Examination of masticatory movement and rhythm before and after surgical orthodontics in skeletal Class III patients with unilateral posterior cross-bite

Abstract

Purpose: We examined the movement of the mandible in skeletal Class III patients with a unilateral posterior cross-bite to clarify whether the correction of the cross-bite caused conversion of the masticatory movement from a reverse to a grinding pattern.

Materials and methods: We studied 10 adults with mandibular prognathism who had been treated with surgery. The masticatory movement and rhythm (cycle time) during gum chewing were recorded before and after treatment.

Results: The results before treatment demonstrated a high frequency of patterns IV, VI, and VII and a low frequency of patterns I, II, and III on the cross-bite side. After treatment, the masticatory movement on the cross-bite side showed different patterns than from before treatment. The high frequency of pattern VI (reverse pattern) before treatment was significantly reduced, and patterns I and III had significantly increased in frequency after treatment. No significant changes were seen in cycle time, opening phase, occlusal phase, or the closing phase before and after treatment.

Conclusions: These results suggest that correction of a unilateral posterior cross-bite induces conversion of the masticatory pattern from the reverse pattern to the grinding pattern.