Application of morphometrical methods in studies of the mandibular condyle.

Two mandibular condyles of a growing monkey (Macaca fascicularis) were used for developing and testing a morphometrical model system suitable for generating quantitative data about the structure of and the growth activities in the articulating surface layers. The animal received 3H-proline (1 mCi/kg body weight) 24 h and 3H-thymidine (0.5 mCi/kg body weight) 3 h prior to killing. Using standardized conditions, 1-2 microns thick histological sections were processed for autoradiography. The morphometrical analysis was carried out using light microscopy at two levels of magnification. Sampling of tissue fields was performed at twenty-four (level I) and twelve (level II) different sites, respectively. These sites were distributed systematically in the anteroposterior and lateromedial dimension of the cartilaginous condylar covering. Using a multivariate analysis of variance, a parameter comparison revealed significant differences between single sampling sites in the anteroposterior as well as in the lateromedial direction, suggesting that the articulating condylar surface is inhomogeneous with respect to both structures and growth activities. The sampling mode eventually arrived at in this study was shown to be sufficient for the recording of gradients within the condylar surface layers. The model system presented permits simultaneous quantitative characterization of structure and growth activities such as mitotic cell division and extracellular matrix production of the condylar cartilage including the zone of its replacement by bone.