“…Moreover, the magnification power used in the current study was 1,000 x while that in the previous study was 2,000 x. Additionally, different scoring systems were used to assess "smear layer removal", such as Zmener et al, 2005 [31] scoring system used in this study and Hülsmann et al, 1997 [70] scoring system used in the previous study. Our findings can be interpreted by the fact that the "smear layer" cannot be completely removed from the apical third, due to the presence of sclerotic dentin in the apical part of the canal impeding the irrigants' flow [49,71] and larger width of the canal at the "coronal and middle thirds" in comparison to the "apical third", that is the narrowest area, allowing higher flow of the irrigants [21,72,73] . Within the control group, there was "no significant difference" in "smear layer" score between "the apical and middle thirds", while "the coronal third" showed significantly lower "smear layer" score "than the middle and apical thirds", which is in accordance with Dal Bello et al, 2019 [69] .…”