Ion release from NiTi orthodontic wires in artificial saliva with various acidities.
NiTi orthodontic wire products from different manufacturers would have different corrosion resistance. We assayed the corrosion resistance, in terms of ion release, of different NiTi orthodontic wires in artificial saliva with various acidities. Four types of as-received commercial NiTi orthodontic wires were immersed in artificial saliva (37 degrees C) at pH 2.5-6.25 for different periods (1-28d). The amount of Ni and Ti ions released from NiTi wires was determined using an atomic adsorption spectrophotometer. Surface morphology and roughness of wires were related to the corrosion resistance. Results showed that the manufacturer, pH value, and immersion period, respectively, had a significantly statistical influence on the release amount of Ni and Ti ions. The amount of Ni ions released in all test solutions was well below the critical value necessary to induce allergy and below daily dietary intake level. The amount of Ti ions released in pH>/=3.75 solution was mostly not detectable, representing that the TiO(2) film on NiTi wires exhibited a good protection against corrosion. Pre-existed surface defects on NiTi wires might be the preferred locations for corrosion. The NiTi wire with the highest release amount of metal ions had the maximal increase in surface roughness after immersion test, while a rougher surface did not correspond to a higher metal ion release.
Huang
Her-Hsiung
HH
Institute of Dental Materials, Chung Shan Medical University, Taichung 402, Taiwan.
Chiu
Yu-Hui
YH
Lee
Tzu-Hsin
TH
Wu
Shih-Ching
SC
Yang
Hui-Wen
HW
Su
Kuo-Hsiung
KH
Hsu
Chii-Chih
CC
D003343:Corrosion; D003722:Dental Alloys / Q000737:chemistry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007477:Ions / Q000378:metabolism*; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D009532:Nickel / Q000737:chemistry*; D009969:Orthodontic Wires; D012464:Saliva, Artificial / Q000737:chemistry*; D013499:Surface Properties; D013997:Time Factors; D014025:Titanium / Q000737:chemistry*
D003722:Dental Alloys; D007477:Ions; D012464:Saliva, Artificial; D009532:Nickel; D014025:Titanium