Definition: A cyst that forms around the crown of an unerupted tooth. This is most commonly associated with third molars and maxillary canines. A hyperplastic follicle has a very similar appearance to a dentigerous cyst. A hyperplastic follicle is an enlarged follicle with less than 5 mm of space from the enamel to the edge of the lesion. Once the lesion edge is more than 5 mm from the enamel, it is classified as a dentigerous cyst.
Location: Around the crown of a tooth.
Edge: Well-defined. Corticated.
Shape: Round to ovoid.
Internal: Radiolucent, unilocular.
Other: The border of the cyst is continuous at the cemento-enamel junction of the unerupted tooth. As it grows, it will displace the associated tooth apically. It may displace or resorb adjacent teeth as it enlarges.
Number: Typically single, but may be multiple (rare).
Dentigerous cyst/Hyperplastic follicle
(this is a borderline case – maxillary left third molar)