This is one of the most common questions parents ask during their initial consultation. Many dentists will tell parents, “The child is too young to start orthodontics until he or she is 12 years old and has replaced his or her teeth.” In fact, there is a misconception here, there are many misaligned teeth are formed due to abnormal tooth replacement. With the improvement of living standard in China, the incidence of tooth replacement abnormalities such as early loss of milk teeth, ectopic eruption of permanent teeth, and retention of milk teeth is also increasing, so the incidence of tooth misalignment is also increasing year by year. In order to prevent tooth replacement anomalies from causing malocclusion in children later in life, many children in developed countries in the West have annual checkups during the tooth replacement period (7-12 years old) to detect and intervene in a timely manner. This practice is worth advocating because timely intervention not only reduces the likelihood of malocclusion in children, but also reduces the complexity of orthodontic treatment later on and reduces the proportion of orthodontic extractions. Therefore, when parents notice that their children’s tooth replacement is not the same as other children, they should go to a professional orthodontist for an examination.