Effectiveness of conservative instrumentation in root canal disinfection Nur Usta, Sila Solana, Carmen Ruiz-Linares, Matilde Baca García, María Pilar Ferrer-Luque, Carmen María Cabeo, Mónica Arias Moliz, María Teresa Conservative instrumentation Disinfection Polymicrobial infection Root canal preparation The authors acknowledge Francisca Castillo Pérez for her technical assistance Ethical approval. This study was performed in line with the principles of the Declaration of Helsinki. The study protocol was approved by the ethics committee of the university where the study was conducted (no. 1076 CEIH/2020). Objectives: The impact of conservative instrumentation on the disinfection of root canals with different curvatures has not yet been determined. This ex vivo study aimed to evaluate and compare the effect of conservative instrumentation with TruNatomy (TN) and Rotate and a conventional rotary system, ProTaper Gold (PTG), on root canal disinfection during chemomechanical preparation of straight and curved canals. Materials and methods: Ninety mandibular molars with straight (n = 45) and curved (n = 45) mesiobuccal root canals were contaminated with polymicrobial clinical samples. Teeth were divided into three subgroups (n = 14) according to the file systems and the curvature. Canals were instrumented with TN, Rotate, and PTG, respectively. Sodium hypochlorite and EDTA were used as irrigants. Intracanal samples were taken before (S1) and after (S2) instrumentation. Six uninfected teeth were used as negative controls. The bacterial reduction between S1 and S2 was measured by ATP assay, flow cytometry, and culture methods. Kruskal-Wallis and ANOVA tests were followed by the Duncan post hoc test (p < 0.05). Results: Bacterial reduction percentages were similar for the three file systems in straight canals (p > 0.05). However, PTG showed a lower reduction percentage of intact membrane cells in flow cytometry than TN and Rotate (p = 0.036). For the curved canals, no significant differences were obtained (p > 0.05). Conclusion: Conservative instrumentation of straight and curved canals using TN and Rotate files resulted in similar bacterial reduction compared to PTG. Clinical relevance: The disinfection efficacy of conservative instrumentation is similar to conventional instrumentation in straight and curved root canals. 2023-05-08T09:43:28Z 2023-05-08T09:43:28Z 2023-03-03 journal article Sıla Nur Usta et al. Clinical Oral Investigations. [https://doi.org/10.1007/s00784-023-04929-z] https://hdl.handle.net/10481/81383 10.1007/s00784-023-04929-z eng http://creativecommons.org/licenses/by/4.0/ open access Attribution 4.0 Internacional Springer