Electron microscopic observations on the interrelationship between the processes of ameloblasts and odontoblasts. On the porcine amelogenesis.

The odontoblasts are differentiated from certain cells of the pulp by the induction of ameloblasts, which are also differentiated from the inner enamel epithelium. Thus, there are many evidences on the epitheliomesenchymal interactions during the development of the tooth, although the morphological grounds are hitherto poorly established. In the porcine amelogenesis, 2 kinds of processes are derived from the ameloblast. One is known as an apical process (Kallenbach, 1976), which originates from the basal end of the cell and proceeds into the dental papilla penetrating the basal membrane in the early stage of ameloblast differentiation. The other is termed as an ameloblast fiber (Lester, 1970) and originates from the secretory end of Tomes' process entering into the enamel at a much later stage. The apical process contacts with the odontoblastic process in the early stage of enamel formation, and the phenomenon may be considered to be the morphological expression of the epitheliomesenchymal interactions. The ameloblast fiber channels the enamel tubule, which is similar to those of the tubular enamel in the marsupials. The tubules may be the precursor of the enamel spindle.