Comparative evaluation of the efficiency of different files in removing gutta -percha from curved root canals during root canal retreatment

Present study aimed to compare the cleanliness of root canal walls after using ProTaper Universal Retreatment, NRT GPR nickel-titanium systems and Hedstrom hand files in curved root canals during root canal retreatment.
Thirty simulated canals with a 30-degree curvature in resin blocks were instrumented up to #30.04 with ProTaper Next nickel-titanium rotary instruments and obturated using gutta percha and AH plus root canal sealer. The specimens were randomly divided into three groups (n=10 each). Removal of gutta-percha was performed with the following devices and techniques: Group 1 (H-files), Group 2 (ProTaper Universal Retreatment), and Group 3 (NRT GPR). The retreatment time was recorded for each specimen using a stopwatch. After radiographing in buccolingual and mesiodistal directions, the amount of remaining gutta-percha in the roots was quantified using Image J 2X software. Apically extruded debris was weighted using analytical balances.
Statistical analysis was performed with one-way ANOVA test.
The volume of remaining filling material was significantly less in H-files and NRT GPR groups than in ProTaper Universal Retreatment group (p<0.05). The total retreatment time was significantly shorter in the ProTaper Universal Retreatment and NRT GPR groups compared with the manual group (p<0.05). NRT GPR files were associated with significantly less extruded debris than with the ProTaper Universal Retreatment (p<0.05).
Neither of the studied instruments completely removed the root filling material. NRT GPR files left less gutta-percha and sealer than ProTaper Universal Retreatment and H-files. The nickel-titanium rotary systems were significantly faster than the manual group in the time required for gutta-percha removal.