The normal teething time for infants is between 4-10 months, but because of differences in individual growth and development and different dietary structures, there may be differences in early and late teething. Delayed teething in babies is mainly related to the following factors: 1. nutritional factors, if the baby is deficient in nutrients, such as vitamin D and calcium, as well as iron, magnesium and other trace elements, it will easily lead to delayed teething. 2. disease factors, such as having 3, genetic factors, because some family parents also have late teething. 4, environmental factors, such as the time of daylight and different living environment in some regions also affect the baby’s teething time. Therefore, the baby’s teething time still needs to be analyzed comprehensively, but parents need to follow the law of children’s growth and development, supplemental food and vitamin D supplementation, which is conducive to the growth and development of children.