Random spectrum fatigue of zirconia oral implants in air and saline solution

Zirconia oral implants are increasingly considered as an alternative to metallic (titanium) ones, mostly for their aesthetic properties and their metal free composition that enables soft tissue integration. We report a systematic comparison of the fatigue performance of oral implants of identical geometry, made of partially stabilized zirconia (Y-TZP) and titanium as a reference group, using random spectrum fatigue testing in both air and saline solution. The spectrum data clearly points unequivocally to the operation of a fatigue (damage accumulation) failure mechanism in the zirconia implants. Saline solution reduces the quasi-static fracture strength. It also causes a marked degradation of their spectrum fatigue longevity, but it does not affect their spectrum fatigue fracture strength. Given that the quasi-static fracture strength of the tested implants is smaller in saline solution than in air, the results suggest that the maximum admissible design loads for spectrum loaded zirconia oral implants are of the order of 0.8 times their wet (saline) quasi-static fracture strength.