Double row of teeth is a condition in which the permanent teeth have erupted, but the baby teeth are not lost in time, causing the baby teeth and permanent teeth to grow side by side on the jawbone and alveolar ridge, thus causing the permanent teeth to deviate from the dental arch, which is known as retention of baby teeth. In addition to retained milk teeth, multiple teeth can also cause double rows of teeth. The main reasons for retained milk teeth are as follows: 1, fine diet: if the child’s food is too soft and fine without sufficient chewing, it will lead to the milk teeth not getting the corresponding exercise and physiological stimulation, and the roots of the teeth will not be absorbed, and also reduce the chewing to promote the development of the jaw bone, resulting in the milk teeth can not fall off, and the permanent teeth can only grow in the back and sides; 2, permanent teeth problems: due to the abnormal eruption direction of permanent teeth, not according to the original track When the permanent teeth erupt, they do not reach the position of the roots of the milk teeth, and the roots of the milk teeth are not absorbed or not completely absorbed, resulting in double rows of teeth; 3. Milk teeth problem: When the periapical lesion of the milk teeth occurs, it may destroy the alveolar bone, resulting in the early eruption of the permanent teeth without the loss of the milk teeth, forming double rows of teeth. When double-row teeth symptoms appear, it will affect the normal teeth biting relationship, cause food embedding, and then affect the oral hygiene, leading to the appearance of dental caries. In addition, it will also make the teeth unevenly arranged, so when the permanent teeth erupt, the retained milk teeth should be extracted, and when the multiple teeth cause double rows of teeth, the multiple teeth should be extracted.