Macroscopic enamel defects of primary anterior teeth--types, prevalence, and distribution.

A total of 40.7% of 509 exfoliated primary anterior teeth from children who were healthy products of uneventful pregnancies exhibited at least one macroscopic enamel defect. Twenty percent of the teeth exhibited hypoplastic defects (HD), 12.4% exhibited white-cream opacities (WCO), and 9.8% exhibited yellow-brown opacities (YBO). Slightly more than a third (33.6%) of the teeth had defects we considered to be developmental enamel defects (DED). The occurrence of DED did not vary with gender, side of mouth, individual tooth types, or racial background. DED occurred with increased frequency on maxillary teeth, facial surfaces, and the middle third of affected surfaces. These locations have thicker enamel than other sites and may be more susceptible to insult if vulnerability is a function of metabolic demand of the rapidly secreting ameloblasts. Twenty-five per cent of the maxillary incisors and 10.1% of the mandibular incisors exhibited HD whose locations coincided with enamel forming at birth. A third (33.3%) of the canines exhibited HD, which occurred most commonly in the middle third of the facial surfaces. These defects are believed to occur approximately six months postnatally and may be primarily due to mechanical trauma. YBO most commonly occurred on the middle third of the facial surfaces, while WCO on the gingival third. Neither YBO nor WCO followed a chronologic pattern.