Gold and silver and other teeth fillings are not magnetic.
What about Kryptonite?
A Mexican dentist "trainee" broke a drill bit off in one of my molars, and never told be about it.
When I started having problems, and went to a dental specialist in the USA (Yuma). I asked what the chance was of being able to remove the bit and save the tooth.
He said about 50-50. Of the five he worked on in the last week, he got three of them out...
All from dentists in Mexico. The US specialist said no malpractice in Mexico, and they reuse the drill bits there, which is why they break so many.
Yes, I know it is not exactly an "intentional" filling. I expect, though, the drill bit was steel and magnetic.