Aligners have been developed for more than 100 years, and currently metal bracket aligners are the mainstream aligners for orthodontics. Metal brackets are characterized by the absence of additional fixation, less auxiliary devices, foreign body sensation in the mouth will be reduced accordingly, wearing such brackets is relatively high comfort, cleaning becomes easier, oral hygiene is easy to maintain throughout the treatment period. But there are also certain orthodontic risks, mainly the following: 1, alveolar bone compressive resorption: mainly in adults, because adult jawbone development has ended, if the application of a certain pressure later, will lead to alveolar bone resorption; 2, orthodontic relapse disorder: mainly in adults, it is recommended that the best orthodontic age of 12 years old, timely orthodontic; 3, root resorption. If the traction force in the orthodontic treatment process is too large, it will lead to a certain amount of root resorption, more serious or even induce root resorption; 4, oral mucosal injury: located on the lip and buccal side or tongue and waist side of the force device, such as springs, traction hooks, a variety of rings, wire free end and the edge of the overstretched abutment, may cause irritation to the oral soft tissues and the formation of damage, and sometimes can cause traumatic ulcers .