Which premolar is most likely to present with three canals?

Correct answer: B. Maxillary first premolar

• A. The mandibular first premolar is notorious for a bifurcating canal in the apical third and a prominent lingual groove, but three separate canals are uncommon.
• B. CORRECT. The MAXILLARY FIRST PREMOLAR is the premolar most likely to have three canals — mesiobuccal, distobuccal and palatal, mirroring a molar in miniature. The incidence is low (in the order of 5–6%) but it is by far the highest of any premolar, and it is the classic three-canal premolar of examination questions.
• C. The maxillary second premolar most often has a single root with one or two canals; three canals are rare.
• D. The mandibular second premolar most typically has a single canal.

Note: Also worth holding: the mandibular first premolar's severe apical bifurcation makes it one of the most difficult single-rooted teeth to treat, and the maxillary first premolar's mesial concavity is a strip-perforation danger zone.