title: Two-year survival analysis of twisted wire fixed retainer versus spiral wire and fiber-reinforced composite retainers: a preliminary explorative single-blind randomized clinical trial.
abstract: OBJECTIVE
  Traditional retainers (both metal and fiber-reinforced composite [FRC]) have limitations, and a retainer made from more flexible ligature wires might be advantageous. We aimed to compare an experimental design with two traditional retainers.
  
  
  METHODS
  In this prospective preliminary clinical trial, 150 post-treatment patients were enrolled and randomly divided into three groups of 50 patients each to receive mandibular canine-to-canine retainers made of FRC, flexible spiral wire (FSW), and twisted wire (TW). The patients were monitored monthly. The time at which the first signs of breakage/debonding were detected was recorded. The success rates of the retainers were compared using chi-squared, Kaplan-Meier, and Cox proportional-hazard regression analyses (α = 0.05).
  
  
  RESULTS
  In total, 42 patients in the FRC group, 41 in the FSW group, and 45 in the TW group completed the study. The 2-year failure rates were 35.7% in the FRC group, 26.8% in the FSW group, and 17.8% in the TW group. These rates differed insignificantly (chi-squared p = 0.167). According to the Kaplan-Meier analysis, failure occurred at 19.95 months in the FRC group, 21.37 months in the FSW group, and 22.36 months in the TW group. The differences between the survival rates in the three groups were not significant (Cox regression p = 0.146).
  
  
  CONCLUSIONS
  Although the failure rate of the experimental retainer was two times lower than that of the FRC retainer, the difference was not statistically significant. The experimental TW retainer was successful, and larger studies are warranted to verify these results.
authors.affiliation: Department of Orthodontics, Dental Faculty, Mazandaran University of Medical Sciences, Sari, Iran.
authors.forename: Farhad
authors.initials: F
authors.lastname: Sobouti
authors.affiliation: The Research Council, Iranian Tissue Bank and Research Center, Tehran University of Medical Sciences, Tehran, Iran.; Department of Dental Anatomy and Morphology, Dental Branch, Islamic Azad University, Tehran, Iran.
authors.forename: Vahid
authors.initials: V
authors.lastname: Rakhshan
authors.affiliation: Department of Restorative Dentistry, Dental Faculty, Mazandaran University of Medical Sciences, Sari, Iran.
authors.forename: Mahdi Gholamrezaei
authors.initials: MG
authors.lastname: Saravi
authors.affiliation: Department of Restorative Dentistry, Dental Faculty, Mazandaran University of Medical Sciences, Sari, Iran.
authors.forename: Ali
authors.initials: A
authors.lastname: Zamanian
authors.affiliation: Craniomaxillofacial Surgery Research Center, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Mahsa
authors.initials: M
authors.lastname: Shariati
keywords: Fiber-reinforced composite; Fixed orthodontic retainers; Ligature wire; Multi-stranded wire