In-vitro evaluation of shear bond strength of different veneering materials to CAD/CAM zirconia ceramics

Abstract

Introduction: Zirconia ceramics have been widely used as a framework material for all-ceramic restorations. The high crystalline content of zirconia renders the material quite opaque, requiring frameworks to be laminated with a veneering material for optimum color and translucency. Aim: The present study evaluated the core-veneer shear bond strength of zirconia-based restorations veneered by four different veneering techniques. Methods: Twenty rectangular shaped zirconia blocks (19×15×2mm) were cut from presintered yttria-stabilized zirconia CAD/CAM blocks with a low speed precision cutting saw using water irrigated diamond disk. Sectioned zirconia blocks were cleaned, dried, sintered then assigned to four groups in accordance with the veneering technique (n=5). Finished zirconia blocks were veneered by either fused lithium disilicate discs, bonded lithium disilicate discs, conventionally layered ceramic discs, or composite discs. Shear bond strength test was performed using a computerized universal testing machine. Results: Zirconia blocks veneered with fused lithium disilicate discs revealed the highest mean shear bond strength, while the lowest mean value was reported with the zirconia blocks veneered with composite discs. Statistical analysis revealed that differences among all groups showed statistical significance. Conclusion:Veneering technique and material significantly affected shear bond strength of zirconia-based restorations.