Effect of anodization on friction behavior of ß­titanium orthodontic archwires.

PURPOSE: To evaluate the effects of anodization on the friction behavior of beta-titanium (ß-Ti) orthodontic archwires in conventional or self-ligating brackets in vitro. METHODS: ß­Ti archwires (0.018â€¯× 0.025 inch) pre- and postanodization were tested in combination with 0.022-inch stainless steel conventional and self-ligating brackets. The surface composition and oxide thickness of the ß­Ti archwires pre- and postanodization were measured using Auger electron spectroscopy (AES) and transmission electron microscopy (TEM). Detailed surface topography and roughness were assessed using atomic force microscopy (AFM). Surface topographies of the ß­Ti archwires pre- and postanodization were examined using scanning electron microscopy (SEM). Friction was measured using a universal testing machine; the data were statistically analyzed. RESULTS: Postanodization, the identified titanium oxide layer on the surface of the ß­Ti archwires increased in thickness from 10 to 100 nm; at the same time, the values for surface roughness were significantly reduced by half (p < 0.001). The archwire surfaces post anodization were harder and had fewer scratches after the friction test. Anodization significantly reduced 23.77% of the static (p < 0.01) and 25.61% of the kinetic (p < 0.001) friction of the ß­Ti archwires in conventional brackets, while it significantly reduced 85.71% of the static and 84.38% of the kinetic friction (p < 0.01) in self-ligating brackets. CONCLUSION: Anodization reduced the ß­Ti archwire friction, which was particularly more effective in combination with self-ligating brackets. The friction reduction via anodization could be attributed to the increased thickness, surface hardness, and decreased surface roughness of the titanium oxide layer.