Surface roughness of a microhybrid composite polished with abrasive pastes

Methods: Sixty composite discs (Filtek Z250, 3M ESPE, USA) were assigned to six experimental groups (n=10), each one established to be the sequential step of a polishing protocol based on abrasive pastes (Diamond ACI, ACII and Excel, FGM, Brazil): G1, simulated finishing with 40 μm diamond bur; G2, as G1 + 75-80 µm paste; G3, as G2 + 30-35 µm; G4, as G3 + 2-4 µm; G5a, as G4 + felt wheel; G5b, as G4 + resin coating (Seal Coat Fast, DEI Italia, Italy) and felt wheel. The profilometric superficial parameter S_awas taken into account as measure of the roughness on the treated surfaces. Non-parametric statistical analysis was used to assess differences among groups (α=0.05).

Results: The registered mean S_avalues ±SD expressed in μm were: G1, 0.31±0.06; G2, 0.11±0.01; G3, 0.11±0.02; G4, 0.12±0.02; G5a, 0.17±0.07; G5b, 0.09±0.03. The decrease in surface roughness among groups representing subsequent steps was statistically significant between G1 and G2 (p<0.001) and between G4 and G5b (p<0.01). Similar surface roughness was observed in groups 2 to 5a.

Conclusion: Polishing pastes were effective in improving the surface smoothness of the composite after the finishing procedure. The 30-35 µm and the 2-4 µm pastes and the felt wheel alone did not influence the surface roughness obtained after the use of the 75-80 µm paste, which was already low. The resin coating yielded the smoothest surface.