الفهرس 
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Abstract
SUMMARY
Problem Statement: With the advent of ultra-high translucent cubic zirconia in the market, glass ceramic and hybrid zirconia ceramic were compared with respect to their translucency and shear bond strength during thermal ageing.
Aim of This Stud: The purpose of this study was to compare the translucency and colour change both before and after ageing, as well as shear bond strength of two distinct zirconia materials to that of ordinary glass (LDS) ceramic after aging.
Material and Methods: 21 ceramic samples (n=7) of lithium disilicate ceramic (IPS e.max CAD), hybrid lithium reinforced zirconia (ZirCADPrime), and ultra-high translucent zirconia (KATANA Zirconia) were prepared by CAD/CAM milling into square-shaped specimens with dimensions of 10 X 10 mm in diameter and 0.5 mm in thickness. then each group was further subdivided into two subgroups (n=14) according to the test method (translucency and shear bonding strength). The ageing process was carried out in an autoclave with a temperature and pressure setting of 134 C° under 0.2 MPa pressurer respectively, for five hours. To measure each group’s translucency and colour shift, a spectrophotometer was employed. Shear bond strength was tested using a universal testing machine.
Results: Before and after aging there was a significant difference between different groups. The highest value was found in IPS e.max, followed by KATANA, while the lowest value was found at ZirCAD Prime. Moreover, for all tested ceramics, the measured translucent parameter value after aging was significantly higher than before aging value.
Furthermore, there was a significant difference between different groups regarding the colour change. The highest value was found in KATANA, followed by ZirCAD Prime, while the lowest value was found at IPS e.max.
However, regarding the bond strength, there was a significant difference between different groups. The highest value was found in IPS e.max, followed by KATANA, while the lowest value was found at ZirCAD Prime. However, the mode of failure was pure adhesive with IPS e.max.