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

PHYSIOLOGY OF
STOMATOGNATHIC
SYSTEM
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com


INTRODUCTION OF
PHYSIOLOGY OF STOMATOGNATHIC SYSTEM
STOMA
GNATHIA

- MOUTH
- JAWS

THE STRUCTURES OF THE MOUTH AND JAWS,
CONSIDERED COLLECTIVELY AS THEY SUBSERVE
THE FUNCTIONS OF MASTICATION, DEGLUTITION,
RESPIRATION AND SPEECH IS CALLED AS
STOMATOGNATHIC SYSTEM
( DORLAND MEDICAL DICTIONARY )


CONTENTS

OSTEOLOGY
FUNCTIONAL OSTEOLOGY
MYOLOGY
MUSCLES OF FACE , TONGUE,
MASTICATION
TEMPOROMANDIBULAR JOINT
ANATOMY OF TMJ
MOVEMENTS OF MANDIBLE
FUNCTIONS OF STOMATOGNATHIC
SYSTEM

BONE
INTRODUCTION
WHAT IS BONE
FUNCTIONS
CLASSIFICATION OF BONE
BONE MORPHOLOGY


MICROSCOPIC STRUCTURE
PHASES OF BONE
BONE MINERAL
MECHANICAL PROPERTIES OF BONE


INTRODUCTION OF BONE


WHAT IS BONE ?

SPECIALISED FORM OF CONNECTIVE TISSUE

EXTRACELLULAR MATRIX –
COLLAGEN , PROTEINS,
PROTEOGLYCANS , MINERAL


FUNCTIONS OF BONE
PROTECTION
SITE OF MUSCLE ORIGIN AND INSERTION
RIGIDITY
HAEMOPOIESIS
LABILE MINERAL POOL


BONE MORPHOLOGY
CATEGORISATION:
TUBULAR

--

FEMUR

CUBOIDAL

--

CARPUS

FLAT

--

FRONTAL BONE

IRREGULAR --

VERTEBRAE


ACCORDING TO DEVELOPMENTAL ORIGIN

ENDOCHONDRAL BONE

INTRAMEMBRANOUS BONE


ENDOCHONDRAL BONE FORMATION


BONE FORMATION IS PRECEDED BY FORMATION
OF CARTILAGENOUS MODEL – REPLACED BY BONE



MESENCHYMAL CELLS - CONDENSED –
CHONDROBLASTS -- HYALINE CARTILAGE
(PERICHONDRIUM, VASCULAR AND OSTEOGENIC CELLS)
– INTERCELLULAR – CALCIFIED BY ENZYME ALKALINE
PHOSPHATASE SECRETED BY CARTILAGE CELLS
– EMPTY SPACES ---PRIMARY AREOLAE ---SECONDARY
AREOLAE
– OSTEOGENIC CELLS – OSTEOBLASTS – OSTEOID –
CALCIFIED - LAMELLA OF BONE

INTRAMEMBRANOUS BONE


BONE LAID DOWN DIRECTLY IN FIBROUS MEMBRANE



MESENCHYMAL CELLS – BUNDLES OF COLLAGEN FIBRES



ALSO ENLARGE – BASOPHILIC CYTOPLASM –
OSTEOBLASTS – GELATINOUS MATRIX(OSTEOID) –BONE
LAMELLAE – OSTEOBLASTS MOVE AWAY – OSTEOID –
CALCIFIED – BONE



OSTEOBLASTS TRAPPED BETWEEN TWO LAMELLAE k/a
OSTEOCYTES.


CLASSIFICATION OF BONE TISSUE


WOVEN BONE



LAMELLAR BONE



COMPOSITE BONE



BUNDLE BONE


WOVEN BONE


WEAK, DISORGANIZED, POORLY MINERALIZED



SERVES WOUND HEALING BY :





RAPIDLY FILLING OSSEOUS DEFECTS
INITIAL CONTINUITY FOR FRACTURES AND OSTEOTOMY
SEGMENTS
STRENGTHENING BONE WEAKENED BY SURGERY OR
TRAUMA

 FIRST

FORMED BONE TO ORTHODONTIC
LOADING




NOT FOUND IN ADULT SKELETON



FUNCTIONAL LIMITATIONS :
IMP. ASPECTS OF ORTHODONTIC RETENTION
HEALING PERIOD FOLL. ORTHOGNATHC SURGERY


LAMELLAR BONE


STRONG,HIGHLY ORGANISED, WELL MINERALIZED



99% ADULT SKELETON



STRENGTH OF BONE DIRECTLY RELATED TO MINERAL
COMPONENT

WOVEN BONE < NEW LAMELLAR BONE < MATURE LAMELLAR
BONE


COMPOSITE BONE


LAMELLAR BONE WITH IN WOVEN BONE LATTICE



PRODUCES STRONG BONE



PRIMARY OSTEONS



SECONDARY OSTEONS


BUNDLE BONE


FUNCTIONAL ADAPTATION



ATTACHMENTS OF TENDONS , LIGAMENTS



SHARPEY’S FIBRES


MICROSCOPIC STRUCTURE
CANCELLOUS BONE (SPONGY BONE) ---TRABECULAE ----OSTEOCYTES ---LACUNAE

CORTICAL BONE ( COMPACT BONE) –
BASIC STRUCTURE – HAVERSIAN SYSTEM


HAVERSIAN
SYSTEM
CENTRAL VASCULAR
CANAL
8 -10 CONCENTRIC
LAMELLAE
CEMENT LINES
VOLKMAN’S CANAL

PHASES OF BONE
OSSEOUS MATRIX

----

CELLULAR COMPONENTS

ORGANIC,INORGANIC
COMPONENTS

----

OSTEOBLASTS,OSTEOCYTES,OSTEOCLASTS


BONE MINERAL

RESEMBLES PRECIPITATED HYDROXYAPATITES.
DISTINCTIVE FEATURES OF BONE APATITE :
SMALL CRYSTAL SIZE
LACK OF CHEMICAL PERFECTION
INTERNAL CHEMICAL DISORDER


MECHANICAL PROPERTIES OF
BONE
TENSILE STRENGTH:
DEPENDS ON ORIENTATION AND NUMBER OF
COMPONENT COLLAGEN FIBRES.
SUPERIOR WHEN COLLAGEN FIBRES ARE PARALLEL TO
LONG AXIS OF TENSION.
HAVERSIAN SYSTEMS WITH HIGH LEVEL OF
CALCIFICATION ARE STIFFER.

COMPRESSIVE PROPERTIES
DEPENDS ON ARRANGEMENT OF COMPONENT COLLAGEN
FIBRES
CIRCUMFERENTIAL COLLAGENOUS FIBRES

-------

SUPERIOR COMPRESSIVE STRENGTH,
INFERIOR TENSILE PROPERTIES
LONGITUDINAL COLLAGEN FIBRES

--------

SUPERIOR TENSILE ,
INFERIOR COMPRESSIVE PROPERTIES


FUNCTIONAL OSTEOLOGY


TRAJECTORIAL THEORY OF BONE
FORMATION
MEYER (1867) , CULMANN
TRAJECTORIAL THEORY OF BONE
FORMATION
BENNINGHOFF -(STRESS TRAJECTORIES)
JULIUS WOLF (1870)
(LAW OF ORTHOGONALITY)
ROUX

(LAW OF TRANSFORMATION OF BONE)




VANDERKLAU
(FUNCTIONAL CRANIAL COMPONENT)



MELVIN MOSS
(FUNCTIONAL MATRIX HYPOTHESIS)


MECHANISMS OF BONE GROWTH


BONE DEPOSITION AND RESORPTION
BONE DEPOSITION
BONE RESORPTION
BONE REMODELING
BONE REMODELING


MODELING AND REMODELING
SKELETAL ADAPTATION :


ALTERATION IN MASS



GEOMETRIC DISTRIBUTION



MATRIX ORGANISATION



COLLAGEN ORIENTATION OF LAMELLAE


BONE MODELING
INDEPENDENT SITES , CHANGE THE
FORM OF BONE

BONE REMODELING
SPECIFIC, REPLACES PREVIOUSLY
EXISTING BONE


INTERNAL REMODELING VIA AXIALLY ORIENTED
CUTTING /FILLING CONES


MODELING CHANGES

-- CEPHALOMETRIC TRACINGS

REMODELING CHANGES -- MICROSCOPIC LEVEL
TRUE REMODELING

--

NOT IMAGED ON CLINICAL
RADIOGRAPHS

CONSTANT REMODELING –- COUPLING FACTORS
( INTERNAL TURNOVER)


ORTHODONTIC BONE MODELING




REGIONAL ACCELERATORY PHENOMENON



CLINICAL IMPORTANCE :


ORTHOPEDICALLY POSITION MAXILLA

 RAPID

ORTHODONTIC ALIGNMENT OF TEETH FOLL.
ORTHOGNATHIC SURGERY


CONTROLLED BY :
METABOLIC AND MECHANICAL SIGNALS


MODELING : CONTROLLED BY :
 FUNCTIONAL

APPLIED LOADS

 HORMONES
 METABOLIC

AGENTS

 PARACRINE

AND AUTOCRINE MECHANISMS

( LOCAL GROWTH FACTORS , PROSTAGLANDINS )




REMODELING :
METABOLIC DISORDERS
( PARATHYROID HORMONES AND ESTROGENS )


BOIMECHANICS


GRAVITY



MECHANICAL LOADING


 FROST’S

MECHANOSTAT THEORY

 MARTIN

AND BURR

 DISUSE

ATROPHY -- < 200 µE

200 - 2500µE
 HYPERTROPHIC INCREASE -- 2500 - 4000 µE

PATHOLOGIC OVERLOAD -- > 4000µE
 PHYSIOLOGICAL

PHYSIOLOGICAL LOADING

--


 CLINICAL

REFERENCE

 BIOMECHANICAL

LOADS

RESPONSES TO APPLIED


IMP. OBJECTIVES OF ORTHODONTIC TREATMENT


AVOIDING OCCLUSAL PREMATURITIES



GUARDING EXCESSIVE TOOTH MOBILITY



OPTIMAL DISTRIBUTION OF OCCLUSAL LOADS


DISTRACTION OSTEOGENESIS


BONES CAN BE INDUCED TO GROW AT
SURGICALLY – CREATED SITES.



A PROCESS OF NEW BONE FORMATION BETWEEN
SURFACES OF BONE SEGMENTS SEPARATED BY
INCREMENTAL TRACTION (COPE -- 1999)


ALIZAROV
(1950)


GROWTH OF MAXILLA :
AT SUTURES
 DIRECT REMODELING
 TRANSLATED DOWNWARDS AND FORWARDS


GROWTH OF MANDIBLE :
 ENDOCHONDRAL

PROLIFERATION AT THE CONDYLE
 APPOSTION AND RESORPTION OF BONE


Steps involved :


Corticotomy/Osteotomy



Latency period



Distraction phase



Consolidation phase


TENSION STRESS EFFECT


CURRENT SCOPE :


Correction of Maxillo-Mandibular deformities
Maxillary lengthening
Mandibular lengthening
Maxillary and Mandibular widening
Lengthening of the Hard palate
Distraction in other cranio-facial areas




Alveolar ridge augmentation



Transport disc and Transformation
osteogenesis.



Dental Distraction.


TISSUE CHANGES FOLLOWING DO
HISTOLOGIC CHANGES :




During latency phase – formation of a
fibrous bridge.
During distraction phase – distinct zones
seen


FACTORS AFFECTING DO
Biologic :
 AGE
 SITE

OF SURGERY

 LATENCY
 RATE

PERIOD

AND RHYTHM


BIOMECHANICAL FACTORS :


Planning the distraction vector



Device fixity



Need for ‘ Bone moulding’


Mandibular Distraction
INDICATIONS:
Hemifacial Microsomia
Treacher Collin Syndrome etc.
TMJ ankylosis and condylar fractures
Transverse deficiency of the mandible


BIOMECHANICAL EFFECTS OF DISTRACTON
VECTOR


THE SKULL
INTRODUCTION


SKULL

CALVARIA
(BRAIN BOX)

FACIAL SKELETON




BONES OF THE SKULL

:

22 BONES

CALVARIA OR BRAIN CASE:
PAIRED

8 bones

UNPAIRED

PARIETAL
TEMPORAL

FRONTAL
OCCIPITAL
SPHENOID
ETHMOID


FACIAL SKELETON : 14 bones
PAIRED

UNPAIRED

MAXILLA
ZYGOMATIC
NASAL
LACRIMAL
PALATINE
INFERIOR NASAL CONCHA


MANDIBLE
VOMER

MANDIBLE
LARGEST,STRONGEST BONE
FIRST PHARYNGEAL ARCH
HORSE SHOE SHAPED BODY
PAIR OF RAMI


BODY OF MANDIBLE
SURFACES:
OUTER SURFACE
INNER SURFACE

BORDERS:
UPPER BORDER
LOWER BORDER


OSSIFICATION
Greater part ossifies in membrane
Parts ossifying in cartilage –
incisive, coronoid, condyloid, upper half
of ramus.
Each half ossifies from only one centre – 6th
week of intra uterine life -- in mesenchymal
sheath of meckel’s cartilage – mental foramen.
Symphysis menti


AGE CHANGES IN THE MANDIBLE
IN INFANTS AND CHILDREN:
Two halves fuse -- first year of life
At birth – mental foramen opens below the sockets
Angle is obtuse -- 140 degrees or more


IN ADULTS
Mental foramen opens mid-way
Angle reduces – 110 or 120 degrees


IN OLD AGE

Alveolar bone resorbed.
Mental foramen and mandibular canal – close to
alveolar border.
Angle again – obtuse– 140 degrees.


MAXILLA
-- second largest bone of the face, first being
mandible
FEATURES:
BODY.
FOUR PROCESSES:
Frontal, zygomatic,
alveolar, palatine.


BODY:
pyramidal in shape , base directed medially,
apex laterally.
four surfaces
encloses maxillary sinus.


OSSIFICATION
OSSIFIES IN MEMBRANE
FROM THREE CENTRES :
ONE FOR MAXILLA PROPER
TWO FOR OS INCISIVUM OR PREMAXILLA


MAXILLA PROPER
CENTRE:
ABOVE CANINE FOSSA,
6TH WEEK OF INTRAUTERINE LIFE


PREMAXILLA
MAIN CENTRE:
ABOVE INCISIVE FOSSA
7TH WEEK OF INTRAUTERINE LIFE
SECOND CENTRE (PARASEPTAL / PREVOMERINE):
VENTRAL MARGIN OF NASAL SEPTUM
10TH WEEK
FUSES WITH PALATAL PROCESS


AGE CHANGES
AT BIRTH:
TRANSVERSE AND AP DIAMETER MORE THAN
VERTICAL.
FRONTAL PROCESSES WELL MARKED.
BODY LITTLE MORE THAN ALVEOLAR PROCESSES
TOOTH SOCKETS REACHING FLOOR OF ORBIT
MAXILLARY SINUS MERE FURROW ON LATERAL WALL
OF NOSE.


ADULT:
VERTICAL DIAMETER GREATEST

OLD:
REVERTS TO INFANTILE CONDITION
HEIGHT REDUCED


 Sutures

of maxilla

– Frontomaxillary suture
– Lacrimomaxillary
– Zygomaticomaxillary
– Ethmoidomaxillary
– Palatomaxillary
– Nasomaxillary
– Sphenomaxillary
– Intermaxillary

MYOLOGY
STUDY OF MUSCLES,MUSCULAR SYSTEM
AND THEIR FUNCTIONS AND DISORDERS.

MUSCLE:
Physical properties: kinetic activity

1: Elasticity.
2: Contractility.


Elasticity:
a) length.
b) cross- section.
c) force exerted.
d) constant coefficient.
RATIO IN UNIAXIAL CASE :

FΔ = AEL


Hooke’s law :
Muscle returns to exact original shape after being
stretched.
The linear elastic range is dependent upon the
nature of material involved.
Valid and linear only at initial stage.


CONTRACTILITY:
The ability of a muscle to shorten it’s length under
innervational impulse


SHERRINGTON : ALL OR NONE LAW
The intensity of contraction of any fibre is
independent of the strength of the exciting
stimulus, provided the stimulus is adequate.
The strength of muscle contraction depends on :
The frequency of stimuli.
No. of fibres involved.
Applies only when muscle is in physiologic reacting
state


ISOMETRIC CONTRACTION :
Occurs when a muscle is simply resisting an
external force without any actual shortening.
ISOTONIC CONTRACTION :
there is actual shortening. Eg.flexing the
biceps.


PRINCIPLES OF MUSCLE
PHYSIOLOGY
Visualisation by Electromyogram.
EINTHOVEN (1918).
(Action current)
ADVANTAGE :
Relatively accurate picture of muscle activity
under diverse functional conditions.




Muscle Tonus:
is a state of slight constant tension .
Serves to obviate the muscle.
Basis of reflex posture.
Maintenance of various positions.



Resting Length:
Permits maintenance of postural relations and
dynamic equilibrium -- contraction of minimal
no. of fibres.




Stretch or Myotactic reflexes:
The reflex contraction of a healthy muscle which
results from a pull on its tendon.
(Achilles Tendon Reflex)



Reciprocal Innervation and Inhibition:
Given by Sherrington.
Brought about by excitation of its antagonist.


THE FACE
MUSCLES OF THE FACE




FACIAL MUSCLES
SUBCUTANEOUS MUSCLES

EMBRYOLOGICALLY:
Mesoderm of second branchial arch
supplied by facial nerve

MORPHOLOGICALLY:
remnants of panniculus carnosus




TOPOGRAPHICALLY:
SIX HEADS;

MUSCLES OF THE SCALP
MUSCLES OF AURICLE
MUSCLES OF EYELIDS
MUSCLES OF THE NOSE
MUSCLES AROUND MOUTH
MUSCLES OF THE NECK


ORBICULARIS ORIS
Composed of eight segments, each
segment resembles a fan wth its stem at
the modiolus.
Each fan is open in peripheral segments
and closed in marginal segments.
ORIGIN AND INSERTION :
Intrinsic part :
superior incisivus from maxilla and inferior
from mandible –inserting into the angle of
mouth.



Extrinsic part :
– middle strata from buccinator and superficial
from lips and inserts into lips and angle of
mouth.

ACTIONS :

Closing the mouth.
whistling.

BUCCINATOR
Thin , quadrilateral muscle between maxilla
and mandible.


ORIGIN AND INSERTION :
Upper fibres – opposite maxillary molars –
insert in upper lip.
Middle fibres – pterygomandibular raphe –
decussate.




Lower fibres -- opposite mandibular molars
– insert in lower lip.
ACTIONS :

Compresses the cheeks against teeth,
passsing food inbetween them in
mastication.
Expelling air when the cheeks are distended.


THE BUCCINATOR MECHANISM


FACTORS

IN ENVIRONMENTAL BALANCE :

MUSCULATURE :
A RESTING MUSCLE IS STILL PERFORMING A FUNCTION –
ENVIRONMENTAL FACTORS :
CONTACT RELATIONSHIP AND RESISTANCE
OFFERED BY :
Buttressing effect of contiguous teeth.
Occlusal interdigitation
Bone building resorption balance
Actual size and shape of roots of teeth
Total amount of periodontal fibres









STABILITY DEPENDS ON :
GENETIC
EPIGENETIC
ENVIONMENTAL
MORPHOLOGIC
PHYSIOLOGIC FACTORS


 Winders:
During mastication and deglutition, tongue
may exert two or three times much force on
the dentition as lips
and cheeks at any one
time.




Lear and Moorrees:
Substantiate the imbalance of buccolingual
forces,
Limitations –
measuring equipment
hydraulic nature of response
size of sample
geometry of dental arch


 Proffit:

Labial pressures are easier to measure than
lingual pressures.

Fry (1960)
Data for lingual pressure must be recorded
with some suspicion.


BUCCINATOR MECHANISM


TONGUE


Muscular organ situated in the floor of the mouth.

Associated with functions of taste, speech,
Mastication and deglutition.





Has two parts :
Oral part - lies in the mouth.
Pharyngeal part -- lies in the pharynx.



These parts are separated by V –shaped sulcus
k/a sulcus terminalis.



External features:
ROOT .
TIP.
BODY.


ROOT ;
attached to mandible and soft palate above
hyoid bone below.
BODY –

upper surface – curved k/a dorsum.

Dorsum : divided into :
oral part
pharyngeal part

Inferior surface – confined to oral part.


PAPILLAE OF TONGUE :

CIRCUMVALLATE PAPILLAE
FUNGIFORM PAPILLAE
FILIFORM / CONICAL PAPILLAE

MUSCLES OF TONGUE
INTRINSIC MUSCLES
SUPERIOR LONGITUDINAL
INFERIOR LONGITUDINAL
TRANSVERSE
VERTICAL


EXTRINSIC MUSCLES :
GENIOGLOSSUS
HYOGLOSSUS
STYLOGLOSSUS
PALATOGLOSSUS


ARTERIAL SUPPLY :
LINGUAL ARTERY – EXTERNAL CAROTID ARTERY
ROOT OF TONGUE – TONSILLAR AND ASCENDING
PHARYNGEAL ARTERIES.

VENOUS DRAIN :
DEEP LINGUAL VEIN


LYMPHATIC DRAINAGE :
TIP OF TONGUE – bilaterally into submental nodes.
RIGHT AND LEFT HALVES – submandibular nodes.
POSTERIOR ONE- THIRD – jugulo-omohyoid nodes.


NERVE SUPPLY :
MOTOR NERVE :
HYPOGLOSSAL NERVE -- ALL INTRINSIC AND

EXTRINSIC MUSCLES EXCEPT

PALATOGLOSSUS

PALATOGLOSSUS

– CRANIAL ROOT OF ACCESSORY

PHARNGEAL PLEXUS

NERVE THROUGH

SENSORY NERVE :
LINGUAL NERVE
–
CHORDA TYMPANI –

NERVE OF GENERAL SENSATION
NERVE OF TASTE


DEVELOPMENT OF TONGUE
EPITHELIUM :
ANTERIOR TWO-THIRDS –
two lingual swellings , one tuberculum impar.
arise from first branchial arch.
supplied by lingual nerve.
POSTERIOR ONE –THIRD –
cranial part of hypobranchial eminence.
arise from third arch.
supplied by glossopharyngeal nerve.


MUSCLES :
OCCIPITAL MYOTOMES – hypoglossal nerve
CONNECTIVE TISSUE :
local mesenchyme.


MUSCLES OF MASTICATION
MASSETER
TEMPORALIS
LATERAL PTERYGOID
MEDIAL PTERYGOID


MASSETER


TEMPORALIS


LATERAL PTERYGOID


MEDIAL PTERYGOID




MUSCLES PRODUCING MOVEMENTS
DEPRESSION :

LATERAL PTERYGOID,DIGASTRIC,
GENIOHYOID, MYLOHYOID
– ELEVATION:
MASSETER, TEMPORALIS,
MEDIAL PTERYGOID
– PROTUSION :
LATERAL ,MEDIAL PTERYGOID
– RETRACTION :
POSTERIOR FIBRES OF TEMPORALIS
–

LATERAL OR SIDE MOVEMENTS :
LEFT LATERAL PTERYGOID AND RIGHT MEDIAL
PTERYGOID

TEMPOROMANDIBULAR JOINT
IS A SYNOVIAL JOINT OF CONDYLAR VARIETY.


ARTICULAR SURFACES:
UPPER ARTICULAR SURFACE :
ARTICULAR EMINENCE
ANTERIOR PART OF MANDIBULAR FOSSA
LOWER ARTICULAR SURFACE :
HEAD OF MANDIBLE


LIGAMENTS:
FIBROUS CAPSULE
LATERAL LIGAMENT
SPHENOMANDIBULAR LIGAMENT
STYLOMANDIBULAR LIGAMENT




FIBROUS CAPSULE



ATTACHED ABOVE :

Articular tubercle
Circumference of mandibular fossa
Squamotympanic fissure
BELOW ;
Neck of condyle.



LATERAL/TEMPOROMANDIBULAR
LIGAMENT :

Reinforces and strengthens lateral part .
 Fibres directed downwards and backwards.
 Attached above :
articular tubercle
Below :
posterolateral aspect of neck of condyle

SPHENOMANDIBULAR LIGAMENT


Accessory ligament.



Lies on deep plane away
fromfibrous capsule.



ATTACHED SUPERIORLY :
Spine of sphenoid.






INFERIORLY ;
Lingula of mandibular foramen.

STYLOMANDIBULAR LIGAMENT


ACCESSORY LIGAMENT.

ATTACHED ABOVE :
Lateral surface of styloid process


BELOW :
Angle and posterior border of ramus of mandible.





ARTICULAR DISC

OVAL FIBROUS PLATE
DIVIDES JOINT INTO:
UPPER COMPARTMENT
PERMITS GLIDING
MOVEMENTS
LOWER COMPARTMENT
ROTATORY AND GLIDING
MOVEMENTS

ARTERIAL

SUPPLY

SUPERFICIAL TEMPORAL ARTERY
MAXILLARY ARTERY
NERVE

SUPPLY

AURICULOTEMPORAL NERVE
MASSETERIC NERVE




MOVEMENTS OF TMJ
BETWEEN UPPER ARTICULAR SURFACE
AND ARTICULAR DISC
(MENISCOTEMPORAL COMPARTMENT)
BETWEEN DISC AND HEAD OF MANDIBLE




PROTRACTION OF MANDIBLE
– Articular disc glides forwards over upper
articular surface, head of mandible moving
with it.
– Reversal of this movement is c/a retraction.


SLIGHT OPENING OF THE MANDIBLE



Head of the mandible moves on the undersurface
of the disc like a hinge.


WIDE OPENING OF MANDIBLE


Hinge like movement is followed by gliding of the
disc and head of the mandible as in protraction.



At the end of this movement, head comes to lie
under articular tubercle.


CHEWING MOVEMENTS


Involve side to side movements of mandible.





Head of right side glides forward along the disc as
in protraction,
Head of the left side rotates on vertical axis.



As a result chin moves forwards and to left side




MUSCLES PRODUCING MOVEMENTS
DEPRESSION :

LATERAL PTERYGOID , DIGASTRIC
GENIOHYOID,MYLOHYOID

ELEVATION: MASSETER, TEMPORALIS,MEDIAL
PTERYGOID
PROTUSION : LATERAL ,MEDIAL PTERYGOID
RETRACTION : POSTERIOR FIBRES OOF
TEMPORALIS
LATERAL OR SIDE MOVEMENTS ; LEFT LATERAL
PTERYGOID AND RIGHT MEDIAL PTERRYGOID


FUNCTIONAL MOVEMENTS
The mandible is the only movable bone
in the head and face and can only
be moved in certain directions
because of limitations of morphology
And structure of temporomandibular
articulation.


OPENING MOVEMENT OF THE MANDIBLE
Condyle brought downward and forward as chin
drops downward and backward.
Gravity and primary contraction of lateral pterygoid
muscles.
Stabilizing and adjusting activity seen in
suprahyoid ,infrahyoid groups ,in the geniohyoid ,
mylohyoid, and digastric muscles.
Stylohyoid muscle changes in length.

Hyoid bone moves downward and backwards.
Temporal , masseter and medial pterygoid muscles
show relaxation – opening movement smooth.
(paralysis of these makes opening movement jerky
and uncontrolled).
Articular disc brought forward by lateral pterygoid
muscle and capsular ligaments as condyle rotates
against inferior surface of the disk.


CLOSING MOVEMENT OF THE MANDIBLE
More power is elicited on mandibular closure.
Hyoid bone moves upward and forward .
Controlled relaxation of lateral pterygoid muscles
helps in smooth closure of mandible.


PROTUSION OF THE MANDIBLE
Brought about when medial and lateral pterygoid
muscles contract in unison, in conjunction with
controlled stabilizing relaxation of opening muscles.


RETRUDING ACTION OF MANDIBLE
By contraction of posterior fibres of temporalis
muscles with some assistance from geniohyoid ,
digastric and mylohyoid muscles.
Hyoid bone moves posteriorly.
Electromyographic research indicates that deep
fibres of masster muscle assist in retrusion of the
mandible.


WORKING BITE
To establish a working bite , the mandible must be
moved to the right or left.
This lateral movement is initiated by the contraction
of lateral pterygoid muscles on one side and
relaxation on the opposite side.


As the teeth are brought closure to an end to end
relationship, masseter contracts on left side,
assisting in ipsilateral activity.

As the teeth are brought together , strong activity is
elicited in both masseter and temporalis muscles
on both sides.


BENNETT MOVEMENT
In the lateral shift of the mandible, the articular disk
moves toward the side of the working bite.
The condyle moves
slightly laterally
and rotates on the
working side.


Primary contraction in the middle and posterior fibres
of temporalis muscle and in the posterior fibres of
masseter and some increased activity in hyoid
group.
BALANCING SIDE :
Condyle and disc moves downward and forward on
the articular eminence
Muscle activity consists largely of lateral pterygoid
contraction and controlled relaxation of masseter ,
temporalis and suprahyoid group.


POSITIONS OF THE MANDIBLE


Posselt recorded graphically various positions and
movement area in sagittal plane


POSTURAL RESTING POSITION
In infants ,muscles associated with suckling or
intake of food are well developed from the
beginning.
When child is not engaged in taking food,mandible
assumes position of rest whether the teeth are
present or not.


Mandibular resting position is one of the earliest
positions to be developed.
Mandible is suspended from
cranial base by
cradling musculature.


Posselt observes that “ Postural position can be
altered by conditions in masticatory system as well
as by systemic factors.”
Factors influencing postural position :
Body and head position.
Sleep
Psychic factors influencing muscle tonus
Age
Proprioception from the dentition and muscles.
Occlusal changes.
Pain.
Psychic factors.
Temporomandibular joint disease.

CENTRIC RELATION
Refers to the position of
the mandibular condyle
in the articular fossa.

Defined as:
unstrained ,neutral position of the mandible in
which the antero- superior surfaces of the
mandibular condyles are in contact with the
concavities of articular discs as they approximate
the postero- inferior third of their respective
articular eminentia.

Can be the same as postural resting position, initial
occlusal contact and centric occlusion.
Centric occlusion requires contact of teeth in
addition to unstrained position whereas centric
relation does not require occlusal contact.

INITIAL CONTACT
In normal occlusion :
It maintains centric relation position as far as
articular fossae are concerned.
movement in TMJ is almost completely rotation of
condyle.
the point of initial contact produces no change in
function of TMJ.

Initial contact in the ideal
individual is usually
synonymous
with centric occlusion.

In malocclusion or premature contact, initial contact
is no longer the same as centric occlusion.

CENTRIC OCCLUSION

Implies a state of balance .
must be harmonious
with centric relation


Premature contacts , loss of teeth ,overeruption of
teeth , overextension of artificial restorations ,
Malpositions of individual teeth -- mitigate
against centric occlusion.


MOST RETRUDED POSTION
(TERMINAL HINGE POSITION)
To establish mandibular
and maxillary
casts in their proper
positions on the articulator.


starting point in occlusal analysis and
rehabilitation.

Many dentists believe that by forcing the
mandible into its most posterior position , it is
easier to eliminate occlusal prematurities that
exists.


MOST PROTRUDED POSITION

More variable from individual
to individual.

Condyle drawn anterior to
lowest point of articular eminence.


HABITUAL RESTING POSITION
May not be the same as postural resting position.
Pathologic conditions that interfere in establishment
of normal postural position of the mandible are :
Abnormal atmospheric pressure.
Paralysis induced by poliomyelitis
Enlarged adenoids
Pain
TMJ pathology
Trauma
Mouth breathing

HABITUAL OCCLUSAL RELATION
In normal occlusion, centric occlusion and habitual
occlusion should be the same.
Occlusal relationship is much more susceptible :
Environmental assaults
Functional aberrations
improper restoration of carious teeth
Tooth loss
Malposition of individual teeth
Premature contacts.


FUNCTIONS OF
STOMATOGNATIC SYSTEM


MASTICATION:
Mastication in infants


MASTICATION IN ADULTS
FLETCHER – masticatory stroke in adult using
six phases ; outlined by MURPHY.
PHASES:
PREPARATORY PHASE
FOOD CONTACT
CRUSHING PHASE
TOOTH CONTACT
GRINDING PHASE
CENTRIC OCCLUSION


DEGLUTITION


FLETCHER --

divided deglutitional cycle into :

Preparatory swallow.
Oral phase of swallowing.
Pharyngeal phase of swallowing.
Esophageal phase of swallowing.


PREPARATORY SWALLOW :


ORAL PHASE :


PHARYNGEAL PHASE :


ESOPHAGEAL PHASE :


TONGUE THRUST
Condition in which tongue makes contact with any teeth
anterior to the molars during swallowing.


Factors :
Genetic .
Learned behaviour (habit).
Maturational.
Mechanical restrictions.
Neurological disturbance.
Psychogenic factors.


OTHER TITLES FOR TONGUE THRUSTING :
PERVERTED OR DEVIATE SWALLOW.
REVERSE SWALLOW.
RETAINED INFANTILE SWALLOW.
TOOTH APART SWALLOW.


CLASSIFICATION OF TONGUE THRUSTING
BY JAMES S. BRANER AND HOLT :
TYPE I : Non – deforming tongue thrust.
TYPE II : Deforming anterior tongue thrust.
subgroup
subgroup
subgroup

1:
2:
3:

Anterior openbite.
Anterior proclination.
Posterior crossbite.


TYPE III : Deforming lateral tongue thrust.
subgroup 1 : Posterior openbite.
subgroup 2 : Posterior crossbite.
subgroup 3 : Deep overbite.
TYPE IV : Deforming anterior and lateral tongue thrust.
subgroup
subgroup
subgroup

1:
2:
3:

Anterior and posterior open bite.
Proclination of anterior teeth.
Posterior cross bite.


Also classified as :
SIMPLE TONGUE THRUST

COMPLEX TONGUE THRUST


RESPIRATION


Mouth breathing
classified as :
Obstructive .
Habitual .
Anatomic .


Clinical features :
Adenoid faces.


Management :
Removal of nasal and pharyngeal
obstruction.
Interception of habit.
Rapid maxillary expansion.


SPEECH
defined as ordered utterance of a language.


Vowels : a e I o u
Consonants :p,g,m,b,s,t,r,z.
Bilabial sounds :
b, p, m.
Labiodental sounds :
f , v.


Linguodental sounds :
th.
Linguoalveolar sounds :
t,d,s,z,v,l.
sibilants : s ,z ,ch ,sh.
Linguopalatal and linguovelar sounds :
year, she, vision, onion.
k ,g , ng.


LINGUOALVEOLAR SOUNDS


Classification of consonants :
Plosive or stop plosives :
/p/,/b/,t/,/d/,/k/,/g/.
Fricatives :
Affricatives :
Glides :
Nasals :

/f/,/v/,/th/,/s/,/z/,/sh/.
/ch/,/dz/
/l/,/w/,/r/,/j/.
/n/,/m/,/ng/.


Speech mechanisms acts on breath stream in no. of
ways :
Controlling the air mechanism.
Air direction.
Air flow.
Air release.
Air pressure.
General air path and
Lingual airpath.


REFERENCES


T.M GRABER- ORTHODONTICS:PRINCIPLES AND PRACTICE
III Ed.



BONE BIODYNAMICS IN ORTHODONTIC AND ORTHOPAEDIC
TREATMENTVOL 27 CRANIOFACIAL GROWTH SERIES



PROFFIT- CONTEMPORARY ORTHODONTICS III Ed.



STRANG- TEXTBOOK OF ORTHODONTIA



MICHAEL.H.ROSS, EDWARD.J.REITH-HISTOLOGY, A TEXT
AND ATLAS




WILLIAM.F.GANONG-REVIEW OF MEDICAL
PHYSIOLOGY 20TH Ed.



GRANT’S ANATOMY- ATLAS



GRAY’S ANATOMY



SALZMANN-ORTHODONTICS IN DAILY PRACTICE



HOUSTON,STEPHAN,TULLEY-TEXTBOOK OF
ORTHODONTICS



ANGLE ORTHODONTIST(1994)-WOLFF’S LAW

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