Twenty-nine odontogenic tumours were found in 134 Fischer F344 rats injected once only with methylnitrosourea (MNU, 0.4 millimole/kg body weight) via the portal vein within 48 h after partial hepatectomy. Whenever the site of origin of the tumours could be distinguished, they were observed to arise near the roots of the incisor teeth. Of these tumours, 26 were complex odontomas, consisting of well differentiated but haphazardly arranged cementum, dentine, enamel and pulp. Dentine comprised the bulk of the tumour masses. Two tumours were largely ameloblastic and exhibited squamous differentiation, although these growths also contained scattered foci of dentine deposition, while a third tumour contained a focus of purely ameloblastic tissue in an otherwise typical complex odontoma. Two of these tumours were classified as odontoameloblastomas, while the third, because of hypercellularity, nuclear pleomorphism, high mitotic rate and local invasiveness, was classified as ameloblastic carcinoma. This protocol, which requires only a single systemic administration of carcinogen, may serve as a model for the chemical induction of odontogenic neoplasms.
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Berman et al. (1980) studied this question.