Patient: Description of the condition (onset time, main symptoms, hospital visited, etc.): The gap between the two teeth in the middle of the upper row of teeth is too big, and I want to narrow the gap between them! Yan Congqing, Department of Stomatology, Shanghai Ruijin Hospital: Hello! There are several cases of incisors with gaps: 1, genetic, parents have this condition. 2, multiple teeth, there are multiple teeth buried between the two incisors. 3, the labial tether attachment is too high, affecting the closure of the incisors. 4, periodontal disease, the original no gap will also appear, increase. It is recommended to check clearly and then do the treatment. Moreover, after correction, it takes longer time to wear retainer.