Recently, there has been a non-invasive cosmetic skin suture needle. The characteristic of the needle is that a titanium-nickel memory alloy wire is connected to the rear end of the suture needle as a suture thread and is plated with metallic zinc. Since the memory alloy wire has temperature memory, it will form a straight line when it reaches the original set temperature, showing the elastic properties of metal materials, which are not available in general metal materials. This method is used to suture the skin to make the surgical wound The healing is ideal. To achieve suture setting and muscle banding, suture setting and muscle banding are achieved by using the various suture needles mentioned above, using seam removal sutures, and hinge banding to pull out the metal wires in the healed wound like straight lines, making the person No foreign matter remains in the body. The feature of being able to pull out metal wires lies in the metal's temperature memory and superelasticity which is not affected by temperature.
Titanium-nickel alloys have two unique characteristics, shape memory and superelasticity, after being processed through different processes. Applying these characteristics to medical treatment, they will be made into medical sutures, which can be used for non-damaging muscles and skin according to clinical suture requirements. For internal suturing, temperature memory metal sutures can be used for those that need to be shaped, and super-elastic metal sutures that do not need to be shaped. After the wound is healed, the metal thread is pulled out so that no foreign matter is left in the human body, so that the wound does not have hard edges, pinholes, etc. Undesirable situation, it is a medical product with no damage after surgery.
Special properties of nickel-titanium alloy:
Shape memory characteristics (shape memory): Shape memory is when the parent phase of a certain shape is cooled from above the Af temperature to below the Mf temperature to form martensite, the martensite is deformed at a temperature below Mf, and heated to below the Af temperature, accompanied by inversion. Phase change, in which a material automatically returns to its original shape in its parent phase. In fact, the shape memory effect is a thermally induced phase transformation process of nickel-titanium alloys.
Superelasticity: The so-called superelasticity refers to the phenomenon that the specimen produces a strain far greater than the elastic limit strain under the action of external force, and the strain can automatically recover when unloaded. That is, in the parent phase state, due to the action of external stress, stress-induced martensitic transformation occurs, so the alloy shows mechanical behavior different from ordinary materials. Its elastic limit is much larger than ordinary materials, and it no longer obeys the tiger Gram's law. In contrast to shape memory properties, superelasticity has no thermal involvement. All in all, superelasticity means that the stress does not increase with the increase of strain within a certain deformation range. Superelasticity can be divided into two categories: linear superelasticity and nonlinear superelasticity. In the stress-strain curve of the former, the relationship between stress and strain is close to linear. Nonlinear superelasticity refers to the result of stress-induced martensitic phase transformation and its reverse phase transformation respectively during the loading and unloading processes within a certain temperature range above Af. Therefore, nonlinear superelasticity is also called phase transformation pseudoelasticity. The phase transition pseudoelasticity of nickel-titanium alloy can reach about 8%. The superelasticity of nickel-titanium alloys can change with changes in heat treatment conditions. When the archwire is heated above 400oC, the superelasticity begins to decrease.
Sensitivity to temperature changes in the oral cavity: The correction power of stainless steel wires and CoCr alloy dental orthodontic wires is basically not affected by the temperature in the oral cavity. The orthodontic force of superelastic nickel-titanium alloy dental orthodontic wire changes with changes in oral temperature. When the deformation amount is constant. As the temperature rises, the correction force increases. On the one hand, it can accelerate the movement of teeth, because the temperature change in the oral cavity will stimulate the blood flow in the areas where the blood flow is stagnant due to capillary stagnation caused by the orthodontic device so that the repair cells are fully nourished during the movement of the teeth. Maintain its vitality and normal functions. Orthodontists, on the other hand, cannot precisely control or measure orthodontic forces in the oral environment. The titanium-nickel memory alloy material is selected, and its temperature memory and superelastic properties that are not affected by temperature will play a unique orthodontic role in correction.
