- Email: [email protected]
Research on the Reaction of Tissues Supporting Full Dentures
RESEARCH ON THE REACTION OF TISSUES SUPPORTING FULL DENTURES*
By ELBERT C. PENDLETON, D.D.S., and HENRY GLUPKER, D.D.S., Chicago, 111. H IS report deals with the tissue re actions most commonly present in the months o f edentulous persons wearing artificial dentures. It is the hope that these observations and the studies in the minute anatomy of the jaws may be correlated to broaden our knowledge o f the structures in the denture area and contribute to successful treatment in full denture prosthesis. In selecting material for this study, a few models were chosen that were thought to be representative of the many case records showing the edentulous up per ja w which supports a fu ll maxillary denture opposed by the partially eden tulous lower jaw . T his choice o f mate rial was based upon the assumption that tissue reactions to full dentures are com mon to both the upper and the lower jaws. T h e character o f the structures in each ja w is similar, although their form and distribution show considerable varia tion. T h e edentulous upper ja w presents a field favorable for study when considered separately, and it was thought that a more dependable analysis o f tissue reac tions o f the upper ja w could be made by considering cases having the maxillary dentures opposed by natural teeth in the lower jaw . It is regrettable and quite
remarkable that no records are available o f cases presenting the completely eden tulous upper ja w opposed by a low er jaw with the complement o f natural teeth. These records were secured at the time when the maxillary dentures had proved unsatisfactory. T h e models record the condition o f the tissues which had de veloped during the period that the den tures were worn. T h e models o f each case were first studied singly; then, the group was examined for characteristics common to each case, which w ere: the general form and condition o f the bone and soft tissues in the palate; the general form and condition o f the bone and soft tissues o f the residual alveolar ridge of the upper jaw , and the number, position and condition o f the natural teeth in the opposing ja w as related to the different regions o f the maxillary denture area. Functional stress, which is considered as the condition most commonly influenc ing the reaction of the tissues supporting full dentures, is the only etiologic factor considered in this study. T h e possible results o f the normal change in the form o f the residual ridge follow ing the loss of the natural teeth and those resulting from pathologic conditions or injuries are not taken into account. Reactions from these causes are classed among un usual influences and are not considered as pertinent to the problem. In the interpretation o f these clinical studies, the forces o f mastication are ana lyzed according to W ilso n ’s use of the
T
*Read at the Seventieth Midwinter Clinic of the Chicago Dental Society, Feb. 27, 1934. *From the Prosthetic and Research depart ments, Chicago College of Dental Surgery, Dental Department of Loyola University.
Jour. A .D .A ., January, 1935
76
Pendleton and Glupker— Reaction of Tissues Supporting D entures terms positive and negative force. A posi tive force is one that tends to seat the denture more firmly in contact with the supporting tissues; a negative force one that tends to displace the denture.1 “ Posi tive force” as used herein is synonymous with function. “ Negative force” indi cates the lack o f function. Figure 1 shows models o f the eden tulous maxillary denture area and the partially edentulous mandibular dental arch in a man, aged 45. In this case, the reactions o f the tissues o f the maxillary
77
opposite side o f the arch is irregular. Its vertical height is reduced and the buccolingual width o f the ridge is narrow as far posteriorly as the maxillary tuber osity, which shows a covering o f pendu lous tissue. T h e palate appears smooth, with a thin soft tissue covering. T h e labiobuccal structures are thin and loosely attached except in the regions o f the tuberosity. T h e natural teeth in the mandibular arch are somewhat unequal in length.
F ig. 1.— M a x illa r y and m an d ibu lar m odels from m an, aged 45.
denture area w ere studied as affected by the forces transmitted by the six anterior teeth o f the opposing arch. T h e right side of the residual ridge of the maxillary model is quite symmetrical from the me dian line to the molar region. Here, the ridge widens and terminates at the tu berosity, which is covered with hyper plastic tissue. T h e residual ridge on the
F ig. 2.— M a x illa r y and m an d ibu lar m odels from w om an , aged 39. A fu ll m a x illa ry d en ture and partial m an d ibu lar denture had been w orn ten years.
T hose on the right are in a vertical po sition, while those on the left side of the arch are rotated and present a labial inclination. It is assumed that the posi tion o f the natural teeth directed mastica tion toward the right side o f the arches. T h e “ positive force” was transmitted to 1. W ils o n , G . H .: M a n u a l o f D ental P ros the right side of the maxillary arch. thesis, E d . 4, P h ila d e lp h ia : Lea and Febiger, T h e maxillary tuberosity o f the left 1920, p. 318.
78
T h e Journal o f the American D en tal Association
side, which is diagonally opposite the area receiving “ positive force,” shows a pendulous development of hyperplastic tissue. Figure 2 shows the edentulous maxil lary and partially edentulous mandibular models from the case o f a woman, aged 39. T h e residual ridge on the right side of the maxillary model is of normal form. O n the left side o f the median line, the arch o f the anterior portion o f the ridge is reduced in size. T h e cuspid region is prominent and the bicuspid area is about one-third the size o f the same area on the opposite side o f the arch. T h e tuberosity
T h e right side o f the mandibular arch presents a more favorable number and arrangement o f natural teeth for mastica tion than does the left side. T h e abrasion o f these teeth bears evidence of their use. Again, it is assumed that “ positive forces” in mastication were directed toward the right side of the maxillary arch. Figure 3 is one o f the typical exhibits o f the reaction o f tissues to full dentures. T h e edentulous maxillary denture area,
F ig. 3.— M a x illa r y and m an d ibu lar m odels fro m m an, aged 55.
shows a region considerably enlarged and covered by hyperplastic tissue. T h e vault o f the palate is irregular and has a thin covering o f mucosa. T h e six natural teeth o f the mandibu lar arch present irregularities in vertical length. T h e left central incisor is longer by one-half the length o f its visible crown than the right bicuspid measured from the mesial surface area. T h e right cuspid and the left bicuspid are in about the same horizontal plane.
F ig . 4.— M a x illa r y and m and ibu lar m odels fro m w om an , aged 6 0 ; fu ll m a x illa ry denture w orn five years.
and the partially edentulous mandibular arch of a man, aged 55, are shown. T h e abrasion o f the natural teeth on the right side, as w ell as the absence o f the man dibular molar and bicuspid teeth on the left side, identifies the right side o f the arches as that habitually used in mastica tion.
Pendleton and Glupker— Reaction of Tissues Supporting Dentures T h e model o f the maxillary denture areas shows the residual ridge on the right side o f the median line to be smooth and symmetrical. T h e left side records struc tural changes in the bone and its cover ing o f soft tissue. A general reduction in size and change in form o f the ridge are noted on the left side of the median line, except in the cuspid and tuberosity re gions, where the unused side presents characteristic irregularities in structure. T h e lingual portion o f the ridge appears considerably reduced in size as compared
F ig. 5.— M a x illa r y and m an d ibu lar m odels from w om a n , aged 52. A fu ll upper denture had been w o r n six years.
to the opposite side o f the arch. Evidence o f hyperplastic tissue is seen at the left maxillary tuberosity region. These con ditions indicate that the “ positive forces” acted on the right side o f the maxillary denture area. T h e record o f M rs. C., aged 60, is seen in Figure 4. A full maxillary den ture was w orn five years. T his case pre sents a rather striking picture on account o f the location o f the remaining teeth
79
and the order in which they appear in the mandibular arch. T h e first and second molars o f the left side are missing. T h e third molar is elongated and inclined mesially. T h ere are signs o f considerable abrasion on the lingual cusps and the distal portion o f its occlusal surface. T h e abrasion o f the buccal cusps o f the right mandibular first molar and first bicuspid and o f the labial surfaces o f the lateral and central incisors points to a predomi nate function on the right side of the arch. T h e position o f the left molar tooth in the arch and the abrasion o f its lingual cusps indicate its use as a balancing mem ber in stabilizing the maxillary denture. T h e maxillary model shows a w ellformed palatine surface. T h e residual alveolar ridge presents a smooth, even ap pearance on the right side o f the arch. T h e ridge on the left side presents a char acteristic depression in the region dia metrically opposite the natural right first molar. T h e maxillary tuberosity on the left side shows evidence o f the develop ment of hyperplastic tissue. T h e inter pretation given after the study of this case is that the “ positive force” was di rected to the right and “ negative force” to the left side o f the maxillary denture area. Figure 5 shows the record o f M rs. B., aged 52, w ho has been under intermit tent observation for six years. T h e max illary denture area presents a condition interpreted as chronic inflammation, which is attributed to stresses from the mandibular teeth that are prominent and o f unequal vertical length. T h e tuber osity regions o f the alveolar ridge are dense and the anterior portion o f the arch o f the ridge is covered by a mass o f hyper plastic tissue. T h e structures o f the vault o f the palate are soft and acutely in flamed. T h e most abraded surfaces ap pear on the posterior molar teeth, the left cuspid, the incisors and the mesial
80
T h e Journal of the American D ental Association
plane o f the buccal cusps o f the mandibu lar right first bicuspid. T h e tissues o f the upper and lower jaws that support fu ll dentures seem to react favorably to functional stresses when the denture base bears a reciprocal relation to these structures. Therefore,
sented by the tissues. T h e dense fibrous tissues are suited by nature to bear the greatest burden during function. T h e highly vascular tissues must be protected from excessive stresses and the freedom of muscle action must not be impeded by the form o f the denture base.
F ig . 6.— B u ccolin g u a l section in third m ola r region o f upper ja w fr o m a m an, aged 38. N C , nasal c a v ity ; P N , palatine n e r v e s ; P A , p alatin e a rte ry ; S D , secretory duct fr o m palatine g la n d s; O M , oral m u cosa; F T , fa t tissu e; E , oral e p ith e liu m ; F C T , fibrous con n ectiv e tissue; M S , m ar ro w sp aces; L C T , loose con n ectiv e tissue on bu ccal su rface o f residual a lv e o la r r id g e ; B M , bu c cin ator m uscle.
the stress o f mastication should be distributed according to the natural characteristics and qualities o f adaptability pre-
T here can be no doubt that the probIem o f tissue reaction to full dentures is one that is influenced by functional
Pendleton and Glupker— Reaction o f Tissues Supporting Dentures stresses.2 N o one factor is o f greater significance than that o f localized func tion. T ench calls our attention to “ the startling difference between the ease with which younger persons learn to wear ar tificial dentures and the continuous d if ficulties o f some o f their elders.8 T his condition is attributed to the universal tendency among adults toward prefer ence for a certain region o f the arch in mastication. T his tendency has a de m oralizing effect on the stability o f the
81
terpretation o f the clinical manifesta tions o f the tissues supporting full den tures : Though the influence of mechanical fac tors on the general morphology of bone tis sue is well established, we know, on the contrary, almost nothing of the exact mech anism of this influence. It is difficult to state the problem, and in short it but gives us an idea of our ignorance. Mechanical actions, especially pressure and traction, can act on the cells, the fibrils, the pre-osseous substance, calcification and
F ig. 7.— B u ccolin gu a l section in bu ccal region o f upper ja w o f w om an, aged 51. P A , palatine a rte ry ; F T , fa t tissue; M S , m arrow sp aces; F C T , fibrous conn ective tissue; E , epithelium c o v e r in g residual a lv eola r r id g e ; B T , bone tra b ecu la e; V , v e stib u lu m ; M , m ucosa o f ch eek; B M , bu ccin a tor m u scle ; L C T , loose con n ective tissue.
artificial denture and the health o f the tissues which form its support. T h e w ork o f Leriche and Policard has been found extremely helpful in the in2. Stansbery, C. J .: T issu e C hanges U nder D entures, J .A .D .A ., 15:3+9-353 (F e b .) 1928.. 3. T e n ch , R . W . : A rtificia l D entures— Final Stage in R estorative Dentistry, J .A .D .A ., 20:1234-1246 (J u ly ) 1933.
the vasculation of bone. . . . When there is no pressure, bone is form ed; when there is strong enough pressure, it disappears. . . . The role of strain on the preservation and thickening of the bone framework is incontestable. This generally arises from the load carried by bone, an organ of sup port; the skeleton is preserved through the exercise of this function. The removal
82
T h e Journal of the American D ental Association
o f a ll s tra in t h r o u g h th e r e m o v a l o f all lo a d has a fa t a l in flu e n ce o n h o n e s t r u c t u r e .4
T h e study o f tissue reactions to arti ficial dentures is both interesting and per plexing. It is deemed more pertinent to the success of full dentures to become fa miliar with the form, character and dis tribution o f the structures normally found in the region o f denture support than to pursue the analysis o f tissue re actions.
study o f the minute anatomic structure o f the denture supporting tissues. T h e structure of the upper and the lower ja w varies greatly in the degree of density. T h e arrangement and distribu tion o f the tissues are uniform ly constant although their character varies somewhat in different persons.5 T h e quality of the tissues has a marked influence on the stability of the artificial denture when it is subjected to func tional stresses. T h e most satisfactory re-
F ig. 8.— A nteroposterior section in m a x illa ry tuberosity region o f man, aged 62. M S , m a x il la ry sin u s; F C T , fibrous con n ectiv e tissu e; M T , m a x illa ry tu berosity; L C T , loose con n ectiv e tissue; P G , palatine g la n d s ; P N , p tery g oid notch (p tery g om a x illa ry n o t c h ); P P , p yram id al plate o f palate b o n e ; 1P M , internal p terygoid m uscle.
According to W ilson , “ N o one factor has so much to do with retention o f arti ficial dentures as the soft tissues.” 1 T his principle is accepted as the premise in the
tention is assured when the soft tissues maintain contact with the entire area of the denture base. T h e denture base must be adapted to the tissues in each region of the denture area according to their
4. L eriche, R ., and P olica rd , A . (trans. by 5. P endleton, E. C. : A n a tom y o f M a x illa Sherw ood M o o re and J. A lb e rt K e y ) : N orm al and P ath olog ica l P h y sio lo g y o f Bone, St. from V iew p oin t o f F u ll D en tu re Prosthesis, L ou is: T h e C. V . M o sb y C om pany, 1928. J .A .D .A ., 19:543-572 (A p r il) 1932.
Pendleton and Glupker— Reaction o f Tissues Supporting D entures capacity to accommodate themselves to the load imposed on them. T h e regions in both the upper and the low er jaw s subjected to the greatest stress during the function o f artificial dentures are the residual alveolar ridges. T h e form and character o f their struc-
83
enough to absorb shock. Its mucous cov ering is dense and well suited to with stand great stress. T h e labiobuccal structures o f both jaw s are elastic, with an abundance of fat and glandular tissues about the muscle fibers. T h e mucosa in this region
F ig. 9.— B u ccolin g u a l section in m a x illa ry tuberosity region o f w om an, aged 58. M S , m ax il lary sin u s; L C T , loose con n ective tissue; B M , bu ccin a tor m u scle ; V , vestibulu m o f ch eek ; M A , bu ccinator m uscle attach m en t; F M , fa t m a r r o w ; F C T , fibrous con n ectiv e tissue; F T , fa t tissue; S D , secretory d u c t; P N , palatine n e rv e s; P G , palatine g la n d s ; P A , palatine a rtery ; N C , nasal cav ity .
tures are adaptable to the function imposed on them. T h e bony process is firm yet cancellous
is w ell lubricated and maintains a quality that is ideal for creating a seal at the denture borders. T h is feature is char-
84
T he Journal o f the American D ental Association
acteristic of the tissues that form the floor o f the mouth and o f those that con stitute the soft palate. W herever valve seal is a requisite to denture stability, the structures seem to have a peculiar quality perfectly adapted to the scheme o f denture retention. T h e vault o f the palate presents many
sis have an intimate knowledge o f these tissues. T h e anatomic material was selected to exhibit the structures typical o f the va rious regions o f the upper ja w that are utilized for denture support. T h e speci mens were chosen from subjects o f va rious ages and from both sexes so that
F ig. 10.— Sagittal section in m edian line in central in cisor region o f upper ja w fro m w om an, aged 58. P P M , palatine process o f m a x illa ; E , oral e p ith eliu m ; F T , fa t tissu e; P R , palatine ru g a e ; 1C , in cisive c a n a l; F C T , fibrous con n ective tissu e; R A R , residual a lv eola r r id g e ; M A , low est p oint o f attachm ent o f depressor alae nasi m u scle ; M G , m ucous g la n d s o f l i p ; L C T , loose conn ective tissue; D A N , depressor alae nasi m u scle ; A N S , anterior nasal spine.
hazards to the stability o f the artificial denture, owing to its form and the varied character o f its structures. It is important that the student o f denture prosthe-
the consistency in tissue quality and distribution in the several regions might be emphasized. Figure 6 shows a section o f the residual
Pendleton and Glupker— Reaction of Tissues Supporting D entures
85
F ig. 11.— S agittal section o f in fe rio r surface o f palatine process o f m a x illa o f w om an, aged 58. P P , palatine p rocess; P A , palatine artery ; S, spinous process on in ferior su rface o f palatine process; O M , o ra l e p ith e liu m ; F C T , fibrous con n ective tissu e; R , palatine rugae.
Fig. 12.— Frontal section in m olar region at union o f palatine processes o f m a x illa o f w om an, aged 51. N C , nasal c a v ity ; IM S , interm axillary su tu re; P G , palatine g la n d s ; F T , fa t tissue; F M , fa t m a r ro w ; R M S , rid g e o f interm axillary su tu re; E , e p ith eliu m ; F C T , fibrous conn ective tissue.
86
T h e Journal of the American D en tal Association
alveolar ridge from a man, aged 38, that is typical of the molar region. In Figure 7, a section from the bicuspid region from a woman, aged 51, shows the same general character and arrangement o f structures. Figure 8 is a sagittal section in the tuberosity region from a man, aged 62, in which the character o f the bone is in marked contrast to that in the pre ceding sections. In the oldest person examined, the trabeculae are line and the m arrow spaces are large. In the youngest
and glands are found beneath the epi thelium at its lingual surface. Swenson refers to this region as the “ pterygomaxillary notch.” 6 Figure 9 shows a section o f the tuber osity region o f a woman, aged 58. C over ing this region is a pendulous area o f dense fibrous connective tissue. Such a de velopment o f hyperplastic tissue is not uncommon in the mouths o f edentulous persons. It presents a condition where surgical measures should usually be rec-
F ig. 13.— F rontal section in bicuspid region o f w om an, aged 51. R M S , rid g e o f interm axillary su tu re; E , e p ith e liu m ; F C T , fibrous connective tissue; P N , palatine n e rv e s; F T , fa t tissue; P A , palatine a rte ry ; C T F , con n ective tissue fibers; B T , bone tra b ecu la e; F M , fa t m arrow .
person, the trabeculae are strong and the m arrow spaces small. (T h e fact that the sections were prepared in a different plane in the young and in the older per sons has no bearing on the character of the bone structure.) T h e mucosa cover ing the alveolar ridge o f the upper ja w is normally dense and symmetrical except at the posterior extremity o f the tuber osity region where loose connective tissue
ommended before impressions are taken for fu ll dentures as hyperplastic tissue is unstable and therefore not suited for den ture support. Figure 10 is taken from the anterior portions o f the alveolar ridge and pala tine process in the median line. T h e 6. Swenson, M . G . : A n a tom y in R elation to E dentulous Im pressions, J .A .D .A ., 20 :10781082 (J u n e) 1933.
Pendleton and G lupker— Reaction o f Tissues Supporting D entures mucosa in this region is firm and some what irregular. Some adipose tissue is found beneath the tunica propria linguad from the incisive foramen. O n the labial surface o f the ridge, the fibrous connec tive tissue is dense as high as the line o f lip reflection, where the muscle attachments are seen. H igh in the incisive fossa toward the anterior nasal spine, there is a considerable quantity o f loose areolar tissue supporting the fibers o f the de pressor alae nasi muscle. From clinical
87
Figure 11 shows a higher magnifica tion o f the palatine rugae in the cuspid region from the same specimen. In mouths that present these highly de veloped folds in the mucosa, great care should be exercised in impression taking for denture construction. W h en these folds, compressed by a closely adapted denture, are irritated by movements o f the denture during function, unfavorable reactions may result in these tissues. D en tures adapted to the palatine surfaces so
F ig. 14.— Frontal section in m ola r region o f w om an, aged 51. E , oral ep ith eliu m ; F C T , fibrous con n ective tissu e; P G , palatine g la n d s ; P P M , palatine process o f m a x illa ; P N , palatine n e r v e s ; S D , secretory d u cts; L P , lin g u a l plate o f residual a lv e o la r r id g e ; F M , fa t m a r r o w ; F T , fa t tissue; P A , palatine artery.
observations, it is known that the struc tures in this region are loose and elastic. T h e incisive fossa region presents an area that may be utilized to considerable ad vantage in denture retention provided its structures are not compressed to in terfere with the functional movement of the labial muscles.
closely as to produce continuous pressure on its tissues are not recommended. Im pressions should not be taken in trays that confine the impression material to the extent o f causing compression of the palatine structures. A close observation o f the inferior surface o f the palatine process shows many irregular projections,
88
T h e Journal o f the American D en tal Association
as spines, that cause congestion of the soft tissue coverings when they are sub jected to harsh treatment. T h e ridge o f the intermaxillary suture, commonly called the median raphe, is shown in Figure 12. T h e section was prepared from the molar region in a woman, aged 51. T h in , firm mucosa covers its surface. T h e size and the de velopment o f this ridge varies greatly in different persons and presents a region unfavorable to the stability o f the artifi cial denture. O n either side o f the ridge of the intermaxillary suture, the tissues are soft.
Figure 15 shows a frontal section in the bicuspid region in a woman, aged 51, and presents a cross-section o f the vault o f the palate, alveolar ridges and buccal tissues in the maxillary denture area. In this region, the mucosa is quite thick and dense. T h e fatty submucosa increases in thickness in the posterior part o f the mouth. T h e molar area presents a simi lar picture with the exception that the mucosa becomes thinner, the fat decreases in abundance and the mucous glands in crease proportionately in size and num ber as sections are prepared from the posterior regions of the vault. I f a cross-
F ig . 15.— F rontal section in bicu sp id region o f u p p er ja w o f w om an, aged 51. N C , nasal c a v i ties ; M S , m a x illa ry sin u ses; F T , fa t tissu e; B M , b u ccin a tor m u s c le ; B P , bu ccal plate o f a lv eola r p rocess; E , e p ith e liu m ; F C T , fibrous con n ective tissu e; L P , lingu al plate o f a lv e o la r p ro ce ss; P P , palatine process o f m a x illa ; R M S , rid g e o f in term a xillary su tu re; IM S , interm axillary su tu re; R/1R, residual a lv eola r r id g e ; M , m u co sa ; V , v e stib u lu m ; B A , bu ccinator artery.
Figure 13 shows the fat tissues in the bicuspid regions, and Figure 14 the glan dular tissues in the molar regions be tween the ridge o f the intermaxillary suture and the residual alveolar ridges. T h e structures in these regions are highly vascular. O n clinical observation, they present an area that is resilient and usually compressible at the posterior por tion o f the vault o f the palate.
section o f a full denture were superim posed upon this specimen, its palatine surface should, we may assume, rest in reciprocal contact with all o f the in ferior surface o f the vault o f the palate, alveolar ridges and buccal soft tissues. T h e difficulties experienced may well be understood in constructing artifi cial dentures that are supported by foundation structures so varied in form
Fum as— Problem of Establishing Centric Relation and character and irregular in surface outline. CONCLUSIONS
From the study o f these and similar clinical records, together with the regular examination o f many patients wearing complete maxillary and mandibular den tures, the follow ing conclusions are o f fered : T h e regional reactions o f the support ing tissues to full dentures are influenced by the unequal distribution of functional stresses resulting from acquired habits in mastication, the signs o f which are im portant in the diagnosis o f conditions of the edentulous jaws. T h e soft tissues are the index to the changes displayed by the bone structures supporting the full denture. T h e preservation and functional adap tation o f bone depends on the degree of mechanical action imposed on it. T h e result on the whole w ill vary according
89
to predominance o f the periods o f pres sure and rest. Areas of hyperplastic tissue indicate resorption of bone and are found in re gions diametrically and diagonally oppo site to the areas subjected to “ positive force.” T h e regions stimulated by the denture maintain normal form and appearance owing to the positive forces exerted in mastication. T h e tissues of the mouth react favor ably to artificial full dentures in those regions receiving a well-distributed load from the functional stresses. Tissues subjected to “ negative forces” usually show a reaction that indicates a degenerative or inflammatory process. T h e supporting bone diminishes and dense fibrous connective tissue develops to fill the space between the bone and the denture base. T his tissue reaction is a pathologic process resulting from me chanical injury.
PROBLEM OF ESTABLISHING CENTRIC RELATION: ITS IMPORTANCE AND SOLUTION*
By I. L. FURNAS, D.D.S., Cleveland, Ohio
I
N constructing artificial dentures, it can scarcely be said that any one step in the technic involved is more im portant than another. A ll are of equal importance and each must be carried out with accuracy and detail if the finished product is to function as desired. T h e purpose of this treatise is to deal with but one phase o f this technic, namely, that o f establishing centric rela *Read before the Section on Full Denture Prosthesis at the Seventy-Sixth Annual Session of the American Dental Association, St. Paul, M inn., A ug. 7, 1934. Jour. A .D .A ., January, 1935
tion or, as it was originally termed, “ tak ing the bite.” It has been variously estimated by operators in position to know that from 50 per cent to 80 per cent o f the denture cases which must be reconstructed are failures because the operator did not es tablish the centric ja w relation. T h e great variety o f different methods employed throughout the profession to establish this relation is sufficient evidence in itself o f the difficulties encountered by almost every operator in attempting to supply denture service.
By ELBERT C. PENDLETON, D.D.S., and HENRY GLUPKER, D.D.S., Chicago, 111. H IS report deals with the tissue re actions most commonly present in the months o f edentulous persons wearing artificial dentures. It is the hope that these observations and the studies in the minute anatomy of the jaws may be correlated to broaden our knowledge o f the structures in the denture area and contribute to successful treatment in full denture prosthesis. In selecting material for this study, a few models were chosen that were thought to be representative of the many case records showing the edentulous up per ja w which supports a fu ll maxillary denture opposed by the partially eden tulous lower jaw . T his choice o f mate rial was based upon the assumption that tissue reactions to full dentures are com mon to both the upper and the lower jaws. T h e character o f the structures in each ja w is similar, although their form and distribution show considerable varia tion. T h e edentulous upper ja w presents a field favorable for study when considered separately, and it was thought that a more dependable analysis o f tissue reac tions o f the upper ja w could be made by considering cases having the maxillary dentures opposed by natural teeth in the lower jaw . It is regrettable and quite
remarkable that no records are available o f cases presenting the completely eden tulous upper ja w opposed by a low er jaw with the complement o f natural teeth. These records were secured at the time when the maxillary dentures had proved unsatisfactory. T h e models record the condition o f the tissues which had de veloped during the period that the den tures were worn. T h e models o f each case were first studied singly; then, the group was examined for characteristics common to each case, which w ere: the general form and condition o f the bone and soft tissues in the palate; the general form and condition o f the bone and soft tissues o f the residual alveolar ridge of the upper jaw , and the number, position and condition o f the natural teeth in the opposing ja w as related to the different regions o f the maxillary denture area. Functional stress, which is considered as the condition most commonly influenc ing the reaction of the tissues supporting full dentures, is the only etiologic factor considered in this study. T h e possible results o f the normal change in the form o f the residual ridge follow ing the loss of the natural teeth and those resulting from pathologic conditions or injuries are not taken into account. Reactions from these causes are classed among un usual influences and are not considered as pertinent to the problem. In the interpretation o f these clinical studies, the forces o f mastication are ana lyzed according to W ilso n ’s use of the
T
*Read at the Seventieth Midwinter Clinic of the Chicago Dental Society, Feb. 27, 1934. *From the Prosthetic and Research depart ments, Chicago College of Dental Surgery, Dental Department of Loyola University.
Jour. A .D .A ., January, 1935
76
Pendleton and Glupker— Reaction of Tissues Supporting D entures terms positive and negative force. A posi tive force is one that tends to seat the denture more firmly in contact with the supporting tissues; a negative force one that tends to displace the denture.1 “ Posi tive force” as used herein is synonymous with function. “ Negative force” indi cates the lack o f function. Figure 1 shows models o f the eden tulous maxillary denture area and the partially edentulous mandibular dental arch in a man, aged 45. In this case, the reactions o f the tissues o f the maxillary
77
opposite side o f the arch is irregular. Its vertical height is reduced and the buccolingual width o f the ridge is narrow as far posteriorly as the maxillary tuber osity, which shows a covering o f pendu lous tissue. T h e palate appears smooth, with a thin soft tissue covering. T h e labiobuccal structures are thin and loosely attached except in the regions o f the tuberosity. T h e natural teeth in the mandibular arch are somewhat unequal in length.
F ig. 1.— M a x illa r y and m an d ibu lar m odels from m an, aged 45.
denture area w ere studied as affected by the forces transmitted by the six anterior teeth o f the opposing arch. T h e right side of the residual ridge of the maxillary model is quite symmetrical from the me dian line to the molar region. Here, the ridge widens and terminates at the tu berosity, which is covered with hyper plastic tissue. T h e residual ridge on the
F ig. 2.— M a x illa r y and m an d ibu lar m odels from w om an , aged 39. A fu ll m a x illa ry d en ture and partial m an d ibu lar denture had been w orn ten years.
T hose on the right are in a vertical po sition, while those on the left side of the arch are rotated and present a labial inclination. It is assumed that the posi tion o f the natural teeth directed mastica tion toward the right side o f the arches. T h e “ positive force” was transmitted to 1. W ils o n , G . H .: M a n u a l o f D ental P ros the right side of the maxillary arch. thesis, E d . 4, P h ila d e lp h ia : Lea and Febiger, T h e maxillary tuberosity o f the left 1920, p. 318.
78
T h e Journal o f the American D en tal Association
side, which is diagonally opposite the area receiving “ positive force,” shows a pendulous development of hyperplastic tissue. Figure 2 shows the edentulous maxil lary and partially edentulous mandibular models from the case o f a woman, aged 39. T h e residual ridge on the right side of the maxillary model is of normal form. O n the left side o f the median line, the arch o f the anterior portion o f the ridge is reduced in size. T h e cuspid region is prominent and the bicuspid area is about one-third the size o f the same area on the opposite side o f the arch. T h e tuberosity
T h e right side o f the mandibular arch presents a more favorable number and arrangement o f natural teeth for mastica tion than does the left side. T h e abrasion o f these teeth bears evidence of their use. Again, it is assumed that “ positive forces” in mastication were directed toward the right side of the maxillary arch. Figure 3 is one o f the typical exhibits o f the reaction o f tissues to full dentures. T h e edentulous maxillary denture area,
F ig. 3.— M a x illa r y and m an d ibu lar m odels fro m m an, aged 55.
shows a region considerably enlarged and covered by hyperplastic tissue. T h e vault o f the palate is irregular and has a thin covering o f mucosa. T h e six natural teeth o f the mandibu lar arch present irregularities in vertical length. T h e left central incisor is longer by one-half the length o f its visible crown than the right bicuspid measured from the mesial surface area. T h e right cuspid and the left bicuspid are in about the same horizontal plane.
F ig . 4.— M a x illa r y and m and ibu lar m odels fro m w om an , aged 6 0 ; fu ll m a x illa ry denture w orn five years.
and the partially edentulous mandibular arch of a man, aged 55, are shown. T h e abrasion o f the natural teeth on the right side, as w ell as the absence o f the man dibular molar and bicuspid teeth on the left side, identifies the right side o f the arches as that habitually used in mastica tion.
Pendleton and Glupker— Reaction of Tissues Supporting Dentures T h e model o f the maxillary denture areas shows the residual ridge on the right side o f the median line to be smooth and symmetrical. T h e left side records struc tural changes in the bone and its cover ing o f soft tissue. A general reduction in size and change in form o f the ridge are noted on the left side of the median line, except in the cuspid and tuberosity re gions, where the unused side presents characteristic irregularities in structure. T h e lingual portion o f the ridge appears considerably reduced in size as compared
F ig. 5.— M a x illa r y and m an d ibu lar m odels from w om a n , aged 52. A fu ll upper denture had been w o r n six years.
to the opposite side o f the arch. Evidence o f hyperplastic tissue is seen at the left maxillary tuberosity region. These con ditions indicate that the “ positive forces” acted on the right side o f the maxillary denture area. T h e record o f M rs. C., aged 60, is seen in Figure 4. A full maxillary den ture was w orn five years. T his case pre sents a rather striking picture on account o f the location o f the remaining teeth
79
and the order in which they appear in the mandibular arch. T h e first and second molars o f the left side are missing. T h e third molar is elongated and inclined mesially. T h ere are signs o f considerable abrasion on the lingual cusps and the distal portion o f its occlusal surface. T h e abrasion o f the buccal cusps o f the right mandibular first molar and first bicuspid and o f the labial surfaces o f the lateral and central incisors points to a predomi nate function on the right side of the arch. T h e position o f the left molar tooth in the arch and the abrasion o f its lingual cusps indicate its use as a balancing mem ber in stabilizing the maxillary denture. T h e maxillary model shows a w ellformed palatine surface. T h e residual alveolar ridge presents a smooth, even ap pearance on the right side o f the arch. T h e ridge on the left side presents a char acteristic depression in the region dia metrically opposite the natural right first molar. T h e maxillary tuberosity on the left side shows evidence o f the develop ment of hyperplastic tissue. T h e inter pretation given after the study of this case is that the “ positive force” was di rected to the right and “ negative force” to the left side o f the maxillary denture area. Figure 5 shows the record o f M rs. B., aged 52, w ho has been under intermit tent observation for six years. T h e max illary denture area presents a condition interpreted as chronic inflammation, which is attributed to stresses from the mandibular teeth that are prominent and o f unequal vertical length. T h e tuber osity regions o f the alveolar ridge are dense and the anterior portion o f the arch o f the ridge is covered by a mass o f hyper plastic tissue. T h e structures o f the vault o f the palate are soft and acutely in flamed. T h e most abraded surfaces ap pear on the posterior molar teeth, the left cuspid, the incisors and the mesial
80
T h e Journal of the American D ental Association
plane o f the buccal cusps o f the mandibu lar right first bicuspid. T h e tissues o f the upper and lower jaws that support fu ll dentures seem to react favorably to functional stresses when the denture base bears a reciprocal relation to these structures. Therefore,
sented by the tissues. T h e dense fibrous tissues are suited by nature to bear the greatest burden during function. T h e highly vascular tissues must be protected from excessive stresses and the freedom of muscle action must not be impeded by the form o f the denture base.
F ig . 6.— B u ccolin g u a l section in third m ola r region o f upper ja w fr o m a m an, aged 38. N C , nasal c a v ity ; P N , palatine n e r v e s ; P A , p alatin e a rte ry ; S D , secretory duct fr o m palatine g la n d s; O M , oral m u cosa; F T , fa t tissu e; E , oral e p ith e liu m ; F C T , fibrous con n ectiv e tissue; M S , m ar ro w sp aces; L C T , loose con n ectiv e tissue on bu ccal su rface o f residual a lv e o la r r id g e ; B M , bu c cin ator m uscle.
the stress o f mastication should be distributed according to the natural characteristics and qualities o f adaptability pre-
T here can be no doubt that the probIem o f tissue reaction to full dentures is one that is influenced by functional
Pendleton and Glupker— Reaction o f Tissues Supporting Dentures stresses.2 N o one factor is o f greater significance than that o f localized func tion. T ench calls our attention to “ the startling difference between the ease with which younger persons learn to wear ar tificial dentures and the continuous d if ficulties o f some o f their elders.8 T his condition is attributed to the universal tendency among adults toward prefer ence for a certain region o f the arch in mastication. T his tendency has a de m oralizing effect on the stability o f the
81
terpretation o f the clinical manifesta tions o f the tissues supporting full den tures : Though the influence of mechanical fac tors on the general morphology of bone tis sue is well established, we know, on the contrary, almost nothing of the exact mech anism of this influence. It is difficult to state the problem, and in short it but gives us an idea of our ignorance. Mechanical actions, especially pressure and traction, can act on the cells, the fibrils, the pre-osseous substance, calcification and
F ig. 7.— B u ccolin gu a l section in bu ccal region o f upper ja w o f w om an, aged 51. P A , palatine a rte ry ; F T , fa t tissue; M S , m arrow sp aces; F C T , fibrous conn ective tissue; E , epithelium c o v e r in g residual a lv eola r r id g e ; B T , bone tra b ecu la e; V , v e stib u lu m ; M , m ucosa o f ch eek; B M , bu ccin a tor m u scle ; L C T , loose con n ective tissue.
artificial denture and the health o f the tissues which form its support. T h e w ork o f Leriche and Policard has been found extremely helpful in the in2. Stansbery, C. J .: T issu e C hanges U nder D entures, J .A .D .A ., 15:3+9-353 (F e b .) 1928.. 3. T e n ch , R . W . : A rtificia l D entures— Final Stage in R estorative Dentistry, J .A .D .A ., 20:1234-1246 (J u ly ) 1933.
the vasculation of bone. . . . When there is no pressure, bone is form ed; when there is strong enough pressure, it disappears. . . . The role of strain on the preservation and thickening of the bone framework is incontestable. This generally arises from the load carried by bone, an organ of sup port; the skeleton is preserved through the exercise of this function. The removal
82
T h e Journal of the American D ental Association
o f a ll s tra in t h r o u g h th e r e m o v a l o f all lo a d has a fa t a l in flu e n ce o n h o n e s t r u c t u r e .4
T h e study o f tissue reactions to arti ficial dentures is both interesting and per plexing. It is deemed more pertinent to the success of full dentures to become fa miliar with the form, character and dis tribution o f the structures normally found in the region o f denture support than to pursue the analysis o f tissue re actions.
study o f the minute anatomic structure o f the denture supporting tissues. T h e structure of the upper and the lower ja w varies greatly in the degree of density. T h e arrangement and distribu tion o f the tissues are uniform ly constant although their character varies somewhat in different persons.5 T h e quality of the tissues has a marked influence on the stability of the artificial denture when it is subjected to func tional stresses. T h e most satisfactory re-
F ig. 8.— A nteroposterior section in m a x illa ry tuberosity region o f man, aged 62. M S , m a x il la ry sin u s; F C T , fibrous con n ectiv e tissu e; M T , m a x illa ry tu berosity; L C T , loose con n ectiv e tissue; P G , palatine g la n d s ; P N , p tery g oid notch (p tery g om a x illa ry n o t c h ); P P , p yram id al plate o f palate b o n e ; 1P M , internal p terygoid m uscle.
According to W ilson , “ N o one factor has so much to do with retention o f arti ficial dentures as the soft tissues.” 1 T his principle is accepted as the premise in the
tention is assured when the soft tissues maintain contact with the entire area of the denture base. T h e denture base must be adapted to the tissues in each region of the denture area according to their
4. L eriche, R ., and P olica rd , A . (trans. by 5. P endleton, E. C. : A n a tom y o f M a x illa Sherw ood M o o re and J. A lb e rt K e y ) : N orm al and P ath olog ica l P h y sio lo g y o f Bone, St. from V iew p oin t o f F u ll D en tu re Prosthesis, L ou is: T h e C. V . M o sb y C om pany, 1928. J .A .D .A ., 19:543-572 (A p r il) 1932.
Pendleton and Glupker— Reaction o f Tissues Supporting D entures capacity to accommodate themselves to the load imposed on them. T h e regions in both the upper and the low er jaw s subjected to the greatest stress during the function o f artificial dentures are the residual alveolar ridges. T h e form and character o f their struc-
83
enough to absorb shock. Its mucous cov ering is dense and well suited to with stand great stress. T h e labiobuccal structures o f both jaw s are elastic, with an abundance of fat and glandular tissues about the muscle fibers. T h e mucosa in this region
F ig. 9.— B u ccolin g u a l section in m a x illa ry tuberosity region o f w om an, aged 58. M S , m ax il lary sin u s; L C T , loose con n ective tissue; B M , bu ccin a tor m u scle ; V , vestibulu m o f ch eek ; M A , bu ccinator m uscle attach m en t; F M , fa t m a r r o w ; F C T , fibrous con n ectiv e tissue; F T , fa t tissue; S D , secretory d u c t; P N , palatine n e rv e s; P G , palatine g la n d s ; P A , palatine a rtery ; N C , nasal cav ity .
tures are adaptable to the function imposed on them. T h e bony process is firm yet cancellous
is w ell lubricated and maintains a quality that is ideal for creating a seal at the denture borders. T h is feature is char-
84
T he Journal o f the American D ental Association
acteristic of the tissues that form the floor o f the mouth and o f those that con stitute the soft palate. W herever valve seal is a requisite to denture stability, the structures seem to have a peculiar quality perfectly adapted to the scheme o f denture retention. T h e vault o f the palate presents many
sis have an intimate knowledge o f these tissues. T h e anatomic material was selected to exhibit the structures typical o f the va rious regions o f the upper ja w that are utilized for denture support. T h e speci mens were chosen from subjects o f va rious ages and from both sexes so that
F ig. 10.— Sagittal section in m edian line in central in cisor region o f upper ja w fro m w om an, aged 58. P P M , palatine process o f m a x illa ; E , oral e p ith eliu m ; F T , fa t tissu e; P R , palatine ru g a e ; 1C , in cisive c a n a l; F C T , fibrous con n ective tissu e; R A R , residual a lv eola r r id g e ; M A , low est p oint o f attachm ent o f depressor alae nasi m u scle ; M G , m ucous g la n d s o f l i p ; L C T , loose conn ective tissue; D A N , depressor alae nasi m u scle ; A N S , anterior nasal spine.
hazards to the stability o f the artificial denture, owing to its form and the varied character o f its structures. It is important that the student o f denture prosthe-
the consistency in tissue quality and distribution in the several regions might be emphasized. Figure 6 shows a section o f the residual
Pendleton and Glupker— Reaction of Tissues Supporting D entures
85
F ig. 11.— S agittal section o f in fe rio r surface o f palatine process o f m a x illa o f w om an, aged 58. P P , palatine p rocess; P A , palatine artery ; S, spinous process on in ferior su rface o f palatine process; O M , o ra l e p ith e liu m ; F C T , fibrous con n ective tissu e; R , palatine rugae.
Fig. 12.— Frontal section in m olar region at union o f palatine processes o f m a x illa o f w om an, aged 51. N C , nasal c a v ity ; IM S , interm axillary su tu re; P G , palatine g la n d s ; F T , fa t tissue; F M , fa t m a r ro w ; R M S , rid g e o f interm axillary su tu re; E , e p ith eliu m ; F C T , fibrous conn ective tissue.
86
T h e Journal of the American D en tal Association
alveolar ridge from a man, aged 38, that is typical of the molar region. In Figure 7, a section from the bicuspid region from a woman, aged 51, shows the same general character and arrangement o f structures. Figure 8 is a sagittal section in the tuberosity region from a man, aged 62, in which the character o f the bone is in marked contrast to that in the pre ceding sections. In the oldest person examined, the trabeculae are line and the m arrow spaces are large. In the youngest
and glands are found beneath the epi thelium at its lingual surface. Swenson refers to this region as the “ pterygomaxillary notch.” 6 Figure 9 shows a section o f the tuber osity region o f a woman, aged 58. C over ing this region is a pendulous area o f dense fibrous connective tissue. Such a de velopment o f hyperplastic tissue is not uncommon in the mouths o f edentulous persons. It presents a condition where surgical measures should usually be rec-
F ig. 13.— F rontal section in bicuspid region o f w om an, aged 51. R M S , rid g e o f interm axillary su tu re; E , e p ith e liu m ; F C T , fibrous connective tissue; P N , palatine n e rv e s; F T , fa t tissue; P A , palatine a rte ry ; C T F , con n ective tissue fibers; B T , bone tra b ecu la e; F M , fa t m arrow .
person, the trabeculae are strong and the m arrow spaces small. (T h e fact that the sections were prepared in a different plane in the young and in the older per sons has no bearing on the character of the bone structure.) T h e mucosa cover ing the alveolar ridge o f the upper ja w is normally dense and symmetrical except at the posterior extremity o f the tuber osity region where loose connective tissue
ommended before impressions are taken for fu ll dentures as hyperplastic tissue is unstable and therefore not suited for den ture support. Figure 10 is taken from the anterior portions o f the alveolar ridge and pala tine process in the median line. T h e 6. Swenson, M . G . : A n a tom y in R elation to E dentulous Im pressions, J .A .D .A ., 20 :10781082 (J u n e) 1933.
Pendleton and G lupker— Reaction o f Tissues Supporting D entures mucosa in this region is firm and some what irregular. Some adipose tissue is found beneath the tunica propria linguad from the incisive foramen. O n the labial surface o f the ridge, the fibrous connec tive tissue is dense as high as the line o f lip reflection, where the muscle attachments are seen. H igh in the incisive fossa toward the anterior nasal spine, there is a considerable quantity o f loose areolar tissue supporting the fibers o f the de pressor alae nasi muscle. From clinical
87
Figure 11 shows a higher magnifica tion o f the palatine rugae in the cuspid region from the same specimen. In mouths that present these highly de veloped folds in the mucosa, great care should be exercised in impression taking for denture construction. W h en these folds, compressed by a closely adapted denture, are irritated by movements o f the denture during function, unfavorable reactions may result in these tissues. D en tures adapted to the palatine surfaces so
F ig. 14.— Frontal section in m ola r region o f w om an, aged 51. E , oral ep ith eliu m ; F C T , fibrous con n ective tissu e; P G , palatine g la n d s ; P P M , palatine process o f m a x illa ; P N , palatine n e r v e s ; S D , secretory d u cts; L P , lin g u a l plate o f residual a lv e o la r r id g e ; F M , fa t m a r r o w ; F T , fa t tissue; P A , palatine artery.
observations, it is known that the struc tures in this region are loose and elastic. T h e incisive fossa region presents an area that may be utilized to considerable ad vantage in denture retention provided its structures are not compressed to in terfere with the functional movement of the labial muscles.
closely as to produce continuous pressure on its tissues are not recommended. Im pressions should not be taken in trays that confine the impression material to the extent o f causing compression of the palatine structures. A close observation o f the inferior surface o f the palatine process shows many irregular projections,
88
T h e Journal o f the American D en tal Association
as spines, that cause congestion of the soft tissue coverings when they are sub jected to harsh treatment. T h e ridge o f the intermaxillary suture, commonly called the median raphe, is shown in Figure 12. T h e section was prepared from the molar region in a woman, aged 51. T h in , firm mucosa covers its surface. T h e size and the de velopment o f this ridge varies greatly in different persons and presents a region unfavorable to the stability o f the artifi cial denture. O n either side o f the ridge of the intermaxillary suture, the tissues are soft.
Figure 15 shows a frontal section in the bicuspid region in a woman, aged 51, and presents a cross-section o f the vault o f the palate, alveolar ridges and buccal tissues in the maxillary denture area. In this region, the mucosa is quite thick and dense. T h e fatty submucosa increases in thickness in the posterior part o f the mouth. T h e molar area presents a simi lar picture with the exception that the mucosa becomes thinner, the fat decreases in abundance and the mucous glands in crease proportionately in size and num ber as sections are prepared from the posterior regions of the vault. I f a cross-
F ig . 15.— F rontal section in bicu sp id region o f u p p er ja w o f w om an, aged 51. N C , nasal c a v i ties ; M S , m a x illa ry sin u ses; F T , fa t tissu e; B M , b u ccin a tor m u s c le ; B P , bu ccal plate o f a lv eola r p rocess; E , e p ith e liu m ; F C T , fibrous con n ective tissu e; L P , lingu al plate o f a lv e o la r p ro ce ss; P P , palatine process o f m a x illa ; R M S , rid g e o f in term a xillary su tu re; IM S , interm axillary su tu re; R/1R, residual a lv eola r r id g e ; M , m u co sa ; V , v e stib u lu m ; B A , bu ccinator artery.
Figure 13 shows the fat tissues in the bicuspid regions, and Figure 14 the glan dular tissues in the molar regions be tween the ridge o f the intermaxillary suture and the residual alveolar ridges. T h e structures in these regions are highly vascular. O n clinical observation, they present an area that is resilient and usually compressible at the posterior por tion o f the vault o f the palate.
section o f a full denture were superim posed upon this specimen, its palatine surface should, we may assume, rest in reciprocal contact with all o f the in ferior surface o f the vault o f the palate, alveolar ridges and buccal soft tissues. T h e difficulties experienced may well be understood in constructing artifi cial dentures that are supported by foundation structures so varied in form
Fum as— Problem of Establishing Centric Relation and character and irregular in surface outline. CONCLUSIONS
From the study o f these and similar clinical records, together with the regular examination o f many patients wearing complete maxillary and mandibular den tures, the follow ing conclusions are o f fered : T h e regional reactions o f the support ing tissues to full dentures are influenced by the unequal distribution of functional stresses resulting from acquired habits in mastication, the signs o f which are im portant in the diagnosis o f conditions of the edentulous jaws. T h e soft tissues are the index to the changes displayed by the bone structures supporting the full denture. T h e preservation and functional adap tation o f bone depends on the degree of mechanical action imposed on it. T h e result on the whole w ill vary according
89
to predominance o f the periods o f pres sure and rest. Areas of hyperplastic tissue indicate resorption of bone and are found in re gions diametrically and diagonally oppo site to the areas subjected to “ positive force.” T h e regions stimulated by the denture maintain normal form and appearance owing to the positive forces exerted in mastication. T h e tissues of the mouth react favor ably to artificial full dentures in those regions receiving a well-distributed load from the functional stresses. Tissues subjected to “ negative forces” usually show a reaction that indicates a degenerative or inflammatory process. T h e supporting bone diminishes and dense fibrous connective tissue develops to fill the space between the bone and the denture base. T his tissue reaction is a pathologic process resulting from me chanical injury.
PROBLEM OF ESTABLISHING CENTRIC RELATION: ITS IMPORTANCE AND SOLUTION*
By I. L. FURNAS, D.D.S., Cleveland, Ohio
I
N constructing artificial dentures, it can scarcely be said that any one step in the technic involved is more im portant than another. A ll are of equal importance and each must be carried out with accuracy and detail if the finished product is to function as desired. T h e purpose of this treatise is to deal with but one phase o f this technic, namely, that o f establishing centric rela *Read before the Section on Full Denture Prosthesis at the Seventy-Sixth Annual Session of the American Dental Association, St. Paul, M inn., A ug. 7, 1934. Jour. A .D .A ., January, 1935
tion or, as it was originally termed, “ tak ing the bite.” It has been variously estimated by operators in position to know that from 50 per cent to 80 per cent o f the denture cases which must be reconstructed are failures because the operator did not es tablish the centric ja w relation. T h e great variety o f different methods employed throughout the profession to establish this relation is sufficient evidence in itself o f the difficulties encountered by almost every operator in attempting to supply denture service.