Factors affecting the color stability and staining of esthetic restorations.

This study aimed to assess the color stability of two composite resins, unprotected or protected with a hydrosoluble gel (oxygen inhibitor) during final polymerization, when subjected to different staining solutions and daily tooth brushing simulation. Nanohybrid composite (IPS Empress Direct) or nanofilled composite (Filtek Z350) were used to produce round samples that were either unprotected or protected with a hydrosoluble gel before the final cycle of polymerization. For 5 days, the samples were immersed for 1 h/day in four different staining solutions: distilled water (control), coffee, soft drink, and red wine. Once a day, the samples were also subjected to mechanical brushing with soft-bristled brushes for 30 min. The combination of experimental conditions produced 16 groups (n = 10). Color changes (ΔE) were evaluated at baseline and after mechanical brushing cycles for 1, 3, and 5 days. Data were analyzed by linear regression models. Protection with hydrosoluble gel was able to significantly reduce the color change only on the first day (p = 0.001). The type of composite resin did not significantly affect the color change over the days. Wine affected composite resin color change only on the first day (p = 0.002). Over time, color stability of composite resins did not improve with the protection of a hydrosoluble gel before the final polymerization.