Ex vivo comparative study of at home bleaching products on whitening efficacy and enamel integrity

Abstract

To compare the efficacy and safety of at-home bleaching products on dental enamel using an ex vivo bovine enamel model. The study aimed to evaluate the whitening effectiveness and the structural impact of these treatments on enamel integrity. Four at-home bleaching agents [BlancOne Home Night + (BlancOne; 12% carbamide peroxide/4.2% hydrogen peroxide + nano-hydroxyapatite), Opalescence PF Regular (Opale; 16%/5.7% + potassium and fluoride nitrate), Zoom Nite White (Zoom; 16%/5.7% + amorphous calcium phosphate), and Pola Night (Pola; 16%/5.7% + potassium fluoride)] were tested on bovine enamel samples according to ISO 28,399:2021 standards. Whitening efficacy was measured spectrophotometrically before and 48 h after treatments. Enamel surface changes in topography and mechanical properties were analyzed using Atomic Force Microscopy (AFM) and nanoindentation. The pH values of the agents were monitored throughout the treatment to assess their acidity. All agents effectively whitened enamel, with BlancOne demonstrating greater whitening efficacy than Zoom (ΔOD: 5.7 ± 1.1 vs. 3.7 ± 0.9; p < 0.001) and Pola (ΔOD: 5.6 ± 1.7 vs. 1.8 ± 1.0; p < 0.001). No significant difference was observed between BlancOne and Opale (ΔOD: 5.1 ± 0.9 vs. 4.4 ± 1.9; p > 0.05). AFM and nanoindentation analyses revealed significant differences in the integrity of the enamel surface. BlancOne, Zoom and Pola induced only minimal increases in surface roughness and reductions in hardness, whereas Opale resulted in the most pronounced enamel alterations [Control = 4.75 (× 1000 GPa) ± 1.57; BlancOne = 3.1 ± 1.4; Opale = 0.1 ± 0.03; Zoom = 2.9 ± 1.0; Pola = 3.2 ± 0.9. Control vs BlancOne, Zoom, and Pola: p < 0.05; Control vs Opale: p < 0.001]. The pH analysis indicated that BlancOne and Opalescence had less acidic profiles (pH 6-7) than Zoom and Pola (pH ≈ 5.5). This study demonstrates that although all tested agents effectively achieve whitening, they differ in consistency and impact on enamel integrity. Among the tested agents, the formulation containing 12% carbamide peroxide (equivalent to 4.2% hydrogen peroxide) and nano-hydroxyapatite demonstrated a favorable balance between bleaching efficacy and enamel structure preservation. These findings provide valuable insights for clinicians in selecting whitening protocols that minimize enamel damage while achieving satisfactory cosmetic outcomes.

Keywords: Bleaching; Carbamide peroxide; Demineralization; Enamel erosion; Esthetic dentistry; Gingival irritation; Home-based bleaching; Hydrogen peroxide; Tooth discoloration; Whitening.