Radicular Cyst

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  • Odontogenic cyst of inflammatory origin
  • Preceeded by pulp necrosis and chronic periapical granuloma
  • Most common odontogenic cyst
  • Also known as periapical cyst
  • Described as a residual cyst if present following tooth extraction
  • Lateral radicular cyst - occasionally form at the side of a non-vital tooth as a result of the opening of a lateral branch of the root canal

Epidemiology[edit]

  • Commonest type of jaw cyst (~60% of all cases)
  • Most common between ages of 20-60yrs old – rare <10yrs old
  • ♂ > ♀ (3:2)
  • Maxilla > Mandible (3:1)
  • Incidence of different types of radicular/peripical cysts:
    1. Apical - 70%
    2. Lateral - 20%
    3. Residual - 10%

Clinical Features[edit]

  • Slowly progressive painless swellings
  • Usually cause no symptoms unless large enough to be conspicuous
  • Can get infected → painful and rapid expansion (inflammatory oedema)
  • If visible, swelling is usually round and hard
  • If left to enlarge →
    • Bone can be reduced to egg shell thickness and a crackling sensation may be felt on gentle pressure
    • Finally if part of the wall is resorbed entirely the swelling is soft, fluctuant and bluish in colour
  • A necrotic tooth from which the tooth has originated is (by definition) present (if not then the cyst is termed a residual cyst)

Differential Diagnosis[edit]

Aetiology and Pathogenesis[edit]

Aetiology[edit]

  • Radicular cysts are cysts of inflammatory origin
  • Preceded by necrotic tooth and periodical granuloma

Pathogenesis[edit]

  • Major factors in the pathogenesis of cyst formation:
    1. Proliferation of epithelial lining and fibrous capsule
      • Apical periodontitis → resorption of alveolar bone via immune-inflammatory process
      • Inflammtory cytokines and growth factors released in apical periodontitis can stimulate epithelial cell rests of Malassez (remnants of Hertwig's epithelial root sheath)
        • Basal cells of the epithelial cell rests of Malassez are stimulated to proliferate and form the cyst
    2. Hydrostatic pressure of cyst fluid
      • Cyst fluid (inflammortary exudate and necrotic cellular debris) contains straw-coloured fluid containing cholesterol cystals with protein content >5g/dL
      • ∴ osmostic tension can cause cysts to expand in balloon like fashion
      • Expansion tends to occur in pathway of least resistance therefore tend to be less destructive
      • Hydrostatic pressure within cysts is ~70cm of water (higher than the capillary blood pressure)
    3. Resorption of surrounding bone
      • Cyst tissues have been shown to release bone-resorbing factors (prostaglandin E2 and E3) and collagenases
      • It is not fully clear what affect these have on cyst growth

Investigations[edit]

Orthopantogram of a radicular cyst in the mandible. Image from AboulHosn et al. 2019[1]
Histopathology of a radicular cyst, with metaplastic changes of mucous secreting cells, and ciliated cells
Histopathology of cholesterol clefts of a radicular cyst

Imaging[edit]

Plain film[edit]

  • Commonly an incidental finding on routine intra-oral or panoramic radiographs
  • Cysts only make up ~15% of all periapical radiolucencies[2]
    • Consider a cyst as opposed to periapical abscess when lesion is larger than 2cm2[3]
  • Common radiographic features:
    • Round radiolucent area
    • Unilocular
    • Sharply defined
    • Condensed radio-opaque periphery is present in long standing cysts
    • Associated with necrotic tooth
    • Large lesions can cause displacement/tilting of adjacent teeth
    • Large cysts in maxilla may extend in irregular shapes
    • Infected cyst may cause hazy outline and resorption of surrounding bone

Computed Tomography[edit]

  • Can facilitate diagnosis, and 3D characterisation for surgical planning

Histopathology[edit]

  • Common histopathological findings:
    1. Epithelial lining
      • Stratified squamous epithelium (non-keratinised) - except when near maxillary sinus where there is respiratory epithelium (pseudostratified ciliated columnar epithelium)
      • Varying thickness
      • Lacks well defined basal cell layer (may be missing)
      • Hyaline bodies and mucous cells may be present ∵ of metaplasia
      • Longstanding cysts = thin epithelial lining, thick fibrous wall and minimal inflammatory infiltrate
    2. Cyst capsule and wall
      • Collagenous fibrous connective tissue
      • Vascular during active growth
    3. Clefts
      • Clefts are present in cyst capsule
      • These occur ∵ breakdown of blood cells → cholesterol formation → cholesterol then dissolves out → clefts
    4. Cyst fluid
      • Usually watery and opalescent
      • Sometimes viscid and yellowish
      • Microscopy (after smear) shows cholesterol crystals
      • Histology shows protein (broken down leucocytes and cells distended within fat globules)

Management[edit]

  • Cyst enucleation - usually treatment of choice along with one of the following:
    1. Orthograde endodontic treatment
    2. Apicectomy
    3. Extraction
  • Orthograde endodontic treatment alone is suitable for small cysts (<1cm) as the cyst may subsequently heal
  • Marsupialization may sometimes be needed for very large cysts

Prognosis and Complications[edit]

  • Recurrence is uncommon if capsule is completely removed

Follow-up[edit]

  • Routine follow-up not needed
  • Suitable for results to be given to patient via remote consultation/mail

References[edit]