Aim: To evaluate the microcrack propagation after root canal instrumentation using instruments operating in rotary, reciprocating, translinear, and centrifugal motions.
Materials and methods: An estimated 80 mandibular molars were divided into three experimental groups (n = 20). Group I—rotary motion (ProTaper Universal Dentsply, Maillefer, Ballaigues, Switzerland, and F2 file). Group II—reciprocating motion (WaveOne Dentsply, Maillefer, Ballaigues, Switzerland, Primary Files ISO 25, and 8% taper). Group III—translinear motion (Self-Adjusting File, ReDent Nova, Ra'anana, Israel). Standard access cavities were prepared and the canals were manually prepared up to a 15-K file to establish patency. Shaping and cleaning was performed according to manufacturer's instructions for each group, keeping the irrigation protocol constant. The samples were then scanned in a four-dimensional X-ray microscopy machine (ZEISS Xradia 510 Versa) and were virtually sectioned. The Z test was applied for statistical analysis.
Results: No significant difference was found between rotary (ProTaper Universal) and reciprocating groups (WaveOne) (p = 0.3112). Translinear motion (Self-Adjusting File) showed statistically significant least microcracks (p = 0.000).
Conclusion: (1) Self-adjusting file proved to be the most minimally invasive file system. (2) Reciprocation showed lesser samples with cracks than rotary motion. (3) Apical sections showed significantly higher cracks than the other sections. (4) Four-dimensional X-ray microscopy could be a promising tool for dental imaging.
Clinical significance: The stress induced by aggressive preparation procedures of certain file systems have led to microcrack propagation, reduction in the resistance form, and subsequently failure of endodontic therapy owing to vertical root fracture. Literature suggests that kinematics of the file influences crack propagation in a radicular dentin. Hence, this study has been undertaken to compare and evaluate the effect of four different kinematics of nickel–titanium file systems on microcrack propagation in a radicular dentin.
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