2) Cobalt-based alloy Cobalt-based alloy is an early medical metal. Cobalt-based alloys for medical use mainly include CoCrMo, CoCrWNi, CoNiMoWFe and MP35NCoNi alloys, among which cast cocrmo is the most widely used alloy, which has been listed in China's ISO5582/4 standard and GB 124 190 standard in/kloc-0. Cobalt-based alloys not only generally meet the requirements of biological, physical and chemical properties of materials, but also have better corrosion resistance, wear resistance and excellent casting performance than stainless steel, which is easy for product molding and processing. Cobalt-based alloys have been widely used in plastic surgery and dentistry, such as hip, shoulder, elbow and knee joint, as well as various bone plates and dentures.
The main problem of cobalt-based alloy is that dissolved Co and Ni plasma can cause skin allergy and toxic reaction, which may lead to tissue necrosis and implant loosening. The strength and fatigue properties of hip joint and other implants made of cast cobalt-based alloy are still insufficient, and the casting performance is sensitive to notch.
3) Medical titanium and its alloys Titanium and its alloys are a kind of biomedical materials that entered the field of medical metal materials late. Because of its high specific strength, low elastic modulus, good comprehensive mechanical properties and better biocompatibility and corrosion resistance than stainless steel, it has become the most promising medical material. The research and development of titanium-based medical materials is a hot spot at home and abroad. Since the mid-1970s, titanium-based materials have been widely used in clinic. At present, it has been used in plastic surgery (various joints and fixation instruments) and oral and maxillofacial surgery (dentures, implants, etc.). ), brain surgery, cardiovascular system (heart valve, pacemaker sealed box) and other fields. Although the proportion of titanium products in the whole field of medical metal materials is still relatively small (~ 6%), from the development trend, the proportion of titanium medical materials is on the rise. One problem of titanium-based medical materials is that there are too few varieties. Among the two varieties listed in the standard, the strength of industrial pure titanium is lower. TC4 alloy is a structural material developed for aerospace. As a medical alloy, there are some problems, such as poor processing performance, unsatisfactory fatigue fracture performance, high elastic modulus and toxic vanadium component. Therefore, all countries are committed to developing new medical titanium alloys with better biocompatibility and comprehensive mechanical properties.
Like other metals such as stainless steel and cobalt-based alloys, titanium implants also have the problem of combining with living hard tissues. In order to make the morphological combination become a better bioactive combination, many domestic units conducted extensive and in-depth research on porous titanium implants, porous artificial hip joints and titanium-based composite medical materials with active surfaces in the mid-1980s.
4) NiTi shape memory alloy 4) NiTi shape memory alloy is the latest metal material to enter the field of medical biomaterials. Because it not only has good mechanical properties and biocompatibility required by biomaterials, but also can be transformed into a pre-designed shape by thermoelastic martensite at ~ 37℃ through special heat treatment, it is an ideal biomedical material for orthopedic surgery and tubular tissue and organ treatment. At present, NiTi orthodontic wire, crown, support ring, spine, cervical orthosis, thrombus filter, vasodilator stent, embolic device, snorer, prostate dilator stent, contraceptive ring, etc. have been initially applied.
It can be predicted that with the deepening of research and development, the application fields of shape memory alloys will continue to expand. The main problems of NiTi shape memory alloy are that its properties are sensitive to composition, its process performance is poor, its cost is high, and the diffusion of dissolved nickel ions into the structure may be toxic. Therefore, a nickel-free titanium-based shape memory alloy is being developed.
5) Medical precious metals Precious metals, such as gold, silver, platinum and their alloys, are the oldest medical metals with stable physical and chemical properties, excellent processability, good biocompatibility and gorgeous and precious texture. At present, it is still widely used in dental restoration as crown, bridge, bracket, clasp, filler and implant. For a long time, the research progress of medical precious metals has been slow. Most of the precious metal dental alloys widely used in modern times are old alloys developed on the basis of AuAgCu ternary system, including soft casting alloys, hard casting alloys and silver amalgam alloys. The rising price of precious metals promotes the research and development of non-precious metal dental alloys. Non-precious metal dentures such as Ni-Cr alloy and Co-Cr alloy have been widely used in clinic abroad since 1950s, while domestic non-precious metal dental alloys began in 1960s, but the formal promotion results are few. In 1980s, Northwest Nonferrous Metals Research Institute developed a nickel-based non-precious metal dental porcelain alloy (YKH- 1), which has been mass-produced and applied in clinic. As an implant material for medical materials, metal materials still expose some problems in clinical use. Mainly: corrosion problems, toxicity problems, interface problems, mechanical compatibility problems, and unsatisfactory comprehensive performance. The above problems involve materials science, materials engineering, biology, medicine and other fields, and multidisciplinary cooperation is a necessary condition to solve the problems. From the material properties, it is difficult for stainless steel and cobalt-based alloys to solve all the above problems, and titanium alloy is the only medical material that can meet the requirements, so the development of new titanium alloy has become a research hotspot of biomedical metal materials.