:Stepwise clenching

概要

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Occurrences of the quiet period (silent period, QP) in activities of the masseter and the anterior part of the temporalis (both sides) were investigated during the clenching movement of nine human subjects with normal occlusion. The subjects were asked to increase their bite forces, in a stepwise manner voluntary isometric contraction to maximun bite force levels. QP (duration 20-70 msec) was observed (66.6%) almost simultaneously in four muscles during the experimental conditions of changing the bite force rapidly to a higher level. The computer analysis of EMG wave form by means of FFT (discussed earlier) was carried out in order to determine the qualitative differences in the motor unit discharge frequency patterns before and after the onset of QP. Power spectrum "BEFORE QP 1" was distributed in a higher frequency band with high energy, whereas "AFTER QP 2" was charactcrized by a low frequency band with low energy. From these results, it is reasonable to assume that after the temporal cessation of electrical activity (QP), there exist some changes in the muscular activation set by the α-γ inkage (coactivation). QP observed in this study may, therefore, be assumed to be accompanied with a transitional phase of motor control.
歯科基礎医学会の論文