Break the Matrix

I have a retainer that i can use for facepulling but i need to know what type of wire is ok to use as hooks. I went to a general hardware store and found coated steel wire but im pretty sure thats not really safe for the mouth so i need advice on what wire to use and if anyone knows where i can get some (preferably not ordering online) i would appreciate it. You may PM me or just reply to this thread as others may be having similar issues?

Thank you!