Etching effect of acidic fluorides on human tooth enamel in vitro.

This in vitro study aimed to examine the etching effect of acidic fluoride solutions on enamel. 24 human teeth divided into 48 enamel-specimens were partly isolated with impression material. Specimens were exposed for 10 min to 20ml of the following solutions: 1.6% TiF4, 3.9% SnF2, 0.2% HF and 1.8% citric acid (CA). The isolation was removed and 24 specimens analysed by profilometry (Δheight: exposed/isolated enamel surfaces, surface roughness parameters). For the remaining 24 specimens [Ca(2+)] in the test solutions was analysed by atomic absorption spectroscopy. Median Δheights (μm) after exposure were: TiF4 0.07, SnF2 -0.03, HF -0.14 and CA -5.92. TiF4-exposed surfaces showed both deposits and etched areas and exhibited statistically significant different surface roughness parameters compared to the HF- and SnF2-exposed surfaces. Median [Ca(2+)] values (ppm): TiF4 1.88, SnF2 0.11, HF 0.10 and CA 2.17. At the [F] tested in this study it can be concluded that SnF2- and HF solutions had negligible erosive effects on enamel. TiF4 solution resulted in an incomplete surface deposition associated with calcium dissolution suggesting that TiF4 applied as solution may not be advisable.