Effect of highly concentrated bleaching gels on enamel microhardness and superficial morphology, and the recovery action of four remineralizing agents

BACKGROUND: Dental bleaching is a common clinical practice. The aim of this study is to investigate the effect of 35% hydrogen peroxide (HP) bleaching gel on the morphology and microhardness of enamel, and to analyze the effect of four remineralizing agents. METHODS: One hundred blocks were prepared. The enamel surfaces were bleached with 35% HP in one session. The specimens were divided into four remineralization treatment groups (n = 25). G1: Tooth Mousse, G2: Remin-Pro, G3: Colgate Pro-Relif, G4: Mirafluor. The remineralizing protocol was applied 3 min per day for one week. Vickers microhardness (HV) measurements and SEM observations were performed at baseline, after bleaching, and after remineralizing treatment in all groups. Statistical analyses were performed using the paired t-test and ANOVA. RESULTS: After bleaching, SEM showed an increase of irregularities on the surface of the samples. Enamel microhardness decreased a mean of 47.7 HV, equivalent to a mean decrease of 18.3% (p < 0.05). After remineralization, the HV increased in all groups between 16 and 33% (p < 0.01), recovering the initial microhardness of enamel samples. SEM images revealed a higher quantity of superficial mineral deposits in groups 1 and 2 compared to the rest of the groups. CONCLUSIONS: The application of remineralizing products generates a significant increase in enamel microhardness. Tooth Mousse-treated samples showed a greater microhardness recovery, followed by Remin Pro. The superficial morphology of the samples reflects the results obtained in the HV tests.