Histological changes in the articular eminence and mandibular fossa during growth of the rhesus monkey (Macaca mulatta).

Unlike the mandibular condyle, the temporal component of the temporomandibular joint (TMJ) has been the object of relatively few investigations concerning its growth and remodeling. This report provides qualitative and quantitative documentation of microanatomical changes in the mandibular fossa and articular eminence during growth of the rhesus monkey (Macaca mulatta). The thickness of the fibrous articular tissue and the presence of cartilage cells in its deeper layers were examined histologically in 43 rhesus monkeys at five maturational levels (neonate, infant, juvenile, adolescent, and young adult). Absolute thickness of the articular tissue increased with maturational level in all areas studied, with the increase somewhat more pronounced on the posterior slope and crest of the articular eminence than in the roof of the mandibular fossa. Relative to condylar size, an increase in articular-layer thickness characterized the first three maturational levels, and was followed by a decrease during adolescent and young-adult stages. Articular tissue in the fossa roof constituted a steadily decreasing fraction of the total articular-tissue thickness with age, while relative thickness of the tissue on the posterior slope and crest of the eminence increased with age. These results parallel those obtained for the mandibular condyle, and they are best interpreted to indicate that forces delivered to the joint become directed more anteriorly with age. The overall pattern of topographical variation in articular-tissue thickness and cartilage-cell distribution suggests that greater loading of the lateral aspect of the TMJ, postulated in the human TMJ by various workers, may not be as pronounced in the monkey.