EDIT TO ADD: I also wondered if the writers know that fillings in teeth are not made of magnetic metals.
Did they say the filling was pulled through his brain because of the magnetics? I just assumed it was an 'island' thing. like he was somewhere where he shouldn't have been.
No they didn't explicity say that, but I'm sure that's what we're going for since they have previously established the highly magnetic field around "the hatch" (I don't pay attention to the names of the stations).
But this is LOST afterall, with time travel, dead people walking around, and a smoke monster, so I guess non-magnetic materials being yanked out by a magnet is not that far-fetched relatively speaking.