Many have thought that chewing sugarless gum is okay, and may even help to keep teeth clean.

http://www.juiceguy.com/gum_mercury.shtml

Good article.

For those who don't know...

It's been determined that any abrasion on the surface of amalgam fillings increases the rate that they off-gas mercury vapor. This includes brushing, grinding teeth, and dental cleanings.

Good Video: http://urlbam.com/ha/2zz