Surface geometry of four nanofiller and one hybrid composite after one-step and multiple-step polishing

This study assessed the surface quality of four nanoparticle composites and one hybrid composite after polishing with three different techniques. Nanocomposites Premise (KerrHawe), Tetric EvoCeram (Ivoclar Vivadent), Filtek Supreme (3M ESPE) and Ceram X Duo (Dentsply) and the hybrid composite Herculite XRV (KerrHawe) were selected. Sixty specimens 7x7 mm each were fabricated from these materials. After light curing, the specimens were treated with 600 grit sandpaper discs. Fifteen specimens of each composite were polished using flexible Sof-Lex discs (3M ESPE). The remaining 45 specimens of each material were prepared with three finishing protocols: a single 30 mu m diamond (n=15), a sequence of a 30 mu m and a 20 mu m diamond (n=15) and a 30 mu m diamond followed by a tungsten carbide finishing bur (n=15). Each series of 15 specimens was then subdivided into three groups of five and polished with the Astropol system (Ivoclar Vivadent), OptiShine brushes (KerrHawe) and the Enhance/PoGo system (Dentsply). Quantitative evaluation of surface roughness was done with the help of optical laser stylus profilometry. Average roughness (Ra) was calculated, and the effect of the materials, the finishing regimen and the polishing methods on surface roughness were analyzed by three-way and two-way Anova and Scheffe post-hoc tests. Qualitative evaluation of the surfaces was done with the help of scanning electron microscopy (PSEM 500, Phlipps). Photomicrographs were assessed with respect to surface quality in four gradings. Surface roughness after polishing was significantly influenced by three factors: composite material (p < 0.001), finishing protocol (p < 0.001) and polishing method (p < 0.001). There were strong interactions between the finishing and polishing methods (p < 0.001). Two of the nanocomposites were significantly smoother (p <= 0.001), while the other two had a surface quality similar to that of a hybrid composite. Astropol achieved the lowest average roughness on all composites. Except for a combination of a 30 pm diamond and OptiShine brushes, which caused severe roughness, all the polishing methods produced surfaces that were significantly smoother than using the Sof-Lex discs.