Evaluation of microcracks formed by three different rotary file systems used in root canal preparation on dentin

Root canal preparation is one of the most important stages in the success of root canal treatment. In addition, this process may cause fractures and cracks in the root dentin. Nickel-Titanium (Ni-Ti) based rotary attachment systems produced by different companies are frequently used by dentists due to their advantages such as time saving and cutting efficiency. In this study, it was aimed to compare Reciproc, TruNatomy, Mtwo Ni-Ti rotary attachment systems and K type hand file in terms of micro-cracking on root dentin during root canal preparation.In the study, 80 lower incisors were divided into 4 groups. The length of the teeth was fixed to 18 mm and prepared with Reciproc, TruNatomy, Mtwo Ni-Ti file systems and K type hand insert. In order to mimic the periodontal ligament and to distribute the stresses evenly, the teeth were embedded with autopolymerizing repair acrylic in a mold obtained from the dental injector during the preparation. The teeth in the first group were prepared using the Reciproc file system, the teeth in the second group were prepared using the TruNatomy file system, and the teeth in the third group were prepared using the Mtwo file system. The teeth in the fourth group were prepared by step-back method using type K file. Then sections were taken from the samples with the Precision Cutting Device (Isomet 1000, Buehler, Lake Bluff, IL, USA) at levels of 3, 6, 9 mm. The samples obtained were examined and scored for the presence of microcracks in the dentin at x40 magnification under stereomicroscope (Zeiss Stemi 2000-C Stereomicroscope, Zeiss, Jena, Germany). The results obtained were evaluated from a statistical point of view. In the obtained data, as a result of shaping with Reciproc rotary system file at all cross-section levels, statistically significantly more cracks were detected compared to hand files. When cross-sectional levels are ignored; The Reciproc file system generated statistically more microcracks than the hand file and TruNatomy, and the Mtwo file system created statistically more microcracks than the hand file. When the section levels were compared, it was observed that there were significantly more cracks in the coronal region than in the other sections. It has been determined that the factors affecting the formation of cracks in dentin are the different designs of the files, their movement patterns, the size of the taper angle. In addition, it was determined that more microcracks occurred in the root canal as a result of the preparation made with the reciprocating movement compared to the rotation movement.