The current study evaluated the effects of various pretreatments and aging in water on the bond strength to hot isostatic pressed yttrium-oxide partially stabilized zirconia. Sixty zirconia ceramic specimens (Denzir) were randomly divided into three groups of 20. One group of specimens (n=10) was then bonded to each other using a resin composite cement (RelyX Unicem), the second group (n=10) was bonded with RelyX Unicem and a metal primer (Metal Primer II), while the third group (n=10) was bonded with RelyX Unicem and a ceramic primer (Ceramic Primer). The specimens were then subjected to shear force before and after sandblasting and before and after aging in water for 180 days. Before aging, no significant differences (p > 0.05) were seen within the different groups, either before or after sandblasting. Sandblasting and pretreatment with the metal (p < 0.01) or ceramic (p < 0.001) primers significantly improved the bond strength compared to that of the non-treated specimens. After aging, the bond strength of the sandblasted specimens with metal primer was significantly higher than that of the sand-blasted specimens with ceramic primer (p < 0.01) and the specimens with no primer (p < 0.001). For the specimens that were sandblasted and pretreated with the metal primer, the bond strength was not significantly affected after aging (p > 0.05), whereas, for those specimens with the ceramic primer (p < 0.001) and no primer (p < 0.05), the bond strength significantly decreased. Thus, air abrasion and pretreatment with a metal primer seems to be an appropriate method for improving bond strength.

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