Effectiveness of hand versus rotary instrumentation on retreatment of curved canals

Abstract

Background: Various nickel–titanium (NiTi) rotary endodontic instruments have been developed to facilitate cleaning and shaping of root canals. This study aimed to evaluate the efficiency, cleaning ability and safety of two different rotary NiTi instruments with a solvent versus hand files in the removal of canal fillings. Methods: Forty five simulated canals with 35° curves made of clear polyester resin were used in this study. All canals were prepared with K-files and filled using cold lateral compaction of gutta-percha and AH Plus sealer. The teeth were randomly divided into three groups of 15 specimens each. Removal of gutta-percha was performed with the following techniques: Hedstrom files, ProTaper Universal rotary retreatment system and Mtwo-R. All techniques were used with the solvent chloroform. The followings factors were evaluated: time taken to reach working length, time for gutta-percha removal, total time, apically extruded material during filling removal and number of fractured instruments. Pre- and post-reinstrumentation weights of all the blocks were recorded and efficacy capacity of each retreatment technique was assessed. Results: The canal wall clearance efficiency of ProTaper retreatment files were more successful than Mtwo-R and hand instruments. With respect to the difference between pre- and post-reinstrumentation weights, Mtwo-R was the most effective instrumentation technique. Regarding the mean time of retreatment and time required for reaching the working length, Mtwo-R instruments were significantly faster than the others. In addition, the hand instrumentation was more successful comparing to others in terms of the amount of apically extruded material. Conclusion: Under experimental conditions, Mtwo-R/Mtwo and ProTaper retreatment instruments proved to be efficient and time-saving devices for the removal of gutta-percha .