Calcium Hydroxide Mechanism — ORE Part 1 MCQ

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EasyEndodonticsCalcium Hydroxide MechanismORE Part 1

During endodontic treatment, calcium hydroxide paste is placed as an intracanal medicament. What is its primary antimicrobial mechanism of action?

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Reveal the answer and explanation

Correct answer: A — Release of hydroxyl ions, producing a highly alkaline environment

Explanation lettering: E = shown as B · B = shown as E

Calcium hydroxide dissociates to release hydroxyl ions. This produces a very high pH (about 12.5), creating conditions that damage bacterial cellular components and make the medicament bacteriostatic/antimicrobial. Therefore, A is the best answer. Fluoride release is not a property of calcium hydroxide (B). Chelation is the relevant action of agents such as EDTA, not calcium hydroxide (C). Osmotic dehydration is not its principal antibacterial mechanism (D). Although the paste occupies the canal, mechanical occlusion is not the biological mechanism for its antimicrobial effect (E). Calcium hydroxide may also support hard-tissue formation, but this is not its primary antimicrobial action.

Reference: Faculty of Dental Surgery, Royal College of Surgeons of England. National Clinical Guidelines: The Management of Traumatic Dental Injuries in Children, section 3.2, 2000. https://www.rcseng.ac.uk/-/media/files/rcs/fds/publications/ncg97.pdf