objectives: This clinical study was conducted to evaluate and compare the post-operative pain after the using of two different irrigation tips: end-vented NaviTip tip and double sideport NaviTip irrigator tip immediate postoperatively and 4, 12, 24 ,48,
 72 hours and 7 days utilizing a numerical rating scale (NRS). Methods: 38 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 gropus according to the needle used for irrigation group(A) NaviTip® 29-gauge 27 mm with End vented Tip and Group (B) NaviTip® 31-gauge 27 mm with Side vented Irrigator Tip. 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, 48 hours and 7 days. There is no statistical significance difference between End vented NaviTip and Side vented NaviTip , while in both groups there was a statistically significant decrease in pain intensity preoperatively compared with all other time periods.Conclusion:  there was a statistically significant decrease in pain intensity preoperatively compared with all other time periods