There are many reasons a tooth can be knocked out, including sports or activities, slips or falls, accidents, or other impacts to the face.
There are several ways a child can lose a baby tooth before it is naturally pushed out by a permanent tooth. A tooth might be knocked out accidentally. If this occurs, it's important to contact your child's dentist immediately. In other cases, a tooth may need to be removed by a dentist if it becomes chipped, cracked, decayed, or otherwise damaged.
Most often, a front tooth is knocked out. If there is a permanent tooth underneath the primary tooth, it may not be necessary to replace the missing baby tooth. Your dentist will determine if that is the case.
If your child loses a primary back tooth before the adult tooth is ready to replace it, a gap will remain in your child's mouth. A missing back tooth may also make it more difficult to eat. This gap may need to be maintained (for example, with a space maintainer) to keep other teeth from shifting.
If you know the tooth is a primary tooth, or if you're unsure, don't try to put it back in the socket.