Once the orthodontic treatment is complete and the aligners are removed, it is important to wear a retainer. This is because the teeth are not yet stable in their new positions when the orthodontic treatment is completed, and the retainers must be used to stabilize the teeth in their new positions. When the reconstruction of the tissues around the teeth and the alveolar bone is completed, usually about 2 years, the retainer can be gradually removed. Some special patients, such as those with periodontal disease, are advised to wear retainers for life to prevent the teeth from shifting again.