A comparative investigation of the cleaning efficacy of different manual and mechanical endodontic instruments (SEM study)

The purpose of this SEM study was to evaluate the cleaning effects of different manual and mechanical endodontic instruments. Sixty single canal human teeth were selected for this study. The root canals were instrumented by seven types of manual endodontic instruments (K-enlargers, K files Rattail files, K-Flexofiles, K Flex files, Hedstrom and NiTi Flex files) and five different mechanical endodontic instruments (Rispi, Rat tail Hedstrom, NiTi Flex files and K-enlargers). During and after the instrumentation, the canals were irrigated by 2.5% sodium hypochlorit. After splitting the roots longitudinally, the amount of debris and smear layer was quantified on the basis of a numerical evaluation scale, using scanning electron microscope. Results were statistically analysed using the Kruskal-Wallis test and t-test. There were no statistically significant differences between hand instrumentation and machine instrumentation with different endodontic instruments for any of the variables tested. Best instrumentation results in removing the smear layer and dentinal debris from the root canal were obtained with Kerr, NiTi and Hedstrom hand files and with K-enlargers, NiTi and Rat-tail mechanical files. In the apical thirds of root canals prepared using hand and mechanical endodontic instruments the smear layer and dentinal debris were always more abundant when compared with the middle and coronal thirds. In conslusion, cleaning efficacy differed slightly among the techniques and instruments, none of them completely removed smear layer and all left some debris.