They don't have any evidence of safety so they obfuscate what we do know and pontificate about relative risks. The IAOMT has enumerated numerous clear and cogent reasons to avoid using mercury fillings. Link
For a brief video of mercury being released from set mercury/silver filling and a summary of the research funded by the International Academy of Oral Medicine and Toxicology (www.IAOMT.org) over the last 20 years, watch the YouTube video
See with your own eyes how mercury vapor escapes from dental amalgam. It's odorless, colorless, and tasteless, but it casts a shadow in black light!
The invisible UV light can be turned visible by using fluorescent materials, which are used for example for optical effects. In the video, such a fluorescent screen (green, directly behind the tooth) is used to make the shadow, that mercury casts in UV light, visible.
Dr. Layton uses a Jerome Mercury Vapor Analyzer to demonstrate that it really is Mercury.
Earlier criticism by advocates for continued mercury use in dentistry have been addressed in a follow-up video from the documentary film "The beautiful truth".
I've got the dentists this saturday, and am getting two teeth out, also I think I may need a filling or two. Are they alternatives I can ask for? What do you do if you need a filling but dont want mercury in your mouth?