Muscles of mastication

Muscles of mastication

1. MUSCLES OF MASTICATION dr. chaithra prabhu 1st year pg department of prosthodontics vsdc 85

2. CONTENTS INTRODUCTION EMBRYOLOGY PHYSIOLOGY ANATOMY OF MUSCLES OF MASTICATION CLINICAL CONSIDERATONS COORDINATED MUSCLE ACTIVITY PALPATON OF MASTICATORY MUSCLE DISORDERS OF MUSCLES OF MASTICATION CONCLUSION REFRENCES 85

3. INTRODUCTION MUSCLE: An organ that by contraction produces movement of an animal; a tissue composed of contractile cells or fibers that effect movement of an organ or part of the body GPT 9 85

4. EMBRYOLOGY FORMATION OF MUSCLES Skeletal muscles are derived from somites , somitomeres and lateral plate mesoderm Intra embryonic mesoderm divided into Paraxial mesoderm Lateral plate mesoderm Intermediate mesoderm 85 Paraxial mesoderm divided into Somites Somitomeres - head region Human Embryology Inderbir Singh 9 th ed

5. 85

6. CLASSIFICATION OF MUSCLES Muscles may be grouped according to Their location Their histology The way their action is controlled 85

7. ANATOMY AND ULTRA STRUCTURE OF SKELETAL MUSCLE 85

8. GENERAL MECHANISM OF MUSCLE CONTRACTION Action potential ( motor nerve) Neurotransmitter Ach release Opening of acetylcholine gated channels Na++ diffusion into interior of muscle fiber Action potential along muscle fiber(depolarization) Opens Ca++ release channels in sarcoplasmic reticulum at the center of muscle fiber 85 CONTRACTION

9. MASTICATION ‘The act of chewing foods’ It represents the initial stage of digestion, when food is broken down into small particle sizes for ease of swallowing - JEFFERY P OKESON The process of chewing food for digestion and swallowing -GPT 9 85

10. MASTICATORY SYSTEM Extremely complex primarily made of bones, muscles, ligaments and teeth. Functional unit of the body responsible for chewing, speaking, swallowing Intricate neurologic controlling mechanism. Maximize function while minimizing damage to any structure. 85 Management of TMJ disorders and occlusion Jeffrey P Okeson 2 nd ed

11. ANATOMY OF MUSCLES OF MASTICATION Primary Muscles of mastication are Masseter Temporalis Lateral pterygoid Medial pterygoid 85

12. Masseter Quadrilateral shape Has three layers Superficial layer Middle layer Deep layer 85 B D Chaurasia’s Human Anatomy vol 3 6 th ed

13. ORIGIN Superficial Layer : anterior 2/3rd of the lower border of the zygomatic arch and the adjoining zygomatic process of the maxilla Middle Layer : from lower border of posterior 1/3 rd of the zygomatic arch Deep Layer : from deep surface of zygomatic arch 85 B D Chaurasia’s Human Anatomy vol 3 6 th ed

14. INSERTION Superficial Layer : lower part of lateral surface of ramus of mandible Middle Layer : central part of ramus of mandible Deep Layer : rest of the ramus of the mandible 85 B D Chaurasia’s Human Anatomy vol 3 6 th ed

15. NERVE AND BLOOD SUPPLY Nerve supply Massetric nerve from anterior division of mandibular nerve Blood supply Massetric branch from the 2 nd part of the maxillary artery 85 B D Chaurasia’s Human Anatomy vol 3 6 th ed

16. ACTIONS Elevation of the mandible Superficial fibers cause protrusion 85 B D Chaurasia’s Human Anatomy vol 3 6 th ed

17. Clinical considerations in prosthodontics MASSETER It affects the border of mandibular denture on the disto - buccal corner of the buccal flange Its action pushes the buccinators fibers against the denture border For this reason the border must converge rapidly towards the retro-molar pad 85 Boucher’s prosthodontic treatment for edentulous patients 9 th ed

18. 85

19. TEMPORALIS ORIGIN Temporal fossa, excluding zygomatic bone Temporal fascia 85 ANTERIOR POSTERIOR MIDDLE B D Chaurasia’s Human Anatomy vol 3 6 th ed

20. INSERTION Margins and deep surface of coronoid process Anterior border of ramus of mandible 85 B D Chaurasia’s Human Anatomy vol 3 6 th ed

21. NERVE AND BLOOD SUPPLY Nerve supply Two deep temporal branches from anterior division of mandibular nerve Blood supply Deep temporal branch from the 2 nd part of the maxillary artery 85 B D Chaurasia’s Human Anatomy vol 3 6 th ed

22. ACTION Elevation of mandible Side to side movement Post. Fibers retract the protruded mandible 85 B D Chaurasia’s Human Anatomy vol 3 6 th ed

23. Clinical considerations in prosthodontics TEMORALIS Temporalis muscle does not participate in biting force when the mandible is in protrusion Therefore the action of this muscle is sometimes used as a test to determine whether the patient is closing in centric relation No bulging can be felt with fingers when mandible is in protrusion 85 Boucher’s prosthodontic treatment for edentulous patients 9 th ed

24. LATERAL PTERYGOID Short conical Upper head Lower head 85 B D Chaurasia’s Human Anatomy vol 3 6 th ed

25. ORIGIN Upper head : from infra temporal surface and the crest of the greater wing of the sphenoid bone Lower head : from lateral surface of the lateral pterygoid plate 85 Origin is medial to insertion B D Chaurasia’s Human Anatomy vol 3 6 th ed

26. INSERTION Pterygoid fovea on the ant. surface of neck of mandible Anterior margin of the articular disc and capsule of TMJ 85 Insertion is posterolateral and at slightly higher level than origin B D Chaurasia’s Human Anatomy vol 3 6 th ed

27. NERVE AND BLOOD SUPPLY Nerve supply Lateral pterygoid branch from the anterior division of the mandibular nerve Blood supply Pterygoid branch from the 2 nd part of the maxillary artery 85 B D Chaurasia’s Human Anatomy vol 3 6 th ed

28. ACTION Depresses the mandible along with the suprahyoid Lateral and medial pterygoids protrude the mandible Right lateral pterygoid and right medial pterygoid turn the chin to left side 85 B D Chaurasia’s Human Anatomy vol 3 6 th ed

29. MEDIAL PTERYGOID Quadrilateral Superficial head Deep head 85 B D Chaurasia’s Human Anatomy vol 3 6 th ed

30. ORIGIN Superficial head : from maxillary tuberosity and the adjoining bone Deep head : from medial surface of the lateral pterygoid plate 85 B D Chaurasia’s Human Anatomy vol 3 6 th ed

31. INSERTION On the medial surface of angle and adjoining ramus of the mandible, below and behind the mandibular foramen and mylohyoid groove 85 B D Chaurasia’s Human Anatomy vol 3 6 th ed

32. NERVE AND BLOOD SUPPLY Nerve supply Nerve to the medial pterygoid from the main trunk Blood supply Pterygoid branch from the 2 nd part of the maxillary artery 85 B D Chaurasia’s Human Anatomy vol 3 6 th ed

33. ACTIONS Elevates mandible Helps protrude mandible Right medial pterygoid with right lateral pterygoid turn the chin to the left side 85 B D Chaurasia’s Human Anatomy vol 3 6 th ed

34. ACESSORY MUSCLES Digastric Mylohyoid Geniohyoid 85

35. DIGASTRIC Anterior belly Posterior belly ORIGIN Anterior belly : from digastric fossa of the mandible Posterior belly : from the mastoid notch of the temporal bone 85 United by an Intermediate tendon B D Chaurasia’s Human Anatomy vol 3 6 th ed

36. INSERTION Both heads meet at the intermediate tendon which perforates stylohyoid and is held by a fibrous pulley to the hyoid bone 85 B D Chaurasia’s Human Anatomy vol 3 6 th ed

37. ACTION Depresses the mandible It is secondary to the lateral pterygoid Elevates the hyoid bone Nerve supply by Nerve to the mylohyoid – anterior belly Facial nerve – posterior belly 85 B D Chaurasia’s Human Anatomy vol 3 6 th ed

38. MYLOHYOID Flat triangular muscle Forms the floor of the mouth 85 B D Chaurasia’s Human Anatomy vol 3 6 th ed

39. ORIGIN From the mylohyoid line INSERTION Anterior and middle fibers into the median raphe Posterior fibers into the body of the hyoid bone 85 B D Chaurasia’s Human Anatomy vol 3 6 th ed

40. ACTION Elevates the floor of the mouth in the first stage of deglutition Depresses the mandible Elevates the hyoid bone nerve supply by Nerve to the mylohyoid 85 B D Chaurasia’s Human Anatomy vol 3 6 th ed

41. Clinical considerations in prosthodontics MYLOHYOID Among the accessory muscle this is the only muscle that affects the denture borders Mainly helps in elevation of the floor of the mouth during swallowing Consideration of the act of swallowing is extremely important for establishing the stability of the mandibular denture 85 Boucher’s prosthodontic treatment for edentulous patients 9 th ed

42. 85 When mylohyoid muscle is tense- It is pulled away from the mandible, lingual flange can not impinge on muscle without denture being displaced at time of swallowing. When mylohyoid muscle is relaxed- It falls down along the lingual surface of mandible, even below the mylohyoid ridge. Incorrect impression & lingual flange extending into undercut causes restriction of muscle movement and leads to displacement of denture. Boucher’s prosthodontic treatment for edentulous patients 9 th ed

43. 85 In premolar region- mylohyoid is deep to the sublingual gland and doesn’t affect the denture border in this region Lingual flange should extend just beyond the palpable portion of the ridge but not into the undercut ----- lack of direct pressure on the ridge------- no muscle soreness Above ------ no seal Boucher’s prosthodontic treatment for edentulous patients 9 th ed

44. GENIOHYOID Short and narrow muscle lies above medial part of mylohyoid 85 B D Chaurasia’s Human Anatomy vol 3 6 th ed

45. ORIGIN From the inferior genial tubercle INSERTION Anterior surface of body of hyoid bone 85 B D Chaurasia’s Human Anatomy vol 3 6 th ed

46. ACTION Elevates hyoid bone Depresses mandible when hyoid is fixed Nerve supply C1 through hypoglossal nerve 85 B D Chaurasia’s Human Anatomy vol 3 6 th ed ELEVATORS Masseter Temporalis Medial pterygoid DEPRESSORS Lateral pterygoid Digastric Geniohyoid Mylohyoid PROTRACTORS Lateral pterygoid assisted by medial pterygoid RETRACTORS Deep part of masseter Post. Part of temporalis

47. CORDINATED MUSCLE ACTIVITY - Essential goal for all muscle activity We cannot keep teeth in a stable position where muscle does not want them to be Muscle - dominant determinant Compressive force of jaw closing musculature- 975lbs Maximum biting loads Females- 79-99lbs Males- 118-142lbs 85 Functional occlusion from TMJ to smile design Peter E Dawson

48. What is it? Refers to the timely release of a muscle or group of muscle as contraction of antagonistic muscle takes place 85 Functional occlusion from TMJ to smile design Peter E Dawson

49. Coordinated Muscle Function During Jaw Opening 85 Functional occlusion from TMJ to smile design Peter E Dawson

50. Coordinated muscle function during jaw closure 85 LA- Passive In absence of deflective occlusal interference, it stays passive even during firm clenching Functional occlusion from TMJ to smile design Peter E Dawson

51. Coordinated muscle function at maximum inter- cuspation 85 goal of occlusal harmony - release of inferior lateral pterygoid Possible when seating of condyle-disk assemblies completely into their fossae superior lateral pterygoid - active to hold disk in alignment with contact against the posterior slope of eminentia Functional occlusion from TMJ to smile design Peter E Dawson

52. Muscle response to occlusal interference 85 Evokes a response of hyperactivity and incoordinated contraction Interferring tooth also becomes sensitive and sore Functional occlusion from TMJ to smile design Peter E Dawson

53. Muscle response to posterior disclusion Occurs during protrusive and lateral excursions when separation of posteriors occurs , elevator muscle shut off beneficial effects: 1.reduces horizontal forces against anterior teeth (only teeth contacting during excursions) 2.reduces compressive loading forces on the TMJs 85 Functional occlusion from TMJ to smile design Peter E Dawson

54. Muscle response to posterior occlusal interference W hen any posterior tooth interferes with anterior guidance during eccentric movement: 1.lateral pterygoid muscle activated 2.elevators - hyperactivated 3.incoordinated muscle hyperfunction 4.posterior teeth - horizontal overload (excessive attrition, wear, fracture and hypermobility) 85 Functional occlusion from TMJ to smile design Peter E Dawson

55. PALPATION Widely accepted method for determining muscle tenderness and pain 85 No pain or tenderness 1 uncomfortable 2 Definite discomfort 3 Eye tearing or verbalizes not to have the area palpated again Bell’s Orofacial pain Jeffery P Okeson 5 th ed

56. TEMPORALIS ANTERIOR REGION Palpated above the zygomatic arch and anterior to TMJ MIDDLE REGION Palpated directly above the TMJ and superior to the zygomatic arch POSTERIOR REGION Palpated above and behind the ear 85

57. For the temporalis tendon Palpated by placing the finger of the one hand intraorally on the anterior border of ramus and the finger of the other hand extraorally on the same area 85

58. MASSETER The masseter is palpated bilaterally at its superior and inferior attachments Fingers are placed on each zygomatic arch anterior to the TMJ Then slightly dropped down on the inferior border of the ramus 85

59. LATERAL PTERYGOID Intraorally by using the index finger and placing it lateral to maxillary tuberosity and medial to coronoid process. 85

60. MEDIAL PTERYGOID Palpated by placing finger on the medial aspect of the mandible at the floor of the mouth 85

61. PALPATION OF MUSCLES 85

62. MASTICATORY MUSCLE PAIN Protective co-contraction ( muscle splinting) Delayed onset muscle soreness (Local muscle soreness) Myofascial pain (trigger point pain) Travell & Rinzeler Myospasm Myositis Fibromyalgia - chronic 85 Bell’s Orofacial pain Jeffery P Okeson 5 th ed

63. MASTICATORY MUSCLE PAIN MODEL 85 Bell’s Orofacial pain Jeffery P Okeson 5 th ed Local factors Fracture of a tooth Placement of restoration in supra occlusion Tissue damages caused by dental injections Chewing un usually hard food Opening too wide ( long dental procedure ) yawning Systemic factors Emotional stress

64. PROTECTIVE CO CONTRACTION it is CNS response to the injury or threat of injury Also called as protection muscle splinting In case of injury- sequencing of muscle activity altered – to protect from further injury Not a pathologic condition When prolonged leads to myalgic symptoms 85 Bell’s Orofacial pain Jeffery P Okeson 5 th ed

65. DELAYED ONSET MUSCLE SORENESS Primary, non inflammatory, myogenous pain disorder First response to prolonged co contraction Represents a condition characterized by changes in the local environment ( because of release of allogenic substance like bradykinin substance P) Symptoms are Muscle stiffness, tenderness, active muscle contractions 85 Bell’s Orofacial pain Jeffery P Okeson 5 th ed

66. MYOFACIAL PAIN ( trigger point myalgia ) Regional myogenous pain condition Characterized by local areas of firm, hypersensitive bands of muscle tissue known as “ trigger points” 85 Bell’s Orofacial pain Jeffery P Okeson 5 th ed

67. 85 Referral of Trigger point pain in masseter REFERRAL PATTERNS OF MYOFASCIAL PAIN IN THE OROFACIAL REGION

68. 85 Referral of Trigger point pain in temporalis

69. 85 Referral of Trigger point pain in lateral pterygoid

70. 85 Referral of Trigger point pain in medial pterygoid

71. Differentiating various masticatory muscle pains Elevator muscle pain Pain felt in and around the ear, temple and face. Pain increases with opening, chewing food and clenching teeth Pain is accompanied by restriction in mouth opening Deflection of incisal path depends on muscle involved 85 Deflected to affected side Masseter or temporalis ( uni ) defected to opposite side Medial pterygoid ( uni ) Does not occur Masseter & MP ( uni ) combination of bilateral mucle

72. Lateral pterygoid muscle pain Pain is felt in joint proper Acute malocclusion Pain most severe when teeth fully occluded 85 Bell’s Orofacial pain Jeffery P Okeson 5 th ed

73. Therapeutic options Restriction of functional activities within painless limits, analgesics and muscle relaxants for palliative relief, and counseling Cause-related therapy consisting of identification and treatment of etiologic factors and contributing conditions Specific therapy for masticatory pain of muscle origin 85 Bell’s Orofacial pain Jeffery P Okeson 5 th ed

74. TENS 85 Transcutaneous electric nerve stimulation (TENS) is a non-pharmacological method which is widely used by medical and paramedical professionals for the management of acute and chronic pain in a variety of conditions Mechanism of action Analgesic effect of TENS is based on two main theories- Gate control theory of pain and Endogenous opioid theory Classification of TENS High frequency ( > 50 Hz ) – gate control Low frequency (< 10 Hz ) – opioid receptor Transcutaneous electric nerve stimulation (TENS) in dentistry- A review Journal section: Oral Medicine and Pathology 2014

75. The influence of age and dental status on elevator and depressor muscle activity AIM & OBJECTIVE The objective of this study was to determine whether the muscle activity at various mandibular positions is affected by age and dental status. 85

76. MATERIALS AND METHODS 30 edentulous group (21 F & 9 M) 20 Younger dentate (12 F & 8 M) 20 Older dentate (12 F & 8 M ) EMG RECORDINGS FROM Right and Left anterior temporal muscle Right and left masseter muscle Submandibular group of muscle from the anterior belly of digastric region Movements that recorded were Maximum intercuspation Protrusion with the teeth at an edge-to-edge position (P), Maximal protrusion ( Pmax ), RIght lateral excursive position with the teeth at an edge-to-edge position (RO), Maximal right lateral position ( Rmax ) Left lateral excursive position with the teeth at an edge-to-edge position (LO) and Maximal left lateral position ( Lmax ). 85

77. CONCLUSION Dental status (elderly dentates – edentulous subjects) had a significant effect on the muscle activity in different mandibular positions, as edentulous subjects had to use higher muscle activity levels (percentages of maximal EMG value) than age matched dentate subjects in order to perform same mandibular movement. The elevator and depressor muscles need stronger activation by the ageing. 85

78. Influence of lower complete denture use on masseter muscles and masticatory function: a longitudinal study OBJECTIVES: This study verified masticatory function and oral perception in subjects who did not use lower CDs, and whether the insertion of new upper and lower CD s would improve such variables. 85

79. METHOD 15 edentulous elderly who wore only the upper CD were selected and received new upper and lower CD. Volunteers were evaluated at baseline and after 1, 3 and 6 months of new prosthesis use. Masticatory performance (MP)- sieving method ( X50 values ). Masseter thickness (MT) -ultrasonography. Oral sensorial ability (OSA) oral stereognosis test and Maximum tongue pressure (MTP) pressure sensors 85

80. RESULTS: X50 and MTP decreased ( P < 0.05) after 1 month and remained stable ( P > 0.05) for next assessments. After 3 months, MT in rest position was increased ( P < 0.05), while during maximum voluntary contraction 1 month was enough to increase MT ( P < 0.05). There were no differences for OSA ( P > 0.05) and no correlation between OSA and MTP. CONCLUSION: M P and MT of elderly who did not use the lower dentures were improved after 2 months using new upper and lower CDs. However, new CDs in both dental arch decreased MTP. 85

81. The Influence of Emotional State on the Masticatory Muscles Function in the Group of Young Healthy Adults ( Biomed Research International) AIM: To determine the effect of stress on the masticatory muscles function in young healthy adults. MATERIALS AND METHODS: A total of 201 young,( Angle’s first class, healthy volunteers), 103 female and 98 male (age 18 and 21 years) were recruited into the study. The study included the following: (1) clinical examination according to the Slavicek scheme (2) questionnaire survey (Perceived Stress Scale PSS-10); (3) assessment of the masticatory muscles function (electromyography of four pairs of masticatory muscles 85

82. 85 RESULTS: Symptoms of masticatory system dysfunction were found in the group of 86 subjects (46%). All the muscles activity in central occlusion was comparable in female and male groups. Mean values of masseter activity in the group of low stress subjects (75,52 𝜇V ± 15,97) were statistically different from the groups with medium (82,43 𝜇V ± 15,04) and high (81,33 ±12,05) perceived stress (𝑃 < 0.05). CONCLUSIONS: (1) Among young healthy adults with a complete natural dentition, some individuals do not report symptoms of masticatory system dysfunction despite their presence. Those who complain of dysfunction symptoms do not associate them with the masticatory system. (2) Adults with higher level of perceived stress tended to have increased activity of masseters in centric occlusion. (3) Chronic stress may reveal or exacerbate symptoms of masticatory dysfunction

83. CONCLUSION We cannot keep teeth in a stable position where muscle does not want them to be And in war between teeth and muscle, muscle never looses In order to treat dysfunction clinician should be aware of the function We should Rehabilitate the missing teeth maintaining the balance in the masticatory system 85

84. References B D Chaurasia’s Human Anatomy vol 3 6 th ed Human Embryology Inderbir Singh 9 th ed Guyton and Hall medical physiology Boucher’s P rosthodontic Treatment for Edentulous Patients 9 th ed Functional occlusion from TMJ to smile design Peter E Dawson Management of TMJ disorders and occlusion Jeffery P Okeson 2 nd ed Bell’s orofacial pain Jeffery P Okeson 5 th ed 85

85. Cross reference Influence of lower complete denture use on masseter muscles and masticatory function: a longitudinal study The influence of age and dental status on elevator and depressor muscle activity Journal of Oral Rehabilitation 2006 The Influence of Emotional State on the Masticatory Muscles Function in the Group of Young Healthy Adults Biomed research international 2015 85

86. THANK YOU 85