[Comparative study of the movements between condyle and exterior point in lateral movement]

The study was performed on 30 left and right temporomandibular joints of 15 adults with normal occlusion. The exterior point was set on condylar center of each subject. Using cephalometric laminagrams and submental-vertical cephalograms, the movement of condyle and the movement of exterior point were compared on the nonworking side in 3mm lateral movement at incisal region. Also, the relation between the inclination angle of front wall of mandibular fossa and the movement of condylar center was evaluated. The standard of horizontal plane was F-H-L. The results were as follows: 1. The position of exterior point on sagittal plane, 12 examples shifted in front upward, 9 examples shifted in rear downward, 8 examples shifted in front downward and 1 example shifted in rear upward from condylar center. 2. The inclination of moving front downward of condylar center was 47.0 degrees, and that of exterior point was 50.3 degrees. 3. The shifting direction of exterior point was correlative with the shifting direction of condylar center. However, there was an individual difference in the synchronism between the shifting direction of condylar center and the shifting direction of exterior point during lateral movement. 4. The inclination of front wall of mandibular fossa was 50.9 degrees. 5. A coefficient of correlation between the inclination of front wall of mandibular fossa and the shifting direction of condylar center during 3mm lateral movement was small.