[The definition, frequency and etiology of retained teeth].

This paper draws attention to problems of assessment and interpretation of frequencies of the retention/displacement of teeth (impacted teeth and germ impaction), presents diagnostic criteria, comments on the incidence and frequency of retention/displacement and other disturbances in recent probands, lists the order in which teeth are affected, and discusses the causes of these disturbances. Reasons for the existing lack of anthropological data on the subject are suggested, and the potential usefulness of representative surveys of large samples of prehistoric populations is stressed.