It is normal for children to have a gap of about one millimeter between the two incisors (central incisors) in the upper jaw when they first erupt, and the gap will slowly close as the other neighboring teeth erupt in the future. If there is still a large gap between the incisors after three years of eruption, it is time to see a doctor for orthodontic treatment. Gap between the incisors and the following reasons: 1, the upper lip tie position is too low Under normal circumstances, turn over the upper lip can be seen on the inside of the lip in the center of a thin and narrow mucous membrane folds attached to the gingival papilla from the distance of 3-4 millimeters, called the upper lip tie. In infancy, the upper lip tie is connected to the top of the alveolar ridge, and it recedes with physical development and the heightening of the alveolar ridge. If the retraction of the labial tie is not good, the position is still too low, the two incisors will be pulled by the labial tie when they grow out, and a gap will appear between the two teeth. 2, between the two teeth have redundant teeth redundant teeth are often sandwiched between the two incisors or grow together, or buried in the bone of the dental bed. The latter can be detected by X-ray. There is a gap between the middle incisors caused by the low position of the upper lip tie, the tie can be surgically shifted, and the gap can be slowly closed. For gaps caused by extra teeth, the extra teeth should be removed according to the specific situation and then orthodontic treatment should be carried out.