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

https://www.tpbin.com/Uploads/Subjects/643149a0-8194-4c67-bf05-73fae6f0d14f.pdf

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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A new biomedical titanium alloy, Ti-29Nb-13Ta-4.6Zr, composed of nontoxic elements like Nb, Ta, and Zr, has recently been developed in order to achieve a lower Young’s modulus similar to that of human hard tissues in addition to excellent mechanical properties for use as structural biomaterials. The characteristics of this material depend on the microstructures obtained by heat treatments or thermomechanical treatments. Therefore, the relationship between microstructures and basic mechanical properties, the Young’s modulus, tensile and fatigue properties, etc., has been investigated with respect to Ti-29Nb-13Ta-4.6Zr. Further, the practical performance of this alloy as a metallic biomaterial has been evaluated via animal experiments. Moreover, the mechanical functionalities of this alloy, such as superelasticity, were reported recently. In the present paper, the accumulated reports on Ti-29Nb-13Ta-4.6Zr were summarized and the mechanical properties of this alloy were mainly reviewed in order to evaluate its potential for biomedical applications.

Mechanically Multifunctional Properties and Microstructure of New Beta-Type Titanium Alloy, Ti-29Nb-13Ta-4.6Zr, for Biomedical Applications

Ag–Pd–Au–Cu alloys have been used widely for dental prosthetic applications. Significant enhancement of the mechanical properties of the Ag–20Pd–12Au–14.5Cu alloy as a result of the precipitation of the β ′ phase through high-temperature solution treatment (ST), which is different from conventional aging treatment in these alloys, has been reported. The relationship between the unique hardening behavior and precipitation of the β ′ phase in Ag–20Pd–12Au– x Cu alloys ( x =6.5, 13, 14.5, 17, and 20 mass%) subjected to the high-temperature ST at 1123 K for 3.6 ks was investigated in this study. Unique hardening behavior after the high-temperature ST also occurs in Ag–20Pd–12Au– x Cu alloys ( x =13, 17, and 20) with precipitation of the β ′ phase. However, hardening is not observed and the β ′ phase does not precipitate in the Ag–20Pd–12Au–6.5Cu alloy after the same ST. The tensile strength and 0.2% proof stress also increase in Ag–20Pd–12Au– x Cu alloys ( x =13, 14.5, 17, and 20) after the high-temperature ST. In addition, these values after the high-temperature ST increase with increasing Cu content in Ag–20Pd–12Au– x Cu alloys ( x =14.5, 17, and 20). The formation process of the β ′ phase can be explained in terms of diffusion of Ag and Cu atoms and precipitation of the β ′ phase. Clarification of the relationship between hardening and precipitation of the β ′ phase via high-temperature ST is expected to help the development of more effective heat treatments for hardening in Ag–20Pd–12Au– x Cu alloys.

Hardening behavior after high-temperature solution treatment of Ag-20Pd-12Au-xCu alloys with different Cu contents for dental prosthetic restorations.

A peculiar effect of oxygen on ω-phase stability, i.e., the enhancement of the isothermal ω-phase formation during aging due to oxygen addition was observed in the Ti-29Nb-13Ta-4.6Zr; this effect is contradictory to that reported conventionally. The effect was analyzed from the viewpoint of distribution of alloying elements. Oxygen and/or zirconium may dissolve in the ω phase during aging, resulting in the stabilization of the ω phase in this alloy.

Effect of Oxygen Addition on Isothermal Omega Phase Stability in Ti-29Nb-13Ta-4.6Zr

Ti-10Mn and Ti-14Mn alloys were fabricated by metal injection molding method. Their microstructures and mechanical properties, including tensile properties, Young’s modulus, and hardness, were investigated as functions of sintering temperature.

Masaaki Nakai

Papers

Mechanically Multifunctional Properties and Microstructure of New Beta-Type Titanium Alloy, Ti-29Nb-13Ta-4.6Zr, for Biomedical Applications

Hardening behavior after high-temperature solution treatment of Ag-20Pd-12Au-xCu alloys with different Cu contents for dental prosthetic restorations.

Effect of Oxygen Addition on Isothermal Omega Phase Stability in Ti-29Nb-13Ta-4.6Zr

Mechanical Properties of Low-Cost Beta-Type Ti-Mn Alloys Fabricated by Metal Injection Molding

Dependence of high-temperature steam oxidation resistance on the stability of the chromium sulfide in high-chromium heat-resistant steels