Analysis of enamel defects in a cave bear maxillary molar, with remarks on incremental markings in bear enamel

The paper discusses the formation of an enamel defect in the crown of a cave bear (Ursus spelaeus sensu lato) left maxillary second molar (M²), based on macroscopic and microscopic analysis. The tooth belongs to a cranium recovered from the Cerovac caves in Croatia that exhibits a partially healed, depressed lesion in the left squama frontalis and a further lesion in the left maxilla associated with loss of the M¹. Microscopic inspection demonstrated an accentuated incremental line in both enamel and dentin of the left M². It is suggested that in the defect area the outer enamel had been posteruptively lost along the accentuated line in the enamel that constituted a zone of reduced mechanical resistance. Presence of enamel hypoplasia in both M² indicated that these developmental lesions reflect a systemic stress event during crown formation of the teeth. The underlying cause of this stress is assumed to have been a trauma to the skull that caused the lesion in the left squama frontalis. It is further suggested that a later trauma to the left maxilla had led to the loss of the left M¹ and the flaking-off of enamel along the accentuated incremental line in the left M². The defect in the left M² is thus diagnosed as the result of a developmental lesion during crown formation, related to systemic stress due to a skull trauma, followed by posteruptive damage from a second traumatic impact. In addition to reconstructing the formation of the defect in the crown of the left M², the paper, for the first time, describes daily and subdaily incremental markings in ursid enamel and provides preliminary information on enamel secretion rate in a cave bear molar.