Evaluation of an ultrasonic technique to remove fractured rotary nickel-titanium endodontic instruments from root canals: an experimental study.

The use of nickel-titanium rotary instruments in endodontic practice is increasing. One frequently mentioned problem is fracture of an instrument within the root canal. To date, there is no consistently safe and successful technique for removing these fractured instruments. This study evaluates the use of an ultrasonic technique to remove fractured rotary nickel-titanium instruments from narrow, curved canals in both simulated (resin blocks) and mesiolingual canals of extracted mandibular first molars. A technique using ultrasonic tips, combined with the creation of a "staging platform" and the use of the dental operating microscope, was consistently successful and safe at removing fractured rotary nickel-titanium instruments from curved root canals, when some part of the fractured instrument segment was located in the straight portion of the canal. When the fractured instrument segment was located entirely around the curve, the success rate was significantly decreased and major canal damage often occurred.