Cysts, Odontogenic Tumors, and Oral Manifestations of Systemic Disease

Core Review

Odontogenic Cysts

Odontogenic cysts are epithelium-lined pathological cavities derived from odontogenic epithelium (remnants of tooth development). They are classified as developmental or inflammatory.

Radicular (Periapical) Cyst

The most common odontogenic cyst — accounts for approximately 50-70% of all jaw cysts.

Etiology: INFLAMMATORY. Arises from epithelial rests of Malassez (remnants of Hertwig's epithelial root sheath) within the periodontal ligament, stimulated by inflammation from a non-vital tooth (pulpal necrosis). The inflammatory process stimulates epithelial proliferation, which can undergo cystic degeneration.

Radiographic appearance: Well-circumscribed, round/oval RADIOLUCENCY at the apex of a NON-VITAL tooth. Loss of lamina dura at the apex. The cyst is continuous with the periodontal ligament space. If infected, the borders may become less defined.

Clinical features: Associated with a non-vital tooth (caries, trauma, deep restoration). Usually asymptomatic unless infected (acute exacerbation → swelling, pain, pus). Tooth is non-responsive to vitality testing (cold, electric pulp test). The cyst may cause root resorption, displacement of adjacent teeth, or expansion of the cortical bone (if large).

Differentiation from periapical granuloma: Periapical granuloma is a mass of granulation tissue (not epithelium-lined) at the apex, with the same radiographic appearance. The distinction cannot be made radiographically — histologic examination is required. Periapical granulomas are more common than radicular cysts (~60% of periapical radiolucencies are granulomas, ~40% are cysts). Both are treated by endodontic therapy or extraction — both should resolve after successful root canal treatment.

Treatment: Root canal treatment (or extraction if non-restorable). The cyst should resolve after successful endodontic therapy (elimination of the inflammatory stimulus). Persistent lesions after endodontic treatment → apicoectomy and histologic examination.

Residual cyst: A radicular cyst that persists or develops AFTER the associated tooth has been extracted. Radiographically: radiolucency in an edentulous area at a previous tooth extraction site.

Dentigerous (Follicular) Cyst

The second most common odontogenic cyst.

Etiology: DEVELOPMENTAL. Arises from the separation of the dental follicle from around the crown of an UNERUPTED tooth. Fluid accumulates between the reduced enamel epithelium and the crown of the unerupted tooth. The cyst surrounds the crown of the unerupted tooth.

Radiographic appearance: Well-circumscribed, unilocular RADIOLUCENCY attached to the cementoenamel junction (CEJ) of an UNERUPTED, IMPACTED TOOTH. The radiolucency surrounds the CROWN of the tooth (NOT the root). The attachment at the CEJ is the classic diagnostic feature. Most commonly associated with mandibular third molars, followed by maxillary canines.

Clinical features: Most commonly in young adults (teens to 30s). Usually asymptomatic, discovered on routine radiography. If large, can cause bony expansion and displacement of adjacent teeth. Potential complications: pathologic fracture (if very large), development of ameloblastoma (rare) or squamous cell carcinoma (very rare) from the cyst lining.

Treatment: Enucleation (surgical removal of the entire cyst lining) with removal of the associated tooth, OR marsupialization (creating a window in the cyst to decompress it, allowing bone fill and tooth eruption — useful for cysts associated with teeth that may be orthodontically guided into the arch).

Distinguish from:

• Hyperplastic dental follicle (normal): Radiolucency around crown <2-3 mm width — normal finding
• Dentigerous cyst: Radiolucency >3-4 mm around crown
• Odontogenic keratocyst: May mimic dentigerous cyst if associated with an unerupted tooth, but OKC typically extends more apically along the root rather than attaching at the CEJ, and does not cause the same degree of bony expansion

Odontogenic Keratocyst (OKC)

Now classified by WHO as a benign odontogenic tumor (keratocystic odontogenic tumor), though the term "odontogenic keratocyst" remains widely used. OKC is distinctive for its aggressive behavior and HIGH RECURRENCE RATE (25-60%).

Etiology: DEVELOPMENTAL. Arises from remnants of the dental lamina. Associated with PTCH1 gene mutations (same gene implicated in nevoid basal cell carcinoma syndrome/Gorlin syndrome).

Radiographic appearance: Well-circumscribed, unilocular or multilocular radiolucency. Often appears to grow in an anteroposterior direction within the medullary bone, causing minimal buccolingual expansion (unlike dentigerous cyst and ameloblastoma). The lesion may "wrap around" teeth. Commonly in the posterior mandible (ramus, angle).

Clinical features: Peak incidence in 2nd-3rd decades. Often asymptomatic. Can be locally destructive without significant expansion — a "sneaky" lesion. May be discovered on routine radiography. Aspiration yields a thick, cheesy, keratinaceous material (characteristic).

Gorlin Syndrome (Nevoid Basal Cell Carcinoma Syndrome) associations:

• Multiple OKCs (often in younger patients)
• Multiple basal cell carcinomas (skin)
• Bifid ribs, calcified falx cerebri (seen on skull radiograph)
• Palmar and plantar pits
• Autosomal dominant (PTCH1 mutation on chromosome 9q22)

Treatment: Enucleation with peripheral ostectomy (removal of 1-2 mm of surrounding bone) or resection. Carnoy's solution (chemical cautery) may be applied to the bony cavity to reduce recurrence. Long-term follow-up due to high recurrence rate.

NBDHE note: An OKC associated with an unerupted tooth can mimic a dentigerous cyst radiographically. The key distinction: OKC extends more along the root rather than attaching at the CEJ, and aspiration yields keratinaceous material.

Lateral Periodontal Cyst

Etiology: DEVELOPMENTAL. Arises from rests of dental lamina.

Radiographic appearance: Small, well-circumscribed, unilocular radiolucency LATERAL to a VITAL tooth root, in the mandibular canine/premolar region (most common). Distinguished from radicular cyst by the tooth being VITAL.

Clinical significance: Benign, non-aggressive. Treatment: enucleation. Recurrence rare.

Nasopalatine Duct Cyst (Incisive Canal Cyst)

The most common NON-odontogenic cyst of the oral cavity.

Location: Midline anterior maxilla, within the incisive canal. Radiographically: well-circumscribed, round/oval/heart-shaped radiolucency between the roots of the maxillary central incisors. The lamina dura of the central incisors is INTACT (unlike a radicular cyst). The central incisors are VITAL.

Treatment: Enucleation. Recurrence rare.

Odontogenic Tumors

Ameloblastoma

The most common clinically significant odontogenic tumor. Benign but LOCALLY AGGRESSIVE — it can extensively invade the surrounding bone, and if incompletely removed, has a HIGH recurrence rate.

Radiographic appearance: MULTILOCULAR ("soap bubble" or "honeycomb") RADIOLUCENCY. Classic location: POSTERIOR MANDIBLE (ramus and angle). May cause marked buccal and lingual cortical expansion. Root resorption of adjacent teeth is common.

Important NBDHE note: "Soap bubble" is a DESCRIPTIVE term for a multilocular radiolucency, NOT a diagnosis. While ameloblastoma is the most classic lesion described this way, other multilocular lesions (OKC, central giant cell granuloma, aneurysmal bone cyst, myxoma) can also appear multilocular. The NBDHE may try to trick you — don't equate "soap bubble" with ameloblastoma alone; it's the combination of multilocular radiolucency + posterior mandible + aggressive expansion + root resorption that points to ameloblastoma.

Clinical subtypes:

• Solid/multicystic (conventional): Most common (~85-90%). Locally aggressive. Requires resection with 1-2 cm margins.
• Unicystic: Unilocular radiolucency, often associated with an unerupted tooth (mimics dentigerous cyst). Less aggressive. May be treated more conservatively (enucleation with close follow-up).
• Peripheral (extraosseous): Arises in the gingiva, no bony involvement. Least aggressive. Treated with local excision.

Treatment: Surgical resection with 1-2 cm margins for solid/multicystic type. Curettage/enucleation is associated with high recurrence rates (50-75% with curettage alone vs. 10-15% with wide resection). Long-term follow-up required.

Odontoma

The most common odontogenic tumor (though technically a hamartoma — developmental malformation). Completely benign, non-aggressive.

Two types:

• Compound odontoma: Multiple small, tooth-like structures (denticles). Anterior maxilla most common.
• Complex odontoma: Amorphous, disorganized mass of enamel, dentin, cementum, and pulp tissue (no recognizable tooth forms). Posterior mandible most common.

Radiographic appearance: Compound: Multiple small, radio-opaque tooth-like structures. Complex: Amorphous radio-opaque mass surrounded by a thin radiolucent rim. Both may be associated with an unerupted tooth.

Treatment: Simple surgical excision. No recurrence.

Other Odontogenic Tumors

• Odontogenic myxoma: Benign but locally aggressive. Multilocular radiolucency (can appear "soap bubble" like). Mandible. Requires resection.
• Cementoblastoma: True benign neoplasm of cementoblasts. Radiopaque mass attached to the root of a VITAL tooth (usually mandibular first molar). The root outline is OBLITERATED (fused with the lesion). Pain may be present. Treatment: excision; may require tooth extraction.
• Adenomatoid odontogenic tumor (AOT): Benign, unilocular radiolucency in the anterior maxilla, often associated with an unerupted canine. May contain fine calcifications ("snowflake" radiopacities). Female predilection; 2nd-3rd decade. Treated by enucleation.

Oral Manifestations of Systemic Disease

Diabetes Mellitus

Oral manifestations are particularly important for dental hygiene:

• Periodontal disease: Diabetes is a well-established risk factor for periodontitis. The relationship is bidirectional — periodontitis adversely affects glycemic control, and treatment of periodontitis can improve glycemic control (reduction in HbA1c of ~0.4%).
• Xerostomia: Due to polyuria/dehydration and possibly autonomic neuropathy affecting salivary function
• Increased caries risk: Secondary to xerostomia
• Oral candidiasis: Increased susceptibility due to hyperglycemia (glucose in saliva) and impaired immune function
• Burning mouth syndrome/dysgeusia
• Delayed wound healing: Important for surgical procedures and periodontal therapy
• Acetone (fruity) breath odor in uncontrolled/poorly controlled diabetes (ketoacidosis)
• Sialadenosis: Bilateral, asymptomatic parotid enlargement (may occur in poorly controlled diabetes)

AAP/EFP 2017 classification note: Diabetes is a grade modifier in the new periodontal classification. HbA1c <7.0% in a diabetic patient = Grade B; HbA1c ≥7.0% = Grade C (rapid progression rate).

HIV/AIDS

Oral manifestations are often among the earliest clinical signs and are used for staging:

• Candidiasis: Pseudomembranous, erythematous, angular cheilitis — among the most common oral manifestations. Oropharyngeal candidiasis is an AIDS-defining condition (CD4 <200).
• Hairy leukoplakia: EBV-associated, corrugated white plaque on lateral tongue. AIDS-defining.
• Kaposi sarcoma: HHV-8-associated vascular malignancy. Purple/red macules, papules, or nodules. Palate and gingiva most common oral sites. AIDS-defining.
• Linear gingival erythema (LGE): Distinctive band of intense gingival erythema at the free gingival margin, disproportionate to plaque levels. Does NOT respond to conventional periodontal therapy. Previously called "HIV gingivitis."
• Necrotizing periodontal diseases: Necrotizing ulcerative gingivitis (NUG), necrotizing ulcerative periodontitis (NUP). Rapid tissue destruction, pain, bleeding, fetid odor, pseudomembrane, interproximal necrosis ("punched-out" papillae).
• Recurrent aphthous stomatitis: Severe, major ulcerative type, refractory to conventional treatment
• Herpes simplex: Persistent, severe, may involve non-keratinized mucosa (unlike normal recurrent HSV)
• Herpes zoster: May be severe, prolonged, multidermatomal
• Salivary gland disease: Xerostomia, bilateral parotid enlargement (lymphoepithelial cysts)
• Non-Hodgkin lymphoma: Oral involvement may present as a mass or ulceration, often on the palate or gingiva

Hematologic Disorders

Anemia (iron deficiency):

• Atrophic glossitis: Smooth, depapillated, beefy-red, painful tongue (atrophy of filiform papillae)
• Angular cheilitis
• Aphthous-like ulcers
• Burning mouth
• Pallor of oral mucosa (conjunctival pallor is a better diagnostic sign)
• Koilonychia (spoon-shaped nails — chronic severe iron deficiency)
• Plummer-Vinson syndrome: Triad of iron deficiency anemia, dysphagia (esophageal web), and atrophic glossitis. Increased risk of oral and esophageal SCC.

Pernicious anemia (vitamin B12 deficiency):

• Atrophic glossitis (Hunter glossitis — fiery red, smooth, painful tongue)
• Burning mouth, dysgeusia
• Angular cheilitis
• Neurological symptoms: peripheral neuropathy, paresthesia

Leukemia:

• Gingival enlargement: Especially acute myelomonocytic leukemia (AML M4/M5). Caused by leukemic infiltration of the gingiva. Gingiva appears boggy, purple/red, friable, bleeds spontaneously.
• Petechiae, ecchymoses, spontaneous bleeding: Due to thrombocytopenia
• Pallor: Due to anemia
• Oral ulceration: Due to neutropenia (impaired healing, opportunistic infections)
• Candidiasis, HSV infections

Thrombocytopenia:

• Petechiae (palatal petechiae are classic)
• Ecchymoses (bruising)
• Spontaneous gingival bleeding
• Prolonged bleeding after dental procedures

Agranulocytosis/Neutropenia:

• Severe, painful, necrotic oral ulcerations
• Lack of purulence (no neutrophils to form pus)
• Rapidly progressive periodontitis

Nutritional Deficiencies — Key Oral Signs

Other Systemic Conditions

Sjögren's syndrome:

• Autoimmune destruction of salivary and lacrimal glands
• Primary: Sicca complex alone (xerostomia + keratoconjunctivitis sicca)
• Secondary: Sicca complex + another autoimmune disease (rheumatoid arthritis, SLE, scleroderma)
• Oral manifestations: Profound xerostomia → rampant caries, candidiasis, dysphagia, burning mouth, denture intolerance, sialadenitis
• Autoantibodies: Anti-Ro/SSA, Anti-La/SSB
• Diagnosis: Labial minor salivary gland biopsy (focal lymphocytic sialadenitis — focus score ≥1)

Crohn disease:

• Oral manifestations may precede GI symptoms
• Cobblestone (cobblestoning) of the buccal mucosa
• Aphthous-like ulcerations
• Mucosal tags/lip swelling (orofacial granulomatosis)
• Gingival hyperplasia (granulomatous gingivitis)

Addison disease (adrenal insufficiency):

• Diffuse brown melanotic pigmentation of the oral mucosa (buccal mucosa, gingiva, tongue)
• Mechanism: Elevated ACTH stimulates melanocyte-stimulating hormone production

Peutz-Jeghers syndrome:

• Multiple perioral melanotic macules (dark brown/black spots on lips and oral mucosa)
• Associated with intestinal hamartomatous polyposis → increased risk of intussusception and GI malignancy
• Autosomal dominant (STK11 mutation)

Clinical Application

The dental hygienist's recognition of oral cysts and tumors on radiographs is a critical screening function. Any persistent radiolucency should be investigated — referral to an oral surgeon or oral medicine specialist is warranted. For systemic diseases, the oral cavity often provides the first visible signs: undiagnosed diabetes (periodontitis, candidiasis), undiagnosed HIV (candidiasis, hairy leukoplakia), undiagnosed leukemia (gingival enlargement, petechiae), or undiagnosed nutritional deficiencies (glossitis). The dental team plays a crucial role in early detection and referral.

Common Traps

• Confusing dentigerous cyst with OKC when both are associated with unerupted teeth — dentigerous attaches at CEJ; OKC extends along root
• Equating "soap bubble" with ameloblastoma — other lesions can be multilocular
• Forgetting that a radicular cyst requires a NON-VITAL tooth; a lateral radiolucency at a VITAL tooth is a lateral periodontal cyst
• Thinking ameloblastoma is treated by simple enucleation — solid/multicystic requires resection; curettage = high recurrence
• Forgetting that anemia/leukemia can present with oral signs before systemic diagnosis