[The ultrastructure of human enamel organs]

The ultrastructural features of enamel organs from 3 human fetus were examined in this study. There were few and simple organelles in the inner enamel epithelium, this imply that these cells were not active ones. Comparing with the inner enamel epithelium, the ameloblasts showed active functional condition. They had a large amount of mitochondria, enlarged rough endoplasmic reticulum and well developed Golgi apparatus in the distal cytoplasm. On the top of the ameloblasts, Tomes' processes were formed. In the Tomes' processes, there were numerous vesicles containing "stippled material". This kind of material also could be seen in the spaces between the Tomes' processes and the enamel matrix, and in the vesicles of the Golgi apparatus. Ultrastructurally, each enamel matrix invagination received a large part of process of an ameloblast and a small part of another ameloblast. But the meaning of this structure were unclear. Tight junctions were found at the distal part of the ameloblasts. The stratum intermedium cells, beside the ameloblasts, had a lot of small processes protecting into the intercellular spaces. Gap junctions were found between all enamel organ cells, and illustrated that there were active material transmissions between these cells.