title: Color stability of laboratory glass-fiber-reinforced plastics for esthetic orthodontic wires.
abstract: OBJECTIVE
  In our previous study, glass-fiber-reinforced plastics (GFRPs) made from polycarbonate and glass fibers were prepared for esthetic orthodontic wires using pultrusion. These laboratory GFRP wires are more transparent than the commercially available nickel-titanium wire; however, an investigation of the color stability of GFRP during orthodontic treatment is needed. Accordingly, in the present study, the color stability of GFRP was assessed using colorimetry.
  
  
  METHODS
  Preparation of GFRP esthetic round wires (diameter: 0.45 mm [0.018 inch]) using pultrusion was described previously. Here, to investigate how the diameter of fiber reinforcement affects color stability, GFRPs were prepared by incorporating either 13-µm (GFRP-13) or 7-µm glass (GFRP-7) fibers. The color changes of GFRPs after 24 h, and following 1, 2, and 4 weeks of coffee immersion at 37℃, were measured by colorimetry. We evaluated the color stability of GFRPs by two evaluating units: the color difference (ΔE(*)) and National Bureau of Standards (NBS).
  
  
  RESULTS
  After immersion, both GFRPs showed almost no visible color change. According to the colorimetry measurements, the ΔE(*) values of GFRP-13 and GFRP-7 were 0.73-1.16, and 0.62-1.10, respectively. In accordance with NBS units, both GFRPs showed "slight" color changes. As a result, there were no significant differences in the ΔE(*) values or NBS units for GFRP-13 or GFRP-7. Moreover, for both GFRPs, no significant differences were observed in any of the immersion periods.
  
  
  CONCLUSIONS
  Our findings suggest that the GFRPs will maintain high color stability during orthodontic treatment, and are an attractive prospect as esthetic orthodontic wires.
authors.affiliation: Department of Orthodontics, Nihon University School of Dentistry at Matsudo, Chiba, Japan.
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Inami
authors.affiliation: Department of Dental Biomaterials, Nihon University School of Dentistry at Matsudo, Chiba, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Tanimoto
authors.affiliation: Department of Orthodontics, Nihon University School of Dentistry at Matsudo, Chiba, Japan.
authors.forename: Naomi
authors.initials: N
authors.lastname: Minami
authors.affiliation: Department of Orthodontics, Nihon University School of Dentistry at Matsudo, Chiba, Japan.
authors.forename: Masaru
authors.initials: M
authors.lastname: Yamaguchi
authors.affiliation: Department of Orthodontics, Nihon University School of Dentistry at Matsudo, Chiba, Japan.
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Kasai
keywords: Color stability; Esthetics; Fiber-reinforced composite; Wire