Electromyographic investigation of masticatory muscles in unilateral cleftlip and palate patients with anterior crossbite

Objective: To evaluate the characteristics of masticatory muscle activity i n operated unilateral cleft lip and palate (UCLP) patients with anterior cr ossbite compared with normal individuals. Subjects: Sixteen male and 13 female Chinese patients with UCLP and anterio r crossbite, Fifteen male and 13 female Chinese individuals without cleft a bnormalities served as a control group. Design: Electromyographic activity of the masseter muscles and anterior tem poralis muscles was recorded bilaterally in different mandibular positions using bipolar surface electrodes. Results: Compared to noncleft controls, patients with UCLP demonstrated (1) higher activation levels of masseter and temporalis muscles in the rest po sition, (2) lower potential function of masseter and temporalis, (3) inharm onious activity of the masticatory muscles during mandibular border movemen t, (4) a higher asymmetry index of the masseter and temporalis muscles, and (5) longer silent periods of the two muscles. Conclusions: The function of masticatory muscles is different in patients w ith UCLP with anterior crossbite, Muscle function should be considered when evaluating cleft patients for orthodontic treatment and orthognathic surge ry.