Anatomy of stomatognathic system /certified fixed orthodontic courses by Indian dental academy

ANATOMY OF
STOMATOGNATHIC SYSTEM
INDIAN DENTAL ACADEMY

Leader in continuing dental education
www.indiandentalacademy.com


Definition


According to Dorland’s medical dictionaryStomatognathic - stomato (mouth) + gnathic
(jaws) which means mouth & the jaws
collectively forms stomatognathic system.


Components
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Introduction
Osseous anatomy
Temporomandibular Joint.
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Articular Disc.
Condyle/Disc Assembly.

T M Jt Ligaments.
Muscles.
Mastication.
Muscles of mastication.
Tongue
Regulation of muscle activity.
Reflexes.

Introduction






Bones form the basic underlying structure of the
stomatognathic system.
Three main bones make up the skeletal portion of the
stomatognathic system- the maxilla, the mandible,
and a portion of the temporal bone of the skull.
The maxilla and mandible are the bones that hold the
teeth, while the temporal bone is the site of the
mandible’s articulation with the skull.


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



Muscles move the mandible
Contacting bony surfaces, upholstered with
avascular, dense, fibrous connective tissue
influence the direction of the mandible’s
movements
Ligaments limit the mandibles range of
motion, acting as a leash to restrain it from
travelling too far.

•Maxilla & mandible are derived
from 1st pharyngeal arch.

Muscles of mastication are
derived from mesoderm of 1st
branchial arch


The Mandible


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The mandible forms the lower part of our face. It is
suspended from the skull by muscles, ligaments and
soft tissues, and doesn’t itself attach bone-to-bone to
the maxilla, but hangs in space.
U-shaped bone, contains mandibular teeth in alveolar
process.
Suspended from skull by muscles & ligaments.
Major structural parts- condyle, coronoid process,
ramus, angle, alveolar process, mental protuberance.

The Condyle
 Articular portion of the mandibleConsists of a neck- head & the articular
surface
 Head of the condyle
 Oblong (football shaped), convex in all
directions, but more curvature anteroposteriorly
 15-20 mm wide medio-laterally, 8-10mm
antero-posteriorly.
 2 poles- medial & lateral- medial larger.
 Posterior part of articular surface larger
than anterior.

Mandible- looking down from above.
 The condyles are aligned at 90
degrees to the top of the ramus, but
due to the flaring out of the
mandible at the posterior,they are
positioned such that the medial pole
is more posterior than the lateral
pole is- they make an angle to the
horizontal that runs posteriorly at
the medial aspect. Lines going
through the poles of the condyles
aim at the anterior edge of the
foramen magnum of the skull.

The Maxilla





Composes most of upper part of face &
contains maxillary teeth.
Fused to skull & hence non-mobile.
Major intra-oral parts- alveolar process, palatal
process, incisive foramen, mid-palatal suture,
maxillary tuberosity.


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The body of the maxilla has four
surfaces:
Anterior or facial surface
Posterior or infratemporal surface
Superior or orbital surface.
Medial or nasal surface.
It has four processes:
Frontal.
Zygomatic.
Alveolar.
Palatine.


The Temporal Bone
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

Part of the skull with
which the mandible
articulates.
Condyle articulates with
concave mandibular
fossa.


The Temporomandibular Joint
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Main functional parts are mandibular
condyle, mandibular fossa & articular disc.
Ginglymoarthrodial joint- allows hinging
and gliding motions.
Classified as compound joint- articular disc
functions as a third, non-ossified bone.
Articular surfaces covered with dense,
fibrous connective tissue.

Osseous Anatomy Of - T M Jt


The Mandibular Fossa
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Also called articular fossa &
glenoid fossa.
Posterior bordersquamotympanic fissure- thin
bone.
Medial wall -temporal bone- steep
Anterior border - convex articular
eminence-thick, dense bone.
Slope of articular eminence &
Squamotympanic
medial wall are major
fissure
determinants of mandibular
movement.


The Articular Disc
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Composed of dense,
smooth, fibrous
connective tissue.
Mostly devoid of nerves
& blood vessels
Biconcave shape.
Thickest at posterior
border & medial border.
Condyle articulates in
thin intermediate zone.

Saggital veiw


Condyle/Disc Assembly
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Condyle, articular disc & mandibular fossa
surrounded by soft tissue attachments.
Attachments aid in structure of joint,
positioning and function of joint
components.
It consist of ligamentous attachments,
elastic and collagenous connective tissue
attachments and muscle attachment .

LIGAMENTS

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Bands of non-elastic collagenous tissue.

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Function to passively limit range of movement
& protect joint structures.


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5 ligaments associated with TMJt.
3 functional, 2 accessory
Functional:
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Collateral (discal) ligaments
Capsular ligament
Temporomandibular ligament

Accessory:
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Sphenomandibular
Stylomandibular

Collateral (Discal) Ligaments
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2 collateral ligaments- Medial
& lateral.
Stiff, collagenous connective
tissue.
Divide TMJ mediolaterally
into superior & inferior joint
cavities.
Help keep disc positioned on
condyle, allow anteriorposterior rotational movement.

Capsular Ligament
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

Surrounds entire TMJ.
Runs from neck of
condyle to temporal
bone & articular
eminence, surrounds
mandibular fossa, 360
degrees around.


Capsular Ligament
Functions:
Prevent
dislocation of
articulating
surfaces.
 Proprioception.
 Contains synovial
lining – produces
synovial fluid.



Temporomandibular Ligament


Outer Oblique Portion
– articular eminence to neck of
condyle
– limits opening of mouth
– influences nature of opening
movement



Inner Horizontal Portion
– articular eminence to head of
condyle & disc
– limits posterior movement



Both are closely related
physically with capsular
ligament

Accessory Ligaments
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Sphenomandibular Ligament

• Medial view

– sphenoid bone to lingula.
– non-functional
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Stylomandibular Ligament
– styloid process to angle of
mandible
– limits protrusive
movement

Lateral Veiw


Joint Cavities
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TMJ is divided into 2
distinct joint cavities by
articular disc and ligaments:
Superior joint cavity
– Between articular disc &
mandibular fossa
– Responsible for gliding
movements



Inferior joint cavity
– Space between articular disc
& condyle
– Responsible for hinging
movements

Movements Of Mandible


Synovial Fluid
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Joint capsule lined by specialized endothelial
cells- synovial lining.
Produces synovial fluid, fills both joint
cavities.
Function- lubrication & metabolism.
2 mechanisms- boundary lubrication &
weeping lubrication.

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Blood supplyBranches from
superficial temporal and
maxillary arteries. Veins
follows arteries.

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Nerve supplyAuriculotemporal nerve
and massetric nerve.


Muscles
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Muscle fibers grouped into motor units.
Motor unit consists of a group of muscle
fibers all innervated by 1 motor neuron.

Functional unit of muscles
 Number of muscle fibers per neuron varies
according to function of muscle


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fewer fibers/neuron= less force, greater
precision of movement- e.g. lateral pterygoid
more fibers/neuron= greater force of
movement, less precision- e.g. masseter

Actions of Muscles
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3 types of muscle action:
Isotonic- overall muscle length shortens
during contraction- primary movement.
Isometric- overall muscle length does not
shorten during contraction- develops force,
but no movement- stabilization & fixation.
Controlled relaxation- slow, smooth,
relaxation and lengthening of previously
contracted muscle- coordination of
movements.

The origin can be thought of as generally being the
more stable, more “fixed” end of the muscle, and
when the muscle contracts, it pulls the part at the
insertion towards it.

MASTICATION
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Mastication (chewing) is the first
movement of the digestive tract.

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Importance of mastication.

The coarse chunks of food are broken
down to smaller particles. This
breaking down has the following
advantages
(i) It increases the surface area .
(ii) In case of some vegetable foods,
where the surface coating of the food
is made up of cellulose or
hemicellulose, mastication causes
exposure of the inner digestible
material. The cellulose or
hemicellulose is indigestible in human
di-gestive system but the noncellulose
inner material is digesti-ble. Thus
digestion is facilitated
(iii) It helps in the flow of saliva
(iv) It helps in subsequent deglutition.
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The teeth are designed for chewing, the anterior teeth
(incisors) providing a strong cutting action and the posterior
teeth (molars), a grinding action. All the jaw muscles working
together can close the teeth with a force as great as 55 pounds
on the incisors and 200 pounds on the molars.
Much of the chewing process is caused by a chewing reflexThe presence of a bolus of food in the mouth at first initiates
reflex inhibition of the muscles of mastication, which allows
the lower jaw to drop. The drop in turn initiates a stretch reflex
of the jaw muscles that leads to rebound contraction. This
automatically raises the jaw to cause closure of the teeeth, but
it also compresses the bolus again against the linings of the
mouth, which inhibits the jaw muscles once again, allowing
the jaw to drop and rebound another time; this is repeated
again and again.

EQUILIBRIUM THEORY
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States that an object subjected to unequal force will be
accelerated and thereby will move to different position in
space. It follows that if any object is subjected to a set of
force but remains in the same position those forces must be
in a balance or equilibrium . From this perspective the
dentition is obviously in equilibrium since the teeth are
subjected to variety of forces but don’t move to a new
location under usual circumstances
The duration of force is more important than its magnitude,
due to its biological effect.

MUSCULAR WEAKNESS
SYNDROME
• Causes mandible to
drop down away from
the facial skeleton
• Distortion of facial
proportions, increased
facial height
• Excessive eruption of
posterior teeth,
narrowing of maxillary
arch and anterior open
bite.

Muscles producing Movements of
mandible
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Depression- Lateral pterygoid (mainly)
Digastric, geniohyoid and mylohoid muscles
help when the mouth is open wide or against
resistance.

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Elevation - Masseter
- Temporalis
- Medial pterygoid (both sides)

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Protrusion – Lateral & medial pterygoids.

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Retraction – Temporalis (post fibers).

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Lateral or side to side movement - Medial &
lateral pterygoids together.


Muscles of mastication
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

There are several different groups of muscles
associated with the masticatory system- some are
directly involved with mandibular function, others are
accessory in nature and just help out.
The muscles of mastication are the primary functional
muscles that perform the majority of mandibular
movements. The suprahyoid group contains the
muscles responsible for mouth opening, along with
others , the infrahyoids, help to co-ordinate
mandibular function. The posterior neck musculature
is active in stabilizing and balancing the head, allowing
the other muscleswww.indiandentalacademy.com to perform the many
to work together
complicated movements that are possible.

Muscles of mastication
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Masseter .
Temporalis.
Medial pterygoid.
Lateral pterygoid.
Hyoid muscles.
Auxillary oral muscles.


Masseter
Superficial portion

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Origin-anterior 2/3rd of zygomatic
arch.
Insertion-coronoid process,ramus
and angle of mandible.
Function-powerful elevator

Deep portion

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Origin-medial surface of
zygomatic arch
Insertion-coronoid process,ramus
& angle of mandible.
Function- elevation & retrusion.




A study was done by( Gedrange T etal J Appl Gnet 46
,2005) to determine the myosine heavy chain proteins
(MyHC) and MyHC mRNA in masseter muscles of
patients with different mandibular positions. 10
patients were selected with distal and mesial
malocclusion, and amount of MyHC and its different
isoforms was determined by western blot essay and
PCR. The anterior part of masseter muscle showed
more type i and 2x myhc in distal occlusion than in
the mesial occlusion.

Medial pterygoid
Origin :
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Medial surface of lateral
pterygoid plate.

Insertion :
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Medial surface of the angle
of the mandible.

Function :
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Elevation & protrusion.
Medial pterygoid


Temporalis muscle
Anterior portion
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Origin : anterior temporal fossa
Insertion : coronoid process
Function : elevation

Middle portion
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Temporalis
muscle

Origin : Mid temporal fossa
Function : elevation & retraction

Posterior portion
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Origin : posterior temporal fossa
Function : retrusion


Temporalis muscle function


Lateral pterygoid
Inferior head of lateral pterygoid
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Origin:lateral surface of lateral
pterygoid plate.
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Insertion:neck of condyle.
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Function : protrusion
Superior head of lateral pterygoid
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Origin : infratemporal surface of
greater sphenoid wing.
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Insertion : articular capsule,disc
& neck of condyle.

Function : protractor of disc in
conjuntion with elevator muscles

Lateral pterygoid muscle function


Nerve supply
Motor nerve supply of
masticatory muscles
-Mandibular division of
trigeminal nerve


Blood supply to masticatory muscles
Blood supply to
muscles of masticationMaxillary Artery


• A study [Gedrange T etal Rofo. 2005
Feb;177(2):204-9 ] was done to determine the
relationship between the morphological parameters of
the masticatory muscles and the jaw bone by
computer tomography, lateral cephalogram and
denture models. It showed higher densities of medial
pterygoid, masseter and genioglossus in deep bite
individuals than in the open bite cases. Significant
difference in the muscle cross section of the masseter
muscle was found in individuals with retroclined
maxillary incisors and the individuals with open
bite.

Orbicularis oris & buccinator muscles
Orbicularis oris
Intrinsic part
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Origin - superior incicivus from
maxilla;inferior incicivus,from
mandible
Insertion – angle of mouth

Buccinator
Orbicularis
oris

Extrinsic part
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Origin - thickest middle
stratum,derived from buccinator &
thick superficial stratum
Insertion - lips & the angle of the
mouth.

Action
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Closes & purses the mouth


Buccinator muscleOrigin :
Upper fibers from maxilla opposite

Insertion :
straight to the upper lip

to molar teeth.

Lower fibers

from mandible opposite
to molar teeth

straight to the lower lip

Middle fibers

from ptergomandibular

decussates before

raphe

passing to the lips

Action – flattens cheek against gums & teeth.
It is also called as whistling muscle.

• A study done by Jung MH et al (Am J Orthod
Dentofacial 2003 Jan) to evaluate the influence of
force of orbicularis muscle on the incisor position
and craniofacial morphology where average and
maximum upper lip force was determined by a device
‘y’ meter. The skeletal structure and the incisal
angulation were recorded by lateral cephalogram. The
result showed that the upper incisor proclination was
significantly related to the magnitude of the
orbicularis oris force. So the disuse atrophy of
orbicularis might be an significant factor in the
development of malocclusion.

BUCCINATOR MECHANISM
It is a continuous muscle band that encircles the
dentition and is anchored at the pharyngeal tubercle.
Components  Orbicularis oris
 Buccinator
 Pterygomandibular raphae
 Superior constrictor of pharynx
 Opposing the buccinator mechanism there is a very
powerful muscle – tongue; which begins it’s activity
even before birth.



BUCCINATOR MECHANISM


Suprahyoid muscles




Geniohyoid .
Mylohoid .
Digastric .
Stylohyoid.

Function :


Elevate hyoid bone &
depress mandible when the
mouth is wide open
or against resistance ; it is
secondary to lateral
pterygoid .

Suprahyoid muscle function


Infrahyoid muscles
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Thyrohyoid .
Sternohyoid .
Omohyoid .

Function :
 Lowers hyoid bone
allowing suprahyoids to
depress mandible.

Tongue


Development of tongue


Papillae of the Tongue


These are projections of mucous
membrane or corium which give
the anterior two-thirds of the
tongue its characteristic
roughness. These are of the
following three types.



Vallate or circumvallate
papillae - They are large in size

1-2 mm in diameter and are 8-12
in number. They are situated
immediately in front of the sulcus
terminalis. Each papilla is a
cylindrical surrounded by a
circular sulcus. The walls of the
papilla are raised above the
surface.



Fungiform papillae are

numerous near the tip and
margins of the tongue but some of
them are also scattered over the
dorsum. These are smaller than
the vallate papillae but larger than
the filiform papilla consists of a
narrow & a large rounded
head.they are distinguished by
their bright red colour.


Filiform papillae cover the

presulcal area of the dorsumof the
tongue & give it a characteristic
velvety appearance, they are the
smallest & most numerous of the
lingual papilla.


Muscles of tongue
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

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Each half contains four intrinsic
and four extrinsic muscles.
Intrinsic muscles
1. Superior longitudinal
2. Inferior longitudinal
3. Transverse
4. Vertical

Extrinsic muscles
1. Genioglossus
2. Hyoglossus
3. Styloglossus
4. Palatoglossus


Nerve supply of tongue

Sensory supply

Root
Ant 2/3-lingual Post 1/3
nerve for
Vagus
Both general and
general
nerve
taste sensation are
sensation.
carried by
Chorda
glossopharyngeal
tympani for
nerve
special taste
sensation.

Motor supply
Hypoglossal
nerve except
palatoglossus
which is
supplied by
cranial part of
the accessory
nerve.

Blood supply of tongue




Arterial supplyLingual artery branch of
ECA
Root of tongue is supplied
by tonsillar & ascending
pharyngeal arteries.
Venous drainage2 venae comitantes
accompany lingual artery.
Deep lingual vein is the
principal vein of tongue.

Lymphatic drainage of tongue






Tip of tongue bilaterally
drains to submental
nodes.
Right & left ½ of the
remaining part of the
anterior 2/3rd of the
tongue drain unilaterally
to the submandibular
nodes.
Posterior 1/3rd drains to
Jugulo-digastric nodes.

FUNCTION OF THE TONGUE
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TASTE
SPEECH
MASTICATION
DEGLUTITION


TASTE
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Different type of taste buds are perceived by
different papillae which contain taste buds
Circumvallate –bitter
Foliate – sour
Fungiform - at the tip of the tongue - sweet,
and at periphery - salty
Tastes are transmitted to the CNS by different
nerve roots.

Speech
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Bi labialsounds -[m], [b] and [p] are bilabial stops
(plosives)
Labial-alveolar - [t], [d], or [n] sound.
Labiodental – [f] &[v].
Dento alveolar – [t], [d].
Interdental consonants – [n],[l].
Coronal – [s],[z].
Velar – [g] ,[k] ,[q].
Uvular fricative - [χ].

According to Proffit, the speech problems related to
malocclusions are
Speech sounds

problem

Related
malocclusion

S,Z (sibilants)

lisp

Anterior open
bite

T,D (linguoalveolar)

Difficulty in
production

Lingual position
of max. incisors

F,V (labiodental)

distortion

Skeletal class III

Th, sh, ch
(linguo-dental)

distortion

Anterior open
bite


ANATOMY OF
STOMATOGNATHIC SYSTEM
…..continued part - 2

Presented by- Dr.Neelesh Shah
Done Under The Guidance OfProfessor.Ashima.Valiathan
B.D.S {Pb}, D.D.S, M.S{U.S.A}
Director of P.G studies
Department of Orthodontics,
Manipal College Of Dental Sciences,
Manipal.




Swallowing (Deglutition)



Swallowing is a complicated mechanism, principally
because the pharynx subserves respiration as well as
swallowing. The pharynx is converted for only a few
seconds at a time into a tract for propulsion of food. It
is especially important that respiration not be
compromised because of swallowing.
In general, swallowing can be divided into(1) Voluntary stage.
(2) Pharyngeal stage.
(3) Esophageal stage.






Effect of the Pharyngeal Stage of Swallowing on
RespirationThe entire pharyngeal stage of swallowing usually
occurs in less than 6 seconds, thereby interrupting
respiration for only a fraction of a usual respiratory
cycle. The swallowing center specifically inhibits the
respiratory center of the medulla during this time,
halting respiration at any point in its cycle to allow
swallowing to proceed. Yet even while a person is
talking, swallowing interrupts respiration for such a
short time that it is hardly noticeable.

• Voluntary Stage of SwallowingWhen the food is ready for swallowing, it is
"voluntarily" squeezed or rolled posteriorly
into the pharynx by pressure of the tongue
upward and backward against the palate. From
here on swallowing becomes entirely or almost
entirely automatic and cannot be stopped.


• Pharyngeal Stage of SwallowingAs the bolus of food enters the posterior mouth and
pharynx stimulates epithelial swallowing receptor
areas all around the opening of the pharynx,
especially on the tonsillar pillars, and sends impulses
from the trigeminal and glossopharyngeal nerves into
the medulla oblongata cither into or closely
associated with the tractus solitarius which receives
essentially all sensory impulses from the mouth
which initiate a series of automatic pharyngeal
muscle contractions. The trachea is closed, the
esophagus is opened, and a fast peristaltic wave
initiated by the nervous system of the pharynx forces
the bolus to pass into the upper esophagus, the entire
process occurring in less than 2 seconds.

• Esophageal Stage of Swallowing

The esophagus functions primarily to conduct food
rapidly from the pharynx to the stomach, and its
movements are organized specifically for this function.
The esophagus normally exhibits two types of peristaltic movements: primary peristalsis and secondary
peristalsis. Primary peristalsis is simply continuation
of the peristaltic wave that begins in the pharynx and
spreads into the esophagus during the pharyngeal stage
of swallowing. This wave passes all the way from the
pharynx to the stomach in about 5 to 10 seconds. Food
swallowed by a person who is in the upright position is
usually transmitted to the lower end of the esophagus
even more rapidly than the peristaltic wave itself, in
about 5 to 8 seconds, because of the additional effect of
gravity pulling thewww.indiandentalacademy.com
food downward.

• If the primary peristaltic wave fails to move
into the stomach all the food that has entered
the esophagus secondary peristaltic waves
result from distention of the esophagus itself
by the retained food; these waves continue
until all the food has emptied into the stomach.
The secondary peristaltic waves are initiated
partly by intrinsic neural circuits in the
myenteric nervous system and partly by
reflexes that begin in the pharynx and are then
transmitted upward through vagal afferent
fibers to the medulla and back again to the
esophagus through glossopharvngeal and
vaga! efferent nerve fibers.

Deglutition


Tongue thrust




A case report by Dr.Valiathan A. AND Sameer H Shaikh. (J

Ind Ortho Soc 1998;31:53-57) showed the effect of an
abnormally large tongue in producing the spaces similar in
appearance to primate spaces. A 28 year male patient of south
Indian origin was presented with a chief complain of
proclination of upper anterior teeth along with spacing
between the same. His face was fairly symmetrical with
convex facial profile, prominent nose, acute nasolabial angle
and incompetence of lip. An additional lateral ceph was taken
following the administration of radio- opaque contrast medium
to highlight the dorsum of tongue and related soft tissue.
Based on detailed examination of the tongue dimension,
tongue volume, electromyographic activity and force exerted
by the tongue, it was concluded that excessively large volume
tongue and dimension produce excessive force which possibly
causes the malocclusion.



A study by Dr.Ashima Valiathan & Padmapriya C V was done
on tongue volume & tongue force exerted during swallowing
to evaluate their effect on the dentition. cephalometric findings
of the study group were compared with normal cases as well
as togue volume & pressure were measured. The results
showed an increase in tongue pressure of 33 cN compared to
20.5 cN in control group & also an increase in the occurance
of mouth breathing & tongue & lip habits in the study
group.Thus in the complex etiology of bimaxillary
protrusion,environmental factors in the form of various habits
& excessive tongue force play an important role.


• A study by Jeryl D.English and Kamrin D.G.Olfert (Semin
Orthod 11:164-169 2005 ) The article distinguishes between
dental open bite and skeletal open bite malocclusions and
reviews the etiologic factor and possible treatment options.
The addition of light masticatory muscle exercise on two
mixed detention cases is illustrated. The patients were treated
with a bonded rapid palatal expander followed by a
transpalatal arch and a mandibular lingual arch, high-pull
headgear therapy and light masticatory muscle exercises for 1
minute five times per day. A third case illustrates an increase
in the clenching exercises of at least 5 minutes per hour for 6
hours. This patient had changed her mind on orthognathic
surgical treatment plans. Treatment results suggest that
clenching exercises helped to control the vertical dimension
and assist in closure of open bite malocclusions.

Tooth


Actions of Muscles




Action of different muscles is coordinated,
each performing a specific action to work
together to accomplish a given movement
eg. some contract isotonically to move a
part, some isometrically to stabilize, while
others undergo controlled relaxation.
Movements controlled by CNS.


Neurologic Control of the
Masticatory System






Nerve impulses, picked up by sensory
receptors, travel through afferent neurons to
the CNS
Return impulses travel back from the CNS
through efferent neurons to muscle to
produce an action
Most sensory + motor innervation for
masticatory system provided by trigeminal
nerve

Neurologic Control of the
Masticatory System


Areas of the brain involved are:
– Brain stem (trigeminal nuclei).
– Regulatory and modifying areas (e.g thalamus,
reticular formation).
– Cortex.


Sensory Receptors




Detect stimuli and provide information to
CNS
Types:
– Muscle spindles- proprioception
– Golgi tendon organs- proprioception
– Pacinian corpuscles- movement & firm
pressure
– Nociceptors- pain

Neural Control of Mandibular
Function


Movements can be:
– Voluntary- conscious act
– Involuntary- reflex
– Automatic- acquired patterns of movement
- e.g. chewing


Reflexes







Movement takes place without conscious
control
Occurs without cortex involvement
Protective in nature
Results from stimulation of a receptor
Masticatory reflexes
– Myotatic reflex
– Nociceptive reflex

Reflexes


Myotatic reflex (stretch reflex)






occurs when a muscle is quickly stretched
results in contraction of stretched muscle
involved in determining rest position of jaw

Nociceptive reflex (flexor reflex)




occurs when a hard object is encountered when
chewing
results in jaw dropping open

Regulation of Muscle Activity








Automatic movements are controlled by the
brainstem- central pattern generator.
Coordinates timing of antagonistic muscle
function.
Somewhere between voluntary &
involuntary lies rhythmic, subconscious
functions- e.g. chewing, swallowing, etc.
Can be altered by cortical input- conscious
act or influenced by stress, emotion, etc.

Temporo Mandibular disorder
• Temporomandibular joint
disorder (TMJD or TMD),
or TMJ syndrome, is an
acute or chronic
inflammation of the
temporomandibular joint,
which connects the lower
jaw to the skull. The
disorder and resultant
dysfunction can result in
significant pain and
impairment.


Concepts of orthopedic stability




Musculoskeletal stable position – It is that position
when the condyles are in their most superoanterior
position in the articular fossae, resting against the
poosterior slopes of articular eminences, with the
articular disc properly interposed.
The most stable occlusal position – It is the maximal
intercuspation of teeth. This type of occlusal
relationship furnishes maximum stability for the
mandible while minimizing the amount of force
placed on each tooth during function.

• Optimal orthopedic stability in the masticatory
system is to have even & simultaneous contact
of all possible teeth when the mandibular
condyles are in their most superoanterior
position, resting against the posterior slopes of
the articular eminences, with the disc properly
interposed. ie- the musculoskeletal stable
position of the condyles coincides with the
maximal intercuspation position.

Determinants of orthopedic stable
position


Closed and opened positions

jaw closed

jaw opened

Types of TMD


•
•
•



Three most common temporomandibular disorders
areMyofascial pain and dysfunction,
Internal derangement, and
Osteoarthrosis.
Myofascial pain and dysfunction is by far the most prevalent.
It is primarily a muscle disorder resulting from oral
parafunctional habits such as clenching or bruxism. These
habits are sometimes related to psychogenic disorders such as
headache, chronic back pain, and irritable bowel syndrome.
Stress, anxiety, and depression are key features of myofascial
pain and dysfunction.





The term internal derangement describes a
temporomandibular disorder in which the articular
disc is in an abnormal position, resulting in
mechanical interference and restriction of the normal
range of mandibular activity.
Osteoarthrosis is a localised degenerative disorder
that affects mainly the articular cartilage of the
temporomandibular joint and is often seen in older
people.

Precipitating factors


Over-opening the jaw beyond its range or
unusually aggressive or repetitive sliding of the
jaw sideways or forward (protrusive). These
movements may also be due to abnormal habits
or a malalignment of the jaw or dentition. This
may be due to:












Modification of the occlusal surfaces of the
teeth thorugh dentistry or accidental trauma.
Speech habits resulting in jaw thrusting.
Excessive gum chewing or nail biting.
Excessive jaw movements associated with
exercise.
Repetitive unconscious jaw movements
associated with bruxing.
Size of foods eaten.

Clinical features
There are three cardinal
features of
temporomandibular
disorders
• Orofacial pain,
• Joint noise, and
• Restricted jaw function.


• Patients describe either a generalised tight
feeling, which is probably a muscular disorder,
or the sensation that the jaw suddenly
"catches" or "gets stuck," which is usually
related to internal derangement.
• Headaches, ear aches, tinnitus, and neck and
shoulder pains are just a few of a number of
non-specific symptoms that are often reported
by patients with temporomandibular disorders.

Differential diagnosis






Dental pain.
Disorders of the ears, nose, and sinuses.
Diseases of the major salivary glands.
Neuralgias.
Headaches.


Myofascial pain dysfunction syndrome


There are four cardinal signs and symp-toms of the syndrome:
(1) Pain,
(2) Muscle tenderness;
(3) A clicking or popping noise in the temporomandibular joint,
(4) Limitation of jaw motion, unilaterally or bilat-erally in
approximately an equal ratio, sometimes with deviation on opening.



Two typical negative disease characteristics:
(1) An absence of clinical, radiographic or biochemical evidence of
organic changes in the joint itself,
(2) Lack of tenderness in the joint when it is palpated through the
external auditory meatus.

Functionally dislocated discs


Types of disc displacements


Reciprocal clicking and disc
displacement with reduction (DDR)


The “Road to Perdition”


Adhesions


Temporomandibular disorder screen
examination.



Muscle palpation.
TMJt palpation.

Click
Crepitus.




Range of mandibular motion.
Occlusal evaluation

Muscle palpation.


TMJt palpation


.
Range of mandibular motion Occlusal evaluation


How can i locate the musculoskeletally
stable position of the condyles in fossa ??


Manual method to achieve MSSP


Use of leaf gauge to achieve MSSP


Treatment
Non-surgical treatment of temporomandibular disorders
continues to be the most effective way of managing over 80%
of patients.
• Explanation and reassurance
• Patient education and self care
• Drug treatment (non-steroidal anti-inflammatorydrugs,opiates,tranquillisers,
tricyclic antidepressants)

•
•
•
•

Occlusal therapy – (70% of patients)
Physiotherapy
Behavioural therapy
Surgical treatment – (5% of patients)

Factors that reduce symptoms with
occlusal appliance








Alteration in occlusal condition
Alteration in condylar position
Increase in vertical dimension
Cognitive awareness
Placebo effect
Increase in peripheral input to the CNS.
Regression to mean.

• Study-by Magnusson T (Cranio 4(4):338-344 1986)
A 5years longitudinal study - observed untreated subjects
at age 15 years, & then again 20 years found that
clicking is common in this age group & that clicking can
come & go, unrelated to any major clinical symptoms.
Therefore if patient reports the onset of a joint sound
unrelated to pain and occlusal condition is being
developed in harmony with the stable joint position,
patient education regarding the problem may be all that
is needed.

Conclusion






Anatomy of stomatognathic system is the basic pillar
for any dental clinician whose sound knowledge is
very important; it helps us in diagnosis & treatment
of many oral disorders.
It also helps us in various treatment modalities like
implant placement, diagnosing TMJt disorders,
myofunctional pain dysfunction syndrome,etc.
It’s knowedge helps an orthodontic treatment in such
a manner that the finished result reflects a balance
between the structural changes obtained and
functional forces acting on the teeth and investing
tissue at that time.



The orthodontist is challenged constantly with the
task of providing each patient with acceptable
esthetics and masticatory function. Although
esthetics is often the patient’s immediate and
primary goal, functional outcomes are far more
important over the lifetime of the patient.
Developing a sound functional masticatory system
needs to be the primary goal of all orthodontic
therapy. No other dental specialist routinely alters
the patient's occlusal condition as a part of the
therapy.



The orthodontist is in a unique position to
improve or worsen the occlusal condition
while carrying out the esthetic goals of the
therapy. It therefore behooves the orthodontists
to be knowledgeable of normal masticatory
function and the goals that need to be achieved
to maintain normal function. These goals
should be met in all patients, those with and
without masticatory dysfunction.

References
1.

2.

3.
4.

5.

6.

Atlas of anatomy- Grant`s 11th edition Lippincot
Williams & Wilkins - 2005.
Atlas of human anatomy- Neter`s 3rd edition
Elsevier - 2006.
Gray’s anatomy- 36th edition Elsevier - 2005.
Human anatomy volume -3 B.D.Chaurasia 4th
edition C B S Publication-2005.
Human embryology – Inderbersingh 5th editionMac
Millan India -1993.
William f Ganong- Medical physiology 19th
editionLange medical publication 2005.

8. Sujit Chaudhari- Concise medical physiology.
5th
edition New central book agency - 2004 .
9. Guyton- Human physiology & mechanism of disease
11th edition W.B.Saunders 2006.
10. Langman`s Medical embryology 10th edition
Lippincot Williams & Wilkins - 2006.
11. Jung MH,Yang WS etal- Effect of upper lip closing
force on craniofacial structures.Am.J. Orthod
.Dentofacial.Orthop Jan 2003 123,58-63,

12. Ashima Valiathan,Sameer H Shaikh-Malocclusion
and the tongue :J Ind Orthod Soc,1988,31:53-57
13. T.M.Graber - The “three Ms”: Muscles,
malformation, and malocclusion .Am. J. Orthodontics
vol-49 number- 6 June 1963
14.Thomas P George, Valiathan Ashima, Arji I George
& Denny J Payyappilly: Oral habits (Part II) Tongue
thrusting. Kerala Dental Association. 1992; 15(3 &
4): 721-724

15. Ashima Valiathan ,Padmapriya C V- Comparison of tongue
pressure, tongue volume and cephalometric values in kerela
population with and without bimaxillary protrusion-a clinical
study- J Ind Orthod Soc ,2003, 36;Page-158-163
16. Gedrange T ,Buttner- Myosine heavy chain protein and gene
expression in the masseter muscle of adult patients with distal
or mesial malocclusion. C,J.Apply.Genet,46,227-36.2005
17. Gedrange T etal- Computed tomographic examination of
muscle volume ,cross section and density in patients with
dysgnathia. [, 177(2),204-9,Rofo Feb 2005


18. Robert.E.Moyers-Handbook Of Orthodontics 4th
Edition Year book medical publisher – 1998.
19. William.R. Proffit- Contemporary Orthodontics,3rd
Edition.—Henry W.Fields.JR 3rd Edition
Mosby - 2000.
20. T.M.Graber - Orthodontics Principles and Practice 4th Edition Elsevier - 2005.
21. Thomas M.Graber, Thomas Rakosi, Alexandre
G.Petrovic-Dentofacial Orthopedics with Functional
Appliance 2nd Edition Mosby year book - 1997.

22. Jeryl D.English and Kamrin D.G.OlfertMasticatory muscle exercise as an Adjunctive
treatment for open bite malocclusions .Semin
Orthod 11:164-169 © 2005.
23. Okeson, Jeffrey P. "Management of
Temporomandibular Disorders and Occlusion"4th
edition. Mosby, Inc. 2003
24. D. M. Laskin, C. S. Greene, W. L. Hylander.-TMDs:
An Evidence Based-Approach to Diagnosis and
Treatment. (2006) Eds: Quintessence Books,
Chicago.

25. Clark GT.-A critical evaluation of orthopedic
interocclusal appliance therapy. Design theory and
overall effectiveness. J Am Dent Assoc 1984; 108:
359-364.
26. Clark GT, Adler RC- A critical evaluation of occlusal
therapy. Occlusal adjustment procedures. J Am Dent
Assoc 1885; 110: 743-750.
27. Stuart.C.White & Micheal.J.Paroah - Oral Radiology
Principles & Interpretation –4th Edition Mosby - 2000.
28. Shafer William.G- A Text Book Of Oral Pathology 4th
Edition W.B.Saunders ompany 1983.

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