Milk teeth that are decayed should be treated to prevent the decay from spreading. Milk teeth should be cared for as they serve the same important purposes as the permanent teeth. These should be kept in place until they are replaced by permanent teeth. They reserve the space for the permanent teeth to grow into. If milk teeth are lost too early, the adjoining teeth can drift into the spaces that are needed for the permanent teeth. This can then cause crowding problems, because there is insufficient space for the permanent teeth.