This site has a wealth of info on it...
http://www.mercurymadness.org/
And it has been know about for a long time how bad it is... There was a panaroma program in 1994 discussing how bad it was and one recently what's in your mouth... This info is on this site a somewhere but I can never find it when I look.
I've had all mine removed and I've read / heard MMS with another DMSO(? maybe please check) is very good for teeth/gums... in the mms interview with Jim H.