Original article
Comparison of friction force between corroded and noncorroded titanium nitride plating of metal brackets

https://doi.org/10.1016/j.ajodo.2009.06.034Get rights and content

Introduction

Titanium nitride (TiN) plating is a method to prevent metal corrosion and can increase the surface smoothness. The purpose of this study was to evaluate the friction forces between the orthodontic bracket, with or without TiN plating, and stainless steel wire after it was corroded in fluoride-containing solution.

Methods

In total, 540 metal brackets were divided into a control group and a TiN-coated experimental group. The electrochemical corrosion was performed in artificial saliva with 1.23% acidulated phosphate fluoride (APF) as the electrolytes. Static and kinetic friction were measured by an EZ-test machine (Shimadazu, Tokyo, Japan) with a crosshead speed of 10 mm per minute over a 5-mm stretch of stainless steel archwire. The data were analyzed by using unpaired t test and analysis of variance (ANOVA).

Results

Both the control and TiN-coated groups’ corrosion potential was higher with 1.23% APF solution than with artificial solution (P <0.05). In brackets without corrosion, both the static and kinetic friction force between the control and TiN-coated brackets groups showed a statistically significant difference (P <0.05). In brackets with corrosion, the control group showed no statistical difference on kinetic or static friction. The TiN-coated brackets showed a statistical difference (P <0.05) on kinetic and static friction in different solutions.

Conclusion

TiN-coated metal brackets, with corrosion or without corrosion, cannot reduce the frictional force.

Section snippets

Sample preparation

In total, 540 bracket samples were used in the present study. Each test condition contained 30 brackets (Fig 1). The metal brackets were selected from Tomy OPAK system bracket with a 0.022-in × 0.028-in slot (Tomy Co., L, Tokyo, Japan). The 0.019-in × 0.025-in stainless steel wire (3M Unitek, Monrovia, Calif) was used for the friction test. The ligation between the bracket and the wire was a clear AlastiK module (Quik-Stick Clear, A-1 AlastiK, 3M Unitek [Monrovia, Calif). The bracket and

Corrosion potential measurement

The control group and TiN group corrosion potential showed a statistical difference in artificial saliva (–0.05 ± 0.01 vs –0.03 ± 0.01, t = 4.47, P <0.05) and a nonstatistical difference in 1.23% APF solution (–0.25 ± 0.05 vs –0.26 ± 0.08, t = –0.355, P >0.05). Both the control and TiN-coated groups’ corrosion potential was higher with 1.23% APF solution than with artificial solution (P <0.05) (Fig 3).

Bracket without corrosion

The friction force was measured in artificial saliva by a universal testing machine. The

Discussion

It is reported that only human saliva can be used to quantify the magnitude or to rank the efficiency or reproducibility of orthodontic sliding.26 To assess friction and its coefficients in the wet state, human saliva is suitable. The present study was tested in a wet solution that contained human artificial saliva.

As reported, the TiN film demonstrates favorable characteristics with regard to corrosion resistance, wear resistance, and increased hardness.4, 5 The present study showed that

Conclusions

Because the oral environment is complex, the metal can be corroded. The TiN ion plating method can improve the metal defect. However, in the present study, applying TiN plating on the metal bracket does not produce an outcome that meets the study purpose. The corrosion potential does not increase and friction force apparently does not reduce. Further study on improving the metal surface smoothness and reducing surface friction is needed.

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    The authors report no commercial, proprietary, or financial interest in the products or companies described in this article.

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