Investigations Concerning Anterior and Posterior Mandibular Guidance

Transcription

1 Investigations Concerning Anterior and Posterior Mandibular Guidance G.K. SiebertD.D. S N. Reu/ing, D.D.S. Marburg, W. Germany INTRODUCTION Ma,ny investigations concerning the dynamics and the movements of the mandible were done in recent years by use of mechanical methods. Extraoral recording systems are superior to all other methods in studying the complicated mandibular movement mechanisms. Because of occlusal interferences most authors used extraoral and intraoral recordings without tooth-contact or with central bearing point and analyzed the three-dimensional movements of the mandible. There was a lot of controversity concerning the question whether TMJ or teeth are dominant in mandibular guidance Until now, both opinions are often topic of scientific discussions; nevertheless, many investigations have shown that in the natural complete dentition, the cuspids work as so called "anterior TMJ". 5, 9, 19, 20, 21, 25, 26 Therefore,in the second dentition the TMJ is forced to adapt to the inclinations of the cuspids as GYSI has often described. 9 Contrary to this, we have to leave the principle of anterior guidance in cases of full dentures because of the specific static and dynamic features of these prosthodontic appliances. It was the aim of this study to evaluate if the teeth or the TMJ or the masticatory muscles are dominant in mandibular guidance. METHOD In our investigation, we used a mechanic and an electronic recording system. The mechanical extraoral recordings were done by use of a modified Stuart-pantograph and paraocclusal splints. Tracing of reproducible three-dimensional border-movements of the mandible with and without a central bearing point were possible by the help of supplementary recording plates. In the TMJ-region a frontal-vertical plate and in the anterior part of the mandible a frontal-vertical and a sagittal-vertical plate were used. By the help of the inductive displacement transducers, placed in paraocclusal The Journal of Gnathology Vol. 5, No. 1,

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4 Siebert, Reuling Table 2. Qualitative gradation for the guidance in natural denti tion. Guidance ~ l ~~ Guidance anterior tooth guidance canine protected occlusion canine and first premolar protected occlusion occlusion with multiple function only on the working side balanced occlusion posterior tooth guidance TMJ-guidance Canine r~~ ~q;, ~~Canine and first.;,~ "\ premolar : \ ~ '-l '> ~ I Fig. 5. Tooth movements during guidance: canine and first premolar or pure canine guidance. Electronic recordings These results prove that anterior teeth work as mandibular guiding elements because of their morphology and topograpy. The study of anterior guidance suggests a qualitative gradation from the pure canine protected occlusion to the most extreme group function and balanced occlusion in natural dentition (Table 2). When the first premolars are dominant in lateral mandibular guidance they show pathophysiologic movements in buccal-distal and distallingual direction ( Fig. 5). When a pure canine guidance is found, the first premolars do not show the afore mentioned movements but remain in their basic position and the canines themselves show a physiologic amount of movement. Following local anesthesia of the upper canines, the amount of movement increased up to twice of the amount of movements without anesthesia. Th is points to the role of proprioceptors in the periodontal tissues of upper canines. Those receptors are apparently the regulatory factor in the cybernetics of mandibular kinesiology and therefore guarantee the TMJ-protection against loading influences during lateral movements of the mandible. The determining factor of anterior guidance is that the anterior teeth have a non-occlusion of about 30 micrometers in centric occlusion, because the anterior teeth will move during clenching in a lingual and distal respectively mesial direction. Electromyography and tooth-kinetics The results of simultaneous measurements of tooth kinetics and masticatory muscle activity show, that there are increased movements of the guiding teeth and also an increased muscle activity on the contralateral side in cases of balancing interferences. After 102

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6 Siebert, Reullng REFERENCES 1. Aull, E.: Condylar determinants of occlusal patterns. J. Prosth. Dent. 15, Bennett, N.G.: A contribution of the study of the movements of the mandible. J. Prosth. Dent. 8, 31, Bewersdorff, H.J. : Elektronische dreidimensional Messung und Registrierung von Kieferbewegungen. Diss. Stockholm Broderson. S.: Anterior guidance - the key to successful occlusal treatment. J. Prosth. Dent. 39, 396, D'Amico, S.: Functional occlusion of the natural teeth of man. J. Prosth. Dent. 11, Eltner, E.: Der anatomische Artikulator Eltner in der Praxis. Schweiz. Viertel jahresschr. Zahnheilk. 12, 7, Fehr, C.U.: Das A.rtikulationsproblem und ein neuer Artikulator. Dtsch. zahnarztl. Wochenschr. 24, 341, Gerber, A.: Die Bewegungen des Unterkiefers und deren Wiedergabe im Artikulator. Zahnarztl. Welt 5, 464, Gysi, A.: Artikulation in: Handbuch der Zahnheilkunde Hrsg. Partsch, C., Brun, C.. Kantorowicz, A.J.F. Bergmann, Munchen Hickey. J.C.: Mandibular movements in three dimensions. J. Prosth. Dent. 13, Kahn, A.E.: Unbalanced occlusion in occlusal rehabilitation. J. Prosth. Dent. 14, 725, Lee, R.L.: Jaw movements engraved in solid plastic for articulator controls. J. Prosth. Dent , McCollum, B.B.: Fundamentals involved in prescribing restorative dental remedies. Dent. It. Int. 61,522,641, Mccollum, B.B.: Oral rehabilitation and occlusion. University of Calif., San Francisco Medical Center. San Francisco, 111, Monson, G.S.: Occlusion as applied to crown and bridgwork. J. Nat. dent. Ass. 399, Muller. M.: Zur Rekonstruktion der anterioren Fuhrung mit Hilfe einer neuartigen Registriereinrichtung. Med. Diss. Mainz, Philipps, G.P.: Graphic reproduction of mandibular movements for full denture construction. J. Am. Dent. Ass , Posselt, U.: Studies in the mobility of the human mandible. Acta Odont. Scand. 10, Suppl. 1 O Rumpel. C.: Das Artikulatorproblem. Dtsch. Mschr. Zahnheilk. 31, 389, Schroder. H.: UberdenUmfang der Mahlbewegungen. Dtsch. Zahnarztl. Wschr. 43, Shaw, D. M.: Form and function in teeth and a rational unifying principle applied to interpretation. Amer. J. Orthodont. 1 O Sittig, W.: Klinisch-experimentelle Untersuchungen zum immediate side shift. Med. Diss. Mainz Stallard. H. and Stuart, C.E.: Eliminating tooth guidance in natural dentitions. J. Prosth. Dent.11, Strack, R.: Die Lateralbewegungen der Gelenkkopfe bei der Leer-und Kaubewegung. Zahnarztl. Welt , Vest, G.: Beitrag zur Zahnbelastung beim Kontakt. Schweiz. Mschr. Zahnheilk , Walker. E.: The facial line and angle in prosthetic dentistry. Dent. Cosmos Weber. A.: Gr6Q.e und Rich tung der Condylenverschiebung bei Unterkieferbewegungen. Med. Diss. Bern Wustrow. P.: Zur Darstellung der Kieferbewegungen. Zahnarztl. Rdsch. 6, Prof. Dr. G.K.Siebert Dep. Stomatognathic Physiology, Dental School, University Marburg, Georg-Voigt-Str. 3, D-3550 Marburg, W. Germany 104