An in vitro comparison of the influence of different surface treatment on shear bond strength between zirconia and enamel

PURPOSE: To compare the shear bond strength of zirconia to enamel using different surface treatments, in order to provide evidence for clinical practice. METHODS: Forty cut and fully sintered Lava frame zirconia blocks (2.7 mm × 2.7 mm × 5 mm) were randomly divided into 4 groups and subjected to 4 different surface treatments: no treatment (control), airborne-particle abrasion; airborne-particle abrasion and silane; airborne-particle abrasion and CoJet sand (silica coating with 30 μm silica-modified alumina particles) and silane. After surface treatment, the zirconia blocks were bonded to acid-etched enamel with self-adhesive resin cement (RelyX Unicem). Half of the specimens in each group were stored in 37 degrees centigrade distilled water for 24 h and the others were thermocycled (5 degrees centigrade and 55 degrees centigrade) for 5000 cycles. All specimens were subjected to shear bond strength (SBS) test. The data was analyzed with SPSS 20.0 software package for two-way ANOVA and t test. Failure mode was observed and analyzed by scanning electron microscope (SEM). RESULTS: Airborne-particle abrasion and CoJet Sand and silane group resulted in a significantly higher SBS than those in other groups (P<0.001), while no significant difference existed between the specimens which were submerged in 37 degrees centigrade water stored and thermocycled (P=0.595) within this group. No adhesive failures were observed by SEM in this group. CONCLUSIONS: The combination of tribo-chemical silica coating with silane coupling can improve the bond of zirconia when self-adhesive resin cement is used and it is recommended as a pre-treatment to increase zirconia retention.