Why is Nitinol used in braces?
What is Nitinol?
Commonly known as nickel titanium, Nitinol is a type of metal alloy that is associated with superelasticity, also known as ‘“shape memory”. What this means is that the metal is able to remember and return to its original shape when heated. It is also able to withstand extreme stress without changing its shape due to its elastic properties.
What is Nitinol used for?
Nitinol has several uses, but is widely renowned for its use in orthodontic and endodontic practices. Nitinol is used for the wiring and brackets that connect teeth. It’s the perfect choice for braces because the alloy is able to bend and shape itself to the requirements of the patient’s tooth formation.
In endodontics, Nitinol is used during root canals, specifically for cleaning and helping to shape the root canal.
Why is Nitinol used in braces?
A braces’ main function is to gently shift and position teeth into their new positions. This is done using wires and brackets that exert just enough force to slowly and gently push and pull the teeth into their new formations. Nitinol wire is perfect for performing this task as it has a high recoverable strain modulus – meaning the wire will continuously attempt to return to its original form and in turn, moving the teeth into position. Once the force is too low to move the teeth, the braces are removed and that part of the treatment is complete.
The advantages of Nitinol for braces over traditional wiring
As the Nitinol is able to remember its former shape, it becomes the perfect material for braces.
Traditional stainless steel wires are likely to lose tension as time passes, meaning you will have to return to your orthodontist to get the wire adjusted. With nitinol wire, your orthodontist will mold the wire to fit the current formation of your teeth. The heat from your mouth will begin to affect the nitinol wire and eventually return to its original shape. This means that as the nitinol wire “straightens out”, it is in turn, shifting your teeth into their new positions.
The biggest advantage of nitinol is less frequent trips to your orthodontist thanks to the alloy being able to “remember” and eventually return to its original form.
What is shape memory?
Shape memory is a term often applied to materials that are able to “remember” and return to their original form. In the context of braces, nitinol is the preferred material to perform such a task.
How does shape memory work?
The easiest way to describe memory shape is to liken it to an elastic band. When you stretch an elastic band, the molecules inside it tear apart but do not break. When you stop stretching it, the molecules return to their original form (pulling back together again).
Shape memory works differently to elasticity, it relies on heat to return to its original form. For example, let’s say you bend an object made from a shape memory alloy (nitinol) it will remain that way because you have deformed its crystalline structure. It will not return to its original form unless heat is applied. When this happens, the crystalline structure reactivates and works to transition itself back to its original form.
Why is stainless steel used for braces?
Stainless steel has long remained the most trusted material for creating archwires since the early 1900s. Steel was preferred over noble metals because it was cheaper and offered better formability – essentially meaning it is easier to shape and mould to the patient’s mouths.
Stainless steel archwires main advantages are that they are corrosion-resistant and offer fantastic formability.
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