title: The effects of first- and second-order gable bends on forces and moments generated by triangular loops.
abstract: BACKGROUND
  Triangular loops are frequently used for space closure. Studies of this loop have focused on dimensional and in-plane (second-order) gable-bend influences on the generated forces and moments, but there have been no investigations into the effects of out-of-plane (first-order) gable bends. Both bends are generally needed to accomplish tooth translation. The primary purpose of this project was to ascertain whether first- and second-order bend effects were uncoupled.
  
  
  METHODS
  Ninety triangular loops were divided into 9 groups with combinations of 0 degrees and 30 degrees first- and second-order gable bends in the anterior and posterior positions. Forces (F(x), F(y), F(z)) and moments (M(x), M(y), M(z)) generated along 3 mutually perpendicular axes-x (mesiodistal), y (occlusogingival), and z (buccolingual)-were measured, and moment/force ratios (M(z)/F(x), M(y)/F(x)) were calculated. Statistical comparisons were made between the 9 groups and between activation distances. The Sidak multiple-comparison adjustment method was used to control the overall confidence level at 95%.
  
  
  RESULTS
  It was shown that the magnitude of M(z)/F(x) increased significantly with second-order gable bends but did not change with first-order bends. The opposite was found for M(y)/F(x).
  
  
  CONCLUSIONS
  Thus, in triangular springs, first- and second-order gable bends produce the desired effects without interfering with each other.
authors.affiliation: Indiana University School of Dentistry, and Mechanical Engineering, Purdue University School of Engineering and Technology, Indianapolis, Ind, USA. tkatona@iupui.edu
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Katona
authors.forename: Yen P
authors.initials: YP
authors.lastname: Le
authors.forename: Jie
authors.initials: J
authors.lastname: Chen
mesh_terms: D001696:Biomechanical Phenomena; D003722:Dental Alloys / Q000737:chemistry; D006801:Humans; D016382:Orthodontic Appliance Design; D016910:Orthodontic Brackets; D019516:Orthodontic Space Closure / Q000295:instrumentation*; D009969:Orthodontic Wires; D013193:Stainless Steel / Q000737:chemistry; D013314:Stress, Mechanical
chemical_list: D003722:Dental Alloys; D013193:Stainless Steel