Etiology
The essential prerequisite is pulp necrosis — caused by caries, trauma, restorative procedures, or periodontal disease — allowing bacteria and their toxins to reach and stimulate the periapical tissues.
Chronic periapical inflammation stimulates the resting epithelial cell rests of Malassez (ERM) in the periodontal ligament to proliferate, forming an epithelial lining around the inflammatory focus.
The inflammatory process initiates this sequence: bacterial toxins → periapical granuloma → ERM proliferation → epithelial-lined cyst cavity → cyst expansion.
Residual radicular cyst: when a tooth is extracted without removing the attached cyst, the cyst may persist and continue growing — a residual radicular cyst.