Which device measures the working length of the root canal electronically?

Which device measures the working length of the root canal electronically?

• A. Rotary paste-filler
• B. Apex locator
• C. Fill canal with paste
• D. Finishing strip

Answer: (B)

An electronic apex locator is used to measure the working length. It works by detecting changes in electrical impedance between a file inside the canal and the surrounding tissues as the file approaches the apical constriction. This allows precise determination of where the canal ends, guiding accurate cleaning and shaping and reducing the risk of over- or under-instrumentation. It can also minimise reliance on radiographs during length determination. The other devices listed serve different purposes: one is for delivering paste during obturation, another describes filling the canal with paste, and the finishing strip is used for polishing, not measurement.

An electronic apex locator is used to measure the working length. It works by detecting changes in electrical impedance between a file inside the canal and the surrounding tissues as the file approaches the apical constriction. This allows precise determination of where the canal ends, guiding accurate cleaning and shaping and reducing the risk of over- or under-instrumentation. It can also minimise reliance on radiographs during length determination. The other devices listed serve different purposes: one is for delivering paste during obturation, another describes filling the canal with paste, and the finishing strip is used for polishing, not measurement.