Aim: The objective of this study was to assess, by means of a scanning electron microscope (SEM), the cleanliness of canal dentine surfaces after post space preparation with the aid of two different magnification devices, either dental loupes or an operating microscope. Materials and methods: Twenty extracted single-rooted human teeth (18 canines and 2 premolars) were selected. Root canals were cleaned, shaped using nickel-titanium instruments and filled with gutta-percha. Samples were divided into two groups (n = 10), according to the device used by the operator: A (microscope) and B (loupes). Gutta-percha/sealer fillings were removed using a sequence of low-speed post drills; root canal walls were also cleaned by means of tips for ultrasound and microbrush. SEM images of post spaces were taken, and the presence of both debris and open dentine tubules was evaluated using a three-step scoring system. Mean scores were calculated at three depth levels of post space. Results: Residual debris was observed in all specimens. Statistically significant differences (P 0.05) between groups were found at both coronal and apical levels, and better scores for debris and open tubules were obtained by group A. Conclusions: The use of an operating microscope allowed the authors to achieve superior debridement scores at specific levels (coronal and apical levels) of the post space area, compared with the use of dental loupes. Keywords: debridement, dental microscope, dentinal surface, magnification, post space