EMG Activity of Chewing Muscles in Dysfunctional Disorders of Temporomandibular Joints

Abstract

Electromyograms were recorded from the main chewing muscles (mm. masseter and temporales) in 184 patients suffering from dysfunction of the temporomandibular joints and 25 healthy subjects (controls). In the patient group, the mean duration of the silence phase in cyclic EMG activity of the above muscles related to normal chewing (293.8 msec, a value averaged for all examined muscles and all examined patients) was by about 30% smaller than the analogous value in the control group. At the same time, the mean duration of the activity phase did not differ significantly from that in the control. The ratio of durations of the activity vs. silence phases in the patient group was 1.352, as compared with 0.946 in control subjects. The mean duration of the chewing cycle (also totally averaged for the patients) was 691.1 sec vs. 814.4 msec in the control; the respective mean values of the chewing frequency in the above groups were 1.447 and 1.228 sec–1. The results obtained confirm the statement that parameters of functioning of the brainstem neuronal central pattern generator (CPG), a neuronal network responsible for generation of cyclic motor commands for chewing muscles, can be significantly modified under the influence of a changed afferent inflow, especially in the case where the latter contains a considerable nociceptive component related to the dysfunctional state of the temporomandibular joints.