title: A comparison of roughness parameters and friction coefficients of aesthetic archwires.
abstract: OBJECTIVE
  Compare surface roughness of 'aesthetic' nickel-titanium (NiTi) archwires with their dynamic frictional properties.
  
  
  METHODS
  Archwires investigated were: four fully coated tooth coloured [Forestadent: Biocosmetic (FB) and Titanol Cosmetic (FT); TOC Tooth Tone (TT); and Hawley Russell Coated Superelastic NiTi (HRC)]; two partially coated tooth coloured [DB Euroline Microcoated (DB) and TP Aesthetic NiTi (TP)]; two rhodium coated [TOC Sentalloy (TS) and Hawley Russell Rhodium Coated Superelastic NiTi (HRR)]; and two controls: stainless steel [Forestadent Steel (FS)] and NiTi archwire [Forestadent Titanol Superelastic (FN)]. Surface roughness [profilometry (Rugosurf)] was compared with frictional coefficients for archwire/bracket/ligature combinations (n = 10). Analysis of variance, Sidak's multiple comparison of means, and Spearman's correlation coefficient were used for analysis.
  
  
  RESULTS
  Roughness coefficients were from low to high: FB; FN; TT; FS; TS; HRR; FT; DB; TP; HRC. Friction coefficients were from low to high: TP; FS; FN; HRR; FT; DB; FB; HRC; TS; TT. Coated archwires generally exhibited higher friction than uncoated controls. TP had the lowest friction but this was not statistically significant (P < 0.05). Friction of tooth coloured coated archwires were significantly different for some wires. Spearman's correlation did not demonstrate consistency between surface roughness (R a) and dynamic friction.
  
  
  CONCLUSIONS
  Aesthetic archwires investigated had either low surface roughness or low frictional resistance but not both properties simultaneously. Causes for friction are likely to be multifactorial and do not appear to be solely determined by surface roughness (measured by profilometry). For selecting the most appropriate aligning archwire, both surface roughness and frictional resistance need to be considered.
authors.affiliation: *Department of Orthodontics, Guy's Hospital, Guy's and St. Thomas' NHS Foundation Trust, London.
authors.forename: Philippa
authors.initials: P
authors.lastname: Rudge
authors.affiliation: **School of Oral and Dental Sciences, University of Bristol, Bristol, UK.
authors.forename: Martyn
authors.initials: M
authors.lastname: Sherriff
authors.affiliation: *Department of Orthodontics, Guy's Hospital, Guy's and St. Thomas' NHS Foundation Trust, London, dirk.bister@kcl.ac.uk.
authors.forename: Dirk
authors.initials: D
authors.lastname: Bister
mesh_terms: D004955:Esthetics, Dental; D017276:Friction; D006801:Humans; D008422:Materials Testing / Q000379:methods; D009532:Nickel; D009969:Orthodontic Wires; D013193:Stainless Steel; D013499:Surface Properties; D014025:Titanium
chemical_list: C040654:titanium nickelide; D013193:Stainless Steel; D009532:Nickel; D014025:Titanium