Apoptosis in the reduced enamel epithelium just after tooth emergence in rats

Abstract

The reduced enamel epithelium transforms into a stratified squamous epithelium, i.e. a junctional epithelium, as the tooth erupts. In this study, we observed apoptosis in the reduced enamel epithelia of rats just after tooth eruption and before complete junctional epithelium formation, by the TUNEL method and electron microscopy. TUNEL-positive reactions were scattered in the reduced ameloblasts and in the external cells of the reduced enamel epithelium. Electron microscopic observation confirmed features of apoptosis, such as nuclei with chromatin condensation, cell shrinkage, and phagocytosis of apoptotic bodies by macro-phage-like cells and epithelial cells. These results suggest that apoptotic cell death is involved in the disappearance of reduced ameloblasts and the external cells of the reduced enamel epithelium during the formation of the junctional epithelium.