Effect of Different Surface Treatments on Shear Bond Strength of Zirconia Based Ceramic and Veneering Porcelain

Aims of the study: Aim of this in-vitro study was to evaluate the shear bond strength of veneering ceramic to Y-TZP infrastructures after different surface conditioning techniques.
Material and Methods: 43 Y-TZP blocks were cut from pre-sintered zirconia disks. Specimens were divided into 4 groups (n=10 in each group) according to the surface conditioning technique used (Diamond grinding, Al₂O₃ air-borne particle abrasion, Silica containing glass-ceramic liner application and Nd:YAG Laser irradiation). 3 of the specimens were used for optimization of Nd:YAG Laser surface conditioning. Lithium disilicate veneer layers were pressed on each Y-TZP specimen. Shear bond strength was tested using a universal testing machine. All specimens of each group were examined for failure mode analysis using an optical microscope. Scanning Electron Microscope (SEM) was used to detect the roughness produced over Y-TZP block surface after different surface conditioning techniques and X-ray diffraction test (XRD) for phase transformation determination. Analysis of the data was done using one-way Analysis of variance (ANOVA) test.
Results: Silica-containing glass ceramic liner application and Nd:YAG Laser irradiation resulted in a significantly higher SBS (p≤0.05) than did Diamond grinding and Al₂O₃ air-borne particle abrasion. Diamond grinding and Al₂O₃ air-borne particle abrasion groups showed more adhesive failure than mixed failure in contrast to Silica containing glass ceramic and Nd:YAG Laser irradiation groups which showed more mixed failure than adhesive failure. SEM revealed great surface irregularities at the Nd:YAG laser irradiated group. XRD test revealed that Al₂O₃ was the only conditioning technique which resulted in monoclinic phase transformation in contrast to the other conditioning techniques used.
Conclusion: Silica containing glass ceramic liner application and Nd:YAG Laser surface conditioning could be considered valuable means of shear bond strength improvement between Y-TZP core and lithium disilicate veneering layer.