? The frenulum of the upper lip is located on the gingival bed at the root between the two central incisors, and is connected with the mucosa inside the upper lip to form a thin strip. ? Labial frenum is quite thick in embryonic stage, or the central dividing line of alveolar ridge. After the baby was born, with the eruption of teeth and the development of alveolar bone, labial frenum gradually retreated. If labial frenum doesn't retract, and still insists on the original position, it is bound to form a crack between the central incisors, so that the two central incisors can't get close. If not corrected in time, it will not only affect the child's development, but also affect the normal eruption of other teeth, resulting in uneven dentition. As shown in the figure below: