Three-Point Bending Tests of Zirconia Core/Veneer Ceramics for Dental Restorations

. The mechanical strength and the surface hardness of commercially available yttrium-doped zirconia were investigated. Furthermore, a comparative study of eight different ceramic veneers, to be used for the production of two-layered all-ceramic restorative systems, was carried out. Materials and Methods . Four types of zirconia specimens were analyzed, according to a standard ISO procedure (ISO 6872). Besides, two-layered zirconia-veneer specimens were prepared for three-point bending tests. Results . A strong effect of the surface roughness on the mechanical strength of zirconia specimens was observed. Finally, a comparative study of eight commercially available veneering ceramics shows different modes of failure between the selected veneers. Conclusion . The results indicate that close attention should be paid to the preparation of zirconia-based crowns and bridges by CAD/CAM process, because surface roughness has an important effect on the mechanical strength of the material. Finally, the results of the mechanical tests on two-layered specimens represent an important support to the choice of the veneering ceramic.