The early stage of amelogenesis as observed in molar teeth of young rats

Abstract

The basal lamina that is seen between the preameloblasts and the odontoblasts is removed before the deposition of mineral in the developing molar tooth of the rat. No dentino-enamel membrane is to be seen between the enamel and dentine. The formation of enamel occurs in such a manner as to indicate that a mineralization front exists. Tomes' processes quickly develop after the initiation of amelogenesis. They extend from the level of the terminal bars, and have been divided into proximal and distal parts. The proximal part extends as far as the mineralization front and is surrounded by stippled material. The distal part dips into the enamel. The processes contain: coated vesicles, multivesiculated bodies, dense granules, large granules, microtubules, filaments, and agranular endoplasmic reticulum. Microvilli project from the sides of the Tomes' processes, into the stippled material. The presence of coated vesicles and microvilli are interpreted as evidence that absorptive activity also occurs at the distal end of “secretory” ameloblasts. Correlation of electron and light micrographs clarifies the nature of “pre-enamel.”