Bleaching procedures

After the initial readings, 5 enamel samples and 10 specimens of each sealed and unsealed composite resin were subjected to bleaching with 35% hydrogen peroxide or 16% carbamide peroxide, with the control group exposed to distilled water.

The bleaching procedure with 35% hydrogen peroxide (Whiteness HP Maxx, FGM) involved the application of 0.1 mL of the product for 15 minutes, followed by 2 additional applications in the same session. Between each application, the specimens were washed with distilled water and dried with sterile gauze, yielding a total of 45 minutes per session. One session involving 3 applications of the product was conducted per week, at 0 (baseline), 7, and 14 days, according to the manufacturer's specifications. After each bleaching procedure, the samples were washed and were stored in distilled water at 37ºC until the next session.

Bleaching with 16% carbamide peroxide (Whiteness Perfect, FGM) was performed by applying 0.1 mL of the product to the samples once a day for 4 hours; this was repeated for 14 days. After bleaching sessions, the samples were washed and stored in distilled water at 37ºC until the next session. The samples of the control group were kept in distilled water during the 14 days of the experimental period. The surface roughness and microhardness values were evaluated again after the bleaching procedures.