A comparison of the relative efficacies of four hand and rotary instrumentation techniques during endodontic retreatment

Aim The purpose of this study was to quantify the amount of remaining gutta -percha/sealer on the walls of root canals when two engine-driven instrumen ts (Quantec and ProFile) and two hand instruments (K-file and Hedstrom file ) were used to remove these materials. The amount of apically extruded debr is and the time required for treatment were also recorded. Methodology One hundred extracted mandibular premolars were prepared using a modified step-back, flare technique and obturated with the lateral conden sation technique. After repreparation with the test instruments, the specim ens were cut transversally at the cervical, middle and apical thirds with s teel discs and the three sections were split longitudinally. The amount of residual debris on the canal walls in each section was examined using a ste reomicroscope. Results In all groups the cervical and middle thirds showed no debris. In t he apical third, obturating material was observed in some specimens. No sta tistically significant difference was found between the two groups for inci dence of debris, although the Hedstrom group showed a greater number of sam ples with remaining gutta-percha/sealer. When analysing dirty specimens onl y, there was a statistically significant difference between the four groups (P < 0.01) with the Hedstrom group having significantly less length of can al wall with remaining obturation material than the Quantec group. There wa s no significant difference amongst the groups for weight of extruded debri s. However, there was a significant difference amongst the groups for mean treatment time with the Hedstrom file group requiring significantly less ti me than the Quantec group (P < 0.001); no significant differences were foun d between the other groups. Six instruments fractured in the Quantec group, four in the ProFile group, two in the Hedstrom group and two in the K-type group. Conclusions The results showed that overall, all instruments may leave fill ing material inside the root canal. During retreatment there is a risk of i nstrument breakage, especially rotary instruments.