Usually about two years, but also varies from patient to patient, with some patients requiring a shorter retention period, while for some extremely recurring cases, such as severe tooth twisting and gaps, a longer retention period, or even lifelong retention, is required. In general, it takes at least one year for the tissues around the teeth to regain stability, and the first three months of orthodontic treatment are particularly prone to relapse. Currently, for the first year of aligner removal, the aligners are worn carefully during the day and night. Later, the retainer will be worn at night for 6 months. If you feel comfortable wearing the retainer, you can further gradually reduce the wearing time of the retainer: one night every other day, one night a week, until you stop wearing it completely.