Transcript The Temporomandibular joints, muscles, and teeth, and their

Group 9
Te, Krista Isabella V.
Clemente, Paolo
Domingo, Paolo
Luzadio, Cheery
Gutierrez, Juan Antonio
Primary teeth should be in normal alignment
And occlusion shortly after age of 2, with all
the roots fully formed by the time the child is
3 years old.
After a teeth have fully erupted and have
assumed their respective positions in the
arches, the rapid development of the jaws
is sufficient to create a slight space between
some of them.
Separation of anterior teeth because
of the
process that is caused by the growth
of the
jaws and the approach of the
permanent
teeth from the lingual side.
TEMPOROMANDIBULAR
ARTICULATION
- An example of diathrosis and its
movements are a combination of
gliding movements and a loose hinge
movement.
- The osseous portions of the joints are the
anterior portions of the mandibular fossa
and articular eminence of the temporal
bone and the condyloid process of the
mandible.
-Articular disc: interposed between the
condyle and temporal bone.
* acts as a cushion; for support
* dense collagenous connective tissue
MANDIBULAR FOSSA
- Oval or oblong depression in the temporal bone just
anterior to the auditory candl.
- Bounded anterior by the eminentia articularis
externally by the middle root of the zygoma and the
auditory process and posteriorly by the zygopanic plate
of the petrous portion of the bone.
CONDYLOID PROCESS
- Convex on all bearing surfaces, althoug somewhat
flattened posteriorly, and its knoblike form is wider
lateromedially than anteroposteriorly.
- The condyle is perpendicular to the ascending ramus of
the mandible.
JOINT CAPSULE
- TMJ is enclosed in a capsule that is attached at the
border of the articulating surfaces of the mandibular
fossa and eminence of the temporal bone and to the
neck of the mandible.
- Anterolateral side of the capsule may be thickened to
form a band
→ temporomandibular ligament
- It appears to originate on the zygomatic arch and to
pass backward to attach on the lateral and/ or distal
surface of the neck of the mandible.
MANDIBULAR LIGAMENT
- Accessory ligament are considered part of the
masticatory apparatus, including yellow
stylomandibular and sphenomandibular articulation,
although they may stabilize the articular system
during jaw movements.
- Sphenomandibular ligament: from the angular spine of
the sphenoid bone and from the petrotympanic
fissures and ends broadly at the lingual of the
mandible.
- Otomandibular ligaments: connect the middle ear and
temporomandibular joint.
- Articular disc: interarticular dick consists of fibrous
tissue shaped to accommodate the shape of the
condyle and concavity of the mandibular fossa.
- Thicker anteriorly and posteriorly and a central zone.
- Superior ad inferior heads of the lateral pterygoid
fovea of the mandible w/ a part of the superior head
inserting into the disk and capsule.
MANDIBULAR POSITIONS
- Tooth determined position
- Centric relation: defined as maximum intercuspation
of the teeth
- Centric relation: jaw to jaw relation determined by the
condyles position of the mandible in w/c the condyles
are in their upperment midmost position in the
mandibular fossae and related anteriorly to the distal
slope of the articular eminence.
 - Rest position: postural position of the mandible
determined largely by neuramuscular activity and to a
lesser degree by the viscoelastic properties of the
muscles.
MUSCLES
 Mastication functions, as well as speaking and
swallowing, involve reflex contraction and relaxation of
the muscles of mastication whose activity is initiated
voluntarily.
 The masticatory muscles concerned with mandibular
movements include the lateral pterygoid, digastric,
masseter, medial pterygoid, and temporalis muscle and
also the mylohyoid and the geniohyoid muscles.
Lateral Pterygoid Muscle
 Origin:
 Inferior head: outer surface of
lateral pterygoid plate
 Upper or superior head:
greater sphenoid wing
 Insertion: anterior surface of the
neck of the condyle.
 Note! There is an insertion of
some fibers to the capsule of the
joint and to the anterior surface of
the articular disc.
 Inervation: nerve V
 Action:
 The Lateral Pterygoid is anatomically suited for
protraction, depression and contra lateral abduction and
may also be active during other movements for joint
stabilization.
Superior Head
1.
2.
Active during various jawclosing movements only as
chewing, clenching of teeth
and during swallowing.
Positions or stabilize the
condylar head and discs
against the articular
eminence during mandibular
closing
Inferior Head
1.
2.
Active during jaw-opening
movements and protrusion
only
Assists the translation of the
condyle downward, anteriorly,
and contra laterally during
jaw opening.
Masseter
Muscle
arch to ramus and body of
 Origin: from zygomatic
the mandible.
 Insertion: from the region
of the second molar on
the lateral surface of the
mandible to the posterior
lateral surface or the
ramus.
 The superficial part of the
masseter muscle is
separated distinctly only
from the deeper layer of
the muscle at the
posterior upper part of the
muscle.
 Partial coverings:
 Platysma Muscle
Activated during firm clenching
in some individuals and
sometimes active in facial
expressions (because it has some
insertion in the orbicular muscle)
 Risorius Muscle
 Is affected by emotions and is
active in facial expressions.

 The masseter muscle is covered partly
and to a variable degree with the parotid
gland tissue.
 Action:
 Active during forceful jaw closing
and may assist in protrusion of
the mandible.
 The center of lower third of the
masseter muscle is about 2 to 3 cm
from the anterior border
sternocleidomastoid muscle, which
contracts during clenching in some
individuals.
 Innervation: fifth nerve (masseter
nerve)
 Zygomaticomandibular Muscle
 Origin: Inner surface of the
zygomatic arch
 Insertion: Coronoid process
 It may be an antagonist to the
posterior temporalis and a
synergist for the lateral pterygoid
muscle.
Medial
Pterygoid Muscle
 Origin: Medial
surface of the lateral
pterygoid plate and
from the palatine
bone
 Insertion: medial
surface of the angle of
the mandible and on
the ramus up to the
mandibular foramen.
 Action:
 Elevation and lateral positioning of the mandible
 Active during protrusion
 Innervation: a branch of the mandibular division of
the fifth nerve.
Temporalis Muscle
 Fan shaped muscle that
passes the zygomatic arch
 Origin: temporal fossa
 Insertion: anterior border
and mesial surface of the
coronoid process of the
mandible and along the
anterior border of the
ascending ramus of the
mandible.
 The anterior fibers extends
along the anterior ramus
almost to the third molar.
 Innervation: temporal branches of the mandibular
division of the fifth nerve.
 The muscle has 3 component parts and appears to
behave as if it consisted of 3 distinct parts.
 Action:
 Principal positioner of the mandible during
elevation.
Anterior Part
Posterior Part
1.
2.
Active in retruding the
mandible
Act as an antagonist to the
masseter in retruding jaw
1.
2.
Active in clenching
Act as a synergist with the
masseter in clenching
Digastric
Muscle
 There is a tendon
between the anterior and posterior




digastric muscle that is attached by a hooplike strip of
fascia to the hyoid bone
The attachment of the anterior digastric muscle is at or
near the lower border of the mandible and near the midline
The anterior digastric muscle is covered by platysma
muscle, and beneath lie the mylohyoid and geniohyoid
muscles.
All of these muscles are considered to be active during
various jaw opening.
Innervation:
 Anterior digastric muscle: A mylohyoid branch of the mandibular
division of the fifth nerve
 posterior digastric muscle: The digastric branch of the fascia nerve