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Efficacy of sodium and stannous fluoride mouthrinses when used before single and multiple erosive challenges.

BACKGROUND
Application of fluoride mouthrinse before an acidic challenge may decrease enamel erosion. This paper compares the efficacy of stannous (SnF2 ) and sodium (NaF) fluoride when facing single and multiple erosive cycles in vitro.


METHODS
Human enamel samples (N = 60) were randomly assigned to groups testing SnF2 and NaF mouthrinses (225 p.p.m.) and a water control. Samples were allocated into subgroups testing one or five erosive cycles. Samples were immersed in test solution for 1 min prior to citric acid immersion (0.3%, pH 3.2, 10 min), and the cycle repeated either one or five times. Analysis was done using profilometry and microhardness change.


RESULTS
After one cycle, SnF2 resulted in least step height followed by NaF and water (1.3 μm (0.63), 2.3 μm (0.39), 4.3 μm (0.41) respectively; P < 0.0001). After five cycles SnF2 continued to reduce step height but pre-application of NaF was no different to water (4.6 μm (0.7), 10.5 μm (1.1) and 11.1 μm (0.38) respectively; P < 0.0001). There were no statistical differences in microhardness change between fluorides. After one erosive cycle, fluoride application resulted in statistically softer enamel compared with water.


CONCLUSIONS
Both SnF2 and NaF reduced erosion after one cycle. After five cycles, SnF2 continued to offer protection whereas NaF was statistically comparable with water. Softening of enamel may not imply less erosion has occurred.