Comparative evaluation of the effect of hand file, different nickel-titanium retreatment files, and self-adjusting file system on the incidence of dentinal microcrack formation during the removal of root canal filling material: An in vitro stereomicroscopic study

Abstract

Aim: The aim of the study is to evaluate the effect of hand files, rotary nickel-titanium files, and self-adjusting file (SAF) on the incidence of crack formation during retreatment. Materials and Methods: Eighty extracted human mandibular molar teeth with intact mesial roots were selected. They were divided into 8 groups of 10 teeth each; Group 1: Control, Group 2: Obturated control, Group 3: Hand files, Group 4: ProTaper Universal Retreatment, Group 5: Twisted File Adaptive, Group 6: Reciproc Blue, Group 7: XP-endo Finisher R, Group 8: SAF system. All teeth had the coronal portions and distal roots removed by a diamond-coated disc with water cooling, leaving roots approximately 13 mm in length. Except for Group 1, all canals were similarly instrumented and obturated at an apical size of 40.02. Retreatment was performed in each group according to manufacturer's recommendations except for Groups 1 and 2. The roots were sectioned horizontally at 3, 6, and 9 mm from the apex with a low-speed saw. Stereomicroscopic evaluation of the sections was done to assess the presence or absence of defects. Results: The groups that were not retreated (Groups 1 and 2) showed no defects. Hand files showed the least number of defects followed by the SAF. Reciproc Blue showed the most dentinal defects. Conclusion: All NiTi instruments tend to induce various degrees of dentinal damage during retreatment procedures. The SAF and hand instrumentation presented satisfactory results with minimal dentinal microcracks.