Evaluation of apical transportation and centering ability of three single‑file systems in severely curved canals using micro‑computed tomography

This study aimed to compare the apical transportation and centering ability of One Curve, HyFlex EDM, and EdgeFile X1 in curved mesiobuccal and mesiolingual canals of mandibular first molars.

In this in vitro experimental study, 60 mesiobuccal and mesiolingual canals of the mandibular first molars with a minimum length of 19 mm and 25°–40° curvature were randomly divided into three groups (n = 20) for root canal preparation with One Curve, HyFlex EDM, and EdgeFile X1. After access cavity preparation and confirming the glide path, the baseline micro‑computed tomography (micro‑CT) scans were obtained, and the root canals were instrumented with the respective systems according to the manufacturers’ instructions. Apical transportation and centering ability were assessed at 1, 3, 5, and 7 mm from the apex by comparing pre‑ and postinstrumentation micro‑CT scans. One‑way ANOVA, independent t‑test, and Duncan’s post hoc test were used to statistically compare the groups, and data were analyzed by SPSS version 24 (alpha = 0.05).

The three groups were not significantly different regarding apical transportation at 5 and 7 mm from the apex (P > 0.05). At 1 mm level, One Curve caused significantly lower apical transportation; while, at 3 mm level, HyFlex EDM resulted in significantly higher apical transportation (P < 0.05). No significant difference was noted in the centering ability of the three groups at 1, 3, and 5 mm from the apex (P > 0.05). At 7 mm level, EdgeFile X1 showed significantly lower centering ability (P < 0.05).

One Curve caused lower canal transportation in the apical third compared with EdgeFile and HyFlex EDM, but no significant difference was noted among the three in the coronal third of the roots.