Surface nanostructures orienting self-protection of an orthodontic nickel-titanium shape memory alloys wire

Abstract

Shape memory alloys (SMA) have been applied to a wide variety of applications in a number of different fields such as aeronautical applications, sensors/actuators, medical sciences as well as orthodontics.It is a hot topic to enhance the anti-corrosion ability of orthodontic wires for clinical applications. In this letter, a very nice fractal structure, micro-domains with identical nanometer sized grooves, was obtained on the surfaces of the orthodontic wires with an oxygen plasma and acid corrosion. The concave parts of the grooves were dominated by titanium and convex parts were the same as the bulk wires. The micro-nano fractal structure generated a hydrophobic surface with the largest contact angle to water being about 157°. The titanium dominated nanolayer and the hydrophobicity of the surface resulted in jointly the great improvement of the anti-corrosion ability of the orthodontic wires. Because the fractal structures of the wires were formed automatically when they immersed in acidic environment, hence, the self-protection of the oxygen plasma-treated orthodontic wires in acidic environment indicates their potential applications in orthodontics, and should be also inspirable for other applications of SMA materials.nanostructures, self-protection, orthodontics, nickel-titanium shape memory alloys wire Shape memory alloys (SMA) have been applied to a wide variety of applications in a number of different fields such as aeronautical applications, sensors/actuators and medical sciences because of their very unique properties, super-elasticity and the shape memory effect (originating from the solid-to-solid phase transformation from martensite to austenite). The first application of SMA to orthodontics could be tracked back to the 1980s, in which Andreasen and Hilleman [1] used nickel-titanium alloys wires to align the teeth. The success of their attempt accelerated the application of various SMA wires in orthodontics (Figure 1). The SMA wires for orthodontics require the wires with not only superelasticity, but also good bio-compatibility and better anti-corrosion ability. The corrosion of the nickel-titanium orthodontic wire will influence not only the superelasticity of the wire and its clinical treatments, but also influence the bio-compatibility. For example, the corrosion products such as Ni 2+ of the wire adsorbed by gum will make the gum become black, and some people are even allergic to Ni 2+ . Hence, it is rather important to enhance the anti-corrosion ability of orthodontic wires for clinical applications.Orthodontic wires stay in oral environment every day, i.e., in a "water" (saliva) environment. There is a little influence of neutral and alkaline foods to the wires by virtue of our clinical experiences. But acidic foods (e.g., vinegar and Chinese sauerkrauts) are corrosive due to the long stay of the wires in mouth. As we know, the corrosion of alloys takes place when the corrosion "micro-

The applications and research progresses of nickel–titanium shape memory alloy in reconstructive surgery

“…Compared with the biomedical criteria for choice of implanting materials, porous NiTi alloy is satisfying to a great degree [57]. In the study of Nie [58], a very nice fractal structure, microdomains with identical nanometer sized grooves, was obtained on the surfaces of the orthodontic wires with an oxygen plasma and acid corrosion. The concave parts of the grooves were dominated by titanium and convex parts were the same as the bulk wires.…”

Effect of Co on the martensitic transformation, crystal structure and magnetization of Ni52.5Mn23.5Ga24 based ferromagnetic shape memory alloys

“…The martensite phases in all the alloys are domained in three different orientations, the domain boundary was determined to belong to the family of {1 1 2} lattice planes. a magnetic field than thermally controlled shape memory alloys [5,6], which makes them highly interesting for many novel technological applications especially as actuators [7,8]. The induced strain from the magnetic field forces a rearrangement of the crystallographic orientation of the martensitic variants formed during the thermoelastic martensitic transformation [9].…”