Biomedical Engineering Reference
In-Depth Information
Fig. 10
Mandible FE model
with a TMJ implant in
left
condyle
regions where the rosettes were placed on the mandible. The convergence rate for
the displacements and the equivalent strains was reached for a mesh of more or
less 40,000 DOF. Other authors, e.g. Hart et al. [
51
], considered convergence for
25,000 DOF and Lovald et al. [
50
] used a model with 47,525 elements with a model
convergence.
The simulations took into account the mechanical properties of the mandible,
where cortical bone was considered to have a Young's modulus of 14,700 MPa and
a Poisson coefficient of 0.3, similar to models used by other authors [
24
,
35
]for
experimental validation. The implants were fixed with four screws and, as is often
the case, there was no screw in the proximal position, which was also suggested
by a surgeon. The Young's modulus (titanium alloy) and Poisson coefficient of the
implant and screws were 110 GPa and 0.3 respectively.
The implant was applied to the left side of the mandible. The implant position
with respect to the mandible was defined by the surgeon. In this study we used
the same upper part of implant in the same position because the main goal was to
analyze the behavior of the condyle region where the implant was placed.
The screw positions were also chosen by the surgeon. As in a real clinical
situation, four screws were used to fix the implant to the mandible. Screws of 2 mm
diameter were used and these have been considered as the minimum diameter that
can provide sufficient stability [
55
,
56
]. To simulate the screws they were considered
completely bound to cortical bone. For the screw-implant contact we considered
a touching contact situation. We also considered the contact between implant and
bone with a 0.3 coefficient of friction.
