Biomedical Engineering Reference
In-Depth Information
1
2
4
3
Fig. 3
Geometry of the temporal and mandibular surfaces (Bones
left
and model
right
)
2.1.2
Geometry of Articular Surfaces, Nature of Contacts
Geometric readings were taken of the bony areas at the end of dissection. The results
established at this time were later confirmed in the 27-case statistical study [
17
].
The functional temporal articular surface consists essentially of the temporal
slope (Fig.
3
)
.
Tension in the external lateral ligament limits the extent of the contact
zone around the condyle eminence. Accidental anterior luxation and the blocking of
the mandibular fossa in the mandibular condyle in the zygomatic fossa result from
ligament distension or even rupture.
The temporal condyle, the root of the zygomatic arch, forms a double convex
eminence, transversally and from front to back (frontal and sagittal planes). It
extends forwards along an almost plane surface and backwards towards the glenoid
fossa, which is doubly concave.
The glenoid fossa is about
7mm
deep and the walls are
1mm
thick at the bottom
of the fossa. Around the condylar eminence, cortical thickness can be
10 mm
.
Only the anterior zone of the mandibular condyle is involved during contact.
The condyle head, which is doubly convex, very often seems to be almost ellipsoid.
The horizontal view of the semi-mandible shows an angle of about
90
ı
between the
transverse axis of the condyle and the lateral axis of the mandible. When viewed
from behind, the angle formed by the transverse axis and the rising branch is also
about
90
ı
.
Except in pathological situations (perforation of the meniscus), the mandibular
condyle and the temporal area do not come into direct contact. The meniscus, which
is deformable, is interposed and takes on the shape of the two articular surfaces to
modify the distribution of pressure on contact.
2.1.3
Elementary Contacts, First Models
When plane opening and protrusion movements are extremely wide they displace
the centre of the mandibular condyle by about 22 mm. The relative position of the
