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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- 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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Actinomycosis (Sulfur Granules):
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Yellow sulfur granules: Are actually bacterial colonies.
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Histopathology: Colonies appear "cotton wool" shaped. (Note: "Cotton wool appearance" is seen radiographically in Paget's disease).
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Tuberculosis (TB):
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Diagnosis (Gold Standard): Presence of acid-fast bacilli in sputum.
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Staining Method: Ziehl-Neelsen staining method is used to identify acid-fast bacilli.
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Scrofula: TB of cervical lymph nodes.
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Lupus Vulgaris: TB of skin.
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Tongue & Gingival Appearance in Systemic Conditions:
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Strawberry tongue and Raspberry tongue: Seen in stomatitis of Scarlet Fever.
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Strawberry Gingivitis: Seen in Wegener's Granulomatosis.
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Streptococcus mutans Mechanism
- Key Substrate: Sucrose
- Metabolic Pathway: Phosphorylation → Glycolysis → Lactic acid
- Enzymes:
- Invertase: Converts sucrose to glucose + fructose
- Glucosyltransferase (GTF): Forms sticky glucans
- Fructosyltransferase (FTF): Produces fructans
Actinomyces naeslundii
- Fimbriated surface → fuzzy texture
- Type 1 fimbriae: Bind tooth surfaces/collagen
- Type 2 fimbriae: Bind galactose/galactosamine (epithelial/bacterial targets)
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Inverted Pear-shaped Radiolucency: Globulomaxillary cyst.
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Associated teeth need not be non-vital.
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Klestadts’s cyst: Soft tissue variant of Globulomaxillary cyst.
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Tear Drop-shaped Radiolucency: Lateral Periodontal Cyst.
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Associated teeth are vital.
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Cluster of Similar Cysts / Cluster of Grapes: Botryoid Odontogenic Cyst.
Macroglossia
- Feature: Crenated (scalloped) lateral tongue borders
Lymphangioma of Tongue
- Appearance: Tapioca pudding/Frog's egg
Geographic Tongue
- Associated With: Fissured tongue
- Histopathology: Similar to psoriasis
- Key Feature: Munro's abscesses
Median Rhomboid Glossitis
- Unique Sign: "Kissing lesion" on soft palate due to tongue contact
Hairy Tongue
- Misnomer: Elongated filiform papillae—not actual hair
Acute suppurative osteomyelitis
- Serious sequela of periapical infection.
- Leads to spread of pus through the medullary cavities of bone.
- Depending upon the main site of involvement of bone, can be of two types-
- Acute intramedullary
- Acute subperiosteal
Acute Intramedullary Osteomyelitis
CLINICAL FEATURES:
- Patient experiences dull , continuous pain , indurated swelling forms over the affected region of jaw involving the cheek , febrile.
- When mandible involved, loss of sensation occurs on lower lip on affected side due to involvement of inferior alveolar nerve.
- Teeth become loose later along with tender on percussion
- Pus discharge , trismus , foul smell , regional lymphadenopathy , weakness
RADIOGRAPHIC FEATURES
- Earliest radiographic change is that trabeculae in involved area are thin, of poor density & slightly blurred.
- Subsequently multiple radiolucencies appear which become apparent on radiograph.
- In some cases there is saucer shaped area of destruction with irregular margins.
- Loss of continuity of lamina dura, seen in more than one tooth.
HISTOLOGIC FEATURES:
- Dense infiltration of marrow by polymorphonuclear leukocytes.
- Bone trabeculae in involved site (sequestrum) are devoid of cells in the lacunae.
- separation of considerable portions of devitalized bone.
Acute Subperiosteal Osteomyelitis
CLINICAL FEATURES
- Pain , febrile condition , i/o and e/o swelling , parasthesia
- Bone involvement limited to localized areas of cortex.
- Pus ruptures rapidly through the overlying cortex, tracks along the surface of mandible under the periosteal sheath.
- Elevation of periosteum from cortex is followed eventually by minute cortical sequestration.