다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Human tissue is structured mainly of self-assembled polymers (proteins) and ceramics (bone minerals), with metals present as trace elements with molecular scale functions. However, metals and their alloys have played a predominant role as structural biomaterials in reconstructive surgery, especially orthopedics, with more recent uses in non-osseous tissues, such as blood vessels. With the successful routine use of a large variety of metal implants clinically, issues associated with long-term maintenance of implant integrity have also emerged. This review focuses on metallic implant biomaterials, identifying and discussing critical issues in their clinical applications, including the systemic toxicity of released metal ions due to corrosion, fatigue failure of structural components due to repeated loading, and wearing of joint replacements due to movement. This is followed by detailed reviews on specific metallic biomaterials made from stainless steels, alloys of cobalt, titanium and magnesium, as well as shape memory alloys of nickel–titanium, silver, tantalum and zirconium. For each, the properties that affect biocompatibility and mechanical integrity (especially corrosion fatigue) are discussed in detail. Finally, the most critical challenges for metallic implant biomaterials are summarized, with emphasis on the most promising approaches and strategies.

Metallic implant biomaterials

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Development of new metallic alloys for biomedical applications

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 beta phase, and multifunctional deformation behaviours of titanium alloys.

Mechanical biocompatibilities of titanium alloys for biomedical applications.

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Y2O3 was added to β-type Ti-29Nb-13Ta-4.6Zr (TNTZ) in order to achieve excellent mechanical performance and low Young’s modulus. TNTZ specimens with 0.05%–1.0% Y are all found to be composed of a β phase. Young’s moduli of TNTZ with 0.05–1.0% Y are all maintained low, and are almost the same as that of TNTZ without Y2O3. The grain size of TNTZ with 0.05%–1.0% Y is smaller than that of TNTZ without Y2O3. Moreover, Y2O3 precipitates can prevent the texture movement, and this effect becomes more obvious with an increase in the Y concentration. The tensile strength of TNTZ is successfully improved by adding Y2O3. TNTZ specimens with 0.2% and 1.0% Y exhibit good balance between the tensile strength and the elongation.

Effect of Y2O3 on Mechanical Properties of Ti-29Nb-13Ta-4.6Zr for Biomedical Applications

In order to improve the mechanical properties of Ti-29Nb-13Ta-4.6Zr (TNTZ) alloy without increasing Young's modulus for application in bone prostheses, dispersion strengthening of TNTZ using yttrium oxide (Y2O3) particles was studied. The formation of well-dispersed Y2O3 particles inside grains of Y-added TNTZ is achieved through the reaction of added Y with the oxygen contained in TNTZ. The size and its standard deviation of obtained Y2O3 particles increased at Y concentrations of 0.2 and 0.5 mass%. The addition of Y led to a decrease in the grain size in Y-added TNTZ. Low Young's modulus was retained in the Y-added TNTZ subjected to cold rolling. The tensile strength and 0.2% proof stress slightly increased in Y-added TNTZ with Y concentrations below 0.1 mass%, whereas they decreased significantly in Y-added TNTZ with Y concentrations of 0.2 and 0.5 mass%. Large Y2O3 particles that formed in Y-added TNTZ with Y concentrations of 0.2 and 0.5 mass% worked as sources for the formation of voids during fracture, which resulted in a decrease in the tensile strength and 0.2% proof stress. Elongation tended to decrease in the Y-added TNTZ as compared to that of TNTZ without any Y addition. As a result, it is found that Y-added TNTZ with improved mechanical properties was obtained at a Y concentration of 0.05 mass% in this experiment. The fatigue strength of Y-added TNTZ was also improved at the Y concentration of 0.05 mass%.

Effect of Oxide Particles Formed through Addition of Rare-Earth Metal on Mechanical Properties of Biomedical β-Type Titanium Alloy

The number of hydroxyl groups on a Ti-29Nb-13Ta-4.6Zr (TNTZ) alloy surface was controlled through H₂O₂ treatment for further improvement of the adhesive strength and durability against water of TNTZ/silane layers (SILs)/segmented polyurethane (SPU) composites. The effect of the terminal functional groups on the adhesive strength of SPU on TNTZ, and the adhesiveness of SPU on TNTZ against water was investigated. Three types of silane-coupling agents were used to bind TNTZ and SPU: methacryloxypropyltrimethoxysilane (γ-MPTS), aminopropyltriethoxysilane (APS), and mercaptopropyltrimethoxysilane (γ-MPS). The adhesive strength of each composite was evaluated by shear bonding tests. The number of hydroxyl groups increases with an increase in treatment time at a H₂O₂ concentration of 5% (v/v). On the other hand, an increase from 5% (v/v) to 30% (v/v) in H₂O₂ concentration leads to a decrease in the number of hydroxyl groups on the TNTZ surface because at higher H₂O₂ concentrations, the reaction that consumes the hydroxyl groups is dominant. The shear bonding strength is doubled compared with the untreated TNTZ/SIL/SPU interface. Although the shear bonding strength decreases after immersion in water for 30 days when APS and γ-MPS are used, TNTZ/γ-MPTS/SPU composites exhibit good durability to water and maintain an equivalent shear bonding strength before immersion in water.

Improvement of adhesive strength of segmented polyurethane on Ti–29Nb–13Ta–4.6Zr alloy through H2O2 treatment for biomedical applications

Development of New Ti‐Mn‐Mo Alloys for Use in Biomedical Applications

/pdf/low-springback-and-low-young-s-modulus-in-ti-29nb-13ta-4-6zr-1p8gdlfs0l.pdf

Masaaki Nakai

Papers

Effect of Y2O3 on Mechanical Properties of Ti-29Nb-13Ta-4.6Zr for Biomedical Applications

Effect of Oxide Particles Formed through Addition of Rare-Earth Metal on Mechanical Properties of Biomedical β-Type Titanium Alloy

Improvement of adhesive strength of segmented polyurethane on Ti–29Nb–13Ta–4.6Zr alloy through H2O2 treatment for biomedical applications

Development of New Ti‐Mn‐Mo Alloys for Use in Biomedical Applications

Low Springback and Low Young’s Modulus in Ti–29Nb–13Ta–4.6Zr Alloy Modified by Mo Addition