This document provides an overview of the muscles of mastication. It begins with definitions of muscle and mastication. It then discusses the development, classification, anatomy, properties, and functions of the primary and secondary muscles of mastication. The document outlines the mandibular movements and muscle activity involved in opening, closing, retrusion, protrusion, and lateral movements. It also discusses masticatory muscle disorders including myofascial pain, myositis, myospasm, local myalgia, and myofibrotic contracture. Finally, it briefly mentions disorders of the muscles of mastication due to external factors such as trismus, bruxism, and tetanus.

1. Dr. Tanya Anand Student Id : 19MDS15 Department of Periodontology
MUSCLES OF MASTICATION

2. CONTENTS
• Definitions
• Development of muscles
• Classification of muscles
• Anatomy of skeletal muscles
• Properties of muscles
• Primary muscles of mastication
• Secondary muscles of mastication
• Mandibular movements
• Okeson’s classification of masticatory muscle disorders
• Masticatory disorders of Temporo-mandibular joint
• Disorders of masticatory muscles due to external factors
• Related articles
• References 2

3. DEFINITIONS
 MUSCLE ( Glossary Of Prosthodontic Terms , Eighth
Edition)- Journal Of Prosthetic Dentistry- 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 ( Glossary Of Prosthodontic Terms ,
Eighth Edition)- Journal Of Prosthetic Dentistry- The
process of chewing food for swallowing and digestion.
3

4. DEVELOPMENT OF MUSCLES
LATERAL VIEW OF FOUR WEEK EMBRYO SHOWING MUSCLE
DERIVED FROM BRACHIAL ARCHES 4

5. CLASSIFICATION
DEPENDING UPON STRIATIONS
DEPENDING UPON CONTROL
DEPENDING UPON SITUATION
5

6. ANATOMY OF SKELETAL MUSCLES
• Skeletal muscle consists of large number of muscle
fibres and a connective tissue framework .
• Each muscle fibre is surrounded by a delicate
connective tissue called endomysium.
• These muscle fibres are grouped into number of bundles
called fasciculi. Each fasciculi is surrounded by
stronger sheath of connective tissue called as
perimysium.
6

7. • All fasciculi collectively form the muscle belly. The
connective tissue that surrounds the entire muscle belly is
called epimysium.
• At junction of muscle with its tendon , fibres of endomysium,
perimysium and epimysium become continuous with fibres of
tendon.
• Tendons are fibrous terminal ends of the muscles made up
with collagen fibres
7

8. 8

9. PROPERTIES
1. Excitability
2. Contractility
3. Muscle tone
9

10. PRIMARY MUSCLES OF MASTICATION
The masticatory muscles are concerned with movements
of mandible at the temporo- mandibular joint.
PRINCIPAL MUSCLES
1. Temporalis
2. Masseter
3. Lateral Pterygoid
4. Medial Pterygoid
5. Spheno-mandibularis
10

11. CHARACTERISTICS OF PRIMARY
MUSCLES OF MASTICATION
• All are located in and around the infratemporal fossa.
• All are inserted into the ramus of the mandible.
• All are innervated by the mandibular division of the
trigeminal nerve.
• All are concerned with movements of the mandible on
the TMJ.
• All develop from mesoderm of the first pharyngeal
arch.
11

12. SECONDARY MUSCLES OF MASTICATION
SECONDARY MUSCLES
1. Digastric
2. Buccinator
3. Mylohyoid
4. Geniohyoid
12

13. TEMPORALIS
• ORIGIN- Bone of Temporal fossa and Temporal Fascia
• INSERTION- Coronoid process of mandible and
anterior margin of ramus of mandible to the last molar
tooth
13

14. 14
• INNERVATION
Deep temporal nerves from the anterior trunk of the mandibular
nerve
• FUNCTIONS
It is the principal positioner during elevation
The posterior part is active in retruding of the mandible and the
anterior part is active in clenching

15. CLINICAL EXAMINATION OF
TEMPORALIS
• The muscles of mastication and their motor innervation can be
tested clinically by asking the patient to clench his teeth
repeatedly and the palpating the temporalis in the temporal
fossa and over the mandible respectively.
15

16. MASSETER
• ORIGIN- Zygomatic arch and zygomatic process of
maxilla.
• INSERTION- Lateral surface of the ramus of the
mandible
16

17. 17
• INNERVATION
Masseteric nerve from the anterior trunk of the mandibular
nerve
• FUNCTION
It is active in forceful jaw closing and may assist in
protrusion of the mandible

18. CLINICAL EXAMINATION OF MASSETER
MUSCLE
18
Fingers are placed over
the patient’s zygomatic
arch, angle of the
mandible and body to
feel the muscle.

19. LATERAL PTERYGOID
• ORIGIN-
Upper head- Roof of infratemporal fossa and crest of
greater wing of sphenoid bone.
Lower head- Lateral surface of lateral pterygoid plate
• INSERTION- Capsule of TMJ in the region of
attachment to the articular
disc and to the pterygoid fovea
on the neck of mandible
19

20. 20
• INNERVATION
Nerve to lateral pterygoid directly from the anterior trunk of the
mandibular nerve or the buccal branch.
• FUNCTION-
The inferior head is active during jaw opening movements and
protrusion.
Right lateral pterygoid turns the chin to left side.

21. CLINICAL EXAMINATION OF LATERAL -
PTERYGOID
21
The muscle is palpated using the little or index finger and placing
it lateral to maxillary tuberosity and medial to coronoid process.
The finger presses upwards and inwards and a painful response
can be determined.

22. MEDIAL PTERYGOID
• ORIGIN-
Deep head- Medial surface of the lateral pterygoid plate and
adjoining process of palatine bone
Superficial head- Tuberosity and pyramidal process of
maxilla
• INSERTION- Medial surface of
angle and adjoining ramus of
mandible
• INNERVATION-
Nerve to medial pterygoid from the
mandibular nerve
• FUNCTION-
• Elevation and lateral positioning of
the mandible.
• It is active during protrusion. 22

23. CLINICAL EXAMINATION OF MEDIAL
PTERYGOID
23
Palpate over retromolar
area at the medial surface
of the mandibular angle

24. SPHENO-MANDIBULARIS
• It is considered to be an elevator muscle of the mandible
and thus assist the temporalis in the closure of the mouth
• This was found by Dunn et al in early 1990s at University
of Maryland
• ORIGIN- Anterior aspect of facies temporalis
surface ( a roughened ridge of bone ) of
the sphenoid bone behind the orbit.
• INSERTION- Inserts at the junction
of the ramus and body of the
mandible onto the internal oblique line.
• INNERVATION- Has not been
identified but it is likely derived
from the first branchial arch
24

25. DIGASTRIC
• ORIGIN- Anterior belly- From Digastric fossa of
mandible
Posterior belly- From mastoid notch of temporal bone
• INSERTION- Both heads meet at the intermediate tendon
which perforates SH and is held by a fibrous pulley to the
hyoid bone.
25

26. 26
• INNERVATION-
Anterior belly by nerve to mylohyoid
Posterior belly by facial nerve
• FUNCTIONS-
Depresses mandible when mouth is widely opened or against
resistance and elevates hyoid bone

27. BUCCINATOR
(Bugler’s or Trumpeter’s muscle)
• ORIGIN-
Upper Fibres- From maxilla opposite
molar teeth
Lower Fibres- From mandible,
opposite molar teeth
Middle Fibres- From pterygo-
mandibular raphae
• INSERTION-
Upper Fibres- Straight to upper lip
Lower Fibres- Straight to lower lip
Middle Fibres- decussate
27

28. • INNERVATION-
Buccal branches of fascial nerve
• FUNCTIONS
Flattens cheek, whisteling
Prevents accumulation of food in the vestibule during
mastication
28

29. MYLOHYOID
• ORIGIN- Mylohyoid line of mandible
• INSERTION-Anterior and Middle fibres- Median raphae ,
between mandible and hyoid bone
Posterior fibres- Body of hyoid bone
29

30. 30
• INNERVATION- Nerve to mylohyoid
• FUNCTIONS-
Elevates floor of the mouth in first stage of
deglutition
Helps in depression of mandible and elevation of
hyoid bone

31. GENIOHYOID
• ORIGIN- Inferior mental spine
• INSERTION- Anterior surface of hyoid bone
• INNERVATION- C1 through hypoglossal nerve
• FUNCTIONS- Elevates hyoid bone
31

32. MANDIBULAR MOVEMENTS AND
MUSCLE ACTIVITY
MANDIBULAR OPENING
• The digastric, mylohyoid and geniohyoid muscles
are active during jaw opening, either slowly or
maximally against resistance.
• No activity occurs in the temporalis and masseter
muscle when mouth is opened slowly and jaw is
opened maximally
• In forced depression the digastric is activated
almost as soon as the lateral pterygoid muscle.
32

33. MANDIBULAR CLOSING
• Elevation without contact or resistance is
bought by contraction of the masseter and
medial pterygoid muscle
• The temporalis, masseter and medial
pterygoid affect elevation against resistance.
33

34. RETRUSION
• Voluntary mandibular retrusion with the mouth
closed is brought by contraction of the posterior
fibres of the temporalis muscle and by the
suprahyoid and infrahyoid muscles.
• Retraction of the mandible from protrusion and
without occlusal contact is effected by posterior
and middle fibres of the temporalis muscle.
34

35. PROTRUSION
• Protrusion of the mandible without occlusal
contact results from contraction of the lateral
and medial pterygoid muscles and also
masseter muscle.
• Protraction against resistance is brought by
contraction of the lateral and medial
pterygoid, masseter and suprahyoid muscle
group.
35

36. LATERAL MOVEMENTS
• Lateral movement of the mandible to the right
side
Ipsilateral contraction of the posterior and the
middle fibres of the temporalis muscle
• Lateral movement of the mandible to the left
side
Contralateral contraction of the lateral and medial
pterygoid muscles and the anterior fibres of the
temporalis muscle
36

37. 37

38. OKESON’S CLASSIFICATION OF
MASTICATORY MUSCLE DISORDERS
• Myofascial Pain
• Myositis
• Myospasm
• Local Myalgia
• Myofibrotic contracture
38

39. MYOFASCIAL PAIN
• Certain muscles tend to develop trigger areas within the
muscles or tendons
• When these sites are stimulated by ordinary function, pain
impulses are generated.
• There is secondary referred pain which is felt in structures
located at some distance from the trigger site and thus, pain
may be felt in adjacent normal structures.
• It may be caused by atrophied muscles due to inactivity,
sustained emotional illness and nutritional deficiency.
• Once the myofascial triggers develop they tend to persist as a
source of intermittent and recurrent pain when triggers are
stimulated
39

40. ZONES OF PAIN REFERENCE FROM
MYOFASCIAL TRIGGERS
• Masseter Muscle-The masseter muscle refers to the
ear, TMJ and mandibular teeth
• Temporalis Muscle- The temporalis to the temple, orbit
and maxillary teeth
• Medial Pterygoid- The Medial Pterygoid to the infra
auricular and post mandibular area
• Lateral Pterygoid- To the TMJ
40

41. 41

42. MYOSITIS
• It is characterised by inflammation of the muscle due to
spreading infection, external muscle trauma or muscle strain.
CLINICAL FEATURES
• Acute pain within the muscle
• Limited range of motion
42

43. MASTICATORY MYOSPASM
• Continuous involuntary contraction of the masticatory muscle.
• Masticatory myospasm can be classified
1. Jaw closing which involves masseter and/or temporalis
2. Jaw opening which involves lateral pterygoid muscles
• Botulinum toxin injection has been found as the most effective
therapy for masticatory myospasm. But it was observed that
the pain returned after 5 months.
43

44. LOCAL MYALGIA
• Mechanism of myalgia or muscle pain is related to the
accumulation of metabolites after excessive use of muscles.
• This will result in distortion of blood vessels within the
muscle, causing ischemia and hyperaemia.
CAUSES
• Unusual yawning,
• Biting
• Chewing
• Emotional tension
• Minor trauma
44

45. MANAGEMENT
• Patient education and reassurance
• Control of parafunctional oral behaviours like clenching
or chewing gum
• Intra-oral appliance therapy
• Pharmacology- NSAIDs, Acteaminophen, Muscle
relaxants, anti-anxiety agents
• Relaxation therapy
45

46. MYOFIBROTIC CONTRACTURE
Chronic resistance of a muscle to passive stretch as a result of
fibrosis of the supporting tendon, ligaments, or muscle fibres
themselves.
CHARACTERISTICS
• Limited range of motion of mandible
• Unyielding firmness on passive stretching
• History of trauma or infection
MANAGEMENT
Treatment of the etiological cause
46

47. 47

48. MASTICATORY MUSCLE DISORDERS
OF TMJ
According the Classification by WELDON AND BELL
• Protective muscle splinting
• Masticatory Muscle Spasm
• Masticatory Muscle inflammation( Myositis)
48

49. EPIDEMIOLOGY
• Signs and symptoms of masticatory muscle dysfunction are
commonly observed in children and adolescents.
• Among adolescents in Sweden between the ages of 12-19
years, 4.2% reported TMD pain and girls reported twice more
frequently as boys
• A wide variety of TMD characteristics observed in adults also
occur to largely in the same extent in children and adolescents
• Eg: a group of 40 children between ages 10-16 years presented
with signs and symptoms of TMD, 35% were diagnosed with
having acute reactive depression.
49

50. MYOFASCIAL PAIN SYNDROME
It is initiated as a spasm of one or more masticatory muscles
Patient presents with complaint of noise on rubbing, grinding,
clicking, popping snapping sounds on mandibular movement,
tinnitus, otalgia or toothache.
ETIOLOGY
• Hypermobility of the TMJ
• Faulty Prosthesis
• Malocclusion
• Oral habits
50

51. CLINICAL FEATURES
(LASKIN’S DIAGNOSTIC CRITERIA)
Four cardinal signs:
• Unilateral pain
• Muscle Tenderness present on the region distal and
superior to maxillary tuberosity
• Clicking
• Limitation of Jaw function
Negative characeristics:
No radiographic and/or biochemical evidence
No tenderness in TMJ area
51

52. INVOLVEMENT OF THE
MASTICATORY MUSCLES
MUSCLE PAIN REFERS TO CLINICAL EFFECT
Temporalis Temple, Maxillary
teeth, TMJ
Restriction of mandibular
opening, Ipsilateral
deviation of mandible,
deviation of inter-occlusal
space
Masseter Mandible, Maxillary
Molar, TMJ, Ear
Same as above
External
Pterygoid
TMJ Contralateral deviation of
the mandible, protrusion of
condyle, acute malocclusion
Internal
Pterygoid
TMJ, Retromandibular
area, Tongue
Restriction of mandibular
movements, contralateral
deviation of the mandible.
52

53. MANAGEMENT
• Removal of etiological cause
1. MUSCLE RELAXATION TECHNIQUES
• Tongue and Mouth Exercise
• Voluntary resistance (reflex inhibition)
2. PHARMACOLOGICAL
• Analgesics: Most common Asprin
• Tranquilizers: Phenothiazine
3. PHYSICAL STIMULATION
• Hot packs
• Diathermy
• TENS
53

54. DISORDERS OF MUSCLE OF
MASTICATION DUE TO EXTERNAL
FACTORS
• Trismus
• Bruxism
• Tetanus
• Temporal Tendonitis
54

55. TRISMUS
It is defined as a condition in which muscle spasm or contracture
prevents opening of the mouth (due to infection or other conditions
that alter muscle structure)
ETIOLOGY
• Orofacial infections
• Trauma
• Inflammation
• Tetany
• Lockjaw
55

56. Trismus can also be seen following Inferior alveolar nerve
block with local anaesthetic agent. Bleeding created by
needle puncture in the medial pterygoid muscle produces a
hematoma followed by fibrosis and trismus.
MANAGEMENT
• Manipulation of the jaw under sedation or GA
• Manipulation of jaw under sedation with jaw stretcher
to break the adhesions
56

57. BRUXISM
• An oral habit consisting of involuntary rhythmic or spasmodic
non-functional gnashing, grinding, or clenching of teeth, in
other than chewing movements of the mandible, which may
lead to occlusal trauma. (Glossary of Prosthodontic terms)
• Ramfjord and Ash described it as nocturnal, subconscious
activity, but can occur in day or night and may be performed
consciously or subconsciously
• Sleep bruxism is more common in children.
57

58. CLINICAL FEATURES
• Hypertrophy of masseter jaw muscles
• Teeth are abnormally worn down out, chipped
• Increased tooth sensitivity
• Jaw pain or tightness in jaw muscles
• Ear ache and headache
TREATMENT
• Psychological counselling
• Correction of occlusal interferences
• Splints or bite pates
• Oral analgesics
• Physiotherapy
58

59. TETANUS
• It is a disease characterised by intense activity of motor
neurons and resulting in severe muscle spasm
• It is also called lock jaw.
TRANSMISSION
• Injury
• Intra venous drug user
• Contamination
• Tetanus neonatorum
59

60. ORAL MANIFESTATION
• Rigidity of muscles of mastication
• Risus Sardonicus- corners of the mouth are drawn back
with protruded lip
• Difficulty in chewing and swallowing
• As spasm increases jaw is locked and mouth cannot be
opened
TREATMENT
• Antitoxin: Immediate I.V. of immune serum containing
20,000 IU of antitoxin
• Penicillin: 1,000,00 Penicillin G, IV 6 hourly for 10
days
• Sedation with diazepam
• Supportive care
60

61. TEMPORAL TENDONITIS
• It is disorder of fibrous insertion of the temporalis muscle
tendons on the coronoid process of the mandible
• It is characterised by both inflammation and degeneration
• It may or may not co-exist with Temporo- mandibular Disorders.
• The spheno-mandibularis being a skeletal muscle that elevates
the jaw, is a frequent source of headache. If the temporalis
muscle or tendon is painful in a patient then often the spheno-
mandibularis tendon is painful as well and should be tested.
• For proper diagnosis, diagnostic block is given slowly intra-orally
at the ramus and body of the mandible on the medial surface.
One quarter cc. of local anaesthetic is given slowly.
• If the temple pain is remitted then a cocktail of ¼ cc
Cyanocobalmin, ¼ cc steroid, ¼ cc sarapin is injected in the same
area for healing
61

62. RELATED ARTICLES
• BMC Public Health 2012 Pires et al. There is some evidence of the
benefits of breastfeeding to masticatory function, but no studies
have evaluated the influence of breastfeeding duration on the
quality of this function.
• Cross-sectional study nested in a contemporary cohort of 144
randomly selected Brazilian infants. Data on sociodemographic,
dietary, and sucking-related parameters were collected shortly after
birth and at 7, 30, 60, 120, and 180 days of life. Masticatory
function was assessed between the ages of 3 and 5 years, using a
standardized procedure involving three foodstuffs of different
consistencies, for evaluation of incision, lip competence,
masticatory patterns, masticatory movements, and perioral muscle
use.

63. The quality of masticatory function was scored, and multiple linear
regression was used to test for association between this score and the
duration of breastfeeding. A positive correlation was found between
duration of breastfeeding and masticatory function scores.Children
breastfed for at least 12 months had significantly higher average
scores, regardless of bottle-feeding or pacifier use. Children who
were breastfed for longer were more likely to score satisfactorily
across all tested parameters.
Pires SC, Giugliani ER, da Silva FC. Influence of the duration of breastfeeding on quality of muscle function during mastication in preschoolers: a
cohort study. BMC Public Health. 2012;12(1):934.

64. A/c MARCIA et al. :The aim of the article was to review the
literature concerning ultrasonography imaging (US) of the
muscles of mastication and to discuss its use, advantages and
disadvantages and the findings of the authors. A web search was
performed using the terms “ultrasound” and “muscles”. US has
been shown to be a reliable method of great utility in the field of
diagnosis of alterations in the muscles of mastication and for the
study of changes during growth and aging. It should be preferred
in comparison to computerized axial tomography (CT) and
magnetic resonance imaging (MRI) because of its safety and cost
advantages since it is as reliable and precise as these other
techniques.
Serra MD, Gaviao MB, dos Santos Uchoa MN. The use of ultrasound in the investigation of the muscles of mastication. Ultrasound
in medicine & biology. 20081;34(12):1875-1884

65. • A/C to “FIXED PROSTHODONTICS OPERATIVE
DENTISTRY” David et all stated effects of bruxism may be
divided into the six major categories of:
(1) effects on the dentition,
(2) effects on the periodontium,
(3) effects on the masticatory muscles,
(4) effects on the temporomandibular joint.,
(5) head pain, and
(6) psychological/behavioral effects.

66. EFFECT ON PERIODONTIUM
• Karolyi was the first to associate periodontal lesions with hypertonic or
spastic conditions of the masticatory musculature produced by clenching
teeth.
• Boyens reported that 78 per cent of 100 periodontal patients had bruxistic
activity.
• Similarly, Leaf” reported 81 per cent involvement in 171 periodontal
patients.
• Thompson and associates noted no relationship between periodontal status
and bruxism in 516 patients.
• Several authors have described the effects of bruxism on gingival tissues.
Both gingival recession and inflammation of the gingiva, have been
attributed to the steady irritation of bruxism.
• Resorption of the alveolar bone has also been considered a common
symptom of bruxism.
Glares AG, Rao SM. Effects of bruxism: a review of the literature. The Journal of prosthetic dentistry. 1977;1;38(2):149-157

67. EFFECT ON MASTICATORY MUSCLES
• Chronic bruxism has also been implicated as a primary cause of
hypertrophy of the masticatory muscles, especially the masseter muscle.
• The only evidence against the clinical descriptions of the relationship
between bruxism and hypertrophy of the masseter muscles is derived from
a study of Lindqvist and Ringqvist. These researchers compared the closing
force of the jaws of 12-year-old bruxists and similarly aged nonbruxists. It
was assumed that since bruxism develops more powerful masticatory
muscles, the closing force of the bruxists would be greater than that of the
controls. The diagnosis of bruxism was made by recording facets on the
teeth and by confirmation of audible bruxism by the parents of the subjects.
The closing force was measured on the first molars. No relationship was
found between the degree of tooth abrasion and the closing force for either
a light or a maximum effort. The results of this study do not necessarily
negate the clinical observations, since the subjects were somewhat young
and only a small percentage of bruxists eventually develop muscular
hypertrophy, a result of severe and persistent grinding pressures.
Glares AG, Rao SM. Effects of bruxism: a review of the literature. The Journal of prosthetic dentistry. 1977;1;38(2):149-157

68. • A/c to Journal of Periodontology Daniele et al performed a
review .Despite the scarce quantity and quality of the literature
prevents from drawing sound conclusions on the causal link
between bruxism and the periodontal problems assessed in this
review, it seems reasonable to suggest that bruxism cannot
cause periodontal damage per se, but it is also important to
emphasize that due to methodological problems more and
better studies should be performed in order to further clarify
this issue.
Manfredini D, Ahlberg J, Mura R, Lobbezoo F. Bruxism is unlikely to cause damage to the periodontium: findings from a systematic
literature assessment.Journal of periodontology. 2015;1;86(4):546-555.

69. REFERENCE
• Singh V. Anatomy of Head, Neck and Brain. 3rd ed. Elsevier
India; 2014.
• Nelson, Ash. Wheeler’s Dental Anatomy, Physiology and
Occlusion. 9thed.
• Ghom Govindrao A, Ghom Anil S. Textbook of Oral medicine.
3rded.
• Glick M. Burket’s ORAL MEDICINE. 12th ed
• Jain Ak.
• Manfredini D, Ahlberg J, Mura R, Lobbezoo F. Bruxism is
unlikely to cause damage to the periodontium: findings from a
systematic literature assessment. Journal of periodontology.
2015;1;86(4):546-555.

70. • Glares AG, Rao SM. Effects of bruxism: a review of the
literature. The Journal of prosthetic dentistry.
1977;1;38(2):149-157
• Pires SC, Giugliani ER, da Silva FC. Influence of the duration
of breastfeeding on quality of muscle function during
mastication in preschoolers: a cohort study. BMC Public
Health. 2012;12(1):934.
• Serra MD, Gavião MB, dos Santos Uchôa MN. The use of
ultrasound in the investigation of the muscles of mastication.
Ultrasound in medicine & biology. 20081;34(12):1875-1884