Aim:The aim of this investigation is to evaluate fracture resistance of veneer materials which prepared in two different methods with two different cement thicknesses by CAD/CAM. Material and Method: Forty maxillary incisors in similar sizes were used in this study. Each tooth restored with laminate after preparation. Teeth were divided into 4 groups according to preparation techniques; traditional preparation and incisal-overlap preparation, and cement thicknesses; 50 µm and 200 µm. Laminates were milled with Cerec CAD/CAM device (Sirona) from feldspathic ceramic blocks and applied using self etch resin cement. Fracture tests were performed applying load with constant speed using a universal testing machine (Instron 3344) to teeth embedded into cylindrical self-cure acrylic resin blocks with 125-degree angle. Fracture load values of laminates were recorded. Results were evaluated statistically with one-way ANOVA and Tukey post hoc tests using SPSS 20 software. Results: In terms of cement thickness, 50 µm showed statistically higher fracture strength values than 200 µm. In terms of preparation technique, traditional technique showed higher fracture strength than incisal-overlap technique. The highest mean fracture strength was recorded for traditional preparation with 50 µm (643 N), while the lowest was for incisal-overlap preparation with 200 µm (359.8 N).
Conclusion:Traditional preparation technique increases fracture strength of laminate veneers. Fracture strength increases as cement thickness reduced.