Functionally generated amalgam paths for complete dentures

Functionally dentures

generated amalgam

Akihiko Shiba, D.D.S.,* Toshio Hayashi, Osamu Tanaka, D.D.S.*** Showa University,

School of Dentistry,

D.D.S.,**

and Tokyo Medical

paths for complete

Jiro Yoshida,

D.D.S.,***

and Dental University,

and

Tokyo, Japan

F

or various reasons, mandibular movements cannot be reproduced on an articulator, regardless of how precise and high in performance the articulator may be.le5 This article describes a technique which produces a functionally balanced occlusion of complete dentures that is generated by the patient’s mandibular movements. It is a modification of the technique of articulator-generated amalgam paths in resin posterior teeth, as reported by Lauciello6 and Ortman,? in that the amalgam paths are generated directly in the mouth. No high-accuracy articulator is required, and the concept of lingualized occlusion is similarly used.

LINGUALIZED

OCCLUSION

This type of balanced occlusion, advocated by Payne’ and by Pound and MurrelP” has the posterior teeth arranged so that the resultant functional forces are distributed lingually to the residual ridge. This enhances the stability and retention of the lower denture. Lingualized occlusion is essential for this technique since denture movement will introduce inaccuracies in the functionally-generated paths. Fig. 1. Posterior denture teeth that can be used for technique. A, Upper so-degree porcelain teeth. B, Lower 20-degree plastic teeth.

TOOTH SELECTION AND OCCLUSAL ADJUSTMENT Jaw records are made, final casts are mounted on an articulator, and the artificial teeth are arranged according to the techniques of Pound and Murrell.“‘* ‘* Upper 30-degree porcelain teeth and lower 20-degree plastic teeth (Livdent, G-G Go., Tokyo,

*Professor, Department of Prosthetic Dentistry, Showa University, School of Dentistry. **Professor, Department of Prosthetic Dentistry, Tokyo Medical and Dental University, School of Dentistry. ***Assiitant Professor, Department of Prosthetic Dentistry, Showa University, School of Dentistry.

494

NOVEMBER

1981

VOLUME

46

NUMBER

5

Japan) are used (Fig. 1). Lower plastic teeth are used to facilitate cavity preparation for the amalgam paths. The porcelain teeth are to develop the desired working, balancing, and protrusive occlusal facets. The buccolingual width of the posterior teeth is made narrow to enhance stability of the lower denture. After processing, the dentures are remounted on an articulator, and changes in vertical dimension and occlusal contacts are corrected by selective

0022-3913/81/110494

+ 04$00.40/00

1981 The C. V. Mosby

Co.

FUNCTIONALLY

GENERATED

AMALGAM

PATHS

Fig. 2. Posterior teeth prepared for reception of amalgam. Channels are prepared from distal grooves of lower first premolars to distal grooves of second molars. Walls of channels are undercut. grinding. Grinding is confined to the lower plastic teeth, except when the upper buccal cusps interfere in eccentric excursions. The upper lingual cusps should never be ground.

TOOTH PREPARATION AND MAINTENANCE OF VERTICAL

DIMENSION

For articulator-generated paths, cavities are prepared on the parts of lower occlusal surfaces that are contacted by the upper lingual cusps in excursive movements.6, ’ With functional jaw movements, contacts may be made outside of these articulatorgenerated paths. Thus, cavity preparation for functionally generated paths consists of continuous occlusal channels on the lower posterior teeth that extend from the distal fossae of the lower first premolars to those of the lower second molars (Fig. 2). When the lower posterior teeth are prepared in this manner, retaining the established vertical dimension becomes impossible. As a means of retaining it, a modified version of the Simple Intraoral Gothic Arch Tracer (Dentsply International Inc., New York, N.Y.) is used. The regular recording stylus is used on the upper denture, and a specially designed copper plate is attached to the lower denture (Figs. 3 and 4). It is designed so that the stylus contacts the plate in centric relation to maintain vertical dimension and to permit freedom of movement in eccentric excursions. Functional paths can thus be formed without interference. If a flat plate is used, the formation of the functional paths would be controlled by the contact of the recording stylus with the flat plate.

THE

JOURNAL

OF PROSTHETIC

DENT&TRY

Fig. 3. Recording stylus is attached to upper denture, and plate for maintaining intermaxillary vertical dimension is attached to lower denture.

Fig. 4. Contact relation between recording stylus and lower plate in centric relation. Conta,ct part of plate is elevated. After the tracer components are attached to their respective dentures, a plaster core of centric occlusion is made on the articulator. This may be used to verify the occlusal relation when the dentures are removed from the articulator.

495

SHIBA

Fig. 5. Occlusal paths generated in amalgam. GENERATION

OF AMALGAM

PATHS

The dentures are inserted in the mouth and centric jaw relation is confirmed. Amalgam powder and mercury in a 314 ratio are mixed, packed, and condensed in the channels that have been prepared in the lower posterior teeth (Fig. 2). The denture is then placed in the mouth, and the patient is directed to close with a tapping action until the recording stylus and the plate for preserving the intermaxillary vertical dimension come in contact. When centric contact at the correct vertical dimension is established, the patient is instructed to brux the teeth in all directions and swallow. This is continued until the excursions become smooth and paths that are harmonious with the patient’s mandibular movements are formed on the amalgam surfaces. The lower denture is then removed (Fig. 5) and the excess amalgam trimmed from the teeth. The denture is reinserted, and the procedure is continued to refine the paths. After the amalgam has hardened, any further excess is trimmed from the channel margins, and the recording stylus and plate are removed from the dentures. The amalgam paths now provide a functionally balanced occlusion. The dentures are placed, and the patient is requested to return the next day to have the amalgam surfaces polished (Fig. 6).

Fig.

6.

Amalgam

ET AL

paths have been polished.

articulator may require correction in the mouth after the dentures are placed. Such correction is difficult and not always satisfactory. A technique of intraorally generating amalgam paths for two lower posterior teeth simultaneously has been reported.’ This technique has the advantage that the balanced occlusion can be developed without grinding posterior teeth. However, since the amalgam paths are generated in accordance with the cusp angles of the other posterior teeth, the occlusion will not be entirely in harmony with the patient’s actual mandibular movements. In view of this, a special lower tracer plate has been developed which is contacted only in centric relation by the upper recording stylus to maintain intermaxillary vertical dimension. The stylus becomes free of contact during eccentric jaw movements, and no restraint is present to the generation of functional paths in the amalgam insets in the lower posterior teeth. Stability of the dentures is vital for this technique and lingualized occlusion should be used for posterior tooth arrangement. Articulatorgenerated amalgam pathse, ‘I and fillings’ in plastic teethI are not sufficiently extensive t.o maintain contact with upper lingual cusps during all functional movements.

SUMMARY DISCUSSION There are limitations to the duplication of mandibular movement even on highly accurate articulators’s5, I2 due to such factors as tissue resiliency, neuromuscular physiology, and varying shapes of the glenoid fossa, meniscus, and condyle.13 There are also possible errors in the mounting of casts and recording of condyle movements.4j s A balanced occlusion for complete dentures developed on an

4%

A technique for generating intraoral functional paths in lower posterior teeth of complete dentures has been described. Lower plastic teeth prepared to receive amalgam insets, are used. A special tracer assembly is attached to the processed dentures to permit maintenance of vertical dimension and to allow freedom of upper lingual cusp movement to generate functional paths in amalgam that has been packed in the prepared plastic teeth.

NOVEMBER

1981

VOLUME

46

NUMBER

5

FUNCTIONALLY

GENERATED

AMALGAM

PATHS

REFERENCES 1.

2.

3.

4.

5.

6. 7.

a.

Posselt, U., and Skytting, B.: Registration of the condyle path inclination: Variations using the Gysi technique. J PROSTHET DENT 10~243, 1960. Posselt, U., and Franzen, G.: Registration of the condyle path inclination by intra-oral wax records: Variations in three instruments. J PROSTHET DENT 10~441, 1960. Posselt, U., and Nevstedt, P.: Registration of the condyle path inclination by intraoral wax records-Its practical value. J PROSTHET DENT 11:43, 1961. Watt, D. M.: A study of the reproducibility of articulator settings from graphic records of mandibular movement. Dent Prac Dent Ret 19:119, 1968. Rea, T. J.: Human Variance in Adjusting a Fully Adjusted Articulator by Means of a Pantograph. Thesis, University of Michigan, 1972. Lauciello, F. R.: Articulator-generated amalgam stop for complete dentures. J PROSTHET DENT 41:16, 1979. Winkler, S.: Essentials of complete denture pmsthodontics. In Ortman, H. R., and Ortman, L. F., editors: Arrangement of the Posterior Teeth. Philadelphia, 1979, W. B. Saunders CO., pp 383-387.

ARTICLES

Ameye,

The design Donald

D.D.S.,

Paul

M.D.S.,

D.D.S.,

C. Christensen,

Reprint requests to: DR. AKIHIKO SHIBA SHOWA SCHOOL 2-I-1,

UNIVERSITY

OF DENTISTRY KITASENZOKLJ,

OHTA-KU

TOKYO 145, JAPAN

D.D.S.,

resins. Part I: Color and

Guido

Vanherle,

stability

M.D.,

and

D.D.S.

pontics Ph.D.,

F.R.A.C.D.S.

of provisional on ceramometal

J. Dent, D.D.S., Jack A. Caputo, Ph.D.

D. Preston,

Effect of self-curing acrylic crevicular fluid volume

THE JOURNAL

14.

H. Garvin, M.S., and

OF PROSTHETIC

restorations

D.D.S.

Effect of oxidation

Patrick D.D.S.,

13.

M.S.D.

Color characterization

Robert Angelo

12.

shade work authorizations

R. B. Blackman,

Loren

11.

composite

Lambrechts,

of multiple

A. Behrend,

Ceramic

10.

TO APPEAR IN FUTURE ISSUES

Conventional and microfilled marginal adaptation Cathy

9.

Payne, S. H.: A posterior set-up to meet individual rcquirements. Dent Dig 47:20, 1941. Pound, E.: Utilizing speech to simplify a personalized denture service. J PROSTHET DENT 24:586, 1970. Pound, E., and Murrell, G. A.: An introduction to denture simplification. Phase I. J PROSTHET DENT 26:570, 1971. Pound, E., and Murrell, G. A.: An introduction to denture simplification. Phase II. J PROSTHET DENT 29:598, 1973. Swanson, K. H.: Complete dentures using the TMJ articulator. J PROSTHET DENT 41:497, 1979. Watt, D. M., and MacGregor, A. R.: Designing Complete Dentures. Philadelphia, 1976, W. B. Saunders Co., p 166. Sowter, J. B., and Bass, R. E.: Increasing the efficiency of resin posterior teeth. J PROSTHET DENT 19:465, 1968.

D.D.S., Boleslaw

DENTISTRY

bond strength D.D.S.,

Joseph

resin treatment

M.S., William F. P. Malone, Mazur, D.D.S., M.S.

P. Moffa,

D.D.S.,

restorations D.D.S.,

M.S.,

M.S.D.,

and

on the Ph.D.,

Patrick

D. ‘I’oto,

497