Generally, the age of children’s teeth replacement is six to eight years old. Children’s teeth loss may be related to premature loss of milk teeth, congenital loss of permanent teeth, and malposition of permanent teeth. 1. Early loss of milk teeth: If children eat hard food, it will lead to the absorption of the root tip of milk teeth, which will lead to the premature loss of milk teeth. However, it is not yet time to grow permanent teeth, so they never grow out. 2. Congenital absence of permanent teeth: If the tooth germ of permanent teeth is congenitally missing, the permanent teeth will not grow after the milk teeth fall out, so they never grow out. 3. The permanent teeth are not in the right position: sometimes, although the milk teeth fall out, the roots are still there, which conflicts with the position of the permanent teeth, resulting in the permanent teeth never grow out. If the child lost teeth have not grown out beyond the normal eruption time, it is recommended to go to the hospital stomatology department in time to avoid delaying the best time for treatment.