Effect of Polishing Technique on Surface Roughness of Resin Composites

Objectives: to evaluate the effect of different finishing and polishing techniques on the surface roughness of five composite resins under perfilometer and SEM analysis. Methods: Thirty cylinder specimens (6mm diameter x 2mm depth) of each composite resin (light-cured for 60 seconds) were built: MH - microhybrid (Filtek Z250, 3M ESPE); MF - microfilled (Micronew, Bisco); NH - nanohybrid (Grandio, VOCO); NB - body-shaded nanofilled (Filtek Supreme B3D, 3M ESPE); NT - translucent nanofilled (Filtek Supreme VT, 3M ESPE). The specimens were randomly assigned to three groups (n=10): G1 = mylar matrix without finishing (control); G2 = sequential flexible aluminum oxide disks (Flexidisc, Cosmedent) + polishing paste (Enamelize, Cosmedent); G3 = fine and extra-fine diamond points (KG Sorensen) + rubber cups (Flexicups, Cosmedent) + polishing paste (Enamelize, Cosmedent). Surface roughness (Ra) was measured after 24-hour storage in distilled water using a perfilometer (Surftest 211, Mitutoyo), and mean values were statistically analyzed with two-way ANOVA (p<0.01) and Tukey's post-hoc test (p<0.01). One composite specimen of each group was selected for SEM analysis (XL30, Philips). Results: The mean values of surface roughness (µm) were (mean±SD): G1 – MH: 0.06±0.01; MF: 0.06±0.01, NH: 0.05±0.01, NB: 0.03±0.01, NT: 0.02±0.01; G2 – MH: 0.20±0.02; MF: 0.16±0.01; NH: 0.10±0.02; NB: 0.03±0.01; NT: 0.02±0.01; G3 – MH: 0.30±0.02; MF: 0.21±0.01; NH: 0.14±0.01; NB: 0.09±0.02; NT: 0.07±0.02. There was statistical difference between composite types and between polishing techniques. The higher to smoother surface roughness between composites were: MH>MF>NH>NB=NT. The association of diamond points, rubber cups and polishing paste (G3) resulted in the high surface roughness for all composites, as observed in SEM analysis. Conclusions: The surface roughness is dependent of polishing technique. The nanofilled composites (NB and NT) have more polishability than all other composites.