What is the typical method for initial working length estimation and what confirmatory step should precede obturation?

• A. Rely on tactile feedback.
• B. Use CBCT for length estimation in all cases.
• C. Use a file with an electronic apex locator for working length and confirm with periapical radiographs before obturation.
• D. Estimate length by measuring from incisal edge.

Answer: (C)

Accurate working length estimation relies on using an electronic apex locator with a file to determine where the canal ends, followed by radiographic confirmation before obturation. The apex locator measures electrical impedance as the file reaches the apical region, giving a precise initial length that is less dependent on subjective feel. Before obturation, this length should be verified with a periapical radiograph to ensure the file tip ends near the apical constriction (slightly short of the radiographic apex), preventing over- or under-instrumentation.

Relying on tactile feedback alone is unreliable due to variations in canal anatomy and curvature, and measuring from the incisal edge is imprecise. While CBCT can aid in complex cases, it isn’t used routinely for initial length estimation due to radiation exposure and cost.