This is the process of removing the apical portion of the root to remove a periapical cyst, correct a failed root canal, or seal a root canal that cannot be completed from the occlusal of the tooth.
Periapical Cyst:
A periapical abscess is usually the result of the patient clenching to such a degree that the tooth involved loses it seal around the tooth (torn epithelial attachment) and the periodontal ligament tissues break down (alveolar bone dissolve). The connective tissue is unable to repair the damage under the constant pressure from the clenching allowing bacteria to move down the side of the tooth to the periapical foramen.
Upon entering the foramen, the bacteria attack the tissues dissolving the blood vessel sending blood into the closed pulp chamber. The pressure builds as the clenching continues. The combine pressure (clenching and the buildup of blood pressure) causes the alveolar bone at the apical foramen to dissolve from the pressure creating a cyst.
The thick membrane lining the alveolar bone retains its integrity keeping the bacteria contained....