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Clinical application of Nitinol alloy wire

  1. Due to the hyperelasticity, shape memory performance and low stress-strain curve of Nitinol alloy bow wire, Nitinol alloy bow wire is currently routinely used as the bow wire that is initially incorporated into the orthodontic system, so that patients' discomfort will be greatly reduced.Because there are several different straight wire bow rectification technology, MBT technology is recommended to use 0.016 inches thermal activated nickel titanium arch wire (HANT silk), DEMON self-locking braces technologies recommended by Omcro company production of thermal activated nickel titanium alloy containing copper arch wire (phase change temperature about 40 degrees or so), O - PAK rectification technology is recommended to use 0.016 inches hyperelastic nickel titanium alloy used in early row of neat the arch wire.

  2. Niti spring: niti push and pull spring is a kind of spring used for orthodontic teeth. It has the special super elasticity of niti, and is suitable for orthodontic treatment to expand the space between teeth and pull teeth in different directions.The niti coil spring can produce a force of about 50g by stretching by 1mm.The ni-ti coil spring has a high elastic property, which can produce a relatively soft and stable sustained force in the tensile state.The reduction of force is very small, which can produce the ideal orthodontic force for clinical tooth movement.Meet the physiological requirements.Niti wire tension spring high elasticity, permanent deformation rate is very low, compared with the same diameter of stainless steel wire, the release of the correction force difference of 3.5-4 times.Therefore, in the application of orthodontic treatment, the patient not only has light pain, soft and lasting sensation, but also reduces the time of return visit, shortens the course of treatment, and improves the curative effect, which is a new excellent mechanical device in orthodontic treatment.

  3. L-h bow wire is developed by Dr. Soma in Japan and produced by Tomy.LH is named after LowHysteresis that is, the stress that occurs when the bow wire is activated when the bow wire is ligated to the bracket, and there is a very small difference between the stress that occurs when the bow wire is moved and when the bow wire slowly returns to its original shape.The lag is small.SOMA and compared the LH arch wire and other nickel titanium alloy wire stress strain curve of L - H minimum range of the lag of the arch wire, this feature makes the arch wire has the advantage of low load and constant light force, low initial slope of the curve at the same time, show that the stiffness of the arch wire is low, the rest of the type of nickel and titanium alloy hysteresis curve indicates that the arch wire, which has less rigidity are clearly L - H arch wire has obvious mechanical advantage.As the content of titanium in LH wire is higher than that in general niti wire, it is called niti wire, and experiments have proved that it has a strong shock absorption effect.LH nickel titanium wire of another characteristic can be bending, and can be used to heat treatment equipment heating sizing, therefore LH nickel titanium wire can also be from a row of neat flat, open bite to close the gap, and finally completed stage, the upper one is the arch wire can complete treatment, as long as each phase remove arch wire bending shape needed for good, then use heat treatment of the instrument will be shaped, strengthen the hardness.At present, l-h arch wire is used in clinical treatment of arch expansion to correct open jaw, partial jaw and anti-jaw, which has a good effect due to its continuous stability and softness of force.At the same time, J hook is often used to improve the weakness of bow wire.Although the MEAW technique is also ideal for correcting malocclusion, the complexity of wire bending often discourages many physicians.

So some physicians to adopt rocking chair similar to that of the mechanical system model of nickel titanium arch wire with front teeth vertical traction, though this has a similar effect, but always felt that, compared with MEAW individual tooth MEAW technique is better than moving aspect, the reason is that rocking chair type nickel titanium wire is a continuous arch wire, and also have no way to bend.Therefore, the Angle of the groove bonding and the curve of the rocker determines the Angle of each tooth, unlike the MEAW technique where the Angle of each tooth has more room for individual adjustment.Using LH nickel-titanium bending rocking chair and bending back or forward with bow wire shaper in the mouth, the effect is quite ideal.Although I have been frequently exposed to the term thermal activation, I know little about it. I consulted relevant knowledge in a book, hoping to increase everyone's understanding of thermal activation of nickel-titanium wire.

There are two main aspects to describe the hardness of niti wire. Martensite state refers to the state with the softest bow wire and the highest degree of bending.The austenite state is the hardest state of the bow wire.These are the bow wires at room temperature.When the martensitic bow wire is heated, it will change into austenite state, which is called thermal activation.Although similar changes occur in austenitic bow wires, the degree of change is small and almost imperceptible.

The bow wire in martensite state is much more elastic than that in austenite state, that is, it has a strong ability to recover to the initial shape after deformation and is not easy to be broken.The austenitic bow produces 42 percent more force than the martensitic bow, but the martensitic bow releases more constant force.

The elastic deformation capacity of the two types of bow wires is similar, but the markovnikov state bow wires can undergo temporary deformation at room temperature and return to the initial shape at the oral temperature environment, thus greatly increasing the actual deformation range.

Thermally activated bow wire is an ideal choice for early treatment. Due to its wide range of actual deformation and its soft and durable strength, it is suitable for initial bow wire.In theory, it is perfectly positioned in the socket of a badly dislocated tooth.Both round and rectangular wires can be used as initial bow wires.

Advantages of heat-activated niti wire:

  1. less pain:

    This is due to gradually increasing force and eventually light force. Controlled thermal activity prevents a sudden increase in force during the consumption of hot drinks or hot food. Patients can relieve excessive force by drinking cold water.

  2. The supporting groove falls off and the ceramic supporting groove breaks less:

    This is due to the gradual increase in the force of the light force.This bow wire is ideal for ceramic brackets.The bow wire can maintain its martensitic state at low temperature, which is helpful to further reduce the initial force and make the bow wire easy to place.

  3. less bow wire breakage:

    Because it is softer than the austenite bow wire, it is not easy to break under stress.

  4. Reduced working time beside chairs:

    Because of the large deformation range, the number of adjustment and the number of wire replacement can be reduced.

  5. shortened treatment time:

    Preliminary studies have shown that early torque control and the use of light and sustained force can shorten the total treatment time, and early use of rectangular wires on straight wire brackets can cause teeth to move directly to the desired position.

Disadvantages:

If the arch shape cannot be maintained effectively, it is best not to use it to close the gap, because the force of the elastic ring and the spiral spring will deform the arch wire and tilt the teeth.In addition, although the heat-activated niti wire can shorten the working time beside the chair, it takes longer to move the teeth. Doctors should be patient and wait for the wire to fully play its role.Objective to compare the stiffness, elasticity, strength and fatigue resistance of austenitic steel wire, American orthodontic steel wire, imitation austenitic steel wire, domestic stainless steel wire and domestic stainless steel wire after heat treatment.Methods the elastic modulus, elastic limit, rebound Angle, tensile strength, torsional strength and fatigue strength of five kinds of orthodontic steel wires were tested and compared.

Results the stiffness, elasticity, strength and fatigue resistance of five kinds of orthodontic steel wires were compared.Conclusion steel wire should be selected according to the needs of different treatment opportunities and different properties of steel wire.

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