Mandible / maxilla
Odontogenic cysts
Eruption cyst




Topic Completed: 1 December 2013

Revised: 8 February 2019

Copyright: 2004-2018, PathologyOutlines.com, Inc.

PubMed Search: Eruption cyst [title]

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Cite this page: Morrison A. Odontogenic cysts: eruption cyst. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/mandiblemaxillaeruptioncyst.html. Accessed February 18th, 2019.
Definition / general
  • Develops in soft tissues overlying alveolar bone due to separation of dental follicle from crown of erupting tooth
Terminology: normal cells / structures
  • Ameloblasts:
    • Specialized epithelial cells that form tooth enamel
  • Deciduous tooth:
    • Also called baby tooth or primary tooth
    • Falls out during childhood
  • Succedaneous tooth:
    • Also called permanent tooth or adult tooth
    • Replaces deciduous teeth
    • Ideally lasts throughout life under most normal circumstances
  • Natal tooth:
    • Tooth or teeth present at birth
  • Neonatal tooth:
    • Tooth or teeth present during the first 30 days of life
Terminology: cysts
  • Dentigerous cyst:
    • Developmental odontogenic cyst occurring within the jawbone, originates by separation of dental follicle from around the crown of an unerupted tooth
  • Follicular cyst:
    • Synonym for dentigerous cyst
  • Eruption cyst:
    • Soft tissue counterpart to dentigerous cyst involving an erupting tooth
    • Whereas dentigerous cyst develops around crown of an unerupted tooth lying in the bone, eruption cyst occurs when a tooth is impeded in its eruption within the soft tissues
    • The epithelium lining the dilated cystic space is reduced enamel epithelium
  • Eruption hematoma:
    • Surface trauma may result in a considerable amount of blood in the fluid of the eruption cyst, which imparts a blue to purple-brown color
  • Reduced enamel epithelium:
    • Tooth enamel is normally composed of two cell layers: inner layer of reduced or atrophied ameloblasts and external layer, probably stratum intermedium cells
    • Reduced enamel epithelium is normally found overlying an unerupted, otherwise developed tooth
Epidemiology
  • 1 - 10% of submitted jaw cysts, but may be underrepresented since cysts that rupture spontaneously are not submitted for examination
  • Age: usually < age of 10, occasionally older patients with delayed tooth eruption, rarely congenital
  • Gender: male to female ratio 2:1
Sites
  • Mandibular central incisors and permanent first molars most common sites affected
Pathophysiology
  • Accumulation of fluid or hemorrhage between crown of erupting tooth and the reduced enamel epithelium of the surrounding dental follicle
  • In eruption cyst, tooth is within oral soft tissues, not bone, as occurs in dentigerous cyst
  • Factors actually impeding eruption through soft tissues are unknown, possibly dense fibrous tissue
Etiology
  • Develops secondary to accumulation of blood or fluid between tooth crown and an erupting primary or permanent tooth and the overlying mucosa
Clinical features
  • Raised, bluish or mucosal colored dome shaped gingival mass on alveolar ridge
  • Variable size, dependent on size and number of associated teeth, but usually < 1.5 cm
  • Usually asymptomatic but, if inflamed, may be painful and tender
  • Occasionally multiple cysts
Diagnosis
  • Radiographic findings, in combination with clinical information, can support a histomorphologic diagnosis
Radiology description
  • Usually no bone involvement except the dilated erupting tooth crypt
  • Soft tissue "shadow" of cyst may be seen on radiograph
Case reports
Treatment
  • None:
    • Treatment not likely required if the cyst ruptures spontaneously, permitting the tooth to erupt
  • Marsupialization:
    • If tooth eruption appears to be impeded by the lesion, the cyst can be unroofed, which usually allows the tooth to erupt
    • The dome of the cyst is excised, exposing the crown of the tooth, which is allowed to erupt
    • Submission of the cyst roof is recommended to confirm the clinical impression and exclude other pathology
Clinical images

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Large eruption cyst

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Eruption cyst associated with #11

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Exposure of #11 crown

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Eruption cyst of #13


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Eruption cyst (arrow) of #44

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Eruption cyst of #21

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Eruption cyst to left lower second molar

Microscopic (histologic) description
Epithelial surface facing oral cavity:
  • Keratinized squamous oral epithelium on superior / external or oral aspect of specimen corresponding to gingiva or alveolar ridge tissue
  • Lamina propria underlying the oral epithelium and overlying the roof of the cyst shows a variable inflammatory cell infiltrate
  • May be possible to distinguish a line of demarcation between gingival and follicular connective tissues: the gingival connective tissue is relatively acellular and densely collagenous and so has an eosinophilic hue; the follicular connective tissue is more densely cellular, less collagenous and has a more basophilic hue, presumably because of a higher content of sulphated glycosaminoglycans in the ground substance
  • Odontogenic epithelial cell rests may be present in the connective tissue
Roof of cyst:
  • The deep portion of the specimen, which represents the roof of the cyst, shows a thin layer of nonkeratinizing squamous epithelium
  • In non-inflamed areas, the epithelial lining of the cyst is characteristically of reduced enamel epithelial origin, consisting of 2 - 3 cell layers of squamous epithelium with a few foci where may be thicker
  • If the epithelial lining is inflamed, acute inflammatory cells are found in the epithelium which proliferates and shows reactive spongiosis
Differential diagnosis
  • Correlation with patient age, specific anatomic location at tooth bearing area of jaws, and radiographic findings is essential
  • Congenital, neonates, infants:
    • Epstein pearls
    • Bohn nodules
    • Gingival cyst of newborn
  • Children (less than 14 - 16 years of age):
    • Buccal bifurcation cyst
    • Dentigerous cyst
    • Dental follicle
    • Unicystic ameloblastoma
    • Soft tissue keratocystic odontogenic tumor
  • Adults:
    • Gingival cyst
    • Dentigerous cyst
    • Dental follicle
    • Paradental cyst
    • Unicystic ameloblastoma
    • Soft tissue keratocystic odontogenic tumor