1. 1
DR. CHARANJEET SINGH
ASSOCIATE PROFESSOR
DEPT. OF PEDODONTICS AND PREVENTIVE
DENTISTRY
RAMA DENTAL COLLEGE AND HOSPITAL
RAMA UNIVERSITY
2. Mastication is defined as the process of chewing food in
preparation for swallowing and digestion. Four pairs of
muscles in the mandible make chewing movements
possible.
These muscles along with accessory ones together are
termed as ‘MUSCLES OF MASTICATION’.
2
4. These muscles can be divided into:
BASIC MUSCLES:
-MASSETER
-TEMPORALIS
-MEDIAL PTERYGOID
-LATERAL PTERYGOID
ACCESSORY MUSCLES:
-BUCCINATOR
-DIGASTRIC MUSCLE (ANTERIOR BELLY)
-MYLOHYOID
-GENIOHYOID
-ORBICULARIS ORIS
4
5. The basic muscles of mastication develop from the
mesenchyme of the first branchial arch.
So they receive all their innervations from the mandibular
branch of the trigeminal nerve, all from the anterior
division except the medial pterygoid which gets its nerve
supply from the main trunk.
Also they originate from the same origin from temporal
and infra-temporal fossa of the skull and are inserted in the
mandible.
5
6. Movements that the mandible can undergo are:
1. Depression: as in opening the mouth.
2. Elevation: as in closing the mouth.
3. Protraction: horizontal movement of the mandible anteriorly.
4. Retraction: horizontal movement of the mandible posteriorly.
5. Rotation: the anterior tip of the mandible is “slewed” from
side to side.
6
7. These movements of mandible are performed by various
muscles involved in it. So, functionally, the muscles of
mastication are classified as:
Jaw elevators:
Masseter
Temporalis
Medial pterygoid
Upper head of lateral pterygoid
Jaw depressors:
Lower head of lateral pterygoid
Anterior digastric
Geniohyoid
Mylohyoid
7
8. It is the largest among all the mastication muscles and
is a fan shape muscle.
Origin: from the inferior temporal line , floor of the
temporal fossa and from the overlaying temporal
fascia.
Insertion: anterior and medial tip of the coroniod
process.
It has been divided into 2 heads:
Deep head (anterior, middle and posterior fibers)
Superficial head (much smaller)
8
10. Action:
Elevation (anterior
fibers)
Retraction (posterior
fibers)
Nerve supply:
Anterior division of the
mandibular nerve
(by 2 deep temporal
nerves)
10
11. Its action is done by;
The anterior fibers during function act vertically and
elevate the mandible.
The posterior fibers diverge and become horizontal
and retract the mandible.
Blood supply; from the maxillary artery (one of 2
termination of external carotid artery).
11
12. It consist of 2 overlapping heads:
The origin of the whole muscle is mainly from the
zygomatic process, in which:
-The superficial head arises from the lower border of
the zygomatic arch .
-The deep head arises from the inner surface of the
zygomatic arch .
12
14. Insertion of both the heads is into the outer surface of
the ramus of the mandible:
The superficial head passes downwards and backwards
to insert into the lower half of the lateral surface of the
ramus.
While in the deep head, the fibers is more vertically
oriented and inserted into the upper half of the lateral
surface of the ramus.
14
15. Action of masseter is mainly to elevate the mandible
(antigravity action) and also helps in protrusive
movement.
It is the main muscle involved in the elevation of the
mandible
Nerve supply: by the mandibular branch of the
trigeminal nerve, from the anterior division(massetric
nerve).
15
16. Blood supply is from the maxillary artery which is a
terminal branch from external carotid artery.
One of the interesting property of this muscle is that,
internally, the muscle has many tendinous septa that
greatly increase the area for muscle attachment and so
increase its power.
16
17. It is also called as the Pterygoideus internus (Internal
pterygoid muscle).
It consist of 2 heads which differ in origin:
Origin:
The deep head originates from the medial surface of lateral
pterygoid plate of the sphenoid bone.
While the superficial head originates from the maxillary
tuberosity.
17
19. The muscle inserts into the inner surface of the
angle of the mandible.
Nerve supply of the muscle comes from the main
trunk of the mandibular nerve.
Blood supply is chiefly from the maxillary artery.
19
20. Action:
1. Elevate the mandible .
2. Protrusion of the mandible (lateral & medial
pterygoid on one side protrude the mandible to the
opposite side).
3. Side to side movement (these lateral movements are
achieved by lateral & medial pterygoid on both sides
acting together to produce side to side movements).
20
21. Also called as the Pterygoideus externus (External
pterygoid muscle).
It is a short conical muscle, having 2 heads:
upper and lower.
Upper head:
Origin: infra-temporal surface & crest of the greater
wing of sphenoid
21
22. Insertion: enters the TMJ & inserted into:
a) Pterygoid fovea of the neck of the mandible
b) Articular disc
c) Capsule of TMJ (anterior aspect)
22
23. Lower head:
Origin: Lateral surface of the lateral pterygoid plate
Insertion: its insertion is same as that of the upper
head, it enters the TMJ & gets inserted into:
a) Pterygoid fovea of the neck of the mandible
b) Articular disc
c) Capsule of TMJ (anterior aspect)
23
24. The insertion of the lateral pterygoid in the articular
disc occurs in the medial aspect of the anterior border
of the disc and thus it plays a role in the T.M.J. diseases
especially internal derangement.
Some of the T.M.J. diseases have been due to an
attributed variation of the function and attachment of
the superior head as an etiological factor in T.M.J.
diseases.
Nerve supply is from the anterior division of the
mandibular branch of trigeminal nerve(nerve to
lateral pterygoid).
24
25. Blood supply of lateral pterygoid muscle is from
maxillary artery .
Actions of lateral pterygoid:
1. Depression of the mandible .
2. Side to side movement (lateral movement) .
3. Protrusion of the mandible.
If the Pterygoid muscles of one side act, the other side
of the mandible is drawn forward while the same
condyle remains comparatively fixed.
25
26. Muscle Origin Insertion Description
Masseter Zygomatic arch External surface of
Mandible
Thick muscle.
Closure of jaw.
Temporali
s
Temporal bone Coronoid Process at
the Anterior Border of
Ramus
Fan shaped.
Closure of jaw.
Medial
Pterygoid
Sphenoid,
Palatine and
Maxillary bone
Medial surface of
Ramus
Parellels Masseter.
Closure of jaw.
Lateral
Pterygoid
Sphenoid bone Anterior surface of
Condyle
Opens jaw.
Protrudes Mandible.
Side to side grinding
movement of mandible.
26
27. 1. BUCCINATOR:
It is an accessory muscle of mastication, occupying
the gap between mandible and maxilla forming
important part of the cheek.
Its origin is from buccal plate of bone of the
sockets of the upper and lower three molars and
pterygomandibular ligament.
27
29. Course and insertion ;
Upper fibers gets inserted into upper lip,
Lower fibers gets inserted into lower lip,
Middle fibers decussate at the angle of the mouth, the
upper fibers pass to lower lip while the lower fibers
pass to the upper lip .
Nerve supply is from buccal branch of facial nerve.
Blood supply is from facial artery.
The main action of buccinator is to prevent the
accumulation of food in the vestibule of mouth.
29
30. 2. ANTERIOR BELLY OF DIGASTRIC:
Origin; it arises from the digastric fossa on the lower
border of mandible on both sides of symphysis menti.
Insertion; into the intermediate tendon which is connected
to the hyoid bone by a fibrous loop.
Nerve supply; is through anterior division of mandibular
branch of trigeminal nerve.
Action; its main action is to depress the mandible .
30
32. 3. MYLOHYOID MUSCLE:
It form the floor of the mouth.
Origin is from mylohyoid line on the internal
aspect of mandible.
Insertion; The fibers slops downwards and
forwards to inter-digitate with the fibers of the
other side to form the median raphe.
This median raphe insert in the chin from above
and the hyoid bone from below.
32
33. Action: Elevates hyoid bone,
supports and raises floor of
mouth which aids in early
stage of swallowing, depress
the mandible.
Nerve supply; by nerve to
mylohyoid: which is a branch
of Inferior alveolar branch of
mandibular nerve, which
originates just before it enters
inferior alveolar canal.
MYLOHYOID MUSCLE
33
34. Blood supply; by Facial artery and Lingual artery.
This muscle provides a separation between the
submandibular and sublingual salivary glands.
34
35. 4. GENIOHYOID:
Origin; from inferior genial tubercle (in the midline of
inner surface of mandible).
Insertion; is into the hyoid bone.
Action; depresses the mandible.
Blood supply; is through lingual artery.
Nerve supply; is by hypolossal nerve.
35
37. 5. ORBICULARIS ORIS:
It has two parts: intrinsic and extrinsic part.
Intrinsic part is a very thin sheet and originates from
superior and inferior incisivus. It inserts into the angle of
mouth.
The extrinsic part is actually formed by elevator and
depressor muscles of the lips and their angles, and inserts
into the angle of the mouth.
The orbicularis oris functions to close and shut the mouth
and formes the most versatile types of grimaces.
37
39. 1. EXAMINATION OF MASSETER:
The patient is asked to clench their teeth and, using
both hands, the practitioner palpates the masseter
muscles on both sides, making sure that the patient
continues to clench during the procedure.
Palpate the origin of the masseter along the zygomatic
arch and continue to palpate down the body of the
mandible where the masseter is attached.
39
40. The masseter is most often tender along the central
fibers at its insertion.
Masseter hypertonicity is found in patients who have
premature contacts on the nonworking side.
Parafunctions such as bruxism and clenching also give
rise to masseter pain that is frequently associated with
pain in the temporalis muscle.
2. TEMPORALIS:
The temporalis is palpated in much the same manner
to detect lateral interferences.
40
41. 3. LATERAL PTERYGOID:
In patients with nonworking side interferences, the
lateral pterygoid muscle on the opposite of the
interference is sometimes painful.
In addition, this muscle will be painful whenever there
is a centric slide with an anterior component and the
patient is bruxing or clenching in this anterior
position.
The lateral pterygoid, despite its commonality in
displaying a spasm, cannot be palpated intraorally.
41
42. 4. MEDIAL PTERYGOID:
The medial pterygoid muscle is not usually involved in
gnathic dysfunctions but when they are hypertonic,
the patient is usually conscious of a feeling of fullness
in the throat and an occasionally pain on swallowing.
42
43. Two separate acts are recognized in the chewing
process.
First is a combination of prehension and incision in
which the food is secured by the lips and bitten by the
front teeth.
The second is mastication, the major activity during
which the food is mashed between the back teeth.
43
44. The total chewing cycle occurs through three phases:
1. The opening stroke during which the mandible is
lowered.
2. The beginning closing stroke during which the
mandible is rapidly raised until the entrapped food
is felt and
3. The power stroke in which the food is compressed,
punctured, crushed and sheared.
44
46. The chewing process generally acts as a 2nd order lever
system resulting in compression at TMJ.
The turning moment generated along mandibular
body and ramus creates a sheer at TMJ.
46
47. Chewing in humans is actually asymmetrical and
unilateral.
At the working side:
• It possesses the greatest adductor force, but articular
emminence is less substantially loaded.
At the balancing side:
• It possesses the less adductor force and the articular
emminence is substantially loaded.
• At the initial action, contraction of inferior head of
lateral pterygoid muscle occurs to initiate mandibular
deviation to working side.
47
48. Some of the common masticatory muscle disorders
involve:
Congenital hyperplasia/ hypoplasia
Hypermobility/ hypomobility of the muscle
Muscle pains
MPDS
Myositis ossificans etc.
48
49. It occurs very rarely, and is more common in masseter
and orbicularis oris.
Its oral symptoms include enlargement or decreased
size of the affected muscle, which may show an
asymmetric facial pattern and stiffness in the
temporo-mandibular joint.
It may or may not be associated with hypermobility/
hypomobility of the muscles.
49
50. This disorder involves extreme or diminished activity
of the masticatory muscles.
Its etiology includes various factors such as:
Decreased/ increased threshold potential of neural
activity.
Parkinsonism
Facial paralysis
Nerve decompression
Secondary involvement of systemic diseases.
50
51. It usually occurs as a result of reflex protective mechanism
and myofacial triggers.
It is usually felt as a non-pulsatile variable aching
sensation, with a boring quality. It may also present with
tightness, weakness, swelling or tenderness.
It includes 3 types:
1. local muscle soreness:
it is a primary hyperalgesia with lowered pain threshold
due to local factors such as stress, injury, infection etc.
51
52. This may be due to:
1. distortion of blood vessels within the muscle or
2. forceful or sustained contraction repeatedly.
2. Muscle splinting pain:
it is defined as rigidity of the muscle occuring as a means of
avoiding pain caused by movement of the part.
it is a reflex protective mechanism.
Splinting of masticatory muscle may occur as a protective
mechanism in conditions such as toothache, overstressed
teeth, effect of local anaesthetics, trauma etc.
52
53. 3. Non-spastic myofacial pains:
There is no spasm and pain is the only complaint and
this is generally referred to structures outside the
muscle proper.
it may be due to atrophied muscle mass because of
inactivity, illness or nutritional deficiency.
53
54. The masseter muscle pain refers to the ear, TMJ and
the mandibular teeth.
The temporalis refers to the temple, orbit and
maxillary teeth.
The medial pterygoid refers to the infra-auricular and
post-mandibular area.
The lateral pterygoid always refers its pain to the TMJ.
54
55. Muscular Disorders (Myofascial Pain Disorders) are
the most common cause of TMJ pain associated with
masticatory muscles.
Common etiologies include:
1. Many patient with “high stress level”
2. Poor habits including gum chewing, bruxism, hard
candy chewing
3. Poor dentition
55
56. Its treatment includes 4 phases of therapy which
includes muscle exercises and drugs involving NSAIDs
and muscle relaxants.
A bite appliance is also worn by the patient in the
furthur stages to ‘splint’ the muscle movement.
56
57. It is a condition wherein fibrous tissue and
heterotropic bone forms within the interstitial tissue
of muscle, as well as in associated tendons or
ligaments.
It is of two types: localized and generalized.
Localized myositis ossificans:
It is caused by trauma or heavy muscular strains or by
metaplasia of pluripotential intermuscular cnnective
tissue.
57
58. The affected site remains swollen and tender, and the
overlying skin may be red and inflamed.
There may present a difficulty in the opening of the
mouth.
management is done by giving sufficient rest to the
muscle and excision of the involved muscle after the
process has stopped.
58
59. Generalized myositis ossificans:
In this, formation of bone in tendons and fascia occurs
alongwith subsequent replacement of muscle mass by
the bony tissue.
The masseter muscle is the most frequently involved.
It usually occurs in children less than 6 years of age.
It shows an evidence of dense osseous structures in the
greater part or whole of the muscle.
59
60. There is a gradual increase in stiffness and limitation
in the motion of masticatory muscles. Ultimately, the
entire muscle may get transformed into bone resulting
in no movement.
Management: there is no specific treatment. The
muscles involved are to be excised.
60
61. The masticatory muscles include a vital part of the
orofacial structure and are important both
functionally and structurally.
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.
61
62. Human anatomy by B.D. Chaurasia, 3rd ed.
Textbook of oral pathology by Shafers, 4th ed.
Textbook of oral medicine, by Avindrao ghom, 1st ed.
Burket’s oral medicine: diagnosis and treatment, 10th
ed.
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