What are the special properties of medical nickel-titanium guidewires?
Release Date:
05 Aug,2022
What special properties do medical nickel-titanium guidewires have?
The continuous advancement of medical technology has extended human lifespan. With the development of new applications for metal-grade alloys in outdoor and indoor environments, new progress has been made. What special properties do medical nickel-titanium guidewires have?
What special properties do medical nickel-titanium guidewires have?
1. Shape Memory: Shape memory refers to the phenomenon where the parent phase of a certain shape cools from above the Af temperature to below the Mf temperature to form martensite. When the martensite is deformed below the Mf temperature and then heated back to above the Af temperature, the material automatically recovers its shape in the parent phase through a reverse phase transformation. In fact, the shape memory effect is a thermally induced phase transformation process of NiTi alloy.
2. Superelasticity: Superelasticity refers to the phenomenon where the strain of a specimen under external force is much greater than the elastic limit strain, and the strain energy automatically recovers during unloading. That is, in the parent phase state, due to the external stress, a stress-induced martensitic transformation occurs, causing the alloy to exhibit mechanical behavior different from ordinary materials. Its elastic limit is much higher than that of ordinary materials and no longer follows Hooke's law. Compared to shape memory characteristics, superelasticity does not involve heat.
3. Sensitivity to intraoral temperature changes: The orthodontic force of stainless steel wires and CoCr alloy orthodontic wires is basically unaffected by intraoral temperature. The orthodontic force of superelastic NiTi alloy orthodontic wires changes with intraoral temperature. When deformation remains constant, the higher the temperature, the greater the orthodontic force. On one hand, this can accelerate tooth movement because temperature changes in the oral cavity stimulate blood flow in areas where orthodontic devices cause stagnation, providing sufficient nutrients to repair cells during tooth movement, maintaining their vitality and normal function. On the other hand, orthodontists cannot precisely control or measure the orthodontic force in the oral environment.
4. Corrosion resistance: Studies have shown that the corrosion resistance of nickel-titanium wires is similar to that of stainless steel wires.
5. Anti-toxicity: Ni-Ti shape memory alloys have a special chemical composition, being Ni-Ti equiatomic alloys containing about 50% Ni, which is known to have carcinogenic and tumor-promoting effects. Overall, the titanium oxide surface layer acts as a barrier, giving nickel-titanium alloys good biocompatibility. The surface TiXOy and TixNiOy inhibit the release of Ni.
6. Gentle orthodontic force: Currently commercial orthodontic wires include austenitic stainless steel wires, cobalt-chromium-nickel alloy wires, nickel-chromium alloy wires, Australian alloy wires, gold alloy wires, and titanium alloy wires. Regarding the load-displacement curves of these orthodontic wires under tensile and three-point bending tests, nickel-titanium alloys have the lowest and flattest unloading curve plateau, indicating their ability to provide lasting and gentle orthodontic force.
7. Good shock absorption characteristics: The greater the vibration caused by chewing and bruxism on the archwire, the greater the damage to the tooth root and periodontal tissues. According to different archwire attenuation experiments, the amplitude of stainless steel wires is greater than that of superelastic NiTi wires. The initial amplitude of superelastic NiTi archwires is only half that of stainless steel wires. Good vibration and shock absorption characteristics of archwires are very important for dental health, while traditional archwires such as stainless steel often exacerbate root resorption.
Keywords:
Medical Nickel-Titanium Guidewire
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