Effect of Accelerated Aging on the Translucency of Monolithic Zirconia at Minimal Thickness

Objective: The objective of this study was to evaluate the effect of accelerated aging on the translucency of two monolithic zirconia ceramics used at their minimal thickness. Materials and methods: A total of 20 disc-shaped specimens (10x10x0.5 mm) were prepared from two zirconia blanks, high-translucent partially-stabilized tetragonal zirconia (Zolid ht+) and ultra-translucent fully-stabilized cubic zirconia (Zolid fx), and divided into two groups (n=10). An integrating sphere reflective light recording spectrophotometer was used to assess the color parameters L*, a*, and b* before and after artificial accelerated aging for 5 hours in an autoclave at 134°C with 2 bar steam pressure. The Translucency Parameter (TP) was calculated based on TP=[(∆L*)²+(∆a*)²+(∆b*)²]^1/2. The tests of homogeneity of variance, normality, and 1-way ANOVA statistical analysis of variance were performed by Graph Pad InStat software for windows (α=.05). Results: A statistically significant higher mean TP value was recorded with fully-stabilized cubic zirconia group compared to that of partially-stabilized tetragonal zirconia, both before (P=.003*˂.05) and after (P<.0001*<.05) accelerated aging. Artificial accelerated aging had a significant effect on the translucency of both fully-stabilized cubic zirconia (P=.0227*<.05) and partially-stabilized tetragonal zirconia (P=.023*<.05) increasing the mean TP value of both materials. Conclusions: Within the limitations of this in vitro study, it was found that accelerated aging had a significant effect on the translucency of both fully-stabilized cubic and partially-stabilized tetragonal monolithic zirconia, causing an increase in the mean TP value of both materials.