Complete dentures

Occlusion as reked to co

prosthodontics

refrtow~e

H. 0. Beck, D.D.S., MS.* The University of Texas Dental Branch at Houston,, Texas

0 cclusion of complete dentures has been a concern since ancient times when attempts were made to replace lost teeth. Teeth carved from ivory and fastened to gold plate have been found in mummies dating back more than 2,400 years.

Others found were made of bone and wood. Although those who practiced this art of carving possessed certain degrees of skill the occlusal surfaces may be said to be nondescript or unclassifiable and often of several forms in the same series of carvings.

Among the principal contributors in the development of posterior denture teeth of different occlusal forms in the last 50 years have been Sears,l Gysi,2 Hal&:

French,4 Kurth,5 and Hardy.G Many other occlusal forms appear to be modifications of the original patterns.

The designs of posterior teeth generally have been based on the morphology of the natural teeth and the temporomandibular joints, observation of movements of the mandible, clinical observations of wear facets on the natural teeth, chewing

efficiency, and/or empirical and subjective values assigned by the the designers based on clinical experience and judgment. Other contributions have been made in other continents. Thus, a variety of occlusal forms have been accepted for complete dentures without long-term investigations and statistical analyses of the advantages which may be attributed to each form.

Woelfelt recently reported on a five-year clinical study of a comparison of three occlusal forms, i.e., 0, 20, and 33 degree teeth in complete dentures. He suggests as one result of his study that the selection of 0 and 20 degree teeth should be based on other factors than an attempt to maintain the supporting structures of the dentures. Another long-term study of a different nature relates tooth form to two different techniques. It was begun several years ago and hopefully will disclose further statistical s&nificance after the ten-year period of study is completed. Progrrss of the study has been reported by Hickey, Henderson, and Straus7

Read before the Academy of Denture Prosthetics, Detroit, Mich.

*Professor and Chairman, Removab!e Prosthodontics.

TWoelfel, J. B.: Personal communication.

246

Volume 27 Number 3

Occlusion and removable prosthodontics 247

Paynes listed definable guidelines for the selection of occlusal patterns based on anatomic oral tissue conditions and jaw positions in centric relation. A chart which

outlines the selections has been exceedingly helpful for dentists who do not strictly subscribe to one tooth form and concept for all patients.

In the broadest sense, complete dentures should fulfill the requirements of ( 1) esthetics, (2) harmonious function, and (3) maintenance of hard and soft tissues of the edentulous arches. Important contributions enabling the dentist to attain these goals have been made by the Academy of Denture Prosthetics through periodic pub-

lications.g-ll Important information and suggestions have been detailed in statements covering various phases of prosthodontic treatment including conditioning and prep- aration of the patient for dentures, the making of impressions, the recording of jaw positions, the transfers of records, and the use of articulators, as well as provisions

for an esthetic denture. Very little guidance is given for the selection and arrange- ment of one or more occlusal forms of denture teeth, except in stating that bilateral balance is desirable and that teeth should allow for unlocking in centric occlusion.

ESTHETICS

One of the factors in developing an esthetic denture is dependent upon the re- action of the patient and the dentist to the color (shade) of the teeth to be chosen. Color is a three-dimensional entity consisting of hue, chroma, and value.* Hue is the designated color such as red, yellow, or green. Chroma is the strength or purity of the color, and value is the lightness or darkness of the color as compared to a

gray scale ranging from white to b1ack.S Another factor to be considered in esthetics is the arrangement of anterior and

posterior teeth. Judicious proximal spacing between the teeth will result in depth perception. Tinting of the bases where they are visible will add to depth perception by the observer.

HARMONIOUS FUNCTION

Harmonious function of complete dentures is the requirement which exhibits harmonious occlusal contacts in centric and eccentric maxillomandibular relations and which is in harmony with the neuromuscular mechanism and the temporo- mandibular joints in the functional ranges of speaking, chewing, and swallowing, and with parafunctional movements including exploratory or nonfunctional move-

ments.$ In narrowing the part of function applicable to the occlusal and incisal areas of the denture teeth, occlusal balance is defined as, . . . a condition in which there are simultaneous contacts of the occluding units on both sides of the opposing dental arches.12 This definition can be applied to centric occlusion as well as eccentric occlusal contacts.

Occluding units in complete dentures under functional contacts away from cen- tric occlusion are referred to as being in a balanced occlusion or in a nonbalanced occlusion.

A balanced occlusion is defined as . . . the simultaneous contacting of the upper

*Munsell Color Order System, Munsell Color Company, Inc., Baltimore, Md.

+Sproul, R. C.: Personal communication.

SLarkin, J. D.: Personal communication.

24% Beck J. Prosthet. Dent. March. 1972

and lower teeth on the right and left sides and in the anterior and posterior occlusal areas of the jaws. This occlusion is developed to prevent a tipping or rotating of the denture base in relation to the supporting structures.12 It must follow that a non- balanced occlusion would not fulfill the conditions of simultaneous contacting of the* upper and lower teeth in eccentric positions. The question of immediate concern is how far from centric occlusion do teeth contact in their functional ranges and how

far should potential deflective contacts be avoided to eliminate tilting or rotating actions on the denture bases?

Jankelson, Hoffman, and Hendronl suggested that there were not enough factual reports in the literature to substantiate a balanced occlusion. They further suggested, as evidenced by cinefluorographic studies, that centric occlusion is the only tooth

rontact of any significance. They stated that, There was no evidence that balance

of teeth in eccentric positions is a physiologic necessity, or that lack of eccentric. balance is less conducive to masticatory function. The cusp angulation in six pa- tients who had 0 to 45 degree cusp teeth in dentures appeared to have no influc,nct* on the manner of incision. Occlusal balance was not observed as long as the bases

remained in contact with the supporting tissues. The influence of the tongue in rt- taining the dentures, however, was obvious.

Yurkstas and Emerson reported that twelve patients with nonanatomic teeth (0 degree) in dentures had considerable contact of teeth on the working sides. and

nearly 100 per cent had contact on the balancing sides. Dentures made with post- molar ramps exhibited no contact on the working sides but did show some contact on the balancing sides. Their investigation was comparable in method to part of that

of Jankelson, Hoffman, and Hendron.13 Brewer and Hudsonlj used radio signals to record chewing contacts of teeth. This

procedure was the first to eliminate direct wiring out of the mouth to the recording unit. This pilot study on two patients showed that chewing contacts occur on thr cusp heights as well as in centric occlusion. A later report by BrewerI indicated that the type of cusp form and harmony of balanced occlusion caused variation in the

number and type of contacts. Experiments with natural teeth by other investigators disclosed contacts in the

intercuspal position. increasing in frequency toward the end of mastication. Lat- eral tooth contacts did occur although less frequently than in the intercuspal po- sition, and they occurred before and after the centric occlusal contacts were reached.lR

MAINTENANCE OF HARD AND SOFT TISSUES

The maintenance of hard and soft tissues of the dental arches is difficult to re- late to occlusal patterns and occuding concerns alone. Other factors, such as (1 : properly fitted bases, (2) correct jaw relation records and transfers to an instrument capable of holding what is recorded, and (3) the arrangement of teeth for the best

stability, and other procedures have an influence on tissue maintenance. Cn- doubtedly, occlusal patterns and the types of occlusions developed must exert con- siderable influence on the soft and hard tissues. When more long-term independent studies with statistical evidences are completed, guidelines for the selection of oc-

Volume ?i Number 3

Occlusion and removable prosthodontics 249

OCCLUSAL PLANE -

U OVERLAPS CENTRIC OCCLUSION

HORIZONTAL 33 - 30 - 20 - 12 VERTICAL

OCCLUSAL PLANE

RIGHT

OCCLUSAL PLANE -

., RIGHT

STABILIZED

OCCLUSAL PLANE

.. RIGHT Fig. 1. (A) Diagram of anatomic or semianatomic cusp teeth in centric occlusion with overlaps in the anterior region. The composites of the contact forces are directed toward the ridges. (B) From a right lateral movement, cusps glide on opposing inclines. Although bilateral con-

tacts stabilize the dentures, the contact forces are directed away from the ridges. (C) In a condition of deflective occlusal contact on the balancing side, the contact force is directed out-

side of the ridges. (D) In strong working-side contacts on both cusp inclines, contact forces are also directed outside of the ridges.

clusal patterns may be forthcoming. Investigations as designed by Woelfel* and by Hickey and associates have stimulated further research in depth and scope. The Academy of Denture Prosthetics should then be in the position to include definable guidelines for occlusal concerns in its pub1ications.l

Ten contemporary occlusal concerns will be reviewed by schematic drawings, several of which appear to be used more than others. Of these, the first five are in the balanced occlusion concept, and the remaining five are in the nonbalanced cate- gory in eccentric occlusal positions. Undoubtedly, more exist, but they should be in one of the ten categories by virtue of being modifications. Detailed techniques and procedures, efficiency and mastication performances will not be evaluated. However, forces exerted by tooth contacts which could be transmitted to the basal seat areas are illustrated in the diagrams. The directions of these forces are usually perpendicu-

*Woelfel, J. R.: Personal communication.

250 Beck ,I. Prosthet. Dent. March. 1972

OCCLUSAL PLANE OCCLUSAL PLANE ------ .

OVERLAPS CENTRIC OCCLUSION HORIZONTAL VERTICAL

RIGHT

Fig. 2. (A) In centric occlusion, half of the width of lower posterior teeth helps to direct the occlusal contact forces on the lingual side of the ridges in a buccal direction to the lower ridge. (B) From a right lateral position toward centric occlusion, the contact forces are di- rected toward the ridges on the working side (W) and away from the ridges on the balancing side (B) (Frenchs posterior teeth).

lar to the opposing surfaces in gliding contacts. Small frictional forces present would

alter the directions by small unknown amounts, and variations in the positioning of the teeth to obtain a balanced occlusion would also alter the directions of these con- tact forces.

BALANCED OCCLUSIONS

( 1) The definite cusp form which represents anatomic and semianatomic con- figurations dates back to 1909 when twentieth-century anatomical bicuspids and

molars were introduced by the Dentists Supply Company.* This culminated in the 33 degree cusp form in 1914 as advocated by Gys? (Fig. 1, A) . A classical lateral

movement is shown where cusps contact bilaterally to enhance the stability of the dentures (Fig. 1, B) . Fig. 1, C and D, depicts deflective contacts in extreme lateral positions which may cause tilting actions of the bases.

(2) Fig. 2, A and B, illustrates the reduction of the occlusal table of the lower posterior teeth to increase the stability of the dentures as advocated by French.4 The upper posterior teeth have slight lingual occlusal inclines of 5 degrees for the first bicuspids, 10 degrees for the second bicuspids, and 15 degrees for the first and second molars, so that a balanced occlusion could be developed laterally as well as an- teroposteriorly by the arrangement of the teeth on a curved occlusal plane.

(3) Sear? was one of the greatest exponents of the nonanatomic tooth forms. He introduced his chewing members in 1922 and his channel type posterior teeth in 1927. These teeth had a restricted acceptance at first. Modified nonanatomic tooth patterns from the early types have been accepted much more extensively since then. A balanced occlusion can be developed by a curved occlusal plane anteroposteriorly and laterally or with the use of the second molar ramp (Fig. 3, A and B)

(4) The next occlusal concern employs a posterior reverse lateral curvature except for the second molar which is set with the customary lateral curvature (Wil- son curve) to provide a balanced occlusion (Fig. 4, A and B) . Pleasurels rational- ized that the occlusion should be of special design due to the instability of the lower

*Densply International, York, Pa.

Occlusion and removable prosthodontics 251

OCCLUSAL PLANE

HORIZONTAL WITH RAMP

OCCLUSAL PLANE /

HORIZONTAL WITH RAMP-

OVERLAPS CENTRIC 2nd HORIZONTAL OCCLUSION MOLAR :. RIGHT

MOLAR

VERTICAL CONTACT CONTACT

Fig. 3. (A) Nonanatomic teeth will exert contact forces toward the ridges in centric occlusion. (B) From a right lateral position toward centric occlusion, gliding surfaces will direct contact forces toward the ridge on the working side (W) but will direct contact forces toward the buccal side of the ridge on the balancing side (B), depending on the degree of lateral inclina- tion of the second mo!ars.

OCCLUSAL PLANE OCCLUSAL PLANE I

HORIZONTAL WITH RAMP HORIZONTAL WITH RAMP

WT B STABILIZED

RIGHT WITH

RAMP

OVERLAP CENTRIC OCCLUSION 2nd LA

HORIZONTAL REVERSE MOLARS

VERTICAL LATERAL CURVE

Fig. 4. (A) An arrangement of teeth with a reverse lateral curve through the first molars will direct contact forces toward the lingual side of the lower ridge and toward the buccal side of the ridge at the second molar ramp. (B) Gliding surfaces will direct contact forces toward the lingual side of the lower ridge on the working side (W) and toward the buccal side of the ridge on the balancing side (B), depending on the inclination of the second molar ramp.

denture. Resultant forces should be directed vertically and/or lingually. He further envisioned that research should result in a machine which could test, . . . (1) the forces encountered in closing through food; (2) the number of chewing cycles re- quired; (3) the amount of lateral displacement induced in the tooth support during a normal chewing cycle against resistant food. He stressed that forces of cutting and shear with a reduction in the displacement of bases are more important than the triturating efficiency to evaluate posterior tooth form in terms of maintaining the

supporting structures. (5) The last occlusal design in the balanced category employs an arbitrary ar-

ticulator balance, followed by intraoral corrections to obtain balance, and it illus- trates a linear occlusion which is intended to give a one-dimensional contact be- tween the opposing posterior teeth as advocated by Frush20 (Fig. 5, A and B) . A blade on the lower posterior teeth contacts essentially flat surfaces of the upper

252 Beck

OCCLUSAL PLANE OCCLUSAL PLANE

6 6

A

=t

_- 6===- =-6

OVERLAPS CENTRIC OCCLUSION HORIZONTAL VERTICAL

Fig. 5. (A) In a linear occlusal concept the contact force would be directed toward the ridges and slightly toward the buccal side at the given inclination of 6 degrees. (A) From a right

lateral movement, the directions of contact forces would be maintained toward the ridges and slightly toward the buccal side of the lower ridge.

OCCLUSAL PLANE OCCLUSAL PLANE - -

OVERlAPS CENTRIC OCCLUSION 1 - 1 J2 mm. ~~ RIGHT HORIZONTAL 33 UPPERS 2 - 3 mm. 20 LOWERS

VERTICAL

Fig. 6. (A) One of several combinations of posterior tooth designs is illustrated in which upper lingual cusps make contact in lower fossae and in which the contact forces are directed toward

the ridges. Gold occlusal inlays help maintain the occlusal vertical dimension. (B) From a right lateral position, only the upper lingual cusps glide on low opposing inclines into enlarged fossae in the lower teeth. The buccal cusps on the working side are out of contact, and there

are no balancing-side contacts. The contact forces on the working side are directed toward the lingual side of the lower ridge. Accurate retentive bases are indicated. This concept also uses phonetic sounds of F, V, and 3 for the placement of the anterior teeth before the posterior teeth are arranged.

teeth set at a slight angle to the horizontal. The intent in this concern is to elim- inate occlusal deflective contacts and, thus, provide greater stabilization of the den- tures.

NONBALANCED OCCLUSlONS

(6) Fig. 6, A and B, depicts a concept as advocated by Poundr which stresses the positions of the anterior teeth to preserve or re-establish the phonetic values of the patient in harmony with increased denture stability and efficiency with the chewing cycle. Several characteristics of this concept are the incorporation of sharp

Volume 27 Number 3

Occlusion and remouable prosthodontics 253

OCCLUSAL PLANE OCCLUSAL PLANE

CUSPID Wf B

OVERLAPS CENTRIC OCCLUSION GUIDANCE i,

HORIZONTAL RIGHT

VERTICAL Fig. 7. (A) A concept which uses deep vertical overlaps, when indicated phonetically and

esthetically, and anatomic posterior teeth with full gold occlusal surfaces is illustrated. The upper hngual cusps and lower buccal cusps contact opposing fossae, and the composite direc- tions of contact forces are exerted toward the ridges. (B) From a right lateral position to

centric occlusion, cuspid guidance disoccludes the posterior teeth until occlusal contact is made

in centric occlusion. Accurate retentive denture bases are a requirement in this concept.

upper lingual cusps in opposing widened fossae of the lower teeth in centric oc-

clusion, the reduction of the buccal cusps of the lower posterior teeth, and the elim- ination of deflective contacts by the use of occlusal adjustment wax on the completed dentures. In effect, the occlusion is lingualized by the elimination of contacts on the buccal cusps and by the anteroposterior arrangement of the lower posterior teeth so that their lingual surfaces are on or within the lingual side of a triangle from the mesial area of the lower cuspid to the sides of the retromolar pad. Partial

occlusal metal inlays may be used to minimize wear on teeth and, thus, help main- tain the vertical dimension of occlusion.

(7) Another concept utilizes a 33 degree cusp form with full occlusal gold sur- faces (Fig. 7, A and B) .* The anterior teeth are set to the requirements of phonetic

values. Extreme vertical overlaps producing cuspid guidance are frequently used, resulting in disocclusion of the posterior teeth away from centric occlusion. Charac- teristic of this concept is the use of pantographic tracings and the transfer of these recordings to an instrument to eliminate all potential deflective contacts in the ar- rangement of the posterior teeth.

(8) A contemporary occlusal design which is used extensively utilizes nonan- atomic teeth in a straight occlusal plane, usually horizontal, when the casts are mounted horizontally in an instrument (Fig. 8, A and B) . All-porcelain or all-plastic posterior teeth may be used, or combinations of posterior teeth of porcelain upper and plastic lower teeth, or metal shearing blades may be incorporated in a block of

the upper posterior teeth occluding against lower porcelain teeth as advocated by

Hardy. (9) Occlusal pivots were advocated by Sear? (Fig. 9, A and B) . The primary

concerns are that the mandible be placed in equilibrium by maintaining the load

in the molar regions, that the procedure protects the temporomandibular joints

*Aull, A. E.: Personal communication.

254 Beck J. Prosthet. Dent. March, 1972

OCCLUSAL PLANE OCCLUSAL PLANE

HORIZONTAL HORIZONTAL

OVERLAP CENTRIC OCCLUSION HORIZONTAL

RIGHT

Fig. 8. (A) Nonatomic posterior teeth in a flat plane with a minimal vertical overlap in the

anterior region is a widely used concept. The contact forces are directed toward the ridge bilaterally in centric occlusion. (B) From a right lateral position to centric occlusion, only the

buccal cusps on the working side (W) contact if the path of the condyle is not parallel to the occlusal plane. Tilting of the bases and shear lateral forces may result if extreme gliding OC-

clusal contacts are made (B).

OCCLUSAL PLANE

HORIZONTAL WITH PIVOTS

OCCLUSAL PLANE

*~ - DIVERGENT

HORIZONTAL WITH PIVOTS

OVERLAP CENTRIC OCCLUSION HORIZONTAL AT PIVOT

? 2nd RIGHT MOLARS

Fig. 9. (A) Pivoting in the posterior region of a flat occlusal plane has been used to alleviate temporomandibular joint symptoms. Contact forces are directed toward the ridges in centric

occlusion. (B) From a right lateral position to centric occlusion, only the working-side pivot will contact if the path of the condyle on the balancing side (B) is not parallel to the occlusal plane.

against injury, and that the stresses are also reduced in the anterior regions of the

ridges in anticipation of tissue maintenance. (10) A reverse lateral curvature in the occlusal arrangement is used infrequently

(Fig. 10, A and B) . The mounted casts and the occlusal plane are on a horizontal plane in the instrument without a posterior ramp which results in a nonbalanced oc- clusion in eccentric positions. One type of this occlusal ,pattern was developed by Kurth5 and consisted of posterior tooth blocks in series of four teeth which were

arranged on a flat anteroposterior occlusal plane with a reverse lateral curve (reverse of Wilson curve) .

CONCLUSIONS

( 1) Ten occlusal concepts with different occlusal arrangements for complete dentures have been reviewed.

p"l;;;ry

OCCLUSAL PLANE

HORIZONTAL

A b -- --

a

=--=

Occlusion and removable prosthodontics 255

OCCLUSAL PLANE

HORIZONTAL

OVERLAP CENTRIC OCCLUSION TW B

HORIZONTAL REVERSE LATERAL CURVE

,, RIGHT

Fig. 10. (A) A concept which utilizes a flat anteroposterior occlusal plane and a reverse lateral curve is not used extensively. Contact forces are directed toward the lingual side of the lower ridge in centric occlusion. (B) 0cc1~sa.l contact is maintained in a movement from a right lateral position to centric occlusion on the working side (W) only, with contact forces directed toward the ridges. (B, balancing side.)

(2) Five of these designs are in the balanced concept, and five in the non- balanced concept.

(3) Contact forces which are transmitted to the basal seat areas of dentures vary with different occlusal patterns and designs.

(4) Efficiency of the teeth in triturating food in mastication is a factor which also needs evaluation relative to maintenance of supporting tissues.

(5) A few long-term investigations are in progress to evaluate statistically (a) several tooth forms and compare them and (b) the use of one tooth form with dif-

ferent clinical procedures. (6) It is conceivable that more than one occlusal design can provide satisfac-

tory denture service and fulfill the requirements of esthetics, function, and main- tenance of supporting tissues.

SUMMARY

Occlusal designs and their resulting functions are of concern to the dentist so that loss of the remaining tissues of the mouth, which may be attributed to the oc- clusion, can be minimized. This is difficult to assess since living tissues change and physiologic tolerances vary. More long-term statistical investigations are necessary

to compare the various occlusal designs so that more definable guidelines may evolve. Until such guidelines are available, the dentist must rely on his clinical experience and clinical judgment to select the occlusal design or designs of his choice in the treatment of complete denture patients.

References

1. Sears, V. H.: Thirty Years of Nonanatomic Teeth, J. PROSTHET. DENT. 3: 596-617, 1953.

2. Gysi, A.: Research in Denture Construction, J. Am. Dent. Assoc. 16: 199-223, 1929. 3. Hall, R. E.: Full Denture Construction, J. Am. Dent. Assoc. 16: 1157-1158, 1929. 4. French, F. A.: The Problem of Building Satisfactory Dentures, J. PROSTHET. DENT. 4:

769-781, 1954. 5. Kurth, L. E.: Balanced Occlusion, J. PROSTHET. DENT. 4: 150-167, 1954.

256 Beck .I. Prosthet. I)ent March, 1Yi

6. Hardy, I. R.: The Developments in the Occlusal Patterns of Artificial Teeth, J. PROSTHK

DENT. 1: 14-28, 1951. 7. Hickey, J. R., Henderson, D., and Straus, R.: Patient Response to Variations in Denture

Technique. Part I. Design of a Study, J. PROSTET. DENT. 22: 158-170, 1969.

8. Payne, S. H.: Selective Occlusion, J. PROSTHET. DENT. 5: 301-304, 19.?5. 9. Schuyler, C. H., Jordan, L. G., and Sears, V. II.: Report of the Committee on Principlcr.

Practices and Nomenclature, J. PROSTHE?. DENY. 2: 573-574, 19j2, and J. PROS~XXUI. DENT. 3: 595, 1953.

10. The Academy of Denture Prosthetics: Principles, Concepts and Practices in Prostho-

dontics, J. PROSTHET. DENT. 13: 283-294 ,1963.

11. Lytle, R. B., Atwood, D. A., and Beck, H. 0.: Minimum Standards of Adequate Prosthr+

dontic Service, J. PROSTHET. DENT. 19: 108-109, 1968. 12. Boucher, C. 0.: Current Clinical Dental Terminology, St. Louis, 1963, The C. V. Mosby

Company. 13. Jankelson, B., Hoffman, G. M., and Hendron, J. A., Jr.: The Physiology rlf the

Stomatognathic System, J. Am. Dent. Assoc. 46: 375-386, 1953.

14. Yurkstas, A. A., and Emerson, W. H.: A Study of Tooth Contact During Mastication With Artificial Dentures, J. PROSTHET. DENT. 4: 168-174, 1934.

15. Brewer, A. .4., and Hudson, D. C.: Application of Miniaturized Electronic Devices to

the Study of Tooth Contact in Complete Dentures. J. PROSTHET. DENT. 11: 62-72, 1961.

16. Brewer, A. A.: Prosthodontic Research in Progress at the School of .4erospace Medicine. J. PROSTHET. DENT. 13: 49-69, 1963.

17. Anderson, D. J., and Picton, D. C. A.: Tooth Contact During Chewing, J. Dent. Res.

36: 21-26, 1957.

18. Adams, S. H., and Zander, H. A.: Functional Tooth Contacts in Lateral and in Centric Occlusion, J. Am. Dent. Assoc. 69: 465-473, 1964.

19. Pleasure, M. A.: Anatomic Versus Nonanatomic Teeth, J, PROSTHET. DENT. 3: f47-i.54. 1953.

20. Frush, J. P.: Linear Occlusion, Swissedent Foundation, June, 196;.

21. Pound, E.: Utilizing Speech to Simplify a Personalized Denture Service, J. PROSTHEF. DENT. 24: 586-600, 1971.

22. Sears, V. H.: Occlusal Pivots, J. PROSTHET. DENT. 6: 332-338, 1956.

UNIVERSITY OF TEXAS DENTAL BRANCH AT HOUSTON

P. 0. Box 20068 HOUSTON TFXAS 77023 >