Abstract
This article reviews the pathological changes in the enamel of permanent mandibular cheek teeth and their sequelae in European roe deer from regions polluted by anthropogenic fluoride emissions. The primary (developmental) changes of fluorotic roe deer enamel are hypomineralization and microstructural aberrations, including enamel hypoplasia. The hypomineralized fluorotic enamel is whitish-opaque on eruption and gets stained following tooth eruption. Moreover, it is prone to excessive wear and mechanical breakdown, resulting in posteruptive enamel lesions. These posteruptive lesions can morphologically clearly be distinguished from hypoplastic defects. Due to the impaired mineralization of fluorotic enamel, affected cheek teeth lack the prominent enamel ridges normally present on the occlusal surface. The severity of dental fluorosis typically varies among the permanent mandibular cheek teeth of more severely fluorotic dentitions. While the permanent premolars and the third molar show marked pathological changes, the first molar is largely unaffected, and the second molar is less affected by fluorotic alterations. These differences have been related to protective mechanisms (placental barrier and milk-blood barrier to fluoride) operating during prenatal and early postnatal life that prevent excessive plasma fluoride levels during crown formation of the M(1) and partly also of the M(2) in individuals from fluoride-polluted habitats. Observations on the fluoride content of early-formed and late-formed dentin of cheek teeth from individuals with severe dental fluorosis support this hypothesis. The findings in the European roe deer constitute the most comprehensive characterization of dental fluorosis currently available for a wild ruminant species.