ABSTRACT
Objective: This study evaluated the effect of different preparation times on the taper and shape of simulated root canals using the XP-endo Shaper rotary file Materials and methods: A total of 54 resin blocks made of clear polyacrylic resin with simulated root canals were used in this study. They were photographed using a stereomicroscope. They were prepared using the XP-endo Shaper instrument up to the working length (WL) according to the manufacturer's recommendation for 30 seconds (s), 60 s and 90s. Postoperative photographs were performed after canal preparation at each time-point. Then, the registered pre and postoperative datasets were examined to evaluate the canal taper and apical tip diameter. Repeated measures general linear model was used to compare the differences in either the increase or the reduction of the parameters amongst the time-points. Alpha-error was set at 5%. Results: Extending the period of XP-endo Shaper active instrumentation at WL significantly influenced several parameters such as apical tip diameter (P < 0.05) and canal taper (P < 0.05) of the instrumented canal. Conclusions: Extending the activation time of XP endo Shaper instruments at WL resulted in a more comprehensive root canal preparation, increasing the canal taper and the apical tip diameter.