Comparative Analysis Between Strip and Gels Indicated for at Home Bleaching: Analysis of Color Alteration, Roughness and Microhardness of Dental Enamel

Purpose

To compare the color alteration, surface roughness and microhardness and cross-sectional microhardness of bovine enamel treated with at-home whitening strips and gels.

Materials and Methods

Sixty-six pigmented specimens (n = 11) were allocated to six groups: C—cotton wool moistened with distilled water for 1 h; SDS—sodium dithionite strip, for 1 h; HPS—6.5% hydrogen peroxide strip, for 1 h; CPS—20% carbamide peroxide strip, for 1 h; HPG—7.5% hydrogen peroxide gel, for 1 h; CPG—10% carbamide peroxide gel, for 4 h. The treatments lasted 10 days, calculating the ∆E, ∆E ₀₀, and ∆W _ID at baseline, 5 and 10 days, and 14 days after completion. Additional 66 polished discs (n = 11) were used to analyze the surface roughness and microhardness of enamel before and after bleaching, cross-sectional microhardness and integrated mineral loss (ΔZ; %Vol × μm). Data were subjected to statistical analysis by two-way Anova RM and Tukey post-test (α = 0.05).

Results

In ∆E and ∆W_ID analysis, greater values were obtained in CPG (p < 0.001), followed by HPG and HPS (p = 0.271). SDS and CPS (p < 0.001) exceeded only C (p < 0.001). In ∆E ₀₀, at completion of treatments, the results were similar; however, HPG = HPS = CPS (p = 0.237). There was an increase in roughness and decrease in surface microhardness in all bleaching groups (p < 0.005). Concerning the cross-sectional microhardness, the treatments were equal to C at 150 μm, the last depth analyzed. For ΔZ, the values of SDS, CPS, HPG, and CPG groups showed similar mineral loss (p > 0.001), and the lowest value was exhibited in the Control group, followed by HPS group (p < 0.001).

Conclusion

Although the strips were aesthetically effective, the CPG and HPG groups presented highest values in the ∆E ₀₀ and ∆W _ID analysis. However, all treatments influenced the enamel surface, increasing roughness and decreasing surface and transverse microhardness.

Clinical Relevance

The whitening gels promoted greater chromatic changes, but all treatments affected the enamel surface, increasing roughness and decreasing surface and transverse microhardness.