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Endodontics · single question

In tooth #14 (maxillary left first molar), which root is MOST likely to contain two canals?

  1. The palatal root
  2. The distobuccal root
  3. The mesiobuccal root
  4. All three equally
Show answer and explanation

Correct answer: C. The mesiobuccal root

  • A. The palatal root is the largest and longest but is essentially always a single canal; its notable feature is a buccal curvature in the apical third that is invisible on a straight radiograph.
  • B. The distobuccal root is almost always a single, round, relatively straight canal.
  • C. CORRECT. The MESIOBUCCAL root of a maxillary first molar contains a second canal (MB2) in the large majority of cases — reported at 60–95% depending on the method of detection, with the highest rates found using the dental operating microscope, ultrasonic troughing, and CBCT. MB2 typically lies mesiopalatal to MB1, often beneath a dentin shelf, and the two canals may join apically or remain separate.
  • D. The three roots are not equal — MB is the outlier.

Note: Troughing the developmental groove between MB1 and the palatal orifice under magnification is how you find MB2.

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