title: Tension-compression viscoelastic behaviors of the periodontal ligament.
abstract: OBJECTIVE
  Although exhaustively studied, the mechanism responsible for tooth support and the mechanical properties of the periodontal ligament (PDL) remain a subject of considerable controversy. In the past, various experimental techniques and theoretical analyses have been employed to tackle this intricate problem. The aim of this study was to investigate the viscoelastic behaviors of the PDL using three-dimensional finite element analysis.
  
  
  METHODS
  Three dentoalveolar complex models were established to simulate the tissue behaviors of the PDL: (1) deviatoric viscoelastic model; (2) volumetric viscoelastic model; and (3) tension-compression volumetric viscoelastic model. These modified models took into consideration the presence of tension and compression along the PDL during both loading and unloading. The inverse parameter identification process was developed to determine the mechanical properties of the PDL from the results of previously reported in vitro and in vivo experiments.
  
  
  RESULTS
  The results suggest that the tension-compression volumetric viscoelastic model is a good approximation of normal PDL behavior during the loading-unloading process, and the deviatoric viscoelastic model is a good representation of how a damaged PDL behaves under loading conditions. Moreover, fluid appears to be the main creep source in the PDL.
  
  
  CONCLUSIONS
  We believe that the biomechanical properties of the PDL established via retrograde calculation in this study can lead to the construction of more accurate extra-oral models and a comprehensive understanding of the biomechanical behavior of the PDL.
authors.affiliation: Graduate Institute of Clinical Dentistry, School of Dentistry, National Taiwan University, Taipei, Taiwan, ROC.
authors.forename: Chen-Ying
authors.initials: CY
authors.lastname: Wang
authors.forename: Ming-Zen
authors.initials: MZ
authors.lastname: Su
authors.forename: Hao-Hueng
authors.initials: HH
authors.lastname: Chang
authors.forename: Yu-Chih
authors.initials: YC
authors.lastname: Chiang
authors.forename: Shao-Huan
authors.initials: SH
authors.lastname: Tao
authors.forename: Jung-Ho
authors.initials: JH
authors.lastname: Cheng
authors.forename: Lih-Jyh
authors.initials: LJ
authors.lastname: Fuh
authors.forename: Chun-Pin
authors.initials: CP
authors.lastname: Lin
mesh_terms: D001696:Biomechanical Phenomena; D004548:Elasticity / Q000502:physiology*; D020342:Finite Element Analysis; D006801:Humans; D008954:Models, Biological; D010513:Periodontal Ligament / Q000502:physiology*; D013314:Stress, Mechanical; D013718:Tensile Strength / Q000502:physiology*; D055682:Viscoelastic Substances / Q000032:analysis*
chemical_list: D055682:Viscoelastic Substances