Objectives: The aim of this study was to assess and compare the effect of a newly introduced irrigant (Qmix) on Enterococcus Faecalis biofilm (biofilm susceptibility test), to assess and compare the antibacterial effect of (Qmix) against Enterococcus Faecalis and to study and compare the surfacetopographic changes of root canal dentin walls irrigated with the tested irrigant using scanning electron microscope (SEM). Materials and methods: A cellulose nitrate membrane was cut into small discs, placed on the surface of blood agar. A bacterial suspension of E. faecalis was prepared, adjusted to 0.5 McFarland and 10 microliters were placed on each disc and incubated for 48h. Four discs were used for the first part of this study. One was left untreated and the remaining 3 were treated with the 3 selected test solutions then the membranes were treated with the neutralizer of each irrigant. The untreated and treated membranes were placed on blood agar plates. Then, they were transferred to the Central Laboratory at the NRC for SEM examination. The remaining 18 discs were transferred to tubes containing the selected irrigants for 2 and 5 minutes. Then the discs were transferred to tubes containing the neutralizing materials of the irrigants then to tubes containing phosphate buffered saline and vortexed. Serial 10-fold dilutions of the suspension were made from which a volume of 20 microliters of each dilution was taken and plated on bile esculin plates. These plates were incubated for 24 hr at 37°C. After 24 hr, the approximate number of colony forming unit (CFU) per ml was calculated. Thirty extracted single rooted human teeth was collected, decapitated, prepared with Protaper universal nickel titanium rotary instruments to size 50,0.06 taper and sterilized. They were classified into 3 groups each containing 10 teeth according to the irrigant used: GROUP Ι: Qmix. GROUP ΙΙ: Sodium hypochlorite 5.25%. GROUP ΙΙΙ: Saline. A bacterial suspension of E. faecalis was prepared, adjusted to 0.5 McFarland. Ten microliters of the bacterial suspension were transferred to the canal lumen then the teeth were incubated for 48h at 37°C. After 48h, irrigation of the canals with 5 ml of the corresponding irrigants was done. A sterile paper point was placed inside each canal lumen then it was transferred to tubes containing BHI and tubes were vortexed. Serial 10-fold dilutions of the suspensions were made. Twenty microlitres were taken from each dilution and plated on bile esculin plates and incubated for 24 h at 37°C. After 24 h, approximate number of colony forming unit per ml was calculated. Fifteen extracted single rooted human teeth was collected, decapitated, prepared with Protaper universal nickel titanium rotary instruments to size 50,0.06 taper and sterilized. They were classified into 3 groups each containing 5 teeth according to the irrigant used: GROUP Ι: Qmix + 5.25% sodium hypoclorite. GROUP ΙΙ: Sodium hypochlorite 5.25% + 17% EDTA GROUP ΙΙΙ: Saline. For group Ι , irrigation with 2 ml of 5.25% NaOCl was done after each file, after the preparation finished it was rinsed with 5ml of saline then irrigated with 5ml of Qmix as final irrigant and then 5 ml of saline to stop the action of the irrigant. For group ΙΙ, , irrigation with 2 ml of 5.25% NaOCl was done after each file, after the preparation finished irrigation with 5ml of 17% EDTA as final irrigant was done then 5ml of saline to stop the action of the irrigant. For group ΙΙΙ, irrigation with 2 ml of saline was done after each file, after the preparation finished it was rinsed with 5 ml saline. The teeth were splitted longitudinally into two halves, each half was prepared to be examined by SEM.Results: Sodium hypoclorite succeeded in complete degradation of the bacterial biofilm, Qmix produced an effect slightly less than that of sodium hypoclorite while saline produced no or very little effect on the bacterial biofilm. At 2 and 5 minutes, sodium hypoclorite showed the most potent action on the bacteria with the least number of colony forming units per milliliters followed by Qmix then saline which showed the weakest action on the bacteria, it was also observed that the number of the bacteria decreased with increasing the time of immersion from 2 minutes to 5 minutes for the three irrigants. Qmix and sodium hypoclorite had nearly the same antibacterial action on the bacteria present in the canal with significant reduction in the number of colony forming units per ml while saline showed the weakest action on the bacteria. There was an insignificant difference between the antibacterial action of both Qmix and sodium hypoclorite.Qmix was found to be as effective as sodium hypoclorite + 17% EDTA in removal of smear layer from the the canal wall and obtaining a clean surface and opened dentinal tubules while saline showed no action on smear layer leaving the surface covered by debris and heavy smear layer with no visible dentinal tubules.Conclusion: Qmix proved to be an acceptable irrigating solution, getting the benefits of chlorohexidine for its antimicrobial effect, EDTA as a chelating agent and the surfactant to avoid dentinal erosion. In this way we can avoid the un wanted effects and drawbacks of sodium hypoclorite such as toxicity, unpleasant taste and odour. When ranking the antimicrobial effect of the two tested solutions against E. faecalis, they are nearly the same. However, Qmix due to its chlorohexidine content possess the property of substantivity. When comparing the dentin surface topographic changes in relation to the 2 irrigants, they are equally the same. However, due to its content of surfactant it is proposed that Qmix may prevent dentinal erosion, which is considered a benefit over sodium hypoclorite.