Anatomy of the masticatory machine. It consists of a fixed and a movable member. The movable member is activated by a series of voluntary muscles, and its efficiency is increased by another set of voluntary muscles that feed the machine.

2. CONTENT
 Introduction
 Definition
 Classification of muscle
 Development of muscle
 Features of masticatory system
 Muscles of mastication
 Significance in Prosthodontics
 Masticatory muscle disorder
 Review of literature
1

3.  FISH = necessity for making positive use of
certain muscles to gain denture stability and
retention.
 Anatomy of the masticatory machine. It consists
of a fixed and a movable member. The movable
member is activated by a series of voluntary
muscles, and its efficiency is increased by
another set of voluntary muscles that feed the
machine.
JPD, vol-4, issue-3, p327-334, may 1954
2

4.  As prosthodontists, we are chiefly concerned
with the activating muscles from the
standpoint of their power and the load they
may impose upon the tissues under a saddle
that supports an artificial replacement for lost
teeth.
 The muscle that are intimately involved in
complete denture service are defined as
skeletal muscle, striated,& voluntary.
3

5.  Their chief point of interest to us arises from
the fact that they can be tensed independent
of the relation of the mandible to the maxilla.
 Also, they impinge not only on the denture
borders, but also on the polished surfaces of
dentures. So, they immediately become of
prime importance in securing denture
stability.
 During impression making we must be
actively aware of their location and direction
of action, as well as their effect.
4

6. DEFINATION
• MUSCLE= An Organ that by contraction
produces movements of an animal; a tissue
composed of contractile cells or fibers that effect
movement of an organ or part of the body.
-GPT 9
 MASTICATION= The process of chewing
food for swallowing and digestion.
5

7. classification
skeletal
Smooth
Cardiac

8. skeletal muscle
 The skeletal muscle is made up of many long
thin cells called muscle cells or muscle fibers.
 The muscle origin and insert in the tendons
and muscle fibres are arranged parallel.
 The muscle fibres are made up of many fibrils
called myofibrils.
Human physiology, Dr. A K jain 6th edition
7

9. 8

10.  Each myofibril is 1-2micrometer in diameter, lies
parallel to each other and are striated.
 The cytoplasm in the muscle fiber, called
sarcoplasm, contain numerous
mitochondria(sarcosomes), smooth muscle
endoplasmic reticulum(sarcoplasmic reticulum
and is rich in glycogen.
Human physiology, Dr. A K jain 6th edition
9

11. Light microscopic appearance
 The cross striation in the skeletal muscle are
due to alternate dark and light bands.
 A band(1.5micrometer)-The dark band is made
of highly refractile material(anisotropic).
H band(0.5micrometer) - In the center of each A
band, a slightly less refractile region called H band
is found.
Human physiology, Dr. A K jain 6th edition
10

13.  I band(1micrometer) -The alternate light band
is made of lower refractile material(isotropic).
 Z line – in the center of each I band is found a
narrow line of highly refractile material which
looks dark.
 Sarcomere(2.5micrometer) – the contractile
unit of the muscle is the substance included
between two adjacent Z lines .
12

14. Electron microscopic appearance
 The myofibrils are made up of two sets of
protein filaments,
• thick and thin filaments

15. Thick filament:
 It is approx. twice the diameter of thin filament
and is made up of myosin.
 It is responsible for the formation of 'A ' band .
 There are several hundred (about 500) myosin
molecules in each thick filament.
Human physiology, Dr. A K jain 6th edition
14

16.  Myosin filaments are 10-11 nm thick and approx.
45 nm apart extending from one end of the 'A'
band to the other.
 Transverse section through 'A' band shows that
each myosin filament is surrounded by 6 actin
filaments in a regular hexagonal manner.
15

17.  The myosin molecule is composed of two large
polypeptide heavy chains and four smaller light .
 These polypeptides combine to form a molecule
that consists of two globular heads (containing
heavy and light chains) and a long tail formed by
the two twisted heavy chains.

19.  Function : Each globular head has two
important sites:
A. Actin binding site, where myosin comes in
contact with actin.
B. ATPase (catalytic) site, that hydrolyzes
(breaks) ATP.
The myosin molecules aggregate with their heads
pointed in one direction along one half of the
filament and in the opposite direction along the
other half.The heads serve as the cross-bridges.
18

21. THIN FILAMENT
 It is made up of Actin,Tropomyosin andTroponin.
 They arrange themselves to form 2 chains of
globular units that form a long double helix (i.e.
spiral chain).
 It is responsible for the formation of 'I' band. Each
thin filament contains 300-400 actin molecules
and 40-60 tropomyosin molecules.
20

22. ACTIN
 Actin filaments are thinner, 4-5 nm in diameter
and stretch from 'Z' lines to the edge of the 'H'
zone.They occur in 2 forms:
a) G actin(Globular Actin):Each molecule binds one
molecule of ATP firmly.
b) F actin(Fibrous Actin):Formed by polymerization
of 'G' actin molecule with liberation of energy.
G-actin ATP F-actin ADP+ inorganic PO4 +
Energy (7 Kcal)
21

23. TROPOMYOSIN
 Tropomyosin molecules are long filaments
located in the groove between two chains in the
actin.
 It covers the binding site of actin where myosin
head comes in contact with actin i.e. prevents
the interaction between actin and myosin
filaments.
22

25. TROPONIN
 Troponin molecules are small globular units
located at intervals along the tropomyosin
molecules. It is made up of 3 subunits.
a) TROPONINT: binds the other troponin
components to tropomyosin.
b) TROPONIN I: inhibits the interaction of myosin
with actin.
c) TROPONINC: contains binding site for Ca2+ that
initiates muscle contraction
24

26.  At rest, i.e. when the muscle is relaxed the
thin filaments interdigitate with the thick
(myosin) filaments only outside the 'H' band.
 During muscle contraction, the length of 'A'
band (thick filament) remains constant,
whereas 'Z' lines move close together.
25

27. Sequence of events in
excitation contraction
STEPS IN MUSCULAR CONTRACTION
• Stimulation of motor nerve with threshold
intensity produces propagated action potential.
• Release of Acetylcholine (A-ch) into synaptic
cleft which binds with "nicotinic A-ch receptors"
concentrated on motor end plate causing
generation of end plate potential.
26

28.  Depolarization of muscle membrane
(sarcolemma) by increasing its permeability to
Na+.
 Generation of action potential in the muscle
fiber.
 Inward spread of action potential alongT
system.
27

29.  ROLE OF CALCIUM
 Ca2+ binds to troponin C to saturation point
causing tropomyosin to move laterally.This
exposes the binding sites for myosin heads on
actin.
28

30.  Activates prosthetic group of myosin filament
which acts as enzyme (ATPase) catalyzing the
breakdown of ATP to produce energy for;
1. contraction of actomyosin complex.
 Muscular contraction

31. STEPS IN MUSCULAR RELAXTION
 A few milliseconds after the action potential is
over, sarcoplasmic reticulum begins to
reaccumulate Ca.The Ca ions are actively pumped
by Ca2+- Mg2+ ATPase .
 Once Ca2+ concentration decreases in ICF
sufficiently to 10-7 moles/L, chemical interaction
between myosin and actin ceases and muscle
relaxes.
30

32. CARDIAC MUSCLE
 Cardiac muscle is an involuntary, striated
muscle.
 The individual muscle cell is 100 μm long and 15
μm broad.
 The fibers are branched and interlock freely
with each other, but each is a complete unit
surrounded by a cell membrane, sarcolemma.
31

34.  At the point of contact of two muscle fibers,
extensive folding of cell membrane occurs, called
intercalated discs.
 They provide a strong union between fibers,
thereby help in increasing force of contraction.
 GAP JUNCTION;a specialized intercellular junction
is present in the intercalated disc along the sides
of the adjacent myocardial cells.
33

35.  Here ions, electrical currents and other
molecules can be transferred from one cell to
other without coming in contact with the ECF.
 Thus, they provide low resistance bridges for the
spread of excitation from one muscle fiber to the
next and permit cardiac muscle to function as if it
is a functional syncytia (i.e. a single cell).

36.  There are two such separate syncytia in the heart.
The atrial and ventricular syncytia, connected with
each other by A-V bundle.
 The cardiac muscle fibers are highly vascular i.e.
surrounded by a very rich capillary network. They
show well developed sarcoplasmic reticulum with
plenty of cytoplasm, mitochondria and rich in
glycogen.

37. Electrical properties
EXCIBILITY
 Cardiac muscle is excitable, i.e. it forms a wave
of depolarization (excitation impulse) in
response to a stimulus.
 The 'extracellular' recording of the electrical
event generated with each heart beat is called
Electrocardiogram(ECG).
36

38. At rest, myocardial fibers (atrial and ventricular) show a
resting (polarised) membrane potential (RMP) of
approx. -90 m V (negative inside with reference to
outside).
On stimulation there occurs;
Phase 0 = rapid depolarization and potential reaches
+20 to +30mv.this is due to
o 100 fold increase in Na+ permeability resulting
in Na+ influx, which appears when membrane
potential is -60 mV; but it is short-lived and
self-limiting;

40. o marked increase in Ca2+ permeability causing
Ca2+ influx which appears at membrane
potential of -30 to -40 mV.
 Depolarization lasts for approximately 2 msec
and is followed by slow repolarization.
 Repolarization occurs in 3 phases
39

41. PHASE 1 = A rapid initial fall from +30 mV to -10
mV due to five fold increase in k+ permeability
causing k+ efflux.
Phase 2 = A plateau phase in which the
membrane potential falls slowly only to -40 mV
due to:
 inactivation of Na+ influx which starts appearing
at zero potential, and
 Ca2+ influx and K+ efflux continue at a slow rate.
40

42. PHASE 3 = A rapid fall during last stage in which
membrane potential falls to the resting value of -
90 mV due to inactivation of Ca2+ and Na+ influx
with rapid K+ efflux.
PHASE 4 = Polarised state. During this phase,
though RMP is achieved yet resting ionic
composition is restored by the activation of Na+
- K+ pump.
41

43. Autorhythmicity
The heart continues to beat for quite some time
even after all nerves to it are cut or even if it is cut
into pieces.
This is because of the presence of the specialized ,
pacemaker tissue in the heart that can initiate
repetitive action potentials.
 'Pacemaker' tissue includes sinu atrial node
(SAN); atria ventricular node (AVN); atrio
ventricular bundle and purkinje fibers.
42

44. SMOOTH MUSCLE
o Involuntary muscle, i.e. not under the control of
will.
o Unstriated (lacks visible cross striations),
therefore also called plain muscle.
o Smooth muscle cells are smaller, spindle shaped
with varying dimensions e.g. fibers in digestive
tract are 30-40μm long and 5μm diameter; in
blood vessels, 15-20μm long and 2-3μm
diameter.
43

45. o In general, it contains few mitochondria and
depends largely on glycolysis for its metabolic
needs.
o Sarcoplasmic reticulum is poorly developed.
o The contractions in smooth muscle have a
longer duration.
o they are more variable and they produce less
tension than in skeletal muscle.

46.  The muscular system develops from intra
embryonic mesoderm.
 Muscle tissue develop from embryonic cells
called myoblast.
 Muscles of mastication are derived from first
or mandibular arch.

47. FEATURES OF MASTICATORY SYSTEM
 The masticatory system comprises three major
skeletal component.
 Two support the teeth: the maxilla and the
,mandible.
 The third, the temporal bone, supports the
mandible at its articulation with the cranium.
Okeson, 6th edition
46

48. Maxilla
 Developmentally, there are two maxillary bones,
which are fused together at the midpalatal
suture.
 These bone make up the greater part of upper
facial skeleton.

 The border of the maxilla extends superiorly to
form the floor of the nasal cavity as well as the
floor of each orbit,

49.  Inferiorly maxillary bone form the palate and the
alveolar ridge, which support the teeth.
 Because the maxillary bone are intricately fused
to the surrounding bony components of the
skull, the maxillary teeth are considered to be a
fixed part of the skull and therefore comprise
the stationary component of the masticatory
system.

50. MANDIBLE
 Mandible is U shaped bone that supports the
lower teeth and makes up the lower facial
skeleton.
 It has no bony attachment to the skull. It is
suspended below the maxilla by muscle.
 The superior aspect of arched shaped mandible
consist of the alveolar process and the teeth

51. Temporal bone
 The mandibular condyle articulate at the base
of the cranium with the squamous portion of
temporal bone.

52. MUSCLES OF MASTICATION
 These are the muscle that move the mandible
during mastication, speech,& deglutition.
 They move the mandible quickly & precisely
to enable different speech sounds & they are
also capable of exerting enormous forces that
are required to break down tough food.
52

54. Principle MUSCLES OF
MASTICATION
MASSETER
TEMPORALIS
MEDIAL
PTERYGOID
LATERAL
PTERYGOID

55. Accessory Muscles Of
Mastication
BUCCINATOR
DIGASTRIC
MYLOHYOID
GENIOHYOID

56.  Greek word masseter a
chewer
 It is a quadrilateral
muscle that covers
most of the lateral
aspect of the ramus of
mandible
 Consist of 3 layers
Human anatomy, 3rd edition

57. ORIGIN INSERTION
Superficial layer
from anterior 2/3 of
lower border of
zygomatic arch and
adjoining zygomatic
process of maxilla
pass downwards and
backwards at 45
into lower part of
lateral surface of ramus
of mandible
57

58. Middle layer
from lower border of
poterior 1/3rd of zyg-
omatic arch
pass vertically
downwards
into the central part of
ramus of mandible
58

59. Deep layer
From deep surface of
zygomatic arch
ass vertically
downward
Into the rest of the
ramus of mandible

60. NERVE SUPPLY
 Masseteric nerve a branch of anterior division of
mandibular nerve

61. ACTION
Retraction of mandible
(deep fibers)
Protrusion of mandible
(superficial fibre)
Elevation of mandible

62. PALPATION
 The patient is asked to clench their teeth &
the practitioner perform extra oral palpation
of the masseter muscle bilaterally along the
origin (zygomatic arch) to down the ramus of
mandible where it turns to body of mandible.

63. PROSTHODONTIC CONSIDERATION
 Contraction of masseter muscle affect the
distobuccal corner of the lower denture border
 The distobuccal area of the impression will
appeared grooved or reflected superiorly ;this is
the masseteric groove ,the result of masseter
muscle pushing against the buccinator muscle
63

64. Masseteric notch action on
denture border
 An active masseter muscle will creat
concavity in the outline of the distobuccal
border & less active muscle may result in
convex border
64

65. Activation of masseteric
notch & distal area
 Instruct the patient to open mouth widely &
then close against the resting force of finger.
 Opening wide activates the muscle of
pterygomandibular raphae by stretching
,which thereby define the most distal
extension.

66. Instructing the patient to
close against your finger on
tray handle causes masseter
muscle to contract & push
against the medially situated
buccinator muscle.

67.  A fan shaped ,fills the temporal fossa

68. ORIGIN INSERTION
 Floor of temporal
fossa
 From overlying
temporal fascia
 Margins & deep
surface of coronoid
process
 Anterior border of
ramus of mandible

69. NERVE SUPPLY
 Two deep temporal branches from
anterior division of mandibular nerve

70. BLOOD SUPPLY
 TEMPORAL ARTERY
BRANCH OF
MAXILLARY ARTERY

71. ACTION
 Elevates the mandible
 Helps in side to side
grinding movement
 Posterior fibers retract the
protruded mandible

72. PALPATION

73. PROSTHETIC CONSEDATION OF
TEMPORALIS MUSCLE
 It act as a stabilizer of tmj when the condyle is
translated into a more protruded position these
posterior fibers are aligned more horizontally.
 It suspends the mandible in centric relation
.anterior group of fibers which are aligned
vertically hold the mandible in superior most
position.

74.  It is a short thick muscle with two parts or
head

75. ORIGIN INSERTION
 Upper head
from infratemporal
surface & crest of
greater wings of
sphenoid bone
 Lower head
from lateral surface of
lateral pterygoid plate
Pterygoid fovea on the
anterior surface of
neck of mandible
Anterior margin of
articular disc & capsule
of tmj

76. NERVE SUPPLY
 A branch of anterior division of
mandibular nerve

77. BLOOD SUPPLY
 Pterygoid branch of 2nd part of
maxillary artery

78. ACTION
 Depress mandible to open mouth
 Protrusion of mandible
 Right pterygoid turn the chin to left side as a
part of grinding movements

79. PALPATION

80. PROSTHODONTIC CONSIDERATION
 During closure of the mouth the backward
gliding of the articular disc & condyle is
controlled by slow elongation of lateral
pterygoid while masseter & temporalis
restore the jaw to the occlusal position, thus
act as stabilizer of tmj.
 It holds the condyle in centric relation
position.

81.  Quadrilateral ,has a small superficial & a large
deep head

82. ORIGIN INSERTION
 Superficial head
from tuberosity of
maxilla
 Deep head
from medial surface
of lateral pterygoid
plate
roughened area on
the medial surface
of angle & adjoining
ramus of
madible,below &
behind the
mandibular foramen

83. NERVE SUPPLY
 Branch of the main trunk of the
mandibular nerve

84. BLOOD SUPPLY
 Pterygoid branch of 2nd part of
maxillary artery

85. ACTION
 Elevate mandible
 Protrude the mandible
 Right medial pterygoid with right lateral
pterygoid turn the chin to left side

87.  Has two bellies united by intermediate
tendon

88. ORIGIN INSERTION
 Anterior belly
From digastric fossa
of
mandible
 Posterior belly
from mastoid notch of
temporal bone
 Both head meet at the
intermediate tendon &
is held by fibrous pully
of hyoid bone

89. Blood supply
• Anterior belly –submental branch
of facial artery
• Posterior belly-occipital artery

90. •Anterior belly-mandibular division of trig-
eminal via the mylohyoid –
nerve
•Posterior belly-facial nerve
NERVE SUPPLY

91. ACTION
Depresses mandible Elevates hyoid bone

92. MYLOHYOID MUSCLE

93. ORIGIN INSERTION
 Mylohyoid line of
mandible
 Posterior fibre- body of
hyoid bone
 Middle &anterior
fibres-
inti the fibrous median
raphae between the
mandible & hyoid bone

94. Mylohyoid nerve - A motor
branch of the inferior alveolar
nerve branch of the mandibular
division of the trigeminal nerve
NERVE SUPPY

95. BLOOD SUPPLY
 Sublingual artery

96. ACTION
 Elevates floor of mouth in first step of
deglutition
 Help in depression of mandible & elevation of
hyoid bone

97. Prosthodontics consideration
 Instruct the patient to place the tip of his
tongue into the upper & lower vestibules on
the right & left side .
 The area to be moulded is reheated & patient
is instructed to swallow two or three times in
rapid succession
 The tongue movements raise the level of the
floor of the mouth through contraction of
mylohyoid muscle

98. GENIOHYOID
 Short and narrow muscle lies above
mylohyoid

99. ORIGIN INSERTION
 Inferior mental
spine
 Fibers runs
backward,
downward to be
inserted into the
anterior surface of
the body of hyoid
bone

100. 1st cranial nerve ,the fibers pass
through hypoglossal nerve
NERVE SUPPLY

101. ACTION
 Move hyoid bone & tongue upward during
deglutition

102. PROSTHODONTIC CONSEDIRATION
 On recording labial flange &labial frenum, the
lip is massaged from side to side to mold the
compound to desired extension

103. BUCCINATOR

104. ORIGIN INSERTION
 Upper fibers
From maxilla opposite
molar teeth
 Lower fibers
from mandible opposite
molar teeth
 Middle fibers
from pterygomandibular
raphae
straight to the upper lip
straight to the lower lip
Decussate before passing
the lip

106. NERVE SUPPLY
 Buccal branch of facial nerve

107. BLOOD SUPPLY

108. ACTION
 Flatten cheek against gum & teeth
 Prevent accumulation of food in the vestibule
of mouth &bring the food on occlusal table
during mastication

109. Prosthodontic consideration
BUCCAL FLANGE
the area is moulded by massaging the check
in an anterior – posterior direction ,this
moves the buccinator fiber & tissue in the
direction of functional action of buccinator
muscle

110. REFERRENCES
 Human physiology, Dr. A K Jain 6th Edition.
 Human anatomy, B D Chaurasia 3rd Edition.
 Okeson 6th Edition
 JJ Sharry
 shafer’s textbook of oral pathology 6th
Edition