I’m wondering if you might be able to help me track down a book that my SIL vaguely remembers from her childhood. The main character is surrounded by people who have magical gifts, but he (she?) apparently has no gifts. Then he/she gets his/her braces removed, and it turns out that the silver was inhibiting the magic, and he/she actually does have magical powers.

She read it in the mid-80s, and the fact that there were braces in it leads me to believe that it wasn’t written too much earlier than the 70s or 80s.