Role of Meckel's Cartilage in the Development and Growth of the Rat Mandible

Abstract

DEPORTS on the role of Meekel's cartilage' in the development and growth of the mandible are conflicting. While some investigators have shown that this cartilage plays no role in mandibular growth,1 2 Baumiiller3 reported that the anterior section of Meckel's cartilage promotes growth of the anteromedial surface of the pig mandible. A number of studies have shown that this cartilage ossifies,4-5 while others report that it does not undergo endochondral ossifications9 This disagreement in the literature concerning the fate or function of Meckel's cartilage is due to the fact that in the normal growth of bones resorption of bone tissue occurs simultaneously with apposition, and thus the growth pattern of bones is erased. Furthermore, due to the resorption, no fixed point is preserved in bones from which quantitative studies can be made. The cartilages which undergo endochondral ossification also show rapid resorption of their bony splints and a destruction of their path of growth. In the present investigation a new method has been used. It consist; of a serial histologic study of Meekel's cartilage in ia (incisor absent) rats in which growth of bone and cartilage occurs more or less normally, but the resorption of bone tissue is absent or severely retarded. Consequently, the perichondral bony splint which forms around Meckel's cartilage prior to, and during, its ossification persists and serves not only as an indicator of the path of growth of this cartilage, but also as a fixed point from which quantitative studies can be made., By comparing the ia rats at successive stages of development, the increment of bone and cartilage can be determined. Furthermore, by using certain fixed points on the ia Meekel's cartilages, the direction of growth of these cartilages can be ascertained. Finally, by comparing Meckel's cartilage of ia and normal rats at the same developmental stage, the extent of the resorption of calcified cartilage could be measured. These methods have been used previously in describing the growth pattern of the rat tibia'0 and mandible.' The present investigation on the growth pattern of Meckel's cartilage showed that it not only is a center of endochondral ossification, but that it also plays an important role in the growth of the mandibular process and in the growth of the rat mandible.