الفهرس 
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Abstract
Purpose : The study was aimed to evaluate the effect of different preparation designs (line angle preparation and middle contact preparation) and different surface treatments (selective infiltration etching and fusion sputtering) on translucency and surface topography of zirconia laminate veneers. Materials and Methods : A total of (28) zirconia laminate veneers were prepared with even (0.5 mm) thickness and A3 shade. The veneers were divided into two groups according to preparation design, group L : just beyond line angle preparation and group C : middle contact preparation then each group was divided into two sub groups according to surface treatment of internal surface of laminate veneers. group LS : Line angle preparation and received selective infiltration etching; group CS : Middle contact preparation and treated with selective infiltration etching; group LF : line angle preparation and received fusion sputtering; group CF: Middle contact preparation and received fusion sputtering. Translucency was measured with spectrophotometer and Translucency Parameter evaluated before and after the surface treatment. Surface roughness was measured with noncontact optical profilometer. Scanning electron microscope was used for examination of surface topography after surface treatment. One way ANOVA and (t) test were used for data analysis. Results : There was significant difference in translucency between different preparation designs (P = 0.001). There were also significant differences in translucency after surface treatment (P<0.001) .One way ANOVA revealed no significant difference in roughness of different types of surface treatments (P=0.5). Scanning electron microscope revealed Nano porous surface of selective infiltration etching and granular and micro rough surface of fusion sputtering surface treatment. Conclusions: Laminate veneers prepared with just beyond line angle preparation design were more translucent than these prepared with middle contact preparation design. selective infiltration etching caused the zirconia laminate veneers to be more opaque but the differences in translucency were still within the clinically acceptable limit of the translucency parameter. Fusion sputtering surface treatment makes the zirconia laminate veneers to be more opaque but the differences were below the detectability threshold of the human eye. The two types of surface treatment showed rougher surface topography.