ALKALI-SOLUBLE AND INSOLUBLE FLUORIDE IN ERUPTED AND UNERUPTED HUMAN ENAMEL FROM A HIGH FLUORIDE AREA WITH A LOW FLUOROSIS SCORE

The amounts of fluoroapatite and 'CaF2-like' fluoride (F) were determi ned in enamel of unerupted and erupted teeth that had been exposed in vivo to 1.8-2.6 parts/10(6) F in the drinking water and to brushing wi th F dentifrice at least once a day, and occasionally to a F mouth-rin se (0.022% F). Enamel was sampled by acid-etching and the F levels wer e measured with an adapted F ion-selective electrode. More F was built into the deeper enamel in the high-F area than in a similar low-F are a. Unerupted enamel did not etch significantly (p > 0.05) deeper than erupted enamel. No significant differences (p > 0.05) were found in th e F concentrations amongst the following: alkali-washed erupted, unwas hed erupted, alkali-washed unerupted and unwashed unerupted at the out er most enamel (approx. 6 mu m). However the erupted enamel (alkali-wa shed or not) showed higher F levels than unerupted enamel (alkali-wash ed or not) between approx. 6 mu m and greater than 100 mu m. The incre ase of F for this high-F area was about 100% in the deeper enamel whil e for a low-F area it was approx. 78% in the most outer enamel with no increase after a depth of about 20 mu m. In contrast to a similar low -F area (water F < 0.10 parts/10(6)), no significant 'CaF2-like' F cou ld be detected in erupted or unerupted enamel for the high-F area.