Dentigerous cysts are usually detected incidentally on dental imaging as a radiolucent cystic lesion associated with the crown of an unerupted tooth, commonly the mandibular third molar.
Description
A dentigerous cyst, or follicular cyst, is a developmental odontogenic cyst that forms from the dental follicle surrounding the crown of an unerupted tooth. It is the second most common type of odontogenic cyst after the radicular cyst and the most common cause of a pericoronal area of lucency associated with an impacted tooth.
Pathogenesis
The cyst arises from the accumulation of fluid between the enamel epithelium and the crown of an unerupted tooth, usually at the cementoenamel junction. The size of a typical follicle space is 2–3 mm; the presence of a dentigerous cyst should be suspected if the follicle space is greater than 5 mm. The exact pathogenic mechanism is not fully understood but may involve local inflammatory factors, trauma, or developmental disturbances.
Subtypes
There are no specific subtypes of dentigerous cysts, but variations can occur in size, location, and the impacted tooth involved.
Epidemiology, Risk Factors & Associations
- Typically occurs in the second and third decades of life.
- More common in males than females.
- Most often associated with the mandibular third molars, followed by maxillary canines.
Clinical Features
- Often asymptomatic, detected incidentally on routine dental X-rays.
- Larger cysts can cause swelling or displacement of adjacent teeth.
- Rarely, pain or infection may occur if the cyst becomes secondarily inflamed.
Complications
- Potential for infection leading to pain and swelling.
- May cause displacement or resorption of adjacent teeth.
- Rarely, transformation into a more aggressive lesion like an ameloblastoma.
- Possible hindrance to the eruption of the associated tooth.
Pathological Features
Histopathology
- Macroscopic: Cystic cavity surrounding the crown of an unerupted tooth.
- Microscopic: Lined by a thin layer of non-keratinised stratified squamous epithelium.
Radiological Features
General Features
- Well-defined, round or ovoid, corticated, lucent, unilocular, expansile lesion surrounding the crown of an unerupted tooth, usually the third molar1.
- The roots of the involved tooth are often outside the lesion and in mandibular bone. Resorption of the root apex is uncommon.
- Can expand the mandible and displace adjacent teeth.
- Significant cortical expansion or thinning of the buccal and lingual cortical plates may be seen with larger lesions
XR
- OPG: Well-defined unilocular radiolucency often extending from the cementoenamel junction.
CT
- Non-contrast: Clearly delineates the extent of the lesion and its relationship with adjacent structures.
- C+ Arterial/Venous: Not typically required unless assessing for secondary changes.
MRI
- Not commonly used, but can provide detailed soft tissue contrast.
- T1: Low- to intermediate signal within the cyst. Tooth appears as a signal void.
- T2: Hyperintense lesion
- T1 Gd+: Enhancement of the thin cyst wall.
Grading and Staging
No grading or staging system is applicable for dentigerous cysts as they are benign lesions.
Diagnosis
Based on radiographic findings showing a radiolucent lesion associated with the crown of an unerupted tooth, and confirmed by histopathological examination after enucleation.
Differential Diagnosis
- Odontogenic Keratocyst: Usually unilocular with thin walls.
- Radicular cyst: The most common type of odontogenic cyst. Associated with the apex of a non-vital tooth.
- Ameloblastoma: Usually multicystic soap bubble appearance, with resorption of adjacent teeth and root blunting. Unicystic ameloblastomas can be indistinguishable from other pericoronal lesions such as dentigerous cysts and odontogenic keratocysts. Presence of a thick irregular wall or a solid component favours ameloblastoma.
Management
- Enucleation and curettage of the cyst.
- Removal of the associated impacted tooth is often recommended.
- Regular follow-up to monitor for recurrence.
References