Effect of Hydrothermal Aging on Translucency of Different Types of Zirconia and Lithium Disilicate at Variable Thicknesses

Objective: The aim of this in vitro study was to investigate the effect of hydrothermal aging on translucency parameter (TP) of different zirconia ceramics in different thicknesses. Material and Methods: This is an in-vitro study in which translucency of six pre-sintered and pre-shaded zirconia materials (In Coris ZI, In Coris TZI, Bruxzir Solid, KATANA HT, KATANA ST, and KATANA UT) was compared to a low-translucency, lithium disilicate glass-ceramic material (IPS e.max CAD LT, Ivoclar Vivadent). The ceramic blocks were cut in the form of plates of dimensions (14x10 mm) and of different thicknesses (0.5, 0.7,1 mm). Thirty specimens of each ceramic material were classified into three groups according to thickness (n=10) such that the total number of specimens is 210. After all zirconia specimens were sintered and lithium disilicate samples were crystallized, TP was determined using dental spectrophotometer VITA Easyshade Compact. Same procedure of translucency measurement was done again after samples were subjected to accelerated autoclave aging. Results: Paired-Samples T- Test showed that aging caused significant reduction in TP in all materials in all thicknesses. Moreover, there was statistical significant difference (P < 0.05) between different ceramic materials where e.max CAD LT showed the highest (TP) and In Coris ZI showed the lowest TP in all thickness groups. Conclusions: TP was both thickness and material dependent. TP was also affected by LTD.