Epithelium-connective tissue junction in follicular ameloblastoma and ameloblastic fibroma: an ultrastructural analysis.

The ameloblastoma and ameloblastic fibroma are tumors of odontogenic origin. During odontogenesis, there is a sequence of inductive stimulations, or interactions, between the epithelium of the enamel organ and the connective tissue of the dental papilla. We review 7 cases of follicular ameloblastoma and 1 case of ameloblastic fibroma under the electron microscope to investigate possible induction-stimulated changes at the epithelium-connective tissue junction. Thickening of the basal lamina by a granulo-filamentous material was a universal finding. Horizontal proliferation and convolutions of this thickened material were found in 2 ameloblastomas. The ameloblastic fibroma evidenced fine aperiodic fibers perpendicular to the basal lamina. These changes are consistent with attempted inductive stimuli directed toward tooth formation.