Rubber point polishing and resin coating of a micro-hybrid composite

Objectives: Finishing and polishing are essential phases of composite restoration. There is not agreement in literature regarding the gold standard technique to achieve a polished surface under a 0.2 ìm Ra threshold. The present rugosimetric study investigates the effectiveness of each step of a polishing protocol by using a diamond bur, decreasing particle size rubber points and resin coating. Methods: Seventy-two composite discs (Filtek Z250, 3M ESPE, USA) were prepared and randomly divided into 6 groups (n=12); each group represented a step of the following polishing protocol: G1, 40 ìm diamond bur; G2, bur and 70 ìm black rubber point; G3, bur, black and 40 ìm yellow rubber points; G4, bur, black, yellow and 5 ìm grey rubber points; G5 as G4 + felt wheel; G6 as G4 + resin coating and felt wheel. Specimens underwent profilometric analysis by considering a superficial parameter (Sa). Data were statistically analyzed by means of Kruskal-Wallis and Conover tests (p<0.05). Results: The mean Sa values ±DS (ìm) were: G1, 0.50 ±0.21; G2, 0.18 ±0.01; G3, 0.19 ±0.04; G4, 0.11 ±0.04; G5, 0.12 ±0.02; G6, 0.10 ±0.03. Maximum roughness values were found in G1; a significant surface roughness decrease was registered in the groups in which the black (G2) and grey rubber points (G4) were used. Conclusions: The black rubber point step already produced roughness values lower than the established threshold; therefore, it is possible to shorten the polishing sequence by excluding the yellow rubber point. Felt wheel and resin coating did not seem able to further decrease surface roughness.