Depends wether is broken off or complete tooth falls out due to trauma.  I have known people who pushed it back it, went to dentist and they saved it.  Don't know details.

If broken they ususally put a pin to strenghthen the tooth, after doing a root canal and then they build around it.  It is not a bad procedure.  Had it done with a fractured tooth.  Lasted for years and years until ran off the road by a camper and hit mouth in same area.