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).
Key words: Atomic force microscopy, endodontics, fracture, nickel‑titanium