Which instrument is used for routine cleaning and shaping of root canals by twisting action?

• A. Root canal file
• B. Apex locator
• C. Rotary paste-filler
• D. Fill canal with paste

Answer: (A)

Root canal files are the instruments used for routine cleaning and shaping of the canal when a twisting or filing motion is employed. These slender, tapered tools cut dentin as they are rotated or twirled within the canal, removing debris and soft tissue and creating the tapered shape needed for effective cleaning and for the canal to be properly obturated later. Different file designs, like K-files and Hedstrom files, are used in a controlled twisting or watch-winding motion to advance apically and maintain the canal’s curvature. Other options serve different steps: an apex locator helps determine working length, while paste-filling or paste obturation tools are used to fill the canal, not for cleaning or shaping.