Effect of zirconia etching solution on the shear bond strength between zirconia and resin cement.

STATEMENT OF PROBLEM: The bond between resin cement and zirconia is essential to the long-term retention of a zirconia crown. However, it is unclear if the existing methods provide a long-term bond between resin cement and zirconia. PURPOSE: The purpose of this in vitro study was to evaluate the effects of a zirconia etching solution on the shear bond strength between zirconia and resin cement. MATERIAL AND METHODS: Sixty yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) disks (O8x5 mm) were divided into 4 groups (n=15). Each group was then treated with 1 of the following methods: airborne-particle abraded with 50-mum Al(2)O(3) (AA); etched with zirconia etching solution (ZES); airborne-particle abraded with 50-mum Al(2)O(3) and then etched with ZES (AA-ZES); etched with ZES and then airborne-particle abraded with 50-mum Al(2)O(3) (ZES-AA). Sixty composite resin cylinders (O2.3x2.4 mm) were luted to the zirconia disks with a self-adhesive resin cement under constant load and then light-polymerized for 40 seconds. Specimens were stored in a 37 degrees C incubator in distilled water for 24 hours and then thermocycled for 1000 cycles between 5 degrees C and 55 degrees C. A universal testing machine with a crosshead speed of 0.5 mm/min was used to measure the shear force (N). The shear bond strength (MPa) was then calculated. One-way ANOVA was used to compare the mean shear bond strength among the groups (alpha=.05). The failure mode was evaluated by using light microscopy at x90 magnification and categorized as an adhesive, cohesive, or mixed failure. RESULTS: Mean +/-standard deviation shear bond strength for AA, ZES, AA-ZES, and ZES-AA groups were 9.9 +/-2.6, 8.9 +/-2.9, 9.6 +/-3.9, and 11.0 +/-2.3 MPa, respectively. There was no significant difference among the treatment groups (P>.05). CONCLUSIONS: A zirconia etching solution did not significantly improve the shear bond strength between zirconia and resin cement compared with airborne-particle abrasion with Al(2)O(3).