Overbite as an Etiological Factor of TMJ Disorders. Clinical and Electromyographic Exploration

Abstract

INTRODUCTION: The intermaxillar relationship in overbite is one of the etiological factors of TMJ disorders (Pulinger, Sellingman and Gorbeirn, 1993). Nevertheless, it does not always cause malfunction. Sometimes the compensating mechanisms of the individual prevent the occurrence of symptoms and it only appears when parafunctional habit overloads the stomatognathic apparatus. OBJECTIVE: The aim of this study was to escamine neuromuscular behaviour in patients with such occlusal alteration. MATERIAL AND METHODS: We present two cases with overbite: one bruxist with malfunction and one nonbruxist without symptoms of malfunction. An occlusal analysis and clinical, kinesiographic and electromyographic exploration was performed in both patients. For the analysis we used a Dentatus A.R.L. articulator, Myotronics electromyograph and K6 kinesiograph. RESULTS AND CONCLUSIONS: The results of the exploration were compared with those of a healthy individual with normal occlusion, used as a reference. Lateral movements were restricted and with a mainly vertical component. In both cases there was an increase in electromyographic activity during normal mastication and swallowing, and in maximum force bite there was the same response between anterior temporalis and masseter muscles. The study demonstrated that the mandibular movements in both patients were very similar, and determined by the occlusal factor, in comparison to normal individuals. Nevertheless, the electromyographic exploration shows a different neuromuscular response by the patient adapted to this occlusal problem and the dysfunctional patient