Biomedical Engineering Reference
In-Depth Information
7.3 Implants
The main purpose of this section is to verify the efficiency of the proposed
remodelling approach in the prediction of the correct final trabecular architecture
when rigid implants are inserted in the bone structure. As in the previous bone
remodelling analyses, the initial bone apparent density is not relevant. All the
studies in this section will start considering an initial maximum apparent density,
and then the remodelling process will continue until a final configuration is
obtained. Nevertheless, the proposed remodelling algorithm is capable of starting
with any initial apparent density. The final result, regardless the initial values, must
be always the same.
Medical implants are devices manufactured to: functionally improve existing
biological structures; to replace lost biological structures; or to reinforce damaged
biological structures. Generally, biocompatible materials cover the implant sur-
face, in order to increase the success rate of the implant osseointegration.
In this section it is studied the bone tissue remodelling due to the insertion of
two distinct types of implants: a dental implant, inserted in the mandibular bone;
and a femoral prosthesis.
7.3.1 Dental Implants
Here, the presented bone tissue remodelling algorithm, combined with the
NNRPIM, is used in the analysis of a single dental implant inserted in a mandible
patch bone, Fig.
7.51
, which corresponds to the position of the first premolar. The
mandible patch is sectioned in two distinct analysis planes, Fig.
7.52
. Each one of
these planes are analysed separately considering a two-dimensional approach. In
both analyses, the obtained trabecular bone architecture shows a good agreement
with mandible/implant X-ray images.
In this section, for all the studied examples, an initial uniform density distri-
bution q
max
app
¼ 2
:
1 g/cm
3
is imposed in order to define the initial bone tissue
material properties using the phenomenological bone tissue material law proposed
in this topic. In all the presented studies it is considered that the Poisson ratio does
not depend on the apparent density, being a constant value: t ¼ 0
:
3. The a and b
parameters, required by the remodelling algorithm to govern the growth and the
decay of the bone tissue, are considered: a = b = 0.01.
7.3.1.1 NNRPIM/FEM Comparison
Considering the section plane indicated in Fig.
7.52
b, a two-dimensional model of
the mandible bone patch was developed, Fig.
7.53
a. The proposed model is based
on a computational model presented in the literature [
27
], which was obtained
