Normally, new teeth (i.e. permanent teeth) erupt at the same time as milk teeth fall out or within a short period of time, usually around 3 months. However, if the milk teeth are lost prematurely or the permanent teeth are congenitally missing, the permanent teeth cannot erupt within a short period of time after the milk teeth fall out. If the milk teeth are lost prematurely due to trauma or decay, the permanent teeth will not erupt with them, but will not erupt until the normal eruption time. If there is insufficient space between the teeth due to premature loss of milk teeth or if the gum mucosa becomes tough due to friction, this will lead to obstacles to the eruption of the inherited permanent teeth, and medical intervention is needed to open the space and cut the gums to help the permanent teeth erupt. If the permanent teeth are congenitally missing, and it is determined by dental radiographs that there is no permanent tooth germ, then no new teeth will ever grow, and a denture will need to be fabricated to replace the permanent teeth to perform the chewing function and to maintain the aesthetics.