In vitro friction of stainless steel arch wire–bracket combinations in air and different aqueous solutions.

Al-Khatib S, Berradja A, Celis J-P, Willems G. To investigate the in vitro coefficient of friction of stainless steel arch wire–bracket combinations under fretting contact test conditions performed in air and in different aqueous solutions, like Ringer solution, Ringer with addition of a buffer, Ringer with addition of glucose, and Coca Cola^®. The fretting test set-up used allowed to control on-line the contact configuration and the positioning of the contacting parts. A specific positioning method was used to achieve a parallel alignment of arch wire and bracket slot. The effect of arch wire size, roughness, and test environment were investigated. It was found that the aqueous solutions act as a lubricant compared to air. Friction was affected by the arch wire width while the roughness was found to have a limited effect. Stainless steel 0.018′′ × 0.025′′ arch wires exhibited higher frictional forces than stainless steel 0.017′′ × 0.025′′ arch wires on sliding against stainless steel 0.018′′ × 0.025′′ brackets in the selected test environments when tested under identical fretting test conditions. The wear damage on the arch wire after these in-vitro fretting tests was investigated. It revealed that these in-vitro tests are governed by a competition between oxidational wear and abrasive wear taking place at contact areas between brackets and arch wires. For all aqueous solutions a lower coefficient of friction was found compared to tests performed in ambient air. [ABSTRACT FROM AUTHOR]