Having diabetes of course can cause you not to heal well, but the mercury and root canals are putting an extreme burden on your immune system. They alone can cause your gum problems. If you have any crowns or bridges with nickel under them, that causes it as well. As far as pulling all your teeth, not a good idea unless they are loose and not going to heal, because it will cause bone loss. The dentist has to assess whether they should be pulled. Here is some things you may want to read: