Objectives: To evaluate the influence of accelerated aging on color and translucency parameter (TP) of composite bleaching shades. Methods: Thirty-three bleaching shades of 10 manufacturers' microhybrid (MH) and microfill (MF) composites were analyzed. Specimens (n=5) were discs, 10 mm in diameter and 2-mm thick, aged in an accelerated aging chamber with exposure to a total ultraviolet irradiation of 450 kJ/m². Data were recorded using a spectrophotometer (CIELAB, D55, 10° standard observer) against white and black custom-made molds. Specimen color coordinates were determined four times: at baseline and at 150, 300, and 450 kJ/m². Data were analyzed by ANOVA. Results: The ranges of color coordinate changes (DL*, Da*, Db*) for MH were as follows: -5.6 to 5.3, -0.5 to 2.1, -5.4 to 0.4 (at 150 kJ/m²); -1.6 to 5.0, -0.5 to 1.2, -6.8 to -0.2 (at 300 kJ/m²); -0.8 to 5.0, -0.6 to 1.2, -8.3 to 0.0 (at 450 kJ/m²), respectively. The DL*, Da*, Db* ranges of MF were as follows: 0.1 to 1.0, 0.3 to 0.9, -1.9 to 2.5 (at 150 kJ/m²); 0.1 to 0.9, 0.1 to 1.2, -2.1 to 1.9 (at 300 kJ/m²); 0.2 to 1.3, 0.1 to 1.3, -2.5 to 1.1 (at 450 kJ/m²), respectively. At 150, 300 and 450 kJ/m², MH color difference relative to baseline was 3.2, 4.0 and 4.7, respectively. Corresponding values for MF were 2.0, 2.0 and 2.1, respectively. Compared to baseline (2.3 for MH and 1.7 for MF), TP values at 150, 300, and 450 kJ/m² were 2.2, 2.2, 2.1 for MH, and 1.6, 1.6, 1.7 for MF, respectively. Conclusions: Accelerated aging caused decrease in L* and a* values, while b* values increased for both MH and MF composites. MH were less color stable after accelerated aging, while TP values were relatively stable for both MH and MF composites. This project was partialy funded by Ultradent, Dentsply/Caulk, and Bisco.

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