Histological analysis of the growth of the mandibular condyle in the rhesus monkey ( Macaca mulatta ) This research was supported by the National Institute of Dental Research, NIH Research Grant DE 03610 and Post-Doctoral Research Fellowship DE 05101.

Abstract

Qualitative and quantitative data on the growth of the mandibular condyle in the rhesus monkey ( Macaca mulatta ) are limited. The purpose of this investigation was to provide such data, with emphasis on variation in the size of the cartilaginous layers in the condyle and on condylar growth at five maturational levels (i.e., neonate, infant, juvenile, adolescent and young adult). Two regions of the mandibular condyle, the articular tissue and the prechondroblastic-chondroblastic (growth) layer, were examined histologically in 38 rhesus monkeys. The absolute area of the articular layer increased dramatically from the neonatal through the juvenile age groups and then decreased gradually through the adult group. When the absolute values were expressed relative to condylar size, the first three maturational levels shared a common trend of increasing growth of the articular layer, with a cessation of growth in this tissue occurring during the adolescent period. This variation in articular layer tissue is probably the result of progressive alteration in the function of the temporomandibular joint. The size of the prechondroblastic-chondroblastic (growth) cartilage increased dramatically between the neonatal and juvenile age groups, and subsequently decreased in older age groups. The relative thickness of the prechondroblastic-chondroblastic cartilage reached its peak within the infant and juvenile levels, being greatest in the posterior region among the infants and in the postero-superior region among the juveniles. This corresponds to previous investigations which have shown that greater vertical growth of the rhesus monkey mandible occurs during the infant period, while the direction of mandibular growth is more horizontal in subsequent age groups.