C-Shaped Canal — MFDS Part 1 MCQ

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HardAnatomy (Head & Neck)C-Shaped CanalMFDS Part 1

During assessment for non-surgical root canal treatment, CBCT shows a permanent tooth with fused roots, a longitudinal radicular groove and an axial canal outline that changes from a continuous C coronally to separate canal components apically. In which tooth is this configuration most commonly encountered?

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Correct answer: C — Mandibular second molar

The correct answer is C, the mandibular second molar. Fused roots, a longitudinal radicular groove and a canal cross-section that changes along the root are characteristic of a C-shaped canal system. A systematic review found a pooled prevalence of approximately 12% in mandibular second molars, compared with only 0.3% in mandibular first molars; prevalence was substantially higher in East Asian populations. Maxillary second molars can rarely have fused roots and C-shaped canals, but this is not their usual configuration. C-shaped anatomy has also been reported in mandibular premolars, although it is uncommon and therefore does not displace the mandibular second molar as the single best answer.

Reference: Martins JNR et al. Prevalence of C-shaped canal morphology using cone beam computed tomography—a systematic review with meta-analysis. International Endodontic Journal. 2019;52:1556–1572. https://pubmed.ncbi.nlm.nih.gov/31215045/