Odontogenic Cysts
Radicular Cyst
aka Periapical Cyst · Apical Periodontal Cyst · Root End Cyst
The most common inflammatory odontogenic cyst; a sequela of pulp necrosis stimulating epithelial cell rests of Malassez at the apex of a non-vital tooth.
Red Flags
- ·Rapid growth
- ·Paraesthesia of lip or teeth
- ·Cortical perforation with soft-tissue mass
- ·Failure to heal 6 months after adequate RCT — biopsy mandatory to exclude neoplasm
Clinical Tips
- ·A periapical radiolucency ≥ 1 cm is more often cystic than granulomatous; still confirm histologically
- ·Never treat a periapical lesion without vitality testing
- ·Residual cysts occur when a cyst is left behind after extraction — biopsy any post-extraction radiolucency
Examination Checklist
- ·Inspect for sinus / swelling / discolouration
- ·Palpate for expansion, egg-shell crackling
- ·Percuss suspected tooth
- ·Cold and EPT vitality tests
- ·Periapical + panoramic radiograph
- ·CBCT if extension unclear
- ·Aspiration in-office
§ figuresFigures (4)
Fig. 1Dr. T. Balasubramanian www.drtbalu.com
“Den cyst” · Drtbalu at English Wikipedia · CC BY 2.5 · Wikimedia Commons
Fig. 2Dr. T. Balasubramanian www.drtbalu.com
“Den cyst ct” · Drtbalu at English Wikipedia · CC BY 2.5 · Wikimedia Commons
Verified open-access images only, reproduced for education under their stated licences · no AI-generated or illustrative artwork · Radicular Cyst figures pending faculty review.
§ overviewOverview
An inflammatory odontogenic cyst arising from the epithelial cell rests of Malassez in the periodontal ligament, triggered by pulpal necrosis and periapical inflammation.
§ icdICD Classification
ICD-10 K04.8
§ etiologyEtiology
- 01Pulp necrosis from dental caries
- 02Traumatic pulp injury
- 03Failed root canal treatment
- 04Deep restorations reaching pulp
§ riskRisk Factors
- 01Untreated deep caries
- 02Chronic periapical granuloma > 3 months
- 03Cracked tooth
- 04Prior trauma to anterior teeth
§ geneticsGenetics & Molecular Biology
- 01No germ-line predisposition
- 02Upregulation of IL-1, IL-6, TNF-α, RANKL, MMP-9 drives epithelial proliferation and bone resorption
§ epidemiologyEpidemiology
Accounts for 52–68% of all jaw cysts. Peak incidence: 3rd–5th decade. M > F (~1.5:1). Maxilla > mandible (~3:1); most common at maxillary anteriors.
§ pathogenesisPathogenesis
Pulp necrosis → periapical inflammatory infiltrate → cytokine-mediated activation of epithelial cell rests of Malassez → three-phase development: (1) initiation of epithelial proliferation, (2) cyst formation by central necrosis of epithelial mass or coalescence of microcysts, (3) enlargement by osmotic pressure gradient and bone resorption via RANKL/OPG imbalance.
§ clinicalClinical Features
- 01Usually asymptomatic — incidental radiographic finding
- 02Non-vital associated tooth (negative to EPT and cold)
- 03Slow painless bony swelling as cyst enlarges
- 04Egg-shell crackling when cortex thins
- 05Occasional discharging sinus
§ signsSigns & Symptoms
- 01Discoloured non-vital tooth
- 02Tenderness on percussion when acutely infected
- 03Fluctuant swelling in vestibule
- 04Rarely paraesthesia (excludes malignancy)
§ differentialDifferential Diagnosis
- 01Periapical granuloma
- 02Periapical cemento-osseous dysplasia (early stage)
- 03Lateral periodontal cyst
- 04Traumatic bone cyst
- 05Central giant cell granuloma
- 06Ameloblastoma (in molars)
§ criteriaDiagnostic Criteria
- 01Radiolucency (usually > 1 cm) associated with a non-vital tooth
- 02Well-defined corticated margin
- 03Histologic confirmation of non-keratinised stratified squamous epithelial lining with inflammatory infiltrate
§ histopathHistopathology
- 01Non-keratinised stratified squamous epithelium (6–20 cell layers, arcading pattern)
- 02Fibrous connective tissue capsule densely infiltrated by lymphocytes, plasma cells and neutrophils
- 03Rushton hyaline bodies (~10%) — eosinophilic, hairpin-shaped intra-epithelial structures
- 04Cholesterol clefts with foreign-body giant cells
- 05Haemosiderin pigment; occasional dystrophic calcification
§ radiographicRadiographic Features
- 01Round to oval well-circumscribed radiolucency at root apex
- 02Corticated margin (lost when acutely infected)
- 03Continuous with lamina dura of offending tooth
- 04Root resorption in long-standing cysts (~30%)
§ opgOPG Findings
- 01Best initial screening; assess extent, cortical integrity, relation to sinus/IAN canal
- 02Loss of lamina dura is the earliest sign
§ cbctCBCT Findings
- 013D delineation of buccolingual expansion
- 02Relation to maxillary sinus floor or inferior alveolar canal
- 03Small-FOV CBCT preferred to limit dose
§ ctCT Findings
- 01Reserved for large lesions or infected cysts extending into deep spaces; assess cortical perforation
§ mriMRI Findings
- 01Hypointense on T1, hyperintense on T2, no enhancement of contents; peripheral rim enhancement of lining
§ investigationsInvestigations
- 01Vitality testing (EPT + thermal) — pathognomonic negative response of causative tooth
- 02Percussion & palpation
- 03Aspiration — straw-coloured fluid, cholesterol crystals shimmer
- 04Biopsy for histopathologic confirmation after enucleation
§ labsLaboratory Findings
- 01Aspirate protein > 5 g/dL (< 4 g/dL suggests OKC)
- 02Cholesterol crystals on microscopy
§ ihcIHC / Special Stains
- 01Cytokeratin 13/14 positive lining
- 02Ki-67 low (< 5%) — distinguishes from OKC (10–35%)
- 03p53 low
§ whoWHO Classification
WHO 2022 Classification of Head & Neck Tumours: Inflammatory odontogenic cyst — Radicular cyst (apical, lateral, residual variants).
§ classificationClassification
- 01Apical radicular cyst — at root apex
- 02Lateral radicular cyst — from lateral accessory canal
- 03Residual cyst — persists after tooth extraction
§ planTreatment Planning
- 01Confirm non-vitality of associated tooth
- 02Small (< 2 cm) cysts amenable to endodontic therapy alone
- 03Large cysts or failed RCT → surgical management
- 04Assess relation to vital structures on CBCT before surgery
§ treatmentTreatment
- 01Non-surgical root canal treatment for small lesions — up to 85% heal without surgery
- 02Apicoectomy + retrograde MTA seal for persistent apical pathosis
- 03Enucleation ± peripheral ostectomy for lesions > 2 cm
- 04Marsupialisation (Partsch I) for very large cysts adjacent to vital structures, followed by staged enucleation
- 05Extraction of hopeless tooth with enucleation of cyst
§ medicalMedical Management
- 01Antibiotics only if secondary infection (amoxicillin 500 mg TID × 5 d ± metronidazole)
- 02Analgesics as required
§ surgicalSurgical Management
- 01Enucleation (Partsch II) — cyst removed en bloc with lining
- 02Marsupialisation (Partsch I) — decompression via window
- 03Apicoectomy with retrograde filling
- 04Guided bone regeneration with membrane + graft for large defects
§ reconstructionReconstruction Options
- 01Small defects: heal by secondary intention with clot
- 02Medium: xenograft (Bio-Oss) or autogenous chin/ramus graft
- 03Large: iliac crest graft; rarely microvascular flap
§ complicationsComplications
- 01Secondary infection → cellulitis
- 02Pathologic fracture of atrophic mandible
- 03Displacement into maxillary sinus or IAN canal injury
- 04Recurrence if lining incompletely removed
- 05Very rare: SCC or mucoepidermoid carcinoma arising in cyst lining
§ recurrenceRecurrence Rate
< 2% after complete enucleation; residual cyst if incomplete removal.
§ followupFollow-up Protocol
- 01Clinical + radiographic review at 3, 6, 12 months post-op
- 02Annual OPG until complete bony infill (usually 12–24 months)
- 03Long-term follow-up for large lesions or those adjacent to vital structures
§ prognosisPrognosis
Excellent. Endodontic success rate 85–90%; surgical enucleation > 95% cure.
§ preventionPrevention
- 01Early caries management
- 02Prompt endodontic treatment of pulpal disease
- 03Regular dental review
- 04Trauma prevention (mouthguards)
§ examKey Examination Points
- 01Always test pulp vitality of adjacent teeth
- 02Radiolucency + non-vital tooth = radicular cyst until proven otherwise
- 03Aspiration protein content > 5 g/dL supports diagnosis
§ revisionQuick Revision Summary
- 01Most common odontogenic cyst
- 02From cell rests of Malassez
- 03Always non-vital tooth
- 04Non-keratinised stratified squamous lining
- 05Rushton bodies pathognomonic when present
- 06Enucleation is curative
§ vivaBDS Viva Questions
- 01Define radicular cyst.
- 02Which cells give rise to a radicular cyst?
- 03Describe the three phases of cyst development.
- 04How do you differentiate a radicular cyst from a periapical granuloma?
- 05What is a Rushton body?
- 06List the contents of aspirated cyst fluid.
- 07Describe Partsch I vs Partsch II operations.
- 08What is a residual cyst?
- 09Complications of an untreated radicular cyst?
- 10Recurrence rate after enucleation?
- 11When would you choose marsupialisation?
- 12How does cholesterol accumulate in a radicular cyst?
- 13Role of RANKL/OPG in cyst enlargement?
- 14Radiographic differential diagnosis for a periapical radiolucency?
- 15How is the maxillary sinus involvement managed?
- 16Antibiotic regimen if infected?
§ bdsBDS Professional Examination
- 01Long essay: Classify odontogenic cysts. Describe aetiopathogenesis, clinical & radiographic features, and management of radicular cyst.
- 02Short essay: Rushton bodies.
- 03Short note: Residual cyst.
- 04Short note: Marsupialisation vs enucleation.
§ fcpsFCPS Residency Questions
- 01Discuss the molecular pathogenesis of inflammatory odontogenic cyst enlargement and evidence-based rationale for surgical vs non-surgical management.
- 02Compare radicular cyst with OKC in terms of biology, imaging, histology, treatment and recurrence.
- 03Discuss reconstruction of a large mandibular cystic defect following enucleation.
§ pearlsClinical Pearls
- 01Not every periapical radiolucency is a cyst — histology is the arbiter.
- 02Failed RCT + persistent radiolucency at 6 months → surgical exploration.
§ mnemonicsMnemonics
- 01Radicular = Rest of Malassez, Rushton bodies, Root apex, Rotten (non-vital) tooth
§ readingSuggested Reading
- 01Shear M, Speight PM. Cysts of the Oral and Maxillofacial Regions, 4e — Wiley-Blackwell
- 02Nair PNR. On the causes of persistent apical periodontitis: a review. Int Endod J 2006.
- 03Lin LM et al. Periapical bone regeneration after endodontic microsurgery. J Endod 2020.
§ differentialDifferential Comparison
| Entity | Feature | Distinguisher |
|---|---|---|
| Periapical granuloma | < 1 cm, ill-defined | Histology required; cannot distinguish reliably on radiograph |
| Dentigerous cyst | Surrounds crown of unerupted tooth | Attached at CEJ, associated tooth is vital |
| Nasopalatine cyst | Heart-shaped, midline | Between vital central incisors |
| COD (early) | Multiple periapical radiolucencies | Associated teeth are vital; middle-aged Black females |
§ mcqsMCQs — Assessment (20)
Question 1
The most common odontogenic cyst is:
Question 2
Radicular cyst arises from:
Question 3
Rushton bodies are found in:
Question 4
Aspirated protein > 5 g/dL suggests:
Question 5
Vitality of the associated tooth in radicular cyst is:
Question 6
Partsch I refers to:
Question 7
The most common site is:
Question 8
Recurrence rate after enucleation is:
Question 9
Lining of radicular cyst is:
Question 10
Cholesterol clefts arise from:
Question 11
Which imaging is gold standard for extension?
Question 12
Ki-67 index in radicular cyst is:
Question 13
Which mediator drives bone resorption?
Question 14
A cyst persisting after extraction of the offending tooth is called:
Question 15
Best endodontic outcome is expected when the cyst diameter is:
Question 16
Which is NOT a feature of radicular cyst?
Question 17
Most reliable radiographic differentiator from granuloma is:
Question 18
Malignant transformation of radicular cyst is:
Question 19
Which antibiotic is first-line for an infected radicular cyst?
Question 20
Which cell type predominates in the cyst wall infiltrate?
§ evidenceReferences & Evidence
Current Classification
WHO Classification of Head and Neck Tumours
5th Edition — Volume 9
WHO Classification of Tumours Editorial Board · 2022
The authoritative international classification of head and neck, odontogenic and salivary gland tumours. Current terminology on this site follows this edition.
Evidence summary
Highest level of evidence linked to this page: WHO / Official Classification.
- L1 · Classification — 3
- L4 · Research — 1
- L6 · Textbook — 3
1 linked source was published from 2024 onwards. Where guidance is limited or contested, rely on the higher-level sources above rather than this summary. Educational use only — not a substitute for clinical judgement.
Content last reviewed
September 2026
Evidence last reviewed
September 2026
Next scheduled review
September 2027
Review status
EVIDENCE REVIEWED
Search latest PubMed evidence
Last literature search: 7 September 2026
Current Classification
WHO Classification of Tumours Editorial Board. IARC / World Health Organization · 2022
The authoritative international classification of head and neck, odontogenic and salivary gland tumours. Current terminology on this site follows this edition.
Vered M, Wright JM. Head and neck pathology · 2022 · 16(1):63-75
Summary of odontogenic and maxillofacial bone tumour changes in the 5th edition WHO classification.
IARC / WHO. IARC · 2022
Continuously updated online edition of the WHO head and neck tumour classification.
Radiology References
Dunfee BL, Sakai O, Pistey R et al.. Radiographics : a review publication of the Radiological Society of North America, Inc · 2006 · 26(6):1751-68
Radiologic-pathologic correlation of benign and malignant odontogenic lesions of the jaws.
Histopathology References
Barnes L. CRC Press · 2008
Detailed histopathological reference for head and neck diagnostic criteria.
Textbook References
Neville BW, Damm DD, Allen CM et al.. Elsevier · 2024
Standard reference textbook of oral and maxillofacial pathology used throughout this atlas.
Rajendran R, Sivapathasundharam B. Elsevier · 2020
Undergraduate and postgraduate oral pathology textbook widely used in BDS and FCPS curricula.
Additional sources cited on this page
- WHO Classification of Head and Neck Tumours, 5e (2022)
- Neville BW et al. Oral and Maxillofacial Pathology, 4e
- Shafer WG et al. Textbook of Oral Pathology, 9e
- Peterson LJ. Contemporary Oral & Maxillofacial Surgery, 7e
- Nair PNR. Non-microbial etiology: periapical cysts sustain post-treatment apical periodontitis. Endod Topics 2003.
Draft — pending faculty review. Educational use only; verify against current guidelines and primary sources before clinical application.