THE RAT INCISOR IN TOXICOLOGIC PATHOLOGY

Microscopic examination of the incisors of rats and mice may reveal to xicologically significant changes. First, the incisor morphology refle cts the nutritional status of the animal: fluctuations of mineral meta bolism and vitamin availability are disclosed by the rodent incisors, because the incisors continue to grow during life. Similarly, direct o r indirect changes of mineral metabolism by a test substance are refle cted in the morphological appearance of the incisor dentin. In additio n, hormonal disturbances may give rise to typical structural alteratio ns of the incisor in the test animal. Certain chemicals may have delet erious effects upon the odontogenic tissues, resulting in tooth malfor mation and malocclusion and eventually in odontomas. Apparent nasal tu mors may rum out to be of dental origin. Nasal luminal masses that are discussed within this scope are dental malformation, dental callus, a nd true odontogenic tumors. According to our experience, odontogenic t umors might possibly develop within the scope of a reaction to mechani cal tooth trauma as well. In carcinogenicity studies, this considerati on deserves attention when evaluating treatment-related putative odont ogenic tumors.