Background: Decontamination of root canal is a crucial step in achieving successful endodontic outcome. In order to achieve this, absolute eradication of microbes from root canal is of great importance. This in vivo study aimed at comparing the Conventional, Passive Ultrasonic Irrigation (PUI) and EndoVac irrigation system in reducing intracanal bacterial load. Methods: 60 necrotic, single rooted teeth having chronic periapical lesions were selected for endodontic therapy and randomly assigned into three groups. • Group 1 – 20 teeth treated using Conventional needle irrigation. • Group 2 – 20 teeth treated using Passive ultrasonic irrigation (PUI) with Irrisafe. • Group 3– 20 teeth treated using EndoVac system. After the surface disinfection, access opening was done. Group wise irrigation with NaOCl (VISHAL DENTOCARE PVT.LTD.) and EDTA (AMMDENT CANALARGE) was done with each canal in between instrumentation. Data were obtained by culturing bacterial samples of root canal before and after chemomechanical preparation under both aerobic and anaerobic conditions and CFU was counted. Statistical analysis- Paired ‘t’ test was used for intra group comparisons while ANOVA test followed by multiple comparison: Tukey test. Results: Significant post-operative reduction in bacterial colony counts was seen with all thegroups. Conclusion: EndoVac group had significantly higher mean log reduction in CFU counts followed by Passive ultrasonic irrigation and least mean log reduction was seen with Conventional group.

Passive ultrasonic Irrigation, EndoVac, Disinfection, Colony Forming Unit