title: Effects of nanostructured, diamondlike, carbon coating and nitrocarburizing on the frictional properties and biocompatibility of orthodontic stainless steel wires.
abstract: OBJECTIVE
  To evaluate and compare the effects of nanostructured, diamondlike, carbon (DLC) coating and nitrocarburizing on the frictional properties and biocompatibility of orthodontic stainless steel archwires.
  
  
  METHODS
  Plasma-enhanced chemical vapor deposition technology was applied to coat DLC films onto the surface of austenitic stainless steel wires, and salt-bath nitrocarburizing technology was employed to achieve surface hardening of other wires. Surface and cross-sectional characteristics, microhardness, modulus of elasticity, friction resistance, corrosion resistance, and cell toxicity of the modified and control wires were analyzed.
  
  
  RESULTS
  The surfaces of the DLC-coated and nitrocarburized wires were both smooth and even. Compared with the control, the DLC-coated wires were increased in surface hardness 1.46 times, decreased in elastic modulus, reduced in kinetic friction coefficient by 40.71%, and decreased in corrosion current density by two orders of magnitude. The nitrocarburized wire was increased in surface hardness 2.39 times, exhibited an unchanged elastic modulus, demonstrated a decrease in maximum static friction force of 22.2%, and rose in corrosion current density two orders of magnitude. Cytotoxicity tests revealed no significant toxicity associated with the modified wires.
  
  
  CONCLUSIONS
  DLC coating and nitrocarburizing significantly improved the surface hardness of the wires, reduced friction, and exhibited good biocompatibility. The nanostructured DLC coating provided excellent corrosion resistance and good elasticity, and while the nitrocarburizing technique substantially improved frictional properties, it reduced the corrosion resistance of the stainless steel wires to a lesser extent.
authors.affiliation: a  Masters Student, Jiangsu Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, China.
authors.forename: Hao
authors.initials: H
authors.lastname: Zhang
authors.affiliation: a  Masters Student, Jiangsu Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, China.
authors.forename: Shuyu
authors.initials: S
authors.lastname: Guo
authors.affiliation: a  Masters Student, Jiangsu Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, China.
authors.forename: Dongyue
authors.initials: D
authors.lastname: Wang
authors.affiliation: a  Masters Student, Jiangsu Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, China.
authors.forename: Tingting
authors.initials: T
authors.lastname: Zhou
authors.affiliation: b  Professor, Jiangsu Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Wang
authors.affiliation: c  Associate Professor, Jiangsu Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, China.
authors.forename: Junqing
authors.initials: J
authors.lastname: Ma
mesh_terms: D002244:Carbon; D003430:Cross-Sectional Studies; D003722:Dental Alloys; D017276:Friction; D008422:Materials Testing; D016910:Orthodontic Brackets; D009969:Orthodontic Wires; D013193:Stainless Steel; D013499:Surface Properties; D014025:Titanium
chemical_list: D003722:Dental Alloys; D013193:Stainless Steel; D002244:Carbon; D014025:Titanium
keywords: Biocompatibility; Frictional properties; Nanostructured, diamondlike, carbon coating; Nitrocarburizing; Orthodontic wire