[EMG analysis of masticatory muscle fatigue and recovery rate during gum chewing].

An EMG computer analysis system was developed to analyze the mandibular function. The system enabled measurements of the masticatory muscle's rhythm, activity, and power spectrum for the same EMG burst during mastication. This study revealed that a power spectrum analysis was able to be carried out by a fast Fourier transform algorithm of the isometric contraction components of EMG bursts during mastication. The normal regulatory mechanism of the mandibular function was temporarily disturbed by clenching to inflict fatigue upon the masticatory muscles. EMG analysis of the masticatory muscles during gum chewing were observed before and immediately after clenching, and during their recovery periods. After fatigue induction, all of the masticatory rhythms of the masticatory muscles showed a decrease in EMG burst duration time (duration) and duration per cycle (D/C) that recovered with time. However, only the coefficient variation of the duration and D/C in the working side increased immediately after fatigue induction. The power spectrum shifted to a lower frequency immediately after fatigue induction, and recovered along with time. Furthermore, it was found that EMG activity influenced the power spectrum during gum chewing. In conclusion, this EMG analysis system may be used as a possible future diagnostic aid for mandibular dysfunction syndromes.