Effects of different surface treatments on the bond strength of resin cement to zirconia-based CAD-CAM materials

Purpose: To assess the effect of surface treatments on the shear bond strength of resin cement to zirconia-based CAD-CAM materials. Materials and Methods: Four CAD-CAM blocks (Vita YZ HT, Sirona inCoris TZI, IPS e.max ZirCAD, Vita Suprinity) were divided into six groups according to the surface treatment received: no treatment (control), 9.5% HF acid etching, sandblasting with 50 μm Al2O3, sandblasting with 50 μm Al2O3 + Er:YAG laser irradiation, Er:YAG laser irradiation and Cojet. Composite resin cylinders were bonded to blocks with Theracem self-adhesive resin cement. All specimens were thermocycled (5000 cycles at 5oC/55oC). Shear bond test was performed using universal testing machine. Failure modes were examined using SEM. Data were analyzed statistically by using two-way ANOVA and post hoc Tukey's multiple comparison test. Results: The bond strength was significantly affected by the surface treatment and the type of CAD-CAM blocks (p<0,001). The highest shear bond strength for Vita YZ HT was reported in group Cojet (19,43±0,76 MPa). Tribochemical silica coating showed significantly better results rather than sandblasting in monolithic and Y-TZP zirconia groups. Monolithic zirconia (Vita YZ HT, Sirona inCoris TZI) had higher bond strength values than Y-TZP zirconia (IPS e.max ZirCAD) in sandblasting and Cojet groups. Conclusion: Sandblasting and Cojet enhanced the bond strength of Vita YZ HT, Sirona inCoris TZI and IPS e.max ZirCAD. Also, HF acid etching established strong bond between Vita Suprinity and resin cement. Key Words: bond strength, CAD-CAM, monolithic zirconia, self-adhesive resin cement, surface treatment