Occlusal control of mandibular elevator muscles.

Occlusal stability and mandibular elevator muscle function was studied in 25 women (20-30 yr of age). They had 27-32 fully erupted teeth with few treated occlusal surfaces, and craniomandibular function including mandibular mobility was normal. The aim was to analyze the influence of natural patterns of occlusal contact on electromyographic activity, unaffected by pain and functional disorders. Occlusal stability was assessed in the intercuspal and in lateral contact positions as the number of teeth with physical contact and the number of opposing pairs of teeth in contact. Electromyographic activity was recorded by surface electrodes over anterior and posterior temporalis and masseter muscles. In general, positive correlations were found between occlusal stability in intercuspal position and moderate to strong static and dynamic contractions, most significant in masseter muscles, indicating that forceful contraction of these muscles implies stable occlusion. Systematically, the duration of activity during chewing was negatively correlated with occlusal stability in the intercuspal position, most pronounced in working-side muscles. This pointed to shorter contractions with stable occlusion and is interpreted as the result of less need for stabilizing activity. It is concluded, that the correlations between occlusal stability and elevator muscle function are probably based on feedback mechanisms from periodontal pressoreceptors.