The review article describes the current trends in the development of some groups of metal biomaterials used in implantology for the manufacture of biodegradable (temporary) implants. The “biodegradation” concept is that implants are not intended for long-life application to be gradually dissolved in human body. There are requirements for such materials which are biocompatibility, strength and rate of biodegradation (dissolution) in a physiological environment. It is shown that biodegradable metallic materials are divided into magnesium alloys, iron alloys and zinc alloys. These alloys can have significant benefits because magnesium, iron, and zinc are among the elements vital for human wellbeing, so dissolving them in patient body is potentially safe for health when removing excess from the body. Each of the listed metals has its own disadvantages related to certain physical and chemical properties; the elimination of these disadvantages is aimed at the development of suitable alloys with improved performance. Magnesium has a very high dissolution rate and instability of mechanical properties that are improved by doping (Mg – Y – REM – Zr, Mg – Al – Zn, Mg – Al – Zn – Mn, Mg – Li – Al – RZM – Mn, etc.) and by deposition of different coatings with protective abilities such as ceramics (Al2O3), hydroxyapatite, biodegradable polymers (PGA, PLLA, PDLA, PHA), sylane, graphene and its derivatives, composite “ceramics/biopolymer, etc. Trademarks of implants made of Mg-based alloys have already been developed and tested. The iron is characterized by too low biodegradation rate. Increased corrosion resistance of iron causes its accumulation in human body with a prolonged negative effect. The rate of iron biodegradation is increased by doping, for example, the introduction of palladium (forms intermetallides), or manganese (causes deformation of epsilon-martensite). Zinc has been found to have an acceptable rate of biodegradation, but it has low mechanical properties. To increase the properties, alloying elements (Zn – Mg, Zn – Fe, Zn – Ca, Zn – Sr, Zn – Al, Zn – Cu, Zn – Al – Mg – Bi, Zn – Li, Zn – Ag) are added into zinc; the proper heat treatment and cold plastic deformation are applied also. It is concluded that among the biodegradable materials only magnesium-based alloys are already commercialized to be widely proved in extended clinic trials. The article describes the main technological approaches to improving the complex properties of metallic materials for biodegradable implants.
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