Applicability of acid-etching techniques for fluoride determination on enamel after topical fluoride treatment

A common technique for fluoride gradient determination of enamel is based on acid-etching of thin enamel layers. The dissolution of CaF2-like material in two different acid-etching solutions was compared with the dissolution of pure CaF2. The results showed that the CaF2-like material deposited on enamel after a topical treatment with 2% NaF dissolved almost completely in the 1 M HClO4 and 1.6 N HCl/70% glycerol solutions. The dissolution of pure CaF2 in the same solutions was low. Even after 30 min, less than 9% of the CaF2 had dissolved. It was concluded that acid-etching techniques for fluoride determination could be used on enamel treated topically with fluoride. The study also indicated that CaF2-like material may have chemical properties different from pure CaF2.