When you find out that you need braces, it’s usually not the greatest feeling. The idea of having metal connected to your teeth for a year or more is not what you would necessarily wish for even if it will give you a great smile. It’s probably normal to wonder about the material they use for braces. What is that metal they are putting in your mouth? Can it rust or corrode in there? How strong is it? Is it stiff or flexible? If they’re putting metal in your mouth for over a year, you ought to know something about it.

People have tried to straighten teeth with some form of braces for a long time. According to the American Association of Orthodontists, ancient human remains have been discovered with metal bands around their teeth. Researchers have also found later examples of teeth with metal on them that could be identified as gold. These discoveries of metal on very old teeth may have been early attempts at moving teeth with braces.

For a material to be in the mouth for a long time, gold is actually a pretty good choice because it doesn’t corrode easily. It’s also a relatively soft metal so it can be bent easily around the teeth. But gold is probably too soft to be the best material for braces. Braces made entirely of gold would tend to loosen over time and would need a lot of adjusting.  They would also be way too expensive!

As the centuries went on, different metals were used such as copper, silver, zinc, and brass. Copper, silver, and zinc are elements because they are made of only copper, silver, or zinc atoms.

But brass is a mixture of the metals copper and zinc. When two metals are thoroughly mixed, the metal that results is called an alloy. The alloy has characteristics that are different from either of the original metals that are mixed. It might be more flexible, stronger, a different density or have a different melting temperature.

These days, the two main metals used for braces are stainless steel and nitinol which are both alloys. Stainless steel is the most common metal used for braces. It is often used for both the brackets attached to the front of the teeth and for the wire that goes across the teeth that is attached to the brackets.

Regular steel is made from iron with a small amount of carbon and sometimes some other elements. But stainless steel is an alloy made of iron and the metal chromium. Stainless steel is good for braces because it doesn’t rust like regular steel. But stainless steel braces do have a tendency to get a little loose over time. This means that you have to go to the orthodontist to have your braces adjusted and tightened.

This is where the metal nitinol comes in. Nitinol is an alloy made from the metals nickel and titanium. It is also commonly called “memory wire”. Nitinol wire can be formed into a particular shape using high temperature. Later, when the wire is at room temperature the shape can be bent and changed. But if the wire is warmed again, it will return to its original heated shape.

NASA developed nitinol to help extend the flexible solar panels on satellites. When the nitinol gets warm enough it returns to a previous shape and helps extend the arms holding the satellite’s solar panels.

Now, NASA technology is being used in braces.

Nitinol wire is used in braces because the orthodontist can create a shape that is just right for your teeth and how they need to move. The warmth of your mouth causes the wire to go back to its original shape. This movement helps bring your teeth to the position they should be.

Check out this video to see a piece of nitinol wire go back to its original coiled shape by being warmed by hot water.

Using nitinol wire usually means that your braces can come off sooner. So don’t be mad when science and chemistry are all up in your face.