Investigating on surface roughness of nanohybrid and micro-hybrid composite resins following the use of a simplified polishing system

This in vitro experimental study compared the average surface roughness (Ra value) of Z250 microhybrid and Z350 nanohybrid composite resins following polishing with the EVE simplified polishing system versus the multi-step Sof-Lex discs. Ninety-six composite discs (8 x 2 mm) were randomly divided into four subgroups: control (surface under the Mylar strip, no finishing/polishing), polishing with Sof-Lex discs, polishing with EVE discs, and polishing with EVE discs + EVE polishing paste. Prior to polishing, the specimens were ground with 1200-grit silicon carbide abrasive paper. The average surface roughness of each specimen was measured before (baseline) and after polishing using a profilometer. The results were analyzed using ANOVA and Bonferroni tests. The control subgroups showed the smoothest surfaces. A significant difference in surface roughness was found in the Z350 subgroups, with the Sof-Lex system yielding the roughest surface (P<0.05). The EVE discs + EVE paste system yielded the smoothest surface after the control subgroup. The difference in surface roughness was also significant among the Z250 subgroups, with the Sof-Lex system creating significantly rougher surfaces than the EVE discs + paste system. A significant difference in surface roughness was observed in all eight subgroups, with Z350 specimens polished with Sof-Lex discs and Z350 control specimens showing the maximum and minimum roughness, respectively. The study concludes that the two-step EVE polishing system may be preferred over the multi-step Sof-Lex discs for polishing Z250 and Z350 composites, as it provided significantly smoother surfaces.