Irrigating solutions are used during instrumentation of the root canal system to increase cutting efficiency of the instruments and to flush away pulp tissue, bacteria, and to remove the smear layer produced on cut dentinal surfaces. The purpose of this investigation is to conduct a comparative study between three irrigating solutions for the removal of the smear layer using the Scanning Electron Microscope. Forty eight freshly extracted single rooted human teeth (n=48) will be used. Conventional access openings and canal instrumentation will be performed using rotary NiTi files with a crown down technique. Two milliliters of NaOCL 6% will be used after instrumentation with each file followed by the delivery of the tested solutions for the removal of the smear layer. These irrigants will be used according to the manufacturer's instructions. Samples will be randomly divided in three treatment groups: Group I, EDTA 17% (n=12 teeth), Group II, Calcinase (n=12 teeth), and Group III, Smear Clear (n=12 teeth). Positive controls (n=12 teeth) will consist of teeth in which no chelating agent will be used after instrumentation of the canals. Teeth will be sectioned in half, numerically coded, and prepared for SEM analysis. Photomicrographs will be taken at the coronal, middle, and apical thirds of the root. Canal cleanliness and smear layer removal will be evaluated at 200x magnification. The assessment of the photomicrographs will be performed using a semi-quantitative scale by one single evaluator. The Mann-Whitney U-test and the Kruskal-Wallis test will be used to statistically analyze our data at a significance level p<0.05. The results of this study will allow us to evaluate the efficiency of these new products and ascertain manufacturer's claims.