Histological evaluation of the effectiveness of five instrumentation techniques for cleaning the apical third of root canals

The efficacy of five instrumentation techniques for cleaning the apical third of curved root canals was assessed by histological examination. Mesial root canals of freshly extracted human mandibular molars were prepared by the following instrumentation methods: step-back technique using stainless steel files; step-back technique using nickel-titanium files; ultrasonic technique; balanced force technique; and Canal Master U technique and instruments. The apical portion of the root was histologically processed, and cross-sections were examined for remaining soft tissue, predentin, and debris. The results showed no significant differences among the techniques. Although the five instrumentation methods were effective in removal of major amounts of tissue from the canals, none totally debrided the entire root canal system, especially when variations in the internal anatomy were present.