Aim: the objective of our study is to investigate the effect of two preparation designs on Emax occlusal veneers fracture resistance.
Methodology: Fourteen epoxy dies were duplicated from two Typodont acrylic teeth. Two preparation designs were used. Group (1): represented butt margin occlusal preparation. Group (2): represented occlusal preparation with chamfer finish line. Seven dies duplicated from each group. Occlusal veneer restorations were constructed from CAD/CAM system. Each occlusal veneer cemented to the crossponding die. Universal testing machine was used to measure fracture resistance values. Load to fracture for all samples was recorded in Newton.

Results: Butt joint samples (1649.84±349.53) had significantly higher fracture resistance value than chamfer samples (1273.63±232.58) (p=0.039).
Conclusion: Within the limitations of this in-vitro investigation, it might be concluded that butt margin design provides better fracture resistance values that chamfer finish line design using lithium disilicate occlusal veneers.

Keywords: different preparation design; occlusal veneer; lithium disilicate; fracture resistance.