You can't sue an individual dentist for using mercury, or sue a mercury-free dentist for using a bad removal protocol. The reason is that mercury fillings are an "approved medical practice". Please keep in mind, I'm not an attorney, and it has been several years sine I checked.
It would be great if someone could start a class-action lawsuit to win treatment for those damaged by mercury and assistance with replacements, or force the government to ban mercury fillings...but compensation, I think its just a pipe dream.