Three-Dimensional Study of the Morphology of the Central Bearing Plate

Abstract

The morphology of two types of the central bearing plates, namely the Stuart and the Denar, were examined by means of the three-dimensional measuring system. The equal altitude graphs and the section diagrams for the protrusive and the lateral pathways were evaluated. The following conclusions can be drawn.
1. The bearing plate of the Stuart clutch possesses the flat surface in the initial 1.5 mm, and the 16.9 mm and the 18.8 mm radius concave curvatures for protrusive and lateral pathways respectively in the following 7 mm.
2. The bearing plate of the Denar clutch possesses the flat surface in the initial 0.4 to 0.7 mm, the 20 mm radii concave curvature for both protrusive and lateral pathways in the following 1 mm, and the inclined flat surface in the final 6 to 7 mm.
3. According to the equal altitude diagrams, Denar's bearing plate shows more concavity and steeper inclination than Stuart's one does. However, the difference was not so great that less influence was expected for the mandible to rotate along the terminal hinge axis during translatory movement.
4. The inclination of the bearing plate is not steep enough to represent the sagittal incisal path. However, the flat bearing plate is effective to avoid the occlusal contacts and undue neuromuscular interference.
5. When wearing the clutches, the mandible rotates toward closing direction and trans lates forward and downward during eccentric movement. Because the clutch enhances the condyles to direct upward against the articular eminence, it is mandatory to record the reproducible border movement.