Orthodontics is a clinical medicine with a scientific treatment procedure. Orthodontic treatment must be completed in three stages. The first stage is to align and straighten the teeth. To align the teeth so that the misaligned teeth are in the row, which generally must be completed in 9-12 weeks (3-4 months); to straighten the teeth means to adjust the high and low position of the teeth to a normal relationship, so that the contact between the cusps of each tooth in the row and the normal plane is normal, and there is no deep overlap or gap between the upper and lower front teeth, the straightening process also takes about 9-12 weeks (3-4 months) to complete . Phase 2: The second phase is to adjust the posterior tooth relationship, internalize the anterior teeth and close the extraction gap. Closing the extraction gap, which is usually 7 mm, the teeth move towards the extraction gap at a rate of 1 mm per month, and then inwardly collect the four anterior teeth, which takes about 6-9 months to complete. The third stage: for the micro-adjustment of tooth position and occlusal relationship, belongs to the completion stage of orthodontics, which takes about 5-9 months. So it takes about two years to straighten the teeth.