Biomedical Engineering Reference
In-Depth Information
Max: 0.482MPa
Max: 15.24MPa
Max: 13.75MPa
Max: 0.491MPa
S, Mises
(Avg: 75%)
+
1.524e
+
01
+
1.000e
+
01
+
5.000e
+
00
+
5.000e
-
01
+
4.000e
-
01
+3
.000e
-
01
+
2.000e
-
01
+
1.000e
-
01
+
8.000e
-
02
+
6.000e
-
02
+
4.000e
-
02
+
2.000e
-
02
+
0.000e
+
00
(a)
(b)
(c)
(d)
FIgure 22.5
(See color insert.)
The von Mises stress distributions of the disc under the three occlusions
(the maximum stresses were listed): (a) central occlusion (left disc), (b) anterior occlusion (left disc), (c) right
side molar occlusion (left disc), and (d) right side molar occlusion (right disc).
Similar to the condyle, the stress of the left disc was significantly greater than the right side under
the right side molar occlusion. The average von Mises stress of the left disc was 0.5 MPa in the
anterior band, 3.2 MPa in the intermediate zone, and 1.4 MPa in the posterior band. The average von
Mises stress of the right disc was 0.32 MPa in the intermediate zone and much smaller in the ante-
rior and posterior bands (Figure 22.5). The stresses in the dorsal side (contacting with the articular
fossa) were less than those in the ventral side (contacting with the condyle).
The stress of the articular fossa-eminence was much less than the condyle and disc under the
three occlusions. The maximum stress of articular fossa-eminence also occurred at the right molar
occlusion with a value of 0.12 MPa located at the posterior articular eminence of the left articular
fossa-eminence.
22.3.3 a
nalySiS
and
a
pplication
The stress of the anterior condyle was greater than at other regions under the three occlusal
conditions, consistent with the related research (Beek et al. 2001; Liu et al. 2008). In the same
sagittal plane, most regions of the ventral disc contacted the condyle, but only small regions of
the dorsal disc contacted the articular fossa-eminence, similar to results reported by Tanaka
et al. (2001b). The fiber network and proteoglycans of the discs dispersed the load between the
condyle and articular fossa through their interaction, consistent with the physiological structure
and the function of the disc. The discs can buffer shocks imposed on the TMJ and protect the
tissues of the brain. The maximum disc stress occurred at the intermediate zone, which is clini-
cally susceptible to perforation and rupture (Tanaka et al. 2004; del Palomar and Doblare 2007,
2008; Liu et al. 2008). This phenomenon showed that the collagen fibers in the intermediate zone
of the disc absorbed a large amount of energy and acted as a stress buffer, consistent with the
structure and weight-bearing characteristics. The stress of the posterior articular eminence, the
functional area of the TMJ, was greater than at other regions. Therefore, the models of this study
can be deemed valid.
The stresses of the condyle under the anterior occlusion and the right molar occlusion were sig-
nificantly greater than the central occlusion. Stress concentrations occurred at some areas. The ten-
sile and compressive stresses of the disc under the anterior occlusion were 4.0 MPa and 17.4 MPa,
respectively, greater than the magnitudes under the central occlusion and the right side molar occlu-
sion. This can explain why some patients with TMD feel pain when biting using anterior teeth. The
deformation of the left disc was more than the right disc under right molar occlusion, so chewing
with both sides of the molars should be recommended in order to avoid facial deformities. Likewise,
the stresses of the contralateral TMJ were significantly greater than the chewing side under the
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