All of the following teeth have a similar OVAL access cavity outline EXCEPT:

Correct answer: B. Mandibular first molar

• A. Mandibular premolars have an oval access oriented buccolingually.
• B. Correct — this is the EXCEPTION. The MANDIBULAR FIRST MOLAR requires a TRAPEZOIDAL or rhomboidal access outline to encompass three to four canal orifices. The general principle is that access outline mirrors the arrangement of the canal orifices at the pulp chamber floor: single-canalled anteriors and premolars give an oval outline, while multi-rooted molars give a triangular (maxillary) or trapezoidal (mandibular) outline.
• C. The mandibular canine has a narrow oval access.
• D. The maxillary canine has an oval, incisogingivally elongated access.