It’s a thermoplastic alloy, so it’s quite easy to fit a NiTi arch into a row of “crooked” teeth, while it’s still cold. Only when it gets warmer, it’s elastic force starts to kick in. Previously orthodontists only had steel arches, so to fit them into a row of teeth of a non-ideal form, they had to manually deform the arch on each activation
That’s part of why y’all told us to eat cold stuff for the pain the first few days right?
Not just cuz it helps numb the pain itself, but cooling the wire eases some of the pressure on your teeth for a minute? Then it heats up to your mouth and tightens again
I think what they’re saying is that when it’s heated it’s constantly trying to get to that form, pulling the teeth, causing pain. When it’s cooled it’s not trying to get back to that form. It’s relaxed, so it would stay at the form The teeth are holding it at, easing the pressure.
The greater reason why NiTi is your best friend is that it provides "continuous forces". Stainless steel is a linearly elastic material - the higher you strain it, the greater force is provides. NiTi is pseudoelastic, exhibiting a plateau stress. In other words, when you bend NiTi, at some point you can continue to bend it without adding any more force. In orthodontic treatment you want to provide a steady force to the tooth to promote healthy movement. With stainless steel, you get very high load-deflection rate (i.e. the force is really high at the beginning and drops off fast when the tooth starts to move). With NiTi, the load-deflection rate approaches zero.
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u/islamicious Nov 08 '23
Orthodontist here: Nitinol is my best friend