This study was aimed at clarification of the advantages of the use of electromyograms recording multiple muscles with different functions in evaluation of muscle activity during sleep at night. We, there-fore, investigated the durations of the activity and the ratios of the magnitudes of the activity of the temporal muscles and the masseters during sleep at night.
The subjects were 5 healthy adults. Electromyograms recording the temporal muscles and masseters of the subjects during sleep at night were made using a simplified electromyograph, and the muscle activity durations and magnitude ratios were determined from the records.
In three subjects the activity of the temporal muscles lasted longer than that of the masseters, whereas in the other two subjects that of the masseters lasted longer than that of the temporal muscles. The temporal muscle was activated more strongly than the masseter muscle in three subjects and in the other two subjects it was activated more strongly than a masseter muscle.
The masticatory muscle activities during sleep at night, thus, showed two different features: temporal muscle dominance and masseter dominance.
The above results suggest that analysis of electromyograms recording multiple muscles is necessary in investigation of masticatory muscle activity during sleep at night, since they can reveal differences in muscle activities.