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EDTA in Endodontics — MFDS Part 1 MCQ

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ModerateRestorative PrinciplesEDTA in EndodonticsMFDS Part 1

During chemomechanical preparation of a root canal, sodium hypochlorite has been used throughout instrumentation. Before obturation, 17% EDTA is introduced into the canal. What is the principal reason for using EDTA at this stage?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: A — Chelate dentinal calcium and remove the inorganic smear layer

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

EDTA is used principally as a chelating irrigant. It binds calcium ions in dentine and removes the inorganic component of the smear layer produced during instrumentation, exposing dentinal tubules and improving canal-wall cleanliness before obturation. Sodium hypochlorite, rather than EDTA, provides the main dissolution of organic pulp tissue and much of the antimicrobial activity, so B and C are not the primary function of EDTA. EDTA is subsequently removed and is not an obturation material, excluding D. It also does not stimulate odontoblasts or reparative dentine formation, excluding E. The preceding use of sodium hypochlorite distinguishes its organic tissue-dissolving and antimicrobial actions from EDTA's complementary chelating action.

Reference: British Endodontic Society, A Guide to Good Endodontic Practice, irrigation guidance, 2022. https://www.rcseng.ac.uk/-/media/FDS/The-British-Endodontic-Society-guide-to-Good-Endodontic-Practice.pdf