title: Nickel titanium springs versus stainless steel springs: A randomized clinical trial of two methods of space closure.
abstract: OBJECTIVE
  To compare the clinical performance of nickel titanium (NiTi) versus stainless steel (SS) springs during orthodontic space closure.
  
  
  METHODS
  Two-centre parallel group randomized clinical trial.
  
  
  METHODS
  Orthodontic Department University of Manchester Dental Hospital and Orthodontic Department Countess of Chester Hospital, United Kingdom.
  
  
  METHODS
  Forty orthodontic patients requiring fixed appliance treatment were enrolled, each being randomly allocated into either NiTi (n = 19) or SS groups (n = 21). Study models were constructed at the start of the space closure phase (T0) and following the completion of space closure (T1). The rate of space closure achieved for each patient was calculated by taking an average measurement from the tip of the canine to the mesiobuccal groove on the first permanent molar of each quadrant.
  
  
  RESULTS
  The study was terminated early due to time constraints. Only 30 patients completed, 15 in each study group. There was no statistically significant difference between the amounts of space closed (mean difference 0.17 mm (95%CI -0.99 to 1.34; P = 0.76)). The mean rate of space closure for NiTi coil springs was 0.58 mm/4 weeks (SD 0.24) and 0.85 mm/4 weeks (SD 0.36) for the stainless steel springs. There was a statistically significant difference between the two groups (P = 0.024), in favour of the stainless steel springs, when the mean values per patient were compared.
  
  
  CONCLUSIONS
  Our study shows that stainless steel springs are clinically effective; these springs produce as much space closure as their more expensive rivals, the NiTi springs.
authors.affiliation: a Orthodontic Department , University of Manchester Dental Hospital , Higher Cambridge Street, M15 6JH , Manchester , UK.|b Faculty of Dentistry , Universiti Teknologi MARA , Malaysia.
authors.forename: Noraina Hafizan
authors.initials: NH
authors.lastname: Norman
authors.affiliation: c University of Manchester , Higher Cambridge Street, M15 6JH , Manchester , UK.
authors.forename: Helen
authors.initials: H
authors.lastname: Worthington
authors.affiliation: d Orthodontic Department , Countess of Chester Hospital, Chester , UK.
authors.forename: Stephen Mark
authors.initials: SM
authors.lastname: Chadwick
mesh_terms: D000293:Adolescent; D000328:Adult; D000497:Alloys; D002648:Child; D003722:Dental Alloys; D005260:Female; D006801:Humans; D008297:Male; D009532:Nickel; D016382:Orthodontic Appliance Design; D019516:Orthodontic Space Closure; D009969:Orthodontic Wires; D013193:Stainless Steel; D014025:Titanium; D006113:United Kingdom; D055815:Young Adult
chemical_list: D000497:Alloys; D003722:Dental Alloys; D013193:Stainless Steel; C013616:nitinol; D009532:Nickel; D014025:Titanium
keywords: Nickel titanium spring; orthodontic space closure; rate; stainless steel spring