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Anesthesia · single question

What is the mechanism of action of the intrapulpal injection?

  1. It acts by calcium channel blockade in the pulpal nerves
  2. It produces a systemic effect via rapid pulpal venous absorption
  3. Anesthesia is produced primarily by strong back-pressure of the solution within the confined pulp chamber
  4. It works through profound local vasoconstriction
Show answer and explanation

Correct answer: C. Anesthesia is produced primarily by strong back-pressure of the solution within the confined pulp chamber

  • A. Local anesthetics act on voltage-gated SODIUM channels, not calcium channels — and in any case the pressure effect is what characterises this particular technique.
  • B. The intrapulpal injection is a purely local technique; no systemic mechanism is involved.
  • C. CORRECT. The intrapulpal injection works chiefly through PRESSURE. Solution delivered into a rigid, confined pulp chamber generates high hydrostatic BACK-PRESSURE that mechanically disrupts nerve conduction, producing near-immediate anesthesia. The pharmacological action of the anesthetic contributes, but the pressure effect is the dominant and defining mechanism — which is why a snug needle fit that resists back-flow is essential for the technique to work.
  • D. Vasoconstriction from the epinephrine contributes to haemostasis and duration but does not explain the immediate onset.

Note: Practical points: the injection is briefly but sharply painful, so warn the patient. Onset is immediate and duration is short (15–20 minutes), so proceed with pulp extirpation straight away.

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