Materials Science, Vol. 47, No. 6, May, 2012 (Ukrainian Original Vol. 47, No. 6, November–December, 2011) INFLUENCE OF ARTIFICIAL SALIVA ON NiTi ORTHODONTIC WIRES: A STUDY ON THE SURFACE CHARACTERIZATION İ. Ünal, 1 S. Zor, 2 and H. Atapek 1 Nickel- and titanium-based alloys are promising materials for dental orthodontic wires due to their supe- rior mechanical properties and corrosion resistance. The studies of the corrosion resistance of these ma- terials according to their surface characterization in artificial salivas are limited. We study the changes of the surfaces of NiTi-alloy-based orthodontic wires in artificial salivas with (or without) additions of F - and PO 4 3- after a period of time by the SEM and EDS methods. Keywords: orthodontic materials, corrosion, scanning-electron microscopy, energy-dispersive spectros- copy. There are several metals and metal alloys used in dentistry and orthodontic applications. The traces of cor- rosion on the surfaces of metals used in any application can be formed after a period of time depending on the environment of mouth [1]. The corrosion process occurs as a result either of the loss of metal ions directly into the solution or of the progressive dissolution of the surface films, as a rule oxide or sulfide. The stainless-steel, cobalt-chromium, and titanium alloys used in orthodontic appliances rely on the forma- tion of passive surface oxide films to resist corrosion. These protective layers are not reliable. They are suscep- tible to both mechanical and chemical degradation. Even without destruction, oxide films often slowly dissolve only to reform as the metal surface is exposed to oxygen from the air or the from surrounding medium [1]. The acidic drinks and foods containing sodium chloride are corrosive materials. The aggressive media, such as chloride ions and acidic conditions, accelerate the process of corrosion. Moreover, the fluoride ions in toothpaste and in the products used as mouthwash play the role of an important factor accelerating corrosion. Several studies reported that fluoride-based acidic solutions increase the corrosion of titanium [1–5]. Therefore, clinically, the role of fluoride in the corrosion of orthodontic appliances might be not as important as suggested by the in vitro studies. Schiff, et al. compared the corrosion resistances of three types of orthodontic brackets (stainless steel, co- balt-chromium, and titanium) placed in a reference solution of artificial saliva and in three commercially avail- able fluoride mouthwashes. According to the electrochemical results, all three mouthwashes exhibited a weak effect on the cobalt-chromium brackets but the presence of stannous fluoride in one mouthwash caused consid- erable corrosion of the stainless-steel and titanium brackets [2]. Some nickel and titanium alloys were developed as orthodontic materials. The studies on the corrosion re- sistance of these materials in artificial salivas are very popular. In the present work, the changes of the surfaces of NiTi-alloy-based orthodontic wires in artificial salivas with (or without) additions of F - and PO 4 3- after a period of time are investigated by the SEM (Scanning Electron Microscopy) and EDS (Energy-Dispersive Spec- troscopy) methods. 1 Kocaeli University, Metallurgical & Materials Engineering, Umuttepe Campus, Turkey. 2 Kocaeli University, Department of Chemistry, Umuttepe Campus, Turkey; e-mail: szor2001@yahoo.com (corresponding author). Published in Fizyko-Khimichna Mekhanika Materialiv, Vol. 47, No. 6, pp. 101–106, November–December, 2011. Original article submit- ted December 9, 2009. 830 1068-820X/12/4706–0830 © 2012 Springer Science+Business Media, Inc.