21-year-old man with a sense of gradual increase of pressure in the left part of the face.
Panoramic radiography shows an absent third molar tooth (wisdom tooth) associated with a cortical breakthrough of the maxillary sinus floor (Fig.1). This image also depicts an unerupted and impacted left canine tooth as an incidental finding (also in Fig. 6).
Axial (Fig. 2) coronal (Fig. 3 and Fig. 5) and sagittal (Fig. 4) reformatted CT examination of the paranasal sinuses shows well-defined, corticated, large cystic mass involving the left maxillary sinus. This mass markedly displaces the floor of the maxillary sinus (making it convex upwards), occupying a substantial portion of the sinus. This cystic lesion enclose a displaced third molar tooth. A double bony margin is seen along the roof of the maxillary antrum in the coronal plane (Fig. 3 and Fig. 5). These findings support the diagnosis of dentigerous cyst.
The dentigerous cyst is the most common type of noninflammatory odontogenic cyst  and the most common cause of a pericoronal area of lucency associated with an impacted tooth. They develop within the normal dental follicle surrounding an unerupted tooth and are a result of fluid accumulation between the follicular epithelium and the crown of the tooth; thus, at radiography, an unerupted tooth with its crown centred in a lucent mass is suggestive of a dentigerous cyst . The roots of the tooth typically are seen outside the lucent lesion, and the cortical bone is preserved; however, large lesions may cause osseous expansion [2, 3] like our case depicts. Most dentigerous cysts manifest in adolescents and young adults and often form around the crown of an unerupted mandibular third molar. Patients are typically pain-free. The most important features of this cyst are its ability to expand asymptomatically and its potential to displace or resorb adjacent teeth or bone .
At radiography, dentigerous cysts appear as well-defined, round or ovoid, corticated, lucent lesions around the crowns of unerupted teeth, usually third molars . Dentigerous cysts can vary in size; cysts 2 cm in diameter or larger may cause mandibular expansion . The radiographic appearance of such dentigerous cysts is comparable with that of cystic, unilocular odontogenic keratocysts. Extremely large dentigerous cysts often develop undulating borders due to uneven rates of expansion through areas of varying bone density; the resulting radiographic appearance is comparable with that of a larger odontogenic keratocyst or ameloblastoma.
Treatment includes extraction of the associated tooth and removal of the entire cyst. Removal of extremely large cysts may require stabilisation of the bone with metal plates and bone grafting into the surgical site .
Differential Diagnosis List