Microstructure alterations of rotary files after multiple simulated operative procedures

Abstract

Aim: To assess morphological alterations of ProTaper rotary NiTi files before and after continuous use by scanning electron microscopy (SEM). Study Design: 30 root canals were chosen with an angle between 15 and 30º. Before starting to prepare the canals the files were observed microscopically using a scanning electronic microscope. The ProTaper sequence recommended by the manufacturer was used, with NaOCl as irrigant. The instruments were sterilised after every three canals were shaped. The instruments were observed with the same microscope after shaping each canal, until 30 root canals were shaped. The criteria used for checking the instruments were: blunt cutting edges, disruption of cutting edge, microfractures, fatigue cracks, metal flash, dentine remains. Results: Many microscopic defects were found such as: cutting edge breaks (up to 70%); fatigue cracks, between 33 and 100%. No microfractures were found. An S1 and an SX file were fractured. Conclusion: ProTaper instruments are quite reliable if used following usual requirements.

Scanning electron microscopy of superficial defects in Twisted files and Reciproc nickel–titanium files after use in extracted molars

“…This method has been used in other studies (Tripi et al 2001, Troian et al 2006, Luzi et al 2010) and has been accepted for the accurate evaluation of deformation of instruments (Troian et al 2006). This method has been used in other studies (Tripi et al 2001, Troian et al 2006, Luzi et al 2010) and has been accepted for the accurate evaluation of deformation of instruments (Troian et al 2006).…”

Electrochemical corrosion assessment of RaCe and Mtwo rotary nickle-titanium instruments after clinical use and sterilization

“…In addition, the presence of surface irregularities on NiTi files (24) may compromise their cutting efficiency (25) and probably make them more susceptible to corrosion and fracture (26). The s-shaped cross-sectional design of Mtwo files results in very aggressive cutting edges and a positive rake angle, which is known to require less energy to cut dentin than blades with a neutral or negative rake angle (27), leading to less crack and surface irregularities on the file, which increases corrosion resistance.…”

Deflecting load of nickel titanium rotary instruments during cyclic fatigue

“…This is very troublesome, especially in clinical use where the mean lifetime (mean NCF) has shown no clinical relevance. In addition, using scanning electron microscopy 24,25) , unused NiTi instruments were found to contain at least one defect. After clinical single use, Arens et al 26) found that 14% of NiTi instruments showed various defects and 0.9% fractured.…”