1. Characteristics of shape memory: shape memory is when the parent phase of a certain shape is cooled above the temperature of Af to below the temperature of Mf to form martensite, and then the martensite is deformed below the temperature of Mf and heated below the temperature of Af. With the reverse phase transformation, the material will automatically recover its shape in the parent phase. In fact, the shape memory effect is a thermally induced phase change in Nitinol alloys.
2. Superelasticity: the so-called superelasticity refers to the phenomenon that the strain of the sample under the action of external force is much larger than the strain of the elastic limit strain, and the strain can be recovered automatically when unloading. In other words, under the condition of parent phase, the stress-induced martensitic transformation occurs due to the action of applied stress.
3. Corrosion resistance: studies have shown that the corrosion resistance of nickel-titanium wire is similar to that of stainless steel wire.
4. Sensitivity to temperature changes in the oral cavity: the orthodontic power of stainless steel wire and CoCr alloy orthodontic wire is basically not affected by the oral cavity temperature. The orthodontic force of hyperelastic Nitinol dental orthodontic wire varies with the change of oral temperature. When the deformation is constant. As the temperature increases, the orthodontic force increases.
5. Anti-toxicity: in general, the surface layer of titanium oxidation ACTS as a barrier, making the ni-ti alloy have good biocompatibility. TiXOy and TixNiOy of the surface layer can inhibit Ni release.
6. Gentle orthodontic force: currently the commercial application of dental orthodontic wires include austenitic stainless steel wire, cobalt-cr-nickel alloy wire, nickel-chromium alloy wire, Australian alloy wire and titanium alloy wire. The load-displacement curves of these orthodontic wires under tensile and three-point bending test conditions.
7. Good shock absorption: the greater the vibration caused by chewing and night molars to the arch wire, the greater the damage to the root and periodontal tissues. Through different attenuation experiment results, the study found the arch wire stainless steel wire vibration amplitude is larger than hyperelastic nickel titanium silk, super elastic nickel-titanium arch wire the initial vibration amplitude is only half of stainless steel wire, good vibration and shock absorption characteristics of the arch wire is important for the health of the teeth, and traditional arch wire such as stainless steel wire, tend to increase the root absorption.
