Improvement in smoothness of the chewing cycle following treatment of anterior crossbite malocclusion: a case report.

This is a report of a case in which improvement in masticatory jaw movement kinematics occurred following orthodontic treatment. A patient who demonstrated a skeletal Class II jaw relationship, with anterior crossbite between the right upper and lower lateral incisors, underwent treatment with an edgewise appliance. The trajectories and smoothness of the patient's jaw-closing movement were compared before and after orthodontic treatment. The correction of the anterior crossbite allowed the patient to consistently close the jaw with wider lateral excursion. Furthermore, after treatment, smoothness of the jaw-closing movements increased significantly, and the velocity profile was characterized as closer to that predicted by the minimum jerk (maximum smoothness) kinematic model. These findings suggest the value of trajectory smoothness (jerk-cost) as an objective indicator of kinematic improvement in gum chewing. In addition, the correction of anterior crossbite is demonstrated to enable the patient to perform smoother jaw-closing movements during chewing.