muscles of mastication

2. INDEX:
1. Introduction
2. Types of muscle
3. Development of muscle
4. Primary muscles of mastication
5. Suprahyoid muscles
6. Infrahyoid muscles
7. Masticatory system disorders
8. Conclusion
9. References

3. NOTHING IS MORE FUNDAMENTAL TO
TREATING PATIENTS THAN KNOWING THE
ANATOMY
- JEFFERY P OKESON

4. Muscle: A tissue composed of contractile cells or fibers that effect movement of an
organ or part of the body.(GPT 9)
Mastication: The process of chewing food for swallowing and digestion.(GPT 9)
There are basically three types of muscles:
1. Skeletal muscle
2. Smooth muscle
3. Cardiac muscle
INTRODUCTION
Glossary of prosthodontic terms-9

5. 1.Have light and dark
bands or striations.
2.Cylindrical
multinucleated
unbranched cells
3.Voluntary
4.Contract quickly but
get fatigued easily
5.Seen in
limbs,tongue,body,face,
neck
1.Do not show light and
dark bands.
2.Spindle shaped
uninucleated cells
3.Involuntary
4.Contract slowly but
don’t get fatigued easily
5.Seen in
ureters,bronchi of
lungs, ailmentary canal
and blood vessels.
1.Structure in between
striated and non
striated muscle
2.Cylinder shaped
uninucleated branched
cells.
3.Involuntary
4.Contract rhythmically
and quickly ,hence do
not get fatigued
5. Seen in walls of heart

6. DEVELOPMENT
First
pharyngeal
arch
Intra
embryonic
mesoderm
Myoblast
MyotubeMuscle fibre
Textbook Of Embryology- Inderbir Singh

7. CLASSIFICATION:
Muscles of
mastication
Accesory
1.Masseter
2.Temporalis
3.Lateral
pterygoid
4.Medial pterygoid
Suprahyoid:
1.Digastric
2.Stylohyoid
3.Mylohyoid
4.Geniohyoid
Primary
Infrahyoid:
1.Sternohyoid
2.Thyrohyoid
3.Omohyoid
HUMAN ANATOMY VOL 3- B.D. CHAURASIA

8. FUNCTIONAL
CLASSIFICATION:
Muscles of
mastication
Elevators
1.Masseter
2.Temporalis
3.Medial pterygoid
4.Upper head of
lateral pterygoid
Depressors
1.Digastric
2.Mylohyoid
3.Geniohyoid
4.Lower head of lateral
pterygoid

9. Masseter
• Thick quadrilateral muscle
• Second most efficient masticatory muscle
• Multipennate arrangement
• Buccal pad of fat seperates the muscle from
buccinator.
HUMAN ANATOMY VOL 3- B.D. CHAURASIA

11. ORIGIN:
• By a thick tendinous aponeurosis from the
zygomatic process of maxilla
• From the anterior 2/3rds of the lower border of
zygomatic arch.
Superficial head
• Posterior third of the lower border of zygomatic
arch.
• Whole of the medial surface of the zygomatic
arch
Deep head
HUMAN ANATOMY VOL 3- B.D. CHAURASIA

12. INSERTION:
Superficial
head
• Middle and lower part of lateral
surface of ramus of mandible
Deep head
• Upper part of ramus and coronoid
process of mandible
HUMAN ANATOMY VOL 3- B.D. CHAURASIA

13. Actions:
Elevates the mandible
HUMAN ANATOMY VOL 3- B.D. CHAURASIA

14. Vascular Supply
Vascular
supply
Massetric
artery
Facial
artery
Transverse
facial
artery
HUMAN ANATOMY VOL 3- B.D. CHAURASIA

15. Nerve Supply:
Massetric nerve
HUMAN ANATOMY VOL 3- B.D. CHAURASIA

16. Examination:
Burket’s Oral Medicine –Eleventh Edition

17. Temporalis:
• Largest among all the mastication muscles.
• Broad ,radiating and fan shaped
• Fills the temporal fossa

18. HUMAN ANATOMY VOL 3- B.D. CHAURASIA

19. Actions
• Anterior Vertical Fibers
- Elevates the mandible
- Side to side grinding movements
• Posterior Horizontal Fibers
- Retracts the mandible
HUMAN ANATOMY VOL 3- B.D. CHAURASIA

20. Vascular Supply
• Supplied by deep temporal branches from second part of maxillary artery.
HUMAN ANATOMY VOL 3- B.D. CHAURASIA

21. Nerve Supply
Deep temporal branches of anterior division of
mandibular nerve.
HUMAN ANATOMY VOL 3- B.D. CHAURASIA

22. Examination:
Anterior region Middle region Posterior region
BUREKET’S ORAL MEDICINE-ELEVENTH EDITION

23. Lateral Pterygoid
• Also called as external pterygoid muscle.
• Short and conical
• Has upper and lower heads

24. Origin:
Upper head Lower head

25. INSERTION:
• Fibers Run Backward And Laterally And Converge
To Be Inserted Into :
-Pterygoid Fovea On The Anterior Surface Of Neck
Of Mandible
-Anterior And Medial Border Of The Articular Disc
And Capsule Of TMJ.
HUMAN ANATOMY VOL 3- B.D. CHAURASIA

26. Actions:
Depression
of
mandible
Protrusion
of
mandible
Side to
side
movement

27. • Vascular supply:
Pterygoid branches from the maxillary artery.
The ascending palatine branch of the facial artery.
• Nerve supply:
Branch from anterior division of mandibular nerve.
HUMAN ANATOMY VOL 3- B.D. CHAURASIA

28. Examination:
Functional manipulation of Superior lateral
pterygoid :
Contraction – if it is source of pain, clenching
increases pain.
If a tongue blade is placed between posterior
teeth bilaterally and patient clenches on the
separator pain increases with contraction of SLP
Burket’s Oral Medicine- 11th Edition

29. Functional manipulation of inferior
lateral pterygoid :
Contraction – Ask the patient to
protrude against resistance
provided by the examiner.
If ILP is the source of pain – activity
will increase pain
Burket’s Oral Medicine -11th Edition

30. Medial Pterygoid
• Quadrilateral muscle
• Has a small superficial and large deep head
• Deepest among the muscles of mastication
• Also known as internal pterygoid muscle

31. Origin And Insertion:

32. Actions:
Elevation Protrusion
Contralateral
excursion

33. • Vascular supply: Pterygoid branch of second part of maxillary artery.
• Innervation: Nerve to medial pterygoid ,branch of main trunk of mandibular nerve.
HUMAN ANATOMY VOL 3- B.D. CHAURASIA

34. Examination:
• Palpation is done mainly by intra oral approach.
• The region of its attachment to inner aspect of
angle of mandible can be palpated by sliding finger
lingually and applying pressure at the insertion
of muscle and placing one hand extraorally below
the border of mandible

35. • Functional Manipulation:
1. Contraction: 2.Stretching:
If it is
source of
pain
Clenching
teeth together
wil increase
pain
If it is
source of
pain
Opening
mouth wil
increase pain

36. ACCESORY MUSCLES OF
MASTICATION

37. Suprahyoid Muscles
1. Digastric
2. Geniohyoid
3. Mylohyoid
4. Stylohyoid

38. DIGASTRIC:

39. Innervation
• Anterior belly: Nerve to
mylohyoid
• Posterior belly: Facial nerve
Actions
• Depresses the mandible
• Elevates hyoid bone
HUMAN ANATOMY VOL 3- B.D. CHAURASIA

40. GENIOHYOID

41. Innervation
First cervical nerve
through hypoglossal nerve
Actions
Elevates hyoid bone
When hyoid bone is fixed,
depresses mandible
HUMAN ANATOMY VOL 3- B.D. CHAURASIA

42. Mylohyoid

43. • Innervation: Nerve to mylohyoid,branch of inferior alveolar nerve
• Vascular supply: By facial and lingual artery
• This muscle separates sublingual and submandibular salivary glands

44. Actions:
Actions
Elevates floor of
mouth
Elevation of hyoid
bone
Depression of
mandible

45. Stylohyoid

46. •Innervation Facial nerve
•Actions
Elevation of hyoid
Pulls the hyoid
backwards
HUMAN ANATOMY VOL 3- B.D. CHAURASIA

47. INFRAHYOID MUSCLES:
Infrahyoid group of muscles consist of:
1. Omohyoid
2. Thyrohyoid
3. Sternohyoid
4. Sternothyroid

48. Omohyoid:
Origin: Upper border of scapula near
suprascapular notch
Insertion: Lower border of body of hyoid bone
Innervation: Superior belly by superior
root of ansa cervicalis
Inferior belly by ansa cervicalis
Action: Depresses the hyoid bone
HUMAN ANATOMY VOL 3- B.D. CHAURASIA

49. Sternothyroid
Origin: Posterior surface of manubrium
sterni,adjoining parts of first costal cartilage
Insertion: Oblique line of thyroid cartilage
Innervation: Ansa cervicalis
Actions: Depresses the larynx and helps in
swallowing
HUMAN ANATOMY VOL 3- B.D. CHAURASIA

50. Thyrohyoid
Origin: Oblique line of thyroid cartilage
Insertion: Body of hyoid bone
Innervation: First cervical nerve
through hypoglossal nerve
Actions: Depresses the hyoid bone and
elevates the larnyx
HUMAN ANATOMY VOL 3- B.D. CHAURASIA

51. Sternohyoid
Origin: Posterior surface of manubrium sterni and
adjoining part of clavicle
Insertion: Medial part of lower border of hyoid bone
Innervation: Ansa cervicalis
Actions: Depresses the hyoid bone
HUMAN ANATOMY VOL 3- B.D. CHAURASIA

52. Masticatory Muscle
Disorders

53. • Muscle tissue becomes compromised or unhealthy –
- due to muscle overuse
- physical trauma
- over stretching
- receiving a blow to muscle tissue itself.
• Muscles of mastication become compromised through increased activity.

54. • Some of the common masticatory disorders are as follows:
1.Trismus
2.Protective co contraction
3. Local muscle soreness
4.Myospasm
5. Myofascial pain
6.Centrally mediated myalgia(chronic myositis)
7.Myofibrotic contracture

55. Trismus:
What is trismus?
Trismus is inability to open
the jaw
Etiology:
Trauma, infection, drugs,
dental treatment, congenital
problems
Management:
Heat therapy
Analgesics
Physiotherapy
Soft diet
Muscle relaxants
Dhanrajani PJ, Jonaidel O. Trismus: aetiology, differential diagnosis and treatment. Dent update 2002;29:88-94

56. Protective Co Contraction:
• Protective co-contraction is the initial response of a muscle to altered sensory or
proprioceptive input or injury (or threat of injury).
• This response has also been called protective muscle splinting.
• When protective co contraction occurs ,CNS increases activity of antagonistic
muscle during contraction of agonist muscle
• For example,patient who is experiencing protective co contraction wil demonstrate
slightly increased muscle activity in the elevators durimg mouth opening .
• Not a pathological condition but a normal guarding or protective mechanism
Management Of Occlusion & TMD – Okeson

57. Etiology
1. Altered
sensory or
proprioreceptory
input.
2.Constant deep
pain input
3.Increased
emotional stress
Symptoms
1.Structural
dysfunction
2.No pain at rest
3.Increased pain
with functuon
4.Feeling of
muscle weakness
Treatment
1.No indication to
treat the muscle
condition itself.
Treatment
should instead be
directed toward
the reason for
the co-
contraction
Management Of Occlusion & TMD – Okeson

58. Local muscle soreness:
• Local muscle soreness is a primary noninflammatory myogenous pain disorder.
• It is often the first response of the muscle tissue to continued protective co-
contraction and therefore the most common acute muscle pain disorder in dental
practice.
• Although co-contraction represents a cns-induced muscle response, local muscle
soreness represents a change in the local environment of the muscle tissues.
• It represents the initial response to overuse, which we think of as fatigue.
Management Of Occlusion & TMD – Okeson

59. Myospasm
• Involuntary cns-induced tonic muscle contraction often associated with local
metabolic conditions within the muscle tissues.
• Following conditions are etiologic factors in myospasm:
1. Continued deep pain input
2. Local metabolic factors within the muscle tissues associated with fatigue or
overuse
3. Idiopathic myospasm mechanisms
Management Of Occlusion & TMD – Okeson

60. • The following clinical characteristics are associated with myospasms:
1. Structural dysfunction: There is marked restriction in range of mandibular
movement according to the muscle or muscles involved. Acute malocclusion is common.
2. There is pain at rest.
3. The pain is increased with function.
4. The affected muscle is firm and painful to palpation.
5. There is a generalized feeling of significant muscle tightness
Management Of Occlusion & TMD – Okeson

61. Management Of Occlusion & TMD – Okeson

62. Centrally mediated myalgia:
• Chronic, continuous muscle pain disorder originating predominantly from CNS
effects that are felt peripherally in the muscle tissues.
• This disorder presents clinically with symptoms similar to those of an inflammatory
condition of the muscle tissue; therefore it is sometimes referred to as myositis.
Management Of Occlusion & TMD – Okeson

63. Etiology:
• As the CNS becomes exposed to prolonged nociceptive input, brainstem pathways
can functionally change.
• This can result in an antidromic effect on afferent peripheral neurons.
• When this occurs, the afferent neurons in the periphery can release nociceptive
neurotransmitters such as substance p and bradykinin, which in turn cause
nociception and pain in the peripheral tissues. this process is called neurogenic
inflammation.
Management Of Occlusion & TMD – Okeson

64. Symptoms:
1. Structural dysfunction: Patients experiencing centrally mediated myalgia present with a
significant decrease in the velocity and range of mandibular movement.
2. There is significant pain at rest.
3. The pain is increased with function.
4. There is a generalized feeling of muscle tightness.
5. There is significant pain to muscle palpation.
6. As chronic centrally mediated myalgia becomes protracted, the lack of use of the muscle
owing to pain may induce muscle atrophy and/or myostatic or myofibrotic contracture.
Management Of Occlusion & TMD – Okeson

65. Myofascial Pain Dysfunction Syndrome:
When muscle spasm develops ,dysfunction as well as pain occurs and the condition
usually is designated as MPDS.
It is initiated as spasm of one or more masticatory muscle.
Regional myogenous pain condition characterized by local areas of firm,
hypersensitive bands of muscle tissue known as trigger points.
• Textbook of oral medicine- Anil Ghom (Second edition)

66. • Etiology:
1.Abnormal occlusion
2. Prosthetic problems
3.Orthodontic problems
4.Emotional stress
5. Dental restoration
6. Joint problems
7.Oral habits
Textbook of oral medicine- Anil Ghom (Second edition)

67. Pathogenesis:
Energy released
during muscle
contraction
Accumulation of
lactic acid
Change in pH
Muscle receptor
prone to impulse
excitation
Infusion of
histamine,bradykinin
Pathological
muscular
derangement
Textbook of oral medicine- Anil Ghom (Second edition)

68. • Treatment:
1.Educate the patient
2.Muscle relaxation techniques
3. Pharmacotherapy
4. Biofeedback
5. Bruxism prosthesis
6. Anesthesia
7.Physical medication
Textbook of oral medicine- Anil Ghom (Second edition)

69. Treatment component Description
1.Education • Explanation of the diagnosis and treatment
• Reassurance about the generally good prognosis for recovery and natural
course
• Explanation of patient’s and doctor’s roles in therapy
• Information to enable patient to perform self-care
2.Self care • Eliminate oral habits (eg, tooth clenching, chewing gum)
• Provide information on jaw care associated with daily activities
3. Physical therapy • Education regarding biomechanics of jaw, neck, and head posture
• Passive modalities (heat and cold therapy, ultrasound, laser, TENS)
• Range of motion exercises (active and passive)
• Posture therapy
• Passive stretching, general exercise and conditioning program.
4.Intra oral appliance therapy • Cover all the teeth on the arch the appliance is seated on
• Adjust to achieve simultaneous contact against opposing teeth
• Adjust to a stable comfortable mandibular posture
• Avoid changing mandibular position
• Avoid long-term continuous use.
5.Pharmacotherapy NSAIDs, acetaminophen, muscle relaxants, antianxiety agents, tricyclic
antidepressants
6. Behavioral/relaxation techniques Relaxation therapy, Hypnosis ,Biofeedback ,Cognitive-behavioral therapy

70. Conclusion
Nature has blessed us with marvelously
dyamic masticatory system allowing us to
function and therefore exist.

71. References:
• Glossary of prosthodontic terms-9
• Human anatomy,volume 3 – B.D chaurasia
• Human embryology – Inderbir Singh
• Management of occlusion & Tmd – Okeson
• Burket’s oral medicine –Eleventh edition
• Textbook of oral medicine- Anil Ghom (Second edition)
• De Rossi, Scott S. et al. “Disorders of masticatory muscles”. Dental clinics ,Volume 57(3), 449-
464.
• Dhanrajani PJ, Jonaidel O. “Trismus: aetiology, differential diagnosis and treatment”. Dent update
2002;29:88-94