Chapter 25

Cysts of the maxilla and mandible are common occurrences. Bone cysts occur more frequently in the jawbones than in any other bone because of the presence of epithelium from odontogenic elements (eg, teeth) and nonodontogenic epithelial remnants of embryonic structures.

A cyst is defined as an epithelial-lined pathologic cavity that may contain fluid or a semisolid material. A group of cystic lesions devoid of an epithelial lining is classified as pseudocysts. A jaw cyst is usually located deep within the jawbone, but it may occur on a bony surface, producing a saucerization.

### Essentials of Diagnosis

• Well-defined, totally or predominantly radiolucent, and sometimes expansile lesions.
• Usually slow growing and benign.
• Initially asymptomatic unless long-standing with significant enlargement or secondary infection.
• Usually initially discovered on routine dental X-rays.
• Requires histopathologic examination for diagnosis.

### General Considerations

Jaw cysts encompass a group of lesions that are variable in their incidence, etiology, location, clinical behavior, and treatment. The most common jaw cyst is the radicular cyst, which is odontogenic and inflammatory in nature. The odontogenic developmental cyst is the second most common jaw cyst. Nonodontogenic cysts, pseudocysts, and ganglionic cysts of the temporomandibular joint (TMJ) are much less common. Cysts occur in both the mandible and the maxilla: inflammatory radicular cysts occur around the roots of nonvital teeth; odontogenic developmental dentigerous cysts and keratocysts occur in the common regions of impacted and unerupted teeth; nonodontogenic developmental cysts are found in regions of epithelial embryonic remnants; pseudocysts usually present in site-specific regions; and ganglionic cysts develop in the TMJ. Each type of jaw cyst usually has a specific behavior pattern, ranging from small 5- to 6-mm osteolytic defects to massive involvement of the jaw and contiguous structures.

### Classification of Jaw Cysts

The classification of jaw cysts includes (1) odontogenic cysts, (2) nonodontogenic cysts, and (3) pseudocysts. The ganglion cyst, which presents in the TMJ, has been added to this conventional classification for completeness; it is significant to clinicians managing the pathology of the head and neck region.

### Pathogenesis

The pathogenesis of jaws cysts varies according to the specific cyst type. Inflammatory cysts derive their epithelial lining from the proliferation of odontogenic epithelium within the periodontal ligament; dentigerous developmental cysts result from the proliferation of reduced enamel epithelium. Figure 25–1 illustrates the development of dentigerous and radicular cysts. Cystic lesions may also result from cortical bone defects or trauma, they may represent reactive lesions, or they may have an unknown pathogenesis. It has been shown that there is an osmotic pressure gradient that produces fluid accumulation within the cyst lumen and generates pressure, creating cyst expansion.

###### Figure 25–1.

(A) Development of the dentigerous cyst around the crown of an unerupted tooth. (B) Development of a radicular cyst ...

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