Nano-hydroxyapatite-induced remineralization of artificial white spot lesions after bleaching treatment with 10% carbamide peroxide.

Objective: To assessed in vitro the effect of nanohydroxyapatite (n-HA) to improve the aesthetic appearance and microhardness of white spot lesions (WSL) when associated with a low-concentration bleaching agent (carbamide peroxide-CP10%).

Material And Methods: Enamel/dentin specimens (n = 60) of 5 × 5 × 2.2 mm were prepared, of these, 48 were submitted to pH-cycling to create artificial WSL. Subsequently, these were allocated into five groups (n = 12): n-HA; n-HA + CP10%; CP10%; WSL control (WSL ); sound control (Sound). The color was assessed at baseline, pre-treatment, and post-treatment using a spectrophotometer, and the color (ΔE/ΔE ) and whiteness index (ΔWID) alterations were determined. The enamel cross-sectional microhardness (CSMH) was evaluated (post-treatment) with a Knoop indenter, 25gf/5 s, 20-200 μm. The data was analyzed through generalized linear models (α = 5%).

Results: ΔE and ΔE were significantly higher for the bleached groups (n-HA + CP10% and CP10%), and the n-HA was higher than the WSL group (p < 0.05). ΔWID was significantly higher for the bleached groups (p < 0.05). The CSMH values were significantly higher in the sound group than in the n-HA, CP10%, and WSL groups (p < 0.05). The WSL had lower microhardness than the n-HA + CP10% and sound groups (p < 0.05).

Conclusion: n-HA is suitable to remineralize and recover the color of the WSL. However, its association with CP10% maintains the esthetical outcome while increasing its in-depth remineralizing effect.

Clinical Significance: Considering the aesthetic and functional repercussions of the WSL persistence, treatments that tend to improve its physical appearance and reinforce its weakened substructure in a non-invasive way are ideal. For this associating low-concentration, bleaching agents to the remineralizing treatments is promising to treat this type of lesions.