Children generally start to replace their teeth at the age of five or six. In this process, if the baby teeth are not loosened as expected, but the new teeth grow out from the inner side, there is a “double row of teeth”, this is due to the permanent tooth germ of the front teeth not moving forward enough during the development process, the root of the baby teeth can not be completely absorbed, resulting in the baby teeth have not fallen out, the permanent teeth are not in the correct position to erupt. In this case, you should seek a doctor to extract the retained baby teeth and make room for the permanent teeth. After the baby teeth are extracted, parents may find that the new teeth are crooked. There is no need to worry too much, as with the stimulation of chewing and jawbone development, the new teeth will gradually grow into the vacated position. As long as there is enough space for the jawbone to develop, the new teeth will gradually line up.