Short Root Filling — ORE Part 1 MCQ

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

ModerateEndodonticsShort Root FillingORE Part 1

A lower first molar has been instrumented to the confirmed working length. After obturation, a periapical radiograph shows that each root filling terminates 3 mm short of the radiographic apex. What is the most likely cause?

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

Reveal the answer and explanation

Correct answer: D — The master cones failed to reach the working length

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

A is correct. The canals were instrumented to the confirmed working length, whereas the shortfall is seen only after obturation. The error is therefore at the obturation stage: the master cones failed to seat to working length, for example because of inadequate apical fit, unsuitable cone selection, or obstruction by debris. Evidence on master-cone fitting identifies apical-stop quality and cone selection as determinants of the radiographic cone length. An inaccurate apex-locator reading or an overestimated pre-operative radiograph would have caused an error during working-length determination and preparation, contrary to the stem. A lateral canal does not make the main root filling end short, and rapid apical resorption during a single treatment visit is not a credible explanation.

Reference: Alfouzan K, et al. Assessment of dental students' knowledge and performance of master gutta-percha cone selection and fitting during root canal treatment: a pilot study. 2024. https://pubmed.ncbi.nlm.nih.gov/38575914/