Radicular cyst is the most common inflammatory cyst arising due to the proliferation of the epithelial rests in the periodontal ligament. This proliferation is a result of the inflammation induced by bacteria and necrotic products, seeping into the periapex through the infected pulp. Hence radicular cysts are most often found in the apices of infected teeth or sometimes in the lateral aspects of roots, when the inflammtion spreads through the lateral canals.
   
    Once the tooth is infected and not adequately treated, the cavitation extends, with the infection advancing to the pulp.The infection could elicit an inflammatory response, assuming treatment is not initiated and could cause necrosis of the pulp. Alternatively, necrosis of pulp could also be caused of the tooth is severely traumatized. The bacterial components could seep through the dead pulp to the underlying periapex, further eliciting a periapical bone inflammation. The body’s immune system responds with a periapical granuloma formation, that is the tissue tries to heal itself.
   
    Periapical granuloma is basically composed of granuloma tissue and a lot of inflammatory cells. Do not confuse a periapical granuloma to a tuberculous granuloma or any other granuloma due to a granulomatous infection. The “periapical granuloma” is a misnormer and is only composed of granulation tissue.
   
    The pathogenesis of a radicular cyst could be spaced into 3 phase namely, a phase of initiation, a phase of cyst formation and a phase of cyst expansion.