1. TiNi shape memory alloys used in medical field should not only make use of their shape memory effect or superelasticity, but also meet the requirements of chemistry and biology. Good biocompatibility. TiNi can form a stable passivation film with organisms.

2. At present, TiNi alloys are mainly used in medicine.
Dental orthodontic wires: Super elastic TiNi alloy wires and stainless steel wires are used as dental orthodontic wires, among which super elastic TiNi alloy wires are the most suitable. Stainless steel wire CoCr alloy wire is usually used for orthodontics, but these materials have the disadvantages of high elastic modulus and small elastic strain. In order to give an appropriate correction force, the arch should be machined before the correction, and the ligation and fixation require proficiency. If TiNi alloy is used as orthodontic wire, the plastic deformation will not occur even if the strain is as high as 10%. Moreover, stress-induced martensite makes the modulus of elasticity non-linear, that is, the fluctuation of orthodontic force is very small when the strain increases. This material is not only simple to operate and has good curative effect, but also can alleviate the discomfort of patients.

3. Scoliosis correction: Various scoliosis diseases (congenital, habitual, neurotic, rickety, idiopathic, etc.) not only suffer serious physical and mental injury, but also internal organs are oppressed, so it is necessary to carry out surgical correction. At present, this kind of operation is made of stainless steel Hayden rod. When the rod is placed in the operation, the orthodontic force of the fixed spine should be kept below 30-40 kg. Once the force is too large, the rod will be destroyed. As a result, not only the spine, but also the nerve will be damaged. At the same time, the orthodontic force will change with time after placing the rod. When the orthodontic force drops to about 30% of the initial value, surgery is needed to adjust the orthodontic force again, which causes great mental and physical pain to patients. The Harenton rod made of shape memory alloy only needs to be fixed by placing the orthodontic rod once. If the orthodontic force of the rod changes, enough orthodontic force can be restored by heating the shape memory alloy in vitro and raising the temperature to about 5℃ higher than the body temperature.

4. In addition, TiNi shape memory alloy is used to make various bone connectors, vascular clamps, coagulation filters and vasodilator elements in surgery. It is also widely used in stomatology, orthopaedics, cardiovascular, thoracic surgery, hepatobiliary, urology, gynecology and so on. With the development of shape memory, medical applications will be more extensive.