The use of hand techniques with rotary motions, such as the balanced force technique, have partially overcome this problem. Engine-driven stainless steel instruments have been around for a number of years, but never gained widespread use because of breakage and other problems. Rotary instruments are also marketed by Brassler, Union Broach, and others. It is recommended that instruments with a U-file design be used. An electric handpiece is also recommended because it provides constant speed and torque.
Rotary instruments offer several advantages for the instrumentation of root canals.
They provide a pure rotary motion, which minimizes transportation and straightening of the canals. They stay well centered in the canal and make a smooth, round, and tapered preparation which is easy to obturate. Under magnification, a canal prepared with rotary instrumentation demonstrates dentin walls that are very smooth and clean. Rotary instruments are effective at maintaining curvatures and the position of the apical foramen. They also tend to prepare canals faster than hand instruments.