Evaluation of Shear Bond Strength and Biaxial Flexural Strength of Zirconia Cores Veneered Using CAD-on and Press-on Techniques

Abstract

Objectives: This in vitro study compared the shear bond strength and biaxial flexural strength of CAD/CAM-fabricated zirconia cores veneered using CAD-on and Press-on techniques and evaluated their modes of failure. Materials and Methods: Twenty zirconia core discs were fabricated from IPS e.max Zir CAD using CAD/CAM technology. Ten specimens were prepared for shear bond strength testing and ten for biaxial flexural strength testing, with five specimens allocated to each veneering technique per test. The CAD-on group was veneered using IPS e.max CAD, whereas the Press-on group was veneered using IPS e.max ZirPress. All specimens underwent thermocycling before testing. Failure modes were evaluated using scanning electron microscopy, and data were analyzed using SPSS software with the level of statistical significance set at p≤0.05. Results: The t-test analysis of the shear strength test showed a statistically significant difference (p < 0.05) for the CAD-on group. There were no statistically significant differences (p > 0.05) for the biaxial flexural strength test between the two groups. The CAD-on group showed adhesive/cohesive failure, while the Press-on group showed cohesive failure within the veneering ceramic. Conclusion: Within the limitations of this in vitro study, the veneering technique affected shear bond strength. The CAD-on technique showed significantly higher shear bond strength than the Press-on technique. Biaxial flexural strength did not differ significantly between the techniques.