title: Analysis of the torque capacity of a completely customized lingual appliance of the next generation.
abstract: BACKGROUND
  In lingual orthodontic therapy, effective torque control of the incisors is crucial due to the biomechanical particularities associated with the point of force application and the tight link between third order deviations and vertical tooth position.
  
  
  OBJECTIVE
  The aim of the present in vitro investigation was to analyze the torque capacity of a completely customized lingual appliance of the next generation (WIN) in combination with different finishing archwire dimensions.
  
  
  METHODS
  Using a typodont of the upper arch carrying the WIN appliance, slot filling and undersized individualized β-titanium archwires were engaged. Horizontal forces ranging from 0 to 100 cN were applied at the central incisor by means of spring gauges. The resulting angular deviations were recorded and the corresponding torque moments were calculated.
  
  
  RESULTS
  For fullsize archwires (0.018"×0.018" β-titanium and 0.018"×0.025" β-titanium), an initial torque play of 0-2° had to be overcome prior to the development of an effective torque moment. Thereafter, a linear correlation between torque angle and torque moment developed for both archwire dimensions with steeper slopes calculated for the specimens with the larger dimension. A torque moment of 2 Nmm required for effective torque correction was noted after a minimum of 2-3° of twist for the 0.018"×0.018" β-titanium wires as compared to 2-4° for the 0.018"×0.025" β-titanium study sample. When undersized archwires were analyzed (0.0175"×0.0175" β-titanium), the measured torque play ranged from 5-7°. After 8-12° of torque angle, the threshold of 2 Nmm was reached. A linear relationship between twist angle and torque moment in which the steepness of the slopes was generally flatter than the ones calculated for the slot filling archwires was noted.
  
  
  CONCLUSIONS
  Given the high precision of the bracket slot-archwire-combination provided with the WIN appliance, an effective torque control can be clinically realized.
authors: Department of Orthodontics, Dental Clinic, University of Bonn, Welschnonnenstr 17, Bonn 53111, Germany. s.lossdoerfer@gmx.de.
authors: Stefan
authors: S
authors: Lossdörfer
authors: Carsten
authors: C
authors: Bieber
authors: Rainer
authors: R
authors: Schwestka-Polly
authors: Dirk
authors: D
authors: Wiechmann
mesh_terms: D001696:Biomechanical Phenomena / Q000502:physiology; D003799:Dental Stress Analysis / Q000379:methods; D006801:Humans; D007180:Incisor; D008422:Materials Testing; D016382:Orthodontic Appliance Design; D016910:Orthodontic Brackets; D009969:Orthodontic Wires; D013314:Stress, Mechanical; D014087:Tooth Movement Techniques / Q000295:instrumentation; D019415:Torque