Histologic examination reveals a more collagenized fibrous connective tissue wall, with a variable infiltration of chronic inflammatory cells. Cholesterol slits and their associated multinucleated giant cells may be present and are generally associated with the connective tissue wall. The cyst is lined mostly or entirely by non-keratinizing squamous epithelium which display varying amounts of hyperplasia with the development of anastomosing rete ridges and more definite squamous features. Dentigerous cysts presenting with these features may histologically be indistinguishable from radicular cysts. A keratinized surface is occasionally present, which must be differentiated from those observed in the odontogenic keratocyst(OKC). Focal areas of mucus cells or rarely, ciliated columnar cells may be found in the epithelial lining of dentigerous cysts. 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. Careful examination of these areas microscopically is mandatory to rule out the presence of early neoplastic change. 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.
There were three possible mechanisms exist. Firstly, surrounding the crowns of affected teeth, the intrafollicular developmental dentigerous cysts may be formed. These cysts may be secondarily inflamed and infected as a result of periapical inflammation spreading from non vital deciduous predecessors. Benn and Altini (1996) claimed that this possibility was unlikely as all the cases reported were not associated with tooth impaction. Secondly, radicular cysts developed at the apices of non vital primary teeth. These radicular cysts may fuse with the follicles of the unerupted successors, causing the eruption of the successors into the cyst cavity. This may result in the formation of extrafollicular dentigerous cyst. Shear regarded this to be exceptionally rare because radicular cyst is uncommon in the primary dentition. 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 inflammatory exudate causes separation of reduced enamel epithelium from the enamel with resultant cyst formation. Clinical Features
The dentigerous cyst commonly involves a single tooth and rarely affects multiple teeth. The most frequently involved tooth is the mandibular third molar followed by the maxillary canine, but they may be associated with supernumerary or ectopic tooth. Any permanent tooth can be involved. Regezi and Sciubba stated that the impacted teeth were most commonly seen in the third molar and maxillary canine teeth, and hence dentigerous cysts occur most frequently in these teeth. The involved teeth may be displaced into ectopic positions.