Surface roughness of orthodontic wires via atomic force microscopy, laser specular reflectance, and profilometry

The surface roughness of orthodontic archwires is an essential factor that determines the effectiveness of arch-guided tooth movement. Using the non-destructive techniques of atomic force microscopy (AFM) and of laser specular reflectance, the surface roughness of 11 nickel-titanium orthodontic wires, a stainless steel and a beta-titanium wire was measured. The results were compared with those obtained using surface profilometry. The smoothest wire, stainless steel, had an optical roughness of 0.10 micron, compared with 0.09 micron from AFM and 0.06 from profilometry. The surface roughness for the beta-titanium wire measured by all three methods was approximately 0.21 micron, while that of the NiTi wires ranged from 0.10 to 1.30 microns. As the surface roughness not only affects the effectiveness of sliding mechanics, but also the corrosion behaviour and the aesthetics of orthodontic components, the manufacturers of orthodontic wires should make an effort to improve the surface quality of their products.