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Enamel Microhardness of Resin-Infiltrated White Spot Lesions After Bleaching With and Without ACP: An In Vitro Study
Pauravi Hegde1, Shashi Rashmi Acharya2, Arun Mayya2
1Department of Conservative Dentistry and Endodontics, DY Patil School of Dentistry, DY Patil (Deemed to be) University, Navi Mumbai, Maharashtra, India.
Background:
White spot lesions (WSLs) represent the earliest clinical manifestations of enamel demineralization. Resin infiltration (RI) is a minimally invasive method used to mask WSLs for esthetic improvement; however, infiltrated enamel may remain prone to staining and surface degradation. Carbamide peroxide bleaching agents have been reported to reduce enamel microhardness, while the inclusion of remineralizing components such as amorphous calcium phosphate (ACP) may mitigate these effects.
Objectives:
To compare the microhardness of resin-infiltrated enamel with artificial WSLs following the application of 22% carbamide peroxide bleaching systems with and without ACP.
Methods:
Thirty extracted noncarious maxillary premolars were prepared with artificial WSLs and treated with RI. The samples were randomly divided into three groups (n = 10): Group 1-RI only; Group 2-RI + 22% carbamide peroxide; and Group 3-RI + 22% carbamide peroxide + ACP. Vickers microhardness was measured at baseline (after RI and prior to intervention) and after 7 days. Data were analyzed using paired t-tests for within-group comparisons and one-way ANOVA with Tukey's post hoc test for intergroup comparisons.
Results:
One-way ANOVA revealed a statistically significant difference in microhardness among the three groups (p = 0.039). The highest mean microhardness was observed in the group treated with 22% carbamide peroxide + ACP, demonstrating approximately a 10% increase in Vickers hardness compared with the resin-infiltrated control group. Post hoc Tukey's test showed a significant difference between the untreated and ACP-treated groups (p = 0.031), while other comparisons were not statistically significant. Baseline microhardness values did not differ significantly among groups (p = 0.882), confirming comparability prior to intervention.
Conclusion:
Bleaching agents containing 22% carbamide peroxide, particularly when combined with ACP, were associated with higher posttreatment microhardness compared with the RI-only group.
