الفهرس 
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Abstract
Dental ceramics and zirconia are increasingly being used with outstanding outcomes for various restorations such as fixed dental prosthesis, resin bonded FDPs, and implant restorations. Zirconia is a polymorphic ceramic that can be found in three various crystalline forms depending on temperature: monoclinic, tetragonal, and cubic. The monoclinic phase is stable at room temperature; unfortunately, its mechanical and optical properties are insufficient for clinical application; nonetheless, the tetragonal and cubic phases can be rendered stable at room temperature by applying stabilizing oxides. The multi-layered technology has shown an improvement in color of zirconia to mimic the natural teeth without affecting its mechanical properties.
The long sintering procedure of zirconia became a problem with the advancement of ceramics and the increasing popularity of one visit chairside restorations. It has been stated that modifying the sintering settings has a number of effects on the structure of zirconia which affects its physical properties such as translucency and flexural strength.
Objective: The aim of this in vitro study is to evaluate the effect of two sintering protocols: Conventional firing cycle and Speed firing cycle on translucency and Flexural strength of the novel color gradient zirconia and compare it to different monolithic zirconia material.
Methods: 54 discs were constructed to be divided into 3 different groups each group sub divided to speed cycle group and conventional cycle group for materials: IPS e.max® ZirCAD® Prime, Katana ultra-translucent zirconia and BruxZir anterior, To compensate for sintering shrinkage, the zirconia samples were milled with dimensions bigger than the required final dimension. The discs were then sintered in a sintering furnace group conventional sintering and group speed sintering for each material.
All samples were tested for translucency using Aligent Cary 5000 spectrophotometer once for speed sintering samples and once for conventional sintering samples to know the effect of changing sintering settings on the translucency.
All samples were tested for biaxial flexural strength using a universal testing machine for speed sintering samples and once for conventional sintering samples to know the effect of changing sintering settings on the zirconia strength.
Results for translucency: for conventional firing There was a significant difference between different groups The highest value was found in Katana UTML, followed by Zircad prime,while the lowest value was found at BruxZir and for speed firing There was a significant difference between different groups. The highest value was found in Katana UTML, followed by Zircad prime, while the lowest value was found at BruxZir.
Results for flexural strength: for conventional firing There was a significant difference between different groups. The highest value was found in Zircad prime, followed by BruxZir, while the lowest value was found at Katana UTML; and for speed firing, there was a significant difference between different groups. The highest value was found in Zircad prime, followed by BruxZir, while the lowest value was found at Katana UTML.