1. Early alignment of patients'dentition: Because of the superelasticity and shape memory properties of nickel-titanium alloy archwire and the low stress-strain curve, the nickel-titanium alloy archwire is routinely used as the initial archwire in the orthodontic system, so that patients' discomfort will be greatly reduced. Because there are several different straight wire orthodontic technologies, MBT technology recommends using 0.016 inch thermal activated nickel-titanium alloy arch wire (HANT wire), DEMON self-locking bracket technology recommends using copper-containing thermal activated nickel-titanium alloy arch wire (transformation temperature is about 40 degrees), O-PAK technology recommends using 0.016 inch superelastic nickel-titanium alloy arch wire for early alignment.
2. NiTi spring: NiTi push spring and pull spring are springs used in orthodontics. They have the characteristics of NiTi superelasticity. They are suitable for opening up the gap between teeth and pulling teeth in different directions during orthodontic treatment. The elongation of nickel-titanium coil spring by 1 mm can produce about 50 g of force. Nickel-titanium coil springs have high elastic properties and can produce relatively soft and stable persistent force under tension. The attenuation of force is very small, which can produce ideal orthodontic force for clinical tooth movement. It meets the physiological requirements. Compared with stainless steel wire of the same diameter, nickel-titanium wire spring has a high elasticity and a very low permanent deformation rate, and its released corrective force is 3.5-4 times less than that of stainless steel wire of the same diameter. Therefore, in the application of orthodontic treatment, patients not only have light pain, soft and lasting sensory strength, but also reduce the time of re-examination, shorten the course of treatment and improve the curative effect. It is a new excellent mechanical device in orthodontic treatment.
3. L-H archwire is developed by R. Soma of Japan and produced by Tomy Company. "LH" is named "Low Hysteresis". That is to say, when the arch wire is tied to the bracket, the difference between the stress produced when the arch wire is activated and the stress produced when the arch wire is slowly restored to its original state is very small. That is, the lag is very small. SOMA compares the stress-strain curves of LH arch wire with those of other Ni-Ti alloy wires. The lag range of L-H arch wire is the smallest. This characteristic makes the arch wire have the advantages of low load and sustained light force. At the same time, the initial slope of the curve is low, which indicates that the rigidity of the arch wire is low. The lag curves of other types of Ni-Ti alloy arch wire show that its rigidity is large. Obviously, L-H arch wire has obvious mechanical advantage. Because the proportion of titanium in the nickel-titanium component of LH wire is higher than that of the general nickel-titanium arch wire, it is called titanium-nickel wire, and its shock absorption effect has been proved by experiments. Another feature of the LH nickel-titanium wire is that it can be bent and heat-treated by heat treatment instrument. Therefore, the LH nickel-titanium wire can also complete the treatment from alignment, opening occlusion to closing gap, and the final completion stage. As long as the arch wire is taken out of the required shape at each stage, it can be shaped by heat treatment instrument and hardness is strengthened. At present, L-H arch wire is used to expand the arch in clinic to correct jaw opening, deviation and anti-jaw, because of its continuous stability and softness of strength, the effect is better. At the same time, J hook is often used to improve the weakness of the arch wire. Although MEAW technology has ideal effect in correcting upper malocclusion, the complicated bow wire bending often makes many doctors hesitate. Therefore, some physicians use rocking chair-type nickel-titanium arch wire with vertical traction of anterior teeth similar to mechanical system. Although this has similar effect, they always feel that compared with MEAW, each independent tooth movement is not as good as MEAW technology, because rocking chair-type nickel-titanium arch wire is a continuous arch wire, and there is no way to bend. Therefore, the angle of bracket bonding and the curvature of the rocking chair determine the angle of each tooth, unlike MEAW technology, the angle of each tooth has a more individual adjustment space. Using LH nickel-titanium bent rocking chair, and then using arch wire forming machine to bend back or forward in the mouth, the effect is quite ideal.
