title: Finite element analysis of stresses in molars during clenching and mastication.
abstract: BACKGROUND
  During physiological functions of the masticatory system such as swallowing and chewing, teeth are subjected to variations in force application. Most in vitro analyses of stress have not analyzed the combined forces acting on teeth.
  
  
  OBJECTIVE
  The purpose of this study was to analyze the stresses induced in a mandibular molar during clenching and chewing of morsels with various elastic moduli.
  
  
  METHODS
  The investigation was performed by means of finite element analysis with the use of contact elements. Two-dimensional models of the mandibular first molar and the crown of the opposing maxillary molar were created. The computerized simulation evaluated the clenching and chewing of 4 morsels with different elastic moduli (similar to hard gum, tough meat, bone, and combination of hard gum and bone). The movement of the studied teeth was simulated in the frontal plane. Teeth models crushed morsels and closed into the maximal intercuspation position. The values of stresses in the mandibular molar were calculated during these situations.
  
  
  RESULTS
  The study revealed that clenching of molars and chewing morsels of high elastic moduli resulted in maximal equivalent stresses within occlusal enamel. During mastication of morsels of low elastic moduli the stress concentration was located in the cervical region of the lingual side of the mandibular molar. Masticating a low-elasticity morsel containing a fragment of bone caused the highest equivalent stresses in the lingual wall and high tensile stresses in enamel near the central intercuspal fissure of the tooth studied.
  
  
  CONCLUSIONS
  During mastication of various morsels, maximal equivalent stresses occurred in occlusal enamel and in the cervical region of the lingual wall of the first mandibular molar. The more unfavorable and highest stresses were exerted during mastication of nonhomogeneous morsels.
authors.affiliation: Department of Prosthetic Dentistry, Institute of Dentistry, Medical University of Lodz, Poland. bdejak@poczta.onet.pl
authors.forename: Beata
authors.initials: B
authors.lastname: Dejak
authors.forename: Andrzej
authors.initials: A
authors.lastname: Młotkowski
authors.forename: Maciej
authors.initials: M
authors.lastname: Romanowicz
mesh_terms: D001732:Bite Force; D003743:Dental Enamel / Q000502:physiology; D003799:Dental Stress Analysis / Q000379:methods*; D004548:Elasticity; D020342:Finite Element Analysis; D006801:Humans; D008409:Mastication; D008954:Models, Biological; D003765:Models, Dental; D008963:Molar / Q000502:physiology*; D009119:Muscle Contraction; D013718:Tensile Strength; D019237:Tooth Cervix / Q000502:physiology; D019228:Tooth Crown / Q000502:physiology