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NEET MDS Quiz - Practice Test
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Practice Test

Oral Surgery - 3 Questions

1
Oral Surgery
A patient presents with a painless, bluish, translucent vesicle on the mucous membrane of the lower lip The most likely diagnosis is
1. cheilitis glandularis
2. mucocele
3. cystic hygroma
4. hemangioma

📝 Explanation:

A mucocele is the most likely diagnosis for a painless, bluish, translucent vesicle on the mucous membrane of the lower lip. This common lesion results from trauma to a minor salivary gland duct, causing mucus to spill into the surrounding connective tissue.

2
Oral Surgery
The following history and laboratory values contraindicate extraction of mandibular first molar
1) Hb% is 15 g% and hematocrit value is 42 per cent
2) Five months pregnant lady without any complications
3) Rheumatic patient taking penicillin
4) Prothrombin time is 45 seconds

📝 Explanation:

A prothrombin time of 45 seconds (normal 11-15 seconds) indicates severe coagulopathy and contraindications extraction. This prolonged PT suggests either excessive anticoagulation or severe liver dysfunction, both of which significantly increase bleeding risk. The procedure should be postponed until coagulation parameters are normalized.

3
Oral Surgery
In which type of nerve fibres is sensitivity to local anaesthetics greater?
1) Type B fibres
2) Type C fibres
3) Type A‑delta fibres
4) Fibres supplying the muscle spindles

📝 Explanation:

Local anaesthetics act by blocking voltage‑gated sodium channels, preventing depolarization and conduction of nerve impulses. The sensitivity of different nerve fibres depends on their diameter, myelination, and conduction velocity.

  • Type B fibres

    • Small, myelinated preganglionic autonomic fibres.

    • Moderately sensitive to local anaesthetics.

  • Type C fibres

    • Smallest, unmyelinated fibres.

    • Carry dull, aching pain and temperature sensations.

    • Most sensitive to local anaesthetics because of their small diameter and lack of myelin.

  • Type A‑delta fibres

    • Small, thinly myelinated fibres.

    • Carry sharp, pricking pain.

    • Less sensitive than Type C fibres but more sensitive than larger A‑alpha fibres.

  • Fibres supplying muscle spindles (Type A‑alpha fibres)

    • Large, heavily myelinated fibres.

    • Conduct proprioception and motor signals.

    • Least sensitive to local anaesthetics due to their large diameter and thick myelin sheath.

 Local anaesthetics preferentially block small, unmyelinated fibres first (Type C), followed by small myelinated fibres (Type B, A‑delta). Large myelinated fibres (A‑alpha) are blocked last. This explains why pain sensation is lost before motor function during local anaesthesia.

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