title: Periodontal ligament hydrostatic pressure with areas of root resorption after application of a continuous torque moment.
abstract: OBJECTIVE
  To evaluate the risk of root resorption, individual finite element models (FEMs) of extracted human maxillary first premolars were created, and the distribution of the hydrostatic pressure in the periodontal ligament (PDL) of these models was simulated.
  
  
  METHODS
  A continuous lingual torque of 3 Nmm and 6 Nmm respectively was applied in vivo to the aforementioned teeth. After extraction, FEMs of these double-rooted teeth were created based on high-resolution microcomputed tomographics (micro CT, voxel size: 35 microns). This high volumetric resolution made the recognition of very small resorption lacunae possible. Scanning electron micrographs of the root surfaces were created as well. This enabled the investigation of advantages and disadvantages of the different imaging techniques from the viewpoint of the examination of root resorption. Using the FEMs, the same loading conditions as applied in vivo were simulated.
  
  
  RESULTS
  The results of clinical examination and simulations were compared using the identical roots of the teeth. The regions that showed increased hydrostatic pressure (>0.0047 MPa) correlated well with the locations of root resorption for each tooth. Increased torque resulted in increased high-pressure areas and increased magnitudes of hydrostatic pressure, correlating with the experiments.
  
  
  CONCLUSIONS
  If hydrostatic pressure exceeds typical human capillary blood pressure in the PDL, the risk of root resorption increases.
authors.affiliation: Department of Orthodontics, University of Ulm, Ulm, Germany. ansgar.hohmann@uni-ulm.de
authors.forename: Ansgar
authors.initials: A
authors.lastname: Hohmann
authors.forename: Uwe
authors.initials: U
authors.lastname: Wolfram
authors.forename: Martin
authors.initials: M
authors.lastname: Geiger
authors.forename: Andrew
authors.initials: A
authors.lastname: Boryor
authors.forename: Christian
authors.initials: C
authors.lastname: Sander
authors.forename: Rolf
authors.initials: R
authors.lastname: Faltin
authors.forename: Kurt
authors.initials: K
authors.lastname: Faltin
authors.forename: Franz Guenter
authors.initials: FG
authors.lastname: Sander
mesh_terms: D001641:Bicuspid / Q000503:physiopathology; D001794:Blood Pressure; D003799:Dental Stress Analysis / Q000379:methods; D020342:Finite Element Analysis; D006801:Humans; D006874:Hydrostatic Pressure; D008437:Maxilla; D008855:Microscopy, Electron, Scanning; D010513:Periodontal Ligament / Q000098:blood supply / Q000503:physiopathology*; D012391:Root Resorption / Q000209:etiology* / Q000503:physiopathology; D014057:Tomography, X-Ray Computed; D014087:Tooth Movement Techniques / Q000009:adverse effects*; D019415:Torque