Electromyographic activity of the temporal and masseter muscles at different occlusal positions

Abstract

Normal occlusion or eugnathia, is a morphologically and functionally balanced bite. Differences in the form and function of orofacial structures cause morphological and functional deviations of the orofacial system. Irregular occlusal postitions may consequently change the electromyographic activity of the muscles of orofacial region. The aim of the research was an analysis and a comparative analysis of the bioelectrical activity of masticatory muscles in normal occlusion and distocclusion, in rest position, in the position of the central occlusion of the mandible and at the maximum voluntary muscle contraction. The metodology of the research is based on electromyographic recording of the action potentials of the examined muscles in different mandibular positions. Registration of action potentials of the masticatory muscles was done using, facial, intramuscular, and coaxial electrodes, (Greenfield scheme) and measurements were performed on both sides. The research was carried out on a sample of 60 patients with an average age of 14,25 years. 30 subjects had normal occlusion and 30 had distal occlusion. The results were expressed in microvolts, as average cumulative amplitude voltages of action potentials, by means of which changes in the masticatory muscles were established and the degree of correlation between the electromyographic activity of the masticatory muscles and the occlusal type was analyzed. The results of the research show that the bioelectrical activity of the examined masticatory muscles falls in the group of subjects with distal occlusion, which is the result of a decreased number of active muscular tissues, or a decreased number of impulses coming into the muscle, or the combination of both.