Power spectral analysis of electromyographic signal of masticatory muscles at rest position and habitual clench.

Thirteen normal subjects were selected for this investigation. At the vertical dimension of rest position and habitual clench, their myoelectric activities of the masseter, anterior and posterior temporal, and digastric muscles on the left and right sides were simultaneously sampled and processed by computer, and the mean power frequency (MPF) and the mean amplitude (MA) of the myoelectric signal were calculated. At rest position, the temporal muscles were major muscles and the MPF differences of various masticatory muscles were not significant. At habitual clench, with the increase in MA, the MPF of various muscles increased. The results show that MPF may have application in describing a central tendency of myoelectrical signal frequency distribution and in evaluating recruitment of motor units. MPF and MA are the quantitative indices reflecting masticatory muscle function.