The primary teeth erupt from the first two and a half months. Children begin to change teeth around the age of 6, and the deciduous teeth gradually fall off and are replaced by permanent teeth. At about 12 years old, all primary teeth are replaced by permanent teeth. Permanent teeth are the second set of teeth in life and serve people all their lives. < / P > < p > many parents don’t pay attention to their children’s deciduous teeth. They think that they have to be replaced anyway, so they take it lightly. In fact, deciduous teeth play an important role in children’s growth. From the age of 2.5 years old, the primary teeth grow up to the age of 12 years. Before all the primary teeth are replaced, the primary teeth and permanent teeth are equally important. Deciduous teeth are very important for chewing, pronunciation and appearance. Deciduous teeth are indispensable tools for children to chew food. If deciduous teeth can not play their role well due to dental caries and other reasons, digestion and absorption will be affected and adverse consequences will be produced for children’s growth and development. In the masticatory process, deciduous teeth can effectively stimulate the development of jaw, and create good conditions for the smooth eruption of permanent teeth and beautiful facial appearance. The unsightly appearance and unclear pronunciation caused by caries of deciduous teeth may cause psychological harm such as inferiority complex and lack of self-confidence of children, which will affect their normal social intercourse and growth. The deciduous teeth also play a guiding role in the eruption of permanent teeth. Under normal circumstances, the deciduous teeth must be maintained to the age of natural shedding before the permanent teeth can sprout to the normal position. < / P > < p > if the deciduous teeth fall off prematurely and lose their normal position, there will not be enough space for permanent teeth to sprout out, resulting in crowding arrangement of permanent teeth. However, the crowded teeth are not easy to be brushed clean, which is easy to form caries and periodontal diseases, and also cause greater difficulties for future orthodontic treatment.