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

AIM: To evaluate ex vivo the effectiveness of hand files, ProTaper and R-Endo rotary instruments when removing gutta-percha from curved root canals.
METHODOLOGY: Ninety severely curved teeth were divided into three groups. The root canals were accessed, prepared and filled with vertically condensed gutta-percha and sealer. Removal of gutta-percha was performed with the following devices and techniques: Hedström files (Vereinigte Dentalwerke, Munich, Germany), ProTaper (Dentsply Maillefer, Ballaigues, Switzerland) and R-Endo (Micro-Mega, Besançon, France). All techniques were used with the solvent eucalyptol. The amount of filling material debris remaining on root canal walls was assessed radiographically from two directions: mesio-distal and bucco-lingual. The images were digitized and analysed with autocad 2000 software. Total canal area, area of the cervical, middle and apical thirds, and area of remaining filling material from both directions were outlined by two different operators and calculated. Statistical analysis of remaining filling material within each third of the canals was performed by 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, the canal third was of relevance in all groups; the apical third had the most remaining filling material compared with the middle and cervical thirds (P = 0.0012).
CONCLUSION: All instruments left filling material inside the root canal. ProTaper and R-Endo rotary instruments were inadequate for the complete removal of filling material from the root canal system.