Evaluation of surface characteristics of rotary nickel-titanium instruments produced by different manufacturing methods

Background: Instrument fracture is a serious concern in endodontic practice. Objective: The aim of this study was to investigate the surface quality of new and used rotary nickel-titanium (NiTi) instruments manufactured by the traditional grinding process and twisting methods. Materials and Methods: Total 16 instruments of two rotary NiTi systems were used in this study. Eight Twisted Files (TF) (SybronEndo, Orange, CA, USA) and 8 Mtwo (VDW, Munich, Germany) instruments were evaluated. New and used of 4 experimental groups were evaluated using an atomic force microscopy (AFM). New and used instruments were analyzed on 3 points along a 3 mm. section at the tip of the instrument. Quantitative measurements according to the topographical deviations were recorded. The data were statistically analyzed with paired samples t-test and independent samples t-test. Results: Mean root mean square (RMS) values for new and used TF 25.06 files were 10.70 +/- 2.80 nm and 21.58 +/- 6.42 nm, respectively, and the difference between them was statistically significant (P < 0.05). Mean RMS values for new and used Mtwo 25.06 files were 24.16 +/- 9.30 nm and 39.15 +/- 16.20 nm respectively, the difference between them also was statistically significant (P < 0.05). Conclusion: According to the AFM analysis, instruments produced by twisting method (TF 25.06) had better surface quality than the instruments produced by traditional grinding process (Mtwo 25.06 files).