Fractographic characterization of fatigued zirconia dental implants tested in room air and saline solution

The identification of the fractographic signature of monotonic and fatigue loads in ceramic materials is far from being straightforward, as embodied in a subtle blend of cleavage (trans.) and intergranular fracture. As of today, most fractographic analyses are carried out at low/middle magnifications. In this research, we have systematically examined commercial zirconia dental implants that were fractured in the laboratory under monotonic overload and random spectrum fatigue, thus generating a bank of well controlled fractured reference specimens. The tests were carried out in both room air and in 0.9% saline solution. Our results show that it is difficult to distinguish static fracture in room air from saline solution. By contrast, spectrum fatigue in either air or saline solution, results in observable differences from dominantly trans. to a mixed trans.-intergranular fracture at the origin of the crack (first 60 μm, as an upper bound value). Further down the unstable propagation zone, an increased tendency for intergranular fracture is observed, which seems to be exacerbated by the saline solution when compared with room air. Overall, it is observed that static and fatigue fractures can be distinguished from one another. It is believed that this fractographic database will serve as a reference for future analyses of broken ceramic dental implants and identification of their fracture mechanism.