Most malocclusions can be corrected when permanent tooth replacement is complete, usually around 11-13 years of age for girls and 12-15 years of age for boys. Early treatment is necessary for malocclusions that may interfere with jaw development (e.g., retrusion and bad oral habits). Mastoid retrognathia is usually corrected when the patient is 3-4 years old, using movable orthodontic appliances, and can usually be corrected in 3-6 months, but some patients will relapse during replacement or early permanent teeth, and need to be closely monitored. For serious bony malocclusion, it is necessary to wait until the full development of maturity (about 18-20 years old) for orthognathic surgical treatment in order to achieve satisfactory results. Yu Zhe, Department of Stomatology, Xuanwu Hospital, Capital Medical University, Beijing, China