Statement of the problem: posterior quadrants of the oral cavity are subjected to high occlusal loads. Performance of occlusal veneers is affected by fabrication material and veneer thickness.

Objective: This study was conducted to assess the effect of veneer material and thickness on fracture resistance of CAD/CAM occlusal veneers.

Materials and Methods: Sixty human premolars were prepared for occlusal veneers manufactured from three CAD/CAM materials; IPS E-max (E.max), Vita Enamic (VE) and Lava Ultimate (LU). Veneers were manufactured in 1 mm and 0.5mm thicknesses. (n=10). After cementation, specimens were subjected to Fracture resistance test and failure mode analysis.

Results: Two-way ANOVA showed that both material and thickness had significant effect on the fracture resistance. Significant differences were present between the two thicknesses for VE and LU. For IPS E-max, no significant difference was present between the two thicknesses.

Conclusion: E.max showed the highest fracture resistance in both thicknesses followed by LU and the lowest was recorded with VE. Results of 1mm Veneers were significantly higher than 0.5 mm.