This study was undertaken to reveal the changes in the fluoride distribution in the developing enamel of rat upper incisors with varying fluoride administration. The work was carried out on four groups of Wistar rats, which received water containing 0, 25, 50 and 100 ppm fluoride, respectively, for 10 weeks. Six sites were selected in the developing enamel, corresponding to the stages of (A) matrix formation, (B) early maturation, (C) late maturation, (D) pigmented enamel in contact with alveolar bone, (E) enamel attached to gingivae and (F) erupted enamel. Five different enamel specimens were removed from each site except site A. The fluoride distribution in each specimen was analyzed from the enamel surface to the EDJ.
The following results were obtained;
1) The fluoride concentration was invariably highest at the surface and decreased sharply towards the interior of the enamel at every site in both control and experimental groups. The rat incisor enamel had a clear fluoride-gradient from surface to interior.
2) The fluoride concentration increased with fluoride intake throughout the tissue and at each stage of development.
3) The fluoride-gradient curves resembled each other at the different sites of tooth development. However, the fluoride concentration of the enamel interior was significantly higher at site B than it was at the other four sites.
