An In vitro comparadve evaluadon of a hand file and three rotary Nill Instruments for removing gutta percha during root canal re-treatment

Objective: To evaluate the efficacy of NITI mechanical rotary instrumentation and Hedstrom file for gutta percha removal using dearing techniqueMethod: Forty extracted human single rooted premolar, each with a single canal were selected. The samples were decoronated to leave 17 mm root and Instrumented with K-flles upto MAF 30 using step back technique. Samples were obturated using cold lateral condensation of gutta-perdta and AH Plus sealer. The teeth were then randomly divided Into four groups of 10 specimens each. After 2 weeks all the canals were then retreated by either ProTaper re-treatment files, M--two re-treatment files, R-Endo re-treatment flies or Hedstrom flies. The amount of remaining filling materials after re-treatment procedures was assessed by stereomlcroscope. Also time required for reaching original working length and for removal of obturating material (in min) was measured. Statistical analysis was accomplished using one way Kruskal-Wallls ANOVA and Mann-Whitney U testResult: M-two re-treatment flies showed least amount of gutta perdta/sealer followed by Pro Taper re-treatment files, R-Endo re-treatment flies and Hedstrom files.Conclusion: Under the experimental conditions, significant difference was observed between Pro Taper re-treatment flies&... Hedstrom flies and Mtwo re-treatment flies&... Hedstrom flies for gutta percha/sealer removal. Complete removal of materials did not occur with any of the instrument systems investigated.Keywords: Clearing technique, re-tteatment, rotary Instrument