Caries, pulp and periodontal disease: second mesiobuccal canal: practice question

A Dentistry question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Dentistry · Caries, pulp and periodontal disease: second mesiobuccal canal

Sample item

During root canal treatment of a maxillary first molar, only three canals are found, yet the mesiobuccal root remains symptomatic. Where should the clinician search for an additional canal?

AIn the palatal root, distal to the main canalBIn the mesiobuccal root, palatal to the main mesiobuccal canalCIn the furcation, between the two buccal rootsDIn the distobuccal root, mesial to the main canal

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

B. In the mesiobuccal root, palatal to the main mesiobuccal canal

The maxillary first molar often has a second canal in the mesiobuccal root, called MB2, usually lying palatal and slightly mesial to the main canal. Missing it is a frequent cause of endodontic failure. It is located with magnification and troughing of the isthmus.

Option by option

A. In the palatal root, distal to the main canal
The palatal root usually has one large canal.
B. In the mesiobuccal root, palatal to the main mesiobuccal canal (correct)
Correct. MB2 lies palatal to MB1 in the mesiobuccal root.
C. In the furcation, between the two buccal roots
The furcation has no canal in a typical molar, though accessory canals may exist.
D. In the distobuccal root, mesial to the main canal
The distobuccal root normally has a single canal.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this Dentistry question

What is the answer to this Dentistry question?

The best answer is B, In the mesiobuccal root, palatal to the main mesiobuccal canal. The maxillary first molar often has a second canal in the mesiobuccal root, called MB2, usually lying palatal and slightly mesial to the main canal.

Why is "In the palatal root, distal to the main canal" not the answer?

The palatal root usually has one large canal.

Why is "In the furcation, between the two buccal roots" not the answer?

The furcation has no canal in a typical molar, though accessory canals may exist.

Why is "In the distobuccal root, mesial to the main canal" not the answer?

The distobuccal root normally has a single canal.

What concept does this question test?

It tests Caries, pulp and periodontal disease: second mesiobuccal canal in Dentistry. Missing it is a frequent cause of endodontic failure. It is located with magnification and troughing of the isthmus.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Caries, pulp and periodontal disease: second mesiobuccal canal?

Learn the dental formula, eruption ages and tooth structure once, as tables. Then use the flashcards and the other Dentistry questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.