applied aspects of muscles of mastication

2. GOOD MORNING
LAB
WORK

4. ANISH YOGESH AMIN

5. INTRODUCTION TYPES OF
MUSCLE FIBERS
FUNCTIONS OF
MUSCLE
FIBERS
REFLEX
MECHANISMS
PROSTHODONTIC
IMPLICATIONS
MASTICATORY
MUSCLES
CONCLUSION
DISORDERS OF
MASTICATORY
MUSCLES REFERENCES

6. MUSCLE is defined as a
tissue composed of
contractile cells or fibers
that effect movement of an
organ or part of the body.
TYPES OF MUSCLES
Glossary Of Prosthodontic
Terms 8

7. ISOTONIC CONTRACTION
ISOMETRIC CONTRACTION
CONTROLLED RELAXATION

8.  Stimulation of large no of motor units
 Overall shortening of muscle under constant load
 Eg: Occurs in Masseter muscle(during elevation of mandible)
forcing teeth through bolus of food
ISOTONIC CONTRACTION

9.  Proper no. of motor units are stimulated
 Muscle does not shorten
 Eg: Occurs in Masseter muscle, when an object is
held between the teeth
ISOMETRIC CONTRACTION

10.  Stimulation of motor units discontinued
 Muscle returns to its normal length
 Eg: Occurs in Masseter muscle when the mouth opens
to accept a new bolus of food
CONTROLLED RELAXATION

11. “MANDIBULAR
ARCH”
The basic muscles of mastication develop
from the mesenchyme of first branchial arch

12. MASTICATION
Mastication (1649):
Process of chewing food for
swallowing and digestion
GLOSSARY OF PROSTHODONTIC
TERMS 8

13. Four major muscles
 Masseter
 Temporalis
 Medial pterygoid(internal)
 Lateral pterygoid (external)

14. • DIGASTRIC
• MYLOHYOID
• GENIOHYOID
• INFRAHYOID

15. ORIGIN INSERTION
Superficial
layer
Anterior
2/3rd
of
lower border
of zygomatic
arch
Lower part
of lateral
surface of
ramus
Middle layer Posterior
1/3rd
of
lower border
of zygomatic
arch
Middle part
of ramus
Deep layer Deep surface
of zygomatic
arch
Upper part
of ramus &
coronoid
process
NERVE SUPPLY:
MASSETERIC BRANCH OF
MANDIBULAR NERVE

16. •May become overdeveloped due to
bruxism
•Parotid gland lies on the top of this
muscle
•Masseter hypertrophy may shut off flow
from parotid
 Elevates mandible
 Brings molars together for crushing
and grinding-”chewer “ muscle
 Forms half of mandibular sling
(medial pterygoid forms the other half)

17. ON DENTURE BORDER:
 An active masseter muscle will create concavity in the outline
of the distobuccal border
 A less active masseter may result in convex border
 In this area the buccal flange must converge medially to avoid
displacement due to contraction of the masseter muscle, because
the muscle fibers in that area are vertical and oblique

18. Instruct the patient to open mouth wide and then close
against the resting force of your finger
Opening wide activates the muscles of
pterygomandibular raphe by stretching,
which thereby defines the most distal
extension
Instructing the patient to close
against the finger on tray handle
causes masseter muscle to
contract & push against the
medially situated buccinator
muscle
MASSTERIC
NOTCH REGION

19. •
NERVE SUPPLY: 2 deep temporal
branches of mandibular nerve
ORIGIN INSERTION
Temporal fossa
& temporal fascia
Coronoid process
and anterior border
of ramus
•Largest and most powerful muscle of
mastication
•Fan shaped muscle
•Fibres are vertical and horizontal-
accounts for different actions this
muscle can perform.
•Often visible when chewing

20. Anterior and superior fibers
elevate mandible
Posterior fibers retract
mandible

21. NERVE SUPPLY
•Nerve to medial pterygoid (branch.
of main trunk of Mandibular
Nerve)
ORIGIN INSERTIO
N
Superficial Maxillary
tuberosity
Medial
surface of
angle of
mandible
Deep Medial
surface of
lateral
ptergoid
plate
Mylohyoid
groove

22. •Elevates &
Protrudes
mandible, also
causing jaw closure
ACTION OF MEDIAL PTERYGOID
•Unilateral
contraction –
mediotrusive
movement of the
mandible

23.  Most commonly involved in MYOFACIAL PAIN
DYSFUNCTION SYNDROME
 Trismus following inferior alveolar nerve block is
mainly due to involvement of medial pterygoid
muscle

24. ORIGIN INSERTION
UPPER
HEAD
Infratemporal
surface of crest
of greater wing
of sphenoid
Pterygoid
fovea
LOWER
HEAD
Lateral surface
of lateral
pterygoid plate
Articular
surface and
capsule of
TMJ
NERVE SUPPLY
• Branch of anterior division of
mandibular nerve

25. •Depresses mandible
On unilateral contraction
causes the lateral
movement of mandible to
the opposite side
•Along with medial pterygoid protrudes
mandible

26. Most commonly involved muscle in
MYOFACIAL PAIN
DYSFUNCTION SYNDROME
Unilateral failure of lateral
pterygoid muscle to contract
results in deviation of the
mandible toward the affected
side on opening
Bilateral failure results in
limited opening, loss of
protrusion & loss of full lateral
deviation

27. NERVE SUPPLY
•Anterior belly-mylohyoid
branch of inferior alveolar
nerve
•Posterior belly-Facial nerve
ORIGIN INSERTION
Anterior
Belly
Posterior
Belly
Digastric
fossa
Mastoid
notch
Tendon
attached to
body &
greater
cornua of
hyoid bone

28. •Depresses mandible while
opening mouth
•Elevates hyoid bone
during swallowing

29. NERVE SUPPLY:
Mylohyoid branch of inferior
alveolar nerve
ORIGIN INSERTION
Mylohyoid line of
mandible
Postreior fibers-to
body of hyoid bone
Middle & anterior
fibers-decussate to
form fibrous band

30. •Depresses mandible while
opening mouth
•Elevates hyoid bone and floor of
mouth during deglutition

31. NERVE SUPPLY
1ST
cervical spinal nerve
through Hypoglossal nerve
ORIGIN INSERTION
Inferior Genial
Tubercle of
mandible
Anterior
surface of hyoid
bone

32. •Depresses mandible while
opening mouth
•Eelevates hyoid bone

33. Sternohyoid
•Depresses
hyoid bone
Sternothyroid
•Depresses
larynx
Thyrohyoid
•Depresses
hyoid bone
•Elevates
larynx
Omohyoid
•Depresses hyoid
bone & larynx
•Carries hyoid
bone backwards
& to the side

34. ARTERIAL SUPPLY- MAXILLARY ARTERY-2ND
PART(TERMINAL BRANCH OF ECA)
VENOUS DRAINAGE-RETROMANDIBULAR
VEIN
LYMPHATIC DRAINAGE- SUBMANDIBULAR
& SUBLINGUAL LYMPH NODES.

35. PAIN-
Compromised
No PAIN-Healthy
Palmar surface of
middle, index, fore
finger used for
palpation
LEFT & RIGHT
palpated
simultaneously

36. ANTERIOR
FIBERS-ABOVE
THE ZYGOMATIC
ARCH,ANTERIOR
TO TMJ
MIDDLE REGION-
ABOVE
TMJ,SUPERIOR TO
ZYGOMATIC
ARCH
POSTERIOR FIBERS-
ABOVE & BEHIND
THE EAR

37. Fingers placed on
each side of
zygomatic arch,just
anterior to the TMJ
Fingers dropped down
slightly to the portion
of masseter attached to
zygomatic arch
Palpated bilaterally,at superior & inferior
attachments
The fingers drop to the
inferior attachment on the
inferior border of the ramus

38. INTRAORAL METHOD
Palpated by sliding finger
lingually and by applying
pressure at the insertion of muscle
above the angle of mandible

39. Superior head – equal pressure on
lateral poles of condyle as patient opens
and closes his mouth
Inferior head- Placing the forefinger,
over the buccal area of the maxillary
third molar region & slide in medial
direction behind the maxillary
tuberosity
Many anatomical and clinical studies have
demonstrated the inability to digitally
contact the Lateral pterygoid muscle due
to its location and surrounding tissues.

40. CONTRACTING
Protruding against
resistance – increases
pain
STRETCHING
• Clenching on teeth–
increases pain.
• Clenching on
separator–no pain
INFERIOR LATERAL
PTERYGOID

41. SUPERIOR LATERAL
PTERYGOID
CONTRACTION
• Clenching on teeth –
increases pain.
• Clenching on separator –
increases pain
STRETCHING
• Clenching on teeth –
increases pain.
• Clenching on separator –
increases pain
• Opening mouth – no pain

42. CONTRACTION
• Clenching on teeth –
increases pain.
• Clenching on separator –
increases pain
STRETCHING
Opening mouth –
increases pain
MEDIAL PTERYGOID

43.  If a second stimulus is given before the muscle comes to a relaxed
state the muscle does not respond for the second stimulus of
whatever strength it might be. This period of inactivity where the
muscle does not respond is termed as Massetric silent period
 A part of the complex feedback mechanism of mandibular control
involving receptors in the periodontal ligament and muscles.
 Journal of Oral Rehahilitation 1995 22; 49-55

44. A) MYOTACTIC REFLEX MONOSYNAPTIC REFLEX
Sudden downward force
applied to the chin with a
small rubber hammer
This will cause the jaw to be
reflexly elevated resulting in
masseter contraction and
tooth contact
When a skeletal muscle is
quickly stretched, this
protective reflex brings about
a contraction of the stretched
muscle

45. B)NOCICEPTIVE REFLEX POLYSYNAPTIC REFLEX
Hard object is suddenly
encountered during
mastication
Jaw quickly drops and the
teeth are pulled away from the
object
Protects the teeth and
supportive structures from
damage created by sudden and
unusually heavy forces

46. MASSETER/MONOSYNAPTIC reflex
•Used to test the status of a patients trigeminal nerve
Masseter muscle will jerk
the mandible upwards
The mandible is tapped
at a downward angle
just below the lips at the
chin while mouth is held
slightly open
Upper motor neuron
lesion-pronounced
reflex

47. POLYSYNAPTIC
REFLEX
RESULT OF
MECHANICAL/ELECTRICAL
STIMULATION OF LIPS,ORAL
MUCOSA OR TEETH
A SLIGHT OPENING MOVEMENT OCCURS
DUE TO INHIBITION OF ACTIVITY IN THE
MANDIBULAR ELEVATORS WITHOUT
SIMULTANEOUS CONTRACTION OF
DEPRESSORS

48. PROTECTIVE REFLEX
ON SUDDEN ENCOUNTER WITH A HARD
OBJECT,MASTICATION IS STOPPED
REFLEX INHIBITION OF ELEVATORS +
REFLEX EXCITEMENT OF DEPRESSORS
DUE TO PDL RECEPTORS
PROTECTS TEETH FROM DAMAGE

49. REFLEX CHANGES OCCURING IN ELEVATOR MUSCLES WHEN UPPER
& LOWER TEETH ARE SNAPPED TOGETHER
TRANSIENT ACTIVATION > SILENT PERIOD > PHASE OF INCREASED
& DECREASED ACTIVITY OF ELEVATOR MUSCLES
NO EFFECTS ON THE DEPRESSORS

50. LATERAL,PROTRUSIVE &
RETRUSIVE REFLEX
MANDIBULAR REFLEXES

51.  The average maximum sustainable biting force is 756N (170
pounds)
Normal Dentition:80 N
Dentures: 64N
Males: 520N
Females: 350N
Incisor region: 89-111 N
Cuspid region: 133-334 N
Premolar region:222-445 N
Molar region: 400-890 N

52.  15 Chews in a series from the time of food entry until
swallowing
 Average jaw opening during chewing is between 16-20mm
 Average lateral displacement on chewing is between 3-
5mm
 Duration of masticatory cycle varies between 0.6 and 1
sec
 Men chew faster and have a shorter occlusal phase than
women,it also depends on the type of food

53.  Have shorter contraction time than most other body
muscles
 Incorporate more of muscle spindles to monitor their
activity
 Do not have golgi tendon organs to monitor tension
 Do not fatigue easily
 Psychological stress increases the activity of jaw closing
muscles
 Occlusal interferences cause a hypertonic synchronous
muscle activity
 Closing movement also determined by the height of the
teeth

54. MASTICATORY ENVELOPE
“TEAR- DROP SHAPE”
•Slight displacement at the beginning of
the opening phase
•In most cases it deviates to the chewing
side
•The maximum extent of vertical and
lateral movement in normal masticaton
is about half of the maximum vertical
and lateral movement possible.

56. ATROPHY: Decrease in the mass
of the muscle; it can be a partial or
complete wasting away of muscle.
HYPERTROPHY : Involves an increase
in mass of a muscle through an increase in
the size of its component cells.
HYPERPLASIA: Increase in number
of muscle fibers due to extreme muscle
force generation

57.  Initial response of a muscle to altered sensory or
proprioceptive input or injury.
 Antagonistic muscle groups seem to fire during
movement in an attempt to protect the injured part.
 Increased activity of the jaw – opening muscles
during closure and an increase in closing muscle
activity during mouth opening.
ETIOLOGY- Altered sensory or proprioceptive input,
Constant deep pain input, Increased emotional stress

58. Eliminate etiology either by
correction of functional
discrepancies or relieving stress
Structural dysfunction – velocity and
range of mandibular movement is decreased
Minimal pain at rest & Increased pain
with function
Feeling of muscle weakness
CLINICAL FEATURES

59. Acquired auto immune
disorder of neuromuscular
transmission characterized by
muscle weakness.
Antibodies to
Acetyl choline
receptor on
skeletal muscle
fiber

60. Protrusive movement of
the tongue becomes weak
Dysphagia
Dysarthria
Impaired salivation
Muscle fatigue
Facal paralysis
SYMPTOMS
•Dental procedure- after 1-2 hours
following intake of medicine,
•Preferably in the morning
•Stress reduction prior to dental
treatment
MANAGEMENT

61. Glossary of Prosthodontic Terms (GPT-8)
defines BRUXISM as parafunctional
grinding of teeth or an oral habit consisting
of involuntary rhythmic or spasmodic non
functional gnashing, grinding or clenching
of teeth in other than chewing movements
of the mandible which may lead to occlusal
trauma.

62. ETIOLOGY:
•STRESS
•PSYCHOLOGICAL DISTURBANCES
•BITE DISCREPANCIES AND
TEMPEROMANDIBULAR DISORDERS
•NUTRITIONAL DEFICIENCIES
CLINICAL FEATURES
•Occlusal wear
•Periodontal destruction
•Muscular hypertrophy and
tenderness
•Headache
Treatment :
•Coronoplasty
•Occlusal splints

63. Journal of Prosthodontic Research 55 (2011) 127–136
•When prosthetic intervention is
indicated in a patient with bruxism,
efforts should be made to reduce the
effects of likely heavy occlusal loading
on all the components that contribute
to prosthetic structural integrity.
•Failure to do so may indicate earlier
failure than is the norm.

64. DIFFERENT DEGREES OF
LATERAL PTERYGOID
HYPERACTIVITY

65. Causes :
•Intracapsular :Arthritis,
condylar fractures
•Pericapsular –
irradiation, dislocation,
infection and inflammation
•Muscular – TMJ
dysfunction syndrome,
tetanus (lock jaw
•Others – systemic
sclerosis, fracture
TRISMUS LEADS TO:
•Difficulty in eating,
maintaining oral hygiene, in
speech & swallowing
•Joint immobilization

66. TREAT THE UNDERLYING CAUSE
JAW OPENING EXERCISES
SYMPTOMATIC RELIEF

67. •Sectional impression trays
and Sectional dentures
PROSTHODONTIC MANAGEMENT

68. J Prosthet Dent. 2000 Sep;84(3):269-73
Vinyl polysiloxane occlusal-
registration material mixed in an
automix dispenser - superior flow,
ease of mixing, convenient
dispensary,rigidity, and quick-setting
properties, which allow it to be used in
the mandibular arch successfully as a
custom-diagnostic impression tray

69. J Prosthet Dent. 2000 Sep;84(3):269-73
In the maxillary arch, the diagnostic impression is
made using a combination of wooden spatula,
thermoplastic modeling plastic impression
compound, and irreversible hydrocolloid.
The modeling plastic impression compound is more
viscous and it prevents slumping when it is being
used in the maxillary arch
Because of the relatively simple anatomy on the
maxillary arch, the modeling plastic provides
enough working time to capture the required
anatomic landmarks
This molding procedure should be performed in
an incremental manner to ensure that the
modeling plastic impression compound is
retrievable

70. If the modeling plastic impression tray
becomes too large to be retrieved, it
can be broken down into smaller pieces
and carefully removed from the oral
cavity.
•Border molding in such a situation
should be re-attempted using elastomeric
material.
•The rest of the clinical procedures follow
traditional complete denture fabrication.
No change in the laboratory phase is
needed
J Prosthet Dent. 2000 Sep;84(3):269-73

71. Preliminary impressions were made
with polyvinyl siloxane putty
material-Flexible impression tray
technique

72. Two-piece custom tray design with sections
of the tray that can be joined firmly and
oriented accurately both in patient’s mouth
and after removal of the tray from the mouth.

73.  Impression is made by orienting the respective
sections of the trays with the help of a lock
system or screw,

74. And then unlocking it inorder to take it out of the
mouth,again rejoining outside the mouth for further lab
procedure

75.  Mastication is oral motor behavior reflecting central
nervous system commands, and many peripheral sensory
inputs to modulate the rhythmic jaw movements.
 Since tooth guidance has an enormous influence on
muscle activity during chewing and swallowing, it is
advisable to make restorations and replacements as much
compatible as possible, with the functional movement
patterns of the patient, rather than expect the patterns of
the mastication to adapt to the new made replacements.

76. •Gray’s anatomy.
•B .D Chaurasia’s. Human Anatomy . Head , neck and
Brain
•G.H. Sperber. Craniofacial embryology.
•Guyton and hall.2001.Textbook of medical
physiology.10th edition,Harcourt Asia PTE LTD.
•William F Ganong,Review of Medical
Physiology,Eighteenth edition 1997

77. •George A.Zarb,Charles L Bolender,Prosthodontic Treatment for
Edentulous Patients, twelth edition 2004
•Sheldon Winkler,Essentials of complete denture
Prosthodontics,second, edition 2000.
•Okeson JP.2002 Management of temporomandibular disorders
and occlusion.5th edition. St Louis: Mosby Publishing.
•Evaluation , diagnosis and treatment of occlusal problems –
2nd edn, Peter Dawson John W. E. Snawdon Fibrositis in the
Muscles of Mastication(With Reference to the Masseter Muscle)

78. •Proc R Soc Med. 1949 ; 42(3): 153–154 Yasmin et al Published
online 2013 doi: 10.1186/1745-6215-14-316
•The Glossary of Prosthodontic Terms
•Cheng AC, Wee AG, Shiu-Yin C, Tat-Keung L. Prosthodontic
management of limited oral access after ablative tumor surgery: a
clinical report. J Prosthet Dent. 2000 84(3):269-73.
•Johansson A, Omar R, Carlsson G.E Bruxism and prosthetic
treatment: A critical review Review Article
Journal of Prosthodontic Research, Volume 55, Issue
3, 2011, Pages 127-136.

79. THANK YOU