Bleaching of simulated stained-remineralized caries lesions in vitro

Non-invasive esthetic treatment options for stained arrested caries lesions have not been explored. This study aimed to develop laboratory models to create stained-remineralized caries-like lesions (s-RCLs) and to test the efficacy of bleaching on their esthetic treatment.

One hundred twelve enamel/dentin specimens were prepared from human molars, embedded, and had their color measured spectrophotometrically at baseline and after demineralization. They were randomly divided into four groups (n = 14) based on the staining/remineralization protocols for a total of 5 days: G1, no staining/no remineralization; G2, no staining/remineralization in artificial saliva (AS); G3, non-metallic staining/remineralization with sodium fluoride/AS; and G4, metallic staining/remineralization with silver diamine fluoride/AS. The lesion mineral loss (ΔZ) and depth (L) were measured using transverse microradiography along with color change (ΔE). Specimens were bleached and color was re-evaluated. Data were analyzed using ANOVA models followed by Fisher's PLSD tests (α = 0.05).

s-RCLs in G4 were significantly (p < 0.001) darker than G3, G2, and G1 regardless of substrate type and condition. s-RCLs in G2, G3, and G4 showed significantly lower ΔZ and L than G1 (all p < 0.001), confirming occurrence of remineralization. G4 exhibited significantly lower ΔZ and L compared to G2 (p < 0.001). Bleaching was more effective in non-metallic than in metallic stained lesions regardless of substrate type (p < 0.001).

The proposed models created distinct s-RCLs. Non-metallic s-RCLs were lighter and more responsive to bleaching compared to metallic s-RCLs.

The developed experimental models allow the further investigation of the efficacy and safety of different clinical strategies for the esthetic management of s-RCLs.