Unusual impaction of inverted primary incisor: report of case.

A tooth that fails to erupt into a normal functional position by the time it normally should is considered impacted. Impactions of primary teeth are extremely rare, but when it does occur it usually involves the first and second molar. The purpose of this article is to present a case of a four-year-old patient with an impaction of an inverted primary mandibular incisor. On the basis of the patient's family history, the case might be considered as microform of ectodermal dysplasia.