The in-vitro investigation of the effect of finishing and polishing methods on the surface roughness of composites

Abstract Background Surface roughness of resin composite restorations is influenced by both the restorative material and the finishing/polishing protocol. Because rougher surfaces may favor plaque retention, staining, and wear, material-dependent responses to polishing systems remain clinically relevant. This in vitro study evaluated the effect of five finishing and polishing systems on the surface roughness of two anterior resin composites with different filler characteristics. Methods One hundred and twenty disk-shaped specimens (6 mm diameter × 2 mm thickness) were prepared from two resin composites, G-aenial Anterior and Estelite Asteria. Each composite was randomly allocated to six groups ( n = 10). Five groups were finished and polished with the assigned system: Sof-Lex and OptiDisc (multi-step aluminum oxide disc systems), Clearfil Twist Dia (two-step diamond-impregnated spiral system), OneGloss (one-step rubber system), and Sof-Lex Spiral (two-step rubber spiral system). As a control, composite specimens were light-cured against a Mylar strip, resulting in a smooth, unpolished reference surface. Surface roughness was measured with a contact profilometer and reported as Ra (µm). One representative specimen from each group was examined qualitatively by scanning electron microscopy (SEM). Data were tested for normality using the Shapiro-Wilk test and analyzed using the Kruskal-Wallis test with Bonferroni-adjusted pairwise post hoc comparisons and the Mann-Whitney U test (α = 0.05). Results In both composites, the Mylar strip control produced the lowest Ra values. Among the polishing systems, Sof-Lex and OptiDisc produced lower roughness values than OneGloss and Sof-Lex Spiral. Estelite Asteria generally showed lower roughness than G-aenial Anterior; this difference was significant in the control, OptiDisc, Twist Dia, and overall material comparisons. SEM observations qualitatively illustrated smoother surfaces in the control and disc-polished groups. Conclusions Within the limitations of this in vitro study, both composite type and finishing/polishing system affected surface roughness. Multi-step aluminum oxide disc systems were associated with lower Ra values than the tested one-step rubber system and Sof-Lex Spiral. The findings should be interpreted as initial surface roughness data and should not be extrapolated directly to long-term clinical performance without aging, wear, gloss, hardness, and biofilm-related outcomes.