Late teething is often associated with family genetics, malnutrition, irrational addition of complementary foods, and the effects of disease. 1. Family Heredity: The eruption time of baby’s milk teeth is generally affected by the parents, if both parents are late teething, the probability of the baby’s late teething will also increase. 2. malnutrition: baby in the embryonic development period, if the embryo lacks calcium, vitamins and other substances, will affect the growth and development of the fetus embryonic period of milk teeth, will also lead to the baby late teething. Baby in the period of eruption of milk teeth, the whole body bone tissue is also developing, the baby needs a lot of nutrients to maintain normal growth and development, especially vitamins, calcium intake, when the intake of nutrients to meet the needs of the baby, it will lead to malnutrition. 3. Complementary foods added unreasonably: complementary foods added too late or too fine, is not conducive to the development of chewing function, easy to lead to the baby late teething. 4. Disease effects: babies with some systemic diseases such as pituitary insufficiency, Down’s syndrome and local infections can trigger late teething, in addition to rickets children will also appear late teething symptoms, should be combined with other symptoms and diagnostic tests, the cause of the treatment.