Developmental defects of enamel in Chinese girls and boys in Hong Kong.

The FDI (DDE) Index--with some modifications and a re-designed recording sheet--was used to determine the prevalence of the different types of developmental defects of enamel. The public water supply contained 1.0 ppm when the children were bron and 0.7 ppm at the time of the examinations. All surfaces of the teeth of 460 female and 484 male, 12-year-old, Chinese children were examined after the teeth had been cleaned and dried. Mouth prevalences for all types of opacities, hypoplasia, and discoloration were 99.6%, 82.8%, and 16.6%, respectively. There was no apparent statistically significant difference between girls and boys. However, a statistically significant difference was seen between the sexes for white patches (p less than 0.05), missing enamel (p less than 0.05), and horizontal grooves (p less than 0.01). There were 811 (85.7%) children with more than 13 teeth affected by opacities, and 417 (44.2%) children had more than four teeth affected by hypoplasia. The most common defect was the diffuse white patch, and the least common was the vertical groove. There were 189 (39.0%) boys with between four and 12 teeth affected by more than two types of defect per tooth. White lines were the most difficult defect to diagnose reproducibly. Intra-examiner reproducibility for all other defects achieved levels of "almost perfect" and "substantial" by calculation of the Kappa coefficient.