الفهرس 
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Abstract
The aim of this in vitro study was to evaluate the color and fracture load of laminate veneers on tooth preparation located entirely on dentin except their margins that are located on enamel and prepared with two incisal design and cemented using conventional and immediate dentin bonding agent application methods .48 Ceramic veneers were divided in two groups, prepared with two incisal designs, divided into 2 sub-groups fabricated from two materials (e,max, Tzr) and each half of the sub group were bonded by conventional method (dentin adhesive applied to dentin when proceeding to luting the veneer) and the other half of each sub-group bonded b used (luting composite reuniversal bond) and same sin (relyx ultimate). Color and translucency measured by vita easy shade.
Fracture loads were recorded with a mechanical testing machine, the data were analyzed for both ceramic veneers and natural teeth using three-way ANOVA and Tukey comparison test, the results showed significant difference in the translucency and contrast ratio between the two ceramic materials, and no significant difference on color change, fracture load was significant according type of ceramic, while non-significant according to different incisal design and method of cementation. On examination of the mode of failure, most of the teeth in all groups showed similar mode of failure which was root fracture.
CONCLUSION
With the limitation of this study, the following conclusions were drawn:
1-Both ceramic materials; lithiumdisilicate and translucent zirconia showed clinically acceptable color reproduction.
2-Regarding translucency; Lithiumdisilicate (e.max) was more translucent and less opaque than translucent zirconia. Also, veneers prepared using Butt-joint incisal preparation revealed higher translucency than those prepared using overlap design.
3-Strength of veneers was affected by ceramic material; where translucent zirconia laminate veneers showed significant high fracture resistance in comparison to e.max.
4-The new method of cementation; immediate dentin bonding did not negatively affect the color reproduction of laminate veneers; or their fracture resistance.
Clinical recommendations:
1-The immediate dentin bonding application provide slghter better veneer fracture resistance; further studies are needed to evaluate its advantage clinically or after cyclic and thermal loading.
2-Translucent zirconia showed acceptable color reproduction but lower translucency, which is in a way, considered as alternative treatment option to aggressive full crown reduction that done to mask the sever discoloration of anterior teeth.