Effect of heat treatment of dental zirconia ceramic treated with three different primers on the bonding durability of resin cement

Establishing a durable bond with dental zirconia ceramic remains difficult. This study investigated the effect of heat treatment of primer-coated dental zirconia on the bonding durability of resin cement to the zirconia. Each of three types of primers (silane primer, acidic monomer-containing primer, and silane/acidic monomer containing two-component primer) was applied to sandblasted zirconia surfaces. For subsequent heat treatment, half were then put in a furnace for 60 min at 150 °C. All specimens were bonded with resin cement and aged using thermocycling (0, 5,000, and 20,000 cycles) prior to a shear test. The surface energy parameters of the zirconia were also calculated from the contact angle measurements based on the acid-base theory. The heat treatment enhanced the bonding durability of the zirconia pre-treated with the silane primer and the acidic monomer-containing one, the shear test and Weibull analysis results showed that the former performed better than the latter. In contrast, the two-component primer-coated zirconia showed poor bonding durability after the heat treatment. The bonding performance was related to the surface characteristics of the zirconia. Thus, we suggest that heat treatment of zirconia pretreated with silane primer effectively improves bonding durability with resin cement.