Plotino G, et al. - Researchers gauged whether or not a minimally invasive basic root canal preparation technique has an influence on root canal cleanliness in extracted mandibular molar teeth. In the middle and coronal thirds, the basic root canal preparations resulted in less debris and smear layer on the canal walls, while debris and smear layer was always present. In the apical third, significantly less residual debris and smear layer were resulted by an apical size of 25 vs a size 20.