Morphological types of epithelial-mesenchymal cell contacts in odontogenesis.

During early stages of odontogenesis, differentiating ameloblasts form cytoplasmic processes which penetrate deeply into developing uncalcified dentine. Some of these cytoplasmic protrusions form close approximations or contacts with odontoblast processes. The contacts are of a variety of morphological types, but their membranes never fuse or form any known type of cell junction. The present results, together with those derived from other studies, suggest that the approximations or contacts may play a role in inductive mechanisms of the cytodifferentiation of odontogenic cells.