Effect of Light-polymerization of Universal Adhesive on Zirconia Bond

Objectives: MDP-containing primers and adhesives are known to be able to improve resin-zirconia bond strength. The aim of this study was to evaluate the effect of light-curing of an MDP-containing universal adhesive on resin-zirconia bond strength.
Methods: Zirconia specimens (LAVA Zirconia, 3M) were air-abraded (3 bar) with alumina sand (50µm) for 20 sec each, rinsed with water, and dried. Zirconia specimens were treated with a universal adhesive (All-Bond Universal, Bisco) or a control zirconia primer (Z-Prime Plus, Bisco). The adhesive was air dried, and then was either light-polymerized (10 sec at 500mw/cm²) or not polymerized. Shear bond strength was tested using the notched-edge shear bond strength test method (ISO 29022:2013). Resin cement (Duolink Universal, Bisco) was placed on the zirconia surface and polymerized (either light-polymerized for 40sec at 500mw/cm², or self-polymerized for 15 min/37 °C). The specimens were then stored in water at 37°C for 24 hours and tested by universal testing machine (Instron, crosshead-speed 1mm/min). The data were analyzed statistically by one-way ANOVA and Student-t Test.
Results: Mean shear bond strengths (standard deviation, n=5) of resin cements on zirconia are shown in Table 1 . When resin cement was self-polymerized, the universal adhesive without light-polymerization (prior to cementation) had the significantly lower bond strength than the control. When resin cement was light-polymerized, the universal adhesive without light-polymerization (prior to cementation) had the same bond strength as the control group.
Conclusions: The light-polymerization of universal adhesive prior to cementation has the significant effect on resin-zirconia bond strength only when resin cement is self-polymerized.