Ossification of the Human Temporomandibular Joint

¹ School of Dentistry, University of Washington, Seattle, Washington

The soft tissues of 23 human fetal specimens, 35 to 160 mm. in crown-rump length, were cleared with potassium hydroxide, and their osseous skeletons were stained with alizarin red S. The approximate ages ranged from 8 to 18 weeks. The ossification pattern and relative positions of the temporomandibular joint's skeletal components were correlated to the histomorphologic pattern of development.

It is in the 8-week fetus that ossification of the temporomandibular joint components is first apparent in the cleared and stained specimens. The temporal squamous component lagged slightly behind in development compared with the mandibular component during its early stages. It nevertheless reached the mandibular rate of development by the 12th-week stage. The primordial components of the joint were situated at some distance from each other in early stages of development, and came into closest apposition during the 12th-week period. The cartilaginous condylar core initiated the rapid development of the condyle and contributed to the formation of the highly organized growth center of the mandible. An osseous shell surrounding most of this core, except its dorsolateral and dorsosuperior aspects, gave the growth process of the condyloid process specific direction that was in a superior, lateral and dorsal direction.

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