Muscles of Mastication and its implication in Prosthodontics.

1. GOOD
MORNING

2. Muscles of
Mastication
Dr Jamshid Usman
PG Prosthodontics
Royal Dental College
Chalissery,Palakkad

3. • Introduction
• Types
• Palpation
• Clinical significance
• Literature review
• Summary
• Conclusion

4. DEFNITIONS
GPT 8
• Muscle:
• an organ that by contraction producesmovements of an
animal; a tissue composed of contractile cells or fibersthat
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.
•

5. • Mastication- four muscles of
mastication (or musculi masticatorii) -
adduction and lateral motion of the jaw.
• Muscles associated hyoid also responsible for
opening the jaw

6. Primary Muscles Of Mastication
• Temporalis
• Masseter
• Lateral Pterigoid
• Medial pterigoid

7. Accessory Muscles Of Mastication
• Suprahyoid • Infrahyoid muscles
• Digastric • Sternohyoid
• Stylohyoid • Thyrohyoid
• Mylohyoid • Omohyoid
• Geniohyoid

10. • Functionally, the muscles of mastication are classified as
• Jaw elevators
• Masseter
• Temporalis
• Medial pterygoid
• Jaw depressors
• :Lateral pterygoid
• Anterior digastric
• Geniohyoid
• Mylohyoid
•

11. Functionally, the muscles
of mastication are classified as
Jaw elevators Jaw depressors
• Masseter • Lateral pterygoid
• Temporalis • Anterior digastric
• Medial pterygoid • Geniohyoid
• M ylohyoid

12. Temporalis
Muscle

13. Temporalis Muscle
• elevation of the mandible.
• Large fan shaped.
• Origin and Insertion:
• From the Parietal bone of the skull and is
inserted on the coronoid process of the
mandible.

23. • Arterial supply:
• The Deep Temporal
• Nerve Supply:
• Deep temporal n

24. Functions:
• Elevation of the mandible
• Retraction of the mandible.
• Crushing of food between the molars.
• Posterior fibers draw the
mandible backwards after it has been
protruded.
• It is also a contribute side to side grinding
movement

25. Temporalis
Muscle

26. Palpation
• To locate the muscle ,have the patient clench.
• Apply two pounds of pressure

27. • 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
•

29. Clinical Importance of Temporalis
Muscle:
• Sudden contraction of temporalis muscle will
result in coronoid fracture, which is rare.
• The patient is instructed to close and move his
mandible from side to side and then
immediately asked to open wide.
• The side to side motion records the activity
of the coronoid process in a closed
position whereas opening causes the coronoid
to sweep past the denture periphery

30. LITERATURE REVIEW
• Antje Tallgren, Dr.Odont, et al. studied jaw muscle activity
incomplete denture wearers :A longitudinal
ectromyographic study
. J ProsthetDent August 1980 Vol44 (2) Pg 123-32
• Tallgren studied the patterns of activity of some
masticatory muscles in partially edentulous subjects & fully
edentulous.
• The study indicated that loss of posterior teeth causes
imbalance in muscular patterns concerning masseter,
anterior temporal muscle and digastrics muscle
and wearing immediate complete upper and
lower dentures revealed inactivity of the jaw closing
muscles during the biting actions.

31. • Bengt ,Ingervall, Dr Odontet al. did an
electromyographic study of masticatory and lip
function in patient with complete
dentures (J ProsthetDent March 1980 Vol43(3) pg 266-
71
• T wo groups of patients having new and old dentures
were studied.
• The results showed muscle activity during maximal
biting was markedly lower in patients with new
denture than in patients using the old ones
• No difference in chewing activity was seen with old and
new dentures

32. Masseter muscle

33. Masseter muscle
• The second most efficient masticatory muscle.

34. • Multipennate arrangement of fibers
• Superficial
• Middle
• Deep

42. • The main function of masseter muscle is
• Elevation of the mandible
• lateral movements of the mandible for
efficient chewing and grinding of the food
• unilateral chewing
• Retraction of the mandible

43. • Blood supply:
• Masseteric artery .
•
• Nerve supply:
• Massetric nerve.

44. Palpation
• The patient is asked to clench their teeth and,
using both hands, the practitioner palpates
the masseter muscles on both sides
extraorally, making sure that the patient
continues to clenchduring 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

45. • Palpate multiple areas of
masseter muscle

47. Clinical Importance of Masseter
Muscle of Mastication:
• On Denture border
• 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

48. Activation of massetric notch and
distal areas
• Instruct the patient to open wide and then to
close against the resing force of your finger

49. • Opening wide activates the muscles
of pterygomandibularrapheby stretching,
whichthereby defines the most distal extension
• Instructing the patient to close against your
fingers on the tray handle causes masseter
muscle to contract and push against the medially
situated buccinator muscle
• .
•

50. LITERATURE REVIEW
• According to Garrett NR, Kaurich M et. al a cross-
sectional study on Masseter muscle activity in
denture wearers with superior and poor
masticatory performance was done.
JProsthetDent 1995 Dec vol74 (6) 628-36
• The results indicated that application of more
equivalent force by the right and left masseter
muscles during unilateral chewing is consistent
with improved chewing ability indenture wearers

51. Lateral Pterygoid
Muscle:

52. Lateral Pterygoid Muscle:
• It is divided into 2 heads
• Origin:
• Upper head – infratemporal surface & crest of
greater wing of sphenoid bone
• Lower head – lateral pterygoid plate
• Insertion :
• Pterygoid fovea on the anterior surface of neck of
mandible
• Anterior margin of articular disc & capsule of TMJ

60. • Nerve Supply:
• Pterygoid branch of Trigeminal nerve.
• Arterial supply:
• Pterygoid branch of Maxillary artery.
• Functions:
• Depresses the mandible
• Protrudes it forward for opening of the jaw
• Side Movements

61. PALPATION OF THE LATERAL
PTERYGOID

62. • 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

63. Clinical Importance of Lateral
Pterygoid Muscle:
• Most commonly involved muscle in MPDS
• 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 and loss of full lateral deviation
•

64. LITERATURE REVIEW
• R. Johnstoneand Mc cormick templetonstudied
the feasibility of palpating the lateral pterygoid
muscle ( JProsthetDent Vol44 (3)
Sept 1980 Pg 318-23) and came to a conclusion
through dissections and lateral head radiographs
that it is not possible to palpate the lateral
pterygoidmuscle directly by conventional clinical
techniques without applying pressure through
the overlying superficial head of medial pterygoid
muscle

65. Medial Pterygoid muscle

66. Medial Pterygoid muscle:
• It is a thick muscle of mastication.
• Origin and Insertion :
• It Arises lateral pterygoid plate, and from the
maxillary tuberosity.
• Insertion is seen on the Medial angle of the
Mandible

70. • Arterial supply:
• Pterygoid branch of Maxillary artery.
• Nerve Supply:
• Mandibular nerve through the medial
pterygoid.

71. • Functions:
• Elevates the mandible,
• Closes the jaw,
• Helps in side to side movement.

72. Palpation of medial pterigoid

73. • gently palpate them on the medial aspect of the jaw,
• simultaneously from both inside and outside the mouth

74. Clinical Importance of Medial
Pterygoid Muscle:
• Medial Pterygoid muscle can be palpated only
intraorally
• Most commonly involved in MPDS
• Trismus following inferior alveolar nerve block
is mostly due to involvement of medial
pterygoid muscle

75. LITERATURE REVIEW
• Wodd WW studied the medial pterygoid
muscle activity during chewing and clenching.
J ProsthetDent.1986 May;Vol 55 ( 5):615-21
• Patterns of medial pterygoidmuscle activity
were consistentfor ipsilateralchewing
• Intercuspal clenching initiated less activity
when force was directed posteriorly and more
activity when directed anteriorly

76. Accessory muscles

77. Accessory Muscles Of Mastication
• Suprahyoid • Infrahyoid muscles
• Digastric • Sternohyoid
• Stylohyoid • Thyrohyoid
• Mylohyoid • Omohyoid
• Geniohyoid

79. Digastric
• Origin anterior belly - digastric fossa
(mandible); posterior belly -mastoid
process of temporal bone
• Insertion Intermediate tendon (hyoid bone)

89. • Artery
• anterior belly - Submental branch of facial
artery;
• Posterior belly -occipital artery
• Nerve
• anterior belly - mandibular division (V3) of
the trigeminal(CN V) via the mylohyoid nerve;
posterior belly - facial nerve (CN VII)

90. Stylohyoid Muscle

91. Origin and insertion

96. MYLOHYOID MUSCLE

102. • Artery
• Mylohyoid branch of inferior alveolar artery
• Nerve
• mylohyoid nerv e, from inferior alveolar branch
of mandibular nerve
• Actions
• Raises oral cavity
floor, elevateshyoid, elevates tongue, depresses
mandible

103. GENIOHYOID MUSCLE

107. • Artery : Facial artery
• Nerve : C1 via hypoglossal nerve
• Action: carry hyoid bone and the tongue
upward during deglutition

108. STERNOHYOID MUSCLE

111. • Artery : Superior Thyroid Artery
• Nerve : C1-C3 by a branch of Ansa cervicalis
• Action : Depress Hyoid bone

112. THTROHYOID MUSCLE

115. • Artery : Superior Thyroid Artery
• Nerve : C1 via of Ansa cervicalis
• Action : Elevates thyroid Depress Hyoid bone

116. OMOHYOID MUSCLE

119. • Artery
• Infrahyoid artery from the superior
thyroid artery, suprahyoid branch of the
lingual artery.
• Nerve
• Ansa cervicalis (C1-C3)
• Actions
• Depresses the larynx and hyoid bone. Also carries
hyoid bone backward and to the side.

120. Features of Masticatory muscle
• Have shorter contraction times than most other body muscles
• Incorporate more of muscle spindles to monitor their activity
• Do not have golgi tendon organs to monitor tension
• Elevators predominantly white fibrous which perform fast twitching
• Do not get fatigued 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

122. SUMMARY

123. Primary Muscles Of Mastication
• Temporalis
• Masseter
• Lateral Pterigoid
• Medial pterigoid

124. Accessory Muscles Of Mastication
• Suprahyoid • Infrahyoid muscles
• Digastric • Sternohyoid
• Stylohyoid • Thyrohyoid
• Mylohyoid • Omohyoid
• Geniohyoid

125. CONCLUSION
• The masticatory muscles include a vital part of
the orofacial structure and are important both
functionally and structurally
• It can be influenced by a variety of factors
many of which are controlled by the
practicing prosthodontist

126. • During functional impression making
• Accurate recording of various clinical parameters
like vertical dimension, centric relation
• Morphology of artificial tooth
• Maintenance of arch form
• The proper management and periodical self -
examination of the muscles may provide a
greater chance of catching the disease process at
an early stage which may be useful for its better
prognosis.

127. REFERENCES
• Human anatomy A K Dutta -#rd Edition
• Grays Anaatomy
• Burkitsoral medicine diagnosis & treatment 10
th edition
• Textbook of Complete dentures by Charles
M Heartwell
• Journal Refernces

128. Thank
You