title: Periodontal ligament strain induced by different orthodontic bracket removal techniques: nonlinear finite-element comparison study.
abstract: OBJECTIVE
  The goal of this work was to biomechanically analyze several different methods of bracket debonding and compare the strain they induce in the periodontal ligament (PDL).
  
  
  METHODS
  The CT dataset of an anatomical specimen was divided into four segmental models of the mandible. Each model covered one tooth (32, 42, 44, and 47). One of these teeth (32) was characterized by marked loss of periodontal attachment. After suitable finite-element models were generated, material properties were defined as nonlinear for PDL and anisotropic for the alveolar bone. This was followed by simulating four bracket debonding techniques: frontal and lateral torquing, bracket-wing compression, and shear stress applied with specially designed pliers.
  
  
  RESULTS
  The greatest strain was measured at the periodontally compromised tooth site 32 in response to frontal and lateral torquing. Both techniques also resulted in great strain around the other three teeth. Strain was markedly lower with the shear technique and virtually negligible with the compression technique. All simulated tooth sites confirmed the PDL-sparing effect of bracket-wing compression.
  
  
  CONCLUSIONS
  The severity of PDL strain during orthodontic bracket removal depends on the debonding method used. The technique of compressing the bracket wings appears to trigger the smallest effect on PDL. Clinical studies should be undertaken to confirm these findings.
authors: Faculty of Medicine, Ludwig-Maximilians-University, Geschwister-Scholl-Platz 1, 80539, Munich, Germany, cholberg@med.lmu.de.
authors: Christof
authors: C
authors: Holberg
authors: Ingrid
authors: I
authors: Rudzki-Janson
authors: Andrea
authors: A
authors: Wichelhaus
authors: Philipp
authors: P
authors: Winterhalder
mesh_terms: D003198:Computer Simulation; D017005:Dental Debonding / Q000379:methods*; D003799:Dental Stress Analysis / Q000379:methods*; D020878:Device Removal / Q000379:methods*; D055119:Elastic Modulus / Q000502:physiology; D020342:Finite Element Analysis; D006801:Humans; D008954:Models, Biological; D017711:Nonlinear Dynamics; D016910:Orthodontic Brackets; D010513:Periodontal Ligament / Q000502:physiology*; D013314:Stress, Mechanical; D013718:Tensile Strength / Q000502:physiology