[2][3][4] It is formed when there is an alteration in the reduced enamel epithelium and encloses the crown of an unerupted tooth at the cemento-enamel junction.

Ectopic tooth eruption may result due to pathological process, such as a tumor or cyst or developmental disturbance.

A potentially erupting tooth on an impacted follicle can obstruct the venous outflow, inducing rapid transudation of serum across the capillary walls.

On the contrary, Toiler[9] suggested that the breakdown of proliferating cells of the follicle after impeded eruption is likely to be the origin of the dentigerous cyst.

The exact histogenesis of dentigerous cysts remains unknown, but most authors favor a developmental origin from the tooth follicle.

Azaz and Shteyer[11] similarly suggested that the persistent and prolonged periapical inflammation caused chronic irritation to the follicle of the successors.

They reported five cases of dentigerous cysts which involved the second mandibular premolar in four children aged 8 to 11 years old.

These children were referred for extraction of carious, nonvital primary molars with swelling of the surrounding soft tissue.

These cysts may be secondarily inflamed and infected as a result of periapical inflammation spreading from non vital deciduous predecessors.

The third possibility is that periapical inflammation could be of any source but usually from a non vital deciduous tooth spreading to involve the follicles of unerupted permanent successors.

The dentigerous cyst commonly involves a single tooth and rarely affects multiple teeth.

The specimen will present with loosely arranged fibrous connective tissue wall that contains considerable glycosaminoglycan ground substance.

These rests may appear numerous in the fibrous connective tissue wall occasionally, which may be misinterpreted as ameloblastoma by some pathologists who are unfamiliar with oral lesions.

The epithelial lining is composed of two to four layers of flattened non-keratinizing cells, with a flat epithelium and connective tissue interface.

Histologic examination reveals a more collagenized fibrous connective tissue wall, with a variable infiltration of chronic inflammatory cells.

In addition, small nests of sebaceous cells infrequently may be present within the fibrous connective tissue wall.

These mucous, ciliated and sebaceous elements are postulated to represent the multipotentiality of the odontogenic epithelial lining in a dentigerous cyst.

One or several areas of nodular thickening may be seen on the luminal surface in the gross examination of the fibrous wall of a dentigerous cyst.

As the dental follicle surrounding the crown of an unerupted tooth usually is lined by a thin layer of reduced enamel epithelium, this may render it difficult to distinguish a small dentigerous cyst from a normal or enlarged dental follicle based on microscopic features alone.

However, a large dentigerous cyst may give the impression of a multilocular process due to the persistence of bone trabeculae within the radiolucency.

Some dentigerous cysts may also grow to considerable size and produce bony expansion that is usually painless, unless secondarily infected.

[23] On CT imaging, a mandibular dentigerous cyst appears as a well-circumscribed unilocular area of osteolysis that incorporates the crown of a tooth.

Large cysts which may project into the nasal cavity or infratemporal fossa and may elevate the floor of the orbit can be noted on CT imaging.

[27] Jagged or irregular margins with indentations and indistinct borders are considered to be suggestive of possible malignant change.

[28] Due to the potential for occurrence of an odontogenic keratocyst or the development of an ameloblastoma or, more rarely, mucoepidermoid carcinoma, all such lesions, when excised, should be submitted for histopathologic evaluation.