Chronic apical periodontitis cannot heal itself. Chronic apical periodontitis, which is a bacterial infection that leads to necrosis of the pulp tissue, infection of the entire pulp tissue and the root canal pulp tissue, cannot be cured without eliminating the cause of the disease. Bacteria enter the pulp, the pulp cavity, and the root canals and multiply, producing various toxins. The toxins spread down the root canal system into the root canals and periapical tissues and enter the bone, leading to the destruction of the bone around the apical tissues, which produces obvious clinical symptoms, interfering with eating, pain, discomfort in biting, and the inability to bite, and in the acute stage of the attack there is a need for treatment of the very severe pain. The treatment is open drainage in the acute phase to remove the infection and unblock the pulp cavity or root canal system so that the periapical tissues are open with gas or pus and blood, as the pus leads to a very high pressure, resulting in great pain.