The influence of rotating fatigue on the bond strength of zirconia-composite interfaces.

Objectives: To evaluate the effect of cyclic loading on the bond strength of resin composite to zirconia framework material.

Methods: Bar shaped zirconia/composite specimens (2 mm x 2 mm x 25 mm) were prepared using three different resin cements and placed in a four-point bending test setup. The flexure strength (F(s)) was calculated by placing the bars (n=10) fixed between the four supports (at 10 and 20 mm) with the interface centered between the inner rollers and subsequently loaded (1 mm/min crosshead speed) until fracture. Rotating fatigue resistance (RFR) was determined in a rotating bending cantilever test setup (104, 1.2 Hz) with the highest stress located at the interface (n=20). The RFR was determined by the staircase method and the mean RFR was calculated using logistic regression analysis.

Results: Resin cement composition had no significant influence on the bond strength value obtained by both F(s) (F=0.6, P> or =0.5) and RFR (F=1.1, P> or =0.3) tests. However, after rotating fatigue testing there was a significant reduction in bond strength between 46 and 50% of the three resin cements.

Conclusion: Zirconia resin bond strength is liable to deterioration under the influence of fatigue.