There are many theories held about the mercury in amalgam fillings leaching into the body and causing toxicity. While I do not support those theories, I do recognize that mercury is a toxic substance that should be handled responsibly. While bound with the other metals in the amalgam material, the mercury poses no threat to your body or the environment. However, in removing old fillings, some mercury is released, and while we use filtration devices (and an EPA-approved disposal system) to catch it before it washes down the drain, some will inevitably escape into the environment and likely into your body as well. This is why I do not recommend replacing amalgam fillings unless medically necessary due to recurrent decay, fracture, or abscess.

For new, small cavities, I prefer to use composite (also called ‘resin’) material for two reasons: it looks better and, should it need to be replaced in the future, there is no risk of mercury release. Unfortunately, composite materials do not compare to amalgam in compression strength so for large fillings, the only amalgam-free option is to place a crown (or ‘cap’) over the tooth. Online Articles about mercury in amalgam fillings:

The "Mercury Toxicity" Scam: How Anti-Amalgamists Swindle

Mercury Fillings: Are They Really Safe?

American Dental Association: Fillings