I use an alloy of titanium, which means it is a metal made almost entirely of titanium but with a little bit of some other metals. Mine has a little bit of vanadium and aluminium.
We use it mainly because it is what other people use, this means it has been heavily tested and also has been used in the body lots before so we know it is safe, and we know lots about how it interacts with the body.
I was originally used to make parts of airplanes so it is well understood how it 3D prints which is useful to me too.
It is a strong material that is also tough, this means that is can be used for a long time and still look like new. This is useful in the body because we don’t want to have to open someone up to change a part.