Shaping ability of different single-file systems in severely curved root canals of extracted teeth

Aim To compare the shaping ability of three different single-file systems with Mtwo rotary instruments during the preparation of curved root canals in extracted teeth. Methodology A total of 80 root canals with curvatures ranging between 25 degrees and 35 degrees were divided into four groups of 20 canals. Based on radiographs taken prior to instrumentation, the groups were balanced with respect to the angle and the radius of canal curvature. Canals were prepared to the following apical sizes: Mtwo: size 30 using the single-length technique; Reciproc, F360, and OneShape: size 25. Using pre- and post-instrumentation radiographs, straightening of the canal curvatures was determined with a computer image analysis programme. Preparation time, changes in working length, and instrument failures were also recorded. These data were analysed statistically using anova and StudentNewmanKeuls test. Results During preparation, no file fractured. All instruments maintained the original canal curvature well with no significant differences between the instrument systems (P=0.792). Instrumentation with Reciproc and OneShape was significantly faster than with F360 and Mtwo (P<0.05), while F360 was significantly faster than Mtwo (P<0.05). No significant differences were obtained regarding changes in working length during instrumentation with the different instruments (P=0.784). Conclusions Under the conditions of this study, all instruments respected the original canal curvature well and were safe to use. The use of Reciproc and OneShape instruments required less time to prepare the curved canals compared with Mtwo and F360.