Laser has an effective role in endodontic treatment. Most studies have examined the effects of laser radiation on straight canals. The aim of this study was to review the therapeutic effect of laser radiation on curved root canals. Methods: First, the related keywords were searched in four databases: Scopus, PubMed, WOS and Google Scholar. After merging the collected titles, original eligible articles published by the end of February 2021 were scrutinized. Results: Out of 16 collected titles,

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... articles met the study criteria. The lasers used included Er, Cr: YSGG (2780 nm), Nd: YAG (1064 nm), Er: YAG (2940 nm) and diode (660,940,980 nm). The canal curvature in 6 studies was between 5-33°. Also, the degree of curvature was described > 20° in three studies, and in one study it was 31± 9°. Therapeutic goals of laser irradiation included root canal shaping, smear layer removal, anti-enterococcus faecalis and anti-candida albicans effect, levels of filler and sealer penetration into dentin tubules. The results of the studies showed that the laser radiation was not effective for curved root canal shaping; however, it was effective on other mentioned purposes compared to the control group. Conclusion: Radiation of the above lasers in curved canals, despite the weakness in canal shaping, can be effective as an adjuvant tool for canal cleaning, disinfecting and sealing improvement.