ANALYSIS OF OPEN-CLOSE AND ANTEROPOSTERIOR JAW MOVEMENT IN PATIENTS WITH TEMPOROMANDIBULAR DISORDERS : MOVEMENT AND PATHS OF MANDIBULAR CENTRAL INCISOR AND CONDYLES

Mandibular condylar motion in patients with temporomandibular disorders (TMD) has not been fully examined during open-close and anteroposterior jaw movement. The purpose of this study was to investigate this motion in such patients. Using a six-degrees-of-freedom jaw movement recording system, movement of a lower central incisor point and hinge axis of the condyles 20 mm medial from the skin on the right and left sides were calculated during voluntary open-close jaw movement and anteroposter- ior movement of the joint. The data were recorded for eleven patients with unilateral TMD (TMD group) and eleven control group subjects without temporomandibular disorders but whose occlusal condition otherwise almost matched that of the TMD group. The condylar points in the sagittal plane were mathematically calculated by solving the most minimized point of the moving distance around the condyle on the sagittal plane on each side when minor jaw opening and closing tapping movement was parformed for 10 seconds. During open-close jaw movement, there were no significant differences between the TMD and control groups due to a large SD in all measurements for both groups. The maximum anteroposterior displacements of condyles on both the affected and healthy sides during anteroposterior jaw･movement were significantly larger in the TMD group than the control group. There were no significant differences between groups in other measure- ments. These results suggest that condylar translation is inhibited on both sides during antero- posterior jaw movement in patients with unilateral TMD. They also suggest that although open-close jaw movement may not be useful, anteroposterior jaw movement may be useful in order to diagnose TMD