Abstract
This paper is designed to study the histogenesis of odontogenic tumors induced by transplacental administration of N-methylnitrosourea (MNU) to Sprague-Dawley rats. MNU was given in a single intragastric dose of 50 mg/Kg body weight to female rats on 19 th, 20 th and 21 st day of gestation.
Six of 170 offsprings developed odontogenic tumors. The observations made on these tumors was previously reported (Tani, Y: Jpn. J. Oral Biol. 28 (5): 551-564). The present paper reports the results of a histological examination of the denal apparatus of the other 164 rats which did not develop tumors.
The chief histological changes were found in the incisors, which consisted of foldings of the basal enamel organ, atrophy or disappearance, double layers and outward over-growth of enamel epithelium, and disturbance of odontogenesis.
Among the above mentioned findings, the proliferation of the enamel epithelium with droplets of enamel matrix-like substance is the most characteristic feature of this experiment. It is considered that the odontogenic tumors developed in this experiment were derived from the labial enamel epithelium of the erupting incisors.
