Evaluation of shear bond strength of a novel nano-zirconia and veneering ceramics

The core-veneer bond strength of zirconia is believed to be influenced by various factors, including zirconia types. To date, studies on bond strength between veneering porcelain and zirconia core fabricated by slip-cast technique are few. The aim of this study was to investigate and compare the shear bond strength (SBS) of three core materials with two veneering porcelains. Sixty cylindrical discs (11 mm in diameter and 3 mm in thickness) were fabricated and divided into Experimental zirconia (Zir), Cercon® (Cer) and metal (Met) core group. Ceramkiss® (Ck) and InLine® (IL) veneering porcelains were fired to each core at a thickness of 3 mm. Before veneering, all core materials were sandblasted with 100 µm Al2O3, and a layer of opaque liner was applied in the first firing. The bonded samples were subjected to shear bond test following storage in distilled water (37 °C) for 24 h. Scanning electron micrograph (SEM) was used to identify the mode of bonding failure. The results were analyzed with One-way ANOVA and Independent t-test with Tukey post-hoc test. Interaction effect analysis was performed using two-way ANOVA. Met-IL showed the highest mean SBS value (28.9±3.8 MPa), whereas Cer-IL group obtained the lowest value (2.8±0.7 MPa). The mean SBS values of Zir-Ck and Zir-IL were found to be 23.1±2.4 MPa and 4.1±0.9 MPa respectively. When veneered with the same veneering porcelain, both experimental zirconia and Cercon® were comparable, whereas significant differences were observed between metal and zirconia groups. All core materials exhibited significant differences in terms of shear bond strength when veneered with different veneering ceramics. Cohesive failure occurred in the high SBS group, whereas mixed cohesive-adhesive failures were seen in the other groups. The core-veneer SBS is material dependent. The types of core and veneering materials significantly affected the SBS. Slip casted experimental zirconia and commercial zirconia demonstrated similar bonding capabilities with the existing veneering porcelain designed for zirconia core.