Background and Aim: To evaluate the effects of 1.25% and 2.5% sodium hypochlorite (NaOCl), 17% ethylenediaminetetraacetic acid (EDTA) and mixture of Doxycycline, citric acid and a detergent (MTAD) solutions on the surface free energy of dentin. Materials and Methods: The roots of freshly-extracted wisdom teeth (n=42) were removed at the cemento-enamel junction, and the crowns were sectioned horizontally at the mid-coronal level to obtain crown halves with similar area of exposed dentin. In each crown, one half was irrigated with saline (control), and the other half was treated with one of the following experimental solutions: 1.25% NaOCl, 2.5% NaOCl, 17% EDTA, MTAD, 17% EDTA+2.5% NaOCl and 1.25% NaOCl+MTAD. The surface free energy was calculated by measuring the contact angles of control and treated surfaces with distilled water, diiodomethane and formamide. Surface tension measurements of the test solutions were performed using the pendant drop method. The data were analyzed statistically. Results: MTAD displayed lowest surface tension level and decreased the surface free energy of dentin as with EDTA (p<0.05). 2.5% NaOCl significantly increased the energy level of dentin compared to EDTA and MTAD (p<0.05). The combined use of NaOCl in conjunction with EDTA and MTAD increased the surface free energy, but to a level that was still lower than that of the control group (p<0.05). Conclusions Although MTAD has a lower surface tension level, it does not possess better wettability than EDTA. It was concluded that surface tension of an endodontic irrigant may not be a unique requirement for good wettability of dentin.