title: Torque Loss in En-Masse Retraction of Maxillary Anterior Teeth Using Miniimplants with Force Vectors at Different Levels: 3D FEM Study.
abstract: OBJECTIVE
  This FEM study was conducted to quantify the amount of torque loss in maxillary anterior teeth by applying force vectors from different levels to the anterior retraction hook at various heights and comparing with that of molar anchorage system.
  
  
  METHODS
  Five 3D FEM models were constructed with force vectors at different levels: HOT-High Orthodontic Traction (13.5mm from archwire) to ARH1- Anterior Retraction Hook (5mm), HOT to ARH2 (8mm), LOT- Low Orthodontic Traction (8 mm) to ARH1, LOT to ARH2 and from conventional molar hook to ARH1. Mini-implants were placed buccally between the roots of second premolar and first molar. Torque loss was calculated by measuring the displacement of the teeth at crown tip and root apex in two planes i.e. sagittal and vertical using Y and Z axis respectively in all the five models. The results were statistically analyzed by using Kruskal Wallis ANOVA and Mann-Whitney U-test.
  
  
  RESULTS
  HOT to ARH1 showed that the anterior teeth moved bodily (p =0.5127), followed by molar hook - ARH1(p=0.0495*) which showed mild uncontrolled tipping. Whereas the HOT- ARH2, LOT - ARH1,and LOT - ARH2 models exhibited uncontrolled tipping with maximum torque loss in LOT - ARH1 (p=0.0001*).
  
  
  CONCLUSIONS
  It can be concluded that bodily movement with very minimal torque loss was observed in HOT-ARH1 model whereas the maximum torque loss was recorded in LOT-ARH2 model. Conventional molar anchorage group showed uncontrolled tipping with some amount of extrusion and anchor loss of posteriors.
authors: Senior Lecturer, Department of Orthodontics, Jodhpur Dental College , Jodhpur, Rajasthan, India .
authors: Abhishek
authors: A
authors: Parashar
authors: Associate Professor, Department of Orthodontics, Faculty of Dentistry AL-JOUF UNIVERSITY , Sakaka Al-Jouf ProvinceKingdom of Saudi Arabia .
authors: Kaladhar Reddy
authors: KR
authors: Aileni
authors: Associate Professor, Department of Orthodontics, SVS Institute of Dental Sciences , Mahabubnagar, Telangana, India .
authors: Madhukar Reddy
authors: MR
authors: Rachala
authors: Professor, Department of Orthodontics, SVS Institute of Dental Sciences , Mahabubnagar, Telangana, India .
authors: Nagam Reddy
authors: NR
authors: Shashidhar
authors: Senior Lecturer, Department of Orthodontics, SVS Institute of Dental Sciences , Mahabubnagar, Telangana, India .
authors: Vankre
authors: V
authors: Mallikarjun
authors: Clinician, C-111, Bangur Avenue, Kolkata, West Bengal, India .
authors: Nupur
authors: N
authors: Parik
keywords: Anterior retraction hook; En-masse retraction; Finite element method; Mini-implants; Torque loss
references: J Clin Orthod. 1990 Nov;24(11):678-83
references: 2084156
references: J Clin Orthod. 1983 Apr;17 (4):266-9
references: 6574142
references: J Orthod. 2001 Mar;28(1):29-38
references: 11254801
references: Angle Orthod. 2004 Oct;74(5):703-10
references: 15529508
references: Am J Orthod. 1980 Apr;77(4):396-409
references: 6928741
references: J Clin Orthod. 2008 Feb;42(2):79-83
references: 18477820
references: Eur J Orthod. 2014 Oct;36(5):563-8
references: 24265465
references: Am J Orthod Dentofacial Orthop. 2010 May;137(5):648-57
references: 20451784
references: Am J Orthod. 1974 Mar;65(3):250-9
references: 4521359
references: Am J Orthod Dentofacial Orthop. 2008 Jul;134(1):18-29.e1
references: 18617099
references: Am J Orthod Dentofacial Orthop. 1993 May;103(5):428-38
references: 8480711
references: Angle Orthod. 2007 Mar;77(2):214-20
references: 17319754
references: Am J Orthod Dentofacial Orthop. 2005 Jun;127(6):713-22
references: 15953897
references: J Clin Orthod. 1997 Nov;31(11):763-7
references: 9511584
references: Eur J Orthod. 2004 Jun;26(3):339-45
references: 15222721
references: Am J Orthod Dentofacial Orthop. 2011 Jul;140(1):72-80
references: 21724090
references: Am J Orthod Dentofacial Orthop. 2003 Apr;123(4):441-50
references: 12695772
references: Br J Orthod. 1977 Jan;4(1):23-7
references: 273433