Adults with milk teeth not replaced may be due to congenital absence of permanent teeth or permanent teeth obstruction, and the treatment methods include retaining milk teeth for observation, restoration after extraction of milk teeth, and assisted eruption after extraction of milk teeth, as follows. 1. Congenital absence of permanent teeth: the treatment method needs to be chosen according to the health status of the milk teeth. (1) Observation of retained milk teeth: If the milk teeth are healthy and secure in the alveolar bone, and there is no adverse effect on the surrounding hard and soft tissues, the milk teeth can be retained to exercise the function and observation is sufficient. (2) Repair after extraction: If the milk teeth are loose or have disease symptoms, they should be extracted as soon as possible, after which implant denture and fixed partial denture can be chosen for repair. (2) Permanent tooth obstruction: If there are permanent teeth in the jawbone that cannot erupt, the milk teeth should be extracted and then assisted in eruption, which can be done by orthodontic traction. It is recommended to go to the hospital to receive regular treatment.