Abstract

The habilitation thesis is a summary of teaching and research activities within the past years in materials engineering field (research, obtaining and analysis of biomaterials, respectivelly failure analysis of orthopedic implants). The habilitation thesis involves presenting the personal research activity from the doctoral thesis final (in February 2007) until the completion of this work presentation. The research started from ideas discussed until the development of some courses and research activities focused on metallic biomaterials in the Department of Metallic Materials Science and Physical Metallurgy, Faculty Materials Science and Engineering, University Politehnica of Bucharest, many years ago. In this abstract, the framework of the habilitation thesis paper is presented and the contributions in these areas and proposals for further research are briefly reviewed. In the first chapter of the habilitation thesis, some results about the biomaterials used for treatment, repair and regeneration of hard tissue are presented, the objective being focused on two main issues. The first involved the obtaining, characterization and testing some metallic biomaterials used for orthopedic implants. It was investigated the influence of chemical composition of these biomaterials but also was followed the influence of different obtaining and processing techniques for these biomaterials on the microstructure and functional properties, in correlation with functional requirement for each orthopedic implant. Also, was evaluated the effect of different coating techniques and coating materials used for surface modifications of metallic biomaterials on the biocompatibility and functional properties. The second important aspect consisted in obtaining and complex characterization of new biomaterials which can be used for orthopedic implants. Following this objective, it was obtained and characterizated different metallic biomaterials with modified surface, biodegradable composite biomaterials used in bone regeneration, and new biodegradable magnesium alloys. The use of advanced surface characterization techniques of these various biomaterials make possible to obtain advanced knowledge and strong skills in this field. Based on these knowledges, it was possible to obtain and characterize new biodegradable magnesium based alloy without aluminium, from the system Mg-Ca, potentially used for manufacturing different orthopedic implants like ostheosynthesis implants used in different surgical interventions for fracture fixation. The preliminary results obtained confirm that these biodegradable metallic alloys could be a new paradigm for orthopedic biomaterials. The 2nd Chapter of the habilitation thesis focuses on the possibilities of analysis the failure causes in the case of different orthopedic implants. Analyzing different orthopedic implants failed from different reasons, it was possible to establish a clear protocol for the analysis of failed orthopedic implants, according with the international standards, and give the solutions for improing the surgical act in some cases or for developping new orthopedic implants with a better design. The research aspects were carried out in several steps, aiming a complex analysis of very different orthopedic implants, from intramedullary nail and hip prosthesis to bioresorbable composite screws used in arthroscopy and knee prosthesis. For the characterization of failed orthopedic implants was used modern microscopical and spectral techniques: light microscopy, stereomicroscopy, scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (ATR-FTIR), atomic force microscopy (AFM). Also, histological analysis of the tissue obtained from the near area of the failed orthopedic implants was made. An important aspect for the succes of our investigations was the carefully collection of all clinical data together with a biomechanical analysis, who support the experimental results obtained after the analysis of biomaterials, tissue and the interfaces. In Chapter 3 are presented the evolving plans, to the development and future research directions. Essencially, the proposals for further research are based on the two themes from materials engineering field who was discussed in the first two chapters of the habilitation thesis: metallic biomaterials and failure analysis of orthopedic implants for the development of new biomaterials and new orthopedic implants. Both suggested topics are new issues at international, confirmed by many scientific collaborations and recognition at international level.