| Abstract [eng] |
Yttria stabilized zirconia (Y-TZP) has good mechanical and biological properties, which makes Y-TZP an attractive material for medical device manufacturing. Nevertheless, material is prone to degradation in a humid environment (as well as in human body), during which Y-TZP becomes unstable, mechanical properties of the material reduce. During hydrothermal degradation, due to water-induced stresses, the metastable tetragonal phase transforms to the monoclinic, particles can be released from the implant surface and cause infection. The mechanism and control of hydrothermal degradation until these days are not well known and the production of Y-TZP medical devices is limited. The surfaces of implants must be roughened or smoothened in order to achieve the best possible integration of bones and soft tissues, and must therefore be machined. Like hydrothermal degradation, mechanical processing of Y-TZP causes transformation of the tetragonal phase to monoclinic (this process is known as transformation toughening), making such surfaces particularly sensitive to the effects of degradation in humid environment. In this work, the sensitivity of Y-TZP machined using different methods (sandblasting, polishing) to hydrothermal degradation was investigated. It was found that in order to minimize Y-TZP sensitivity to hydrothermal degradation, surface machining has to be performed on partially sintered surfaces, so monoclinic phases formed during machining, transform to tetragonal during sintering. |
