ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

processing application STL Model Creator programmed in a numerical computing
environment (Matlab 2010, MathWorks, Natick, MA, USA) to construct the 3D STL
model of the mandible segment [6, 7]. Fig. 2 shows the STL models of both segments.
Because of the very complex geometry of the inner trabecular architecture, which is
highly time consuming from hardware point of view, only a limited volume
representing the immediate vicinity of the future implant was finally created (6-mm
thick segment was further limited by the mandibular canal). For the implant/bone
interaction study the screw implant of the Branemark type (diameter 3.8mm, length
11mm) was chosen as a typical representative of dental implants. The geometry model
of this implant was created in CAD software SolidWorks 2010 (Dassault Systems,
Vélizy-Villacoublay, France) - see Fig. 2.
2 mm
a) b) c) d)
Fig. 2. a) Implant geometry; b) Model in buccolingual section; c) FEM mesh;
d) Model with the bone layer around the implant (sectional view)
The final geometry model was created by assembling the implant and the bone together.
In this way two models were created: One with the lower BVF and the other with the
higher BVF. Two additional models were created by adding a 0.1mm-thick layer of the
bone covering the implant (Fig. 2d). This layer represents the phenomenon which
accompanies the osseointegration, i.e. overgrowing the bone around the implant.
Therefore four final models were created for analyzing four cases: 1st case with lower
BVF and without the bone layer around the implant (labeled as BVF0.149_00), 2nd
case with higher BVF and without the bone layer around the implant (BVF0.377_00),
3rd case with lower BVF and with the bone layer around the implant (BVF0.149_01)
and 4th case with higher BVF and with the bone layer around the implant
(BVF0.377_01).
The finite element method was used for the computational solution and the software
Ansys 12.0 (Ansys Inc., Canonsburg, PA, USA) for the practical realization of the
calculations. All four cases were discretized by 10-node quadratic element SOLID187
with global size ranging from 0.01 to 0.5mm; the contact between the bone and the
implant was modeled using elements CONTA175 and TARGE170. Total number of
elements in all four cases oscillates around 7.5 million with approx. 10 million nodes.
Material properties of the bone tissue were modeled using homogeneous isotropic
linearly elastic material model. Despite the fact that the bone is composed of two types
of tissue, i.e. of the cancellous bone and of the cortical bone, the assumption that the
mechanical properties of these two tissues are same at the microlevel was adopted [8].
In this study typical values E = 13700 MPa and µ = 0.3 were used [9]. The same
material model was used also for the dental implant which is made of titanium alloy.
For this component E = 110 000 MPa and µ = 0.3 [10].