Long-term Bonding to Modified Zirconia Surface

Objectives: The purpose of this study is to evaluate the shear bond strength (SBS) to a new zirconia surface (NobelBond, Nobel Biocare) using different luting techniques after artificial aging.

Methods: Composite cylinders were bonded to zirconia ceramics with a new surface (NB) and a machined surface (MaZ). Three different adhesive luting cements (Panavia F2.0, Kuraray; RelyX ARC and RelyX Unicem, 3M ESPE), with and without air–abrasion (AA; 50µm, 110µm Al₂O₃), before and after artificial aging (3/90 d water storage, 20,000 cycles thermocycling; TC) were tested for shear bond strength. Test combinations for NB: (1) Panavia, no AA (NBP); (2) ARC, no AA (NBARC); (3) Unicem, no AA, (NBUNI); (4) Panavia, 50µm AA (NBS50P); (5) Panavia, 110µm AA (NBS110P); (6) ARC, 50µm AA (NBS50ARC); (7) Unicem, 50µm AA (NBS50UNI). Test combinations for MaZ: (8) Panavia, no AA (MaZP); (9) Panavia, 50µm AA (MaZS50P); (10) Panavia, 110µm AA (MaZS110P). Statistical analysis was performed using Kruskal-Wallis and Mann-Whitney tests with α=0.001.

Results: The mean SBS ranged from 10.1 to 20.0 MPa after three days and from 0.033 to 14.8 MPa after aging. TC decreased bond strength values significantly, except for NBARC. AA of machined surface increased bond strength, regardless of Al₂O₃ particle size, in comparison to non-AA machined surface. AA of the new surface decreased bonding significantly regardless of cement used and Al₂O₃ particle size. Bonding to the new zirconia surface without AA was significantly higher than to machined surface with AA.

Conclusion: Bond strength to the modified zirconia surface is higher than to air-abraded machined zirconia. This fact could lead to wider applications for zirconia ceramic restorations, especially for those which rely heavily on bonding. Air-abrasion of the modified zirconia surface is absolutely not recommended.