title: Torsional properties and microstructures of miniscrew implants.
abstract: BACKGROUND
  Titanium miniscrew implants are popular in orthodontics, but there is little information about their torsional performance.
  
  
  METHODS
  Four brands of miniscrew implants (A-D) with 1.6-mm diameters were compared, with miniscrew A implants also having diameters of 1.2 to 2.0 mm. Nominal compositions of the implants were determined by x-ray fluorescence (n = 8). The miniscrews were loaded to failure in torsion, and the mean moment and twist angle were determined for each group (n = 8). Data were compared by ANOVA and the Tukey multiple range tests. Micro x-ray diffraction (n = 3) was used to identify phases in the implants, and the phases were also examined in etched cross-sections with a scanning electron microscope.
  
  
  RESULTS
  Miniscrew A and C implants were pure titanium, whereas miniscrew B and D implants contained small amounts of vanadium, aluminum, iron, and manganese. Only alpha-titanium peaks were detected for all implants by micro x-ray diffraction, but beta titanium was observed in the microstructures of miniscrew B and D implants, which had significantly higher torsional moments at failure.
  
  
  CONCLUSIONS
  Addition of small amounts of other elements to titanium yielded significantly improved torsional performance for miniscrew implants. Research to develop optimum compositions for mechanical properties and biocompatibility is needed.
authors.affiliation: Division of Orthodontics and Dentofacial Orthopedics, Department of Oral Growth and Development, School of Dentistry, Health Sciences University of Hokkaido, Ishikari-tobetsu, Hokkaido, Japan. iijima@hoku-iryo-u.ac.jp
authors.forename: Masahiro
authors.initials: M
authors.lastname: Iijima
authors.forename: Takeshi
authors.initials: T
authors.lastname: Muguruma
authors.forename: William A
authors.initials: WA
authors.lastname: Brantley
authors.forename: Miki
authors.initials: M
authors.lastname: Okayama
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Yuasa
authors.forename: Itaru
authors.initials: I
authors.lastname: Mizoguchi
mesh_terms: D000704:Analysis of Variance; D001863:Bone Screws; D003722:Dental Alloys / Q000737:chemistry*; D015921:Dental Implants; D003799:Dental Stress Analysis; D008855:Microscopy, Electron, Scanning; D008904:Miniaturization; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation*; D014025:Titanium / Q000737:chemistry; D019415:Torque; D014961:X-Ray Diffraction
chemical_list: D003722:Dental Alloys; D015921:Dental Implants; C023988:beta titanium; D014025:Titanium