Evaluation of Radicular Dentin Microcracks Formation after Instrumentation with NiTi Hand and Rotary File System: A Stereomicroscopic Study

Abstract

The present study aimed to assess the formation of microcracks in root dentin post-instrumentation with nickel-titanium (NiTi) hand and rotary file system. Totally, 80 freshly extracted mandibular premolar teeth with single roots were chosen for this study. Access opening was performed and #10 K-file was used to attain patency of canal. All specimens were divided into four groups (each group having 20 specimens), i.e., Group I: Unprepared, Group II: NiTi hand K-files, Group III: Self-adjusting file, and Group IV: XP-Shaper single file. Complete irrigation of all the canals was performed after instrumentation. All roots were cut horizontally at three levels [apical third (3 mm), middle third (6 mm), and cervical third (9 mm)] from the apex with diamond disc. A stereomicroscope was used to view the sections under 20× magnification. Self-adjusting file showed least number of defects with a percentage of 75% followed by XP-Shaper and NiTi hand K-files with a values of 65 and 60%, respectively. Use of hand K-files resulted in greater number of incomplete cracks (30%) and use of XP-Shaper demonstrated greater number of craze lines (15%). A statistically significant difference was found between the experimental groups in the formation of dentinal defects of root at apical third (3 mm) (p < 0.031) and middle third (6 mm) (p < 0.001), whereas the sections at cervical third (9 mm) did not show any statistically significant difference (p > 0.312). The present study concluded that the self-adjusting file system gives promising better results in cleaning ability with minimal incidence of radicular dentin microcracks than XP-Shaper and NiTi hand K-files system. The root dentin may unavoidably get damaged during instrumentation resulting in the formation of dentinal cracks and tiny complicated fractures, thus leading to endodontic failures. Various factors cause dentinal cracks, but the flexibility of file due to heat treatment, kinematics of the file, and the basic architecture of the file are the most significant ones. Self-adjusting file system represented satisfactory results with minimal microcracks defects.