Bonding to zirconia ceramic: adhesion methods and their durability.

Objectives: Resin bonding to yttrium-oxide--partially-stabilized zirconia ceramic (YPSZ) cannot be established by standard methods that are utilized for conventional silica-based dental ceramics. It was our hypothesis that adhesive bonding methods suitable for glass-infiltrated alumina ceramic can also be used to bond successfully to YPSZ. To prove this hypothesis, bonding methods suitable for alumina ceramic were used on YPSZ and the tensile bond strength and their durability evaluated in vitro.

Methods: Plexiglass tubes filled with resin composite were bonded to YPSZ discs following various adhesion protocols. Groups of 16 samples were bonded using seven different bonding methods. Subgroups of eight bonded samples were tested for tensile strength following storage in distilled water (37 degrees C) for either 3 or 150 days. In addition, the 150 day samples were thermal cycled 37,500 times as a method to stress the bond interface. The statistical analysis was made with the Kruskal-Wallis test followed by multiple pair-wise comparisons of the groups using the Wilcoxon rank sum test.

Results: Sandblasting alone, the additional use of a silane or acrylizing resulted in an initial bond of a conventional BisGMA resin composite to YPSZ which failed spontaneously over storage time. The use of the BisGMA resin composite after tribochemical silica coating of YPSZ and the use of a polyacid-modified resin composite after sandblasting of YPSZ resulted in an initial bond which decreased significantly over storage time (p = 0.05). A durable resin bond to YPSZ was achieved only after sandblasting the ceramic and using one of two resin composites containing a special phosphate monomer.

Significance: A durable bond to YPSZ was achieved only by using resin composites with a special adhesive monomer. Therefore, the hypothesis of the study was partially proved as a durable bond to alumina ceramic is achieved with the same resin composites. However, it was partially disproved as tribochemical silica coating of YPSZ did not result in a durable resin bond as it does on glass-infiltrated alumina ceramic.