Progressive structural deterioration of an endodontic instrument – A preliminary micro-computed tomography study

Abstract The aim of this study was to investigate the methodological potential of a new application of micro-computed tomography in providing an external and internal assessment of the structural integrity of an endodontic test file, and its progressive structural deterioration after repeated use in simulated root canals (resin blocks), until fracture. The progressive deterioration of the instrument was observed, and the external and internal defects were described. Radiolucent images suggestive of micro-cavities were observed in the instrument's core prior to its first use, and the formation and subsequent propagation of cracks in an apparently non-linear manner were observed after consecutive uses, until the final collapse of the whole structure. This novel assessment method allowed the visualization the external surface and the core of the same instrument at different time points in the instrumentation process, thus enabling researchers to identify where the cracks started and their progression during the course of instrument use.