Knocking out a permanent tooth is a true dental emergency. Don’t be afraid to contact your dentist right away. If you knock out a permanent tooth, here is what to do. 1. Hold the tooth by the crown and not the root so as not to spread bacteria unto the root. 2. Rinse dirt or any debris off with room temperature water but be gentle with the root. 3. Try to reinsert the tooth until you get to the dentist and hold it into place. 4. If reinserting is not an option, keep it moist by covering it with milk or water. 5. For optimal outcome, try to get to a dentist within 30 minutes.