[Natal and postnatal teeth: their enamel].
The enamel of a natal tooth in a healthy full-term child and the enamel of a postnatally erupted tooth in a premature child have been studied with scanning electron microscopy on longitudinal and cross sections. The first case shows that following a normal development, amelogenesis was arrested. This is evident by the presence of the external aprismatic layer in spite of the narrowness of the enamel which corresponds to about a third of the normal thickness. This premature arrest of amelogenesis can be dated to about the 6th month "in utero". In the second case we observed a reversible amelogenesis disturbance as attested by the absence of the external aprismatic layer as well as by a new and fast enamel apposition that took a pseudonormal course. Happening about 10 weeks before birth, this disturbance has probably been induced by factors of maternal origin. In both cases, the eruption anomaly was associated with an enamel anomaly. These observations open new perspectives in the study of natal and neonatal teeth. By extension, such observations are likely to produce complementary informations in neonatology.