First Aid: Injury to a permanent tooth

Injury to a permanent tooth, however, is a medical emergency that could have long-term effects if not handled quickly and properly. Follow these steps in the event of an injury:

• If the tooth is still in your child's mouth, that's the best place for it. If the tooth has fallen out, find it.
• When you find the tooth, hold it by the crown (the enamel-covered part of the tooth, the widest part of the tooth).
• Using cool water, rinse the tooth. Don't scrub away or remove any tissue fragments.
• If your child's mouth is injured and you can't put the tooth back, put it in milk or saline solution. The PH level of milk is similar to that of saliva and can help preserve the tooth. Parents can ask their pediatric dentists how to obtain a "tooth saver kit," which has all of the necessary supplies to save a child's tooth for transport to the dentist's office.
• Take your child and the tooth to the dentist immediately. If your dentist is unavailable, go to the emergency room.

source:
http://www.mayoclinic.com/