Color stability of resin cements after ultraviolet artificial aging

Introduction: Porcelain laminate veneers are popular for use in achieving an esthetic outcome. However, resin cements gradually degrade overtime, resulting in marginal defects and discoloration. The color stability of restorative materials, especially the indirect composite resins, is well documented. But only a few studies have focused on resin cements with conflicting results. Therefore, this study was to evaluate the color stability of resin cements after accelerated aging by ultraviolet irradiation. Material and methods: Three shades of four commercial resin cements were tested in this study (RelyX Veneer, Variolink Veneer, VariolinkII, and NX3). Specimens were prepared using acrylic split molds and subjected to artificial aging with a UVA intensity of 62 W/m2. Color measurement was done before and after accelerated aging for 1, 3, 5, and 7 days, and 2, 3, 4, 8 and 12 weeks. Color was measured using the CIE L*a*b* system with a spectrophotometer. ∆L*, ∆a*, ∆b*, and ∆E* were calculated between baseline values and subsequent measurements. Statistical analysis was performed using Two ways repeated measures ANOVA and Tukey post hoc test (P<0.05). Results: After 12 weeks, the ∆E values ranged from 1.07 to 5.30 for control groups and from 1.66 to 6.31 for the artificial aging groups. ∆L* values were negative except for RelyX Veneer A3 and Translucent. Δa* values for the exposed groups were positive except for NX3 Yellow. ∆b* values were different among brands and shades. Statistical analysis showed that the aging conditions and times significantly influenced the color change of each material except for RVA3 which there was no significant difference between the aging conditions. All interactions were significant. Conclusion: Ultraviolet light can induce resin cements to become darker and more reddish in color. All of the resin cements tested in this study exhibited perceptible color changes after artificial aging. Variolink Veneer exhibited the greatest ∆E* values and RelyX Veneer exhibited the lowest ∆E* values after artificial aging.