Bond strength evaluation of lithium disilicate and zirconium oxide-based substructures using two different veneering techniques

The aim of this study was to evaluate the shear bond strength (SBS) between a substructure and veneer using two different veneering techniques: (i) liner and (ii) liner + dentine powder sprinkling). The first technique simply uses liners that act as bonding layers between the substructure and veneering material; the second technique consists of liners on which there has been dentine powder sprinkled. The SBS tests were performed using a universal testing machine (UTM) and the modes of failure were identified for various samples. The results revealed that the mean SBS of the zirconium oxide (ZrO₂) of the sprinkling group was significantly higher (p < 0.001) than that of the ZrO₂ without sprinkling group (27.2 ± 3.95 MPa and 22 ± 3.30 MPa, respectively). Likewise, the mean SBS of the lithium disilicate (LDS) with sprinkling group was significantly higher (p < 0.001) than that of the LDS without sprinkling group (33.1 ± 3.24 MPa and 19.9 ± 3.82 MPa, respectively). The ZrO₂ samples without sprinkling exhibited a combination of adhesive failure and cohesive failure in the veneer itself, whereas with sprinkling exhibited mostly adhesive failure, not cohesive failure. The LDS samples without sprinkling exhibited all types of failures with predominantly cohesive failure of the core; however, the LDS with sprinkling exhibited commonly the cohesive failure of the core.