People with lordosis need tooth extraction for correction. Self-locking is most suitable for correcting congestion, and the later torque is difficult to control and the later operation is difficult. Self-locking is most suitable for cases without tooth extraction, cases with long follow-up and patients who are afraid of pain. The correction force is small and the pain is small. The impact on the face is not an appliance, but a corrective method, such as whether to extract teeth. Whether to expand the bow and so on.