The following reasons are common for slow teething in babies: 1, genetic factors, there are late teething in the family father, mother or within three generations. 2, eating too thin and soft or fine, so that the baby has less opportunity to chew, because chewing can stimulate tooth eruption. 3, vitamin D deficiency rickets, when the lack of calcium, lack of vitamin D, can lead to late teething, you can supplement vitamin D and calcium, more outdoor activities, sunshine, reasonable 4, no tooth root, when the baby still has not teething after 14 months of age, to consider the root development is incomplete, timely to the hospital for oral radiography examination.