[Fine structural observations of age changes in cementocytes of human permanent teeth].

Human cementum formation is a continuous process which occurs throughout life. Young cementocytes are situated near the periodontal membrane and old cementocytes towards the cementodentinal junction. Electron microscopic observations on 110 cementocytes of human permanent teeth were carried out to analyze the morphological and morphometric changes due to ageing. Cementocytes with ageing showed a rapid decrease in the number of the cell and a gradual decrease in the size of the cell, nucleus and cytoplasm. The location of the nucleus was changed from the periodontal side to the dentinal side and was hyperchromatic. Organelles showed a decrease in the size of the mitochondria, the rough-surfaced endoplasmic reticulum and the Golgi apparatus, meanwhile showing a gradual increase in the number of vacuoles and lysosomes. The cell death with ageing showed a rapid increase in number and their lacunae contained nuclear remnants, mitochondrial-like structures and fine fibrillar materials. Two distinct types of age changes were recognized: cytoplasmic swelling with scanty organelles and pronounced vacuoles, and cytoplasmic atrophy preserving the rough-surfaced endoplasmic reticulum in the narrowing cementum lacuna.