Objective: The aim of this study was to evaluate the effect of different irrigating solutions containing surfactants on the microhardness and smear layer removal of root canal dentin. Methods: Twenty extracted human single-rooted teeth were selected and sectioned to obtain standardized root segments. The root canal spaces were prepared using a standardized protocol. The samples were randomly divided into four groups (n=5) according to the irrigating solution used: Group 1 - 2.5% sodium hypochlorite (NaOCl); Group 2 - 2.5% NaOCl with 2% chlorhexidine gluconate (CHX); Group 3 - 2.5% NaOCl with 1% cetrimide; and Group 4 - distilled water (control). Each group underwent irrigation using their respective solutions. After irrigation, the samples were evaluated for smear layer removal using scanning electron microscopy (SEM) and microhardness testing.