Children with double-layer teeth may be may be some kind of physiological phenomenon, may also be the diet is soft, jawbone development is not sufficient, etc. caused. 1. Physiological phenomenon: double-layer teeth are usually seen in the anterior region of the retained milk teeth. In some children, if the position of the permanent tooth embryo is skewed towards the lingual side, it may lead to the situation that the milk teeth have not been lost and the permanent teeth erupt from the lingual side of the milk teeth, presenting the situation of double-layered teeth. 2. Soft diet: If the child often eats soft food, the lack of sufficient chewing stimulation of the jaws and teeth may lead to insufficient movement of the permanent teeth to the labial side in the process of eruption, resulting in the phenomenon of unerupted milk teeth and the eruption of permanent teeth from the lingual side of the milk teeth. 3. Inadequate development of jawbone: When milk and permanent teeth begin to be replaced, due to inadequate development of jawbone, there is a distance between the crowns of milk teeth and the width of the crowns of permanent teeth, which will make the permanent teeth temporarily located on the lingual side of the milk teeth, thus forming a double layer of teeth. Children with double-layer teeth should go to the hospital stomatology department in time, and be treated by the doctor according to the actual situation, so as not to affect the teeth alignment and malocclusion.