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Shaping ability of ProTaper Next and Navigator EVO rotary nickel–titanium file systems in simulated L-shaped and S-shaped root canals

Objective: The objective of this study is to evaluate and compare the shaping ability of ProTaper Next (PTN) and Navigator EVO (N-Evo) rotary file systems in L- and S-shaped simulated resin root canals. Materials and Methods: A total of forty L-shaped (n = 20) and S-shaped (n = 20) resin block root canals were randomly assigned into four groups (n = 10) based on the PTN and N-Evo rotary file systems. Before the instrumentation, simulated root canals were filled with the India blue ink and preinstrumentation images were taken using a digital camera. Each canal was prepared to the standard working length 16 mm, 0.15 mm apical foramen diameter, and 0.2 initial tapers. After the canal preparation, red India ink was filled in each canal and postoperative images were obtained. The two images were superimposed, five points were selected, and canal widths were measured with image analysis software. Canal preparation time, file failure, and presence of aberrations were recorded and compared between the two systems. Descriptive statistics of mean and standard deviation and inferential statistics of Independent samples t-test and analysis of variance tests were applied to the data. Results: PTN file system showed significantly lesser preparation time (L-shape, 2.55 ± 0.38 min, and S-shape, 2.57 ± 0.44 min) in comparison to N-Evo file system (L-shape, 5.01 ± 0.37 min, and S-shape, 5.21 ± 0.30 min) (P < 0.001). N-Evo file removed significantly less resin in many positions and exhibited lesser canal straightening in both S- and L-types of canals compared to the PTN file system (P < 0.05). Both file systems created danger zone and outer widening of the canal. Three N-Evo files fractured in L-shaped canals. Conclusions: N-Evo file system demonstrated better shaping ability compared to PTN in L- and S-shaped simulated canals. PTN file system prepared the canal in less time and maintained the original curvature. An almost similar number of canal aberrations found between tested file systems. However, three N-Evo files broke in L-shaped canals indicating possible limitation in this area.