There is a hole in the gums of the most common clinical disease for the root tip of the fistula, apical fistula is due to the further development of dental caries, dental caries due to the hard tissues by the bacterial invasion, from the beginning of shallow caries, caries in the caries to the deep caries, and further development of pulpitis, the patient will feel obvious pain, at this time, if still left untreated, the pulpitis will be developed into the periapical periodontitis. In the periapical formation of gradual inflammation deposits, if the patient is still not treated, periapical inflammation will break through the alveolar bone and gums, in the part corresponding to the root tip of the tooth to form a fistula, which is often seen in the gingival fistula, the need for systematic opening of the pulp of the tooth and endodontic treatment, most of the fistula in the endodontic treatment, fistulas will be gradually closed.