Biomechanical analysis of stress distribution in the temporomandibular joint

The positions of the head of the mandible, the articular disc and the outline of the temporal surface are digitised from sagittal MRT-scans of the mandibular joint of a 32-year-old subject in five different positions of occlusion. The stress distribution in the joint is calculated on the basis of these data. For each position of the condyle, the momentary point of rotation in the head of the mandible and the tangent attached to the temporal surface are determined. The line connecting these two points indicates the direction of the resulting bearing force. Furthermore, the extension of the area available to the force transmission is estimated. By means of these parameters, the stress distribution is calculated independently of the position. The analyses show that the mandibular joint is slightly eccentrically loaded in all positions. The increase in stress is in all cases oriented caudo-ventrally. The results are verified in an anatomical specimen of the articular tuberculum. The trabecular structures as well as the subchondral bone-lamella of the articular tuberculum are functionally adapted to the analysed stress situations.