title: Joining characteristics of orthodontic wires with laser welding.
abstract: Laser welding 0.016 x 0.022 in. beta-Ti, Ni-Ti, and Co-Cr-Ni orthodontic wires was investigated by measuring joint tensile strength, measuring laser penetration depth, determining metallurgical phases using micro X-ray diffraction (micro-XRD), and examining microstructures with an scanning electron microscope (SEM). Welding was performed from 150 to 230 V. Mean tensile strength for Ni-Ti groups was significantly lower (p < 0.05) than for most other groups of laser-welded specimens. Although mean tensile strength for beta-Ti and Co-Cr-Ni was significantly lower than for control specimens joined by silver soldering, it was sufficient for clinical use. The beta-Ti orthodontic wire showed deeper penetration depth from laser welding than the Ni-Ti and Co-Cr-Ni orthodontic wires. Micro-XRD patterns of laser-welded beta-Ti and Ni-Ti obtained 2 mm from the boundary were similar to as-received specimens, indicating that original microstructures were maintained. When output voltages of 190 V and higher were used, most peaks from joint areas disappeared or were much weaker, perhaps because of a directional solidification effect, evidenced by SEM observation of fine striations in welded beta-Ti. Laser welding beta-Ti and Co-Cr-Ni wires may be acceptable clinically, since joints had sufficient strength and metallurgical phases in the original wires were not greatly altered.
authors.affiliation: Department of Orthodontics, 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: William A
authors.initials: WA
authors.lastname: Brantley
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Yuasa
authors.forename: Takeshi
authors.initials: T
authors.lastname: Muguruma
authors.forename: Isao
authors.initials: I
authors.lastname: Kawashima
authors.forename: Itaru
authors.initials: I
authors.lastname: Mizoguchi
mesh_terms: D000497:Alloys / Q000737:chemistry; D001672:Biocompatible Materials; D012994:Dental Soldering; D007834:Lasers; D008855:Microscopy, Electron, Scanning; D009969:Orthodontic Wires; D014025:Titanium; D014961:X-Ray Diffraction
chemical_list: D000497:Alloys; D001672:Biocompatible Materials; C013616:nitinol; D014025:Titanium