Effect of zirconia surface treatments on the shear bond strength of veneering ceramic.

STATEMENT OF PROBLEM Various surface treatments of zirconia have been recommended for veneering ceramics. However, it has not been determined which of these treatments produces the highest bond strength. PURPOSE This study examined the effects of various surface treatments on the shear bond strength of zirconia and veneering ceramic. MATERIAL AND METHODS Square-shaped (5 × 10 × 10 mm) zirconia (Everest) specimens were divided into 4 groups (n=8) according to surface treatment as follows: group C, grinding with #320 diamond disc (control); group A, airborne-particle abrasion with 110 μm Al(2)O(3); group L, application of liner (Cerabien); and group AL, airborne-particle abrasion with 110 μm Al(2)O(3) and application of liner. A cylinder of veneering ceramic (2.4 mm in diameter and 3 mm in height) (Cerabien) was fabricated and fired on the zirconia specimens. The shear bond strength was tested using a universal testing machine. The data were analyzed statistically using a 1-way ANOVA and Tukey's multiple comparisons test (α=.05). The interface and fractured surfaces of the specimens were also evaluated by field emission scanning electron microscopy (FE-SEM). RESULTS The mean and SD values for the shear bond strength of the groups ranged from 27.87 ± 3.59 MPa (for group L) to 36.63 ± 2.96 MPa (for group A). The 1-way ANOVA revealed a significant difference between groups (P=.001). The airborne-particle abrasion group showed significantly higher bond strength than liner applied groups (L, AL) (P<.05). The SEM revealed that liner-applied groups (L, AL) showed primarily adhesive failure. Complete delamination and microspaces were also observed in the liner-applied groups. CONCLUSIONS The mean in vitro shear bond strength of veneering ceramic on zirconia treated with airborne-particle abrasion was significantly higher than that subjected to liner-applied treatments.