Considering that the eroded dental tissue is more susceptible to be wear off by toothbrushing abrasion, and that the combination between fluoride and stannous (F+Sn) can induce precipitates that are relatively resistant to toothbrushing (short brushing times), the objective of this study is to evaluate whether the use of fluoridated oral rinses containing F+Sn could reduce the magnitude of wear of the eroded enamel and dentin, using a 4-phase, single bind, cross over in situ trial. The experimental groups will be the following: C: Control (toothbrushing with artificial saliva); E(F+Sn) - toothbrushing with F+Sn dentifrice (1400 ppm F, as AmF and NaF + 3500 ppm Sn, as SnCl2); E+B(F+Sn) - toothbrushing with F+Sn dentifrice, followed by rinse with F+Sn solution (500 ppm F, as AmF and NaF + 800 ppm Sn, as SnCl2); B+E(F+Sn) - rinse with F+Sn solution, followed by toothbrushing with F+Sn dentifrice). Twelve subjects will participate in the study after signing a written informed consent. In each study phase, the subjects will use removable mandible devices containing 4 enamel and 4 dentin specimens, which will submitted to an erosion-abrasion cycling model of 5 days. The erosion-abrasion cycling will consists of 2min extra-oral immersion in 3% citric acid (pH=2.6), followed by 60min remineralization in situ. This procedure will be repeated 4x/day. Immersion into the rinse solutions will be performed 2x/day, immediately after the first and the last erosive challenges or after toothbrushing, for 30s. Toothbrushing 2x/day will be performed immediately after the first and the last erosive challenges or after immersion into the rinse solutions, with an electric toothbrush and a dentifrice slurry, or without dentifrice (according to the experimental group), for 5 s, in a total of 2min exposure to the slurry. At the end, enamel surface loss (in µm) will be evaluated with optical profilometry. Surface loss data will be analyzed with ANOVA suitable for crossover studies and Tukey, or Krukal-wallis and Tukey, depending on the normality and homoscedasticity distribution of the data. The significance level will be set at 5%.
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