A comparison of canal preparations by Mtwo and RaCe rotary files using full sequence versus one rotary file techniques; a cone-beam computed tomography analysis

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Objectives: Using one rotary file can result in a faster canal preparation. This can be done with several file systems and endodontic motors. In the present study, a newly single file technique (one rotary file technique) with available rotary file systems is introduced. The aim of the present study was to evaluate centering ability and remaining dentin thickness of 2 rotary nickel-titanium systems (Mtwo versus RaCe) and instrumentation techniques (conventional versus one rotary file) by cone-beam computed tomography. Materials and Methods: A total of 76 mandibular molar teeth were selected and divided to 4 groups (n = 19 teeth with 57 canals). The teeth were mounted in resin and pre-instrumentation scans were prepared by Cone Beam Computed Tomography (CBCT). The canals instrumented with Mtwo and RaCe rotary files either in conventional or one rotary file technique (ORF). After cleaning and shaping of distal and mesial canals, post instrumentation scans were performed by CBCT in the same position as pre instrumentation scans. Centering ability and remaining dentin thickness were evaluated by Planmeca Romexis viewer. The data were analyzed with analysis of variance and post hoc t test (P < 0.05). Results: Mean centering ratios for Mtwo/conventional, Mtwo/ORF, RaCe/conventional and RaCe/ORF groups were assessed. At overall, there were no significant differences between instrument types and instrumentation techniques (P > 0.05). However, in a few cross-sections, conventional technique and/or RaCe showed higher centering ability. One rotary file technique with either RaCe or Mtwo was significantly faster than conventional technique (P = 0.02). There was no significant difference among groups regarding file fracture. Mesiolingual canals showed more transportation compared with mesiobuccal and distal canals. Conclusions: Both of the instrumentation systems and techniques produced canal preparations with adequate centering ratio. One rotary file technique prepared canal significantly faster than conventional technique.