When a tooth has been completely knocked out, root and all, it is called a tooth avulsion.  The area will bleed a lot, so it is important to apply pressure to help stop the bleeding.  If the tooth can be found, it is best to place it in milk or saliva to preserve it until the person is taken to the dentist.  Try not to touch or scrub the tooth’s root surface.  Time is of the essence, so it is crucial to get to a dentist or possibly even the emergency room as quickly as possible.  If possible, the dentist may actually be able to reinsert the tooth.  Hopefully this will not happen to you or anyone you know, but it is always good to know what to do in a difficult and stressful situation!