Instrument Fractures - Etiology

Instrument fracture is a potential hazard for both stainless steel and NiTi endodontic files. The forces applied during mechanical instrumentation may exceed the strength of the instrument, resulting in separation. The first sign of an increased risk of fracture with steel instruments and with many mechanical nickel-titanium instruments is visible distortion of the instrument structure. If force is applied to such an instrument, fracture will rapidly occur. All instruments are gradually weakened by use. Repeated use over that recommended by the manufacturer results in an increased fracture risk.