Root Canal Irrigation — ORE Part 1 MCQ

Instant feedback + full explanation. One question, done properly.

ModerateEndodonticsRoot Canal IrrigationORE Part 1

Following instrumentation with sodium hypochlorite irrigation during root canal treatment, which final irrigant is most appropriate for removal of the smear layer?

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

Reveal the answer and explanation

Correct answer: C — 17% ethylenediaminetetraacetic acid

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

A is correct. Sodium hypochlorite is valuable for dissolution of organic tissue and antimicrobial action, but it does not reliably remove the inorganic component of the smear layer produced by instrumentation. A final rinse with 17% EDTA chelates calcium ions and is the conventional chelating irrigant for this purpose. Chlorhexidine is antimicrobial rather than a preferred smear-layer chelator; it should not be placed directly after sodium hypochlorite without an intervening rinse because precipitate may form. Saline is a flushing solution only. Citric acid has chelating properties, but 50% citric acid is not the standard preferred final irrigant over 17% EDTA. Hydrogen peroxide does not effectively remove the smear layer.

Reference: Crespo-Garcia V, et al. Update on chelating agents in endodontic treatment: A systematic review. 2024. https://pubmed.ncbi.nlm.nih.gov/24651335/