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Endodontics · single question

What is the endodontic access preparation shape for tooth 19 (mandibular first molar)?

  1. Triangular
  2. Oval
  3. Rhomboid
  4. Trapezoid
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Correct answer: D. Trapezoid

The endodontic access cavity for the mandibular first molar (tooth 19/30) is TRAPEZOID in shape — wider mesially (accommodating the mesiobuccal and mesiolingual canals) and narrower distally (one or two distal canals). The shape reflects the typical 3-4 canal anatomy: two mesial canals widely spaced, one or two distal canals. This trapezoidal shape provides straight-line access to all canals.
  • A. INCORRECT. Triangular access is used for maxillary central incisors and some single-rooted teeth.
  • B. INCORRECT. Oval access is used for single-canal teeth (mandibular incisors, canines, maxillary premolars).
  • C. INCORRECT. Rhomboid (parallelogram) shape is not the standard description for mandibular first molar access.
  • D. CORRECT. TRAPEZOID is the standard access shape for the mandibular first molar — wider mesially to accommodate the two mesial canals (MB and ML) and narrower distally for the distal canal(s).

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