Fracture Resistance of CAD/CAM Lithium Disilicate Versus Reinforced Composite Occlusal Veneers with Two Preparation Designs (An in vitro study)

This study was conducted to assess the effect of preparation design and material type on the fracture resistance and failure mode of occlusal veneers after thermocycling.A total number of twenty extracted lower premolar were randomly divided into two main groups according to occlusal veneer preparation design; either with or without a circumferential chamfer finish line. Each group was subsequently divided into two subgroups according to the materials used; Group (R): Rosetta SM Lithium disilicate ceramics blocks and Group (B): Brilliant Crios reinforced composite blocks. Occlusal veneers were fabricated and cemented following the manufacturer instructions after surface treatment of both occlusal veneers and natural teeth. All the samples were thermally aged for 3000 cycles then subjected to a compressive load through fracture then was examined to identify the failure mode. Data were statistically analysed via two-way ANOVA test (p<0.05).It was found that Reinforced composite block exhibited superior fracture resistance and advantageous failure characteristics compared to lithium disilicate ceramic. The planar preparation with a circumferential chamfer finish line yields superior outcomes compared to the group without a chamfer finish line.