الفهرس 
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Abstract
Aim of the study: Evaluate the effect of surface treatment and thickness of CAD/CAM fabricated lithium disilicate occlusal veneers Material and Methods: A total of 42 maxillary molars were prepared to receive CAD-CAM fabricated lithium disilicate occlusal veneer either with 0.5mm (n=21) or 1 mm thickness (n=21). Each main group was divided into 3 subgroups (n=7), according to surface treatment, hydrofluoric acid & Monobond N (HF), acidulated phosphate fluoride & Monobond N (APF) and Monobond Etch&Prime. Multilinik N adhesive resin cement was used for bonding according to the manufacturer instructions, (Ivoclar-Vivadent). One hour after bonding, specimens were stored in water bath for 75 days followed by cyclic loading fatigue for 240000 cycles to simulate clinical situation. Finally, specimens were fractured under compressive load in (N) using a universal testing machine. Two and one-way ANOVA and Post Hoc Tukey test were used for statistical analysis. Results: The means±SD (N) fracture load for each group were calculated. Monobond etch & prime 1mm thick showed the highest fracture load (1644.7±155.3) followed by HF & Monobond N with 1 mm thickness (1514.6±212.5). Meanwhile, APF & Monobond N 0.5 mm showed the lowest fracture load (962±249.6). Conclusion: 1-Monobond Etch &Prime could be used for conditioning lithium disilicate occlusal veneer to avoid the health hazards of HF acid in the dental office. 2-Fracture load of lithium disilicate occlusal veneer with 0.5 mm thickness was significantly lower than that of 1mm thickness regardless of surface treatment.