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IMPACTS OF THE CONDYLE GEOMETRY OF A MANDIBLE IMPLANT
Presentation 1794 − Topic 25. Implant biomechanics
S345
IMPACTS OF THE CONDYLE GEOMETRY OF A MANDIBLE IMPLANT Michel Mesnard (1), António Ramos (2)
1. Univ. of Bordeaux, I2M, CNRS UMR 5295, F-33400 Talence, France; 2. TEMA, Departamento Engenharia Mecânica, University of Aveiro, Aveiro, Portugal
Introduction The replacement of the temporomandibular joint (TMJ) involves both, the removal of the natural joint and placing an artificial one. Due to the nature of the bones, to the articular forces and to the joint kinematics, design of condyle replacement is complex. Mercuri showed that the implant stability is an important factor in the success of a TMJ implant [Mercury, 2007]. The TMJ prosthesis must allow the anteriorposterior movements of the mandible when the mouth opens and must also allow some mediolateral displacements. The fitting to the skull is still a major problem [van Loon, 1995]. Because of these displacements and of the geometry of the condyle implant when chewing, the contact point moves along the articular, temporal and mandibular surfaces (inside to outside). The objective of the present study was to analyse the strain distributions in the mandible bone and near the surgical screws.
contacts may slide with a 0.3 friction coefficient. The FE model allowed analysing the impact of the condyle geometry considering three different situations: contact in the condyle centre (sphere geometry), contacts on the right (point I) and left sides (point O) of the condyle.
Results Results were registered around the fixation screws and on the external surface of the mandible. Figure 2 presents the minimum strain distribution on the external mandible surface in the medial plane of the screws and point out the influence of the contact point position or of the condyle geometry. The inside contact reduces the strain values around the screws, but the strain increases in proximal region in the medial plane of the condyle. The first and last screws determine the connection of the implant.
Methods The finite element (FE) model was based on a previous validated model [Ramos, 2011]. This FE model involved a commercial TMJ implant (similar to Stryker’s®) fixed on the left condyle using four screws witch diameter value was 2 mm. The loads, presented on figure 1, were calculated in in vivo studies [Mesnard, 2011]. The fixation point was then situated on the central incisive teeth and the mouth aperture reached 15 mm.
Figure 2: Minimum strain distribution in the bone around the screws.
Discussion The results obtained for different contact points and for the same load show that the strain distribution is influenced by the condyle geometry. The strain increases near the screws for the outside point of contact. The third screw is not necessary and will probably be loosed due to the very low solicitation.
References
Figure 1: Mandible and TMJ implant geometries. Implant and screws were built using an isotropic Titanium alloy. Bone-screw contacts were glued. Both implant-screw and implant-bone touching
Mercuri LG., et al, J Oral M. Surgery, 65:11401148, 2007. Mesnard M., et al, J Oral M. Surgery, 69:10081017, 2011. Ramos A., et al, Exp. Mech, 51:1053-1059, 2011. Van Loon JP., et al, J Oral M. Surgery, 53:984-996, 1995.
ESB2012: 18th Congress of the European Society of Biomechanics
Journal of Biomechanics 45(S1)
S345
IMPACTS OF THE CONDYLE GEOMETRY OF A MANDIBLE IMPLANT Michel Mesnard (1), António Ramos (2)
1. Univ. of Bordeaux, I2M, CNRS UMR 5295, F-33400 Talence, France; 2. TEMA, Departamento Engenharia Mecânica, University of Aveiro, Aveiro, Portugal
Introduction The replacement of the temporomandibular joint (TMJ) involves both, the removal of the natural joint and placing an artificial one. Due to the nature of the bones, to the articular forces and to the joint kinematics, design of condyle replacement is complex. Mercuri showed that the implant stability is an important factor in the success of a TMJ implant [Mercury, 2007]. The TMJ prosthesis must allow the anteriorposterior movements of the mandible when the mouth opens and must also allow some mediolateral displacements. The fitting to the skull is still a major problem [van Loon, 1995]. Because of these displacements and of the geometry of the condyle implant when chewing, the contact point moves along the articular, temporal and mandibular surfaces (inside to outside). The objective of the present study was to analyse the strain distributions in the mandible bone and near the surgical screws.
contacts may slide with a 0.3 friction coefficient. The FE model allowed analysing the impact of the condyle geometry considering three different situations: contact in the condyle centre (sphere geometry), contacts on the right (point I) and left sides (point O) of the condyle.
Results Results were registered around the fixation screws and on the external surface of the mandible. Figure 2 presents the minimum strain distribution on the external mandible surface in the medial plane of the screws and point out the influence of the contact point position or of the condyle geometry. The inside contact reduces the strain values around the screws, but the strain increases in proximal region in the medial plane of the condyle. The first and last screws determine the connection of the implant.
Methods The finite element (FE) model was based on a previous validated model [Ramos, 2011]. This FE model involved a commercial TMJ implant (similar to Stryker’s®) fixed on the left condyle using four screws witch diameter value was 2 mm. The loads, presented on figure 1, were calculated in in vivo studies [Mesnard, 2011]. The fixation point was then situated on the central incisive teeth and the mouth aperture reached 15 mm.
Figure 2: Minimum strain distribution in the bone around the screws.
Discussion The results obtained for different contact points and for the same load show that the strain distribution is influenced by the condyle geometry. The strain increases near the screws for the outside point of contact. The third screw is not necessary and will probably be loosed due to the very low solicitation.
References
Figure 1: Mandible and TMJ implant geometries. Implant and screws were built using an isotropic Titanium alloy. Bone-screw contacts were glued. Both implant-screw and implant-bone touching
Mercuri LG., et al, J Oral M. Surgery, 65:11401148, 2007. Mesnard M., et al, J Oral M. Surgery, 69:10081017, 2011. Ramos A., et al, Exp. Mech, 51:1053-1059, 2011. Van Loon JP., et al, J Oral M. Surgery, 53:984-996, 1995.
ESB2012: 18th Congress of the European Society of Biomechanics
Journal of Biomechanics 45(S1)