Durability of Resin Bonding to Lithium Disilicate and Zirconia Ceramic using a Self-etching Primer

Purpose: The purpose of this in vitro study was twofold: 1. To evaluate the surface conditioning effect of a self-etching ceramic primer on lithium disilicate and zirconia ceramics; (2) to study the bond durability provided by the self-etching ceramic primer after artificial aging compared with conventional ceramic conditioning methods. Materials and Methods: Lithium disilicate blocks (10 x 10 mm, 3.4 mm thick) and zirconia disks (8 mm diameter, 3.4 mm thick) were each divided into two groups. In group 1, the lithium disilicate disks (Li) were etched with hydrofluoric acid (HF), while zirconia (Zr) disks were treated with airborne-particle abrasion, both followed by application of a universal primer for restorative materials (MP; Monobond Plus, Ivoclar Vivadent). In group 2, Li disks were not etched with HF, while Zr disks were treated with airborne-particle abrasion, both followed by a self-etching primer (ME; Monobond Etch & Prime, Ivoclar Vivadent). Surface conditioning effects were evaluated using SEM. The specimens in both groups were bonded to a composite with a luting resin and divided into two subgroups. Subgroup 1 was stored in water (37 degrees C) for 3 days, and subgroup 2 was stored in water for 30 days before undergoing 7500 thermal cycles (5 degrees C to 55 degrees C). Results: The self-etching ceramic primer had a significant effect only on the lithium disilicate surface topography. The mean initial bond strength of ME-Zr was relatively low (24.4 MPa) in comparison with all other material combinations (MP-Li: 34.3 MPa; ME-Li: 33.5 MPa; MP-Zr: 31.1 MPa). After 30 days of water storage and thermocycling, the bond strength decreased significantly in all groups. Conclusion: The self-etching primer provided bond strengths to lithium disilicate ceramic comparable with those of the well-established bonding method using hydrofluoric acid etching and a primer containing silane. To zirconia ceramic, however, it provided statistically significantly lower bond strength than did the established bonding method.