title: Innovative design of closing loops producing an optimal force system applicable in the 0.022-in bracket slot system.
abstract: BACKGROUND
  Most closing loops designed for producing higher moment-to-force (M/F) ratios require complex wire bending and are likely to cause hygiene problems and discomfort because of their complicated configurations. We aimed to develop a simple loop design that can produce optimal force and M/F ratio.
  
  
  METHODS
  A loop design that can generate a high M/F ratio and the ideal force level was investigated by varying the portion and length of the cross-sectional reduction of a teardrop loop and the loop position. The forces and moments acting on closing loops were calculated using structural analysis based on the tangent stiffness method.
  
  
  RESULTS
  An M/F ratio of 9.3 (high enough to achieve controlled movement of the anterior teeth) and an optimal force level of approximately 250 g of force can be generated by activation of a 10-mm-high teardrop loop whose cross-section of 0.019 × 0.025 or 0.021 × 0.025 in was reduced in thickness by 50% for a distance of 3 mm from the apex, located between a quarter and a third of the interbracket distance from the canine bracket.
  
  
  CONCLUSIONS
  The simple loop design that we developed delivers an optimal force and an M/F ratio for the retraction of anterior teeth, and is applicable in a 0.022-in slot system.
authors.affiliation: Postgraduate student, Department of Orthodontics and Dentofacial Orthopedics, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan.
authors.forename: Mayumi
authors.initials: M
authors.lastname: Sumi
authors.affiliation: Associate professor, Department of Orthodontics, Nagasaki University Hospital, Nagasaki, Japan. Electronic address: koga@nagasaki-u.ac.jp.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Koga
authors.affiliation: Assistant professor, Department of Orthodontics and Dentofacial Orthopedics, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan.
authors.forename: Jun-Ya
authors.initials: JY
authors.lastname: Tominaga
authors.affiliation: Postgraduate student, Department of Orthodontics and Dentofacial Orthopedics, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Hamanaka
authors.affiliation: Clinical fellow, Department of Orthodontics, Nagasaki University Hospital, Nagasaki, Japan.
authors.forename: Hiroya
authors.initials: H
authors.lastname: Ozaki
authors.affiliation: Resident, Aich Gakuin University Dental Hospital, Nagoya, Japan.
authors.forename: Pao-Chang
authors.initials: PC
authors.lastname: Chiang
authors.affiliation: Professor and chair, Department of Orthodontics and Dentofacial Orthopedics, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan.
authors.forename: Noriaki
authors.initials: N
authors.lastname: Yoshida
mesh_terms: D003799:Dental Stress Analysis; D006801:Humans; D016382:Orthodontic Appliance Design; D016910:Orthodontic Brackets; D019516:Orthodontic Space Closure / Q000295:instrumentation / Q000379:methods*; D009969:Orthodontic Wires; D014087:Tooth Movement Techniques / Q000295:instrumentation / Q000379:methods*