5. 6. 7. 8. 9. 10. 11.
Friedman, S.: Edentulous impression procedures for maximum retention and stability. J PROSTHETDENT 7:14, 1957. Lott, F., and Levin, B.: Flange technique: An automatic and physiologic approach to increased retention, function, comfort, and appearance of dentures. J PROSTHETDENT 16~394, 1966. Fry, K.: The retention of complete dentures. Br Dent J 44:97, 1923. Moses, C. H.: Physical considerations in impression making. J PROSTHETDENT 3~449, 1953. Howland, C. A.: The retention of artificial dentures. Dent Digest 27~159, 19’1. Stamoulis, S.: Physical factors affecting the retention of complete dentures. J PROSTHETDENT 12:857, 1962. Brill, N.: Factors in the mechanism of full denture retention-A discussion of selected papers. Dent Pratt (Bristol) l&9, 1967. Stanitz, J. D.: An analysis of the part played by the fluid film in denture retention. J Am Dent Assoc 32:445, 1948. Snyder, F. C., Kimball, H. D., Bunch, W. B., and Beaton, J. H.: Effect of reduced atmospheric pressure upon retention of dentures. J Am Dent Assoc 32~445, 1945. Tyson, K. W.: Physical factors in retention of complete upper dentures. J PROSTHETDENT 18~90, 1967. Skinner, E. W., and Chung, P.: The effect of surface contact in the retention of a denture. J PROSTHETDENT 1:229, 1951.
14. 15. 16. 17. 18.
Tilton, G. E.: The denture periphery. J PROWHET DENT 2:290, 1952. Lammie, G. A.: The retention of complete dentures. J Am Dent Assoc 55:502, 1957. Edwards, L. F., and Boucher, C. 0.: Anatomy of the mouth in relation to complete dentures. J Am Dent Assoc 29:331, 1942. Barone, J. V.: Physiologic complete denture impressions. J PROSTHETDENT 13~800, 1963. Jacobson, T. E., and Krol, A. J.: A contemporary review of the factors involved in complete denture retention, stability and support. Part I: Retention. J PROSTHETDENT 49:5, 1983. Jacobson, T. E., and Krol, A. J.: A contemporary review of the factors involved in complete dentures. Part 11: Stability. J PROSTHETDENT 49:165, 1983. Jacobson, T. E., and Krol, A. J.: A contemporary review of the factors involved in complete dentures. Part III: Support. J PROSTHETDENT 49:306, 1983.
Rqmnt reques1s to: DR. D. RAY MCARTHUR UNIVEKSITYOF NORTH CAROLINA SCHOOLOF DENTISTRY 209 H CHAPEL HILL, NC 27514
The ala-tragus line in complete denture prosthodontics F. W. van Niekerk, B.D.S., D.D.S.,* V. J. Miller, B.Ch.D., B.Sc., M.R.I.C., C.Chem.,* and R. E. Bibby, B.M.Sc., B.D.S., M.M.Sc., M.Dent.** University
of the Western Cape, Faculty of Dentistry, Tygerberg, Republic of South Africa
any methods have been used to establish the occlusal plane in complete denture prosthodontics. However, no single method seems to be fully accepted.‘z2 Anteriorly, esthetic considerations help define the occlusal plane, and posteriorly the tongue, retromolar pad, and Stenson’s duct are considered.1-5Some dentists bisect the space between the residual ridges.6 The technique of using the ala-tragus line (Camper’s line) to establish the occlusal plane is well documented.2,4~7-”However, definitions of the ala-tragus line cause confusion, because the exact points of reference do not agree. For example, the Glossary of Prosthodontic TermslO states that the ala-tragus line runs from the inferior border of the ala of the nose to the superior
border of the tragus of the ear, while Spratley’ describes it as running from the center of the ala to the center of the tragus; and Ismail and Bowman2 define it as a line that passes from the ala of the nose to the center of the tragus of the external auditory meatus. The latter plane proved unsatisfactory in our prosthetic clinic, because the plane thus established often allowed insufficient space to arrange the maxillary molar teeth. Therefore, the posterior reference point was dropped to the inferior border of the tragus (Fig. 1). This article concerns the relationship of the newly defined ala-tragus line to an occlusal plane established with criteria that ignore the ala-tragus line during jaw registration procedures.
*Senior Lecturer, Prosthetic Department. **Professor and Head, Orthodontic Department.
Thirty-three sets of complete dentures were made with criteria other than the ala-tragus line used to
Fig. 1. Ala-tragus line with inferior
border of tragus.
establish the occlusal plane. Patients were completely satisfied with esthetics, function, and comfort. Lead foil adapted to the right mandibular posterior teeth indicated the occlusal plane. A strip of foil taped to the’ face pointed at the inferior borders of the ala and tragus. Lateral cephalometric radiographs were made of each patient by a standard method and traced on acetate paper to show the functional occlusal plane and the ala-tragus line. All radiographs were made with the teeth in centric occlusion (Fig. 2). The relationship between the two planes was measured and the angle between them given a positive value for posterior convergence. Mean and standard deviation values were then calculated for the relationship.
RESULTS The angle formed by the functional occlusal plane and the ala-tragus line had -a .mean of +2.45 degrees, a standard deviation of 3.24 degrees, and a range of +8-to -7.5 degrees. The mean difference between the planes was 2.45 degrees with a standard deviation of 3.24 degrees. Such relatively narrow limits showed’s close relationship between the two planes. I3IscUSSK)N It is easier for the less experienced dentist to use the ala-tragus line rather than intraoral reference points when the upper occlusion rim is trimmed to the occlusal 68
Fig. 2. Foil strips show relationship between occlus~i plane and ala-tragus line with teeth in centric occiirsion.
plane. Conflicting definitions of the ala-tragus line must affect the usefulness of this technique. The location of the posterior landmark of the ala-tragus line defined in this article required investigation. In this study, the ala-tragus line was ignored during the jaw registrations and the try-in. The occlusal plane of the dentures was checked against the ala-tragus line only at the final visit. Results showed a close relationship between the two planes. It is interesting to speculate on the reason for the close correlation between the two planes. A radiographic investigation of the bony landmarks involved could throw light on the question.
CONCLUSION The ala-tragus line described in this article has a close relationship with the occlusal plane and could be used as a landmark when the maxillary occlusion rim is trimmed to the occlusal plane. Positioning of the occlusal plane depends on mature clinical judgment and must ultimately satisfy esthetics, function, and denture stability. REFERENCES 1. Spratley, M. Ii.: A simplified technique for determining rhe occlusal plane in full denture construction. 1 Oral Rehabil 73 1, 1980. JANUARY
Ismail, Y. H., and Bowman, J. F.: Position of the occlusal plane in natural and artificial teeth. J PROSTHET DENT !20:407, 1968. 3. Yasaki, M.: Height of the occlusion rim and the interocclusal distance. J PROSTHETDENT 11:26, 1961. 4. Boucher, C. O., Hickey, J. C., and Zarb, G. A.: Prosthodontic Treatment for Edentulous Patients, ed 7. St. Louis, 1975, The C.V. Mosby Co. 5. Standard, S. G.: Establishing the plane of occlusion in complete denture construction. J Am Dent Assoc 54845, 1957. 6. De Van, M. M.: An analysis of stress counter action on the part of the alveolar bone with a view to its preservation. Dent Cosmos 77:109, 1935. 7. Landa, S. L.: Practical guidelines for complete denture esthetics. Dent Clin North Am 21:289, 1977.
Sharry, J. J.: Complete Denture Prosthodontics, ed 3. New York, 1974, McGraw-Hill Book Co., p 236. 9. Payne, S. H.: The trial dentures. Dent Clin North Am 21:326, 1977. 10. Academy of Denture Prosthetics: Glossary of Prosthodontic Terms. St. Louis, 1977, The C.V. Mosby Co. Refmnt request, to: DR. F. W. VAN NIEKERK UNIVERSITYOFTHE WESTERNCAPE ORAL AND DENTAL TEACHING HOSPITAL FACULTYOF DENTISTRY PRIVATE BAG Xl2 TYCERBERC7505 REPUBLICOF SOUTH AFRICA
Studies of biologic parameters for denture design. Part III: Effects of occlusal adjustment, base retention, and fit on masseter muscle activity and masticatory performance Paul Perez, D.M.D.,* Krishan K. Kapur, D.M.D., M.D.,** and Neal R. Garrett, Ph.D.*** Veterans
lhe influence of denture factors on masticatory performance is limited.le6 It was unexpected to find that neither denture retention nor occlusal scheme affects the masticatory ability of denture wearers significantly. The denture factors that did influence masticatory performance were those related to the manipulation of food during chewing. It is important to recognize that masticatory performance in these studies was measured merely in terms of the ability of denture wearers to pulverize food. No attention was paid to the force or muscle effort exerted by denture wearers during chewing. Results of several studies indicate that poor masticatory function in denture wearers may stem from alterations in oral neuromuscular activity.‘-” An impairment in the ability of denture wearers to discriminate particle size and texture has been shown. A previous study also revealed that integrated masseter muscle activity, recordPresented at the 58th Annual Meeting of the American Association for Dental Research, Los Angeles, Calif. Supported by the Medical Service of the Veterans Administration. *Staff Dentist and Adjunct Assistant Professor, University of California, School of Dentistry, Los Angeles, Calif. **Chief, Dental Service, Professor-in-Residence, University of California, School of Dentistry, Los Angeles, Calif. ***Staff Physiologist. THE JOURNAL
ed during chewing of test foods, was markedly less in denture wearers than in subjects with natural dentition.” It was hypothesized that the reduced muscle effort applied by denture wearers might contribute to their diminished chewing ability. The present study was undertaken to determine the effects of denture base fit and occlusal correction on the masseter muscle activity during chewing and the relationship between the electromyographic (EMG) activity and masticatory performance.
METHODS Twenty denture wearers, ranging from 46 to 80 years of age (g = 62.7 years), were selected from the patient population of the Veterans Administration Medical Center in Sepulveda, Calif. The total complete denture experience for patients ranged from 2 to 46 years (Z = 22.5 years). Subjects were screened to be healthy through a medical history and examination of the oral cavity. Each denture was assessedseparately for retention and stability on a four-point ordinal scale. The maxillary and mandibular dentures were evaluated together on a three-point scale separately for the vertical and horizontal occlusal relationships. Similarly, the ridge shape and size, mucosal consistency, and location 69