Alkali-soluble and insoluble fluoride in erupted and unerupted human enamel from a high fluoride area with a low fluorosis score

Abstract

The amounts of fluoroapatite and ‘CaF 2-like’ fluoride (F) were determined 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 with F dentifrice at least once a day, and occasionally to a F mouth-rinse (0.022% F). Enamel was sampled by acid-etching and the F levels were 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 area. Unerupted enamel did not etch significantly ( p > 0.05) deeper than erupted enamel. No significant differences ( p > 0.05) were found in the F concentrations amongst the following: alkali-washed erupted, unwashed erupted, alkali-washed unerupted and unwashed unerupted at the outer most enamel (approx. 6 μm). However the erupted enamel (alkali-washed or not) showed higher F levels than unerupted enamel (alkali-washed or not) between approx. 6 μm and greater than 100 μm. The increase of F for this high-F area was about 100% in the deeper enamel while for a low-F area it was approx. 78% in the most outer enamel with no increase after a depth of about 20 μm. In contrast to a similar low-F area (water F < 0.10 parts/10 6), no significant ‘CaF 2-like’ F could be detected in erupted or unerupted enamel for the high-F area.