Effects of fluoride-contained oral rinses on the corrosion resistance of titanium alloy (Ti-6Al-4V)

Abstract

A fluoride-contained adhesive, paste, and oral rinse are commonly used to prevent dental caries and tooth demineralization in orthodontic treatment. According to many findings, the presence of fluoride had been reported to cause corrosion of the titanium which can lead to fracture of the implant due to stress corrosion. When the metal corrosion occurred, it can not only cause the reduction of mechanical strength but also cause the inflammation and toxicity to the surrounding tissue by release of metal ions which can stimulate carcinogenic reactions. The purpose of this study is to examine the effects of commercially available fluoride-contained oral rinses on the corrosion behaviors of titanium alloys which are main component of orthodontic miniscrew implant. Four oral rinses [Listerine® (IDS Manufacturing Ltd. Thailand) Natural Green Tea (Solution A: pH 4.46/ 260 ppm F), Listerine® Teeth & Gum Defence (Solution B: pH 4.41/ 178 ppm F), Listerine® Tartar Control (Solution D: pH 4.17/ 3.92 ppm F) and Garglin® Regular Solution (Dong-A Pharm. Korea) (Solution C:pH 6.30/ 117 ppm F)] were tested on titanium alloys (Ti-6Al-4V) circular plates TC4® (Sheng Xinyuan Titanium Industry Co., LTD. Baoji City. China) and saline Klenzo® (JW Pharmaceutical. Korea; pH 6.24/ 3.56 ppm F) was used as control group. Electrochemical corrosion tests such as Open circuit potential measurements and Potentiodynamic polarization measurements were conducted for these materials, using four oral rinses and saline as the electrolytes. After the electrochemical measurements, all the samples were evaluated by examining the specimens using a scanning electron microscope.

1. In the tested oral rinses except solution D, corrosion potential of titanium alloy samples exposured in the solution containing more fluoride showed more obvious downtrend.

2. In the tested oral rinses except solution D, the more fluoride a solution contained, the significantly lower corrosion resistance the titanium alloy sample showed (P < 0.05).

3. Observed the surface morphology of titanium alloy samples by SEM, all the samples showed some defects, crevices or pittings in the 4 oral rinses compared with the sample before being tested, especially the samples in the solution A showed the most changes.

As a result of this, it was confirmed that commercially available fluoride treatment oral rinses could reduce the corrosion resistance of titanium alloy after using them more than 6 months (40 seconds use per day).

Although fluoride is useful to prevent caries, if patients use high concentration of fluoride-contained oral rinses during orthodontic treatment, the corrosion resistance of titanium alloy devices such as miniscrew implant could be affected.