Only few studies have shown that TiF4 is more or equally effective than NaF on dentin erosion. The lack of data requires further studies dealing with the impact of TiF4 solution on dentin erosion. Additionally, there is no study testing the impact of TiF4 varnish on dentin erosion so far. Objectives: This in vitro study aimed to analyse the effect of a single application of TiF4 and NaF varnishes and solutions to protect against dentin erosion. Methods: Bovine root dentin samples were pre-treated with NaF-Duraphat varnish (2.26%F, pH 4.5), NaF/CaF2-Duofluorid varnish (5.63%F, pH 8.0), NaF-experimental varnish (2.45%F, pH 4.5), TiF4-experimental varnish (2.45%F, pH 1.2), NaF solution (2.26%F, pH 4.5), TiF4 solution (2.45%F, pH 1.2) and placebo varnish (pH 5.0, no-F varnish control). Controls remained untreated. Ten samples in each group were then subjected to an erosive demineralization (Sprite Zero, 4x90s/day) and remineralization (artificial saliva, between the erosive cycles) cycling for 5 days. Dentin loss was measured profilometrically after pre-treatment and after 1, 3 and 5 days of de-remineralization cycling. The data were statistically analysed by two way ANOVA and Bonferroni's post-hoc test (p<0.05). Results: After pre-treatment, TiF4 solution significantly induced surface loss (1.08±0.53 µm). Only Duraphat reduced the dentin loss overtime, but it did not significantly differ from placebo varnish (at 3rd and 5th days) and TiF4 varnish (at 3rd day). Conclusion: Duraphat varnish seems to be the best option to partially reduce dentin erosion. However, the maintenance of the effects of this treatment after successive erosive challenges is limited. Financial Support: FAPESP (Proc. 08/07105-4 and 08/03727-0)