1. In 1940, gold arch wire, cobalt-chromium alloy wire and stainless steel round wire.
2. In 1960, martensite stabilized alloys: mostly nickel-titanium alloys were made after deformation in martensitic state. This kind of arch wire has low stiffness and can produce lighter orthodontic force. There is no martensitic transformation caused by stress or temperature, so there is no memory effect and superelasticity.
3. In 1980, Chinese and Japanese nickel-titanium alloy archwires were austenite-activated alloys: austenite was present in any state, and there was no martensite state caused by temperature in or out of the mouth. The martensite state could only be caused by stress and had superelasticity, but did not have shape memory function. This kind of arch wire has excellent resilience and low stiffness, and can produce weak orthodontic force. The most important feature is that the force generated is constant from the initial start to the final stage, and the effect is better in the treatment of early teeth irregularity. The disadvantage is that it can't be bended and welded at room temperature. If the company is used as the main arch wire, it often causes unwanted expansion or contraction of the arch, and it is difficult to establish a good arrangement of premolars and molars.
4. In 1990, martensite activated nickel-titanium alloy: TTR is lower than or very close to the oral temperature, and exists in a multivariate state at room temperature, which is easy to deform. When placed in the oral cavity, martensite caused by stress and room temperature simultaneously transforms to austenite, that is, shape memory function and superelasticity exist. It is easy to deform at room temperature (about 25℃) and below, but when it reaches a certain temperature (about 32℃), it will return to the original preform, showing the characteristics of shape memory and superelasticity. The Smart Brand of Beijing Saint Matt Technology Co., Ltd. and NitinolHA Brand of 3M Company are typical representative products. Thermally activated nickel-titanium archwire can be easily shaped and placed in the bracket because of this characteristic. When activated by the temperature and heat of the receptor in the oral cavity, it can produce shape restoring force and provide the required strength for orthopedics. Because the thermally activated nickel-titanium orthodontic wire has the characteristics of "softening in cold and becoming elastic in heat activation", patients can change the orthodontic force by means of cold and hot water in mouth under the guidance of doctors, which is more convenient for Orthodontists and reduces the discomfort of initial orthodontic treatment.
5. Gradedthermodynamic: Increased thermodynamic nickel-titanium alloy: TTR temperature is higher than oral temperature, about 40 degrees Celsius, so that when the nickel-titanium arch wire is placed in the mouth, it is still in a pluralistic state, the arch wire is relatively soft, and austenitic transformation occurs only when the mouth contains hot water. Therefore, the orthodontic force is weaker and can be used as the initial arch wire for adult patients and periodontal patients. The copper-nickel-titanium wire produced by Omcro and the Japanese low-lag L-H nickel-titanium arch wire have this property.
