Different responses of masticatory movements after alteration of occlusal guidance related to individual movement pattern.

We hypothesized that the motor response of the masticatory system to peripheral inputs varies according to the functional potential of an individual. The specific aim of the present study was to determine whether individually different types of masticatory patterns, especially with respect to the closing movement pattern, would produce different motor responses to an alteration of occlusal guidance. The inclination of the occlusal guidance was steepened by approximately 10 degrees by attaching a metal overlay to the lingual surface of the maxillary working-side canine. The masticatory movements of 20 young adults were measured using a three-dimensional mandibular movement analysis system before and after the alteration of occlusal guidance. The individual masticatory patterns were divided into two groups based on the closing movement pattern before the alteration of occlusal guidance, i.e. vertical and lateral types. The alteration of occlusal guidance significantly influenced the masticatory closing angle, closing time, occlusal time, the stability of the opening angle and the cycle time in the lateral-type group (n = 9, paired t-test; P < 0;05), while no significant changes were found in the vertical-type group (n = 11). These differences in motor response between the two groups were not found in the overall analysis of all the 20 subjects. We concluded that the oral motor response to the alteration of occlusal guidance depends on the individual masticatory movement pattern. Because the present analysis of subgroups of the subjects revealed motor response findings different from those in the overall analysis of all the 20 subjects, such potential subgroupings should be considered as an attempt to identify a specific effect of peripheral inputs on masticatory function in humans.