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

DuBrul 1975, Kurokawa 1986). The horizontal part limits
retrusion (Hylander 1992) as well as laterotrusion (DuBrul
1980) and thereby protects the sensitive bilaminar zone
from injury. The vertical part of the lateral ligament, on the
other hand, limits jaw opening (Osborn 1989, Hesse and
Hansson 1988). The superficial portions of the lateral ligament
contain Golgi tendon organs (Thilander 1961). These
nerve endings are very important for the neuromuscular
monitoring of mandibular movements (Hannam and Sessle
1994, Sato et al. 1995). For this reason, anesthetizing the lateral
portion of the joint permits a 10-15% increase in jaw
opening (Posselt and Thilander 1961).
Ligaments of the Masticatory System 29
The stylomandibular ligament is a part of the deep fascia of
the neck and runs from the styloid process to the posterior
edge of the angle of the mandible. While part of the ligament
inserts onto the mandible, its largest part radiates into
the fascia of the medial pterygoid muscle (Sicher and
DuBrul 1975). Although the stylomandibular ligament is
relaxed during jaw opening, it restricts protrusive and
mediotrusive movements (Burch 1970, Hesse and Hansson
1988). Even so, it should prevent excessive upward rotation
of the mandible (Burch 1970), which sometimes causes
problems in patients with a significantly reduced vertical
dimension.
Stylomandibular ligament
66 Situation with jaws closed
Lateral view of a macroscopic
anatomical preparation approximating
the habitual condylar position.
The ligament runs from the
styloid process (1) to the posterior
border of the angle of the jaw. In
this mandibular position the ligament
(arrows) is essentially free of
tension.
Chronic nonphysiological loading
(Fig. 68) can lead to insertion tendinosis
(Ernest syndrome; Brown
1996).
67 Situation during rotational
jaw opening
Preparation shown in Figure 66
after the initial opening rotation.
Rotational movement of the
condyle against the articular protuberance
causes a relaxation of the
ligament (arrows). With further
rotational opening, the angle of the
jaw would swing farther posteriorly
and allow even more slack in the
ligament.
68 Situation during translation
Same preparation following anterior
translation (= protrusion). Anterior
translational movements in the
temporomandibular joint always
increase tension in the ligament
(arrows). This helps to protect more
sensitive structures (such as the superior
stratum) from overextension
during protrusion. Excessive closing
rotation of edentulous jaws can
likewise produce tension in the ligament.