Surface roughness of a microhybrid composite polished with abrasive pastes

Objective: Occlusal surfaces of dental restorations should reestablish the anatomy of cusps, pits and fissures that has been lost. Since this complex area of the restoration is difficult to polish properly with rigid and semi-rigid rotary instruments, the benefits of polishing pastes have been highlighted and their use advocated. The present study aims to individuate a polishing protocol for a microhybrid composite using abrasive pastes with decreasing grit. 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 Sa was 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 Sa values ±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.