Loose milk teeth did not fall out, the new tooth grows out behind, usually need to extract the milk teeth, to be fully erupted after the permanent teeth, if its alignment position is abnormal, orthodontic treatment can be carried out, as follows. 1. If the permanent teeth erupt when the milk teeth are loose but not yet lost, it may be caused by stagnant milk teeth or early eruption of permanent teeth, and the loose milk teeth should be extracted so as not to affect the subsequent eruption of permanent teeth. After the permanent teeth have fully erupted, if there is any malocclusion, it can be adjusted to the correct position through orthodontic treatment. 2. It should be noted that temporary malocclusion can exist during the period of tooth replacement, such as gaps between maxillary central incisors, maxillary lateral incisors skewed towards the distal center, and mild crowding of the whole mouth, etc., which will gradually improve with the growth and development and do not require orthodontic treatment. It is recommended to go to the hospital in time to receive professional treatment as soon as possible.