Dr P. S. Prabu MDS Malabar Dental College & Research Centre

1. Good morning
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2. MUSCLES OF
MASTICATION
Dr P. S. Prabu MDS
Malabar Dental College & Research
Centre
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4. CONTENTS:
1. Introduction
2. Definition
3. Development
4. Classification
5. Movements of mandible
6. Muscles of mastication
7. Masticatory muscle disorders
8. Conclusion
9. Reference
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5. INTRODUCTION:
 Masticatory system is a complex, highly refined, functional unit,
regulated and coordinated by a neurological control system, which
involves nerves and muscles.
 Muscles of mastication are the group of muscles that helps in
movement of the mandible as during chewing and speech. They also
play a role in the configuration of face
 Four pairs of the muscles in the mandible makes the chewing
movement possible. These muscle along with accessory ones together
are termed as “MUSCLES OF MASTICATION”.
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6. DEFINITION:
 MUSCLE: a tissue composed of contractile cells or fibers that effect
movement of an organ or part of the body.
 MASTICATORY MUSCLE: any of the muscles that elevates the mandible to
close the mouth (temporalis muscle, superficial and deep masseter muscle,
medial pterygoid muscle)
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MASTICATION: the process of chewing food for swallowing
and digestion.
MASTICATORY SYSTEM: the organs and structures primarily
functioning in mastication, these includes the teeth with their
supporting structures, craniomandibular articulations, mandible,
positioning and accessory musculature, tongue, lips, cheek, oral
mucosa, and the associated neurologic complex.

8. DEVELOPMENT:
 The basic muscles of mastication develops from the mesoderm of the first
pharyngeal arch.
 The muscular tissue develops from embryonic cells called myoblast.
 Muscular components of branchial arch form many striated muscles in the head and
neck region.
 Muscles of mastication are derived from the first branchial arch that is the
MANDIBULAR ARCH, which is innervated by the mandibular branch of
trigeminal nerve.
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Development of maxilla:
 Maxilla forms within the maxillary prominences extending ventrally from
the dorsal aspect of a much larger mandibular swelling. Ossification of
maxilla begins slightly later than in the mandible.
 The primary ossification center appears for each maxilla in the 7th week.
The secondary centers are at the zygomatic, nasopalatine and orbitonasal
areas.
 Maxilla forms within the maxillary prominences extending vertically from
the dorsal aspect of a much larger mandibular swelling.

10.  The primary ossification centre appears for each maxilla in the 7th week. The
secondary centres are at the zygomatic, nasopalatine and orbitonasal areas.
 Of lies in the angle formed by the infraorbital nerve and anterior superior alveolar
nerve, above the part of the dental lamina from which the canine tooth germ develops.
 The premaxilla begins to ossify from the two centres in the latter part of the 7th week.
 Postnatal growth of maxilla occurs by:
Apposition of the bone
surface remodelling.
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11. Development of Mandible:
 Development of mandible starts at the 2nd week of intrauterine life. 36 –
38th day, mandibular ectomesenchyme interacts with the mandibular
epithelium before primary ossification.
 First ossification centre for each half arises in the 6th week in region of
bifurcation of Inferior Alveolar Nerve into Mental, the ossification
spreads dorsally and ventrally to form ramus and body.
 Ossification stops at site where it would be lingual.
 Medially it meets its fellow counterpart, distally up to middle ear.
 Secondary accessory cartilages occurs between 10th – 14th weeks to form
head of condyle, coronoid, mental protuberances.
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12.  Coronoid cartilage fuses with expanding intramembranous ramus before birth. Condylar cartilage
appears at 10th week.
 This is primordium for future condyle. Cartilage differentiate by interstitial n appositional growth.
 By the 14th week, 1st evidence of endochondral bone formation is seen.
 Condylar cartilage is an important growth centre for ramus. Condylar growth at its peak at puberty.
 Occurs 12-14 months’ post natally,2 halves fuse into synostosis.
 Mandible appears as a single bone. Basal bone forms one unit to which alveolar, condylar, coronoid,
angular process and chin is attached.
 They grow by functional matrix theory. Teeth acts as functional matrix for the development of alveolar
bone. Temporalis influences coronoid process. Masseter and medial pterygoid at angle and lateral
pterygoid at the condyles.
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13. Post-natal growth of mandible:
 Growth of width of mandible is completed first, then growth in length and finally growth in
height.
 Growth in width is completed before adolescent growth spurts. Growth in length continues
through puberty.
 Main sites of post-natal growth in the mandible are:
- Condylar cartilage
- Posterior border of the rami
- Alveolar ridges
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14. CLASSIFICATION:
Primary muscles:
a. Temporal
b. Masseter
c. Medial pterygoid
d. Lateral pterygoid - superior & inferior
Accessory muscles:
a. Mylohyoid
b. Geniohyoid
c. Anterior belly of digastric
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Based on functional movements:
Jaw elevators Jaw depressors
- Masseter - Lateral pterygoid
- Temporalis - Anterior belly of digastric
- Medial pterygoid - Geniohyoid
- Mylohyoid

16. MANDIBULAR MOVEMENTS:
1. Depression : As in opening of mouth.
2. Elevation : As in closing of mouth.
3. Protrusion : Horizontal movement of the mandible anteriorly.
4. Retraction : Horizontal movement of mandible posteriorly.
5. Rotation : The anterior tip of the mandible is slewed from side to side.
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17. MUSCLES OF MASTICATION:
1.TEMPORALIS:
 It is the largest among all the masticatory
muscles.
 Fan shaped muscle
 Fills the temporal fossa.
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18. Origin:
 Lateral surface of the skull
Insertion:
 Coronoid process and anterior border of
ramus of mandible
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Innervations:
 Temporal nerve (branch of mandibular nerve).
Blood supply:
 Middle and Deep temporal arteries (branches of superficial temporal
& maxillary artery).
Functions:
 Elevates and retracts jaw.
 Assists in rotation.
 Active in clenching.

20. Palpation:
Patient is asked to clench the teeth
a. Anterior region is palpated above
the zygomatic arch and anterior to
the TMJ.
b. Middle region is palpated above the
TMJ and superior to zygomatic
arch.
c. Posterior region is palpated above
and behind the ear.
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Clinical significance:
 Recording coronoid process area.
 The patient is instructed to close and move his mandible from side to
side and then immediately asked to wide open.
 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.

22. 2. MASSETER
 It is quadrilateral in shape & covers the
lateral surface of ramus of mandible.
 The origin of the whole muscle is from
the zygomatic process & consists of three
layers i.e. superficial, middle and the
deep layer.
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23. Origin:
 Zygomatic arch
Insertion:
 Angle of mandible.
Innervation:
 Masseteric nerve (division of trigeminal
nerve).
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24. Blood supply:
 Masseteric artery(branch of maxillary artery)
Functions:
 Elevates and protracts jaw.
 Assist in lateral movement.
 Active in clenching.
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Palpation:
 The patient is asked to clench their teeth
and using both hands, the practitioner
palpates the masseter muscle 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.

26. 26Clinical significance:
 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 fibres in that
area are vertical and oblique.
 Effects of masseter muscle on the distobuccal border
a. Moderate activity will create a straight line.
b. An active muscle will create a concavity.
c. An inactive muscle will create a convexity.

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Activation of masseteric notch and distal areas:
 Instruct the patient to open their mouth widely and then to close against
the resting forces of your finger.

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 Opening wide activates the muscles of pterygomandibular raphe by
stretching, which thereby 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
buccinators muscle.
 Masseter hypertonicity is found in patients who have premature contacts
on the networking side.

29. 3. MEDIAL PTERYGOID:
 It is also called Pterygoideus internus or internal pterygoid muscle.
 Quadrilateral in shape. Consists of two heads: superficial & deep.
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30. Origin:
 Pterygoid fossa and medial surface of lateral
pterygoid plate.
Insertion:
 Medial surface of angle of mandible.
Innervation:
 Medial pterygoid nerve (division of trigeminal
nerve).
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31. Blood supply:
Branch of maxillary artery.
Functions:
 Elevates jaw
 Causes lateral movement and protrusion.
 The lateral and medial pterygoid on one side protrude the mandible to the
opposite side.
 Lateral and medial pterygoid on both side acting together to produce side
to side movement.
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32. 32Palpation:
 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.

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 Functional manipulation is done when the muscle becomes fatigued
and symptomatic.
 The muscle contracts as the teeth are coming in contact.
 They also stretches when the mouth is wide open.

34. 34Clinical significance:
Mandibular dysfunction:
 The medial pterygoid muscle is not usually involved in gnathic
dysfunction but when they are hypertonic, the patient is usually conscious
of a feeling of fullness in the throat and an occasional pain on swallowing.

35. LATERAL PTERYGOID
It is also known as pterygoideus externus or external pterygoid muscle
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36. 4. SUPERIOR LATERAL PTERYGOID
Origin:
 Infratemporal surface of greater wing of sphenoid.
Insertion:
 Articular capsule and disk, neck of condyle.
Innervation:
 Branch of masseteric or buccal nerve.
Blood supply:
 Branch of maxillary artery.
Functions:
 Positions disk in closing
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37. 5. INFERIOR LATERAL PTERYGOID:
Origin:
 Lateral surface of lateral pterygoid plate.
Insertion:
 Neck of condyle.
Innervation:
 Branch of masseteric nerve or buccal nerve.
Blood supply:
 Branch of maxillary artery.
Function:
 Protrudes and depresses jaw
 Causes lateral movements
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38. Palpation:
 The little finger is inserted facial to the maxillary teeth and around distal to
the pterygomaxillary or hamular notch to palpate the lateral pterygoid
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39. 39Clinical significance:
 Unilateral failure of lateral pterygoid muscle to contract results in
deviation of the mandible towards the affected side on opening.
 Bilateral failure results in limited opening, loss of protrusion and loss
of full lateral deviation.
 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 TMJ diseases especially in internal derangement.

40. 5. MYLOHYOID:
Origin:
 Inner surface of mandible.
Insertion:
 Hyoid and mylohyoid raphe.
Innervation:
 Branches of mylohyoid nerve (division of trigeminal nerve).
Blood supply:
 Submental artery.
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41. Functions:
 Elevates and stabilizes hyoid bone.
Clinical significance:
On denture borders: Mylohyoid area
 Instruct the patient to place the tip of his/her tongue into the upper and
lower vestibules on the right and left sides.
 The area to be moulded is reheated and the patient is instructed to swallow
two or three times in rapid succession.
 The tongue movements raises the floor of the mouth through contraction
of the mylohyoid muscle.
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42. 6. GENIOHYOID
Origin:
 Genial tubercle.
Insertion:
 Hyoid bone.
Innervation:
 First cervical via Hypoglossal nerve
Blood supply:
 Branch of lingual artery.
Functions:
 Elevates and draws hyoid forwards.
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43. Clinical significance:
 For mandibular impressions:
 On recording labial flange and labial frenum. The lip is massaged from side
to side to mold the compound to desired functional extension. In order to
activate the mentalis muscle the patient is asked to lick his lower lip.
 For maxillary impressions in labial flange and labial frenum areas:
 Manually, mold the compound by externally moving the lip side to side,
simultaneously applying finger pressure to control the width of the border.
Lift the upper lip and vertically place the frenum into the softened
compound and mold with your fingers using side to side external motion.
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44. 7. ANTERIOR BELLY OF DIGASTRIC:
Origin:
 Tendons linked to hyoid by fascia.
Insertion:
 Digastric fossa (lower border of mandible).
Innervation:
 Branch of mylohyoid nerve (division of trigeminal).
Blood supply:
 Branch of facial artery.
Functions:
 Elevates hyoid & depresses jaw.
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45. 45Gnathology:
The study of biology of masticatory mechanisms and the kinematic recording
of the mandibular positions. (GPT 9)
Aims and objectives of Gnathology
1.Optimum oral health
2.Anatomic harmony
3.Functional harmony
4.Occlusal stability

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Gnathology deals with the whole apparatus of mastication.
 According to Stallard “it was proposed as the science that would
concentrate on the gnathic system – Gnathology- to emphasis how
important the knowledge of gnathodynamics is in caring for teeth”.
 When studies in Gnathology were instituted, it was accepted that balanced
occlusion was the answer to occlusal problems.
 Gysi suggested the research tool that McCollum used in 1920 to locate the
opening and closing axis position and to transfer a patients
maxillomandibular relations to an articulator.

47. 47 For his research McCollum fastened the snow face bow rigidity to the
lower teeth and located the axis position.
 When he had done this, he discovered other facts.
i. When the patient closed on a hard object anterior or posterior teeth, the
point of stylus did not change position.
ii. Translation on the horizontal axis made constant paths.
iii. The axis remained constant to the mandibular teeth when the jaws were in
protrusion during opening and closing of the jaw if the openings were not
excessive.
iv. The coincidence of repeated terminal hinge positions was so regular that
it indicated that the terminal hinge axis position is constant.

48. 48 In 1920’s McCollum learned how to test the accuracy of an articulator and
in 1927 he undertook to test for balanced occlusion.
 It took almost 20 years for Stuart to conclude that balanced occlusion is not
suitable for natural teeth and probably not suitable for dentures.
 Stuart designed his first articulator in 1928-29 but decided not to promote it
out of deference to McCollum.
 The jaw writings are recorded using pantograph, a mechanical device for
reproducing a map and drawing on the same or different scale.

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 The jaw writings are recorded using pantograph, a mechanical device for
reproducing a map and drawing on the same or different scale.
 The purpose of the mandibular recorder(pantograph) is to locate the centers
of mandibular movements and at the same time record the path of motion that
these centers take in relaxation to a given plane in the face.
 The axis- orbital plane is the one most often used.

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54. 54MASTICATORY MUSCLE DISORDERS :
 Functional disorders of mastication are generally known as masticatory
muscle disorders
 The major symptoms are pain and dysfunction.
PAIN:
 Pain felt in muscle is known as MYALGIA.
 Symptoms are associated with feeling of muscle fatigue and tightness.
 Severity of the pain is related to functional activity of the muscle involved.

55. 55DYSFUNCTION:
 Seen as decrease in the range of mandibular movements.
 When muscle is compromised by overuse, stretching or contraction
causes increased pain.
 Acute malocclusion is also a type of dysfunction.
 Sudden change in the resting length of muscle causes an acute
malocclusion.
 Treatment should never be directed towards correcting the occlusion
rather it should be aimed at eliminating the muscle disorder.

56. 56Masticatory muscle disorder:
i. Myospasm
ii. Myofascial pain
iii. Centrally mediated myositis
iv. Myofascial pain dysfunction syndrome
v. Trismus
vi. Bruxism

57. 57
MYOSPASM:
 Involuntary CNS induced tonic muscle contraction often associated with
local metabolic conditions within the muscle tissues.
 Usually short lived.
 When spasm occurs repeatedly, the condition is known as dystonia.
Treatment:
 Etiology of the myospam should be addressed to prevent recurrent
myospasm.
 Pain reduction by vapocoolant spray, ice or even injection of local
anaesthetic into the muscle.
 Once pain is reduced muscle conditioning exercises can be performed.

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MYOFACIAL PAIN:
 Also known as trigger point myalgia.
 Characterized by local areas of firm, hypersensitive bands of muscle tissue
known as trigger points.
 Unique feature of the trigger point is that it can produce constant deep pain.
 Most common effects is reffered pain described as tension type of headache.
 Pain increases with function.
Treatment:
 Eliminate the source of ongoing pain
 Pressure and massage.
 Injection and stretch

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CENTRALLY MEDIATED MYOSITIS:
 Also known as chronic myositis.
 Chronic, continuous muscle pain disorder originating predominantly from
CNS effects that are felt peripherally in muscle tissue.
 Characterized by muscle tightness, pain at rest, pain on palpation, structural
dysfunction.
Treatment:
 Supportive: soft diet, stabilization appliance, application of moist heat or
cold.
 Definitive: treat the underlying cause.
 Emotional stress therapy, occlusal therapy in musculoskeletal stable position.

60. 60MYOFACIAL PAIN DYSFUNCTION SYNDROME:
 Most common type of TMJ pain associated with masticatory muscles.
Etiology:
 High stress level.
 Poor habits including bruxism.
 Poor dentition.
Treatment:
 Involves 4 phases of therapy which includes muscle exercises and drugs
involving NSAIDs and muscle relaxants.
 A bite appliance is worn by the patient in the further stages to splint the
muscle movements.

61. 61TRISMUS:
 Trismus is defined as a prolonged tetanic spasm of the jaw muscle by
which the normal opening of the mouth is restricted.
 Restricted jaw movements regardless to the etiology.
Treatment:
 Removal of the etiology.
 Heat therapy.
 Warm saline rinses.
 NSAIDS.
 Passive muscle stretching exercise

62. CONCLUSION:
 The masticatory system is extremely complex, primarily made of bones, muscles,
ligaments and teeth.
 Precise movement of mandible by the musculature is required to move the teeth
effectively across each other during function.
 The knowledge of the anatomy physiology and mechanism of these ,usc;es are basic to
understand the movements.
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63. REFERENCES:
 Contemporary fixed prosthodontics - Rosenstiel
 Human anatomy by B. D. Chaurasia (3rd edition).
 Complete denture prosthodontics by John. J. Sharry.
 Syllabus of complete denture – Charles M Heartwell
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64. thankyou
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