In vitro evaluation of shear bond strengths of resin to densely-sintered high-purity zirconium-oxide ceramic after long-term storage and thermal cycling

Statement of problem. The few available studies on the resin bond to zirconium-oxidc ceramic recommend airborne-particle abrasion and modified resin luting agents containing adhesive monomers for superior and long-term durable bond strengths. It is unknown whether this regimen can also be successfully applied to the intaglio surface of a commercial zirconia-based all-ceramic system. Purpose. The purpose of this study was to evaluate and compare bond strengths of different bonding/silane coupling agents and resin luting agents to zirconia ceramic before and after artificial aging. Material and methods. Composite cylinders (2.9 mm x 3.0 mm) were bonded to airborne-particle-abraded intaglio surfaces of Procera. AllZirkon specimens (n=80) with either Panavia F (PAN) or Rely X ARC (REL) resin luting agents after pretreatment with Clearfil SE Bond/ Porcelain Bond Activator (Group SE). In another group, Rely X ARC was used with its bonding/silane coupling agent (Single Bond/Ceramic Primer, Group SB). PAN without any bonding/silane agent (Group NO) was the control. Subgroups of 10 specimens were stored in distilled water for either 3 or 180 days before shear bond strength was tested. One hundred eighty-day-old specimens were repeatedly thermal cycled for 12,000 cycles between 5 and 60degreesC with a 15-second dwell time. Data were analyzed with 1- and 2-way analysis of variance and the Tukey multiple comparisons test (alpha=.05). Failure modes were examined under original magnification x25. Results. After 3 days, SE-REL (25.15 +/- 3.48 MPa) and SE-PAN (20.14 +/- 2.59 MPa) groups had significantly superior mean shear bond strengths (P=.0007) compared with either NO-PAN (17.36 +/- 3.05 MPa) or SB-REL (16.90 +/- 7.22 MPa). SE-PAN, NO-PAN, and SB-REL groups were not significantly different. Artificial aging significantly reduced bond strengths. After 180-day storage, SE-PAN (16.85 +/- 3.72 MPa), and SE-REL (15.45 +/- 3.79 MPa) groups demonstrated significantly higher shear bond strengths than NO-PAN (9.45 +/- 5.06 MPa) or SB-RFL (1.08 +/- 1.85 MPa) groups. The modes of failure varied among 3-day groups but were 100% adhesive at the ceramic surfaces after artificial aging. Conclusion. Artificial aging significantly reduced bond strength. A bonding/silane coupling agent containing an adhesive phosphate monomer can achieve superior long-term shear bond strength to airborne-particle-abraded Procera AllZirkon restorations with either one of the 2 resin luting agents tested.