title: Biomechanical analysis comparing natural and alloplastic temporomandibular joint replacement using a finite element model.
abstract: OBJECTIVE
  Prosthetic materials and bone present quite different mechanical properties. Consequently, mandible reconstruction with metallic materials (or a mandible condyle implant) modifies the physiologic behavior of the mandible (stress, strain patterns, and condyle displacements). The changing of bone strain distribution results in an adaptation of the temporomandibular joint, including articular contacts.
  
  
  METHODS
  Using a validated finite element model, the natural mandible strains and condyle displacements were evaluated. Modifications of strains and displacements were then assessed for 2 different temporomandibular joint implants. Because materials and geometry play important key roles, mechanical properties of cortical bone were taken into account in models used in finite element analysis.
  
  
  RESULTS
  The finite element model allowed verification of the worst loading configuration of the mandibular condyle. Replacing the natural condyle by 1 of the 2 tested implants, the results also show the importance of the implant geometry concerning biomechanical mandibular behavior. The implant geometry and stiffness influenced mainly strain distribution.
  
  
  CONCLUSIONS
  The different forces applied to the mandible by the elevator muscles, teeth, and joint loads indicate that the finite element model is a relevant tool to optimize implant geometry or, in a subsequent study, to choose a more suitable distribution of the screws. Bone screws (number and position) have a significant influence on mandibular behavior and on implant stress pattern. Stress concentration and implant fracture must be avoided.
authors.affiliation: Laboratoire de Mécanique Physique, Université de Bordeaux, Talence, France. michel.mesnard@u-bordeaux1.fr
authors.forename: Michel
authors.initials: M
authors.lastname: Mesnard
authors.forename: Antonio
authors.initials: A
authors.lastname: Ramos
authors.forename: Alex
authors.initials: A
authors.lastname: Ballu
authors.forename: Julien
authors.initials: J
authors.lastname: Morlier
authors.forename: M
authors.initials: M
authors.lastname: Cid
authors.forename: J A
authors.initials: JA
authors.lastname: Simoes
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000328:Adult; D001672:Biocompatible Materials / Q000737:chemistry*; D001696:Biomechanical Phenomena; D001732:Bite Force; D001863:Bone Screws; D055119:Elastic Modulus; D004576:Electromyography; D005260:Female; D020342:Finite Element Analysis; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D007595:Joint Prosthesis; D008279:Magnetic Resonance Imaging; D008297:Male; D008334:Mandible / Q000503:physiopathology; D008335:Mandibular Condyle / Q000503:physiopathology; D008406:Masseter Muscle / Q000503:physiopathology; D008422:Materials Testing; D011474:Prosthesis Design; D011626:Pterygoid Muscles / Q000503:physiopathology; D016059:Range of Motion, Articular / Q000502:physiology; D013314:Stress, Mechanical; D013499:Surface Properties; D013703:Temporal Muscle / Q000503:physiopathology; D013704:Temporomandibular Joint / Q000503:physiopathology; D055815:Young Adult
chemical_list: D001672:Biocompatible Materials