In Vitro Evaluation of Bond Strength between Zirconia Core and CAD/CAM-Produced Veneers

Purpose To evaluate the shear bond strength between various CAD/CAM veneer materials and the zirconia ceramic core. Materials and Methods Ninety square prism zirconia specimens (10 specimens per each group, n = 10) in dimensions of 10 x 5 x 5 mm were prepared. Eighty square prism veneering specimens (40 feldspathic ceramic {[}Cerec Bloc] and 40 lithium disilicate {[}IPS e.max CAD]) in dimensions of 3 x 3 x 1 mm were connected to zirconia specimens. Conventional layering was applied to the remaining zirconia specimens as control group (n = 10). CAD/CAM-produced veneers were connected to the zirconia specimens using fusion porcelain or resin cement. One of following treatments were applied to the cemented specimens: no surface treatment, HF etching of the veneering material, or HF acid etching of the veneer in combination with the application of a glaze layer to the zirconia surface. Following the veneering procedures, a shear bond strength test was performed at a speed of 1 mm/min using a universal testing machine. Univariate ANOVA (alpha = 0.05) was performed for statistical analyses of the obtained data. Results Statistically significant differences were not found among the materials (F = 0.176, p = 0.656), while statistically significant differences were found amongst the veneering procedures (F = 57.921, p < 0.001). Statistical differences were observed between the groups (F = 13.766, p < 0.001). The highest shear bond strength values were observed in IPS e.max CAD specimens connected to zirconia with low fusion porcelain (27.11 +/- 7.7 MPa), and the lowest values were observed in IPS e.max CAD specimens connected to zirconia with resin cement without surface treatment (9.82 +/- 2.8 MPa). The application of fusion porcelain with IPS e.max CAD (p = 0.967) and Cerec Blocs (p = 1.00) showed statistically similar results to those with conventional layering. Conclusions The application of fusion porcelain to bond zirconia and digitally produced veneering material can serve as an alternative veneering method to the conventional layering method by accelerating and facilitating clinical and laboratory stages