Investigation of the effects of synthetic food dyes on the color stability of composite resins with different properties

Objective: The aim of this study was to evaluate the color stability of different resin composites upon exposure to synthetic food dyes, the coloring degrees of the food dyes used, and the effect of a bleaching mouthwash on colored resin composites in vitro. Method: Six resin composites [RubyFlow (RBF), Charisma Smart (CHR), Estelite ∑ Quick (EST), Filtek One Bulkfill Restorative (OBF), Filtek Ultimate Universal Restorative (ULT), Spectra ST HV (SPC)] in A2 shade used in different clinical indications were selected to evaluate their color stability. For each composite, sixty disc-shaped specimens of 2 mm thickness and 7 mm diameter were fabricated using a polytetrafluoroethylene mold and Mylar matrix tape (N=360). The samples were divided into 6 subgroups (n=10) and storaged in distilled water at room temperature for 24 hours. The samples were immersed into five different stainig solutions (Tartrazine, Sunset Yellow, Ponceau 4R, Carmosin, Brilliant Blue) throughout the 1 week (7 days) except for the control group. The control group was kept in distilled water for 1 week (7 days). Food coloring solutions were changed regularly every day. For the bleaching protocol, all samples (N=360) including the control group were kept in bleaching mouthwash (Listerin Advanced White) for 1 week (7 days). The whitening mouthwash was renewed periodically every day. At the end of the coloring and bleaching processes, all samples were rinsed under running water for 60 seconds and dried. The color changes of the samples were measured at 3 different times, baseline (T0), after discoloration (T1) and bleaching procedures (T2). The CIE L*a*b* color parameters of the samples were measured using a spectrophotometer (Vita Easyshade, VITA Zahnfabrik GmbH, Bad Sackingen, Germany). Color differences of the samples were calculated using both CIELAB (ΔEab) and CIEDE2000 (ΔE00) formulas. Data were statistically analyzed using repeated analysis of variance ANOVA. Multiple comparisons were made with Tukey's post-hoc test (p=0.05). Results: Statistically significant differences were found in ΔE00 values between the groups at the end of the coloring (T1) and bleaching (T2) procedures in all composite groups. While the most color change was observed in the EST group at the end of the coloring protocol, there was no significant difference between RBF and OBF. The groups that showed the least color change were SPC, CHR and ULT and there was no statistically significant difference between them. The dye that caused the most color change was Brilliant Blue. Brilliant Blue showed statistically significant differences with other dyes. There was no statistically significant difference between the other four colors. In our study, the most color change was detected as a result of keeping the EST group samples in Brilliant Blue dye. The most color change at the end of bleaching was observed in EST, RBF and OBF groups. The ΔE00 values of all samples belonging to these groups were found to be above the perceptible color threshold (ΔE00˃0,8). Conclusion: Brilliant Blue, one of the food dyes evaluated in our study, caused a perceptible color change in all composites. This coloring effect of Brilliant Blue on composite resins is statistically higher than other food dyes. Color stability of composite resins against food dyes shows statistical differences. The tested whitening mouthwash solution was found effective in eliminating the color changes caused by all food dyes on the tested composite resins. Key words: Food additives, Synthetic food dyes, Resin composites, Color stability, Whitening mouthwash