Evaluation of shear bond strength between direct composite and zirconia

Abstract

Zirconia do not respond well to surface treatments. Coating with nano-particles may be able to increase the bond strength of direct composite resin to zirconia. The aim of this study was to evaluate the effect of coating with silicated glass nano-particles on shear bond strength between direct composite resin and zirconia. Thirty-four zirconia discs(Cercon-Germany) were randomly divided into two groups according to surface treatment as follows: group SC(coated with silicated glass nano-particles) and group AS(as-sintered without coating). Surface was assessed with XRD and AFM to evaluate coating and surface roughness. Disks were primed with silane(Prosil- Brazil) and then direct composite(GC Gradia-Japan) was bonded onto the specimens using polyethylene molds and photopolymerized. One half of the specimens in each group were thermocycled. Shear bond strength was tested using a universal testing machine(Zwick-Germany). After that the surface of the specimen were assessed with SEM. For data analysis, One-way ANOVA and student t-test were performed(p=0.05). The mean bond strength in SC group (8.12آ±1.78MPa) was significantly higher than AS group (3.86آ±0.94MPa)(p=0.000). The effect of thermocycling on shear bond strength was not statistically significant in both groups. Considering the increased bond strength of direct composite to zirconia substrate after coating with silicated glass nano-particles, this method can be used to increase the bond strength and success rate of prosthetic treatments in clinic.