Frequency of ultrasonic preparation is:

Ultrasonic preparation: Consists of a peeso electric ceramic unit that generates ultrasonic waves which activate a magnetostrictive hand piece. The hand piece produces movements of the shaft of the file between 0.001 to 0.004 inches in a frequency of 20,000 — 25,000 / sec. NaOCI is used as irrigant solution. Increased thermal and mechanical ability of the irrigating solution removes debris and tissue effectively and removal of smear layer is also efficient.