INDIAN DENTAL ACADEMY
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Craniofacial musculature

Presented by:- Dr.

Apurva k.Chitalia

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Contents:introduction
Development of the muscles.
 classification of craniofacial musculature.
 the buccinator mechanis...
Contents:The

temporo mandibular joint
Physiology of muscles.
Reflex of muscles
 myotactic reflex.
Methods to study m...
Contents:









Muscle and growth.
Muscle adaptation in malocclusion
Soft tissue environment of patients with
ma...
Introduction:A

Man to increase the strength of
skeleton has been blessed by 639
muscles which includes 6 million of
musc...
 In

orthodontics and in real life we
judge / diagnose a individual when we
look at him.
 But here when we look at patie...




This is just the static analysis but important
is the dynamic appreciation on how they
function , as they function, ...
 We

orthodontist try to achieve the
perfect equilibrium between the part of
stomatoganthic system which includes
the mus...
Development of muscle.
During the 3rd week of I.U life the embryo undergoes gastrulation to
form a trilaminar disk i.e.
th...








The mesodermal layer is further divided
into:head
paraxial
intermediate
lateral
The mesoderm on either side ...
There are seven of somitomeres approx. In
register with that of the pharyngeal arches.
The skeletal muscles of the head an...


The branchial arches have incomplete clefts
between the arches, the external ectodermal
branchial grooves and internal ...
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Cartilage components derived from
pharyngeal arches are:


1.
2.


Arch I [mandibular arch]:- this is major contributo...


The ventral part of the meckels cartilage
forms a horse shaped structure in the shape
of the future mandible.



The m...
Arch II [hyoid arch]:- this cartilage is
called as the reicherts cartilage
 It dorsal end becomes ossified to produce
the...


The cartilage of the 3rd arch gives rise to
the greater cornu and the inferior part of the
body of the hyoid bone.



...
Muscle components :

They are derived from the cranial
somites and the cells that migrate at
this region from the somitom...
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Arch II: the muscles of facial expression.
These are relatively thinner and have
their origin and insertion in the skin an...
Classification of
muscles:1.
2.




they can be primarily classified as:facial muscles
Muscles of mastication.
The facia...
Muscles of mastication: they are chiefly
concerned with the movements of the
TMJ
 The division reflects the different
emb...
According to moyers:1.
2.
3.

facial muscles
jaw muscles
Portal muscles.

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Characteristics of the facial
muscles: The

primary function is expression of the emotions.
 The facial muscles are capa...
The

facial muscle also contributes to
stabilization of the mandible during
the infantile swallowing and chewing
and swal...
Characteristics of the jaw
muscles:




The mandible being maintained against the
gravity by the stretch reflex of the ...








The head posture also affects the posture of the
mandible for e.g. when there is extension of the
head there i...
But in case where there is Sunday bite
there is no resultant correction probably
because the dorsal position of the
mandib...
Characteristics of the portal
muscles:Portal muscle is the word coined by
Bosma to denote the upper alimentary
tract and t...


The muscles include the muscles of
the tongue [both the intrinsic and the
extrinsic] the soft palate, the
pharyngeal pi...
According to grays:
1.
2.
3.
4.

they are broadly classifies as:
epicranial muscles
circumorbital muscles
the nasal muscu...
The epicranial musculature

1.
2.

The epicranius consists of two main
parts
occipitofrontalis
Temporoparietalis.

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The scalp:

1.
2.
3.
4.
5.

The scalp essentially consists of five
layers i.e.
superficial fascia
connective tissue
epicr...
The superficial fascia in the scalp is firm and
fibro-adipose adherent to the skin and the
underlying epicranius and the a...
The occipito frontalis
It is a broad, musculofibrous layer,
covers the dome of the skull, from the
nuchal lines to the eye...
 Occipital

part: - each of them are thin,
quadrilateral arises by tendinous fibers
from the lat. 2/3rd of the highest nu...


It has got no bony attachments. Its medial fibers are
contiguous with those of the procerus; its intermediate
fibers bl...
Galea aponeurotica:



It covers the upper part of the cranium and
along with the epicranius it forms the
continuous fib...
It is united to the skin by firm, fibrous
superficial fascia; it is connected to the
pericranium by loose aerolar tissue
w...
Action:- the occipital slips draw the
scalp downward , the frontal slips
acting from above raise the eyebrows
and the skin...
The fourth layer of the scalp:
 it is made up of loose aerolar tissue. it
extends anteriorly to the eyelids; and
posterio...
Temporoparietalis:



It is variably developed sheet of muscle that
lies between the frontal part of the occipito
fronta...
Circumorbital and
palpeberal musculature.

1.
2.
3.

The muscle that come under this
heading are:orbicularis oculi
corruga...
The orbicularis oculi:

it is a broad, flat, elliptical muscle that
occupies the eyelids, surrounds the
circumference of ...
The orbital part






it is reddish and thicker than the palpeberal
fasiculi
Origin:-arises from the nasal part of the...


Insertion:-some of the fibers are
inserted into the skin and the
subcutaneous tissue of the eyebrow.
They constitute th...
The palpeberal part


- it is thin and pale. It arises from the medial
palpeberal ligament chiefly from its superficial
b...
The lacrimal part: 




it lies behind the lacrimal sac but separated
from it by the lacrimal fascia.
It is attached to...
The medial palpeberal ligament:- it is
about 4mm in the length and 2mm in the
breadth, is attached to the frontal
process ...


Nerve supply: - temporal and zygomatic
branch of the facial nerve.



Actions: - the orbicularis oculi: - it is the
sp...


During the eye closure there is lowering of
the upper as well as elevation of the lower
eyelid. thus palpeberal part ha...








The lacrimal part of the muscle draws the eyelids
and the lacrimal papillae medially, and exerts
traction on t...


These action of the upper orbital fibers
and their peripheral extension cause
vertical furrowing above the bridge of th...
The corrugator
supercilli:
it is a small pyramidal muscle, at the
medial end of the eyebrows, deep to the
frontal part of ...
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Nerve supply: - the temporal branches of
the facial nerve.
 Action: - draws the eyebrows medially
and downwards
 Togethe...
The nasal musculature:

1.
2.
3.

This group comprises of three
muscles:the procerus
the nasalis
The depressor septi.

www...
The procerus: it is a small pyramidal slip continuous with
the medial side of the frontal part of the
occipitofrontalis.
...
Action: - it draws down the medial angle
of the eyebrow and incidentally produces
wrinkles over the bridge of the nose.
 ...
The nasalis: it consists of transverse and alar parts
which may be continuous at the origin.
 The transverse part:-[compr...








The alar part [dilator naris]—it arises from the
maxilla, below and medial to the transverse part. It
is attac...
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The depressor septi: often regarded as the part of the
dilator nasi; is attached to maxilla
above the central incisor root...
Action: - it assists the alar part of the
nasalis in widening the nasal aperture
while deep inspiration.
 Nerve supply: -...
buccolabial musculature:

1.
2.
3.
4.
5.
6.

These are the muscle slips which control the
shape of buccal orifice and the...
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1.
2.
3.

the depressor and retractors of the
lower lip viz:depressor labii inferioris
depressor anguli oris
mentalis

www...
The levator labii superioris alaeque
nasi

Origin:-it arises from the upper part of the
frontal process of the maxilla and...


the lateral slip is prolonged into the
lateral part of the upper lip, and blends
with the levator labii superioris and
...
The levator labii superioris: Origin:-it starts immediately above the
infra-orbital margin at the lower margin
of the orbi...









Insertion:-Its fibers converge into the muscular
substance of the upper lip between the lateral slip
of the ...
The zygomaticus minor: 





Origin:-arises from the lateral surface of the
zygomatic bone immediately behind the
zygom...


Action:-it elevates the upper lip and also
produces the nasolabial furrow.



Nerve supply: - it is supplied by the
bu...
The levator anguli oris: Origin: it arises from the canine fossa,
just below the infra –orbital margin.
 Insertion:-it is...
Action: - it raises the angle of the
mouth
 It is instrumental in producing the
nasolabial furrow.




Nerve supply: - ...
The zygomaticus major: Origin:-extends from the zygomatic bone
in front of the zygomaticotemporal suture.
 Insertion:-to ...


Actions: - it draws the angle of the mouth
upward & laterally as in laughing.



Nerve supply: - it is supplied by the...
The depressor labii inferioris:
Origin:-it is quadrilateral in shape and
arises from the oblique line of the
mandible betw...
Action - it draws the lower lip downward
and a little laterally in masticatory
activity
 It contributes to expression of ...
The depressor anguli oris: Origin:-arise from the oblique line of the
mandible, below and lateral to the
depressor labii i...
Some of the fibers are directly continuous
with that of the levator anguli oris, and
others accidentally cross to the othe...
The mentalis:
Origin:-it is a conical fasciculus at the
side of the frenulum of the lower lip. It
arises from the incisive...
Action:- it raises and protrude the lower lip
and at same time wrinkles the skin of the
chin.
 It helps in drinking and i...
The buccinator:
it is thin quadrilateral muscle occupying
the interval between the maxilla and the
mandible, in the cheek....
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Between the maxillary tuberosity and the
upper end of the raphe a few fibers arise
from the tendinous band which bridge th...
The fibers of the buccinator converge
towards the angle of the mouth , where
the central fibers intersect each other,
thos...
Relations:it is covered by the buccopharyngeal
fascia and lies in the same plane as
that of the superior constrictor.
 Su...
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Anteriorly, superficial surface of the muscle
is related to the zygomaticus major
risorius, levator and depressor anguli o...
Nerve supply: - supplied by the lower
buccal branch of the facial nerve
 Action: - it compresses the cheek against
the te...
The buccinator mechanism
There is a strong interdependence of
muscles and bone and the major factor
in this environmental ...
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The integrity of the dental arch and its
relation with the same arch and the
opposing arch is maintained by the
morphogene...
Thus stability is dependent on the 1.
Genetic. 2. Environmental 3. Epigenetic
factors
4.
Morphologic
factors
5.
Physiologi...
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

Acc. to Lear and Moorress the enigma
between the dental arch and the muscle
function remains as there are limitations s...
The buccinator mechanism.
The orbicularis oris muscle decussating fibers joins the
right and left fibers in the lips. The...
The pterygomandibular raphe:
It is the interlacing of the tendinous fibers
stretched from the hamulus of the medial
pteryg...
Laterally, it is separated from the
ramus of the mandible by quantity of
fat.
 Posteriorly, it gives attachment to the
su...
The orbicularis oris: Is made of the several strata which
surround the orifice of the mouth but
have different directions....
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Some of the buccinator fibers viz: those
near the middle of the muscle- decussate at
the angle of the mouth; the uppermost...




Fibers are also derived from the levator labii
superioris, zygomaticus major and minor, and
the depressor labii infe...
Within the lips the fibers of the orbicularis
oris are divisible into two fasiculi, the
marginal and the peripheral.
 The...
Finally there are fibers of the muscle bands
that are attached to the maxilla above and
mandible below.
 In the upper lip...


The additional fibers of the lower lip
constitute a slip of incisive labii inferioris, on
each side; the slips arise fr...
Nerve supply: - it is supplied by the lower
buccal and the mandibular marginal branch
of the facial nerve.
 Actions: - it...
The risorius: Origin:-arises from the parotid fascia
 Insertion:-is inserted into the skin at the
angle of the mouth.
 I...
Nerve supply: - is supplied by the buccal
branches of the facial nerve.
 Action: - it retracts the angle of the mouth
and...
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Muscles of the
mastication:-

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


1.
2.
3.

These muscles immediately are
concerned with the movements of the
mandible [and speech],
These muscles are ...
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The masseter: 

A strong layer of fascia derived from the deep cervical
fascia is named the parotid fascia; it covers the...








It is quadrilateral in shape and consists of three
superimposed layers blending anteriorly.
The superficial la...
The middle layer: - it arises from the deep
surface of the anterior 2/3rd and the
posterior 1/3rd of the lower border
zygo...
The middle and the deep layers constitute
to form a cruciate muscle. [Where the
fasiculi run in 2-3 directions]
 As it is...
Nerve supply: - is supplied by the branch
of the anterior trunk of the mandibular
nerve
 Actions: - it elevates the mandi...
The temporal fascia:



It covers the temporalis muscle. It is a strong,
fibrous investment covered, laterally, by the
a...
A small quantity of fat, the zygomatic
branch of the superficial temporal
artery, the zygomatico temporal
branch of the ma...
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The temporalis: 

Origin:-It is a fan- shaped muscle. It arises from
the whole of the temporal fossa [except the part
for...


Insertion:-Its fibers converge and descend into a
tendon which passes thru the gap between the
zygomatic arch and the s...


About its action on the elevation of the
mandible there are lots of studies that
states the temporalis is active in the...
The lateral pterygoid: 

It is a short and thick muscle with two
parts of the head:-

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1.

2.


Upper from the infra temporal surface
and from the infra temporal crest of the
greater wing of sphenoid bone,
Lo...
In the 3rd month of the I.U life the lateral
pterygoid muscle is inserted in the
mesenchyme condensed around the dev.
Cond...
Nerve supply: - it is supplied by the br.
from the anterior trunk of the mandibular
nerve.
 Actions: - it assists in open...
In the closure the backward gliding of the
articular disk and the condyle of the
mandible is controlled by the slow
elonga...




When the medial and the lateral pterygoid act
together than the mandible protrudes so that the
lower incisors projec...
The medial pterygoid: 





It is quadrilateral in shape and consists of two
heads
Deep head:-attaches to the medial su...
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

Insertion:-its fibers pass downwards and
backwards and are attached to a strong
tendinous lamina, to the posterior-infe...


Nerve supply:-it is supplied by the
branch of the mandibular nerve.



Acc. to a study done by Schumacher
et.Al on the...


Actions: - it assists in elevating the
mandible. Acting with lateral pterygoid it
protrudes the mandible.



When the ...
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Palpation of muscles:





The muscles of mastication are palpated for
tenderness or pain during the screening
examinat...
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A

single firm thrust of 1 or 2 seconds is
usually better than many light thrusts.
 During that the patient is asked for...








Posterior region: - palpated above and behind
the ear. Otherwise, the patient is asked to clench
the teeth so ...
 Medial

pterygoid: - palpated at the
intersection of medial surfaces of
mandibular angles. Finger tips are placed
on the...
 The

lateral pterygoid palpation is difficult.
 It is accomplished by placing the forefinger
behind the maxillary tuber...
 The

finding are classified into four
categories.1. Zero: - no tenderness or pain is reported
by the patient,
2. One: - ...
The accessory muscles of
facial expression:The superficial and the lateral
cervical muscles:
1.
2.
3.

These include viz:...
The platysma: 



Origin:-it is a broad sheet arising form the
fascia covering the upper part of the pectoralis
major an...


Action: - when the entire platysma is in
action it diminishes the concavity
between the jaw and the side of the
neck.

...


Its anterior portion i.e. the thickest part
helps in depressing the mandible



It also serves to draw down the lower ...
The accessory muscles.


These are the muscle’s which when
involved assist the main group of
muscles in the function of
s...
The suprahyoid muscles: 1.
2.
3.
4.

The digastric .
The stylohyoid.
The mylohyoid .
The geniohyoid.

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The digastric: It has two bellies that are united by an
intermediate tendon. Hence the name.
 The posterior belly: - it s...
The anterior belly: - it is attached to the
digastric fossa on the base of the mandible
close to the median plane and pass...


Actions: - it depresses the mandible and can
elevate the hyoid bone.



On EMG studies it has been confirmed that
they...
The tongue:

The tongue begins its
activities even before
the birth when it
function the
swallowing of
amniotic fluid. It...




It is relatively larger than the contiguous
structure and assumes posture
interposed between the gum pads rather
tha...
The extrinsic muscles:1.
2.
3.
4.

Hyoglossus---- attached to the hyoid bone.
Styloglossus----- to the styloid process.
Ge...


As stated by kwamura that
protraction, retraction, and lateral
deviation to these muscles along with
the genioglossus i...
The intrinsic muscles








Four in number named acc to their fibers
position. i.e.
Superior longitudinal
Inferior...
 The

tongue being anchored only at one
end so free to move and this freedom
permits the tongue to deform the dental
arch...
Muscular attachments of
the TMJ.:





- It is by far the most complex joint in the body.
It provides for the hinging m...
Articular disc:

The articular disc is composed of dense fibrous
connective tissue devoid of any blood vessels or
nerve f...
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Synovial membrane: 

The capsule of the TMJ is lined on the inner side by a
synovial membrane. It consists of a cellular ...
Ligaments of the joint:








Collateral [discal] ligament: - they attach to the
medial and the lateral borders of t...
Capsular ligament: 





The entire TMJ is encompassed by the capsular
ligament.
They act to resist any medial, lateral...
Tmj ligament:-[lateral ligament]
Functions: - it resists the excessive drooping of
the condyle and acts as a limit to the ...
Accessory ligaments:1.
2.

Sphenomandibular ligament.
Stylomandibular ligament.

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Concept of orthopedic
stability.
 Orthodontic

correction has always been
the correct contact pattern and not the
orthope...


The TMJ consists of the articular disc which is
non vascular and does not elicit pain. But this
does not find the posit...
 The

temporal muscles also stabilize the
Tmj.They have some horizontal oriented
fibers.



The lateral pterygoid also p...


Thus it is defined as, the position in which the condyles
are in their most superioanterior position in the articular
f...
Physical properties of
muscles:
I)

They help in kinetic activity of the
muscles.
elasticity:-elasticity of a body is
rel...



1.
2.
3.
4.


A relaxed muscle can withstand only a
certain amount of elongation. (about
6/10th of its natural lengt...
Contractibility:





The ability of the muscle to shorten in length
under innervational impulse.
This occurs by:- mus...
 According

to sherrington—
Individual muscle fibers have no variable
contraction status but they are relaxed or
they are...


1.
2.
3.
4.
5.


Shortening of the muscle during the
contraction depends on:Striated or the smooth muscle
No. of the m...
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 The

greatest strength of the muscle
contraction is when the muscle
approximates its resting length and it
diminishes as...
Types of contraction:1.

2.

Isometric contraction:-it occurs when a
muscle is resisting an external force
without actual ...
Tension on the muscles:
1.
2.


Tension: - two type viz:Active
Passive
When a muscle is stretched the
tension in the mus...


Active: - the tension resulting from the
contraction of the muscle tissue is active tension.



In this the result of ...
Different types of the muscles
are:

–
–


–
–


–
–
–

1.
2.
3.

According to the presence of the cross striation:Str...
Morphology of the skeletal
muscles:






Morphology: - the skeletal muscle is primarily made up
of myofibrils.
These ...
Type of muscles fibers:
1.
2.



Slow muscles fibers
Fast muscles fibers

Buller 1969

Acc. To dubowitz 1969 and gaytheir...






Slow muscles fibers:-[Tonic muscles]
This is a slow twitch lasting in mammals
about 75 msec. these are the muscl...










Fast muscles fibers: - it is a phasic type fiber
producing a twitch that last for about 25msec.
They are p...
EMG :

It is the study of the action potential in
the human skeletal muscle. This
machine was designed to study the
bioel...


Basis:-as a part of the electrical currents
generated is transmitted to the outer surface of
the body. The changes in a...






The resting electric charges are positive on the external
surface and negative on the internal surface. When
thes...
 Significance:

In orthodontics this can be
used in the pre, mid and post to analyze
the appraisal of the muscle activity...
Reflexes of the muscles:
1.
2.

They can be in numerated as :Myotactic reflex( stretch).
Nociceptive (flexor) reflex.

ww...
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Myotactic(stretch) reflex.
 It

is the only monosynaptic jaw reflex.
 When the afferent fibers stimulate the
efferent fi...






Observed by the masseter when a sudden
downward force and is applied to the chin.
This force can be applied with ...








Clinically can be observed , by relaxing the jaw
muscles allowing the teeth to separate slightly.
A sudden dow...
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Nociceptive (flexor) reflex:



It is a polysynaptic reflex to noxious
stimuli and is thus considered
protective.
The af...






In the masticatory system this reflex
becomes active when a hard object is
suddenly encountered during masticatio...




It is more complicated than the myotactic reflex
as not only the elevator muscles has to be
inhibited to prevent fur...




The efferent fibers stimulate inhibitory
interneuron's which have their effect on the jaw
elevating muscles and caus...
Other reflexes are:




Simple orofacial reflexes:Facial reflexes: a perioral reflex, which can be
elicited by brief me...





Tongue reflexes: - reflex control of the
tongue posture is essential for the
maintenance of the pharyngeal airway
...


Bruxism: This is a parafuctional activity
along with the tooth clenching. It results
from physiologic stress with or wi...
Methods of the study:1.
2.
3.



Anatomic
Functional
Behavioral
Anatomic: - the types of the muscles.

www.indiandentalac...
Functional: 

1.
2.
3.

This assessment can be done under
the following heading i.e.
Movement
Force and pressure
Emg

www...
Movement:





The study of the movement in the muscles is a
very old concept and is called as kinesiology.
The technol...





Movement of the facial structure can be explored
in the three dimensions by holography.
One of the oldest of the t...
Force and pressure:





Pressure of the orofacial structure like the
tongue, lips and cheeks are measured by
investiga...
Behavioral: 







This is sometimes preferred ones as it is a non
invasive technique and examines the total
activity...


The branches and twigs are consolidated into
the trunks: - an alternative concept is that dev.
Of the behavior takes pl...
Muscle as the etiology:


1.

2.

Muscle dysfunction:The facial muscles can affect the growth of the
jaws in two ways:Th...






When there is birth injury that can result in the
loss of that part of the musculature which will
likely result d...
 If

the reverse happens i.e. there is
decrease in tonic muscles activity that
occurs in muscular dystrophy, this allows
...
The equilibrium theory:



As it is applied in the field of engineering it
states that an object subjected to unequal
fo...
www.indiandentalacademy.com
Equilibrium effects on the dentition: 



One might think that force multiplied by duration would
explain the effects, b...




Second contributor to the equilibrium that
governs the tooth position is pressure from the
lips, cheeks and tongue. ...






If the restraining pressure of the lips and the cheeks is
removed than due to the tongue pressure the teeth tends...
Effects on the jaw size and
shape:




The jaws, particularly the mandible, can be
thought as consisting of the core of...






The position of the tooth not the functional load
determines the position of the alveolar ridge.
The same stands ...
 Since

the condylar process is considered
as the functional process serving to
articulate the mandible with the rest of ...
Muscle adaptation in malocclusion


In case of improper or abnormal
muscle function i.e. compensatory
muscle activities s...






When there is hereditary basal malrelationships
in class II div 1 malocclusion there require the
compensatory mus...








According to moyers, motor impulses initiate
occlusal movements but are modified by
disorganized proprioceptiv...
Soft tissue environment of patients with
malocclusion:

Patterns of muscular activity in patients with
class II div 1 mal...
Here is abnormal buccinator activity
leading to constricted, narrow upper arch
along with low tongue posture.
 Thus muscl...
Patterns of muscular activity in
patients with class II div 2
malocclusion: 

They have low occlusal plane angle.
These p...
Patterns of muscular activity in
patients with mandibular prognathism:

Here the anterior and the posterior
temporal musc...
Patterns of muscular activity in patients with
anterior open bite: -



Here also the occlusal plane is the
related facto...
Thank you
For more details please visit
www.indiandentalacademy.com

www.indiandentalacademy.com
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Craniofacial musculature /certified fixed orthodontic courses by Indian dental academy

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Craniofacial musculature /certified fixed orthodontic courses by Indian dental academy

  1. 1. INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  2. 2. Craniofacial musculature Presented by:- Dr. Apurva k.Chitalia www.indiandentalacademy.com
  3. 3. Contents:introduction Development of the muscles.  classification of craniofacial musculature.  the buccinator mechanism.  the orbicularis oris.  the muscles of mastication.  accessory muscles of mastication  The tongue.  www.indiandentalacademy.com
  4. 4. Contents:The temporo mandibular joint Physiology of muscles. Reflex of muscles  myotactic reflex. Methods to study muscles. Emg Is it the one of them? The equilibrium theory www.indiandentalacademy.com
  5. 5. Contents:       Muscle and growth. Muscle adaptation in malocclusion Soft tissue environment of patients with malocclusion. Muscular adaptation after orthognathic surgery Effects of orthodontic treatment on the neuromuscular functions. Muscles and its treatment modalities. Conclusion www.indiandentalacademy.com
  6. 6. Introduction:A Man to increase the strength of skeleton has been blessed by 639 muscles which includes 6 million of muscle fibers.  Each fibers has 1000 fibrils  Thus there is 6000 billion muscle fiber working at one time. www.indiandentalacademy.com
  7. 7.  In orthodontics and in real life we judge / diagnose a individual when we look at him.  But here when we look at patient we look at him in repose/rest and we try to see the dentofacial complex and their intimate relationship to each other www.indiandentalacademy.com
  8. 8.   This is just the static analysis but important is the dynamic appreciation on how they function , as they function, how they affect the growth and the relationships of parts , these constitutes the stomatoganthic system. Here musculature plays a very important part. www.indiandentalacademy.com
  9. 9.  We orthodontist try to achieve the perfect equilibrium between the part of stomatoganthic system which includes the muscle.  so it is of definite importance that we should know in and out about them. www.indiandentalacademy.com
  10. 10. Development of muscle. During the 3rd week of I.U life the embryo undergoes gastrulation to form a trilaminar disk i.e. the cells from epiblast migrate to primitive streak and to primitive node detach from the epiblast and they invaginated the hypoblast to displace it and form the three layers.  Three germ layers derived from the epiblast  endoderm  mesoderm  ectoderm Three germ layers derived from the cells epiblast www.indiandentalacademy.com
  11. 11.       The mesodermal layer is further divided into:head paraxial intermediate lateral The mesoderm on either side of the notochordal process thickens to form longitudinal columns of tissue called the paraxial mesoderm. These segments into paired blocks of tissue called the somites. Of these the cranial ones are called as somitomeres. www.indiandentalacademy.com
  12. 12. There are seven of somitomeres approx. In register with that of the pharyngeal arches. The skeletal muscles of the head and neck develop from this somitomeres and the most cranial somites. The pharyngeal arches develop during the 4th wk. of the I.U life. They significantly contribute to the development of head, face neck and nasal cavity, mouth and to some extent the larynx and the pharynx. www.indiandentalacademy.com
  13. 13.  The branchial arches have incomplete clefts between the arches, the external ectodermal branchial grooves and internal endodermal pharyngeal pouches.  The branchial groove of the first branchial arch persists as external acoustic meatus which is covered by the tympanic membrane.  All the grooves disappear but they remain as the tympanic cavity, auditory tube, tonsil, thymus, parathyroid, and the thyroid gland. www.indiandentalacademy.com
  14. 14. www.indiandentalacademy.com
  15. 15. Cartilage components derived from pharyngeal arches are:   1. 2.  Arch I [mandibular arch]:- this is major contributor to the development of the face. The cartilage of the first arch is called as the meckels cartilage. The dorsal end of the meckels cartilage becomes ossified to form 2 bones of the middle ear ossicle :malleus Incus The middle portion of the meckels cartilage regresses, but its perichondrium forms the sphenomandibular ligament. www.indiandentalacademy.com
  16. 16.  The ventral part of the meckels cartilage forms a horse shaped structure in the shape of the future mandible.  The mesenchymal tissue lateral to the cartilage undergoes intra membranous ossification to produce the mandible as the original meckels cartilage disappears. www.indiandentalacademy.com
  17. 17. Arch II [hyoid arch]:- this cartilage is called as the reicherts cartilage  It dorsal end becomes ossified to produce the other middle ear ossicle, the stapes, and the styloid process of the temporal bone.  A portion of the perichondrium of the cartilage forms the stylohyoid ligament.  This also contributes in the development of the hyoid bone specially the lesser cornu, and the superior portion of the body.  www.indiandentalacademy.com
  18. 18.  The cartilage of the 3rd arch gives rise to the greater cornu and the inferior part of the body of the hyoid bone.  The cartilage of the 4th and the 6th arches fuses together to form the laryngeal cartilage, including the thyroid, cricoids, and arytenoids cartilage except the epiglottis. www.indiandentalacademy.com
  19. 19. Muscle components : They are derived from the cranial somites and the cells that migrate at this region from the somitomeres.  Arch I: muscles derived are: the muscles of mastication, anterior belly of digastric, mylohyoid, tensor veli palatine, tensor tympani. www.indiandentalacademy.com
  20. 20. www.indiandentalacademy.com
  21. 21. Arch II: the muscles of facial expression. These are relatively thinner and have their origin and insertion in the skin and are present throughout the face and the neck.  Arch III: it gives rise to stylopharyngeous muscle.  Arch IV and arch V: - muscles of the pharynx and the larynx. Arch IV give rise to cricothyroid and arch V to intrinsic muscles of larynx.  www.indiandentalacademy.com
  22. 22. Classification of muscles:1. 2.   they can be primarily classified as:facial muscles Muscles of mastication. The facial muscles: they are related to the orbital margins plus the eyelids, the external nose & nostrils, the lips, cheeks, mouth, the pinna, scalp and the cervical skin. These are also called as muscles of facial expression as that is their function. www.indiandentalacademy.com
  23. 23. Muscles of mastication: they are chiefly concerned with the movements of the TMJ  The division reflects the different embryonic origins and innervations of the two groups.  But all the functions such as mastication, deglutition, respiration, swallowing, speech, communicative and emotional expression, ocular, nasal and aural action are the effect of close cooperation of two groups.  www.indiandentalacademy.com
  24. 24. According to moyers:1. 2. 3. facial muscles jaw muscles Portal muscles. www.indiandentalacademy.com
  25. 25. Characteristics of the facial muscles: The primary function is expression of the emotions.  The facial muscles are capable of performing 7000 expressions according to Coleman.  They are also responsible for the maintenance of the posture of the facial structures.  Paresis of the orbicularis oculi leads to the drooping of the lower eyelid.  Paralysis of the orbicularis oris will lead to angular cheliosis and the drooling. www.indiandentalacademy.com
  26. 26. The facial muscle also contributes to stabilization of the mandible during the infantile swallowing and chewing and swallowing in the occlusally compromised adults. It is also important for the visual and the spoken communications. www.indiandentalacademy.com
  27. 27. Characteristics of the jaw muscles:   The mandible being maintained against the gravity by the stretch reflex of the elevators. EMG studies have shown of [postural position] that the inframandibular groups of muscles are more active than the levator. Mandibular movement assisted by the levator and the depressors can’t be considered just the interplay between these 2 but is very much thought as the intricate muscular web where the teeth and the joints acts as the stops. www.indiandentalacademy.com
  28. 28.     The head posture also affects the posture of the mandible for e.g. when there is extension of the head there is increase in the freeway space and when there is flexion there is decrease in the freeway space. Changes in the head posture also results changes in the anteroposterior positioning of the posture of the mandible. One of the most important factors is the posture of the mandible affecting the development of the jaws. E.g. during the mouth breathing there is effect on the growth of both maxilla as well as the mandible due to alteration in position of the mandible, hyoid and the tongue. www.indiandentalacademy.com
  29. 29. But in case where there is Sunday bite there is no resultant correction probably because the dorsal position of the mandible during the functional activities cancels the biologic signals to the joint structures.  Thus functional appliances work the best as they are worn for the most hours of the day .  www.indiandentalacademy.com
  30. 30. Characteristics of the portal muscles:Portal muscle is the word coined by Bosma to denote the upper alimentary tract and the respiratory tract.  These muscles serve some functions of our interest such as posture, respiration, feeding.  www.indiandentalacademy.com
  31. 31.  The muscles include the muscles of the tongue [both the intrinsic and the extrinsic] the soft palate, the pharyngeal pillars, the pharynx proper, and the larynx. www.indiandentalacademy.com
  32. 32. According to grays: 1. 2. 3. 4. they are broadly classifies as: epicranial muscles circumorbital muscles the nasal musculature the buccolabial musculature www.indiandentalacademy.com
  33. 33. The epicranial musculature 1. 2. The epicranius consists of two main parts occipitofrontalis Temporoparietalis. www.indiandentalacademy.com
  34. 34. www.indiandentalacademy.com
  35. 35. The scalp: 1. 2. 3. 4. 5. The scalp essentially consists of five layers i.e. superficial fascia connective tissue epicranial aponeurosis loose aerolar tissue pericranium www.indiandentalacademy.com
  36. 36. The superficial fascia in the scalp is firm and fibro-adipose adherent to the skin and the underlying epicranius and the aponeurosis, the galea aponeurotica [epicranial aponeurosis.]  It is continuous with the superficial fascia of the back of the neck; laterally, it is prolonged to the temporal region where it losses its texture.  www.indiandentalacademy.com
  37. 37. The occipito frontalis It is a broad, musculofibrous layer, covers the dome of the skull, from the nuchal lines to the eyebrows.  It consists of 4 parts---- 2 occipital and 2 frontal connected by the epicranial aponeurosis  www.indiandentalacademy.com
  38. 38.  Occipital part: - each of them are thin, quadrilateral arises by tendinous fibers from the lat. 2/3rd of the highest nuchal lines of the occipital bone and the mastoid part of the temporal bone. It ends in the epicranial aponeurosis.  Frontal part: - they are thin, quadrilateral, and adherent to superficial fascia. It is broader than the occipital part and its fibers are longer and paler. www.indiandentalacademy.com
  39. 39.  It has got no bony attachments. Its medial fibers are contiguous with those of the procerus; its intermediate fibers blend with the corrugator supercilli and the orbicularis oculi; its lateral fibers are also blended with the latter muscle over the zygomatic process of the frontal bone.  From these attachments the fibers are directed upwards to join the epicranial aponeurosis in front of the coronal suture. The medial margins of the frontal slips are joined together for some distance above the root of the nose; but between the occipital bellies there is considerable, but variable interval occupied by the epicranial aponeurosis. www.indiandentalacademy.com
  40. 40. Galea aponeurotica:  It covers the upper part of the cranium and along with the epicranius it forms the continuous fibromuscular sheet extending from the occipital to the eyebrows. Behind, in the interval between the occipital parts of the occipitofrontalis, it is attached on the external protuberance or highest nuchal lines of the occipital bone. In front it splits to enclose the frontal parts and sends a short narrow prolongation between them. www.indiandentalacademy.com
  41. 41. It is united to the skin by firm, fibrous superficial fascia; it is connected to the pericranium by loose aerolar tissue which allows its free movement. The latter carrying it with the skin of the scalp  Nerve supply: - the occipital part is supplied by the posterior auricular branch and the frontal part by the temporal branches of the facial nerve.  www.indiandentalacademy.com
  42. 42. Action:- the occipital slips draw the scalp downward , the frontal slips acting from above raise the eyebrows and the skin of the root of the nose ; acting from below they draw the scalp forwards; throwing the integument of the forehead into transverse wrinkles.  They act in tandem in expression like surprise, horror or fright etc.  www.indiandentalacademy.com
  43. 43. The fourth layer of the scalp:  it is made up of loose aerolar tissue. it extends anteriorly to the eyelids; and posteriorly to the highest nuchal lines and on each side to the superior temporal lines.  The fifth layer is called as pericranium:-it is loosely attached to the surface of the bones, but is firmly adherent to their sutures where the sutural ligaments bind the pericranium to the endocranium.  www.indiandentalacademy.com
  44. 44. Temporoparietalis:  It is variably developed sheet of muscle that lies between the frontal part of the occipito frontalis and the ant. And sup. Auricular muscles. A thin muscular slip, the transverse nuchae, is present in about 25 percent of the people; it arises from the external occipital protuberance or from the superior nuchal lines, present either sup. Or deep to trapezius; it is frequently inserted with the auricularis posterior, but may join the post. Edge of the sterocleidomastoid. www.indiandentalacademy.com
  45. 45. Circumorbital and palpeberal musculature. 1. 2. 3. The muscle that come under this heading are:orbicularis oculi corrugator supercilli levator palpebrae superioris www.indiandentalacademy.com
  46. 46. The orbicularis oculi: it is a broad, flat, elliptical muscle that occupies the eyelids, surrounds the circumference of the orbit and spreads on the temporal region and the cheek. it consists of the orbital , palpebrae and lacrimal parts. www.indiandentalacademy.com
  47. 47. The orbital part    it is reddish and thicker than the palpeberal fasiculi Origin:-arises from the nasal part of the frontal bone, from the frontal process of the maxilla and from the medial palpeberal ligament, which interrupts the bony attachment. It fibers form the complete ellipses without the interruption on the lateral side, the upper ones blending with the frontal part of the occipitofrontalis and the corrugator. www.indiandentalacademy.com
  48. 48.  Insertion:-some of the fibers are inserted into the skin and the subcutaneous tissue of the eyebrow. They constitute the depressor supercilli. www.indiandentalacademy.com
  49. 49. The palpeberal part  - it is thin and pale. It arises from the medial palpeberal ligament chiefly from its superficial but also from its deep parts, though not from the lower margin, it arises also from the bone immd. Above and below the ligament.  The fibers sweep across the eyelids in front of the orbital septum and at the lateral commissure and interlace to form the lateral palpeberal raphe. A small group of the fine fibers lies close to the margin of each eyelid, behind the eyelashes; it is named as the ciliary bundle. www.indiandentalacademy.com
  50. 50. The lacrimal part:    it lies behind the lacrimal sac but separated from it by the lacrimal fascia. It is attached to lacrimal fascia, to the upper part of the crest of the lacrimal bone, and adjacent part of the lateral part of the lacrimal bone. Passing laterally behind the lacrimal sac the muscle divides into upper and lower slips; some fibers are inserted into the tarsi of the eyelids close to the lacrimal canaliculi, but most continue across in front of the tarsi and interlace in the lateral palpeberal raphe. www.indiandentalacademy.com
  51. 51. The medial palpeberal ligament:- it is about 4mm in the length and 2mm in the breadth, is attached to the frontal process of the maxilla in front of the nasolacrimal groove. Crossing the lacrimal sac it divides into 2 parts i.e. upper and lower parts each one attached to the medial end of the corresponding tarsus.  It is separated from the lacrimal sac by the fascia.  www.indiandentalacademy.com
  52. 52.  Nerve supply: - temporal and zygomatic branch of the facial nerve.  Actions: - the orbicularis oculi: - it is the sphincter muscle of the eyelids.  The palpeberal portion acts under voluntary control closing the lids gently as in sleep or blinking; the orbital portion is more frequently under voluntary control www.indiandentalacademy.com
  53. 53.  During the eye closure there is lowering of the upper as well as elevation of the lower eyelid. thus palpeberal part has depressor and elevator fasicles.when the entire muscle contracts than the skin of the forehead , temple and cheek is drawn towards the medial angle of the orbit, and the eyelids are not only firmly closed but they are moved in toto medially. The skin is thrown in the folds on the lateral angle of the eyelids due to this action which are called as crow’s feet. www.indiandentalacademy.com
  54. 54.     The lacrimal part of the muscle draws the eyelids and the lacrimal papillae medially, and exerts traction on the lacrimal fascia and it dilates the lacrimal sac. Thus the muscle has important action in tear transport. The muscle is also an important element in facial expression and the ocular reflexes. Partial closure of the palpeberal fissure together with bunching and the protrusion of the eyebrows diminish the entry of the light. www.indiandentalacademy.com
  55. 55.  These action of the upper orbital fibers and their peripheral extension cause vertical furrowing above the bridge of the nose. This is called as blink reflex and its protective value is obvious. www.indiandentalacademy.com
  56. 56. The corrugator supercilli: it is a small pyramidal muscle, at the medial end of the eyebrows, deep to the frontal part of the occipitofrontalis and the orbicularis oculi .  From the medial end of the superciliary arch its fibers pass slightly laterally and slightly upwards to the deep surface of the skin above the middle of the supraorbital margin.  www.indiandentalacademy.com
  57. 57. www.indiandentalacademy.com
  58. 58. Nerve supply: - the temporal branches of the facial nerve.  Action: - draws the eyebrows medially and downwards  Together with the orbicularis oculi causing vertical wrinkles of the forehead.  It assists in drawing the eyebrows downwards in the bright sunlight and is also involved in frowning  www.indiandentalacademy.com
  59. 59. The nasal musculature: 1. 2. 3. This group comprises of three muscles:the procerus the nasalis The depressor septi. www.indiandentalacademy.com
  60. 60. The procerus: it is a small pyramidal slip continuous with the medial side of the frontal part of the occipitofrontalis.  Origin:-It arises from the fascia covering the lower part of the nasal bone and the upper part of the lateral nasal cartilage.  Insertion:-it is inserted into the skin over the lower part of the forehead between the eyebrows.  www.indiandentalacademy.com
  61. 61. Action: - it draws down the medial angle of the eyebrow and incidentally produces wrinkles over the bridge of the nose.  It is active in frowning and concentration.  It also aids in reducing the glare of the sunlight.  www.indiandentalacademy.com
  62. 62. The nasalis: it consists of transverse and alar parts which may be continuous at the origin.  The transverse part:-[compressor naris] – it arises from the maxilla just lateral to the nasal notch; its fibers proceed upwards and medially and expand into a thin aponeurosis, which is continuous on the bridge of the nose with that of the muscle of the opposite side, and with the aponeurosis of the procerus.  www.indiandentalacademy.com
  63. 63.     The alar part [dilator naris]—it arises from the maxilla, below and medial to the transverse part. It is attached to the cartilaginous ala nasi. Actions: - the transverse part: - it compresses the nasal aperture at the junction of the vestibule with the nasal cavity. The alar part draws the ala downwards and laterally and so assists in widening the ant. Nasal aperture. These actions are visible in deep respiration, especially in its inspiratory phase, and they also accompany certain emotional states. www.indiandentalacademy.com
  64. 64. www.indiandentalacademy.com
  65. 65. The depressor septi: often regarded as the part of the dilator nasi; is attached to maxilla above the central incisor roots.  Present immediately deep to the mucous membrane of the upper lip.  www.indiandentalacademy.com
  66. 66. Action: - it assists the alar part of the nasalis in widening the nasal aperture while deep inspiration.  Nerve supply: - All the nasal musculature supplied by superior buccal branches of the facial nerve.  www.indiandentalacademy.com
  67. 67. buccolabial musculature: 1. 2. 3. 4. 5. 6. These are the muscle slips which control the shape of buccal orifice and the posture of the lips They include: the retractors and elevators of the upper lip viz:levator labii superioris alaeque nasi levator labii superioris the zygomaticus major the zygomaticus minor risorius levator anguli oris www.indiandentalacademy.com
  68. 68. www.indiandentalacademy.com
  69. 69. 1. 2. 3. the depressor and retractors of the lower lip viz:depressor labii inferioris depressor anguli oris mentalis www.indiandentalacademy.com
  70. 70. The levator labii superioris alaeque nasi Origin:-it arises from the upper part of the frontal process of the maxilla and, passing obliquely downwards and laterally, divides into medial and lateral slips.  Insertion:-The medial slips is inserted into greater alar cartilage and skin of the ala of the nose.  www.indiandentalacademy.com
  71. 71.  the lateral slip is prolonged into the lateral part of the upper lip, and blends with the levator labii superioris and orbicularis oris Action: - the lateral slip raises and everts the lip  The medial slip acts as dilator of the nostril.   Nerve supply: - it is supplied by the buccal branches of the facial nerve. www.indiandentalacademy.com
  72. 72. The levator labii superioris: Origin:-it starts immediately above the infra-orbital margin at the lower margin of the orbital opening.  It arises from the maxilla and the zygomatic bone.  www.indiandentalacademy.com
  73. 73.      Insertion:-Its fibers converge into the muscular substance of the upper lip between the lateral slip of the levator labii superioris alaeque nasi and levator anguli oris. Action: - it raises and everts the upper lip. Along with the zygomaticus major it forms the nasolabial furrow, from the side of the nose to the upper lip. The furrow deepens while expressing sadness and seriousness. Nerve supply: - it is supplied by the buccal branches of the facial nerve. www.indiandentalacademy.com
  74. 74. The zygomaticus minor:    Origin:-arises from the lateral surface of the zygomatic bone immediately behind the zygomaticomaxillary suture. Insertion:-it passes downward and medially into the muscular substance of the upper lip. It is separated from the levator labii superioris by a short interval. www.indiandentalacademy.com
  75. 75.  Action:-it elevates the upper lip and also produces the nasolabial furrow.  Nerve supply: - it is supplied by the buccal branches of the facial nerve.  When the levator labii superioris alaeque nasi, the levator labii superioris and the zygomaticus minor are in action together they express contempt and disdain. www.indiandentalacademy.com
  76. 76. The levator anguli oris: Origin: it arises from the canine fossa, just below the infra –orbital margin.  Insertion:-it is inserted into the angle of the mouth, intermingling with fibers of the zygomaticus major, depressor anguli oris and orbicularis oris...  Between the levator anguli oris and the levator labii superioris are the infra orbital vessels and nerves.  www.indiandentalacademy.com
  77. 77. Action: - it raises the angle of the mouth  It is instrumental in producing the nasolabial furrow.   Nerve supply: - it is supplied by the buccal branches of the facial nerve. www.indiandentalacademy.com
  78. 78. The zygomaticus major: Origin:-extends from the zygomatic bone in front of the zygomaticotemporal suture.  Insertion:-to the angle of the mouth, where it blends with the fibers of the levator anguli oris, orbicularis oris and the depressor anguli oris.  www.indiandentalacademy.com
  79. 79.  Actions: - it draws the angle of the mouth upward & laterally as in laughing.  Nerve supply: - it is supplied by the buccal branches of the facial nerve.  The zygomaticus major and minor and the levator labii superioris are sometimes enclosed by thin sheet of muscle called as musculus malaris and are continuous with the orbicularis oculi. [Lightoller 1925] www.indiandentalacademy.com
  80. 80. The depressor labii inferioris: Origin:-it is quadrilateral in shape and arises from the oblique line of the mandible between the mental foramen and the symphysis menti. At its origin it is continuous with the platysma.  Insertion:-it passes upwards and medially into the skin of the lower lip, blending with its fellow and orbicularis oris.  www.indiandentalacademy.com
  81. 81. Action - it draws the lower lip downward and a little laterally in masticatory activity  It contributes to expression of irony.  Nerve supply: - it receives supply from the mandibular marginal branch of the facial nerve.  www.indiandentalacademy.com
  82. 82. The depressor anguli oris: Origin:-arise from the oblique line of the mandible, below and lateral to the depressor labii inferioris.  Insertion:-it converges into the narrow fasciculus blending with the other muscles at the angle of the mouth.  It is continuous with the platysma at its origin and at its insertion with the orbicularis oris and risorius;  www.indiandentalacademy.com
  83. 83. Some of the fibers are directly continuous with that of the levator anguli oris, and others accidentally cross to the other side these are called as the transversus menti.  Action: - draws the angle of the mouth downward and laterally while opening of the mouth and during expression of the sadness.  Nerve supply: - it receives supply from the mandibular marginal branch of the facial nerve.  www.indiandentalacademy.com
  84. 84. The mentalis: Origin:-it is a conical fasciculus at the side of the frenulum of the lower lip. It arises from the incisive fossa of the mandible.  Insertion:-it descends to be attached to the skin of the chin.  www.indiandentalacademy.com
  85. 85. Action:- it raises and protrude the lower lip and at same time wrinkles the skin of the chin.  It helps in drinking and in expressing disdain and doubt.  There is continuous activity in the muscle also during the sleep according to EMG studies.  Nerve supply: - it receives supply from the mandibular marginal branch of the facial nerve.  www.indiandentalacademy.com
  86. 86. The buccinator: it is thin quadrilateral muscle occupying the interval between the maxilla and the mandible, in the cheek.  It is attached to the outer surfaces of the alveolar processes of the maxilla and the mandible, opposite to molar region and behind, the anterior border of the pterygomandibular raphe, which separates it from the superior constrictor of the pharynx.  www.indiandentalacademy.com
  87. 87. www.indiandentalacademy.com
  88. 88. Between the maxillary tuberosity and the upper end of the raphe a few fibers arise from the tendinous band which bridge the gap between the maxilla and the pterygoid hamulus.  The tendon of the tensor veli palatini on its way to the soft plate pierces the pharyngeal wall in the small gap which lies behind this tendinous band.  www.indiandentalacademy.com
  89. 89. The fibers of the buccinator converge towards the angle of the mouth , where the central fibers intersect each other, those from below being continuous with the upper segment of the orbicularis oris, and those from above with the lower segment of orbicularis oris.  The lowest and the highest fibers are continuous forward into the corresponding lip without decussation.  www.indiandentalacademy.com
  90. 90. Relations:it is covered by the buccopharyngeal fascia and lies in the same plane as that of the superior constrictor.  Superiorly, posteriorly a large mass of fat separates it from the ramus of the mandible, masseter, and small portion of the temporalis.this is called as the suctorial pad.  www.indiandentalacademy.com
  91. 91. www.indiandentalacademy.com
  92. 92. Anteriorly, superficial surface of the muscle is related to the zygomaticus major risorius, levator and depressor anguli oris, the parotid duct which pierces it opposite to the 3rd molar tooth. the facial artery and facial vein crosses it; the facial nerve and the buccal nerves also cross it .  The deep surface is related to the buccal glands and the mucous membrane of the mouth.  www.indiandentalacademy.com
  93. 93. Nerve supply: - supplied by the lower buccal branch of the facial nerve  Action: - it compresses the cheek against the teeth so helps in mastication as the food is passed between them.  It helps in blowing, hence the name buccinator= the trumpeter.  www.indiandentalacademy.com
  94. 94. The buccinator mechanism There is a strong interdependence of muscles and bone and the major factor in this environmental balance is the musculature. They are the potent force whether in active state or at rest.  The teeth and the supporting structure are under constant pressure from the contiguous musculature  www.indiandentalacademy.com
  95. 95. www.indiandentalacademy.com
  96. 96. The integrity of the dental arch and its relation with the same arch and the opposing arch is maintained by the morphogenetic pattern, which is modified by the stabilizing and active functional force of muscles  Environmental factors are the contact relations and resistance afforded by the buttressing effect of contiguous teeth, occlusal interdigitation and the bone building – resorption balance maintained in the periodontal membrane.  www.indiandentalacademy.com
  97. 97. Thus stability is dependent on the 1. Genetic. 2. Environmental 3. Epigenetic factors 4. Morphologic factors 5. Physiologic.  Acc. To Winders the tongue exerts two to three times more pressure on the dentition than the lips and the cheeks but the net effect is maintained as the tonal contraction, peripheral fiber recruitment of the buccal & labial muscles and the atm. Pressure team up to offset the momentarily greater functional force of the tongue.  www.indiandentalacademy.com
  98. 98. www.indiandentalacademy.com
  99. 99.  Acc. to Lear and Moorress the enigma between the dental arch and the muscle function remains as there are limitations such as measuring equipment; hydraulic nature of response, size and sample and even the geometry of the dental arch which do not permit definitive form- function conclusions. www.indiandentalacademy.com
  100. 100. The buccinator mechanism. The orbicularis oris muscle decussating fibers joins the right and left fibers in the lips. The buccinator mech. Runs laterally and posteriorly around the corner of the mouth, joining other fibers of the buccinator muscle which insert into the pterygomandibular raphe just behind the dentition. Here it intermingles with the fibers of the sup. Constrictor muscle and continues posteriorly and medially to anchor at the origin of the superior constrictor muscles, the pharyngeal tubercle of the occipital bone. The tongue pressure opposes the buccinator mech. www.indiandentalacademy.com
  101. 101. The pterygomandibular raphe: It is the interlacing of the tendinous fibers stretched from the hamulus of the medial pterygoid plate to the posterior end of the mylohyoid line of the mandible.  Medially it is covered by the mucous membrane of the mouth.  www.indiandentalacademy.com
  102. 102. Laterally, it is separated from the ramus of the mandible by quantity of fat.  Posteriorly, it gives attachment to the superior constrictor of the pharynx.  Anteriorly to the part of the buccinator.  www.indiandentalacademy.com
  103. 103. The orbicularis oris: Is made of the several strata which surround the orifice of the mouth but have different directions. It consists partly of the fibers derived from the other facial muscles which pass into the lips, partly of fibers proper to them.  Of the former there is no. of them derived from buccinator, and from the deeper stratum.  www.indiandentalacademy.com
  104. 104. www.indiandentalacademy.com
  105. 105. Some of the buccinator fibers viz: those near the middle of the muscle- decussate at the angle of the mouth; the uppermost and the lowermost fibers pass across the lips from side to side without decussation.  Superficial to this is the second strata, formed by the levator and the depressor anguli oris, which cross each other at the angle of the mouth; the fibers from the levator pass to the lower lip and that from the depressor into the upper lip. Along which they run to reach the skin at the anterior median line.  www.indiandentalacademy.com
  106. 106.   Fibers are also derived from the levator labii superioris, zygomaticus major and minor, and the depressor labii inferioris; these intermingle with the transverse fibers described above, and have principally an oblique direction. Thus some eight or nine muscle thus converge at the angle of the mouth and interlace here at a palpable nodular mass , The modiulous. this can be fixed in a given position by the combined action of the depressor anguli oris , zygomaticus major ,levator anguli oris.. This thus serves to fix the attachments of the orbicularis oris and the buccinator. www.indiandentalacademy.com
  107. 107. Within the lips the fibers of the orbicularis oris are divisible into two fasiculi, the marginal and the peripheral.  These combine to form the labial bands that are traceable to the modiulous [lightoller 1925, burkitt and lightoller in 1926, 1927]  The fibers of the lip are in oblique direction, and pass from the deep surface of the skin to the mucous membrane, thru the thickness of the lip.  www.indiandentalacademy.com
  108. 108. Finally there are fibers of the muscle bands that are attached to the maxilla above and mandible below.  In the upper lip these constitute the incisive labii superioris which arises from the alveolar border of the maxilla, opposite to the lateral incisor tooth, and arching laterally which is continuous with the other muscles at angle of the mouth.  www.indiandentalacademy.com
  109. 109.  The additional fibers of the lower lip constitute a slip of incisive labii inferioris, on each side; the slips arise from the mandible; lateral to the mentalis, and mingles with the other muscles at the angle of the mouth.  In a study on children on fetal lips [14-25 weeks] Latham and Deaton in 1976 conclude that orbicular oris fibers interlace and cross the midline to their cutaneous insertions, thus creating the ridges of the philtrum of the upper lip. www.indiandentalacademy.com
  110. 110. Nerve supply: - it is supplied by the lower buccal and the mandibular marginal branch of the facial nerve.  Actions: - its ordinary action is to effect direct closure of the lips, by its deep and oblique fibers it compresses the lips against the teeth.  The superficial part, consisting principally of the decussating fibers , brings the lips together and protrudes them. The orbicularis oris and other muscles of the lips play an important part in articulation, as well as in mastication. [Duckworth 1947]  www.indiandentalacademy.com
  111. 111. The risorius: Origin:-arises from the parotid fascia  Insertion:-is inserted into the skin at the angle of the mouth.  It is a narrow bundle of fibers, broad at its origin.  It may vary much in its size and form; like may arise from the zygomatic arch, external ear or the fascia over the mastoid process.  www.indiandentalacademy.com
  112. 112. Nerve supply: - is supplied by the buccal branches of the facial nerve.  Action: - it retracts the angle of the mouth and produces the sardonic expression.  Facial muscles also play an important role in the speech and feeding and drinking.  Their importance in mastication has always been a topic of EMG study.  www.indiandentalacademy.com
  113. 113. www.indiandentalacademy.com
  114. 114. www.indiandentalacademy.com
  115. 115. Muscles of the mastication:- www.indiandentalacademy.com
  116. 116.   1. 2. 3. These muscles immediately are concerned with the movements of the mandible [and speech], These muscles are viz:Masseter Temporalis Pterygoid muscles. www.indiandentalacademy.com
  117. 117. www.indiandentalacademy.com
  118. 118. The masseter:  A strong layer of fascia derived from the deep cervical fascia is named the parotid fascia; it covers the masseter and is firmly connected with it. It is attached to the lower border of the zygomatic arch and invests the parotid gland. www.indiandentalacademy.com
  119. 119.     It is quadrilateral in shape and consists of three superimposed layers blending anteriorly. The superficial layer, the largest arises by a thick aponeurosis from the zygomatic process of the maxilla and from the anterior 2/3rds of the lower border of the zygomatic arch. Its fibers pass downwards and backwards, to be inserted into the angle and lower half of the lateral surface of the ramus of the mandible. Intramuscular septa in this region are responsible for the ridge on the bone. www.indiandentalacademy.com
  120. 120. The middle layer: - it arises from the deep surface of the anterior 2/3rd and the posterior 1/3rd of the lower border zygomatic arch.  It is inserted in the middle of the ramus of the mandible.  The deep layer: - it arises from the deep surface of the zygomatic arch and is inserted into the upper part of the ramus of the mandible and the coronoid process.  www.indiandentalacademy.com
  121. 121. The middle and the deep layers constitute to form a cruciate muscle. [Where the fasiculi run in 2-3 directions]  As it is close to the skin it can be palpated when it is thrown into contraction vigorously as in clenching of the teeth.  Acc. To mcconnaill 1975 the most superficial fibers are continuous thru their attachment at the lower border of the mandible, into the attachment of the medial pterygoid muscle.  www.indiandentalacademy.com
  122. 122. Nerve supply: - is supplied by the branch of the anterior trunk of the mandibular nerve  Actions: - it elevates the mandible to occlude the teeth in mastication. Its activity in the resting position of the mandible is minimal.  In clenching of the teeth.  It has little effect in side to side movements, protraction and the retraction of the mandible.  www.indiandentalacademy.com
  123. 123. The temporal fascia:  It covers the temporalis muscle. It is a strong, fibrous investment covered, laterally, by the auricularis anterior and superior, the galea aponeurotica and part of the orbicularis oculi.The superficial temporal vessels and the auriculotemporal nerve ascend over it. Above it is a single layer attached to the whole of the sup. Temporal line and below it is two layers one attached to the lateral and the other to the medial margin of the upper zygomatic arch. www.indiandentalacademy.com
  124. 124. A small quantity of fat, the zygomatic branch of the superficial temporal artery, the zygomatico temporal branch of the maxillary nerve lie between these layers.  The deep surface of the fascia affords attachment to the superficial fibers of the temporalis.  www.indiandentalacademy.com
  125. 125. www.indiandentalacademy.com
  126. 126. The temporalis:  Origin:-It is a fan- shaped muscle. It arises from the whole of the temporal fossa [except the part formed by the zygomatic arch] and the deep surface of the temporal fascia. www.indiandentalacademy.com
  127. 127.  Insertion:-Its fibers converge and descend into a tendon which passes thru the gap between the zygomatic arch and the side of the skull, to be attached to the medial surface, apex, anterior and posterior borders of the coronoid process, and the anterior border of the ramus of the mandible nearly as far as the last molar tooth.  Nerve supply: - supplied by the deep temporal branch of the ant. Trunk of the mandibular nerve. Actions: - it elevates the mandible i.e. closes the mouth and approximates the teeth. It is also contributor to the side to side grinding movements.   www.indiandentalacademy.com
  128. 128.  About its action on the elevation of the mandible there are lots of studies that states the temporalis is active in the forcible elevation but not involved in the slow elevation without occlusion. [Vitti and basmajian 1977]  It’s not easy to palpate but the contraction of the temporalis muscle can be felt. www.indiandentalacademy.com
  129. 129. The lateral pterygoid:  It is a short and thick muscle with two parts of the head:- www.indiandentalacademy.com
  130. 130. www.indiandentalacademy.com
  131. 131. 1. 2.  Upper from the infra temporal surface and from the infra temporal crest of the greater wing of sphenoid bone, Lower head from the lateral surface of the lateral pterygoid plate. Insertion:-its fibers pass backwards and laterally to be inserted in the depression on the front of the neck of the mandible, and into the articular capsule and disk of the TMJ. www.indiandentalacademy.com
  132. 132. In the 3rd month of the I.U life the lateral pterygoid muscle is inserted in the mesenchyme condensed around the dev. Condyle of the mandible but a part of its tendon sweeps backwards above the condyle and gains into the portion of the meckels cartilage which later forms the head of the malleus.  Then gets inserted into the articular disk of the TMJ and the attachment with the malleus does not persist.  www.indiandentalacademy.com
  133. 133. Nerve supply: - it is supplied by the br. from the anterior trunk of the mandibular nerve.  Actions: - it assists in opening the mouth by pulling forward the condylar process of the mandible and the articular disk while the head of the condyle rotates on the articular disk. [Posselt 1952]  www.indiandentalacademy.com
  134. 134. In the closure the backward gliding of the articular disk and the condyle of the mandible is controlled by the slow elongation of the lateral pterygoid, while the masseter and the temporalis restore the jaw to the occlusal position  Along with the medial pterygoid of the same side the lateral pterygoid advances the condyle of that side so that the jaw rotates about the vertical axis.  www.indiandentalacademy.com
  135. 135.   When the medial and the lateral pterygoid act together than the mandible protrudes so that the lower incisors project in front of the upper and they also produce the side to side movement as in chewing when the two muscles contract alternatetly. According to [McNamara 1972—EMG study] both the heads of the lateral pterygoid have diff. actions i.e. the upper head is being involved in the chewing and the lower head is in protrusion. www.indiandentalacademy.com
  136. 136. The medial pterygoid:    It is quadrilateral in shape and consists of two heads Deep head:-attaches to the medial surface of the lateral pterygoid plate and the grooved surface of the pyramidal process of the palatine bone superficial head:- from the lateral surfaces of the pyramidal processes of the palatine bone and the tuberosity of the maxilla. www.indiandentalacademy.com
  137. 137. www.indiandentalacademy.com
  138. 138.  Insertion:-its fibers pass downwards and backwards and are attached to a strong tendinous lamina, to the posterior-inferior part of the medial surface of the ramus and the angle of the mandible, as high as the mandibular foramen and nearly as forward as the mylohyoid groove. www.indiandentalacademy.com
  139. 139.  Nerve supply:-it is supplied by the branch of the mandibular nerve.  Acc. to a study done by Schumacher et.Al on the ramifications of the muscular nerve of the masticatory muscles a very similar mode of branching in all these muscles is observed. www.indiandentalacademy.com
  140. 140.  Actions: - it assists in elevating the mandible. Acting with lateral pterygoid it protrudes the mandible.  When the 2 pterygoid of one side are in action the corresponding side is swung forward and to the opposite side with slight degree of rotation. www.indiandentalacademy.com
  141. 141. www.indiandentalacademy.com
  142. 142. Palpation of muscles:   The muscles of mastication are palpated for tenderness or pain during the screening examination. It is accomplished mainly by the palmar surface of the middle finger, with the index finger and the forefinger testing the adjacent areas. Soft but firm pressure is applied to the designated muscles, the fingers compresses the adjacent tissues in a small circular motion. www.indiandentalacademy.com
  143. 143. www.indiandentalacademy.com
  144. 144. A single firm thrust of 1 or 2 seconds is usually better than many light thrusts.  During that the patient is asked for the symptoms.  The temporalis: - it has three functional areas and each is independently palpated.  Anterior region: - palpated above the zygomatic arch and anterior to the TMJ.  Middle region: - directly above TMJ and superior to the zygomatic arch. www.indiandentalacademy.com
  145. 145.     Posterior region: - palpated above and behind the ear. Otherwise, the patient is asked to clench the teeth so that the temporalis contracts and this is felt with hands placed on the above specified locations. The masseter muscles are palpated bilaterally at their superior and inferior attachments. The fingers are placed on the zygomatic arches and then dropped down slightly just anterior to the tmj for palpating superior part. Secondly, the fingers are placed on the inferior border of the rami to palpate inferior attachment. www.indiandentalacademy.com
  146. 146.  Medial pterygoid: - palpated at the intersection of medial surfaces of mandibular angles. Finger tips are placed on the inferior border of the mandible at the angles and are rolled medially and superiorly. Ask the patient to clench the teeth if it is difficult to locate the muscle. www.indiandentalacademy.com
  147. 147.  The lateral pterygoid palpation is difficult.  It is accomplished by placing the forefinger behind the maxillary tuberosity, right above the occlusal plane, with the palmar surface of the finger directed medially toward the pterygoid hamulus.  If there is tenderness in the superior head of the lateral pterygoid muscle than it indicates abnormal functional loading of the joint. www.indiandentalacademy.com
  148. 148.  The finding are classified into four categories.1. Zero: - no tenderness or pain is reported by the patient, 2. One: - patient’s response is recorded. Here the palpations cause discomfort. 3. Two:-there is definite discomfort or pain. 4. Three: - patient shows evasive action or verbally expresses desire not to palpate. www.indiandentalacademy.com
  149. 149. The accessory muscles of facial expression:The superficial and the lateral cervical muscles: 1. 2. 3. These include viz:The platysma The trapezius The sterocleidomastoid muscles www.indiandentalacademy.com
  150. 150. The platysma:   Origin:-it is a broad sheet arising form the fascia covering the upper part of the pectoralis major and the deltoid. Insertion:-it is inserted at the lower border of the body of the mandible and the posterior fibers cross the mandible and the lower anterior part of masseter to be attached to the skin and the subcutaneous tissue of the lower part of the face. And many fibers blending at the angle and the lower part of the mouth. www.indiandentalacademy.com
  151. 151.  Action: - when the entire platysma is in action it diminishes the concavity between the jaw and the side of the neck. www.indiandentalacademy.com
  152. 152.  Its anterior portion i.e. the thickest part helps in depressing the mandible  It also serves to draw down the lower lip and the angle of the mouth as in expression of horror or surprise.  The trapezius and the sterocleidomastoid maintain the posture of the head. www.indiandentalacademy.com
  153. 153. The accessory muscles.  These are the muscle’s which when involved assist the main group of muscles in the function of stomatoganthic function: 1. The suprahyoid muscles 2. The infra hyoid muscles www.indiandentalacademy.com
  154. 154. The suprahyoid muscles: 1. 2. 3. 4. The digastric . The stylohyoid. The mylohyoid . The geniohyoid. www.indiandentalacademy.com
  155. 155. The digastric: It has two bellies that are united by an intermediate tendon. Hence the name.  The posterior belly: - it s longer than the anterior and is attached to the mastoid notch of the temporal bone and passes downwards and forwards.  www.indiandentalacademy.com
  156. 156. The anterior belly: - it is attached to the digastric fossa on the base of the mandible close to the median plane and passes downward and backwards. www.indiandentalacademy.com
  157. 157.  Actions: - it depresses the mandible and can elevate the hyoid bone.  On EMG studies it has been confirmed that they always act together and 2ndary to the lateral pterygoid for the depression the mandible and are required only during the maximal depression. [Moyers 1950]  The posterior belly is active during the swallowing and the chewing. www.indiandentalacademy.com
  158. 158. The tongue: The tongue begins its activities even before the birth when it function the swallowing of amniotic fluid. It is one of the best dev. Muscle / structure in the human body at birth. www.indiandentalacademy.com
  159. 159.   It is relatively larger than the contiguous structure and assumes posture interposed between the gum pads rather than completely contained within them. In infancy extrinsic muscles are attachés to various osseous structures and are largely responsible for the various important movement of the tongue in the horizontal plane like suckle and swallow. www.indiandentalacademy.com
  160. 160. The extrinsic muscles:1. 2. 3. 4. Hyoglossus---- attached to the hyoid bone. Styloglossus----- to the styloid process. Genioglossus --------to the mandible. Palatoglossus ------- to the palatine aponeurosis. www.indiandentalacademy.com
  161. 161.  As stated by kwamura that protraction, retraction, and lateral deviation to these muscles along with the genioglossus involved mostly in the suckle swallow function. www.indiandentalacademy.com
  162. 162. The intrinsic muscles       Four in number named acc to their fibers position. i.e. Superior longitudinal Inferior Longitudinal Vertical Transverse. Nerve supply: hypoglossal nerve {12th} except Palatoglossus which is supplied by the accessory nerve thru the pharyngeal plexus. www.indiandentalacademy.com
  163. 163.  The tongue being anchored only at one end so free to move and this freedom permits the tongue to deform the dental arch when the functn is abnormal. www.indiandentalacademy.com
  164. 164. Muscular attachments of the TMJ.:   - It is by far the most complex joint in the body. It provides for the hinging movement in one plane hence called ginglymoid joint. And it also provides for the gliding motion so called as arthroidal joint. Therefore it is sometime referred to as the ginglymoarthrordial joint. Also called as synovial joint. It is a compound type of the joint. www.indiandentalacademy.com
  165. 165. Articular disc: The articular disc is composed of dense fibrous connective tissue devoid of any blood vessels or nerve fibers.  The condyle lies in the intermediate zone. The articular disc is related posteriorly to an area of loose connective tissue that is highly vascularized and innervated. This is known as the retrodiscal tissue.   www.indiandentalacademy.com
  166. 166. www.indiandentalacademy.com
  167. 167. Synovial membrane:  The capsule of the TMJ is lined on the inner side by a synovial membrane. It consists of a cellular intima and subintima. This membrane is formed of the synovial lining.  This membrane produces the synovial fluid.  The synovial fluid acts as a medium for providing metabolic requirements to these tissues as the articular disk is non-vascular.  It also acts as a lubricant between the articular surfaces during function. www.indiandentalacademy.com
  168. 168. Ligaments of the joint:     Collateral [discal] ligament: - they attach to the medial and the lateral borders of the articular disc to the poles of the condyle. Function: - they restrict the movement of the disc away from the condyle. They permit the disc to be rotated anteriorly and posteriorly on the articular surface of the condyle. They are responsible for the hinging movements. www.indiandentalacademy.com
  169. 169. Capsular ligament:    The entire TMJ is encompassed by the capsular ligament. They act to resist any medial, lateral, or inferior forces that tend to separate or dislocate the articular surfaces. It encompasses the joint thus retains the synovial fluid. www.indiandentalacademy.com
  170. 170. Tmj ligament:-[lateral ligament] Functions: - it resists the excessive drooping of the condyle and acts as a limit to the extent of the mouth opening.  It also influences the normal opening movement of the mandible.  www.indiandentalacademy.com
  171. 171. Accessory ligaments:1. 2. Sphenomandibular ligament. Stylomandibular ligament. www.indiandentalacademy.com
  172. 172. Concept of orthopedic stability.  Orthodontic correction has always been the correct contact pattern and not the orthopedic stabilization.  Its time the clinician better understand the need of orthopedic stability which to appreciate the sound principles if the occlusion and its role in function or dysfunction of the masticatory system. www.indiandentalacademy.com
  173. 173.  The TMJ consists of the articular disc which is non vascular and does not elicit pain. But this does not find the positional stability of the joint.  The positional stability is determined by the muscles that pull across the joint and prevent the dislocation of the articular surfaces.  The direction of forces of this muscle determine the correct position.  The major muscles that stabilize the tmj are the elevator muscle. The direction of the force placed on the condyle by the masseter and the medial pterygoid is superioanterior. www.indiandentalacademy.com
  174. 174.  The temporal muscles also stabilize the Tmj.They have some horizontal oriented fibers.  The lateral pterygoid also plays some part.  In postural position, the muscle without any influence from the occlusal condition place the condyles in the superioanterior direction. In the articular fossae and this most stable position. www.indiandentalacademy.com
  175. 175.  Thus it is defined as, the position in which the condyles are in their most superioanterior position in the articular fossae, resting against the posterior slopes of the articular eminences with the articular disc properly interposed.  This position is also the most musculoskeletally stable position.  The teeth at this position should be in maximum intercuspation to contribute in the orthopedic stability. www.indiandentalacademy.com
  176. 176. Physical properties of muscles: I) They help in kinetic activity of the muscles. elasticity:-elasticity of a body is related to:1. length 2.cross section 3. force exerted 4. a constant coefficient 5. deformation. www.indiandentalacademy.com
  177. 177.   1. 2. 3. 4.  A relaxed muscle can withstand only a certain amount of elongation. (about 6/10th of its natural length.) This further depends on the:Type of the stress Individual resistance Age Possible pathology The process of the material returning to its original shape after being stretched illustrates elasticity. www.indiandentalacademy.com
  178. 178. Contractibility:    The ability of the muscle to shorten in length under innervational impulse. This occurs by:- muscle is stimulated by an electric action potential causing a contraction. Energy for the muscle is provided by the breakdown of the high energy bonds in atp( adenosine triphosphate) Fatigue in muscle is produced when the lactic acid an energy breakdown product collects in tissue lowering the ph to a level at which the muscle can no longer function efficiently. www.indiandentalacademy.com
  179. 179.  According to sherrington— Individual muscle fibers have no variable contraction status but they are relaxed or they are in maximum contraction only on the basis of the stimulus. This is termed as the “all or none” law.  The strength of the muscle contraction depends on the number of the muscle fibers engaged in the activity. Even during rest there are peripheral fibers under stimulus to maintain the posture. www.indiandentalacademy.com
  180. 180.  1. 2. 3. 4. 5.  Shortening of the muscle during the contraction depends on:Striated or the smooth muscle No. of the muscle Cross section Frequency of discharge Muscle fiber length E.g. temporalis muscle due to its relatively longer fibers has a greater contraction length than the masseter muscle. www.indiandentalacademy.com
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  182. 182.  The greatest strength of the muscle contraction is when the muscle approximates its resting length and it diminishes as muscle shortens in length beyond the resting length.  E.G. Mandible closing from physiologic position to occlusion there is reduction in the strength of the contraction if the closure continues beyond occlusal position there is rapid diminution of the contractile muscles. www.indiandentalacademy.com
  183. 183. Types of contraction:1. 2. Isometric contraction:-it occurs when a muscle is resisting an external force without actual shortening Isotonic contraction:-it occurs during flexing of biceps i.e. when there is actual shortening of the muscles. www.indiandentalacademy.com
  184. 184. Tension on the muscles: 1. 2.  Tension: - two type viz:Active Passive When a muscle is stretched the tension in the muscle increases and this increase in tension may be the result of reflex control contraction of the muscle. www.indiandentalacademy.com
  185. 185.  Active: - the tension resulting from the contraction of the muscle tissue is active tension.  In this the result of the reflex activity can also be increased by willed contraction of muscles as in volitional clenching of the teeth.  Passive: - tension which results from the physical properties alone of the tissues is called passive tension.  In many muscles the elongation will increase both active as well as the passive tension.  The sum of both the tension is called as the total tension. www.indiandentalacademy.com
  186. 186. Different types of the muscles are: – –  – –  – – –  1. 2. 3. According to the presence of the cross striation:Striated Non-striated [plain or smooth muscles] Acc. To the nature of the control Voluntary [controlled by the volition] Involuntary [ not controlled by volition]( wish) Acc. To the distribution :Skeletal Cardiac Visceral These classifications can be summarized in the following way: Skeletal- striated voluntary Cardiac-striated involuntary www.indiandentalacademy.com Visceral - non-striated [plain or smooth] involuntary.
  187. 187. Morphology of the skeletal muscles:    Morphology: - the skeletal muscle is primarily made up of myofibrils. These are the characteristic feature and they consist of the alternate light and dark bands [transverse striations] and thick longitudinal strands. On e.m it is revealed that longitudinal striation are due to the presence of the myofibrils of the different thickness whereas the transverse striations are due to the presence of the dark and light segments of longitudinally arranged segments. The myofibrils are separated by sarcoplasmic areas which are called as field of cohnheim. www.indiandentalacademy.com
  188. 188. Type of muscles fibers: 1. 2.  Slow muscles fibers Fast muscles fibers Buller 1969 Acc. To dubowitz 1969 and gaytheir (1974) – – – type I type II type III[ rare in humans] www.indiandentalacademy.com
  189. 189.     Slow muscles fibers:-[Tonic muscles] This is a slow twitch lasting in mammals about 75 msec. these are the muscle which are redder in colour because of some pigment protein myoglobin which has properties similar to that of hemoglobin. These are also called as the type I fibers. E.g. Temporalis, the masseter, the anterior medial pterygoid and the lateral pterygoid are 75 % composed of type I fibers. [Eriksson] www.indiandentalacademy.com
  190. 190.       Fast muscles fibers: - it is a phasic type fiber producing a twitch that last for about 25msec. They are paler in colour They are also considered as the type II muscle fibers Acc. To burke ET .al 1973type can be subdivided into fibers which fatigue easily [type IIB] and the other one which are resistant to fatigue [type II A]. Type IIA is found in 30 % only in digastric muscle. Type IIB is found in 45 % in the superior temporalis, posterior medial pterygoid, and anterior digastric muscle. [Acc to Eriksson] www.indiandentalacademy.com
  191. 191. EMG : It is the study of the action potential in the human skeletal muscle. This machine was designed to study the bioelectric phenomenon of the active muscle. Electric activity in the living tissue is related to the existence of the polarized membranes at the cellular surfaces. www.indiandentalacademy.com
  192. 192.  Basis:-as a part of the electrical currents generated is transmitted to the outer surface of the body. The changes in action potential can be studied by either putting electrodes at the surface of active muscle area or inserting them directly into the muscle concerned. Electrode can be selected according to the size of the muscle i.e. A large portion has to be studied or few motor units of the muscle are studied.  Surface electrodes are used for the larger group of the muscles and needle electrodes fro the smaller ones. www.indiandentalacademy.com
  193. 193.    The resting electric charges are positive on the external surface and negative on the internal surface. When these are activated the charges are reversed i.e. There is reversal of polarization at the tissue surface of which produce the electric current. These signals are then received. Amplified and recorded by the EMG. The measurement can be done by measuring either the height of the action potential or the frequency of the individual action potential. Moyers was the first one to study the orofacial muscles using the EMG. Or The potential can be recorded by cathode ray oscillograph. www.indiandentalacademy.com
  194. 194.  Significance: In orthodontics this can be used in the pre, mid and post to analyze the appraisal of the muscle activity.  The study has a great clinical value in the diagnosis of different types of the neuromuscular functional impairment in which either the rate or the rhythm of nerve impulse is influenced. www.indiandentalacademy.com
  195. 195. Reflexes of the muscles: 1. 2. They can be in numerated as :Myotactic reflex( stretch). Nociceptive (flexor) reflex. www.indiandentalacademy.com
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  197. 197. Myotactic(stretch) reflex.  It is the only monosynaptic jaw reflex.  When the afferent fibers stimulate the efferent fibers directly in the CNS than it is called as monosynaptic.  When a skeletal muscle is quickly stretched , this protective reflex is elicited and it brings about the contraction of the muscle. www.indiandentalacademy.com
  198. 198.    Observed by the masseter when a sudden downward force and is applied to the chin. This force can be applied with a small rubber hammer. As the muscle spindles within the masseter suddenly stretch afferent nerve activity is generated from the spindles to reach the brain stem at the trigeminal motor nucleus ,,here it acts on the primary afferent cell bodies causing synapse with the Alfa efferent motor neurons at the extrafusal fibers of the masseter to cause the muscle to contract www.indiandentalacademy.com
  199. 199.     Clinically can be observed , by relaxing the jaw muscles allowing the teeth to separate slightly. A sudden downward tap on the chin will cause the jaw to be reflexly elevated. The masseter contracts resulting in the tooth contact. Significance:- it occurs without the specific response from the brain and is important in determining resting position of the jaw. It is principle determinant of the muscle tonus. www.indiandentalacademy.com
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  201. 201. Nociceptive (flexor) reflex:  It is a polysynaptic reflex to noxious stimuli and is thus considered protective. The afferent neuron stimulates one or more interneuron's in the CNS which in turn stimulate the efferent fibers. www.indiandentalacademy.com
  202. 202.    In the masticatory system this reflex becomes active when a hard object is suddenly encountered during mastication. As the tooth is forced down on the hard object a noxious stimulus is received by the tooth & the surrounding pdl structures. The associated sensory receptors trigger afferent nerve fibers Interneuron's in the trigeminal motor nucleus. www.indiandentalacademy.com
  203. 203.   It is more complicated than the myotactic reflex as not only the elevator muscles has to be inhibited to prevent further jaw closure on the hard object, but the jaw opening muscles must be activated to bring the teeth away from the potent damage. The excitatory fibers interneuron's leads to efferent fibers of the jaw opening muscles are stimulated which causes muscle contraction www.indiandentalacademy.com
  204. 204.   The efferent fibers stimulate inhibitory interneuron's which have their effect on the jaw elevating muscles and cause them to relax. This produces the antagonistic inhibition and the jaw drops quickly and the teeth are pulled away from the object causing noxious stimuli. www.indiandentalacademy.com
  205. 205. Other reflexes are:   Simple orofacial reflexes:Facial reflexes: a perioral reflex, which can be elicited by brief mechanical or electrical stimulation of the lips. Has been said to play role in voluntary lip motor control in speech . Jaw reflexes:- simple jaw reflexes can be divided into vertical[ jaw closing and opening] and horizontal [anteroposterior and lateral] www.indiandentalacademy.com
  206. 206.    Tongue reflexes: - reflex control of the tongue posture is essential for the maintenance of the pharyngeal airway and plays an important role in the position of the teeth. Complex orofacial reflex:Mastication:- Significant for the orthodontic treatment is the magnitude and the direction of the occlusal forces in mastication and the extent to which these forces contribute to the tooth movement and the mobility. www.indiandentalacademy.com
  207. 207.  Bruxism: This is a parafuctional activity along with the tooth clenching. It results from physiologic stress with or without occlusal interference.  Swallowing:-The most significant feature f swallowing is their role in occlusal and tongue forces in establishing tooth position. It is a protective reflex and is initiated by mechanically stimulation by a bolus in the pharynx. www.indiandentalacademy.com
  208. 208. Methods of the study:1. 2. 3.  Anatomic Functional Behavioral Anatomic: - the types of the muscles. www.indiandentalacademy.com
  209. 209. Functional:  1. 2. 3. This assessment can be done under the following heading i.e. Movement Force and pressure Emg www.indiandentalacademy.com
  210. 210. Movement:   The study of the movement in the muscles is a very old concept and is called as kinesiology. The technology of the mapping can be adapted to study of the face in repose. Observing the movement of the shadow grid projected onto the face during activity of the facial musculature is an old technique which is now updated using moiré fringe and computer technique. www.indiandentalacademy.com
  211. 211.    Movement of the facial structure can be explored in the three dimensions by holography. One of the oldest of the technique to study the movement of the mandible is to record a moving film on the movement of the ball from the lower incisors. This has also been updated so that now a small magnet is attached to the lower incisors which are tracked by three magnetometers and the movement is displayed in three planes of the space with the oscilloscope or x-y recorder. Movement of the condyle and the portal structures can be visualized o the cineradiography, landmarks are digitized and alteration in the position and shape is quantified. This tool is very much useful in understanding the movements associated with the swallowing. www.indiandentalacademy.com
  212. 212. Force and pressure:   Pressure of the orofacial structure like the tongue, lips and cheeks are measured by investigators like profitt using strain gauges. Masticatory, swallowing, and maximal biting forces are recorded on the teeth by Graf et.al Pressure transducers are an important tool in studying the pressure gradients in the upper alimentary tract during swallowing. www.indiandentalacademy.com
  213. 213. Behavioral:     This is sometimes preferred ones as it is a non invasive technique and examines the total activity in the natural state. Windle has explained it looking at complex patterns of the behavior upon the analogy to a tree According to the concepts of the Windle. Discrete reflexes become aggregated into increasingly complicated patterns of behavior. www.indiandentalacademy.com
  214. 214.  The branches and twigs are consolidated into the trunks: - an alternative concept is that dev. Of the behavior takes place in the human fetus, and the gross behavior such as the flexure of the head and the jaw opening precedes more discrete behavior such as eyelid and the tongue reflexes.  To the trunk of the tree are added the branches and the twigs:Mastication can be visualized as the consolidation of simple elements such as jaw opening, jaw closing etc.  www.indiandentalacademy.com
  215. 215. Muscle as the etiology:  1. 2. Muscle dysfunction:The facial muscles can affect the growth of the jaws in two ways:The formation of the bone at the point of muscle attachment depends on the activity of the muscles The musculature is important part of the total soft tissue matrix whose growth normally carries the jaws downward and forward. www.indiandentalacademy.com
  216. 216.    When there is birth injury that can result in the loss of that part of the musculature which will likely result damage to the motor nerve due to which there will be underdeveloped. jaw on that side. Excessive muscle contraction can restrict the growth. This effect is same as that of the scarring after the injury. This effect can be most clearly seen in torticollis i.e. twisting of the head caused by excessive tonic contraction of the neck muscles on one side [primarily the sterocleidomastoid]-this results in facial asymmetry because of the growth direction on the affected side. www.indiandentalacademy.com
  217. 217.  If the reverse happens i.e. there is decrease in tonic muscles activity that occurs in muscular dystrophy, this allows the mandible to drop downward away from the rest of the facial skeleton. This results in increase of the anterior facial height, distortion of facial proportions and mandibular form, excessive eruption of the posterior teeth, narrowing of the maxillary arch and anterior open bite. www.indiandentalacademy.com
  218. 218. The equilibrium theory:  As it is applied in the field of engineering it states that an object subjected to unequal forces will be accelerated and thereby move to different position in the space. If the force is applied onto an object but if it remains in the same space than the forces are said to be in equilibrium or balanced. The dentition is obviously in equilibrium since the teeth are subjected to a variety of forces but do not move to a new location under usual conditions. Even when the teeth are moving the movements are so slow that a static equilibrium can be presumed to exist at any instant in time. www.indiandentalacademy.com
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  220. 220. Equilibrium effects on the dentition:   One might think that force multiplied by duration would explain the effects, but this is not the case .The duration of a force, because of the biologic response is more important than its magnitude. This point is made clear by examining the response to the forces during the chewing. When heavy forces are applied during the mastication to the teeth, the fluid filled pdl acts as a shock absorber, this stabilizes the tooth for an instance, the force than is transmitted to the alveolar bone which bends and the tooth moves for a short distance along with the bone. www.indiandentalacademy.com
  221. 221.   Second contributor to the equilibrium that governs the tooth position is pressure from the lips, cheeks and tongue. These pressures are much lighter from the masticatory forces but are greater in duration. Studies have proved that even the light force can produce tooth movement if the duration is long these duration threshold is 6 hours. Since the pressure from the lips, cheeks and the tongue is maintained most of the time there is indeed tooth movement in conditions when there is loss of equilibrium. Example, in scarring or contracture of the soft tissue of the lips the incisors in the vicinity will move lingually as the lip tightens against them. www.indiandentalacademy.com
  222. 222.    If the restraining pressure of the lips and the cheeks is removed than due to the tongue pressure the teeth tends to jet out. Even if there is alteration of the tongue pressure and the lips and the cheeks are intact than too the teeth tends to move outward as there is loss of equilibrium. In cases with the orthodontic appliances for e.g. If arch expansion plate is given and after that the lips and cheeks pressure tends to increase but there will be balance of forces until the plate is there once that is removed there is unbalance and the teeth would collapse lingually until a new position of balance is achieved. With a habit for e.g. Thumb sucking. If habit like these creates pressure for more than 6hrs than teeth will move but if more force is applied for less duration than there will be no effect. www.indiandentalacademy.com
  223. 223. Effects on the jaw size and shape:   The jaws, particularly the mandible, can be thought as consisting of the core of bone to which the functional processes are attached. The functional processes of the bone are altered if the function is lost or changed. E.g. The alveolar process of the bone exist only to support the teeth that means that if the tooth is absent then the alveolar bone is absent and if it is extracted than the alveolar bone resorbs until it finally atrophies. www.indiandentalacademy.com
  224. 224.    The position of the tooth not the functional load determines the position of the alveolar ridge. The same stands true for the muscular processes: the location of the muscle attachments is more important in determining the shape of the bone than the mechanical loading or degree of activity. Growth of the muscle however determines the position of the attachments, and so muscle growth can produce a change in shape of the jaw, particularly at the coronoid process and the angle of the mandible. www.indiandentalacademy.com
  225. 225.  Since the condylar process is considered as the functional process serving to articulate the mandible with the rest of the facial skeleton then there is possibility that altering the position of the position of the mandible might alter the growth of the mandible.  The effect of the force duration is not clear for the growth of the jaw s as that for the teeth thus the same principle applies that the magnitude of the force is less important than its duration. www.indiandentalacademy.com
  226. 226. Muscle adaptation in malocclusion  In case of improper or abnormal muscle function i.e. compensatory muscle activities such as hyperactive mentalis muscle activity, hypoactive upper lip, increased buccinator pressures and tongue thrust that occur as a result of change in spatial relationships of the jaws and the teeth. www.indiandentalacademy.com
  227. 227.    When there is hereditary basal malrelationships in class II div 1 malocclusion there require the compensatory muscular adaptation. thus to swallow the lower lip cushions the maxillary incisors, the tongue thrusts forward to close off to crate the anterior lip seal required for the deglutition. Even when there are normal jaw relationships and no compensatory activity is required for the mastication and deglutition {class I} individuals elicit a synchronous contraction pattern of the masticatory muscles. www.indiandentalacademy.com
  228. 228.     According to moyers, motor impulses initiate occlusal movements but are modified by disorganized proprioceptive responses from the TMJ. Adaptive activity may induce aberrant patterns of occlusal activity as a result enhancing the original malocclusion. These adaptive responses may alter the degree of the total contraction under peripheral and CNS stimuli. Usually this is a hypertonic response. Thus even the perverted function of the muscle in case of class II div 1 can lead to increase in severity of overjet and overbite. www.indiandentalacademy.com
  229. 229. Soft tissue environment of patients with malocclusion: Patterns of muscular activity in patients with class II div 1 malocclusion:-  These patients have a short hypotonic upper lip. In addition to that the lower lip cushions against the palatal surface of the upper incisors. Causing lip trap.  This abnormal contraction of the hyperactive mentalis muscle increases the proclination of the upper incisors.  In addition there is lack of anterior lip seal due to short upper lip. www.indiandentalacademy.com
  230. 230. Here is abnormal buccinator activity leading to constricted, narrow upper arch along with low tongue posture.  Thus muscle aberration is produced by hyperactive buccinator and the hyperactive mentalis along with altered tongue posture.  www.indiandentalacademy.com
  231. 231. Patterns of muscular activity in patients with class II div 2 malocclusion:  They have low occlusal plane angle. These patients have increased muscular activity of the temporalis and masseter muscle. www.indiandentalacademy.com
  232. 232. Patterns of muscular activity in patients with mandibular prognathism: Here the anterior and the posterior temporal muscle are found to be more active than that of masseter muscle in the interocclusalposition. www.indiandentalacademy.com
  233. 233. Patterns of muscular activity in patients with anterior open bite: -  Here also the occlusal plane is the related factor. Here the plane is high and so the muscular activity of the muscles is low. www.indiandentalacademy.com
  234. 234. Thank you For more details please visit www.indiandentalacademy.com www.indiandentalacademy.com

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