Generally referred to as incisors for the middle incisor, the middle incisor in the mouth of the left and right pairs, up and down coordination, a total of two, the appearance of three incisors may be lateral incisors, but also may be a stagnant milk teeth or multiple teeth. 1. Lateral incisors. The maxillary lateral incisors are similar in appearance to the mesial incisors, but smaller in size than the mesial incisors, so they are easily mistaken for incisors. 2. Retained milk teeth. When the milk incisors are retained and the permanent incisors have already erupted, there will be three incisors, and you need to go to the hospital for examination and radiographs, and then extract the retained milk teeth as soon as possible, so as not to cause malocclusion. 3. Multiple teeth. Due to congenital developmental abnormalities, there may be multiple teeth, the appearance of three incisors, film examination can be judged. The appearance of three incisors, specific recommendations to the hospital film examination, according to the oral situation targeted treatment.