Effect of artificial aging on the translucency of monolithic zirconia materials sintered at different temperatures.

STATEMENT OF PROBLEM: Translucent zirconia materials were developed as an alternative to lithium disilicate materials. However, the effect of sintering temperature and artificial aging on the translucency of zirconia materials is unclear. PURPOSE: The purpose of this in vitro study was to investigate the translucency of recently developed zirconia materials after different sintering temperatures and the effect of artificial aging. MATERIAL AND METHODS: Disk-shaped specimens (O15x1 mm) of 3 different monolithic zirconias (Katana UTML, Prettau Anterior, VITA YZ XT) and a control lithium disilicate reinforced glass-ceramic (IPS e.max CAD LT) were evaluated. The zirconia specimens were divided into 2 subgroups with different sintering temperatures (1450 degrees C, 1550 degrees C) (n=5, N=35). The specimens were artificially aged in a thermocycle tester and a mastication simulator. The translucency parameter (TP) was calculated by measuring with a spectrophotometer. Kruskal-Wallis and Wilcoxon signed-rank tests were used to analyze the data (alpha=.05). RESULTS: While the overall TP of monolithic zirconia increased after artificial aging, the lithium disilicate specimens did not show a statistically significant difference (P=.35). The Prettau Anterior and VITA YZ XT specimens had a statistically significant higher TP than Katana UTML (P=.009). Sintering temperature did not have a statistically significant effect on the TP value of monolithic zirconia materials (P>.05). CONCLUSIONS: Artificial aging increased the TP, and the sintering temperature did not affect the TP of monolithic zirconia. The use of fully stabilized zirconia may be an alternative to lithium disilicate in esthetic restorations in clinical practice.