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Oral Surgery · single question

A periapical abscess is treated with root canal therapy. The access cavity for a MANDIBULAR FIRST MOLAR is described as:

  1. Rhomboid
  2. Trapezoidal (with a wider base toward the distal — reflecting 2 mesial canals and 1-2 distal canals)
  3. Oval
  4. Triangular
Show answer and explanation

Correct answer: B. Trapezoidal (with a wider base toward the distal — reflecting 2 mesial canals and 1-2 distal canals)

  • A. Rhomboid is not a standard access cavity shape for mandibular first molars.
  • B. Correct. The mandibular first molar access cavity is classically TRAPEZOIDAL — wider mesio-distally than bucco-lingually, with a wider base toward the mesial to accommodate the 2 mesial canals (mesiobuccal and mesiolingual) and narrower distally toward the 1-2 distal canals. This shape provides direct access to all canals while conserving tooth structure.
  • C. Oval: canines and mandibular premolars (single oval canal).
  • D. Triangular shape: maxillary incisors and mandibular incisors (narrow teeth).

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