MANDIBULAR MOVEMENT

MANDIBULAR MOVEMENT
OPINING CLOSING PROTRUSION
RETRUSION
LATERAL
Dr Sahar Elkholy

Factors that regulate the mandibular
movements:
• 1- TEMPROMANDIBULAR JOINT.
• 1- TEMPROMANDIBULAR JOINT.
• 2-MUSCLES.
• 3-AXIS OF ROTATION.
• 4-OPPOSING TEETH CONTACT..

Temporomandibular Joint (TMJ)
Composed of
Condyle
Mandibular fossa
Articular capsule
Synovial tissue
Articular disc
Ligaments
3

Fig. from atlas of anatomy

C0NDYLE
• It about two centimeters wide mediolaterally
and one centimetermthik anteroposteriorly.
• Its superior surface is convex from back to
front.
• Medial and lateral ends of condyle called
poles

Fig. from atlas of anatomy

Articular Capsule
Ligamentous capsule surrounds
the joint
Attached to the neck of the
condyle and around the border
of the articular surface of the
temporal bone
anterolateral aspect of the
capsule may thicken form the
Temporomandibular ligament
function as stabilising structure
7

Fig. from atlas of anatomy

Synovial tissue
Synovial cell and connective tissue
covering the lower and upper-joint
spaces
Synovial fluid, acts as a lubricant and
may participated in nutritional and
metabolic interchange for central part.
9

Temporomandibular
ligament
Ligaments
extend from base of
zygomatic process of
the temporal bone
downward and oblique
to the neck of the
condyle
10

Ligaments
Stylomandibular
ligament
From styloid process
and runs downward
and forward to attach
broadly on the inner
aspect of the angle of
mandible
11

Ligaments
Sphenomandibular ligament
arising from the angular
spine of sphenoid bone
and petrotympanic
fissure, ending at lingula
of mandible
12

MUSCLES

MASTICATORY MUSCLES
MASSETER TEMPORAL MEDIAL PTERYGOID LATERAL PTERYGOID

Fig. from atlas of anatomy

Temporal
Massete
r
Medial petrygoid
lateral petrygoid

superior lateral petrygoid
superior lateral petrygoid
inferior lateral petrygoid

Slide 19
D1
D2
superior lateral petrygoid
Dr.Sahar, 3/18/2007
inferior lateral petrygoid
Dr.Sahar, 3/18/2007

Masster muscle
• Superficial layer
– O : lower border of malar
bone, Zygomatic arch &
zygomatic process of maxilla
– R : Downward and Backward
– I : Angle of mandible and
inferior half of the lateral side
of mandible
20

Masster muscle
• Deep layer
– O : Internal surface of
zygomatic arch
– R : Downward (vertical)
– I : Ramus of mandible and
base of coronoid process
– 50 degree between 2 layers
21

Temporalis muscle
• 3 bundles
– Anterior bundle (vertical fibre)
–Action: Mandible elevator
(Close jaws), crushing and
chewing at C.O.
–Inaction: Mandible depression
(except Max. Opening and
Opening against resistance)
22

Temporalis muscle
– Posterior bundle (Horizontal
bundle)
Action: Mand. retraction
and positioner
Inaction: Mand. depression
and protrusion
– Intermediate bundle
Action: Protrisive movement
23

Med. Pterygoid muscle
O : Pterygoid fossa and medial
surf. of the lateral pterygoid
plate
I : Inf. + Post. border of ramus
and angle of mand.
R : Downward and Backward
N : Medial Pterygoid nerve
24

• Superior head
Lat. Pterygoid muscle
O: Wing of sphenoid and
infratemporal crest
R: Downward and Backward
• Inferior head
O: Lateral surf. of lateral
pterygoid plate
R: Upward and backward
25

Lat. Pterygoid muscle
Insertion of superior and inferior
heads
– Ant. portion of the condylar
neck (pterygoid fovea)
–
Ant. surface of the articular
capsule
– Ant. Border of the disk
Function
– Open the jaws, protrude and
lateral movement with moving
disk forward
26

• Superior head
Lat. Pterygoid muscle
Synergistic with elevator
group of muscle for closing
and clenching
• Inferior head
Synergistic with suprahyoid
group of muscle for opening
jaw
• Nerve supply
Lateral pterygoid nerve
27

• Superior head
Lat. Pterygoid muscle
Synergistic with elevator
group of muscle for closing
and clenching
• Inferior head
Synergistic with suprahyoid
group of muscle for opening
jaw
• Nerve supply
Lateral pterygoid nerve
28

AXIS OF ROTATION

• HORIZONTAL AXIS
HORIZONTAL AXIS

• VERTICAL AXIS
VERTICAL AXIS

SAGITAL AXIS
SAGITALAL AXIS

Opposing Tooth Contact
33

• The movements of the condyle during
mandibular movement are either :
• - Rotation (in lower compartment)
• Rotational movements take place in the
lower compartment of the T.M.J. between
the superior surface of the condyle and the
inferior surface of the articular disc
•

• b- Translation (in upper compartment)
Translation or gliding movements of the
mandible takes place in the upper
compartment of the T.M.J. between the
superior surface of the articular disc as it
moves with the condyle and the inferior
surface of the glenoid fossa.

MANDIBULAR MOVEMENTS
• 1-Opening and closing: (depression and
elevation of the mandible):
This movement starts from the rest position
to the maximum opening position. At the
beginning of the opening movement, there is
a rotation in the lower compartment of the
TMJ.

• The mandible can make pure rotational
movements through an arc of 10-20 mm with
further opening a gliding movement occurs in
the upper compartment.
• For the closing movement, the mandible
moves from the maximum opening position
with a reverse movement back to the rest
position.

2- Forward and backward (protrusive
and retrusive)
• The condyles together with their articular
discs move as one unit downwards and
forwards along the glenoid fossa and the
articular eminence.
• Protrusive movements are brought about by
the contraction of the external pterygoid
muscles on each side.

Christensen’s phenomenon
• When the mandible moves forward to an
edge to edge position a separation occurs
distally between the distal arches or
occlusion rims. This distal separation of teeth
is the result of the forward and downward
glide of the condyle on the articular
eminence.

3- Lateral movement (sideways)
• The right and left lateral movements of the
mandible form the rest position and back
again to the same position are asymmetric.
When the mandible moves towards the right
side, the condyle on this side rotates mainly
with a very slight bodily lateral translation
(Bennett movement).

INCISAL PATH
• The incisal path forms an angle with the
horizontal plane that differs form one person
to another with an average 10 degree. The
deeper the overbite, the more is the incisal
angle. While the wider the overget, the less is
the incisal angle.

Condylar Path
• A-The lateral condylar path is the path
followed by the condyle in the glenoid fossa
when a lateral movement is made.
• B-Protrusive condylar path
• B-Protrusive condylar path is the path
followed by the condyle when the mandible
is moved forward from its centric position.

• It varies in individuals and also in the same
individual from the left to the right side. It
ranges between 30°-40°.

Importance of studying mandibular
movements
• 1- designing, selection, and adjustment of
articulator.
• 2-eveloping tooth form for dental restorations.-
• 3-Understanding the basic principles of occlusion.
• 4-Diagnosis and treatment of TMJ disturbances .
• 5-Proper selection of teeth.
• 6-Arrangement of artificial teeth .

MANDIBULAR POSITION

a-REST POSITION
• 1- It is the position of the mandible related to
the cranium in the resting state. Muscles and
joints determine this position. It is a
physiological position.
• 2- All mandibular movements start from and
end at this position.

est vertical dimension

Slide 50
D3
rest vertical dimension
Dr.Sahar, 4/22/2007

-Intercuspal position (ICP) (Centric
occlusion)
• 1- It is the position of the mandible
determined by bilateral maximal contact
(intercuspation of natural teeth). It is the most
important contact position for stomatognathic
functional position.

• 2- This position is used during chewing
and swallowing to stabilize the mandible,
and allow the suprahyoid muscles to pull
the hyoid bone and trachea upward and
forward to prevent inhalation of food,
drinks and saliva

• 3- Setting of artificial teeth and construction
of artificial occlusal surfaces are planned at
this intercuspal position if the remaining
natural teeth are enough to determine this
position correctly.

Importance of studying mandibular
movements
1- Designing, selection, and adjustment of articulator.
2-Developing tooth form for dental restorations.
3-Understanding the basic principles of occlusion.
4-Diagnosis and treatment of TMJ disturbances
5-Proper selection of artificial teeth.
6-Arrangement of artificial teeth.