| Summary: | Abstract Background Comparison of the shaping ability of advanced nickel-titanium (Ni-Ti) instruments is of great interest to the field of endodontics. However, the models used to study canal preparation still lack uniformity, relevance to reality and complexity. The aim of this study was thus to compare the shaping abilities of the ProTaper Next (PN) and WaveOne (WO) Ni-Ti instruments in three-dimensional (3D)-printed teeth, which may overcome the present defects of most real teeth and model teeth including 3D S-shaped canals. Methods Six teeth and their corresponding 3D-printed replicas were prepared using the same kind of Ni-Ti instrument. The pre- and post-preparation volumes, surface areas and transportation of the canals were measured to compare the teeth with their replicas. Twenty 3D-printed teeth with S-shaped canals were used to support the preparation study. The S-shaped canals were then scanned to measure their volumes and surface areas. Next, the two kinds of instruments were used to prepare the 3D-printed canals (n = 10 per group). The volume and surface area of the canals, the transportation along the two curvatures and the percentage of unprepared surface area were measured. Micro-CT and VGstudio2.2 (VG2.2) software were used to perform scans and collect data throughout the research. The paired-samples T test and Kruskal-Wallis H test were used for statistical analysis. Results There was no significant difference between the real canals and the printed ones post-preparation (P > .05). The printed S-shaped root canals had a unified shape, with a small standard deviation and range. The WO group had higher mean values for the volume and superficial area measurements compared with the PN group (P < .05). No differences in the untouched areas were found between the two systems (P > .05). PN caused less transportation at the apical curve than WO did (P < .05). Conclusions In conclusion, 3D-printed teeth are suitable for the study of Ni-Ti rotary instruments. Furthermore, the PN rotary system caused less transportation at the apical curve than the WO system did in complicated root canal procedures.
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