Effect of chemical etching solutions versus air abrasion on the adhesion of self-adhesive resin cement to IPS e.max ZirCAD with and without aging

OBJECTIVES This study evaluated the adhesion of self-adhesive resin cement to zirconia after various surface conditioning methods in non-aged and aged conditions. METHODS Zirconia (IPS e.max ZirCAD, Ivoclar Vivadent) and resin composite blocks were obtained and randomly divided into four groups according to one of the following surface conditioning methods: C: No surface treatment (Control); AS: Air abrasion (50 µm Al2O3) at low pressure (0.2 MPa) plus silane (Monobond Plus, Ivoclar Vivadent); MC: Methylene chloride for 60 min; CE: Chemical etching solution at 100°C for 60 min. Surface roughness (Ra) measurements were performed on the control and conditioned zirconia specimens using a profilometer. Each conditioned zirconia block was bonded to its corresponding resin composite block using self-adhesive resin cement (RelyX Unicem Aplicap, 3M ESPE) under a load of 300 g. Half of the groups were tested without aging; the other half were tested after x6000 thermocycling. Sticks were obtained from bonded specimens and subjected to microtensile bond strength (MTBS) testing in a universal testing machine (0.5 mm/min). Failure types were classified after debonding. Data (MPa) were analyzed using two-way ANOVA and Tukey's tests (α = 0.05). RESULTS The highest mean Ra value was obtained in Group CE (0.52 µm), and the lowest in Group C (0.25 µm). Significantly lower MTBS test results were obtained in Group C, both in non-aged (17.4 ± 1.1 MPa) and aged (5.11 ± 0.5 MPa) conditions than in the other groups (34.6 ± 1.5 to 51.2 ± 1.1 MPa; 28.0 ± 0.9 to 49.5 ± 1.0 MPa in non-aged and aged conditions, respectively) (P < 0.05). Group CE presented the highest MTBS test results in both non-aged and aged conditions (51.2 ± 1.1 MPa and 49.5 ± 1 MPa, respectively) (P < 0.05). Failure types were predominantly adhesive in all groups before and after aging. After aging, less adhesive and more mixed and cohesive failures in cement were observed in Groups AS and CE than in the other groups. CONCLUSION Chemical etching of zirconia may have potential use as a substitute for air abrasion as a surface conditioning method for zirconia