[Densitometry of the bony structures of the human TMJ]

Four millimeter sagittal section of 65 formalin-fixed human TMJs were prepared. The X-rays of these specimen were evaluated numerically in a densitometer. The distribution of bone material and densities in condyle and fossa led to a classification of condylar and fossa types. In 48 specimen a combination of increased density of the condyle on the facial aspect with a thin bony lamella in the roof of the fossa, which either shows high density or very little material of low density, a so-called parchment fossa, was observed. The varying degrees of density as a function of mechanical stresses are discussed. The transfer of forces in the human TMJ during mastication exposes the superio-anterior or superio-facial segments of the condyle and the posterior slope of the articular tubercle to loading forces, while at the same time the roof of the fossa remains free of load.