[Osteogenesis of the rat mandible during development]

The author studied the mandibular osteogenesis process in Wistar rats during extrauterine development using macroscopic and microscopic investigations. Macroscopic investigations were carried out on rats aged 1, 5, 10, 20, 30 and 70 days, for establishing changes in the structure of the mandible and its elements, and autoradiographic determination of the sites of increased osteogenetic activity using Cr-51 chromium was obtained. Microscopic investigations were carried out in rats aged 1 and 5 days. The purpose of these investigations was a study of the morphological structure of the mandible, autoradiographic demonstration of the sites of increased cellular proliferation using 3H thymidine in rats aged 1 day, and osseous matrix formation in rats aged 1 and 5 days using 3H proline. The reported investigations showed that the periosteum and perichondrium were the source of mandibular bone formation. Proliferation of the cartilage of the condylar process and coronoid process occurs from the side of the perichondrium covering both these processes. This type of cartilage growth differs from the growth of the cartilage on the anterior part of mandibular corpus which showed additionally evidence of enchondral proliferation of cells. The process of osteogenesis was most active in the mandibular processes, anterior part of the mandibular corpus and the sites of attachments of muscles. This finding is explained as a result of function influence on the growing mandible. The results of macroscopic autoradiography performed with Cr-51 were confirmed by microscopic examinations.