There are two sets of teeth in a person’s life: milk teeth and permanent teeth. In children from 0 to 6 years old, the milk teeth are used to perform various functions such as chewing, and after 12 years old, the permanent teeth replace the milk teeth. However, the period between 6 and 12 years old is the period of tooth replacement for children, when the situation in the oral cavity is the most complicated, and there are both milk teeth and newly erupted permanent teeth, which is a mixed dental period. Generally speaking, as the permanent teeth develop, the roots of the corresponding milk teeth start to grow and resorb, while the permanent teeth grow into the mouth, and the permanent teeth erupt on the original position of the milk teeth after the milk teeth loosen and fall off. However, when the apical lesion of the milk tooth is caused by caries or other reasons, the root of the milk tooth will become bony adhesion with the alveolar bone, thus affecting the resorption of the root of the milk tooth, and the phenomenon of stubborn refusal to recede. In this case, the permanent teeth, which are normally developed, will find another way to grow in the oral cavity by crookedly drilling out the alveolar and mucous membranes against the milk teeth, thus the phenomenon of double row of teeth appears. It is worth mentioning here that although this is not necessarily a pathological phenomenon, parents should take their children to the hospital in time to check and remove the retained milk teeth to create a good environment for the growth of permanent teeth, otherwise the double row of teeth will cause the permanent teeth to be misaligned and form a misalignment such as anti (dentition).