title: Three-dimensional finite element analysis of cartilaginous tissues in human temporomandibular joint during prolonged clenching.
abstract: OBJECTIVE
  Bruxism, the parafunctional habit of nocturnal grinding of the teeth and clenching, is associated with the onset of joint degeneration. Especially prolonged clenching is suggested to cause functional overloading in the temporomandibular joint (TMJ). In this study, the distributions of stresses in the cartilaginous TMJ disc and articular cartilage, were analysed during prolonged clenching. The purpose of this study was to examine if joint degradation due to prolonged clenching can be attributed to changes in stress concentration in the cartilaginous tissues.
  
  
  METHODS
  Finite element model was developed on the basis of magnetic resonance images from a healthy volunteer. Condylar movements recorded during prolonged clenching were used as the loading condition for stress analysis.
  
  
  RESULTS
  At the onset of clenching (time=0s), the highest von Mises stresses were located in the middle and posterior areas (6.18MPa) of the inferior disc surface facing the condylar cartilage. The largest magnitude of the minimum principal stress (-6.72MPa) was found in the condylar cartilage. The stress concentrations were relieved towards the superior disc surface facing the temporal cartilage. On the surfaces of the temporal cartilage, relatively lower stresses were found. After 5-min clenching, both stress values induced in the TMJ components were reduced to 50-80% of the stress values at the onset of clenching, although the concomitant strains increased slightly during this period.
  
  
  CONCLUSIONS
  It is suggested that both the condylar and temporal cartilage layers along with the TMJ disc, play an important role in stress distribution and transmission during prolonged clenching due to tissue expansion. Furthermore, our study suggests that a development of stress concentrations in the TMJ during prolonged clenching and risk factors for the initiation of TMJ degeneration could not be confirmed.
authors: Department of Orthodontics and Dentofacial Orthopedics, The University of Tokushima Graduate School of Oral Sciences, Kuramoto-cho, Japan.
authors: Hiroko
authors: H
authors: Mori
authors: Shinya
authors: S
authors: Horiuchi
authors: Satoshi
authors: S
authors: Nishimura
authors: Hiroki
authors: H
authors: Nikawa
authors: Takeshi
authors: T
authors: Murayama
authors: Kanji
authors: K
authors: Ueda
authors: Daiichi
authors: D
authors: Ogawa
authors: Shingo
authors: S
authors: Kuroda
authors: Fumiaki
authors: F
authors: Kawano
authors: Hisashi
authors: H
authors: Naito
authors: Masao
authors: M
authors: Tanaka
authors: Jan Harm
authors: JH
authors: Koolstra
authors: Eiji
authors: E
authors: Tanaka
mesh_terms: D000328:Adult; D001732:Bite Force; D002012:Bruxism / Q000150:complications / Q000503:physiopathology*; D002358:Cartilage, Articular / Q000503:physiopathology*; D003799:Dental Stress Analysis / Q000379:methods*; D005260:Female; D020342:Finite Element Analysis; D006801:Humans; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D013704:Temporomandibular Joint / Q000503:physiopathology*; D013705:Temporomandibular Joint Disorders / Q000209:etiology / Q000503:physiopathology*