Aim: Evaluation and comparison the post-operative pain after the using of two different irrigation tips. Materials & Methods: 30 patients with vital lower posterior teeth without periapical radiolucency underwent one-visit root canal treatment, Root canals were prepared using NiTi ProTaper Universal rotary system then randomized into two equal groups according to the needle used for irrigation : Group A: Max-i-Probe, 25mm_ length 30_ gauge irrigation probes with a side-window dispersal port and Group B: NaviTip, 25mm _ length 30_ gauge, flexible, stainless-steel cannula which easily navigates curved canals with an end-vented, The needles of irrigation were penetrated 2 mm shorter than the working length. The trial design of this study is a Parallel randomized controlled trial. All demographic data, clinical and radiographic findings and modified VAS scores obtained from patients were statistically analyzed. Results: showed that there was no statistically difference between the two groups regarding the demographic data, prevalence of pre-operative pain, after 4 hours, 12 hours, 24 hours and 48 hours . Conclusions: There is no statistical significance difference between side vented Max-i-Probe and end vented NaviTip , while in both groups there was a statistically significant decrease in pain intensity preoperatively compared with all other time periods.