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. Rotary instruments may be used effectively with a variety of techniques, but several general guidelines should be followed. Record each instrument use and follow the manufacturer's recommendations for maximum number of uses. The manufacturers also recommend a range of speeds. Instruments should be used with light pressure and should never be forced.