Scanning electron microscopic study of rotary nickel-titanium endodontic file (Rnef)

This study examined RNEF with scanning electron microscope (SEM), for surface flaws, internal voids and inclusions. Six commercial brands of 4% taper RNEF: PF (#25, 25mm, Dentsply Tulsa Dental Specialties, Tulsa, OK), GTX (#20, 25mm, Dentsply Tulsa Dental Specialties, Tulsa, OK), NRT (#25, 25mm, MANI Inc., Tochigi, Japan), FKG (#25, 25mm, FKG, Dentaire), K3 (#25, 25mm) and TF (Twisted File #25, 27mm) (Sybron Kerr, Orange, CA) were examined. Full length and 4mm segment of each RNEF brand was mounted in Al plate for surface morphology and conductive epoxy resin for cross-sectional imaging with SEM (JEOL JSM-820) respectively. EDX spectrum was collected from specimens with EDX spectrometer coupled to SEM. EDX software was used for quantitative analysis. This study demonstrated the existence of surface flaws as machining marks, notches, crevices, fissures and pits. Internal voids of micro- to sub-micrometer magnitude were observed. Ti-rich inclusions were found dispersed in the equiatomic to near-equiatomic NiTi substrate of RNEF. Surface flaws, internal voids and inclusions were common findings on RNEF studied. Their effects on the corrosion and fatigue resistance of RNEF deserve further investigation.© (2013) Trans Tech Publications, Switzerland.