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OSCE Exam - Complete Answers

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OSCE STATION 1 - Oral Lichen Planus (White Patch on Buccal Mucosa, Bilateral, Sore)

1. Probable Diagnosis

2. Clinical Subtypes of Oral Lichen Planus

3. Predisposing Factors

• Immune-mediated (T-cell mediated): CD8+ T-cells attack basal keratinocytes
• Stress and anxiety (psychological factors)
• Systemic medications: NSAIDs, antimalarials, beta-blockers, ACE inhibitors, oral hypoglycemics (cause lichenoid reactions)
• Dental materials: Amalgam restorations can trigger lichenoid contact reactions
• Hepatitis C virus infection (strong association)
• Genetic predisposition
• Diabetes mellitus, hypertension (Grinspan's syndrome triad)

4. Other Sites and Lesion Appearances

• Skin: Purple, polygonal, pruritic papules on wrists, ankles, and lower back
• Genital mucosa: Erosive/reticular lesions on vulva, vagina, glans penis
• Nails: Nail thinning, ridging, pterygium formation, onycholysis
• Scalp: Lichen planopilaris (scarring alopecia)
• Esophagus: Strictures (rare)

5. Differential Diagnoses (at least 3)

1. Leukoplakia - unilateral, no bilateral symmetry, no Wickham's striae
2. Oral Candidiasis (pseudomembranous) - white patches that can be wiped off, not bilateral lacy pattern
3. Lupus erythematosus - can mimic OLP histologically; check ANA
4. Lichenoid drug reaction - identical clinically; rule out by drug history
5. Chronic ulcerative stomatitis - erosive lesions, anti-SPS antibody positive

6. Management

• 0.1% Triamcinolone acetonide in Orabase (Kenalog in Orabase) - 2-6x/day
• 0.05% Clobetasol propionate gel - highly effective
• 0.1% Fluocinonide gel - for resistant cases

• Tacrolimus 0.1% ointment (calcineurin inhibitor) - meta-analysis shows superior to clobetasol
• Pimecrolimus 1% cream

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OSCE STATION 2 - Herpes Labialis (Recurrent Sores on Lip/Perioral)

1. Probable Diagnosis

2. Clinical Appearance

• Prodrome (24-48 hrs before): Burning, tingling, itching sensation at the site
• Vesicular stage: Cluster of small (1-3 mm), fluid-filled vesicles on an erythematous base at the mucocutaneous junction of the lip or perioral skin
• Ulcerative stage: Vesicles coalesce and rupture forming shallow, painful ulcers
• Crusting stage: Lesions dry and form yellowish-brown crusts
• Healing: Complete healing in 7-14 days without scarring

3. Predisposing Factors (Triggers for Reactivation)

• Febrile illness (hence "fever blisters") - any systemic illness raises body temperature
• UV radiation/Sunlight exposure
• Trauma to the lip/face
• Menstruation (hormonal changes)
• Psychological stress and fatigue
• Immunosuppression (HIV, chemotherapy, systemic steroids)
• Dental treatment (manipulation of trigeminal nerve branches)
• Pathophysiology: HSV-1 lies latent in the trigeminal ganglion after primary infection; these triggers reactivate the virus which travels down axons to the lip.

4. Precautions Patient Should Take

• Avoid touching the lesion - highly contagious; wash hands frequently
• Do not kiss anyone, especially infants and immunocompromised individuals, while lesions are active
• Do not share lip balm, cups, utensils, towels
• Use sunscreen/SPF lip balm to prevent UV-triggered recurrence
• Avoid touching eyes - risk of herpetic keratoconjunctivitis
• Notify dental team - defer elective dental treatment until lesions heal (risk of inoculating virus intraorally)
• Antiviral prophylaxis if recurrences are frequent (>6/year) or predictable triggers (e.g., take aciclovir before sun exposure or dental treatment)

5. Management

• Aciclovir 5% cream applied 5x/day for 5 days - most effective if started in prodromal stage
• Penciclovir 1% cream - applied every 2 hours while awake

• Aciclovir 200 mg 5x/day for 5 days (episodic therapy)
• Valaciclovir 2g twice daily for 1 day (single-day therapy)
• Famciclovir 1500 mg single dose (also approved)

• Aciclovir 400 mg twice daily for 6-12 months

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OSCE STATION 3 - Dentoalveolar Abscess (Pericoronitis / Periapical Abscess)

1. Probable Diagnosis

2. Clinical Appearance

• Erythematous, swollen, tender operculum (flap of gum) overlying an erupting/partially erupted lower third molar
• Pus may be expressed from under the operculum
• Trismus (restricted mouth opening) may be present
• Regional lymphadenopathy
• Swelling may spread to the face (buccal space involvement)

• Swollen, boggy, fluctuant swelling at the apex of the offending tooth
• Deep caries visible on the tooth
• Tooth is tender to percussion (TTP positive)
• Tooth may be non-vital (no response to vitality testing)

3. Predisposing Factors

• Impaction/partial eruption of third molars - food and bacteria trap under the operculum
• Poor oral hygiene
• Deep dental caries progressing to pulpitis, then pulp necrosis, then periapical infection
• Immunosuppression (diabetes, HIV, steroid use)
• Trauma to the tooth
• Previous failed root canal treatment

4. Differential Diagnosis

1. Pericoronitis (gum infection around erupting tooth)
2. Periapical/Dentoalveolar abscess (infection at root apex)
3. Periodontal abscess (lateral periodontal pocket)
4. Buccal space cellulitis/abscess
5. Ludwig's angina (bilateral submandibular space infection - medical emergency)

5. Management

• Drainage - incision and drainage if fluctuant abscess; irrigation of pericoronal pocket with saline/chlorhexidine
• Antibiotics (if systemic signs present):
  • First-line: Amoxicillin 500 mg 3x/day for 5 days
  • Alternative: Metronidazole 400 mg 3x/day (anaerobic cover) or Co-amoxiclav (Augmentin)
  • Penicillin-allergic: Erythromycin or Clindamycin
• Analgesics: Ibuprofen + paracetamol
• Warm saline mouthwashes

• Extraction of the offending/non-restorable tooth or impacted third molar once acute infection resolves
• Root canal treatment (RCT) if the tooth is restorable and the patient wishes to retain it
• Operculectomy (removal of operculum) is rarely done as the tooth usually needs extraction anyway

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OSCE STATION 4 - Submandibular/Facial Space Infection (Odontogenic Origin)

1. Probable Diagnosis

2. Clinical Appearance

• Extraoral: Diffuse, asymmetric, doughy-to-fluctuant swelling of the right lower third of face, obliterating the inferior border of the mandible; overlying skin is erythematous, stretched, warm, and tender
• Intraoral: The causative tooth (likely lower right first/second molar or third molar) shows deep caries or periapical tenderness; there may be pus draining from the pericoronal space
• OPG shows: Periapical radiolucency at the root of the offending tooth confirming the odontogenic source

3. Differential Diagnosis

1. Submandibular space abscess (most likely - infection spreads below mylohyoid)
2. Buccal space abscess (swelling in cheek, above inferior border of mandible)
3. Masseteric space infection
4. Parotid abscess/parotitis
5. Ludwig's Angina - bilateral submandibular, submental, sublingual spaces - medical emergency; airway compromise risk
6. Infected lymph node (reactive lymphadenitis)
7. Infected sebaceous cyst

4. Treatment Plan

1. Hospitalization if systemic signs (fever, trismus, dysphagia, dyspnoea, rapid progression)
2. IV antibiotics immediately:
   • IV Amoxicillin-Clavulanate (Co-amoxiclav) + Metronidazole
3. Surgical drainage - incision and drainage (I&D) under LA or GA; drain placement
4. Extraction or RCT of the causative tooth once acute infection controlled
5. Airway monitoring - if Ludwig's pattern (bilateral, floor of mouth raised), secure airway (intubation or tracheostomy)
6. Supportive: IV fluids, analgesics, warm compress

5. Antimicrobial of Choice and Alternative

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OSCE STATION 5 - Mucocele (Lower Labial Mucosa)

1. Probable Diagnosis

2. Clinical Appearance

• Site: Most commonly on the inner surface of the lower lip (most frequent site due to trauma); also floor of mouth (ranula), buccal mucosa
• Size: Typically 5-15 mm diameter
• Shape: Smooth, dome-shaped, sessile nodule
• Colour: Translucent, bluish-pink (due to fluid showing through thin mucosa)
• Surface: Smooth, shiny, intact overlying mucosa (unless previously ruptured and re-formed)
• Consistency: Soft, fluctuant
• Symptoms: Usually asymptomatic, non-tender; patient may notice it "comes and goes" if it ruptures spontaneously and refills
• Two types:
  • Mucus extravasation cyst (more common): Duct of minor salivary gland is traumatically severed; mucus spills into connective tissue - no epithelial lining
  • Mucus retention cyst (less common): Duct obstruction; has epithelial lining

3. Predisposing Factors

• Trauma is the primary cause: habitual lip biting (most common), accidental biting while chewing, trauma from sharp teeth, orthodontic appliances, or lip jewelry
• Trauma ruptures the excretory duct of a minor salivary gland, causing mucus to pool in the surrounding connective tissue
• Children and young adults most affected

4. Differential Diagnosis

1. Irritation fibroma - firm, pale pink, sessile; not translucent or fluctuant; caused by chronic irritation
2. Lipoma - yellowish, soft; very rare in the lip
3. Hemangioma/Varix - deep blue/purple; blanches on diascopy (pressure with a glass slide)
4. Minor salivary gland tumor (e.g., Mucoepidermoid carcinoma) - firm, slow-growing, not fluctuant; must always be excluded in non-typical mucoceles
5. Lymphangioma - vesicular-appearing surface; present from birth/childhood
6. Ranula - mucocele on the floor of the mouth (sublingual gland); can be "plunging" if below mylohyoid

5. Treatment Plan

• Complete surgical excision down to the muscle layer, including the adjacent minor salivary gland lobules responsible, to prevent recurrence
• Performed under local anaesthesia
• Recurrence rate is low with complete excision

• Laser ablation (CO2 or Nd:YAG) - less bleeding, good for anxious patients
• Cryosurgery - freezing with liquid nitrogen
• Marsupialization - used for larger lesions/ranulas (creating a new opening)
• Intralesional corticosteroid injection - rarely used

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OSCE STATION 6 - Periapical Radiolucency (Periapical Abscess/Cyst)

1. Type of Radiograph

2. Identify the Teeth

3. Identify and Describe the Lesion

• Shape: Well-defined, round to oval
• Outline/Margin: May be well-defined (cyst) or poorly-defined/ill-defined (acute abscess)
• Density: Radiolucent (dark area = bone destruction)
• Size: Variable - small (abscess) to large (cyst)
• Location: At or around the apex of the root (periapical)
• Effect on surrounding structures: Loss of lamina dura (white line around root disappears), widening of periodontal ligament space at apex

4. Differential Diagnosis

1. Periapical abscess (acute/chronic) - radiolucency at apex; tooth is non-vital; most common
2. Periapical (Radicular) cyst - well-corticated radiolucency >1 cm; follows pulp necrosis; lined by epithelium
3. Periapical granuloma - small, ill-defined radiolucency; most common periapical lesion
4. Residual cyst - periapical cyst remaining after extraction
5. Lateral periodontal cyst - located laterally on the root, not at apex
6. Surgical defect/Normal anatomic variant (mental foramen, incisive foramen) - correlate clinically

5. Give Differential Diagnosis

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OSCE STATION 7 - Bitewing Radiograph with Dental Caries

1. Type of Radiograph

2. Indications for Bitewing Radiographs

• Primary use: Detection of interproximal (proximal) dental caries - earliest stage before clinical detection
• Detection of recurrent/secondary caries under existing restorations
• Evaluation of alveolar crest bone level (early bone loss in periodontal disease)
• Assessment of the contact point and interproximal space
• Monitoring caries progression at recall visits
• Assessment of restoration margins and overhangs
• Detection of calculus deposits at the interproximal areas

3. Identify the Teeth

4. Tooth of Interest (Radiographic Abnormality)

5. Radiographic Changes in the Crown

• Interproximal caries: Appears as a small, triangular radiolucency at the contact point area, with the base at the enamel surface and apex pointing toward the dentino-enamel junction (DEJ)
• Dentinal caries: Wider, more diffuse radiolucency that has crossed the DEJ, spreading laterally along it
• Deep caries near the pulp: Radiolucency close to or reaching the pulp chamber
• Secondary caries: Radiolucency at the margins of an existing restoration (amalgam or composite)

6. Radiographic Changes in the Alveolar Bone

• Normal: Alveolar crest is 1.5-2 mm below the cementoenamel junction (CEJ); horizontal, white (radiopaque) crestal bone
• Early bone loss: Blunting or fuzziness of the alveolar crest
• Horizontal bone loss: Crest drops below the normal 2 mm from CEJ uniformly
• Vertical/Angular bone loss: Triangular radiolucency at the crest (indicates advanced periodontitis or an infrabony pocket)

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OSCE STATION 8 - Bitewing/Periapical Radiograph (Detailed Interpretation)

1. Type of Radiograph

2. Identify the Teeth

3. Tooth of Interest

4. Radiographic Changes in the Crown

• Caries (radiolucency/dark area) within enamel or dentine
• Existing restorations appear radiopaque (white) - amalgam is very radiopaque; composite is slightly radiopaque
• Fracture line may appear as a thin radiolucent line
• Abrasion/attrition - loss of crown height

5. Radiographic Changes in the Root

• External root resorption - loss of root structure at apex (blunting/shortening)
• Internal root resorption - oval/round enlargement of root canal
• Root fracture - thin radiolucent line perpendicular or oblique to the root
• Dilaceration - sharp bend in root

6. Radiographic Changes in the Periapical Area

• Periapical radiolucency - dark area at apex = granuloma, cyst, or abscess
• Loss of lamina dura at apex - indicates inflammation
• Widening of periodontal ligament (PDL) space at apex
• Condensing osteitis - increased bone density (radiopaque) around apex = chronic low-grade infection

7. Radiographic Changes in Supporting Structures

• Alveolar bone level - measured from CEJ; normal = within 2 mm
• Bone loss pattern - horizontal vs. vertical
• Lamina dura - normally continuous radiopaque white line; loss = pathology
• PDL space - normally uniform thin dark line; widening = inflammation or occlusal trauma

8. Radiographic Diagnosis

9. Faults in the Radiograph

• Elongation - vertical angulation too small (flat); roots appear too long
• Foreshortening - vertical angulation too great (steep); roots appear too short
• Cone-cutting/collimator cut - radiopaque white area at corner; beam not centered
• Overlapping - horizontal angulation wrong; contacts of teeth overlap
• Blurring - patient movement during exposure
• Under-exposure (too light) - insufficient mAs or kVp
• Over-exposure (too dark) - excessive mAs or kVp
• Film bending artefact - curved lines across image
• Double exposure - ghost image; film exposed twice
• Developer/fixer contamination - streaks or spots

10. Normal Anatomical Landmarks on a Mandibular Periapical Radiograph

• Mandibular canal - radiolucent tube running through mandible (lower border to mental foramen)
• Mental foramen - round/oval radiolucency between premolars
• External oblique ridge - radiopaque line on posterior mandible
• Internal oblique ridge (mylohyoid line) - radiopaque line on medial side
• Inferior dental canal
• Nutrient canals - thin radiolucent lines
• Lamina dura - white line around each root
• PDL space - thin dark line around each root
• Alveolar crest - top of interdental bone

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OSCE STATION 9 - Orthopantomogram (OPG) with Taurodontism

1. Type of Radiograph

2. Radiographic Diagnosis

• Enlarged pulp chambers that extend vertically toward the root furcation
• Apically displaced furcation (furcation close to the apex)
• Rectangular or cylindrical crown shape instead of the normal tapered form
• Shortened roots with respect to the crown height
• Lack of constriction at the cementoenamel junction (CEJ)
• Affects multi-rooted teeth (molars) bilaterally
• The word "taurodont" means "bull tooth" (from Latin taurus = bull) due to the resemblance to teeth of hoofed animals

• Hypotaurodont - mild apical displacement of furcation
• Mesotaurodont - moderate
• Hypertaurodont - severe; furcation near apex

3. Differential Diagnosis

1. Isolated/Idiopathic Taurodontism - non-syndromic; occurs as an isolated anomaly; most common form
2. Klinefelter syndrome (47, XXY) - strong association with taurodontism
3. Down syndrome (Trisomy 21)
4. Tricho-dento-osseous (TDO) syndrome - taurodontism + curly hair + sclerotic bone
5. Amelogenesis imperfecta (hypoplastic-hypomaturation type IV)
6. Ectodermal dysplasia
7. Mohr syndrome (OFD II)

4. Normal Anatomical Landmarks on an OPG

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OSCE STATION 10 - Periapical Radiograph (Detailed Interpretation - Single Tooth)

1. Type of Radiograph

2. Identify the Teeth

3. Tooth of Interest

4. Radiographic Changes in the Crown

• Radiolucency (caries): Dark area within the crown suggesting dentinal or deep pulpal caries
• OR existing restoration visible as radiopaque filling material
• Crown may show attrition (flat biting surface)

5. Radiographic Changes in the Root

• Loss of lamina dura - the continuous white line around the root is disrupted or absent at the apex
• Root length - possibly shortened if there is resorption
• Single root with a canal visible running through its center

6. Radiographic Changes in Periapical Area

• Well-defined radiolucency at the apex = suggests a periapical cyst (well-corticated margin, larger size >1 cm)
• Ill-defined radiolucency = suggests periapical abscess or granuloma
• Loss of lamina dura at apex - always indicates pathology
• Widened PDL space at apex - early sign of periapical inflammation

7. Radiographic Changes in Supporting Structures

• Alveolar bone: Assess crest level, any bone destruction extending from the apex
• Interdental bone: Crestal bone pattern (horizontal or angular loss)
• Cortical plate: May show expansion in large cysts

8. Radiographic Diagnosis

9. Faults in the Radiograph

10. Normal Anatomical Landmarks

• Floor of nasal cavity - radiopaque line above upper incisors
• Nasal fossa - radiolucent area
• Nasal septum - vertical radiopaque line
• Incisive foramen - oval radiolucency between upper central incisors
• Anterior nasal spine
• Maxillary sinus floor - for premolar/molar region

• Mental foramen, mandibular canal (as listed in Station 8)

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