NEET MDS Lessons
Oral Pathology
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Dentigerous Cyst (Follicular Cyst):
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Most common Developmental Odontogenic Cyst.
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Always associated with the crown of an unerupted/impacted tooth.
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Derived from Reduced Enamel Epithelium (REE).
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Differential diagnosis: Eruption cyst, Paradental cyst (also from REE).
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Nasopalatine Duct Cyst (Incisive Canal Cyst/Median Anterior Maxillary Cyst - MAMC):
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Most common Developmental Non-odontogenic Cyst.
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Located in the midline of the anterior maxilla.
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Radicular Cyst (Periapical Cyst):
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Most common Odontogenic Cyst overall.
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Always associated with a non-vital tooth.
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Inflammatory origin.
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Odontogenic Keratocyst (OKC) / Keratocystic Odontogenic Tumor (KCOT):
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Primordial Cyst: An OKC found in place of a missing tooth.
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Protein Content: Less than 4 gm/dL.
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Aggressive Behavior: High mitotic activity, high PCNA index, and Ki67 activity.
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Derived from Rests of Serres (remnants of dental lamina).
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Mucocele:
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Common term for:
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Mucous Extravasation Phenomenon (Pseudocyst): No epithelial lining.
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Mucous Retention Cyst (True Cyst): Has an epithelial lining.
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Radicular Cysts: Derived from Rests of Malassez.
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Impacted Canine Associations:
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Most common odontogenic cyst: Dentigerous cyst.
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Most common odontogenic tumor: Adenomatoid Odontogenic Tumor (AOT).
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Eruption Cyst: Considered an extra-alveolar dentigerous cyst (soft tissue counterpart).
| Syndrome | Confirmatory Sign |
|---|---|
| Trigeminal Neuralgia | Relief with carbamazepine |
| Eagle’s Syndrome | Relief after styloidectomy |
| Frey’s Syndrome | Positive Minor’s starch-iodine test (sweat mapping) |
| Ramsay Hunt Syndrome | Vesicular eruptions in ear/oral mucosa + facial palsy |
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Lichen Planus:
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Reticular form: Most common type, characterized by Wickham's striae.
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Malignant potential: Atrophic and erosive forms are associated with significant malignant transformation risk.
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Histology: Saw-tooth shaped rete pegs.
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Solar Elastosis: Characterized clinically by "sailor's skin" or "farmer's skin" (due to chronic sun exposure).
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Psoriasis & Hereditary Gingival Fibromatosis: Both show test tube-shaped rete pegs histologically.
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LE Cell Test: LE cells represent rosettes of neutrophils that have phagocytosed other leukocytes (seen in Systemic Lupus Erythematosus).
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Tzanck Cells: Seen in vesiculobullous conditions like Pemphigus, Herpes Simplex, Varicella, Herpes Zoster, and CMV infection.
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Ectodermal Dysplasia: Characterized by truncated, conical teeth and missing teeth (hypodontia).
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Widened Periodontal Ligament Space: Extreme widening seen in Scleroderma and Osteosarcoma.
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Geographic Tongue & Psoriasis: Share a common histological feature: Munro's abscesses (neutrophilic microabscesses).
- SLE → IgG, IgM, IgA deposits at BMZ + superficial lamina propria
- Lichen Planus (Erosive/Atrophic) → Autoimmune T-cell; BMZ involvement
- Cicatricial Pemphigoid → Subepidermal blistering from anti-BMZ antibodies
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Pioneer Bacteria: S. mutans are considered pioneer bacteria as they multiply and synthesize extracellular matrix polymers, initiating biofilm formation.
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Caries Progression - Key Bacteria:
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Initiation of caries: S. mutans.
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Progression of caries / Dentinal caries: Lactobacillus.
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Root surface caries: Actinomycetes.
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Body of the Lesion (Enamel Caries): Shows increased prominence of the striae of Retzius.
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Sugar Intake: Frequency of sugar intake is of more importance than the total amount consumed in caries development.
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Hyperplastic Candidiasis: The only form of candidiasis that is non-scrapable. Often appears as admixed white and red areas, known as speckled leukoplakia or erythroleukoplakia.
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Median Rhomboid Glossitis: Etiology is controversial (developmental vs. fungal); if forced to choose, developmental.
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Gilchrist's Disease: Another name for North American Blastomycosis.
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Mucormycosis: More common in diabetic patients. Has a strong propensity to invade blood vessels.