if you can get to a dentist's office (or an emergency room) within an hour or two of the injury, the dentist may be able to reimplant the tooth in its socket.
to preserve the tooth until you get to the dentist:
- pick up the tooth at its top, not at the root.
- rinse the tooth with water. do not rub or scrub it.
- put the tooth back in the socket. bite down gently on gauze or a clean cloth to keep the tooth in place, or hold the tooth in place with your finger. (this is not a good idea for anyone who might swallow the tooth.)
- another option is to put the tooth in a small container of milk. use tap water if you don't have milk.