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

Abstract

We hypothesized that the motor response of the masticatory system to peripheral inputs varies according to the functional potential of an individual. The speci®c 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 signi®cantly in¯uenced 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 á 05), while no signi®cant 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 ®ndings different from those in the overall analysis of all the 20 subjects, such potential subgroupings should be considered as an attempt to identify a speci®c effect of peripheral inputs on masticatory function in humans.

Comparisons of Masticatory Movements between Mixing Ability Test and Masticatory Performance Test

“…Opening and closing angles (degrees) were determined at a level 0.5 mm below CO position in the frontal plane. 22 Envelope angle was determined at a turning point to the closing path from the opening path in the frontal plane (Fig. 4).…”