The pus that accumulates near the root tip is usually discharged in the following three ways: 1. through the bone marrow cavity break through the periosteum, from the mucosa or skin outward drainage of pus, inflammatory cells from the root tip near the alveolar bone cavity quickly spread in the alveolar bone, pus through the bone cancellous to reach the outer plate of the bone and then to the periosteum, because the periosteum is dense and hard is not easy to be pierced, pus gathered here local pressure increased, at this time is the most obvious clinical symptoms also This process is the most common and typical natural development process of acute periapical inflammation, the direction of pus breakthrough and the location of the breakthrough is very closely related to the anatomy of the periapical area, some are formed in the oral mucosa of the long-standing sinus tract or fistula, some patients report repeated swelling of the gums with small Some patients report repeated swelling of the gums with small pus pockets, and there is also the possibility of directly penetrating the skin and forming a skin fistula on the skin; 2, drainage of pus from the crown defect through the apical foramen via the root canal, this drainage method is the least destructive to the periapical tissue, such drainage requires several conditions such as a thick apical foramen, a clear root canal, and an open crown defect, but in clinical practice it is difficult for adults with periapical inflammation to have such conditions, so the pulp chamber must be opened as early as possible The prognosis is usually poor because the periodontal membrane fibers are severely damaged during drainage in this way, which aggravates the periodontal disease and makes the affected tooth more loose or even fall off.