Corrosion of orthodontic temporary anchorage devices

Corrosion of orthodontic miniscrews or temporary anchorage devices (TADs) has been proposed as a contributor to inflammation, which in turn is a factor in the clinical success of miniscrews. The purpose of this study was to measure the electrochemical properties of orthodontic miniscrews in artificial saliva with and without fluoride. The corrosion properties of three miniscrew products (VectorTAS, Ormco Corp.; Unitek TAD, 3M Unitek; and Through-Hole Screw, American Orthodontics) were tested in an artificial saliva (Fusayama-Meyer) with (1500 ppm) or without fluoride (n = 10/product/solution). Open circuit potential (OCP), polarization resistance (R p), and corrosion current (I corr) were measured and statistically analysed with the Friedman/Tukey least significant difference tests. No significant differences (P > 0.05) between miniscrews with regard to OCP, R p, and I corr were found except that the American Orthodontics miniscrews had a significantly (P < 0.05) more noble OCP compared to the others. Incorporation of 1500 ppm fluoride in the artificial saliva significantly (P < 0.001) lowered the OCP, reduced the polarization resistance, and increased the corrosion current of each miniscrew product. Few differences existed in the electrochemical properties of miniscrews from the three different manufacturers; however, exposure to fluoride was detrimental to the corrosion properties of all miniscrews.