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Case of the Month Archives

COM August 2008 Diagnosis

Large unilocular radiolucency associated with impacted tooth # 32

Can you make the correct diagnosis?

Figure 1 This is a panoramic view taken at the first clinical presentation.  The radiograph demonstrates a well-defined to corticated unilocular radiolucency around impacted tooth #32 with the tooth displaced inferiorly.

This is a 62-year-old white male referred by his general dentist for a deeply impacted tooth # 32 associated with a large unilocular radiolucency.  This lesion was discovered on routine dental examination.  There was no evidence of a swelling and the patient denied any pain or parasthesia.

Congratulations! You are correct

The radiographic presentation of this case is typical of dentigerous cyst. The age however is on the older age range. It is more common in patients between the ages of 10 and 30 years.

Dentigerous cyst is the most common developmental cyst in the oral cavity, accounting for 20% of the developmental cysts of the jaws, and is almost always associated with the crown of a tooth attached to the cemento-enamel junction as is the case in this patient. It is believed to originate from the accumulation of fluid between the reduced enamel epithelium and the tooth crown, thus expanding the follicle beyond the 3 mm normal diameter (1-3). It is usually associated with impacted or un-erupted teeth. Clinically, it can be an asymptomatic radiolucency discovered during a routine dental examination or can act aggressively by expanding the jaws, leading to facial asymmetry with extreme displacement of adjacent teeth as well as the involved tooth (1-2). It can be painful and cause root resorption especially if it is infected. It is more common in the third molars and upper canines and can also involve supernumerary teeth and odontomas. Radiographically, it presents as a smooth border, usually unilocular or sometimes multilocular radiolucency, located around the tooth circumferentially, laterally or in the form of a “doughnut” ring. The size varies from small to extremely large, extending into the ramus of the mandible. The borders are usually corticated and smooth unless it is inflamed when loss or cortication (usually partial) is present (1). Histologically, the cyst has non-specific features lined by variable thickness of stratified squamous epithelium and supported by connective tissue. Clusters of mucous cells are frequently present, especially in the mandibular third molar areas. Treatment depends on its size, and ranges from thorough curettage to marsupialization. It usually has a good prognosis. Recurrence is uncommon if properly removed. Occasionally this cyst is associated with ameloblastoma, epithelial dysplasia and/or squamous cell carcinoma or mucoepidermoid (1-3).


  1. Hyomoto M, Kawakami M, Inoue M, Kirita T. Clinical conditions for eruption of maxillary canines and mandibular premolars associated with dentigerous cysts. Am J Orthod Dentofacial Orthop. 2003; 124:515-520
  2. Shibata Y, Asaumi J, Yanagi Y, Kawai N, Hisatomi M, Matsuzaki H, Konouchi H, Nagatsuka H, Kishi K. Radiographic examination of dentigerous cysts in the transitional dentition. Dentomaxillofac Radiol. 2004 Jan;33(1):17-20.
  3. Ko KS, Dover DG, Jordan RC. Bilateral dentigerous cysts–report of an unusual case and review of the literature. J Can Dent Assoc. 1999 Jan;65(1):49-51.
  4. Shear M. Odontogenic keratocysts: natural history and immunohistochemistry. Oral Maxillofacial Surg Clin N Am. 2003; 15: 347-362.
  5. Oda D, Rivera V et al. Odontogenic keratocyst: the northwestern USA experience. J Contemp Dent Pract. 2000 Feb 15; 1(2): 60-74.
  6. Zachariades N, Papanicolaou S, Triantafyllou D. Odontogenic keratocysts: Review of the literature and report of sixteen cases. J Oral Maxillofac Surg. 1985; 43: 177-182
  7. Reichart PA, Philipsen HP, Sonner S. Ameloblastoma: biological profile of 3677 cases. Eur J Cancer B Oral Oncol 1995;31B:86–99.
  8. Adekeye EO, McLavery K. Recurrent ameloblastoma of the maxillofacial region. Clinical
    features and treatment. J Maxillofac Surg 1986;14:153-157.
  9. Gardner DG. Some current concepts on the pathology of ameloblastomas. J Oral Maxillofac Surg 1996;82:660-669.

Sorry! you are incorrect

Both the clinical and the radiographic findings of this case are consistent with OKC. The histology, however, is not.

Odontogenic keratocyst (OKC) is an aggressive odontogenic cyst and is known for its rapid growth and its tendency to invade the adjacent tissues, including bone. It has a high recurrence rate and is associated with basal cell nevus syndrome (4-5). The majority of patients are in the age ranges of 20-29 and 40-59, but cases in patients ranging in age from 5 to 80 years have been reported (4). The distribution between sexes varies from equal distribution to a male-to-female ratio of 1.6:1. OKC predominantly affects Caucasian populations and, if one may judge from the limited evidence provided by the literature, is chiefly of Northern European descent (4). Odontogenic keratocysts may occur in any part of the upper and lower jaw, with the majority (almost 70%) occurring in the mandible. They occur most commonly in the angle of the mandible extending superiorly into the ramus (4-5). Radiographically, OKCs present predominantly as unilocular radiolucencies with well-defined or sclerotic borders; they may also present as multilocular radiolucencies or unilocular with scalloped borders (more common) (4-6). They usually penetrate the bone rather than expand; they grow in an anterior and posterior manner with little to no expansion. The larger OKCs, however, tend to expand bone, but mildly. Obvious clinical expansion should be viewed with suspicion for a neoplasm. OKCs can also present as small and oval radiolucencies between teeth simulating a lateral periodontal cyst, in an area of an extracted tooth simulating a residual cyst, at the apex of a vital tooth mistaken for a periapical cyst, or in the anterior maxilla between the central incisors simulating an incisive canal cyst (4-6). OKCs grow to sizes larger than any other odontogenic cysts. Despite this aggressive growth, they often remain asymptomatic, thus growing to large sizes and hollowing the bone (4-6). Like dentigerous cysts, if infected, they can be painful, thus symptomatic. Multiple OKCs are frequently associated with bifid-rib basal cell nevus syndrome (Gorlin syndrome). Odontogenic keratocysts are significant clinical entities due to their tendency for recurrence and destructive behavior. They are known to have a high recurrence rate, ranging from 13% to 60% (4). Complete surgical removal is the treatment of choice. Enucleation combined with Carnoy’s solution or liquid nitrogen treatment has been effective in reducing recurrence rate (5).

Sorry! you are incorrect

The radiographic findings of this case are consistent with cystic ameloblastoma. The age of the patient and the histology, however, are not.

Ameloblastoma is defined as a benign neoplasm of tooth origin and as a benign but locally aggressive neoplasm with potential for invasion of the surrounding bone and soft tissue (7). It also has the potential for local extension to the brain, resulting in the death of the patient. However, not all ameloblastomas behave in that aggressive manner; ameloblastoma is a family of diseases with different biological behaviors. Therefore, it is necessary to distinguish between the various types before a definitive treatment is rendered (7-9). Three clinical types are described, beginning with the solid type (radiographically multilocular) which is treated with complete resection or en bloc (partial) resection depending on the size. The unicystic type includes three histologic types, one of which (the mural cystic ameloblastoma) behaves like the solid type, while the other two types (intraluminal and plexiform unicystic) are less aggressive and treated with curettage. Based on the radiographic presentation of unilocular radiolucency, extending into the ramus and being associated with the crown of an impacted tooth would be more consistent with a plexiform unicystic type of ameloblastoma (7-9). The unicystic type is much less aggressive than the solid type and accounts for about 10% of all ameloblastomas. It occurs in younger patients around 18 to 20 years of age with a strong predilection for the posterior mandible (9). Almost 90% of cases are associated with the crown of impacted third molar teeth with the radiographic presentation similar to a dentigerous cyst. This type of ameloblastoma can arise from a dentigerous cyst or de novo next to a cyst. The former is more commonly seen. In about 10% of cases, it can present as a unilocular radiolucency simulating a residual cyst, periapical, primordial cyst or Odontogenic keratocyst (OKC). Radiographically, it is unilocular and corticated radiolucency and at times, the margins are scalloped, simulating an OKC. One study showed a 35% recurrence rate after four years of the initial treatment. Patients should be placed on follow-up for more than five years.