I had 7 mercury fillings removed about a year ago.
I'm sure you know....but make sure the dentist follows the proper protocol for removing them.
They should use a rubber damn to prevent anything from falling down your throat. And they should use a high powered vacuum system to pull away all vapours (like having a shop vac in your mouth).
And the dentist, the assistant and myself had an external source of air. ie a mask with oxygen.
And she used activated carbon that apparantly helps bind and mercury that might make if down your throat.
I didn't get one bit sick at all. Which is pretty impressive considering how bad my adrenal was at the time.
Anyway....if you haven't already, get some details.