Biocompatibility and Bioactivity of Load-Bearing Metallic Implants

Abstract

The main objective of here presented research is to develop the titanium (Ti) alloy base composite materials possessing better biocompatibility, longer lifetime and bioactivity behaviour for load-bearing implants, e.g. hip joint and knee joint endoprosthesis. The development of such materials is performed through: modeling the material behaviour in biological environment in long time and developing of new procedures for such evaluation; obtaining of a Ti alloy with designed porosity; developing of an oxidation technology resulting in high corrosion resistance and bioactivity; developing of technologies for hydroxyapatite (HA) deposition aimed at composite bioactive coatings; developing of technologies of precipitation of the biodegradable core material placed within the pores. The examinations of degradation of Ti implants are carried out in order to recognize the sources of both early allergies and inflammation, and of long term degradation. The theoretical assessment of corrosion is made assuming three processes: electrochemical dissolution through imperfections of the anodic oxide layer, diffusion of metallic ions through the oxide layer, and dissolution of oxides themselves. In order to increase the biocompatibility, the toxic elements, aluminium (Al) and vanadium (V) are eliminated. The experiments have shown that titanium -zirconium -niobium (Ti-Zr-Nb) alloy may be a such a material which can also be prepared by both powder metallurgy (P/M) technique and selective laser melting. The porous (scaffold) Ti-Zr-Nb alloy is now obtained by powder metallurgy, classical and with space holders used before melting and decomposed, or remained during melting and removed by subsequent water dissolution. The oxidation of porous materials is performed either by electrochemical technique in special electrolytes or by chemical and/or hydrothermal method in order to obtain the optimal oxide layer well adjacent to an interface, preventing the base metal against corrosion and bioactive because of its nanotubular structure, permitting injection of some species into the pores. The Ca, O and N ion implantation or deposition of zirconia sublayers may be used to increase the biocompatibility, bioactivity and corrosion resistance. The HA coating obtained by either electrophoretic, biomimetic or by sol-gel deposition should result in gradient structure similar to bone structure, possessing high adhesion strength. The core material of the porous material should result in a biodegradable material, allowing slower dissolution followed by stepwise growth of bone tissue and angiogenesis, preventing local inflammation processes, sustaining the mechanical strength close to that of non-porous material.

The Properties of Nanosilver – Doped Nanohydroxyapatite Coating On the Ti13zr13Nb Alloy

“…The titanium alloy (such as Ti6Al4V and less Ti6Al7Nb and Ti13Zr13Nb) nowadays are the most frequently used materials for load-bearing orthopedic implants because of their high biocompatibility and proper mechanical properties [1][2][3][4][5][6]. There are some reports on possible adverse e effects of both alloying elements of the Ti6Al4V: vanadium may provoke cytological responses and neurogenic disorders, and aluminum softens bone, do damage to nerve cells and disturbance of the function of enzymes [7][8][9][10].…”

Evaluation of Corrosion Resistance of Titanium Alloys Used for Medical Implants

“…This calls for appropriate barrier layers on titanium alloy implants. There are many methods available to modify the implant surface [5][6][7][8], however the most frequent procedure used to modify titanium alloy implant surfaces has been anode oxidation. Depending on the process parameters, the formed outer layers may show different chemical composition, thickness and morphology [9,10].…”

The Effect of Anodization and Glow Discharge Plasma Oxidation Surface Treatments on the Wear Resistance of Ti6Al4V Alloy

“…Biyomedikal alanda ilk olarak saf titanyum kullanılmış, sonrasında ise Hegzagonal kafes yapısına sahip alfa ve Yüzey Merkezli Kübik (YMK) kafes yapısına sahip beta fazlarından oluşan ikili faz yapısındaki Ti6Al4V alaşımının kullanımına başlanmıştır. Ancak bu alaşım kimyasal olarak soy kabul edilmesine karşın, vücut ortamıyla uzun süreli temasında merkezi sinir sistemi tahribatı ve kanser gibi birtakım problemlere neden olabileceğine dair şüpheler belirtilmiştir (Zieliński et al, 2010). Ayrıca, alaşım yapısında bulunan elementlerin belli bir oranın üzerinde vücuda salınmasının kemik iyileşmesini de yavaşlattığı tespit edilmiştir (Balazic, Kopac, Jackson, & Ahmed, 2007;Kuroda, Niinomi, Morinaga, Kato, & Yashiro, 1998;Y.…”