Metal materials are the earliest biomedical materials used in clinical medicine. Currently, metal materials used in surgical implants and orthopedic instruments mainly include stainless steel, cobalt-based alloy and titanium alloy, which account for about 40% of the market share of the whole biomaterial products.Among them, titanium alloy has been widely used in the repair, correction and replacement of defects, injuries and diseases in hard tissues (including all bones and teeth in the body).Since the middle of the 20th century, begins with a titanium alloy based medical metal materials in human body hard tissue of surgical implants and human tissue (including cardiovascular, peripheral vascular and non-vascular such as liver, bile duct, urinary tract, etc.) in the interventional treatment showed a unique and amazing curative effect, and titanium alloy artificial joints, dental implant, intravascular stent and heart valves with Chinese medical devices with titanium alloy material research and development, production and application, and the typical representative of medical equipment products come out, is of epoch-making significance for the development of medical and revolutionary contribution,It makes clinical treatment from simple "repair and orthopaedic" treatment to higher-level "replacement" treatment of tissues and organs, greatly improves and improves people's quality of life, and overcomes the deficiency of previous major diseases that can only rely on drug therapy.
1、The development history of titanium alloy materials in China
In the early 1970s, China began to adopt domestic titanium and titanium alloy products. In many hospitals in Beijing, titanium and titanium alloy artificial bones and joints were used for clinical treatment and research, and the hips, elbows and mandible were made for clinical treatment of patients.At the same time, some hospitals and the company of the simulated body fluid immersion test and electrochemical anodization experiments and corrosion kinetics curve measurement, proved that the titanium and titanium alloy artificial bones and joints used in the human body has excellent corrosion resistance, the biological reaction are also small, is an ideal medical implants, the implanted bone and joint mechanical properties has been determined, that the strength of the titanium and titanium alloy meet the requirements of the human body implants.
Since the mid-1980s, the number of titanium materials used in the manufacture of human implants in China has increased, among which the development and application of titanium shape memory alloy has reached the international advanced level.By the mid 1990s, domestic titanium and titanium alloy processing materials were widely used in orthopaedic surgery, neurosurgery, cardiovascular system, oral and maxillofacial surgery, human external culture machine and other aspects.In the past five years, a large number of domestic enterprises have become manufacturers of titanium, stainless steel and other human implants.Using titanium and titanium alloy manufacture of femoral head, hip, humerus, skull, knee, elbow, shoulder joint, joint, jaw and heart valves, kidney distinguishes the membrane, blood vessel expander, plywood, prosthesis, fastening screws and other hundreds of transplanted into the body of the metal, has obtained the good effect, gave a high evaluation by the medical profession.
2、Classification and characteristics of biomedical titanium alloy materials
Biomedical titanium alloy material is a kind of functional structure material used in biomedical engineering, mainly used in the production and manufacturing of surgical implants and orthopedic instruments.According to professional standards of surgical implants and orthopedic devices titanium alloy materials can be classified as "surgical implant materials" in the "metal" category, and titanium alloy materials in the active surgical implants, active surgical implants and orthopedic devices in the three types of medical equipment, can act as a cardiovascular, bone and joint, joint bone, spine, orthopedic equipment, pacemakers and defibrillators, cochlear implants, nerve stimulator, and other embedded products of raw materials.Biomedical titanium alloy microstructure by material type can be classified as alpha titanium alloy (such as pure titanium series), alpha + beta type (such as Ti6Al4V) and beta type titanium alloy titanium alloy (such as Ti12Mo6Zr2Fe) and four categories, the observatory shape memory alloy compared with medical stainless steel and cobalt base alloy, they are the proportion of small, high specific strength, lower elastic modulus, corrosion resistance, easy to machining, and good biocompatibility, etc.
3、Research and development of biomedical titanium alloy materials
The development of biomedical titanium and its alloys can be divided into three periods: the first period was represented by pure titanium and Ti6A14V, and the second period was represented by t-qiao A12.The new d+B alloys represented by 5Fe and Ti6A17Nb are in the third era of the development and development of titanium alloys with better biocompatibility and lower elastic modulus. Among them, titanium alloys of type B are the most widely studied.
1).The first generation of biotitanium alloy, represented by pure titanium and Ti6A14V, is the earliest titanium alloy applied in this field.At present, clinical experience of using pure titanium implants is relatively mature, but commercial pure titanium cannot provide comprehensive mechanical properties required by medical weight-bearing materials, such as low strength and poor wear resistance of pure titanium, which limits its application.Although cold processing can increase the strength of pure titanium, it can not meet the actual needs.Therefore, people began to consider the use of titanium alloy.Ti6A14V has become the first titanium alloy to be introduced into the field of biomaterials due to its excellent biocompatibility and good comprehensive mechanical properties. It is also the largest titanium alloy used in biomedical devices.
2)Ti6A17Nb and TiSAl2.The second generation of new type Q+B alloy represented by 5Fe due to the potentially toxic element V contained in Ti6M4V, two new types of "Q+B" medical titanium alloy TiSAl2 were developed in the mid-1980s.5Fe and Ti6A17Nb were developed in Europe.
Ti6A17Nb is comparable to the recognized "all-powerful" Ti6A14V alloy in mechanical properties. It is a safe and promising artificial biomedical implant material, which was successfully developed by Switzerland in 1989.This safe and potential biomedical titanium alloy has been studied in different aspects by experts and scholars from different countries.
4、Production status of titanium alloy materials for medical instruments in China
In 1992, China released the first national standard GB/ t13810-1992 "titanium and titanium alloy processing materials for surgical implants" for the first time, which marked that China began to specialize in the production of titanium alloy raw materials for medical device applications.But 20 years later, the national standard, although the two changes, our country at present can only produce pure titanium (China brand TA1 ~ TA4, the corresponding brand Gr1 ~ Gr4), Ti6Al4V (China brand TC4, the corresponding brand or Gr5 Ti64), Ti6Al7Nb (China brand TC20) three types of titanium alloy materials, there is no a beta type titanium alloy into the national standards, as shown in table 1.Up to now, pure titanium and Ti6Al4V titanium alloy are still the most widely produced and sold traditional main materials for surgical implants in the world, and their sales account for more than 80% of the whole biomedical titanium alloy market in the world.The varieties of titanium and titanium alloy processing materials for surgical implants produced in China are related to plates (thickness 0.8~25mm), bars and wires (diameter 1~90mm), and the supply state can be cold rolled, hot processed and annealed.The indexes of chemical composition, mechanical properties and microstructure of titanium alloy processing materials stipulated in the new national standard GB/ t13810-2007 are equivalent to the requirements of ASTM f136-02a, but at the same time, additional technical requirements such as grading of microstructure, shrinkage of section and ultrasonic examination of plates and bars are also added.Although China's national standard clearly stipulates that the microstructure rating type of Ti6Al4V titanium alloy should conform to the a+b biphasic structure of A1~A9, most of the domestic titanium materials are coarse crystalline A3~A5 grade structure, and the quality stability is poor.And the United States imported titanium microstructure can achieve fine crystallization A1 to A3, bar diameter of 15 mm below the small specification can reach grade A1 (such as axis of a and b phase grain size less than 10 microns), thus has strong toughness, corrosion resistance and mechanical cutting performance, this causes our country artificial joints, dental implant, spinal internal fixation system and other high-end medical equipment products processing still needs a large number of imported foreign high-quality Ti6Al4V titanium alloy material, and domestic medical titanium main meet domestic mid-range of medical equipment products such as bone plate and bone screws, etc.In 2008, the production of titanium sponge and titanium materials in China ranked first and second respectively in the world, and the consumption of titanium materials had taken the second place in the world, becoming a major titanium industry after Russia, the United States and Japan. Among them, the consumption of titanium materials in the United States and Russia was mainly for defense military, while that in China and Japan was mainly for civil industry.
Although the modern sense of biomedical materials originated in the 1940s, and its discipline was only formed in the 1980s, biomedical materials are involved in the health of hundreds of millions of people, and they are necessary to guarantee human health.The application of biomedical materials not only saves tens of millions of lives, makes the early detection and effective treatment of diseases and significantly reduces the mortality rate of major diseases, but also has important civil value and social significance for improving people's health and quality of life.