Finishing/Polishing Treatments on the Surface Roughness of Composites after Bleaching

Objectives: to evaluate the influence of a bleaching agent on the surface roughness of restorations with two composite resins (CR) and their relationship with subsequent finishing and polishing techniques. Methods: it was made 48 specimens of CR, in metallic matrixes with an internal cavity with 2 mm thick and 5 mm diameter. Mylar strips were placed over the top and bottom surfaces of the uncured CRs, and gently pressed between two glass plates.  Each specimen was lightcured with a LED device (LEDemetron) for 40 seconds, and then all specimens were divided into six groups (n=8). The groups G1 to G3 employed a microhybrid (MH) CR – (Opallis, FGM); and groups G4 to G6 a nanohybrid (NH) CR – (Brilliant NewLine, Coltène/Whaledent). After it, all the specimens were subjected to bleaching procedure with 35% hydrogen peroxide (Whiteness HPBlue Calcium, FGM). The surface roughness of all specimens was evaluated before and after the bleaching treatment (Ra parameter) in a roughness meter (Mitutoyo-Surftest). After bleaching, the groups were submitted to finishing and polishing procedures: G2 and G5 with felt discs (Diamond Flex, FGM) and diamond pastes (Diamond AC I and II and Diamond R, FGM) and G3 and G6 with silicon rubber tips (Astropol, Ivoclar-Vivadent). The control groups (G1 and G4) did not receive any finishing or polishing treatment after bleaching. Results: the bleaching procedure significantly increased the roughness values for the NH restorations, but both finishing and polishing techniques were able to reduce significantly the roughness values after bleaching for this CR. For the MH CR, only the silicon rubber tips decreases the roughness values. Conclusions: for both MH and NH restorations, the silicon rubber tips were more effective than the felt discs and diamond pastes to reduce the surface roughness after bleaching procedure.