Effect of Sandblasting ZirLiner on Bond Strength of Veneered-Zirconia Ceramics

Methods: Bilayered zirconia specimens were prepared from e.max^®ZirCAD framework materials and divided into 4 groups. Two veneering techniques were used in this study: layering technique (e.max^®Ceram) for group 1-2 and press-on technique (e.max^®ZirPress) for group 3-4.  ZirLiner was applied onto the surfaces of specimens in group 1 and 3 and fired according to the manufacturer’s instruction. Veneering of these specimens was performed according to the protocol of each group. The surfaces of group 2 and 4 were treated similarly to group 1 and 3, except that sandblasting with 50-μm aluminum oxide particles was performed on the fired liner material. The bilayered blocks were cut into microbars with 1mm x 1mm in cross-section (N=30/group). All specimens were loaded to fracture using a microtensile tester. The fracture surfaces were analyzed using a scanning electron microscope to identify the mode of failure. Independent t-test was used to determine significant differences of the mean microtensile bond strength (MTBS) between unblasted and blasted liner material within the layering and press-on groups at α=0.05.

Results: When the liner material was blasted, the mean MTBS of bilayered specimens in both layering group (14.5±2.7 MPa) and press-on group (15.5±5.0 MPa) were significantly lower than those of unblasted liner groups (16.5±3.5 MPa for layering and 19.8±6.1 MPa for press-on). Most of the fracture occurred in all groups initiated at the zirconia-veneer interface.

Conclusion: Blasting the zirconia liner material could decrease the bond strength between zirconia to layered and pressed veneers. The interfacial failure was predominantly observed in all groups.