Young’s modulus as well as tensile strength, ductility, fatigue life, fretting fatigue life, wear properties, functionalities, etc., should be adjusted to levels that are suitable for structural ...biomaterials used in implants that replace hard tissue. These factors may be collectively referred to as mechanical biocompatibilities. In this paper, the following are described with regard to biomedical applications of titanium alloys: the Young’s modulus, wear properties, notch fatigue strength, fatigue behaviour on relation to ageing treatment, improvement of fatigue strength, fatigue crack propagation resistance and ductility by the deformation-induced martensitic transformation of the unstable
β
phase, and multifunctional deformation behaviours of titanium alloys.
Ti alloys composed of nontoxic and allergy-free elements and Ni-free stainless steels and Co-Cr alloys are currently being developed. Ni-free Ti alloys exhibiting superelastic behavior, or the shape ...memory effect, are also being developed. β-type Ti alloy with a low elastic modulus has proved to be effective for inhibiting bone absorption and enhancing bone remodeling. Simple bioactive surface modifications such as alkali-treatment processes and the calcium phosphate glass-ceramic dip-coating method are applicable to newly developed β-type Ti alloys such as lowmodulus Ti-29Nb-13Ta-4.6Zr. Blood-compatible polymers such as poly(ethylene glycol) have been successfully fixed on the surface of Ti via chemical bonding by an electrodeposition method. Ti alloys for dental applications have also been recently developed.
A
β type titanium alloy, Ti–29Nb–13Ta–4.6Zr, was newly designed and developed for biomedical applications. The new alloy contains non-toxic elements such as Nb, Ta, and Zr. In the present study, ...phases that appeared in the new alloy through various aging treatments were characterized by hardness tests and microstructural observations in order to identify the phase transformation. Fatigue properties of the new alloy were investigated. Young’s modulus and cyto-toxicity of the new alloy were also evaluated.
Precipitated phases distribute homogeneously over the whole specimen, and they are
α phase, a small amount of
ω phase, and
β phase when the new alloys are subjected to aging treatment at 673
K for 259.2
ks after solution treatment at 1063
K for 3.6
ks. The fatigue strength of the new alloy subjected to aging at 673
K for 259.2
ks after solution treatment at 1063
K for 3.6
ks is much better than when subjected to other aging treatments. In this case, the fatigue limit is around 700
MPa. Young’s modulus of the new alloy is much smaller than that of Ti–6Al–4V ELI. The cyto-toxicity of the new alloy is equivalent to that of pure Ti. Therefore, it is proposed that the new alloy, Ti–29Nb–13Ta–4.6Zr, will be of considerable use in biomedical applications.
Biocompatibility of Ti-alloys for long-term implantation Abdel-Hady Gepreel, Mohamed; Niinomi, Mitsuo
Journal of the mechanical behavior of biomedical materials,
April 2013, 2013-Apr, 2013-04-00, 20130401, Volume:
20
Journal Article
Peer reviewed
The design of new low-cost Ti-alloys with high biocompatibility for implant applications, using ubiquitous alloying elements in order to establish the strategic method for suppressing utilization of ...rare metals, is a challenge. To meet the demands of longer human life and implantation in younger patients, the development of novel metallic alloys for biomedical applications is aiming at providing structural materials with excellent chemical, mechanical and biological biocompatibility. It is, therefore, likely that the next generation of structural materials for replacing hard human tissue would be of those Ti-alloys that do not contain any of the cytotoxic elements, elements suspected of causing neurological disorders or elements that have allergic effect. Among the other mechanical properties, the low Young's modulus alloys have been given a special attention recently, in order to avoid the occurrence of stress shielding after implantation. Therefore, many Ti-alloys were developed consisting of biocompatible elements such as Ti, Zr, Nb, Mo, and Ta, and showed excellent mechanical properties including low Young's modulus. However, a recent attention was directed towards the development of low cost-alloys that have a minimum amount of the high melting point and high cost rare-earth elements such as Ta, Nb, Mo, and W. This comes with substituting these metals with the common low cost, low melting point and biocompatible metals such as Fe, Mn, Sn, and Si, while keeping excellent mechanical properties without deterioration. Therefore, the investigation of mechanical and biological biocompatibility of those low-cost Ti-alloys is highly recommended now lead towards commercial alloys with excellent biocompatibility for long-term implantation.
Nb, Ta and Zr are the favorable non-toxic alloying elements for titanium alloys for biomedical applications. Low rigidity titanium alloys composed of non-toxic elements are getting much attention. ...The advantage of low rigidity titanium alloy for the healing of bone fracture and the remodeling of bone is successfully proved by fracture model made in tibia of rabbit. Ni-free super elastic and shape memory titanium alloys for biomedical applications are energetically developed. Titanium alloys for not only implants, but also dental products like crowns, dentures, etc. are also getting much attention in dentistry. Development of investment materials suitable for titanium alloys with high melting point is desired in dental precision castings. Bioactive surface modifications of titanium alloys for biomedical applications are very important for achieving further developed biocompatibility. Low cost titanium alloys for healthcare goods, like general wheel chairs, etc. has been recently proposed.
Metastable β-type titanium alloys are highly suitable for use as structural biomaterials applied to hard tissue, i.e., as cortical bone (hereafter, bone) replacing implants. However, their mechanical ...biocompatibitities, such as the Young’s modulus, strength and ductility balance, fatigue strength, resistance against fatigue crack propagation and fracture toughness, require improvenent for increased compatibility with bone. Through deformation, the metastable β-phase in a metastable β-type titanium alloy is transformed into various phases, such as α’ martensite, α” martensite, and ω-phases with exact phase depending by metastable β-phase stability. In addition, twinning is also induced by deformation. Deformation twinning effectively enhances the work hardening in the metastable β-type titanium alloy, leading to increased strength and ductility. This improvement is accompanied by with other deformation-induced transformations including the appearance of deformation-induced martensite and ω-phase transformation. The enhancement of the mechanical biocompatibility of various materials using the abovementioned deformation-induced transformation is described in this paper, for both newly developed metastable β-type Ti-Mo and Ti-Cr alloys for biomedical applications.
This work looked into the formation of a hybrid composite coating composed of strontium-doped hydroxyapatite (HA) and graphene oxide (GO) on the surface of β-type TiNbTaZr (TNTZ) alloy via a green ...hydrothermal method. To achieve this goal, various GO concentrations, 1.5, 3.0, and 4.5 wt%, were added to autoclave linked solution. The inclusion of GO led to a reduction in the crystallinity of HA/Sr coating where dense homogenous rods nanocrystalline structures were observed in the case of 4.5 wt% of GO. Furthermore, per electrochemical measurements in a simulated body fluid (SBF) solution, it was found that the composite coating was made from a solution with 4.5 wt% GO which had the lowest corrosion density of 83 nA cm
−2
with the highest polarization resistance (237,415 Ω cm
2
). The results showed that the hydrophilic HA/Sr–GO composite coatings prepared in the present work can be used as a potential candidate in orthopedic applications.
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