The Denture Space Through Life*

THE DENTURE SPACE THROUGH LIFE* B y E D S O N J. F A R M E R , D .D .S ., B u ffa lo , N .Y .

H E R E are certain broad fu n d a­ m ental principles w hich form the basis of all preventive and restora­ tive dentistry. I t is essential, therefore, th a t w e have these concepts constantly in m ind, and th a t dental trea tm e n t or diagnosis should alw ays be based upon these principles th a t the quality of our dental service may be of the highest order. Q u ality is never an accident; it is alw ays the result of high intention, sincere effort, intelligent direction and skilful execution. I t represents the wise choice of m any alternatives, a w ealth of cum ulative experience, and it also m arks the quest of an ideal, a fte r necessity has been satisfied and usefulness achieved. I t is my purpose to lay stress upon one of these fundam ental concepts; the subject of occlusion and articulation of the teeth, and, more particularly, a con­ sideration of the denture space. T hese tw o factors in dental w ork are so in­ tim ately related th a t it is almost impos­ sible to consider them separately. W h ile the subjects of occlusion and articulation have had m ore th an th eir share of consideration in dental re­ search and literatu re, the denture space has had but scant notice in com parison. In fact, the very m ention of the w ords d en tu re space usually calls to m ind the image of an edentulous patient, and the subject of prosthesis. I t is hoped th a t

T

*Read before the Section on Full Denture Prosthesis at the Seventy-Fourth Annual Session of the American Dental Association, Buffalo, N. Y., Sept. 15, 1932.

Jour■A. D. A., June, 1933

w h at is here offered w ill change this tendency so th a t the d en tu re space w ill receive th a t consideration w hich it rig h tfu lly deserves; and that, by this means, m ore favorable conditions w ill be m aintained in dental treatm en t, so th at, w hen the necessity fo r full denture replacem ent arises, the m ost favorable conditions w ill exist fo r these resto ra­ tions. Foundations fo r the d en tu re space are laid d u rin g th e early developmental stages. T h e form ation of the dental ridges is one of the early factors in establishing the d en tu re space. C on­ jointly w ith ridge g ro w th are em bry­ onic tooth grow th, form ation of bony and soft stru ctu res th a t w ill ultim ately result in the establishm ent of bounda­ ries and determ ination of the n atu re and characteristics of th a t cavernous portion of the m outh, p a rt of w hich becomes the d en tu re space for n atu ra l dentition. In this early stage, the den­ tu re space is influenced by nutrition, habit and reg u lar eruption of the teeth ; w ith corresponding norm al development of the h ard and soft structures contin­ gent to the d ental mechanism. T h e eruption, alinem ent and m ainte­ nance of the deciduous teeth are next to be considered. H ere, w e have vital units of im p o rtan t bearing on the den­ tu re space. A t this tim e, definite ridge relationships are being established, w ith corresponding stru c tu ra l changes, and the proper care and preservation of deciduous teeth are im portant. T h e

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p rem ature loss or im proper trea tm e n t of these early units produces unfavor­ able conditions as regards denture space. I t m ight be w ell to m ention here such factors as the presence of pathologic tonsils and adenoids and deviated nasal septum s; thum b sucking and im proper postures, w ith consequent- spatial im ­ pingem ent and deform ity. T h e decidu­ ous teeth establish conditions prep ara­ tory to the eruption of the perm anent d e n titio n ; therefore, care and attention are of g reat im port at this early stage. As the perm anent teeth are gradually b ro ught into functional position, w e have an intim ation regarding the course of fu tu re development. O rth o d o n tic trea tm e n t is often indi­ cated here and, a t „ this tim e, is very effective in relation to denture space m aintenance as w ell as tooth alinem ent. I t is wise always to in stitute corrective m easures at the earliest possible tim e w hen abnorm alities appear im m inent. U sually, a t this tim e, operative w ork is in stitu ted w here caries appears, and the long course of dental treatm en t, on w hich the end results are so dependent, is started. In the placem ent of even the sim plest occlusal filling, w e have to con­ sider not only the filling of the cavity, b ut also the m aintenance of balanced occlusion and harm ony of n atu ra l ja w relationships. T h is ideal holds good for all operative procedures from the sim ­ plest to the most complex type. N ext, w e are confronted w ith loss of the teeth. W h e n a u n it of the n atu ra l d ental m echanism is lost, as, for in­ stance, is frequently the case w ith a low er first perm anent m olar, a dishar­ mony exists w hich brings about re tro ­ gressive changes. H ere again, in the field of crow ns and bridgew ork, the ideal is not m erely the replacem ent of the missing unit, but its replacem ent so as to m aintain norm al occlusion and

n a tu ra l den tu re space. T h is is tru e of simple or m ultiple u n it replacem ent. In regard to this w ork, it m ight be w ell to m ention here th a t we can, of course, never com pletely replace n a tu ra l units th a t w ere in norm al function. T h e best th a t w e m ay hope for is th a t re­ placem ents shall be so w ell w ith in the lim its of tissue tolerance th a t the m ini­ m um am ount of tissue change w ill en­ sue. T issu e tolerance is another factor w hich has heretofore been associated alm ost exclusively w ith den tu re w ork. T h e fact is th a t tissue tolerance enters into the situation from the placem ent of the sim plest occlusal filling to th e in ­ sertion of fu ll dentures. A simple operative restoration, if o ut of occlusal balance, w ill produce trau m a. I f this trau m a is w ith in the lim it of tissue tolerance, the supporting stru c­ tu res com pensate fo r th e trau m a by stru c tu ra l changes in th e bone an d soft tissues. I f the tissue tolerance is ex­ ceeded, degenerative processes take place, resulting in the ultim ate loss of the offending unit. I f the replacem ent of this lost u n it is also o ut of harm ony w ith proper function an d beyond tissue tolerance, it accelerates the degenera­ tive changes, producing fu rth e r loss and m utilation. Restorations, either operative, crow n and bridge, or prosthetic, w hich pro­ duce sufficient trau m a to bring about m arked stru c tu ra l change, are d e tri­ m ental even though the supporting units are not lo st; as, for instance, w h en lack of balance of a bridge or p artial denture is com pensated for by the reaction of the supporting tissues. H ere, u n fav o r­ able ridge relationship and im proper spatial conditions occur, w ith th e ir a t­ te n d an t deleterious effects at th e tem ­ porom andibular jo in t, an d accom pany­ ing m uscular changes. So, here too, w e

F arm er— D en tu re Space T h ro u g h L ife m ust realize the great im portance of the establishm ent of balanced occlusion in the m aintenance of proper den tu re space. W ith an increase in extent of the restoration and the num ber of units involved, there is accordingly a m ore m arked effect on the occlusion and den­ tu re space from the replacem ent. T h e need for balance and harm ony becomes increasingly evident, and it is at this ju n c ­ tu re th a t the denture space is ordinarily accorded consideration. I t m ight be appropriate at this tim e to say a w o rd in regard to the retention of n atu ra l teeth w hen they are out of occlusion and cannot be brought into norm al function or w hen they ten d to produce deform ities of the ridges. D e n ­ tal units of this type, even though they be of the n atu ra l dentition, should be elim inated surgically if they in terfere w ith function of the dental mechanism as a whole. T h e re is no reason to be­ lieve th a t the pathologic condition pro ­ duced by a n atu ra l tooth is any m ore to be condoned than th a t produced by a dental restoration. T h e re has been a tendency in this regard to be too lenient w ith n atu ra l units w hen they tend to produce or m aintain pathologic condi­ tions. O ne of the commonest examples of this is the tendency to retain the upper or low er an terio r teeth afte r the pos­ terio r teeth have been lost. I t m ust be borne in m ind th a t these statem ents are m erely generalizations, and th a t w hile each particu lar case m ust be decided according to the circum stances, this p articu lar practice has so often been the cause of producing unfavorable condi­ tions in regard to tissue changes, ja w relationships and tem porom andibular im pairm ent th a t it is necessary to call attention to this p articu la r type of case. As an example, in the typical low er

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lingual b ar case, w e have resorption rapidly tak in g place beneath the sad­ dles w ith resu ltan t lack of proper oc­ clusion ; and even w hen these bridges are kept in occlusion by repeated rebasing, the stru c tu ra l changes taking place in the m andible are such as to cause fu tu re com plications reg ard in g occlusion and denture space. L et us then give th o u g h t to these facts and duly consider w hether, in view of the changes to w hich I have referred, the proposed restoration is still indi­ cated, rem em bering that, in removable w ork, especially dentures, th e coopera­ tion of the patient becomes an increas­ ingly im p o rtan t factor. O ne of the m ain problem s in th e fu ll denture restoration is th e separation of edentulous jaw s in a m an n er w hich is not only physiologically tolerable, but also acceptable for funqtion and es­ thetics. In the den tu re space, the posi­ tion of the restoration is very im portant, bearing directly on balanced occlusion and articulation in obtaining favorable results. T h e den tu re space, as w e visualize it in relation to full den tu re construc­ tion, comprises th a t p a rt of the oral cavity w hich is bounded by the lips an ­ teriorly, the cheeks laterally, the tongue internally, the m axillary ridge and the palatal v a u lt; the m an d ib u lar ridge be­ low, the m uscular attachm ents at the borders of the ridges and palate, and the continuation of the oral cavity pos­ teriorly. T h e fact th a t the den tu re space is modified by ja w relation and occlusion of the n a tu ra l or artificial dentition and functioning muscle attachm ents forces us to seek a den tu re space w hich is in ­ dividually norm al and adapted to the best possible functional requirem ents in the p articu lar case involved. W e m ust appreciate, therefore, th a t the bite is

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only one of four im portant factors and m ust be properly related w ith stru ctu re, function and esthetic values. T h e bite not only has an im portant role in the initial w ork of denture con­ struction, but also m ust be considered in th e tissue changes th a t occur in th e w earing of dentures. W h e n tissue changes occur, such as resorption, th e re is a decrease of the opening com ponent. T h e originally established centric ja w relation becomes changed, ow ing to the alteration of the denture space, cusp interference, loss of balance and tissue trau m a resulting, w ith unfavorable con­ ditions disrupting the denture m echan­ ism as a w hole. A result of this process is seen in the fam iliar flabby ridge w here trau m a has caused extensive bone resorption, and surgical w ork is some­ times necessitated in correction. If bal­ ance is m aintained in keeping w ith tis­ sue changes, flabbiness of ridges is avoided. T h is applies to partial as w ell as to full dentures. T h e initial establishm ent of the bite and centric ja w relation depends, of course, on the case involved; on the condition of the underlying tissues, the m anner in w hich the teeth have been lost, the m usculature, tem porom andib­ u la r conditions, esthetic values and oth er conditions w hich m ay have to do w ith the den tu re space. W h ile w e have no positive means to determ ine the exact opening w hich w ill secure the theoretical m axim um efficiency for musculatory function, th e range of the m usculature is com paratively w ide and th ere are general considerations w hich are of im portance in this respect. T h e patient seems to tolerate too g reat a degree of closure w ith pros­ th etic dentures m uch more readily th an too g rea t an opening, and, in this re­ gard, w e m ust bew are of insufficient tongue space, the presence of bulging

lips and sagging cheeks an d speech im ­ pairm ent. In some cases, th e desired opening cannot be established u n til a num ber of dentures have been m ade. T h is is w h at m ight be called corrective treatm en t, in w hich the desired opening com ponent (b ite ) is g rad u ally ap­ proached w hile w e keep w ith in tissue tolerance an d m aintain th e p atien t’s com fort. T h e field of denture space is a p ro m ­ ising one for fu rth e r study. R udolph H an a u w as ju st em barking on research along these lines and had done consider­ able p rep arato ry study in th is direction. H is unfinished w o rk on tissue changes u nder full dentures promised valuable contributions to come. T h e fact th a t he realized th e im portance of spatial elem ents is evidenced by his trea tm e n t of w h a t he called the plane of o rien ta­ tion, and its inclusion in the articu latio n quint. I t seems th a t he w as about to apply the fo u rth m athem atical concept to d en tistry ; in oth er w ords, th e ele­ m ent of tim e. I have attem pted to present a m ore com prehensive conception of the den­ tu re space, and to show its u n ity w ith balanced occlusion, articu latio n , and com fort. A t the end of the trail of preventive and restorative d en tistry ; afte r the gam ut of treatm en t from all o th er branches of o u r a rt has been run, the patient comes to us relu ctan tly at last fo r fu ll d en tu res; and here, w here w e have the least to w o rk w ith , so much is expected, and w e should give th ought to th e fact th a t dental treatm en t, of w hatever n atu re it may be, should al­ w ays ten d to m aintain a norm al condi­ tion fo r the dental mechanism as a w hole. T h e benefit of the p articu lar type of dental service w hich w e render should not cease w ith th e loss, fo r in ­ stance, of a filling, a bridge or a p artial

F arm er— D en tu re Space T h ro u g h L ife denture, but should be passed on through subsequent stages, so th a t w hen the necessity for full dentures arises, all previous dental trea tm e n t w ill have been conducive to th e m ost favorable conditions for this final service. 333 Linwood Avenue. DISCUSSION I. L ester Furnas, C le v e la n d , O h io : “Quality is never an accident; it is always the result of high intention, sincere effort, intelligent direction and skilful execution. It represents the wise choice of many alternatives, a wealth of cumulative experience, and it also marks the quest of an ideal, after necessity has been satisfied and usefulness achieved.” I have quoted a portion of the first paragraph of Dr. Farm er’s paper because it is one of the finest statements of fact that I have ever read. I wish that this statement could be placed on a suitable card and displayed on the wall of every dental office and laboratory in the country as an inspiration and guide to the members of our profession. It could not but have a good influence on all who read it. The constantly changing and ever varying denture space has offered one of the baffling problems of denture technic throughout the years. It is practically the only dimension in denture construction that has no definite scientific basis for its establishment, being usually a r ­ rived at by guessing based on experience. “Denture space” does not seem to me to be the best term to use. “Vertical dimension” seems more in keeping with the other terms employed and more definitely suggests our problem. It is true that the vertical dimension may be considered by some as only one feature of the denture space, but the fact remains that in constructing the dentures, the dentist is chiefly interested in this opening component or vertical dimension, and he chooses to solve the other problems as they arise. T he term, “vertical dimension” might be defined as the vertical distance at the median line between the crest of the mandibular and maxillary ridges of the edentulous mouth. Of course this definition would not be suitable were a full complement of teeth present, but I am assuming that there is no especial interest here in the correct vertical dimension in such cases. T here is but one method for establish­ ing this correct measurement that is known to me or that even approaches scientific ac­

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curacy, and it has many questionable aspects and is often impossible to u se; that is, the method of making preextraction records. This method is questionable many times because of the fact that it is sometimes difficult to deter­ mine whether it is advisable to reestablish preextraction conditions and, in many in­ stances, such a measure would be very defi­ nitely contraindicated. It is often impossible to use this method regardless of how desirable it might be, because of the inaccessibility of the patient. The various methods of making these preextraction records should have no place in this discussion and will therefore re­ ceive no consideration, but those interested will find the dental literature full of papers covering every detail of the subject. Another method advocated and used by a group of dentists calls for the construction of occlusion rims to a certain definite height. Different men use different measurements varying all the way from 18 to 24 mm., depending on the ideas of the individual. Just how or why any particular measurement is chosen seems to be a mystery, but when once it is selected, it is used in every case regardless of shape or size. This method is obviously very unscien­ tific regardless of how practical it might seem. As fa r as I am aware, only one man has worked out a definite and individual technic for the establishment of this vertical dimen­ sion in each individual case. The method, th at of A. K. Parks of Montgomery, Ala., may be described as follows: W hen the pa­ tient has a full complement of natural teeth and these teeth are in centric occlusion, this affords the correct vertical dimension for the patient at his present age. W hen he becomes edentulous, the stopping place in the closing movement becomes highly problematical. In the former case, the opening and closing movement is centered below and posteriorly from the condyle heads. In the edentulous case, the center of the movement is the same until the condyle heads meet resistance in their backward trend, at which elevation the axis is changed to the condyle heads. If we can know, then, when this change of rotation control takes place, we shall know the correct stopping point or correct vertical dimension of that patient. For determining this correct point, Dr. P arks’ method is as follows: “Fash­ ion from 10 gage stiff round wire an appliance similar to the bandage grip of an old-fash­ ioned interdental mandibular splint and solder a horizontal pencil holder to the anterior ex­ tension. W ith hard wax, attach this to a

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stiff, accurately fitted lower baseplate. Place this in the mouth and secure in position with a rubber band passed under the lower jaw. Place the record card to the side of the face, at right angles to the pencil and in contact with the point. Trace an outline of the upper border of the card on the face to facilitate replacement. Have the patient retrude and move from the extreme open to extreme closed position and vice versa. The pencil will record on the card arcs from two centers. A t the point of intersection of these two arcs will be the correct point of closure for this individual case and if the point of the pencil is held at this point and the distance between the crest of the upper and lower ridges measured at the median line, that measurement will be the correct vertical dimension for the case. The point of division of this distance between the upper and lower occlusion rims depends upon the esthetics of the case.” In my hands, this technic has not been so successful as I had hoped it might be, but I believe that when an accurate method is worked out, it will be based upon a technic similar to that of D r. Parks, and I recommend it to you for further research and investiga­ tion. I believe with D r. Farmer in the im­ portance of the vertical dimension in denture construction, and I know of no better method than the one which employs equal propor­ tions of practical experience and esthetic considerations. D r. F arm er: D r. Furnas stated that it is his practice to establish the desired opening with one set of dentures regardless of the amount of closure which has been present in

previous dentures. There are many factors which should be considered: (1) the degree of opening, which is necessary to establish proper facial contour and function; (2) the age and temperamental make-up of the pa­ tient; (3) whether the previous dentures have been worn long enough for the muscle balance to be quite permanently established, and (4) the shape and density of the ridges. If these factors are favorable, the desired condition might be established at one stroke, but, with unfavorable conditions, it is always the safer procedure to bring about the desired change by a series of dentures and we are sure not to exceed tissue tolerance. If any tissue is subjected to a greater strain than it can safely tolerate, destructive changes are sure to fol­ low. Th e majority of cases can be handled with one set of dentures since the opening is usually not great. There are two basic con­ ditions which we must always bear in mind no matter what branch of dentistry we are considering: balanced articulation and tissue tolerance. Articulation is basic so far as growth and development of the ridges and face is concerned. It is basic in operative and prosthetic dentistry. In orthodontic and pyor­ rhea treatment, occlusion is basic, and success or failure depends on the stresses placed upon the supporting structures. Th e more nearly the occlusion approaches the ideal, the more nearly will there be the muscle balance and proper facial contour. Finally, the more nearly perfect the balance of occlusion in the natural teeth, the more nearly ideal will the ridge relation be for the support of artificial den­ tures when the permanent teeth are lost.