The impact of different kinematics on crack formation in root dentin after endodontic instrumentation

Endodontic instrumentation systems can cause dentinal cracks. These defects may propagate a vertical root fracture to the teeth and extraction will be necessary. The purpose of this study was to compare the formation of root crack caused by the rotatory and reciprocating system. Forty-five extracted human mandibular molars were selected for this study. The mesial roots have been removed and randomly divided into 3 groups according to instrumentation technique: GWG- waveOne Gold primary, GRP: reciproc Blue R25 and GPN – Protaper Next X2. The roots were standardized at 16mm in length and only the mesio buccal canals were prepared by the respective instruments. The mesio-lingual root canal served as control of the research. After root canal instrumentation the roots were the horizontally sectioned at 3, 6 and 9mm from the apex with low-speed saw under water-cooling. The slices were analyzed at X12 magnification with operative microscopy to determine the presence of dentinal cracks. The Friedman test was used to analyze the data. The control did not exhibit and dentinal defects however, all the evaluated systems promoted crack rates. There was no difference among the groups in crack frequency. According to he results, root canal instrumentation with rotatory or reciprocanting files can result in some microcracks in root dentin.