Ameloblastic fibroma with dentinoid formation/immature dentinoma. A microscopic and ultrastructural study of the epithelial-connective tissue interface.

The epithelial-connective tissue interface in an ameloblastic fibroma with dentinoid formation shows four characteristic features: epithelium which is surrounded by a cellular stroma, by a cell-free zone, by a cell-free zone consisting of an amorphous hyaline-like material, and by a dentinoid material. The ultrastructure of these four characteristics resembles stages of the developing tooth. The cellular epithelial-connective tissue interface corresponds to early development before the "bud cap" stage described by Sisca and Provenza (1972). The cell-free zone resembles the "bud cap" stage, and the amorphous layer the "intermediate bell" stage, whereas the interface with dentinoid material has all the features of the "late bell" stage, except for the absence of calcification.