If there are caries in the mouth, resulting in periapical inflammation, which is left untreated for a long time, or if there are residual roots and crowns in the mouth, which are not effectively treated for a long time, it is easy to form an apical cyst. If the diameter of the apical cyst is less than 2-3 cm, root canal treatment can be considered first. After 3 months of root canal treatment, dental radiographs can be taken for observation. If the periapical area is sparse and enlarged, it means that the treatment has failed, and you can consider retreatment at this time. If it is the anterior region of a maxillary tooth, apicoectomy can be considered. Periapical cysts can gradually recover one year after root canal treatment, while periapical shadows after apicoectomy need half a year to gradually return to normal.