Different mandibular movements /certified fixed orthodontic courses by Indian dental academy

DIFFERENT MANDIBULAR MOVEMENTS

INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

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INTRODUCTION

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The masticatory system is extremely complex. It is made up of
bones, muscles, ligaments and teeth. Movement of mandible is
regulated by neurologic controlling mechanism
Mandible performs habitual movements, border movements,
opening movements, closing movements, protrusive and lateral
movements.
The main influences on normal jaw movements are the teeth
the joints and the surrounding muscle and ligaments.

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A basic knowledge of masticatory system starts with
temporomandibular joint, since it is the centre of structural and
functional interrelationships.
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TMJ ANATOMY

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Condyles articulate with temporal bone and are
located in elliptical concave depression called the
glenoid fossa in which they travel forward, from side to
side. Between the dome shaped concavities in the
temporal bones and the condyles are interposed the
interarticular fibrocartilage, the meniscus, which are
attached at their margins in the articular capsule. The
meniscus divides the joints into upper and lower
compartment is chiefly a gliding motion. The
movement in lower compartment is hinge like. The
directional movements of the mandible are results of
combined action occurring simultaneously in both
fossa.

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MUSCLES FOR MANDIBULAR MOVEMENT
The muscles involved in mandibular movements are
muscles of mastication, and suprahyoid muscles.
1)Temporalis
Origin
From temporal fossa, excluding the zygomatic bone.

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Insertion
Coronoid process and along the anterior border of
ascending ramus of mandible.
Action
Normally, the anterior fibers may contract shortly before
the rest of the fibers contract when elevation of mandible begun.
The posterior fibers of one side are active in abductive
mandibular movements of the same side, but bilateral retraction
of the mandible from a protruded position involves all fibers of

Temporal muscle, elevation of
mandible


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2) Masseter
This muscle is rectangular.
Origin
Zygomatic arch and Coronoid process.
Insertion
on the lateral surface of mandibular to the lower one
third of the posterior lateral surface of ramus of the
mandible and Coronoid process.
Action
Mandibular elevation is principle function. Although, it
may assist in simple protraction and plays a dominant
role in elevation if the mandibular is being protracted.

Masseter muscle, elevation of
mandible


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3) Medial pterygoid
muscle
Origin
Pterygoid fossa
Insertion
Medial surface of the angle of mandible and adjoining
part of the ramus of mandible.
Action
Elevation and lateral position of mandible
In protrusion of mandible

Medial pterygoid muscle


4) Lateral pterygoid
 Origin
 Two origins
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One head of muscle originates in the outer surface of lateral
pterygoid plate while a smaller and upper head originates from
greater sphenoid wing.
 Insertion
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Anterior surface of neck of condyle. Also some fibers inserted
into the capsule of join and to the anterior aspect of articular
 The pterygoid muscle appears to be concerned with all degrees of
protraction and opening movements of mandible.
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It is also active during lateral movements but is assisted by the
masseter, med pterygoid and anterior posterior parts of temporal
muscle.
 Action
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Protraction of condyle and at the same time drawing the disc
forward.

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The pterygoid muscle appears to be concerned with all
degrees of protraction and opening movements of
mandible.
It is also active during lateral movements but is
assisted by the masseter, med pterygoid and anterior
posterior parts of temporal muscle


Lateral pterygoid muscle, protrusion
of mandible


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Muscles of depression

There are three groups of muscles that act to depress
mandible.
 Suprahyoid
1. Diagastric
2. Genyohyoid
3. Mylohyoid
4. Stylohyoid
 Platisma act as a group and are primary movers in
opening of mandible.
 Infrahyoid – act to stabilize hyoid bone so the
suprahyoid group can be effective.
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The third group i.e. lateral pterygoid pull the
condyles forward or medial ward as the other group act.
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LIGAMENTS OF TEMPOROMANDIBULAR
JOINT
Lateral ligament of TMJ : limit amount of rotation
of mandible and protract retrodiscal pad from posterior
movement of condyle.
Sphenomandibular ligament :limit separation
between condylar process and the disc.
Stylomandibular ligament: limit separation between
condylar process and the disc as well as limit protrusive
movements of mandible.


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MANDIBULAR MOVEMENTS
Mandibular movement occurs as a complex series of
interrelated three dimensional rotation and transitional
activities. It is determined by combined and simultaneous
activities of both temporomandibular joints
Two types of movement occur in the TMJ.
1)Rotational movement
2)Translational movement
Rotational movement
Movement of body about its axis is called as rotation.
Rotation occurs when mouth opens and closes around a
fixed point or axis within the condyles.
Rotational movement occurs in inferior joint cavity,
between the superior surface of the condyle and the interior
surface articular disc. Rotational movement of mandible
occurs in all three reference planes.

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1.Horizontal axis of
movement : is an
opening and closing
motion. It is referred as
hinge movement,and the
horizontal axis around
which it occure is called
as hinge axis


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2.Vertical axis of
rotation: one condyle
moves anteriorly out
of the terminal hinge
position with the
vertical axis of
opposite condyle
remaining in the
terminal hinge
position.


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3. Sagittal axis of
rotation: one condyle
moves inferiorly while
other remains in
terminal hinge
position.


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Translational movement
This movement is defined as movement in which
every point of moving object has simultaneously the
same velocity and direction. If occurs when the
mandible brought forward during protrusion. The teeth
condyles and the rami all move in same direction and to
the same degree.
Translation occurs in the superior joint cavity
between the superior surface of the articular disc and
the mandibular fossa.

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Border movement
The maximum amount of movement in any plane
or direction is termed the border movement. Within the
confines of the border movements there is an extremely
wide range of movement called intraborder movement.
Most mandibular movement occurs as intraborder
movements. Function at the border limits is usually
demonstrated during parafunctional activities such as
bruxism or wide opening yawning
Border movement demonstrates the movement from
centric occlusion backward to centric relation and
forward to protrusive border movement. The
lowermost point in the point of maximum opening
from where the mandible can be taken to all border
movements

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Physiologic rest position
The position assumed by mandible when the head
is in an upright position, the muscles are in equilibrium
in tonic contraction and condyles are in a unstrained
neutral position is the physiologic rest position of
mandible.
The jaws are not clamped together but, they are
separated by rather constant distance, the muscles are
not in active function, a limited number of fibers are
apparently still contracting to maintain the relaxed
position of the mandible and posture of the head

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Centric mandibular movements
Centric relation
Centric relation is the most posterior position of
the mandible relative to the maxilla at the established
vertical dimension.
Centric relation is not a resting or postural position of
the mandible. Contraction of muscles is necessary to
move and fix the mandible in it
Centric occlusion
Centric occlusion is relation of opposing occlusal
surfaces that provides maximum intercuspation or
planned contact
Once centric relarion is established centric occlusion
can be built to coincide with it or to provide a broad
area of tooth contact in this position.

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Eccentric mandibular movements
Any relation of the mandible to the maxilla other
than centric relation is an eccentric relation.
Eccentric mandibular movements are protrusive
and lateral movements
Protrusive movement
Protrusive relation is the relation of the mandible to
the maxilla when the mandible is thrust forward.
The mandible translate in forward and downward
direction during protrusive movement.
The orbit produced by centers of right and left
condyles during protrusive movements is referred as
protrusive condylar path

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. When the protrusive condylar path projected on to the
sagittal plane, it is called sagittal protrusive condylar
path
The muscles responsible for a straight protrusive
movement are external pterygoid muscles acting
simultaneously.
During protrusive movements, the mandibular anterior
teeth protrude forward and downward, disocluding the
posterior teeth. The orbit of the incisal point from
maximum intercuspation to edge to edge occlusion is
referred to as protrusive incisal path.

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Lateral movement
Lateral movement of mandible occurs when one
condyle rotates within TM fossa and the other condyle
translates forward and inward.
The translating condyle is called the non-working
condyle and the rotating condyle is called the working
condyle.
The lateral movement from occlusal position and back
again is asymmetric.
This movement is mainly turn to one side and only a
very slight bodily lateral translation of entire mandible.
The direction of lateral movements is determined by
external – pterygoid muscle on the non-working side
and by deep capsular ligaments of the condyle on
working side.

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Opening and closing movements
On opening, the mandible rotates around a horizontal
axis of rotation which passes approximately through the
centers of two condyles.
Retruded opening and closing
With effort and patience the mandible can be
pulled back and made to rotate about an axis through
the condyles which is rotational and involves no
translation.
Bennett movement
Bennett in 1908 studied the working condylar path
and called it ‘Bennett movement’ now referred to as
laterotrusion. Bennett movement is a bodily side shift
of mandible that occurs during lateral movement.

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During lateral movement working condyle rotates and
moves slightly outward. This movement is between 2-4
mm.
Functional movements
Functional mandibular movement included all
natural and characteristic movement occurring during
mastication, swallowing, speech and respiration.
Much of the functional movements of the
mandible take place inside the physiologic limits
established by teeth, TMJ, muscles and ligaments.
Among the functions of masticatory system swallowing
and respiration are innate where as chewing and speech
are learned.

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Parafunctional mandibular movements

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Parafunctional movements of the mandible are
activities that serve no useful function and are
potentially harmful to the dentition and its contagious
structures. They can result in tooth mobility, migration,
excessive wear or fracture, PDL widening. TMJ pain,
muscle pain, restricted mandibular movements.
ex. Bruxism
Normal person masticate with chewing strokes that
are well rounded, within definite borders, and less
repeated.
In bruxism the strokes are much shorter and slower
and have an irregular but repeatable pathway appear to
relate to the altered functional movement of the
condyle which the disorder is centered.

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CONCLUSION
The mandibular movement is considered as
the chewing apparatus of masticatory system. It
should be kept in mind that mandibular
movements occurs besides mastication like in
the digestive and respiratory acts, vocal
performances and more or less every day human
activities behaviors.

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Different mandibular movements /certified fixed orthodontic courses by Indian dental academy

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