Apical Preparation Size — NDEB AFK MCQ

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ModerateEndodonticsApical Preparation SizeNDEB AFK

What is the ideal apical preparation size for cleaning and shaping a root canal with a preoperative apical diameter of 0.25 mm (size 25)?

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Correct answer: D — Three sizes larger (40)

The recommended apical preparation size is at least three file sizes larger than the first file that binds at working length (initial apical file/IAF). For an IAF of 25, this means preparing to at least size 40. This removes the innermost layer of infected dentin, allows better irrigant penetration, and improves debridement. Studies show that preparation to sizes 35-40 significantly improves canal cleanliness compared to preparation to size 25 only.

Reference: Torabinejad – Endodontics: Principles and Practice, 6th ed., 2021