Biomechanical analysis of stress distribution in the human temporomandibular-joint

The positions of the head of the mandible, of the articular disc and the outline of the temporal surface are digitized from sagittal MRI-scans of the temporomandibular joint of a 32-year-old subject in 5 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 center 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 compressive 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 from the position. The analyses show that the temporomandibular joint is slightly eccentrically loaded in all positions. The increase of the stresses 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 analyzed stress situations.