title: Numerical simulation and biomechanical analysis of an orthodontically treated periodontally damaged dentition.
abstract: OBJECTIVE
  Once periodontitis has been completely resolved, one common follow-up method is to carry out orthodontic treatment to take advantage of the residual bone, i.e., via tooth intrusion. In this study, the biomechanical behavior of teeth in a reduced periodontium was studied by numerically simulating upper-incisor intrusion accomplished with various orthodontic mechanics.
  
  
  METHODS
  Using the finite element method, a patient-customized 3D model of a periodontally reduced dentition was generated in order to simulate tooth movement. The morphology of this upper-jaw model was derived from cone-beam computed tomography (CBCT) datasets of four patients. Material parameters were adopted from previous investigations, including teeth (E=20 GPa), periodontal ligament (PDL) (bilinear elastic; E1=0.05 MPa; E2=0.20 MPa; ε12=7%), and bone (homogeneous, isotropic; E=2 GPa). Two intrusion scenarios were used, the first drawing from Burstone's segmented-arch technique to intrude four splinted incisors at a time, and the second one using cantilevers to intrude single incisors. The aforementioned PDL material parameters were varied in several ways to simulate different biological and biomechanical states of PDL. All simulations were recalculated with an idealized, periodontally intact model to assess the effect of bone loss by way of comparison.
  
  
  RESULTS
  Single-tooth intrusion via cantilever mechanics was accompanied by less rotation than the segmented-arch approach. Both intrusion systems involved significantly greater degrees of tooth displacement and PDL load in the periodontally reduced model.
  
  
  CONCLUSIONS
  Periodontally reduced dentitions are associated with an increased load on periodontal tissue. This can be counteracted by reducing orthodontic force levels and by selecting mechanics that do not harm the tissue. In so doing, the use of numerical methods may greatly facilitate individualized computer-aided treatment-planning strategies.
authors.affiliation: Endowed Chair of Oral Technology, Rheinische Friedrich-Wilhelms-Universität Bonn, Welschnonnenstr. 17, 53111, Bonn, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Kettenbeil
authors.forename: S
authors.initials: S
authors.lastname: Reimann
authors.forename: C
authors.initials: C
authors.lastname: Reichert
authors.forename: L
authors.initials: L
authors.lastname: Keilig
authors.forename: A
authors.initials: A
authors.lastname: Jäger
authors.forename: C
authors.initials: C
authors.lastname: Bourauel
mesh_terms: D019245:Compressive Strength; D003198:Computer Simulation; D003799:Dental Stress Analysis / Q000379:methods; D020342:Finite Element Analysis; D006801:Humans; D007180:Incisor / Q000503:physiopathology*; D008437:Maxilla / Q000503:physiopathology*; D008954:Models, Biological; D010513:Periodontal Ligament / Q000503:physiopathology*; D010518:Periodontitis / Q000503:physiopathology*; D014086:Tooth Mobility / Q000503:physiopathology*; D014087:Tooth Movement Techniques / Q000379:methods*; D016474:Weight-Bearing / Q000502:physiology