Dentigerous Cyst

Synonym / Acronym

Follicular cyst

Definition

It is a cyst that forms from the accumulation of fluid between the reduced enamel epithelium and the crown of an unerupted tooth and attaches to the tooth neck at the cementoenamel junction.

Clinical Features

Dentigerous cysts are the second most common odontogenic cysts, next to radicular cysts.
The teeth most involved are, in descending order of frequency of occurrence, the third molars, the canines, and the second premolars. Dentigerous cysts can form around supernumerary teeth most commonly found around mesiodens.

Usually there are no symptoms associated with dentigerous cysts. A late noneruption could indicate the possibility of a cyst. A dentigerous cyst can expand causing facial asymmetry. As with other cysts, dentigerous cyst expands the outer cortical plate more than the lingual plate. It may involve other teeth as it expands. The term eruption cyst is used for a cyst that surrounds the crown of erupted tooth in soft tissue.

Radiographic Features

Well-defined unilocular radiolucency associated with the crown of an unerupted tooth. If the cyst become infected the cortex may be absent. The cyst attaches at the cementoenamel junction. It can appear round in shape or eccentric if the cyst develops from the lateral aspect of the follicle. Dentigerous cyst in mandibular third molars can expand to occupy the ramus area which represents an area of least resistance to cyst expansion. It causes displacement of the affected tooth in an apical direction and adjacent teeth in lateral direction. Inferior displacement of the inferior mandibular canal is also possible. Dentigerous cysts associated with maxillary teeth can grow into the maxillary sinus space and may not be discovered till late. The cyst is unlikely to cause resorption of apices of adjacent teeth.

Differential Diagnosis

The lining epithelium when examined histologically cannot be used alone to differentiate the cyst; the diagnosis depends on finding the attachment of the cyst to the CEJ. It is always hard to differentiate between a small dentigerous cysts and hyperplastic follicle. It is more likely to be a cyst if there are signs of tooth displacement and evidence of bone expansion. Usually the size of a normal follicle ranges is less than 5 mm. If the space size exceeds 5 mm, then it is more likely to be a dentigerous cyst. If we are still uncertain whether it is a cyst of hyperplastic follicle, we can wait for 6 months and re-evaluate the area and see if there are signs of enlargement or any influence on surrounding structures.

The differential diagnosis can include also keratocystic odontogenic tumor (KCOT), ameloblastic fibroma, and a cystic ameloblastoma. KCOT has less expansion than dentigerous cyst and less likely to cause root resorption, and may attach more apically instead of at the cementoenamel junction. If there is no internal structure, then it is harder to differentiate dentigerous cysts from ameloblastic fibroma or cystic ameloblastoma. There are other lesions that have similar appearance like adenomatoid odontogenic tumor (AOT) as it also surrounds the crown of the involved tooth. However, adenomatoid odontogenic tumor usually has internal structure which can help to differentiate between the two entities. If there is an apical radiolucency associated with the root apex of a deciduous tooth, it can give the false impression of a dentigerous cyst. A thorough examination of the tooth is necessary.

Treatment

Surgical removal of the cyst alone or along with the associated tooth is carried out. If the cyst is large then marsupialization can be done before the surgical removal. Whenever a diagnosis of a dentigerous cyst is made, the possibility of it containing mural ameloblastoma should also be considered; thus a biopsy is imperative and must always be done to confirm the final diagnosis and eliminate other diseases.

Case Reports

HISTORY: A 68-year-old white male was referred for a Cone Beam CT scan. The alveolar nerve was exposed during the surgery but without damage.


FINDINGS: A well-defined radiolucent lesion is associated with the crown of impacted right lower molar. The lesion shows slight bucco-lingual expansions and thinning of cortical borders especially the lingual cortical border as seen on the cross-sectional image. The tooth is horizontally impacted and in close proximity to the mandibular canal.


IMPRESSION: The radiographic features of the lesion are most consistent with a cyst. A dentigerous cyst would be on the top of the differential diagnosis list since the lesion is associated with the crown of an impacted tooth. Other possible lesions would include keratocystic odontogenic cyst and mural ameloblastoma.

HISTORY: A 13-year-old female patient was referred for a Cone Beam CT evaluation of a radiolucent area associated with her impacted #6.


FINDINGS: There is a well-defined radiolucent lesion associated with the crown of horizontally impacted right maxillary canine. The lesion extends from the crown of the tooth inferiorly. There is slight lingual and buccal expansion in the cortical borders. The lesion exhibits smooth partially corticated margins. The impacted tooth is situated at the level of the floor of the nose and the apex of the tooth extends slightly into the right maxillary sinus. There are signs of soft tissue thickening in the sinus floor. The retained primary tooth #c shows slight root resorption.


IMPRESSION: This is classic appearance of a dentigerous cyst. Although in a differential diagnosis we would include keratocystic odontogenic cyst and mural ameloblastoma; however, those are less likely.

HISTORY: A 10-year-old female patient was referred for a Cone Beam CT evaluation of an expansile lesion in the left mandibular premolar area.


FINDINGS: Mixed dentition is present which is consistent with patient age. There is a well-defined radiolucency that extends from distal of unerupted #22 to the buccal of #19 and it extends from the furcation of #19 till the mental foramen. The lesion is hydrostatic, corticated, and expansile. There is thinning of buccal cortex. Lesion dimensions are 27 mm length x 13 mm width x 14 mm height. The lesion has caused displacement of roots #22 and #21. There is no evidence of root resorption. The follicular space of #20 and #22 are indistinguishable from the lesion. The lesion does not seem to displace the mandibular canal although it surrounds the mental foramen. It is noteworthy that lingual aspect of the lesion appears to intersect the CEJ areas of both #20 and #21..


IMPRESSION: The hydrostatic character of this lesion corresponds well with a cyst. The association of the CEJ(s) of unerupted premolar teeth and buccal expansion are consistent with a dentigerous cyst. KCOT would also be included in the differential. A benign odontogenic tumor is possible but unlikely.