title: The influence of unilateral disc displacement on stress in the contralateral joint with a normally positioned disc in a human temporomandibular joint: an analytic approach using the finite element method.
abstract: OBJECTIVE
  To investigate the influence of unilateral disc displacement (DD) in the temporomandibular joint (TMJ) on the stress in the contralateral joint, with a normally-positioned disc, during clenching.
  
  
  METHODS
  A finite element model of the TMJ was constructed based on MRI and 3D-CT of a single patient with a unilateral DD. A second model with bilateral normally-positioned discs served as a reference. The differences in stress distribution in various TMJ components during clenching were predicted with these models.
  
  
  RESULTS
  In the unaffected joint of the unilateral DD model, the largest von Mises stress at the start of clenching was predicted in the inferior surface of the disc and increased by 30% during clenching. In the connective tissue the largest stress (1.16 MPa) did not reduce during clenching, in contrast to the (unaffected) joints of the reference model. In the affected joint, the largest stress was predicted in the temporal cartilage throughout clenching. In the surrounding connective tissue, the largest stress (1.42 MPa) hardly changed during clenching indicating no, or negligible, stress relaxation.
  
  
  CONCLUSIONS
  This suggested that a unilateral DD could affect the stresses in the unaffected (contralateral) joint during clenching, where it may lead to weakening of the tissues that keep the disc on the top of the condyle. The results may be helpful in counseling worried patients, since they give insight into possible future developments of the disorder.
authors.affiliation: Department of Orthodontics and Dentofacial Orthopedics, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima, Japan.
authors.forename: Erica
authors.initials: E
authors.lastname: Hattori-Hara
authors.affiliation: Department of Orthodontics and Dentofacial Orthopedics, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima, Japan.
authors.forename: Silvia N
authors.initials: SN
authors.lastname: Mitsui
authors.affiliation: Department of Orthodontics and Dentofacial Orthopedics, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima, Japan.
authors.forename: Hiroyo
authors.initials: H
authors.lastname: Mori
authors.affiliation: Digital Solution Co. Ltd., Hiroshima, Japan.
authors.forename: Keiji
authors.initials: K
authors.lastname: Arafurue
authors.affiliation: Digital Solution Co. Ltd., Hiroshima, Japan.
authors.forename: Takuji
authors.initials: T
authors.lastname: Kawaoka
authors.affiliation: Digital Solution Co. Ltd., Hiroshima, Japan.
authors.forename: Kanji
authors.initials: K
authors.lastname: Ueda
authors.affiliation: Department of Orthodontics and Dentofacial Orthopedics, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima, Japan.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Yasue
authors.affiliation: Department of Orthodontics and Dentofacial Orthopedics, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima, Japan.
authors.forename: Shingo
authors.initials: S
authors.lastname: Kuroda
authors.affiliation: Department of Functional Anatomy, ACTA, Amsterdam, The Netherlands.
authors.forename: Jan Harm
authors.initials: JH
authors.lastname: Koolstra
authors.affiliation: Department of Orthodontics and Dentofacial Orthopedics, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima, Japan. Electronic address: etanaka@tokushima-u.ac.jp.
authors.forename: Eiji
authors.initials: E
authors.lastname: Tanaka
mesh_terms: D000328:Adult; D000465:Algorithms; D001696:Biomechanical Phenomena; D002358:Cartilage, Articular / Q000503:physiopathology; D003238:Connective Tissue / Q000503:physiopathology; D005260:Female; D020342:Finite Element Analysis; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D004204:Joint Dislocations / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008335:Mandibular Condyle / Q000503:physiopathology; D009119:Muscle Contraction / Q000502:physiology; D013314:Stress, Mechanical; D013701:Temporal Bone / Q000503:physiopathology; D013704:Temporomandibular Joint / Q000503:physiopathology*; D019224:Temporomandibular Joint Disc / Q000473:pathology*; D013705:Temporomandibular Joint Disorders / Q000503:physiopathology*; D014057:Tomography, X-Ray Computed / Q000379:methods
keywords: Clenching; Finite element method; Stress analysis; Temporomandibular joint; Unilateral disc displacement