Stabilization of jaw-closing movements during chewing after correction of incisor crossbite

Humans with normal occlusion usually perform gum-chewing movements in a characteristic manner. The purpose of present study was to examine whether the variability of masticatory jaw movement in children with incisor crossbite is greater than that in children with normal occlusions, and if so, to examine whether correction of the crossbite results in a significant reduction in the variability. The variance in masticatory jaw movement trajectory was investigated in 10 children with acceptable occlusion and 11 children with crossbite of one or two incisors. The lower incisor-point movements during chewing of standardized gum were monitored using a 3D tracking device. The deviation of the jaw-closing trajectory from a best-fit plane was then evaluated for each chewing cycle. Subsequently, variance in angles of the best-fit planes and variance in the instantaneous curvature of the jaw-closing trajectories were evaluated. Pitch angles of the best-fit planes and curvature of the trajectories during closing in patients were more variable than those in control subjects (P < 0.05). After treatment, the variances decreased significantly (P < 0.05). These findings suggest that the achievement of good occlusion is associated with a reduction of variability of jaw movements in a gum-chewing task.