Cleaning effectiveness of two nickel titanium instruments

Objectives: The design of the rake angle of rotary instruments may affect the cleaning efficiency of root canal instrumentation. This scanning electron microscopic study compared the cleaning effectiveness of ProTaper and Hero Shaper instruments with different rake angle designs. Methods: Forty root canals with curvatures ranging between 20° and 40° were instrumented with ProTaper (negative rake angle) and Hero Shaper (positive rake angle) instruments (20 canals each group). Irrigation for both groups was performed with alternating 5.25% NaOCl and 17% EDTA solutions. Both inner and outer canal walls (coronal, middle and apical thirds) were evaluated for debris and smear layer using SEM. Results: Completely cleaned root canals were not found in either group. At the coronal and middle thirds, the inner and outer canal walls of both groups were clean. At the apical third, there were higher scores in terms of debris and smear layer in both groups. At the inner walls of the apical region there was no significant difference in terms of smear layer in both groups, but the canal walls prepared with ProTaper instruments showed lower debris mean score. At the outer walls of the apical region, significantly less debris and smear layer were found using ProTaper instruments. Conclusion: With the limitation of this study, both instruments produced a clean and debris-free canal surface in the coronal and middle thirds. ProTaper instruments produced cleaner canal walls than Hero Shaper instruments at the apical thirds.