Working Length Determination — NDEB AFK MCQ
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Correct answer: A — 1 mm short of the radiographic apex (at the apical constriction)
The optimal working length for root canal instrumentation is at the apical constriction (minor diameter of the apical foramen), which is typically located 0.5-1.0 mm short of the radiographic apex. This location minimises extrusion of debris and irrigant into periapical tissues while ensuring complete debridement of the infected root canal system. Electronic apex locators (EALs) provide the most accurate determination of working length.
Reference: Torabinejad – Endodontics: Principles and Practice, 6th ed., 2021