If you don't have a well trained dentist with proper equipment and protocol, you can get a lot of mercury exposure from Amalgam work, since mercury vaporizes with temperature or drilling. Also the drill throws a lot of small pieces. It makes as much as 75% difference how much mercury exposure you get depending on the dentist.
But if done correctly, your daily exposure declines about 90% within a few weeks.
Those with several Amalgams on average have about 10 times as much exposure as the average person without amalgams. http://www.flcv.com/damspr1.html