Advantages of titanium in medical treatment
Titanium has a low density of 4.5 g / cubic centimeter, which is about 60% of steel. Its light weight can increase the comfort and activity function of patients. It has high strength and high specific strength. In surgery, the strength level of implants should be higher than that of natural bone. The yield strength of titanium and titanium alloy is 207-1379mpa, while that of natural bone is 83-117mpa, so it can meet the performance requirements. Non magnetic; The thermal conductivity is small, only 1/5 of steel, 1/3 of aluminum and 1/2 of copper; The coefficient of linear expansion is small, which is 1/5 of carbon steel and half of stainless steel; The coordination of elastic modulus between implant and natural bone is very important to prolong the service life, and natural bone must be bent continuously. The low elastic modulus of bone is about 16.5 × 103mpa, while titanium is half of cobalt and stainless steel, i.e. 102.7-113.3 × 103MPa。
Titanium has low elastic modulus, which is very important for human body to accept implants. At the same time, it reduces the additional stress on the bonding interface and prolongs the service life of the system. Low damping resistance; Good heat resistance, and good mechanical properties can still be maintained at about 500 ℃; Good corrosion resistance .
Based on the above characteristics, this provides conditions and foundation for the application of titanium in dentistry, human transplantation, human orthopedics, pharmaceutical equipment, medical devices and other aspects, and has a good prospect. At present, the main titanium alloys used are: pure titanium, Ti-6Al-4V, ti-6al-4veli, Ti-6Al-7Nb, new type β Type titanium alloy, Ti Ni alloy, etc. This paper discusses the application of titanium in these aspects.
Dental applications of titanium and titanium alloys
Because titanium has excellent corrosion resistance and human affinity, and considering metal allergy and specific strength, it is suitable for application in dental field.
Metals used in dental surgery began with amalgam and metal crowns in the 1920s. Gold, silver and palladium alloys were mainly used in the 1960s. After the 1970s, stainless steel became the most commonly used material for permanent and removable instruments for orthodontics. Titanium casting technology was popularized and applied in the 1990s. Dental casting with titanium precision casting machine has the characteristics of high dimensional accuracy, no bubbles and shrinkage cavities
Among the metal materials used for human hard tissue repair, titanium has the closest elastic modulus to human tissue, which can reduce the mechanical incompatibility between metal implants and bone tissue. The thermal conductivity of titanium is the lowest among all metal materials used for dental repair. See Table 1. Low thermal conductivity can reduce the thermal stimulation to the dental pulp of crown teeth, which is very important for dental repair. Titanium inlays and crowns can protect dental pulp and avoid cold and hot stimulation.
In terms of material, most dental titanium was pure titanium, but its strength was insufficient, it was difficult to grind, it had poor wear resistance, it was easy to produce casting defects and unstable quality. Titanium alloy has high strength, and the most commonly used is Ti-6Al-4V alloy. However, because metal V is harmful to human body, Nb is used instead of V, and Ti-6Al-7Nb alloy is successfully developed. It has excellent corrosion resistance, is basically harmless to human body, and has other advantages such as strong plasticity and excellent abrasiveness, which has been recognized by ASTM standards. At present, hyperelastic Ti Ni alloy is being widely used in tooth straightening.
Since the 1980s, developed countries have begun to study the application of titanium in dental restoration, first for dental implants, and then for denture brackets, crowns and bridges, and orthodontics. At present, titanium can be used as crowns, crown nails, fixed bridges, porcelain fused to metal bridges, bonding bridges, denture clasps, bases, connecting devices, and reinforcing devices. Almost all metal parts of dentures can be made of titanium. The research of titanium and titanium alloys has become a hot spot in the research of dental applied alloys.
Titanium alloy porcelain teeth can well restore the shape and function of teeth, with high strength, beautiful appearance, stable color, smooth surface, wear resistance and corrosion resistance. It is a permanent restoration, which is suitable for all fixed teeth, especially for people who are sensitive to nickel ions. It has been widely used in tooth restoration.
Application of titanium in transplantation
Artificial joint and artificial bone substitute materials should have the following basic properties: light and high-strength materials, with biocompatibility and corrosion resistance, the tissue reaction of implants in vivo does not cause material degradation, and the fatigue and damage caused by repeated stress are few.
The most important properties of metal implants are shaping, machining and polishing. They must maintain their functions within the expected service life and will not deteriorate when subjected to fatigue, wear, corrosion and impact loads. Titanium and titanium alloys meet all the above requirements .
The first used artificial joint materials, such as dental support powder, polypropylene, plexiglass, etc., have low strength, easy folding and poor biocompatibility. Later, stainless steel was used, but the proportion of stainless steel was large, about twice that of human bones, and corrosion and fracture would occur under the action of receptor fluid in the body. Co Cr alloy is also an excellent artificial joint material, but unfortunately, cobalt and chromium are toxic to human body. Titanium and titanium alloy are ideal artificial joint materials because of their small specific gravity (similar to that of human bone), high strength, good machining and excellent corrosion resistance.
Titanium materials for surgical transplantation are mainly pure titanium and ti-6al-4veli alloy. Recently, Ti-6Al-7Nb and ti-13nb1-13zr, which have good affinity with human body, have also been recognized by ASTM standards.
When titanium is used to make human bone, cells can regenerate on it, and bones can grow. Titanium has good affinity with human bone, epithelium and tissue. In order to improve the surface quality of implants connected with human bone, bioceramic coating on the roughened surface is also a more effective method.
At present, titanium and titanium alloys have been widely used in artificial bone joints, artificial bones, joint foot plates, broken bone fixers, bone marrow nails, artificial heart valves, skulls and so on. According to statistics, China's annual demand for titanium alloy artificial joints exceeds 5000 sets, and the clinical application effect is good.
Application of titanium in orthopedics
The elastic modulus of medical titanium alloy is closer to human bone than that of stainless steel, which is suitable for human orthopedic surgery.
In orthopedics, titanium nickel shape memory alloy is often used. Studies have shown that nt-sma is a new material that integrates the properties of wear resistance, corrosion resistance, shape memory effect, pseudo elasticity and acoustic damping. It is increasingly widely used in orthopedics. In addition to the commonly used bone plates, intramedullary nails, mandibular internal fixation, scoliosis correction, etc., Shanghai Changhai Hospital has carried out a series of design and clinical applications of nt-sma, such as NT patellar concentrator, NT arc fork nail, NT Archer NT flying Dragonfly apparatus (specially designed for sacral reconstruction) has achieved satisfactory results.
As for titanium alloy materials applied to human body, countries are still making efforts to explore and seek new titanium alloys that are more safe and reliable for the benefit of people all over the world.
Application of titanium in pharmaceutical industry
Titanium is mainly used to make containers, reactors and heaters in the pharmaceutical industry.
In pharmaceutical production, the equipment is often exposed to hydrochloric acid, nitric acid, sulfuric acid and other inorganic acids, organic acids and their salts. The equipment is often damaged due to corrosion, and the product quality is affected by iron ion pollution caused by steel equipment. The use of titanium equipment can solve these problems. For example, penicillin esterification kettle, saccharification tank, chloramphenicol film evaporator, anagin reactor, Metol filter, dimethyl sulfate cooler, liquid medicine filter, etc. have precedents for selecting titanium materials. The quantity and quality of the produced liquid medicine are constantly improving, and the quality is completely in line with the provisions of the Chinese Pharmacopoeia.
Application of titanium in medical devices
Titanium and titanium alloys have good corrosion resistance. Titanium is non-toxic and non-magnetic. It is a good choice of materials for medical devices.
In the history of surgical instruments, the first generation of surgical instruments were mostly made of carbon steel, which was eliminated because the performance after electroplating could not meet the requirements of clinical use. The second generation is austenitic, Ferritic and martensitic stainless steel surgical instruments, but the chromium in the stainless steel composition is toxic, and the falling chromium coating has a certain impact on the human body. Therefore, the third generation - titanium surgical instruments [3]. Titanium is especially suitable for microsurgery because of its light weight. Titanium has corrosion resistance, good elasticity, no deformation, etc., and is resistant to repeated cleaning and disinfection, and the surface quality is not affected; Non magnetic, which can eliminate the threat of damage to small and sensitive implanted electronic devices, makes titanium surgical instruments more and more widely used [3]. At present, it has been used to make surgical blades, hemostatic forceps, scissors, electric bone drills, tweezers and so on.
In medical instruments, titanium vascular suture needle and sternum suture, titanium filter of oxygen filter, one of cardiac surgical instruments, titanium is used as electrode in ECG machine, and titanium is used as incubator in in in vitro culture machine; The probe of medical ultrasonic pulverizer, the automatic controller of blood transport box, and titanium instruments used in ophthalmic surgery are in good use at present
