After treatment, if the defect is very small and the nerve is not injured, there is no need to do braces after filling; if the defect is too big or the pulp is injured by tooth decay, it is recommended to wear braces to protect the teeth after treatment. 1. If a child’s milk teeth or permanent teeth are decayed, the defect is very small and the pulp is not injured, it can be filled directly. 2. If the caries of milk teeth injures the nerve, after the root canal treatment is completed, if the defect is large and the resin filling cannot guarantee the retention, it is recommended to make a pre-formed crown to restore the occlusal function of the teeth. 3. If the nerve is injured by caries in permanent teeth, it is recommended to make permanent crowns for restoration after root canal treatment is completed and after the jawbone and teeth are fully developed, so as to prevent the teeth from splitting due to biting and eating hard objects. 4. If a child’s decayed teeth are milk teeth and are about to be replaced, due to the imminent replacement of the teeth, you can also consider not doing braces according to the situation, and use resin fillings. Whether children need to wear braces after treatment for tooth decay is related to the size of the tooth loss and the permanent teeth, and can only be determined after a specific examination in the hospital.