Rates of enamel formation in human deciduous teeth

The aim of this study was to document rates of enamel formation in deciduous teeth. Little is known about rates of deciduous enamel formation compared to permanent enamel. In permanent teeth, rates vary between 2.5 microm per day at the EDJ to 6.5 microm per day at the enamel surface. Longitudinal ground sections of twenty mandibular deciduous teeth (4 of each tooth type) made through the crown in the buccolingual plane were selected that showed clearly visible daily enamel cross striations using transmitted polarised light microscopy. Ten average measurements, each one made across five daily increments, were recorded within 100-microm thick zones defined between the EDJ and the enamel surface on each tooth section. This procedure was repeated in occlusal, lateral and cervical regions of each tooth. Overall, daily rates varied less than in permanent teeth and did not show the very low rates at the EDJ or the very high rates often found in the outer enamel of permanent teeth. In deciduous enamel, rates varied between 2.5 and 4.5 microm throughout, but often showed a marked reduction in the zone immediately following the neonatal line or other accentuated markings usually associated with stressful events. A catch-up phase usually followed these events during which rates recovered. These data provide clear evidence of enamel hypoplasia associated with both the birth process and other events that cause stress in perinatal life.