The effect of thermal cycling and ultraviolet exposure on the color stability of veneer resin cements in-vitro

Abstract

Objective: To evaluate the color stability of veneer resin cements after accelerated aging process (thermal cycling and UV exposure). METHOD: 80 disc-shape specimens of four various resin cement materials were prepared: RelyX Veneer cement (3M/ESPE), Variolink II (Ivoclar vivadent), Variolink Veneer (Ivoclar vivadent) and Calibra esthetic (Dentsply). Samples were assigned into different groups and the CIELAB system was used to record the colorimetric values of each sample before and after testing. Accelerated thermal cycling and ultraviolet radiation exposure were conducted on separate groups and the color changes were evaluated by calculating [Delta]E values using the CIE76 formula. Further statistical analysis was conducted using t - test, analysis of variance (ANOVA) and Tukey post-Hoc test. RESULTS: After accelerated thermal cycling, all tested resin cements showed [Delta]E values larger than the pre-set critical [Delta]E ([Delta]E[greater than] 2.3). RelyX Veneer possessed the largest [Delta]E value ([Delta]E =16.76), and exhibited significantly more color change than all tested groups (p[less than]0.05). Visual inspection revealed detectable color changes between tested and controlled samples. RelyX Veneer showed the most noticeable color change with increased yellow hue and decreased brightness. On the second set, Variolink II was the only group that showed [Delta]E value ([Delta]E = 2.74) larger than the critical [Delta]E after 72 hours of UV exposure. Also, Variolink II group showed significantly more color change than all tested groups (p[less than]0.05). Visual inspection was not conclusive for any color changes between tested and controlled groups after UV exposure. CONCLUSION: Accelerated thermal cycling has a significant effect on changing the color of resin cement materials. All tested samples appeared darker with more yellow saturation. AIso, UV exposure showed a significant color change in the dual cure group (variolink II) but the color change was not evident by visual inspection.