Durable bonding to mechanically and/or chemically pre-treated dental zirconia

Abstract

Objectives: To evaluate the effect of mechanical and chemical surface pre-treatment on the bond durability of two composite cements to dental zirconia.

Methods: Fully sintered IPS e.max ZirCAD (Ivoclar-Vivadent) blocks were either subjected to tribochemical silica sandblasting (CoJet, 3M ESPE) or not mechanically pre-treated. Next, the zirconia samples were either additionally pre-treated using one of two silane/MDP-combined ceramic primers (Clearfil Ceramic Primer, Kuraray; Monobond Plus, Ivoclar-Vivadent), or not further chemically pre-treated. Finally, two identically pre-treated zirconia blocks were bonded together using either a conventional BisGMA-based (Clearfil Esthetic Cement, Kuraray) or an MDP-based (Panavia F2.0, Kuraray) 'self-etch' dual-cure composite cement. The specimens were trimmed at the interface to a cylindrical hour-glass shape and stored for 7 days in distilled water (37°C), after which they were randomly exposed to one of three ageing protocols: (1) immersed in 37°C water for 10 days (10d); (2) subjected to 10,000 thermo-cycles (TC); or (3) immersed in 37°C water for 6 months (6m). After storage, the micro-tensile bond strength (μTBS) was determined in MPa (n=15-21/group). Fractographic analysis was performed using SEM.

Results: Weibull analysis revealed the highest Weibull scale and shape parameters for the 'CoJet/Clearfil Ceramic Primer/Panavia F2.0/10d' combination. While the BisGMA-based composite cement Clearfil Esthetic Cement (Kuraray) bonded equally well to zirconia using either tribochemical silica sandblasting (CoJet, 3M ESPE) or not, sandblasting appeared indispensable for the MDP-based and more hydrophilic composite cement Panavia F2.0 (Kuraray).

Conclusions: Combined mechanical and chemical pre-treatment can best be recommended to durably bond to zirconia.

Clinical significance: As a standard procedure to durable bond zirconia to tooth tissue, both mechanical (tribochemical silica coating) and chemical (silane/MDP-combined ceramic primers) is clinically highly recommended.