Fig. 179. pared root and proper space between the collar and the sides of the roots of the adjoining teeth. The approximal teeth can be pressed back by packing on eacH side of the root with gutta-percha, or by the SHAPING TEETH AND ROOTS FOR CROWN-WORK 129 insertion of a piece of orange-wood notched on the end, that tightly fits the space, the wood to be removed and increased in length at intervals by the operator or patient (Fig. 179). In cases that prop- erly suggest it, a small portion of the interfering surfaces may be re- moved and polished, as shown in typical cases in Figs. 180 and 181, so as to allow parallel or slightly flaring sides to the collar. Pig. 180. Special Preparation of Badly Decayed Teeth or Roots. — The tem- porary exposure of the end of a root or of the cervical portion of- a crown for the purpose of permitting restoration of the part with an amalgam or gold inlay to simplify a crowning operation, especially in the adaptation of a collar, is effected by inserting in the pulp-chamber or the root-canal a cone-shaped piece of gutta-percha large enough to admit of a portion being brought over against the investing membranes to compress them for a day or more. In some cases to secure attach- ment for the gutta-percha, a wire post or a flat-headed tack may be cemented temporarily in the root with gutta-percha and the gutta-percha packed around it. Roots can thus be exposed to the border of the alveolar process, if desired, by renewals of the packing. In bicus- pids and molars, when the decay extends on the cervLx further than will the edge of the artificial crown or collar, the gum margin should be compressed, as already des- cribed (Figs. 73. and 74), the decay removed, retaining pits made and the cavity filled with amalgam shaped to the con- tour required (Fig. 182). In such cases, when the pulp is vital, the amalgam will generally be in close proximity to it and the cavity fre- quently of a form unfavorable to the retention of the filling. To avoid irritation from thermal changes and to better retain the filling, a moder- ately thin mixture of oxyphosphate may be first placed in the cavity, the amalgam then pressed into it and the oxyphosphate forced out at the margins, where the amalgam must be brought into direct contact with the tooth structure. 9 Fig. 182. I30 CROWN- BRIDGE- AND PORCELAIN-WORK In incisors and cuspids, when decay has deeply destroyed a portion of the side of the root, a tight-fitting tube of platinum veneered with a film of pure gold — to which amalgam will readily adhere — and of such size as to admit the post of a crown, may be inserted in the root- canal, cemented with oxyphosphate and the decayed portion on the side of the root restored with amalgam (Fig. 183 section). A cast gold inlay may be used with the tube instead of the amalgam. (Part III, Chapter II.) The post of the crown should be tapered at the end and inserted in the canal as deeply as possible in the sound portion of the root beyond the end of the tube to gain addi- tional strength by distributing the leverage along the entire line of the root. When the amalgam has set, it should be dressed down at a subsequent sitting evenly with the sur- face of the root and polished, \ / In some cases a better method is to fit and cement a ~ pointed post as far up the canal as it can safely be intro- duced, leaving the end of the post protruding beyond the gum. Then shape the side and end of the root with amalgam or a gold inlay, and cap with a gold or platinum porcelain jacket crown or one entirely of porcelain (See Crowning in Cases of Abrasion, and Part VI, Chapter VII). Fig. 184 shows a typical cuspid and bicuspid of this character. When an incisor or cuspid crown post is to be inserted and the root- canal is enlarged from decay or excessive reaming, the defect in relation to the post of the crown can be remedied in the following manner: Fit a tapering post of medium size with the point reaching the extremity of the canal. Close the foramen with a very small point of gutta-percha, so that it will not interfere with the insertion of the post. Fill the canal with a thin mixture of zinc /MB" ^""IB^ oxychlorid, insert the post and when the cement •■..., -.^T. / is about one-half set remove it. Instantly wipe off the post and reinsert it. The temporary re- moval of the post breaks the adhesion of the cement to the post so that when the cement has set, the post can be removed and you have a close-fitting socket for it. Zinc-oxyphosphate may be used for the same purpose by veneering the post with chloro-gutta-percha to permit re- moval when the cement is set. The oxyphosphate, however, does not possess the antiseptic properties of the oxychlorid. In setting a gold cap-crown on a badly broken-down tooth or root a post of either clasp-gold, platinum or iridio-platinum wire (Fig. 185) should be fitted to the root-canals (Figs. 186 to 188). The end can SHAPING TEETH AND ROOTS FOR CROWN -WORK 131 be bent or a piece of gold or a globule of gold melted to it. The post should then be barbed, the point fastened in the root with a little oxy- phosphate or zinc oxychlorid and the crown built about two-thirds its length with a quick-setting amalgam, to be shaped when hard and then slightly notched to furnish a better attachment for the cement with which the cap is set. Rolling the wire used to form the post under the flat side of a file before using will uniformly roughen the entire surface in a manner most favorable to the adhesion of the cement. Screws may be used as posts to support the amalgam, but cemented posts are preferable. A previously made and properly fitted collar of thin cop- per plate about gage No. 35 may be used to support the amalgam while setting. Restoration with Gold.— The restorations described can be eflfected with gold casting instead of amalgam. Gold is preferable as being more 1 Pig. 185. Pig. 186. Fig. 187. Pig compatible to dentin, especially in cases where decay or a fracture of the delitin extends so far under the gum margin that a collar cannot be properly applied to entirely cover the part, and where an acid condition of the mouth exists. In such cases the post is first heated and veneered with sticky wax, then surrounded with inlay wax, adjusted to posi- tion in the canal and the wax pressed and shaped to the desired form. Fig. 189 shows the post of a central incisor shaped with inlay wax in- stead of amalgam ready for investment for casting (Part III, Chapter XVII). The same result can be obtained by the indirect method by taking an impression with compound placed on the platinum post, re- moving the post in position in the compound, and making an amalgam die. For the use of porcelain in root restoration see Part VI. CHAPTER IV THE ALL-PORCELAIN POST CROWNS ALL-PORCELAIN DETACHED-POST CROWNS — PREPARATION OF THE ROOT END — THE S. S. WHITE DETACHED-POST CROWN — PREPARATION OF THE ROOT — DIRECT METHOD OF FITTING THE CROWN — INDIRECT METHOD — ^THE DAVIS CROWN — THE JUSTI SHOULDER PIN CROWN — ash's TUBE TEETH AND CROWNS — EXAMINATION OF THE PERIPHERY OF A PORCELAIN READY-MADE CROWN — REMOVAL OF EXCESS OF PORCELAIN AT THE PERIPHERY — CEMENTATION — REMARKS ON THE USE OF READY-MADE PORCELAIN CROWNS AND CROWNS WITHOUT COLLARS The all-porcelain post crowns in use at the present time are the result of progressive development of this branch of the art from what was originally styled the porcelain "pivot tooth. " For this reason and because of their simplicity of construction and application they will be described first. All-porcelain post crowns are used by many dentists almost ex- clusively, with the exception of the occasional insertion of an all-gold cap-crown on a posterior tooth. The reasons for this are the greater intricacy of the construction of gold crowns and personal objections to crowns with collars. The advocates of the all-porcelain post crown claim for it natural appearance owing to translucency, the lingual aspect not being covered with metal, restoration of contour, strength and cleanliness, together with simplicity of construction and easy adaptation and attachment to the root, to which the crown is hermetically sealed. All-Porcelain Detached-Post Crowns In this style, which is the one now most largely used, the crown is attached to the root by a post, one end of which is cemented in the root and the other in the crown, such as the S. S. White, Davis, Justi and Ash. Crowns in which the post is to be cemented admit of alignment with the other teeth more easily than those baked with the post in position. The attachment of the crown to the post, however, is not as reliable 132 THE ALL-PORCELAIN POST CROWNS 133 in close "bites" when cemented as when baked in the porcelain like the Logan. The requirements for success in the use of all porcelain detached- post crowns are: First. — A strong, accurately fitted post, the presence of which demands the least possible removal of root structure, , * ^ thereby retaining the greatest amount of strength for re- sistance in occlusion and mastication. Second. — Absolute adaptation of the surface of the base of the crown to the surface of the root end or, in other words, a close joint. Third. — Perfect alignment of the sides of the » * * cervical section of the crown to that of the root. Fourth. — Correct occlusion of the antagoniz- ing teeth, by which abnormal pressure is avoided. Preparation of the Root End. — The prepara- tion of the canal and end of the root to receive and retain posts is about the same for all the different styles of ready-made porcelain crowns. The length of the root-canal is first measured with a root-canal probe or plugger. A small disk of rubber-dam per- forated and slipped up on the shank of the instrument can be used as a gage by adjusting the disk to the end of the root. By this means the proper length for the post is ascertained. The dimensions of the root determine the size. Fill that part of the end of the mal that will not be occupied by the post; enlarge the mal with Gates-Glidden drills as deep as required to commodate the length of the post for the crown that is ) be mounted. Next, with a gage-plate determine the ze of the post and with small-size fissure burs and proper ze root-reamers (Fig. 190) gradually ream the canal to a \. jrm and dimension into which the post will fit closely (Fig. 191). For the anterior teeth the end of the root is trimmed to the gingival margin, slanting slightly below it at the labial side to hide the intended union of porcelain with root. This requires the removal of the enamel at the cervico-labial section but not always around the entire periphery of the root. This is best done after reduction of the end of the root with large carborundum wheels, by the use of smaller sized wheels and points or with safe-side root-facers (Fig. 192).* Fig. 190. Fig. 191. 134 CROWN-, BRIDGE-, AND PORCELAIN-WORK In these operations, as likewise in others, posts of platinum and gold or iridio-platinum are preferable to those made of alloys that contain a large percentage of the baser metals, as the ultimate corro- sion of the latter tends to impair and weaken the dentin. The S. S. White Detached-Post Crown. — This crown possesses the main features of the Logan crown, from which it differs in having the post detachable (Fig. 193). Pig. 192. Fig. 193. Pig. 194. — Enlarged Posts. A, I-beam; B, round. The base is cupped out to receive the post, with a recessed shoulder for the collar. This cup-shape form leaves only a narrow rim of porcelain at the base of the crown to be ground to fit it to the surface of the end of the root. The post is made in two forms, I-beam shaped and round (Fig. 194). Each style is made in two sizes, large and small (Fig. 195). The I-beam post is similar in form to the post of the Logan crown. Both it and the round post taper toward the point. The root section of each style is grooved and the portion that enters the crown has small flanges with a large one that rests on the shoulder of the cup and being close to or against the root end prevents movements of either the post or crown. Preparation of the Root. — The root is prepared the same for either the direct or indirect method. The canal is opened up with a twist drill to the proper depth, and large enough to permit the easy entrance of an Ottolengui reamer (Fig. 191). Shape the canal with the reamer to conform generally to the root section of an S. S. White detached- post, tapering toward the apex, with the labio-lingual diameter greater than the mesio-distal for an I-beam post. Then with a root-facer give the end of the root labio-linguaUy a rounded open V shape (Fig. 192). Side view No. I No. 2 No. 3 No. 4 Fig. 195. THE ALL-POkCliLAtN PO^f CROlVM 135 t)irect Method of Fitting the Crown.— To fit the crown to the prepared root grind freely as indicated, an operation that is greatly facilitated because the cup shape of the cervical portion leaves only a comparatively thin wall of porcelain to cut away. At this stage of A B C D Fig. 196. — Actual size. A, Detached-post crown, cuspid, fitted to root; B, the same, sectional view; C, Detached-post crown, bicuspid, fitted to root; D, the same, sectional view, showing the splitting of the post for a bifurcated root. the fitting the use of a disk of articulating paper will simplify and facihtate the operation by marking on root and crown the point of contact. Another method: Dry the end of the root, rub a carbon pencil point over it and press the porcelain against it. After fitting the crown, adjust the post to root and crown. The shoulder in the recess is intended as a bearing for the circular flange of the post to distribute the stress. In cementing the crown in position, the post can be fixed into the root first or into crown and root together, according to the preference of the operator. The requirements for a lasting operation are a per- fect fit and a reliable cement (Fig. 196). Fig. 197 shows well-fitted and articulated crowns. Indirect Method. — After shaping the root as in the direct method and fitting the post, warm the root sec- tion of the post and veneer it with wax, flowing it into the grooves, and adjust the post in the canal. Next take a "bite" in wax and then an impression in com- pound, which will remove the post in position. Pack amalgam — True Dentalloy- — into that portion of the compound impression which represents the end of the root and sides of the approximal teeth, in quantity suf- ficient to entirely cover the form of the crown end of the post, then fill in the remainder of the impression with plaster. The model must be allowed to remain long enough for the amalgam to set before separation. The result will be a combined plaster and amalgam (metallic) model, an Pig. 197. 136 CROWN-, BRIDGE-, AND PORCELAIN-WORK exact replica of the root and of the approximal teeth with the post in position (Fig. 198). An articulating model is then made. With these models the proper crown can be selected and the fitting done ac- curately. The wax on the surface of the post will allow it to be re- moved easily. In fitting the crown to the model by slight pressure and lateral movement, the places to trim will be distinctly marked on the Fig. 199. porcelain by the amalgam. The countersink in the crown is of suf- ficient diameter to permit the post to be set at various angles, and provides room for any necessary body of cement beside the porcelain, which is roughened to insure it a firm attachment. In the use of detached-post crowns, when neces- sary for some special purpose, the hole in the por- celain may be enlarged or its angle changed slightly with carborundum points or steel points charged with carborundum paste. In this manner the S. S. White Detached-Post Crown can be readily adapted as a jacket crown (Fig. 199). (See Part VI, Chapter VIII.) The Davis Crown. — This crown has a concave base, in the center of which is a depressed rim that affords a rest for the shoulder on the post. A countersunk cavity extends into the crown sufficiently deep to accom- modate the projecting end of the post (Fig. 200). The post is made of German silver in proportioned sizes, also of Fig. 200. THE ALL-PORCELAIN POST CROWNS 137 alloys of gold and platinum, slightly tapered, corrugated its entire length and somewhat flattened on one side to prevent rotation. It 1 11 Pig. 201. Straight Double Offset Pronged Pig. 202. Small Medium Actual size Pig. 203. Pig. 204. has a shoulder which fits the floor of a depression in the base of the crown, but not closely at the sides^ to permit alignment. The Davis crown is selected, fitted (either by the direct or indirect method) and cemented to the root in a manner similar to the S. S. White Detached-Post Crown, with the exception that, the Davis crown post being nearly round requires a correspond- ingly reamed canal. Fig. 201 shows reamers made for the purpose, and Fig. 202 straight, split (for double-rooted bicus- pids), and oif-set center posts. The last are for crowns where the root-canal and the hole in the crown are not in the same line, as shown in Fig. 203. The Justi Shoulder Pin-Crown.— This crown, illustrated in Fig. 204 is very similar in construction to the Davis. The method of its application is identical. Ash's Tube Teeth and Crowns. — These teeth have a perforation through the center with a thin platinum tube baked in the porcelain. They are supported on the root by a fluted post. Figs. 205 to 207 show teeth and post. When the crown is properly ground and fitted, the base is to be countersunk sufficiently to receive the shoulder of the pin. The pin is then bent so as to allow the crown to assume its proper position on the root. The Pig. 205. Pig. 206. Pig. 207. 138 CROWN-, BRIDGE-, AND PORCELAIN -WORK socket-handle instrument, shown in Fig. 208 is the most suitable for this purpose. The attachment of the crown is made by first securing the pin in the crown with sulphur or soft solder and then cementing the fluted post in the root-canal with either gutta-percha or oxyphosphate. Figs. 209 to 214 illustrate Ash's dowel crowns. They are applied in a manner similar to the Davis crown. The dowels or posts are made of what is termed "Dental Alloy" and are the strongest at the part tjJ Fig. 209. Pig. 210. Fig. 2X1. Fig. 212. Fu,. 213. Fig. 214. that bears the greatest strain — the portion where the crown joins the root. Examination of the Periphery of a Porcelain !' U Post Crown. — When a crown of this class has been fitted, before cementation an examination should be made to ascertain whether, as is a common occur- rence, the base of the cervical section extends beyond ^ 9 . 1 , , Fig- 215. the line of the side of the root, formmg a shoulder, as seen in Fig. 215. Its removal is frequently neglected in the Fig. 208 insertion of these crowns. This shoulder forms a ledge which, if allowed to remain, causes and maintains a septic con- dition that impairs the health of the investing membranes and is liable to cause decay of the end of the root. Removal of Excess of Porcelain at the Periphery. ^ — This is easily and accurately done, as follows: Warm a disk of pink base-plate gutta-percha with a large hole in the center to accommodate the post (A, Fig. 216). Wipe the surface with a pellet of cotton moistened with chloroform or oil of cajuput; warm the gutta-percha and press it THE ALL-PORCELAIN POST CROWNS 139 against the base of the crown. Gradually heat crown and gutta- percha until too hot to be comfortably held in the fingers and press to position on the root, chill and remove. On the gutta-percha will be found an accurate impression (B) of the end of the root. The surplus gutta-percha is removed to the surface of the porcelain with a sharp knife (C), and then the porcelain to the line of the root, as indicated by the impression in the gutta-percha, with a carborundum wheel lightly pressed and rapidly revolved in a direction which will not disturb the gutta-percha (D). During the grinding the crown should be frequently dipped in ice- water. One or more adjustments of the crown and gutta- percha should be made on the root and the sides carefully examined with a suitable instrument. After removal of the projecting edge of porcelain, the remainder of the crown should be trimmed to harmonize in contour with the neck, and the surface polished with fine sandpaper disks and oxid of tin (putty). Cementation. — These crowns are generally cemented entirely with zinc oxyphosphate. To cement a detached-post crown the root is Pig. 216. protected and dried with hot air. The cement is mixed to a medium consistence, worked into the root-canals and the countersunk base of the crown, A portion is then applied to the surface of root and crown, and the crown pressed to position and held until the cement has at least partly set. The surplus should not be removed until it has thoroughly set, as the cement will then snap off, not drag from the joint. In cementing all-porcelain detached-post crowns the preferable method is to first cement the post and then instantly place the crown without cement in position over the post to define its alignment posi- tively. When the cement has set then cement the crown to the post. Some conditions may suggest the reverse, i.e., the cementation of the post in the crown first. Another method is to apply a disk of gutta-percha to the base of the porcelain or leave the disk on the crown that was used to outline the periphery of the root and then cement the post in the root and crown with oxyphosphate. The object is to have a cement at the joint that I40 CROWN-, BRIDGE-, AND PORCELAIN-WORK will not wash out. The pink base-plate gutta-percha is the most durable for the purpose. Remarks on the Use of Porcelain Ready-made Crowns and Crowns without Collars. — All-porcelain post-crowns have some decided advantages. They are especially useful in many case where an inex- pensive or easily adjusted crown is required, or where some pathological condition limits the probable durability or permanence of any opera- toin. In the insertion of porcelain crowns the removal of the whole or a part of the natural crown, which could be utilized to some extent as a foundation by another system, has given rise to various objec- tions. If the natural crown is entirely cut away the pin, or post, upon which almost the entire support of the artificial crown is thrown, exerts great leverage in the root-canal when no band or brace is present on the exterior of the root to relieve the strain. With the entire force of mastication bearing directly upon these pulpless roots, whose dis- integration is slowly but continuously progressing, they are liable to be fractured and their usefulness as a foundation ended. These facts and the lack of strength incident to conditions such as close or abnormal occlusions are the principal objections urged against porcelain crowns on uncapped roots as ordinarily inserted. CHAPTER V PORCELAIN-POST CROWNS WITH METALLIC BASE PORCELAIN DETACHED-POST CROWN \\lTIf CAST BASE — DIRECT METHOD — INDIRECT METHOD — PORCELAIN FACED GOLD POST CROWN — ROOT END BEYOND GUM MARGIN Porcelain Detached-Post Crown with Cast Base. — Sometimes the end of the root is decayed under the gum margin so unevenly that the base of the porcelain crown cannot very well be ground to properly fit it (Fig. 217). In such a case a cast floor or cap should first be made and applied, upon which the porcelain crown can rest and to which it can be attached. Direct Method. — Grind the exposed portion of the end of the root well under the gum-margin and remove all decay. Pack and repack Fig. 217. Fig. 218. Pig. 219. Pig. 220. Pig. 221 gutta-percha in the canal and over the end of the root against the tissue for a few days to properly expose the parts. Fit an iridio-platinum post, or an S. S. White or Davis post of the same metal, well up into the canal. Grind a porcelain detached-post crown to fit the cervico-labial section of the root, leaving a V-shape space between the crown end and the root at the lingual side (S, Fig. 218). Vaselin the base of the crown and wipe off all surplus; heat the exposed end of the post and veneer it with sticky wax. Next surround the end of the warm post with inlay wax; insert post in root; dip crown in warm water and press to position. Trim and shape the wax on the sides and chill with a stream of cold 141 142 CROWN-, BRIDGE-, AND PORCELAIN-WORK water. Remove the crown from the mouth, then the post with the wax attached without disturbing its form (Fig. 219). Insert sprue wire in the thickest part of the wax (Fig. 220) and cast with pure or 22- carat gold. Fit casting to root and crown to casting, poHsh and cement. Fig. 221 shows the finished crown. Indirect Method. — Fit an iridio-platinum post in the root the same as for the direct method, Heat the post, veneer it with compound, wet the canal, insert and withdraw the post as the compound hardens so that the post may be easily inserted and withdrawn. Take a "bite " in wax and an impression in compound that will remove the post in position. Vaselin the end of the post, pack in amalgam around the impression of root and post, and run the remainder of the impression with plaster. Adjust "bite" to model and run articulation. Should the cavity on the side of the root extend very far under the gingiva, instead of the method just described take an impression of the root and post in a tube and make an amalgam die with a cone-shaped shank. Take an impression of the case and fit the die in the impression and make models. The models will give the exact form of the root and the position of the post as in the mouth. Remove the post from the die by seizing the exposed end with heated pliers, holding themfor a moment on the post to warm it. Remove any compound on the post and re- place the post again in the model. The construction of the crown on this model is identical with that described in the direct method. Porcelain-Faced Gold Post Crown This form of construction is generally confined to the six anterior teeth. The root of a cuspid will be taken as a typical case to illustrate the construction. The end of the root is prepared the same as for an all-porcelain crown, as shown in Fig. 222. No peripheral trimming is necessary. To have the joint of the porcelain entirely invisible in the finished crown, the surface of the end of the root should be trimmed off enough to allow for the thickness of the metal plate that will cover it, especially at the labial side, and thus admit placing the edge of the porcelain fac- ing well under the cervico-gingival margin. As crowns of this style are principally supported by the post, it consequently constitutes an important factor. Iridio-platinum or gold-platinum wire, about gauge No. 13, is commonly used, but the requirements of some cases call for it much lighter or heavier. The root-canal is enlarged with a reamer and the orifice well counter- sunk. A piece of iridio-platinum or gold-platinum wire, that has been PORCELAIN -POST CROWNS WITH METALLIC BASE 143 rolled under a file and tapered off to a point, is fitted well up the canal, gaged its full reamed diameter, so that greater strength shall be ob- tained and the root rendered less liable to longitudinal fracture from pressure in a forward direction (Fig. 223). A post of the exact size and shape of the canal, made as described in Chapter VIII, of platinum wire, foil and gold (Figs. 316 to 317), is a good form to use in a large canal with this style of crown. A piece of platinum plate in size slightly larger than the end of the root, of gage No. 34 to 36 — the smaller the root the thinner the plate — is adapted to it by pressure with a ball of cotton or the soft rubber tip of a pencil; or an impression may be taken of the end of the root with impression compound, an amalgam die made and the platinum plate or cap first stamped in a swager. (See Part III, Chapter XI.) The platinum is then burnished to the surface of the end of the root and well into the countersunk orifice of the pulp-canal and punctured with a sharp-pointed instrument. The point of the post is next pushed Fig. 222. Fig. 223. Fig. 224. through the perforation to position in the canal. When the post is withdrawn from the root, the platinum generally adheres to it. A par- ticle of pure gold with flux is put in the joint in a Bunsen gas flame. The least quantity of gold that will unite the parts should be used. If the post does not fit sufficiently tight to remove the platinum, it should be connected fast with wax, removed and invested. When soldered, the post and plate are again adjusted in the mouth and the plate malleted and burnished to the end of the root so that the edge of the root shall leave its imprint on the platinum. The plate on being removed should be trimmed to this mark and again burnished on the root. The post is then cut off and trimmed and a porcelain facing fitted, backed, the incisal edge protected, and the facing cemented with wax in position on the cap, as described in Part III, Chapter IX. The whole is then removed, invested and soldered with 20-carat solder, which should be melted in at the base of the post, as the strain is very great at this point, when the crown is in use. 144 CROWN-, BRIDGE-, AND PORCELAIN-WORK The crown is cemented to the root with oxyphosphate cement or gutta-percha, or both combined (Fig. 224). Root End below Gum-Margin. — The crown just described is a suitable form for application in cases where the cervical section of the end of the root because of either decay or fracture is considerably below the surface of the gum and does not admit of the use of a collar. In such cases the end of the root should be first fully exposed with gutta-percha fastened in the orifice of the root-canal and extending over the surface of the end of the root, pressing away the gingiva. Under such a condition shaping the plate or cap to the form of the root by the use of a die facilitates its adjustment. CHAPTER VI A TEMPORARY CROWN Fit into the root-canal a tapered post made preferably of German silver wire. Let the post extend out of the canal about one-eighth of an inch, and roughen its sides. Perforate a disk of the heaviest pattern tin, pure gold, gage No. 28, or Hooo platinum foil, with the post and fit to the end of the root. Fit a suitable two-pin vulcanite porcelain tooth to the disk; groove out the porcelain, if necessary, to fit over the Fig. 225. Pig. 226. post (Fig, 225). Wax the porcelain tooth to the disk and post, remove and invest in plain plaster of Paris. Remove the wax with boiling water and apply a little muriate of tin to the end of the post. In the place occupied by the wax (A, Fig, 226) flow fusible metal which melts at not less than 200° F,, and instantly, while the metal is yet in a molten state, press it down firmly into the investment with the finger covered with a napkin, cool, remove, trim and cement on the root with gutta- percha that softens at a low heat.^ 1 This method of soldering combines the principle of casting under pressure. 145 CHAPTER VII GOLD COLLAR CROWNS CONSTRUCTION AND ADAPTATION OF COLLARS — TO MEASURE THE CIRCUM FERENCE OF A ROOT OR TOOTH — A DENTIMETER — TO DETERMINE THE WIDTH OF A COLLAR — CUTTING THE PLATE FOR THE COLLAR — TO SOLDER THE JOINT OF THE COLLAR — SWEATING METHOD — FITTING A COLLAR TO ROOT OR TOOTH — PLATINUM COLLAR — REINFORCED THIN PLATINUM COLLAR — PLATINUM-LINED GOLD-PLATE COLLAR — APPLICATION OF A LOCAL ANESTHETIC — COLLAR CROWNS HYGIEN- ICALLY CONSIDERED This style of gold crown includes those methods which involve banding, capping and hermetically inclosing with gold the end of a root or the crown of a tooth, for the purpose of securing stabihty to the artificial crown, preventing fracture of the root and decay of the parts. This method possesses much practical value as a preserver of tooth structure and restorer of usefulness to the teeth, and affords excellent supports for bridge-work. Collar crowns of which the part that essentially constitutes the cap is constructed in sections, will be first described. The Construction and Adaptation of Collars. — This may be termed the fundamental part, as on its skilful and proper performance depends the usefulness of collar crown operations. Careful study of the different forms of natural crowns and roots and of the anatomical structure and relationship of the contiguous parts is most essential for the perfection of construction and adaptation required in collars, bands or ferrules, as they are variously designated. Some devices and methods in use facilitate this operation, but its skilful performance can be attained only by study and practice, as is proved by the easy and perfect manner in which it is done by experts in crown- and bridge-work who use no special appliances and are guided by an intuitive perception of the requirements of each case. Gold alloys of at least 22 carats containing 2 to 3 per cent, platinum, gage No. 30, are given the preference for collars, as the joint can be soldered with pure or coin gold, which permits use of a high-grade solder without affecting it. U. S. gold coin is not so much used as formerly, as the 10 per cent, copper it contains tends to cause oxida- 146 GOLD COLLAR CROWNS 147 tion and as it is not high fusing, it requires more care and skill in its use in soldering operations than plate of the higher fusing alloys. The size of the cervix of the root or dimensions of the natural crown to be capped, whether it is to effect only restoration of the crown or to give support to bridge- work, should govern the choice of gage of plate to be used. Cuspids and molars require a heavier plate than small laterals or lower incisors, and in all forms of gold caps the gage should be slightly increased when they are to support bridge-work. To Measure the Circumference of a Root or Tooth. — The natural crown or root having been properly prepared is measured. For the Fig. 227. Fig. 1228. Fig. 229. circumference form a loop of copper or iron wire, gage No. 30 or 31 by twisting the ends together with the pliers. Slip the loop over the tooth or root, press the wire down under the gum margin and twist the ends with the pliers until the loop fits tightly at every point (Figs. 227 and 228). Slip off the loop, extend the wire and cut the center opposite the twist, then extend the ends lengthwise, as shown in Fig. 229. The Dentimeter. — A dentimeter, such as is exhibited in Fig. 230, facilitates measurements with wire. The ends of the wire are passed Fig. 230. into the hole in the point of the head and out through the openings which are cut into it from the two sides. The loop thus formed is adjusted around the tooth or root, and the end of the dentimeter is pressed against the root at the gum margin. A few turns of the den- timeter twist the loop tight, when the dentimeter can be laid aside and the loop removed. Teeth and roots difficult to reach at the buccal side may often be more easily reached at the lingual. 148 CROWN-, BRIDGE-, AND PORCELAIN-WORK To Determine the Width of a Collar. — For an all-gold crown meas- ure from the occlusal surface of the antagonizing teeth to the point at the cervical section showing the greatest recession or curve in the gum- margin in an apical direction. For a collar for a root-cap determine by the eye, or in a similar manner measure apically from the surface of the most projected portion of the end of the root to the cervyc. This measurement is^bestjdone," as shown in the case of a molar in Fig. 231, with a tapering strip of copper or card- board with the end squared. Cut off the narrow end until it gages the space. The measurement may also be taken with a pair of dividers. Fig. 231. Fig. 232. Cutting the Plate for the Collar.— Place the extended wire loop on the surface of the plate of which the collar is to be constructed in the line of the laminae of metal, i.e., the direction it has been rolled, and mark the length. Next mark the width by the measure taken, adding one-sixteenth to one-eighth of an inch additional for the free space under the gum-margin, and any accidental discrepancy. Gage a pair of dividers to the mark and draw a line on the plate, as shown in Fig. Fig. 233. Fig. 234. 232. Cut the plate along this line to the mark indicating the length (L, Fig. 233) and about one-thirty-second to one-sixteenth of an inch beyond it to allow an excess for an overlap. When the collar is to restore a very large amount of contour to a bicuspid or molar, the collar may be cut across on a slight bevel, flaring from the cervical to the occlusal edge, as shown in Fig. 234. The objection to a collar cut in this form is that as the cervical edge is trimmed, the circumference is increased in size, a matter diffi- cult to calculate on by measurement in most cases. GOLD COLLAR CROWNS 149 Taper the edge of the plate for theunder-lap from the mark indicat- ing the length to the edge of the excess, as viewed laterally enlarged at L, Fig. 235. Next slightly taper the other end of the plate for the outer-lap, as shown at OL; bend the plate in a circle, and lap the ends and bring them in contact with suitable pliers (Fig. 236) in the manner shown enlarged in Fig. 237. Seize the collar at the joint with a clamp and hold it in a Bunsen flame until it assumes a dull red, then instantly dip in water. This will cause the metal to retain the curve given it by setting the molecules and will permit the tapering edges of the collar to be brought together more easily. Repeat the OL It I'L Fig. 235. Fig. 236. clamping, annealing and chilling of the collar until as perfect a contact of the ends as is possible is effected. To Solder the Joint of the Collar. — Flux the joint; grasp the over-lap end of the collar, as shown in Fig. 238, and place a minute piece of ^^- solder on the surface of the inner lap close to the joint and hold the collar in a Bunsen flame until the_solder fuses. The presence of the clamp takes enough heat from the overlap side to cause the solder to flow only Fig. 238. Fig. 239. Pig. 240. on the inner lap side and into the joint. The position of the clamp is then changed (Fig. 239), and the solder flowed across the joint. In this way the particle of solder applied is prevented from flowing on the over-lap instead of into the joint. The smallest possible quan- tity of solder only is to be applied, and it should be as hard-fusing as the grade of the gold of the collar respecting fusibility will permit. ISO CROWN-, BRIDGE-, AND PORCELAIN-WORK Another method is to grasp the seam at the cervical side of the collar with the points of a clamp or soldering pHers (Fig, 240) of the styles illustrated in Figs. 241 and 242 and unite the seam only at the extreme outer edge with an atom of solder fused with a blowpipe. The points of the clamp or soldering pliers prevent the solder from flowing along the joint. The cervical side of the collar is left open by this method, which permits the collar to be slightly con- tracted when fitted, if desired; after which the solder is flowed across the entire joint. The collar when soldered is slipped over the point of a small anvil and the joint lightly tapped (Fig. 243). Sweating Method. — To unite the joint by the sweating method, see Union by Sweating, Part I, Chapter VI. Fitting a Collar to Root or Tooth. — When the collar seam has been soldered, it is shaped to the general form (Fig. 244) of the root or tooth for which it is in- tended, as illustrated in Fig. 245. The collar is then placed on the root or tooth and pressed or, with the aid of a piece of wood placed across its outer edges, gently tapped up to the margin of the gum. A line parallel with the margin is marked with a sharp-pointed instru- ment on the collar (A, Figs. 246 and 247), which is then removed, trimmed to this mark, re- adjusted and again marked (B), and the process continued until the collar fits correctly under the gingival margin, using straight or curved small pointed shears (Fig. 248). To definitely determine the distance the edge of a collar fits under the gum margin, especially at the interproximal space, heat the collar, veneer its outer surface with wax, then place a small roll of soft wax around the edge. Slightly warm the wax and press the collar to position and remove. The edge of the gum will Fig. 241. Pig. 242. GOLD COLLAR CROWNS 151 press back the wax and on examination of the collar the wax will ex- actly indicate how far the collar extends under the gum (Fig. 249). If the operation of collar adjustment is skilfully performed and the collar is not forced into the investing membrane of the root, very little pain will be caused the patient. If, on adjusting, a collar is found a trifle too small, it can be slightly enlarged by tapping with a riveting hammer on an anvil the excess of gold usually present at the joint (Fig. 243). By this means any surplus gold at this point in thrown into the collar and its circumference pro- portionately enlarged without materially altering its gage. If, on the contrary, the collar should prove to be too large in circumference, the Fig. 243. difiSculty can only be remedied by cutting the gold across the [side opposite the joint, beveling and lapping the edges slightly, soldering and trimming, or by making a new collar. The collar having been fitted, the edge is burnished to the periphery of the root. For this purpose burnishers shaped to suit the different positions and avoid irritation of the margin of the gum should be used (Fig. 250). Finely serrated foot-shape gold foil condensers can be advantageously used to flatten an edge of a stiff or angular point of a collar. Platinum Collar, — Platinum or iridio-platinum is the ideal metal for collars and is gradually being more used. It withstands the action of the secretions of the mouth better than gold and its presence is 152 CROWN-, BRIDGE-, AND PORCELAIN-WORK consequently more benign to the tissues, in which respect it ranks next to porcelain. Being malleable and infusible, it can be easily and ac- curately adapted. Platinum plate, gages Nos. 31 to 32, is used in the same manner as gold, the soldering of the joint and floors being done with pure gold, or with platinum solder when it is to be used for porcelain crown- work. C3 a a Q Q Fig. 244. — The palatal side of the superior molars, in many cases, is of the large oval form indicated by the outer line to the form of the first molar. The small spurs indicate the points generally found the most suitable to make the joint. In fitting a platinum collar, the cervical portion may at the same time be trimmed to a fine edge to facihtate the adjustment under the gum- margin, as there is no danger of fusing the edge in subsequent soldering. Reinforced Thin Platinim? Collar.— This style of collar is advan- tageous to use in capping roots complex in form and difficult to fit, or in cases where the collar has to extend far under the gum-margin. The GOLD COLLAR CROWNS 153 ^- V Fig. 245. Pig. 246. Pig. 247. Fig. 249 Fig. 250. 154 CROWN-, BRIDGE-, AND PORCELAIN-WORK collar is made of pure thin platinum plate about gage No. 38. At this gage platinum can be easily fitted and accurately adapted. The rein- forcement of the fitted collar is most conveniently done by flowing pure gold over the outer surface. The inner surface; of the collar is painted with a thick coat of rouge. The gold is cut in small pieces and succes- sively applied and fused around the entire circumference of the collar. If there are any uneven places in the surface of the applied gold, they can be trimmed level when the floor has been attached to the collar. Another method is to fit the thin platinum collar to the root, attach the floor and then reinforce the collar by the casting process. The difficulty encountered by this method is that the contraction of the gold is liable to interfere with the adjustment of the collar or cap on the root. Platinum-lined Gold -Plate Collar. — When this form of plate is used, owing to the uneven expansion and contraction of the two metals, the joint requires to be securely clamped while being soldered. For Cast Gold Root Caps and Crowns, see Part III, Chapter XIV. AppUcation of a Local Anesthetic. — The application of a local anes- thetic to the gingivae is suggested in fitting collars. Adrenalin and co- cain are much used, applied as described in Part II, Chapter III. Some of the excess of the application which wijl usually be found at the cervix may be rubbed on the labial and lingual sides of the gum. A little of the solution may be placed on the inner edge of the collar before it is adjusted on the tooth or root. The patient should be directed not to swallow the saliva during, and for some time after, the application of the cocain. The anesthetic effect produced by this method is of such duration that it will usually be found sufficient to partly or entirely divest the operation of pain and will seldom require repetition except in lengthy operations. Collar Crowns Hygienically Considered. — The principal argument against collar crowns is that they are productive of irritation to the peri- dental membrane, ultimately causing its absorption and exposure of the collar. This would be theoretically and practically true of aiough or porous substance encircling the root or of an imperfectly and un- skilfully adjusted or cemented collar, which would by its presence hold a position analogous to a calcareous deposit; but it is not fairly predi- cated concerning a perfectly fitted collar forming at its edge a smooth and imperceptible union with the sides of the root and presenting a uniform and benign surface to the investing membrane. The fact should, however, be borne in mind, that a collar of any form is not applied for hygienic purposes, but as a necessity, and at times as an unavoidable adjunct of some restorative operation. In the cas*^ of perfectly adapted collars, when an irritation of the GOLD COLLAR CROWNS 155 membrane exists, it will usually be found to result from such causes as produce it when the natural crowns are presented, namely, dental concretions. A tarnished and unclean condition of the surface of the gold of the collar will produce irritation of the membranes, which is a ^matter independent of the collar itself and easily remedied by cleaning and polishing the surface. Where an acid condition of the secretions of the mouth exists, a collar of platinum is suggested in preference to gold, as this metal will not be affected, but will constantly present an untarnished surface. Infection of the cement under a collar will cause inflammation of the gingival margin independent of the collar. When evidence of a tendency to pyorrhea alveolaris exists, a collar adjusted to support bridge-work should not be extended under the gin- givae, but a space should be left between the edge and the gingivae so as to better permit treatment of the disease. When this is not practical the collar should be made of thin platinum plate and the edge closely fitted and burnished. CHAPTER VIII ALL-GOLD COLLAR CROWNS FOR BlCUSPmS AND MOLARS CONSTRUCTED IN SECTIONS METHODS OF KNUCKLING THE COLLAR AND GIVING CONTOUR — METHODS OF FORMING THE CUSP-CAP — CLASS A, DIES — METHOD NO. I — SWAGING THE CUSP-CAP — STAMPING THE CUSP-CAP IN A SWAGER — REINFORCE- MENT OF THE CUSP-CAP — FITTING CUSP-CAP TO COLLAR — SOLDERING CUSP-CAP TO COLLAR — SWAGED CUSP-CAP — REINFORCED WITH 2 2- CARAT GOLD — SWEATING — TO UNITE BY SWEATING — METHOD NO. 2, HOLLOW CUSPS — ^CLASS B, INTAGLIO OR DEPRESSED DIES — METHOD NO. 3 — METHOD NO. 4, CUSP BUTTONS — APPLICATION — TO ENLARGE A CUSP BUTTON — METHOD NO. 5, INTAGLIO DIE FROM WAX MODEL — INTAGLIO DIE-PLATE — CLASS C, CASTING — METHOD NO. 6 — SOLID GOLD CUSP-CAP SPECIAL METHOD^ — ^METHOD NO. 7- — SOLID GOLD CUSP-CAP BY SOLDERING METHOD NO. 8 — ^ALL-GOLD CROWNS FOR — INCISORS AND CUSPIDS CASES OF ABRASION The root and crown having been properly prepared, the collar is formed and adjusted as described in Chapter VI, and the edge towards the antagonizing teeth trimmed to the line of the points of the cusps to fully clear them in occlusion and provide space for the placing of a prop- erly contoured cusp-cap. The collar is then slightly expanded toward the occlusal surface for better contour and the edge trimmed perfectly square and level by rubbing on the flat surface of a very fine file. Methods of Knuckling the Collar and Giving Contour. — If the collar is long enough a contour approximating that of a natural tooth can be imparted to the side with the aid of suitable pliers, such as are illustrated in Fig. 251, the Robinson, one beak of which is rounded at the point and shorter than the other. The Peeso contouring and stret- ching pliers, Fig. 252, and the pliers, Fig. 253, are also useful for shaping and removing inequalities caused by the use of the first form. A close knuckling can be insured by pressing the collar against the approximal teeth in the manner shown in Fig. 254. Methods of Forming the Cusp-cap. — For the formation of cusp- caps there are a number of methods, of which only those most practical and most used will be presented. They will be placed in three classes: 156 ALL GOLD COLLAR CROWNS FOR BICUSPIDS AND MOLARS 157 A, Stamping or swaging on the surface of dies; B, Shaping in intaglio or counter dies; and C, Casting. Fig. 251. Fig. 253. Fig. 254. Fig. 252. In class A the outer surface of the cusp-cap is larger than the die the thickness of the gage of gold plate used, and the inner surface the exact size of the die. iss CROWN-, BRIDGE-, AND PORCELAIN-WORK In Class B the outer surface of the cusp-cap is the size of the intaglio or depressed die, and its inner surface is smaller by the thickness of the gold. In class C the casting is an exact replica of the wax model of the required cusp-cap. Class A, Dies Method No. i.^ — The superior molar to which a collar has been fitted, illustrated in Fig. 255, will be used as a typical case. The collar is Fig. 255. Fig. 256. removed from the mouth, warmed and the inner surface veneered with a film of wax to facilitate its subsequent removal. It is then readjusted in the mouth, a wax ''bite" taken and then a compound or plaster impression that will remove the collar in position. (See Part Fig. 257. I, Chapter IV.) Next articulating models are made, using a crown articulator, and the models varnished. Burnish layers of tin foil to the thickness of the gold plate that is to form the cusp-cap over only the surface of the teeth, or portions of the teeth, that will antagonize the cusp-cap as indicated in Fig. 256. ALL-GOLD COLLAR CROWNS FOR BICUSPIDS AND MOLARS 1 59 The form of the occlusal surface of the crown to be swaged is made by placing in the occlusal section of the collar a ball of soft plaster, wax or compound slightly in excess of what is required for the cusp-cap and firmly occluding the models together, Fig. 257. When the material has hardened, open the articulator and remove the surplus with a sharp knife. The impression of the antagonizing teeth will give an outline of the required occlusal surface. Allowing for the lateral movements Pig. 258. of the occluding teeth, carve the cusps, sulci and grooves, to as nearly the natural form as the circumstances will permit. Typical forms of occlusal surfaces can be used as a guide (Fig. 258). As the gold cap will strike up the thickness of the plate larger and the cusps that much longer, an allowance is made for that by the tin foil which was placed on the surfaces of the antagonizing teeth when they were occluded on the plaster (Fig. 257), but the material is to be proportionately removed at i6o CROWN-, BRIDGE-, AND PORCELAIN-WORK the sides of the collar, and its edge left exposed, as shown in Fig. 259, enlarged in Fig. 260. An impression of the model of the occlusal surface extending about one-sixteenth of an inch beyond the edge of the collar is now taken in a copper tube with moldine (Fig. 259). Paper is wound around the tube and a fusible metal die cast (Fig. 261). (See Figs. 19 and 20, Part I, Chapter V.) Pig. 259. A counter-die is made by hammering the die into a block of lead (B, Fig. 262). To slightly enlarge the counter-die and make an allow- ance for the gold plate before swaging and thus avoid the chance of splitting it, cover the male die with a thin piece of kid and drive it into the counter-die. Swaging the Cusp-cap. — ^Cut a disk of the same gold and gage as the collar, in size such as will leave when swaged a surplus of about d Fig. 260. Pig. 261. Pig. 262. one-eighth of an inch at the edge of the cusp-cap; anneal the disk, oil or vaselin the surface of the die and counter-die and conform tlie disk to the surface of the depressions of the counter-die with a pointed piece of wood, by first pressing with the point and then tapping on the end of the wood; remove and anneal (Fig. 263). ALL-GOLD COLLAR CROWNS FOR BICUSPIDS AND MOLARS l6l To swage with the die and counter-die, place the die (A, Fig. 264J over the disk (B) and give the die a moderately hard blow, driving it Pig. 263. Fig. 264. Pig. 26.S. into the counter-die (C). Remove the disk and correct any folds around its margin, anneal and. complete the swaging. Deep lines on the die representing sulci can be developed on the gold with the burnisher. Stamping the Cusp-cap in a Swager. — In the use of a swager, the die of the occlusal surface is cast in a swager cup. The process is as follows: Flatten out a mass of moldine, remove the collar with the form of the occlusal surface from the plaster model and make an impression of the occlusal sur- face in the center of the moldine. (See Fig. 26, Part I, Chapter V.) Adjust the swager cup over the impression and fill it with fusible metal through the hole in the base. A cup with a cast die in it is shown in section in Fig. 265. The disk of gold is annealed, placed in position on the die, conformed to its surface, removed and annealed. The gold is again placed on the die and covered with a disk of rubber-dam. The cavity in the plunger is filled. with moldine, the swager cup inserted in the base and the plunger hammered down on the gold (Fig. 266), or a soft rubber plunger may be used instead of the moldine. Fig. 267 shows the inner surface of the swaged cusp-cap. Reinforcement of the Cusp-cap. — Paint the outer surface of the cusp-cap with rouge or whiting. First melt on the corner of a charcoal soldering-block in the form of a globule the quantity of solder — hard 11 Pig. 266. l62 CROWN-, BRIDGE-, AND PORCELAIN-WORK solder preferred — required to fill the cusp-cap, applying a moderate amount of flux. Next, place the cusp-cap, occlusal side down, in the middle of the soldering block, place the globule of solder in it and fuse the globule into the cusps. This is best done by first uniformly heating both cusp-cap and solder with the large flame of the blowpipe to nearly that of the fusing-point of the solder, a^^d then reducing the blast and size of the flame (Fig. 268) to a small pointed one directed and steadily held on the globule until it gradually melts down and into the cusps of the cap. If necessary to heat up the gold of the cusp-cap during the operation, or at the finish to level the surface of the solder apply only the large flame. Conducted in the manner described fusing of the Fig. 268. edge of the gold of the cusp-cap or flowing the solder over the edge on the outer surface of the cap, which is liable to occur if care is not taken and skill exercised, is avoided. Next boil the cusp-cap in acid and wash. Fitting Cusp-cap to Collar. — Cut a piece of close-grained pine wood about six inches long, two inches wide and one and one-fourth inches thick and square and level the end. Heat the cusp-cap to a dull red and place and press it occlusal side down into the end of the wood level with the surface (Fig. 269). Thus embedded, file the surface of the cusp-cap and wood with a coarse flat file until the surface of the cusp-cap is uniformly level. Finish with fine files. The filing is most conveniently done by fastening the wood in a bench vise, as ALL-GOLD COLLAR CROWNS FOR BICUSPIDS AND MOLARS 1 63 illustrated in miniature in Fig. 270. Remove the cusp-cap, trim the plaster in the collar level to its occlusal edge, fit the cusp-cap to Fig. 269. Pig. 270. collar and return to wood block and again file until it fits perfectly in accordance with the occlusion. To form a perfect and reliable joint, the cusp-cap should extend onto and slightly- over the edge of the collar at all points. The edge of the collar must be square and evenly meet the flat surface of the cusp-cap Over its entire circumference; otherwise, if used in bridge-work, the joint is liable to open in soldering the bridge. Soldering Cusp -cap to Collar. — When fitted, the cusp-cap and collar are boiled in acid and washed. The edges of the collar and the flat filed surface of the edge of the cusp-cap are fluxed, placed in relative posi- PiG. 271. tion and clamped, occlusal side down, with an adjustable clamp (Fig. 271); or wired together with a piece of fine iron wire brought l64 CROWN-, BRIDGE-, AND PORCELAIN-WORK across the cusp-cap and the ends twisted together over the edge of the collar, as shown in Fig. 272. Place around on the inside of the seam several very small pieces of fluxed solder, preferably the next lower- fusing grade to that used to fill the cusps. The crown — occlusal side down, with full view of the inside — is then held in a Bunsen flame and slowly, uniformly heated until the solder fuses and flows. Only sufficient solder to properly unite the parts should be used. If too much solder is applied, it is liable to flow over the inner surface of the cap and on the sides of the collar, or both, and obstruct the adjustment of the crown on the tooth, a defect troublesome to correct. Swaged Cusp-cap Reinforced with 22-carat Gold.^^ — Strike up the cusp-cap of pure or 2 per cent, platinized gold ^fooo g^-ge, which doubled is about gage No. 32. Plate of this gage does not materially affect the thickness of the cusp-cap like the use of No. 30 gage; therefore very little if any allowance is necessary in shaping the model for the cusp-cap. Fill in the cusp matrix with coin gold as follows: Scraps of coin gold enough to fill the matrix are fused into a globule as already described; the globule is placed in the matrix, occlusal side down, and gradually heated and melted with a small blue flame steadily directed on the globule until it fuses and fills the matrix. No flux is applied. Considerable practice, as well as care, is required to successfully fill matrices of this character. Unite the cusp-cap to the collar from the inside by placing there a very small quantity of solder and flux and holding in a Bunsen flame; or use the sweating method. Sweating. — When the cusjp matrix is filled in with the same grade of gold as the collar and the crown is to be used as an attachment to a bridge, this is the preferred method of uniting cusp-cap and collar by many bridge- work specialists. To Unite by Sweating. — The edge of the collar and surface of the cap must meet at every point. The collar and cusp-cap having been boiled in acid are fluxed and clamped or wired together (Figs, 271 and 272), and held cusps down in a Bunsen flame so that the thick cusp-cap will be heated first. They are kept there until nearly at the fusing point. The entire crown is then lowered a little in the flame and held until the gold begins to melt and unites collar and cusp-cap, when they are instantly removed. This method requires practice. It should be first studied before trying it on a practical case. (See Part I, Chapter VI.) Method No. 2, Hollow Cusps. — This form of a cusp-cap is for use when a sound or only slightly decayed bicuspid or molar is to be capped 1 This method of forming a cusp-cap and then sweating it to the collar is that practiced and taught by Dr. Peeso. ALL-GOLD COLLAR CROWNS FOR BICUSPIDS AND MOLARS 165 Fig. 273. with gold, for instance, as an abutment for a bridge, and on account of shortness of crown or some other reason, removal of the least possible portion of the occlusal surface is desired. The inner surface of the cap in such a case must necessarily conform more or less to the occlusal section of the tooth. If antagonizing teeth are present, enough sub- stance must be removed from the occluding teeth or the one capped, or both, to allow for the intervening thickness of the plate forming the cusp-cap. In such a case fit the collar and trim enough off the occlusal edge of the collar to leave the cusps of the tooth exposed. Press a ball of softened impression compound over the occlusal surface and the edge of the collar, allow it to cool and then remove the collar and compound together. Fill the impression inside the collar with plaster and when the plaster has set remove the compound. This gives a plaster model of the occlusal surface within the collar as in the mouth, as outlined in Fig. 273. Take an impression or mold, make die and strike up a cap of gage No. 28 to 30, the same as in Method No. i. Leave a slight overlap edge to the cap as it meets the outer edge of the collar. Remove the plaster from the inside of the collar and attach the cusp-cap to the collar on the outside with wax, flowing the wax over and /A into the seam. Fill the inside of the collar and cap with \ / / j investment material and wire or clamp the cap and collar. Heat the investment slowly so as to burn off the wax and not displace the cap with steam from the investment. Holding cap and collar in position, unite them from the outside by flowing the least possible quantity of solder in the seam. The slightly projecting edge of the cusp-cap will retain the solder, which should be applied in' very small pieces in position. A variation of this method is to mark the outline of the occlusal surface on the inner surface of the collar, then remove the collar and trim so as to leave a border of about one-sixteenth of an inch outside the mark. This border is then thinned with a carborundum wheel, and slit, as seen in Fig. 274. The collar is next adjusted on the natural crown and the slit border bent over to the form of the occlusal surface, to which it is burnished. A cusp-cap stamped with a die of the occlusal surface or one closely approximating it is then adjusted on the collar in the mouth, the occlusion of the cusp-cap tested by occluding the teeth, and the cusp-cap and collar removed. Pig. 274. Pig. 275. i66 CROWN-, BRIDGE-, AND PORCELAIN-WORK They are then clamped, as shown in Fig. 275, and the cusp-cap fastened only at the point A with an atom of solder. The crown is then readjusted on the tooth and the edges of cap and collar brought together with a foot-shape foil condenser, also by occluding the teeth, if any are present, and the soldering completed by degrees. In such cases as described, if the antagonizing teeth are present, the cusp- cap is preferably made of platinized gold (clasp gold) to better resist the wear of mastication. Class B, Intaglio or Depressed Dies Method No. 3. — Form on the collar the required cusp-cap in plaster or metalline^ and embed the collar — cervical end down — in a flattened lump of moldine ex- actly to the line of junction of Fig. 276. the gold collar and cusp-cap model (Fig. 276). Place the swaging cup of the swager over it and pour in fusible metal. When chilled, remove crown and moldine and vaselin the Pig. 278. Pig. 277. — PM, Fusible Metal. surface of the die, then start the gold plate into the depressions with the point of a piece of wood by tapping on the end. Remove, anneal and replace the gold, insert the cup in swager and complete the swag- ing with the plunger (Fig. 277). Method No. 4, Cusp-buttons. — This consists in the use of solid metallic models of the occlusal surfaces of bicuspids and molars to form intaglio cusp-cap dies for crowns or dummies (Fig. 278). 1 A mixture of carbon and impression compound sold for such purposes. ALL-GOLD COLLAR CROWNS FOR BICUSPIDS AND MOLARS 167 Cusp-buttons are made by stamping sheet copper, gage No. 36, to the form of an occlusal surface and filling the matrix with lead or tin by fusing it in a Bunsen flame, using zinc chlorid as a flux. The surface is then filed perfectly level by rubbing on the surface of a fat file. The buttons should be arranged in sets so that the required form or size can be easily selected as shown in Fig. 279. Application. — Fit the collar and select a cusp-button. Remove enough of the occlusal edge of the collar to make room for the cusp- button and file the edge of the collar perfectly level. Place a little wax inside the collar to assist in retaining the cusp-button in position. Pig. 279. The cusp-button selected should be fully as large as the circumference of the collar, should articulate properly and correspond in shape with the other teeth. Remove the button and place it on a level cake of moldine — occlusal side up, — cover it with a swager cup and flow in fusible metal (Fig. 280). When cool, remove cusp-button, place the gold plate over the intaglio or depressed-die and swage the gold into the die with the plunger. This gives a cusp-cap of the exact form and size of the cusp-button the gage of the plate smaller on its cavo-surface. If among the cusp-buttons on hand none articulates perfectly, the difficulty is usually remedied.by taking the button which most i68 CROWN-, BRIDGE-, AND PORCELAIN-WORK nearly answers and building up the cusp with moldine (Fig, 281). If a collar is accidentally cut too short, it may in some cases still be utilized. Place moldine upon the molding plate, set and adjust Fig. 280. Pig. 281. Pig. 282. the cusp-button upon it, press and cut away the moldine enough to make up the deficiency of the collar (Fig. 282). This will, of course, throw the soldering line a little farther up the crown. M_ 0Kf- dtnf- ^KW^ it^ -4k Pig. 283. To Enlarge a Cusp Button. — To make a cusp-cap the thickness of the gold plate larger, fill the swager cup with impression compound and level the surface. Lay the cusp button — occlusal surface upward — on the center. Place and swage the gold plate over the cusp button. ALL-GOLD COLLAR CROWNS FOR BICUSPIDS AND MOLARS 169 Method No. 5, Intaglio Die from Wax Model.- Shape the model of the occlusal surface on the collar with stiff plate- wax. Fill a swager cup with impression compound and level and warm the surface so that it is quite soft. Oil the wax model lightly; chill with cold or ice-water, press into the surface of the warm compound to the line of the occlusal edge of the collar and immediately chill the compound by immersing in or placing under running water. If properly done the heat of the com- pound will not at all disturb the wax form. Remove the wax model. This gives an intaglio die of impression compound into which can easily be swaged pure gold, gage No. 38, and even 22-carat gold by frequent annealing. Paint the outer edge of the swaged gold form of the cusp-cap with rouge, place it on a soldering block and with a blowpipe melt into it globules of coin gold or hard solder until it is full. A satisfactory cusp-cap is quickly made by this method. Intaglio Die-Plate. — Intaglio die-plates (Fig. 283) of the occlusal surfaces of bicuspids and molars are manufactured and sold for use in forming cusp-caps. They are not as convenient to use as the cusp- button method, as the latter permits the required form and size to be more easily determined. Class C, Casting Method No. 6. Solid Gold Cusp-cap. — Casting is the preferred method for cusp-caps. Form on the collar a model of the required cusp-cap with inlay wax, with the collar in position or mounted on a model, as described in Method No. i, using wax instead of plaster. Have the inner edge of the collar slightly embedded in the wax. Chill and re- move the wax cusp-cap model, invest and cast. The sprue is inserted in the thickest part of the wax before or after its removal from the collar, as shown in Fig. 45 (Part I, Chapter VII). The wax model of the cusp- cap may be invested in position on the collar and cast directly on it. In such a case wax not necessary to the cusp-cap should be removed from the inner surface of the collar to in- sure easy adjustment of the finished crown. This method is further varied by capping the occlusal end of the collar with a floor of thin gold plate or i/iooo platinum (A, Fig. 284) and shaping the wax model of the cusp-cap on it. When the cusp-cap is cast (B) clamp and solder it on the floor of the collar. 17© CROWN-, BRIDGE-, AND PORCELAIN-WORK Special Method Method No. 7» Solid Cusp-cap by Soldering. — When intervening space will permit the formation of a soHd gold occlusal surface to a col- lar crown the following is a practical method: Fit the collar and trim the edge toward the occlusal surface so as to leave between it and the cusps of the occluding teeth a space of at least one-sixteenth of an inch. Remove the collar and cap the occlusal surface with a floor of gold plate about gage No. 30, using a very small quantity of hard solder to unite it to the collar. Trim off the surplus plate flush with the collar. To form the cusps, melt scraps of gold plate on the surface of a soldering-block into small globules, one for each cusp, and slightly flatten each globule on an anvil with a hammer. Place the globules on the surface of the cap in proper position to form the cusps and attach each with a small piece of hard-flowing solder (Fig, 285). When all o!eB Pig, 285. Pig. 286. the cusps are attached, add sufficient ordinary solder to properly fill in and give form to the surface of the cap. Adjust the cap in the mouth and trim the gold of the occlusal surface to the form that will suit the occlusion, then polish the crown. This is a very practical and quick method of forming a gold crown, especially in a case of mechanical abrasion and short cusps. Method No. 8. — -When the mere form of the occlusal surface for the crown is all that is required, as in cases of mechanical abrasion, or for a temporary crown, an impromptu one may be made by indenting a piece of pure or soft gold plate with the round end of an instrument han- dle on a piece of lead to form the cusps, then reverse the cap, resting it on a flat surface, and creasing between the cusps with a burnisher. One large indentation, such as is shown at A, Fig. 286, which when indented and creased across the center with the edge of a flat thin ALL-GOLD COLLAR CROWNS FOR BICUSPIDS AND MOLARS 171 burnisher will represent a bicuspid; four indentations closely made, as shown at B, when creased between, can be used to represent an upper or lower molar, and three similar indentations, properly creased, a second or third upper molar, as seen at C. Fig. 287. All-Gold Crowns for Incisors and Cuspids When the teeth are abraded and short, with flat incisal edges or occlusal surfaces (Fig. 287), and the all-gold crown required is to cor- respond in form and be only a little longer, the tooth is first trimmed and properly shaped. The gold collar, after being fitted to the cervical section, is slit on the lingual side and bent and burnished against the tooth. The collar is then removed and the seams soldered together. This is best done by holding the collar in a Bunsen gas flame with the solder placed in position in very small pieces and only sufficient in quantity to join the seams. The collar is next adjusted to the tooth 172 CROWN-, BRIDGE-, AND PORCELAIN-WORK and the gold at the incisal edge trimmed even. A flat thick piece of gold plate or clasp gold, as heavy as 22 gage or No. 30 gage additionally reinforced, is soldered across the incisal edge to form and inclose that portion of the crown. Cases of Abrasion. — Fig. 287 represents a case of abrasion of the lower teeth to which all-gold crowns were applied to open the "bite," as shown in Fig. 288. In such cases, owing to the attrition of the oc- cluding teeth, the cap formmg the occlusal surface should invariably be constructed of heavy gold clasp plate of one or several layers and solder as the case permits or suggests. One or two holes punched through each piece as it is applied facilitates their union with the solder. An artificial plate replaced the upper teeth in the case illustrated. In a case such as this the patient is usually advanced in years. In their treatment the opinion of most practitioners is, that only a partial restoration of the teeth in length is advisable. An operation for a young patient would be under different conditions and would not be included in this opinion. In persons of advanced years the sockets of teeth artificially lengthened do not always readily accept the sudden change respecting leverage and force of occlusion. a To gage the space to open the ''bite," the best method is to first crown a tooth on the right or left side or on both sides with an extra thick occlusal surface, then insert and trim to the length required, which will furnish the proper gage for the others. Gold crowns to be given a normal form require the fitted collar to be cut away at the lingual section, as shown in Fig. 289. The edge of the gold is then chamfered, bent and burnished over the incisal edge and sides close to the natural tooth. To this open section is next adapted a curved piece of gold plate, the collar is removed and the parts are soldered together, using only a small quantity of hard solder. Small pieces of ordinary solder or solder filings can be melted in the interior of the incisal edge to resist attrition. A fusible metal die of the prepared form of the natural tooth is a material aid in the construction of any of these styles of crowns. In pulpless teeth with only a little or none of the natural crown remaining, the root can be shaped and capped the same as for a collar crown with a porcelain facing, with a post in the root-canal. A gold facing is then applied instead of one of porcelain. This is done by shaping or stamping the form of the labial face of the tooth required in gold plate, filling it with hard solder, mounting it in position on the cap, as in the case of a porcelain facing, and attaching and giving any neces- sary shape to the lingual side with ordinary solder. ALL-GOLD COLLAR CROWNS FOR BICUSPIDS AND MOLARS 173 To make an intaglio die to shape a gold facing, select a suitable sized porcelain tooth, place it face upward on a flat piece of moldine, place the swager cup over it and cast in fusible metal. (See Part I, Chapter V.) The construction of an all-gold cap-crown for an incisor or cuspid is most easily accomplished by the seamless method described in Chap- ter XI. CHAPTER IX GOLD COLLAR CROWNS WITH PORCELAIN FACINGS INCISORS AND CUSPIDS — ADAPTATION OF THE COLLAR — TO FORM FLOOR OF THE COLLAR — -INDIRECT METHOD — ^PREPARATION OF CANAL TO RECEIVE POST — ^POSTS — UNION OF POST AND CAP — SELECTION AND ADAPTATION OF THE PORCELAIN FACING — TO PROTECT THE INCISAL EDGE OF THE PORCELAIN FACING — ^BACKING THE PORCELAIN FACING ONE-PIECE BACKING — ^POINTED-PIN FACINGS — USE OF SWAGER PREPARATION FOR INVESTMENT — ^INVESTMENT— SOLDERING AND FINISHING — -DIVERSITY OF CONSTRUCTION — METHOD OF FORMING POSTS TO ACCURATELY FIT CANALS — ^HOLLOW POSTS — ^CONSTRUC- TION — TO SEPARATELY BACK OR VENEER THE BASE OF A PORCELAIN FACING WITH PLATINUM TWO-PIECE BACKING — REINFORCED BACKING This style of crown, for incisors and cuspids, as originally made by Dr. C. M. Richmond and with which his name is commonly associated, originally consisted of a cap for the root formed of a band of gold with a platinum floor on which was soldered a tooth with a slot in the center between the pins. Through this slot and the center of the cap a screw passed, which entered into a cylinder previously screwed and cemented into the root-canal. The form of gold collar crown with porcelain facing now in general use is in principle the same as what was formerly known in dentistry as a gold pivot tooth, with the addition of a gold collar for the root and having the advantage of zinc-oxyphosphate for its cementation. These improvements enhance its value as a crown and materially changfe the process of its construction. Incisors and Cuspids Adaptation of the Collar. — In making an incisor or cuspid crown of this style the root-canal is treated, the root shaped and a collar made and fitted, as described in the preceding chapters. The collar is held in position on the root, a sharp-pointed instrument introduced inside the collar, and the line of the surface of the root scratched on the metal around the circumference. The collar is removed and trimmed a trifle flush to this mark with small pointed shears. It is then adjusted on the 174 GOLD COLLAR CROWNS WITH PORCELAIN FACINGS 175 root and the edge of root and collar ground even, removing some of the surface of the root if necessary for this purpose. In the operation of grinding, the collar should first be firmly held in position on the root at the labial side while the lingual section is ground, then at the lingual while the labial is being reduced. At the labial section, the collar and surface of the root should be removed so as to be invisible if the patient exposes the gum-margin in speaking or laughing. To positively insure such a result in the finished crown, it is advisable to first grind and shape the end of the root and the base of the porcelain facing, the one to the other, with the collar removed, making an allowance for the thickness of the floor of the cap. In cases where there is no exposure of the gum-margin in the movement of the lips, a proportionate amount more of the collar and root may remain. This is often desirable, as it affords additional strength, especially when the crown is to be used as Fig. 290. Fig. 291. Fig. 292. an abutment in bridge-work. The work then will present the appear- ance about the collar shown in Figs. 290 and 291. As the sides of the collar are parallel with the line of the cervical section of the root, the edge of the collar at the lingual side forms an angle with the surface of the end of the root (A, Fig. 290). In close occlusions this is liable to give a conformation to the finished crown at that point quite perceptible and objectionable to the patient. This can be avoided by slightly rounding off the lingual side of the root to the form illustrated at B, Fig, 291. The collar is then slit two-thirds across, as outlined at S, the edges beveled slightly, lapped, fitted on the root, pressed and burnished to form and soldered. In the finished crown the collar will then present a form nearer that of the natural tooth, as illustrated in Fig. 292. To Form the Floor of the Collar. — The floor of the collar that com- pletes the cap is made of gold gage No. 30 or thin platinum plate gage No. 38 to 40. Thin platinum plate or 3^1000 platinum foil is preferable 176 CROWN; BRIDGE-, AND PORCELAIN-WORK when it is desirable to have the least possible space occupied by the floor at the labial section. The thinness of the platinum forming the floor to the cap does not materially affect the strength of the finished crown, as that part is reinforced by the solder subsequently applied. When the cap is for a removable tube and split-post crown, the floor is to be made of the same grade of plate as the collar, gage No. 28. A piece of the gold or platinum plate is cut — square or round — con- siderably larger than the circumference of the collar. The outer edge of the collar having been filed level is placed against the floor and adapted to its surface by slight pressure between the fingers. With the collar resting on the floor, the edge is seized with a clamp, a piece of solder with flux is placed on the gold or platinum outside of the collar, as shown in Fig. 293. The whole is then held in the flame of a Bunsen burner, the solder fused and collar and floor united. The quantity of solder applied must be very small, barely sufficient to unite the parts, so that it shaU not flow over the inside of the cap and interfere with its . fit on the root. All parts of the edge of the ^^^pl collar should touch the floor before they are ^^ \ soldered; otherwise, in subsequent soldering, WMlif the seam is liable to open. Perfection in \ \ 111 ^^^^ P^^*' ^^ ^^^ work is most easily attained lilil ^y ^^^^ attaching the gold or platinum to WmM the edge of the collar at one point with a in mere particle of solder to retain and hold it in position, and then readapting the re- mainder of the edge and completing the soldering. The position of the tweezers should be changed during the soldering, as they conduct the heat from the metal at the point held. When the collar and floor are united, the plate is trimmed flush with the outline of the collar with small shears and finished smooth with a carborundum point. At the cervical edge, in some cases, it is well to have the floor extend slightly beyond the collar so as to accommodate proper align- ment of the facing in a labial direction and to assist in shaping the collar with solder at that point later on. The cap is next adjusted on the root. Should any part of the cap not seem to fit in position accurately, a foot-shape foil condenser pressed or malleted along the edge of the collar at the part soldered to the floor will correct it, if the soldering has been properly conducted. Pressure is next exerted with the finger on the palatal side of the cap to retain it in position while the labial section of both floor and collar is burnished to the root. This adaptation steadies the cap on the root. The cap is then ready to receive the post. GOLD COLLAR CROWNS WITH PORCELAIN FACINGS 177 Indirect Method. — If this method is pracliced in forming a collar and floor on a die (Part I, Chapter V), swaging should be omitted, as it distorts the position of the collar. Swaging is best applied to seamless root-caps, (Formation of Cast Root-Caps is described in Part III, Chapter XIII.) Preparation of Canal to Receive Post. — In a collar crown of the style described, the collar is largely relied upon for retention on the root, and the post is therefore not usually so important a part as in a crown where a partial collar or no collar is used. To receive the post, the root- canal is first opened up with Gates-Glidden drills and then with suitable reamers enlarged to the size of the intended post (B, Fig. 294). The orifice of the canal should be countersunk a little with a large round bur to give it a slightly cup-shape form. Into this depression the gold or platinum of the floor of the collar can be burnished with a cone-pointed burnisher. The object of the depression is to provide a space to flow the solder m aiound the post to reliably attach it to the floor, especially Pig. 295. Pig. 296. should conditions require that the end of the post be ground off close to the surface of the floor (Fig. 295, in section). Post. — Gold clasp or iridio-platinum wire, preferably round, gage No. 14 to 18 — a little smaller for laterals or other roots which require its reduction — is used for posts. The use of posts made of alloys of the base metals is to be con- demned for this style of work. The wire for the posts may first be rolled under a flat file to roughen its surface. It should be slightly rounded or tapered at the point and introduced one quarter of an inch, more or less, up the canal, as indicated by the conditions of the case respecting length of root, size of artificial crown to be mounted and character of the occlusion (Figs. 294 and 296). A large, long crown, or a close occlusion, suggests a longer and heavier post than a small or short crown or a more favorable occlusion. If the canal is for any reason much enlarged, the point of the post should be tapered and extended to its extremity in order to strengthen the root as well as anchor the crown. When gutta-percha is used to attach the crown, a 12 178 CROWN-, BRIDGE-, AND PORCELAIN-WORK longer post is required than for zinc oxyphosphate, and the post should fit the canal in such a manner as to require the presence of only a very small quantity of gutta-percha to secure it (Figs. 296 and 298). Union of Post and Cap. — -The post having been fitted, the cap is 'ad- justed on the root, the floor over the canal is burnished into the orifice and punctured. The end of the post is seized with wire pliers and the point inserted and forced through the puncture in the floor to position in the canal, and the correctness of its relations with the cap observed and decided. Cap and post are next removed, dried, slightly heated, and the surface of the floor and exposed end of the post veneered with adhesive wax. The cap and post are again adjusted to position on the root, protected from moisture, and a small pellet of slightly heated wax is placed over the end of the post and pressed against the surface of the cap and around the post. The wax is chilled with water and the cap and post carefully removed and invested. The investment ma- terial should be run into the interior of the cap so as to fill every crevice. When set, the wax is removed by pouring on boiling water and the investment is trimmed and reduced to as small a size as permissible (Fig. 297). It is next heated and solder flowed into the depression around the post flush with the surface p of the cap, also over the surface of the floor at the lingual Fig 207 ^^^^' ^^ made of thin platinum. Should any extensive aperture exist in the gold or platinum around the post at the orifice of the canal before soldering, a pellet of Corona gold may be gently pressed in the place to aid the solder in filling it up. After removal from the investment and boiling in acid, the cap and post are adjusted in position on the root. 'p> Selection and Adaptation of the Porcelain F^ing. — The adaptation of the porcelain facing to the cap is next made, either directly in the mouth, or by the aid of a model of the case. When a model — which is the best method — is to be used, the impression and bite are best taken together preferably in plaster, or impression compound maybe used; or the bite can first be taken in wax, then the impression in either plas- ter or impression compound. The impression and "bite" are best taken together if the shape of the teeth permits easy removal. To permit easy removal of the cap from the model during its construction, a veneer of paraffin should be placed with a heated spatula around the inner surface of the collar and on the sides of the posts. (See Part I, Chapter IV). A plaster model is made, the wax "bite," if separate, adjusted on it and an articulating model made. The projecting end of the post is cut off with a thin carborundum disk a little above the surface of the floor. The end of the post is next GOLD COLLAR CROWNS WITH PORCELAIN FACINGS 179 reduced with a carborundum wheel to the surface of the floor at the labial side, but left slightly projecting above it lingually for additional strength, should such a form offer no obstruction to the setting of the porcelain facing (B, Fig. 298). The porcelain facing is formed of a cross-pin plate tooth. The shade selected should be at least as dark as that of the opposite cor- responding natural tooth, if present, or if absent that of the adjoining teeth. The general form, while suitable in appearance, should be such as will permit proper adaptation without excessive reduction by grind- ing. The curve of the sides toward the base should be such that when the facing is ground the base will not greatly exceed the surface of the cap in width, and the pins be so located that their strength will not become impaired in the required removal of the porcelain for the proper adjustment of the facing. There are two methods of setting the por- celain facing to the cap. In the first metho I the facing is ground to position with the bas of the porcelain closely fitted to the surfac of the cap (Fig. 299). Fig. 298. Pig. 299. Fig. 300. In the second method the facing is fitted at the cervico-labial sec- tion to rest on the cap while the remainder of the base is ground so as to form a slightly increasing space toward the lingual side just over the post (P, Fig. 300). As the porcelain rests on the cap at only one point it simplifies the work of correctly positioning the facing with the other teeth. The facing should be ground so as to locate the pins a little toward the incisal edge for strength. The cervico-labial edge of the facing should be placed even or flush with the edge of the collar. When a model is used to fit the porcelain facing, although it facilitates the operation, the exact alignment of the facing should be determined by a final adjustment in the mouth. To Protect the Incisal Edge of the Porcelain Facing. — To protect the incisal edge of the porcelain facing against fracture in such a way i8o CROWN-, BRIDGE-, AND PORCELAIN-WORK that the gold shall be invisible, the porcelain should be ground and beveled ofif at an angle of about 45 degrees to the incisal edge at a proper distance from the pins, as shown in Figs. 298, 299, and 300, and also at A, Fig. 301. In grinding and polishing the porcelain, revolve the wheel in the direction shown in Fig. 312 to avoid chipping the enamel. Polish the edge with fine sandpaper disks. In the final finishing the gold is brought on a straight line, or nearly so, with the edge of the porcelain, as shown at B, Fig. 301. By this plan the porcelain is protected and the gold rendered invisible when viewed from the front. Backing The Porcelain Facing One-Piece Backing. — When the porcelain facing has been fitted to the cap by the aid of a model, it is best to retain and define its position on the cap before removing it for the application of the backing, by forming a removable matrix of plaster on the labial aspect, as shown in Fig. 302. This permits removal of the facing and in- sures its replacement when backed in exact posi- tion on the cap. The backing of the facing must be absolutely adapted to the surface of the porce- FiG. 302. lain to afford strengtTi and continuity of structure and prevent intrusion of secretions or extraneous matter in use. To effect this the porcelain facing before backing should be first divested of every particle of wax by immersing in boiling water. The edge of the backing should be flush with the edge of the porcelain on the sides to draw the solder and permit finish. The backing should never be rounded or looped over an edge of the porce- lain. The backing is made of platinum, gage No. 38, or crown metal, which is platinum on one side and gold on the other, or of 24-carat pure gold plate, gage No. 30 to 31. Gold imparts a slightly yellow and platinum a bluish shade to the porcelain; So the platinum or gold side of the crown metal can be placed accordingly. When the entire base of the porcelain facing is fitted to rest on the floor of the cap according to the first-mentioned method, the backing is applied to extend from the base to and over the trimmed incisal edge, as shown in Fig. 299. If the facing is fitted according to the second method with a V-shaped space at the lingual side of the base, the backing is extended to also cover the base, as shown at P, Fig. 300. To ascertain the exact position of the pins, the plate is placed on a flat GOLD COLLAR CROWNS WITH PORCELAIN FACINGS wooden surface or a piece of cork, the pins are made perfectly straight and the facing placed over the plate, pins downward, and enough pres- sure applied to make a slight indentation (Fig. 303). Holes are now punched through the indentations with punch forceps and the backing closely adapted to the surface of the porcelain by annealing and burnishing. Pointed-Pin Facings lately introduced are intended to punch their own holes through a backing of moderate gage by pressure. This simplifies the operation of backing and forms a flux-tight joint between pins and backing that prevents solder from flowing through and checking the porcelain, which is liable to occur when the pin-holes in the back- ing are loose or open. Fig. 304 illustrates this form of facing. Use of Swager. — An assured adaptation of a backing to a facing is obtained by placing the facing, labial aspect downward, in impres- sion-compound in a swager cup (Fig. 305), and swaging the backing Fig. 304. Fig. 305. Pig. 306. Fig. 307. Fig, 308. against the porcelain. To avoid fracture, the backing should first be burnished, then annealed and not too much force should be applied. When the backing is adapted, the pins are bent down on the surface in either of the positions shown in Figs. 306 and 307. When bent as in Fig. 306, they assist in retaining the solder in position, in solder- ing and thickening the backing at that point. The backing is trimmed straight to the sides of the porcelain except at the incisal edge, where it is left extended, as shown in Fig. 307. This extension is removed to the edge of the porcelain after the crown is soldered. Removal of a small portion of the pins on the side they are to be bent (A, Fig. 308) with a stiff sand-paper disk will permit them to be bent downward on the surface of the backing with less strain upon the porcelain. The backing should be in position on the porcelain when the pins are trimmed to avoid their removal below the line of the surface of the backing; preferably they should be trimmed a little above it. 1 82 CROWN-, BRIDGE-, AND PORCELAIN -WORK Preparation for Investment. — The porcelain facing when backed is adjusted on the cap. Should the metal backing on the base of a facing in the second method interfere with its proper adjustment on the cap at the cervico-labial section, as is generally the case, it should be thinned with a small carborundum cone or entirely removed at the obstructing point, as indicated at C, Fig. 307, and that portion of the porcelain allowed to xest directly on the cap. The facing is first at- tached to the cap with only a small quantity of adhesive wax until its alignment is quite accurately determined, then hard wax is added to more securely retain it. The whole is chilled in cold water and a final adjustment made in the mouth to positively assuie its correctness. Before investing, additional wax is added to the metallic paits of the crown to be soldered, suf- ficient to impart to them the desired form for the solder and allow a slight excess for finishing. A little wax is generally Fig. 309. placed on the sides of the collar at the cervical section of the porcelain facing, especially when any portion of the porcelain projects over the line of the collar, for the purpose of providing space in the investment for the solder to flow and contour the part, as shown in Fig. 309, which illustrates the waxed-up crown ready for investment. Investment. — Calcined marble-dust or fine silex and plaster are the preferred materials for investment. They are used in the propor- tions of two parts marble-dust or silex to one of plaster. First thor- oughly mix the dry ingredients, then add the water. The crown is first wet by dipping in water and then the ^,*^-w:?>, inside of the cap is filled with the investment ^^z..,^.-M \ material. A small camel's-hair brush will f' '' ~~--~-,..\\ * facilitate this; also the use of a hand air- K- I syringe to blow the investment into the in- ^^^ terstices. A portion of the investment in the _, '^ Fig. 310. form of a small mound is next placed on a sheet of paper and the crown is gently pressed into it until all the parts are covered except the wax on the lingual side of the backing. When the investment has set, the wax is removed by pouring boiling water on the investment. Instruments should not be used to remove wax as they are liable to disturb delicately adjusted parts. The investment is next trimmed and reduced in size as much as it properly can be, and the investment material removed so that the metallic parts of the crown are slightly exposed at the sides, as shown in Fig. 310, for the first described method of fitting a facing, and in Fig. 311 for the second method, to fully expose the V-shaped space. GOLD COLLAR CROWNS WITH PORCELAIN FACINGS 1 83 Borax, finely ground and mixed with waler or liquid flux, is applied with a brush to the metallic parls and in the seams before heating. When Parr's fluxed wax is used for the benefit of the flux it contains, the wax is allowed to burn cut as the investment is heated. The objection to burning wax out is that it does not leave as clean a surface of metal to solder. Soldering and Finishing. — The investment should first be dried and then heated to a dull red over a Bunsen flame (see Part I, Chapter VII), and removed to a soldering-block. Gold solder cut in small pieces in quantity only sufficient to fill interstices and unite the facing to the cap is first placed in and over the space between the facing and cap. The solder should have been previously immersed in borax finely ground in water and then dried, or, after it is placed in position, it should have a small quantity of calcined borax sprinkled over it. Fig. 311. Fig. 312. Fig. 313. Solder is also used in strip form, as it can be more rapidly applied and the application instantly stopped by withdrawing the strip. Sol- dering of places difficult to reach is facihtated, as illustrated in Fig. 315. Heating the investment uniformly, especially underneath, and in the direction indicated by A, Fig. 311, with the deoxidizing section of the large flame of a gas blowpipe, will cause the solder as it melts to gradually flow downward into the interstices. More solder is added by degrees and fused in this manner with some use of a smaller flame directly applied to the gold until the spaces between the porcelain facing and cap and at the sides are filled in and continuity of structure assured. After letting the body of the investment cool slightly, so as not to draw hack the solder that has been already fused in the deep- portions, additional solder is placed on the backmg and cap, and with a small-pointed flame flowed over these parts. Only sufficient gold should be applied to properly contour the parts and allow for finishing. When soldered, the investment should be allowed to cool slowly. The crown is next removed and boiled in sulfuric acid, 20 per cent., to thoroughly remove the borax, and it is ready for finishing. 1 84 CROWN-, BRIDGE-, AND PORCELAIN-WORK In finishing, the movement of wheels and files in trimming and polish- ing should be so directed that the edge of the metal adjusted to the porcelain is pressed against it, as is indicated in Fig. 312, showing the use of a wheel in reducing and trimming the surplus gold at the incisal edge. The finishing with sandpaper disks should be done in the same direction. Fig. 313 represents the completed crown. When the porcelain projects beyond the edge of the collar at the cervico-labial section, as shown at A, Fig. 314, and the form will not permit of sufficient removal, as frequently occurs in the case of cuspids, the space left should be evenly filled with gold solder when the facing is being attached to the cap. To accomplish this the backing applied to the base of the facing should be thinned or made of platinum foil (see PF, Fig. 319), and extended slightly beyond the edge of the porce- lain at the cervico-labial section. The open space is filled and shaped Fig. 314. evenly with wax a little more than flush at the edge of the collar and extended backing. In such cases the flow of solder to the part is effected by forming a space on each side and through the investment which will expose it and permit solder to be applied directly, preferably in the form of a narrow strip, as shown in Fig. 315. Diversity of Construction Method of Forming Posts to Accurately Fit Canals.^ — To form a post that will accurately fit a canal, especially a canal that for some reason is considerably enlarged, slightly taper the point of a piece of iridio-platinum wire, gage No. 20 to 21, and a half inch long, fit it to the extremity of the canal and bend the end of the wire toward the labial side at a right angle to indicate its position when inserted (Fig. 316), and veneer the point of the wire with pure gold by fusing on it a pellet of gold foil. Cut a strip of platinum foil, gage 3=-l!ooo> about one-eighth of an inch wide and an inch or more in length; bend the end of the strip of foil over the end of the wire close to the point, and unite the wire and GOLD COLLAR CROWNS WITH PORCELAIN FACINGS 185 foil in a Bunsen flame. The veneer of gold at the point of the wire on fusing will be just enough to attach the strip (A, Fig. 317). Next wind the strip around the wire, as shown at B, and insert in the canal. The coils of foil will press down on the wire in conformity with the size and shape of the canal, as illustrated at C. Seize the exposed portion of the foil and wire firmly with small-pointed pliers, remove in position and solder in a Bunsen flame with pellets of gold foil. Apply only enough gold to unite the layers of platinum, for if an excess is used the shape of the post will be altered and it will not fit the canal. The cor- rugations on the post formed by the layers of platinum foil afford an attachment for the cement. Hollow Post. — This consists of a post with a small canal running through the center. The advantage it offers is the comparative ease with which it can be drilled out of the canal, if \) for any reason it becomes necessary to remove the crown, as the drill will follow the hole in the center of the post. Construction. — Select the smallest carbon used for pencils '^ (A, Fig. 318). Heat and veneer the surface with a film of wax cement. Cut a strip of platinum foil \iooQ, at least three-eighths inch wide and about an inch long. Warm the carbon enough to soften the veneer of wax and attach the end of the foil the same as to the platinum wire, as shown at A, Fig. 317. Next wind the foil around the carbon (A and B, Fig. 318) and unite the layers of foil with pure gold. The carbon may be removed or allowed to remain. The gage of the post is regulated by the quantity of foil that is wound around the carbon. A B To Separately Back or Veneer the Base of a Porcelain Facing with Platinum. — This method consists in the use of a piece of platinum foil — instead of an extension of the backing — ^to cover the base of the porcelain facing when a V-shaped space exists between the porcelain and the floor of the cap, for the purpose of drawing the solder into the space so that Fig. 318. when in use the secretions will be excluded. ^ B Fig. 317. 1 The best method is to procure the hardest made drawing pencil, which is marked 8H, and remove a piece of the carbon about three-fourths of an inch long and trim it down in a chuck on the lathe to about No. 22 or 23 gage, which with care is easily done. i86 CROWN-, BRIDGE-, AND PORCELAIN-WORK The process is as follows: The base of the facing is heated and its surface veneered with adhesive wax. While the wax is in a melted condition, a piece of 3^^0 platinum foil is pressed against the wax with the finger or a tightly twisted ball of cotton with force enough to squeeze out the hot wax and bring the foil close to the porcelain (PF, Fig. 319). The base is reheated enough to soften the wax and pressure is again applied until the foil is brought against the porcelain. The surplus foil is cut flush with the porcelain and the facing is then mounted on the cap. Platinum foil is preferable to gold because less liable to melt and be absorbed by the solder. The foil at the extreme cervico-labial edge may be removed, as illustrated at C, Fig. 307, as in the case of a plate backing, and that portion of the porcelain permitted to rest directly on the floor. The crown should be invested as shown in Fig. 311. Fig. 319. Fig. 320. Fig. 320. — lEB, incisal edge backing; B, backing; W, and facing on cap. Fig. 321. — FB, first backing; SB, second backing. Fig. 321. wax to retain backing Two-F*iece Backing. — The one-piece backing previously described is the one most used. The two-piece backing is also in favor. The lingual surface of the facing alone or with the base is first backed with either pure gold, gage No. 30 or 31, or platinum %000; the pins bent and the backing trimmed to the line of the porcelain, as shown at B, Fig. 320. When the facing is mounted on the cap with wax ready to invest for soldering, an incisal edge backing of either gold or platinum is added and attached with wax, as shown at lEB. In the soldering, the backing to the porcelain facing is first soldered and connected to the cap, then the solder placed on the incisal edge backing and the two connected. Reinforced Backing. — This consists of first adapting a backing to only the lingual or both lingual and base surfaces of the facing and then adapting another backing over the first which will also include the incisal surface. The first backing (FB, Fig. 321), is made of pure gold, GOLD COLLAR CROWNS WITH PORCELAIN FACINGS 187 gage No. 32, or platinum plate Kooo gage, closely adapted or swaged. The second backing (SB) of 20-carat gold plate, gage No. 26 to 30— the lighter the first backing the heavier the second— is extended from below the pins to and over the incisal surface. It should be carefully adapted by burnishing and annealing. Punching holes in the second Fig. 322. backing (E, Fig. 322), which is to protect the incisal edge (C) will permit the solder to flow to the first backing (D) and unite it in the soldering of the facing to the cap. Another method is to remove the backings in position from the facing before investment, paint the under side of the first backing and Fig. 323- .fill the pin hole with rouge or antiflux. Next clamp the backings to- gether, as shown in Fig. 323, and unite them with solder, using no more than enough to barely show at the edges of the seam. The double backing when adjusted on the facing will appear as outlined in Fig. 321. CHAPTER X GOLD COLLAR CROWNS WITH PORCELAIN FACINGS, CONTINUED BICUSPIDS AND MOLARS — TO FORM A CUSP-CAP — INLAYING PORCELAIN FACINGS IN GOLD CROWNS — APPLICATION TO A SEAMLESS GOLD CROWN — INLAYING PORCELAIN FACINGS IN SECTIONAL CROWNS — A FAULTY METHOD — CROWNING IN CASES OF ABRASION — ^GOLD CROWNS WITH PORCELAIN FACINGS FOR TEETH WITH VITAL PULPS Bicuspids and Molars. — Bicuspids crowned by the method de- scribed for incisors and cuspids will have greater strength if a portion of the lingual section of the natural crown is preserved (Fig. 176), because of the support it will afford to the collar which will cover it. The end of the root is capped after the manner of the typical central already described, one or two posts being used in the canals as required. Where only one post is used, it is best inserted in the lingual canal. If desired, a "bite" impression is then taken and models made. A Fig. 324. Fig. 325. Pig. 326. Fig. 327. Fig. 328. porcelain cuspid tooth, or a bicuspid facing is then ground, backed and adjusted on the cap to represent the labial aspect, and secured with wax. It is carefully adjusted in the mouth and the occluding edge of the porce- lain ground to clear the antagonizing teeth (A, Fig. 324). To Form a Cusp-cap. — A cusp-cap is made by one of the methods described in Part III, Chapter VII. The preferable method — No. 6 — is to form a wax model of the cusp-cap and cast it, especially if the oc- clusion is abnormal. When a cast cusp-cap is used, all or a portion of the coronal section of the crown to the floor of the cap maybe addi- tionally included in the casting, as illustrated in Fig. 325. A cusp-cap may also be formed by stamping a disk of pure gold, gage No. 34, with a suitably sized die (Figs. 326 and 327), or by the use of a cusp- button — Method No, 4 — and reinforcing it with coin gold. GOLD COLLAR CROWNS WITH PORCELAIN FACINGS 189 The cusp-cap when formed is trimmed (P'ig. 328), ground and fitted to the occluding edge of the porcelain facing (Fig. 329J, in proper posi- tion as regards occlusion, and the wax attaching it is shaped to the contour of the crown (A). A piece of very thin pure gold plate gage No. 40 or Mo 00 platinum foil (B) is adjusted on each approximal side of the crown, which is then invested (Fig. 330). The long ends of the side pieces of metal are designed to retain them in position in the investment so that the investment may be removed from the portion enclosing the sides of the crown (A). Mica (isinglass) may also be used as suitable for this purpose instead of gold or platinum. In the process of soldering the solder is placed in the aperture at B and the flame of the blowpipe directed under the investment, then on the exposed sides of the metal or mica at A. The solder is thus flowed into every part, forming perfect continuity of structure of the metallic portion of the crown. If the crown is short and the aperture at A is left open without the gold or mica, and the solder is first flowed in the interstices, as Fig. 330. Fig. 331. Fig. 332. described in soldering an incisor crown, the remaining solder necessary to contour the part can be added if the pointed flame is used and not too much heat applied to the other portions of the crown and investment. In finishing, the surplus gold is trimmed to the contour of a bicuspid tooth. Fig. 331 represents the finished crown. In difficult cases and occlusions the work is simphfied by first sold- ering the porcelain facing to the cap. The crown is then adjusted in the mouth and the porcelain ground to properly clear the occluding teeth and allow space for the cusp-cap, and the work then completed as described. This method produces a perfect and artistically formed crown, but simpler and quicker methods are practiced. One of these is to build up the palatal cusp with pieces of gold plate which have previously been melted into globules and flattened out on an anvil. These, laid in position and united with solder, are shaped in finishing to represent the lingual cusp (Fig. 332). The porcelain facing should be backed so that the solder can be flowed over its occlusal edge. I go CROWN-, BRIDGE-, AND PORCELAIN-WORK Another method is to extend the palatal part of the collar down, as shown in Fig. 333, and then fill in the space and form the sides and occlusal surface with solder. In finishing, the gold is trimmed to the form of the crown. As much as possible of the natural crown should be left at the palatal side of the collar, the exposed occlusal edge of which may be slit and brought in against the side of the tooth, and soldered to give contour. With this form of collar one post in the lingual root-canal is sufficient. The end of the post should be allowed to extend out of the floor of the cap enough to just touch the lower teeth when they are occluded. The exposed end of the post will be an exact guide as to the quantity of solder required to form the occlusal surface. In this and in the method previously described, the porcelain facings may be soldered and the lingual cusp formed in one investment. The method of construction of molar crowns with porcelain facing is similar to that of bicuspids (Fig. 334). Inlajdng Porcelain Facings in Gold Crowns. — In this method the porcelain facing is inlaid or set after the construction of the gold crown. The crown used may be either seamless or one constructed in sections, but the seamless crown is preferable. Fig. 333. Fig. 334. Pig. 335. Fig. 336. Fig. 337 Application to a Seamless Gold Crown. — A seamless gold bicuspid crown will be used to explain the method. The crown is fitted to tooth or root and the occlusal surface reinforced, using Corona gold and solder — preferably hard solder — and boiled in acid to remove all flux. (See Fig. 387.) The crown is adjusted in the mouth and a mark made with a pointed instrument on the labial face of the gold to indicate where the porcelain facing is to appear (Fig. 335). The crown is removed and the marked piece of gold is cut out with a saw or a knife-edged wheel (Fig. 336), and the edge of the gold beveled to receive the facing when backed (Fig. 337). Grind the facing (Fig. 338) to accurately fit the space (Fig. 339). Next back the facing with pure gold, gage No. 36, extend- ing the gold just over the edges, annealing and burnishing, or swaging, to secure accurate adaptation (Figs. 340 and 341). Trim backing to one-sixteenth of an inch of the edge of the porcelain. Adjust facing and backing in crown and attach the backing to the crown by flowing wax along the seam at the edge of the backing inside and outside the GOLD COLLAR CROWNS WITH PORCELAIN FACINGS igi crown. Next remove the porcelain facing, leaving the hacking attached to the gold crown. Invest as shown in Fig. 342, paint exposed surface of the backing with rouge, and solder the edges of the backing to the gold crown, using as little solder as possible. Shorten the pins in the porcelain facing, insert it in position in the backing (Fig. 343) and slit the ends of the pins. Invest, as indicated in section in Fig. 344, and unite pins to backing by doing the soldering on the inside of the crown. A ver> small quantity of 14-carat or very easy-flowing solder filings should be used, the investment well heated and solder fused with a small pointed flame. Fig. 339. Fig. 342. Fig. 343. Pig. 340. Pig. 341- Fig. 344. Fig. 345- This last described soldering may also be done by wrapping the crown in asbestos paper, winding around it a wire and suspending in a Bunsen flame (Fig. 345). In finishing, remove surplus edge of backing around the porcelain, burnish, trim and polish. Inlaying Porcelain Facing in Sectional Crown. — The occlusal surface of the gold crown should be made of gage No. 36 to 38 pure gold, rein- forced with coin gold and united to the collar by sweating or with hard- flowing solder. The constructive details of the inlaying of the porcelain facing are similar to the method already described except that the pins of the facing are preferably first soldered to the backing. The facirig and backing are inserted in position in the crown, the edge of the back- ing attached all around with wax, both inside and outside of the crown, and the crown invested. The soldering of the seam around the facing 192 CROWN-, BRIDGE-, AND PORCELAIN-WORK is more safely done by investing so as to expose and solder only one-half of the seam first, then reinvest and do the other half. A Faulty Method of forming bicuspid crowns, especially in a close occlusion, and therefore one to avoid, is the shaping of the lingual side, as shown at W, in Fig. 346. The occlusal surface should be shaped so that the cusp of the occluding tooth shall be interlocked in occlusion, as illustrated at R, instead of glancing off. In the latter event, the root is liable in time to be forced outward and loosened. Crowning in Cases of Abrasion. — In a case of extensive abrasion of the incisal edges of the anterior teeth with vital pulp considerably calcified in the coronal section, crown-work to restore the length and form of the teeth is best performed by removing a portion of the labial aspect in the preparatory operation of trimming the natural crown (Fig. 347), and forming the artificial crown similar to a gold collar crown with a porcelain facing without a post. Fig. 348 gives the outline of the Fig. 347. Fig. 348. Fig. 349. Fig. 348. — RC, root cap; SS, soldered section. Fig. 350. construction of such a crown. If a case having the natural crown worn down very short should suggest the necessity of a post, a short one can be inserted between the line of the pulp-chamber and the lingual wall. In case the tooth is pulpless, the canal can be opened and the post extended into the root. The incisal edge of the porcelain should be well protected by the use of clasp gold and solder instead of the ordinary gold plate. When an incisal surface of considerable thickness is suggested, it is best built to the desired length after the first protecting piece has been soldered, by applying successive layers of plate rolled thin, of the size of the incisal edge, each being perforated with two or three holes with punch forceps, so that the solder shall more easily flow between and unite them. (See article on "Gold Tips," Part III, Chapter XVIII.) Gold Crowns with Porcelain Facings for Teeth with Vital Pulps. In the anterior teeth, in a case of atrophy, erosion or where decay has destroyed the approximal sides of a tooth in such manner that crowning GOLD COLLAR CROWNS WITH PORCELAIN FACINGS 193 is considered desirable, the pulp is frequently found unexposed and in a normal condition. Its preservation in such a case is desirable. The crowning of such teeth with gold jacket-crowns, carrying a por- celain facing attached with solder is generally a questionable procedure, unless considerable calcification of the pulp exists, as the room required for the gold and the small space left for the porcelain, together with the difificulty of securely attaching the latter, renders such a construc- tion impracticable. Jacket-crowns for such cases are best made of porcelain. (See Part VI, Chapter VII.) When calcification of the pulp has progressed so as to permit con- struction of a crown with gold and porcelain, the natural crown should be reduced as much as possible, especially on the labial side. It is then capped, as outlined in section Fig. 349, and a porcelain facing ground, fitted and adjusted on the gold cap. The facing is then soldered to the cap and the cap reinforced, as seen in Fig. 350. 13 CHAPTER XI THE GOLD SEAMLESS CAP-CROWN SYSTEM SEAMLESS ROOT-CAPS FOR INCISOR, CUSPID AND BICUSPID CROWNS WITH PORCELAIN FACINGS — IMPRESSIONS AND DIES — METHOD OF STAMP- ING SEAMLESS METAL CAPS — ALL-GOLD SEAMLESS BICUSPIDS AND MOLARS — ALL-GOLD SEAMLESS INCISORS AND CUSPIDS This method consists in the use of a gold seamless cap for the con- struction of the required root-cap or crown. Through improved methods seamless root-caps and crowns can be used by those versed in the method, to largely answer the purposes of caps constructed in sections. Seamless Root-Cap for Incisor, Cuspid and Bicuspid Crowns with Porcelain Facing. — The advantage of this style of cap is simplicity, as the formation of a collar is avoided. Fig. 351. Pig. 353. For a seamless root-cap the natural crown is ground down to within one-eighth of an inch of the gum at the lingual wall, or enough to fully clear the antagonizing teeth when occluded, and slanting from the lingual side of the pulp-chamber to or slightly under the cervico-labial edge of the gum. The periphery is shaped the same as for a collar crown. For a partial seamless root-cap, which avoids extension of the collar around the cervico-labial section (Fig. 351), that side of the root is left intact, as shown at A, Fig. 352. Impressions and Dies. — A die of the end of the root is first made. For this purpose an impression is taken in a tube about an inch long formed of a strip of copper, or in a ready-made tube such as are sold for the purpose. The tube must be the size of the end of the root. 194 THE GOLD SEAMLESS CAP-CROWN SYSTEM 195 It should be first cut and shaped to the curve of the gum so that the edge fits uniformly well under the free margin, especially at the lingual side (Fig.353). The impression is best taken with impression compound. It should be heated, the tube entirely filled with the compound and the end to take the impression, again heated sufficiently to render that part of the compound very soft just before being applied to the root. The tube is then adjusted and pressed to position on the root, held firmly, and the extra compound which has been forced out of the other end of the tube pressed on by the finger and so held with the tube in position, until the compound cools. The cooling may be hastened by applying a stream of cold water with a syringe. When the tube is removed the impression of the root end will be found proportionately as perfect as an impression procured for the formation of an inlay by the indirect method. Form the die of amal- p^^ am and the result will be as near an approach to a^bsolute accuracy in detail as it is possible to procure. The amalgam must be thoroughly mixed and carefully packed, as described in Part I, Chapter V, and allowed to set until the next day. Plaster may be used instead of impression compound to take the impression in the tube and the die cast immediately of fusible metal, but it will lack the accuracy in detail obtained by the previous method with amalgam. The die when removed from the impression should be lengthened by removing from the cervix about one-eighth of an inch of the shoulder of metal formed by the edge of the im- pression tube (shown at T, Fig. 354), to the dotted line marked L. The lengthening should be ac- complished without altering or marring the die in the slightest degree. The trimming is preferably Fig. 355. done with a chisel resting against the side of the die, pointed in a downward direction toward the shank, then smoothed with a file. A fissure bur also assists in remov- ing surplus metal. The bur should be positioned at a right angle to the shank and revolved so that it will be thrown downward on the shank instead of upward on the die. The die is next mounted in a swager cup, as outlined in Fig. 355, and described in Part I, Chapter V. As the fine lines of an amalgam die would be impaired by the preliminary shaping of the cap, a duplicate in fusible metal should be made and first used to shape the cap and then the amalgam die to 196 CROWN-, BRIDGE-, AND PORCELAIN-WORK give it the finish. To do this quickly and easily, press the mounted amalgam die down into the surface of a flat piece of moldine, remove and place the cup of the s wager over the mold and fill the cup with fusible metal through the hole. Method of Stamping Seamless Metal Caps.^ — The gold plate gen- erally used for seamless caps is 22 carats, or platinized gold 23 carats, termed non-oxidizable gold, gage No. 29 to 30. The gold plate is first cut in a circular piece by a disk cutter. It is next pressed through a steel die-plate with punches gaged to the holes. Each time the disk is punched only a small portion of the gold is turned over, thus preventing it from lapping or creas- ing. A properly constructed press should be used for the purpose, such as is illustrated in Fig. 356. The cap (A, Fig. 355) is annealed and swaged on the die to the typical form B. The palatal portion of the cap should be allowed to go well up under the free margin of the In the process of adjustment, Fig. 356. Fig. 357. Fig. 358. Fig. 359. edges that fit under the gum should be marked and trimmed as directed in describing the construction of a collar crown and then burnished close to the sides of the root and into the orifice of the root-canal, forming a perfect-fitting seamless cap (Fig. 357). In cases of partial caps not all the gold at and over the cervico-labial edge should be removed until the post has been soldered. An iridio-platinum post is next fitted in the root-canal and soldered to the cap (Fig. 358) as in the construction of the gold collar crown with porcelain facing (Chapter VIII), with which operation the remainder of the process of construc- tion is identical. Fig. 359 represents the completed crown in section. All-gold Seamless Bicuspids and Molars. — All-gold seamless crowns for bicuspids and molars that will accurately fit the natural THE GOLD SEAMLESS CAP-CROWN SYSTEM 197 crown and root and occlude properly with the antagonizing teeth are formed as follows: The natural crown is jjroperly prepared. If de- cayed or broken down on the side, it should be shaped up with amal- gam (Part III, Chapter III). A copper tube — seamless or soldered — is accurately fitted to the prepared tooth. At the cervix it is placed the same distance under the gum margin as for a gold crown. An impression is then taken in compound and an amalgam die made (Part I, Chapter V). Lengthen the neck and taper the shank of the die. Take a wax "bite" and then an impression in wax or compound. If you intend to remove the die from the model veneer the shank with wax. Insert the die in the imprint of the tooth in the impression and run a plaster model. On removal of the impression the die will be found in position in the model an exact replica of the tooth in the mouth (Fig. 360). The wax "bite" is then adjusted and an articu- lating model made. Drill one or more holes in the occlusal surface of the die and do any necessary shaping or contouring of the form of the Fig. 360. Fig. 361. tooth with hard wax or, better still, oxyphosphate. A space should be left between the antagonizing teeth and the occluding surface, and between the approximal teeth the thickness of the gage of gold to be used (Fig. 361). An impression is taken of the amalgam die in a tube with moldine and a fusible metal die run. The die on which a gold cap is swaged should always be lengthened at the neck so that the crown when con- structed shall have a surplus in depth of gold to allow for any trimming of the collar that may be required (A, Fig. 362). A s wager is used as a counter-die or a counter-die (B) can be made by punching a hole in a block of lead and hammering the die into it. (See Part I, Chapter V.) The cap (A, Fig. 363), gage No. 29 to 30, is placed on the die, tapped with horn hammer to the general shape, and with the aid of the swager or counter-die swaged to the form of the crown (B). When a lead counter-die is used an allowance for the thickness of the gold should be first made by driving the die with two thicknesses of kid into the igS CROWN-, BRIDGE-, AND PORCELAIN-WORK counter-die to enlarge it. If this space is not made the gold is liable to be torn in the swaging. A piece of kid leather or rubber-dam should be used to cover and protect the gold cap in the swaging and facilitate its removal from the counter-die. The amalgam die is next divested of the wax or oxyphosphate contouring material which was added to its surface, and it is restored to the original form of the tooth in the mouth. The gold crown is then adjusted, trimmed to the curve of the gingiva at the cervix and burnished, and it is ready for adjustment in the mouth. The method described is the most approved. Another method is to fit a copper collar to the periphery of the root, take a "bite," then Pig. 362. Fig. 363. Pig. 364. an impression that will remove the collar in position, and run plaster models. When the models are made, slit and remove the copper collar. This gives a plaster form of the tooth, which is built up and shaped to the required form of the crown and the crown then made by it, as in the preceding method. All-gold Seamless Incisors and Cuspids.' — Incisor and cuspid crowns from which a portion of the gold on the labial aspect is to be removed (see Open-faced Crowns, Part IV, Chapter IV) or which are to be used entire as supports for bridge-work can usually be advantageously formed with seamless caps (Fig. 364). The necks of these crowns often have to be contracted in fitting by slitting, lapping and soldering. CHAPTERXII IMPARTING CONTOUR TO SEAMLESS GOLD CROWNS CROWNS SWAGED ON DIES — METHOD OF SLITTING AND CONTRACTING THE NECK — USE OF CONTOURING PLIERS — EXTERNAL APPLICA- TION OF CONTOUR — TO CONTOUR ON THE DIE WITH A SWAGER — SECTIONAL MOLD METHOD — FORMATION — SHAPING THE CAP Crowns Swaged on Dies Method of Slitting and Contracting the Neck. — Crowns for cases in which decay has extensively involved the approximal sides, owing to encroachment of the adjoining teeth, generally require very little if any contouring. It should be borne in mind that a swaged seamless crown at the approximal surfaces is always the thickness of the, gage of the gold cap larger in circumference. Some form can be imparted to a swaged straight-sided seamless crown by slitting the collar directly in the center of the lingual side, contracting the neck, tapering the underlapping portion, adjusting on the ^fc^ /^^ tooth, burnishing the gold, removing and soldering |: R ,:i|||i l/iMl (Fig. 365). This contraction also imparts a very i|||Pr ^ip^ close fit to the neck. When more contour is required pj^, ^65. than that obtained by the thickness of the gold plate that covers the die, the crown may be formed with the desired size and shape of occlusal surface and then slit and contracted at each of the approximal sides, fitted and soldered. Use of Contouring Pliers. — Contouring pliers are used to give form to a seamless crown sufficient to knuckle it against the adjoining teeth, but the bulge that is imparted by this means is not located close enough to the occlusal surface, where it is most required. External Application of Contour.^ — Contour may be added to a seamless gold crown by soldering so as to knuckle in a very accurate form to an adjoining tooth or teeth as follows: When the gold crown has been fitted and articulated heat the crown and veneer the approximal surfaces with sticky wax. Soften two pellets of adhesive wax and press and shape them against the sides of the gold crown. Adjust the crown on the tooth and press both crown and wax to position and occlude teeth. Remove and trim wax to exact form of desired contour. Place 199 200 CROWN-, BRIDGE; AND PORCELAIN-WORK over the surface of the wax representing the approximal surfaces a layer of platinum foil ^^ooo> as marked PF, Fig. 366. Reinsert crown in mouth, occlude teeth and remove. Invest crown, leaving occlusal surface of wax exposed as shown in Fig. 367. Burn out wax or remove with hot water. Pack pellets of Corona gold between the crown and platinum foil to prevent the foil being drawn from position in soldering. Heat and flow solder or coin gold if cap is made of platinized gold, into the space occupied by the Corona gold, between the crown and the platinum foil, trim and polish. This method gives a close, accu- rate knuckling for a seamless crown or any form of constructed crown to which it is applied. Coin gold or hard solder should be used to contour when the crown is to support bridge- work, so as to jnaintain the form of contour in subsequent soldering. In the case of a single crown, 20-carat solder is suitable. To Contour on a Die with a Swager.— A seamless crown may be given a moderate amount of contour on the swaging die in the follow- ing manner : Form a model of the crown with the addition of the required Fig. 367. — SS, spaces to be filled. contour, take a plaster sectional impression formed longitudinally in halves (See Part I, Chapter IV), and cast a die of fusible metal that melts below the boiling point of water. Place oyer the die a tight- fitting seamless gold cap, swage the occlusal surface if a bicuspid or molar, then mallet and burnish the gold lengthwise as closely as pos- sible to the die. Next mount the die in a swager by inserting the base in impression compound (Fig. 368). Swage the gold cap to the sides, using moldine or fine shot in the swager. When the swaging is com- pleted, remove the die from the crown by placing it in boiling water to melt out the fusible metal. Should any of the metal adhere to the gold, remove it by placing the crown in nitric acid. Sectional Mold Method. — The artistic requirement of all-gold crown-work is that it shall reproduce the anatomical contour of the natural teeth. Such a form can be given seamless gold bicuspid and molar crowns by the sectional mold method (Figs. 369, 370 and 371).^ iThis is the style of molds as originally introduced by the author in 1888. IMPARTING CONTOUR TO SEAMLESS GOLD CROWNS 201 Formation. — To describe and illustrate the process, fit a collar of copper, No. 30 gage, knucl. The pins should be inserted and soldered one at a time in the gold or platinum plate which has been fitted to the abraded incisal surface of the tooth, the plate being readapted each time. Tht first pin, if fitted tightly in the hole through the plate, may be soldered without investing, but an investment should be made for the soldering of each subsequent pin, as otherwise the previously soldered pin or pins are liable to be moved from correct position. The least possible quantity of solder should be used on the first two pins. After all the pins have been soldered in position in the plate, it is adjusted on the Pig. 464. 234 CROWN-, BRIDGE-, AND PORCELAIN-WORK tooth and the gold very carefully burnished with revolving burnishers to its surface, trimmed, and the ends of the pins cut off so that they just touch the antagonizing teeth when occluded. The floor is next shaped up with wax and a matrix formed, as previously described, invested and the matrix filled with solder. The gold tip is then finished and cemented. In a case with a vital pulp or in a pulpless tooth, if the gold tip required is very short, the ends of the pins extending above the plate will hold and maintain enough solder in position to furnish material for proper contouring without enveloping the wax model with a matrix of gold or platinum foil. Another method^ of building the tip to any required length is: Having made and invested the plate with the three pins for the abraded surface of the tooth (A, Fig. 465), roll down a piece of solder very thin. Fig. 465. Fig. 466. Pig. 467. about gage No. t,t, to 34, cut it to the size of the plate and punch holes in it for the pins to protrude through (B). Next cut a piece of 20 or 22-carat gold plate or clasp gold to the same size and also punch holes in it for the pins in the same manner as for the solder (C). Place the solder on the plate and the supplementary plate over the solder, and apply the broad flame of the blowpipe. When the solder melts, the supplementary piece of plate will settle into position. If one piece of plate does not give sufficient length to the tip, attach in the same man- ner another layer of gold solder and plate. When extreme hardness is required, use clasp gold instead of plate. If three pins are used, it is very seldom necessary to extend the plate for stability beyond the incisal surface over the lingual side of the tooth. A slight depression in the incisal surface may be formed if it does not already exist in the central part between the pins, as shown in section in Fig. 466. This depression aids in steadying the finished tip. 1 Dr. Milton Smith's method. PARTIAL CROWN-WORK 235 Fig. 467 shows the reproduction of the occlusal surface of a molar by the methods described, in which three pins are inserted. Some cases of reproduction of the occlusal section may be done to advantage by the casting method. In such cases the matrix should be made of platinum, gage MooOj and the pins are best soldered with 15 per cent, platinum solder instead of pure gold. When pins are used to retain a gold tip in the reproduction of an occlusal surface, the matrix method is generally preferable. When the entire "bite" is to be opened, one tooth on each side should be first elongated and used to gage the space for the lengthening of the others. CHAPTER XIX PARTIAL CROWN-WORK, CONTINUED INDIRECT METHOD OF FORMATION OF INLAYS — COMPARATIVE MERITS — IMPRESSION MATERIALS — PROCESS — ^IMPRESSION TUBES, CAPS AND TRAYS — FORMATION OF TUBES AND CAPS — METHOD OF FORM- ING TRAYS AND TAKING IMPRESSIONS — INLAY DIES — INDIRECT INLAY WAX MODEL FORMATION — METALLIC MATRICES, INDIRECT METHOD Indirect Method of Formation of Inlays. — The construction of inlays by the indirect method differs from that already explained in that the work is done on a model instead of directly in the mouth. Comparative Merits. — In the direct method the labor of taking an impression and making a die and models is avoided and accuracy of the occlusion in the finished inlay is assured. By the indirect method the formation of the wax inlay model is comparatively simplified, especially in positions difl&cult to reach in the mouth. In removal of the wax model, distortion of the body or edges is less liable to occur, a matter difficult or impossible to correct in the cast inlay. Any slight discrepancies in the cast inlay are more easily detected and corrected by the metal model than they can be in the mouth. As articulating models can seldom be depended upon as absolutely correct, inaccuracies of the occlusal surface are more liable to occur in their use than when made directly in the mouth. Such inaccuracies call for alterations which are not always as easily made with gold as with porcelain and which at times destroy the sulci and cusps which have involved labor and skill in their formation. Impression Materials. — Inlay impression compound that softens at a low temperature, hardens quickly and reproduces the smallest details of form, is used for taking inlay impressions in preference to gutta-percha or any of the other materials and preparations formerly used. Process. — The impression compound is softened by dry heat to a doughy consistence, the proper quantity is then placed in a cap, tube or tray with a cone-shaped extension to press into the cavity. Just before the impression is taken the cone and the surface of the compound 236 PARTIAL CROWN -WORK 2.37 are additionally softened by holding above a flame for a moment.. The softened part, especially the cone, is then more easily pressed into the cavity and the harder part back of it offering greater resistence forces the soft portion forward. The surplus compound that is forced out of the rear end of the tube or cap should be pressed back at once, forming a piston to drive the soft portion into the cavity and onto and over its edges. An impression should be allowed to remain in position before removal until the compound is hard. The hardening may be hastened by the application of cold water or a draught of cool air. Impression Tubes, Caps and Trays. — Various forms of small im- pression tubes, caps and trays are given preference for gold and por- celain inlay impressions. The use of caps and tubes is confined to those cases where the impression is inserted and removed in an incisal or occlusal direction, such as approximal-occlusal, occlusal and incisal Pig. 468. cavities. Trays are used generally, but especially for cervico-Iabial and buccal cavities and such approximal and other positioned cavities as require the impression to be removed in a more or less lateral direc- tion. In the use of tubes and caps, the metal partly or entirely sur- rounds the tooth, and with trays, only fits over the cavity and adjacent portion of the crown. In the use of either form, the metal when trim- med should always be allowed to entirely cover the cavity and extend beyond the margin at least one-eighth of an inch on the surface of the crown and one-sixteenth of an inch on the root at the cervico-approxi- mal section. Formation of Tubes and Caps. — These are generally made of copper No. 32 or thinner, and when annealed are very flexible. (See Part I, Chapter V.) The tube or cap used should be one selected or made which will closely fit over and encircle the tooth. Fig. 468 represents, in section a tube fitted to a molar. The dotted line indicates the position a cap would take if used instead of a tube. Fig. 469 illustrates the Roach im- pression cup or tray with a hole for a detachable handle. The cup 238 CROWN-, BRIDGE-, AND PORCELAIN-WORK should be bent and trimmed to the form of the tooth and requirements of the case, the same as a tube would be. Pig. 469. Methods of Forming Trays and Taking Impressions. — Trays are generally made to meet the special requirements of a case. German silver plate or an alloy of nickel and silver termed platinoid, about No, B Pig. 470. 30 gage, is very suitable. The plate is cut and bent to fit the approxi- mal space and side or sides of the crown, or to cover only the cavity and a portion of the crown, as in cervical and occlusal cavities. PARTIAL CKOWN-WOKK 2.39 A simple labial cavity/ as illustrated at A, Fig. 470 will be used as a typical case to explain the formation and use of a tray. A strip of platinoid is cut to the shape shown at B, and perforated with a plate- punch to aid in retaining the impression compound. A small piece of the compound is softened over a flame formed in a cone on the tray, as shown at C, the tray being first heated sufficiently to secure good adhesion. The cone is then partly chilled by dipping it in cold water, after which the point of the cone is softened by holding for a moment in a flame and then quickly carried to, and pressed into the cavity with the index finger resting against the lingual side of the tooth, while the thumb carries the compound to place, as shown at D, and holds it rigid in position during the cooling. When occasion re- quires, the position of the fingers may be reversed. The removed im- pression is shown at E. Fig. 471. The hardening of the compound may be hastened by cold water. If the cavity has been properly prepared, the tray correctly shaped and the compound suitably applied, the impression is usually dislodged without much difficulty. The imprint of the cavity and margins should be sharply defined. Rough places indicate either faulty shaping of the cavity or imperfections in the impression. In cervical cavities extending under the gingival margin it is ad- visable to first prepare the cavity for the inlay, pack it with gutta- percha and press back the gum for a day or two before taking the im- pression. In such cases the tray should be shaped and curved so that, if necessary, one edge may be forced up under the gum between the soft tissues and the concealed margin of the cavity. The compound is attached to the tray, leaving the extreme edge exposed, or nearly so, and the edge introduced beyond the concealed margin of the cavity before the tray is pressed down. In cases where there is convexity of surface, such as is illustrated at A, Fig. 471, the metal is cut and bent in forming the tray to accurately fit over the tooth surface as shown at B and C. 1 Dr. F. T. Van Woert's method of formation is here presented. 240 CROWN-, BRIDGE-, AND PORCELAIN-WORK Fig. 472. Fig. 473- Fig. 474. PARTIAL CROWN-WORK 241 When a cervical cavity extends around the approximal side, as illustrated at A, Fig. 472, the metal should be cut and the tray shaped as shown at B and C. In cases of molars, as illustrated at A, Fig. 473, the tray is formed and impression taken, as shown at B, C, D and E. Fig. 475- For a cavity wholly in the distal surface of a molar with space posterior to it, as shown at A, Fig. 474, the tray is shaped and impres- sion taken, as shown at B, C, D and E. The taking of approximal cavity impressions in trays is more complex 16 242 CROWN-, BRIDGE-, AND PORCELAIN-WORK than those just explained. Fig. 475 shows a cavity in the labial ap- proximal surface of an upper central incisor. The tray is shaped, as shown at A. Only enough metal is used to completely cover the mar- gins of the cavity and thus avoid injury to the tissue by overhanging edges of the compound, which will interfere with removal of the im- pression. The surface of the compound is quickly heated and placed in the cavity, as shown at B, and a small cement spatula is forced be- tween the outer surface of the tray and the adjoining tooth. Fig. 476. After cooling and before removing the spatula, any excess of the compound that may be forced through upon the lingual side, as shown at C, should be cut away with a lance. The spatula is first removed and then the impression. A spatula forced in as described, on being removed, furnishes a slight space for displacement and removal of the tray. In the lingual approximal surface (Fig. 476) a similar tray (A) is used but it is bent end curved to fit the lingual surface. When the impression is taken, it is pulled to place (B) and a bent spatula (C) PARTIAL CROWN -WORK 243 is inserted from the lingual side. Its further treatment is identical with the previous case. Approximal cavities involving both the labial and lingual surfaces, such as is shown in Fig. 477, present complications as the impression cannot be removed in one piece but must be taken in a tray formed in two sections. The first is like that shown at A; the second is cut in shape as depicted at B, and bent as at C. This should fit the first section closely without lateral motion, yet slide up and down freely (D). The impression is taken by introducing the compound lingually on the firstjsection (E). The spatula should be held in place by an assist- 244 CROWN-, BRIDGE-, AND PORCELAIN-WORK ant at the angle shown, so that it will not interfere with the second part of the tray, when it is subsequently forced to place. The surplus compound is next removed and that remaining carved to the contour of the labial surface and flush with the cavity margin, as shown at F. The surface of the tooth and the carved impression are coated with vaselin. The second section (C) is prepared by attach- ing to its surface a small quantity of impression compound but not Fig. 478. enough to press beyond the margins of its attachment. The compound is heated and this second section is slipped over the first section (F) and pressed to place as shown at G. When chilled the second section is first removed, the spatula next and then the first section. After removal the parts are adjusted together and fastened with adhesive wax. If properly performed the result will not exhibit a perceptible seam. This sectional method is applicable to a variety of cases. Fig. 479- Fig. 478 shows the form of a tray and method of shaping suitable for an occlusal cavity extending into the buccal region. Fig. 479 shows a distal cavity in a molar and the formation of a tray suitable for it. For cavities in the mesial approximal surface, the tray described for the distal approximal surface is to be bent over on itself as seen in Fig. 480. When a cavity includes the occlusal, buccal and both approximal surfaces, a tray slightly more intricate, such as is shown in Fig. 481 is PARTIAL CROWN-WORK 245 req\iired. The main part of the tray is first bent to fit the distal and lingual sides as has been shown in Fig. 479. Next a piece of plate is cut and bent as shown at A and B, Fig. 481, and soldered to the first or main part as illustrated at C. Fig. 482 shows a tray for a bicuspid where the cavity involves the mesial, occlusal and distal surfaces. The metal is cut and bent, as Pig. 480. seen at A, B and C, to form the tray, which is applied from the buccal side. Fig. 483 shows an upper central prepared for a porcelain or gold contour corner restoration. A, B and C show the formation of the tray and D the tray and impression. When the cavity is deep-seated, as shown by dotted line in Fig. 484, the cavity is first filled with a cone of the impression compound A, and pressed in as seen at B. The surface of the cone is then heated Fig. 481. with a hot spatula and the impression is taken as in the previous case. When the impression is removed, it appears as though in one piece (C). Before inserting the cone plug, slightly vaselin the cavity to aid removal. In cases of extensive restoration of the incisal end of a pulpless tooth, represented in Fig. 485, an iridio-platinum post is fitted to the proper depth in the canal and the protruding end flattened. The post is heated, surrounded with a cone of the impression compound A, and pressed to place as in the previous case. The remainder of the impres- 246 CROWN-, BRIDGE-, AND PORCELAIN WORK B ^^ V_ Fig. 482, / Fig. 483. PARTIAL CROWN-WORK 247 sion is taken in a loose-fitting tube or cap, B and C. Before pressing the tube or cap to place with the impression compound, the end of the post and also at the same time the exposed surface of the compound should be heated with a very hot spatula. B Pig. 484. In cases of similar restoration for a vital tooth two or three pins of platinum wire, about No. 20 or 21 gage, should be fitted closely but easily in holes drilled parallel on each side of the pulp, at right angles to the incisal edge, as shown in Fig. 486. The impression is taken in a Fig. 485. manner similar to the case in Fig. 485, the pins being drawn in the compound. Inlay Dies. — Various materials have been recommended for the formation of dies for inlay work. Practical experience suggests amal- gam as the most suitable. A silver-tin^ or copper amalgam is most used. 1 S. S. White True Dentalloy is of this form. 248 CROWN-, BRIDGE-, AND PORCELAIN-WORK The silver-tin amalgam is preferred to the copper, as it hardens quickly. The copper amalgam is less expensive as it can be used several times. (See Part I, Chapter V.) The die should be inserted in a wax or compound impression of the tooth and the adjoining teeth, with "bite" and plaster models made from which the die may be removed and replaced. The shank of the die should be tapered and veneered with wax to permit easy withdrawal from the plaster model. Indirect Inlay Wax Model Formation. — The process of wax model formation from a model is the same in principle as the process in the mouth. The die may be removed from the model to facilitate the work and replaced again in the model to accurately determine the Pig. 486. contour, also the form of the occlusal surface, by closing the articulat- ing model on the wax. Should the wax become chilled during the operation, the model and wax in position may be immersed for a while in tepid water of about 110° F. The sprue wire is best inserted in the wax model while it is still in the die. The whole is then chilled and the wax model removed. Metallic Matrices, Indirect Method.^MetalHc matrices are shaped on an amalgam model as in the mouth. Any post or pins present in the model are to be attached in position with wax to the matrix, invested and soldered to it. The wax model is then formed and cast in the matrix. For further descriptive details and use of a swager to shape a matrix, see Part VT, Chapter VI. CHAPTER XX SPECIAL OPERATIONS IN CROWN-WORK CROWNING MOLAR ROOTS DECAYED APART AT THE BIFURCATION — CANII- LEVER CROWN — METHOD OF CONSTRUCTION — METHODS OF CROWN- ING IN CASES OF IRREGULARITY Crowning Molar Roots Decayed Apart at the Bifurcation.— The roots of a molar decayed apart at the bifurcation can often be crowned serviceably. The roots having been treated the ends are trimmed and paralleled, the one to the other, giving the sides a slightly tapering form. Platinum collars No. 38 gage are made and fitted to each root, reinforced with pure gold, floors added and the two caps soldered together (Fig. 487). An occlusal cast section can then be added. The most serviceable method of restoration in such cases is accomplished with platinum and porcelain. (See Part VI, Chapter VIII.) Pig. 487. Pig. Pig. 489. In cases of pyorrhea alveolaris, when the buccal roots of a first superior molar are only slightly affected but the connective tissue of the palatal root is nearly or entirely destroyed, — a condition impossible to treat successfully, — ^the usefulness of the tooth may be retained in part by the removal of the palatal section of the crown and with it the root. The buccal roots having been treated and filled, a fissure bur is inserted in the pulp-chamber, and the crown cut in half mesially and distally through its center. The palatal half of the crown and the palatal root are then removed. The buccal half of the pulp-chamber is shaped (Fig. 488) to retain either a gold inlay or an amalgam filHng, or preferably a porcelain inlay such as will give form to the part as illustrated by Fig. 489. In case of extensive decay being present, cap- ping with metal may be resorted to. 249 250 CROWN-, BRIDGE-, AND PORCELAIN-WORK Cantilever Crown. — A cantilever crown is one with a lug on the side which rests on but is not connected to an adjoining tooth or crown, for the purpose of bridging a small space. Fig. 490 shows the applica- tion of a cantilever crown set upon a second bicuspid with a lug that bridges the space formed by the loss of the first bicuspid and resting on the cuspid so as to connect the broken line of masticating surface and prevent tilting forward of the second bicuspid. Fig, 491 illustrates the application of two cap-crowns which are constructed so as to form Pig. 490. Fig. 491. Fig. 492. a cantilever bridge over a small space, in such a manner as to prevent tilting or sliding of surfaces and at the same time be easily cleaned with floss silk. A single root of a lower molar may be capped with a lug extending to and resting on an adjoining tooth in the manner described in either of these cases. Method of Construction. — A lug such as has just been described to span a wide interdental space is conveniently formed by first attach- ing the edge of a piece of platinum plate about gage No. 30 to the side Fig. 493. of the gold crown with wax or solder. The crown is then fitted in the mouth, the platinum bent and burnished over on the adjoining tooth or crown, as shown in Fig. 492, and removed. The space A is filled with wax and the crown invested. The wax is removed with boiling water, the aperture A,filled with gold foil or Corona gold to prevent contrac- tion of the platinum by the solder, heated and soldered. The surplus metal is trimmed away, as indicated on adjustment in the mouth. SPECIAL OPERATIONS IN CROWN-WORK 251 Method of Crowning in Cases of Irregularity. — Fig. 493 represents a case of irregularity as treated by Dr. Bonwill. On account of the poor character of the teeth, their position in the palatal arch and the age of the patient, it was considered beyond correction. Fig. 494 shows a method of treating a case of irregularity without destroying the vitality of the pulp.^ The tooth at B which stood inside Fig. 494. the line of the lower teeth when the mouth was closed, was trimmed, shaped and capped without removing the pulp. To this cap was attached the tooth A, with an oval-shaped piece of gold for cleanliness that cleared the lower teeth in occlusion. The cap, which was then cemented over the natural crown, was entirely hidden from view by the artificial tooth or porcelain facing. 1 Case of the author's. CHAPTER XXI TREATMENT BY CROWN-WORK OF FRACTURED TEETH AND ROOTS FRACTURED CROWNS AND ROOTS — LONGITUDINAL FRACTURES — SLANT- ING FRACTURES — ^INLAY CASTING METHOD — USE OF A CAST OF A FRACTURED PORTION — AMALGAM — POST AND AMALGAM Fractxired Crowns and Roots. — The fracture of teeth or roots is caused either by a blow, or strain of mastication. Fractures are longi- tudinal or slanting. The longitudinal fracture passes lengthwise through the crown, dividing the tooth into two parts (Fig. 495). The slanting extends from the center or between the cusps to the side on the line of the cervix or beyond it. The crowning of fractured teeth or roots is an operation that re- quires skill and delicate treatment. Its practicability depends on the nature of the fracture, the present health of the parts and the length of time that has elapsed since the occurrence of the injury. Longitudinal Fractures. — Foreign substances having been removed from within and around the parts, the crevice of the fracture is syringed thoroughly with tepid saline solution and then with alcohol. The fractured parts of the root are drawn together and ligated with a piece of orthodontia wire fastened by twisting the ends. If considerable inflammation is present, allow the tooth to rest until the inflammation subsides. If there is no inflammation, or only a slight amount, immediately shape up the coronal section for the col- lar. Trim the sides to the inner line of the wire ligature, fit a copper tube, take an impression of the tooth in impression compound and make an amalgam die. If the condition of the fracture will permit, the liga- ture should be removed when the impression is taken, but, if not, allow it to remain and trim, also deepen the cervical shank of the die enough to remove the form of the wire. The root-canals should be opened, dried and heated with a current of hot air from a hot-air syringe and packed with a saturated solution of aristol and oil of cloves and sealed with gutta-percha. This treatment, with renewal of dressings, is to be continued until a sterilized condition is estab lished. The root-canals only are to be first filled and not the trunk of the pulp cavity where the fracture is. Use oxyphosphate instead of oxy- 252 CROWN-WORK OF FRACTURED TEETH AND ROOTS 253 chlorid of zinc in the filling of the canals if there is any danger of the oxychlorid invading the crevice of the fracture and causing inflamma- tion, which is usually the case. When the collar has been made, the ligature is removed, the collar fitted and the remainder of the artificial crown completed. When the crown is ready to insert, the fractured parts are again syringed with saline solution, then alcohol, and the cavity filled with cotton saturated with alcohol. The tooth is protected from the secretions, the cotton removed and the cavity dried with hot air. A quantity of copper oxyphosphate is mixed to the consistence of a thin cream, the fractured parts are slightly separated and the cement gently pumped into the crevice of the fracture and the cavity in the crown filled. A ligature is then instantly applied and made as tight as possible. As the parts are brought together, the surplus cement in the fracture is forced back into the cavity of the tooth. Any pressure the cement may exert against the pericementum is so slight that no serious or permanent inflammation is likely to follow. The tooth should not be disturbed until the cement has thoroughly set. The ligature is then removed and the finished cap-crown cemented in position. The intro- duction of the cement in the fracture, as described, shows better re- sults than when confined only to the cavity of the tooth, as by its presence the secretions are more effectually excluded. The cervical edge of the collar should be brought to a feather edge and thoroughly burnished to the sides of the root. The crown should be favored by leaving a very slight space between it and the occluding teeth. This space will gradually close in time and the tooth may be better able to withstand the force of occlusion. Another method in the case of molars with comparatively Pj^7497. straight root-canals is: With the ligature in position drill the root-canals as deep as possible parallel to each other; fit a post with a long end in each canal, wax and remove the posts together in position, invest and connect with a piece of plate, trim off the surplus ends, as shown in section in Fig. 496 and cement the posts in the roots. Cap with a closely fitted collar crown. Another method, if the dentin is strong enough to favor it, is to ligature the roots, drill two dovetail slots — one in each fractured sec- tion — and having filled the root-canals and the inner section of the pulp-chamber with cement, fill the slots with a hard, quick-setting amalgam (Fig. 497). In shaping the crown and roots for the gold collar, care should be taken not to loosen the amalgam splint. 254 CROWN-, BRIDGE-, AND PORCELAIN-WORK A great drawback in these cases is that the patient generally fails to present himself immediately for treatment, and foreign substances invade the fracture, causing infection and inflammation which is impossible to control. Even in the apparently most favorable case, subsequent to treatment a septic condition of the fracture usually super- venes in time, the irritation caused thereby and the exudations from the fracture compelling the patient to resort to extraction. Slanting Fractures.^ — Fractures of this form occur in bicuspids and molars where large fillings are inserted from the mesial to the distal side, leaving the separated buccal and lingual cusps to bear the brunt of mastication. The fracture seldom extends beyond the edge of the alveolar process. Fractures of this kind usually occur with pulpless teeth. The fractured part is removed. The hemorrhage is checked and the part anesthetized with cocain and adrenalin. If the fracture extends .:j Fig. 498. Pig. 499. Fig. 500. Fig. 501. Fig. 502. below the edge of the alveolus, the bone is removed to the line of the fracture. The canals are prepared for treatment and gutta-percha packed into the cavity of the tooth and the tissue pressed back to expose the surface and margins of the fracture. Inlay Casting Method.- — ^In the case of a bicuspid fractured as shown in Fig. 498, a large platinum or iridio-platinum post is fitted into the canal. The post is heated and veneered with adhesive wax. A pellet of inlay wax is softened and pierced with the post. The post is ad- justed to position in the canal, the wax adapted and shaped to the form of the lost fractured part and all removed. A sprue wire is in- serted in the wax form as shown in Fig. 499, and invested and cast with pure gold. The casting is then polished, the excess of post cut off and the inlay cemented to position with oxyphosphate. In such a case the cusps should be shortened by grinding to lessen stress in occlusion. CROWN-WORK OF FRACTURED TEETH AND ROOTS 255 Use of Cast of Fractured Portion. — Another method, where the fracture is of the form shown in Fig. 498, is to cast the removed frac- tured portion, then place and retain the cast replica in position by soldering it to a root post. The gold repHca of the fractured part is made by pressing the fractured side into the surface of impression compound; chilling, removing, trimming compound close to the edge of the impression, and forming the wax model, then casting. Fig. 500 illustrates a prepared fractured root with a casting for a porcelain-faced jacket-crown, and Fig. 501 for a gold cap-crown. Amalgam. — The preceding methods present an artificial restoration having a metallic surface only slightly oxidizable, which is not the case when amalgam is used and the surface is left exposed, even though polished. The use of amalgam is preferably confined to fractures which will be entirely covered with the collar; or to those that extend so far under the gum margin that a gold inlay cannot well be applied. Post and Amalgam. — A post in a root-canal reinforced with amalgam affords great security. Such an application in the restoration of a bicuspid for a porcelain-face jacket-crown is illustrated in Fig. 502. The post should be made of gold or platinum, with a globule of gold ^solder melted on the part that will rest in contact with the amalgam. The use of posts or screws made of alloys of the base metals is not permissible in these operations. When amalgam is used to restore a fractured root, the collar of the crown is supposed to cover it except in cases where the restoration is very deep and of a shape that is preferably left uncovered. CHAPTER XXII PROCESSES CONNECTED WITH CROWN- AND BRIDGE-WORK CORRECTION OF EXCESS OF SOLDER — TO SECURELY ATTACH A CROWN — IMPORTANCE OF REMOVAL OF FLUX FROM INTERIOR OF CROWNS —CORRECTION OF INTERFERING POINTS IN ADJUSTMENT AND OCCLUSION Correction of Excess of Solder. — To correct the accidental presence of solder on the inside of a gold crown, dry the surface of the metal and tooth with a wisp of cotton on the point of an instrument, and with the cotton paint the surface of the natural tooth or root, with a spat- ulated paste of rouge and oil and then adjust the crown. The inter- fering spot will be accurately marked on the gold. This should be trimmed with a small carborundum point and the crown again inserted to determine whether enough has been removed. If preferred, the paste may be placed on the inside of the gold crown. In that Vvay the Fig. 503. Fig. 504. interfering point will be marked on the natural tooth or root, which can be trimmed instead of the gold to permit proper adjustment. The latter method is more suitably appHed to pulpless teeth. To Securely Attach a Crown. — Cases present where the tooth is short and the occlusion of a character requiring the reduction of the collar to such a degree as to suggest insecurity when the crown is ce- mented. In such a case with a living pulp, a short barbed or headed pin that will anchor in the natural crown should be soldered in the center of the gold crown, as shown in Fig. 503. This is done by passing the pin from the cavo-surface through a hole drilled in the occluding surface of the crown and cementing with wax. It is then adjusted in the mouth, removed, invested and the pin soldered from the outside. In a pulpless tooth the pin may be extended into the pulp- chamber or a root-canal (Fig. 504). 256 CROWN- AND BRIDGE-WORK 257 Importance of Removal of Flux from Interior of Crowns.^Always boil a crown in acid to remove the flux. The removal of the flux from the cavo-surface of the crown is absolutely necessary if it is intended to be used in bridge-work, as solder will have to be melted on the outer surface of the crown. Correction of Interfering Points in Adjustment and Occlusion. In adjustment, especially of bridge- work, interfering points are indi- cated by veneering the cavo-surface of the cap or crown with a paste of rouge and oil. On adjusting the work the interfering point will be marked on the root or tooth, which should be trimmed accordingly. The method can be reversed by applying the rouge on the root or tooth. In occlusion use marking paper or apply the rouge and oil on a strip of paper and occlude the teeth on the paper. Another method is : Warm the occlusal surface of the crown and veneer it with a film of wax then occlude the teeth on the wax. (See Part IV, Chapter I, Adjust- ment and Insertion.) 17 CHAPTER XXIII CEMENTATION OF CROWN- AND BRIDGE-WORK ZINC OXYPHOSPHATE — METHOD OP MIXING — APPLICATION — GUTTA- PERCHA METHOD OP CEMENTING WITH GUTTA-PERCHA OR GUTTA- PERCHA CEMENT — METHOD OF MEASURING GUTTA-PERCHA — ^TO APPLY GUTTA-PERCHA IN THE FORM OF A FILM OVER A SURFACE TO CEMENT THE CROWN OR BRIDGE — FOR TEMPORARY INSERTION — ■ REQUIREMENTS FOR SUCCESS — OXYPHOSPHATE IN COMBINATION WITH GUTTA-PERCHA OR GUTTA-PERCHA CEMENT — SILICATE CEMENT — AMALGAM Zinc Oxyphosphate As a cement for effecting the proper union between the natural tooth or root and the artificial crown, zinc oxyphosphate is generally preferred and in many respects is the most suitable cement that has yet been found. If exposed, even the best preparations are slowly soluble in the mouth and the compound permits it to absorb gases and fluids and gradually become septic. At the present time to impart anti- septic properties to zinc oxyphosphate, compounds of copper are in- corporated by several manufacturers in a proportion of at least 25 per cent. A silver chlorid cement has been introduced by The S. S. White Dental Manufacturing Co., for which antiseptic properties are claimed. Exact scientific proportions of the chemical substances of which a cement is composed are essential in its preparation. The zinc oxid should be calcined at a high heat and then ground to an impalpable powder. Cement should possess the property of being uniformly dense and hard clear through the center when set, after being mixed thin and formed in a mass. The density of one preparation of zinc phosphate in comparison with another can be tested by placing samples of each of the same size, mixed under similar conditions, in red ink. After immersion for one or more weeks, the samples can be removed, washed, then cut through the center and their comparative density determined approximately by the depth of the stain. The setting of the best preparations of pure zinc oxyphosphate is materially affected by temperature. Thus, a cement which is slow- setting at 50° F. is liable to be quite quick-setting at 80° F. In some 258 CEMENTATION OF CROWN- AND BRIDCE-WORK 259 of the preparations of cement, an effort is made to remedy this variation by adulterating with various ingredients, but this tends to increase the solubility of the compound. A standard preparation of cement answering the requirements previously outlined should be used in crown- and bridge-work. Method of Mixing. — For all styles of crowns with collars and for bridge-work depending on crowns of similar construction, the cement should be mixed to the consistence of a thick cream, but for crowns without a collar or ferrule, it may be moderately thicker. For mixing the cement, a piece of plate-glass about five inches long and three inches wide as a slab, and a small spatula, are suitable. The surface of the slab should be perfectly clean, and the acid and powder separately //i dcCiud di^i Fig. 505. — One-half actual size. placed on the glass — the powder to the right and the liquid to the left — (Fig. 505), the quantity of the powder being fully equal to the require- ments of the acid. A portion of the powder should be drawn over and mixed with the acid and then more of the powder added, a little at a time, until a suitable consistence — which is that of a thick cream — is reached, when the surplus powder should be instantly pushed aside and the mixing, which must be rapid and thorough, continued. It is not a good plan to mix cement excessively thin and then wait until it becomes thickened by the process of setting to a consistence suitable for use. The resulting compound is unnecessarily acid, the overplus of acidity being proportioned to the excess of acid used over the quan- tity required, and its character as a cement impaired. On the other hand, if mixed too thick, force is required to bring the crown or cap to position^ and the thin edges of collars are liable to be sprung from the 26o CROWN-, BRIDGE-, AND PORCELAIN-WORK sides of the roots; neither will the cement adhere with such tenacity to the parts as when mixed to a proper consistence. If the slab is placed on a towel that has been saturated with ice water, the cold will re- tard the setting, which is quite advantageous in many cases, especially in the use of quick-setting preparations of oxyphosphate. In this respect the sides of a square glass bottle filled with tap, or ice water, and well corked has its advantages as a mixing slab in hot weather. Fig. 506 is a bottle with a thermometer inserted to indicate the temperature.^ In cementing a collar crown it is always preferable to have the cement mixed a trifle too thin rather than too thick. This should be borne in mind, as the adjustment of many a well-fitted crown is im- paired by having the cement mixed too thick. Application. — If the gum-margin has been slightly lacerated and is inclined to bleed, adrenalin or adrenalin and cocain should be applied Fig. 506. for a few minutes. The parts to be crowned are then syringed with tepid water, protected by a napkin, bathed with alcohol applied on cotton with tweezers and dried with absorbent cotton or bibulous paper. In cases where the prepared teeth or roots have been exposed to the action of the secretions of the mouth for one or more days during the construction of the work, before its final insertion the surface of the tooth structure also should be thoroughly cleaned and sterilized. This is effectively done with fine pumice moistened with compound tincture of iodin diluted with peroxid of hydrogen, appHed with a stick or brush point over the entire surface of the tooth-structure and under the gum- margin. The iodin not only aids in cleansing and sterilizing the parts but also acts on the membrane of the gingiva as an astringent. A rope of tightly twisted absorbent cotton may be wound around each crown to be capped and pressed close against the gum, with the ends twisted together at the labial side so that the cotton may be easily seized and instantly removed at the moment the cement is ' Introduced by Dr. W. V. B. Ames. CEMENTATION OF CROWN- AND BRIDGE-WORK 261 ready. The cotton can be retained in position over and around a root end by inserting a portion in the orifice of the canal. Crown posts may be slightly barbed or roughened. Collar crowns should have been previously inserted and given a final burnishing. Each cap or crown, having been thoroughly cleaned and dried, is filled with enough cement to insure a slight surplus. A small portion is then put in each root-canal or hollow part of a natural crown present, and the artificial crown or bridge immediately adjusted in position. In most cases it is best to remove the napkin or absorbent cotton quickly and close the mouth to insure the occlusion of the teeth, and then open the mouth and replace the napkin. The crown, or bridge, should be held under pressure until the cement has set. For this pur- pose a piece of wood notched on the end may be used. In setting bi- cuspid or molar crowns and in bridge-work, it is better in the majority of cases to occlude the teeth and keep them in position under a steady pressure until the cement sets. Under these circumstances, the saliva can reach only the surplus portion of the cement and cannot interfere with that under the cap or crown. One thickness of thin tin foil placed over the crown as the teeth are occluded will slightly increase the pressure. When the cement has set perfectly hard, the surplus around the edges should be removed. In collar or cap crowns the extreme edges of the gold of the collar or cap should be given a final burnishing, but force should be avoided, as tending to injure the cement under the col- lar. A fine-pointed instrument and floss silk should be passed between and around the teeth to remove any particle of the superfluous cement, and finally the parts should be syringed with tepid water. An applica- tion may be made of a saturated solution of aristol and oil of cloves with cotton twisted on the point of a probe to relieve pain and allay irritation. The patient should be requested to call in a few days so that an examination may be made to see if any particles of the cement were overlooked. Cleansing at this time facilitates the healing of the gum around the edge of a collar. Care in such details tends to prevent an inflamed appearance and recession of the gum often seen around crowns, and also insures a satisfactory result to the patient and commendation to the dentist. Gutta-Percha The fact that recent improvements in oxyphosphate cement have rendered it so dense and hard that crowns and bridges cemented with it are so difficult to remove they are generally destroyed beyond re- 262 CROWN-, BRIDGE-, AND PORCELAIN-WORK placement or repair, has prompted an endeavor in the use of gutta- percha alone or in combination with oxyphosphate. Gutta-percha will allow the work to be removed generally intact, although after a time it does not soften as easily as when it was applied. Its lack of rigidity confines its use to crowns and bridges that rest steadily on their foundation and require the gutta-percha only as a medium of attachment. The slightest vibration of a cemented cap or crown on its foundation will more or less admit the permeation of agents which will result in the dentin and gutta-percha gradually be- coming infected and the attachment of the gutta-percha impaired. Oxyphosphate combined with gutta-percha may be utilized in many instances to overcome this difficulty. One of the greatest objections to the use of gutta-percha is its refractory behavior in application, as it cannot be rendered more than Pig. 507. semi -plastic with heat and accordingly is difficult to manipulate as a cement. Gutta-percha will adhere to a heated metallic surface but does not adhere as well proportionately to tooth structure. The pink base-plate gutta-percha or gutta-percha of a similar character is the form most used to cement crowns and bridges. This form being generally accepted as the most suitable, similar preparations that can be more easily manipulated have been introduced. Method of Cementing with Gutta-Percha or Gutta-Percha Cement. The description given will apply to both gutta-percha and gutta- percha cement, but the latter will be found much easier of manipula- tion. First. Clean perfectly each post and the inside of each cap. Second. Place the cement-heater (Fig. 507) on a support over a Bunsen flame, remove the handle, and heat until a drop of water placed on the surface will instantly boil and be evaporated. Insert the handle, remove the cement heater and place it on a small asbestos pad, or a CEMENTATION OF CROWN- AND BRIDGE-WORK 263 couple of instruments laid upon a table, and again remove the handle; or use a How gutta-percha heater (Fig. 508). Third. Place the crown or bridge in a slot in the cement heater, or on the surface of the How gutta-percha heater. Heat a spatula (Fig. 509 in miniature) and place the requisite amount of gutta-percha on the gutta-percha cement heater (A Fig. 507) or on the central section of the How gutta-percha heater. If gutta- percha cement is used, manipulate it with a hot spatula and it will immediately assume a plastic consistence. To Fig. 508. Pig. 509. apply either the gutta-percha or the cement, steady the crown or bridge with tweezers on the slab or in the slot of the cement heater, or remove and hold in a napkin with the fingers. Reheat when necessary and return it to the heater when the gutta-percha has been applied. The gutta-percha or cement should be applied with the hot spatula a very little at a time as a surplus will not press out like oxyphosphate. In the case of collar crowns the proper and simplest method is to first measure the amount of gutta-percha or cement required. Method of Measuring Gutta-Percha. — This is easily done by first placing a little of the gutta-percha or cement on the sides of the in- terior of the collar of a cap or of a gold crown, as shown in section at A, A, Fig. 510, adjusting the work in exact position in the mouth on the wet natural teeth by pressure and occlusion of the antagonizing teeth, and then instantly removing. The saliva on the teeth will prevent adhesion of the gutta-percha. The surplus on the sides will be pushed Fig. 510. 264 CROWN-, BRIDGE-, AND PORCELAIN-WORK to the bottom of the cap and when the cap is removed will show the impression of the natural tooth, as illustrated in Fig. 511, Any vacancy at the point B in the bottom of the cap will very accurately indicate the deficiency. Next wash the saliva out of the cap with a Fig. 511. syringe full of water, rinse with alcohol by pouring in a few drops, and place the work on the heater and wait until the alcohol has evaporated, then apply the required additional gutta-percha or cement. A small straight, blunt-pointed instrument — ^such as a broken excavator — is useful to carry small pieces or pellets to the bottom or corner of a cap. To distribute the gutta-percha or cement in the case of a Richmond crown, place a little on the inner edge of the collar as indicated at S, S, Fig. 512. By one or more in- sertions, the necessary quantity for the remainder of the surface of the crown can be accurately determined. Next and last apply the gutta-percha on the post. Should any vacuoles exist they will be filled by the film of oxyphosphate applied to the surface of the crown or bridge abutments in the final act of cementation. In any form of crown with a closely-fitting post with- out a collar, first measure the quantity of cement required at the base or floor, by placing the gutta-percha or cement on that part, inserting the crown in the mouth and remov- ing before applying to the post. To Apply Gutta-Percha in the Form of a Film over a Surface. — Place a little of the gutta-percha or cement in the concavity formed in the bottom of a cup or jar, add chloroform, mix with a camel's-hair brush and apply the solution evenly over each post and on the inner surface of each metallic cap. Next place the crown or bridge in the slot of the cement heater to evaporate the chloroform. As only a very small quantity of gutta-percha will in- tervene between a close-fitting post or metalhc cap and the tooth structure, the adjustment is more easily effected in the mouth when the cement is evenly placed over the sur- face as desciibed. The best possible adhesion of gutta-percha to metal is secured by slightly scratching intersecting lines on the posts and inner surface of metallic crowns, in the form shown in Fig. 513, with a fine sharp-point- ed instrument previous to the process of cementation. In open-faced crowns this process applied to the inner surface of a strip of the metal traversing the cervical portion of the labial face, very materially aids in the retention of the gutta-percha. Pig. 512. Fig. 513. CEMENTATION OF CROWN- AND BRIDGE-WORK 265 When the gutta-percha or cement has been measured, the crown or bridge is left on the cement-heater until ready to be cemented in the mouth. Gutta-percha does not adhere to tooth-structure as well as to metal. For permanent insertion to secure a reliable adhesion of the gutta- percha, varnish the root or tooth with a very thin film of oxyphosphate. This is best done by mixing a portion of oxyphosphate to the consist- ence of a very thin cream and applying it with a small stiff camel's-hair brush on the sides of the crown or root. As the cap or caps are brought to position the pressure will be sufficient to make the oxyphosphate adhere securely to the tooth-structure and the gutta-percha. The oxy- phosphate also excludes air by creating a slight surplus. To Cement the Crown or Bridge.— Syringe the tooth or teeth to be crowned with water, protect from saliva, bathe with alcohol applied with a pellet of cotton, dry and evaporate all moisture with a hot-air syringe. Mix the oxyphosphate and apply it quickly as described, then immediately remove the crown or bridge from the cement heater, and when it has cooled to a point that will permit it to be held between the fingers, instantly place and press it to position in the mouth, and in the case of a gold crown or bridge have the patient forcibly occlude the teeth and hold them firmly in position until the oxyphosphate cement has set, when the surplus at the edges can be removed. For Temporary Insertion. — ^Instead of using oxyphosphate as described, varnish the root or tooth with a thin coating of fig. 514. chloro-gutta-percha or in the use of gutta-percha cement, with the adhesive fluid that comes with it. The gutta-percha can be chilled with cold water from a syringe. It is hardened to a certain extent by the application of cold but does not acquire its greatest density for some time. Requirements for Success.— For the successful use of gutta-percha, crown- and bridge-work must be constructed with that intention, and every detail connected with the cementation carefully carried out. Richmond crowns should have long substantial posts, either round or of the Logan pattern, properly fitted to the canal (Fig. 514). If the canal is enlarged from some cause or is of irregular form, after closing the foramen with gutta-percha, taper the end of the post and fit the point deeply in the canal, varnish the post all over with a film of chloro-percha, evaporate the chloroform, fill the canal with oxyphos- phate and insert the post. When the oxyphosphate has set, heat the post or crown, withdraw it, and wipe out the canal with a wisp of cot- ton saturated with chloroform, to remove the gutta-percha adhering 266 CROWN-, BRIDGE-, AND PORCELAIN-WORK to the oxyphosphate. This furnishes a close-fitting socket for the post. For all-gold crowns, badly decayed teeth should have their sides restored with amalgam or gold inlays. Roots for gold crowns should have posts or screws cemented in them and be shaped up with amalgam, as shown in Pigs. 187 and 188. Short gold crowns support- ing bridge-work require one or two pins that will fit in small holes drilled in the deep fissure of the occlusal surface, as shown in Fig. 515 or in a slot or cavity in the side extending nearl}. to the cervical margin as illustrated in Fig. 516. A pin, no matter how short, inserted in the center of the occlusal surface of an all-gold crown steadies the crown ^^^^^ and thus assists in its retention. Rolling wire under the fflHIln flat side of a file before using in the construction will FT JJ roughen it and offer a better surface. Pjg Favored by proper construction, many cases of bridge- work can be reliably cemented with gutta-percha. Among the exceptions are very short caps or open-faced crowns in which pins or a post cannot well be inserted and which in supporting bridge-work are subjected to a great strain or pressure in occlusion; also all cases of extension bridge-work. Oxyphosphate in Combination with Gutta-Percha or Gutta-Percha Cement. — Gutta-percha or gutta-percha cement may be used in com- bination with oxyphosphate by applying the gutta-percha scantily, removing it from the entire cavo-edge or border of the cap and in the final insertion of the work, coating the natural crowns or roots with oxyphosphate applied in sufficient quantity with a small brush to fill any vacancies. This method will result in the presence of a coating of oxyphosphate over the surface of the tooth or root and a larger proportion of pic. 516. gutta-percha over the cavo-surface of the cap, and will in- crease the security of attachment and the gutta-percha which will simplify removal. (For the removal of crowns and bridges cemented with gutta-percha, see Part IV, Chapter VIII.) Silicate Cement. — ^This cement in an improved form is commencing to take the place of oxyphosphate of zinc for cementation of porcelain inlays, as it closely resembles porcelain and is less soluble than the oxyphosphate. Amalgam. — The use of amalgam for purposes of cementation has been superseded by the oxphosphate and silicate cements. n PART IV BRIDGE-WORK INTRODUCTION SCIENTIFIC MECHANICAL PRINCIPLES — DENTAL BRIDGE-WORK — ANTI- QUITY — PRIMITIVE METHODS — MODERN LITERATURE — MODERN ME- THODS — ADVANTAGES — OBJECTIONABLE FEATURES — PROPHYLAXIS — IMPARTIAL CONSIDERATION — FORMS OF BRIDGE CONSTRUCTION Scientific Mechanical Principles A bridge is a structure that spans a space and is supported by solid bases termed abutments and piers. The abutments are located at each end of the structure and the piers at intervals between the abut- ments. A bridge is designed to support not only its own weight but additionally such pressure and stress as its structural capacity is calculated to bear. A bridge consists of a substructure and a superstructure. The substructure consists of the foundations and the superstructure of the portion that rests on the foundations and spans the space. Bridges are classified as of five forms; Arch bridges, in which the pressure is vertical and outward against the terminal abutments; Truss bridges, in which one girder or several connected girders form a rigid span between the abutments; Suspension bridges, in which platforms are supported by cables that pass over abutment-towers, the ends of the cables being anchored in the ground; Pontoon bridges, formed of platforms resting on boats anchored in a stream; Cantilever bridges, formed of two trusses, the central section of each truss resting on a pier, with the longer ends of the trusses weighted and anchored in the shore, and the shorter or river ends extended so they meet. Dental Bridge-work In dental prosthesis bridge-work is the utilization of natural teeth or roots as the substructure-abutments and of artificial teeth as the superstructure-spans. Antiquity. — The artificial repair of the loss of a portion of the teeth by bridging the vacant spaces with substitutes, supported in position by means of their attachment to adjoining or intervening natural teeth, is, as we have seen in the introduction, of ancient origin, having been practiced long before plates came into use. 269 270 CROWN-, BRIDGE-, AND PORCELAIN-WORK Primitive Methods. — Originally the application and mechanical construction of such dentures was of a most primitive character, and as the attachments were simply ligatures, or clasps of gold, the teeth were more ornamental than useful. Figs. 517, 518 and 519 illustrate some antique methods.^ Fig. 517 is an illustration of a specimen of ancient Phoenician dentistry. Fig. 518 is that of one of the Etruscan age, Fig. S17. Fig. 51 dating about 500 B. C. Fig. 519 gives a view of the same denture inverted. Dentures constructed on the bridging plan by various methods have been occasionally employed from the earliest days of modern dentistry, although until recent years the method has not obtained general recognition or been extensively practiced as a system. Modem Literature. — Dental literature presents bridging operations as described by Dubois de Chemant in 1802; J. B. Gariot in 1805; Fig. 519. Pig. 520. C. F. De la Barre in 1820; Dr. S. S. Fitch in 1829; William Imrie in 1834; J. Patterson Clark in 1836 (Fig. 520) and Dr. W. H. Dwindle in 1856. Figs. 521 and 522 are copies of illustrations in Dr. Fitch's work, published in New York in 1829, and Fig. 523, one from a trans- lation of F. Maury's work in 1843. ^^ 187 1 the bridging process or bridge principle was again brought to notice by a patent applied for in England by Dr. B. J. Bing, of Paris, for an improved means of sup- 1 See "Independent Practitioner," Vols. VI and VIT, " Evidences of Prehistoric Dentistry," by J. G. Van Marter, D. D. S., Rome, Italy. Figs. 517, 518 and 519 are copies of the illustrations of specimens, the first of which is represented as being in the museum of the Louvre, Paris, France, and the second in the Corneto Museum, Corneto, Italy. INTRODUCTION 271 porting and securing a bridge by anchoring with cement or filHngs, clasps or bars, extending from it into holes formed in the adjoining teeth (Fig. 524). The system was also practiced by the late Dr. M. H. Webb and is described in his " Notes on Operative Dentistry." Modem Methods. — The facilities afforded by the artificial crown- work now in vogue for supporting and securing bridge dentures have caused a revival of the system in an improved form, now termed "Bridge- Work," in which artificial crowns cemented to natural teeth or roots are Pig. 521. Fig. 522. employed as abutments to support artificial teeth which span or bridge the space between them. These bridges are so devised in the best methods that, while supplying the patient with the means of masti- cating food, the cleanliness of the denture is also provided for. Advantages. — Ordinarily bridge-work is immovably cemented in position. The claims set up in its favor are as follows: First. — The perfect replacement of lost teeth by artificial substi- tutes without the use of a plate. Pig. 523. Fig. 524. Second. — The absence of any mechanical contrivance to interfere with the tongue in articulation. Third. — The functions of the sense of taste are more perfectly performed and a healthy condition of the tissues preserved because the gums and palate are not covered over with a plate. Fourth. — The soHdity and security of the denture at all times, both in speech and mastication. Fifth. — The weight of the denture and the strain of mastication are proportionately distributed over the natural teeth, which are better suited to sustain them than the contiguous alveolar surfaces. 272 CROWN-, BRIDGE-, AND PORCELAIN-WORK Sixth. — Its special adaptation to the replacement of single teeth or of a small number of teeth, where bridge-work is usually superior to any other device. Seventh. — While all operations performed for the restoration of lost teeth, like other remedial operations, are temporary rather than per- manent in their results, bridge- work as regards permanency takes equal rank with any other operative procedure. Objectionable Features. — The following, on the other hand, are the objections raised, particularly so against cemented unremovable bridge-work as generally constructed. First. — It fails to restore the contour of the soft tissues above the bridge, as in cemented bridges artificial gums cannot properly be used. Second. — The slots under the artificial teeth fill with particles of food. Third. — The speech and comfort of the wearer are often affected by these slots, especially when under the front teeth. Fourth. — The natural teeth employed as abutments are permanently mutilated by the process of crowning. Fifth. — ^An extensive bridge made of gold, when immovable, cannot possibly be kept perfectly clean, as the metal will gradually tarnish in parts out of reach of the brush and offensive matter will gather on its surface and in its interstices and become septic. Sixth. — In cases where it becomes necessary to temporarily remove a cemented bridge for the purpose of repair, or because of disease in the teeth that support it, the operation is difficult and the bridge is usually injured so as to unfit it for reinsertion. Seventh. — The teeth that support a bridge, whether fixed or re- movable, are required to bear more force and pressure than nature intended — where the piece is large, many times more — and at no time can rest be given the abutments or the contiguous parts. Thus, in a piece of bridge-work of fourteen teeth supported by caps or crowns on four to six natural teeth, each one of the natural teeth may have to bear two or more times the strain in supporting the weight of the den- ture and the force of mastication that was intended. The ultimate result is evident to anyone who is experienced in dental practice, and unless the anatomical conditions are most favorable, the usefulness and durability of such work is liable to be limited in character, consider- ing the time, trouble and great expense attending its construction. Prophylaxis. — The most forcibly urged objection advanced against cemented unremovable bridge- work is that it is uncleanly and that a septic condition supervenes which in time becomes infectious. Small bridges comprising only a few teeth are much less open to INTRODUCTION 273 this criticism than large ones. The proposition depends piincipally on judgment respecting the suitability of a case for bridge-work, the form of bridge applied, and the skill employed in its constructive details, especially the continuity of all its parts. In properly applied and constructed bridge-work, uncleanliness is usually attributable to lack of knowledge on the part of the patient of proper methods of prophylaxis, or neglect. Consequently, the tendency is to confine the application of bridge- work to favorably positioned small cases and to make large ones removable. Such are the arguments that have been put forth for and against bridge-work; and yet, whatever may be urged against it, its advantages are recognized by a majority of the profession, including accepted authorities, some practitioners even going so far as to proclaim it the only true method for the insertion of partial dentures. Impartial Consideration. — Judged impartially, bridge-work has many advantages when practiced by experts who properly construct and apply it. Without doubt it has been, and is still, and will be abused. Bridges have been inserted where the support was insufficient or the construction was wrong in principle or faulty from lack of skill. Moreover, bridge-work is yet passing through the experimental period when failures are apt to appear more prominently than successes. The chronicles of dental literature, however, offer in this respect only a repetition of the historical difficulties that attend all new methods in the arts. Forms of Bridge Construction Bridge-work is constructed either Fixed, Detachable or Removable. A fixed bridge is permanently cemented; a detachable bridge can be detached by the dentist, and a removable bridge by the patient. Of these three forms of bridges there are several subdivisions differing in application, details of construction and materials, each of which will be separately discussed in this and the succeeding section. 18 CHAPTER I CONSTRUCTION OF BRIDGE- WORK PRINCIPLES INVOLVED — ABUTMENTS, RETENTIVE AND SUPPORTING — OCCLUSION — THE ARTISTIC AND ESTHETIC — PORCELAIN FACINGS AND TEETH FOR DUMMIES — -CLASSIFICATION OF BRIDGE-WORK — PREPARATION OF THE SUPPORTING TEETH OR ABUTMENTS — CON- STRUCTION — ^lAIPRESSIONS AND MODELS — SELECTION AND ADJUST- MENT OF ARTIFICIAL TEETH — ^BACKINGS — OCCLUSAL CUSP-CAPS — INVESTING THE BRIDGE — SOLDERING — FINISHING — ^VARIATIONS IN METHOD OF CONSTRUCTION — CONSTRUCTION IN SECTIONS — SOLDER- ING ON THE MODEL — CORRECTION OF WARPING — ^ADJUSTMENT AND INSERTION — CONSTRUCTION OF BRIDGE-WORK EMBRACING BOTH SIDES OF THE MOUTH — CONSTRUCTION OF SMALL PIECES OF BRIDGE-WORK To those who are properly informed in mechanical dentistry and versed in metal and crown-work, bridge- work does not present extreme difl&culty. The foundations or abutments, that is, the teeth or roots on which the bridge will rest, are first to be considered, due respect being paid to the mechanical principles controlling the leverage and the force of occlusion in mastication. Principles Involved The proper selection of abutments, and the type and form of con- struction of bridge-work are fundamentally dependent on a knowledge of and application of the principles of the sciences of anatomy, physi- ology, orthodontia, metallurgy and mechanics, oral surgery and hygiene. Failure to comply with the principles and requirements of these sciences will invariably partially if not entirely destroy the functional effici- ency and permanency of the operation, and establish conditions detri- mental to the health of the patient. Abutments, Retentive and Supporting The abutments in cemented bridge- work are divided into two classes, retentive and supporting. A retentive abutment retains as well as supports a bridge. A supporting abutment supports a bridge but does not retain it in position. 274 CONSTRUCTION OF BRIDGE-WORK 275 Mechanics In the selection of abutments the amount of stress that can be borne by the different teeth, individually and collectively, according to their position and condition of health, should be carefully calculated. A relative estimate of the ability of different teeth to resist stress when used as abutments would place them in the following order: (a) First Molars, (b) Second Molars, (c) Cuspids, (d) Bicuspids, (e) Central Incisors (d) Lateral Incisors. In dental bridge-work the stress on the abutments is both direct and lateral, divided proportionately according to their position and the character of the occlusion. As a rule the force upon the incisors and cuspids in occlusion will be directed outward on the upper and inward on the lower. Therefore the tendency, when any of these teeth or roots support a bridge, is to gradually press them and the bridge out of line in these directions. In the case of molars the force is mostly direct in an apical direction in a normal occlusion, with some lateral pressure caused by contact of ^ the cusps in the movement of the mandible in mastication. Occlusion In the planning of bridge-work there is no other factor on which the future success of the bridge as a serviceable and lasting denture depends so much as a properly arranged occlusion. Pressure on abut- ment teeth should be placed as nearly as possible in line with the axis of their crowns and roots, and occlusal surfaces of both abutment crowns and dummies should be positioned and shaped with this object in view. The greater the proportion of the vertical stress to the antero- posterior or lateral, the greater the probability that two or more abutments combined will be able to withstand the stress placed upon them in occlusion and mastication, and the longer is the term of their usefulness assured. In the construction of bridge- work the occlusal surfaces of abut- ments should be given normal dimensions, but the cusps should be so shaped as to minimize stress in mastication in the lateral movements of the mandible when brought into contact with the cusps of antagoniz- ing teeth. Short cusps cause less lateral stress than long ones. This point should be borne in mind, not only in relation to the occlusal cusps of abutment crowns, but especially in regard to those of dummies, the occlusal surfaces of which should be additionally favored by being made slightly narrower bucco-lingually than the abutments and very narrow when there are no antagonizing teeth. 276 CROWN-, BRIDGE-, AND PORCELAIN-WORK A normal line of occlusion of the teeth favors the construction and use of bridge-work. When such a condition does not exist, the defect should be remedied as much as possible by trimming the incisal edges and occlusal surfaces of such antagonizing teeth as are out of line and restoring as far as may be the line of the occlusal plane. Procedure under such conditions is illustrated in Fig. 525, a case in which the occlusion is not uniform. The dotted line indicates how much of the teeth requires to be removed to remedy the defect and render the occlusion favorable to the insertion of bridge- work that will permit proper performance of the masticatory function. Sometimes the removal of a pulp may become necessary in order to effectually shorten a tooth which has become excessively elongated. Pig. 525. The Artistic and Esthetic In dental prosthesis bridge- work does not always enable the operator to improve the appearance of the patient as well as it can be done with plate-work. The teeth or roots present that have to be utilized as abutments may not be in normal position or occlusion and the labial surfaces of teeth used as abutments with inlay attachments or open- face crowns, may be more or less disfigured by erosion or abrasion. Deep depressions caused by absorption of the alveoli cannot be entirely concealed with fixed bridge-work, as the utilization for the purpose of metal or vulcanite and even porcelain, except to a very small extent, would not be sanitary. Such restoration demands the use of a remov- able bridge or a plate. These conditions, also that of abnormally large or small spaces requiring to be filled with only a certain number of artificial teeth, tax the ingenuity and mechanical skill of the operator. Correct arrangement and harmony of form should prevail wherever possible. Porcelain Facings and Teeth for Dummies Facings and teeth should be selected that in form and shade will not appear artificial in contrast with adjoining natural teeth. A dis- CONSTRUCTION OF BRIDGE-WORK 277 play of gold, especially in connection with the eight anterior teeth, should be avoided wherever possible. The truly artistic and esthetic demand a restorative operation that will pass unnoticed to an observer. Classification of bridge-work A simple bridge is unilaterally straight in alignment, or nearly so, and supports but one or two teeth or dummies. A compound bridge is unilaterally curved in alignment, is supported by end abutments and intervening piers, and replaces from three to five teeth. A complex bridge is bilaterally curved, crossing the median line, having the necessary abutments and intervening piers. It replaces from four to ten teeth. Under normal conditions the rules that generally govern the number and position of the teeth or roots required as foundations for bridges are as follows: One central crown or root as a retentive abutment will support the adjoining central with the aid of a lug resting on or anchored in an inlay or filling in the lateral as a supporting abutment. A cuspid will support a central and lateral with retentive abutment on the other central. Two central crowns will support the laterals with the aid of support- ing abutments in the cuspids. . The cuspids alone or with the additional aid of a central pier or inlay or of lugs securely anchored in the bicuspids will support the incisors. One molar or bicuspid on one side and a bicuspid or molar on the other, and two reliable piers in an intermediate position, will support a bridge between them. One first or second molar on one side and one molar on the other with the assistance of the two cuspids, will support a bridge comprising the arch between them; termed a complex bridge. Two or three suitable teeth or roots on one side of the mouth can support between them a bridge on that side. The cuspids always afford a reliable anterior support. In a cuspid anterior bridge, such as is shown in Fig. 526, its outward curve, especially when the articulation of the antagonizing teeth is close and deep, causes lateral stress or leverage in excessive proportion to the direct. Such a dental bridge in form is equivalent to a curved truss bridge, which in principle would be condemned as con- trary to engineering principles unless supported by at least one cen- trally located pier to rv-^lieve the lateral stress on its terminal abutments. 278 CROWN-, BRIDGE-, AND PORCELAIN-WORK In the case of a cuspid anterior bridge, a centrally located pier not being available, the bridge should be made removable, with a saddle as a substitute; or the cantilever principle should be employed by ob- taining support distally from the bicuspids. Such support may be obtained for this bridge, as for other differently located bridges, in a variety of ways, the character or form of device to be determined by the conditions and requirements of each case. In the case illustrated in Fig. 526, when the adjoining first bicuspid has a vital pulp, either a partial or an entire gold cap-crown can be placed upon it, as shown at CB, Fig. 527, or an MO inlay may be inserted, extended across the occlusal surface with the distal end ad- ditionally secured with a post, as shown at D. Another method is to insert a triangular bar with the end bent and extended as seen at E. A pulpless tooth admits of a deep extension of the post into the pulp- chamber. Fig. 526. Fig. 527. In the case of a cuspid anterior cantilever bridge and in all cases where either inlays or crowns are joined together as abutments, the construction should be so conducted as to leave the interproximal spaces open and free to insure the presence of the gum septa in a normal con- dition. In a compound cuspid anterior and second bicuspid bridge, the four incisors and two first bicuspids being replaced, the second bicuspid abutment crowns act as cantilever supports and usually are reliable anchorages. In a cuspid posterior second molar bridge car- rying the two bicuspids and the first molar, the cuspid and second molar have to withstand the force of the occlusion of five teeth and the cuspid lateral stress in addition. Such a bridge is best made of the removable saddle type, as in the fixed form the abutments in a short time will become impaired. In all cases where there is an extensive span between the abutments, a removable saddle bridge-piece is the most suitable form to construct. CONSTRUCTION OF BRIDGE-WORK 279 The rules given, applied to these cases, will enable the operator, governed by the special conditions presented in each individual case, to properly select and decide the character of the abutments and piers. The relative resistance of individual teeth and the conditions respecting occlusion are here given as a general guide, but several contributing fac- tors may upset any plan which affords no scientific basis for comparison. Selection of the most suitable teeth as abutments or piers in bridge- work operations so as to most effectively distribute the force of occlusion, will assure the best practical results, especially as regards the mainte- nance and stability of the abutments, on which depends the durability of the work. Preparation of the Supporting Teeth or Abutments. — The prepara- tion of teeth or roots to support a bridge is the same as for ordinary crowns, except that the trimming of the sides and the reaming of the root-canals of the various anchorages must be in parallel lines, so that the collars and posts of the crowns will move readily to their places in he adjustment of the finished bridge. Teeth or roots which are to be Pig. 528. supplied with porcelain-faced or all-gold cap-crowns are crowned by some of the methods already described. In the first stage of the con- struction of the bridge, the roots that are to carry porcelain-faced crowns may be only capped, the posts being soldered and allowed to project a short distance beyond the caps. The lines of the crowns of teeth or root-canals to be used as abut- ments or supports for bridge-work are seldom exactly parallel. This fact should be borne in mind and receive proper consideration in their preparation. When one of the bridge-supporting teeth tips, or when two of them lean toward each other, the tipping side or sides may re- quire extensive trimming, while the other side or sides will usually require much less. This is finely exemplified^ in Fig. 528, which represents a molar and cuspid with living pulps. The cuspid in tipping forward has straightened the line of the posterior or distal side, so that it requires very little trimming. The portion requiring removal at the point A, will be regulated to some extent by the shape given the molar. By considerable reduction of the distal side of the molar at the 28o CROWN-, BRIDGE-, AND PORCELAIN-WORK point B to a line parallel with the anterior or mesial side of the cuspid, a form is given to both teeth which, with a moderate reduction of the anterior or mesial side of the molar and proper shaping of the other sides, will permit the removal and insertion of the caps in the construc- tion, and ready adjustment at the cervical section when permanently inserted. It is not essential that the parallel lines of the sides of prepared teeth or roots shall form a right angle to a straight hne between the cervices of the abutment teeth or the space between them. Teeth or roots may slightly converge in the occlusal direction, but they must not diverge. The application of this principle to the preparation of a lower molar and bicuspid for an intervening bridge is shown in Fig. 529, which is typical of cases frequently presented. Here straightening of the pos- terior or distal side of the bicuspid and removal of a portion of the an- terior or mesial side of the molar, as indicated by lines, will considerably Pig. 529. Pig. 530. aid in obtaining a form that will permit of correct adjustment of the caps. This principle is further exemplified in Fig. 530, where the inferior cuspid and the lateral incisor are used to support a bridge. The presence of decay on the side of a tooth requiring the most shaping, facilitates the operation, as chisels and cross-cut burs may be used to remove the main portion of the bulging enamel. The cavity should be excavated and filled with a cement, or preferably amalgam, previous to the final shaping. Plain thin carborundum disks will remove the approximal surface towards the adjoining tooth more rapidly than those of vulcarbo, but they must be used with greater precision to avoid their fracture. Com- mence with a disk of moderate circumference and follow with larger sizes. Removal or mutilation of the contour of an adjoining tooth must be avoided. Frequently the formation of a space can be advan- tageously commenced with a thin safe-sided separating file, then in- creased with paper carborundum-disks. These may be followed with a regular disk. Small, moderately thick carborundum wheels or disks, whose circumference has been considerably reduced by use, may be CONSTRUCTION OF BRIDGE-WORK 281 advantageously employed on the sides of the teeth approximal to the space to be bridged. The reduction of the labial and lingual sides must be such as will give a form that will permit the edge of the collar of the crowns to slide over the coronal section, and assume the proper position under the gum margin. The occlusal surfaces of teeth should be re- moved sufficiently to permit the presence of an intervening surface of metal capable of resisting attrition. The proper thickness of the metal for this purpose is regulated by the character of the occlusion. The hardness of the metal to be used for forming the occlusal surfaces, whether it is a gold alloyed with copper and platinum, or largely with copper only, in contrast to the gold plate used to form the sides of the crown, may also be considered in calculating its resisting power. The reduction of sound teeth to be used as abutments in bridge- work to an actual thimble-shaped form is not always necessary, as such reduction would demand in many cases the devitalization of the Fig. 531. Fig. 532. Fig. 533. Fig. 534. pulp, the vitality of which might be preserved by the adoption of less extreme trimming. The removal of contour and enough tooth-struc- ture to parallel the sides so as to permit the edge of the collar of a gold cap to fit perfectly at the cervical section, just under the free margin of the gum, is sufficient. To pass deeper than this point will usually demand considerably more reduction of the coronal section. Figs. 53ij 532, 533 and 534 illustrate upper and lower bicuspids and molars of normal form. The lines indicate the amount of tooth substance usually necessary to remove in such cases when the pulps are vital. The proportion of bulging constituting the contour of teeth varies considerably. Short bicuspids and molars demand less shaping to prepare them for the reception of caps than longer teeth. The lingual sides of lower bicuspids and molars require much more to be removed than the labial. Second and third molars free of decay when the gingi- val margin covers the coronal section considerably, seldom require extensive shaping. In sound bicuspids and molars with the crown fully exposed and slight recession of the gum; also in teeth with small necks and large contour, 282 CROWN-, BRIDGE-, AND PORCELAIN-WORK a reduction of their form sufficient to permit proper adjustment of the collar of the metallic cap at the neck usually demands pulp extirpation. A secure anchorage to vital molars and bicuspids, especially those in the mandible, is easily obtained by reducing the sides and occlusal surfaces sufiSciently to allow the formation of a cast or swaged cap that will only partly cover the coronal sec- tion, and fit at the margins of the portion Pig. S3S-— a, A.istheiine removed, as shown in Fig. 535. One, two to which the enamel is re- . . i • i moved, leaving a slight OT three pms may be mser ed m the cap for shoulder for the edge of the security. Fig. 536 shows Dr. Edward T. Tinker's method of shaping a molar tooth for a cap of this style. It requires a greater removal of tooth struc- ture than that shown in Fig. 535. MODL and MOD crowns may also be utihzed. (See Figs. 624, 625, 626 and 627). In a case where a molar tips in the manner shown in Fig. 537, the most advisable plan is to either insert an inlay in the occlusal surface that can be inserted in the same line as the bicuspid cap; or to crown the molar and place at the mesial side a lug or attachment for the distal end of the bridge. (See Part IV, Chapters VI and X.) The presence of decay with extensive calcification of the pulp in a tooth will admit of the removal without pulp extirpation of^more enamel and dentin than if it were pef- fectly normal. 1 When teeth are pulpless, shaping always can be more freely prac- ticed. In such cases the collar should be carried well under the gingi- val margin as a protection for the devitalized dentin against decay, Pig. 536. Fig. 537- and the occlusal surface may be more extensively removed. Extreme reduction of the coronal section of a tooth does not always facilitate the work of construction, but often the reverse, as straight or shghtly tapering sides and the presence of a reasonable proportion of the crown will steady the collar-cap during its formation. It will also assist in its CONSTRUCTION OF BRIDGE-WORK 283 retention in correct position in the mouth for the construction of the bridge-work. In the preparation of the anterior teeth for post crowns with porce- lain facings, the canal, when necessary, may be reamed a little to one side at the orifice and the post of the crown correspondingly tapered on that side to favor its insertion and removal from the canal. As to whether an incisor or cuspid should be entirely capped with gold, or a method be adopted by which the metal will be only slightly exposed or entirely invisible, in preference to excising the crown and inserting on the root a cap with porcelain facing, is a question to be determined by the conditions and circumstances attending the case. The position and occlusion of a tooth, its shape and general appearance, whether it is sound, free from decay, or partially or extensively decayed; whether the pulp is living or almost entirely calcified or has al- ready been devitalized; also the age and sex of the patient, are condi- tions which should influence the operator in the adoption of the form of construction. The illustrations in the succeeding chapters on bridge- work show numerous methods which may be practiced. Construction The operative procedure as generally practiced in construction of all bridge-wojk is classified as follows: First. Take two impressions and two articulating impressions, termed "bites," of the case when presented before operating on it, and make models and articulating models, one set to use as a study and reference model, and the other as a preparatory model for outlining and indicating the forms to which the teeth require to be trimmed.^ Second. Prepare the abutment roots or teeth. Third. Make the abutment caps, crowns or attachments. Fourth. Take a "bite" and impression with the crowns or at- tachments in position. When a "bite" is taken separately or addition- ally to the impression, the ''bite" should always be taken first. Fifth. Make a model and articulating model. Sixth. Select the porcelain facings for the dummies between the abutments and grind and fit them to position in accordance with the occlusion of the articulating teeth. Cover the labial facings with a plaster matrix. Seventh. Apply metallic backings to the porcelain facings and additionally, occlusal cusps to the bicuspids and molars. 1 A study model is valuable to refer to during the work and especially so in case of subsequent discussion over operations performed. 284 CROWN-, BRIDGE-, AND PORCELAIN-WORK Fig. 538. Fig. 539. Fig. 540. CONSTRUCTION OF BRIDGE-WORK 28s Eighth. Cement dummy teeth and crowns together with adhesive wax on model, remove, invest and join together with solder; trim and polish. The case represented in Fig. 538 will be used to illustrate and explain constructive details.^ The abutments consist of the right cuspid root, the crown of which is to be excised, and the first molar. The cuspid root and molar crown having been properly prepared in parallel lines, as shown in Fig. 539, a gold collar crown with porcelain facing (Rich- mond) is made for the cuspid and an all-gold crown constructed in sections for the molar (Fig. 540). Impressions and Models. — With the crowns in position in the mouth, an impression of the case and of the occluding teeth is taken Fig. 541. with plaster slightly colored with carmine, to which may be added, if the plaster is slow-setting, a little potassium sulfate, less in proportion than salt, to cause it to set quickly. The plaster is mixed moderately thick and either rolled in a mass between the fingers, which should be wet to prevent adhesion of the plaster, or with the aid of a spoon it is placed around in the mouth on the crowns and parts to be included in the bridge, and the antagonizing teeth occluded tightly and so held, until the plaster sets (Fig. 541). The mouth is then opened and the pilaster carefully removed. Should the plaster break, the pieces are adjusted together and cemented with hard wax. The crowns are gen- erally removed in the impression; if not, they should be transferred to it from the mouth. The inside of the molar crown and the cuspid cap, also the post, are thinly veneered with paraffin. to obliterate recesses, and later permit * New York State Board Bridge. 286 CROWN-, BRIDGE-, AND PORCELAIN-WORK their removal from the plaster model. (See Part I, Chapter IV.) The entire impression is varnished, then oiled and a plaster model first run in the upper impression carrying the crowns. When the model has become well set, it is mounted with plaster on an articulator — an- atomical type preferred — and the other side of the plaster impres- PlG. 542. sion, giving the articulation, is run and the opposite section of the articulator adjusted. When the impression plaster is removed (an operation which is facilitated by its having been colored with carmine), a correct model and articulation of the case will be found, with the crowns and caps in exact position as they were in the mouth (Fig. 542). Fig. 543. Fig. 544. Danger of fracture of the form of the occluding teeth of the articu- lating model or "bite," in their removal from the plaster impression may be avoided by giving them the shapes illustrated in Figs. 543 and 544. This is done by trimming and shaping the mold of the teeth in the plaster impression at the lingual side to form C and C, and thor- oughly varnishing and oiling before running the plaster. CONSTRUCTION OF BRIDGE-WORK 287 The shape given in no respect impairs their form for the articu- lating work. Selection and Adjustment of Artificial Teeth.— In bridge-work, cross-pin flat-back plate teeth, now known as porcelain facings or veneers, are used for incisors and cuspids, and partial teeth, represent- ing the buccal section of the teeth and also termed porcelain facings — especially designed for crown and bridge- work— are used for bicuspids and molars (Fig. 545). Cuspids are sometimes used to form the facings for bicuspids. The facings in appearance should be selected in accord- ance with the rules given in "Selection of Porcelain Teeth," Part III, Chapter II. They should be of such a length that when ground in place, the base at the cervix will touch or rest on the gum, and the occlu- sal end on the antagonizing teeth, as shown in Fig. 546. Pig. 546. Fig. 547- To determine the proper position of facings for producing the best appearance, they can be adjusted in the mouth supported on a narrow wax plate, with or without the gold crown or cap of the abutments. The facings having been ground and adjusted to correct position on the model, plaster is placed on the outside of the model, over the labial and buccal aspects of the facings, in sufi&cient quantity to hold them in position, thus forming a matrix, as seen in Fig. 547. The wax is then removed, exposing the lingual portion and permitting the forms and position of the teeth to be studied (Fig. 548). The base of the porcelain facings for the bicuspid dummies can be allowed to rest on the gum as ground, or they can be removed from their investment and the base of each uniformly ground from the lingual side beyond the pins (A, Fig. 549), straight to the labio-cervical edge (B), so that it only touches or leaves a slight space. This gives the form termed self-cleansing space. Forming the porcelain facing with the base resting on the gum, as 288 CROWN-, BRIDGE-, AND PORCELAIN-WORK indicated in Fig. 546, is in the opinion of the author preferable, as it excludes particles of food. Another favorably considered method, as it eliminates the so-called self-cleansing space and offers a more agreeable surface to the tongue, is to form the dummy with a base of slightly smaller circumference than the cervix of the natural tooth would be, as shown in Figs. 883, 884 and ^ Pig. 548. 885, and as used in removable bridge-work. The occlusal edge of the cuspid facing is shaped and protected with the backing, as explained in crown- work (Fig. 301). To make room for the gold occlusal cusp that is to be added to the bicuspid facings, the porcelain is ground off at an angle of 45° to the line of the hngual side, as shown at A, Fig. 550, leav- ing a space at the extreme edge of about one-thirty-second of an inch, or, Fig 549. Fig. 550. Pig. SSI. if protection of the porcelain is more to be considered than appear- ance, the entire end can be removed and restored with gold, as indicated in Fig. 551. To effect a uniform line of the gold and porcelain for ap- pearance, the angle for removal should be the same on all the facings and the line continuous, as shown in Figs. 552 and not as in Fig. 553. Backings. — The bicuspid porcelain facings are next backed as in the case of a crown. (See Part III, Chapter IX.) The backings, if CONSTRUCTION OF BRIDGE-WORK 289 preferred may be extended down on the curve of the self-cleansing spaces. A more desirable result is secured if the backing extends only to the edge of the self-cleansmg space and the porcelain is polished, as its surface is superior in cleanliness to that of gold. Occlusal Cusp-Caps. — Gold cusp-caps are made in accordance with the occlusion to form the occlusal portion as described and illustrated in the construction of gold crowns, either by swaging gold plate and Pig. 552. Fig. 553. Fig. 554. filling in the cusps with hard solder or by casting (Fig. 554). (See Part III, Chapter VIII.) The matrix is next removed from the surface of the model by prying it loose. The cuspid and molar crowns are warmed, removed and boiled in water and soda to entirely remove the paraffin from inside the caps. The outside metallic surface of each crown adjacent to the dummy teeth, is veneered with a film of hard wax, by heating the gold enough Fig. 555- - ' to melt the wax, when touched to its surface, which causes it to adhere with great tenacity to the gold. An ensemble is next made of the crowns, dummy bicuspids and occlu- sal cusp-caps with the matrix on the model. The different porcelains should appear to touch on the sides but should not actually do so — a slight space is necessary to allow for expansion and contraction of the porcelain without checking when heated in soldering. Should any touch, trim the side or sides with a sandpaper disk. The dummy bicuspids and occlusal cusp-caps and crowns are first connected with a small amount of adhesive wax, and when correctly adjusted, rein- 19 290 CROWN', BRIDGE-, AND PORCELAIN-WORK forced with a large quantity of hard wax, and are then waxed to the abutment crowns. Wax should be placed in any seam or place where it is desired to have the solder flow. A trifle of wax is applied in excess of the amount of solder required, so as to give a slight surplus of solder for finishing. A piece of iron wire about gage No. 12 to 15, bent on the ends, as shown in Fig. 555, maybe heated and inserted in the wax as a brace. The wax is chilled, the matrix removed and then the bridge from the model, which is then invested, as seen in Fig. 556. Fig. 556. Investing the Bridge. — In investing a bridge, it is first dipped in water, then a httle investment material is placed in each cap or crown and in every crevice, with a small camel's-hair brush or a chip-blower, to insure it against air bubbles. A little more of the material than is sufficient to invest the bridge is next placed on a sheet of paper and the bridge is pressed into it, occlusal side up, and the material brought over in quantity a little more than enough to cover the occlusal surfaces, but the surface of the wax should be left exposed. To prevent fracture of the investment during the solder- ing process — which is liable to occur — and also to control its expansion and contraction and proportionately a displace- ment of the parts of the bridge, an iron wire about gage No. 15 with the ends twisted together, or a narrow strip of sheet iron or nickel with the ends joined, may be placed in the investment to encircle it, about one-eighth of an inch from the outer surface of the bridge, and low enough on the lingual side not to obstruct the exposure of the parts to be soldered (Fig. 556.) When the investment is set, the wax is removed with boiling water and the investment trimmed. If any of the parts that are to be united in the soldering do not touch each other, the space between them should be packed with gold foil or Corona gold to act as a bridge for the solder. Pieces of gold wire may be used to aid in filling in the right-angle space between the occlusal cusp-caps and the backing of the dummies, as indicated in section in Fig. 557. Fig. 557. CONSTRUCTION OF BRIDGE-WORK 291 Soldering. — ^Thc case should be heated slowly. The soldering is best done on a concave soldering block or a piece of charcoal with a similar depression. (See "Soldering," Part I, Chaptei- VI.) Finishing. — After the soldering the bridge is removed from the investment and boiled in acid. The joints of the backings and crowns are trimmed and smoothed with carborundum wheels and points, finishing burs and leather points on the engine, also by a cord drawn between them (Fig. 65, Part I), and the entire bridge finely polished with whiting or rouge, carried by a brush wheel on a lathe. Any little pits that may exist can be shaped with a small bur and filled in with Pig. 559. gold foil or Corona gold. (See Part I, Chapter VIII.) The bridge is then ready for insertion (Fig. 558). If the construction details have been performed as described, a finished piece of bridge-work is the result. ;•>, Fig. 559 shows the finished bridge inserted in position. : 292 CROWN-, BRIDGE-, AND PORCELAIN-WORK Variation in Method of Construction Construction in Sections. — To overcome warping and displacement of the abutment crown and dummy teeth from expansion and contrac- tion of the investment material and gold solder, which occur especially when large bridges are soldered in one investment, the soldering is done in sections, to be connected in one or more soldering operations, as the case may suggest. For instance, in the finished typical case (Fig. 558) the bicuspid dummies could be removed in position, invested and sol- dered together, trimmed and replaced on the model, cemented with wax to the abutments, removed, invested and soldered to them. Soldering on the Model. — Another method of constructing bridge- work is to form a model of the case of investing material and do the final soldering on the model. (See "Models," Part I, Chapter IV.) Fig. 560. The abutment crowns are left in position on the model. The dummies are fitted between them and cemented with wax, the matrix removed, the model and bridge invested and soldered together. Correction of Warping.^ — When warping occurs to such an extent as to interfere with proper adjustment, the bridge should be sawed apart where the displacement apparently has mostly occurred, in the manner least hkely to affect its appearance. The parts are then cemented together with hard wax, adjusted in the mouth and an impression taken in an impression tray, using only sufiicient investing material to cover the points of the teeth and crowns, as shown in the case of a larger bridge in Fig. 560. The bridge and the investing material are then removed from the impression tray and more investing material added to complete the investment. The sections of the bridge to be united are next exposed and soldered together. To permit the investing CONSTRUCTION OF BRIDGE-WORK 293 material to be easily removed from the impression tray, it is well to melt a film of wax on its interior surface, then cool and serrate the surface of the wax. The plaster will adhere firmly to the wax but will loosen when the tray is heated. Adjustment and Insertion. — The bridge when finished is adjusted in the mouth, every point carefully examined and any alterations re- quired made. Should the edge of one or more of the abutment caps strike the edge of the occlusal surface of an abutment tooth or the end of a root, so as to interfere with the adjustment of the bridge, paint with a paste of rouge and oil the inside of that section of the cap, dry the surface of the crown or root and insert the bridge so that the rouge on the cap shall mark the interfering part of the tooth or root. Grind off the marked interfering part, and repeat the process if necessary. Should the point of a post strike the dentin to one side of the orifice of a canal it is to enter, trim off the point of the post slightly on the inter- fering side and if necessary also the dentin at the edge of the orifice, sufficiently to permit the post to glide to position. Painting with rouge, either the post or abutment surface, as the case suggests, accurately defines the interfering point. If -extensive warping has occurred in the soldering so as to prevent correct adjustment of the bridge, it must be remedied as described under head of "Correction of Warping." Interfering points in the occlusion can be determined either by the use of marking paper, or by warming the surface of the gold, veneering it with wax and then occluding the teeth. By the latter method the interfering point or points are definitely marked in the wax. When the adjustment of the bridge is accomplished, if desired, it may at first be temporarily inserted for a day or two, to permit it to settle into position and define any slight points in the occlusion that may require alteration. If the bridge is warmed and paraffin to which a little aristol has been added is placed in the caps before inserting, the secretions will be better excluded and a septic odor avoided. Burnish- ing the collars will usually secure the bridge; if not, it can be cemented with a little gutta-percha placed in each cap instead of paraffin. Should there be evidence after temporary use of the need of changes, the re- moval of a little of the occluding surface of a crown or dummy at the required point, and of the antagonizing teeth, will generally be sufficient to correct it. For its permanent attachment the post of the cuspid crown is barbed and the cuspid and molar crown treated the same as for single crowns, and the bridge cemented on with oxyphosphate or gutta-percha, or a combination of both. (See Part III, Chapter XXIII.) 294 CROWN-, BRIDGE-, AND PORCELAIN-WORK Fig. 562. Fig. 563. CONSTRUCTION OF BRIDGE-WORK 295 Construction of Bridge-Work Embracing Both Sides of the Mouth. This is exemplified by the case illustrated in Fig. 561. Retaining abut- ment caps with posts are made for the two cuspid roots, a gold crown for the right second molaF and a gold inlay for the left molar (Fig. 562) . The walls of the inlay cavity should be inclined so as to permit insertion and removal of the inlay in an occlusal direction. A piece of iridio-platinum wire, gage No. 12 or heavier, should be inserted in the inlay wax, with its end protruding and cast in the inlay to afford easy and better attach- ment to the bridge. (See Part IV, Chapter IV.) Impressions are taken; the inner and outer cervical surface of the caps, the gold crown Fig. 564. — Shows "dummies" in various stages of construction A, Central incisor, and B, bicuspid, ready for m.etallic backing. C is la central backed. D D D, porcelain fronts as they appear on insertion after the process of backing, capping, and soldering. and the cavo-surface of the inlay are veneered with paraffin to later permit their removal, and models made and mounted on an articulator, as shown in Fig. 563. (See Part I, Chapter IV.) Porcelain facings are selected and ground to position. The incisal edge of the cuspid crowns should be ground and shaped so that they can be protected with metal by extension of the backing, and the incisor, bicuspid and molar dummies treated in hke manner. The model is then surrounded with a matrix and the facings backed and occlusal cusps made for the bicuspids and molars, as illustrated in Fig. 564. The two cuspid crowns are removed from the model, invested, soldered and then readjusted on it. 296 CROWN-, BRIDGE-, AND PORCELAIN-WORK The right section of the bridge from the second molar to the cuspid, and the left from the inlay to the cuspid, are cemented together with wax, removed, invested and united with solder. The incisors are next cemented together with wax, removed, invested, soldered and read- justed. The side bridges are then readjusted on the model, the four Pig. 565. incisors cemented in position to the cuspids, with hard wax, and all removed together, invested (Fig. 565), and the three sections united with solder. Fig. 566 shows the finished bridge, and Fig. 567 the bridge in position. The inlay can be removed by means of the shank and Fig. 566. Strongly united to the bicuspid dummy. It is often necessary, to over- come contraction and secure a better relationship of the parts, ^ to soldei^ together the entire bridge without the inlay and then adjust and unite the inlay to the bridge in a final soldering operation. ^ In some cases, the best plan is to have the patient wear the bridge for a day before attaching the inlay, to allow the bridge to settle to position. CONSTRUCTION OF BRIDGE-WORK 297 A variation in the inlay abutment in a case such as this is to use a supporting instead of a retaining abutment, as shown in Fig. 568, the construction of which is described in Part IV, Chapter IV and in Part V, Chapter I, Removable Bridge- Work. Pig. 567. Pig. 568. Construction of Small Pieces of Bridge -work This is much simplified by the following methods: Crowns are first made for the teeth or roots that form the abutments and temporarily placed in position. The teeth — dummies — which form the span, having Fig. 569. been ground and backed, preferably with the aid of a model, are ad- justed and attached with wax cement in proper position between the crowns. The crowns and dummies are then removed together in an impression tray filled with investing material, the inside surface of 298 CROWN-, BRIDGE-, AND PORCELAIN-WORK which has been veneered with wax and the surface serrated. The im- pression tray is then heated and the investment with the crowns and dummies removed. More investing material is mixed and the exposed parts of the crowns and teeth covered. The investment when set is cut away sufficiently to expose the parts that are to be filled in and united together in the soldering process. Figs. 569 and 570 represent cases of bridge-work constructed in this manner. Parts of a larger Pig. 570. bridge constructed in sections may be similarly formed and then united. In an extension bridge of one tooth with the addition of a supporting abutment, a method that can often be practiced is; to properly adjust crown and dummy tooth or teeth cemented together with wax in the mouth, carefully remove them in position, invest and unite with solder. The supporting lug can then be added to the dummy, to rest on or in the intended tooth and form the supporting abutment. CHAPTER II REPLACEABLE PORCELAIN FACINGS AND TEETH REPLACEABLE ORDINARY PORCELAIN FACINGS WITH CAST BOX BACKING — A PLATE BOX BACKING — MANUFACTURED REPLACEABLE FACINGS AND TEETH — THE STEELE — THE IDEAL — THE EVSLIN — THE STEWART — THE DIMELOW — IMPARTIALLY CONSIDERED The replacement of a fractured porcelain facing that has been at- tached by soldering to a bridge permanently cemented with oxyphos- phate is frequently attended with great difficulty, and the result is often unsatisfactory and doubtful regarding permanency. Change of shade of the porcelain facing or tooth is liable to occur, especially when subjected to more than one soldering operation, when accuracy in shade is a positive requirement. Fracture of porcelain in soldering retards the construction of the work and involves the labor of its replacement. a b c The desire to obviate such difficulties has caused the introduction of various methods of construction, in which the porcelain facings are removed from ^1, • •.• • ^ ■, -, . , Fig. 571. their position previous to the soldering process and afterwards readjusted and cemented so as to be easily replaceable by duplicates in case of fracture when the work is being worn in the mouth. To simplify the application and increase the use of replaceable porcelain facings, special forms are now manufactured and sold. Replaceable Ordinary Porcelain Facings with Cast Box Backing. In making a cap for a crown to receive a facing sweat the collar to the floor or solder it with the least possible quantity of hard solder; also use very Httle solder to connect the post. Select a porcelain facing with long pins and register the number of mold and shade. This should always be done in all styles of replaceable porcelain facing work.^ Grind, fit and bevel off the incisal edge of the facing in the usual manner for a crown or dummy. Point the pins in a cervical direction with a slight curve, as shown at A, Fig. 571, or incisally, as illustrated at B, if the condition suggests it, or does not permit the cervical. If the porcelain must be removed close on both sides of the pins, an up- 1 To have on hand a duplicate set ground and ready to replace the worn one is a good plan. 299 300 CROWN-, BRIDGE; AND PORCELAIN-WORK right direction at a right angle to the surface of the porcelain with the ends slightly hooked towards each other may be preferable, as indicated at C. When the facing is ground and fitted, remove, cleanse in boiling water, dry, oil the surface and wipe off surplus. If it is the case of a crown, remove all the wax on the cap. Remount the facing on the cap and shape up the lingual side with inlay or hard pink base-plate wax (A, Fig. 572). Chill wax and remove the porcelain facing, leaving the wax on cap (B). Insert graphite points in pin holes in wax (C), insert sprue wire, invest in casting flask and cast in 22-carat gold. When cast, adjust porcelain facing to backing. Ream out with a small bur any obstructions that it may offer to the proper insertion of the pins and enough to provide space for their bent form (B). Ce- ment facing to position and retain under pressure for a few minutes (D). If possible, avoid insertion in the mouth until the next day. The same method of construction is applied to dummies. The backings can be cast together or separately, then joined with solder and united to the PM-^-« -^ -PM LT c c Pig. 573. Pig. 574. Pig. 575. Pig. 576. Pig. 577. Pig. 578. abutments in the usual manner. It is not advisable to cast backings of abutment crowns and dummies in one piece. A Plate Box Backing. — An easy method of constructing a backing for a replaceable facing instead of casting, is to slit the ordinary plate backing, and bend it over the pins to form the box and then enclose the sides. The process is as follows: Place the plate to be used as a backing, which may be platinum about gage No. 34 to 36, or 22 to 24-carat gold, gage No. 36, over the pins and extending one-fourth of an inch REPLACEABLE PORCELAIN FACINGS AND TEETH 301 beyond the cervical edge of the base of the pjorcelain, and mark or indent the metal with the pins, as shown at the pin marks PM and PM, Fig. 573. Slit the plate to the pin marks on the line of their outer side as indicated at C and C, Fig. 574, and bend up the piece of plate marked L. Place the backing on the facing in the open space, and then bend the fl:ap over and against the pins close to the porcelain, as shown in Figs. 575 and 576. Clo'fee the open ends of the box with two narrow strips of the same plate as the backing with the pins in the open space bent as shown in Fig. 577, and attach* with wax, as seen at B and B. Remove the backing, paint the under side of the backing and box with rouge, and invest with the ends of the pieces of plate extended into the investment. Solder with hard solder, pure or coin gold, as the character of the backing will permit. Trim ofif surplus metal and adjust porcelain to backing, also pins to box. If any obstruction to pins exists, remove it with a small bur and also give the interior of the box a slightly countersunk form. Fig. 578 shows the finished backing. Manufactured Replaceable Facings and Teeth Manufactured porcelain facings and teeth with metallic backings of special forms aie preferably used by many. The Steele. — This form has a round slot in the center of the porce- lain facing into which is closely fitted, and glides a metal flange, which is united to the backing, as shown in Fig. 579. Fig. 579. For posterior teeth, as the manufactured backing covers only a part of the facing, it generally requires to be additionally extended over the porcelain, after the facing is fitted. The backing is placed on the facing, a piece of pure gold, gage No. 35, is burnished over the part not covered by the backing, large enough to extend slightly over the sides and edges of the backing and porcelain, as shown at A, Fig. 580. This extra plate is waxed to the backing, removed, invested and attached with solder. It is then burnished and swaged to accurately fit. 302 CROWN; BRIDGE-, AND PORCELAIN-WORK Fig. 581 shows a finished dummy and crown with Steele facings. The backings of Steele facings are extended slightly to protect respectively the incisal and occlusal edges of the porcelain. Fig. 582 shows a Steele bicuspid porcelain tooth with a porcelain occlusal section Fig. 580. Fig. 581. Fig. 582 A B Pig. 584. ideal bridge with cuspid removed Fig. 585. IDCAt POSTERIORAND'READYT BACKrNG Fig. 586. with another form of backing. Fig. 583 shows the facings and tooth applied to a bridge. The Ideal. — In this style the porcelain facing is attached by a rounded flange on a manufactured backing with a pin on the point of the flange that enters the facing. The flange fits into a round slot REPLACEABLE PORCELAIN FACINGS AND TEETH .303 with an extension for the pin, as shown in Fig. 584. A shows the facing in section, and B, the backing viewed from the side. The end of the slot forms a shoulder to the hole for the pin. The pin additionally secures the flange. The position of the pin in the porcelain is such as to leave the incisal edge of the facing intact. Fig. 585 shows a bridge with Ideal facings, the left cuspid removed. Fig. 586 illustrates a posterior Ideal backing and tooth. Pig. 588. Fig. 589. The Evslin. — In this form the porcelain facing is made with a dove- tail socket to receive a lug extending from the backing. Fig. 587 shows an anterior facing and flange, and Fig. 588 a posterior tooth with a porcelain occlusal section. After the porcelain facing has been fitted, the gold or platinum back- ing is swaged to the porcelain. The end of the flange that fits into the socket of the facing is protruded through a perforation in the backing and cemented with wax (Fig. 589). It is then removed, invested and soldered to the backing. Pig. 590. Pig. 591. Fig. 592. Fig. 593. Fig. 594 As the porcelain is tipped at an angle as it is adjusted to the back- ing, it admits of the incisal edge of anterior teeth being protected, as shown in Fig. 590. The Stewart. — This is one of the latest forms of replaceable porce- lain facings. The facing is made with two slots that curve toward the incisal edge, into which two flanges fit, as illustrated in Fig. 591. The angle at which the flanges are inserted into the backing — which is supplied by the manufacturer — is such as to permit protection of the incisal edge by the metal. The pressure on the porcelain facing in 304 CROWN-, BRIDGE-, AND PORCELAIN-WORK mastication is in an opposite direction to that in which the flanges are inserted. In this way the porcelain is made safe from displacement. The Dimelow. — The principle in the construction of this facing is to secure mechanical ancliprage by having the pins, which are fastened in the backing, slant in the porcelain from lingual to labial, incisally. The facing has two holes placed in the location to be occupied by the pins, as shown in section Fig. 592, the backing in Fig. 593, and the facing backed in Fig. 594. In the construction, the backing is swaged to the facing. Holes are made for the pins, which are then adjusted in the porcelain through the backing, cemented with wax, backing and pins removed, invested and united with hard solder. The angle at which the facing is cemented to the backing permits protection of the incisal edge, as is indicated in Fig. 594. The methods and forms of replaceable porcelain facings presented are the representative ones mostly now in use. Impartially Considered. — Fracture of porcelain facings is not to be seriously considered, except in unfavorable occlusions. In the con- struction of the work the percentage of such accidents is small, and usually attributable to carelessness in soldering or lack of skill. Change of shade in porcelain will occur, when heated several times, but generally it is only slightly apparent. In respect to strength and liability to fracture in use, a properly applied and constructed soldered porcelain facing is stronger than a replaceable one. If fracture of a soldered facing should occur, its replacement on a cemented bridge is difficult and uncertain in result. Therefore in cemented bridge-work where removal would involve par- tial or entire destruction, unless conditions of the case permit of proper and most reliable protection for the porcelain, the use of replaceable porcelain facings is advisable. The cementation of facings to backings and caps provides contin- uity of structure for the parts under and around the porcelain. This is not entirely secured in soldered facings, no matter how carefully con- structed. In the use of one of the best preparations of silicate cement, we have an agent that competes with zinc oxyphosphate for strength and reliability for the cementation of replaceable facings. CHAPTER III FORMS OF ATTACHMENTS FOR BRmGE-WORK SHOULDERS ON SUPERIOR INCISOR AND CUSPID CROWNS OR ARTIFICIAL TEETH — SOLID GOLD DUMMIES — CASTING METHOD — SECTIONAL METHOD — SEAMLESS CAP METHOD — ALL-GOLD HOLLOW DUMMIES — ANCHORAGE CAVITY IN A SOLID GOLD CROWN — ANCHORAGE CAVITY IN A GOLD CAP-CROWN Shoulders on Superior Incisor and Cuspid Crowns or Artificial Teeth. — Shoulders on these teeth at the point of occlusion with the inferior are sometimes desirable, especially when it is necessary to open the "bite." To so construct, bevel the lingual side of the incisal edge of the porcelain facing and back with platinum, gage Nos. 38 to 40, or pure or platinized gold plate, gage Nos. 31 to 32, allowing it to extend over the incisal edge one-thirty- second inch, as shown at A, Fig. 595. To form the shoulder, cut a piece of gold plate, bend and adjust it to the incisal section in accordance with the occlusion, Fig. 595. Pig. 596. Pig. 597. Pig. 598. as shown at B, Fig. 596, and cement it with wax to the backing, re- move backing, invest and unite plate to backing with a small quantity of solder, as indicated at the point C, Fig. 597. Replace backing on porcelain facing, bend the pins, and fill in the space to the dotted line D, Fig. 596, in the soldering of the bridge. A cuspid crown may be advantageously used at times to open the "bite" to assist in supporting the force of occlusion by giving it the form of a bicuspid. The following is descriptive. Make cuspid crown for root with beveled and protected incisive edge, using enough hard solder to connect backing to cap. Shape up the lingual side with inlay wax to a form approaching that of a bicuspid, remove the wax model and cast with pure gold (Fig. 598). When cast, wax to backing and invest. 20 30s 3o6 CROWN-, BRIDGE-, AND PORCELAIN-WORIf Heat casting with pointed flame sufficient to melt the solder already on the backing and attach the casting, then flow i8- to 20-carat solder over the seam to entirely fill it and insure a slight surplus for finishing. Solid Gold Dummies In a close occlusion, when the patient prefers strength to appearance, the bicuspid and molar dummies may be made of solid gold. Casting Method. — For one or more dummy teeth, moisten or slightly vaselin the surface of the model and press inlay wax between the abut- ments, tightly occlude the articulating model, and get an imprint of the antagonizing teeth. Chill the wax, trim and carve it to the desired form, removing and placing it on the model during the operation. In- sert a sprue wire, as shown in Fig. 599, which illustrates a single dummy. Sectional Method. — Stamp a piece of pure gold plate, gage No. 31, to represent the occlusal surface (A, Fig. 600) . Shape up the form of the remainder of the dummy in wax, and over the wax adapt an annealed piece of pure gold (B), gage No. 32, to the buccal, mesial and distal sides, leaving the lingual open. Invest buccal side down and fill from the lingual side with scraps of 20-carat plate or coin gold. Fig. 599 Seamless Cap Method. — Stamp and fit a seamless crown to the space. SHt and lap the sides, if necessary to bring them into form, and then partly or entirely remove the lingual side. Fill the inside with wax, invest and melt-in a lower-fusing gold than the cap. All-Gold Hollow Dummies. — All-gold hollow dummies are recom- mended in a large proportion of cases in preference to solid ones, es- pecially for lightness. They are formed as follows: Take a seamless gold contour croAvn of suitable size, articulate it to the antagonizing teeth and reinforce the interior of the occlusal surface with a slightly lower-fusing gold plate. Cut away the gold of the lingual section of the collar to the form termed self-cleansing and shape the neck of the crown. Melt a small quantity of hard solder with flux into the form of a globule; fit a piece of gold or platinum plate, about gage No. 32, over the open side, flux the edge of the gold crown and place the ball of solder on the gold or platinum, within the gold cap (Fig. 601). Hold FORMS OF ATTACHMENTS FOR BRIDGFl-WORK 307 the cap in a Bunsen flame and heat slowly until the solder melts and appears upon the edge of the cap, then instantly remove from the flame, trim the gold or platinum and stone the edges. This gives a hermeti- cally enclosed dummy tooth of gold, from the interior of which the air has been practically exhausted by the heat. The dummy can then be placed in its position on the bridge and soldered in the usual manner. Fig. 602 gives the lingual aspect of a bridge, the dum- mies of which were constructed in the manner des- cribed. The bicuspid dummy is given a self-cleans- ing form and the molar is shaped to rest on the gum. Anchorage Cavity in a Solid Gold Crown. — An anchorage cavity in a solid gold crown, to support the end of a bridge with an inlay or bar (Fig. 603) is constructed as follows: The natural crown is ground down and the cervix shaped, banded, capped and pivoted, as shown in Fig. 604. The gold or platinum forming the floor of the cap on the root is made flat and left projecting a little at the sides. The form of the remainder of the crown is shaped in wax on the root- cap and chilled. A cavity is then made in the wax of the form required for the slot or cavity to receive the inlay or bar. This is best done with a fast revolving fissure bur in the engine. Remove the wax model from Fig. 603. Fig. 604. Fig. 605. Fig. 606. the root-cap, invest and cast. The cast crown is then adjusted in proper position on the cap. The cap is filled with investing material and the gold crown wired or clamped to it, as shown in Fig. 605, and united with solder to the cap, making a perfect joint. Fig. 606 illustrates from the palatal side a bridge of two. solid gold bicuspid dummies supported by a bar anchorage in a solid gold crown on the roots of a molar, and an open-face crown on a cuspid. Anchorage Cavity in a Gold Cap-Crown. — A heavy seamless crown is a very suitable form for insertion of a socket. If a crown made in 3o8 CROWN-, BRIDGE-, AND PORCELAIN-WORK sections is used, the cusps should not be reinforced until after the socket has been attached. Cut out of the side and occlusal surface of the crown the required space for the socket, as shown at A, Fig. 607. Fit a box formed of two L-shaped pieces of gold or platinum plate in Pig. 608. Fig. 609. the space, as seen at A and B, Fig. 608, cement with wax, invest, and solder from the inside, also reinforcing the cusps. Fig. 609 shows the finished socket. Anchorage cavity in a cast occlusal cusp-crown is described in Part V, Chapter V. CHAPTER IV ATTACHMENTS FOR BRIDGE-WORK (CONTINUED) OPEN-FACE CROWNS — PREPARATION OF THE TOOTH — TO FORM A DIE — SEAMLESS OPEN-FACE CROWN CONSTRUCTION — OPEN-FACE SEC- TIONAL CROWN — CEMENTATION OF OPEN-FACE CROWNS — CAR- MICHAEL ATTACHMENT — THE STAPLE ATTACHMENT — MOD AND MODL OR TINKER ATTACHMENTS- — SHAPING — CONSTRUCTION — PLATE AND PIN ATTACHMENTS — CONSTRUCTION — USE WITH PULPLESS TEETH — INLAY AND BAR-BRIDGE ATTACHMENTS — INLAY ATTACHMENTS — IN- CISORS AND CUSPIDS — CAVITY FORMATION — ^BICUSPIDS AND MOLARS — ANOTHER METHOD — FORMATION — ^BAR ATTACHMENTS — CONSTRUC- TION — CONNECTING BARS FOR BRIDGES — INTERVENING ROOTS Open-face Crowns The use of the open-face crown as a bridge abutment is often ad- vantageous and serviceable, when properly con- structed and applied in suitable cases. Its use is mostly confined to superior cuspids and bicuspids and inferior incisors and cuspids. It does not re- quire removal of the pulp. Preparation of the Tooth. — Parallel the sides and remove enough of the contour on the cervico- lingual section to permit the gold to fit at the neck. Grind off enough of the lingual or occlusal surface of a superior tooth, to allow a space at least equal to gage No. 23 between it and the antagonizing teeth. Slightly bevel the lingual side of the incisal edge of the inferior teeth, to avoid showing gold. If possible, avoid removal of any of the labial surface. To Form a Die. — Take an impression in a tube (A, Fig. 610) with plaster, and make a fusible metal die (Part I, Chapter V) or take the impres- sion with compound in a tube and make an amalgam die (B). If an amalgam die is formed, it is advisable to first take a moldine im- pression of the die in a tube and run a fusible metal die for the pre- 300 Fig. 610. 3IO CROWN-, BRIDGE-, AND PORCELAIN-WORK Fig. 6ii. liminary shaping of the gold cap, reserving the amalgam die for the final details. Seamless Open-face Cap -Crown Construction. — Select a gold cap that fits the neck of the die closely. Tap and shape the cap to the form of the die. Remove the gold cap and anneal it. Replace on die and swage in a counter-die. A swager can be used as" a counter-die (Part I, Chapter V). Fit the crown on the tooth and mark on the gold the por- tion necessary to remove to expose the labial surface. Make a hole with a bur through the gold, and with a fine fissure bur cut out the marked portion and finish with carborundum points. Reburnish the crown on both die and tooth. To better resist the strain of the bridge at the cervico-labial part, especially when the strip is cut narrow, reinforce it with an addi- tional shghtly narrower strip of the same gold as the crown, soldered across the surface and extended around on the sides, as shown in Fig. 6ii. The strip should be beveled off evenly to the surface of the remainder of the gold. Open-face Sectional Crown Method. — Fit a gold collar around the tooth long enough to extend shghtly beyond the incisal edge and remove the gold at the labial aspect, as shown at A, Fig. 612. Partly remove the gold on the lingual side and adapt the collar to the sides of the tooth, as seen at B. In the vacancy between the collar and tooth at the lingual side, fit and burnish a piece of pure gold or, in the case of a very close "bite," thin platinum plate, which will cover the exposed sur- face at that part and fit in under the edge of the collar. C shows the usual form of the piece of plate before it is fitted to the collar. Fill in the space between the collar and piece of plate with adhesive wax; re- move the collar, invest and flow hard solder into the space between the piece of plate and the collar, remove the surplus gold and trim level. D and E show a finished open-face crown with an incisal edge covered and exposed. Another method for the construction of an open-face crown prefer- FiG. 613. Fig. 614. Fig. 612. FORMS OF ATTACH MRNTS FOR BRIDGE-WORK 311 ably practiced by some is; form a gold collar wide enough to extend a little beyond the incisal edge, remove the portion of the gold from the center of the incisal section, and slit the palatal surface on both sides of its center, as represented in Figs. 613 and 614. The part at A is bent back, the edges of the parts at BB are beveled and bent down on the tooth and burnished close to its surface. The piece A is next brought down in position over the parts BB, and adapted to the crown. Fig. 615. The collar has now assumed the shape of a gold crown with an open face and seams (Fig. 614). The seams are next united by flowing solder into each of them — a little at a time — by holding the crown with tweezers in a Bunsen flame. The seams will hold and retain solder sufficient to join and fill them without the solder flowing over the adja- cent parts, unless an excess of heat or solder is applied. When the soldering is completed, the crown is adjusted, a line showing the exact portion of the labial aspect to be exposed marked on the gold, the crown removed, its edges trimmed to the mark and the soldered parts trimmed level. Fig. 615 illustrates a bridge in which the inierior incisors are sup- ported by open-face crowns on the cuspids. Fig. 616 represents the restoration of the inferior bicuspids and a molar on the right side by a bridge with an open-face crown on the cuspid and an all-gold crown on the molar. The Cementation of Open-Face Crowns. — To secure a better adhe- sion of the cement in the cementation of such crowns, the surface of the enamel .should be cleaned with pulverized pumice, wet with aromatic 312 CROWN-, BRIDGE-, AND PORCELAIN-WORK sulfuric acid. The tooth is washed and dried perfectly. The cement should be thoroughly mixed to the consistence of a thick cream, the inside of the crown and band covered with it, then the surface of the tooth — especially the cervico-labial section — and the bridge brought to position. When the strip of gold which traverses the cervico-labial section is made narrow, the liability of the cement to wash out at that part in time is one of the difficulties connected with the use of this form of crown. Fig. 617 shows forms of cap crowns for bicuspids. When the gold is removed at the cervico-buccal part, the crown can be additionally secured by a pin introduced and soldered, as shown at A, also in Fig. 618, supporting a dummy. A more secure form is to cut two grooves, as shown in Fig. 619, on the mesial and distal sides of the natural tooth, for the reception of two iridio-platinum pins passed through and soldered to the occlusal surface. If a line of wax is placed between the pins and the cap on the inner surface before investing, the solder may Pig. 617. Fig. 618. Fig. 619. be partly drawn in between each pin and the gold of the cap, to better secure the pins, by directing a large flame under the investment. In most cases where open-face crowns are used on the upper teeth, the gold forming the distal side of the cap can be brought around slightly on the labial surface of the tooth, without being observable when viewed from the front; but it must be cut short at the mesial side, and not allowed to extend beyond the line of the porcelain facing placed beside it, as seen in Fig. 618 and 619. On the inferior teeth the band of gold which extends across the cervico-labial aspect needs to be removed only enough to avoid exposure in speaking. Consequently much more gold may be left at that section on inferior than on superior teeth. The cast Carmichael or MODL Attachment is a good form to apply in many cases, such as seen in Figs. 618 and 619. The Carmichael^ Attachment. — This consists of a gold cap that covers the prepared natural crown on the lingual, occlusal and approxi- 1 Dr. J. P. Carmichael. FORMS OF ATTACHMENTS FOR BRIDGE-WORK 313 Fig. 620. A, Groove in tooth B, Cap. a. Cap in po?itioD. Pig. 621. Pig. 622. Pig. 623. 314 CROWN-, BRIDGE-, AND PORCELAIN-WORK mal sides. It is retained by a groove which runs across the occlusal surface and at right angles along the approximal sides towards the gum-margin (Fig. 620). Its use is largely restricted to cuspids and bicuspids. As originally constructed, a thin platinum or gold cap was first shaped to the form of the prepared section of the tooth and then reinforced with small pieces of clasp gold, united with solder. Fig. 621 shows such a crown off and in position on a tooth, and Fig. 622 a case of bridge-work constructed with these attachments. Fig. 623 shows Dr. Carmichael's device for gaging the lines of the grooves and sides of the teeth that are capped. The Staple Attachment. — The Staple attachment differs from the Carmichael in that a wire staple is placed in the groove instead of burnishing the matrix into it and flowing in solder. MOD and MODL or Tinker^ Attachments The Carmichael and Staple attachments are being superseded by similar improved cast forms termed MOD and MODL attachments and crowns. The first mentioned covers only the mesial, occlusal and distal Fig. 624. Fig. 625. Fig. 626. surfaces and the latter the mesial, occlusal, distal arid lingual. The caps are extended to within about one-sixteenth inch of the gum margin, requiring only a moderate removal of tooth structure; this, as the caps are intended for use on teeth with vital pulps, makes this method com- paratively preferable to others requiring a more extensive removal. Shaping. — For an MOD crown the tooth generally is best first trimmed on the approximal sides with a slight slant to the line of the cervical third (AA, Fig. 624). The occlusal surface is next uniformly re- moved one-thirty-second inch or more as conditions suggest, forming a depression (B, Fig. 625). This removal is next extended to and on the approximal sides, forming a small ledge. Occluding the teeth on a piece of wax, then holding the wax up to the light, will show any point requiring additional trimming at the occlusal or anchorage surface. For the MODL crown the enamel of the lingual side is uniformly additionally removed to within about one-sixteenth inch of the gum, 1 Dr. Edward T. Tinker. FORMS OF ATTACHMENTS FOR BRIDGE-WORK 315 to the line of the removal of the mesial and distal section, forming a small shoulder, as shown at C, Fig. 626. Two slight parallel grooves are made on each side of the tooth at the part G, to secure retention of the cap. The line of these grooves must permit removal in an occlusal direction, also be parallel with the line of any other crown or attach- ment present. In trimming use a small disk in cutting across the incisal or occlusal surface. The cut should not be made so close to an incisal edge as to weaken it. In bicuspids and molars the same precaution should be taken not to weaken the cusps in shap- ing, or if necessary they may be reduced and entirely covered with the cap. Fissure burs aid in forming the grooves. Construction. — The wax model is made by form- ing a wax cap over and around the tooth the shape of the required crown by either the direct or indirect method, or preferably the combined use of both. The form of the occlusal surface is defined by occluding the teeth. The sides of the wax cap are trimmed and shaped to make a flush joint with the cervical ledge (C, Fig. 626), and the wax on the labial or buccal surface entirely removed. The sprue wire is inserted as shown in Fig. 627, and the wax cap removed, invested and cast. An alloy formed of two parts 22-caratgold plate and one part clasp gold is recommended for these caps.^ It contains about four per cent, platinum. Fig. 627. Fig. 628. Fig. 629. Fig. 628 shows an MODL crown utilized to support a first bicuspid dummy with a lug to rest on the cuspid. Plate and Pin Attachment.— This form of attachment when apphed to a tooth with a vital pulp is mostly used to support a lost adjoining tooth, or to assist in supporting the end of a bridge in connection with other abutments. Fig. 629 will be used as a typical case to explain the method. Re- move enough of the lingual side of the cuspid and, if necessary, the in- 1 Formula of Dr. E. T. Tinker. 3i6 CROWN-, BRIDGE-, AND PORCELAIN-WORK cisal edge of the lower tooth, to leave a space equal at least to gage No. 22.' The trimming is best done with small wheels or points, so that the part assumes the shape of a depression with a defined ledge forming the margin, as shown at L, Figs. 629 and 630. Three holes, size of gage No. 20, are next drilled on the palatal side, one each being placed at the approximal sides and towards the cervico-lingual section. These holes are drilled in a direct line with the axis of the tooth, as indicated in Fig. 630. The holes at the approximal sides are to occupy that por- tion of the tooth structure which is generally included in approximal de- cay that does not expose the pulp. If a gold filling or inlay occupies that portion, it should be drilled into the same as though it were the tooth. If the filling or inlay is a substantial one, it will not be disturbed. Construction. — Take an impression in compound of the lingual side of the tooth, make an amalgam die and mount in a swager. Swage Fig. 630. Pig. 632. Fig. 633. and adapt to the lingual surface, extending onto the approximal side where the artificial tooth is to be adjusted, a piece of thin platinum about gage No. 38. This little plate of metal is fitted to the surface of the tooth and perforated over the holes. Three iridio-platinum pins, gage No. 20, which have been roughened by rolling under a file, are next inserted in the holes, attached to the plate with wax, the whole removed, invested and soldered with pure gold. Only one pin may first be in- serted and soldered and then the others added. Fig. 63 1 shows the cavo- surface side of the plate. The plate is next refitted, edges trimmed, removed, invested and reinforced with a veneer of pure gold. It is then fitted, invested and reinforced with coin gold. The artificial tooth is attached to the plate and a lug added, resting on the central incisor, as shown in Fig. 632. The line of the pins in the tooth structure being close to that of the line of force exerted in mastication prevents displacement and better permits insertion and removal of the attachment during the construction. FORMS OF ATTACHMENTS FOR BRIDGE-WORK 317 As a support for teeth loosened by pyorrhea, this pin cap attach- ment, in some cases, may be used without removal of the pulp. On account of the narrowness of the lower incisors, its application is confined to the cuspids. Use with Pulpless Teeth. — In pulpless teeth only one pin extended into the pulp-canal is necessary, as illustrated in Fig. 633. Small or narrow teeth require the removal of the pulp and the use of a single pin. Inlay and Bar-Bridge Attachments Attachments of this style are employed to anchor the ends of a bridge in the coronal section of natural teeth used as abutments. Fail- ure to appreciate the limitations of this device and faulty construction are responsible for disappointments in its use. Its employment should be confined to pulpless teeth, or to teeth where extensive calcification of the pulp exists, to permit a deep and secure anchorage of the inlay or bar. When one end of the bridge is retained by a crown, the other end may be retained by an inlay or bar. In the case of pulpless teeth, an inlay or bar in certain cases may be used on each end of a bridge of one or two teeth, and occasionally three teeth, but not reliably on more. Inlay Attachments Incisors and Cuspids. — This form of attachment is seldom used except in pulpless incisors, or where extensive calcification is present, owing to the difficulty of obtaining suf- ficient depth for an anchorage inlay when the pulp is present. The Pin and Plate, | i!iaa;i/ /;JM 1\ Fig. 634. Fig. 635. and Carmichael attachments offer preferable forms of support. In the case of cuspids, the use of an inlay is more frequent, as their form is more favorable. Cavity Formation. — In an incisor or cuspid with a vital pulp the anchorage cavity is formed in the Ungual portion of the tooth, extend- ing from the approximal surface next to the space to be bridged, two- thirds to three-fourths or entirely across to the other approximal side. 3i8 CROWN-, BRIDGE-, AND PORCELAIN-WORK The cavity should be given a retentive form with a flat base and with sides cut straight or diverging only very slightly from a right angle to the orifice, as shown in Fig. 634. One or two pins may also be in- serted. When the cavity is to constitute one of the supports of a bridge with a crown that, can only be adjusted in an occlusal direction, the cavity should be shaped so that the inlay can also be inserted in the same direction. In a pulpless tooth a smaller sized inlay can be used and anchored in the root-canal with a post, as shown in Fig. 635. Thus anchored an inlay furnishes a most reliable sup- port. The post or pins should be paralleled to the other abutments the same as the inlays are, to permit insertion in an occlusal direction. Bicuspids and Molars. — ^For these teeth various shaped inlays are used as a retentive abutment. The approximo-occlusal and the occlusal are the forms generally applied. To both these forms, espe- cially the occlusal in cases with vital pulps, one to four small pins should be inserted for the reason that an inlay used as a retentive abutment must withstand a stress not required in a merely restorative operation. When the tooth is pulpless one inserted pin of proper size is sufficient. In teeth with vital pulps, the anchorage cavity should be extended well across the occlusal surface, as shown in Fig. 636 (a bicuspid), and Pig. 636. Fig. 637. [Fig. 638. Pig. 639. Fig. 637 (a molar). The cavity should be cut as deep as the presence of the pulp will properly permit. Pins may be inserted at points that will give stability and not impinge on the pulp, as shown at A, Fig. 636, also in Fig. 637 and Fig. 638 in section. In an anchorage inlay of the form shown in Fig. 639 pins inserted at the pomts C, D and E, will maintain it securely in position. In pulpless teeth the inlay cavity can be made smaller, as a large post can be used to anchor it. Pins are best made of iridio-platinum wire, gage Nos. 19 to 21, which has been rolled under a file. To secure adhesion of the pin to the gold in the casting, veneer the portion of the end to be extended into the FORMS OF ATTACHMENTS FOR BRIDGE-WORK 319 inlay wax with a film of pure gold. This is easily done by perforating a pellet of gold foil with the end of the wire and holding it in a Bunsen flame. The pin is heated and the shank veneered with adhesive wax to insure adhesion of the inlay wax. The pin is placed in the warmed inlay wax, inserted in the hole in the dentin and the wax pressed into the cavity and shaped as required. It is then chill#d, removed, in- vested and cast with the pin. Another Method.— When the inlay model is formed as above described, slightly warm and remove the pin or pins, by first placing a hot instrument against the end to loosen them, then chill the wax and remove the inlay model. In the place of each pin insert a carbon of the same gage slightly roughened to catch in the wax and with the extended end long enough to engage in the investment. When the inlay has been cast and fitted to the cavity, the pin is adjusted to position, the hole in the gold being enlarged if necessary attached with wax, the inlay removed, invested and the pin united with solder, using the smallest pos- sible quantity; or the inlay may be cemented, the pin then introduced and cemented in the hole and inlay, the excess of the pin cut off, the end trimmed level and the end of the pin and inlay burnished and polished. This latter method is advantageous when it is ^^^' ^'^°' desirable to have a pin or pins at a tangent to avoid impingement on the pulp, in a case of bridge-work where the pins in two inlays re- quire to be pointed in opposite directions, as shown in Fig. 640. Formation. — This is usually done by the cast gold inlay method. (See Part III, Chapter XVII.) When pins are to be inserted in the ca- vity of an incisor or cuspid, the matrix method is often preferable, to permit adjustment of the pins by soldering them in position ui the matrix with pure gold to secure accuracy of position in the finished inlay. The inlay can be finished either by investing the matrix and flowing in pure or 22-carat plate, or it can be shaped with wax and completed by the casting method. (See matrix gold inlays, pages 219, 233 and 248.) The inlay attachment is especially applicable to cases of teeth which tip mesially, where the use of an inlay as an abutment frequently simplifies construction and permits formation of a better occlusion, as shown in Fig. 641. Bar Attachments. — This form of attachment, though seldom used since the advent of the cast inlay, is often a preferable method for the 320 CROWN; BRIDGE-, AND PORCELAIN-WORK posterior teeth when conditions favor its apphcation. A bar requires less removal of the occlusal surface to properly secure it, and is more easily removed from the cavity without mutilation than an inlay, when circumstances require it. For stability, as compared to an inlay, it is fully equal to the requirements when properly formed and inserted. Construction. — Enough tooth structure is removed to place the bar, as shown in section in Fig. 642. Fig. 643 illustrates the mesial side, showing the dovetail form of cavity. The wire forming the bar is given the shape illustrated and about the width of the orifice of the cavity. The bar is made of heavy iridio-platinum wire, or it may be formed of three wires, gage No. 20, arranged in triangular form, as seen in Fig. 643, the wires being soldered together with pure gold. This Fig. 641. Fig. 643. Fig. 644. triangular shaped bar, when fastened with filling materials in the dove- tail cavity in the tooth, with the right-angled point on its end addition- ally anchored in the distal hole, is secured in a manner that can be relied upon. The bar is fixed in the cavity and slot with amalgam, and its position is secured against disturbance while the amalgam is setting, by a few pellets of gold foil condensed in two or three pits drilled in the tooth structure on each side of the bar, just before the amalgam is placed at those points, as shown in Fig. 644. The amalgam should be used soft, so that the bar can be imbedded in it. The surplus mercury is then worked out by compression with pellets of cotton. The triangular shape of the cavity and of the bar permits the amalgam to lock the bar securely. CHAPTER V BRIDGE CONSTRUCTION ON VITAL TOOIH ABUTMENTS AND PIERS Recent scientific investigation of the subject of focal infection caused by pulpless teeth, and the serious pathological conditions in many cases traced as directly attributable thereto, has demonstrated to the dental profession the importance of pulp conservation in all classes of operations. In the preparation of vital teeth as supports for bridge-work many methods require an extensive removal of the enamel and of the dentin. Proportionate to the area of enamel removed, and more especially of dentin, is calcification of the pulp induced. Calcification of the pulp Fig. 645. lessens it in size and impairs its function more or less. Extensive progressive calcification frequently results in complete calcification and obliteration of the pulp. Consequently, those forms of attachments suitable for use in fixed or removable bridge-work that require the least alteration or mutilation of the coronal section of a vital tooth are the most favorably considered. For retentive attachment in fixed bridge-work various methods can be practiced that do not necessitate pulp extirpation. Of this class as here mentioned or described, those demanding the removal of the smallest quantity of tooth structure will be enumerated first. All-gold cap-crowns for short teeth made seamless or in sections, cuspids and such as have but slight contour stamped on a die cast from a mold of the teeth. 21 321 322 CROWN-, BRIDGE-, AND PORCELAIN-WORK Open-face all-gold cap-crowns (Figs. 6 lo to 615). Plate and pin attachment (Figs. 629 to 632). Inlay and bar attachments (Figs. 634 and 636 to 644). Carmichael and MODL crown attachments (Figs. 620 to 628). The typical case described in Fig. 538/ is here shown (Fig. 645) constructed with a partial crown (Carmichael) on the cuspid and a cast partial cap-crown on the molar. The attachments are made, placed in position on the abutments and an impression and bite taken with plaster that will remove the attachments in position. A model and articulating model are then run and mounted on an articulator and the remainder of the construc- tion conducted as described in Part IV, Chapter I, Figs. 542 to 558. All-gold cap and open-face crowns, also inlay and bar attachments that likewise permit pulp conservation, as has been described, may be used as conditions suggest. 1 State Board bridge model. CHAPTER VI PORCELAIN CROWN (d.ETACHED-POSt) BRIDGE-WORK — CAST SANITARY BRIDGE — ^SANITARY PORCELAIN AND GOLD BRIDGE — EXTENSION BRIDGES — MECHANICAL PRINCIPLES GOVERNING CONSTRUCTION — A LUG SUPPORT — LUG ANCHOR WITH LOCK-PIN Porcelain Crown (Detached-post) Bridge-work. — The construc- tion of bridge-work with a display of gold visible when the patient is talking or laughing, in very objectionable to many for esthetic reasons and the necessity for it frequently questioned by patients. The objectionable displiay of gold in these cases is mostly located at the buccal cusps of the upper bicuspids, the incisal tips of the anterior lower teeth, and the occlusal surfaces of the lower bicuspids and molars. These objectionable features prompted the application of detached- post crown teeth to such cases, and the manufacture of special forms of teeth. Besides their cosmetic effect, other advantages are claimed for their use, viz. (a) As the porcelain is removed from the work in soldering operations, the risk of fracture and change of shade is eliminated, (b) They are replaceable in case of fracture in use,^ In the use of detached-post crowns as dummies for bridges, the backings or supports which are joined together to form the bridge must either rest directly on the gum or leave only a shallow V-shaped space which cannot be termed self-cleansing as well as that which is made with the ordinary porcelain facings. The S. S. White, Davis, Ash's detached-post crowns, the Goslee tooth with a specially designed base, and diatoric teeth are mostly used in this style of work. Detached-post crowns and diatoric teeth, when used for abutment crowns, are ground, fitted and backed as described in "Detached-post Collar Crowns," (Part III, Chapter XVI) with the addition that on the sides of the crowns approximal to the bridge a slot is ground, into which the hacking on the base and lingual side is extended and burnished. This side flange to the backing should be reinforced with hard solder or, when a cast backing is used, the flange should be made proportion- ately strong, as shown in Fig. 646, which illu;strates a porcelain cuspid ^ In the use of all forms of replaceable teeth, the number and shade should be recorded with the name of the patient, as it simplifies the procuring of an exact duplicate. 323 324 CROWN-, BRIDGE-, AND PORCELAIN-WORK crown ground and backed. In the case of dummies this flange should extend up on both sides of the tooth. The Goslee tooth is made with a slot on each side that inclines from the base toward the occlusal surface, and provides for the extension of the backing and its union to adjoining backing in soldering. Fig. 647 shows Goslee teeth unbacked and Fig. 648 backed. Fig. 649 is a bridge supporting a lateral. In the construction of a bridge the base of a dummy crown when fitted should be ground enough to provide room for the backing, also to correspond to the surface of the model. When fitted on the model, the further work is simplified by supporting the dummies with wax in exact position and covering their labial or buccal sides with a removable Pig. 647. Fig. 646. Pig. 648. Pig. 649. plaster matrix, to permit their removal and replacement. The dummies and all wax present on "them and on the surface of the model are then removed. Cover the space between the abutments with tin foil and vaselin its surface, to prevent further adhesion of the wax in the ad- justment. Replace the dummies in the matrix to ascertain if there is sufficient space for the backings; if not, provide it by trimming the porcelain. Back the dummies, adjust them in position, and cement the backings and cusps of the crowns with wax. Insert a piece of wire lengthwise in the wax to act as a brace (see Fig. 555). Chill the wax, detach the plaster matrix and remove the porcelain crowns and dum- mies from the backings. Examine and fill in with wax any vacant places between the backings. Again chill the wax, carefully remove wax and caps, and invest in the manner shown in Fig. 650. In solder- BRIDGE CONSTRUCTION 325 ing, all the joints between dummies and abutments should be carefully united, and the base formed by the surface of the backings reinforced sufficiently to reliably sustain the strain that will be exerted on it in occlusion. When the bridge is properly finished, the porcelain teeth are cemented in position. Fig. 650. Fig. 651 Wlien a bridge includes two or more dummies, an advisable plan is to remove two at a time from the matrix and solder the backings together. When the several dummies are united, they are waxed fast to the abutments, removed and soldered to them. In this way, warping of the backing is avoided which, if it occurs, prevents the Pig. 653. Figs. porcelain from fitting into place and is very difficult to remedy. 651 and 652 show bridges with Goslee teeth. Casting Method. — The base of the porcelain duminies may be cast separately (see Part III, Chapter XVI) and soldered together or cast in one piece and then united to the abutments. Fig Cast Sanitary Bridge.— To illustrate this method, we will take the case illustrated in Fig. 653, consisting of bicuspid and molar dummies supported by gold crowns on the first bicuspid and a second molar. The space between the crowns on the model of the case is filled in with plaster as a support, as shown at A, Fig. 654, and the surface of the 326 CROWN-, BRIDGE-, AND PORCELAIN-WORK plaster at the occlusal side is given a concave form, to impart a cor- responding oval curve to the surface of the wax. The surface of the support is varnished and then lubricated to pre- vent adhesion of the wax. The wax for the casting model is placed on the support between the crowns and the antagonizing teeth occluded. The wax model is then chilled, trimmed, shaped, removed and cast. The cast gold dummies are waxed in position to the abutment crowns, all is removed and abutment crowns and dummies united. The curved surface of the base of the dummies permits it to be more easily reached and cleaned by the tooth-brush than a flat surface. Fig. 655 shows the completed bridge. Pig. 655. Sanitary Porcelain and Gold Bridge In this style, in contradistinction to the preceding method, the coronal section of the absent teeth is restored entirely of polished, or better still, glazed porcelain. Pig. 656. As the surface of porcelain is not affected by the secretions and as deposits cannot well adhere to its surface, it is as near being sanitary as a material as possible. A bridge of this form is seen in Fig. 656. Pig. 657. Either detached-post crowns or English tube teeth are ground and fitted as dummies and covered on the buccal side with a plaster matrix, as seen in Fig. 657. The holes in the center of the porcelain, when detached-post crowns are used, are drilled through to the occlusal surface, and at the cervical end or base the holes are closed by baking BRIDGE CONSTRUCTION 327 into them porcelain body. A high-fusing body should be used so that the heat required to fuse it will be sufficient to re-gloss the ground sur- face of the porcelain. The occlusal surfaces are then ground down so as to provide sufficient space for the thick cusp-caps, as illustrated in Pig. 658. Fig. 658. The cusp-caps are cast with posts extended into the holes in the dummies, or the posts are afterwards inserted and soldered. The cusp-caps are adjusted in position, and the ends cemented to the abut- ments with wax, and the bridge removed. The porcelain dummies are Pig. 659. removed from the cusp-caps (Fig. 659, in section), the bridge invested and the parts soldered together. The bridge is then trimmed and pol- ished and the porcelain dummies cemented in position. The bridge then appears as shown in Fig. 656. Pig. 660. The cervical sections or bases of upper dummies are best reduced in size and given a surface approximating that of the shape of the gingival border and on the lower jaw more of an oval form, as seen in section in Fig. 659. To avoid exposure of metal, and for esthetic reasons, especially on superior dummies, the cusp or metallic portion and the porcelain can be shaped as indicated in Fig. 660. CHAPTER^VII EXTENSION BRIDGES GOVERNING MECHANICAL PRINCIPLES — CONSTRUCTION- — A LUG SUPPORT ■ — A LUG ANCHOR WITH LOCK PIN INTERVENING ROOTS The term "Extension" is applied to bridges chiefly or entirely sup- ported by one abutment. In relation to the anterior teeth, it means attaching a dummy to an artificial crown, or other form of retentive abutment to replace an adjoining absent tooth, with or without a lug resting on an adjoining tooth as a supporting abutment. A bridge of this style when it replaces two or three posterior teeth is formed by using two of the anterior teeth as an abutment, and extending the dummy teeth from it, suspended, or on a saddle. A saddle is an oval-shaped gold or platinum plate of the form of the alveolar ridge, placed under the extension dummy teeth for them to rest on and obtain alveolar support to resist direct and lateral stress in occlusion. Although a most serviceable adjunct to a remov- able bridge, its use has been condemned and dispensed with in fixed bridge-work, as being insanitary. When a metallic base is applied under a dummy tooth, it should not exceed the size of the base of the dummy and be of a form that will permit the passage of floss silk between it and the surface of the gum for cleanliness and the health of the mem- brane. While such a base — sometimes incorrectly termed a saddle — may slightly aid to steady a dummy, it furnishes no material alveolar support. Governing Mechanical Principles. — In extension bridge- work, the portion that constitutes the bridge exerts on the abutment, in resist- ing the force of occlusion, an action like that of a lever. This principle must receive consideration in the employment of this form of bridge. A lug support or supporting abutment on the extended end, if attain- able, should always be applied even to one tooth. More than one tooth should not be extended from an abutment without such support. When two approximal crowns support an extension bicuspid or molar bridge dummy, occlusal force on the dummy is counterbalanced by the resistance of the further anchorage crown from the bridge, the pressure on which is in a line from the socket occlusally; the crown approximal to the dummy acting as a fulcrum the force on which is in the di- 328 EXTENSION BRIDGES 329 rection of the apex of the root. The occlusal surface of the bridge tooth should be narrower from buccal to lingual side than the natural tooth, to offer less occlusal surface to the antagonizing teeth, between which and the dummy tooth, there should be a space of about one-sixteenth of an Fig. 661. Pig. 662. inch.- In fact, such an extension dummy tooth should be inserted principally for appearance and not for actual use. Pig. 663. Fig. 664. Construction. — The abutment is first constructed. If it consists of two crowns they are soldered together. An articulation and im- pression are taken which will remove the abutment in position, and models are made. The extension tooth or teeth are then fitted to position and soldered to the abutment. Figs. 661, 662, 663 and 664 show small extension bridges. A Lug Support. — This consists of a lug formed at the end of an extension bridge to rest on either an inlay, a gold or amalgam filling in the adjoining tooth, or the surface of the tooth acting as a supporting abutment. Fig. 665 illustrates a case with a lug resting on a cuspid. A lug support is formed as follows: When the dummies are mounted on the model ready for investment, adapt on the model of the inlay filling or tooth where the lug is to rest, a piece of thin platinum, gage No. 36 to 38. Place on the surface of the platinum, when adjusted, a still narrower piece of gold clasp plate. Wax them in position to the Fig. 665. 330 CROWN-, BRIDGE-, AND PORCELAIN-WORK dummy tooth and invest. The projecting ends of the platinum and gold plate should be long enough to extend entirely across the tooth over on the adjoining one, to furnish a means of retaining the metal in posi- tion in the investment during soldering. The wax should cover only a little more than the portion of the metal to form the lug when sold- ered. In finishing the surplus metal is cut off and the lug reduced so as to extend not quite to the edge of the inlay or filling it rests on. Some- times in the case of an incisor, a lug is allowed to rest directly on the Pig. 666. lingual side of the adjoining tooth as shown in Fig. 665. A lug so applied should be reduced in size and the edge slightly rounded so that floss-silk may be freely passed under it, which should be done at least twice daily. In the case illustrated in Figs. 666 and 667, the lug rests with the end curved in a countersunk amalgam filling. A Lug Anchor with Lock Pin. — This consists in addition to a lug of a pin that anchors in, but is not cemented in the inlay or filling it rests upon. For this purpose a gold inlay or amalgam filling is inserted Pig. 667. in a deep cavity formed in the side of a tooth, as illustrated in Fig. 668, which represents a typical case. The filling or inlay is slightly countersunk and a hole is drilled in the center about one-sixteenth of an inch in depth, large enough to freely receive an iridio-platinum pin of about gage No. 16. A disk of platinum, gage No. 36, large enough to cover the filling, is adapted to its surface and perforated over the orifice of the hole. The point of the pin is inserted in position through the hole in the platinum, into the hole in the amalgam, attached with wax, removed, invested and connected to the platinum with a small EXTENSION BRIDGES 331 quantity of pure gold. The lug is trimmed and fitted in the mouth, the bridge inserted and the lug attached with wax to the bridge. Bridge and lug are removed, invested, united and the lug reinforced with solder and a narrow strip of gold clasf) plate. A supporting abutment as constructed for removable bridge-work and described in Part V, Chapter I, may in some cases be used for a fixed bridge. Fig. 668. Connecting Bars for Bridges. — Connecting bars, to obviate the removal of crowns of natural teeth intervening between the sections of a bridge, are formed by passing a heavy bar of round or oval shaped clasp gold or iridio-platinum wire, about gage No. 14, around the inter- vening teeth, close to but not touching them, and resting lightly against the gum, so as not to cause too pronounced interference with the tongue This is accomplished by very slightly indenting the bar in the surface of the model before soldering (Fig. 669). Waxed floss-silk should be daily drawn under such a bar. Intervening Roots.^ — An intervening root not suitable for crowning, but free from disease, between the abutments of a projected bridge, when necessary and practicable, may be allowed to remain. The root is to be given preparatory treatment and a porcelain or gold inlay in- 332 CROWN-, BRIDGE-, AND PORCELAIN-WORK serted that will cover the end of the root and be even with or a little above the surface of the gum, especially on the lingual side. A root so Pig. 670. treated can be utilized to afford some support by resting the bridge upon it. Fig. 670 represents a case in which the root of the cuspid on the right side has been so treated and utilized. CHAPTER VIII BRIDGE-WORK AND SPLINTING IN CASES OF PYORRHEA ALVEOLARIS THE PLATE AND PIN ATTACHMENT — USE OF CONNECTING COLLARS — POSTERIOR TEETH — ^BICUSPIDS AND MOLARS In cases of pyorrhea alveolaris, when the teeth are loose, connecting them with bridge-work or a spHnt steadies them in their sockets and consequently permits more effective treatment. The method here described relates to teeth not affected, or only slightly so by decay. Fig. 671. The Plate and Pin Attachment. — This attachment may occasionally be applied in cases of pyorrhea alveolaris. By its use loosened teeth can be joined together and supported without exposure of metal. Fig. 672. In such cases, when the tooth has a vital pulp, a plate with two or three pins is used, and when the tooth is pulpless one pin. The pins and plates are made and fitted to each tooth, the ends of the pins being left protruding from the plates. An impression is taken, removing the 333 334 CROWN; BRIDGE; AND PORCELAIN-WORK plates and pins in position. They are next invested and soldered together. (See Part IV, Chapter IV.) An intervening absent tooth or teeth may be supported between sections of the plates. The method is especially applicable in cases involving the lower front teeth. Fig. 671 illustrates such a case with the teeth prepared, pulps having been removed; Fig. 672 the plates with their projecting posts in position; Fig. 673 the constructed denture, and Figs. 674 and 675 the denture in position on the teeth. ^ Pig. 673. Use of Connecting Collars. — ^Fig. 676 illustrates and explains a method of replacing an incisor and supporting the adjoining loosened teeth with successive cemented connecting collars of gold, in cases of pyorrhea alveolaris. This method does not require removal of the pulp. For the application of such collars, the teeth require to be trim- med the thickness of the plate used. The collars may be formed of a strip of pure gold plate about gage 32 to 7,;^, or platinum, gage Nos. 36 Fig. 675. to 38, by bending and fitting the strips to the form of any two teeth, in the shape shown at A, Fig. 677. This leaves but one thickness of plate between the teeth. An additional loop can then be added, as shown at B, for one adjoining tooth. The soldering may be done quickly with a Bunsen burner without investing. Parts of the loops which demand it should be slit and lapped to allow the plate to be adapted closely to the surface of the tooth. 1 Dr. D. D. Smith. BRIDGE-WORK AND SPLINTING 335 The bands of metal should be })laced toward the incisal section of the teeth, leaving the interproximal spaces between the teeth enturely free. The cementation can be done with zinc phosphate, or if removal is contemplated, with gutta-percha cement. A fusible metal die will assist the operation before fitting the collar in the mouth. To form the metal model, take a plaster impression in a sectional impression cup, and fill with fusible metal. Cut the spaces between the teeth on the model with a saw of the same gage as the gold or platinum plate to be used. Fig. 676. Fig. 677. Posterior Teeth Bicuspids and Molars. — ^These teeth may be bridged or splinted by the use of inlays, bars or small caps or plates. Pins should be inserted in the mesial and distal ends of an inlay or, if pulpless, a single post can be extended into the pulp-canal. Sufi&cient of the natural crown and of the antagonizing teeth must be removed to allow ample space for the intervening metal applied. Fig. 678. Fig. 679. Fig. 680. Fig. 678 shows in section a molar with living pulp in which is inserted a bar or inlay, with two pins in the line of the sulci, and the inlay or bar extended into an adjoining pulpless molar. Fig. 679 represents in section, viewed from the lingual side, a small plate and pin attachment on a pulpless cuspid and bicuspid. Fig. 680 and 681 illustrate in section pulpless bicuspids and molars prepared with an iridio-platinum bar, with pins to be inserted and anchored in them with amalgam. Veneering the bar with a film of pure 336 CROWN-, BRIDGE-, AND PORCELAIN-WORK gold by melting pellets of gold foil over it with a blowpipe, then rolling it under a file, will facilitate a better adhesion of the amalgam to the bar. In the formation and adjustment of these applicances, close adapta- tion of the metal to the surface of the teeth and avoidance of pockets should be observed. The incisal edges and cusps of affected teeth Pig. 68i. Fig. 682. should be trimmed and shortened so that while the teeth occlude evenly, the cusps only touch their antagonizing teeth in the lateral movements of the jaw. The object is to retain direct pressure but do away with lateral strain (See Fig. 682). Constant care regarding cleanliness by the frequent and regular practice of prophylactic measures is required of the patient. (See Part IV, Chapter XL) CHAPTER IX REPAIR OF CROWN- AND BRIDGE-WORK THE ORDINARY METHOD — DR. BRYANt'S METHOD — COUNTERSUNK PIN- HOLE METHOD — TO REPAIR WITH A DIMELOW FACING — ASH'S RE- PAIR FACINGS — INLAY METHOD — REPAIR OF AN INCISOR OR CUSPID GOLD-BACKED CROWN WITH A DETACHED-POST CROWN — ADVANTAGES OF DETACHABLE BRIDGE-WORK — REMOVAL OF CROWNS OR BRIDGES CEMENTED WITH ZINC OXYPHOSPHATE — REMOVAL OF A POST — A POST PULLER — DIFFICULT POST REMOVAL REMOVAL OF CROWNS OR BRIDGES CEMENTED WITH GUTTA-PERCHA, ALONE OR COMBINED WITH OXYPHOSPHATE — REPAIR OF A GOLD COLLAR CROWN The fracture of a porcelain facing on a permanently attached bridge is an annoying incident for both patient and dentist. It is usually attributable to failure to properly protect the incisal edge or occlusal surface of the porcelain with metal, a precaution rendered necessary by the rigid character of the resistance offered the antag- onizing teeth through the abutments, or by exposure of the porcelain in time through loss by attrition of the metal protecting it. In most cases the porcelain can be replaced without the removal of the bridge, but the attachment is seldom as reliable as in the original piece. The Ordinary Method. — The following is the method commonly adopted with incisors or cuspids: The pins of the broken facings are cut off, the surface of the backings trimmed level, and a suitable long- pin facing selected. Mark the position of the pins of the new facing on the backing by drying, heating and flowing over its surface a film of wax, then with small pliers place the facing in position, and press the pins in the wax; or place a little rouge and oil on the end of the pins and mark the backing with them. At the points marked, drill holes in the backing to receive the pins of the new facing, countersinking the holes at the lingual side. After the backing is drilled, grind the porcelain to fit it as perfectly as possible, place in position and grind off the pins so that they protrude enough to form a head when riveted. If a suitable long-pin tooth is not procurable, the short pins of an ordinary tooth can be lengthened by bending a piece of platinum wire in the form of a semicircle and soldering its ends to the ends of the pins with pure gold. The wire is then cut in the center and the length- ened pins trimmed as required. 22 337 338 CROWN-, BRIDGE-, AND PORCELAIN-WORK The pins are riveted on the h'ngual side into the countersunk holes of the backing. The riveting should be done with punch forceps hav- ing a large punch (Fig. 683), the porcelain facing being protected by a piece of lead placed against the labial aspect, or by the use of a matrix formed of impression compound softened and then chilled. The heads of the pins should be burnished smooth with a revolving burnisher. In case of fracture of the porcelain facing of a bicuspid crown or dummy with a thick gold backing, a corresponding facing with very long Pig. 683. pins is selected and ground to fit, and holes in proper position drilled in the gold, to receive the full length of the pins. Roughen the pins a little with a sharp instrument and cement pins and facing to the gold. Should the holes extend through the gold at the lingual side, the open- ing should be slightly countersunk and filled with gold or amalgam. Any gold present to protect the occluding edge of the porcelain should be burnished against its surface. The Improved Bryant Method The technic of the Bryant bridge-repair method, as recently modi- fied, to assure easier, more accurate work, and greater strength is thus described : Clip off the pins from the bridge and grind to a flat surface, and cover the surface with a film of wax. Hold the new facing in exact position and press the pins through the film of wax. With a pointed instrument and hand mallet center-punch the position of the pins as shown in the wax, thus giving a starting point for the drill No. loi (Fig. 684), with which drill two holes through the backing to receive the pins of the new facing. Next grind the facing to exactly fit the surface REPAIR OF CROWN- AND BRIDGE-WORK 339 of the backing, and with counterbore No. lo enlarge the holes in the backing. Using reamer No. 3A, from the lingual side, enlarge the lingual opening of the holes, taking care to stop this operation just before the end of the reamer is flush with the labial surface of the backing. Care- fully cut a shallow thread on the tooth pins with die No. i and follow with die No. 2 to complete the thread to full depth. See that the pins are threaded their full length close up to the porcelain. Cover the lingual surface of the facing with cement or gutta-percha, keeping the pins clean, and press to place. Use nut-holder No. 6 to carry the nuts No. 5 to place over the threaded pins, and with nut- FlG. 684. driver No. 4 screw alternately to seat. The nuts should be tightened sufficiently to bring the facing and backing into contact, but without excessive force, which might cause fracture of the porcelain. If the nut or pin extend beyond the backing, grind off flush and polish. If below the surface of the backing, fill in with Corona gold or gold foil. Countersunk Pin-Hole Method. — This method is to be used only when the pins remain intact in the backing. Remove all the fractured facing. Select a facing of the same make and mold; if not procurable, one of the same size, thickness of porcelain and location of pins. Cut the pins off close to the porcelain; drill out the portion of the pins left and 340 CROWN-, BRIDGE-, AND PORCELAIN-WORK enlarge and slightly countersink the holes with carborundum paste and a copper or steel drill/ so that the pins in the backing shall enter the holes in the porcelain facing easily and permit the new facing to come to place, as shown in Fig. 685. To correct any discrepancies in conformation between the surface of the gold backing and the facing, paint the surface of the gold with a coat of rouge and oil and press the facing against it. The rouge will mark on the porcelain the exact spot to remove. When Mitted by this method and cemented with zinc oxy- phosphate or silicate cement, a very reliable replacement of the facing is effected. To Repair with a Dimelow Facing. — A Dimelow facing may be utilized to replace a fractured facing of the ordinary type when the pins are broken from the backing. Clear the backing of fractured porce- lain and pins. Select a Dimelow facing (See Fig. 592) and grind it to position against the backing. Dry and heat the backing and melt a little wax over the part that corresponds to the position of the pin-holes in the facing. Moisten the facing and press it firmly against the wax. On removal, the position for the pin-holes through the backing will be indicated by two raised points of wax, formed by the holes in the facing. With a spear-shape drill corresponding in size to the holes in the porcelain, drill two holes through the backing in the places indicated by the wax points in a linguo-gingival direction, in a line with the holes in the facing. Follow the drill with a tap, and screw into the holes two threaded pins, and cement facing to pins and backing.^ Pig. 685. Fig. 686. Ash's Repair Facings. — Fig. 686 illustrates these facings. They are made with a slot for the ends of the pins of the broken porcelain facing to fit into and be connected. As the position of the pins usually varies, the replacement may call for considerable fitting. This can be simplified as follows: After removing all remnants of the broken facing and exposing the pins, place a little cement around the shanks of the 1 Use one of the drills of the set sold for drilling holes in porcelain teeth to insert imitation gold filling. ^ An especially prepared outfit is manufactured and sold for repairing with the Dimelow facing. REPAIR OF CROWN- AND BRIDGE-WORK 341 pins to even them with the heads, then take an impression of the back- ing and pins with impression compound, and form an amalgam replica or model (Fig. 687). Place some white gutta-percha in the place of the porcelain to represent the facing and dismiss the patient. By the next engagement, grind and fit an Ash porcelain facing to the amalgam model, a much easier task than fitting it to the backing in the mouth. Cement facing in position with silicate cement. Inlay Method. — This method is applicable if the pins are still in the backing. Select porcelain facing, if possible of the same mold as the fractured facing. Remove the pins of the facing, and using as a model an amalgam replica made as described in the preceding method (Fig. 687), grind down the facing to a veneer that will fit in position over the pins of the backing. Adapt by burnishing to the surface of the cavity of the backing that was occupied by the porcelain, a piece of i/ioQo platinum foil, as a matrix, and if necessary, by swaging the platinum to the amalgam die. Shape the platinum over the pins but not in on the sides so as to obstruct easy removal of the matrix. Fill the matrix with Close's porce- lain body. Vibrate the body and absorb the moisture with blotting paper, then press the porce- lain veneer on the surface and into the porcelain body to proper position. Remove the porcelain veneer so as to leave the impression in the porce- lain body, then remove matrix and body from the mold, place it on pulverized silex on a slab and give it a good biscuit bake. Replace matrix in amalgam model, correct any warping incidental to the shrinkage in baking, add body and again place the veneer in position. Remove both together and give the fusing bake. When the platinum matrix is removed from the body of porcelain, you have a porcelain facing the exact form of the cavity of the backing. The cavity or box in the porcelain that receives the pins may be slightly countersunk with an old wheel bur and carborundum powder. Cement to place with silicate cement and burnish the incisal edge of the gold backing to the incisive edge of the porcelain. Repair of an Incisor or Cuspid Gold-Backed Crown with a De- tached-Post Crown. — Remove fractured porcelain and pins, grind and shape the gold backing and floor of the cap as nearly as possible to a form approximating that of a gold root-cap, with a post to receive a detached-post crown. Fig. 688 shows the relative comparison. Take an impression in compound; cut and shape a piece of coin silver the size of the trimmed post on the root-cap, insert the piece of coin silver 342 CROWN-, BRIDGE-, AND PORCELAIN-WORK Fig. in the impression of the post and make an amalgam die. Allow the amalgam to crystaUize until the next day. Select a suitable detached- post crown. As the post on the cap will be found a little back of the line of the hole in the porcelain in a lingual direction, remove with fissure-shaped carborundum points enough porcelain to freely admit the post. Should the carborundum point go through the porcelain in making the space for the post, trim off a little of the end of the post and bake over the hole a thin layer of Close, Jenkins or other suitable porcelain body. If necessary, build the applied body a little above the surface of the porcelain of the crown, as shown in section at point A, Fig. 689. The post is notched and the crown cemented on with silicate or some equally hard cement, that will adhere to the porcelain and gold. In suitable cases, this method gives very satisfactory results and is often equal in re- liabihty to an entire new crowning operation. Silicate Cement. — ^This cement can be used to temporarily replace a porcelain facing. When the metallic incisal edge of the backing or occlusal surface and the pins are present, repair work of considerable durability may be effected. The fractured porcelain having been re- moved, the backing is protected from moisture, and a mixture of the silicate cement of the proper shade applied and shaped with a spatula to the form of the former porcelain facing. When the cement has set it is shaped in detail. A matrix approximating the facing in form may be used to condense and shape the cement when setting. Advantages of Detachable Bridge-Work.— If the character of the break in a porcelain facing will not permit repair in the mouth, the bridge must be re- moved, repaired and reinserted. Under such circum- stances, the advantages of a detachable form of bridge are evident. The additional time required to construct cases of bridge-work that will properly admit of being made detach- able and cemented with gutta-percha or gutta-percha cement combined with oxyphosphate is not as much as that which would be consumed in the construction of the same work with replaceable porcelain facings. Removal of Crowns or Bridges Cemented with Oxyphosphate. — When it is necessary to remove an artificial incisor or cuspid crown, whether inserted singly or as a support for a bridge, it can be detached by grinding the gold or porcelain away at the lingual section over the Fg. 689. REPAIR OF CROWN- AND BRIDGE-WORK 343 post, which when exposed is severed, and the attachment of the cement broken up, as shown at A, Fig. 690. In a case where the facing is fractured or absent, as illustrated in Fig. 691, the post may be more easily reached from the labial side (B). The collar may also be sUt and bent aside, if found necessary. When a post of a crown is veneered with a film of gutta-percha previous to cementation, the re- moval of the post is easily effected. In the case of an all-gold crown, usually the collar on one or both sides has to be divided and pried up from the root by first making a groove with a small vulcarbo disk, and then cutting the gold with a small bur and a sharp instrument. A crown-slitter, an instrument made for. the purpose, will facilitate the operation (Fig. 692). In an all-gold crown on a very short posterior tooth, a large hole drilled in the grinding surface will sometimes admit of removal of a sufiicient quantity of the cement to enable the attach- ment to be loosened by prying up- ward. With care and patience in the operation of removing a gold Pig. 690. Pig. 691. Pig. 692. crown, it will often not be injured beyond repair, but usually the time spent in repairing, considering the result, suggests a new crown instead. Removal of Post.^ — To remove a post, first drill away the cement around the post at the orifice and a short distance up the canal with the smallest size round-head bur, keeping the bur against the surface of the post. Next seize the end of the post with phers and with a moderate amount 5f force carefully applied endeavor to remove it. If this does not succeed, use a post puller. A Post Puller.— Fig. 693 illustrates the S. S. White post puller outfit. It consists of a straight (i) and right-angle (2) reamer to 344 CROWN-, BRIDGE-, AND PORCELAIN-WORK ream the end of a post (3) and a screw stock to cut a thread on the reamed end. The screw socket of the puller is next screwed on the end of the post, the thumb-screw that lifts the socket is screwed down against the end of the root, and the socket of the post lifted incisally, (^ I A B C 4 ■ Fig. 693. — Trepine for direct aand 2, Trephine for angle handpieces. 3, Screw- stock. 4, Post-extractor. A' h, C, D, Post and root at various stages of the operation. removing the post. A rubber washer around the socket with a metal washer behind it ag?jnst the body of the puller, gives the necessary bearing, equalizes tne pressure and avoids fracture of the root by cush- ioning it. Fig. 694 shows another style of post puller, called the "Little Giant," that can be quickly apphed when the end of the post extends beyond the surface of the end of the root. The end of the post is seized between the /_\ large ■ beaks of the puller by tightening them with a Pig. 695. screw and the shoulder is screwed down on the end of the root, lifting the post incisally. Difficult Post Removal. — Some posts are so deeply inserted and firmly cemented that they cannot be safely removed with a post puller as ordinarily apphed. In such cases a very small space should be cut around the post, removing any cement present and as Httle REPAIR OF CROWN- AND BRIDGE-WORK 345 dentin as possible, with the smallest sized round-head bur. A post puller can then usually be effectively applied. When a post cannot be removed by any of the methods mentioned the only resource is to drill it out, a tedious operation and one re- quiring great care. In the upper section of the canal where the post cannot be seen while drilling, use a new sharp round-headed bur. Apply the bur with a light steady pressure that will indicate when the bur is on the metal of the post, and when off of it in the dentin. By taking time and ex- ercising patience, the post can be removed without material injury to the root. Smooth-sided drills with several small blades that cut only on the end, as shown in Fig. 695 may be used effectively to cut into the center of the post in the lower section of the canal. Removal of Crowns or Bridges Cemented with Gutta-Percha Only or Combined with Ox3rphos- phate. — In metallic collar or cap- crowns, first slightly raise the edge of the collar. Fig. 696 shows a crown-heater for cementation and removal of incisors and cuspids. It is to be moderately heated and applied as illustrated. Fig. 697 shows a small-sized crown-heater for general use. The membrane should be protected by spreading a napkin across the mouth over the lower lip. In using the form of heater shown in Fig. 697 heat it almost to a red heat, place a Fig. 696. finger against the artificial crown and apply the crown-heater to the crown. For bicuspids and molars, apply the crown-heater to the occlusal surface and for incisors and cuspids at the lingual side toward 346 CROWN-, BRIDGE-, AND PORCELAIN-WORK the incisal edge. As the crown absorbs the heat, it is indicated by the finger. When the heat is raised as high as the finger can comfort- ably bear, the crown-heater should be removed for an instant to permit the crown to cool slightly, then again applied. In heating a crown, it is well to instruct the patient to raise the left hand should the heat become painful at any time. The application of the heat should be continued as directed for at least three to five or more minutes until the gutta-percha in all parts of the crown is thoroughly softened, which proceeds slowly owing to its con- tact with the natural crown or root. In bridge-work, as soon as the first crown is heated, instantly pass the crown-heater along the surface of the bridge to another crown or crowns and then back and forth on the surface of the bridge until all the attachments are uniformly heated. When this has been effected, start the bridge at one end and then at the other, or at both together, and lift it from position. Repair of a Gold Collar Crown. — A hole or slit in a gold collar or crown is easily repaired, by first placing and press- ing on the outer surface over and into the hole or slit soft adhesive wax, (W, Fig. 698). Next adapt a piece of platinum foil (PF) larger than the aperture on the inside close against the sur- face and extended beyond the edge of the collar, and attach it to the wax by placing a hot instrument against the surface of the platinum inside the crown. The interior of the crown is next filled with investing material. The wax is washed off the outside of the crown, exposing the hole or slit, and solder is melted and flowed over the platinum and gold collar. ITie crown should be heated slowly to allow the investment to dry out thoroughly before the soldering is begun. In miniature. Fig. 697. Pig. 698. CHAPTER X GENERAL APPLICATION OF FIXED CROWN- AND BRXDGE-WORK CENTRAL OR LATERAL INCISORS, CUSPIDS OR BICUSPIDS — CENTRALS, LATERALS AND CUSPIDS COMBINED — CUSPIDS, BICUSPIDS AND MOLARS COMBINED — BICUSPIDS AND MOLARS COMBINED — USE OF PARTIAL CAP — ^INCISORS, CUSPIDS, BICUSPIDS AND MOLARS COMBINED — EXTEN- SIVE APPLICATION OF FIXED CROWN- AND BRIDGE-WORK — CRITICISM The construction and general application of fixed bridge-work, as explained in the foregoing chapters, are additionally explained and illustrated in the following typical cases. Central or Lateral Incisors, Cuspids or Bicuspids. — The restora- tion of a central or lateral is an operation that calls for the exercise of judgment and in some methods of procedure, tests the skill of the operator. When the other teeth are present, the subject of support involves the question of the mutilation or excision of one or both the adjoining natural crowns. The condition of the adjoining teeth respecting freedom of the crowns from decay, whether vital or pulpless, health of the roots and contiguous membranes and occlusion, will suggest the most suitable method of procedure. When a central is to be replaced and a normal condition of teeth and occlusion is present, the support preferably should be obtained by the adjoining central, or central and lateral combined, if possible with- out removal of the pulp. If the abutment tooth is favorable in form and occlusion, this may be done either by the use of the three-pin plate 347 348 CROWN-, BRIDGE-, AND PORCELAIN-WORK or a Carmichael crown on the central, with the aid of a lug resting on the lateral. The three-pin plate is frequently suitable in the case of a central. Fig. 699 shows a typical case. A is the bridge viewed from the lingual side and B from the labial. When the central is short, the incisal edge worn down by attrition so that the dummy tooth will have to resist directly, or nearly so, the force of occlusion, the Carmichael crown is preferable, as such an attach- ment is comparatively stronger. An anchorage lug resting in an inlay in the lateral is also advisable, as illustrated, viewed from the labial side in Fig. 700, or instead the use of another Carmichael crown as a support, as shown in Fig. 701, lingual aspect. If either the central or lateral is pulpless, an inlay or plate with a post extending partly up the pulp-canal is the preferable support, as shown in Fig. 702. As removal of a pulp to form an attach- ment involves opacity and in time dis- FiG. 700. Pig. 701. Pig. 702. coloration of the tooth, it should be avoided if possible in the case of young patients. In the case of patients over thirty years of age discoloration from removal of the pulp need not be so seriously considered, but it will certainly occur to some extent in time, no matter how scientifically and skilfully the operation is performed. It is never- theless a method preferred and extensively practiced. Many operators in such cases remove the pulps of both adjoining teeth to insure a more positive support and prevent spreading of the supporting teeth, also to avoid pressure on the dummy tooth that would push it forward and twist the central on its axis when that alone is used as the abutment. When a puJp is to be removed from an incisor for such a purpose, it should be done instantly by the use of local anesthesia or under ni- trous oxid alone or combined with oxygen. The upper section of the root-canal can be sealed to stop all hemorrhage with a dressing of color- less essential oil, such as oil of myrtle, or Geminol, a highly refined French preparation of the Eucalyptus class. The rubber-dam should be applied, no saliva allowed to enter the canal and the dressing herme- tically sealed with gutta-percha, covered, if necessary, with oxyphos- FIXED CROWN- AND BRIDGE-WORK 349 phate. The dressing should be removed within three days, the extreme end of the canal filled with gutta-percha and the remainder of the canal and cavity of the crown filled with absolutely white zinc oxychlorid. No further antiseptic treatment than mentioned should be practiced, as the canal is not infected and only needs protection. In this manner the natural color of the tooth will be maintained to the greatest possible degree. Later drill out enough oxychlorid to admit the retaining post. Fig. 703 shows a case treated in this manner, the central and lateral being used as supports. Fig. 704 illustrates a lateral and central supported by a central and cuspid. Inferior incisors are seldom lost except by pyorrhea. In such a case, plates with pins, or collars may be used on the adjoining teeth, as was illustrated in Figs. 671 to 675. When an open-face crown is used as an abutment, the labial surface of the gold needs to be removed enough to avoid its exposure in the movement of the lips. Pig. 703. Pig. 704. The pin-plate method is described in Part IV, Chapter III, The pulps of the teeth in the mandible require to be removed in this method, except in the case of a cuspid, when the size, shape and con- dition of the tooth will permit of the insertion of three pins. Excision of the natural crown of the adjoining central and mounting a collar crown on the root simplifies the operation of restoration of either a central or lateral. When a central is disfigured or weakened with decay or fillings, this is the best method (Fig. 705). A lateral can be supported in like manner by the adjoining central or cuspid in accordance with any of the methods described. As a rule, preference should be given the cuspid as a support for a lateral, unless the condition of the central suggests its utilization by being pulpless, or its appearance suggests that an artificial crown would be an improvement. 350 CROWN-, BRIDGE-, AND PORCELAIN-WORK The replacement of a superior incisor by an extension bar support from a bicuspid, as shown in Figs. 706 and 707 is not now favoraby considered. In a few years the leverage exerted loosens the bicuspid. Preferably place an open-face cap with a pin or pins on the bicuspid, and extend a narrow iridio-platinum bar across the lingual side of the cuspid to support the lateral (Figs. 708 and 709), The cuspid in this Pig. 70s. Fig. 707. way relieves the strain on the bicuspid. The surface of the enamel of the cuspid can be cleaned by daily passing floss silk under the bar. The method of construction is as follows: An open-face crown is constructed for the bicuspid by one of the methods already described. The crown is placed on the tooth, the dummy lateral fitted and ce- mented in position with sticky wax, an impression taken and ja model run of investment material. The model will Pig. 708. Pig. 709. show the crown and lateral in position. Place a narrow strip of platinum plate, gage No. 38, across the lingual side of the cuspid touching the gold cap and backing of the lateral. Over the platinum place a still narrower piece of gold clasp plate, about gage No. 28, or a piece of half round wire, gage No. 14, wax the ends to the crown and lateral and hold it in position in the center with investing material. FIXED CROWN- AND BRIDGE-WORK 351 When the ends of platinum and plate or wire have been attached with solder to the crown and lateral, the investing material should be re- moved from the center and the solder flowed across the piece forming the bar. This makes a bar with a surface of platinum resting against the tooth. In finishing it should be reduced in width as much as re- quirements for strength will permit. Fig. 710. Fig. 711. Centrals, Laterals and Cuspids Combined. — Two laterals supported by two central crowns are shown in Figs. 710 and 711 and in position in 712. Lugs are best additionally formed on the laterals to rest on the cuspids. When approximal crowns are united to support bridge- work, as in this case, a free space should be preserved at the cervices between their respective collars to properly admit the gum septa. Fig. 712. Figs. 713 and 714 show a bridge of the incisors supported by two collar crowns on the cuspid roots. Open-face cap-crowns may also be used in a case suitable for their application. Figs. 715, 716 and 717 illustrate a case with open-face cap-crowns for supports. In the construction the best method is to 352 CROWN-, BRIDGE-, ANDPO RCELAIN-WORK form and fit the caps or crowns to the cuspids, remove them in a plaster impression and "bite," make models and then bridge between /'i>. ^ W f h V\ < V3 '"''I I I I j_j_^,| iiL.LIi.i.iniiiiimiii,i iiii|i|UlJ||||[| Pig. 717. the crowns with the incisors. The edges of the collars of open-face crowns should be leveled and burnished close to the teeth. If pro- FIXED CROWN- AND BRIDGE-WORK 353 perly done in a case when only the edge is visible in laughing, they will resemble cervical gold filHngs. Inlays, bars or lugs extending from the cuspid crowns into the first bicuspids can be utilized as an additional anchorage should the occlusion of the anterior teeth indicate it. Gutta-percha alone or in combination with zinc oxyphosphate is suggested for cementation in many of these cases (see Part III, Chapter XXI). Fig. 718. " In the method shown in Figs. 718 and 719, for the insertion of two centrals, the leverage exerted on the bicuspids will in a few years loosen them in their sockets. The addition of lugs placed on the distal sides of the centrals resting on the laterals will, in a measure, relieve the stress, but will have a tendency to press the laterals forward; conse- quently the method is one not at present favorably considered. Fig. 719. Cuspids, Bicuspids and Molars Combined. — ^Figs. 720 and 721 show bridge-work supported by a cuspid porcelain-faced crown and a molar gold cap-crown. If the cuspid is sound and contains a vital pulp, its vitality should be preserved and either an all-gold, an open- face cap-crown, or a Carmichael attachment, be applied in preference to the form illustrated. In the case of a pulpless cuspid an inlay in- 23 354 CROWN-, BRIDGE-, AND PORCELAIN-WORK serted on the lingual side with a post in the canal, is often preferable to applying an artificial crown as illustrated. Fig. 722. Bicuspids and Molars Combined. Use of Partial Cap.— fig. 722 presents a bridge on the mandible from the first bicuspid to the second FIXED CROWN- AND BRIDGE-WORK 355 molar. The inclination of the teeth toward each other suggested the construction of the bridge in the form illustrated. The molar is entirely covered with a gold cap. The bicuspid is capped only on the occlusal third (A). A pin inserted in the cap .fitting a hole drilled in the sulcus of the bicuspid secures the cap in position. A gold inlay extending across the sulcus with a short pin in the mesial end might be used in preference. This latter method is very suitable in a case where the crown of the bicuspid is long and the root sHghtly exposed. Molars in a similar condition may be capped in like manner for bridge-work. Pig. 724. Pig. 723. Fig. 723 and 724 illustrate a bridge supported by short gold caps on both bicuspid and molar. The caps in such cases may be swaged or cast. (See Figs. 535 and 536.) Fig. 725 illustrates a case of bridge-work supported on an abraded bicuspid and molar by gold partial caps or tips with pins, the construc- tion of which is described in Part III, Chapter XVIII. It will be noticed that the molar tips forward considerably. The use of this method is preferable to using gold crowns, which in this case would Pig. 725. involve extensive trimming and probably the removal of the pulps of the teeth. Fig. 726 represents a case in which the superior third molar and the first bicuspid are utilized for the attachment of a bridge to support the loss of the intervening teeth. Fig. 727 represents the teeth prepared for the bridge. A, the Ungual cusp of the bicuspid is cut down to allow the placing of a sufficiently thick cusp-cap; B, a hole between the cusps for a retaining pin; C, the third molar made uniform in size from neck to occlusal surface, the Matter having been su€iciently trimmed without 356 CROWN-, BRIDGE; AND PORCELAIN-WORK removal of the pulp; D, a partial cap constructed so as to cover every portion of the bicuspid except its buccal surface, the edge of the cap Fig. 726. passing under the gum margin; E, a retaining pin adapted to the open- ing B; F, the gold cap for the molar. D-, Pig. 727. Fig. 728 represents the bridge anchored in position with cement. As the gold attachments and backings are out of sight, the appearance presented is natural. There is this fact to be considered in regard to Pig. 728. the use of the partial caps; many patients can be induced to consent to their employment who would refuse to submit to more radical meas- ures, and thus, even when the latter would be advisable, the former FIXED CROWN- AND BRIDGE-WORK 357 may be employed as a compromise or even as a temporary expedient. Having once tested the advantages of a well-fitting bridge, the wearer is more likely to consent at some future time to a more suitable form of construction. Incisors, Cuspids, Bicuspids and Molars Combined. — Figs. 729 and 730 represent a piece of bridge-work extending from a central incisor to Fig. 729. a molar. In such a case the best method, especially the one most likely to prevent misfit from warping, is to construct the front section, consisting of the central, lateral and cuspid first, then form the molar cap, fit it with the front section of the bridge in position in the mouth, remove in plaster impression and "bite," and then construct the bicuspid Pig. 730. Pig. 731- and molar dummies between the cuspid and the molar crowns. First solder the bicuspid and molar dummies together to avoid warping and then unite them to the cuspid and molar crowns. In a bridge of this character, an open-face cap or other suitable form of crown, may be used for the cuspid in cases where the natural crown is intact. 358 CROWN-, BRIDGE-, AND PORCELAIN-WORK Fig. 732. Fig. 733. Fig. 734. FIXED CROWN- AND BRIDGE-WORK 359 Extensive Application of Fixed Crown- and Bridge-work.— The following illustrations show cases of extremely large operations in fixed crown and bridge-work. Ill the case illustrated in Figs. 731, 732 and 733, crowns on a second bicuspid, a pulpless molar and the roots of a cuspid and lateral con- stitute the abutments. Figs. 734 and 735 illustrate an extensive case of artificial replacement by crowning and bridging operations. Fig. 734 represents the case as presented for treatment. The few remaining superior and inferior natural teeth had no corresponding antagonists, which caused the inter- locking and abnormal occlusion shown. The superior right bicuspid, the left central and the left cuspid were crowned, the bicuspid being Fig. 735- shortened and the cuspid lengthened in the operation. The intervening lateral root between the central and cuspid, having been treated and filled, was allowed to remain. With the three crowns to serve as abut- ments, the intervening spaces were bridged with artificial teeth, the extension on the left side being supported by a narrow saddle. The spaces between the inferior cuspids and molars on both sides were bridged, the bicuspid on the left supporting the bridge of the cuspid as on the right ; the left cuspid was crowned and the incisal edges of the incisors trimmed even. Fig. 735 illustrates the finished case and shows the artificial restoration of the parts. ^ 1 Fifteen years after the performance of this work by Dr. H. A. Parr, the case was examined by the author. The membranes under the saddle on the left side had settled, leaving a space, but otherwise the work seemed to be in fair condition. 36o CROWN; BRIDGE-, AND PORCELAIN-WORK aimiiiiiiiiiiiiii;ii:niniiiim Fig. 736. Fig. 737. FIXED CROWN- AND BRIDGE-WORK 361 Figs. 736 and 737 represent an extensive case of crown- and bridge- work. The occlusal surfaces of the teeth were affected with abrasion. Gold crowns with porcelain facings which viewed laterally presented the form illustrated in outline in Fig. 736, were mounted on the incisors and cuspids, the pulps of which were preserved. The posterior teeth were crowned with all-gold crowns. The missing teeth, except those on the lower left side, were artificially restored with bridge-work. Criticism. — Fixed bridge-work of the extensive character illustrated in some of the cases shown is seldom constructed now, for reasons which have been discussed and explained in Part IV, Chapter XL Remov- able forms with saddles affording alveolar support are adopted in pref- erence. These cases are therefore presented to illustrate what has been done in the past history of the art, and not as methods recommended for practice at the present time. CHAPTER XI SECTIONAL AND DETACHABLE BRIDGE-WORK Pig. 738. CONSTRUCTION IN SECTIONS — -BAR ATTACHMENT — DOVETAIL LUG AT- TACHMENT — DETACHABLE DOUBLE-CAP BICUSPID AND MOLAR CROWNS — DETACHABLE GOLD SEME-CIRCULAR POST CROWNS Construction in Sections. — The construction of bridges, especially- large cases, in detachable sections, is often desirable and advantageous. This is owing to the tilted position of some of the abut- ment teeth or roots which, in a case of bridge- work extended to both sides of the mouth, renders paralleling of their sides extremely difficult. Also, that plan is to be considered when the condition of some tooth or teeth present, in- cluded or not included in the bridge, as for instance when affected with pyorrhea, may suggest the probable necessity of removal of the cemented bridge in the future for altera- tion or addition. Removal of abutment crowns set with oxyphosphate is usually so difficult that they are mutilated or destroyed. In such cases, the most stable section or sections of the bridge — that is, the section or sections least liable to be removed should be made first and then the other section or sections formed to connect with them. This is accompHshed by the use of a detachable connecting attach- ment or anchorage. To explain such construction we will take the case shown in Fig. 729. The section from the molar to the cuspid can be made as the first section, and the central and lateral added, with a lug from the lateral as a support- ing abutment anchored in the gold forming \ \ 'I \ \ : i the lingual side of the cuspid, as shown in ^^^ Fig. 738, and ready for insertion in Fig. 739. , Any required removal of the front section will leave the remainder of the work intact. Bar Attachment.— This form cemented to position with amalgam has the advantage over the use of an inlay in that removal of the amal- gam will loosen the bar without injury to the anchorage cavity, it is 362 739- SECTIONAL AND DETACHABLE BRIDGE-WORK 363 practically applied to a gold bicuspid or molar crown. The method of construction is explained in Part IV, Chapter IV. Dovetail I/ug Attachment. — In this method the attachment is formed on the outside of the abutment crown in contradistinction to the others desciibed, which are inserted in the crown. Fig. 740 il- FiG. 740. lustrates a case of this kind. The teeth forming the abutments lean toward each other distally and mesially over the space to be bridged, as shown on the original model, Fig. 741. The bridge is supported by two lugs or shoulders on the abutment crowns, which slide into the slots Fig. 741. in the dummies (Figs. 742 and 743). These supporting shoulders and slots are made by shaping two pieces of platinum plate to the form shown in Fig. 744, so that one will telescope the other. The inner one is then invested on the outside surface and the inside filled in with gold Pig. 742. CD Fig. 743. Fig. 744. plate. The outer piece is filled inside with investing material and gold plate is flowed over the outside surface. The inner pieces which form the shoulders are first soldered to the crowns and afterward the outer ones forming the slots are adjusted to them in the dummies and soldered in position in the bridge. Fig. 745 shows a bridge constructed with an attachment similar to 364 CROWN-, BRIDGE-, AND PORCELAIN-WORK that just described at one end and a double-cap attachment at the other. ^ In either of these forms, gutta-percha can be used to attach the bridge, which can be de- tached by the dentist in case of need: A pin that glides into a tube placed in or on the side of the crown approximal to the Pig. 745. Fig. 746. bridge, such as is shown in Fig. 746, can be utilized instead of the attachment described in the above cases. Fig. 747. Detachable Double-cap Bicuspid and Molar Crowns. — Such forms are at times desirable and preferable to the use of the previously de- scribed attachments, to permit the removal of a retaining cap or caps. Fig. 748. In the case illustrated in Fig. 747 the lines of the sides of the bi- cuspid and molar were trimmed parallel or only slightly tapering. The natural crowns having been considerably broken down by decay were shaped up with amalgam. Impressions of them were next taken in tubes with impression compound and amalgam dies made. On ' Case of Dr. C. L. Alexander. SECTIONAL AND DETACHABLE BRIDGE-WORK 365 each of the dies a close-fitting cap of thin platinum about gage No. 38 was made in sections. The cap was first swaged on a fusible metal die made from the amalgam die, and transferred to the latter for the final shaping. The caps were fitted in the mouth and a plaster im- FiG. 749. pression taken, removing the caps in position. The amalgam dies were then inserted in the caps and a model and articulation made, with the caps on their dies in the exact relationship they will hold in the mouth, as shown in Fig. 748. Fig. 750. Over each cap a second cap of gold was made which did not extend to the gingival margin by one-sixteenth of an inch (Fig. 749). The dummy or bridge teeth were then constructed between the caps, as shown in Fig. 750. Fig. 751. The platinum caps were first cemented with oxyphosphate on the teeth. When it had set the gold crowns were cemented with gutta- percha cement over the platinum tooth-caps, from which they may 366 CROWN-, BRIDGE-, AND PORCELAIN -WORK be detached at any time.^ The thin platinum caps appKed as de- scribed were quickly and easily constructed. Where erosion is active and pyorrhea present, as in this case, they can be extended far under the gum margin to protect the dentin of the root without producing irri- tation, if the platinum is tapered to a feather edge and closely fitted and burnished to the surface of the root. Detachable Gold Semi-circular Post Crowns. — The use of detach- able gold abutment crowns cemented with gutta-percha is a method that permits removal of the bridge very easily, and is especially applica- F G. 752. Pig. 753. ble to cases of pyorrhea requiring periodical treatment that suggest the temporary removal of the bridge for the purpose. Fig. 751 shows a lower case with a sectional bridge. In this case the roots are trimmed to within about one-eighth of an inch of the gingival margins and gold collar caps with posts are fitted to ach. Solid all-gold crowns are made for the molars and crowns with porce- lain facings for the cuspids and first bicuspids. To each crown is fitted a large half-round or oval-shaped post attached to the cap, A, B and C, Fig. 752, show their construction in section. The teeth were reproduced in three separate bridges, as shown at A, B and C, Fig. 753- ^ This case was constructed in this manner by the author, for the reason that the remainder of the teeth were being rapidly shortened by mechanical abrasion, and the intention is to open the "bite" later on and protect the other occluding surfaces. When this is done, the occluding surfaces of the bridge can be proportion- ately increased in thickness. A detachable form of construction was considered advisable for the reason also that the patient exercised such an unusual amount of force in occlusion, that repair or restoration of occluding surfaces was liable to become necessary at times. CHAPTER XII THE HYGIENIC CONDITION OF THE MOUTH AS AFFECTED BY FIXED BRIDGE-WORK CONSIDERATION OF THE SUBJECT — REQUIREMENTS — METHOD TOR CLEAN- LINESS AND HEALTH Consideration of the Subject. — The probable future condition of the mouth in which a piece of bridge-work is permanently cemented is a matter of the deepest interest to both patient and operator. There is no valid reason why an artificial structure in the mouth should be more hurtful than the natural teeth, provided that correct conditions are observed in its construction, and proper measures are taken for their maintenance. Collars imperfectly fitted at the cervix cause in- flammation of the gingival margin and permit infection of the cement under them, which contributes additionally to the inflammation. In pulpless teeth this infection in the cement penetrates the dentin, in time reaches the pulp-canal and finally the apex of the root. This is one of the reasons why the apices of roots the canals of which have been properly treated and filled show areas of focal infection. The natural teeth demand care on the part of their owners, and equally or more so do all forms of artificial dentures require attention to secure their cleanliness and thus preserve the health of the adjacent tissues. The result of wearing a piece of fixed bridge-work is entirely depend- ent, in the first place, on the proper apphcation of principles and skill in every detail of construction of both crowns and bridge; and in the second place, upon the maintenance of cleanhness. Neglect of a single requirement will so far detract from the usefulness of the work, that it may influence the final result disastrously. Requirements. — Firm, properly selected abutments will not redeem incorrect conception or faulty construction; neither will the best con- struction remedy that which is wrong in principle or application. Self- cleansing spaces, if improperly formed, have exactly the contrary effect from what is intended, by becoming receptacles for particles of food debris, instead of preventing their accumulation. Inaccessible spaces or interstices, which are apt to cause uncleanli- ness, should be avoided. Continuity of structure of the several parts of crowns and bridges is essential to fully insure a perfect hygienic condition. Methods of Cleanliness and Health. — The health of a mouth con- taining a piece of bridge-work constructed under these precautions can be readily maintained. For this purpose a suitably formed tooth-brush and properly shaped bristle points in a porte carrier, which will reach places not cleaned by the tooth-brush, and a dentifrice, are necessary. 367 368 CROWN-, BRIDGE-, AND PORCELAIN-WORK Floss silk charged with tooth-powder or paste can be passed through interstices between the necks of the crowns by the aid of a slightly- curved blunt-pointed needle and drawn along the gum under the bridge to remove accumulation of debris otherwise inaccessible. A solution of detergent mouth-lotion or disinfectant in water, injected with a dental syringe, can be used advantageously to wash out such places and maintain a healthy condition of the gums. The prophylactic measures, 'as outlined, should be practiced at least once or twice daily; if only once, preferably before retiring. In addition to the above, bridge- work should be thoroughly cleansed by the dentist at regular intervals. So cared for, a fixed bridge will not militate against the absolute wholesomeness of the mouth; but it can hardly be expected that the insertion of bridge-work will insure a state of the mouth which for cleanliness will be superior to the presence of the natural teeth. Neg- lect on the part of the patient to perform such duties as are necessary to preserve the natural teeth in a healthy state wiU have about the same or worse effect on an artificial denture. The attention required to be given to bridge-work is not greater than is commensurate with the advantages which it confers on the wearer. To offset the objections used against fixed bridge-work regarding hygiene in this era of oral prophylaxis, many practitioners favor the re- movable form. So constructed, the patient is able to remove, cleanse and replace the denture. This certainly is advantageous in an ex- tensive piece of bridge-work. In the use of small cemented bridges towards the front of the mouth, involving the use of not more than two abutments, if the work is properly constructed, especially respecting interproximal spaces and continuity of structure, the comparison is modified, as no appreciable advantage is gained by making it remov- able. The two crowns that constitute the abutments, if they stood alone, would not be classed as insanitary, if properly constructed and united to the roots or teeth with an antiseptic cement; why then, should the cemented abutments of an unremovable bridge be so con- sidered? The dummy teeth that intervene between the abutments and lock in particles of food with the secretions constitute the objec- tionable factor. Cleaning the surfaces and interstices of such a bridge in the front of the mouth can be effectively performed by proper means, but not so easily as when removable. An unclean condition of properly constructed fixed bridge-work is frequently attributable more to the fact that patients were not informed as to just how to take care of it, or did not possess the necessary means to carry out that care than to neglect on their part. In the former event the practitioner is at fault in having failed to properly instruct the patient and prescribe the needed care. PART V REMOVABLE BRIDGE-WORK CHAPTER I REMOVABLE BRIDGE-WORK Limitations — requirements — examination models — forms of crowns, attachments and supports — removable retaining abutments — removable supporting abutments — the tube and split-post attachment — construction of the split post — split-post swaging device — split-post burnisher — tele- scope crowns — the outer or telescoping cap — contour — the cusp-cap — telescope crown with tube and split post — removal of the cap from the die — tube and split-post an- terior crowns — incisors, cuspids and bicuspids avith porce- LAIN FACINGS — ^THE OUTER CAP — CONVERGING TEETH AND ROOTS — RETAINING INLAY ABUTMENTS — ^BICUSPIDS AND MOLARS — THE MATRIX OR FEMALE INLAY — SPLIT POST AND SUPPLEMENTARY OR MALE INLAY — ^A PIN BENDER — VARIATIONS IN METHOD — INCISORS AND CUSPIDS — ^TO TAKE THE IMPRESSION — INSERTION OF THE SPLIT POST — THE SUPPLEMENTARY INLAY — USE OF SWAGED FIRST OR FEMALE MATRIX — SUPPORTING ABUTMENTS — SPECIAL FORMS OF ATTACHMENTS — COLLAR AND PARTIAL CAP — FLANGED COLLAR ATTACHMENT — LUG COLLAR SUPPORT — SPLIT-BAR ATTACHMENT — CONSTRUCTION — THE SPLIT BAR — THE BOX — PARALLELING THE BOX — THE SHIELD — WINGED LUG ATTACHMENT — ^DOVE-TAIL FLANGE AND SPLIT-POST ATTACHMENT — SOLID PIN AND TUBE ATTACHMENT — COMPARATIVE VALUES OF THE SEVERAL FORMS OF ATTACHMENTS — RETENTIVE ATTACHMENTS — RETENTIVE INLAY ATTACHMENTS — SUPPORTING ATTACHMENTS The evident advantages of bridge-work early stimulated the in- ventive genius of dental mechanists to improve the methods and forms of its construction and extend its application. With these objects in view, methods have been introduced by which bridges are so constructed as to be removable and replaceable by the patient. The importance of oral hygiene is now generally recognized, and the use of fixed bridge- work, as it cannot be removed for the purpose of cleansing, is criti- cised and by some entirely condemned. As a result, the subject of removable bridge-work is being more actively discussed than formerly, its construction studied and more generally adopted. Its use over- comes the chief objections urged against the system. 371 372 CROWN-, BRIDGE-, AND PORCELAIN-WORK Limitations. — ^Large bridges are usually much more easily made in a removable form than small pieces, which in contradistinction present some of the best features of the permanently attached methods. Many of the smaller bridges cannot be made removable as practically as the larger ones. In a large proportion of cases where properly constructed fixed bridge-work is applied, the removable feature would be of no material benefit as far as regards the health of the abutments or of the adjoining teeth; neither would it be of any great advantage regarding cleanliness. These reasons, together with the fact that removable bridge- work is most intricate and laborious in construction, largely combine to restrict its use to large bridges or those requiring saddles, and the form termed removable plate bridge-work, which imperatively demands removal for cleanliness and health of the membrane on which it rests. Requirements. — In the construction of removable bridge-work the prime requisite is that the posts and collars, or other form of attach- ments used, shall be so constructed that the denture will move evenly on and off the supporting capped roots or crowns in adjustment and removal. To secure this, removable attachments and gold crowns must be so shaped that the lines of the different parts are parallel to one another. This is absolutely necessary, if the denture extends to both sides of the arch, as otherwise the stabiHty of abutment roots and crowns would be impaired, and in time irreparably destroyed by daily removal and insertion of the denture. Examination Models.— Two wax or compound impressions and "bites" should be first taken, that will include all the teeth in each jaw, then plaster models made and mounted on articulators. One of these models is for the purpose of studying the case outside of the mouth and the preparation of the abutments, the other is to refer to later on. The most advisable method may be determined more easily by the aid of a model than in the mouth. Forms of Crowns, Attachments and Supports In removable bridge- work two classes of abutments are used: Re- taining and Supporting. Removable Retaining Abutmients. — These forms hold the bridge firmly in position in the mouth, preventing its dropping or shifting. Split-post and tube collars, telescope crowns, inlay and split-post abutments, or any devised abutments that firmly retain a bridge are Retaining Abutments. Removable Supporting Abutments. — These are such forms as sup- port an end or any part of a bridge, but do not retain it in position. A REMOVABLE BRIDGE-WORK 373 countersunk inlay or gold filling in which a lug rests or anchors, or any contrivance designed to support, but not retain a bridge, is a Supporting Abutment. A knowledge of and practical experience in the formation of remov- able bridge abutments should first be acquired before commencing the construction of practical work. Accordingly, the constructive details of Retaining and Supporting Abutments, such as are used in the Peeso^ and similar styles of bridges, will be given first so that they can be preliminarily practiced by the construction of one or more specimens. The Tube and Split-post Attachment. ^ — This is the most used re- tentive abutment. The tube is made on a small steel mandrel. These mandrels are termed "Tube Mandrels" and are of six sizes, Nos. i, 2, 3, 4, 5, and 6 3 4 5 ± Ul '_*, Pig. 754- Fig. 756. (Peeso), closely corresponding to Nos. 48, 49, 50, 51, 52, and 53, twist drill and steel wire gage (B. & S.), as shown in Fig. 754. The tube is made of ten per cent, iridio-platinum plate gage No. 32. As the tube when finished will be one or two sizes larger than the mandrel on which its shaping is started, calculation should be made accordingly in selecting the size of the mandrel. A canal, for instance, that will receive a tube on a No. 4 mandrel requires mandrels Nos. 2 and 3 for shaping and No. 4 for finishing. To systematize the subject of the size of tubes in their application to canals, the tube is given the number of the size of the last mandrel it was swaged on or the one over which it fits tightly. So regulated in size, Nos. i and 2 tubes are used in small roots, such as the superior laterals and bicuspids, Nos. 2 and 3 in superior central incisors, Nos. 3 and 4 in large superior centrals and in both superior and inferior bicuspids and Nos. 5 and 6 in superior and inferior molars. 1 So termed, as Dr. F. A. Peeso's systematic constructive details have contributed so much to improving the art. 2 Iridio-platinum hollow wire is considerably used for tubes of late in preference to making them. Ready-made tubes with split posts are also manufactured. 374 CROWN-, BRIDGE-, AND PORCELAIN-WORK A piece of plate seven-sixteenths of an inch wide is cut in the direction the metal has been rolled, perfectly square on the end and beveled to a knife edge (Fig. 755). Anneal the plate, dip it in acid and wash and dry perfectly. Turn the edge of the platinum evenly at an angle, as shown in Fig. 756. This is best done by seizing the edge in a hammer- headed hand-vise with seven-eighths-inch jaws, the serrations of the jaws having been removed and the edge of one of them rounded (A, Fig. 757), and bending the platinum over the rounded edge (B). The platinum is laid on the surface of a flat anvil, the mandrel selected for starting is placed in the fold of the platinum, the shank of the mandrel being held by a pin vise, and the edge of the platinum gradually turned Pig. 757. Pig. 759. over with a fine flat file to meet the surface of the platinum strip, as shown in Fig. 758. The mandrel can be slightly rolled in the operation to bring the edge against the surface of the plate (Fig. 759), but it must not be rolled beyond that point, as that would double the plate, as shown in Fig. 760. The mandrel is removed, a very small piece of pure gold is placed in the seam and the tube is held in a Bunsen flame (Fig. 761). When a sufficient degree of heat is reached, the gold will flow along the seam and form a joint without obstructing the passage of the mandrel inside. If it does obstruct, too much gold has been used. Heating the tube to a high heat may correct this by diffusing the gold through the platinum. If not, a new tube must be formed. The next size larger mandrel is then forced through the tube to REMOVABLE BRIDGE-WORK 375 stretch the metal and smooth the inside. This is best accomphshed by placing the end of the tube against the surface of an anvil, and tap- ping the mandrel through, as shown in Fig. 762. The^ tube is then annealed and enlarged to the size of the next larger mandrel. The surplus metal is removed with shears, resting the flat side of one of the blades against the surface of the metal. The joint is trimmed even with the rest of the tube with a fine flat file. Should the tube fit the mandrel so tightly as to be diflicult to remove, roll the tube and man- drel under a dull, smooth flat file, to shghtly stretch the tube. To close the end of the tube trim the metal even, slightly burnish in the edge (Fig. 763), and over the opening solder a piece of metal of the same gage as the tube. This is most easily done by placing a small piece of the platinum on a charcoal block, melting a particle of pure gold on its surface, and then fT^ Fig. 760. Fig. 761. Fig. 762. Pig. 763. placing the end of the tube against it and again fusing the gold, as shown in Fig. 764. The surplus plate is then removed and the part finished with a fine file. The point of the mandrel selected as the size for the tube is inserted in the orifice of the tube, its closed end placed on a block of lead, and the mandrel driven into the tube, giving it the exact dimensions and the end a slightly coned form. Construction of the Split Post. — The post is made of half-round platinized gold wire (gold clasp metal), gage No. 12 to 15, and when doubled about one-fourth inch longer than the tube. The most 376 CROWN-, BRIDGE-, AND PORCELAIN-WORK convenient way is to use a long piece of wire and double one end of it for a post as required. The gage of the wire when doubled should be slightly greater than the diameter of the hole in the tube. The average is gage Nos, 14 for No. i and 2 tubes; gage No. 13 for Nos. 3 and 4, and gage No. 12 for No. 5 and 6. The sharp edge of the wire should be rounded so that the finished post will have a very small seam on each side that will indicate and easily permit the introduction of a thin knife blade to effect expansion, as shown at A and B, Fig. 765. The required length of wire is bent about one-eighth of an inch from the center and the flat side of the shorter end brought against the side of the other so that the longer end extends as shown in Fig, 766. The wire should be well annealed before being bent, and each time between the bendings. Fig. 765. Fig. 767. Fig. 764. Fig. 768. When the shorter end of the wire meets the longer one, the flat sides are brought together, as shown in Fig. 767, and so held by a soldering clamp and heated to a red heat, then plunged into water. This sets the portions of the metal brought together in close contact, in which position they remain while being soldered. The loop portion is next held by a clamp and the ends united by the least possible quantity of coin gold, using the long end of the wire as a shelf to hold the solder, as seen at A, Fig. 768. The ends connected in this way leave the loop section to form the spHt-pin post. The extending end of the wire is grasped in a pin vise and the loop portion hammered together first on the face, and then in. the groove of an anvil. Between the blows of the hammer the post must be rotated so that the two sides will be forged round as they come in contact (Fig. 769). As a safeguard against invasion of the solder in the seam of a spHt post in any of the subsequent soldering operations, rouge or a very thin film of mica may be placed to REMOVABLE BRIDGE-WORK 377 remain in the seam between the two halves of the wire before they are brought together. The wire, still grasped in the pin vise is next trimmed uniformly round with a flat file. The fit of the wire to the tube should be tested frequently by placing the orifice of the tube over the point. When the post begins to approach the required size, it is mounted in a true-run- ning chuck on a lathe, and further uniformly reduced with a very fine flat file, the serrations of which are worn smooth, applied lightly against its surface with the smooth surface of a burnishing file against the other. When the post nearly enters the tube, it may be further sufficiently Pig. 769. reduced with fine emery cloth applied on a flat stick. The post, having been reduced to very tightly fit the tube, is "then burnished by passing a burnisher lengthwise over its surface to remove the fine scratches of the emery cloth, and give it a uniformly smooth polished surface. This generally permits the post to freely enter, if not, it must be further reduced and again burnished. The post should enter and move in the tube uniformly the entire length, and require but a moderate amount of force to insert or remove it. The use of a spHt post with a closed point, is confined to a long tube and where the post when removed from the tube will be so exposed that the slit can be easily reached and expanded. The open end split post is the best form to apply in short tubes and in all-gold bicuspid 378 CROWN-, BRIDGE-, AND PORCELAIN-WORK and molar telescope crowns, as in the latter the slit at the end of the post is more easily reached than on the side. When the end of a split post is being removed sufficiently to slightly expose the slit (Fig. 770), the move- ment of the file or stone should be directed in the line of the slit, to avoid springing the sides of the post apart as the slit is reached. Split-post Swaging Device. — Fig. 771 illustrates the Weinstein swaging block for shaping split posts by swaging. The groove on the top of the block is to be used in hammering the half round wire when it is brought together to form the post. The ends of the two wires having been united with solder, the soldered end is seized with a pin vise; the post is then placed in one of the grooves in the center of the block, two sizes larger than the required size for the finished post, and swaged between the two sections of the swager, twisting the post in the groove Fig. 770. Fig. 771. Fig. 772. between the blows of the hammer. The post is then transferred to the next smaller hole and again swaged. This swaging process is continued until the post is uniformly reduced to a suitable size. REMOVABLE BRIDGE-WORK 379 Split-post Burnisher. — Fig. 772 illustrates the Weinstein burnisher. The post is placed in a revolving chuck of a lathe, the burnishing tool is opened, the post placed in the grooved side and the smooth side closed gently on the post. The chuck is then revolved and the post burnished by its revolutions against the burnished steel. The tool is gradually clamped together tighter on the post as the burnishing progresses. The use of tubes and spht posts is much facilitated by having on hand a number of different sizes ready-made. The most suitable size can then be immediately selected. These posts may be formed at a convenient time, or by an assistant. Telescope Crowns This is the form generally preferred for gold bicuspid and molar crowns in removable bridge- work. When used as a supporting abutment they are made without a post; as a retaining abutment, with a post. The sides of the natural crown are trimmed as for an ordinary gold crown, but given a slightly more conical form. The occlusal section requires to be removed enough to allow for the thickness of not only Pig. 773. Fig. 774. Fig. 775. Fig. 776. the inner, but also the outer cap (Fig. 773). Gold coin or a corre- spondingly hard gold plate, which will not stretch in wear, is absolutely necessary, especially for the outer telescope crown. The collar is made of gold, gage No. 30, cut with a very slight flare toward the cervical edge, as indicated in Fig. 774. The joint is sweated, or united with hard solder. The collar is fitted closely to the cervix of the tooth and uniformly extended well under the gum. The sides and occlusal end of the collar should be given the same curve as the cervical section, so that the outer collar shall fit and move uniformly over it (Fig. 775)- The edge of the occlusal end of the collar is trimmed off enough to leave room for the floor and a thick cusp-cap. The extreme occlusal 38o CROWN-, BRIDGE-, AND PORCELAIN-WORK edge of the collar is turned inward with small pointed pliers so as to give it a rounded form, as shown in Fig. 776. This is for the purpose of permitting a slightly rounded edge to be given to the occlusal end of the cap. This rounded edge is to facilitate the adjustment of the collar of the finished outer crown by allowing it to more easily slip to place, especially should it be inserted a trifle out of line.. The rounded edge of the collar is filed level so that all parts are in the same plane. The floor is made of the same gold as the collar, gage No. 28, cut to the required size. The plate is made perfectly flat by swaging in the Peeso swaging device. Fig. 777, The plate is annealed, dipped in acid, washed and sweated or soldered to the collar. The edge Pig. 777- of the surplus gold is cut and ground level with the sides of the collar and polished (Fig. 778). The Outer or Telescoping Cap. — The inside of the inner cap is varnished, a strip of paper is wound closely around it and secured with a wire or rubber band (Fig. 779). Fusible metal that melts below 212° F. is then poured into the paper Lube (see "Casting the Die," Part I, Chapter V). This practically makes the gold cap a die on which to form the outer cap. The fusible metal is later removed by immersion in boiling water. The measure of the circumference of the outer collar is taken at about the middle line of the inner cap, a little towards the occlusal end, as indicated at A, Fig. 780. The gold is cut with a slight flare as for the REMO VA BLE BRIDGE-WORK 381 inner cap. The joint of the collar is made with a slight overlap. The collar is slipped over the horn of the anvil, the joint hammered and then filed level. The collar is annealed and placed on the inner cap-die and pressed down with the finger as far as it will go. The occlusal edge of the collar, which must be level, is placed on the flat surface of the anvil and the die is hammered into it to position (Fig. 781). If difficulty is experienced in the removal of the collar from the inner cap, burnish with a plate burnisher on the sides in a circular direction around the collar, especially toward the cervical section; wind a piece of cloth Fig. 778. Fig. 780. Pig. 779. Fig. 782. Pig. 781. around the collar, then seize and remove with the fingers. The collar is replaced on the inner cap, the cervical edge is marked and trimmed off to about one-sixteenth of an inch short of the line of the gum margin of the inner collar, as shown in Fig. 782. The occlusal edge of the outer collar is trimmed a trifle flush with the surface of the floor of the inner cap, the edge is pressed inward with a flat file and then filed per- fectly level with the surface of the floor. The collar is removed and a floor of gold, gage No. 30, sweated or soldered to it. The floor is either trimmed flush at the mesial and distal sides and allowed to only sHghtly extend at the lingual and buccal, or it is trimmed even with the sides of 382 CROWN-, BRIDGE-, AND PORCELAIN-WORK the collar, as required by the method of construction of the cusp-cap. Remove the inner cap from the die, place it in the mouth, adjust the outer cap, take a "bite" and make models. Contour. — ^As the outer cap sits on the inner one, it presents no contour. Contour can be formed by three different methods in ac- cordance with conditions presented, (a) Trim the floor of the outer cap even with the collar. Form on the cap a wax model of the required cusp-cap, that will also include the required contour on the sides, as outlined by the dotted line in Fig. 783 ; remove wax model and cast it in gold. When cast, fit it on the outer cap, making any necessary altera- tions for contraction of the metal in casting, and wax it fast around the edge to the collar of the outer cap. Remove the outer cap from the inner with the cusp-cap in position, paint the cavo-surface of the outer cap with rouge and fill it with investment material. The cap will then ?Pi^?:v-;Si-i M Fig. 783. Fig. 784. — IM, Investing material. Fig. 786. Fig. 785. appear as shown in Fig. 784. Solder the cusp-cap to the outer cap by fusing the solder in small pieces around the edge and drawing it under the cusp-cap, as described in Part III, Chapter XIV. This method of contouring is best suited to short crowns, crowns requiring only a small amount of contour, or crowns on lower teeth where weight is not a factor. (b) Trim the floor of the outer cap on all sides to the full and exact line of the size and shape of the required contour, as illustrated at A and B, Fig. 785. Form a cusp-cap by casting a wax model of the required form or by the cusp-button method (Part III, Chapter VIII), and solder it in position on the floor. When the cusp-cap is soldered, fill the inside of the crown with investment material, heat the crown slowly to dry out the investment, and contour the collar to the dotted line SS, Fig. 786, with as hard-flowing solder as the collar will bear, using the extension of the floor as a shelf on which to place the solder. This REMOVABLE BRIDGE-WORK 383 method is for short crowns, or long ones requiring but very little forma- tion of contour. (c) This consists in the addition of hollow hermetically sealed con- tour to the mesial and distal sides of the outer cap. It is a form es- pecially desirable for large upper crowns or any crown to which it can be applied in which weight is a factor to be considered.^ The process of construction is as follows: The floor of the outer cap is trimmed to extend mesially and distally to the size and form of the required contour less the thickness of gage of the metal that will be used to form the wings or contour. Two pieces of gold plate, gage No. 28, are cut to form the contour wings, each fully the width of the outer collar and in length about one and three-quarters the diameter of the cap, from mesial to distal side (Fig. 787), and then trimmed and festooned, as shown in Fig. 788. One of the wings is placed against either the mesial or distal side of the cap, with the edge resting one thirty-second of an inch from the cervical edge, as shown at A, Fig. 789, and the other edge resting on Fig. 787. Fig. 788. Fig. 789. Fig. 790. Fig. 791. and extending above the floor of the cap, as indicated at B. The con- tour plate is then balanced on the side of the collar, or waxed at the point to be soldered and retained in position with investing material. The cervical edge of the contour wing is just attached, and no more, with a very small piece of hard solder, not larger than a fraction of a pin head, as indicated at the point A, Fig. 788. It is next boiled in acid to remove flux and the wing for the opposite side added in like manner (Fig. 790). The cap with its contour plates is then placed on the inner cap and the plates, being attached at only one point, are bent out at an angle, and brought around on the buccal and lingual sides, and the ends trimmed to meet (AA, Fig. 791) and afford the required contour, as indicated on the model or in the mouth. Every part of the cervical edge of the contour plates is brought to touch the surface of the collar and the occlusal edge to rest against the edge of the floor (Fig. 796). This is assisted by removing the outer cap from the inner and over- coming the spring of the gold by clamping the edge of the contour plates to the collar, one point of the clamp being placed outside the collar and the- other inside, and annealing, but not heating enough to fuse the ' Dr. Peeso's method. 384 CROWN-, BRIDGE-, AND PORCELAIN-WORK solder already applied to the contour plate, and chilling by dipping in water. The seam all around is then fluxed and the whole securely united with 21-carat solder. The intention in soldering is to securely unite the contour plates to the collar, and to the edge of the floor, and effectively close the seam with the least possible quantity of solder. The soldering can be done by placing the cap on a charcoal block, applying the solder in small pieces or in strip form on the buccal and lingual sides at the ends of the contour plates — one end at a time — and drawing the solder down in the seam; or the parts can be united by separately waxing, investing and soldering one side at a time, as shown in Fig. 792. Trim the contour plate to the Kne of the surface of the floor. To assure perfect closure of the parts, the cap is heated, dipped in water, then reheated, and if the slightest opening exists, an issue of steam will indicate the spot to be closed. The cap is then ready for the applica- tion of the cusp-cap. The Cusp-cap. — The cusp-cap for this method, as in that previously described, is made by casting from a wax model of the required form. Pig. 792. Fig. 793- Fig. 794. Fig. 795. Fig. 796. or by the use of a cusp-button (see Methods Nos. 4 and 6, Part III, Chapter VIII). A hole is drilled through the center of the cusp-cap, in the deep fissure, a little larger than a pin head (A, Fig. 793, in section). The base of the cusp-cap and the surface of the floor are fluxed and the parts wired together, passing the wire on both sides of the hole, as , shown in Fig. 794. The parts are placed on a soldering block, cusp side up, and slowly heated to evaporate the moisture from the flux, and the heat then increased slowly to the fusing point of the solder. A small piece of solder, which has been melted into a globule, is placed in the hole in the center of the cusp-cap. The crown is uniformly heated, a small flame is first passed over the surface of the cap and then directly on the globule, and it is fused down into the hole. More solder is added, and the flame passed over the surface of the cap, until the solder appears at the edge of the cusp-cap, showing that it is completely united to the floor and edges of the plates. Another method that insures against affecting the solder on the wings, is to invest the crown after wiring, nearly up to the floor, as REMOVABLE BRIDGE-WORK 3»5 Fig. 797. shown in Fig. 795. When soldered the crown is boiled in acid, then trimmed and polished. Fig. 796 shows a finished crown. Telescope Crown with Tube and Split Post. — When a telescope crown is to be used as a retaining abutment, the addition of a tube and split post is re- quired. When two telescope crowns alone are used on the same bridge, one of them should contain a tube and split post. The use of telescope crowns with tube and split post is principally confined to molars. The inner collar having been formed, the tube selected is mounted on a mandrel and placed in the collar with the point resting on the floor of the pulp- chamber. A wire representing the tube in gage may be used instead. When necessary for a more secure attachment, as in the case of an upper molar, the tube or wire is inserted a short distance in the palatal root, and in a lower molar in the mesial root. The tube is to be paralleled to any other tube or tubes and abutments present, as described in the construc- tion of a removable bridge. The tube also must be parallel to the _ median line of the sides of the inner collar to permit the post to move in and out freely in the tube of the inner cap when the crown is finished. The tube and collar, having been waxed together, are removed in the impression taken for the bridge and a model made. When a post in an outer cap that has been paralleled to the other tubes and posts does not properly adjust itself to the orifice of the tube in the inner cap, the defect is attributable to the fact that the sides of the inner cap are not shaped in con- formity with the line of the other abutment, or the inner collar had not been suitably shaped when A----li4i,;jiii!i!!|.)| constructed. The sides of the inner collar should slightly taper to the lines of the post. This is tested by placing a narrow separating file against the side, as shown in U Fig. 797. Fig. 798 shows a cap in which the collar on one side leans toward the post and on the other side from it. In the latter case, although the end of the root and cap are slightly cone-shaped, the edge of the outer collar would meet the inner cap at the point A, and prevent adjustment of 25 Pig. 798. 386 CROWN-, BRIDGE; AND PORCELAIN-WORK the post in the tube. This can only be corrected by trimming the side of the root at that point and fitting a suitably shaped new collar and cap. The tube having been properly paralleled it is removed and a floor of gold, gage No. 28, is sweated or soldered to the outer collar and the excess removed. A hole is made through the floor over the hole in the impression formed by the tube or wire about one and one-half times the diameter of the tube. This extra space is later on to allow for the formation of a countersunk approach to the tube for the post, as shown in section in Fig. 799. The tube is placed in the hole in the floor and paralleled with the other abutments and also adjusted to con- form to the sides of the inner cap. The tube is then waxed to the floor. The wax should be melted into the space around the tube and under the edge of the floor, as seen at B. The '^^ wax is chilled, the mandrel removed from the tube, the cap and tube invested, dry asbestos fiber being packed in the tube. The tube is then soldered to the floor. In soldering, the flame should be directed around the tube and then under the investment to draw the solder down into the space around the tube. The cap having been boiled in acid, the tube is cut off and filed even with the floor and the cap polished. The inside of the cap is next varnished. When the varnish is dry the crown is filled with fusible metal. The outer collar and floor having been made and contoured, the location of the orifice of the tube is marked on the inner surface of the floor, by holding the cap firmly on the die, tapping the end of a piece of wood over the spot, or by passing a revolving burnisher over it. A hole is then made large enough only to admit the split post. For a telescoping gold crown the point of the post should be re- moved sufficiently to expose the slit, so as to permit the post to be expanded at the point instead of the side, or so little of the gold should be left at the point of the post that it can be easily removed and the post expanded. The orifice to the tube is next countersunk with a cone- shape fine bur, the debris washed out with a fine-pointed syringe and the split post fitted. Countersinking the neck of the tube removes the contraction caused by the solder and enables the point of the split post to more readily find the opening when the crown is finished; it also allows the post to adjust itself better to the deeper portion of the tube (Fig. 800 in section). The cusp-cap is next made and fitted. The orifice of the tube on the inner side of the cusp-cap is indicated by placing on its surface a REMOVABLE BRIDGE-WORK 387 thin layer of wax and pressing to position. A hole is drilled through the cusp-cap large enough to freely admit the split post. When a cast cusp-cap is used, if a carbon the size of the post is placed in position in the wax model before casting, it will facilitate the forming of the hole. The cusp-cap when constructed is temporarily laid aside. The outer cap is adjusted on the inner cap, the split post is placed in position in the tube with the slit in the post set in a bucco-lingual direction, the post cemented with wax to the floor of the outer cap, removed, invested and soldered with 20-carat solder. The hole in the cusp-cap is next trimmed and enlarged so as to leave a slight space on all sides around the split post when it is adjusted to position. The end of the split post is cut off a little below the surface of the cusp-cap to permit the end to be covered with solder. The floor of the outer cap and the base of the cusp-cap are cleaned and coated with ^^^ g^^^ liquid flux, and the cusp-cap placed in position on the floor and waxed around the edge, and the outer cap removed. A strand of wire may be used to secure the cusp-cap immovably to the floor. The inside of the outer cap is painted with rouge and invested nearly up to the edge of the cusp-cap, as shown in section in Fig. 801. The wax is removed and the investment slowly heated. The cusp-cap is then united with solder fused in the hole around the end of the post. The solder is applied a Httle at a time in small pieces or globules, or in strip form. A small flame should be directed on the solder and then around the sides to draw the solder beween cap and floor until it shows in the seam, which indicates complete union. The crown is finished in the usual manner. Fig. 802 outlines in sec- tion the finished crown. J Removal of the Cap from the Die. — Any time during the construction that removal of the fusible metal from the cap is required, the die and crown are placed in boiling water and the metal melted out. The crown on removal from the water is placed for a time or boiled in nitric acid, to insure the entire removal of the fusible metal, as a minute particle left adhering would cause a perforation when the crown is heated. Tube and Split-post Anterior Crowns Incisors, Cuspids and Bicuspids with Porcelain Facings. — For these crowns the end of the root is given a form similar to that required for a collar crown (Richmond). The sides of the root must be shaped and L " 388 CROWN-, BRIDGE-, AND PORCELAIN-WORK the canal reamed for the tube so that it shall be parallel with the other abutments. The end of the root is trimmed in a slanting plane from the lingual to the cervico-labial side. At the cervico-labial section the end of the root should be trimmed not more than one-thirty-second of an inch under the gum margin, or only enough to hide the edge of the collar. When more of that part is removed the edge of the gum is liable to crowd over the edge of the floor of the cap and be pinched in the reinsertion of the crown (Fig. 803). The canal is enlarged lin- gually a little with a reamer, so as to permit as good an attachment as possible for the end of the split post, and later facilitate correct placing of the facing. The end of the root should be left extending slightly above the gum until the collar has been fitted. The collar is made of coin or 22-carat gold, gage No. 30. After the collar is fitted the end of the root and collar are trimmed to the same level, as indicated in Fig. 804. The edge of the collar and the floor must meet at every point and are either sweated or soldered to- FlG. 803. Pig. 804. Fig. 805. gether. If soldered, the smallest possible quantity of hard solder should be used. The surplus metal of the floor is removed and a hole made through the floor for the tube. The hole in the floor for the tube, as in the case of the telescope crown with tube and split post, should be made at least half again larger than the tube to allow the solder to flow around the tube and permit the orifice to be countersunk (Fig. 805). The cap is adjusted on the root, the tube mounted on a mandrel and placed in the reamed canal and paralleled to the other abutments. The tube is then waxed to the cap and removed. The tube and cap should now be examined to see if the fine of the tube with the collar is such as will permit the outer cap when finished to move on and off without interference. This is easily determined by the eye — with a mandrel in the tube — or more positively by placing a flat separating file against the sides, the same as in the case of a tele- scope crown. Fig. 806 shows a correct alignment of the tube, and Fig. 807 an incorrect alignment. If the alignment is incorrect, it must RRMO Vy\ BLE BRIDGE- WORK be changed by trimming the root and making a new collar. If correct, the mandrel is seized with pliers, a small chisel is placed against the edge of the tube, which is pushed off the mandrel, invested and soldered to the floor. The solder is flowed down and around the tube, as ex- plained in the construction of a telescope crown with a tube and split post. Having been boiled in acid, the tube is cut off and ground level with the floor. The neck of the tube is countersunk with a cone-shape finishing bur, and reamed enough to correct the contraction of the solder. The cap is then polished, the debris in the tube removed by a fine-pointed syringe with water, the tube dried and the split post fitted. The Outer Cap. — This is a half-collar cap, retained by the spHt post fitted to the tube of the inner cap. It is to carry a porcelain- faced gold crown or one of porcelain. The half-collar lessens the strain on the split post and aids in strengthening the crown. To avoid irri- FlG. Fig. 806. Fig. 807. Fig. 809. tation, the edge of the half collar must be trimmed free of the gum margin one-sixteenth inch. To prevent any accidental disturbance of the form of the inner cap during the fitting of the outer one and to facilitate the work, the inside of the inner cap should be filled with fusible metal that melts below 212° F. This is best done by inserting the cap in moldine in a flask ring, as shown in Fig. 808. The half collar is made of the same plate as the inner collar gage No. 30. It is most easily constructed by first forming the outer collar to entirely encircle the inner collar. The edge is trimmed even with the floor of the inner cap, a floor of gold plate, gage No. 28, adapted, collar and floor removed and united to it with 21 -carat solder. In uniting the collar to the floor the attachment with the solder should be confined to the lingual section that is to remain. This is best ac- complished by notching the collar on both sides, as shown in Fig. 809, 390 CROWN-, BRIDGE-, AND PORCELAIN-WORK The solder, if only a small quantity is used, will be confined to the lingual section by the vacancy caused by the notches in the collar, which will consequently leave the labial portion ununited and easy to remove. The floor of the outer cap is next trimmed even with the sides of the collar. The outer cap is ' fitted on the inner, burnished or swaged to its surface, and the floor perforated. It is then held firmly on the inner cap, and the hole enlarged sufficiently to allow the post to pass through. The post is waxed to the floor, the cap and post removed, invested and soldered together. The slit in the spHt post should be placed in a labio-lingual direction for strength, as shown in Fig. 8io. The loose labial section of the collar in front of the notches is next removed and the lingual section remaining trimmed and finished, as shown at A, Fig. 8ii, and at B, Fig. 8io. Pig. 8ii. Pig. 8i2. in position on the inner cap. The inner cap is released from the die with boiling water and nitric acid. If properly constructed in all its details the result will be a crown base reliable as a retaining abutment and uniform in adjustment and removal. The porcelain facing is fitted to the outer cap, the outer cap removed, invested, and facing and cap united with solder the same as in the case of an ordinary crown. Converging Teeth and Roots When a molar converges as shown in Fig. 812, it can be paralleled to the anterior abutment, for a telescope gold crown, by shaping as indicated by the line A. For porcelain-faced crowns, when the convergence is of the charac- ter illustrated in Fig. 813, the tubes and split posts must be located in the crowns instead of the roots. The sides of the roots are trimmed parallel. The distal sides require very little trimming (Fig. 814). The inner caps are made and fitted to the roots. The split posts are REMOVABLE BRIDGE-WORK 391 formed of half-round platinized gold wire. The slit in the portion of the post inserted in the root is soldered together, leaving the section open that is to extend above the floor of the cap. The posts are to be bent at a point in the canal a little below the floors, so that the portion extending above the floors shall be parallel. The canals should be reamed sufficiently to permit the posts to be placed as far as possible toward the lingual side, to leave space for the porcelain facing, as Pig. 813. Fig. 814. illustrated in Fig, 815. Holes are made in the floors of the inner caps to allow the posts to pass through. The posts are then attached to the floors with a small quantity of wax. Plaster is placed over each cap and post, they are removed, invested, the plaster and wax removed and posts soldered to the floors. Any excess of solder present must be removed perfectly even with the floor. Fig. 815. Pig. 816. The outer caps are constructed with floors of gold plate gage No. 28. Tubes with closed ends are fitted over the posts and holes made in the floors large enough to allow them to pass through. The tubes are attached to the floor of each outer cap with wax, removed, invested and soldered to the floor. Investing material and a piece of iron wire or a nail, must be inserted into each tube to retain it in position when the wax is removed, as shown in Fig. 816. The porcelain facing is ground in position on the cap. When neces- sary a Httle of the porcelain between the pins can be removed to better 392 CROWN-, BRIDGE-, AND PORCELAIN-WORK Fig. 817. accommodate the' tube. The facing is backed with thin platinum. In soldering the facing or bridge, the investing material and wire should be again inserted into the tube to prevent its displacement. The bulky form on the lingual side of this style of crown will not permit its use in many cases for superior cuspids. In cementation the inner caps should be first placed in position with the cement and immediately the bridge set over them. Vaselin placed in the tubes and outer caps will prevent invasion of the cement. Retaining Inlay Abutments Retaining Abutments. — For attachments of this style, the pulp is removed, but the natural crown is preserved. The attachment consists of a countersunk gold inlay with a tube into which fits a supplementary or m.ale inlay, with a split post. This form of attachment is used where it is desirable to preserve the abutment tooth or teeth as nearly as possible intact, as in a case where a sound central is used as an abutment for an adjoining central or lateral. It is preferably used in a cuspid which is to act as an abutment to support the lateral with the assistance of a lug on the central. It also is used as an anterior abutment to a molar abutment, and in cases where the shape or position of a tooth suggests its use as being preferable to a crowning operation. Bicuspids and Molars. — A molar will be used to explain the method. The pulp is removed and canals treated. The cavity for the inlay is made in the occlusal surface about one-hall the length from mesial to distal side, as shown at A, Fig. 817, and in the mesial or approximal side, large enough to furnish room for the matrix or female inlay that is to carry a supplementary or male inlay with a tube and split post, as shown at B, Fig. 818 outlines in section the assembled por- tions of a removable inlay attachment with a split post. The orifice to the canals and the body of the pulp-chamber are first filled with cement, preferably oxychlorid of zinc. To prevent pressure on the inlay splitting the tooth, the side walls should be made nearly straight, slanting but very slightly out- ward — and the bottom of the cavity flat or nearly so. Provision for the tube should be made, which should extend to the floor of the pulp- chamber and, if necessary for security, be inserted a short distance into one of the roots. Fig. 818. — A, Matrix or female inlay; B, supple- mentary or male inlay; C, tube; D, bent splint post. REMOVABLE BRIDGE-WORK 393 Pig. 819. The palatal root of an upper molar or the mesial root of a lower molar is usually selected. The tube should be the largest the tooth will properly allow, so as to carry a correspondingly large tube, if possible, gage No. 5 or 6. The Matrix or Female Inlay.— This can be made by the direct method but not with the same facility or accuracy as by the indirect, consequently the latter will be described. The cavity having been shaped, as outHned in Fig. 817, an impression is taken with impression compound and an amalgam die made. A cast matrix of gold alloyed with three to five per cent, of copper is made for the cavity. This is done by shaping a sheet of wax, about one-sixteenth inch in thickness, to the cavity and shghtly over the margins (Fig. 819). The wax is perforated over the indentation in the die for the tube and a carbon inserted. A sprue wire is inserted in the edge of the wax, and the wax matrix is lifted from the cavity, in- vested and cast. The cast matrix is first fitted to the die and next in the tooth. The edge of the casting is brought close to the margins of the cavity with a piece of orange wood, tapped on the end with a mallet and a revolving burnisher passed over the part. The hole in the matrix for the tube is enlarged to fully the size of the di- ameter of the tube (Fig. 820). The tube mounted on a mandrel, is in- serted in the hole (Fig. 821 in section) surrounded with wax and par- alleled to the other abutments. Matrix and tube are removed and then the mandrel from the tube, and matrix and tube are invested and united with solder. The matrix and tube having been adjusted in the cavity to deter- mine the accuracy of the position of the tube,, they are removed and the extended end of the tube trimmed level with the floor of the matrix, and its orifice shghtly countersunk, so thaf the spHt post may enter more freely (Fig. 822). The gold of the side walls of the matrix cavity are to be trimmed so as to give them proper form in detail. The forward section of the cavity should be deep and narrow for strength in preference to being made broad and flat. The cavity having been properly shaped the surface of the gold is then smoothed and burnished with a revolving burnisher. Fig 820.. Fig. 822. Fig. 821. 394 CROWN , BRIDGE-, AND PORCELAIN-WORK Split Post and Supplementary or Male Inlay. — A post is fitted to the tube. The sHt in the post should be placed in a labio-lingual direc- tion. The slit at the point of the post should be left closed, so that it will not open when the post is bent. The point, though, should be filed flat, moving the file in the line of the slit, and the edges slightly rounded. Enough should be removed at the point to closely approach the slit so that at any time, if desired, the filing of a slight groove will reach the slit and permit the post to be expanded from the point. The matrix to the supplementary or male inlay is made by shaping and burnishing a matrix of pure gold, gage No. 36, or /-looo platinum, into the female cavity and well over the edges, frequently removing the matrix and annealing. A hole is made in the matrix over the tube, the split post inserted, the line of the floor of the matrix marked on the side of the post, the post withdrawn and bent level with the floor of the matrix, preferably using a pin bender instead of a pin vise or pliers. A Pin Bender. — ^A post can be bent with a pin vise, but the bending is best done by the use of a pin bender, which is really a tube in which the post fits accurately. The set consists of three tubes. The holes in the ends of each are proportionately increased in size, so as to accommodate six sizes ...... — of posts, as shown in Fig. 823. Select a size corresponding to the post, anneal and insert the post — closed end first — as shown in Fig. 824, and bend it to the required angle, anneal- ing two or three times. Pig. 823. Fig. 824. ^j^^ ^^.^^^ ^^ ^-^^ ^^^^ -^ ^i^^-^^^^y oiled. The male matrix is annealed, adjusted in the cavity and the post inserted. Adhesive wax is then melted into the matrix and arouDd the post, and pressure exerted on the wax to bring all parts to position. The wax is chilled, the matrix and post removed, invested and the matrix filled with coin gold. It is next boiled in acid, the edges trimmed to that of the first or female inlay — revolving the stones from the center outward — then polished. Variations in Method A method of constructing the first or female section of inlay abut- ments, is to cast it with the tube in position. REMOVABLE BRIDGE-WORK 395 Another method is: Swage in the cavity a piece of pure gold gage /■fooO) oil the surface, burnish and swage over it another piece of the same gage of gold and punch a hole through each side of the second piece with a punch forceps. Invest and unite the two matrices with a particle of solder, fused through the two holes in the sides. Insert the matrix in the cavity and burnish. Add another layer of gold to the matrix in the same manner when the case so suggests. Fit the matrix in the cavity, trim and burnish the edges, place the tube in position, remove and solder. By this method a perfect fitting edge can be obtained for the female inlay. In cases where extensive decay has involved the occlusal surface, shorten the cusps, bevel and cover the edges to avoid the possibility of the tooth splitting (Fig. 825). Incisors and Cuspids. — The use of the inlay abutment attachment for the front teeth is confined chiefly to upper central incisors and cus- pids, and lower cuspids. It is seldom applied to upper laterals and Pig. 825. Fig. 826. never to lower incisors, as the teeth are too small. To explain the construction, a cuspid will be used as a typical case. An opening is made at the lingual side of the crown in the line of the pulp-canal, the pulp devitalized, removed, the foramen closed with gutta-percha, and the canal filled with zinc oxychlorid. (See Part II, Chapter III.) The treatment must be so conducted as not to affect the shade of the tooth. The cavity in the crown is enlarged and shaped for the inlay and the canal reamed for the tube, as shown in Fig. 826. The side of the cavity approximately to the bridge should be shaped so as to allow as nearly as possible direct connection with it, as indicated at A. To avoid weaken- ing the labial section of the crown, the reaming for the tube should be carried lingually as far as it properly can be, and kept within the line of the axis of the tooth. The sides of the cavity must taper slightly to the line of the tube. The edges should have a slight bevel. The canal is reamed to receive a No. 4 or No. 5 tube. Centrals generally take a smaller size. The depth varies in accordance with the size and 396 CROWN-, BRIDGE-, AND PORCELAIN-WORK length of the root, but usually it is from five-sixteenths to three-eighths of an inch. The first or female inlay is made either by the direct or indirect method. As the process of the formation by either method is about the same, the indirect will preferably be explained. The tube having been fitted to the canal, is removed. To Take the Impression. — Fit a brass wire in the canal the size of the selected tube. Soften a small piece of compound, slightly heat the wire and surround it with the compound. Wet the cavity, force the wire to position in the canal, press the compound around the wire, into the cavity and over the edges, chill and remove. An amalgam die is then made. To enable the amalgam to be properly pressed into the impression, embed the impression in a funnel of plaster, as shown in section. Fig. 827. (See Part I, Chapter V.) When the amalgam has Pig. 827. Fig. 828. Fig. 829. set, the wire and compound are removed. The die will be a replica of the cavity and canal. The surface of the die is lubricated, and then wiped with cotton to prevent adhesion of the wax. The tube, mounted on a mandrel, is inserted in the canal, the cavity filled with wax pressed well around the tube, and then trimmed to a uniform thickness over the surface of the cavity, leaving a slight surplus beyond the edge, into which the sprue wire is inserted. The wax is removed, the mandrel seized with pliers, and the tube pushed off the mandrel. The tube is filled with asbestos, the wax model invested, and cast with pure gold alloyed with two per cent, of copper (Fig. 828). Some practitioners prefer to first cast the matrix inlay without the tube, placing carbon in the wax model instead. After the inlay is cast and fitted, the tube is inserted, invested and soldered in posi ion. At this stage the work may be fitted to the mouth, to determine its REMOVABLE BRIDGE-WORK 397 accuracy respecting adaptation and occlusion. The remainder of the construction of the inlay attachment can be done either directly in the mouth or indirectly on the model. The tube is cut off at the floor of the cavity and the inlay trimmed and symmetrically shaped. Enough gold is removed to make space for the supplementary or male inlay, leaving the gold at the edge of the cavity intact, as shown in Fig. 829. The orifice to the tube should be slightly countersunk, and the contraction at the neck from the casting or soldering removed with a dull cone-shape finishing bur. The surface of the cavity and the orifice of the tube are smoothed and polished and a revolving burnisher lightly passed over the surface. Insertion of the Split Post. — The split post is next fitted in the tube. It should be nearly twice the length of the tube, and fit accurately but easily. The point of entrance of the tube is marked on the post. The post is removed and bent one-thirty-second of an inch farther from the cavity towards the shank than the mark, using a pin bender as already described. The Supplementary Inlay. — This is best made by the matrix method. A piece of pure gold plate, gage No. 36, or yiooo to 3^^00 platinum,- preferably the latter, is shaped to the cavity and into the orifice of the tube. When gold plate is used, it is removed and the metal that has been burnished into the orifice of the tube is removed by grinding it on the cavo-side of the matrix, making the hole a little larger than the post, so as to allow it to enter the tube freely. When platinum foil is used it is trimmed at the orifice of the tube. The orifice of the tube is vaselined, the matrLx adjusted in the cavity, the post inserted in position and the wax melted with a heated spatula into the matrix and around the post. The matrix and post are re- moved, invested, and the matrix filled with coin gold. The gold should be drawn around the shank of the post, by heat applied under the in- vestment. After being cleaned in the usual manner, it is adjusted to the inner or female inlay. The edges should be left a little flush until the final finishing when the bridge is inserted. In finishing, stones and polishing points should be revolved outward from the center. The attachment is now ready for connection to the bridge, to which che shank of the post is waxed, and the wax chilled. The bridge is removed, the tube is held by the fingers, and by pressing on the post with the point of an instrument, the inner or male inlay is released and the bridge with post invested. Another method for removing the post is to heat the point of a stick of hard adhesive wax and attach it to the metal over the post, chill and pull the post from the tube. 398 CROWN-, BRIDGE-, AND PORCELAIN-WORK Use of Swaged First or Female Matrix. — Female matrices for in- cisors and cuspids may preferably be made by the swaging instead of the casting method, using pure gold plate as heavy as the size and shape of the cavity will admit, which varies from gage No. 32 to No. 36, or Ho 00 platinum. First shape the gold or platinum matrix in a fusible metal die of the cavity taken from the amalgam die, and then transfer it to the amalgam die for finishing. The matrix should be extended well over the margins of tne cavity. When a platinum matrix is used, it should be reinforced after shaping it to the cavity, by veneering the outer surface with two or three applications of pure gold, readapting the matrix to the cavity between the applications. In this way a most accurately fitting matrix is obtained. To reinforce the matrix, paint the cavo-surface with rouge, place pure gold — a few small pieces at a time — in the matrix and fuse it by holding the rriatrix in a Bunsen flame. Flux may be used, but is not necessary. (See "Matrix Gold Inlay," Part III, Chapter XVII.) The tube is next fitted and soldered in position with coin gold. The subsequent procedure is conducted the same as with a cast matrix. The matrix method is preferable to casting in the construction of these attachments for small anterior teeth. Supporting Abutments This form consists of a lug, with or without an anchorage point, that rests in a countersunk gold filling or inlay, or a socket formed in an artificial crown. It supports and steadies one end of the bridge but does not retain it. A lug attachment on one end of a bridge, in conjunction with a reliable retaining abutment on the other, is usually suflicient to support a bridge of one or two teeth. On the mandible in conjunction with a retaining molar abutment it will in many cases afford additional reliable supports to a bridge of two and occasionally three teeth. It can also be used to furnish additional support to a large bridge with two or more retaining abutments. In teeth with vital pulps, the cavity should be made large enough without impinging on the pulp to accommodate the lug and allow a sub- stantial lining of gold between it and the walls. To prevent displacer ment, an undercut form should be given the cavity for a filling, and a retentive form for an inlay. As retentive a form as possible should also be given the lug. As the lug will be adjusted and removed in an occlu- sal direction, calculation should be made accordingly. The cavity in a cuspid is usually given the form illustrated in Fig. 830. The filling or inlay may be slightly exaggerated in contour by REMOVABLE BRIDGE-WORK 399 expanding its bulk, as illustrated at A, Fig. 831, by extending it over the margin of the cavity, to increase the depth of the slot for the lug. If a filling is used it should be made entirely of cohesive gold foil thor- oughly condensed. When an inlay is used, the slot for the lug may be cut in the inlay after it is cast, or a depression maybe made in the wax model, and the slot shaped additionally after the casting. The lug is made of clasp gold wire, gage 12 to 14, the gage being regulated by the size of the tooth and the stress it will have to withstand. Usually some trimming of the wire is necessary. A slot in a filling is best cut by first drilling an indentation in the center or slightly past it on the lingual side (A, Fig. 832), close to the bottom of the cavity with a spear-pointed drill, and then shaping it with a pear-shape bur to the size of the wire used. A slot (B) is cut the same size as the hole, from its orifice to the side of the filling or inlay. The removal of gold for the slot should be so conducted as not to weaken the efl&ciency of the filling or inlay. Pig. 830. Fig. 831. Pig. 832. The point of the wire lug is slightly rounded and the end bent at a right-angle and' filed (C) so that the point rests in the indentation at the end of the slot. The shank of the wire lug is made long enough to extend to the backing of the adjoining dummy, so that it can be soldered under the cusp-cap, if one be present. In bicuspids and molars with vital pulps, the cavity of the filling or inlay is extended about two-thirds or three-fourths across the occlu- sal surface, and down on the side approximately to the bridge, so as to give such a length to the filling or inlay as will admit of a proportionate length to the wire lug, as shown in Fig. 833. Bicuspids do not admit of the use of a large wire lug except when pulpless. A much more substantial wire lug can be applied to molars. To fill in the space on the sides and around a wire lug and anchorage point so that there shall be no perceptible seam: Burnish a matrix of Ho 00 platinum foil in the groove, and fill the matrix with wax before or after the lug is attached to the bridge. Warm the wire lug and press it 400 CROWN-, BRIDGE-, AND PORCELAIN-WORK to position in the wax of the matrix, remove, invest, wash out the wax and melt hard solder in the matrix around the wire lug, trim and adjust. The additional metal increases the size and strength of the lug and causes it to assume the form of a supplementary inlay. If the cavity in the inlay is given the slight retention form seen in Fig. 833, the lug is rendered additionally secure. The greatest stress on a support of this form is on the part that spans the space between the bridge and the entrance to the slot of the abut- PlG. 833. Pig. 835. Fig. 836. ment. This portion can be reinforced quite effectively by flaring the entrance to the slot, as shown at A, A, Fig. 834, burnishing the platinum matrix to the flare, and extending the matrix under the lug to the dummy, then investing and filling the matrix with solder. Fig. 835 shows the reinforced attachment finished in the matrix of the molar, and Fig. 836 the same in a bicuspid. A socket for a lug attachment in a gold crown is described in Part IV, Chapter III, Figs. 603 to 609 inclusive. Special Forms of Attachments Collar and Partial Cap. — This is a form of attachment made to fit over a gold crown. It is seldom used on a natural tooth. For the Y^L A Pig. 837. Fig. 838. Fig. 839. Pig. 840. gold crown, the sides of the tooth are to be shaped straight and parallel to the sides of any other supporting crown or Hne of attachment. A straight-sided gold crown is made and fitted. The gold crown is removed, a strip of paper wound around it, and fusible metal melted and poured into crown and paper tube. This forms a die of the crown REMOVABLE BRIDGE-WORK 401 with a shank, as seen in Fig. 837. The crown is encircled with a strip of pure gold, about gage No. 30, one part of which, B, Fig. 838, will extend above the remainder in the form shown in Fig. 839. The sec- tions of the gold at A, A, Fig. 838, are to reach from the edge of the neck of the crown to, or slightly above the occlusal surface. The gold is fitted evenly, but not tightly around the crown, the ends, A, A, Fig. 839, being placed at the side where the collar will be joined to the bridge and united with hard solder. The collar is readjusted on the crown, and the part at B, Fig. 840, bent down over the occlusal surface. On the outside of the collar a slightly narrower strip of clasp gold, gage No. 30, is adjusted in the position shown at the line C, then removed, and the joint, which had best be located at the point C, soldered. It is next readjusted on the gold collar, removed with it, and soldered to it. The collar can be invested for this purpose, or the soldering done by holding it in a Bunsen flame and placing small pieces of solder in position in the seam. Only enough solder should be used to unite the parts, any excess being Fig. 841. Fig. 842. Fig. 843. carefully avoided. Painting the inner surface of the collar with rouge will prevent the solder flowing there. The collar section of the removable cap is then trimmed smooth. The flap section at B can be adapted to the occlusal surface of the gold crown and reinforced with solder, or preferably after the collar section has been united to the bridge, and its relative position on the fixed gold crown in the mouth is accurately determined. Fig. 841 shows the gold crown with the finished removable partial gold cap. Flanged Collar Attachment.^ — Fig. 842 shows another form of removable partial cap. In this the entire edge of the collar is bent over on the occlusal surface of the crown and thereby supported in position. This form of collar is made entirely of clasp gold, gage No. 28 for molars and No. 29 or 30 for bicuspids. The process is as follows: An accurately fitting collar is first made. The collar is then, by tapping with a small horn or copper hammer, aided by frequent annealings, shaped on the gold crown or a die of the tooth. The flange section can be slightly thinned with a small carborundum wheel, and tapped 402 CROWN-, BRIDGE-, AND PORCELAIN-WORK to position over the edge of the occlusal surface. To shape the collar over the gold crown, the crown should be first filled with fusible metal as previously described. Lug Collar Support.— Fig. 843 illustrates a form in which a straight- sided removable collar is maintained in position by a lug on the side of a gold crown. Trimming the lug or edge of the collar will at any time permit the denture to press more forcibly on the tissues. The Split-bar Attachment This attachment is used as a retentive abutment. Its merit is that it does not require paralleling of the sides or canals of the abutment teeth. The roots consequently are not weakened by reaming as in the Pig. 846. Pig. 845. — B, Position box is to occupy; P, porcelain facing. use of tubes with split posts, as no space is required within the root for this attachment. The split-bar attachment consists of a flat spring bar, as shown at A, Fig. 844, with a lug B, on the lingual side. This bar and lug fit into a socket termed a box, C, embedded in the gold of a crown or an inlay. By means of the slit the bar is expanded and tightened in the box. For porcelain-faced crowns the bar is placed back of the facing, and for all-gold bicuspids and molars toward the lingual side. Both styles must be so formed as to furnish ample space for the box that carries the split bar. This consequently requires the natural crown to be removed for porcelain-faced crowns, and either considerably or entirely removed for all-gold crowns. Construction.- — For a porcelain-faced crown the root is capped, with a post in the canal. A detachable porcelain facing that allows REMOVABLE BRIDGE-WORK 403 room for the box is ground to position on the cap and attached with wax. A removable matrix of plaster is placed on the labial side of the facing and crown, as shown in Fig. 845. The facing is then removed, backed, replaced in position, and the backing attached to the floor of the cap with a particle of hard wax. For all-gold bicuspids and molars the natural crown is prepared with a step on the Ungual side, as shown in section at A, Fig. 846. A gold collar is made and a floor of thin platinum is added, as seen at B. An occlusal cusp-cap that will cover the buccal section is next added, as shown at C, leaving space for the box. The Split Bar. — ^The split bar is made of iridio-platinum gold (clasp gold) or iridio-platinum plate, by evenly doubling on itself a piece of the plate, gage 22, about one and one-quarter inches long and three-eighths inch wide. The two ends of the plate are first brought together the same as in the construction of a split post, and then gradually at the sides, frequently annealing. When the sides touch they are brought in close contact by swaging in a No. 2. s wager. The split bar then assumes the thickness of gage 16 (Fig. 847). Fig. 847. Fig. 848. Fig. 849. Fig. 850. The lug is made of a V-shaped piece of plate, gage No. 30, flattened in the swager. The lug should be placed a little distance from the edge of the bar, as shown in Fig. 848, and attached with hard solder. A very small quantity of solder should be used and antifiux or rouge placed along the slit of the bar to prevent the solder accidentally flowing into it. The edges of the lug and bar are then trimmed even, as shown in Fig. 849. The Box. — The box is made of platinum plate gage 37 to 38 by looping the plate around the closed end of the bar, adapting it uniformly to its surface and then trimming it even with the edge of the other end of the bar and the edge toward the alveolus. A floor is added to the box by fitting over the bottom and the open end a strip of the platinum that will a little more than cover the edges, attaching it with wax to the sides. The bar is removed, the box invested and soldered with pure gold. The surplus edge of the floor is then removed. Fig. 850. In some cases when conditions suggest it, the bar can be placed in either the center of the approximal side of a crown as shown at A and B, Fig. 851, or at an angle as seen at C. When a bar is placed in an 404 CROWN-, BRIDGE-, AND PORCELAIN-WORK inlay, the pulp must usually be removed, to permit the inlay to be securely anchored. Paralleling the Box. — ^The box is next mounted on a mandrel and paralleled in proper position on the crown to any other abutment present. The alignment of the bar must be such as will favor the insertion of the point of the lug, as the sides of the lug will then guide the bar to position in the box (Fig. 852). The box is attached with hard wai melted with a hot spatula between it and the crown. The wax is chilled, the mandrel lifted out of the box, the crown removed from the model, and shaped and contoured with ordinary wax to the required form. If a porcelain facing is present, it should be removed. The crown is then ready for investment. To aid in holding the box securely in position in the investment during the soldering, a flat piece of graphite with a long shank that easily fits into the box, should be used. The box should be filled with a very thin mixture of the invest- ment material and the graphite immediately carefully inserted and the shank embedded in the investment. The soldering of the box to the crown should be done first with as hard a solder as possible and then the contouring with lower grades. Apply a slight surplus for finish- ing. Soldering is preferred to casting, as the contraction that occurs by the latter method interferes with the fit of the bar in the box. When soldered, the excess of the box at the occlusal edge is re- moved and the crown trimmed and polished. The split bar is next fitted into the box. Some trimming is usually necessary to make allowance for slight changes resulting from the manipulation of the box and soldering (Fig. 853). Fig. 852. Fig. 853. REMOVABLE BRIDGE-WORK 405 The Shield. — This consists in the placing of platinum plate pene- trated by and attached to the split bar, against the approximal surface of the crown. In the construction it acts as an approximal surface for the adjoining bridge-tooth (dummy) and forms a dividing line in uniting the bar to the bridge. It is made of a piece of platinum plate, gage No. 38, about three-sixteenths inch wide and one-fourth inch long (Fig. 854). The contour of the crown, approximal to the split bar is beveled slightly to the line of the insertion and removal of the bar. The Fig. 854. Pig. 855. Fig. 8:56. platinum plate is perforated to admit the split bar, and adapted to the side of the crown with the split bar in position in the box (Fig. 855). The platinum attached to the split bar with wax, split bar and platinum are removed and invested, as shown in Fig. 856, and united with hard solder. At the same time solder is flowed into the slit between the exposed ends of the split bar, to unite them and thus permit the split bar to be shortened without separating the bars, as they are only united at the end where the strip was bent. M I Fig. 857. Fig. 858. Fig. 859. Fig. 858. — A, shows the box with hole for pin in inlay; B, bar and pin. Fig. 857 shows another style of split-bar attachment. It differs from the form preceding in that the lug is made of solid or split round wire. The construction is: The bar and lug are made of clasp gold. A piece of clasp gold plate, gage No. 22 or 23, js doubled to form the split bar. For the lug a solid or split wire is fitted to a hole formed in the end of the slot, in the inlay or gold crown (A, Fig. 858). The split bar is fitted to rest on the bottom of the slot, its extended end is sold- ered in a groove made in the wire to receive it (B). When a split wire is used to form the lug, its united end should be extended from the 406 CROWN-, BRIDGE-, AND PORCELAIN -WORK split bar far enough to retain it in position in the investment while being soldered (Fig. 859). A very thin sheet of mica inserted in the slit of the wire and bar will prevent invasion of the solder (M, Fig. 859). The mica can be removed later with hydrofluoric acid and the parts pinched together. The box to the split bar is soldered in the inlay or crown, holding the box in position while being soldered by a piece of carbon fitted into it, with the end extended into the investment. I This form of split bar is suggested as suitable for a shallow box ap- plied to an inlay in a tooth with a vital pulp. The split wire or lug is more retentive than the solid one. Fig. 860 shows a split bar and lug in position in an inlay in an inferior molar. . Winged Lug Attachment. — ^This is simple in construction and appli- cation. It is made by doubling on itself a strip of clasp gold gage 22, clamping it in a vise and bending the extended ends outward as shown in Fig. 861 . A piece of thin mica is placed in the slit as far as S, and the end of the shank is soldered together, using solder filings or an atom of Fig. 860. Fig. 861. Pig. 862. Fig. 863. hard solder. A box is made of platinum, gage No. 40, as illustrated at B. The corners and edges of the wings at C C are slightly rounded. The box is either inserted in the wax model of the inlay and embedded in the casting, or soldered in a slot provided for it in the inlay. Fig. 862 shows this attachment in an inlay in a molar. By slightly expand- ing the center or by bending the wings, the friction is increased. As this attachment is flat and small in size, it may be used when proximity to the pulp limits the available space. To prevent invasion of food into seams of the attachment in masti- cation, an oval-shaped plate may be placed over the flanges made of platinum, gage 38, or 22-carat gold, gage 30, as shown at C, Fig. 863. The plate is united to the bridge and flanges and reinforced with solder. A thin sheet of mica placed between the plate and the wings of the flanges will obstruct the solder at that point if it is desirable to leave the wings free. Dovetail Flange and Split-post Attachment. — This attachment is shown on the side of a gold crown in Fig. 864. It consists of a dove- REMOVABLE BRIDGE-WORK 407 tail flange that fits into a socket (B) in the adjoining bridge tooth. A split post (C) fits in a tube in the dovetail flange. The form of the flange locks the bridge tooth and consequently the end of the bridge to the gold crown, while the split post secures the dove-tail flange in posi- tion. The dovetail form of the flange relieves the split post of lateral stress. The dovetail socket with the tube hole (D) is first made by shaping a wax model of the form of the dovetail flange, around the tube, in- vesting and casting. It can also be made by filing a piece of fusible metal to the form and size of the dovetail flange, then shaping a thin piece of platinum plate over it, placing the tube supported with wax in position in the shaped plate, investing, melting out the wax, and either by soldering or the casting process, filling in the space between the tube and the plate with coin gold. Fig. 865. Fig. 866. The split post (E) is next fitted in the tube. The point of the post is best extended at least one-sixteenth inch through the end of the tube. The flange is next soldered to the crown, a platinum box formed around the flange, the post soldered in the box, and post and box soldered in position in the bridge tooth. Both flange and post must be aligned with the other abutment. This attachment is of a design suitable to apply to a gold crown on a tooth with a vital pulp. Solid Post and Tube Attachment. — This consists in the use of a solid post of clasp gold, gage 15 to 17, instead of a split post. Fig. 865 shows the attachment applied in an inferior bicuspid gold crown. It can be advantageously used in roots too small, or too long and narrow to properly receive a tube and split post. In the use of a soHd wire post a short slit may be cut in the extreme point with a very thin saw-edged ■ separating strip, as shown in Fig. 866. The slit point is then pinched together and burnished. By slightly opening the slit, or slightly bend- ing the post at any time, friction is created. 4o8 CROWN-, BRIDGE-, AND PORCELAIN-WORK Comparative Values of the Several Forms of Attachments The form of attachment used, especially the retentive, constitutes an all-important factor, for on it depends the treatment of teeth or roots selected as abutments. At the present period of development in bridge-work art, greater efforts are being made than in the past to conserve pulps and to avoid the mutilation of the coronal sections of natural teeth used as abutments. This latter is permissible in removable bridge dentures to an extent not allowable in the fixed forms. In accordance therewith a knowledge of the various forms of attachments in use and a study of their practical values in different positions and under various conditions is essential in what must be considered at the present time as the most approved construction in removable bridge denture operations. An impartial discussion of the relative values of the several removable bridge attachments analytically considered respecting application and construction is here given. Retentive Attachments Tube and Split-post Attachment. — This is one of the most reliable of all attachments for retentive power. Its greater value, which is proportioned to the length and size of the spUt post, is attributable to the character of its construction and to the greater amount of friction obtained in a given space compared with that procured by other means. In the application of this means of attachment to a central or cuspid the root-canal should not be excessively reamed in paralleling the tube to other abutments. The other abutment or abutments instead should be paralleled to the central or cuspid by some permissible method, such as an inlay, a tube and split post in a molar, or a tube and split post in a lug on the mesial side of a posterior gold crown. Either of these methods allows setting the tube and post at the required angle. The tube and spht post inserted in a telescope crown is classed as one of the most reliable of all forms of attachments. Tube and Split-post Anterior Crowns The amount of retentive power of this form of abutment is depend- ent on the friction of the post in the tube, as the half-collar only tends to steady the crown. The retentive power of such an abutment therefore is proportionate to the gage and length of the tube and split post. Split -bar Attachments This form is seldom used except in a pulpless tooth employed as a retentive abutment, owing to lack of space. It possesses the advantage REMOVABLE BRIDGE-WORK 409 over a tube and split post, in that it can be set in a tipped tooth or crown at any angle necessary to have it move in a vertical direction or parallel to another abutment. In its application, while the root of the tooth is left intact, the coronal section will be so weakened that a gold crown must generally be substituted to receive it. Again, split-bar attach- ments compared to other styles of attachments require considerable skill and practice for their successful employment. A split bar to support an adjoining single dummy can occasionally be inserted in a tooth with a vital pulp which has become considerably calcified owing to the presence of a large filling. At the present time in a case of this class a saddle bridge with either a rolled gold, a wire, or a cast clasp with a lug is preferably employed. Retentive Inlay Attachments As the retentive power of the inlay attachment is dependent chiefly on the friction of the split post in the tube inserted in the inlay, as a retaining abutment it may be classed as equal or next to the tube and split-post crown. It admits of considerable deviation from the vertical in paralleling other abutments when inserted in molars but not in centrals, cuspids or bicuspids. Other Forms of Retentive Attachments. — The respective merits of clasps with lugs and other forms of retentive attachments are stated in connection with the description of their construction. Manufactured Retentive Attachments. — These are described in Part V, Chapter VII. They furnish an additional variety of forms of attachments. Supporting Attachments Telescope Crown. — This form should properly be classed as a support- ing abutment, as it cannot always be relied on as retentive, especially on a superior molar or bicuspid. On the mandible enough friction may be obtained to retain it when applied to a small bridge extending from the first bicuspid to the second molar if the inner cusps are long and only slightly cone-shape in form. A telescope crown usually is best applied as a supporting abutment in combination with one that is retentive. When the axis of a tooth is greatly out of line the use of a telescope crown is contraindicated in favor of a more suitable form of attachment. Supporting Lug Attachment A lug extended from a dummy to rest on the lingual surface of an adjoining central or cuspid, resists stress in a la bio- vertical direction; 4IO CROWN-, BRIDGE , AND PORCELAIN WORK if it is inserted in a socket in an inlay or filling, the resistance effected is more vertical. A lug resting on the occlusal surface of a bicuspid or molar resists stress only in a vertical direction, but when inserted in a socket in an inlay or gold crown it also acts laterally. When the socket and lug are oval or dovetail shaped in form, addi- tional resistance in either a distal or mesial direction is obtained. Such a form of lug in combination with a clasp usually constitutes a reliable retentive attachment for a saddle denture. CHAPTER II CONSTRUCTION OF REMOVABLE BRIDGE-WORK METHOD OF CONSTRUCTION THE PARALLELING STAPLE REMOVABLE BRIDGE EXTENDING ON BOTH SIDES OF THE MOUTH — CONSTRUC- TION DIVERSITY OF CONSTRUCTIVE DETAILS — USE OF PARALLEL- ING INSTRUMENTS THE CHAYES PARALLELOMETER Method of Construction 1. Determine the most suitable teeth and roots to use as abutments by examination of the case in the mouth, and study of plaster models of the same, as described in the preceding chapter. 2. Have radiographs taken of the teeth or roots selected as abut- ments, to positively determine their suitability and also as a guide in their treatment. 3. Take radiographs of all teeth and roots to be used as abut- ments, perform such necessary preparatory treatment of teeth and roots as is required, and shape coronal sections and crevices properly. Guided by the eye and study of the model and radiographs of the roots, ream and parallel the root-canals that are to receive the tubes, and fit in each of them the intended tubes mounted on steel or brass wire mandrels. Brass mandrels can be made of straight brass wire, gage No. 12, placed in a chuck and turned on a lathe to the required size. The mandrels should be of a length that will permit their insertion in proper position and the taking of an impression. Encircle each tube on its mandrel with a mark to show how far it enters the root or tooth. In reaming canals for tubes the rule to follow is: ream the larger canal to the line of the smaller as the smaller allows the least lateral reaming, whereas for instance a molar permits considerable lateral placing of a tube. In paralleling canals to place the tubes, it will be found necessary in many cases to ream one or more of the roots considerably away from the central section or line of the pulp-canal, using the Peeso reamers (Fig. 867). Such reaming, if done at the orifice of the canal in the case shown in Fig. 868, will frequently leave but a small quantity of tooth structure at one side, as illustrated in the diverging lines of the canals. The reaming that would be necessary to so parallel if confined to one 411 412 CROWN-, BRIDGE-, AND PORCELAIN-WORK root is shown in Fig. 869. To avoid weakening the root at the point A by this excessive reaming, the Hne of the space for the tubes is carried a Httle to one side in each canal and the amount of necessary reaming at the orifices of the canals is proportioned between the two ,1 I J S U Fig. 867. Fig. 868. A Fig. 869. roots, as shown in Fig. 870. In reaming canals of abutments on oppo- site sides of the mouth, the relationship bucco-lingually, as well as laterally, is also to be considered. In the construction of removable bridge-work the abutment roots and crowns that carry collar attachments require to be shaped parallel CONST RUCTION OF REMOVABLE BRIDGE-WORK 413 to each other, also to the line of attachments, such as tubes and split posts and all forms of attachments that directly enter abutments. The typical case used in describing fixed bridge-work will be utilized to describe the construction of removable bridge-work (Fig. 871). A tube and spht-post crown with a porcelain facing will be used on the cuspid and a telescope crown with split post on the molar. A No. 4 Fig. 870. tube is indicated for the cuspid and a No. 5 tube for the molar. In accordance with_,the methods described, the cuspid root is first reamed for the tube and then such reaming as is necessarily indicated by the eye in the molar to parallel the molar tube to the one in the cuspid. The tubes are next encircled with a mark to indicate their depth in the canal. Fig. 871. The abutment cuspid root and molar crown are next trimmed and shaped for gold collars so that the collars will move on and ofif in cor- responding parallel lines with each other and the mandrels. This is done first by paralleling the sides of the abutments and then slightly tapering them in the occlusal direction (Fig. 872). Next make the 414 CROWN-, BRIDGE-, AND PORCELAIN-WORK gold collars. Leave each collar a little longer than is required so thai they can be more easily removed in the impression (Fig. 873). Place the collars on the cuspid root and molar crown and insert the tubes mounted on the mandrels in the same previously paralleled Fig. 872. position in the canals and secure the tubes in the collars with wax (Fig. 874). Take a plaster impression, removing the collars with the tubes on the mandrels. Varnish the surface of the plaster impression Fig. 873. and outer surface of the tubes, veneer the cavo-surface of the caps with parafl&n and oil the several parts. Pack around the portions of the tubes that are to enter the roots amalgam or copper oxyphosphate cement, and run a plaster model. When the amalgam or cement is set remove the plaster impression and the resultant model will be a replica of the condition in the mouth with the tubes on the mandrels in sockets CONSTRUCTION OF REMOVABLE BRIDGE-WORK 415 of amalgam or cement. Remove the tubes with the mandrels, which is facihtated by heating both mandrels and tubes, and boil the tubes in nitric acid if amalgam was used. The Paralleling Staple. — Select straight brass rods three to five inches in length and of a gage such as will fit, or by turning down on the lathe, can be made fit the tubes. The tubes on the ends of the brass rods are inserted into the holes on the model. The extending ends of the brass rods will plainly indicate any divergence from parallel lines Fig. 875. should it exist, as shown in Fig. 875. Such divergence is corrected by removing the rods and tubes, and reaming the holes in the model, guided by the radiographs of the roots and the marks made on the tubes to indicate their depth in the roots. When the brass rods appear to be properly paralleled, they are tested by cementing the tubes with wax on the model and removing and replacing the rods, either by holding the ends together or cementing a cross-bar with hard wax. When there are three or more rods, two are first joined together and then the others connected to them. 4i6 CROWN-: BRIDGE-, AND PORCELAIN-WORK The rods having been paralleled, are retained in relative position with two cross-bars cemented with wax cement (Fig. 876). They are next removed from the model, each rod separately seized with a small hand-vise or phers and the tube pushed off with an instrument (Fig. 877). The rods are then invested and the wax washed out. The cross bars will fall off when the wax is removed. Two short cross bars are then fitted in between the brass rods, about three-fourths of an inch from the points of the rods as they enter, and one-fourth of an inch Fig. 876. apart. • ^ The investment is heated and the rods joined together with silver solder. The excess length of the rods is then cut away, leaving them in the form of a staple projecting about three-eighths of an inch beyond the line of the molar collar so that when later placed in the mouth the staple will not interfere with the taking of the impression (Fig. 878). The tubes are placed back on the staple, which is adjusted on the model to verify its accuracy, and at the same time the collars are carefully examined to see if they parallel favorably with the rods of the CONSTRUCTION OF REMOVABLE BRIDGE-WORK 417 Staple, as the rods indicate the ultimate position of the tubes (Fig. 879). If the collars are not parallel with the brass staples they must be made Fig. 877. Fig. 878. Fig. 879. The staple and tubes are next adjusted in the canals in the mouth and any necessary additional reaming done. The collars are removed from the model, adjusted in the mouth, trimmed to the surfaces of the 27 4i8 CROWN-, BRIDGE-, AND PORCELAIX-WORK abutment roots or teeth and the lloors soldered on. Holes for the tubes are then made in the lloors with drills, and enlarged with burs sufficiently to allow the tubes on the staple to move in and out freely without touching the lloors. The caps are placed in the mouth, the staple with tubes inserted, and wax pressed in the opening in the floor around the tubes. Plaster is separately placed around each cap abutment and all removed. The rod of each staple is next grasped with a small vise and by pressing on the end of the tube with a small chisel, the tube and cap are pushed ofif the rod. The tubes and caps are each invested, asbestos packed in the Pig. 8So. Fig. 8Si. tubes and the tubes united to the floors with 20-carat solder. The solder should be flowed down into the opening around the tubes in the floors. The ends of the tubes are next trimmed level with the surface of the floors. An outer cap with a split post is next made for the cuspid and a telescoping cap with a split post for the molar, with the slits of the posts placed in a linguo-buccal direction (Fig. 880). All the parts are placed in position in the mouth and an impression and "bite" taken with plaster as for flxed bridge-work (see Part IV, h^ Fig. 883. Fig. 884. Fig. 885. Chapter I). The cavo-surfaces of the caps and the outer surfaces of the tubes are veneered with paraffin and models are made and mounted on an articulator. The occlusal cusps of the molar and the porcelain facing of the cuspid are added in accordance with the antagonizing teeth (Fig. S81). The bridge teeth (dummies) are next constructed and united to the outer caps of the abutment crowns. In removable bridge-work, if a saddle is not used, the bases of the artificial teeth (dummies) are generally made to rest closely on the membrane of the alveolar ridge. For this purpose the surface of the plaster model is slightly scraped and a piece of platinum foil or pure gold CONSTRllCriON OF REMOV A ni.l: I'.KI DCEWORK 419 ])lalc adaplcd ovc^r ihe surfjuc. The Ijuscs of I Ik- jjort elain facings arc ground with a nnrrow V-sha[)C(i space aL the cervico-lahial side, and backed, as illustrated in Mg. 882. This space is to be fdled with gold in the soldering, and when finished appears as shown in I'"ig. 88;?. The metallic section of such a dummy (an be made entirely of gold by the casting process and the porcelain facing then cemented to jjlace (Fig. 884), as described in relation to replaceable incisor facings (\'\g. 885). Mg. 886 shows the completefl removabh- bridge. In removable bridge construction, the contraction of gold in solder- ing must be more carefully considered than in the fixed f(jrm, as the align- ment of the parts, especially the tubes knd split posts, is easily afYected. For this reason, the solrlering should be done in sections and the sections then united in a final soldering operation. 'I'he dummies should be formed first, next they should be soldered together, and thea united to the outer caps of the abutment crowns. In the tyjjical case shown in Fig. 886, the bicusf)id dummies were made in this manner. ■frn'"l"lnr„K I''ri.. ««6. In the construction of removable bridge work, the ( orrect readjust- ment of caps, crowns or dummies that are removed from the moflel can be assured by the use of a r(;movable f)laster matrix. Removable Bridge Extending on Both Sides of the Mouth. In the case illustrated in I''ig. 887, the tvVo cuspid roots, right second molar and left first molar are the abutments. Split posts and tube crowns with 'porcelain facings are made for the cuspids, a telescope crown with split post for the right second molar, anrl an inlay with sf)lit (K)st for the left first molar. The pulps of the four abutment teeth are devitalized and the root-canals filled.' Construction. Ream and jjarallel root-canals to receive tubes and fit the tubes on the brass rcKJs int.o them. Trim and shaf^e the cusjjid roots and molar so that caps will move on and oil in line with one an- other, parallel with the brass rods, and sfiajie the cjivity in the Ic-ft 'Same as case shown in l''ij<. 561. 420 CROWI^-, BRIDGE-, AND PORCELAIN-WORK first molar for the inlay attachment, as described in Chapter I. If possible, have the line of the side walls of the inlay cavity parallel with that of the rods and sides of the other abutments, so that the inlay can be removed with them when an impression is taken. Next make the abutment gold collars and the matrix section — female inlay — for the inlay attachment in the molar with a hole for the tube. Fig. 887. Pig. 888. Place the gold collars on the abutments and the gold inlay matrix in the cavity of the molar in the mouth, and insert the brass rods with the tubes in the canals, surrounded with wax packed in the collars and inlay matrix (Fig. 888), and take an impression in plaster, removing in the impression the collars, inlay matrix and brass rods with the tubes. Veneer cavo-surface of inlay matrix with paraffin, also the inside surface of the caps, varnish, oil and make a model, as already described. CONSTRUCTION OF REMOVABLE BRIDGE-WORK 421 Next form a paralleling staple, as previously described, to accurately parallel the several tubes, which is very necessary in this case. Place the tubes for the canals on the rods of the staple, and examine the collars to see that they are favorably paralleled with the tubes on both sides of Fig. 8i the model (Fig. 889). Next fit the tubes mounted on the staple in the root-canals in the mouth, then remove. Remove collars and inlay matrix from the model and adjust them in the mouth. Trim collars and Fig. 890. add floors. Make holes in floors and insert the tubes mounted on the staple, through the floors and matrix (Fig. 890). Press wax in the open- ings around the tubes in floors and inlay matrix, place plaster around on each and remove all together with the staple. 422 CROWX-, BRIDGE-. AXD PORCELAIN -WORK Remove separately from the staple all the tubes with the caps, invest them separately and solder the tubes to the floors. Remove the protruding portions of all the tubes. Outer caps with split posts are next made for the cuspids, the telescoping cap with split post for the right molar and the male inla}' with split post for the left molar. An ensemble of all the parts is then made in the mouth, an impres- sion and "bite" taken, and models made mounted on an articulator. The porcelain facing of the cuspids and the occlusal cusp of the right molar are then added (Fig. 8qi). In the construction of the bridge, the second bicuspid dummy on the left side is securely united to the male section of the removable split-post inlay attachment. In a case where the conditions do not permit the inlay attachment to be removed with the bridge in the con- struction, it is united after the remainder of the bridge is formed, in a Fig. 891. separate fitting and soldering operation. Fig. 892 shows the completed bridge. Diversity of Constructive Details. — In paralleling the canals for the tubes, place the tubes on brass rods or the steel mandrels on which they were formed, and with them parallel the tubes in the mouth, guided only by the eye. Each mandrel tube and cap is then covered with plas- ter, removed, the mandrels removed from the tubes, each tube and cap separately invested, and the tube soldered to the cap. Detached-post crowns, Goslee teeth or replaceable porcelain facings may be used instead of the ordinary two-pin porcelain facings, as de- scribed in tixed bridge-work. Use of Paralleling Instruments. — In the construction of a removable bridge, the paralleling of the abutments and tubes is simplified and the making of a paralleling staple avoided, by the use of a paralleling instrument. CONSTRUCriOS 01' REMOVABLE BRIDGE-WORK 423 The Weinstein paralleling device, large size, illustrated in Fig. 893, and small size in Fig. 894, consists of a semicircular flat bar, as marked Fig. 893. in each illustration, B B, with round holes to recieve the screws S,S, that fasten the cross bars, C B, when they are positioned. In the ends 424 CROWN-, BRIDGE-, AND PORCELAIN -WORK of these cross-bars, the several mandrels to gage the line of the canals are fastened in a horizontal position by the end screws, E S. In practical application each cross-bar, C B, is loosened by the screw S, which allows it to be pushed inwardly, outwardly, or turned to the right or to the left, as indicated by the dotted lines in the figures, and then fastened by the screw S at the same time the mandrel is positioned in the root-canal, and fastened by the screw, E S. Two, three, or more canals may be paralleled together at the same time. This instrument may be used for a double purpose, first to assist in gaging and paralleling the canals for the tubes, using mandrels the Fig. 894. size of the intended tubes; and second to position the tubes, by re- placing the large mandrels by a smaller set that will fit into and carry the tubes. Plaster is placed around each mandrel, cap and tube. When the plaster is set, they are removed from the mouth. Each tube and cap is next separately removed from the mandrels, invested, and united with solder. The Chayes Parallelometer. — This instrument and its use in con- nection with the Chayes attachments is described in Part V, Chapter VI. The ordinary mandrels may be used with this instrument to paral- lel removable bridge tubes, in the same manner as with the set that comes with the instrument. CHAPTER III THE SPLIT-BAR BRIDGE The use of the spHt bar instead of the spUt post, will be de- scribed in its application to the typical case shown in Fig. 895. The cuspid is prepared the same as for a gold collar crown with a porcelain facing (A), the molar with a step on the lingual side to form a space to place the box in which the split bar fits (B). The cuspid root Fig. 895. and molar are capped, as described for a spHt-bar attachment, (Part V, Chapter I), A and B, Fig. 896. An impression and "bite" are next taken with the abutment caps in position. The cavo-surf ace of the caps is veneered with parafl&n, and the upper impression is run. When the plaster is set, the articulating model is made. Fig. 896. A Steele facing is ground to position on the cuspid cap and attached with wax. A removable matrix of plaster is placed on the labial side of the cuspid facing and cap, to permit the removal and replacement in position of either during the construction (A, Fig. 897). A matrix should also be placed against the molar cap to insure correct replace- ment (B). The cuspid facing is removed and backed, and the partial cusp-cap is added to the molar (Fig. 898). 425 426 CROWN-, BRIDGE-, AND PORCELAIN-WORK To parallel the boxes, assemble all the parts in position on the model aiid attach the cuspid facing and backing to the floor of the cap with a particle of wax. While it is possible to parallel the boxes the one to >1 I ^ \:-'.'4 Fig. 897. the other, guided by the eye or by using flat bars of brass of the same gage as the split bar, as mandrels, the paralleling is best done with a parallelometer, by soldering the brass bars to brass rods, and setting the rods in the mandrel holes (Fig. 899). In the typical case, Fig. 898, the box is attached to the floor of the cap of the cuspid and backing with hard wax. The brass bar in the Fig. 899. box is next removed by carefully loosening the screw that holds the brass rod in the paralleling tool and withdrawing the bar out of the box. A carbon of the same size as the flat bar is then inserted in the box. THE SPLIT-BAR BRIDGE 427 The box to the molar crown may then be set. The preferable method is to first complete the cuspid crown, readjust it on the^model and set the Fig. 900. box to the molar with hard wax, insert the carbon in the box, invest, unite with solder and trim. The split bars are next fitted into the Pig. 901. boxes and the shields applied, as described in Part V, Chapter I (see Figs. 854 to 856), and shown in Fig. 900. The dummies are next added and the bridge completed, as shown in Fig. 901. CHAPTER IV REMOVABLE SADDLE BRmGE-WORK CONSTRUCTION OF SADDLES — METHOD OP TAKING IMPRESSIONS POR SADDLES — THE ARTICULATION — THE BRIDGE TEETH — ^CONSTRUCTION OF PORCELAIN-FACED SOLID GOLD DUMMIES FOR SADDLES — SOLID GOLD TEETH DUMMIES — \^ULCANITE ATTACHMENT — EXTENSION SADDLE BRIDGE — AN ADJUSTABLE SADDLE — ^VULCANITE EXTENSION SADDLE A dental saddle bridge scientifically defined is a combination of a truss and pontoon bridge. The supporting crowns act as the truss abutments — ^substructure — and the saddle the superstructure — bearing on the ridge as the pontoon. A saddle should fully cover the area of the absorption of the alveolar ridge caused by the loss of the teeth to be replaced, and when permissi- ble should extend a little beyond it. In removable bridge- work a saddle is not open to the same objections as in the fixed form. The use of saddles, in the construction of removable bridge-work, especially on the mandible, is gradually becoming the preferred method. A saddle of the proper size will materially aid the abutments in sustaining a bridge by relieving the direct and lateral stress on the abutments. It also permits restoration of the contour of the parts absorbed, thus avoiding spaces under the artificial teeth. Construction of Saddles. — In the typical case. Fig. 88 1, the appli- cation of a saddle under the bicuspids will be described. The abutment crowns are placed in position and an impression taken of the pbrtion of the alveolar ridge that is to be occupied by the saddle. In the construction of saddle bridge-work, interchangeable facings or detached-post crowns, are preferably used on the porcelain-faced abutment crowns, as the porcelain can be removed during soldering operations. In the typical case in hand, an interchangeable porcelain facing will accordingly be used on the cuspid. Methods of Taking Impressions for Saddles. — A plaster impression is the most reliable and most used. The following method is one that will depress the soft parts of the membrane of the alveolar ridge, make an allowance for the movement of the muscles of the cheek and in the case of a lower impression, the muscles of the tongue. A wax or com- 428 REMOVABLE SADDLE BRIDGE-WORK 429 pound impression of the part to be covered by the saddle is first taken in a small impression cup, and a plaster model run. The part to be occupied by the saddle is marked on the model, as shown at A, Fig. 902, and the surface of the model given a coat of sandarac varnish. When the varnish has dried, the surface is wet with water, and upon it is shaped a piece of softened compound about the size of the intended saddle, and extended up on the mesial side of the molar crown and the distal side of the cuspid. The compound is then chilled, removed from the model and trimmed, guided by readjustment on the model, so that it will only cover the portion outlined for the saddle, less about one-eighth of an inch at the buccal side, as shown at B, Fig. 903. The object of this reduction of the area for the saddle is to give the muscles that much more room for movement. The impression compound is intended as a medium to carry and compress the plaster on the central portion of the ridge, and allow it to press out at the side and take the form of that part in a manner that will leave more room for movement of the muscles. Fig. 903. The compound having been trimmed as described, the surface of the impression is slightly serrated. The plaster is then mixed to the consistence of a thick cream, the compound dipped in water, the surplus water shaken off, and the surface of the compound evenly covered with the plaster inserted and pressed to position in the mouth, and the pa- tient instructed to instantly contract the muscles of the cheek and so hold them until the plaster sets. In a lower impression the patient should raise the tongue and so hold it. This gives an impression of the contracted form of the tissue and muscles, that allows space for their movement, which aids in avoiding irritation for want of room when the saddle is worn, an important matter from a practical standpoint. The impression when removed is varnished and oiled and a plaster model run and the exact size of the saddle is marked on the model. On the palatal side the space marked should entirely cover the area of absorption of the alveolar process. The surface of the plaster model should be scraped at the edge of the space at the palatal side about one- thirty-second inch in depth to countersink the edge of the saddle and cause it to slightly indent the membrane. 43° CROWN-, BRIDGE-, AND PORCELAIN-WORK The saddle is made with a turn-over rounded edge. For this pur- pose a wax ridge one-sixteenth of an inch high, is built around on the model at the line marked as the size for the saddle, as illustrated in Fig. 904 and in section in Fig. 905. To lessen the pressure of the sad- dle on the gingival margins of the membrane at the abutments, that part is marked on the model, and narrow layers of thick tin foil added until a thickness represented by about gage No. 26 is obtained, as indicated at T F, Fig. 904. The same result may also be effected by scraping the same area in the impression around the abutments before running the plaster model. Fig. 904. A zinc die and lead counter-die are made in the usual manner. To simplify the making of the mold for the casting, trim the plaster model and cut off the teeth to the line to which the plate will extend. The saddle is made of platinized gold, gage No. 28 to 29, or platinum, gage No. 32 to 33. Platinum is the metal preferred for the health of the membranes, but as it has to be reinforced with 22-carat gold, and the difference of the expansion and contraction of the two metals when heated, is such as to slightly warp the saddle, a preference is now being given to platinized gold. Fig. 905. Fig. 906. The metal plate for the saddle should be cut enough larger to allow for the turned-up rim and provide a slight surplus for trimming. The plate is swaged to the form of the die in the usual manner and the turned-up edge is trimmed evenly all around. The under side of the saddle is painted with rouge, and coin or 22-carat gold is flowed evenly into the groove of the turned-up edge and on the adjacent surface of the saddle, to reinforce the saddle and permit a rounded form to be given the edge later on. When platinum is used for the saddle, a film of pure gold should first be flowed over its surface before the coin or 22-carat gold is applied. The surface of the metal is smoothed with a car- borundum wheel and the edge rounded, as shown in section in Fig. 906. REMOVABLE SADDLE BRIDGE-WORK 431 The saddle is next cleaned in acid and again swaged, to correct any- warping occasioned by the gold that was flowed over its surface. When a cast saddle is used, a correspondingly shaped ridge of wax is placed around the margins of the wax model to secure an oval edge. In both swaged and cast saddles, the metal should be extended around and sHghtly up on the sides of the abutments approximal to the saddle to aid in retaining it in correct position on the ridge when fitted in the mouth and to facilitate uniting it with solder to the abutments. f 1" Fig. 907. When the saddle is swaged, it is fitted in the mouth and note is taken whether the flanges of the metal extending up on the abutments press on them in such manner as to interfere in the slightest degree with the saddle freely taking its position on the ridge. The edge of the saddle when fitted against the molar crown should extend from the mesial side slightly around on the buccal and lingual sides, as indicated at A and B, Fig. 907, in all about one-third the cir- cumference of the cervix, and in the case of the cuspid, from the labio- distal edge of the partial collar, as indicated at D, Fig. 908, and well around on the lingual side, to the point marked E. Fig. 909 shows the fitted saddle in position. Fig. 909. In all forms of removable saddle or plate bridge-work, when the crowns and attachments are in position in the mouth, the plate constitut- ing the saddle should not merely rest on but should press on the inter- vening alveolar border, to better afford support. Such construction is obtained by applying a suitable amount of pressure on the saddle with the abutment crowns in the mouth and taking an impression. In taking the impression in the case shown in Fig. 909, pressure is exerted on the saddle with the finger, and plaster applied on and around the abutments, saddle and adjacent parts. The finger is held steadily until the plaster sets (Fig. 910). 432 CROWN-, BRIDGE-, AND PORCELAIN-WORK Another method is to exert pressure on the saddle with an instru- ment, and apply the plaster in an impression tray with an opening in Fig. 910. the bottom to accommodate the instrument, as shown in Fig. 911. A little compound previously melted on the center of the surface of the saddle will prevent the point of the instrument from slipping (Fig. 912). Pig. 911. The model made will show the abutments and saddle in position as in the mouth. The ends of the bridge are next waxed to the outer crowns. To pre- vent the slightest displacement in removal or investing, a piece of iron Pig. 912. wire, about gage No. 15, is bent to rest on the surface of the saddle with the ends extended on the lingual and occlusal surface of the outer or REMOVABLE SADDLE BRIDGE-WORK 433 removable section of the molars and cuspid crowns, as shown in Fig. 913. The wire is waxed in position to the saddle and to the removable section of the crowns only, with hard adhesive wax. The saddle and crowns are removed from the model and the inner caps are removed from the outer crowns. When the crowns waxed in position with wax cement cannot be removed without displacement, plaster should be applied. This is often necessary when a model is made with- out provision for the removal of the inner caps from the model. The outer crowns with the saddle are invested. The investment should extend up over the sides of the saddle to retain it in position for the Fig. 913. soldering. If a replaceable porcelain facing or detached-post crown has been used, it is removed from the outer cap and the vacancy filled with additional investing material. The invested case will then appear as illustrated in Fig. 914. The soldering is preferably done with 21- carat solder. The solder should be first drawn into the seams and the parts then united by the addition of sufficient solder. After it is cooled and cleaned in acid, it is adjusted on the model with the inner caps in place. If any slight warping has occurred through con- PiG. 914. traction of the solder, it can generally be remedied by holding the crowns firmly in position on the model and then pressing on the saddle. If the contraction is considerable, the end at which it occurred must be detached from the cap, the warping corrected and the saddle and caps reinvested, and the warped end again soldered. Contraction can usually be controlled by investing so as to expose and solder only one end of a saddle at the time, readjusting on the model and then again investing and soldering the other end. 28 434 CROWN-, BRIDGE-, AND PORCELAIN-WORK The Articulation. — An articulation is next taken, preferably with plaster, for accuracy. The plaster should be applied so as to include one or two of the adjoining teeth, as a new model must also be run, for the reason that the plaster articulation will seldom allow the bridge to fit on the model previously used. The plaster is mixed moderately thick and placed over the saddle, also the abutment crowns and one or two of the adjoining teeth, and the patient directed to occlude the teeth. It is well to carefully ex- amine and see that the teeth have been properly occluded. When the impression is removed, the model and articulation are made in the usual manner. The Bridge Teeth. — In removable all-gold saddle bridge- work, detached-post crowns or English tube teeth are most commonly used on the saddle, as they are light in weight, replaceable in case of fracture, and more artistic in appearance than porcelain facings with gold back- ings. They are set in gold sockets soldered to the saddle. Pig. 915. Fig. 916. Fig. 917. The porcelain crowns selected are ground to articulate and their bases to conform to the shape of the saddle, leaving sufficient interven- ing space for the gold bases or sockets. They are then beveled around the edge of the cervical section, as shown in Fig. 915, to make room for the rim of the gold base. The gold bases are formed by casting, or by swaging pure gold gage No. 35 or 36 (see Part III, Chapter XIV) . The rim of each socket should be extended up on the porcelain suffi- ciently to allow for soldering and finishing. In the formation of cast bases for porcelain teeth, an allowance should be made for the shrinkage of the metal. To this end the bases should be varnished with collodion and vaselined as described in Part III, Chapter XIV, or a piece of tin foil, .005 to .009 of an inch in thickness should first be adapted or swaged over the base of the porcelain tooth. The thickness of the foil should be increased in proportion to the size of the base. The surface of the foil is lubricated to permit easy re- moval of the wax model. Wax models of the bases are best made singly, formed with a thin layer of wax extending down on the sides of the saddle, to aid later in contouring its surface when soldered, as shown at E, E in Fig. 916, which also shows the sprue wire inserted. REMOVABLE SADDLE BRIDGE-WORK 435 The post or pins are soldered in cast or swaged bases with coin gold. The teeth are adjusted in the bases and fitted to position on the saddle. This is more easily done with cast than with swaged bases, as they fit the form of the surface of the saddle. When the teeth and bases have been fitted on the saddle, th teeth are removed from the bases and each base is held in position on the saddle with wax and invested. Fig. 917 shows the case invested, leaving the lingual surface of the saddle and base exposed. The inside of the base into which the crowns fit are coated with rouge or antiflux be- fore investment to prevent invasion of the solder and interference with the fit of the porcelain. In the operation of soldering, the bases of the crowns are first united to the saddle by flowing under them 20-carat gold solder from one side to the other. This is- assisted by the applica- ' tion of the large flame under the investment. Sufficient solder is then added by degrees to fill in depressions between the bases and the rounded Fig. 91 Pig. 919. edge of the saddle so as to even its surface and admit of proper finish. To accomplish this at the buccal side, it is frequently necessary to again invest the bridge and apply solder at that part. The teeth are then cemented with oxyphosphate in their bases and the edge of the gold burnished closely against the porcelain. When the cement has thoroughly set, all parts of the metal are finished. Any interstices that may exist between the porcelain and the gold should be filled with foil or Corona gold so as to effect continuity of structure. Fig. 918 illustrates the finished removable bridge. Fig. 919 shows the same method of investing the gold base of a cuspid detached-post crown to solder it to the floor of the outer cap when used as an abutment. A small cast saddle may be made to include in one casting bases for the artificial teeth by forming them on the wax model of the saddle. Saddles could be advantageously applied to the typical case, Fig. 892, under the teeth on the right and left sides, and under the anterior teeth. But it could not be as advantageously done in the latter case. 436 CROWN-, BRIDGE-, AND PORCELAIN-WORK as the base of each of these teeth can be made to rest and slightly press directly against the tissues, which makes an agreeable form for the patient. Fig. 920 illustrates the case with saddles under the side teeth. In taking an impression in a case with saddles on both sides of the mouth, pressure must be applied equally to both saddles at the time Fig. 920. the impression is taken. To accomplish this, first take an impression in the compound with the saddles and crowns in position, chill and re- move. Take sadidles and crowns from the impression and replace them in the mouth. Trim the compound so that it will rest only against the saddles when inserted, as shown in section for one side in Fig. 921. The impression tray is then filled with plaster and brought to position, Fig 921. with the exertion of sufficient force on the tray to cause the compound to press the saddles firmly against the alveolar ridge. Another method of producing pressure on a saddle when taking an impression, is to place small wooden posts between the surfaces of the occluding teeth and the saddle, of sufficient length to permit the introduc- tion of the tray. The patient is instructed to compress the tissues under the saddle with the occluding teeth during the setting of the REMOVABLE SADDLE R RIDGE-WORK 437 plaster. An impression tray with slots on both sides that will ac- commodate the posts must be used.^ Construction of Porcelain-Faced Solid Gold Dummies for Saddles. — Short bicuspids and molars of this form may be constructed as follows: The porcelain facing is ground to position on the saddle and a plaster matrix is made against the labial aspect, to permit the facing to be removed and replaced in position. A wax model of the required form of the remainder of the dummy, is made in accordance with the articu- lation, as shown in section, Fig. 922. The porcelain facing is then removed, carbon points inserted in the pin holes and a cast of the wax section made of pure or slightly alloyed gold, the same as in the case of a "Cast Box Backing," as described on pages 300 and 418. The porcelain facing is next fitted in the cast section, the dummy adjusted, the gold section waxed in position on the saddle, and the porcelain facing removed. The saddle is invested, and the base of the gold sec- tion of the dummy soldered to the saddle on both sides, and the depres- sion between it and the rounded edge of the saddle leveled with 21- PiG. 922. Fig. 923. carat solder. Fig. 923 shows the case ready to receive the porcelain facings, which are next cemented in position. Any interstices are filled with foil or Corona gold and the surface of the gold smoothed and polished. Solid Gold Tooth Dtmimies. — In a case requiring very short gold dummy teeth without porcelain facings, a wax model of each tooth is made and cast. The gold tooth is then fitted on the saddle as in the previous case, invested and soldered to it, on buccal and lingual sides. The weight of all forms of cast solid gold dummies, either with or without porcelain facings may be lessened by the removal of a portion of the interior of the wax model with a wax absorber (see Figs. 457 and 458). Vulcanite Attachment. — In saddle and plate bridge-work the arti- ficial teeth — dummies — can be attached to the saddle or plate with vulcanite, the use of which considerably lessens the labor of construc- tion, and for upper cases has the advantage of lightness as compared with gold. Ordinary porcelain teeth for vulcanite, or Diatoric teeth, are mostly used. Two or three loops of wire or a narrow strip of plate 1 Dr. Hart J. Goslee's method. 438 CROWN-, BRIDGE , AND PORCELAIN-WORK should be soldered on the saddle as an attachment (Fig. 924). When a strip of plate or a small wire is used, it is best attached before the final swaging of the saddle, to avoid warping that might occur in a subsequent soldering. Rouge or mica placed under the strip or wire between the points to be soldered, will prevent the solder from uniting the strip or wire to the saddle and allow it to be raised up subsequently when the rubber is applied; as shown in Fig. 925. When a vulcanite attachment is used, the work should be so con- ducted as to secure not only an attachment, but an adhesion of the vulcanite to the gold. This can be effected by cleaning the surface of the metal that comes in contact with the rubber, then going over it lightly with a small scraper. The packing of the rubber should be done entirely by dry heat; water, steam, oil or grease being excluded from direct contact with the surface of the gold or rubber. During vulcani- zation the flask should be placed on a stand above the water in the vulcanizer. When so conducted the result will amply repay for any extra labor the method involves. Fig. 924. Fig. 925. Extension Saddle Bridge This form, which in principle is a cantilever, is employed to replace l^icuspids and molars by the use of only an anterior abutment. The abutment should properly consist of at least two teeth to resist the leverage that will be exerted in occlusion. Fig. 926 illustrates a removable saddle bridge to replace two lower molars. The abutment consists of a first bicuspid porcelain-faced tube and split-post collar crown, united to a second bicuspid all-gold tele- scope, tube and split-post crown. Fig. 927 shows the lingual aspect of an extension bridge retained by a split bar in both of the bicuspids, and the method by which the bar to the first bicuspid is attached to the second bicuspid bar by a flange extended around the lingual side of the latter resting on a ridge. Fig. 928 shows the bridge from the buccal side in position. An Adjustable Saddle. — ^The gradual settling of the saddle and the consequent stress exerted on the abutment in occlusion is an objection to extension bridge-work. Injury from this cause may be remedied by the use of a readjustable saddle. To effect such a form of construc- tion, the artificial extension teeth are first united with gold to the abut- REMOVABLE SADDLE BRIDGE-WORK 439 ment independent of the saddle, and then attached to the saddle with gutta-percha. This permits the saddle to be easily readjusted to the alveolar ridge without changing the occlusion of the teeth. Fig. 926. To readjust the saddle, heat and remove it and slightly increase the quantity of gutta-percha. The bridge and saddle are then heated sufficiently to soften the gutta-percha, the bridge is adjusted to posi- tion in the mouth by first using pressure with the fingers and next by the Pig. 927. patient occluding the teeth. Remove and reheat bridge and gutta- percha and readjust until the bridge assumes its proper position. Fig. 929 outlines in section the plan of the formation of a porcelain tooth with a gold base for such a bridge and the pin that secures it to the saddle. Fig. 930 is another form consisting of a hollow gold tooth with a loop of wire instead of a pin. This latter form is the best to use when short teeth are required. 440 CROWN-, BRIDGE-, AND PORCELAIN WORK Vulcanite Extension Saddle. — Fig. 931 outlines a bridge of this style. The dummy teeth are formed of hollow reinforced gold crowns. The gold dummies are placed in occlusion, leaving a space of about one-eighth inch between the cervices and the alveolar ridge, and in this position are securely soldered to each other and to the abutment. An impression is next taken of the alveolar ridge in correct relationship Fig. 929. Pig. 930. to the bridge with impression compound. This is done by placing a suitable quantity of the compound over the necks and in the hollows of the gold dummies, then adjusting and pressing the bridge to position in the mouth. The bridge is removed, a plaster model made, and a vulcanite saddle formed. The base of such a saddle can be renewed at any time in exact conformation with the alveolar ridge, by removing Fig. 931. the bridge and slightly indenting the surface of the vulcanite over the alveolar ridge, placing impression compound or wax upon it, taking an impression of the ridge, and substituting vulcanite for the compound or wax. This is a form of saddle very suitable to apply when teeth have been recently extracted and absorption of the alveolar process is still taking place. CHAPTER V REMOVABLE PLATE BRIDGE-WORK MERITS— LIMITATIONS — CLASPS WITH LUGS — ^PREPARATION FOR CLASP ATTACHMENT — SHAPING CLASPS — COLLAR METHOD — CAST CLASPS — CLASPS AND LUGS — FORMATION OF INLAY LUGS — LUGS FOR NATURAL CROWNS — CONSTRUCTION OF A PLATE BRIDGE — UNITING ATTACHMENTS TO PLATE — TO CORRECT WARPING — A FREQUENT CAUSE OF WARPING. Removable Plate Bridge-work is practically plate-work sustained by clasps or collars with anchorage lugs, or some form of attachment that fastens or anchors on the abutment teeth, crowns or inlays. The in- sertion of dentures of this form of construction and which of late is growing in favor, is not of recent conception, having been described in this treatise in 1888 and by Dr. W. G. A. Bonwill in 1893. Fig. 932. Fig. 932 shows a plate bridge to replace two superior bicuspids sup- ported by clasps on the cuspid and molar with lugs resting on shoulders at the points A A, Fig. 933. In this case the clasps after having been shaped and soldered to the plate were heated and their inner surface veneered with wax. When the veneer had cooled, a layer of soft wax was placed over the approximal and lingual surfaces of the veneer and the plate and clasps pressed to position in the mouth and removed. Platinum foil >^ooo to 3-f 000 was annealed and evenly placed over that part of the surface of the wax that had covered the approximal and lingual surfaces and also the edge of the occlusal surface of the molar. 441 442 CROWN-, BRIDGE-, AND PORCELAIN-WORK The plate was inserted, pressed firmly against the tissues and the edge of the wax pressed with the finger against the foil. The plate was removed, invested and solder flowed between the clasps and foil. Surplus foil and gold were removed, leaving only enough at the edges Fig. 933. of the clasps on the edge of the occlusal surface of the molar and lingual surface of the cuspid for support. Fig. 934 shows a plate bridge to replace a left superior lateral. Figs. 935, 936 and 937 illustrate and explain the form of the construc- tion.^ Figs. 938 and 939 show Dr. Bonwill's method of replacing a bicuspid and a molar. ^ Fig. 934- Merits. — In artificial restorative methods by removable plate bridge- work, mutilation of the supporting teeth or removal of pulps is seldom necessitated. For these reasons replacement of absent teeth may often be effected, which would not be considered advisable by other methods or be sanctioned by the patient. ^ The cases shown in Figs. 932 to 937 were described in the first edition of this treatise in 1888. 2 Cases described by Dr. W. G. A. Bonwill in the International Dental Journal in 1893. REMOVABLE PLATE BRIDGE-WORK 443 Pig. 935. — Shows in section, central incisor root with tube and split post in canal. A B Fig. 936. — A, Cap and tube for central; B, half-collar central crown with split post; C, clasp for cuspid. Fig. 937. — Shows cuspid with gold filling. A, Notch for lug. A Pig. 938. Fig. 939. 444 CROWN-, BRIDGE-, AND PORCELAIN-WORK Limitations. — The use of removable bridge plates is best confined to cases of replacement of posterior teeth where the alveolar ridge is ab- sorbed: also where the character of the abutment teeth for stability, health or other conditions suggests the method. It is a method seldom used for incisors or cuspids except when such teeth can be placed on the same plate that is being used to replace posterior ones. Clasps with Lugs. — In removable plate bridge-work, clasps with lugs are used on either natural or artificial crowns. In natural teeth the lug is usually set in an inlay or filling, and in artificial crowns in a socket made in the crown. A lug aids in retaining a clasp in position to better resist lateral strain, enables it to bear pressure exerted on the denture in occlusion, prevents impingement on the gingival margin, and when applied to a natural crown lessens liability to abrasion of the enamel by steadying the clasp. The use of this form of clasp is increas- ing in favor, as its application often avoids the alternative of a capping or crowning operation. The clasps are made of iridio-platinum gold or clasp gold. The portion of the clasp requiring resiliency should be left entirely free and not reinforced with solder. In the formation and use of clasps, the following points are to be considered: 1. Flat plate clasps are most suitable when the natural crowns are nearly straight-sided and for clasping similarly shaped artificial crowns. Half-round wire clasps are best applied to natural crowns with contour and to short crowns. 2. A clasp that encircles four angles of a crown, obtains a better hold than if it encircles only three, and a clasp to reliably grasp must encircle at least three angles. When less in length a clasp will only press against the tooth or crown unless it is retained in position by a lug. 3. For strength the widest or heaviest part of the clasp should be nearest its union with the denture. 4. The strength and rigidity of a clasp lessens as it extends from where it is united with the denture. Consequently a clasp should be uniform in width and thickness, and if it tapers, should do so only slightly towards the ends or points. 5. A clasp should extend over the surface of the sides of a natural or artificial crown, not nearer than one-sixteenth to one-eighth of an inch from the gingival margin, to avoid irritation of that membrane. The edge of a clasp must entirely clear the occlusion. Preparation for Clasp Attachment. — Clasps should be placed and shaped to move on and off as nearly as possible parallel with each other and any other attachments present. The adaptation of a clasp as REMOVABLE PLATE BRIDGE-WORK 445 close as is practical to the contour of a natural tooth when adjusted is all that is expected or required. Adjustment and adaptation to some teeth is much facilitated by slightly trimming and then polishing one or more projecting points of the enamel. This is especially the case when teeth tip out of line. A plaster study-model of the case will guide this part of the work. In the case of artificial crowns, fiat plate clasps should be used, shaped as straight and close as possible to the sides. As a pattern for a plate clasp, shape on the model or die of the tooth a piece of thin annealed sheet copper or tin a shade wider and longer than required. Use gold clasp plate not less than gage No. 24 and half-round wire, gages Nos. 12, 13, or 14; the larger the tooth, the greater the thickness of wire, so as to proportionately insure strength and permit any necessary trimming. The labial section of a plate clasp on an inferior cuspid ought to be made wide, and on a superior cuspid as wide as it properly can be, without causing too much exposure of the metal. Fig. 941 Fig. 942. Fig. 943. Shaping Clasps.— A clasp after being bent with suitable pliers is most easily shaped to the form of a natural crown by the aid of a die. The best method is to take a sectional impression of the tooth and make an amalgam die. From the amalgam die take an impression in a tube with moldine and run a fusible metal die. Use the fusible die for the preliminary shaping and the amalgam for the final. In the case of a gold crown, fill the interior with fusible metal, and use the crown as a die. In the shaping and trimming of clasps, frequent transferring from the die to the model and annealing are necessary. In the construc- tion of the half-round wire clasp, it should be brought just over the curve of contour of the tooth so that it springs to position. Collar Method.— To accurately shape clasp gold plate to the curved form of many crowns is very difficult, owing to the rigidity and resili- ence of the alloy. The following method has lately been practiced by the author: Shape around the die of the tooth or crown, a wide band of thin copper and lap and solder the ends together, thus forming a collar, Fig. 940. Trim and shape the cervical and occlusal edges of this band to the form and width desired for the clasp, as shown in the case of a 446 CROWN-, BRIDGE-, AND PORCELAIN-WORK cuspid in Fig. 941, usually a difficult tooth to clasp. Cut the band midway between the intended separation of the ends. of the clasp, as marked in this case at S, Fig. 940. Open out the band and use it as a pattern to cut the clasp gold (Fig. 942). Anneal the gold clasp,- bend it in a circle and solder the ends together with a very small piece of solder. Slip the gold clasp band over the die of the tooth and by fre- quent bending, tapping with a riveting hammer and annealing, it can be accurately shaped. When shaped, cut the gold collar where the ends were joined, and trim the ends to the desired length, making it a clasp (Fig. 943)- Cast Clasps. — Cast clasps are used to some extent in preference to shaping plate or wire to the form of the tooth. A cast clasp will fit the contour of the crown more accurately but will lack the strength and resiliency of rolled or drawn metal. The lack of resiliency and the close fit of a cast clasp will not permit it to be adjusted on a crown with Fig. 944. Fig. 945. sharp points of contour. Its use must therefore be confined to artifi- cial crowns, or to natural crowns whose contour is or can be made favorable to its application. Molars and bicuspids require httle or no reduction of contour, while the form of cuspids usually necessitates considerable shaping. The cuspid illustrated at A in Fig. 944 will be used as a typical case. The distal side requires to be shaped to the form shown at B, and the surface of the enamel polished. A sectional impression is taken with impression compound, and a model made of inlay investing material. On this model a wax pattern of the clasp is formed, Fig. 945. This is best done by first veneering the surface of the model with melted wax, using a hot spatula, then shaping inlay wax over the veneer to the required form for the clasp and lug. A sprue wire is inserted in the heaviest part of the wax, and both wax pattern and the model invested in a casting flask and the clasp cast. The lug is cast with the clasp as a part of it. In the case of a cuspid or incisor, a small portion of the gold placed over the surface of the contour on the lingual side will act as a lug. Fig. 946 illustrates an inferior right REMOVABLE PLATE BRIDGE-WORK AAl second molar with a wax model of a clasp, and a sprue inserted ready to invest. Another method of cast clasp construction is; make an amalgam die of the prepared tooth, lubricate the surface and wipe off all surplus. Form on the die a wax model of the required clasp and lug, insert sprue, cover the surface of the wax with a thick coating of the investing ma- terial and when it has thoroughly set, remove, invest and cast. The wax clasp model is best formed by first adapting a layer of stiff wax to the surface of the die and finishing with a softer grade. Clasps and Lugs. — Cuspids are not so well suited for clasp and lug attachments as bicuspids and molars. When a lug is applied to a cuspid with a vital pulp, the gold to support the lug can usually be more reliably supported by a filling with undercuts, than in the form of a cemented inlay (Fig. 947). If the tooth is pulpless, a lug with a lock pin is the preferable form to apply with the clasp (Fig. 948). Pig. 947. Fig. 948. Fig. 949. An occlusal lug without the use of an inlay may be applied to a clasp to rest on the enamel of a tooth when no occluding tooth is present, as shown in Fig. 949. A piece of as heavy half-round clasp wire as the case will permit is best used to form the lug. The sides and end of the lug should be closely fitted and tapered off to the surface of the tooth. Formation of Inlay Lugs. — Inlay lugs are usually made by casting or by the use of a matrix. A wax model or matrix of the form of the lug is made in accordance with the occlusion. Applied to a flat clasp the lug is made to fit against the inner side of the clasp (Fig. 950). 44S CROWN-, BRIDGE-. AXD PORCELAIN -WORK For a half-round wire clasp, the lug is formed to extend over the wire clasp so that the lug can be securely united, as shown in Fig. 951. A cast lug is cast separately, then soldered to the clasp. In the use of a matrLx lug, the matrix is formed, the clasp adjusted, the matrix filled with wax and attached to the clasp. Clasp and matrix are re- moved, invested, and the matrix filled and attached to the clasp with hard solder, and the lug is trimmed to shape. A small lug to rest in a correspondingly small slot in a gold tilling should be made by the matrix method, using 3^2000 platinum foil for the matrix. Lugs for Natural Crowns. — Lugs to clasps that only rest on the teeth clasped are to be extended but a short distance on their surface (Fig. Fig. 950. Pig. 951. Fig. 952. Fig. 953. Pig. 954. Pig. 955. 949'). The slot for the lug in an inlay or filling should be given a slight retentive oval form, as sho-mi in Fig. 952. A lug in a gold cap crown is inserted in a slot or box (Fig. 953). It is made by removing the re- quired portion of the occlusal surface and approximal side of the crown before the cusps are reinforced, then inserting the box and soldering it in position from the inside, and at the same time reinforcing the cusps. (Fig. 607, Part IV, Chapter III). Another method, when a cast gold occlusal cusp-cap is used, is to solder a gold floor to the occlusal edge of the collar, and cast an occlusal cusp-cap with a slot (Fig. 954). and solder the cusp-cap to the floor. In case of a porcelain-faced gold bicuspid crown, the slot for the lug is made as follows: A vertical hole is first drilled in the finished REMOVABLE PLATE BRIDGE-WORK 449 crown to within a short distance of the floor of the root-cap, when two cuts are made with a fine saw on the side, the gold gradually removed, and the cavity shaped with small stones and burs. If exposure of the clasp on the buccal side is objectionable, form a narrower and deeper ^ Fig. 956. FxG. 957. slot, of retentive form, from the occlusal surface toward the floor, and extend the clasp only on the approximal and lingual sides. So placed, it will furnish a fairly reliable attachment (see Fig. 955, viewed from fe 0j] % ^ D Pig. 958. Fig. 959. the occlusal surface). The use of such a lug and clasp on a natural crown is not practicable, unless the tooth is pulpless, so as to admit of the insertion of a securely anchored inlay and a small pin in the lug. BCD E F Fig. 960. Fig. 956 illustrates a gold crown with an oval-shaped lug rest cavity, and a cast lug united to a flat gold clasp. Fig. 957 shows a gold porcelain-faced bicuspid crown, in which is cut a narrow deep cavity for the lug; to further elucidate the method 29 4 50 CROWN-, BRIDGE- AND PORCELAIN-WORK two friction lugs are also shown, one united to a flat, and the other to a half-round clasp. Fig. 958 is a bicuspid, A, with a cast inlay, B, wire clasp with lock- pin lug, C, and a die in which the inlay was made and the matrix for the lug swaged, D. Fig. 959 is an inlay in a molar. A, plain matrix, B, pin matrix, C, and parts assembled to form the lock-pin lug, D. Fig. 960 illustrates the construction of a lock pin in a central used as a supporting attachment ; A and B show the cavity prepared for the cast inlay with pin; C, compound impression with a steel pin embedded; D, same in flask ready to pack an amalgam die; E, die completed; F, matrix for lug and same adjusted in inlay. Construction of a Plate Bridge The plate used is made either by swaging or casting, preferably by swaging for large plates and by casting for small ones. The swaged plate is formed of 18- to 20-carat gold, gage No. 26, reinforced across the connecting sections. The plate is cut a trifle larger in size than is re- quired. The cross sections are reinforced by the addition of successive narrow layers of plate about gage 32 to 34 swaged one at a time, and united with the least possible quantity of solder. The swaged plate is fitted in the mouth, and to the abutment attachments. Uniting Attachments to Plate. — A small plate with two attachments may often be cemented with wax to them separately or together, pressure exerted on the plate, the wax chilled, plate and attachment or attachments removed, invested and united with solder. In this method it is preferable to first unite the most difiicult attachment to remove. The method generally practiced is to place each attachment in position, exert pressure on the plate., take a plaster impression and remove plate and attachments in position. Fill impression with investing material, remove plaster impression, add more investing material and solder attachments to plate. A Roach sectional impres- sion tray is useful in this part of the work, as pressure can be exerted on the plate by the flange of the tray in taking the impression. When clasp lug attachments are the form to be used, plate bridges can be constructed by forming the plate first, taking a plaster impres- sion with pressure on the plate, filling the impression of the teeth with amalgam and the remainder of the impression with plaster. Clasps with lugs are then made on the amalgam models of the abutment teeth, plate and clasps cemented together, removed and united to the plate. REMOVABLE PLATE BRIDGE-WORK 451 Pig. 961. Fig. 962. Fig. 963. 452 CROWN-, BRIDGE-, AND PORCELAIN-WORK Before investing attachments and plate see that the attachments touch or nearly touch the plate; if they do not, add an extension by separately investing and soldering. The plate and attachments are adjusted in the mouth, any inter- ference with the occlusion corrected, and a "bite" taken with plaster or compound. The case is then finished, using porcelain teeth at- PlG. 964. tached either with gold or vulcanite, as in saddle bridge-work. When the plate extends on both sides of the mouth, vulcanite is preferably used for lightness and to avoid risk of warping. Figs. 961 and 962 show the restoration of a lower molar with half- round wire and lug attachments. Figs. 963 and 964 show a removable extension plate bridge. It consists of a gold crown with porcelain facing on the right cuspid, all- REMOVABLE PLATE BRIDGE-WORK 453 gold crowns on the adjoining bicuspids, and a gold crown on the left bicuspid. The denture is made of a swaged plate with reinforced palatal bar and vulcanite attachment for the porcelain teeth. The lugs are oval-shaped and are connected by bars. ' The case illustrated in Fig. 965 shows a method of constructing a partial lower denture in which the stress on the retaining teeth is re- lieved by the use of elliptical springs to join the clasps and the plate. Fig. 965. The practical value of such a method is as yet problematical. The right and left sections of lower dentures can be connected by a narrow reinforced strip of plate or a bar. Made in either form, a slight space should be left between the strip or bar and the surface of the model, so that no pressure shall be brought to bear upon the tissue under it. This is definitely and uniformly accomplished by placing on this part of the plaster model successive layers of pattern tin to form a thickness of Pig. 966. about gage No. 22 to 24 before making the mold for casting the die (Fig. 966). When a connecting strip of the plate is used instead of a bar in a lower case, such as is described, it should be reinforced by at least three additional strips of clasp gold, gages Nos. 32 to 34, each strip being cut a little narrower than the preceding one as they are swaged (Fig. 967). Each strip should first be caught at the ends with 1 Case of Dr. R. F. Getz. 454 CROWN', BRIDGE-, AND PORCELAIN-WORK an atom of hard solder to retain it in position when swaged. Only enough solder to barely unite the several strips should be used. The united strips are then trimmed to the required width, the edges rounded Pig. 967. Fig. 968. Fig. 969. Fig. 970. and the whole polished and given a final swage. A very rigid slightly oval-shaped connecting link is thus formed and one that will offer the least possible. obstruction to the tongue, as shown in Fig. 968. REMOVABLE PLATE BRIDGE-WORK 455 Figs, 969 and 970 show a lower removable plate bridge with clasp and lug attachments that was made to replace a cemented bridge. The method of the construction of the cemented bridge kept the mouth in a septic condition, as it could not be properly cleaned by the patient, by whom the denture with which it was replaced has been satisfactorily worn for several years. Pressure of the narrow reinforced strip con- necting the right and left sides of the plate was obtained as described in the preceding case."^ To Correct Warping. — In removable plate bridge-work, if warping occurs in the soldering of attachments on opposite sides of the mouth, it should be corrected before the artificial teeth are attached. This was done in the case illustrated in Fig. 969, as follows: An impression of the Fig. 971. surface of the zinc die on which the plate was swaged was taken in plaster. On its removal from the die, the plaster around the locality of the clasps and attachments was trimmed so that the plaster mold would rest on the surface of the plate without touching them, as shown in Fig. 971. This impression mold was then cast in lead and used as a die to swage the plate against the zinc die and remedy the warping. Should any part of a die under the attachments interfere with the ad- justment of the plate on the die, remove the metal of the die at those points with a file or coarse carborundum wheel. A frequent cause of warping is immersion in water of an invested gold plate immediately after a soldering operation to gain time. The water absorbed is instantly converted into steam. The steam by press- ing against the surface of the plate tends to distort it. ' Case of the author's. CHAPTER VI GENERAL APPLICATION OF REMOVABLE BRIDGE-WORK CENTRALS, LATERALS AND CUSPIDS — ^BICUSPIDS AND MOLARS — CON- NECTING BARS TO SADDLES — CAST SADDLES AND PLATES The form and construction of removable bridge-work is further explained in its application to the following typical cases. Centrals, Laterals and Cuspids. — Fig. 972 shows one of the methods of constructing a removable central. The pulp is removed from the adjoining central and an inlay tube and split post inserted to support the dummy central. A lug resting on the lateral is used to assist the Fig. 972. Fig. 973. abutment in resisting pressure in occlusion on the dummy central. Fig. 973 shows the bridge in position. Fig. 974 shows another method in which a removable half-collar crown with a tube and split post is used for an abutment. The re- mainder of the construction is the same as in the preceding method. A filling or inlay for the lug to rest on is not always indicated. If injury results from the presence of the lug, a filling or inlay can at any time be easily inserted, as the denture is removable. In cases of short teeth or forcible and direct occlusion, the restoration of a single central may demand the lateral in addition to the central as a retaining abutment, as shown in Fig. 975, in which inlays with tube and split-post attachments are used. 456 GENERAL APPLICATION OF REMOVABLE BRIDGE-WORK 457 The restoration of a lateral is best effected by using the cuspid as a retaining abutment, as shown in Fig. 976. The restoration of two centrals generally requires the support of the cuspids as retaining abutments. Bars are extended from the cus- pids to the artificial centrals over the lingual side of the laterals, resting either on the surface or in a groove in an inlay. Fig. 974. Fig. 975- A cuspid dummy, to resist the force of occlusion, requires two re- taining abutments, the bicuspid and lateral. Bicuspids and Molars. — A first bicuspid is best replaced by a retaining abutment on the second bicuspid and a lug on the cuspid, as shown in Fig. 977, and in position in Fig. 978. A second bicuspid Pig. 976. Pig. 977. demands a retentive abutment on the first molar and a supporting abutment additionally on the first bicuspid. Fig. 979 shows a bridge of the superior right first and second bi- cuspids supported by a tube and split-post crown on the cuspid and a split bar in the molar gold crown. The replacement of a lower second bicuspid and a molar with a 458 CROWN-, BRIDGE-, AND PORCELAIN-WORK saddle bridge is shown in Fig. 980. A porcelain-faced gold crown with a split post was placed on the first bicuspid as the anterior abutment. As the second molar, forming the posterior abutment, tipped forward, a gold crown with a split bar was preferably used. Pig. 978 Fig. 981 shows the typical case already described (Fig. 892), re- tained with tube and split-post crowns on the cuspids, a split bar in an inlay in the left molar and a split bar in an all-gold crown on the right molar. Fig. 979. Fig. 982 shows a case replacing the right superior first and second molars and the left second bicuspid and first molar, by the split-bar method and saddles. On the right side the extension saddle is con- PlG. 980. nected by a bar to the saddle on the left side to counteract leverage and for additional support. Fig. 983 shows the denture in position. To obtain alveolar support for the saddle a small space can be left GENERAL APPLICATION OF REMOVABLE BRIDGE-WORK 459 Fig. 982. 460 CROWN-, BRIDGE-, AND PORCELAIN-WORK under each of the spht bars in the boxes. This space is evenly propor- tioned by placing in the bottom of each box, a piece of pure gold, gage 22, when the bars are adjusted to the saddles, and removing the pieces of gold after the bars are united to the saddles. In this manner saddles are permitted to settle uniformly. In the case of an extension saddle it prevents the saddle from settling at only the posterior end and thereby straining the abutments. This method of constructing superior dentures of right and left saddles connected by a bar is not regarded with favor by the author, who considers a gold plate covering a portion of the palate supported by clasps with lugs preferable. The latter form of denture lessens the stress on the abutment teeth or crowns and is not so complicated in construction. If the anterior portion of such a plate is removed, so as Fig. 983. to leave a space between the edge and the anterior teeth of at least one-eighth inch, and the posterior edge is extended back a moderate distance, the additional portion of the palate covered compared to that covered by a bar will not make a very material difference to the patient. What is here stated respecting superior right and left saddles connected by a bar is also applied to a single right or left saddle from which a bar is extended to the other side of the arch and attached to one or two crowns to counteract leverage. When a saddle on one side is extended from the cuspid to the third molar the necessity for the last mentioned application of a bar is more indicated. Connecting Bars to Saddles. — Such bars are generally made by burnishing a strip of pure gold, one-fourth inch or less wide, then bend- ing to and soldering on its surface with hard solder, two, three or more pieces of the same length of gages 18 to 20 gold clasp wire. The GENERAL APPLICATION OF REMaVABLE BRIDGE-WORK 461 gage of the wire and the number of pieces are to be regulated by the length and width of the bar. The following method minimizes warping and insures a reliable bar: Cut a strip of pure or platinized gold, gage 30, of the required length, one-fourth inch wide, and adapt it to the intervening space between the saddles, as shown at A, Fig. 984. Cover the outer surface B Pig. 984. of the gold with wax, leaving the extreme ends exposed. Invest and remove the wax with boiling water and trim the investment so as to expose its surface except at the extreme ends. Place pieces of gold clasp wire of about gage 20, cut one-fourth of an inch in length, evenly over its surface, in three consecutive rows, with one-sixteenth inch interstices between the ends, as shown at B. When ready to solder, Fig. 985. first place and fuse only a small quantity of hard solder in the center and then gradually diffuse it to each side until all the pieces of wire are caught. Next, by degrees add more solder and shape the bar to the desired form. The bar is then trimmed and polished, when it is ready to be adjusted and united to the saddles. Cast Saddles and Plates. — The formation by the casting method of saddle and; plate bridge dentures for both sides of the mouth connected 462 CROWN; BRIDGE-, AND PORCELAIN-WORK by bars is considerably practiced. In a case such as is shown in Fig. 968, and similar ones, the wax model having been formed, sprues are placed in the manner illustrated in Fig. 985. The wax pattern is chilled, removed from the model and invested, using a large flask and cast. A slight space should be provided for under the wax bar to allow for the settling of the denture when in use. The preferable method of constructing dentures of the form shown in Fig. 969 is to first cast each saddle separately. Position each attachment and saddle separately, and take an impression with pres- sure on the saddle, remove, invest and solder attachment to saddle. Adjust both saddles, take an impression in plaster with pressure on the saddles, remove, make model and unite the saddles with a con- necting bar by soldering. (See Part I, Chapter VII.) The formation of saddle and plate bridges with the clasps and lugs or other forms of attachments all in one casting is not approved by the author, for the reason that the denture will rest proportionately more on the abutments than the alveolar ridge. The practice of scraping the model of the ridge to obtain the necessary pressure is also criticized, as uniform removal of the surface of the model is doubtful. CHAPTER VII MANUTACTURED ATTACHMENTS THE ROACH ATTACHMENT — METHOD OE APPLICATION — CONSTRUCTION OF BRIDGE — THE MORGAN ATTACHMENT — REMOVABLE BAR-BRIDGE ATTACHMENTS — THE GILMORE ATTACHMENT — SPLIT-BAR BRIDGE ATTACHMENT — THE CHAYES METHOD ANT) ATTACHMENTS — THE PARALLELOMETER — THE PARALLELODRILL — THE ATTACHMENTS — THE BUCCO-LINGUAL ATTACHMENT — THE UPRIGHT ATTACHMENT — THE DISTAL EXTENSION ATTACHMENT — CONSTRUCTION — SPLIT- POST AND BAR ATTACHMENT To simplify the construction of removable bridge-dentures, es- pecially of the saddle or plate type, several styles of ready-made attach- ments have been introduced and are manufactured. A description of the most used of such attachments will be here given, but only a limited statement respecting their application, as each manufacturer pubhshes directions that can be procured on application, giving such information in extensive detail. The Roach Attachment^ This is one of the simplest of the manufactured attachments. It is on the ball-and-socket principle, which greatly reduces leverage or A BCD. Pig. 986. tipping stress on the supporting teeth and obviates accurate parallehng. In use, while the denture is more or less retained, some degree of mo- bility is allowed. It may be classed as either a retaining or supporting abutment. 1 Consolidated Dental Manufacturing Co., agents for the Roach Attachment. 463 464 CROWN-, BRIDGE-, AND FORC EL A IN-WORK The attachment consists of two parts (Fig. 986), a round slotted tube of gold clasp metal (A) , into which fits a solid ball with a stem for attachment to the denture (B). A shoulder set on the stem, close to the socket where the stem enters the slot, furnishes strength and acts as a finishing mark. The form of the socket permits settling of the denture, and tightening of the sides of the socket on the ball increases retention. Method of Application. — Either the ball or the socket may be attached to an abutment crown, but the ball portion is the one usually applied, and is the proper one to connect to an inlay abutment. The abutment crown is adjusted in the mouth and the place for the ball or socket marked on it. The spot should be about one-sixteenth of an inch from the gum and towards the lingual side, sufficient to give room for proper adjustment of an adjoining porcelain facing or artificial tooth. The locating of attachments is simplified in many cases by taking an impression, which removes the crown or inlay in position. A model is then made and the attachment located on it. Cut off the stem to the shoulder. Guided by the mark, adjust to position on the side of the crown, invest and connect with solder. For strength, a more reliable method is to adjust and wax to the end of the stem, a small circular piece of platinum or plate as shown at C in Fig. 986. Invest and attach with hard solder, then adjust and wax the disk to the side of the crown, as shown at D, invest and solder in position. The same method of locating and soldering the stem of the ball may be followed with an inlay, or if the case suggests it, the stem may be shortened and placed in the wax model of the inlay and united in the casting. In cases of porcelain-faced gold crowns, when the cap is con- structed, the attachment may be adjusted and connected to it with hard solder. Construction of Bridge. — The impression is taken, pressure being exerted on the saddle or plate in the usual manner with abutments in position, and models are made. The sockets are placed over the balls and soldered to the saddle or plate, and the reverse when the socket instead of the ball is attached to the abutment. The socket when attached should be left exposed on one or both sides, so that it may be expanded or contracted. During the construction of the work, it is best to slightly expand the socket to facilitate removal. To tighten it, use pliers and insert a round piece of wood about the gage of the ball to avoid over-contraction. The best method of uniting the socket to the saddle, is by the use MAN UFA CTURED A TTA CHMENTS 465 of what is termed a contact bar. A piece of gold clasp wire, gage No. 15, from one-half to three-quarters of an inch long, is slightly flattened on the side that is to go next to the socket (A, Fig. 987), and bent at a right angle so that it will rest with one arm against the side of the abut- ment crown and the other on the surface of the saddle. The socket is next fitted over the ball, the side of the bar is brought in contact with the side of the socket as shown at B, and the ball and socket only ce- FlG. 987. mented together with wax. The bar and socket are removed, invested and strongly united with hard solder. They are then adjusted in position to ball and saddle, the end of the bar attached to the saddle, with hard wax, bar and saddle removed, invested and securely united with solder. When in use the end of the contact bar resting on the side of the abutment crown prevents raising of the end of the saddle, but does not interfere with its compression in mastication. Pig. 988. Fig. 989. Fig. 988 shows the Roach attachment on a lower denture with a connecting bar and cuspid and bicuspid as abutments. Fig. 989 illustrates another style of Roach attachment. In this form the ball section is made oval and fits into a box from which extends the flange A, to rest on the abutment and act as a contact bar. The flange B is to connect the attachment to the denture. 466 CROWN-, BRIDGE-, AND PORCELAIN-WORK The Morgan Attachment^ The Morgan attachment consists of a flattened loop of clasp metal called the keeper (Fig. 990) into which fits a two-winged piece called the anchor (Fig. 991). The keeper is soldered to the abutment, and the shank and cover of the keeper to the denture. Fig. 990. Fig. 991. Fig. 992 Fig. 993. Fig. 994. The attachments must move parallel. A paralleling appHance called a jig (Fig. 992) is used to parallel and also to hold them in posi- tion while being soldered to the abutments. When the denture is constructed it is properly secured in position by tightening the attach- ments sufficiently to increase friction of their parts. Fig. 993 shows ^ The Morgan Specialty Co., Manufacturers. MA NUFACTURED A TTA CIIMENTS 467 the Morgan attachment on the side of a gold collar crown with porcelain facing, and Figs. 994 and 995 its application to bridges. Fit.. 995- Removable Ear -Bridge Attachments In removable bar bridge attachments, the bar is permanently attached to the abutments and spans the space between them inde- FiG. 996. Fig. 997. Fig. 958. pendent of the bridge. The main removable portion of the denture consists of either a bridge or a plate bridge with a slot or countersunk base that contains one or more clamps that fit over and lock to the bar. This form of construction as originally introduced is illustrated in Figs. 996 and 997, which show an upper denture of this style as made 468 CROWN-, BRIDGE:, AND PORCELAIN-WORK by the late Dr. J. Gardiner Morey in 1887, originator of the method. Fig. 998 illustrates the construction. A and B, Fig. 999, are side and front views of a dummy tooth with the clamp attachment; C shows the bar anchored in a bicuspid and molar. Fig. 1000 shows the denture in position. The Gilmore Attachments. ^ — These are manufactured attachments for this style of work. They consist of an assortment of clamps made Fig. 999. Fig. iooo. Fig iooi. Fig. 1002. Fig. 1003. Pig. 1004. of clasp gold to fit over bars, Fig. looi. They are made of platinized gold for attachment to gold dentures by soldering and with the addition of flanges for their retention when used with vulcanite. The abutment roots are capped with a plate and root post and the teeth are capped with gold crowns. The bar to support the clamps is soldered to root-caps and gold crowns, as seen in Fig. 1002. The ends of a bar may be extended beyond the abutment root-caps to afford additional space on the bar for more attachments, as seen in the case of a lower denture in Figs. 1003 and 1004. ^ The Detroit Dental Manufacturing Co., Detroit, Mich., Manufacturers. MANUFACTURED A TTA CIIMENTS Split-bar Bridge Attachment^ 469 This consists of a manufactured iridio-platinum split bar with a V- shaped flange, as shown in Fig. 1005, that fits into a correspondingly- shaped platinum box. The bars are made in four sizes, for right and left sides. The angles given the edges of the bar and the V-shaped form to the flange Fig. 1005. Fig. 2 Pig. 3 *is- * Fig. 1006. Fig. 1007. are for the purpose of meeting the various lines of natural teeth in an occlusal direction. Fig. 1006 shows the application of the attachment in different crowns. Fig. 1007 shows a partial denture with this attachment applied to a bicuspid and tipped molar. ^As devised by Mr. H. A. Gollobin and Dr. W. A. Bernstein. Manufactured l)y K. A. Gollobin, no West 40th St., New York. 470 CROWN-, BRIDGE-, AND PORCELAIN-WORK The Chayes Method and Attachments ^ In this method the intention is to impart a sHght resilient mobihty to the denture to permit it to respond to the vibratory as well as mas- ticatory force of the maxilla. The denture is formed of a saddle and retentive abutments, which allows direct pressure of the saddle on the membrane of the alveolar ridge and also permits a slight rotary-lateral Fig. 1008. motion labio-lingually. For the construction of dentures of this style, the following described instruments and attachments are used. The Parallelometer. — Fig. 1008 illustrates an instrument for paral- leling abutments and their attachments, also for measuring spaces. It consists of two sections or bars, the outer one. A, into which sHdes the inner one, B. The thumb screw C extends or draws back the inner section B. Fig. 1009 shows the instrument extended. The body of the 110 IjS '210 Z|5 3{j 315 410 Fig. 1009. instnlhient is 40 mm. long and it can be extended to 55 mm. Each section has three clamps, marked D, E, F, G, H, I, for holding in place the mandrels for carrying the attachments. The Parallelodrill. — Fig. loio illustrates a right-angle attachment for the denal engine with sockets for two drills for enlarging or drilling root-canals in parallel Hues. It is operated in conjunction with the parallelometer. The space between canals is measured by the parallelo- 1 As devised by Dr. Herman E. S. Chaj^es and manufactured by the Noemeteric Dental Instrument Co., 17 West 45th St., New York. MA N UFA CTURED ATTACH M EX TS 471 meter, as shown in Fig. loii, then the measurement transferred to the parallelodrill and the canals enlarged, as shown in Fig. 1012. Fig. ioii. Fig. 1012. The Attachments.— The attachments consist of the bucco-lingual, upright and the distal extension. 472 CROWN-, BRIDGE-, AND PORCELAIN-WORK The Bucco-Lingual Attachment. — This is formed of a rectangular box of platinum termed the "hood" with a slot in the side facing the bridge, as illustrated at A, Fig. 1013. The anchorage or friction sec- A B c Pig. 1013. Fig. 1014. tion, B, fits into the "hood." It is formed of a strip of elastic gold bent and doubled in the form of a T, as shown at B and C. When the arms of the metal forming the shank, S, Fig. 1013, are united with Pig. 1015. Fig. 1016. solder, the anchorage section, B, takes the form of a flattened post with a seam in the center, which permits it to be expanded and tightened to the "hood." The shank S is the part to be connected to the bridge. Fig. 1017 Fig. X018. Fig. 1 014 shows the anchorage inserted in the hood, and Fig 1015 the "hood" in position in an inlay in a molar with the anchorage in- serted. The Upright Attachment.— This consists of a flat spHt bar, as illustrated at A, Fig. 1016, that fits into a seamless rectangular tube, B. MAN UFA CTURED ATT A CHMEN TS 473 It is intended to retain the end of a bridge on a bicuspid or molar abut- ment, and is made in two corresponding sizes. Figs. 1017 and 1018 show the attachment applied to a molar crown. The Distal Extension Attachment. — This attachment is illustrated partly in section in the bicuspid crown in Fig. 1019. One end of the Fig. 1019. Fig. 1020. bar (A) is united to the male section of a tube and split-post inlay at- tachment, in a right superior cuspid and the other end is inserted into a corresponding socket in the adjoining bicuspid crown, or a dummy, where it is anchored with a screw in a countersunk cavity (S). An Fig. 1021. arched form is given a portion of the bar to allow it to move slightly in the socket so as to permit a similar proportionate movement at that end of the bridge. Fig. 1020 shows the attachment on the-side of an artificial crown. 474 CROWN-, BRIDGE-, AND PORCELAIN-WORK Construction.— Fig. 102 1 shows a case with these attachments. In the construction the attachments are accurately paralleled when Fig. 1022. Fig. 1023. Fig. I024. Fig. 1025. Fig., 1026. Pig 1027. Fig. 1026. — A, shank of split bar; B, split post; C, platinum box; D bottom of box. united to abutments and bridges. Fig. 1022 shows the bridge in position. In the finished denture, to permit the bridge to yield slightly buc- MANUFA CTURED A TTA CHMEXTS 475 cally and lingually as well as vertically under the stress of mastica- tion, the sides of the bucco-lingual anchorage (Fig. 1023) are slightly tapered from the central part towards the ends. Fig. 1024 shows the Chayes method of shaping the end of a cuspid root and the form of cap applied. Fig. 1025 illustrates a molar. The Split-post and Bar Attachment^ This attachment consists of a combined spUt post and bar. Fig. 1026 shows one form and Fig. 1027 the other. The split bar terminates Fig. 1028. with a spHt post, to which the bar acts in the relationship of a shank. The combined split post and bar fit into a platinum box or hood which sits in the abutment inlay or crown. The end of the split bar is at- tached to the bridge. Fig. 1028 shows two hoods of the form shown in Fig. 1026, being located in two abutments by the aid of a specially designed parallelo- meter. Fig. 1029 shows the hoods and attachments as they appear in the abutments, and above them the ftnished bridge and attachments. 1 The Combined Split -post and Bar Attachments are manufactured by Mr. John Yirikian, 391 Central Park, West, New York, from whom descriptive details of their application can be obtained. 476 CROWN; BRIDGE-, AND PORCELAIN-WORK Fig. 1030 illustrates the other form of this attachment, shown in Fig. 1027, in a bicuspid and molar, and in a completed bridge. Fig. 1029. Fig. 1030. Fig. 1 03 1 shows the several sizes and shapes of the two styles of the attachments. To allow for settling of the denture and corresponding MANUFA CTURED A TTA CHMEXTS 477 pressure on the alveolar ridge, a small space is secured under the split post in the box by inserting there, as indicated at E, Fig. 1032, a very Li- (^ 10 O C_3 CcS (E3 c^ ^ CE) r^ o