in vitro comparison of gutta-percha removal with h-file and protaper with or without chloroform

introduction : removal of root filling materials is one of the key steps in success of root canal retreatment. the purpose of this study was to evaluate the efficacy of h-file and protaper with or without chloroform in the removal of gutta-percha during retreatment of mandibular premolars. materials and methods: sixty mandibular premolars with one canal, and curvatures less than 30 degrees were used in this experimental study. they were instrumented with k-files and laterally obturated with condensed gutta-percha using ah26 as the sealer and were stored in 100% humidity at 37 ° c for 2 weeks. the teeth were randomly divided into four groups of 15 teeth each. removal of gutta-percha was performed with h-file and protaper. all techniques were used with or without chloroform. the teeth were split longitudinally and the area of remaining gutta-percha/sealer on the root canal wall was explored under stereomicroscope. retreatment time duration was also recorded for each sample. data were analyzed statistically by two-way anova, t-test and tukey’s. results: in all groups, no significant difference was found in remaining gutta-percha and sealer with or without using chloroform, but chloroform shortened the time of retreatment. protaper left significantly less remaining filling materials than h-file ( p <0.05). retreatment time was significantly different between the studied groups ( p <0.001). conclusion: protaper ni-ti instruments proved to be more efficient and time-saving devices for removal of gutta-percha compared to h-file in canals with no or slight curvature.