Classification of Nickel-Titanium Alloy Wires Evans and Durning Classification Classification of nickel-titanium alloy wires-Evans and Durning classification 1) In 1940, gold arch wire, cobalt-chromium alloy wire and stainless steel round wire. 2) Martensitic stabilized alloys in 1960: most of them are made of nickel-titanium alloys after deformation in the martensitic state. This kind of arch wire has low rigidity and can produce light orthodontic force. There is no martensitic transformation caused by stress or temperature, so there is no memory effect and superelasticity. 3) In 1980, China Nitinol and Japan Nitinol archwires were austenitic activated alloys: they were austenitic in any state, and did not have martensitic state caused by temperature when placed inside or outside the mouth. Martensitic state could only be caused by stress,titanium round bar, and had superelasticity, but did not have shape memory function. The archwire has excellent resilience and low stiffness, and can produce weak orthodontic force. It is characterized by a constant force from the initial start to the final stage,titanium sheet grade 5, and has a better effect in the treatment of early tooth irregularity. The point removal can not be bent and formed at normal temperature, and is not easy to weld. If this wire is used as the main arch wire, it will often cause unwanted arch expansion or arch contraction, and it is difficult to establish a good premolar and molar alignment. 4) In 1990, nickel titanium wire ,3d titanium wire, the martensite activated nickel-titanium alloy: TTR is lower than the oral temperature or very close to the oral temperature, it exists in a multi-component state at room temperature and is easy to deform. When it is placed in the oral cavity, the martensite caused by stress and room temperature transforms to austenite at the same time, that is, it has shape memory function and superelasticity. It is easy to deform at room temperature (about 25 oC) and below, and when it reaches a certain temperature (about 32 oC), it will return to its original shape, showing shape memory and superelasticity. Smart brand of Beijing Shengmat Technology Co., Ltd. and Nitinol HA brand of 3m Company are typical representative products. Because of this property, the heat-activated nickel-titanium archwire can be easily shaped and placed in place in the bracket when it is maintained at room temperature or below, and when it is activated by body temperature and heat in the mouth, it can produce shape recovery force and provide the required force for orthopedics. Because the heat-activated nickel-titanium orthopedic wire has the characteristic of softening when cold and becoming elastic when activated by heat, a patient can change the orthodontic force by holding cold and hot water in the mouth under the guidance of a doctor, which is more convenient for the orthodontist to correct and reduces the discomfort of initial orthodontic treatment. 5) Graded thermodynamic: increased thermodynamic nickel-titanium alloy: the TTR temperature is higher than the oral temperature, about 40 oC, so that when the nickel-titanium arch wire is placed in the oral cavity, it is still in a multi-element state,6al4v titanium bar, the arch wire is relatively soft, and the austenitic phase 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 patients with periodontal disease. The copper-containing nickel-titanium archwire produced by Omcro Company and the low-hysteresis L-H nickel-titanium archwire produced by Japan have this property. Contact us Back to Sohu to see more Responsible Editor:.