Quantitative evaluation of masticatory muscle function during clenching using EMG power spectral analysis

Abstract

The purpose of this experiment was to investigate the possibility of quantitatively evaluating masticatory function. Twenty healthy subjects and 20 TMD patients in their twenties were selected. The masseter muscular activity during 80% clenching (80% MVC) of the maximum clenching for 20 seconds was recorded with EMG. The 20-second clenching was divided into four 5-second periods, and for each period the cumulative 100% value, the mean power frequency (MPF) value and the cumulative 80% frequency (80% F) value of EMG power spectrum were calculated and were compared between healthy subjects and TMD patients. When the first period was set to 100%, the cumulative 100% values for the second, third and fourth periods were all close to 100% also for both groups which indicated that they both can maintain 80% MVC for 20 seconds. In the healthy subject group, the MPF and 80% F values for the first period was the largest and decreased dramatically for the second period and decreased slightly for the third and fourth periods. On the other hand, for the TMD patient group the MPF and 80% F values were the largest for the first period and thereafter decreased gradually from the second period to third and fourth periods. They clearly showed a different pattern from the healthy group and a significant statistical difference was found between the two groups. When the first period was set to 100%, the MPF and 80% F values for the second, third and fourth periods were much larger for the TMD patient group than for the healthy subject group and a significant statistical difference was found between the two groups. It was concluded that the MPF and cumulative 80% frequency values of the EMG power spectrum at 80% MVC for 20 seconds could be used as a quantitative indicator for evaluating masticatory function.