A brief ppt on stomatognathic system and its working.Function can influence the overall pattern and the relationship of parts, the very foundations of stomatognathic system. We should do more than just analyze teeth in occlusion. It is equally important to appreciate respiration, mastication, deglutition, speech and even maintenance of head in constant postural position.

1. STOMATOGNATHIC
SYSTEM
BY : Shristi Chahal
MDS Ist Yr
Under the Guidance of: Dr. Hemant Garg

2. CONTENTS
• Introduction
• Functional Osteology
• Myology
– Elasticity
– Contracility
– Principles of muscle physiology
– Muscles of Mastication
– The buccinator mechanism
– The tongue
– Muscles in mandibular
movement
• The temporomandibular joint
– Clicking
– Bennett movement
– Position of mandible
• Functions of stomatognathic
system
– Mastication
– Deglutition
– Respiration
– Speech
2

3. INTRODUCTION
• Function can influence the overall pattern and the
relationship of parts, the very foundations of stomatognathic
system.
• We should do more than just analyze teeth in occlusion.
• It is equally important to appreciate respiration, mastication,
deglutition, speech and even maintenance of head in constant
postural position.
• Stomato (mouth) + Gnathic (jaws)
3

4. • The stomatognathic system can be broadly divided into
– Functional osteology
– Myology
– Temporomandibular Joint
– Functions of Stomatognathic system
4

5. FUNCTIONAL OSTEOLOGY
• Bone is one of the hardest materials in
the body, it is one of the most plastic
and responsive to functional forces.
• TRAJECTORIAL THEORY OF BONE
FORMATION - 1867 anatomist Meyer
and mathematician Culmann .
5

6. •LAW OF ORTHOGONALITY
•1870 Julius Wolff - Trabecular alignment was primarily due to
functional forces . Changes in intensity and direction of these
forces produce change in internal and external form of bone.
•Roux and others . Stresses of tension or pressure on bone
stimulate bone formation

7. 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.

8. Trajectory Pillars of Maxilla
• Canine pillar
• Zygomatic pillar
• Pterygoid pillar.
8

9. Trajectory Pillars Of Mandible
• From beneath the teeth in
alveolar process and join
together in a common stress
pillar – terminating in condyle.
• Accessory stress trajectories
seen at
 symphysis,
 the gonial angle
 leading downwards from
coronoid process into ramus
and body of mandible
9

10. MYOLOGY
• The study of the structure, arrangement, and action of
muscles.
• In humans, the ability to communicate, whether by speech,
writing, or artistic expression, also depends on muscle
contractions. Indeed, it is only by controlling the activity of
muscles that the human mind ultimately expresses itself.
• Two main physical properties of muscle
– Elasticity
– Contractility
10

11. Elasticity
• HOOK’s LAW
– relatively small deformations of an
object, the displacement or size of the
deformation is directly proportional to
the deforming force or load.
•Normal relaxed muscle can withstand only a
certain amount of elongation (about 6/10 its
natural length before rupturing).
11

12. Contractility
• Ability of a muscle to shorten its length under innervational
impulse.
• Energy for muscle action potential (breakdown of ATP)
• Fatigue lactic acid (by product )collects in tissue decrease
in pH  no function of muscle.
12

13. Excitation contraction coupling

15. Isotonic and Isometric Contractions

16. Principles of Muscle Physiology
• All or None law
• Muscle tonus
• Resting length
• Stretch, or Myotatic reflexes
• Reciprocal innervation and Inhibition.
16

17. All or None law
• Sherrington  individual fibers have no variable contraction
status but are either relaxed / going into maximum
contraction by virtue of adequate stimulus
• Strength of contraction depends on number of fibers engaged
in activity
• Some muscles shorten to 50-75 % its natural length
17

18. 18
• Strength of muscle
contraction depends
on:
– Number of fibres
involved
– Frequency of stimuli

19. Yildirim E. And De Vincenzo – (1971) Angle Orthodontist.
Maximum opening and closing forces exerted by diverse
skeletal types
• Greatest strength of contraction is elicited when muscle
approximates its resting position.
• In open bite – 97 lbs
• In closed bite - 118 lbs
• Attributed to the fact that mouth is propped open 2.5 – 3 cm
anteriorly by the gnathodynamometer, preventing over closure in
closed bite cases and opening the open bite cases to a greater
distance from postural resting position.
19

20. Muscle tonus
• State of slight constant tension.
• Serves to obviate the muscle taking up slack when it enters
into contraction.
• Tonus is the basis of reflex posture – its purposive and
coordinated in maintenance of various positions
• Example : anti gravity muscles
20

21. Resting Length
Constant and predeterminable relationship, permitting the
maintenance of postural relations and dynamic equilibrium by
contraction of the minimal number of fibres, consistent with the
demands of a particular moment.
21

22. Reflex contraction
resulting from a pull
on its tendon is called
a stretch or myotatic
reflex
22
Stretch, or Myotatic Reflexes

23. Reciprocal Innervation and Inhibition
23
Sherrington (1906)
described reciprocal innervation as
the process that controls agonist
and antagonist muscle actions. One
muscle group (agonists) must relax
to allow another group (antagonists)
to contract. This is called reciprocal
inhibition.

24. Muscle of Mastication
• Muscles of mastication develops from the mesoderm of the
first brachial arch that is also called mandibular arch.
• Muscles begins differentiation in seventh week of intra
uterine life. Although the muscle of mastication develop at
first in close relationship to meckel’s cartilage and the cranial
base cartilages, they are independent and only later attach to
the bony skeleton.
24

25. Masseter
• This is a quadrilateral muscle.
• It covers the lateral surface of the
ramus of mandible.
• Its fibres has 3 layers
– Superficial
– Middle
– Deep layers

26. Origin and Insertion:
• Superficial layer –Originates from
anterior 2/3rd of the lower border of
zygomatic arch and from zygomatic
process of the maxilla. They pass
downwards and backwards to insert
into the angle and lateral surface of
the mandibular ramus.
• Middle layer --From anterior 2/3rd of
deep surface and posterior 1/3rd of
lower border of zygomatic arch. Insert
into the central part of the
mandiblular ramus
• Deep layer -from the deep surface of
the zygomatic arch. Insert into upper
part of the mandibular ramus and into
it's coronoid process.

27. Temporalis muscle
• Large, fan – shaped muscle.
• Origin:
originates from the temporal fossa and lateral
surface of skull.
• Insertion:
It's fibers converge and descend into a tendon
which passes through the gap between
zygomatic arch and side of skull and attaches to
the medial surface, apex, anterior and posterior
borders of the coronoid process and the
anterior border of ramus of the mandible.

28. Medial Pterygoid
Deep head:
• Origin: Medial surface of the
lateral pterygoid plate of shenoid
bone.
• Insertion : Medial surface of the
ramus of Mandible near the angle.
Superficial head:
• Orgin:Tuberosity of the maxilla
• Insertion : it joins deep head to
insert on the Mandible

29. Lateral Pterygoid
Upper head:
• Origin : It arises from the infratemporal
surface and crest of the grater wing of
the sphenoid bone.
• Insertion: The upper head passes
posteriorly and lateraly to insert into the
articular capsule and the articular disc.
Lower head:
• Origin :It arises from the lateral surface
of lateral pterygoid plate of sphenoid
bone.
• Insertion : The inferior head passes back
ward , upward and slight laterally to
insert into the pterygoid fossa of
condylar neck.

30. Accessory muscles of mastication
• Accessory muscles are :
– Digastric(anterior and posterior)
– Stylohyoid
– Mylohyoid
– Buccinator

31. Digastric
Posterior belly:
– Origin : Mastoid process of Temporal bone
Anterior belly:
– Origin : Body of Mandible
– Insertion : Intermediate Tendon is held to
hyoid bone by fascial sling
Nerve supply :
– Facial Nerve (post belly)
– nerve to mylohyoid (ant belly)
Action :
– Depresses Mandible or elevates Hyoid bone

32. Stylohyoid:
• Origin : Styloid process
• Insertion : Body of Hyoid bone
Nerve supply : Facial nerve
Action : Elevates hyoid bone

33. Mylohyoid:
• Origin : Myloid line of body of
Mandible
• Insertion : Body of Hyoid bone and
fibrous raphe
Nerve supply : Inferior Alveolar nerve
Action : Elevates floor of mouth and
hyoid bone or depresses mandible

34. • It arises from the outer surfaces of
the alveolar processes of the
maxilla and mandible.
• The fibers converge toward 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; the
upper and lower fibers are
continued forward into the
corresponding lip without
decussation.
The Buccinator Mechanism

35. The decussating
fibres of
obricularis oris
muscle, the
anterior
component of
buccinator
mechanism.

36. • During mastication &
deglutition
Tonal contraction +peripheral
fiber recruitment of Buccal &
labial muscles + atmospheric
pressure = force by Tongue
(3 : 1)
WINDERS

37. • An arch form is defined
by its encompassing
soft-tissue Drape.
Passive muscle function / Neutral zone

38. After a paralytic stroke in this patient,
the side of the tongue rested against
mandibular left posterior teeth.

39. Importance of the Buccinator mechanism
• Force exerted by the lip musculature and buccinator (anteriorly)
muscles of the cheek (posteriorly) is counteracted by the force
exerted by the tongue.
• Thus balanced force is
transmitted to the
teeth & supporting
bone

40. THE TONGUE
40

41. Tongue Muscles
(i) Intrinsic: These group of muscles are confined to the tongue and not
attached to bone. They consist of longitudinal, tranverse and vertical
muscles.Fine, detailed movement are attributed to the intrinsic muscles.

42. (ii)Extrinsic: The extrinsic muscles
connect the tongue to the
mandible, styloid process, hyoid
bone and the palate.
• Hyoglossus - hyoid bone
• Styloglossus - styloid bone
• Genioglossus - mandible
• Palatoglossus - palatine
aponeurosis
Supplied by hypoglossal nerve
except palatoglossal which is
supplied by pharyngeal plexus.
42

43. • The tongue has amazingly versatile functional possibilities by
the virtue of the fact that it is anchored at one end.
• This freedom permits the tongue to deform the dental arches
when function is abnormal.
• A malocclusion is in dynamic balance at that particular time.
43

44. FUNCTIONAL MOVEMENTS
• The mandible is the only movable bone in the head and face,
and can be moved in certain directions because of
morphologic limitations.
• An analysis of the precarious balance that the head maintains
on the vertebral column illustrates the constant demand for
activity in holding the head erect.
44

45. • Opening
- Condyle  downward & forward
- Chin  downward & backward
- Hyoid  downward & backward
- Primary contraction of lateral pterygoid
- Stabilizing & adjusting activity 
geniohyoid, mylohyoid, digastric, suprahyoid & infrahyoid
muscles
- Controlled relaxation of temporalis, masseter & medial
pterygoid
Muscles for Mandibular movements

46. • CLOSING
- Bilateral activity of masseter ,medial pterygoid & temporalis
- Hyoid  upwards & forwards
- Controlled relaxation of lateral pterygoid
• PROTRUDE
- Lateral & Medial pterygoid contract
- Opening muscles in controlled relaxation
• RETRUDE
- Contraction of posterior fibers of temporalis, geniohyoid,
digastric & mylohyoid muscles
- Hyoid  posterior

47. 47
Muscles primarily responsible
for mandibular functional
movements.
1. Anterior and posterior fibres
of temporalis
2. Lateral pterygoid
3. Anterior, middle and
posterior components of
masster.
4. Suprahyoid
5. Infrahyoid

48. The head is balanced, eyes open and mandible suspended in postural rest during
the waking hours. During sleep the muscle activity drops to a minimum, allowing
the head , mandible and eyelids to drop.

49. Normal muscle activity associated with normal jaw relationship
and normal occlusion

50. In Class II malocclusion

51. In Class II malocclusion with deep overbite

52. • TEAM WORK – to establish a balance between
morphogenetic, functional & environmental components
• Certain compensatory or adaptive muscle functions may
arise, to restrain the dental malocclusion or to actually
increase discrepancy.
Compensatory Muscle Functions

53. THE TEMPOROMANDIBULAR JOINT
53

54. 54
TMJ
BONY COMPONENTS SOFT-TISSUE COMPONENTS
1. Glenoid fossa 1. Articular disk
2. Condylar head 2. Joint capsule
3. Articular eminence 3. Ligaments
MUSCLES
1. Muscles of mastication
2. Muscles attached to the joint
3. Muscles of facial expression
4. Muscles of the neck

55. 55

56. Capsular ligament
• Fibrous, non-elastic
membrane surrounding the
TMJ
• Retains synovial fluid
• Resists medial ,lateral
inferior forces that separate
the articulating surfaces

57. 57
Articular disc
• Biconcave
• Upper & lower
compartments
• Dense fibrous connective
tissue – Type I Collagen
• Centre – devoid of blood
vessels & nerves

58. 58
Retrodiscal tissue
• ‘POSTERIOR ATTACHMENT’
•Between bilaminar zone of disc
• SRL – Superior retrodiscal lamella
(elastic fibres)
• IRL – Inferior retrodiscal lamella
(collagenous fibres)
• Loose connective tissue
• Compressible
• Rich blood supply & nerve supply

59. 59
Ligaments
• Non-elastic collagenous structures which restrict and limit the
movements a joint can make
• True ligaments:
1. Collateral / discal ligaments
2. Capsular ligament
3. Temporomandibular / lateral ligament
• Accessory ligaments:
1. Sphenomandibular ligament
2. Stylomandibular ligament

60. 60

61. Movement involving the joints has been divided into different
phases
• Occlusal or rest position
• Retruded opening phase or rotation
• Early protrusive opening phase or functional opening
• Late protrusive opening phase or translation
• Early closing phase
• Retrusive closing phase

62. Occlusal or rest position
• The rest position is the
first step and involves a
static jaw position with
maximum intercuspation.
• In this, the joint is in
loose position, the
connective tissue at rest.

63. Retruded opening phase or rotation
•The condyle rotates and
moves 5 to 6 mm inferior to
the intermediate zone
•The shape of inferior
compartment changes the most
•The upper lateral pterygoid
relaxes and the lower lateral
pterygoid contracts
•The posterior connective
tissues is in a functional state
of rest

64. Early protrusive opening phase or
functional opening
•The condyle moves inferiorly and
anteriorly approximately 6 to 9
mm below the intermediate zone.
•The disk and the condyle
experience the short anterior
translatory glide
•The upper and lower head of
lateral pterygoid contract to guide
the disk and the condyle shortly
forward
•The posterior connective tissues
is in a functional tightening

65. Late protrusive opening phase or translation
• The condyle moves
inferiorly and anteriorly
beneath the anterior
band i.e there is full
opening more, space
develops in the
superior compartment

66. Early closing phase
The condyle translates posteriorly, about 6 to 9 mm, to the
intermediate zone
There is simultaneous reduction of space posteriorly in the
superior compartment

67. Retrusive closing phase
• The condyle rotates superiorly
but remains inferior to the
posterior band
• This movement reduces the
space in the inferior compartment
•This tightens the mandibular
attachment, and forces blood
from the posterior compartments

68. 68

69. Clicking
• It occurs due to the
uncoordinated movement of
condylar head and T.M.J
disc.
• Joint clicking is differentiated
as:
Initial
Intermediate
Terminal
Reciprocal

70. • Initial clicking : It is a sign of retruded condyle
• Intermediate clicking : Is a sign of unevenness of the condylar
surfaces and articular disc
• Terminal clicking : is an effect of the condyle being moved too far
anteriorly in relation to the disc on maximum jaw opening.
• Reciprocal clicking : is an expression of
incordination between displacement
of the condyle & the disc.

71. 71
Working bite

72. 72
Bennett movement

73. Positions of Mandible
• Basic sagittal plane positions of the mandible with respect to maxilla and
cranium:-
1. Postural rest position (physiologic rest)
2. Centric relation
3. Initial contact
4. Centric occlusion
5. Most retruded postion (terminal hinge position)
6. Most protruded position
7. Habitual resting position
8. Habitual occulusal position
73

74. • Posselt – 1952 had
recorded graphically the
various positions and
movement area in sagittal
plane.
74

75. •Mandible assures a rest position when no action -
earliest postural position- mandible suspended from
cranial base by the cradling musculature.
•The REST POSITION is an equilibrium between all
the forces operating on the mandible.
•At rest position the elevators and depressors of the
mandible exhibit minimal electrical activity.
•Physiological rest position is not necessarily
identical with the usual or habitual mandibular
posture of the individual.
1.Postural resting position (PVD)

76. A maxillomandibular relationship,
independent of tooth contact, in which
the condyles articulate in the anterior-
superior position against the posterior
slopes of the articular eminences
2. Centric Relation

77. INTERCUSPAL POSITION AND POSTURAL POSITION

78. 3. Initial Contact
-mandible moves from PVD toward occlusion of teeth
-rotation of condyle in lower joint cavity
-all inclined planes of mandibular & maxillary teeth brought
together
4. Centric Occlusion (OVD)
- a static position & can be easily reproduced by bringing teeth
together
- HABITUAL OCCLUSION
- CO must be harmonious with CR

79. Centric relation and intercuspal position

80. 5. Terminal Hinge Position
- Habitual, normal, bilaterally symmetrical & unstrained
positions of the condyles in articular fossa
6. Most Protruded Position
- Inclination of condylar path is considered more important
than actual terminal protrusive path
- chances of dislocation of mandible seen
- condyle drawn anterior to lowest point of articular eminence

81. Movement of the mandible on protrusion

82. 7. Habitual Resting Position
- not same as PVD
- we should eliminate all conditions that might prevent
establishment of normal postural position
- Class II div 2  Retroclined incisors push Condyle posterior &
superior in fossa.
8. Habitual Occlusal Relation (OVD)
- CO=HO should be same in normal occlusion
- In harmony with CR & PVD

83. 83
Bennett movement

84. 84
Contraction of Lateral
pterygoid muscle

85. FUNCTIONS OF STOMATOGNATHIC
SYSTEM
• By 14 weeks in utero – stimulation of lips causes tongue to
move.
• 18½ weeks – gag reflex
• 25 weeks – respiration is possible
• 29 weeks – suckle can be elicited
• 32 weeks – both suckling and swallowing
85

86. Mastication
• INFANTS – food intake by suckling
• Classic – suckle – swallow position
• During function ,stabilization of mandible –there is rhythmic
contraction of tongue & facial muscles
• As infant learns to take solid food
Muscles of cheek, tongue & floor of mouth mostly involved
Lips used to keeps food in mouth + tongue & cheeks pushes it
into pharynx
Bolus mixed with saliva & positioned between teeth occlusal
surface by active tongue function

87. Phases of masticatory stroke or chewing
cycle

88. Deglutition
Moyers lists the characteristics of
infantile swallow as:-
- Jaws apart with tongue
between gum pads
- Mandible stabilized by
contraction of muscles
- Swallow guided & controlled
by sensory interchange
between lips & tongue

89. MATURE SWALLOW
Usually by 18 months of age the
mature swallow characteristics can
be observed:
– Teeth together
– Mandible stabilized by
contraction of mandibular
elevator muscles
– Tongue held against palate,
above & behind incisors
– Minimal contractions of lips
during mature swallow

90. 91
Deglutition Cycle
1. Preparatory phase
2. The oral phase of
swallowing
3. The pharyngeal
phase
4. The esophageal
phase

91. Respiration
• Inherent reflex activity
• INFANTS – quiet respiration carried out by nose & tongue in
proximity with palate and obturating oral passageway.
• Respiration maintains the patency of pharyngeal area
• Development of respiratory spaces & maintenance of airway
significant factors of OROFACIAL GROWTH

92. Speech
• Muscles involved in sound production
- Walls of torso, respiratory tract
- Pharynx , soft palate
- Tongue, lips & nasal passage way
• Learned activity on maturation of organism
• Speech production dependant on coordination action & precise
activity of muscles
• Lips , velopharyngeal structures & tongue modify outgoing breadth
to produce variation in sound
• Simultaneous breathing  produce vibrations necessary for sound

93. 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’

94. CONCLUSION
95

95. References
• Graber TM. Current concepts of orthodontic treatment in the United States. Australian Dental
Journal. 1962 Oct;7(5):355-62.
• Berry DC. The buccinator mechanism. Journal of dentistry. 1979 Jun 1;7(2):111-4.
• Warren JJ, BISHARA SE, STEINBOCK KL, YONEZU T, NOWAK AJ. Effects of oral habits' duration on
dental characteristics in the primary dentition. The Journal of the american dental association. 2001
Dec 1;132(12):1685-93.
• Graber TM. The “three M's”: Muscles, malformation, and malocclusion. American Journal of
Orthodontics. 1963 Jun 1;49(6):418-50.
• Posselt U. Ansikts-och käkledssmärtor—diagnos och behandling Göteborgs Tandl. Sällskaps Arsbok.
1958;9:104-24.
• Posselt U. Physiology of occlusion and rehabilitation.
• Bosma JF. Maturation of function of the oral and pharyngeal region. American Journal of
Orthodontics and Dentofacial Orthopedics. 1963 Feb 1;49(2):94-104.
• Baker RE. The tongue and dental function. American Journal of Orthodontics. 1954 Dec
1;40(12):927-39.
• Management of temporomandibular disorders and occlusion – Jeffrey P. Okeson.
• Functional occlusion – From TMJ to Smile design – Peter E. Dawson.
96