Objective: To investigate whether there are differences between the root canal disinfection, comparing the passive ultrasonic irrigation technique with the conventional technique.
Materials and methods: The following electronic databases were searched: Pubmed; VHL; Web of Sciences and OVID with no publication date restriction. The study's quality evaluation was carried out using the Handbook by Cochrane. The online research identified 5464 studies. From the nine studies selected for a full reading of the text, five were included in the present systematic review. Meta-analysis was performed in three articles, which evaluated the root canal's cleanness through microbiological analysis.
Results: Only one article concluded that the ultrasonic passive irrigation showed a better performance compared with the conventional irrigation. None of the articles analyzed presented a low risk of bias in all domains. According to the results of the meta-analysis, there was no statistical difference between the groups (OR = 0.34, IC 95%: 0.10-1.19).
Conclusions: The level of evidence comparing the two techniques is fragile since in all studies some type of bias was observed which may interfere in the results and conclusions.
Keywords: Endodontic irrigation; bacterial reduction; conventional irrigation; passive ultrasonic irrigation.