Effects of silica-coating and a zirconate coupling agent on shear bond strength of flowable resin–zirconia bonding

The aim of this in vitro study was to evaluate the effect of tribochemical silica-coating and a zirconate coupling agent application on bonding between a resin composite and zirconia. Firstly, it was hypothesized that the zirconate coupling agent modified surface would promote higher and more stable shear bond strength than a surface treated with tribochemical coating only. Secondly, the modified surface would retain its bond strength after artificial aging. The shear bond strength between a resin composite bonded to surface treated zirconia was measured. Hydrolytic stability of this bond was verified after water storage while the interface chemistry was evaluated using energy dispersive x-ray analysis. Surface treatment showed significantly greater shear bond strength compared with no treatment before artificial aging while specific surface treatments showed higher shear bond strength compared with no treatment after artificial aging. The predominant mode of failure after shear bond testing was adhesive. Energy dispersive x-ray analysis at the surface revealed elemental C_1s, O_1s, Si_1s and Zr_2p. As a result, tribochemical silica-coating followed by application of a zirconate coupling agent was suggested to create a successful a resin-to-zirconia bonding. Further investigation is required as reference for clinical approach in the cementation of zirconia restorations.