Influence of autoclave sterilization on bond strength between zirconia frameworks and Ti-base abutments using different resin cements.

STATEMENT OF PROBLEM: Zirconia frameworks luted on titanium bases have been increasingly used for implant-supported prostheses. A reliable bond strength between the framework and the base is a key factor for clinical success. Autoclaving of the abutments before clinical use has been strongly suggested since abutments have been classified as class II medical devices. However, comprehensive knowledge on the susceptibility of the composite resin luting agents' adhesion to autoclave sterilization is lacking. PURPOSE: The purpose of this in vitro study was to assess the bond strength between zirconia frameworks and titanium bases using different composite resin luting agents with and without thermocycling and autoclaving. MATERIAL AND METHODS: A total of 200 titanium implants were copy milled and 200 zirconia frameworks (Cercon) were generated by computer-aided design and computer-aided manufacturing (CAD-CAM). They were adhesively luted using Multilink Hybrid Abutment (MHA), Panavia F2.0 (PF2), Panavia V5 (PV5), RelyX Ultimate (RXU), or Panavia SA Cement Plus (PSA). Autoclaving (134 degrees C, 0.21 MPa, 5.5 minutes) and thermocycling (3000 cycles, 5 degrees C and 55 degrees C) were performed. The push out bond strength was tested at a crosshead speed of 1 mm/min. Statistical analysis was performed by using the Mann-Whitney U test (alpha=.05) and the family-wise error rate method. RESULTS: Median bond strength values (interquartile range) after autoclaving and thermocycling ranged between 33.7 (26.7-41.8) MPa for MHA and 7.6 (7.3-8.5) MPa for PF2. MHA showed significantly higher values than all other composite resin luting agents regardless of thermocycling or autoclaving. PV5 showed equal or higher bond strength values than PSA, RXU, and PF2. Autoclaving had no significant influence on MHA or PV5, but had a negative effect on PSA and RXU. The family-wise error rate method showed that both the composite resin luting agent and autoclave sterilization had an overall influence on bond strength. CONCLUSIONS: MHA and PV5 were not significantly influenced by autoclaving and showed acceptable bond strength values. Because MHA showed significantly higher bond strength than all other materials and is released for autoclaving by the manufacturer, it is the first choice for extraoral bonding of zirconia frameworks to titanium bases. Manufacturers who state the indication of extraoral cementation of frameworks on titanium bases should also indicate whether their composite luting material is affected by autoclaving.