Evaluation of microcracks on dentin that created with protaper universal, protaper next and reciproc rotary file systems used in root canal preparations

The preparation of ducts during root canal preparation is one of the most important steps in the success of root canal treatment and plays an important role in the effectiveness of all subsequent procedures. However, the steps in the preparation of the root canals can cause damage on root dentin as crack and fracture. Nickel-Titanium (Ni-Ti) based rotary tools were produced by different companies. Many clinicians prefer these instruments because of the benefits regarding their time saving and cutting efficiency. In this study, it was aimed to compare the effectiveness of ProTaper Universal, ProTaper Next and Reciproc Ni-Ti rotary file systems of creating microcracks on dentin during root canal shaping. In our study, 100 lower anterior teeth were used. 20 teeth were separated as negative control group without any intervention. The crowns of the teeth in the groups were stretched out for equalize to 13 mm. During tooth expansion and forming operations, 80 were embedded into a mold prepared from a dental syringe by using autopolymerizing repair acrylic to mimic the periodontal ligament. Five groups were formed each consists 20 teeth. No procedure was performed on group 1 (control group). In group 2, preparation was made with step-back technic by using K-type file to have an apical diameter of 25 size. The 3rd group was formed by using the ProTaper Universal file system, Protaper Next file system was used for the 4th group, and Reciproc file system was used for the 5th group. Then, sections were taken from the samples with Minitom Precision Cutting Device of 3, 6, 9 mm levels. The obtained samples were examined under the stereomicroscope for the presence of microcracks in the dentin under x40 magnification. Triple scoring was performed as no microcrack, incomplete microcrack, and vertical root fracture. The results were evaluated statistically. No microcracks was observed in the control group and hand-training group. According to chi-square analysis, microcrack formation was found statistically significant as a result of using rotating files (p<0,05). When the cross-sectional levels were ignored, microcrack occurred the most in the ProTaper Universal group (20%), in Reciproc group (11,7%) and in ProTaper Next group the least (6,7%). However, the difference between these groups was not statistically significant (p> 0.05). When examining sectional levels with the groups were ignored, microcrack occurred the most in the cross-sectional level in 9 mm (11%), in 6 mm (7%), in 3 mm the least (5%). The presence of microcracks at 9 mm slice level was statistically significant (p = 0.033). According to chi-square test, the difference between 3, 6, and 9 mm cross-sectional levels was not statistically significant (p> 0,05). In the groups ProTaper Universal and Reciproc files were used, 1 vertical root fracture was found in 9 mm sections for each. Taking into account the limitations of in-vitro studies, we concluded that all of the rotary file systems used in our study caused microcracks in the root dentin. According to ProTaper Next and Reciproc, it was found that the ProTaper Universal file system produced more microcracks in the root dentin. Keywords: Microcrack, ProTaper Universal, Reciproc, ProTaper Next