Seminar on stomatognathic system with function and functional abbreviation

1. PRESENTED BY;
Dr NEHA SRIVASTAVA
SR. LECTURER DEPT. PF

2. INTRODUCTION
• What is stomatognathic system?
• Components
• Neurological control
• Static and dynamic apprecitation
• Errors if only static relation is used
• Clinical importance

3. FUNCTIONAL OSTEOLOGY

4. FUNCTIONAL OSTEOLOGY
TRAJECTORIAL THEORY OF BONE FORMATION
1867 ANATOMIST MEYER AND MATHEMATICIAN
CULLMAN . Alignment of bony trabeculae in the spongiosa
follows definite principles. If lines are drawn through these
oriented bony elements, they are remarkably similar to
trajectories seen in a crane. Many of these trajectories cross
at right angle to resist stresses.

5. LAW OF ORTHOGONALITY
1870 Julian Wolff. Trebecular alignment was primarily
due to functional forces . Changes in intensity and direction
of these forces produce change in internal and external form
of bone.
Law of transformation of bone
Roux and others . Stresses of tension or pressure on bone
stimulate bone formation

6. BENNINGHOFF
Did extensive study of the architecture of cranial
and facial skeleton. Trajectories involve both
Compact and spongy bone. they obey no individual
bone limits but rather the demands of functional forces.

7. TRAJECTORY PILLARS OF MAXILLA

8. TRAJECTORY PILLARS OF MANDIBLE

9. SKELETAL COMPONENTS

10. MAXILLA

11. MANDIBLE

12. MYOLOGY

13. MYOLOGY
PHYSICAL PROPERTIES OF MUSCLE
1) Elasticity ---- Normal relaxed muscle can withstand
only a certain amount of elongation (about 6/10 its
natural length before rupturing).
Depends upon
• Muscle
• Type of stress
• Individual resistance
• Age
• Pathological condition

14. 2) Contractibility
Ability of a muscle to shorten its length under
innervational impulse. Electric action potential acts on
muscle leads to contraction. Energy is provided by
breakdown of high-energy bonds in ATP. Fatigue in a
muscle is produced when lactic acid an energy
breakdown by product collects in the tissue. Even during
rest a certain no. of peripheral fibers are engaged by the
nerve system for maintenance of posture.

15. Contraction of smooth muscle depends on
No. Of fibers
Cross section
Frequency of discharge
Muscle fiber length

16. •Types of contraction
Isometric
Isotonic
Isometric more stronger than isotonic.
•All or none law (Gun trigger)
•The strength of muscle contraction depends upon
two major factors.
Frequency of stimulus
No. Of fibers involved
MYOLOGY

17. OTHER PROPERTIES OF MUSCLES
•Muscle tonus (Anti Gravity Muscles)
•Resting length
•Stretch or myotactic reflex (Muscle Spindles)
Absent in facial muscles
MYOLOGY

18. Muscle Tonus

19. Muscle Tension (stretch reflex)
• Due to muscle spindles
• Activity of the muscle spindles
• Type of muscle spindles
• Types of tension
- Active Tension
- Passive Tension
- Total Tension

20. Graph depicting Active and Passive Tensions

21. Types of Muscle Fibers
• Classification based on
1. Strength of contraction
2. Speed of contraction
• Types
- Type I (Maintenance of posture)
- Type IIA (Diagastric)
- Type IIB (Sup post temporalis, post med
pterygoid)
• Fatigue resistance depends on blood supply

22. Electromyography
•Basic principle
•Amplification required
•Current methods
•Clinical application

23. OROFACIAL MUSCLE
- FACIAL MUSLCE
Various functions
- JAW MUSCLE
Classified as elevators, depressors, retractors and
protrusers
Act in synergy with facial muscles.
- PORTAL MUSCLES (BOSMA)
Functions
include muscles of tongue, soft palate,
pharyngeal pillars, pharynx proper, larynx.

24. MUSCLES OF MASTICATION
ORIGIN
INSERTION
ACTIONS
MASSETER

25. MUSCLES OF MASTICATION
ORIGIN
INSERTION
ACTIONS
TEMPORALIS

26. MUSCLES OF MASTICATION
ORIGIN
INSERTION
ACTIONS
MEDIAL PTERYGOID

27. MUSCLES OF MASTICATION
ORIGIN
INSERTION
ACTIONS
LATERAL PTERYGOID

28. BUCCINATOR MECHANISM
•Origin and insertion

30. Equilibrium maintenance theory

31. Absence of buccinator mechanism

32. • Digastric
• Stylohyoid
• Mylohyoid
• Geniohyoid
MUSCLES OF FLOOR OF THE MOUTH

33. MUSCLES OF FLOOR OF THE MOUTH
Digastric-elevates hyoid bone and depresses mandible as in
opening the mouth.
Stylohyoid-elevates hyoid bone and draws it posteriorly.
Mylohyoid-elevates hyoid boine and floor of mouth and
depresses mandible.
Geniohyoid- elevates hyoid bone, draws hyoid bone and
tongue anteriorly and depresses mandible.

34. MUSCLES OF FACIAL EXPRESSION

35. MUSCLES OF FACIAL EXPRESSION
Orbicularis oris-closes lips, compresses lips against teeth,
protudes lips and shape lips during speech.
Zygomaticus major-draws angle of mouth upward and
outward as in smiling and laughing.
Levator labii superioris-elevates upper lip.
Depressor labii inferioris-depresses lower lip
Buccinator- major cheek muscle expresses cheek as in
blowing out air of mouth and cause cheek to cave in,
producing the action of sucking.
Mentalis-elevates amd protrudes lower lip and pulls skin
of chin.

36. TONGUE
o DESCRIPTION
o PARTS
o ATTACHMENT
o SULCUS TERMANILIS
o ORAL PART
o PHARYNGEAL PART
o PAPILLAE
o FUNCTION

37. (i) Intrinsic: These group of muscles are confined to the
tongue and not attached to bone. They consist of longitudinal,
tranverse and vertical fibres.
They are supplied by hypoglossal nerve. They alter the shape
of the tongue.
(ii)Extrinsic: The extrinsic muscles are attached to bones and
the soft palate.
They are the genioglossus, the hyoglossus and styloglossus
which are supplied by hypoglossal nerve; and palatoglossus
which is supplied by pharyngeal plexus.
MUSCLES:
Two types of muscles of the tongue are:

38. EXTRINSIC MUSCLE OF TONGUE

39. FUNCTIONS
GENIOGLOSSUS- DEPRESS TONGUE AND
THRUSTS IT FORWARD
STYLOGLOSSUS – ELEVATES TONGUE AND DRAWS
IT BACKWARDS
PALATOGLOSSUS – ELEVATES POSTERIOR PORTION
OF TONGUE AND DRAWS SOFT PALATE DOWN ON
TONGUE
HYPOGLOSSUS – DEPRESSES TONGUE AND DRAWS
DOWN ITS SIDE

40. TASTE
Taste buds are found on tongue, palate and larynx they are
distributed in surface epithelium. Taste bud contact oral cavity by
a specialized apical projection through a taste pore. At the basal
end of the taste buds taste cell contact the primary afferent nerve
fibers responds to more than one of the four basic taste qualities of
sweet, sour, bitter and salty. Several receptors are involved in
taste transduction. Saliva also plays an important role in taste
perception. It acts as a transport medium for taste stimuli and also
provides ion for taste transduction.

41. TASTE BUDS

42. DENTITION AND SUPORTING STRUCTURES
PARTS OF TOOTH
ATTACHMENT APPRATUS
PERIODONTAL LIGAMENTS
TEETH
• INCISORS
• CANINE
• PREMOLARS
• MOLARS

43. TEMPOROMANDIBULAR JOINT
TYPE OF JOINT
ARTICULATING SURFACES
ARTICULATING DISC
• COMPOSITION
• ZONES
LINING
SYNOVIAL FLUID
LIGAMENTS

44. TEMPORO MANDIBULAR JOINT

45. TEMPORO MANDIBULAR JOINT

46. LIGAMENTS
Collateral ligament
Capsular ligament
Temporomandibular ligament
Accessory ligament
Sphenomandibular ligament
Stylomandibular ligament

47. LIGAMENTS OF TMJ

48. LIGAMENTS OF TMJ

49. Collateral [discal ligament]
Attaches the medial and lateral borders of articular disc to the
poles of condyle. Divide joint medio-lateraly into superior and
inferior cavities. Causes disc to move passively with the condyle as it
glides anteriorly and posteriorly.
Capsular ligament
Whole TMJ is surrounded by capsular ligament. Attaches
superiorly to temporal bone, borders of mandibular fossa and
articular emininece. Inferiorly attached to neck of condyle. Resist
any medial, lateral, or inferior forces that tend to dislocate the
articular surface. Retains synovial fluid also.
Stylomandibular ligament
Arises from the styloid process and extends downwards and
forwards to the angle and posterior border of the ramus of the
mandible. It limits excessive protrusive movement of mandible.

50. Temporomandibular ligament
Outer portion extends from outer surface of articular
tubercle and zygomatic process posterioinferiorly to the outer
surface of condylar neck . It limits the extent of mouth opening.
Inner horizontal portion extends from the outer surface of articular
tubercle and zygomatic process posteriorly and horizontally to the
lateral pole of condyle and posterior part of articular disc. It limits
posterior movement of the condyle and disc.
Sphenomandibular ligament
Arises from spine of sphenoid bone and extends downwards
and laterally to a small bony prominence on the medial surface of
ramus of the mandible-lingula.

51. MANDIBULAR POSITIONS

52. • POSSLET
• POSITIONS
1) POSTURAL RESTING POSITION
• EARLIEST POSITION
• NON FUNCTIONAL MANDIBLE
• FACTORS AFFECTING 1. BODY AND HEAD POSTURE
2. SLEEP
3. PSYCHIC FACTORS AFFECTING MUSCLE TONUS
4. AGE
5. PROPIRIOCEPTION FROM DENTITION AND MUSC
6. OCCLUSAL CHANGES SUCH AS ATTRITION.
7. PAIN AND MUSCLE DISEASE
8. TMJ DISEASE

53. 2) INTER CUSPAL POSITION
• DETERMINED FROM HAND ARTICULATED CASTS
• ACTIVE GUIDANCE FROM TEETH
• ERRORS CAUSED IF USED ALONE IN DIAGNOSING MALOCCLUSIONS
3) CENTRIC OCCLUSION
• MAXIMAL OCCLUSAL CONTACT WHEN NO MALOCCLUSION
PRESENT
• BILATERALLY SYMMETRICAL, BALANCED, UNSTRAINED, STATIC
• DIFERENCE FROM PROSTHODONTIC CONCEPT OF CENTRIC
OCCLUSION
• HARMONIOUS WITH CENTRIC RELATION

54. INTERCUSPAL POSITION AND POSTURAL POSITION

55. 3) CENTRIC RELATION
• UNRESTAINED POSITION OF THE CONDYLE IN
ARTICULAR DISC
• NO DEVIATION, BILATERAL SYMMETRICAL ACTIVITY
• RANGE IS 3 – 4 MM.
4) MOST PROTRUDED POSITION
• MOST VARIABLE
• SAME INDIVIDUAL REPRODUCIBLE
• CONDYLAR PATH TRAVERSED MORE IMPORTANT THAN
THE TERMINAL POSITION
• CURVE OF SPEE
• FLACCIDITY - EXTERME PROTRUSION
• DISLOCATION – FATIGUE SYNDROME

56. CENTRIC RELATION AND INTERCUSPAL POSITION

57. MOVEMENT OF THE MANDIBLE ON PROTRUSION

58. 5) MOST RETRUDED POSITION
• UNRESTAINED
• REPRODUCIBLE – REFERENCE POSITION
• DISTANCE BETWEEN INTERCUSPAL POSITION
- IDEAL
- MORE THAN 3 MM.
- COINCIDENT
• DETERMINED BY –
- PASSIVE GUIDANCE – TMJ.
- ACTIVE GUIDANCE – LEVATOR, DEPRESSOR
AND RETRACTOR REFLEXES.
6) INITIAL CONTACT
• COINCIDES WITH CENTRIC OCCLUSION IN IDEAL CASE.
7) POSTURAL REST POSITION

59. GRAPHIC REPRESENTATION OF MANDIBULAR POSITION

60. CHEWING STROKE WITH BORDER
MOVEMENTS IN SAGGITAL PLANE

61. ANTERIOR OPENING BORDER MOVEMENTS IN
SAGITTAL PLANE

62. BIOMECHANICS OF TMJ
• EACH OF THE JOINT CAN ACT EITHER
SIMULTANEOUSLY OR SEPARATELY BUT NOT
COMPLETELY WITHOUT INFLUENCE FROM THE
OTHER.
• TWO JOINT SYSTEMS
• VARIATION OF THE WIDTH OF THE DISC DURING
FUNCTION
• SUERIOR RETRODISCAL LAMINA
• ACTION OF SUPERIOR LAMINA & LATERAL
PTERYGOID DURING FORWARD TRANSALATION
OF CONDYLE.

63. MANDIBULAR MOVEMENTS
• They can be percived as movement of free
body in an intricate muscular web with teeth
and joints acting as stops and guides
• Ex: stabilization of TMJ before and after
eruption of teeth during mastication and
swallowing.

64. MANDIBULAR MOVEMENTS
OPENING
CLOSING
PROTRACTION
RETRACTION
BENNETS MOVEMENT

65. MANDIBULAR MOVEMENTS

66. TYPE OF REFLEXES
TWO TYPES OF REFLEXES
• Unlearned reflex
• Learned reflex
UNLEARNED REFLEX
• fully functional in early fetal life
• muscles are insensitive to feedback
• reflex is all or none.
• ex; genioglossus reflex,jaw
opening.,swallowing

67. - LEARNED REFLEX
Can be readily conditioned.
Ex; posture of tongue
-CLINICAL IMPORTANCE
Treatment of tongue thrust.
Etiological cause should be determined
Mostly directed towards correction of tongue posture

68. MASTICATION
Act of chewing food. It is initial stage of digestion
when the food is broken down into smaller particle sizes for
swallowing. It is a functional activity that is automatic and
practically involuntary, yet when desired it can be readily
brought under voluntary control.

69. CHEWING STROKE
Mastication is made up of rhythmic and well-
controlled separation and closure of maxillary and
mandibular teeth. The pattern of chewing stroke is tear
shaped.
Phases
Opening phase
Closing phase
 Crushing phase
 Grinding phase

70. CHEWING STROKE – FRONTAL VIEW

71. CHEWING STROKES

72. Opening phase
Mandible drops downwards from the
intercuspation position to a point where the incisal
edges of teeth are about 16 to 18mm apart. It then
moves laterally 5-6mm from the midline as the closing
movement begins.

73. OPENING PHASE

74. CLOSING PHASE
Crushing phase
The first phase of closure traps the food between the
teeth and is called crushing phase. As the teeth approaches
each other the lateral displacement is lessened so that when
teeth are only 3mm apart the jaw occupies a portion only 3-
4mm lateral to the starting position of chewing stroke. As
this point the teeth are so positioned that the buccal cusp of
mandibular teeth are directly under the buccal cusp of
maxillary teeth on the side to which the mandible has been
shifted. As the mandible continues to close, the bolus of
food is trapped between the teeth. This begins the grinding
phase of the closure stroke.

75. FUNCTIONAL MOVEMENT OF CONDYLE DURING FULL
RANGE OPENING AND CLOSING

76. Grinding phase
The mandible is guided by the occlusal surface of
the teeth back to the intercuspation position, which
causes the cuspal inclines of the teeth to pass across
each other, permitting shearing and grinding of the
bolus of food.

77. MOVEMENT OF MANDIBLE
DURING MASTICATION

78. • Chewing stroke in saggital plane
- anterior movement depends on phase of mastication.
- working side movement of condyle
- balancing side movement of condyle
• Chewing stroke in frontal plane
- phases observed – opening, crushing and grinding
- lateral movement depends on consistency of food
- movement of condyle on working side and balancing
side

79. Tooth contact during mastication
Types of contact
Gliding
Single
Forces of mastication
Male bite with more force than females
Females-79 to 99 pounds
Males –118 to 142 pounds
Force applied to molar is several times that of incisor
First molar-91 to 198 pounds
Central incisor-29 t0 51 pounds

80. ROLE OF SOFT TISSUE IN MASTICATION
LIPS
TONGUE
CHEEKS
Masticastion accounts for the vertical stability of tooth
position. masticatory occlusal forces cannot move teeth
in normal conditions as they are of very short and
intermittent duration

81. ROLE OF SOFT TISSUE IN MASTICATION

82. SWALLOWING
Swallowing is both an alimentary and a
protective reflex. It can be initiated reflexly by
mechanical stimulation by a bolus in the
pharynx and by chemical stimulation by water
in the larynx
There are three essential features of
swallowing
(1)establishment of a pressure gradient
(2)prevention of reflux
(3)protection of the airway.

83. TYPES OF MUSCLES TAKING PART
• OBLIGATE
• FACULTATIVE
 ACTION
 FEEDBACK MECHANISM
CLINICAL SIGNIFICANCE

84. • Obligate muscles
• Geniohyoid
• Mylohyoid
• Posterior tongue
• Palatopharyngeus
• Superior constrictor.
• Facultative muscles
• Massater
• Orbicularis oris
• Temporalis.

85. DEVELOPMENT OF SWALLOWING PATTERN
• INFANTILE SWALLOW
- DEVELOPMENT
- MUSCLES ACTING
- POSITION OF THE TONGUE
• TRANSITION
• MATURE SWALLOW
- DEVELOPMENT
- MUSCLES ACTING
- POSITION OF THE TONGUE
- STAGES

86. NORMAL INFANTILE SWALLOW

87. STAGES OF SOMATIC SWALLOW

88. ABNORMAL SWALLOWS
• SIMPLE TONGUE THRUST SWALLOW
- ETIOLOGY
- MUSCLES INVOLVED
- TEETH POSITION
- CLINICAL PICTURE
- CLINICAL SIGNIFICANCE

89. SIMPLE TONGUE THRUST

90. • COMPLEX TONGUE THRUST SWALLOW
(TEETH APART SWALLOW)
- ETIOLOGY
- MUSCLES INVOLVED
- TEETH POSITION
- CLINICAL PICTURE
- CLINICAL SIGNIFICANCE

91. COMPLEX TONGUE THRUST SWALLOW

92. OPEN BITE ASSOSIATED WITH COMPLEX TONGUE THRUST

93. •RETAINED INFANTILE SWALLOW
- ETIOLOGY
- MUSCLES INVOLVED
- APPEARANCE OF THE PATIENT
- OCCLUSAL CONTACT
- FUNCTIONAL SIGNIFICANCE
# MASTICATION
# GAG THRESHOLD
- PROGNOSIS

94. SPEECH
It occurs when a volume of air is forced from the
lungs by the diaphragm through the larynx and oral
cavity. Controlled contraction and relaxation of the
vocal cords or bands of the larynx create a sound.
The mouth determines the resonance and exact
articulation of the sound. Because speech is created
by the release of air from the lungs, it occurs during
the expiration stage of respiration. Inspiration of air
is relatively quick and taken at end of sentence of
pause.

95. There are two processes in the production of
speech
1] Phonation –it is the production of airflow and
the establishment of frequency
2] Articulation- it is the modification of airflow by
resonance or various degree of stoppage to produce
vowels and consonants

96. PRODUCTION OF SPEECH

97. Speech problems which may be improved by
orthodontics are those of faulty articulation.
The articulatory valves are
Velopharyngeal valve,
labiodental,
linguodental, and
linguoalveolar valve

98. ARTICULATORY VALVES

99. Labiodental {upper teeth and lower lip} ‘F’ & ‘V’
Bilabial {lips} ‘P’ ‘B’ ‘W’ & ‘M’
Linguo –dental {tongue tip and upper teeth} ‘TH’
Linguo –alveolar {tongue tip alveolar ridge} ‘T’ & ‘D’
Linguo-velor-pharyngeal {tongue back, velum and
pharyngeal wall} ‘K’ & ‘G’
Glottal {glottis} ‘H’

100. Travis has pointed out that "abnormalities of
orofacial structures cannot, of themselves along be
considered as prime causes of defective articulation”.
There is evidence of considerable adaptability in the
use of the lips and tongue in compensating for dental
malformations. Though lisping may be associated with
tongue thrust Fletcher et al found that it is found only in
thirds of abnormal sallower. As with tongue-thrusting.
sibilant distortion spontaneously improves with age.

101. • ACTION OF THE VELOPHARYNGEAL VALVE
• ETIOLOGY
o absence of structure (e.g., cleft palate),
o disproportion of structure (e.g.. short palate, deep
nasopharynx, short functional palate).
o neurologic defects (e.g., muscle or central
nervous
system)
• EFFECT ON SPEECH
•CLINICAL SIGNIFICANCE
VELOPHARYNGEAL INCOMPETENCE

102. VELOPHARYNGEAL INCOMPETENCE

103. RESPIRATORY AIRWAY
MAINTAINENCE
Tongue Posture
The base of the tongue forms the anterior wall of the
pharynx which serves as the portal for both, the
alimentary tract and the airway. Maintenance of the
pharyngeal airway demands that the tongue base not
be allowed to intrude into this airway; and this is taken
care of by the genioglosus muscle.

104. TONGUE POSTURE
• REFLEX AIRWAY MAINTAINENCE
• EQUILIBRIUM
• POSTURE IN NEW BORN
• EFFECT ON THE MANDIBULAR GROWTH
AND DENTITION
( HEAD POSTURE)

105. POSTURE IN NEW BORN

106. ABNORMAL TONGUE POSTURE
TYPES
. RETRACTED
. PROTRACTED
- ENDOGENOUS
- ACQUIRED

107. RETRACTED TONGUE POSTURE
• Seen in less than 10% of all children
• Posterior open bite
• Edentulous adults
• Bilateral loss of several posterior teeth
• Loss of positional sense
• Associated malocclusion

108. 1. ENDOGENOUS PROTRACTED TONGUE POSTURE
• Retention of infantile tongue posture
• Idiopathic
• Prognosis
• Associated malocclusions
PROTRACTED TONGUE POSTURE

109. 2) ACQUIRED PROTRACTED TONGUE POSTURE
• Tongue adaption to inadequate airway or inflammatory
conditions.
• Experimentally spontaneous correction achieved in acute
inflammed throat.
• Precipitating pain mechanism should be removed
• Prognosis

110. THUMB SUCKING AND FINGER SUCKING
• Physiologic – non nutritive
• Theories of etiology
• Associated malocclusions
• Movement of teeth depends on
- amount of force
- duration of force (most imp. factor)
- position of thumb
• Constriction of maxilla not primarily due to
negative pressure but alteration of balance

111. •Buccinator hyperactivity and V- shaped arch
• Early stoppage, normal balance restored]
• Persistence after six years – orthodontic
treatment and expansion
• Stoppage of the habit primarily required

112. THUMB SUCKING

113. MOUTH BREATHING
Linder Aronson and Bushey presented three hypotheses
1] Adenoid enlargement leads to mouth breathing, resulting in a
particular type of facial form and dentition
2] Enlarged adenoids, though may lead to mouth breathing but
do not influence facial form and the type of dentition.
3] Enlarged adenoids in certain types of faces and dentition leads
to mouth breathing.

114.  Change in tongue, lip and mandibular posture
 Alteration in craniofacial form and malocclusion
 Increased anterior facial height
 Narrow and high palate
 Proclined incisors
 Increased lower face height
 Open bite
 High mandibular plane
CLINICAL FEATURES OF MOUTH
BREATHING

115. CLASSIC ADENOID FACIES

116. BRUXISM
Tooth clenching and grinding (bruxism) are
usually considered parafunctions of the adult and are
thought to result from physiological stress with or
without occlusal interferences.
Also found in children and has alleged
associations with allergies, asthma, "digestive
upsets," "nervousness," and other conditions.
It mayor may not alter the tooth position
depending on whether or not it is associated with a
slide into the intercuspation position.

117. Gagging is a reflex initiated from the
oropharynx and can be regarded as protective of
either the upper alimentary tract or the airway.
 Nerves involved
The glossopharyngeal nerve & the trigeminal
nerve
 The reflexogenic sites
The faucial pillars. base of tongue. soft palate.
and posterior pharyngeal wall.
 Increasing central vagal discharge might be
expected to suppress gagging
 Readily conditioned reflex
GAGGING

118. Glands that drain by duct system into oral cavity secrete saliva
Functions
• Lubrication
• Digestion
• Solvent action
• Antibacterial action
• Antifungal action
• Buffering action
• Remineralization
• Temperature regulation
SALIVARY SECREATION

119. Secretion is under control of autonomous nervous system.
Has a high flow during, a low flow between meals and minimum
during sleep. Mostly water containing with a low percentage of
organic and inorganic components. Volume of saliva produced in
one day is 0.5 to 0.75 It. Large bulk of saliva production [90%}
by major paired salivary glands.

120. Muscle dysfunction
Facial muscles can offset jaw growth in two ways
 Formation of bone at the point of muscle attachments
depends on the activity of muscle.
Musculature is an important part of total soft tissue matrix
whose growth normally carries the jaws downward and forward.
Muscle atrophy leads to underdevelopment of that part
of the face
Excessive muscle contraction can restrict growth e.g.torticollis -
twisting of head caused by extensive tonic contraction of neck
muscles on one side primarily by sternocledomastoid.

121. MUSCLE DYSFUNCTION