Seven-year-old incisors fell out and did not grow, considering that it may be caused by gingival hypertrophy, ectopic obstruction of permanent tooth embryo, hereditary congenital absence and other factors. 1. Gingival thickening and hypertrophy: If the milk incisors have been traumatized or decayed, resulting in premature loss, the gingiva at the incisors will be keratinized and thickened during daily pronunciation and chewing, resulting in gingival thickening, which will increase the resistance to the eruption of the permanent tooth embryo, so there may be a long time for the permanent teeth not to erupt after the milk teeth have been lost, and it is generally necessary to conduct eruption guide to help the permanent teeth to erupt. 2. Ectopic obstruction of permanent tooth embryo: If there are abnormal structures such as supernumerary teeth or jawbone cysts in the position of incisor embryo, it may lead to abnormal development direction of permanent tooth embryo, resulting in incisors failing to erupt normally, which needs to be analyzed by taking X-rays in the stomatology department of the hospital. Generally, it is necessary to extract the supernumerary teeth as soon as possible, and carry out cyst removal surgery and other treatments, and also need to cooperate with the later orthodontic treatment in order to make the incisors return to the normal ideal position. 3. Hereditary congenital absence: the developmental abnormality caused by fetal heredity and other factors, there may be deformities leading to congenital absence of permanent tooth embryo, which needs to be examined to determine the absence of permanent tooth embryo, and need to wait for the child to consider dental implant restoration after adulthood.