الفهرس 
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Abstract
SUMMARY
In recent years, trends for aesthetic dentistry surprisingly increased. The demands of patients for tooth-colored restorations and the availability of new types of dental ceramics with good mechanical properties have driven increased use of ceramic materials in a variety of restorative restorations.
Aim: The present in vitro study was carried out to evaluate and compare the translucency and flexural strength of three lithium dislicate ceramics with different thicknesses.
Materials & Methods: Three lithium disilicate glass ceramic materials were used in this study: IPS E.max CAD (Ivoclar Vivadent US), Rosetta SM (HASS corporation korea) and Upcera (Shenzhen upcera co.,Ltd china). A total of 42 discs were prepared with diameter (10 mm) and thickness 0.5mm and 1mm. Discs were divided into three groups according to the material; group (1)Emax, Group(2)Rosetta sm and Group(3)upcera. Each group was further subdivided into two subgroups according to thickness; group (A) 0.5mm and group (B) 1mm. Specimens were placed into a ceramic furnace for glazing and crystallization according to manufacturer’s instructions. Then, the specimens were thermocycled in a water bath for 5,000 cycles between 5ºc and 55ºc with a dwell time of 30 s.
Each disc was tested for translucency using spectrophotometer to calculate the color differences of the specimens over black and white backgrounds. Then, the biaxial flexural strength test was conducted according to ISO 6872:2015 using a Universal Testing Machine.
Results: Finally, the results were analyzed via Two-way ANOVA (p≤0.05) and Bonferroni’s multiple comparison tests. For Translucency, the highest translucency parameter (TP) value was found in Rosetta, followed by Emax, while the lowest value was found in Upcera samples. And value of Upcera samples was found to be significantly lower than values of other materials. Translucency increases with the decrease in ceramic thickness for the three ceramic materials.
While, for Biaxial Flexural Strength, the highest value was found in E.max, followed by Rosetta, while the lowest value was found in Upcera samples. And value of Upcera samples was found to be significantly lower than values of other materials. And 1 mm thick samples had significantly higher value than 0.5 mm thick samples.