A tooth that has been completely knocked out is called an avulsed tooth. If you act quickly enough, the tooth can be saved. Store the tooth in your mouth if possible so that your saliva can keep it moist. If this is not possible, use a glass of water. Visit the dentist as soon as possible, preferably within the hour, so that the socket can be washed out and the tooth replaced. Though the root of your tooth will reattach to your jawbone within a few weeks, the nerves and blood vessels that nourish the tooth will have been severed, so the tooth will need a root canal.