The purpose of this study was to evaluate the color stability of repaired aesthetic restorative resin matrix materials after immersion in coffee and the effect of polishing systems after staining. One hundred and eighty cylindrical discs (8 mm × 2 mm) were prepared using a conventional nano-fill resin composite (Clearfil Majesty Esthetic A2 shade) with round cavities (3 × 1 mm). Cavities were repaired by three resin composite materials: Clearfil Majesty Esthetic A2 shade, one-shaded nano-fill resin composite (Omnichroma) and group-shaded nano-hybrid resin composite (Optishade, medium shade). Each group was polished with three polishing systems (n = 20); aluminum oxide (Soflex Spiral Wheels, 3M ESPE), silicon carbide (Occlubrush, Kerr, CA, USA) and diamond particulate (Twist Dia Spiral Wheels, Kuraray, Okayama, Japan). Color change (ΔE₀₀) measurements were performed with a spectrophotometer at the baseline. Half of the polished samples were either kept in distilled water or immersed in coffee for 15 days, and color measurements were repeated before and after polishing. Statistical analysis was performed using the Kruskal–Wallis test. Repaired samples showed different color correspondence values in all groups. All three restorative materials showed significant color changes (ΔE₀₀) after immersion in coffee (p ≤ 0.05). Repolishing of stained samples showed color improvement values in all groups. The content of the polishing system played an important role in removing the stains.

Objective: The aim of this study was to compare the surface roughness of a conventional composite resin, a one-shade universal composite resin, and a group-shade universal composite resin after bleaching. Methods: A conventional composite resin, Clearfill, and the universal composite resins Omnichroma and Optishade were prepared into discs (2 × 8 mm), with a total of 90 discs. Each group (30) contained three different groups, including a control (n10), coloured with CHX (n10), and after bleaching (n10). The surface roughness of group discs was measured with a 3D profilometer. ANOVA and Kruskal–Wallis Tests were used to analyse data. Analyses were performed in the SPSS programme. Results: Significant Ra values were obtained between subgroups (p < 0.05). Comparisons of surface roughness after discolouring were performed with the control group; the highest surface roughness value (p > 0.05) was found for Optishade after bleaching compared to the control group. The Optishade composite resin showed the highest initial surface roughness value (p > 0.05), and after discolouration followed by bleaching, the Clearfill composite resin showed the highest surface roughness value (p > 0.05). Conclusions: Both immersion and bleaching applications cause surface roughness. As a result, it was determined that the composite resin content has a significant effect on the surface roughness in discolouring and bleaching processes.