Efficacy of automated versus hand instrumentation during root canal retreatment: an ex vivo study.

AIM To compare automated and manual instrumentation techniques for removing filling material from root canal walls during root canal retreatment. METHODOLOGY One hundred extracted human single-rooted teeth were root filled and stored. Specimens were divided into two groups: group A, Endofill plus gutta-percha; group B, Sealer 26 plus gutta-percha. The filling material was removed using the following techniques: group I - Gates-Glidden and K-type files; group II - ProFile; group III - ProTaper; group IV - K3; group V- Micro Mega Hero 642. The remaining filling debris on the root canal walls were assessed radiographically, images were digitized and analysed using Image ProPlus software. The roots were split for evaluation in a stereomicroscope by epiluminescence and photomicrographs were taken for further analysis. The area covered with filling debris was analysed by means of Student's t-test to compare the evaluation methods. The student's t-test was also used to compare the removal of filling materials. An anova test was applied to compare the different techniques (P < 0.05). RESULTS A significant difference occurred between radiographic and photomicrographic evaluation methods (P < 0.05). No significant difference was observed between the filling materials on terms of their removal (P > 0.05). Manual instrumentation left more filling debris on the root canal walls when compared to K3 (P < 0.05) and ProTaper (P < 0.01). CONCLUSIONS A photomicrographic method by epiluminescence was more effective than the radiographic method to evaluate filling debris. There was no significant difference between the filling materials in terms of their removal. K3 and ProTaper were more efficient than manual instrumentation.