The purpose of the study was to investigate the influence of graphene oxide (GO) and hydrothermal aging on the color stability of monolithic zirconia with different yttria concentrations. Disc shaped specimens (N=60) with a diameter of 15.0mm and a thickness of 1.0 mm were prepared from zirconia blocks having different yttria concentrations (HT, ST, and XT). Half of the specimens were immersed in 0.2 wt% GO-water dispersion (HTG, STG, and XTG). Color parameters were assessed using a reflection spectrophotometer before and after 5 and 10 hours of hydrothermal aging. Color differences (∆E₀₀) were calculated and compared to perceptibility and acceptability visual thresholds. Data were statistically analyzed with 2-way ANOVA followed by post-hoc comparisons (α=.05). Regardless of the aging time applied, ΔE₀₀ values below PT were found in the groups of HT, ST, and XT. Hydrothermal aging significantly increased ΔE₀₀ values in the groups of HTG, STG, and XTG that presented values above AT (p<.001). Immersion in GO-water dispersion significantly increased ΔE₀₀ values of zirconia discs (P<.001). Color stability of zirconia ceramics with graphene oxide reinforcement was affected by hydrothermal aging.

Keywords: Color stability, Monolithic zirconia, Graphene oxide, CIEDE2000.