Abnormal dentition usually occurs when permanent dentition is formed, about 12- 14 years old. At this time, the dentition in children's mouth is all permanent dentition, the deciduous teeth are basically replaced, and most of the permanent teeth have erupted.

At this time, if the dentition is irregular or other dentition is abnormal, it can be corrected in time, because the child is in a period of rapid development, and the correction at this time is relatively safe and not easy to recur.

Another important reason for malocclusion is bad habits. Common children suck their fingers, open their mouths to breathe, bite their lips and stick out their tongues. When these bad habits exist, we should correct them in time.