muscles of mustication: 3d representation

1. NAME: Dr. SHRUTI SUDARSANAN
DEPT OF PEDODONTICS AND PREVENTIVE DENTISTRY
SEMINAR TOPIC: MUSCLES OF MASTICATION

2. MUSCLESOF
MASTICATION

3. INTRODUCTION
The muscles of mastication move the mandible during mastication and speech.
MUSCLESOF
MASTICATION
Masseter
Temporalis
Lateral pterygoid
Medial pterygoid

4. DEVELOPMENT
They develop from the mesoderm of the first branchial arch, and are
supplied by the mandibular nerve which is the nerve of that arch.

5. MASSETERMUSCLE
•Quadrilateral
•Lateral surface of Ramus of mandible
•has three layers
• Superficial layer
• Middle layer
• Deep layer

6. MASSETER MUSCLE
Superficial layer :
◦ Origin: Anterior 2/3rd of lower border of
zygomatic arch and adjoining zygomatic
process of maxilla
◦ Fibres : pass downwards and backwards 45
degree
◦ Insertion: Lower part of lateral surface of
mandibular ramus

7. Middle layer :
Origin: Lower border of posterior 1/3rd of
zygomatic arch
Deep layer :
Origin: Deep surface of zygomatic arch
FIBRES: pass vertically downwards
INSERTION: Ramus of mandible

8. Action of masseter muscle
• Elevates the mandible to close the mouth and to occlude the teeth in mastication.
• Superficial fibres cause little protraction

9. Clinical importance of masseter muscle
• Masseter muscle hypertrophy is a rare condition of idiopathic cause
• It clinically presents as an enlargement of one or both masseter muscle
• Most patients complain of facial asymmetry

10. TEMPORALISMUSCLE
Large fan shaped
fills the temporal fossa
Origin
(a)temporal fossa
(b)temporal fascia
FIBRES: Anterior fibres: run vertically
Middle fibres: obliquely
Posterior fibres: horizontally
Insertion
(a) coronoid process
(b)anterior border of ramus of mandible

11. ACTION OF TEMPORALIS MUSCLE
• Elevation of the mandible
• Posterior fibers draw the mandible
backwards after it has been protruded.
• Helps in side to side grinding movement

12. LATERALPTERYGOIDMUSCLE
• Short, Conical
• 2 Heads :- Upper And Lower Head
Origin:
Upper head (small)– from infratemporal
surface & crest of greater wing of sphenoid
bone
Lower head(larger) – from lateral surface of
lateral pterygoid plate

13. MEDIAL PTERYGOID PLATE LATERAL PTERYGOID PLATE
LATERAL
SURFACE
LATERAL
PTERYGOID
MUSCLE
MEDIAL
PTERYGOID
MUSCLE

14. Insertion :
Upper head - pterygoid fovea on the anterior surface of
neck of mandible
Lower head - anterior margin of articular disc & capsule
of TMJ

15. ACTIONS OF LATERAL PTERYGOID
FIBRES: Run backward and laterally
• depresses the mandible
• protrudes it forward for opening of the
jaw
• right lateral pterygoid turn the chin to
left side as part of grinding moments
O
I
O

16. Clinical importance of lateral pterygoid muscle:
• Most commonly involved muscle in Myofacial pain
dysfunction syndrome (mpds)
• Unilateral failure of lateral pterygoid muscle to
contract results in deviation of the mandible toward the
affected side on opening
• Bilateral failure results in limited opening, loss of
protrusion and loss of full lateral deviation

17. MEDIALPTERYGOIDMUSCLE
• Quadrilateral
• Has a small superficial and large deep head

18. Origin :
Superficial head: it arises from the maxillary tuberosity
and adjoining bone
Deep head: from medial surface of lateral pterygoid plate
and adjoining process of palatine bone

19. FIBERS: run backwards, downwards and laterally
Insertion:
Roughened area on the medial surface of angle and
adjoining ramus of the mandible below and behind
the mandibular foramen and mylohyoid bone

20. ACTIONS OF MEDIAL PTERYGOID
 elevates the mandible
 closes the jaw
 helps to protrude the mandible
 Right medial pterygoid with right lateral pterygoid turn the
chin to left side as part of grinding moments

21. Clinical importance :
• commonly involved in MPDS
• Trismus following inferior alveolar nerve block is mostly due to involvement
of medial pterygoid muscle

22. ACCESSORY MUSCLES OF MASTICATION
SUPRAHYOID
Digastric
Stylohyoid
Mylohyoid
Geniohyoid
INFRAHYOID
Sternohyoid
Sternothyroid
Thyrohyoid
omohyoid

23. OKESON’SCLASSIFICATIONOFMASTICATORYMUSCLESDISORDERS
Masticatory Muscle Disorders
1. Protective Co-Contraction
2. Local Muscle Soreness
3. Myofascial Pain
4. Myospasm
5. Chronic Centrally Mediated Myalgia
Trauma and excessive use
of muscles

24. Protectiveco-contraction
a CNS response to injury or threat of injury.
protective muscle splinting.
 In the presence of an injury or threat of injury, normal sequencing of muscle activity
seems to be altered to protect the threatened part from further injury.
This coactivation of antagonistic muscles is thought to be a normal protective or
guarding mechanism .
 If protective co-contraction continues for several hours or days, the muscle tissue can
become compromised and a local muscle problem may develop

25. .

26. Localmusclesoreness
Local muscle soreness is a primary, noninflammatory, myogenous pain disorder (i.e.,
noninflammatory myalgia).
 first response of the muscle tissue to prolonged co-contraction.
Although co-contraction represents a CNS-induced muscle response, local muscle
soreness represents a condition characterized by changes in the local environment of
the muscle tissues.
These changes are characterized by the release of certain algogenic sub-stances (i.e.,
bradykinin, substance P, and even histamine) that produce pain

27. Local muscle soreness presents clinically with
muscles that are tender to palpation
increased pain with function.
Structural dysfunction is common
limited mouth opening results when the elevator muscles are involved.

28. Management
Eliminate any ongoing source of deep pain input (whether dental or other)
Advise the patient to restrict mandibular use to within painless limits
The patient should be encouraged to reduce any nonfunctional tooth contacts
 The patient should be made aware of the relationship between increased levels of
emotional stress and the muscle pain condition
When nighttime clenching or bruxing is suspected (early-morning pain), it is
appropriate to fabricate an occlusal appliance for nighttime
use of a mild analgesic: aspirin, acetaminophen, or another NSAID (i.e., ibuprofen)

29. Myospasms(TonicContractionMyalgia)
involuntary CNS-induced tonic muscle contraction often associated with local metabolic
conditions within the muscle tissues.
it is not as common
History
The patient reports a sudden onset of restricted jaw movement usually accompanied by muscle
rigidity.
Treatment
Myospasms are best treated by reducing the pain and then passively lengthening or stretching the
involved muscle
attempts to eliminate the etiologic factors

30. MyofascialPain(Trigger-PointMyalgia)
Myofascial pain is a regional myogenous pain condition characterized by local areas of
firm, hypersensitive bands of muscle tissue known as trigger points
Clinical characteristics (laskin’s cardinal symptoms) of mpds
 Pain or discomfort anywhere about the head or neck.
 Limitation of motion of the jaw.
 Joint noises– grating, clicking, snapping.
 Tenderness on palpation of the muscles of mastication

31. management
Eliminate any source
If a sleep disorder is suspected, proper evaluation and referral should be made. Often low
dosages of a tricyclic antidepressant, such as 10 to 20 mg of amitriptyline before bedtime, can be
helpful
treatment and elimination of the trigger points. This is accomplished by painlessly stretching the
muscle containing the trigger points. The following techniques can be used to achieve this.
Spray and Stretch
Pressure and Massage
Ultrasound and Electrogalvanic Stimulation
Injection and Stretch

32. LASKIN AND BLOCK 1986
PHASE I THERAPY
psychophysiologic discussion- home therapy (diet & exercise), muscle relaxant &
nsaids (2-4 wks)- 50% resolution
PHASE II THERAPY
•home therapy and medications + bite appliance (2 to 4 wks) 20% to 25%resolution
PHASE III
physiotherapy or relaxation therapy (yoga, biofeedback) (4 to 6 weeks) 10% to 15%
resolution.
PHASE IV
 psychologic counselling

33. CentrallyMediatedMyalgia(ChronicMyositis)
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:
Restrict use of the mandible to within painless limits.
Avoid exercise and/or injections
Disengage the teeth
Begin using an anti-inflammatory medication.
Consider management of sleep

34. TRISMUS
Tonic contraction of the muscles of mastication- (taber’s cyclopedic medical dictionary)
 Reduced mandibular range of motion due to contraction of muscles of mastication
Various criteria for presence of trismus:
 Mouth opening <20mm (jen et. Al., 2002)
 Mouth opening <40mm (nguyen et. Al., 1988)
 Severity scales: mild, >30mm; moderate, 15-30mm; severe, <15mm (thomas et. Al., 1998

35. Treatment:
 Removal of the cause
 Heat therapy
 Warm saline rinses
 Nsaids
 Passive muscle stretching exercises

36. Bruxism is an abnormal repetitive movement disorder
characterized by jaw clenching and tooth gnashing or
grinding. It is classified into two overlapping types: awake
bruxism (AB) and sleep bruxism (SB).
Treatment:
 Coronoplasty
 Maxillary stabilization appliance
 Night guards

37. Diverse methods used in physical therapy improve muscle pain and
activity, mouth opening, oral health, anxiety, stress, depression,
temporomandibular disorder, and head posture in individuals with
bruxism

38. CONCLUSION
 The masticatory muscles include a vital part of the orofacial structures and are important both functionally and
structurally
 Precise movement of mandible by the musculature is required to move the teeth accurately across each other
during function
 The knowledge of the anatomy physiology and mechanism of these muscles are basic to understand the
movements
 It is crucial responsibility of a clinician to recognize each patient’s muscular environment and be aware of the
problems related with excessive or deficient use of muscle and their bearing to the dentition

39. Botulinum toxin (BTX) is a neurotoxin, and its injection
in masticatory muscles induces muscle weakness and
paralysis. This paralytic effect of BTX induces growth
retardation of the maxillofacial bones, changes in
dental eruption and occlusion state, and facial
asymmetry

40. REFERENCES
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