Orthodontic teeth after the end of the gap will become larger for the following two reasons: 1, the orthodontic design of the gap does not close off the teeth or dental occlusion disorders, in the orthodontic design stage to strengthen the rationality of the design, modify the orthodontic program, secondary treatment, can achieve the purpose of closing the gap; 2, orthodontic end of the teeth without gap, but with retainers 2-3 years later, slowly the teeth will appear gap,. The reason is mainly periodontal disease, that is, after the completion of orthodontics period, gums have certain damage, with the passage of time, age, and no orthodontic teeth, as many adults without orthodontics, teeth still appear gaps, mainly the problem of periodontal disease, when periodontal disease patients periodontal situation becomes worse after the gums will shrink, alveolar bone will be absorbed, tooth gaps most mainly in the root of the tooth, the root of the tooth will A triangular black hole will be formed, which is not related to orthodontics. In summary, the gap can be corrected twice after orthodontic treatment, or the gums and alveolar bone can be restored to a certain extent through periodontal treatment to eliminate the gap between teeth.