title: Biomechanical characterization of the periodontal ligament: Orthodontic tooth movement.
abstract: OBJECTIVE
  To quantify the biomechanical properties of the bovine periodontal ligament (PDL) in postmortem sections and to apply these properties to study orthodontic tooth intrusion using finite element analysis (FEA). We hypothesized that PDL's property inherited heterogeneous (anatomical dependency) and nonlinear stress-strain behavior that could aid FEA to delineate force vectors with various rectangular archwires.
  
  
  METHODS
  A dynamic mechanical analyzer was used to quantify the stress-strain behavior of bovine PDL. Uniaxial tension tests using three force levels (0.5, 1, and 3 N) and samples from two anatomical locations (circumferential and longitudinal) were performed to calculate modulus. The Mooney-Rivlin hyperelastic (MRH) model was applied to the experimental data and used in an FEA of orthodontic intrusion rebounded via a 0.45-mm step bend with three archwire configurations of two materials (stainless steel and TMA).
  
  
  RESULTS
  Force levels and anatomical location were statistically significant in their effects on modulus (P < .05). The apical part had a greater stiffness than did the middle part. The MRH model was found to approximate the experimental data well (r = 0.99), and it demonstrated a reasonable stress-strain outcome within the PDL and bone for FEA intrusion simulation. The force acting on the tooth increased five times from the 0.016 × 0.022-inch TMA to the 0.019 × 0.025-inch stainless steel.
  
  
  CONCLUSIONS
  The PDL is a nonhomogeneous tissue in which the modulus changed in relation to location. PDL nonlinear constitutive model estimated quantitative force vectors for the first time to compare intrusive tooth movement in 3-D space in response to various rectangular archwires.
authors.forename: Richard
authors.initials: R
authors.lastname: Uhlir
authors.forename: Virginia
authors.initials: V
authors.lastname: Mayo
authors.forename: Pei Hua
authors.initials: PH
authors.lastname: Lin
authors.forename: Si
authors.initials: S
authors.lastname: Chen
authors.forename: Yan-Ting
authors.initials: YT
authors.lastname: Lee
authors.forename: Garland
authors.initials: G
authors.lastname: Hershey
authors.forename: Feng-Chang
authors.initials: FC
authors.lastname: Lin
authors.forename: Ching-Chang
authors.initials: CC
authors.lastname: Ko
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D002417:Cattle; D055119:Elastic Modulus; D020342:Finite Element Analysis; D066298:In Vitro Techniques; D007180:Incisor; D008334:Mandible; D010513:Periodontal Ligament / Q000502:physiology*; D013314:Stress, Mechanical; D014087:Tooth Movement Techniques
keywords: Bovine; Elastic rebound; FEA; Hyperelastic; Nonlinear; PDL; Tooth movement