title: Prediction at long-term condyle screw fixation of temporomandibular joint implant: A numerical study.
abstract: The fixation of commercial temporomandibular joint (TMJ) implant is accomplished by using screws, which, in some cases, can lead to loosening of the implant. The aim of this study was to predict the evolution of fixation success of a TMJ. Numerical models using a Christensen TMJ implant were developed to analyze strain distributions in the adjacent mandibular bone. The geometry of a human mandible was developed based on computed tomography (CT) scans from a cadaveric mandible on which a TMJ implant was subsequently placed. In this study, the five most important muscle forces acting were applied and the anatomical conditions replicated. The evolution of fixation was defined according to bone response methodology focused in strain distribution around the screws. Strain and micromotions were analyzed to evaluate implant stability, and the evolution process conduct at three different stages: start with all nine screws in place (initial stage); middle stage, with three screws removed (middle stage), and end stage, with only three screws in place (final stage). With regard to loosening, the implant success fixation changed the strains in the bone between 21% and 30%, when considering the last stage. The most important screw positions were #1, #7, and #9. It was observed that, despite the commercial Christensen TMJ implant providing nine screw positions for fixation, only three screws were necessary to ensure implant stability and fixation success.
authors.affiliation: TEMA Center of Mechanical Technology and Automation, Department of Mechanical Engineering, University of Aveiro, Portugal; Université de Bordeaux, Institut de Mécanique et d'Ingénierie, CNRS UMR 5295, Talence, France. Electronic address: a.ramos@ua.pt.
authors.forename: A
authors.initials: A
authors.lastname: Ramos
authors.affiliation: TEMA Center of Mechanical Technology and Automation, Department of Mechanical Engineering, University of Aveiro, Portugal; Université de Bordeaux, Institut de Mécanique et d'Ingénierie, CNRS UMR 5295, Talence, France.
authors.forename: R J
authors.initials: RJ
authors.lastname: Duarte
authors.affiliation: Université de Bordeaux, Institut de Mécanique et d'Ingénierie, CNRS UMR 5295, Talence, France.
authors.forename: M
authors.initials: M
authors.lastname: Mesnard
mesh_terms: D001696:Biomechanical Phenomena; D001863:Bone Screws; D000069343:Bone-Implant Interface / Q000502:physiology; D002102:Cadaver; D017076:Computer-Aided Design; D005260:Female; D020342:Finite Element Analysis; D005544:Forecasting; D006801:Humans; D007595:Joint Prosthesis; D008334:Mandible / Q000601:surgery; D008335:Mandibular Condyle / Q000601:surgery*; D008406:Masseter Muscle / Q000502:physiology; D008875:Middle Aged; D011475:Prosthesis Failure; D060489:Prosthesis Retention; D011626:Pterygoid Muscles / Q000502:physiology; D013314:Stress, Mechanical; D013703:Temporal Muscle / Q000502:physiology; D013704:Temporomandibular Joint / Q000601:surgery*; D014057:Tomography, X-Ray Computed / Q000379:methods
keywords: Long term; Micromotions; Screw fixation; Strains; TMJ implant stability