Fine structural study of rat molar cementum

Abstract

Abstract In cementum of rat molars, the cementoblasts were found to differ from pre‐cementoblasts in having an increased granular endoplasmic reticulum, greater number of polyribosomes and denser material in the cisternae of granular E. R. as well as in the general cytoplasm. The cementocytes with maturation showed a gradual decrease in the size of the Golgi complex and the granular endoplasmic reticulum. On the other hand, an increase in the number of lysosomes was observed. Parallel with these intracellular changes, the pericullular space became irregular in width, its fibrillar material became replaced by a flocculent material. Ocasionally, structurally different matrix was seen. At the cemento‐dentinal junction the cementocytes showed degenerative changes indicative of degeneration and death. The epithelial cells, remnants of Hertwig's root‐sheath, some of which get enclosed in the cementum, accumulated filamentous material as well as spheres of amorphous substance. These cells eventually degenerated, leaving their debris in the lacunae. The degeneration of epithelial cells did not seem to affect the cementum matrix in their immediate vicinity. Some collagen fibrils of the cementum, seemed to differ structurally from those of the periodontal membrane. Thin fibrils, about 160 Å in diameter, were also observed in the cementum.