CYTOCOMPATIBILITY OF TI-6AL-4V AND TI-5AL-2.5FE ALLOYS ACCORDING TO 3SURFACE TREATMENTS, USING HUMAN FIBROBLASTS AND OSTEOBLASTS

Titanium alloys are well known for their superior mechanical propertie s as well as for their good biocompatibility, making them desirable as surgical implant materials. However, these alloys have been proven to behave poorly in friction since wear particles were often detected in tissues and organs associated with titanium implants. In this paper, three surface treatments were investigated in order to improve the wea r resistance and the hardness of Ti-6Al-4V and Ti-5Al-2.5Fe: (a) glow discharge nitrogen implantation (10(17) atoms cm(-2)), (b) plasma nitr iding by plasma diffusion treatment (PDT) and (c) deposition of TIN la yer by plasma-assisted chemical vapour deposition (PACVD) additionally to PDT. Surface characterization after the different treatments showe d considerable improvement in surface hardness, especially after the t wo nitriding processes. Moreover, the good corrosion resistance of unt reated alloys was maintained. A cell culture model using human cells w as chosen to study the effect of such treatments on the cytocompatibil ity of these materials. The results showed that Ti-5Al-2.5Fe alloy was as cytocompatible as the Ti-6Al-4V alloy and the same surface treatme nt led to identical biological consequences on both alloys. Nitrogen i mplantation did not modify at all the cellular behaviour observed on u ntreated samples. After the two nitriding treatments, cell proliferati on and viability appeared to be significantly reduced and the scanning electron microscopy study revealed somewhat irregular surface states. However, osteoblast phenotype expression and protein synthesis capaci ty were not affected. PDT and PACVD may be interesting alternatives to the physical vapour deposition technique.