Purpose: To evaluate the preventive effect of titanium fluoride (TiF4) gel and solution, in different concentrations, on dentin erosion. Materials and Methods: Of 140 root dentin slabs (3 x 3 x 1 mm) cut from 70 freshly extracted human third molars, 70 with intermediate Knoop microhardness and lowest surface curvature were selected and randomly divided into 7 groups (n = 10): G1: negative control (no treatment); G2: positive control (AmF/NaF/SnCl2 solution); G3: placebo gel (no fluoride); G4: 1% TiF4 solution; G5: 1% TiF4 gel; G6: 4% TiF4 solution; G7: 4% TiF4 gel. Samples were subjected to 10 days of erosive cycling, consisting of alternating exposures to citric acid (0.05 M, pH 2.3, 2 min, 6x/day) and remineralizing solution (pH 7.0, 90 min, between acid exposures). Each cycle consisted of a total of 6 immersions in acid per day. After 5 and 10 days of pH cycling, surface loss was assessed by optical profilometry (µm). Results: One-way ANOVA and Tukey's test (p 0.05) showed that after 5 days, G7 revealed a significant reduction in surface loss compared to the other groups, while G4, G5 and G6 did not differ significantly from G1. After 10 days of erosive challenges, G7 did not differ significantly from G2 and there was no difference between G4, G5, G6 and G1. G3 showed the highest surface loss compared to all groups, except G1 and G5. Conclusion: The treatments tested were not able to prevent dentinal erosion, but the application of 4% TiF4 gel did reduce surface loss of dentin. Keywords: dentin, erosion, fluoride, profilometry, TiF4