الفهرس 
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Abstract
Dissertation abstract : Statement of the problem: Occlusal veneer restorations represent a conservative alternative to traditional crowns in treatment of severely worn dentition. However, the data regarding the mechanical performance of occlusal veneer designs and materials are still controversial. Aim of study: Evaluation of the effect of using two different designs and materials on fracture resistance of occlusal veneer restorations. Materials and Methods: Thirty-two freshly extracted premolars were randomly allocated into two main groups (n=16) according to preparation design: group B: butt joint preparation and group M: Modified occlusal veneer preparation with circumferential finish line. Each main group was further subdivided into two subgroups (n=8) according to type of restorative material used for occlusal veneer construction: Lithium disilicate (IPS e.max CAD) and hybrid ceramic (Vita Enamic). Occlusal veneer restorations were constructed by Imes Icore CAD/CAM system and then cemented to their corresponding teeth using Calibra Ceram dual cured adhesive resin cement. Fracture resistance test was done using universal testing machine (Model 3345, Instron, USA). The load needed for fracture of each specimen was recorded automatically in Newtons(N) using a special software. Data were collected, tabulated and statistically analyzed. Results : Student’s t-test results revealed that there was no statistically significant difference regarding the two variables (preparation design and material type). Also, Two-way ANOVA test results showed that there was no statistically significant difference regarding the interaction between the two variables in this study (P=0.309). Conclusions: There was no effect of the preparation designs and the material types on fracture resistance of occlusal veneers. The fracture resistance for all study groups exceeded the reported range of human masticatory forces.