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Long-term resin bond strength to zirconia ceramic.

PURPOSE
The aim of this in vitro study was to evaluate the long-term bond strength of adhesive bonding systems to yttrium-oxide-partially-stabilized zirconia ceramic (YPSZ).


MATERIALS AND METHODS
Plexiglas tubes filled with resin composite were bonded to industrially manufactured zirconia ceramic disks (96% ZrO2 stabilized by 4% Y2O3). After air abrading the ceramic and ultrasonic cleansing, groups of 16 samples were bonded in an alignment apparatus using 7 different bonding methods. Subgroups of 8 bonded samples were tested for tensile strength following storage in distilled water at 37 degrees C either for 3 days or 2 years. In addition, the 2-year samples were thermocycled 37,500 times. The statistical analyses were conducted with the Kruskal-Wallis test followed by multiple pair-wise comparison of the groups using the Wilcoxon rank sum test.


RESULTS
A moderate to relatively high initial bond strength was achieved by air abrasion alone, the additional use of a silane, or acrylizing the YPSZ surface in combination with a conventional bis-GMA resin composite. However, these methods failed spontaneously over storage time. The use of the bis-GMA resin composite after tribochemical silica coating of YPSZ and the use of a polyacid-modified resin composite after air abrasion of YPSZ resulted in a high initial bond strength which decreased significantly over storage time. A durable resin bond strength to YPSZ was achieved only after air abrasion of YPSZ and using one of two resin composites containing a special phosphate monomer.


CONCLUSION
A durable bond strength to YPSZ was achieved only by using resin composites containing a special adhesive monomer.