Adaptability Of Titanium Materials To The Human

In order to observe the response of metal ions to the adaptability of the human body, in the laboratory, Chinese medical experimental mouse lung fibroblast cells (V79 cells) and mouse (20-day postnatal mice) fibroblast cell tissue (I929 cells ), etc., use cells that are sensitive to metal ions to conduct cell adaptability evaluation methods. The individual element ions provided by the independent administrative agency Product Evaluation Technology Basic Organization (Technical Committee for Standardization of Biological Evaluation of Medical Devices) are effective in human body (biological body). ) reactions and divided into 3 groups as shown in Figure 1.

The most toxic ones include vanadium (V), nickel (Ni), copper (Cu), etc. When the above elements are present in parts per million (×10-6), cells will die within a short period of time. Taking vanadium (V) and nickel (N) as an example, the experimental results in V79 cells are shown in Figure 2. The results of the one-week immersion test showed that if the nickel concentration was around 10×10-6 (Translator's Note pm=parts per million), all cells would die. In comparison, the vanadium (V) content was two digits lower at 0.6 Around ×10-6 means all cells are dead. Secondly, when the hard tissues (bones) and soft tissues (muscles) of small animals such as rats and rabbits were buried in metal sheets for testing, it must be that these highly toxic metals are in contact with both the hard tissues (bones) and soft tissues (muscles). Some cause necrosis.

a-The relationship between V79 cell population formation energy and nickel (Ni) ion concentration;

b-The relationship between V79 cell population formation energy and vanadium (V) ion concentration

The other group indicates injury. In the implanted and attached state, a biological reaction is formed on the fibrous tissue at the contact site that is discharged out of the body. Iron, aluminum, gold, silver, etc. all behave in this way. General metal materials such as SUS 304L stainless steel, SUS 36L stainless steel and cobalt-chromium alloys all belong to this type. The metal piece embedded in the hard tissue does not fuse with the bone cells. When the extraction test was performed a few weeks later, it was pulled out smoothly without resistance.

The third group must have the smallest reaction with living organisms. When implanted or attached, titanium (Ti), zirconium (Zr), niobium (Nb), tantalum (Ta) and platinum (Pt) are suitable. When these metals are implanted or attached to the body, they are closely integrated with the cells and tissues of hard and soft tissues, showing a phenomenon of somatization.

In this way, titanium is definitely less harmful to living organisms and is a safe metal. When using titanium alloy, depending on the alloy elements used, the corrosion resistance is lower than that of pure titanium. When corrosion occurs, its elements can be dissolved. It is necessary to select alloy elements that are corrosion-resistant and non-damaging. Among titanium alloys, Ti-6AI-4V alloy has long been used in aircraft manufacturing and seawater-resistant engineering equipment, and has a large number of use cases. In the medical industry, the use of ELI-type alloys with excellent corrosion resistance (low iron, oxygen, and hydrogen content) has long been introduced. However, in the recent research and development of titanium alloys for implants and attachments, based on reports on the damage properties of the single unit, the Ti-13Nb-13Zr alloy has been standardized by replacing vanadium (V) with non-wounding niobium (Nb). (ASTM, ISO). There is also a favorable alloy that actively discharges aluminum and is about to be launched.

As the American ASTM standard (F code) for medical use, it is equivalent to the world standard in Europe. The ISO standard and the ASTM standard were consolidated and merged into a European standard. Japan is sorting out its domestic standards, taking the standards corresponding to ASTM and ISO, and starting to formulate standards based on ISO standards.

The titanium materials stipulated in ASTM standards used in implants and attachments represented by artificial knee joints, hip joints (including femoral heads), etc. are listed in Table 1 according to their shapes. For a long time, pure titanium and Ti-6AI-4V alloys, including powder materials, have been made into components and parts of various shapes.

The parts where titanium materials are widely used are artificial femoral joints, artificial knee joints, bone plates, etc., which are suitable for orthopedic surgery. deforming joint inflammation
Rheumatism [transliterated as "Liumaqizim", which means a severe pain in joints and muscles, and is also an allergic disease - translator's note] and other causes of severe pain, resulting in difficulty walking, will Patients suffering from this disease can completely eliminate pain and be able to walk through artificial hip joint and artificial knee joint replacement surgery. In Japan, 80,000 artificial hip joint replacement surgeries and 40,000 artificial knee joint replacement surgeries are performed in a year (2005 statistics). In the future, with the arrival of an aging society, it can be expected what percentage growth rate will be used to meet this demand.

Titanium is not suitable for all artificial joint parts. In joint parts, parts that often swing are not suitable because titanium is easy to wear (ceramics and cobalt alloys are suitable), and titanium alloys should be used for implanted parts. In order to quickly integrate it with the biological bone, the surface of the titanium alloy must be made uneven and coated with bone sensors such as apatite (Apatite) and bioglass. In addition, titanium alloy intramedullary nails and titanium alloy plates are used for fracture fixation. Figure 3 shows various examples of implantation and attachment.

There is also an increasing trend in the field of dentistry with the use of implants and accessories. The amount of titanium used is small, and it is made of pure titanium, titanium alloy, and shape memory alloy TiNi. Its shapes include plate type, thread type, sleeve type, and basket type as shown in Figure 4. These parts and components are directly driven into the jawbone to be fixed on the implanted gum part, and are coated with apatite that represents bone composition. Generally, titanium is very suitable for metal implants in teeth. There are two methods: precision casting and superplastic forming. Compared with the previous use of cobalt and chromium alloys, it is lighter in weight and does not cause odor change in acidic foods. Since the use of titanium materials is outside the scope of health insurance diagnosis and treatment, the price quite expensive.

As an implant (buried) or accessory for internal medicine, when a patient suffers from a low heart beat rate, a pacemaker (Pacemaker--an automatic ventricular contraction device) can be implanted (buried) to stimulate the heart. A device that ensures the normal number of heart beats - Translator's Note). An electrode wire is embedded from the subclavian vein to the heart. This electrode inputs electronic signals to the pacemaker, which becomes the pacemaker. Recently, the pacemaker product has a mass of 20g and a thickness of 6mm. It is so small that it is connected with electrode wires and embedded under the skin. The battery and control circuit are packed into a small container (box), which is a pure titanium product that is non-harmful to living organisms. The battery life must be maintained at a minimum of 6 years, so this small container (box) is required to have long-term stability and safety. Now, nearly 5,000 people in Japan have benefited.

The results of titanium treatment can also be seen in surgical instruments. Especially in long-term neurosurgery of more than 10 hours, forceps are also required to be lightweight, and hemostatic forceps and other hemostatic forceps must be made of titanium. Many dental treatment equipment, such as implants, surgical instruments for attachment, and vibrators for removing tartar, are made of titanium. In addition to implants (buries) and attachments, assistive equipment and wheelchairs are also being made of titanium. When part of a limb is missing due to illness or an accident, a prosthetic limb must be made to restore function. Since the main part is made of metal, it must be lightweight, durable (mainly corrosion resistance and fatigue damage resistance), and In terms of biological compatibility (Ni, Cr, etc.), it is being applied. In terms of wheelchairs, the main goal is to reduce the weight of the entire wheelchair, so some use titanium in almost all metal parts such as frames and wheels.