Start practicing

Endodontics · single question

What is the correct outline form for the access cavity of a mandibular first molar?

  1. Oval and confined to the distal half of the crown
  2. Trapezoidal or rhomboidal, wider mesially than distally
  3. Circular and centred in the central fossa
  4. Triangular with the base toward the distal
Show answer and explanation

Correct answer: B. Trapezoidal or rhomboidal, wider mesially than distally

  • A. Confining the access distally would miss both mesial canals entirely.
  • B. CORRECT. The mandibular first molar typically has TWO mesial canals (mesiobuccal and mesiolingual) and ONE distal canal, so the access outline is TRAPEZOIDAL — broad across the mesial to capture both mesial orifices, narrower distally. When the distal root houses two canals the outline becomes more rectangular or rhomboidal.
  • C. A circular access confined to the central fossa would fail to expose the widely separated mesial orifices.
  • D. A triangular outline with the base distally reverses the anatomy — the wider dimension belongs mesially.

Note: Access outlines worth memorising: maxillary molars = triangular or rhomboidal (blunted triangle with MB2); mandibular molars = trapezoidal; anteriors = triangular with the base incisal; premolars = oval buccolingually.

Practice Endodontics questions Endodontics study notes

More Endodontics practice questions