Assessment of canal centering and dentinal integrity following root canal preparation with different NiTi file systems: An in vitro CBCT and stereomicroscopic study

The success of root canal treatment largely depends on the canal shaping procedure, which influences subsequent steps, such as cleaning, obturation, and sealing. The present study aimed to evaluate the canal-centering ability, dentin removal, and dentinal crack incidence following root canal preparation with different rotary and reciprocating nickel-titanium file systems using cone beam computed tomography (CBCT) and a stereomicroscope. Forty freshly extracted single-rooted human mandibular premolars were selected and scanned preoperatively by CBCT (KAVO OP 3D Pro, Germany) to evaluate canal curvature. The samples were then randomly distributed into 4 groups (n = 10): Group 1 - ProTaper Next (continuous rotary), Group 2 - MicroMega One RECI (reciprocating), Group 3 - Race Evo (continuous rotary), and Group 4 - R-Motion (reciprocating). Root canals were prepared in accordance with the respective manufacturer's recommendations. Post-instrumentation CBCT scans were obtained to assess canal centering and remaining dentin thickness at 3, 6, and 9 mm from the apex. Root sections were also examined under a stereomicroscope to assess dentinal cracks. The MicroMega One RECI (Group 2) demonstrated superior canal centering, with mean ratios of 0.20 ± 0.05, 0.18 ± 0.04, and 0.17 ± 0.03 in the apical, middle, and coronal thirds, respectively. In contrast, ProTaper Next (Group 1) showed the highest centering ratio (0.35 ± 0.08 at 3 mm), indicating greater deviation from the canal axis. Reciprocating systems exhibited better dentin preservation and fewer dentinal cracks compared with continuous rotary systems. Based on observations from this in vitro study, it can be concluded that the variations in design of file systems and motion patterns critically determine the efficiency and safety of root canal shaping. Reciprocating and rotary motions show different effects on canal centering, dentin removal, crack propagation, and the preservation of root integrity.