Introduction The purpose of this study was to evaluate the apical preparation sizes resulting from repetitive pecking motions at the working length (WL) by using reciprocating files. Methods Sixty simulated endodontic training blocks with a J-shaped root canal were instrumented using Reciproc R25 (VDW, Munich, Germany) or WaveOne Primary (Dentsply Maillefer, Ballaigues, Switzerland) (n = 30 each). Each group was divided into 3 subgroups based on the repetitive pecking times at the WL: 1, 2, and 4 times. All specimens were prepared by 1 operator who was competent in instrumenting canals with both file systems. All of the procedures, including the WL measurement, were performed under an operating microscope. The replica of the prepared canal was taken with silicone impression material. After 24 hours of allowing the impression to set, each sample was evaluated under a scanning electron microscope at the apical tip, and the apical preparation size (diameter) was measured at the D0 level of the impression. The data were analyzed statistically using 2-way analysis of variance and the Tukey post hoc test at P =.05. Results The mean diameter (μm) varied between 253 and 274 and between 258 and 277 for Reciproc and WaveOne, respectively, without significant differences. However, more repetitive pecking motions at the WL resulted in a significantly larger apical preparation size than the subgroups with less pecking times (P <.05). Conclusions Under the conditions of this study, the results indicate that a greater number of repetitive pecking times at the WL may result in an apical preparation size that is larger than the actual file size.
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