Titanium alloy wire is used as the raw material to make titanium straight wire orthodontic braces, which have become the mainstream orthodontic braces used in orthodontic clinics. Its alignment phase can produce weak and lasting forces to complete the tilt, rotation, depression and other tooth movement to achieve the purpose of aligning the teeth, and patients with moderate to severe crowding often need 3 ~ 6 months to complete alignment. Nickel-titanium wire has high elasticity but low stiffness and high brittleness, which may lead to side effects such as unnecessary deformation of the dental arch, prolonged treatment and poor results.
How to make full use of the high elasticity of nickel-titanium wires to align the teeth, while avoiding the side effects of insufficient rigidity on the teeth has been a concern of orthodontists. Lin Juxiang et al. applied the nickel-titanium alloy round wire as aligning auxiliary arch in Begg's orthodontic technique and found that the aligning auxiliary arch and the main arch wire could each play an independent role and ring interference, and the main arch and auxiliary arch could not only give full play to their respective advantages, but also coordinate with each other, so that the orthodontic procedures of opening the occlusion and decongesting and aligning the anterior teeth could be carried out smoothly at the same time.
In the three types of malocclusion patients, the time taken to align the teeth in the NiTi auxiliary arch group was significantly shorter than that in the corresponding control group, and the difference was statistically significant (P<0.05 or 0.01), and none of the cases had arch deformation, whereas in the control group, four patients with An I and two cases with An I had arch deformation after the completion of alignment. This indicates that when using straight arch aligners, compared with the traditional use of nickel-titanium alloy round wire as the main arch wire for alignment, nickel-titanium alloy round wire as an auxiliary arch with high stiffness main arch wire can achieve better treatment results. In this case, the main arch wire plays the role of strengthening the whole tooth support and stabilizing the arch shape, while the nickel-titanium auxiliary arch releases a gentle orthodontic force to guide the ectopic teeth to move to the normal position gradually.
In addition, in other stages of orthodontic treatment, there are often cases where the teeth are displaced after the brackets fall off and the original main arch wire is difficult to enter the sulcus after re-bonding, etc. In clinical practice, we found that the use of nickel-titanium alloy round wire auxiliary arch to align the displaced teeth while retaining the original main arch wire can successfully continue the original treatment plan and complete the realignment of the displaced teeth with good results.
