MASTICATORY ELECTROMYOGRAPHIC ACTIVITY IN HEALTHY-YOUNG ADULTS AND MYOGENOUS CRANIOMANDIBULAR DISORDER PATIENTS

The electromyographic (EMG) activity of the masseter and the anterior temporalis muscles were compared between 60 healthy controls and 61 my ogenous craniomandibular disorder (CMD) patients. Subjects were asked to clench at 10% and at 50% of their maximum voluntary clenching level . The effects of CMD, age and gender were statistically analysed with the use of the analysis of covariance. The correlations between EMG as ymmetries and the lateral slide from the retruded contact position to the intercuspal position and the asymmetry in the number of post-canin e tooth contacts between the left and the right side were investigated . The CMD patients showed lower masseter EMG activities than the contr ols, whereas the anterior temporalis EMG activity was not different be tween the two groups. The activity index, relating the anterior tempor alis EMG activity to the activity of the masseter muscles, confirmed t he presence of a relatively high temporalis activity in the CMD group. No significant differences were found in the EMG asymmetries between the controls and the CMD patients. Males showed higher masticatory EMG activities than females. These gender effects were significant for th e anterior temporalis at the 10% and 50% level and for the masseter mu scle at the 10% level. The anterior temporalis EMG activity declined w ith age. No age related effects were observed in the masseter EMG. The lateral slide was larger and more prevalent in the CMD group. A signi ficant correlation between the lateral slide and the anterior temporal is EMG was found for the CMD group at the 10% level. No correlation wa s found between the EMG asymmetry and the asymmetries in post-canine t ooth contacts. In conclusion: significant CMD, age and gender effects were observed in the masticatory EMG activities of a group of myogenou s CMD patients and a control group.