An analysis of surface congruity in the growing human temporomandibular joint.

The influence of condylar position on congruity of the surfaces of the temporomandibular joint (TMJ) was determined. The degree of congruity between the loading surfaces of the condyle and the eminence varied depending on condylar position. Better congruity of surfaces was found in condylar positions consistent with molar biting. Incongruity between surfaces occurred more frequently at the crest of the TMJ eminence and was related to the degree of eminence development. The evidence supports an hypothesis that growth of the TMJ eminence creates incongruities between loading surfaces that predispose to stress concentrations in the anterior regions of the articular surfaces. The findings may help to explain why degenerative lesions commonly occur at the crest of the eminence.