This article aimed to study the effect of different concentrations of nano zinc oxide particles on the color change of MDX4-4210 facial silicone elastomer after artificial aging.
 Silicone specimens ( = 150) were fabricated by incorporating intrinsic pigments and divided into three groups-white, yellow, and red, each group consisting of 50 specimens ( = 50). In each color, specimens were subdivided into five subgroups according to the quantity of zinc oxide nanoparticles (0, 0.5, 1.0, 1.5, and 2.0% weight), where the 0% weight served as the control in each group. All specimens were then subjected to artificial aging using an accelerated aging machine chamber for 12, 24, 48, and 72 hours. L*a*b* values of specimens were noted after a different aging period by a spectrophotometer and ∆* was calculated.
 Two-way repeated analysis of variance (ANOVA) was done to examine the effects under test conditions (concentration and aging time) of each color group. Then color, concentration, and the aging period were subjected to three-way repeated ANOVA to investigate the effects of different colors and concentrations on ∆*. Bonferroni’s test was performed to identify differences between groups. The significant level was at = 0.05.
 The control group showed significantly higher ∆* values than the test groups. The 1.5% test group showed significantly lower ∆* compared with the others. The 0.5 to 2.0% of nano zinc oxide significantly decreased the color change of the silicone elastomer ( < 0.05), but there were no significant differences among groups.
 Incorporation of 1.5% of nano zinc oxide can improve the color stability of silicone prosthesis (MDX4-4210).