Adhesion Aspect of Incorporating Zirconate Coupling Agent in Resin Composites

Method: Various ratios (0.0 – 4.0wt.%) of zirconate coupling agent (NZ-33, Kendrich Petrochemical, USA) were incorporated in an experimental bis-GMA/MMA-based resin composites. Compressive strength of the experimental resin composite and shear bond strength (SBS) of resin-to-zirconia were evaluated by using universal testing machine. Specimens were stored in dry condition, water storage in 7 days and 14 days for performance evaluation. The data were analyzed statistcally by one-way ANOVA and Tukey post hoc test (α = 0.05).

Result: The compressive strength of zirconate incorporated resin composite increased significantly at 1.5% (p=0.036) and 3.0% (p=0.036) NZ-33. In dry condition, SBS of resin-to-zirconia bonding significantly increase at 1.5% (p=0.01) and 3.0% (p<0.001) NZ-33. However, water storage for 7 days and 14 days significantly decreased SBS of the resin-to-zirconia with no significant difference between groups (p>0.05) for all concentrations of zirconate. 

Conclusion: The hypothesis was partially accepted, at least in dry condition, zirconate coupling agent seems to enhance the resin-to-zirconia bonding. More studies are necessary to investigate the interactions between zirconate and zirconia surface so as to optimize the formulation.