The Predicament of Crown and Bridge Work

THE JOURNAL OF THE

National Dental Association VOL. 4

APRIL, 1917

dû)

NO. 4

Original Communications. T H E P R E D IC A M E N T O F C R O W N A N D B R ID G E W ORK. By Dr. Forrest H. Orton, St. Paul, Minn.

(Read before the National Dental Association a t Its Twentieth Annual Session, Louisville, Ky., July 25-28, 1916.)

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NTROSPECTION w hich is sim ply self an alysis is morbid. Introspection w hich starts out w ith the purpose of finding one’s own absurdities w ith a view to rectifyin g them is not lik ely to be very m ischievous and occasionally is as valuable to a group as to an individual— (for after all w e are only you and I m ag­ nified and our m istakes- as individuals m ake the errors of the comm unity as surely as our achievem ents m ake a na­ tion’s success.) So if my remarks seem in the nature of destructive criticism it is because I feel that it is n ecessary to clear aw ay the debris of our errors in the gross before beginning reconstruc­ tion. 327

It needs but a slig h t acquaintance with the periodical literature of our profession to realize that th ere is an increasingly critical trend toward crown and bridge work. Prom confidential talks w ith den­ tists in alm ost every section of the U n­ ited S tates I am convinced that the aver­ age d entist is not only dissatisfied, but more or le ss discouraged w ith the results of his efforts in th is field; and this is e s­ pecially true of th o se d entists who have had years of experience. Indeed, w e did not need to be informed of our shortcom ings. W e w ere aware of them , and had been aware of them for years before th ey w ere discovered by others. But sin ce popular attention has

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been called by mem bers of th e m edical profession to the serious system ic dis­ turbances w hich it is claim ed m ay follow from a large percentage of our work, we feel that we can no longer m aintain the status quo. To be sure, our first reac­ tion was probably one of resentm ent. I w ell remem ber my own indignation when, som e fifteen years ago, Dr. Eugene Talbot expressed h is opinion that we w ere doing our best to cau se pyorrhea by our crown and bridge operations. But tim e has only too w ell justified his strictures. W e all felt that w e had been challenged, and that th is w as a serious com m entary upon our claim s as public benefactors; but the feeb len ess of our de­ fen se seem ed to me alm ost a virtual ac­ know ledgm ent of the accusation. W e replied that the dental profession should not be judged by the cases under ob­ servation, and that there w ere m en in the dental profession who w ere doing hygienic crown and bridge work. I do not doubt that th is is true, for I have seen som e such work. But is not this, after all, m ere quibbling? For we m ust, acknow ledge that th ese m en are the ex­ ception, an 1 that they are p ossessed of unusual native talent; th is talent, com­ bined with long experience, has develop­ ed in them som ething akin, to genius. A las, the profession as a w hole is not m ade of geniuses! The average man who enters th e dental profession scarcely d oes so because he has an im pressible call, based on an unm istakable talent, but sim ply as a w ay of earning h is liv eli­ hood, and to the beginner, apparently an easy way. That unfavorable prophylactic condi­ tions are established in the m outh as a result of a large percentage o f our crown and bridge operations m ust be fam iliar to any one having the slig h test clinical experience. W e are all more or le ss con­ vinced of the n ecessity for im provem ent. Shall we w ait for th is before w e are forced to it by popular disapproval? W e m ust face the difficulty of th e problem

squarely if w e are to preserve th is im­ portant branch of restorative dentistry. I thoroly b eliev e that th e average den­ tist is both w illin g and anxious to do w hatever is n ecessary to be successful in the b est sen se of th at word. He w ants to be fair, not on ly to h im self but also to his patient, but his great difficulty is that he is not able to obtain the know l­ edge needed to do ¡.he right kind of work. T here is no recognized authority, no authorized opinion, eith er in college or in text. The d en tist has acquired the m echanical tech n ic of a certain type of crown and bridge work, but h is know l­ edge is em pirical. M echanical ingenuity and excellen ce of craftsm anship have been his sole aim — the only part of the work seem ing w orthy of attention. In the absence of any recognized standard of criticism he form s his own standard, and this, as a rule, is one of expediency. H e faces the tem ptation to look upon every mouth m utilated by th e loss of one or more teeth a s an opportunity of plac­ ing a piece of bridge-work, w hich he feels w ill be to h is own m aterial advan­ tage. W hile I am a firm believer that “the laborer is w orthy of h is h ire,” I do not b elieve that m aterial gain should be the guiding thought of one who dedicates his life to our profession. T he opportunity to be of service to on e’s fellow-m an should be th e principal privilege and reward as com m ercial gain is the priv­ ilege and reward of one who dedicates him self to business. A m an who goes into dentistry solely for h is own benefit is not a credit to h im self or h is profes­ sion, w hile h e w ho looks upon h is work as a part of the w hole profession of heal­ ing finds both pleasure and reward in h is work. W hy should w e le ss than other benefactors in th e world look upon our work as an art and scien ce instead of m ere business? W hy not realize that the greatest end of all endeavor should be not to be m inistered unto but to m in­ ister. Only w hen w e 1 \ i i ni s aim shall w e h ear le ss < i u .. i* rj

ORTON—PREDICAMENT OP CROWN AND BRIDGE WORK. “I can’t afford to do that kind of work” as w ell as less criticism of w hat w e do accom plish. And w hile no branch of dentistry can boast of a greater variety of methods than the one under discussion in this paper, the absence of any fundam ental principles governing their application m ake the selection of any particular m ethod a m atter of personal caprice. Som e m ethods, indeed, m ay evince a more accurate technic than others; but if the principles underlying our technic are sound -e method itself is largely a m at­ ter àdual preference and prescripbe out of place to raise here .1 aether indeed the dental 'y in the p ossession of ’ or »zed body of recognized bating to crown and bridge Tiie restoration of the teeth by as of a filling or inlay is an operàj procedure w hose principles have b e­ com e thoroly system ized, classified a n i standardized that the best form is no longer a m atter of conjecture. W e all understand the im portance of restoring contour, contact, and th e proper form of em brasure, but what standards are there relating to crown and bridge work which have found a correspondingly general recognition? Fully forty per cent of the d en tist’s work today is in this field, yet if w e w ere asked to criticise a piece of crown and bridge work in a clinic w hat standard could we apply? W ould any two of us view it from the sam e stand­ point or seek to m easure it by the sam e test? I fear that we are too often w ant­ ing in any fixed standard, and therefore too prone to be dazzled by the brilliant polish of the finish—as satisfied as the patient him self, to whom the brilliancy of the finish is not only the crowning te st but the test of the crown. A s I look back upon m y own many failures, the ignorance of fundam ental principles seem s to me to be their main cause. We have studied individual cases, but have not system atized our deductions. We >7-

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have no generalizations which, when brought together into system , would m ake a theory upon which to work; all our theories are but concrete instances. No am ount of m echanical ingenuity or man­ ual dexterity, for example, w ill compen­ sate for the failure to make a proper diagnosis. The often repeated aphorism of m edical science, “th at to know the cause is half the treatm ent” is a truism which does not too strongly em phasize the im portance of m aking a correct diag­ nosis. In the absence of a manual of princi­ ples w e m ust base our diagnosis on in­ dividual judgment. W e judge by com ­ parison. H ence, only men of experience can be expected to have judgm ent—what, then, can we expect of a beginner? E x­ perience is a dear teacher, and y et is the one upon w hich we must rely. It would be idle to deny that individuals have ac­ com plished som ething—often, indeed, a great deal, but they have accom plished it only as individuals. Their work does not help the science unless it can be given in such form as to be adapted to a number of cases. Each one who ob­ tains any results in this field laboriously works out for h im self his own theory. The thought has been m any tim es driven home to my mind that under proper guidance, using the discoveries of my contem poraries or of those who have preceded me, it would have been easy for m e to have acquired years ago more than that which I have painfully and im ­ perfectly learned by my own experience alone. W e are told, for example, to make study m odels; but we are not told what to study after we obtain such m odels. Had w e a definite classification, suffic­ ien tly com prehensive to embrace all the various typ es of m alocclusion which a l­ most invariably result from the loss of one or more teeth, then the m aking of study m odels would enable us to diag­ nose a case and aid us in the decision of a definite treatm ent for each type of m alocclusion so comprehended. Study

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models would then becom e as im portant a factor in the routine of crown and bridge work as they are at p resen t to the orthodontist. No orthodontist of to­ day, no m atter how ex ten siv e h is exper­ ience or great his ability, would decide on a plan of treatm ent w ithout first m ak­ ing study m odels. L et us define bridge work as a method of correcting m alocclusion in a m utilated

Figure 1.

arch caused by the lo ss of one or more teeth. If w e accept th is definition a knowledge of normal occlusion m ust be regarded as a first principle, the sim ple basic fundam ental requirem ent. B ecause of the orthodontist’s special fitness to judge of the know ledge of occlusion pos­ sessed by the average d entist I have d is­ cussed this question w ith a great many orthodontists and have discovered a t least one bond of harmony am ong them , for they all agree without exception th at den­ tists generally have a very hazy notion of normal occlusion. Now let us define d iagnosis as “the

art of discrim inating betw een d iseases or deform ities and distinguishing them by their characteristic sig n s and sym p­ tom s.” All such judgm ents im ply a com ­ parison with the normal. The value of study m odels as an aid to diagnosis would depend upon the d en tist’s know l­ edge of normal-occlusion; lacking this fundam ental knowledge it would prob­ ably be more instructive for him to make study m odels of h is crown and bridge cases after they w ere inserted in the mouth. If such m odels w ere careful­ ly made and correctly mounted on an an­ atom ical articulator I think he would be chagrined to learn that w hile h is bridges occluded with the opposing teeth when the jaw was closed, they failed to do so during the m asticatory m ovem ents of the jaw. The fact that the crown or bridge occludes, is no evidence that it w ill ar­ ticulate perfectly, and yet a flaw less ar­ ticulation is in my opinion the m ost im­ portant feature in determ ining the sta ­ bility of our work. A rticulation of the teeth is one of nature’s m ost m arvelous creations. It is the object for which teeth were developed and th is arrange­ m ent of the teeth seem s to be the fittest possible for its purpose, for it has sur­ vived from the H eidelberg man to the present day w ith com paratively insignifi­ cant changes. This subject has been treated so exhaustively by previous w rit­ ers that it would seem alm ost trite for m e to dw ell upon it at length, w ere it not for the fact that a practical application of the known law s which govern the temporo-maxillary articulation are utterly ignored by the average d en tist in his crown and bridge work. Furthermore, I am inclined to believe, from the earn­ estn ess w ith which this subject is re­ ceived w herever it is presented, that this is due to a lack of understanding rather than to indifference. I fully recognize the sw eeping nature of th is statem ent, but no better proof of its truth need be presented than the present m ethod of constructing crowns and bridges from an

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im pression and bite w hich represent only a segm ent of the arch and the opposing teeth. (Figure 1.) W hile this m ight serve as a guide to the occlusion of the teeth while at rest, it does not convey the sligh test hint as to how we should arrange the occlusial surfaces in order to m ake them articulate. That fixed bridge work im m obilizes the teeth has been urged as one of the chief objections to the fixed crown and bridge. I am of the opinion that th is is a minor factor, and not to be compared in impor­ tance with the common failure to repro-

buccal cusps of the low er teeth w ill pre­ sen t cusps a trifle higher than the lin ­ gual. W hen th is arrangem ent of the teeth is in harmony w ith the plane of the tem poro-maxillary articulation, the low ­ ering of th e jaw on either lin e is com ­ pensated for, and the stress is evenly distributed. A more graphic representa­ tion m ay perhaps be gained by illustrat­ ing my m eaning w ith the u se of Dr. O. H. W eiss’ apparatus designed by him for show ing lateral articulation. (Figure 2.) W ith the teeth in normal occlusion and arranged as described, when the jaw

Figure 2.

Figure 3.

duce the bucco-lingual inclined planes of the occlusial surface. Buccal and lingual cusps on a level plane as they are usually made m ight serve, if the occlusial of the teeth were directed by a hinge or if the jaw s moved laterally in a straight line, but ow ing to the inclination of the condoloid path when the jaw m oves to the right it is lowered on the left v ice versa. Owing to the slight inclination of the molar teeth th ere is a correspondingly slight deviation of their long axis from the per­ pendicular line. A s a rule the molars of the upper jaw are a little inclined toward the buccal and the corresponding teeth of the lower jaw w ill have a slight lin­ gual inclination. The result is that the buccal cusps of the upper teeth w ill be a trifle shorter than th e lingual, and the

m oves either to the right or the left there is an occlusial contact on both sid es of the arch and an equal distribu­ tion of the stress. (Figure 3.) When the jaw m oves to the right or the left the long buccal cusps of the low er teeth oppose the long lingual cusps of the upper teeth and thus com pensate for the low ering of the jaw on the left side ow ing to the inclination of the condoloid path but the cusps placed on a level plane (Figure 4) when the jaw m oves either to the right or to the left there w ill be occlusal contact on one side only. (Figure 5.) It is not an uncommon fault to see this inclined plane actually reversed on the upper teeth by m aking the buccal cusps longer than the lingual. I believe that this fault w ill account for more broken

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facing than any other factor, for with the teeth properly articulated it is al­ m ost im possible to bring stress to bear against the facing. If the only result of our failure to harm onize the occlusial surface of the teeth w ith the plane of the condoloid path were to impair the m as­ ticating efficiency of the teeth this fault would not be so grave, but the m alocclus­ ion produces resu lts in destroying the attachm ent of the teeth used as piers. The effect of th is condition may fre­ quently be noticed on the natural teeth

changes which alm ost invariably take place in the opposing tooth from lo s s.o f function; the changes in other parts of the arch w hich m ay have been caused by the lo ss of the very teeth we contem ­ plate replacing and which may be a d e­ ciding factor in our diagnosis; the oppor­ tunity to educate the patient as to the far reaching results of the loss of one or more teeth from the arch by the use of such excellen t illustrative m aterial as this visual im age of h is own mouth pre­ sents, should not be neglected. And I

Figure 4.

Figure 5.

ow ing to a nervous habit of grating the teeth or to the natural abrasion which accom panies old age where the greater wear com es on the lingual cusps of the upper teeth and the buccal cusps of the lower, to the extent of reversing the planes of the occlusial surface. H ere a type of m alocclusion is produced which invariably resu lts in the resorbtion of the alveolar process, the recession of the gums, and th e consequent increased range of m ovem ent of the teeth. It has been a m atter of surprise to me that in the volum inous literature on the subject of pyorrhea com paratively little attention has been paid to th is important etiological factor. The possibility of studying the two arches as a unit is in my opinion the .m ost im portant reason for m aking study models. The opportunity to observe the

m ight say in passing that the education of the d en tist h im self w ill be extended. It is w ell to remember that we cannot do all our com prom ising on one jaw. The attem pt to adjust the occlusal surface of our bridge to an elongated tooth on the opposite jaw is sure to result in a m al­ occlusion far more serious to the elongat­ ed tooth than the grinding necessary to bring it into the occlusial plane. The traditional sentim ent which m akes us hesitate to m utilate a so-called “perfectly good tooth” is a m isplaced em otion in this instance. The tooth may be a sound tooth but it is not a good tooth until it is made to function normally. A sin gle tooth is not of much value in itself but m ay be regarded as valuable just in pro­ portion as it contributes to the w elfare of the entire arch. To refer again to the prevailing prac­

ORTON.— PREDICAMENT OF CROWN AND BRIDGE WORK. tice of com pleting our crowns and bridges entirely on a m odel— w hile the various anatom ical articulators on the m arket m ay approxim ate the temporom axillary articulation w ith sufficient ac­ curacy to form an efficient guide in the

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shall throw on the screen illustrations of a m ethod suggested by Dr. Alfred Pagankopf of St. Paul, w hich m akes it pos­ sible to try the waxed-up and assem bled m odel of the bridge in the mouth w ithout danger of distortion. The articulation as w ell as the occlusion m ay thus be ver-

Figure 8. Figure 6.

construction of an artificial denture, in our crown and bridge operations som ething better than m ere approxim ation is n eces­ sary. W e must rem em ber that w e are held accountable for the pathologic se-

ified by using the jaw itself as an artic­ ulator. (F igures 6, 7, 8 and 9.) W e have all m et the hum ilating exper­ ience of having to grind down a carefully carved occlusial surface until nothing w as left of the cusp sulcus and fissures but the O g e e curve itself, but since

Figure 9. Figure 7.

quence that may follow m alocclusion. Owing to the rigidity of a crown or bridge and the increased stress of m as­ tication on bridge abutm ents we must restore articulation w ithout a flaw, in order to avoid the evil consequences of malocclusion. W hile it is not my intention to exploit any particular method I m ight be accused of iconoclasm did I not attem pt to re­ place the goods I have destroyed. I

adopting th is method I have practically elim inated this annoyance. But the occlusion of the teeth is by no m eans the only result w e m ust obtain in producing favorable conditions. No­ where in nature does one cau se produce a given effect, but a m ultitude of causes, direct and indirect, contribute to pro­ duce it. The problem before us presents many difficulties apparently unrelated, but just in proportion as w e are capable of rec­

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ognizing and estim atin g the value of each of th ese factors and their relation to one another, our diagnosis m ay be raised from an em pirical to a scientific art. T hat an unfavorable or abnormal form of the tooth m ay be a predisposing fac­ tor in caries arid g in givitis is now a w ell recognized fact; our atten tion has been repeatedly cai!6d to the im portance of m aintaining the proper form and width of the interproxim ate space and the mar­ ble-like contact; w e realize the im port­ ance of the' em brasures in extending the' areas of im-m'tinity by allow ing the ex­ cursions of food stuffs to pass thru dur­ ing m astication—-these are concrete il­ lustrations; presenting the p ossibility of favorable w ell as unfavorable varia­ tions in t h e . shape of the teeth them ­ selves. Modern operative dentistry has come to recognize in the extension-form given to our cavity preparation and the contouring of the finished filling the im­ portance of restoring the exact surface anatom y of each tooth, and to em phasize as a fundam ental principle, the require­ m ent that each operation ought to be so devised as to prevent recurrence of decay or injury to th e soft tissu e. T hese are all recognized consequences of the fun­ dam ental principle that the operation is incomplete? or u nsu ccessfu l if it does not leave the mouth in th e m ost favorable condition possible. That the sam e principles have an equal application to crown and-bridge work is too self-evident to n eed com m ent, and yet the conventionalized crown in popu­ lar use does not resem ble the natural tooth in a single essen tia l. The patholog­ ical condition of th e so ft tissu e about a large percentage of our crow ns, and the utter disregard of the surface anatom y of the tooth, resulting in the production of unfavorable conditions (favoring th e lodgm ent of secretion s and stagnant sa l­ iva) are the result of our n eglect to take advantage of the guidance afforded by th ese principles. M ight it not be reas­ onable to inquire ju st h ere the cause for this? The dental profession, individually

and collectively, is as capable of deduc­ tive reasoning as are th e individuals of any other group or profession. There may be m any answ ers to our query, but in m y opinion, the ch ief reason w ill be found in the failure to acquire an in ti­ m ate acquaintance w ith dental anatom y “To the rational being it- is the sam e thing to act according to nature and ac­ cording to reason.” P erfect execution depends upon a clear perception of the object to be copied or restored—an ability to recall a clear v is­ ual im age in th e m ind’s eye. In restora­ tive operations m y m eans of m alleted filling or inlay, there is alw ays som e por­ tion of the tooth left, to act as a guide; but in our crown operations w e m ust re­ store the crown of the tooth in its entire­ ty. W e m ust reproduce nature exactly as we find her, and the perfection of our im itation w ill depend absolutely upon our know ledge of dental anatom y. N ot­ w ithstanding the fa ct that this subject form s one of the foundation stones of our education, it is m y experience that students generally fail to realize its im­ portance, and hence fa il to take advant­ age of the opportunities it offers. In fact, a book know ledge of th e subject sufficient to pass the didactic te st and forgotten as soon as th is trial is over, is about the sum total o f the average d en tist’s know ledge of dental anatom y. So thoroly am I convinced of the de­ pendence of the subject under discussion upon dental anatom y, that I cannot see much hope for an im provem ent along th is lin e until we first increase our acquaint­ ance w ith this science. I hope that I may be pardoned for uttering a word of warning just here. I b elieve that dental anatom y, as taught in the m ajority of our colleges, is as a rule as w ell presented as the lim ited tim e—tw o sem esters of the freshm en year— w ill allow. But the stu­ dent at this tim e is m erely on the thresh­ old of dentistry, and his orientation in the subject is lim ited; he cannot be ex ­ pected to understand the specific rela­ tion which the subject bears to the prac­

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tice of dentistry, and he regards it as more or less of a cultural study; or pos­ sibly, a filler put in to round out the curriculum. Now if this subject were repeated in the first sem ester of the junior year from the standpoint of applied anatom y, it would have the effect not only of deepen­ ing the groove of memory by review , but it would further im press the student w ith the fact that every line in the tooth has an im portant bearing upon the estab lish ­ m ent of favorable conditions.

a few specific features of dental an at­ omy, w hose bearing on the subject of crown and bridge work has engaged my personal attention. To those of us who still believe that a banded crown is occa­ sionally indicated, a know ledge of the relation of the enam el and the dentine to the contour of the crown is essential. For example, in the preparation of the root for the reception of the crown the question com es up w hether the removal of the enam el w ill be sufficient to give us parallel walls, or w hether the dentine

Figure 10.

Figure 11.

In estim ating the practical value of general anatom y teachers have come to em phasize th e importance of regional anatom y, and I believe that the student, and hence the profession, would profit by th is experience, and that the view ­ point gained would be as valuable to the dentist as it is to the general surgeon. That the whole is made up of all its parts is as true in dental anatom y as in m athem atics, and it is no more true that one m ay not understand the condition and treatm ent indicated in an y case without a full knowledge of regional an­ atom y than that one may not be an ar­ ch itect w ithout a knowledge of geom e­ try. L et us turn now from generalities to

shall make up part of the contour of the crown. Altho this question has been answ ered in a form er paper, I consider that the m aterial is so pertinent to the present discussion that I am justified in quoting it. A description of the relative propor­ tion of the tooth enclosed by each tissu e will, I think, be convincing on this point. (F igures 10,11,12 and 13, show ing relative portion of tooth occupied by enamel and dentine.) The contour of the tooth is made up alm ost entirely by the enam el. B eginning at the gingival line w ith a beveled feather edge, it gradually increases in thickness until the points of the cusp«! are reached where the th ick est enamel is

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found. This accounts for the lo ss of col­ or at the Incisal, as the tooth receives its principal hue from the dentine and

toward the occlusal surface w ith little or no convexity and only a sligh t inclina­ tion toward the axial line of the tooth. Figure 14.

ENAMEL

Figure 12.

its white, or w hite and gray, value from the enam el. The enam el w ill be found th ickest beneath any ridges or eleva-

Upper molar partially stripped of its enamel, showing inclination of axial walls of dentine.

Now if the anatom ical description just given is accurate, the n ecessity for the entire removal of the enam el seem s obvi­ ous, if we are to have our crown in close Figure 15.

Diagrammatic outline of the first lower molar and second bicuspid in the region of the approximate contact as viewed from the occlusial.

Figure 13.

tions on the various surfaces. This thickness of the enam el is formed by the increased convexity of the outer sur­ face, (Figure 14) the dento-enamel junc­ tion or axial wall of the dentine, passing

contiguity with the entire gingival circum­ ference of the gingival line of the tooth. The m ost difficult feature in the tech ­ nic of constructing the banded crown, and the distinguishing requirem ent of this type of crown, is the rem oval and replacem ent of the gingival enam el. Let us study_ the regional anatom y of

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this portion of the tooth, directing our attention to the shape of the enam el on this portion of the tooth where the diffi­ culty of reproducing normal conditions by the use of a flat band is made clear. (Figure 15.) T h ese slid es show por­ tions of a lower first molar and low er bicuspid som ew hat in detail. If we view from the occlusal aspect

fixed bridge as w ell, it is a common fault to find the dumm ies at the point w here they are attached to the abutm ent crowns, as w ide bucco-lingually as at any other point, giving one good reason why fixed bridge work is considered un­ hygienic. T his slide illustrates the fault I have described. (F igures 16 and 17.) This slide show s the proper form to

Figure 16.

Figure 18.

this outline of the lower molar, the m esial surface is not convex from the buccal to lingual, as it is usu­ ally represented in our crowns, but is inclined sligh tly toward the a x ia l.lin e of the tooth as it goes toward the lingual, bringing the contact point alm ost on a line with the buccal cusps, thus resulting

be given the dumm ies at this point. (Figures 18 and 19.) The form of em brasure is dependent to a large exten t upon the form o f the buccal and lingual surfaces. (Figure 20.) In this slide, the dark lin e is intended to show the outline form of th e buccal, oc­ clusal and lingual surfaces usually em-

Figure 17.

Figure 19.

in a larger lingual than buccal em bras­ ure; on the other hand, the distal sur­ face is convex from buccal to lingual, bringing th e contact point nearer the center of the tooth. N ot only the cleans­ ing action caused by the excursion of the food stuff, but the retention of stagnant saliva is determ ined to a large extent by the w idth and form of th ese embras­ ures. This is true not only of individual crowns, but in the so-called hygienic

ployed. The objection to th is form is that it carries the occlusal third out of alignm ent, prevents a proper formation of the em brasures and allow s the excur­ sion of the food stuff to be forced against and under the free gum margin. The dotted line show s the natural form and the one w hich should be follow ed in or­ der to produce the m ost favorable condi­ tions. In each of th ese cases (Figures 4 A

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and 6 A) the crowns have been ground down to the free gum mar­ gin. N otice the difference in the outline

tooth are about as constant as are any other features of dental anatom y, and form an im portant consideration in re­ storing the enam el contour. The gums should hug the crown as closely as they did th e natural tooth. It is also inter­ estin g to note in this slide (Figure 21.) (w hich is a view obtained by simply cut­ ting off the distal convexity of the root preparation) that the enam el p asses

form of the dento-enam el junction and the periphery of the crown at th is point. Now the outline form of the dento-en-

LOWER MOLARS r>

CONTOUR FOUND BETWEEN GINGIVAL LINE AND FREE GUM MARGIN Flgure 4 A.

am el junction at this point, is practically the sam e as the outline form at th e ging­ ival line. T he varying degrees of thick­ ness of the enam el on this portion of the

higher on the lingual than upon the buc­ cal, and that in this slide, (Figure 22) (a view from the buccal of a longitudinal section passing from the points of proxi­ m ate contact) it p asses higher on the distal than upon the m esial—im portant anatom ical points to remem ber in trim ­ m ing and festooning the gingival end of the band. Altho the anatom ical relations just described are chiefly applicable in the construction of a banded crown, le t it be understood that they are not given w ith any especial desire to advocate this particular type of crown. I sim ply w ish

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to em phasize the fact that if w e are to continue m aking the banded crown, cer­ tain fundam ental reform s are n ecessary before it can hope to rank w ith other modern septic dental procedures. In my opinion its application should be lim ited to th ose cases w here it is possible to prepare th e root not only w ithout injury to the peridental attachm ent but also w ithout injury to the inner epithelial lining of th e free gum margin. A s I have indicated elsew here, I do not believe that

crown upwards of three mm., a condition frequently found in youth, w e may ex ­ pect th e peridental fibers to be attached to the cem entum clear up to the gingival line. Any attem pt to remove the enamel as high up as the gingival line, would resu lt in destroying th ese fibers, many of w hich turn up into the free gum margin and help to hold the m argin tightly a gain st the enam el; and in the interproxim ate space, fibers pass from the ce­ m entum of the tooth and above the alve-

F igu re 21.

Figure 22.

the dental profession can be accused of indifference to the results of their work, and hence w e m ust admit, judging from the lack of respect often shown the ging­ ival and sub-gingival tissu e s during a root preparation, that the vulnerable na­ ture of th ese tissu es is not fully under­ stood. I believe that the detachm ent m ethod of teach in g the histology of the soft tissu e surrounding the teeth may in a m easure account for our failure to appreciate their relation to the tooth. W hile the free gum m argin Is variable, the exact nature of its attachm ent to the tooth form s an im portant diagnostic sign for th e indication of a banded crown. For exam ple, w here the free gum mar­ gin exten ds over the enam el of the

olar septum and are attached to the c e ­ m entum of the adjacent tooth. Further­ more, the epithelium lining the border of the gingiva is folded in against the tooth and is much thinner and softer than the~ epithelium covering the outer portion of the gums. In m aking our diagnosis, the fa ct of even greater im ­ portance is that the portion o f the con­ nectin g periostim um and peridental mem brane in im m ediate conjunction w ith the tooth, is not covered by the epithelium . In other words, there is no attachm ent of the epithelium to the root of the tooth and it is suspected that in­ fection frequently takes place thru this unprotected region. On the other hand, it is a well-known

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clinical fact that the peridental mem ­ brane and gingival m argin recede as age advances, thus favoring the possibil­ ity of a harm less rem oval of the enamel, hence the location of the gum lin e may be taken as a significant factor in de-

sal, the buccal and the m esial aspect, and th ese slid es represent a crown made to replace the one just show n and view ed

Figure 23.

ciding upon the type of crown indicated in any given case. It would be vain for me to attem pt to add to the m any exhaustive descriptions of the proxim ate surfaces of the teeth, or to em phasize the im portance of re­ producing the m ost favorable shape pos­ sible as a prophylactic m easure, except to say that the reproduction of a normal form of embrasure is only second in im-

Figure 25.

from the sam e aspect. (F igures 26, 27, and 28.) W hile I have but touched upon a few

Figure 24.

Figure 26.

portance to the contact form itself, if in­ deed the shape and position of the proxi­ m ate contact are not dependent to a cer­ tain extent upon the form given to the embrasures. My m eaning m ay possibly be m ade more clear by com paring the follow ing slides. (F igures 23, 24 and 25.) T hey represent the conventional crown first lower molar view ed from the occlu-

of the anatom ical points which have a bearing on the production of favorable conditions, I hope that the illustrations which have been shown you in th is ad­ dress are sufficient clearly to indicate the practical value of applied and re­ gional anatom y. In addition to the pres­ ent method of m em orizing a number of disconnected facts, let us em phasize the

OR TO N — PREDICAMENT OF CROWN AND BRIDGE WORK. connection betw een facts, to show how each is related to the other, and how thru them all there runs a certain thread of unity, w hich may frequently

Figure 27.

be form ulated as a general principle of law. W hen this has been accom plished in the field of crown and bridge work, when w e have thus obtained objective and accessib le standards for criticism ,

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tablished standards of the profession as a whole. Thru the centuries th ey have been re­ garded as w orthy of reverence who fo l­ low the call of conscience to save m en’s souls, and the m edical profession is look­ ed upon as alm ost on a level with the m inistry; for the tem ple of the soul must be worthy o f its inhabitant, and he who saves life sa v es the m ost precious thing w ithin human power to save. We have long known the connection existing be­ tw een health of body and the possession of sound, sanitary teeth ; of late years the m edical profession has blazoned it forth to the world, so that there is no one today but understands that m edicine and dentistry are as closely allied as m edicine and surgery. It is not our own fault, then, if our profession is consider­ ed less im portant and dignified than th ese others, and is it not ours to put it upon an equal plane?

Discussions. J . M . Prime, D . D . S , Omaha, Nebraska.

Mr. Chairman, L adies and Gentlemen:

Figure 28.

we may perhaps be able to boast of good and hygienic work done by the profes­ sion as a whole, instead of finding such work exem plified only in exceptional in­ stances of unusual ability; and we m ay be able to require even of the beginner, with ordinary preparation and talent, a reasonable conform ity w ith the w ell-es­

The Chairman says I have but five m inutes. I never had so much to say w ith so little tim e in which to say it. 1 am sorry I have so little tim e to discuss this splendid essay com ing from a scien ­ tific man like Doctor Orton on a subject in w hich we are all so much interested. So I can but touch on one or two points. I would lik e to em phasize what the e ssa y ist says in regard to the inefficiency of crown and bridge work. It is an ac­ cepted fact that in a few cases, few, very few, we se e creditable work, y et the great m ajority of cases are monum ents erected to the m em ory of our m istakes, ignorance and inabilities. The “M other Hubbard” crown is perhaps the greatest sin for w hich we w ill have to answer. A long in the category would come the banded Richmond, devitalization of teeth for abutm ents and for cosm etic reasons and on down the line until we quake w ith fear at the thought of irreparable

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dam age done. T he day ior a m ore sane and sanitary, healthful and physiological system of crown and bridge work is here. U ntil such a system is worked out and tested we m ust em ploy it cautiously and in lim ited cases. (A pplause). N ature de­ signed the root should carry its individ­ ual crown only. In m ost form s of bridge work w e ask the abutm ent teeth to not only do their work but also the work of their departed fellow s. W e have learned by experience th ey w ill do th is extra work for a lim ited tim e only. I w as delighted to hear the essa y ist make prominent m ention of tooth form. T his is a subject to w hich I have given much thought. I have the honor to read an essay on the P hysiological Function of Hum an Tooth form before a section of this Congress. T ooth form lie s at the very foundation of every operation on the natural teeth. W ithout a knowledge of tooth form we are unable to render an efficient service. If I am called upon to m ake an operation on a tooth the de­ gree of m y su ccess w ill be measured very largely by the natural form I give to that m aterial w ith w hich I replace the lost tooth tissu e. (A pplause). T here are three fundam ental principles involved in physiological tooth form. The first is the m asticatory surface. Its function is the object for which th e teeth w ere created. The second is, the lateral w alls of the tooth crowns being so form ed that their surfaces w ill be kept continuously cleansed by th e excursions of food. The third and la st and m ost im ­ portant of all, for on the w hole super­ structure rests, is the gingival constric­ tion. It provides sh elter for the delicate gingival tissu es, a harbor in w hich th ese tissu es lie, allow ing the excursions to pass over them , leavin g them unharmed. Indeed, here is the m ost vulnerable spot in the w hole human body, for it is at this particular place that the m ost prevalent disease of th e human fam ily finds its origin. (A pp lau se). My tim e is up but you w ill pardon me if I say one further word. W hen in

bridge work w here w e ask the abutment teeth to do more than their natural duty, the .occlusal form should receive our careful thought. T he form of this sur­ face governs very largely the degree of interm axillary force. It is here, and per­ haps more h ere'th a n in any other opera­ tions, w e are forced to depart from the natural forms. Indeed the more nearly w e restore the natural form s in som e cases, the greater the interm axillary force and the sooner the abutm ents will be overworked and lost. W e can there fore give a more enduring service by m odifying our occlusal form, shortening our cusps and providing an easy sliding surface. W e have different law s an ] principles involved in bridge work than on sin gle crown teeth. Single crown teeth either in part or in w hole require the m ost faithful tooth form reproduc­ ......... tion. I thank you very kindly. (A pplause). fC. G. Knoche, D . D . S ., Chicago, III.

Mr. Chairman, Dr. Orton, M embers Nat:onal D ental A ssociation, L adies and Gentlemen: Dr. Orton’s paper has placed this sub­ ject before you in a logical and very com plete way. H e has em phasized the need for certain reform s, the n ecessity for w hich is apparent, and lays empha­ sis upon the fact that unless th ese are inaugurated public disapproval w ill bring us to a very costly and sad accounting, to discuss h is paper is but to agree with him, and I w ill try to reiterate much of w hat he has said and to em phasize the principles he has so clearly enunciated. S elf an alysis or introspection is, as he has said, morbid, and much of the an alysis of modern dentistry by men w hose vision is but the sm all end of a m icroscope has given us a picture far too dark and far too unpromising. They have led the profession into believing that nothing in dentistry is good or right. T his kind of introspection pro­ duces chaos and it m akes men lose hold on ideals and all that brings about bet­

ORTON.— PREDICAMENT OF CROWN AND BRIDGE WORK. term ent. The right sort of introspection is th e kind that produces the effort you have ju st been benefited by. I fe e l that it m arks the beginning of work th at w ill bear fruit such as w ill bring the field of crow n and bridge work into the position rightly its due. It is significant that, as Dr. Orton has said, forty per cent of th e dental opera­ tion s performed are so-called crow n and bridge operations, and so w e as bridge workers are responsible for m uch of the su ccess or failure of dental operations. I do not need to dw ell upon the m atter of failures and their cau ses but w ill try to em phasize principles upon w hich this work can be planned and brought to suc­ cess. The fact that som e m en (and they are few ) have been su ccessfu l in the past, sim ply proves th a t it w as but in­ dividual skill, plus personal tech n ic by w hich th is was accom plished. There are but few in the profession who are mark­ ed by genius, and sin ce the great bulk of the profession has had failure follow their operations in crown and bridge, it seem s to me that it is the system of practice th at perm its of so great a per­ centage of failures that should be con­ demned. W e have lacked a standard of operation as w ell as a standard o f criti­ cism , and th ese w e m ust have if w e are to progress. L ast w eek in Pittsburgh I asked the Am erican A cadem y of Oral Prophylaxis and Peridontology to give us a standard of criticism from their view -point o f per­ idental disease. T his is n ecessa ry if we are to prevent failure that produce the conditions they are trying to control. L et us in the entire profession cease b eing intellectual h ypocrites and criti­ cise h onestly and fea rlessly each other’s efforts and soon w e w ill be rewarded by a know ledge 'of all view -points and re­ quirem ents. W hen we p ossess, each one of us, a true know ledge of the im port­ ance of the teeth in normal contour, con­ ta ct and position, know their p hysiologi­ cal and anatom ical relationships to the re st of the head and body, w e w ill have

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gone a long w ay tow ard laying a real foundation upon w hich to build. Some of you know th at I am strongly an advocate of th e rem ovable bridge, and th a t I have little place for the fixed type o f bridge sim ply be­ cause it does not conform to cer­ tain physiological principles to w hich I believe all work should conform. H ow ­ ever, in order to bring this subject into the light, a clear enunciation of a stand­ ard under w hich to proceed to a con­ sideration of principles is n ecessary and of the greatest p resen t im portance. T his standard, I believe, has been given to the profession by Dr. Orton before, and reit­ erated today. T his standard has b een em ­ phasized by modern operative dentistry and really should be th e standard of all dentistry, nam ely, “A ll operations should be so devised as to p revent recurrence of decay or injury to th e soft tissu es.” More specifically, our standard should be, “that all operations should be devised so as to prevent injury to th e so ft tissu es, con­ serve tooth function and leav e the mouth in the m ost favorable condition p ossi­ ble.” If all operations are criticized by this standard, little w ill be lacking. N ow let us reconsider, for purposes of em phasiz­ ing, the principles w hich should be fun­ damental. Here I shall disagree w ith Dr. Orton a bit in the order of im portance. A study of the oral cavity, its teeth and the condition in w hich w e find it, lead m e to the b elief that the fundam ental consider­ ation is that of the physiology of the teeth and their supporting structures. S in ce everything hum an in health or d is­ ea se is based upon th e physiology or its disbalance, I feel th is should be placed first. Organs have certain anatom ical form s since nature h as found those forms best suited for the function (physiology) that organ is to perform.' If w e under­ stand the physiology of the teeth it is lik e know ing the alphabet,—all e lse opens up to us and w e se e reasons in the nor­ mal occlusion, the arrangem ent of the

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teeth, their articulation and their won­ derful anatom y. To the rational being, as Dr. Orton has said, to act according to nature is to act according to reason. Thus, since everything in nature has rea­ son (but to be sought) we must act with her, and in all operations strive to but pattern after her. Since the m ost im ­ portant duty of the tooth is its function, and since the health or balance o f the teeth th em selves and their surrounding tissu e is dependent upon their function­ ing norm ally, this becom es the truly fun­ dam ental principle of all dentistry. A study of the physiological functions of th e teeth brings us to a consideration of th e anatom y of the teeth and of their occlusion and articulation. W e find that any deviation from the true to type anat­ omy or occlusion brings about a physio­ logical disbalance, that allow s degenera­ tiv e changes to follow in their normal sequence. So then, as Dr. Orton has em ­ phasized, a study of dental anatom y and of norm al occlusion by the dental pro­ fession is absolutely n ecessary if we are to produce crowns, bridges, inlays or fillings that perm it of normal p hysiologi­ cal function, w hich m eans health. To- discuss th e portion of th e paper dealing w ith dental anatom y would be but tak in g up time, since I would but be follow in g the leader, and I w ill try to call your attention to certain steps th at can be taken to aid in reformation. W hat do we, as crown and bridge w orkers, lack? F irst, a standard of op­ eration and secondly, a general standard of criticism . There is no authority, no authorized opinion, no uniform ity of tech ­ nic or of teaching, and we believe th is should be remedied. W hat can be done? W e believe in the n ecessity for an organization of crown and bridge workers who can go into this su b ject carefully and sincerely, and not lea v e it to one man or only a fe w to spend a life-tim e, as did Dr. G-. V. Black, for cavity preparation, to bring h is sub­ ject up to a science. W e believe w e can so standardize and cla ssify principles as

to no longer m ake it n ecessary for each m an singly, thru lo n g years o f experi­ ence, to set up a personal standard that m ay or m ay be correct. T.his work is of a highly specialized nature, requires studies of m any subjects, and is so broad that no other field can equal it in its com plexities. To be su ccessfu l m eans great sp ecial­ ization in pulp canal operations, since m any are the teeth that are to be crown­ ed or carry bridges that require expert pulp canal treatm ent. In this connection there is required a know ledge of R oent­ genology as w ell. T he bridge-worker m ust be equipped either to do th is him ­ self, or to refer the patient for that work. It. m eans that a man m ust be a physiolo­ g ist and an anatom ist, both com plex re­ quirem ents. It m eans th at he m ust have a know ledge of normal occlusion and its deviations to' an exten t even greater than the orthodontist. It m eans that he m ust be a diagnos­ tician of the h igh est type since a correct diagnosis is half the treatm ent. It m eans that he m ust have a know l­ edge of anatom ical articulation equal to th at of the m ost expert prosthetist, sin ce a disregard of th is m eans a com plete fa il­ ure and loss of teeth. T his m ost com plex sp ecialty needs for its m aking an organization that w ill bring all of its questions into the light of truth and science, and for th is I am striving. T his organization m ust , be either as a section of the N ational, or independent of it. H ow ever it is to be— le t us have it! I thank you.

,

,

F. IV. F rahm D . D . S ., Los Angeles Calif.

W hen invited by the com m ittee, in re­ sponse to a request from Dr. Orton, that I should d iscuss h is paper, I consented to do so if I could have a copy for se v ­ eral days prior to th e m eeting. I felt that it would not be fair to Dr. Orton and the m em bers of th is association if such an able and very im portant paper

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did not receive careful study and consid­ nicians, each contending that he has eration. m astered the on ly su ccessfu l method. It I tak e great pleasure and consider it a ought not to be so. W e ought to h ave a definite system of applied d en tistry in privilege to m ake the few remarks that crow n and bridge work based upon fun­ 1 shall offer. It is not m y intention to discuss every point or angle of the paper, dam ental principles th at are as fixed as the law of gravity. for I could not hope to do so if I should try, but shall confine m yself to two or If the love that the student of today three phases of th e subject in hand. show s in the work of m aking study casts H aving been a close observer of w hat of the case in hand is a mirror th at re­ the essa y ist is doing in the field of crown flects the tendency of th e practitioner of and bridge work and reading the articles the day, w e can very easily conclude that there are very few such casts made. that he has w ritten from tim e to tim e on this subject, I fee l that he has chosen a L ikew ise if the reports of salesm en for rather w eak man to d iscu ss his very able dental supply houses are worth anything, paper. N everth eless, I trust that my few th ese sam e casts could not be mounted remarks m ay help to em phasize the on anatom ical articulators. Such articu­ points that seem very im portant to my lators are not to be found in m ost of the offices of th is day for one reason or an­ mind. The crown and bridge work of ten other. Many of the larger and m ore dif­ ficult restorations are entrusted to the years ago is no longer to be considered com m ercial laboratory. as standard. The tech n ic follow ed in those days can not hope to bring the re­ I would lik e to urge th e n ecessity of not only m aking ca sts of the case and sults that are dem anded of the operator of this day. the study of th ese after th ey are mount­ ed on an anatom ical articulator accord­ The search ligh t from the R oentgen Ray tube brings out too clearly the de­ ing to the characteristics of the case, but also the need of constructing the restora­ fects that w ere not noticed in those days. tion under the supervision of the opera­ B ecause there w ere flaws in our early tor who studied and planned the case. technic and in the finished product is Som etim es a patient com es to our office no reason w hy th ey should remain this day or condem n th is w hole branch of for a filling and we are perm itted to our endeavor. It should be the clarion look upon a nearly perfect articulated call for more careful tech n ic and a stand­ set of teeth w ith w ell defined cusps and ardization of the m ethods to be followed sulci. H ere is a privilege that each man under given conditions. In guiding the should avail h im self of, nam ely, m aking mind of the student into the labyrinth casts of the case and face bone m easure­ m ents, m ounting th ese ca sts a c c o r d ­ of procedures to be follow ed in restoring ingly, and spending m uch tim e over lost dental organs, w e are im m ediately confronted w ith the question, “W hat them in study. It w ill w ell repay the shall I teach?” The text-books of the tim e and effort. day are largely h istorical in character, T his method w ill give th e student a som e more or le s s ancient, tho they bear clearer conception of the tw o arches as a recent date on the copyright page. a w hole and th eir relation to each other, the relation of each tooth to its neighbor, W hat is the instructor to do? W ell, he does w hat m ost m en under sim ilar con­ its antagonist, and th e whole. It w ill surprise you w hat a liv ely in terest th is ditions would do, teach es w hat he has w ill create for you in dental anatom y. I been taught in college and found in the old school of hard knocks. Thus, from know of nothing more beautiful in na­ the fifty or more colleges of the land, ture than perfect teeth arranged in are turned out the “57 v a rieties” of tech ­ arches that harm onize and functionate as

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God intended th ey should. I h ave visited art galleries and admired th e beautiful pieces of statuary done in m arble by a m aster hand. S till to m y mind, th ese in all their beauty lack som ething when compared w ith a perfect human tooth. W hen w e attem pt to replace som e of th ese lost teeth , build up a broken arch and restore an articulation, w e must have a very intim ate know ledge of each m em ber of the arches, their relations to each other, the relation of th ese arches to each other, and the size of the mandi­ ble and the incline plane of th e temporo­ mandibular articulation. W e cannot ig­ nore this articulation, neith er can we ignore the incline plane along w hich the condyle travels. U pon th ese depend the arcs known as th e com pensating and lat­ eral curves. A s th e e ssa y ist has pointed out, the m axillary m olars and bicuspids incline buccally, w hile th e mandibular teeth in­ cline lingually from th eir lon g axis. T his fact is largely due to th e incline plane of the mandibular articulation,— som ewhat modified by th e triangular construction of the m asticating m achine. B ecause of th is it w ill be noted that th e degree of inclination is not the sam e on both sides of the individual. Our bridge or even crown restoration m ust be of such a character that it w ill not interfere w ith th ese curves, other­ w ise undue stress w ill be placed upon the restoration, w ith a subsequent failure of the abutm ents or piers. H ence th e im ­ portance ' of know ing the exact size and triangular construction of th e mandible w ith its paths of m ovem ent a s governed by the incline plane of th e temporo-mandibular articulation. W e cannot ignore one of the controlling forces and expect to g et la stin g and beneficial results. A fe w words in regard to the contour of th e individual crown. It is a very dif­ ficult m atter to obtain an exact copy of th e natural tooth by th e old band or col­ lar crown. A fine technician m ight suc­ ceed in contouring such a collar and get th e resu lts after som e tim e sp en t at the

chair. The average man could do better if he would adopt the m ethod advocated by the essa y ist. T he lingual and buccal construction of the human tooth is far from being alike. T his holds true of the m esial and distal surfaces. T h ese differ­ ences have a very im portant significance, sorry th a t I do not have the tim e to dw ell on th ese. Suffice to say that the lingual surfaces of the m axillary bicus­ pids and molars and the buccal surfaces o f th ese sam e mandibular teeth are more or le ss flattened in the middle third, w ith a very marked convexity at the gingival. Since the food p asses largely over th ese surfaces in the. process of m astication it would m ean injury to the gum tissu e if this marked curvature w as absent. W hen a crown is m ade that does not embody this feature, the tooth is w ell started on the road toward pyorrhea alveolaris with our consent and encouragem ent. It does not tak e a man w ith a long head to see that th e two incline planes of the occlusal surfaces of a tooth that unite to form the medio-distal sulcus are the sam e length. S till how few crowns and bridges em body th is feature. Nature, in order to m ake the tooth efficient made th e tw o w orking incline planes, (nam ely the buccal incline of the lingual cusps of the m axillary teeth and the lingual in­ cline planes of the buccal cusps of the mandibular teeth ) longer than the other tw o planes that aid in form ing the rect­ angular groove. T his gives the teeth one-third more surface for crushing food. If the reverse condition is carved into the crown or bridge, w e reduce its working capacity, m aking the passive cusps too long and thus bring a leverage on the restoration w hich w ill surely num­ ber the days of u sefu ln ess of the bridge or crown and the life of the abutm ents and pier supporting it. There are m any more features in th is m ost excellen t paper th at I would lik e to discuss, but m ust close for it would make the d iscussion too lengthy. I w ant to thank Dr. Orton for th is ex­

ORTON.— PREDICAMENT OF CROWN AND BRIDGE WORK. cellen t paper and h is appeal for stand­ ardized crown and bridge work. FORREST H. ORTON, D. D. S., St. Paul, Minn: I have nothing further to add excep t to say th at I heartily endorse the su gges­ tion m ade by Dr. Knoche in support of the N ational Crown and Bridge A ssocia­ tion. The m en who are in terested in teachin g crown and bridge work, and those m en who are m aking a sp ecialty of

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it, should g e t to geth er and decide upon som e fundam ental principles; not to get together and exploit som e one method, because a m ethod is only valuable to the man who in ven ts it, or chiefly valuable to him ; but fundam ental principles are im portant to all o f us, and if we can have such an association w e m ight continue to m ake such strid es as have been m ade in recent years by orthodontists. (Ap­ plause) .