In orthodontic treatment, the force transfer process of the aligner is as follows: the orthodontic force acts on the teeth through the rebound force of the wire, the teeth transfer the force to the periodontium, the periodontium distributes the force to the alveolar bone, which undergoes tissue modification and produces tooth movement. The rate of tooth movement is closely related to the type of orthodontic appliance and the amount of force. The orthodontic force can be classified into the following three types according to the size of the force: 1, light force such as rubber bands, the force value of 60g or less. 2, moderate forces such as various archwire reed curves, the force value of 60-350g. 3, heavy forces extra-oral traction force, the force value of 350g or more, used as an orthopedic force to guide the normal growth of the face and jaw.