1. MUSCLES OF MASTICATION Described in detail .pptx

Description of muscles of mastication

1. MUSCLES OF MASTICATION DR. SUSHMITA S. RANE MDS- 1 st YEAR SEMINAR- 1 1/02/2022

2. CONTENT INTRODUCTION BASIC PHYSIOLOGY OF MUSCLE CONTRACTION DEFINITION OF MASTICATION WHAT ARE MUSCLES OF MASTICATION DEVELOPMENT OF MUSCLES OF MASTICATION CLASSIFICATION PRIMARY MUSCLES OF MASTICATION ACCESORY MUSCLES OF MASTICATION SUMMARY OF ACTION OF MUSCLES OF MASTICATION MASTICATORY MUSCLE DISORDERS CONCLUSION REFERENCES

3. INTRODUCTION Muscles are contractile tissues that bring about movements Considered as motors of the body as they produce force and motion

4. The Muscular system in vertebrates is classified based on: STRIATIONS CONTROL FUNCTION Striated Voluntary Skeletal Non Striated Involuntary Cardiac Smooth

5. Skeletal Muscle Forms 40-50% of body mass Skeletal muscles anchored to the bones by the tendons, provides support and gives form to the body Capable of powerful contractions Innervated by somatic and brachial motor nerves Parts of skeletal muscle: 1)fleshy part- belly 2)fibrous part(2 ends) -tendon or aponeurosis

6. BASIC PHYSIOLOGY OF MUSCLE CONTRACTION Ultrastructure of muscle shows the presence of 4 protein molecules(Contractile elements) MYOSIN ACTIN TROPONIN TROPOMYOSIN Sarcomere is defined as the structural and functional unit of a skeletal muscle

7. An action potential arrives at the neuromuscular junction Acetyl Choline is released, binds to the receptors This opens sodium ion channels, leading to an action potential in sarcolemma The action potential travels along the T Tubules (transverse tubules) Entrance of action potential in cisternae of L-tubules and release of large amount of calcium ions

8. This Calcium binds to troponin, which moves the tropomyosin away from actin, exposing the active sites of actin molecule Attachment of Myosin head to Actin POWER STROKE- Tilting of Myosin head and dragging of actin filament This leads to CONTRACTION OF MUSCLE I n relaxed state , Troponin holds tropomyosin with acti n and tropomyosin covers all active sites of actin molecules

9. DEFINITION OF MASTICATION Mastication is defined as the rhythmic opposition and separation of jaws with the involvement of teeth, lips, cheek and tongue for chewing of food in order to prepare it for swallowing and digestion

10. WHAT ARE THE MUSCLES OF MASTICATION Muscles of mastication are the group of skeletal muscles that help in movement of the mandible during chewing and speech

11. FUNCTIONS OF MUSCLES OF MASTICATION To move mandible Secure and stabilize mandibular positions Determine directions of mandibular movements

12. DEVELOPMENT OF MUSCLES OF MASTICATION The muscular system develops from the intra embryonic mesoderm They develop from the embryonic cells called myoblast 5th-6Th week Primitive cells form and differentiate

13. 7th week Mandibular arch mass enlarges Cells migrates to the areas of formation of the 4 major muscles of mastication 10th week Muscle mass well organized Nerve mass gets incorporated

14. PHARYNGEAL ARCH MUSCLES OF MASTICATIONS NERVE AND ARTERY 1 st Arch Mandibular Arch Masseter Medial Pterygoid Lateral Pterygoid Temporalis Mylohyoid Anterior belly of Digastric Mandibular Nerve (branch of Trigeminal Nerve) Maxillary Artery 2 nd Arch Hyoid Arch Posterior Belly Of Digastric Facial Nerve Occipital Myotomes Geniohyoid Hypoglossal Nerve

15. CLASSIFICATION OF MUSCLES OF MASTICATION PRIMARY MUSCLES ACCESSORY MUSCLES (Suprahyoid Muscles) Masseter Digastric Temporalis Stylohyoid Lateral Pterygoid Mylohyoid Medial Pterygoid Geniohyoid

16. FUNCTIONAL CLASSIFICATION JAW ELEVATORS JAW DEPRESSORS Masseter Lateral Pterygoid Temporalis Digastric Medial Pterygoid Mylohoid Geniohyoid

17. PRIMARY MUSCLES OF MASTICATION

18. MASSETER MUSCLE Quadrilateral muscle Partly fleshy, partly tendinous Covers the lateral part of ramus of mandible Multi- pentate arrangement of fibres

19. Consists of 3 layers- LAYER ORIGIN INSERTION Superficial (Largest) From anterior 2/3 rd of lower border of zygomatic arch & adjoining zygomatic process of maxilla Into the lower part of lateral surface of ramus of mandible Middle From lower border of posterior 1/3 rd of zygomatic arch Into the central part of ramus of mandible Deep From deep surface of zygomatic arch Into rest of the ramus of the mandible

20. NERVE SUPPLY- Masseteric Nerve (anterior division of mandibular nerve) BLOOD SUPPLY- Arterial- Masseteric branch of Maxillary artery Venous-Venous drainage through Masseteric vein

21. SUPERFICIAL RELATIONS Parotid gland & duct 4 branches of facial nerve Temporal Zygomatic Buccal Marginal mandibular Transverse facial artery

22. DEEP RELATIONS The insertion of the temporalis muscle Masseteric nerves and vessels Ramus of the mandible

23. ANTERIOR RELATIONS Buccal artery(branch of maxillary artery) Buccal nerve (branch of mandibular nerve) Buccinator muscles Buccal pad of fat

24. FUNCTIONS - Elevates the mandible to close the mouth & to occlude the teeth in mastication Small lateral movements Protrusion

25. PALPATION Patient is asked to clench their teeth The practitioner uses both hands to palpate the masseter muscles on both sides extra orally Palpation is done along- Origin of masseter bilaterally along the zygomatic arch Continue to palpate down the body of the mandible to where the masseter is attached

26. APPLIED ANATOMY Most powerful muscle for the closure of the mandible Masseter is sometimes the target of plastic jaw reduction surgery This muscle commonly undergoes Hypertrophy in Bruxism

27. MASSETER REFLEX/ MANDIBULAR REFLEX/ JAW JERK REFLEX Neurological examination of jaw jerk reflex Keeping the patient’s mouth slight open, Examiner places index finger on chin of the patient and taps the finger with reflex hammer T he masseter stretch provides upward movement of the mandible Indicative of a lesion of the Trigeminal nerve

28. TEMPORALIS MUSCLE Located in the temporal region Fan shaped Largest masticatory muscle

29. ORIGIN Temporal fossa - from the inferior temporal line Temporal Fascia INSERTION Margins & deep surface of the coronoid process Anterior border of the ramus of mandible

30. BLOOD SUPPLY Deep temporal arteries ( branch of maxillary artery) and Superficial temporal artery Superficial temporal vein & middle temporal vein NERVE SUPPLY Two deep temporal branches (branch of Mandibular nerve)

31. FUNCTIONS Anterior fibres - E levate the mandible Posterior fibres - R etract the mandible Middle fibres - E levate and retract the mandible Posterior fibres draw the mandible backwards after it has been protruded Contributes side to side grinding movement

32. SUPERFICIAL RELATIONS Skin Superficial fascia Auricularis muscle (anterior & superior) Temporal fascia Superficial temporal vessels Auriculotemporal nerve Zygomatic arch Masseter muscle

33. DEEP RELATIONS Temporal fossa Maxillary artery and pterygoid plexus of veins Buccal nerve & artery Deep temporal vessels & nerve M edial and lateral pterygoid Buccinator

34. PALPATION Divided into 3 parts that are palpated separately Patient is asked to clench The anterior region is palpated above the zygomatic arch, anterior to the TMJ The middle region is palpated directly above the TMJ & superior to the zygomatic arch The posterior region is palpated above and behind the ear ANTERIOR MIDDLE POSTERIOR

35. APPLIED ANATOMY The temporalis muscle is accessible on the temples and can be seen and felt contracting while the jaw is clenched and unclenched The temporal muscle is covered by temporal fascia, also known as temporal aponeurosis Sudden contraction of temporalis will result in coronoid fracture , which is rare

36. MEDIAL PTERYGOID Quadrilateral Muscle 2 heads- Small Superficial head Large Deep head

37. LAYER ORIGIN INSERTION Superficial Head From tuberosity of maxilla and adjoining bone Roughened area on the medial surface of angle and adjoining ramus of mandible, below and behind the mandibular foramen & mylohyoid groove Deep Head From medial surface of lateral pterygoid plate & adjoining process of palatine bone

38. NERVE SUPPLY Nerve to medial pterygoid (branch of main trunk of Mandibular nerve) BLOOD SUPPLY Pterygoid branch of 2 nd part of Maxillary artery Lingual Vein

39. FUNCTIONS Elevates mandible Help protrude mandible Produce side to side movements

40. SUPERFICIAL RELATIONS UPPER PART OF MUSCLE SEPARATED FROM LATERAL PTERYGOID BY- Lateral Pterygoid Plate Lingual Nerve Inferior Alveolar Nerve UPPER PART OF MUSCLE SEPARATED FROM RAMUS OF MANDIBLE BY Lingual Nerve Inferior Alveolar Nerve Maxillary artery Sphenomandibular ligament

41. DEEP RELATIONS Tensor Veli Palatini Superior Constrictor muscle of Pharynx Styloglossus Muscle Stylopharyngeus Muscle

42. PALPATION Palpated by placing the index finger on the lateral aspect of the pharyngeal wall of the throat This palpation is difficult and sometimes uncomfortable for the patient The muscle contracts as the teeth are coming in contact

43. APPLIED ANATOMY Is sometimes involved in MPDS i.e MYOFASCIAL PAIN DYSFUNCTION SYNDROME Trismus following inferior alveolar nerve block is mostly due to involvement of medial pterygoid muscle When the medial pterygoid muscle is hypertonic , the patient is aware of a fullness in the throat and occasional pain on swallowing

44. LATERAL PTERYGOID Occupies primarily a horizontal position Thick, short, conical and triangular muscle 2 heads Superior head Inferior head

45. LAYER ORIGIN INSERTION SUPERIOR HEAD From infratemporal surface and crest of greater wing of sphenoid bone Pterygoid fovea on the anterior surface of neck of mandible INFERIOR HEAD From lateral surface of lateral pterygoid plate Anterior margin of articular disk and capsule of TMJ

46. NERVE SUPPLY Lateral pterygoid nerve (Anterior branch of Mandibular nerve) BLOOD SUPPLY Pterygoid branches of Maxillary artery Ascending palatine artery of facial artery Lingual vein

47. FUNCTIONS Depresses mandible to open mouth,with suprahyoid muscle Lateral and medial pterygoids protrude mandible and depresses chin Right lateral pterygoid and right medial pterygoid turn the chin to left side as part of grinding movements

48. SUPERFICIAL RELATIONS Masseter Ramus of Mandible Tendon of Temporalis muscle Maxillary artery

49. DEEP RELATIONS Middle meningeal artery Mandibular nerve Sphenomandibular ligament Deep head of medial pterygoid

50. STRUCTURES EMERGING FROM UPPER BORDER: Deep Temporal Nerves Masseteric Nerve

51. STRUCTURES EMERGING FROM LOWER BORDER: Lingual nerve Inferior Alveolar Nerve Middle Meningeal Artery (passes upwards)

52. STRUCTURES PASSING THROUGH THE GAP BETWEEN THE TWO HEADS : Maxillary Artery Buccal Branch Of Mandibular Nerve

53. PALPATION Place the forefinger over the buccal area of the maxillary 3 rd molar region and exerting pressure in a posterior, superior and medial direction behind the maxillary tuberosity

54. APPLIED ANATOMY Most commonly involved in MPDS Unilateral failure- results in deviation of mandible towards the affected side on opening Bilateral failure- limited opening, loss of protrusion, loss of full lateral deviation In patients with occlusal interferences on the non working side , the lateral pterygoid on the opposite side of the interference becomes painful

55. ACCESSORY MUSCLES

56. DIGASTRIC Diagastric has 2 bellies joined by intermediate tendon ORIGIN - Anterior belly-From digastric fossa Posterior belly-from mastoid notch of temporal bone INSERTION - Both ends meet at the intermediate tendon is held by a fibrous pulley to the hyoid bone perforating stylohyoid muscle FUNCTION- Depression of the jaw Elevates the hyoid bone

57. MYLOHYOID Flat, triangular muscle Forms floor of the mouth ORIGIN- Mylohyoid line of Mandible INSERTION- Posterior fibres - Body of Hyoid bone Anterior fibers and middle fibers– On median raphae between mandible and h yoid bone FUNCTION - Helps in depression of the mandible Elevates the hyoid bone Elevates the floor of the mouth during deglutition

58. GENIOHYOID Short, narrow muscle Lies above mylohyoid ORIGIN - Genial tubercle INSERTION - Anterior surface of body of hyoid bone FUNCTIONS Carry the hyoid bone & tongue upward during deglutition

59. STYLOHYOID Small muscle ORIGIN - posterior surface of styloid process INSERTION - junction of body and greater cornua of hyoid bone FUNCTION- Pulls hyoid bone upward and backwards

60. BUCCINATOR FUNCTIONS- Flatten cheek against gums and teeth Prevent accumulation of food in the vestibule of the mouth Brings food to the occlusal table during mastication Fib res origin Insertion Upper From maxilla , opposite molar teeth straight to the upper lip Middle from P terygo mandibular R aphae Decussate before passing to the lips lower from mandible , opposite molar teeth straight to the lower lip Muscle of the cheek (whistling muscle)

61. SUMMARY OF ACTION OF MUSCLES OF MASTICATION ACTION PRIME MOVERS ANTAGONIST ELEVATION MASSETER MEDIAL PTERYGOID TEMPORALIS LATERAL PTERYGOID DEPRESSION LATERAL PTERYGOID DIGASTRIC GENIOHYOID MYLOHYOID ELEVATOR GROUP OF MUSCLES PROTRUSION LATERAL PTERYGOID MEDIAL PTERYGOID MASSETER DIGASTRIC POSTERIOR TEMPORAL FIBRES RETRUSION POSTERIOR & MEDIAL TEMPORAL FIBRES DIGASTRIC MASSETER LATERAL PTERYGOID

62. SUMMARY OF ACTION OF MUSCLES OF MASTICATION LATEROTRUSION- Lateral and Medial Pterygoids ELEVATION OF HYOID BONE- Posterior belly of Digastric Mylohyoid Geniohyoid

63. MASTICATORY MUSCLE DISORDERS

64. TRISMUS Normal opening of mouth is restricted - Spasm of the muscles Masseter m ore commonly affected CAUSES- Due to infections or other causes likes trauma, inflammation, tetany etc CLINICAL FEATURE- Difficulty in eating and swallowing Oral hygiene issues Joint immobilization TREATMENT - Removal of the cause Heat therapy Warm saline rinses NSAIDS Physiotherapy

65. BRUXISM Bruxism is the clenching or grinding of the teeth when the individual is not chewing or swallowing OCCURS AS- Brief rhythmic strong contractions of the jaw muscles in eccentric lateral jaw movements Maximum intercuspation- clenching Bruxism leads to tooth wear fracture of tooth and restoration muscle hypertrophy TREATMENT - Stabilization appliance like mouth guard Coronoplasty

66. MYOFACIAL PAIN DYSFUNCTION SYNDROME (MPDS)- It is a pain disorder in which unilateral pain is referred from trigger points in myofascial structures, to muscles of head and neck region No organic lesion clinically TRIGGER POINTS- Caused by stimuli - pressure on muscles creates trigger points Palpation of trigger points leads to POSITIVE JUMP SIGN

67. 4 CARDINAL SIGNS & SYMPTOMS- Pain and discomfort (especially morning hours) Muscle tenderness Joint noises –grating ,clicking, snapping etc Limitation of mandibular movements unilaterally or bilaterally DIAGNOSIS When no clinically detectable organic lesion but with signs and symptoms

68. TREATMENT Mostly self-limiting Conservative management , Psychological counseling Patient education and self care practices Medications- NSAIDS like Ibuprofen (200-600 m g/ three times a day for 7 days) Skeletal Muscle relaxants only for short duration(Diazepam 2 -5 mg or cyclobenzapine 10mg at bedtime can be given for 10days) Ethyl chloride spray or intramuscular local anaesthesia In the affected M uscle c an also give relief , the patient is asked to follow the stretch exercises subsequently 2% lignocaine or 0.0 5 % bupivacaine c an be used Physiotherapy Relaxation techniques-eliminating muscle spasms

69. MYALGIA Muscle pain disorder SYMPTOMS- Localised pain Fatigue while chewing SIGNS- Tenderness on palpation Sometimes limited active vertical range TREATMENT Rest Pain Relievers Cold application to reduce pain and inflammation

70. Occurs rarely and mostly affects masseter & orbicularis oris Enlargement in size of the affected muscle, which shows an asymmetric facial pattern & stiffness in TMJ Associated with hypermobility of the muscles HYPERPLASIA /HYPERTROPHY

71. ATROPHY Decrease in size ETIOLOGY - Disuse and fixation Aging and cachexia Denervation Muscular dystrophies Muscular hypotonias Nutritional disturbances Infections and toxins Vascular changes TREATMENT- Physiotherapy Ultrasound therapy Dietary changes DISUSE ATROPHY OF MASSETER MUSCLE

72. MYASTHENIA GRAVIS Disease of Neuromuscular junction Acquired autoimmune disorder clinically characterised by weakness of skeletal muscles and fatigability on exertion

73. CLINICAL FEATURES Rapidly developing weakness in voluntary muscles following minor activity Difficulty in mastication and deglutition , drooping of jaw. Speech slow and slurred Disturbance in taste sensation TREATMENT Physostigmine - intramuscularly. Immunosuppressant-Cyclosporin

74. MYOSITIS OSSIFICANS Myositis ossificans is  a condition where bone tissue forms inside muscle or other soft tissue after an injury . ETIOLOGY- Microbial, physical, chemical injuries ORAL MANIFESTATIONS- Masseter and temporalis more commonly affected Have difficulty in opening mouth TREATMENT- Surgical excision of localised inflammatory tissue which is calcified Prognosis is good

75. FASCIAL SPACE INFECTION Secondary spaces are associated with the muscles of mastication Namely- Masseteric, Pterygomandibular, Superficial, Infratemporal & Deep Temporal ETIOLOGY- Odontogenic infections, trauma, oral malignancies etc CLINICAL MANIFESTATIONS- Abcess formation and Swelling Trismus Pyrexia & Malaise

76. TREATMENT- Intraoral or Extraoral incision Antibiotic coverage Hospitalisation may be required in severe cases

77. CONCLUSION The clinician should have a through knowledge about these muscles as they have a prime function in mastication and deglutition for providing nutrition to the body Pathologies in these muscles may affect the patient and the treatment plan we formulate for the patient

78. REFERENCES BD Chaurasia , Human Anatomy (head, neck, face) part 3, 5 th Edition Shafer, Hine, Levy; Shafer’s textbook of Oral pathology, 7 th edition Nelson, Ash; Wheeler’s Dental Anatomy, Physiology and Occlusion, 9 th edition Inderbir Singh, G P Pal; Human Embryology, 9 th edition

79. THANK YOU