The aim of this study was to compare the caries-preventive effect of different fluoride varnishes on sound dentin as well as on artificial dentin caries-like lesions. Bovine dentin specimens (n = 220) with one sound surface (ST) and one artificial caries lesion (DT) were prepared and randomly allocated to 11 groups. The interventions before pH cycling were as follows: application of a varnish containing NaF (22,600 ppm F^-; Duraphat [NaF₀/NaF₁]), NaF plus tricalcium phosphate (22,600 ppm F^-; Clinpro White Varnish Mint [TCP₀/TCP₁]), NaF plus casein phosphopeptide-stabilized amorphous calcium phosphate complexes (CPP-ACP; 22,600 ppm F^-; MI Varnish [CPP₀/CPP₁]), or silver diamine fluoride (SDF; 35,400 ppm F^-; Cariestop 30% [SDF₀/SDF₁]) and no intervention (N_NB/N₀/N₁). During pH cycling (14 days, 6 × 120 min demineralization/day) half of the specimens in each group were brushed (10 s; 2 times/day) with either fluoride-free (“0”; e.g., TCP₀) or 1,100 ppm F^- (“1”; e.g., TCP₁) dentifrice slurry. In another subgroup, the specimens were pH cycled but not brushed (N_NB). Differences in integrated mineral loss (ΔΔZ), lesion depth (ΔLD), and colorimetric values (ΔΔE) were calculated between the values after initial demineralization and those after pH cycling, using transversal microradiography and photographic images. After pH cycling, no discoloration could be observed. Furthermore, N_NB, N₀, and N₁ showed significantly increased ΔZ_DT/LD_DT and ΔZ_ST/LD_ST values, indicating further demineralization. In contrast, CPP₀, CPP₁, SDF₀, and SDF₁ showed significantly decreased ΔZ_DT/LD_DT values, indicating remineralization (p ≤ 0.004; paired t test). CPP₀, CPP₁, SDF₀, and SDF₁ showed significantly higher changes in ΔΔZ_DT/ΔLD_DT and ΔΔZ_ST/ΔLD_ST than N_NB, N₀, and N₁ (p < 0.001; Bonferroni post hoc test). In conclusion, under the conditions chosen, all fluoride varnishes prevented further demineralization. However, only NaF plus CPP-ACP and SDF could remineralize artificial dentin caries-like lesions under net-demineralizing conditions, thereby indicating that NaF plus CPP-ACP and SDF may be helpful to high-caries-risk patients.