[1] Periapical is defined as "the tissues surrounding the apex of the root of a tooth" and a cyst is "a pathological cavity lined by epithelium, having fluid or gaseous content that is not created by the accumulation of pus.

"[2] Most frequently located in the maxillary anterior region, the cyst is caused by pulpal necrosis secondary to dental caries or trauma.

Patient will present negative results to electric and ice test of the affected tooth but will be sensitive to percussion.

[citation needed] Dental cysts are usually caused due to root infection involving tooth decay.

The bacteria gains access to the periapical region of the tooth through deeper infection of the pulp, traveling through the roots.

The resulting pulpal necrosis causes proliferation of epithelial rests of Malassez which release toxins at the apex of the tooth.

The many cells and proteins that rush to an area of infection create osmotic tension in the periapex which is the source of internal pressure increase at the cyst site.

Pressure and concentration differences between the cystic cavity and the growth surroundings influence fluid movement into the cyst, causing size increase.

Substances released by the body's immune system as a result of the connective tissue breakdown, such as cytokines and growth factors, contribute to the mobilization and proliferation of epithelial cells in the area.

This theory is unlikely in the absence of malignant transformation of epithelial cells as it does not follow the existing relationship between connective tissue and epithelium.

[4] Epithelial cells have an inherent quality to reproduce and cover any connective tissue that is not already lined with epithelia.

[6] A non-vital tooth is necessary for the diagnosis of a periapical cyst, meaning the nerve has been removed by root canal therapy.

Circular or ovoid radiolucency surrounding the root tip of approximately 1-1.5 cm in diameter is indicative of the presence of a periapical cyst.

Removal of the necrotic pulp and the inflamed tissue as well as proper sealing of the canals and an appropriately fitting crown will allow the tooth to heal under uninfected conditions.

[2] Surgical options for previously treated teeth that would not benefit from root canal therapy include cystectomy[12] and cystostomy.

[citation needed] A cystostomy is recommended for larger cysts that compromise important adjacent anatomy.