BRIEF DISCUSSION ABOUT MUSCLES OF MASTICATION

1. MUSCLES OF MASTICATION
KHUSHBOO
MDS IST YEAR
Department of
Paedodontics
and Preventive
dentistry

2. CONTENTS
• Introduction
• Development of muscles
• Classification
• Properties
• Muscles of mastication
• Primary muscle of mastication
• Palpation
• Accessory muscles of mastication
• Clinical considerations
• Conclusion
• References

3. DEFINITIONS
• Muscle:- 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 :- is the mechanical process which breaks up
larger food particles into smaller pieces which
• -make it easier for the food to be swallowed
• -mixes the food with the secretions of salivary glands to soften
it.
• -increases the surface area of food particles thus helping in
subsequent digestion of food.

4. • Mastication is a sensory motor activity aimed at the
preparation of food for swallowing. It is complex
process involving activities of facial elevator and
suprahyoid muscles and tongue.
• Rhythmic mandible movements , food manipulation
and crushing of food between the Teeth. Saliva
facilitates mastication, moistens the food particles,
makes a bolus and assists swallowing.
A. Van der Bilt et al/physiology and behavior 89(2006) 22-27

5. INTRODUCTION
• Muscle refers to a group of muscle fibres bound together by
connective tissue.
• Muscle generates force and movements used in the regulation
of the internal environment.
• By controlling the activity of these muscles the human mind
ultimately expresses itself.

6. DEVELOPMENT OF MUSCLES
• The muscular system develops from mesoderm of
first brachial arch
• But the posterior belly of digastric muscle develops
from 2nd brachial arch and supplied by facial nerve

8. CLASSIFICATION OF MUSCLES
• Depending upon striations 1) Striated muscles
• 2) Non- Striated muscles
• Depending upon control 1) Voluntary muscles
• 2) Involuntary muscles
• Depending upon functions 1) Skeletal muscles 2) Cardiac
muscles 3) Smooth muscles

9. • Skeletal – most are attached to the skeleton and form ‘somatic
musculature’
• Shows well developed cross striations thus called striated muscles.
• Generally under voluntary control
• Help to maintain body posture and position.
• Cardiac-present in heart
• Well developed cross striations
• Involuntary control
• Maintain arterial B.P.
• Smooth-mostly in hollow viscera
• Lack cross striations also called plain muscle.
• Involuntary
• responsible for maintaining vegetative function of day to day
living i.e. its action favors digestion, respiration, excretion and
reproduction.

10. MUSCLES OF MASTICATION
 Muscles of mastication- originate skull and insert mandible,
only mandible moves during mastication and other activities.
Four muscles are the primary participants in mastication,
other accessory muscles.
 Each of these primary muscles of mastication is paired.

11. Primary muscles of mastication
• Temporalis
• Masseter
• Lateral pterygoid
• Medial pterygoid

12. ACCESSORY MUSCLES OF MASTICATION
• SUPRAHYOID INFRAHYOID
• Digastric Sternohyoid
• Stylohyoid Thyrohyoid
• Mylohyoid Omohyoid
• Geniohyoid

14. Functionally the muscle of mastication are classified as
• Jaw elevators-
• Masseter
• Temporalis
• Medial Pterygoid
• Jaw depressors-
• Lateral Pterygoid
• Anterior digastric
• Geniohyoid
• Mylohyoid

15. Temporalis Muscle
It is a powerful fan shaped chewing
muscle which feels temporal fossa.
Origin
Temporal fossa from infratemporal lines
excluding
-Zygomatic bone
-Temporal fascia
Insertion
-Margins and deep surface of coronoid
process of mandible
-Anterior border of ramus of mandible
Blood supply- Superficial temporal artery
branch of Maxillary artery
-Superficial temporal vein and middle
temporal vein
Nerve supply- Deep Temporal branches
from anterior division of mandibular
nerve

16. TEMPORALIS MUSCLE

18. FUNCTIONS:-
• Elevation of mandible
• Retraction of mandible
• Crushing of food between the molars
• Posterior fibres draw the mandible backwards after it has been protruded
• It is also a contribute side to side grinding movement.
PALPATION:-
- To locate the muscle, have the patient clench.
- Apply two pounds of pressure.
- The anterior region is palpated above the zygomatic arch and anterior to the
TMJ.
- The middle region palpated directly above the TMJ and superior to the
zygomatic arch.
- The posterior region is palpated above and behind the ear.
APPLIED ANATOMY:
• Sudden reflex contraction of temporalis in times of trauma can cause the
fracture of coronoid process

20. Masseter Muscle
• The second most efficient masticatory muscle.
ARRANGEMENT OF FIBRES:
 Superficial: Origin: thick aponeurosis. From zygomatic process of
maxilla and anterior 2/3 of lower border of zygomatic arch, pass
downward and backwards at an angle of 45 degree.
Insertion: into lower part of lateral surface of ramus of mandible.
 Middle Layer: origin: anterior 2/3 of the deep surface and poterior 1/3
lower border of the zygomatic arch.
Insertion: Middle part of ramus.
 Deep Layer: origin: deep surface of zygomatic arch.
Insertion: upper part of the ramus and into the coronoid process.

22. FUNCTIONS
• The main function of masseter muscle is
• Elevation of mandible
• Lateral movements of the mandible for efficient chewing and grinding of
the food.
• Unilateral chewing
• Retraction of mandible
BLOOD SUPPLY:-
supplied by massetric artery branch of maxillary artery
- Venous drainage through masseteric vein
NERVE SUPPLY :-
Massetric nerve branch of anterior division of mandibular nerve

23. 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 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.
• Palpate multiple areas of masseter muscle.

25. RELATIONS
• SUPERFICIAL-
• Skin
• Platysma
• Risorius
• Zygomaticus major parotid gland and duct
• Temporal branch of the facial nerve
• DEEP-
• Temporalis
• Ramus of mandible

26. LATERAL PTERYGOID MUSCLE
• It is short thick conical muscle with definite upper and lower heads.
• ORIGIN:
• Upper head- infratemporal surface and crest of greater wing of
sphenoid bone
• Lower head- lateral pterygoid plate
• INSERTION:
• Fibres run backwards and laterally and converge into the Pterygoid
fovea on the anterior surface of neck of mandible.
• Anterior margin of articular disc and capsule of TMJ
• NERVE SUPPLY: Pterygoid branch of Trigeminal nerve.
• BLOOD SUPPLY:- Perygoid branch of maxillary artery
- Ascending palatine artery

28. FUNCTIONS
• Depress the mandible to open mouth
• Lateral and medial pterygoid of both sides contract to protrude the
mandible.
• When contract alternatively producing chewing movements
PALPATION
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

29. RELATIONS
• SUPERFICIAL
• Masseter
• Ramus of mandible
• Tendon of temporalis
• Maxillary artery
• DEEP
• Mandibular nerve
• Deep head of medial pterygoid
• Middle meningeal artery
• Sphenomandibular ligament

30. MEDIAL PTERYGOID MUSCLE
• This is quardrilateral muscle having a small superficial head and a large
deep head which forms the major part of muscle
• ORIGIN and INSERTION:
• superficial head from the maxillary tuberosity., deep head from medial
surface of lateral pterygoid plate and part of palatine bone
• Insertion is seen on the medial angle of the mandible
• BLOOD SUPPLY: By facial artery
• by lingual vein
• NERVE SUPPLY:branch of main trunk of mandibular nerve

32. FUNCTIONS
• Elevates the mandible
• Closes the jaw
• Helps in side to side movement
PALPATION
-Gently palpate them on the medial aspect of the jaw.
-simultaneously from both inside and outside the mouth.
APPLIED ANATOMY
- During improper inferior alveolar nerve block, the needle may prick and
irritate the muscle causing spasm and consequently Trismus

34. RELATIONS
• SUPERFICIAL-
• Upper part of muscle is separated from the lateral pterygoid
muscles by;
• LATERAL PTERYGOID PLATE
• LINGUAL NERVE
• INFERIOR ALVEOLAR NERVE
• Lower part of muscle is separated from the
• RAMUS OF MANDIBLE
• MAXILLARY ARTERY
• SPHENOMANDIBULAR LIGAMENT

35. • DEEP
• Superior constrictor of pharynx
• Styloglossus
• Stylopharyngeous

36. ACCESSORY MUSCLES OF MASTICATION
• SUPRAHYOID INFRAHYOID
• Digastric Sternohyoid
• Stylohyoid Thyrohyoid
• Mylohyoid Omohyoid
• Geniohyoid

37. DIGASTRIC
• Two bellies united by Tendon
• Origin anterior belly- digastric fossa
present lateral to the symphysis menti on
lower border of mandible.
• Posterior belly- mastoid notch on temporal
bone
• INSERTION: Intermediate tendon ( hyoid
bone)
• ARTERY: Anterior belly- Sub mental
branch of facial artery
• Posterior belly- occipital artery
• NERVE:
• anterior belly- mandible division of the
trigeminal nerve via the mylohyoid nerve;
• Posterior belly - by facial nerve

39. STYLOHYOID
• Thin muscle sheet
• It accompanies the posterior belly of digastric
• ORIGIN: middle of the posterior surface of styloid process.
• INSERTION: junction of the body and greater cornu of hyoid
bone anteriorly.
• ACTION: draws the hyoid bone upwards and backwards.
• NERVE SUPPLY: Facial nerve

40. GENIOHYOID MUSCLE
Short and narrow muscle lies above mylohyoid
ORIGIN: Inferior mental spine
INSERTION: Anterior surface of body of hyoid
bone
ARTERY: Facial Artery
NERVE: C1 via hypoglossal nerve
• ACTION: - Geniohyoid elevates the hyoid bone
and draws it forward, thus acting as a partial
antagonist to stylohyoid.
• -when the hyoid bone is fixed it depresses the
mandible

41. MYLOHYOID MUSCLE
Flat triangular muscle
ORIGIN: Mylohyoid line of mandible
INSERTION: Middle and anterior fibres into median
raphae. Posterior fibres body of hyoid bone
ARTERY: Mylohyoid branch of inferior alveolar artery
NERVE; Mylohyoid nerve, from inferior alveolar branch
of mandibular nerve
ACTIONS: the secondary role of this muscle is evident as
a depressor seen in action when mouth is to be opened
against resistance.
• It elevates the floor of mouth to help in deglutition.

42. STERNOHYOID MUSCLE
• ORIGIN: Posterior surface of manubrium deep
to sternohyoid
• Adjoining part of medial end of ist coastal
cartilage
• INSERTION: Oblique line of thyroid cartilage
below thyrohyoid
• ARTERIAL SUPPLY: Superior thyroid artery
• NERVE SUPPLY: Ansa cervicalis (C2, C3)
• ACTION: depression of larynx

43. THYROHYOID MUSCLE
• ORIGIN: Upper part of oblique line on thyroid
cartilage
• INSERTION: Lower border of greater cornea of
hyoid bone
• ARTERIAL SUPPLY: Superior thyroid artery
• NERVE SUPPLY: Fibres of c1 via hypoglossal nerve
• ACTION: Depression of hyoid bone

44. •CLINICAL
CONSIDERATIONS

45. BRUXISM
• BRUXISM: Jaw clenching with or without forcible excrusive movements,
where the intensity of the clenching dictates severity (or lack of) grinding.
• CLENCHING: it can occur as a brief rhthmic strong contractions of the
jaw muscles during ecentric lateral jaw movements, or in maximum
intercuspation.
• CAUSES:
1- Associated with stressful events
2- Non stress related or hereditary
 Bruxism may lead to
- tooth wear
- fracture of the teeth or restoration
- uncosmetic muscle hypertrophy
 TREATMENT: - cornoplasty
- maxillary stabilization appliance

46. TETANUS
• Caused by exotoxins of gram positive bacillus Clostridum tetani
• Disease of the nervous system characterized by intense activity of motor
neuron and resulting in severe muscle spasm.
CLINICAL FEATURES:
• Pain and stiffness in the jaw and neck muscles, with muscle rigidity
producing trismus and dysphagia.
TREATMENT:
• All patients should receive antimicrobial drugs
• Active and passive immunization.
• Surgical wound care.
• Anticonvulsant if indicated

47. Stylomandibular Ligament Strain-
This is usually felt as a sharp to aching pain in the region
behind the jaw bone and below the ear. It can be result of bad
bite or from a traumatic injury.
Temporal strain Tendonitis-
This can occur when there is chronic strain from the temporalis
muscle pulling on the tendon that attaches to the mandible.
This can cause sharp headaches in the temples,just to the sides
of the eyes.

48. Okeson’s classification ofMasticatory muscle disorders
• Myofascial pain
• Myositis
• Myospasm
• Local myalgia

49. Myofascial pain
• First described by TRAVELL and RINZLER in 1952.
• In 1969 LASKIN described Myofascial Pain Dysfunction Syndrome
• Regional, dull aching muscle pain and presence of localized tender
sites( trigger points) in muscle, tendon or fascia
• Pathogenesis of myofascial pain is not confirmed.
DIAGNOSTIC CRITERIA
Regional dull, aching pain aggravated by mandibular function
when the muscles of mastication are involved.
Hyperirritable sites(trigger points) frequently palpated with in a taut
band of muscle tissue or fascia;
Greater than 50% reduction of pain with vapocoolant spray or local
anesthetic injection on the trigger point followed by stretch.

50. TREATMENT
Reassurance
• Spray and stretch- flouromethane spray anesthetizes area
allows patient to stretch the muscle in spasm
• Soft diet
• NSAIDS
• Discontinuation of parafunctional habits
• DIAZEPAM 2mg tds-2 weeks (anxiety reducing and muscle
relaxing

51. MYOSITIS
• This disorder is characterized by inflammation of the muscle
due to a spreading infection, external muscle trauma or muscle
strain.
CLINICAL FEATURES-
• Acute pain with in the muscle which may additionally be
swollen and red with an overlying increased temperature.
• The muscle is tender to palpation and may cause a limited
range of motion.

52. Myofascial pain referred from the Masseter muscle
• Trigger points located at sites in the superficial layer of the
Masseter muscle refer to the posterior mandibular and
maxillary teeth , the jaw and the face.
TOOTHACHE is the common complaint from this source.

53. Myofascial pain referred from the temporal muscle
• The reference zone of the temporalis muscle includes all the
maxillary teeth and upper portion of face.
• Headache and Toothache are the commonly complaints.

54. Myofascial pain referred from Medial pterygoid
muscle
• The reference zone for the medial pterygoid muscle includes
the posterior part of mouth and throat. As well as the
tempromandibular and intra auricular areas.

55. Myofascial pain referred from Lateral Pterygoid
muscle
• The lateral pterygoid muscle can not be adequately palpated,
local or referred pains can be provoked only by isometric
contraction of the corresponding muscle.
• The lateral pterygoid muscle pain can radiate to the TMJ and
superior lateral pterygoid muscle refer to zygomatic area.

56. Myofascial pain referred from Digastric muscle
• Myofascial pain in the Anterior belly of digastric muscle often
cause referred pain in the lower incisors.
• Pain felt behind the angle of the mandible and below the ear
common referred site for a trigger point in the posterior
digastric muscle

57. MPDS-Myofascial pain dysfuction syndrome
SYNONYMS
• TMJ pain dysfunction dyndrome
• Maticatory myalgia syndrome
• Costen’s syndrome
Definition- it is pain referred from a localized tender area or
trigger pont in a taut band of skeletal muscle.
ETIOLOGY:
Trauma
Muscular overextension
Muscular over contraction
Muscle fatigue

58. • CLINICAL FEATURES-
• Pain of unilateral origin
• Diffused and less localized
• Patient is unable to identify exact site involved
• Masseter and lateral pterygoid
• Deviation to unaffected site
• Pain is constant more severe in morning
• Gradually worsens as day progresses
• Aggravated by chewing and excessive eating
• Referred to cervical region
• Inability to open mouth

59. TREATMENT
• Removal of the cause
• Diet modification
• Injection on trigger point
• Pharmacotherapy
• Psychotherapy
• Acupuncture
• Moist heat application

60. CONCLUSION
 The masticatory muscles include a vital part of the orofacial
structure and are important both functionally and structurally.
 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 mechanisms of
these muscles are basic to understand the movements.

61. REFERENCES
• Mahindra Kumar Anand- Human Anatomy -3rd edition
• Gray’s Anatomy-38th edition
• BD Chaurasia’s Human Anatomy volume 3- 5th edition