Caries-Preventive Effect of NaF, NaF plus TCP, NaF plus CPP-ACP, and SDF Varnishes on Sound Dentin and Artificial Dentin Caries in vitro

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 (<i>n</i> = 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 (&#x0394;&#x0394;Z), lesion depth (&#x0394;LD), and colorimetric values (&#x0394;&#x0394;E) 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 &#x0394;Z_DT/LD_DT and &#x0394;Z_ST/LD_ST values, indicating further demineralization. In contrast, CPP₀, CPP₁, SDF₀, and SDF₁ showed significantly decreased &#x0394;Z_DT/LD_DT values, indicating remineralization (<i>p</i> ≤ 0.004; paired <i>t</i> test). CPP₀, CPP₁, SDF₀, and SDF₁ showed significantly higher changes in &#x0394;&#x0394;Z_DT/&#x0394;LD_DT and &#x0394;&#x0394;Z_ST/&#x0394;LD_ST than N_NB, N₀, and N₁ (<i>p</i> < 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.