Functional anatomy of the temporomandibular joint. A morphologic study on human autopsy material.

A study of 72 temporomandibular joints of adults without any gross signs of degenerative changes was made, in order to analyse the stress on individual regions of the joint, and to determine the path of the split line pattern in the articular cartilage. The cancellous architecture and the material distribution in the juxta-articular bone were also investigated. Zones of high-density compact substance in the lateral region of the joint, and the presence of attractive singular points in the split line orientation in this localization, suggest great stress on the lateral part of the temporomandibular joint. This increased stress in the lateral region is confirmed by the fact that arthrotic changes in the temporomandibular joint first almost always appear laterally. Degenerative changes usually originate at the articular disc, affect the articular tubercle after a delay, and finally spread to the condyle. Besides the greater physiological, mechanical stress on the lateral region of the joint, the force acting on every individual temporomandibular joint is influenced by the dental condition. The molars and bicuspids serving as a support zone play a decisive role in this context.