Movement of the instantaneous center of rotation and the position of the lateral excursion center during lateral excursion.

The instantaneous center of rotation has been used to describe sagittal plane kinematics of mandibular opening and closing. Although, lateral excursions are also important because the closing pathways of masticatory movements frequently coincide with those of lateral excursions with occlusal contacts, there are no similar descriptions of mandibular lateral excursions. To compensate for this deficiency, lateral excursions of 20 women were recorded in this study. Reference points around each subject's mandible were tracked in three dimensions for each 0.1 mm interval of 3-D distance traveled by the incisor during the first 6.0 mm of lateral excursion. ICR was represented by the point that traveled the least 3-D curvilinear distance during each interval. To describe the entire series of intervals, a lateral excursion center was represented by the point with the smallest 3-D curvilinear distance throughout the excursive movement. In the results of this study, lateral excursions can be described as rotation around a single fixed lateral excursion center that is located close to the intercondylar axis, but 22 mm posterior to the initial position of the working side condyle.