A 26-year-old male presented to a dentists office for evaluation of pain in the mandibular molar

Sept. 1, 1999
A 26-year-old male presented to a dentist`s office for evaluation of pain in the mandibular molar area.

A 26-year-old male presented to a dentist`s office for evaluation of pain in the mandibular molar area.

Joen Iannucci Haring, DDS, MS


When questioned about the area, the patient claimed that he had experienced intermittent pain in the region behind his right mandibular molars. He attributed the pain to what he thought was a problem with a wisdom tooth. The pain had been present for several weeks. No previous history of surgery or tooth extraction in the area distal to tooth #31 was reported. At the time of the dental appointment, the patient appeared to be healthy with no significant past medical history.


Extraoral examination revealed no enlarged or palpable lymph nodes. No soft tissue changes were evident in the right mandibular molar region. Radiographic examination of the area revealed a well-defined unilocular radiolucency with corticated borders distal to the roots of tooth #31. The lesion appeared to be approximately 1 cm in diameter (see radiograph).

A biopsy was performed and histologic examination revealed a thin epithelial lining with a corrugated parakeratin layer. The lumen of the lesion was filled with keratin.

Based on the clinical, radiographic, and microscopic examinations, what is the diagnosis?

* Ameloblastoma

* Dentigerous cyst

* Primordial cyst/OKC

* Residual cyst

* Ameloblastic fibroma


__ Primordial cyst / OKC


The primordial cyst is an odontogenic cyst. Odontogenic cysts are often encountered in dental practices. Many odontogenic cysts do not cause symptoms and, as a result, are only found during routine radiographic examination. Although odontogenic cysts are benign, these lesions have the potential to grow large, destroy bone, and damage adjacent teeth. Therefore, it is very important that the dental professional be able to identify odontogenic cysts.

An odontogenic cyst is a lesion that is found in the bones of the jaws or the soft tissues of the oral cavity. The term odontogenic refers to tooth-forming elements (odont refers to tooth and genic means giving rise to). The term cyst refers to an abnormal epithelial-lined sac or cavity that contains a liquid or semi-solid substance. By combining the terms odontogenic and cyst, an odontogenic cyst can be described as an epithelial-lined cavity that arises from any tissues that give origin to teeth.

An odontogenic cyst is derived from residual tooth-forming epithelium that remains within the jaws after tooth formation. Odontogenic cysts are derived from one of the following sources of epithelium:

- Rests of Malassez, the remnants of the Hertwig epithelial root sheath that remain in the periodontal ligament after root formation is complete.

- Reduced enamel epithelium, the residual epithelium that surrounds the crown of a tooth after enamel formation is complete.

- Remnants of the dental lamina, strands of epithelium that originate from oral tissues and remain in the tissues after stimulating tooth development.

Odontogenic cysts are either inflammatory or developmental in origin. While inflammatory odontogenic cysts form in response to inflammation, developmental odontogenic cysts form for unknown reasons.

Primordial cyst/odontogenic keratocyst

The primordial cyst is an outdated term for a cyst that occurs in place of a tooth. When the primordial cyst is examined under the microscope, its histologic appearance is consistent with that of the odontogenic keratocyst. Since 1992, the World Health Organization (WHO) has recommended using the term odontogenic keratocyst for this lesion. As a result, references to the primordial cyst are almost nonexistent in today?s current literature.

The odontogenic keratocyst (OKC) accounts for 10 to 12 percent of all odontogenic cysts. The OKC is known for its potentially aggressive behavior. Although this lesion is not a malignancy, it is capable of destroying massive areas of bone, moving teeth, and causing root resorption. In addition, it exhibits a significant rate of recurrence and is associated with Nevoid Basal Cell Carcinoma Syndrome.


The OKC is a developmental odontogenic cyst. This lesion is derived from remnants of the dental lamina.

Clinical features

The OKC may occur at any age with a peak incidence in the second and third decades. Some studies suggest that the OKC is found in males more frequently than females, while other studies claim there is no sex predilection. The OKC occurs more often in the mandible than in the maxilla; the majority is found in the posterior mandible/ramus area.

The OKC is usually asymptomatic. There are no characteristic signs or symptoms that suggest an OKC; however, pain, numbness, trismus, bony expansion, or intraoral drainage may occur.

Radiographic features

The OKC does not have a characteristic radiographic appearance that distinguishes it from other radiolucent lesions of the jaws. This lesion may appear as a unilocular, bilocular, or multilocular radiolucency. The size of the OKC varies. The borders may appear corticated or noncorticated.

The OKC may cause displacement of adjacent teeth and resorption of tooth roots both clearly evident on a radiograph. Bony expansion may involve the buccal or lingual cortical plates. Odontogenic keratocysts in the mandibular third molar area may enlarge to involve the entire ramus before bony expansion occurs. The OKC is often seen in association with an impacted tooth. On a radiograph, other apparent effects of the OKC include divergence of the roots of adjacent teeth and extrusion of erupted teeth.

It is impossible to diagnose an OKC from a radiograph alone; additional information is necessary.

Diagnosis and treatment

The diagnosis of an OKC is made based on the histologic appearance of the lesion. The OKC must be surgically removed. The surgical procedure is dictated by the size of the lesion. The complete surgical excision of the OKC is often difficult because the cyst wall is very thin and may easily fragment upon removal.


The OKC has a propensity to recur following surgical removal; an estimated 30 percent of these lesions recur following removal. Recurrences are most likely to take place in the first five postoperative years. A variety of explanations have been proposed as to why the OKC has such a high recurrence rate. Technical difficulty in the incomplete removal of the cyst lining is most often blamed.


Because of the high recurrence rate of the OKC, careful long-term postoperative follow-up is essential. Radiographs should be taken once per year for at least five to seven years following OKC removal. In addition, a patient with multiple odontogenic keratocysts should be evaluated for Nevoid Basal Cell Carcinoma Syndrome.

References available upon request.

Joen Iannucci Haring, DDS, MS, is an associate professor of clinical dentistry, Section of Primary Care, The Ohio State University College of Dentistry.