title: Tight Placement of Erich Arch Bar While Avoiding Wire Fatigue Failure.
abstract: OBJECTIVE
  To determine the number of wire twists needed to acquire ideal Erich arch bar tightness before wire fatigue failure (fracture) in relation to different distances and angles at which different gauge wires are grasped to provide information to improve the efficiency of arch bar application.
  
  
  METHODS
  This study mimicked surgical placement of arch bars with 24- and 26-gauge wires. The number of twists to tightness and failure was evaluated when the wire distance between the arch bar and wire holder tip changed (5 vs 10 mm) and when the degree at which the wire was held relative to the tooth axis was changed (45° vs 90°). A wire shearing test also was used to investigate the fatigability of wires tightened under these same conditions. Wires twisted to tightness, past tightness, and after shearing test movements were visualized with electron microscopy.
  
  
  RESULTS
  For 24-gauge wire held at 5 mm, 2.6 to 2.8 twists were needed for wire tightness, with failure after 1.7 to 1.9 twists past tightness; for 24-gauge wire held at 10 mm, 4.4 to 4.9 twists produced tightness, with failure after 2.3 to 2.9 twists past tightness. For 26-gauge wire held at 5 mm, 3.3 to 3.5 twists provided tightness, with 1.6 to 1.8 twists past tightness causing failure; for 26-gauge wire held at 10 mm, 5.1 to 5.5 twists produced tightness, with 3.1 to 3.7 twists past tightness causing failure. At a 45° angle, the wire tightened with fewer twists and showed more resistance to failure with twists past tightness compared with 90° using 24- and 26-gauge wires. In contrast, 24-gauge wire held at a 5-mm distance showed the opposite result, with decreased resistance to failure at the 45° angle. However, the differences were not statistically meaningful. Scanning election microscopy showed no wire fatigue for either angle for 26-gauge wire held at a 5-mm distance and twisted to tightness. After overtightening and oscillation, the 90° angle trials showed fatigue, whereas the 45° angle trials did not.
  
  
  CONCLUSIONS
  Holding a 24-gauge wire at 45° to the tooth axis is recommended owing to fewer twists to tightness and more resistance to failure. A 5-mm grasping distance is recommended for experienced surgeons owing to fewer twists to tightness, whereas a 10-mm grasping distance is recommended for novice surgeons owing to a greater tolerance for over-twisting before failure.
authors.affiliation: Fourth-Year Dental Student, University of Connecticut School of Dental Medicine, Farmington, CT.
authors.forename: Daniel
authors.initials: D
authors.lastname: Kirk
authors.affiliation: AEGD Resident, Department of Dentistry Danbury Hospital, Danbury, CT.
authors.forename: Joseph
authors.initials: J
authors.lastname: Whitney
authors.affiliation: Associate Professor and Chair, Division of Oral and Maxillofacial Surgery, University of Connecticut School of Dental Medicine, Farmington, CT.
authors.forename: David
authors.initials: D
authors.lastname: Shafer
authors.affiliation: Assistant Professor, Division of Oral and Maxillofacial Surgery, University of Connecticut School of Dental Medicine, Farmington, CT. Electronic address: lsgsong@comcast.net.
authors.forename: Liansheng
authors.initials: L
authors.lastname: Song
mesh_terms: D001864:Bone Wires; D004867:Equipment Design; D004868:Equipment Failure; D006801:Humans; D019248:Jaw Fixation Techniques / Q000295:instrumentation*; D008334:Mandible / Q000033:anatomy & histology; D008422:Materials Testing; D008854:Microscopy, Electron; D008953:Models, Anatomic; D013314:Stress, Mechanical; D013499:Surface Properties