A 9 year old child with half of his tooth knocked out needs to choose treatment options such as restoration or surgical treatment depending on the specific condition of the tooth. 1. Repair: If the tooth is not exposed to the pulp, it is usually just soreness and pain. In this case, the tooth can be repaired with dental materials and restored to its original shape. 2. Surgery: If the pulp of the broken tooth is exposed, you can first do a live pulp amputation, try to retain the vitality of the pulp, it is better to retain the pulp, if you can’t retain the pulp, you need to do root canal treatment. If the pulp cannot be preserved, root canal treatment is needed. Meanwhile, the shape of the tooth should be repaired after root canal treatment. It is recommended to pay attention to your child’s oral hygiene, do not eat too hard, too sweet or cold and spicy food, and develop good hygiene habits of brushing the teeth in the morning and evening. If there are any abnormalities in the teeth, it is recommended to consult a doctor in time.