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

By Ward J, Parashos P, and Messer H

Date: 03/2003
Journal: JOE

Purpose:

 to evaluate the use of an ultrasonic technique combined with the creation of a “staging platform by modified Gates glidden to remove fractured rotary nickel-titanium instruments from narrow, curved canals.

N=  60 simulated canals and 30 mesiolingual canals from extracted mandibular molars. Inclusion criteria: teeth showing two separate mesial canals and completely developed root apices.

Materials/Methods:

•ProFile® .04 taper rotary endodontic instruments 25-mm long, ISO size 25 were obtained.

•These instruments were notched with a high-speed diamond bur at a point 2.5 mm from the tip of the instrument.

•the instruments were driven into the canal until it fractured and became lodged therein.

•Fragments of 2.5 mm in length of these instruments were fractured at three different levels (before, at and beyond the curve)

•The technique used to remove fractured instruments was a variation of the technique first discussed by Ruddle

•After preparing the radicular part, The tip of the Gates glidden was cut at the maximum cross-sectional diameter and were used to create a “staging platform” at the coronal aspect of the fractured instrument.

•An ultrasonic CPR tip was activated and used around the fractured instrument.

•The success of instrument removal in relation to the location of the fractured instrument segment, the time taken to remove each instrument segment and the amount and extent of canal damage produced by this technique were assessed.

Most highlighted Results:  • 100% of the instruments fractured before or at the curve were successfully removed while only 37% of instruments fractured beyond the curve could be removed. •Instruments fractured before or at the curve were removed in shorter time, with less canal aberration and impact on obturation compared to those fractured beyond the curve.

Clinical significance:

to prevent further preparation errors, instruments fractured apically beyond the curve may be best effectively managed by bypassing the instruments rather than attempted to be removed.