Gaps can occur during tooth replacement in children. This is generally due to the difference in the size of milk teeth and permanent teeth and the development of jawbone, which is a normal physiological phenomenon. Gaps between milk teeth or replacement teeth are mostly due to premature loss of milk teeth or late eruption of permanent teeth. For premature loss of milk teeth, gap retainers are often used to maintain the integrity of the dentition, while for late eruption of permanent teeth, incision and eruption-guided surgery is often used to help permanent teeth erupt. Some of the sparse teeth are caused by low or wide attachment of upper lip ties, supernumerary teeth, and bad oral habits, etc. Therefore, upper lip tie revision, extraction of supernumerary teeth, and correction of bad oral habits can be done to address the cause of the disease. After removing the cause of the gap caused by the above local factors, if it is in the period of replacement teeth, the gap can be adjusted by itself by observing the eruption of lateral incisors and cuspids; if it is in the period of permanent teeth, orthodontic appliances must be used to treat the gap. If the gap is caused by congenital absence, small size of teeth or large tongue, etc., and cannot be closed by orthodontic methods alone, restorative treatment or implant treatment will be done after the gap is centralized and after adulthood