title: Evaluation of Mechanical and Physical Properties of Clinically Used and Recycled Superelastic NiTi Wires.
abstract: BACKGROUND
  The initial leveling and aligning phase has been simplified with the introduction of superelastic nickel-titanium archwires. The relatively high cost of these wires has prompted some of the clinicians to reuse them after sterilization. The quantitative changes in the surface properties of superelastic 'NiTi' wires after clinical application and recycling by autoclave method have not been established in earlier studies.
  
  
  OBJECTIVE
  To quantify the changes in mechanical and physical properties of four different commercially available superelastic nitinol (NiTi) archwires after clinical usage and recycling.
  
  
  METHODS
  The superelastic 'NiTi archwires obtained from four different manufacturers: Group I-GAC (McMinnville, USA); Group II- 3M Company (California, USA); Group III- G&H Company(Franklin, USA) and Group IV- American Orthodontics (AO) (Sheboygan, USA) were selected for the study. Each of the four groups comprised of 20 samples of wire with 10 of them selected randomly as control and remaining 10 as test specimen in each group. The experimental archwires were placed on selected patients for a period of three months followed by Standard Autoclave sterilization at 121°C and 15 to 20 psi pressure for 20 minutes and were retrieved. The tensile strength was evaluated by Instron-Universal Testing Machine. The quantification of changes in surface roughness was investigated by grid method using Scanning Electron Microscope (SEM). The Control Wires (C) were evaluated at initial time "T1" where as the Experimental sample of wires (T) were subjected to testing at an initial time 'T1' and after clinical usage and sterilization at 'T2'.
  
  
  METHODS
  Paired t-test was used for intra-group comparison and one way ANOVA and Post Hoc Tukey tests were used for inter-group comparison.
  
  
  RESULTS
  There was significant decrease in tensile strength (p = 0.0015 to 0.001) and surface roughness (p< 0.001) between control and experimental arch wires within each group when properties at T1 and T2 were compared.
  
  
  CONCLUSIONS
  The study suggests discouraging the use of clinically used and sterilized superelastic NiTi archwires.
authors.affiliation: Postgraduate Student, Department of Orthodontics, Narayana Dental College , Nellore, Andhra Pradesh, India .
authors.forename: Venkata Naidu
authors.initials: VN
authors.lastname: Bavikati
authors.affiliation: Professor, Department of Orthoodontics, Narayana Dental College , Nellore, Andhra Pradesh, India .
authors.forename: Gowri Sankar
authors.initials: GS
authors.lastname: Singaraju
authors.affiliation: Professor and Head, Department of Orthodontics, Narayana Dental College , Nellore, Andhra Pradesh, India .
authors.forename: Prasad
authors.initials: P
authors.lastname: Mandava
authors.affiliation: Postgraduate Student, Department of Orthodontics, Narayana Dental College , Nellore, Andhra Pradesh, India .
authors.forename: Sai Sandeep
authors.initials: SS
authors.lastname: Killamsetty
authors.affiliation: Postgraduate Student, Department of Orthodontics, Narayana Dental College , Nellore, Andhra Pradesh, India .
authors.forename: Venkatesh
authors.initials: V
authors.lastname: Nettam
authors.affiliation: Senior Lecturer, Department of Orthodontics, Narayana Dental College , Nellore, Andhra Pradesh, India .
authors.forename: Praveen Kumar Reddy
authors.initials: PK
authors.lastname: Karnati
keywords: Nitinol; Orthodontics; Sterilization