Parents often ask me if their children need to have all their teeth replaced before they can undergo orthodontic treatment. In fact, the timing of treatment is based on the patient’s type of malocclusion, which involves maxillary and mandibular problems that require early treatment, such as “pericoronitis”, which can be treated at the age of 3 years old to prevent it from evolving from the initial dental problems into maxillary and mandibular length imbalance; lip biting, sucking and chewing on one side of the mouth, and other maladaptive habits caused by upper and lower jaw problems, such as open front teeth (anterior teeth without occlusion), mandibular retraction, facial and facial problems. Problems of the upper and lower jaws caused by bad habits such as lip biting, sucking and sideways chewing, such as anterior open jaw (anterior teeth without occlusion), mandibular retraction, facial asymmetry (or chin deviation) should be detected at an early stage and treated at an early stage in order to prevent serious skeletal problems. These problems should be treated during the milk teeth period or during tooth replacement. In children, general malocclusion starts when the permanent teeth erupt (around 6 years old), but some problems are only temporary during tooth replacement, and it is advisable to consult an orthodontist for a checkup. Therefore, it is possible to observe the process of eruption of permanent teeth at an early and regular stage, and to detect and solve problems in time. Early permanent teeth (about 12 years old), this time is in the peak of growth and development, can make use of the growth and development potential to make the treatment twice as effective, all kinds of malocclusion can be actively treated in this period. Orthodontic treatment for adults not only solves the problem of aesthetics, but also improves the health and function of the entire oral cavity. There is no age limit to having an attractive, confident smile.