A dentigerous cyst is an epithelial-lined cyst which involves the crown
of an unerupted tooth in its cavity.
The cysts are the second most prevalent type of odontogenic cysts after radicular cyst. They are usually painless, and many patients (and their dentists) are unaware of them until a routine x-ray is performed.
The reasons for their development are still currently unexplained.
It has been suggested (Thoma, 1960) that dentigerous cysts originated by a degeneration of the stellate reticulum of the enamel organ, the central type originating over the axis of the crown, the lateral type presumably starting a little later in the crown development. However, it has long been observed that teeth contained within a dentigerous cyst generally
do not suffer from abnormalities of enamel.
Source :Origin and growth of cysts of the jaws. Ann R Coll Surg Engl. 1967 May; 40(5): 306–336.