comparative evaluation of dentinal microcracks in root canals prepared by neoniti, reciproc, and protaper instruments

Background: biomechanical preparation of root canals is one of the most important stages in successful root canal treatment. objectives: the aim of this study was evaluating and comparing dentinal micro cracks following root canal preparation with neoniti, reciproc, and protaper rotary systems. methods: fifty mandibular first molars were selected and their distal roots were cut. the roots were randomly divided into three experimental groups of 15 and one control group consisting of 5 teeth. defective specimens were excluded and replaced by sound molar teeth. a silicone-wash impression material was used to cover the root surface for simulating the pdl. the specimens were then prepared by neoniti (25/0.08), reciproc (25/0.08), and protaper rotary systems (up to the f3). the teeth in the control group remained unprepared. the specimens were then sectioned horizontally in of 3, 6, and 9mmdistances from the apex and explored by a stereomicroscope. incidence of micro cracks formation were statistically analyzed by chi-square test. results: the intact specimens were free of cracks, but all root canals prepared with three different files had cracks. the frequency of micro cracks was observed in 46.7%, 40%, and 20% of root canals following the preparation with reciproc, neoniti, and protaper files respectively. the cracks were in the middle thirds in teeth prepared by the reciproc and protaper files and in the coronal and middle thirds in those prepared by the neoniti file. conclusions: all neoniti, reciproc, and protaper systems create micro cracks in the root dentin. more cracks were observed in the reciproc system.