Radiolucent lesion of an unerupted mandibular molar.

A coronal radiolucent lesion of an unerupted and partially developed mandibular second molar was coincidentally found during a routine radiographic orthodontic examination of a generally healthy 9-year old girl. The size of the lesion increased continuously during a 2-year observation period. Histologic examination after extracting the tooth proved the lesion to be an idiopathic external coronal resorption. In a review of the literature, we found no original research on the subject. However, the number of case reports suggests that idiopathic external coronal resorptions are quite common in young patients. Their etiology, however, remains unclear. The case history, histologic findings, differential diagnoses, and possible treatment approaches suggested in the literature are described.