[Biomechanical study on the mechanism of the mandibular condylar fracture. 1]

The condylar process is one of the sites predisposed to fracture clinical and experimental studies on the fracture mechanism have so far been undertaken by a number of our predecessor. However, the difference in the fracture mechanisms of intracapsular and extracapsular fracture has not completely been determined yet. In a Japanese Journal of Oral and Maxillofacial Surgery: Vol.32, 1362-1381, 1986: Shimada have previously reported the strong possibility that the direction and extend of fracture lines in the fracture of condylar process were influenced by the morphological characteristics of the condylar head. In order to verify this postulation, stress distribution patterns by the cross-sectional morphology of various types of condylar heads were investigated by two-dimensional finite element method, using 15 Indian edentulous mandibles. In this analysis, loading was applied to three directions in the model of the mandibular body, and two directions in the model of the mandibular head. The results indicated the following something. 1) With the loading in the direction of condylar head from mandibular angle, compressed stress arose on the condylar head with the surface. And with the loading in the direction of condylar head from chin and mandibular body, tugged stress arose on the condylar neck. 2) With the loading in the direction of vertical, these were conjectured that comminuted fracture arose on convex type, sagittal fracture arose on concave type and a style midway fracture arose on straight type. 3) With the loading in the direction of lateral, these were conjectured that fracture of condylar neck arose on the three types, especially the tendency was remarkable on straight type.