Effectiveness of a hand file and two nickel-titanium rotary instruments for removing gutta-percha in severely curved root canals during retreatment: an in-vitro study

Purpose: To evaluate in vitro, the effectiveness of hand files, ProTaper and R-Endo rotary instruments for removing guttapercha in curved root canals. Material and Methods: Ninety severely curved teeth were divided into 3 groups. The teeth were enlarged and obturated using vertically condensed gutta-percha. Removal of gutta-percha was performed with the following devices and techniques: Hedström files (Vereinigte Dentalwerke, Munich, Germany,) ProTaper (Maillefer, Ballaigues, Switzerland) and R-Endo (Micro-Mega, Besançon, France). All techniques were used with the solvent eucalyptol. The amount of filling debris remaining on root canal walls was assessed radiographically; the images were digitized and analysed using AutoCAD 2000 software. Total canal area, area of the cervical, middle and apical thirds, and area of remaining filling material from 2 directions were outlined by two operators and calculated. Statistical analysis was performed using the Kruskal-Wallis test. Results: Comparisons of the percentages of remaining filling material in the entire canal did not reveal any significant differences between the methods of removal. However, when each third was analysed separately, significant differences for remaining debris were present in the apical third of the 3 groups, while the cervical and the middle thirds were significantly cleaner (P = 0.005). Conclusion: Under the experimental conditions, ProTaper and R-Endo NiTi instruments proved to be efficient and safe devices for the removal of gutta-percha in severely curved root canals.