Biomedical Engineering Reference
In-Depth Information
Fig. 16
Comparative displacement on intact and implanted mandible in the y-direction
The magnitudes of the displacements in the y direction in Fig.
16
are small when
compared with those in the z direction. Differences can be seen between the intact
mandible and the TMJ implant mandible. The TMJ implant not only affects the left
region of the mandible. On the left side displacement increased (50% more) and
also the relative displacement between implant and bone.
We observed that the minimum principal stress is the most important design
factor, but the distribution was almost the same as the equivalent stress. On the right
condyle the influence of the TMJ implant increases the stresses on the mandible.
Identical influence was also verified in the frontal mandible region.
The straight implant also generated a high level of tensile stresses near the
first screw, and this was highest compared with the other implants. The highest
magnitude stress was seen on the right condyle, 20.7 MPa, 14% more than on the
intact mandible.
The minimal principal strain on the external mandible surface is in Fig.
17
.The
TMJ implant increases the strain level in the condyle region, similar to the intact
mandible, and affects the right side of the mandible. In the frontal region of the
mandible the TMJ increases the strain on the TMJ side, and increases the bone
formation.
The screw positions are an important factor in the success of mandible kine-
matics. The four screws were considered and the minimal principal strains are
presented in Fig.
18
. These results reveal two different points. First, when we
analyze the influence of screws we observe that the first and last screws are in the
most critical positions. The geometry of the implant and its stiffness lead to critical
strain distribution around these screws.
The principal strain distributions near the screws are shown in Fig.
19
.The
first and last screws present a
strain of 5,330 and 5,610, respectively. To cause
