Effects of surface treatment methods on the color stability, whiteness, and surface roughness of bleach-shade composite resins

Despite the increasing use of bleach-shade composite resins in recent years, studies examining the optical properties of these materials remain limited. Furthermore, there are insufficient data on the effectiveness of surface treatments for removing stains from these materials. This study evaluated the effects of different surface treatment protocols on the color stability, whiteness index, and surface roughness of bleach-shade composite resins after coffee immersion. A total of 300 specimens were prepared from four bleach-shade composite resins (Estelite Asteria BL, Brilliant EverGlow BL Translucent, G-aenial A’chord BW, and Opallis E-Bleach L) and one multi-shade (Filtek Z250 A2) composite resin ( n = 60 per material). The specimens were randomly allocated to six groups ( n = 10): Group 1 (one-step polishing, OptraGloss), Group 2 (two-step polishing, Nova Twist), Group 3 (bleaching, Whiteness HP), Group 4 (bleaching + one-step polishing), Group 5 (bleaching + two-step polishing), and Group 6 (control). All specimens were immersed in a coffee solution for 12 days. Measurements (color and roughness [Ra]) were performed at baseline (t 0 ), after staining (t 1 ), and after the surface treatments (t 2 ). Color differences were calculated using the CIEDE2000 formula (∆E 00 ), and whiteness index (WI D ) values were determined using the CIELAB-based WI D formula. Statistical analyses were performed using the Kruskal–Wallis, Dunn, and robust ANOVA tests ( p < 0.05). At the t 1 time point, all specimens exhibited clinically unacceptable ΔE 00 values and decreased WI D values. The Asteria group exhibited the highest color stability at t 1 , while the Brilliant and A’chord groups exhibited the highest WI D values ( p < 0.05). At the t 2 time point, while Ra increased in the bleaching groups, the lowest Ra values were found in the one-step polishing group ( p < 0.05). Coffee exposure adversely affected the optical and surface properties of bleach-shade composite resins. Bleaching alone showed limited effectiveness, whereas polishing improved the esthetic outcomes and maintained clinically acceptable surface characteristics. Material-dependent differences were observed among the tested composites.