Myoelectric activity during unilateral chewing in healthy subjects: Cycle duration and order of muscle activation

Abstract Statement of problem. Craniomandibular disorders, unilateral mastication, and asymmetry of masticatory muscles appear to be related to each other. Thus, it is of interest to investigate masticatory muscle activity during unilateral mastication in healthy subjects. Purpose. This study monitored contractile activity of the right and left masticatory muscles during right- and left-side gum chewing. Material and methods. Electromyographic techniques were used to determine chewing cycle duration and duration of contractile activity of the masticatory muscles (right and left masseter and anterior temporalis muscles) during unilateral chewing in 40 subjects without orofacial pain. The time-course of activation of the 4 muscles was also investigated. Results. Electromyographic traces showed extensive interindividual variation. In both right- and left-side chewing tests, and regardless of whether the masseter or the temporalis muscles were considered, mean duration of the contraction phase did not differ significantly between the working and nonworking sides. The working side temporalis contracted first, whether alone or at the same time as the other muscles. Conclusions. In healthy subjects, no significant differences in masticatory muscle activity should be expected between either the right and left or the working and nonworking sides. (J Prosthet Dent 1998;80:462-6.)