| 研究実績の概要 |
This research project provided a further insight on the durability of various ceramic biomaterials applied in orthopaedic prosthetic implants both in-vitro and in-vivo. Simulated wear testing and retrieved materials analysis clearly showed that most commonly applied ceramic biomaterials (monolithic alumina, zirconia and zirconia toughened alumina) degrade in-vivo at a rhythm which is significantly higher when compared to conventional laboratory simulations. It was also shown that metal staining caused by dislocation of the implant, leads to an even faster degradation. The presence of lubrication limits the severity of the tribological contact reducing the friction coefficient but might promote the transformation of tetragonal zirconia into monoclinic, reducing the mechanical properties of the implant. The concept of bioinert biomaterials has then been questioned: even oxides, which are extremely stable from a chemical point of view, have a clear and unexpected interaction with the human body environment. Taking into account these results, silicon nitride has been introduced as an alternative biomaterial. Studies conducted in-vitro clearly showed that Si3N4 positively interact with the human body environment and can thus be successfully used for different applications, from promotion of bone growth and osteointegration (e.g.: in spinal implants or bone fillers) to wear resistance (e.g.: in femoral heads for hip implants). The additional anti-bacterial effect granted by Si3N4 has never been observed before for other conventional ceramic material used in orthopaedics.
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