Resistance to fracture due to cyclic fatigue of stainless steel manual files and its association to surface roughness

Abstract

The aim of this study was to evaluate the possible association between the roughness of 5 brands of stainless steel endodontic files and their resistance to fracture due to cyclic fatigue. The study included five different brands of stainless steel endodontic files: SybroEndo Triple-Flex Files (Kerr, Glendora, USA), Ready Steel K-Flexofile (Dentsply Sirona, Ballaigues, Switzerland), Mani Flexile Files (Mani, Tochigi- Ken, Japan), FKG K-Files (FKG, La Chaux-de-Fonds, Switzerland) and Zipperer Flexicut Files (VDW, Munich, Germany). Twelve files per brand (total 60 files) were evaluated. File surface roughness over an area (Sa) was quantified using a focus variation microscope. Then the files were subject to a cyclical fatigue test to determine the number cycles to fracture due to fatigue and length of fractured fragment. Finally, fractographic analysis was performed using a scanning electron microscope. The electropolished Ready Steel K-Flexofile® files had the highest roughness according to Sa parameters, though they also had the highest resistance to fracture due to cyclic fatigue and the longest fractured fragment. Moderate positive correlation was found between fractured fragment length and roughness. The fractured surface showed characteristics of ductile fracture with cracks and plastic deformation. The electropolished stainless steel Ready Steel K-Flexofile® files were the most resistant to fracture due to cyclic fatigue even though they had highest surface roughness.

Assessment of Extruded Root Canal Filling Materials in Single-Rooted Teeth Using Cone Beam Computed Tomography

“…Conversely, a randomized clinical experiment reported the occurrence of extruded canal filling material in anterior teeth to be greater than in premolars, similar to our findings [48]. In the same study, it was shown that anterior teeth and premolars cause more overfilling than molars, which might be because anteriors and premolars have flatter and larger root canal morphologies compared with molars.…”

“…In the same study, it was shown that anterior teeth and premolars cause more overfilling than molars, which might be because anteriors and premolars have flatter and larger root canal morphologies compared with molars. However, it has been determined that tooth type loses its importance as a determining factor in canal filling material extrusion [48].…”