the dentigerous cyst is a common non - inflammatory odontogenic cyst of the oral cavity .
it 's pathogenesis involves the accumulation of fluid between the unerupted tooth crown and surrounding follicle , giving rise to the characteristic clinical and radiographic finding of a cystic lesion surrounding the neck of the tooth ( latin : dens , tooth + gerere , to bear ) .
treatment involves surgical enucleation or marsupialization with or without preservation of the impacted tooth , followed by histopathological evaluation to rule out an odontogenic keratocyst ( okc ) , ameloblastoma , or rarely , malignant transformation .
we report an unusual histopathological variant of the dentigerous cyst , the keratinizing dentigerous cyst , which has been reported only once previously in literature .
the present case is about a 21-year - old male patient of indian origin reported with a complaint of mild pain and swelling in the lower front region of the jaw for the past 1 year .
intra - oral examination revealed a diffuse swelling in the lower anterior vestibule extending from the region of 43 to 36 . on palpation , the swelling was firm in consistency and egg shell crackling was elicited in some areas .
the panoramic radiograph showed a well - defined unilocular radiolucency extending from the mesial aspect of 44 to the mesial root of 36 , extending to the mental foramen on the left side .
43 was impacted and the cystic lesion surrounded the crown of the tooth and extended for some distance along the mesial aspect of the root ( circumferential variant ) .
cone - beam computed tomography was also performed and revealed involvement of roots of 42 , 41 , 31 , 32 , 33 , 34 , 35 and mesial root of 46 [ figure 1 ] .
cone - beam computed tomography shows a unilocular lesion surrounding the crown of impacted 43 and extending along the mesial aspect of the root ( circumferential type ) an excisional biopsy of the lesion was performed under general anesthesia with conventional pre - operative medication cover and endotracheal intubation .
a mucoperiosteal flap was raised from 44 to 37 region and the lesion was detached from the soft - tissue using blunt dissection and curetted out from the bony walls .
root canal treatment was carried out for 41 , 42 , 31 , 33 , 34 and 35 .
the specimen was sent for histopathological examination to rule out an okc or an ameloblastoma .
the patient was called for review and a post - operative osteoprotegerin after 1 month .
macroscopically , a cyst in - toto with a tooth , measuring 40  30  40 mm in size [ figure 2 ] and four bits of tissue curetted from the surgical site were sent for histopathological evaluation .
the cyst was sectioned in half and processed along with the four bits of curetted tissue .
gross finding of a tooth within a cystic bag filled with keratinaceous material microscopically , a fibrous connective tissue capsule in association with a non - keratinized cystic lining epithelium of varying thickness was observed .
the four bits of curetted tissue microscopically showed the presence of hematoxyphilic substance , suggestive of keratin .
we report a case of keratinizing dentigerous cyst which , to the best of our knowledge , has been reported only once previously in the literature .
philipsen in 1956 suggested the term okc for all odontogenic cysts , regardless of type , showing keratinization of the epithelium .
more recently , an okc is defined by other characteristics of the epithelium such as basal palisading , hyperchromatism of nuclei and cell thickness of the epithelium and not merely the presence of keratinization .
the term  keratinizing odontogenic cyst has been suggested for any cyst , regardless of the type , that shows keratinization .
characteristically , the epithelial lining of a dentigerous cyst is not keratinized and most of those that have been described as keratinized have been ascribed to adjacent okcs .
however , taking into consideration the established criteria , the present case did not show any of the features that currently define okcs .
the patient was followed up after 1 year [ figure 4 ] and showed no clinical or radiographic signs of recurrence .
( a ) intra - oral - labial aspect of the patient 1 year postoperatively ( b ) intra - oral - lingual aspect of the patient 1 year postoperatively ( c ) orthopantamograph ( opg ) of the patient 1 year postoperatively the significance of keratinization in odontogenic cysts is not fully known .
however , dentigerous cysts , thought to arise from reduced enamel epithelium , are products of end cells , i.e. cells that have completed synthesis ( enamel formation ) .
considering the age of the patient , it is possible that the dentigerous cyst is a primordial variant , arising from more primitive cells of the developing enamel organ .
long term follow - up of patients presenting with a keratinizing dentigerous cyst is advised to observe its potential for recurrence or malignant transformation since very little is known about this unusual entity .
 keratinizing dentigerous cyst is a rare entity . this article reports a case of keratinizing dentigerous cyst associated with an impacted mandibular canine . 
 clinical and radiological features , cone - beam computed tomography findings and histological features of the case are reported along with a discussion on keratinizing odontogenic cysts and the need for follow - up . 