Endodontology
Structural effects of sodium hypochlorite solution on RaCe rotary nickel-titanium instruments: an atomic force microscopy study

https://doi.org/10.1016/j.tripleo.2007.11.006Get rights and content

Objective

The aim of this study was to investigate the effect of sodium hypochlorite immersion on the surface characteristics of RaCe rotary nickel-titanium instruments using atomic force microscopy (AFM).

Study design

Four new RaCe instruments were used in this study (two 30.06 and two 30.02). One 30.06 and one 30.02 instrument were immersed in sodium hypochlorite solution for 5 min. Surface topography of the instruments was evaluated using the AFM. The instruments were analyzed on 11 points along a 3-mm section. Root mean square (RMS) values were used to compare the topographic deviations. The data were analyzed using Student t test.

Results

Mean RMS values for NaOCl measurements were higher than the measurements on new files, and the difference was statistically significant (P < .01).

Conclusion

The AFM results show that NaOCl causes deterioration on the surface of RaCe instruments and should be used with care during clinical use because of the risk of unexpected failure.

Section snippets

Materials and Methods

Four new RaCe rotary NiTi files were used in the present study (two 30.06 and two 30.02). One 30.06 and one 30.02 file were immersed in 5.25% NaOCl solution for 5 min. The other two files were used as controls.

All RaCe files were attached to a metal holder using a rapid-setting cyanoacrylate glue. Each sample was placed on the AFM and analyzed on 11 points along a 3-mm section at the tip of the file. The AFM images were recorded using the needle mode operation on an Omicron VT STM AFM (Omicron

Results

Three-dimensional AFM images of the rotary NiTi files are shown in Fig. 2. Topographic irregularities at nanometric scale were observed for all instruments. Mean RMS values for control and NaOCl-treated 30.06 files were 2.06 ± 0.49 nm and 6.99 ± 2.18 nm, respectively, and the difference between them was statistically significant (P < .01). Mean RMS values for control and NaOC-treated 30.02 files were 3.68 ± 0.98 nm and 6.72 ± 1.72 nm, respectively, and the difference between them also was

Discussion

In the present study, the topographic changes occurred on RaCe files immersed in NaOCl solution was evaluated using AFM, and significant deterioration on the surface was detected. It has been reported that topographic irregularities may have a considerable impact on resistance to fracture of endodontic instruments.4, 6, 12

Sodium hyocholorite is used as an endodontic irrigant as it is an effective antimicrobial and has tissue-dissolving capabilities.13 Corrosion and deterioration of NiTi

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Supported by Turkish State Planning Organization (project no. 2001K20590) and Gazi University Research Foundations (BAP 03/2007-13).

These authors contributed equally to this work.

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