Abstract
Orthognathic surgical treatment has been provided for many patients with skeletal Class III malocclusion in order to correct deviated dentofacial morphology and to improve the impeded oro-facial function. In this study, we investigated the relationship between dentofacial morphology and mandibular movement in subjects with skeletal Class III malocclusion, while they were chewing gum. The subjects were 16 patients with skeletal Class III malocclusion scheduled to undergo orthognathic surgical treatment (jaw deformity group) and 21 with normal occlusion (normal group). In the jaw deformity group, records taken before treatment and at 1-6 months after completion of active treatment were used for this study. The dentofacial morphology was analyzed using lateral roentgen cephalograms. The mandibular movement was recorded by tracing the incisal point (the midpoint between mandibular central incisors) while chewing gum using the integrated jaw function testing system (gnathohexagraph system, JM-1000, Ono Sokki Tokyo, Japan). The following results were obtained. 1. The mean duration of a chewing cycle was significantly longer in the jaw deformity group than in the normal group. 2. After treatment, the mean duration got shorter and approached that in the normal group. 3. The maximal distance of mouth opening was larger in the jaw deformity group, and decreased after treatment. 4. The speed of mandibular movement showed no significant difference between the jaw deformity and normal groups, nor between before and after treatment in the jaw deformity group. 5. The variability of masticatory rhythm was significantly higher in the jaw deformity group as compared with that in the normal group. However, it got lower after treatment, and showed no significant difference in comparison with the normal group. Based on these findings, it is suggested that orthognathic surgical treatment for skeletal Class III malocclusion corrects imbalanced dentofacial morphology and improves impeded masticatory movement.
