Introduction definition classification primary muscles of mastication -origin -insertion -surface relation -blood supply -nerve supply -palpation secondary muscles of mastication -origin -insertion -surface relation -blood supply -nerve supply -palpation mandibular movements role in complete denture fabrication conclusion references

1. Muscles Of Mastication and It’s importance in Complete Denture Construction
By- Dr. Kumari Kalpana
PG- I
Department of Prosthodontics and crown
and bridges 1

2. 2
CONTENTS
1. Introduction
2. Definition
3. Mandibular movements
4. Classification
5. Primary muscle of mastication

3. 3
6 .Accessory muscles of mastication
7. Prosthodontic application in Complete denture construction
8. Conclusion
9. References

4. “Nothing is more fundamental to treating patients than knowing the Anatomy.”
-Jefferey.P.okeson
I nt ro d u c t i o n
Muscles of mastication are the
group of muscles that help in
movement of the mandible
during chewing and speech.
We need to study these
muscles as they control the
opening & closing the mouth &
their role in the equilibrium
created within the mouth.
4

5. 5
Definition1
 GPT 8
MUSCLE:
An organ that by contraction produces movements of an
animal; a tissue composed of contractile cells or fibres
that effect movement of an organ or part of the body.
MASTICATION
Is defined as the process of chewing food in preparation
for swallowing and digestion.
1. The glossary of prosthodontic terms. J Prosthet Dent. 2005;94(1):10-92.

6. 6
MANDIBULAR MOVEMENTS
Elevation : closing the mouth.
Depression : opening the mouth.
Protraction : movement of the mandible anteriorly.
Retraction : movement of the mandible posteriorly.
Rotation : The anterior tip of the mandible is “slewed” from side to side.

7. 7
Classification 2,3
FUNCTIONALLY CLASSIFIED AS
JAW ELEVATORS
 Masseter
 Temporalis
 Medial pterygoid
JAW DEPRESSORS
 Anterior digastric
 Lower head of lateral pterygoid
 Geniohyoid
 Mylohyoid
2.Gray’s H, William PL.Gray’s anatomy: The anatomical basis of clinical practice.34thed.Elsevier;p874-878
3.Netter’s Head and neck anatomy for dentistry.2nd ed. Elsevier sundars; p223-35

8. 8
MusclesofMastication
Primary
TEMPORALIS
MASSETER
LATERAL
PTERYGOID
MEDIAL
PTERYGOID
Accessory or
Secondary
DIGASTRIC
GENIOHYOID
MYLOHYOID

10. Temporalis2,3,4,5
10
2..Gray’s H, William PL.Gray’s anatomy: The anatomical basis of clinical practice.34thed.Elsevier;p874-878
3. Netter’s Head and neck anatomy for dentistry.2nd ed. Elsevier sundars; p223-35.
4. Williams PL. Gray’s anatomy in Skeletal System. 38th ed. Churchill Livingstone;1999.p 578-582.
5. Okeson JP. Management of temporo-mandibular disorder and occlusion. 6th ed. Mosby .p3-105

11.  It can be divided into three
distinct areas according to
fiber direction and
ultimate function .
 Anterior
 Middle
 Posterior
11

12. Insertion
Its fibers come together as they extend
downward between the zygomatic arch and
the lateral surface of the skull to form a
tendon that inserts on the coronoid process
and anterior border of the ascending ramus
12

13. BLOOD SUPPLY:
•Superficial temporal artery
branch of maxillary artery
•superficial temporal vein &
middle temporal vein
13

14. NERVE SUPPLY:
•Deep temporal branches from
anterior division of mandibular
nerve
14

15. Relations
15
Superficial:
Temporal fascia
Superficial temporal vessels
Auriculo temporal nerve
Temporal branches of facial nerve
Zygomatico temporal nerve
Zygomatic arch
Masseter
Posterior:
Temporal fossa above
Major components of infratemporal fossa
below
Anterior border:
Seperated from zygomatic
bone by a mass of fat
Behind the tendon of muscle
Massetric nerve and vessels

16. 16
Function
Elevation of mandible
When the anterior portion contracts, the mandible is raised vertically.
Contraction of the middle portion will elevate and retrude the mandible.
Function of the posterior portion is somewhat controversial.
DuBrul suggests that the fibres below the root of the zygomatic process are the only
significant ones and therefore contraction will cause elevation and only slight retrusion.

17. Palpation5
The muscle is divided into three functional
areas and therefore each area is
independently palpated.
To locate the muscle, have the patient
clench.
The anterior region is palpated above the
zygomatic arch and anterior to the TMJ.
The middle region is palpated directly
above the TMJ and superior to the
zygomatic arch.
The posterior region is palpated above
and behind the ear.
17

18. Greek word "maseter-a chewer
MASSETER2,3,4,5
It is one of the most powerful
muscles involved in the power
stroke closure of the mandible
This is a quadrilateral muscle,
partly tendinous, partly fleshy
which covers the lateral part of
ramus of mandible.
It consists of 3 layers which blend
anteriorly.
Multiple arrangement of fibers
Superficial
Middle
Deep
18

19. 19
ORIGIN:
 SUPERFICIAL LAYER (LARGEST)
Maxillary process of zygomatic bone
Anterior 2/3rd of inferior border of zygomatic arch
 MIDDLE LAYER:
Medial aspect of anterior 2/3rd of zygomatic arch
Lower border of posterior third of zygomatic arch
 DEEP LAYER:
Deep surface of zygomatic arch

20. Insertion
SUPERFICIAL LAYER (LARGEST)
• Angle of mandible
• Lower posterior half of lateral
surface of mandibular ramus
MIDDLE LAYER:
• Middle part of the ramus of
mandible
DEEP LAYER:
• Upper part of mandibular ramus
• Coronoid process
20

21. 21
NERVE SUPPLY:
Supplied by masseteric nerve a branch of anterior
division of mandibular nerve
BLOOD SUPPLY:
Supplied by masseteric artery branch of maxillary
artery
Venous drainage through masseteric vein

22. Relations:
22
Superficial relations:
Skin, platysma, risorious, Zygomaticus major,
parotid gland and
duct, branches of facial nerve and Transverse
facial branches of superficial
temporal vessels.
Deep: Temporalis,Ramus of mandible
Anteriorly: separated from buccinator and
buccal branch of mandibular nerve by buccal
pad of fat and crossed by facial vein
Posteriorly: overlapped by the Parotid gland

23. 23
Function
Elevation of mandible
Helps in chewing
Protrudes the mandible

24. Palpation5
The patient is asked to clench their teeth and, using both hands, the practitioner palpates the masseter muscles
on both sides extra orally, making sure that the patient continues to clench during the procedure.
Palpate the origin of the masseter bilaterally along the zygomatic arch and continue to palpate down the body of
the mandible where the masseter is attached.
24
Anterior Superior PositionPosterior Inferior Position

25. 25
Lateral Pterygoid2,3,4,5
 Also called as external pterygoid muscle.
 It is the muscle of mastication that occupy
primarily a horizontal position.
 It is a thick, short, conical and triangular muscle
with two
heads:
Superior head
Inferior head

26. ORIGIN:
Superior head: Infratemporal surface
& infratemporal crest of the greater
wing of the sphenoid bone.
Inferior head: Lateral surface of the
lateral pterygoid plate.
26

27. INSERTION:
Fibers run backwards and laterally and converge into the pterygoid
fovea on anterior surface of neck of mandible
Into anterior margin of articular disc and capsule of TMJ
27

28. 28
NERVE SUPPLY
Mandibular nerve via lateral pterygoid nerve from anterior trunk
BLOOD SUPPLY:
Pterygoid branch of Maxillary artery

29. 29
RELATIONS
Superficial surface
Mandibular ramus
Masseter
Maxillary artery
Superficial head of medial pterygoid
Tendon of temporalis
Deep surface:
Deep head of medial pterygoid
Sphenomandibular ligarment
Middle meningeal artery
Mandibular nerve
Upper border:
Temporal and massetric branches of
mandibular nerve
Lower border:
Lingual nerve
Inferior alveolar nerve

30. 30
INFERIOR LATERAL PTERYGOID
Functions
When the right and left inferior lateral pterygoids contracts simultaneously, the
condyles are pulled down the articular eminences and the mandible is protruded.
Unilateral contraction creates a mediotrusive movement of that condyle and causes a
lateral movement of the mandible to the opposite side.
When this muscle functions with the mandibular depressors, the mandible is lowered
and the condyles glide forward and downward on the articular eminences.

31. 31
SUPERIOR LATERAL PTERYGOID
Inferior lateral pterygoid is active during opening, the superior remains inactive,
becoming active only in conjunction with the elevator muscles.
The superior lateral pterygoid is especially active during the power stroke and when the
teeth are held together.
The power stroke refers to movements that involve closure of the mandible against
resistance, such as in chewing or clenching the teeth together

32. 32
Palpation5
Placing the forefinger, or the little finger, over the buccal area of the maxillary third molar
region and exerting pressure in a posterior, superior, and medial direction behind the
maxillary tuberosity.

33. It is also called as the internal pterygoid muscle.
MEDIALPTERYGOID2,3,4,5
It is
rhomboidal
and runs
practically
in the same
direction of
the inner
surface of
the
mandible
33

34. It consist of two heads which differ in origin:
• Superficial
• Deep
34

35. 35
ORIGIN:
Superficial head from maxillary tuberosity
Deep head from medial surface of lateral
pterygoid plate and part of palatine bone
INSERTION
Fibers run backwards, downwards and
Laterally into the roughened area of
medial
surface of the angle mandible

36. 36
NERVE SUPPLY:
Branch of the main trunk of mandibular
nerve
BLOOD SUPPLY:
Pterygoid branch of 2nd part of maxillary artery

37. Relations
37
• Superficial /lateral:
Mandibular ramus
Sphenomandibular ligament
Maxillary artery
Inferior alveolar nerve and
vessels
Lingual nerve
• Deep/medial surface:
Tensor veli palatini
Styloglossus
Stylopharyngeous
Areolar tissue

38. 38

39. 39
Function
It helps to elevate the mandible and closes the jaws.
Acting together, they help to protrude the mandible.
Acting alone, it protrudes the side of the jaw.
Acting alternately, they produce a grinding motion

40. Palpation5
•It can be palpated by placing the finger on the lateral aspect of
the pharyngeal wall of the throat, this palpation is difficult
and sometimes uncomfortable for the patient.
•Functional manipulation is done when the muscle becomes
fatigued and symptomatic.
•The muscle contracts as the teeth are coming in contact.
•Also stretches when the mouth is open wide.
40

41. 41

42. 42
DIGASTRIC2,3,4

43. 43
Formed by 2 belly like masses of muscle tissue
joined by an intermediate tendon.
ORIGIN:
Anterior belly from diagastric fossa of mandible,
lateral to mental symphysis.
Posterior belly from mastoid notch of temporal
bone.
INSERTION:
Both meet at the intermediate tendon and held
by the fibrous pulley to the hyoid bone.

44. 44
NERVE SUPPLY:
Anterior belly by nerve to Mylohyoid
Posterior belly by -facial nerve
FUNCTION:
Depression of jaw, both sides contract simultaneously
Provide antagonism to elevation of mandible
Elevation of hyoid during swallowing

45. 45
Mylohyoid Muscle2,3,4

46. 46
ORIGIN:
Mylohyoid line of mandible.
INSERTION:
Middle and anterior fibers into median raphae.
Posterior fibers body of hyoid bone.

47. 47
• NERVE SUPPLY:
• Nerve to Mylohyoid
• FUNCTION:
• Helps in depression of mandible, elevation of hyoid bone
• It elevates the floor of mouth to help in deglutition.

48. 48
GENIOHYOID MUSCLE2,3,4

49. 49
ORIGIN:
Inferior mental spine (genial tubercle)
INSERTION:
Fibers run backwards, downwards to be
inserted into the
anterior surface of the body of hyoid bone.

50. 50
NERVE SUPPLY:
1st Cranial nerve, the fibers pass
through hypoglossal nerve.
FUNCTION:
Carry hyoid bone and the tongue
upward
during deglutition.

51. MANDIBULAR MOVEMENTS AND ROLE PLAYED BY MUSCLES:
53
1. ELEVATION:
Prime Movers: (a) Masseter
(b) Medial Pterygoid
(c) Temporalis
Antagonist: (a) Superior Lateral Pterygoid
2. DEPRESSION:
Prime movers: (a) Inferior lateral
pterygoid
(b) Digastric
Antagonist: (a) Elevator group muscles
3. PROTRUSION:
Prime Movers: (a) Inferior Lateral Pterygoid
(b) Masseter
(c) Medial Pterygoid
Antagonist: (a) Digastric
(b) Posterior Temporal

52. 54
4. RETRUSION:
Prime movers: (a) Posterior & Middle Temporal
(b) Digastric
Antagonist: (a) Inferior Lateral Pterygoid
5. LATERAL:
Prime movers: (a) Working side of temporal muscle
Antagonist: (a) Non working side of Pterygoid muscle

53. Prosthodontic application in Complete
denture construction6,7,8
55

54. Temporalis Muscle6,7
56
• Contraction of posterior fibres retrude the mandible in centric
relation or hold it in its most posterior position during
terminal hinge axis.
• Therefore the action of this muscle is sometimes used as a
test to determine whether the patient is closing in centric
relation.
• The temporal muscle doesn't participate in biting force when
mandible is in protrusion.
• When the mandible is in protrusion, no bulging can be felt
with the fingers in the side of the temples.

55. 57
EFFECT OF MASSETER MUSCLE ON THE DISTOBUCCAL BORDER7,8,9,10,11
:
A. Moderate activity will create a straight line
B. An active muscle will create a concavity.
C. An inactive muscle will create a convexity
• We ask the patient to open mouth wide and
then close against the resting force of our finger.
• Opening wide activates the muscles of
pterygomandibular raphe by stretching, which
thereby defines the most distal
extension
• Asking the patient to close against the finger on
tray handle causes masseter muscle to contract
& push against the medially situated
buccinator.

56. On Denture Border12
 An active masseter muscle will create a
concavity in the outline of the
distobuccal border and a less active
muscle may result in a 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
58

57. Mylohyoid Muscle10,11
60
• When the Mylohyoid muscle is in a tense state, it is pulled away from
mandible, therefore the lingual flange cannot impinge on the denture without
the denture being displaced during swallowing and raising tongue.
• When the mylohyoid muscle is relaxed, it falls down the lingual surface of
mandible and even under the mylohyoid ridge.
• If the lingual flange of denture extends into the undercut, it will bind the
muscle so that the muscle will be restricted in movement; otherwise, the
muscle will displacement of the denture when contracted.

58. RECORDING OF MYLOHYOID AREA ON DENTURE BORDERS8,9
61
We ask the patient to place the tip of his tongue into the
upper and lower vestibules on the right and left side.
The area to be molded is reheated and the 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 the mylohyoid muscle.

59. 62

60. 63

61. 64
1. The glossary of prosthodontic terms. J Prosthet Dent. 2005;94(1):10-92.
2. Gray’s H, William PL.Gray’s anatomy: The anatomical basis of clinical practice.34thed.Elsevier;p874-878.
3. Netter’s Head and neck anatomy for dentistry.2nd ed. Elsevier sundars; p223-35.
4. Williams PL. Gray’s anatomy in Skeletal System. 38th ed. Churchill Livingstone;1999.p 578-582.
5. Okeson JP. Management of temporo-mandibular disorder and occlusion. 6th ed. Mosby .p3-105 .
6. Boucher's, Prosthodontic Treatment For Edentuluos patients, 9th ed.

62. 65
7. Levin B. impressions for complete dentures. Chicago: Quintessence publishing co; 1984
8. Regional and Applied anatomy Essentials of Complete Denture, 2nd ed Sheldon Winkler
9. Rahn AO, Heartwell CM. Textbook of complete dentures. 5th ed. Canada: Elsevier; 2002
10. Winkler S. Essentials of complete denture prosthodontics. New Delhi: AITBS publishers and
distributors;2004
11. Zarb AG and Bolender LC. Prosthodontic treatment for edentulous patients. 12th ed. New Delhi, India;
2005
12. Principals and practising of complete dentures. Japan: Quintessence publishing co.

63. Thank You!
66