Whether the primary teeth are healthy or not, children will naturally change their teeth: this is an extremely normal and wrong idea. If the deciduous teeth are seriously decayed, it will not only affect the health of the permanent teeth below, but also lose their position when they should not fall off, and there is insufficient room for the growth of permanent teeth. When an experienced doctor sees that a child's permanent teeth are in the wrong position, he will ask whether the deciduous teeth have fallen off. This brings a lot of trouble to the later treatment and complicates the problem.