In Vitro Re-Hardening of Bleached Enamel Using Mineralizing Pastes: Toward Preventing Bacterial Colonization

The search for materials able to remineralize human hard tissues is a modern medical challenge. In this study, the protective effect on the enamel microhardness by a paste based on hydroxyapatite and sodium fluoride (Remin Pro) was evaluated after two different enamel bleaching procedures. Forty sound human incisors were randomly assigned to different treatments: bleaching with an in-office agent (Perfect Bleach Office+); bleaching with an at-home agent (Perfect Bleach); bleaching with the in-office agent followed by the prophylaxis paste; bleaching with the athome agent followed by the prophylaxis paste; no treatment (control). Bleaching was performed at 0, 8, 24 and 32 h, followed by a 3min remineralizing treatment in the subgroups designed to receive it. Specimens underwent a microhardness tester and a mean Vickers Hardness number was considered for each specimen. ANOVA exhibited significant differences among groups. Posthoc Tukey testing showed significant microhardness decrease after the application of both the two bleaching agents. The treatment with prophylaxis paste significantly increased the microhardness values of bleached enamel.