Surface characteristics of retrieved coated and nickel-titanium orthodontic archwires.

OBJECTIVE The purpose of this study was to investigate the effects of oral fluids and archwire-bracket friction on the surface characteristics of NiTi alloy orthodontic archwires with/without aesthetic coating, in vivo for 2-3 months. MATERIALS AND METHODS Different cross-sections of NiTi Archwires (DENTSPLY GAC International) and Titanol Cosmetic Archwires (FORESTADENT® USA Inc.) were examined by electron microscopy with dual-beam and spectroscopy analysis, before and after a collecting protocol from patients with multi-technique. RESULTS Initially, the orthodontic archwires showed microscopic manufacturing and coating defects in the physiognomic layer. After intra-oral exposure, amorphous organic matter deposits were observed on the surface of the NiTi Archwires and the wire coating presented exfoliation on the oral areas of friction with brackets. X-ray microanalysis revealed changes in all atomic and mass percentages of chemical elements from the surface of all retrieved dental archwires, nickel and titanium ion depletion and the occurrence of additional elements due to interactions with saliva. CONCLUSIONS Intra-oral exposure of NiTi Archwires and the archwire-bracket friction of coated wire altered the morphology and changed the elemental composition of the surface due to the process of corrosion, adhesion of organic matters and ionic exchange with oral fluids.