Effects of staining and bleaching on color change of dental composite resins

Statement of problem. Discoloration of resin-based composites by colored solutions is a common problem. The use of bleaching agents for discolored natural teeth is becoming increasingly popular. It is not clear if bleaching agents can remove the stain from composite resins. Purpose. The purpose of this study was to investigate the effects of 2 staining solutions and 3 bleaching systems on the color changes of 2 dental composite resins. Material and methods. Forty-five disk-shaped specimens (9 x 2.5 mm) of each of 2 composite resins, Filtck Supreme (FS) and Esther X (EX), were prepared. The specimens were then divided into 3 groups of 15 specimens each and immersed in 2 staining solutions (coffee or red wine) or distilled water (control) for 3 hours daily over a 40-day test period. The 3 groups were then divided into 3 subgroups (n=5), and 3 bleaching agents (Crest Night Effects, Colgate Simply White Night, or Opalescence Quick) were applied to the surface of the specimens over a 14-day period. Color of the specimens was measured with a spectrophotometer using CIELAB color space relative to CIE standard illuminant D55 at baseline, after staining, and after bleaching. The color differences (Delta E-ab*) between the 3 measurements were calculated. The value Delta E-ab*=3.3 was used as an acceptable value in subjective visual evaluations. Analysis of variance and nonparametric analysis (Kruskal-Wallis test and Mann-Whitney test) were used to analyze the data. Results. After staining, FS had more color change than EX and was more affected by the wine solution. After bleaching, the color of both EX and FS specimens returned to the baseline. The color differences between bleaching and baseline were less than value Delta E-ab*=3.3 for all groups. Conclusion. The nanocomposite (FS) changed color more than the microhybrid composite (EX) as a result of staining in coffee or red wine solutions. After bleaching, discoloration was removed completely from the composite resins tested.