TMJ Disorders and Orofacial.pdf - E-Lib FK UWKS

Anatomical Disk Position
In a physiological temporomandibular joint, the pars posterior
of the disk lies on the superior portion of the condyle.
In the "centric condylar position" the thinnest part of the
disk, the pars intermedia, is located between the anterosuperior
convexity of the condyle and the articular protuberance
(van Blarcom 1994). This finding is also supported by
studies using measurements and mathematical models
(Bumann et al. 1997, Kubein-Meesenburg 1985). The pars
anterior lies in front of the condyle (Steinhardt 1934, Wright
and Moffet 1974, Scapino 1983). The disk is attached to the
Function Moveable joint
surface Load distribution
Progressive adaptation
Reversible deformation
Regressive adaptation
Permanent deformation
Disk perforation Ossification
Anatomical Disk Position 23
medial and lateral poles of the condyle by means of the
transversely aligned collagen fibers of the pars anterior and
pars posterior. Viewed by itself, this anatomical arrangement
with the condyle allows a great degree of movement
during active mandibular movements (see p. 46). The disk
exhibits viscoelastic properties under compressive loads. Its
resistance is strengthened by the arrangement of the collagen
fibers (Shengyi and Xu 1991). The elastic fibers within
the disk serve primarily to restore the shape of the disk after
a load has been removed (Christensen 1975).
48 Anterosuperior aspect of
the disk-condyle complex
Macroscopic anatomical preparation
of a left temporomandibular
joint showing the relationship between
disk and condyle. The lateral
half of the disk has been removed
fora clearer view. The dorsal border
of the pars posterior is near the region
of the apex of the condyle.
From a functional point of view, this
broad description is not very helpful
for diagnostic purposes because
the physiological position of the
pars posterior depends to a large
extent upon the inclination of the
protuberance.
49 Anterolateral aspect of the
disk-condyle complex
The same preparation in half profile.
Here the pars posterior (1),
pars intermedia (3), and pars anterior
(2) can be clearly distinguished.
Although the posterior border of
the pars posterior lies over the apex
of the condyle, the pars intermedia
is in front of the anterosuperior
convexity (arrows) of the condyle.
The pars anterior is 2.0 mm thick,
the pars intermedia 1.0 mm thick,
and the pars posterior 2.7 mm thick
(Gaa 1988).
50 Function and structural
adaptation of the disk
Functionally, the disk serves as a
"moveable fossa" for the condyle.
Because of its unique tissue structure
it can cushion and dampen
peaks of force. Progressive adaptation
differs from regressive in that
the former is reversible. Strictly
speaking, there is no "positive" tissue
reaction in the disk because
functional loads as well as continuous
nonphysiological loads result in
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