If the baby's permanent teeth have erupted but the corresponding deciduous teeth have not yet fallen out, it is because the child's diet was too refined during infancy and the deciduous teeth were not well cared for. Since the normally developing permanent teeth cannot arch out the deciduous teeth, they will burrow out of the alveolus crookedly, and the mucosa and deciduous teeth will grow in the oral cavity, causing a "double row of teeth" phenomenon, which is medically known as "retained deciduous teeth."

The deciduous teeth should be extracted in time at this time, otherwise it will affect the normal growth of the permanent teeth, leading to tooth misalignment, misalignment, malocclusion and other deformed teeth, which require orthodontic treatment.