Movement of the Condyle Point and Incisal Point during Exercise

Abstract

Generally, although the mandible is considered to be fixed during body movement, its dynamics have not been clarified. In this study, we investigated the condylar movement pattern in extension⁄flexion movement of the body trunk. Six healthy dentulous subjects performed extension⁄flexion movement of the body trunk using a multipurpose muscle function training system. The condylar and incisal point movement patterns were measured using a jaw movement analyzer and 3D ultrasonic navigator. The maximum displacements of the condylar and incisal points in the mouth opening were measured. The relative percentages of condylar point displacements in extension⁄flexion of the body trunk to the maximum displacements were calculated, and displacements in the anterior, and posterior, superior, and inferior directions were compared. The condylar point displacements in the anterior, posterior, superior, and inferior directions in extension⁄flexion of the body trunk were 8.1%, 30.1%, 73.2%, and 10.7% on the right side and 5.8%, 55.1%, 31.3%, and 13.0% on the left, respectively. The incisal point on mouth opening was 7.1%. Based on the above findings, the mandible is not fixed at the intercuspal position by clenching, but is displaced during muscle force exertion by the body trunk.