Muscles of mastication


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Muscles of Mastication and its implication in Prosthodontics.

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Muscles of mastication

  2. 2. Muscles of Mastication Dr Jamshid Usman PG ProsthodonticsRoyal Dental CollegeChalissery,Palakkad
  3. 3. • Introduction• Types• Palpation• Clinical significance• Literature review• Summary• Conclusion
  4. 4. DEFNITIONS GPT 8• Muscle:• an organ that by contraction producesmovements of an animal; a tissue composed of contractile cells or fibersthat effect movement of an organ or part of the body.• Mastication• is defined as the process of chewing food in preparation for swallowing and digestion.•
  5. 5. • Mastication- four muscles of mastication (or musculi masticatorii) - adduction and lateral motion of the jaw.• Muscles associated hyoid also responsible for opening the jaw
  6. 6. Primary Muscles Of Mastication• Temporalis• Masseter• Lateral Pterigoid• Medial pterigoid
  7. 7. Accessory Muscles Of Mastication• Suprahyoid • Infrahyoid muscles• Digastric • Sternohyoid• Stylohyoid • Thyrohyoid• Mylohyoid • Omohyoid• Geniohyoid
  8. 8. • Functionally, the muscles of mastication are classified as• Jaw elevators• Masseter• Temporalis• Medial pterygoid• Jaw depressors• :Lateral pterygoid• Anterior digastric• Geniohyoid• Mylohyoid•
  9. 9. Functionally, the muscles of mastication are classified asJaw elevators Jaw depressors• Masseter • Lateral pterygoid• Temporalis • Anterior digastric• Medial pterygoid • Geniohyoid • M ylohyoid
  10. 10. TemporalisMuscle
  11. 11. Temporalis Muscle• elevation of the mandible.• Large fan shaped.• Origin and Insertion:• From the Parietal bone of the skull and is inserted on the coronoid process of the mandible.
  12. 12. • Arterial supply:• The Deep Temporal• Nerve Supply:• Deep temporal n
  13. 13. Functions:• Elevation of the mandible• Retraction of the mandible.• Crushing of food between the molars.• Posterior fibers draw the mandible backwards after it has been protruded.• It is also a contribute side to side grinding movement
  14. 14. Temporalis Muscle
  15. 15. Palpation• To locate the muscle ,have the patient clench.• Apply two pounds of pressure
  16. 16. • The anterior region is palpated above the zygomatic arch and anterior to the TMJ• The middle region is palpated directly above the TMJ and superior to the zygomatic arch• The posterior region is palpated above and behind the ear•
  17. 17. Clinical Importance of Temporalis Muscle:• Sudden contraction of temporalis muscle will result in coronoid fracture, which is rare.• The patient is instructed to close and move his mandible from side to side and then immediately asked to open wide.• The side to side motion records the activity of the coronoid process in a closed position whereas opening causes the coronoid to sweep past the denture periphery
  18. 18. LITERATURE REVIEW• Antje Tallgren, Dr.Odont, et al. studied jaw muscle activity incomplete denture wearers :A longitudinal ectromyographic study . J ProsthetDent August 1980 Vol44 (2) Pg 123-32• Tallgren studied the patterns of activity of some masticatory muscles in partially edentulous subjects & fully edentulous.• The study indicated that loss of posterior teeth causes imbalance in muscular patterns concerning masseter, anterior temporal muscle and digastrics muscle and wearing immediate complete upper and lower dentures revealed inactivity of the jaw closing muscles during the biting actions.
  19. 19. • Bengt ,Ingervall, Dr Odontet al. did an electromyographic study of masticatory and lip function in patient with complete dentures (J ProsthetDent March 1980 Vol43(3) pg 266- 71• T wo groups of patients having new and old dentures were studied.• The results showed muscle activity during maximal biting was markedly lower in patients with new denture than in patients using the old ones• No difference in chewing activity was seen with old and new dentures
  20. 20. Masseter muscle
  21. 21. Masseter muscle• The second most efficient masticatory muscle.
  22. 22. • Multipennate arrangement of fibers• Superficial• Middle• Deep
  23. 23. • The main function of masseter muscle is• Elevation of the mandible• lateral movements of the mandible for efficient chewing and grinding of the food• unilateral chewing• Retraction of the mandible
  24. 24. • Blood supply:• Masseteric artery .•• Nerve supply:• Massetric nerve.
  25. 25. 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 clenchduring 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
  26. 26. • Palpate multiple areas of masseter muscle
  27. 27. Clinical Importance of Masseter Muscle of Mastication:• On Denture border• An active masseter muscle will create a concavity in the outline of the distobuccal border and a less active muscle may result in a convex border.• In this area the buccal flange must converge medially to avoid displacement due to contraction of the masseter muscle because the muscle fibers in that area are vertical and oblique
  28. 28. Activation of massetric notch and distal areas• Instruct the patient to open wide and then to close against the resing force of your finger
  29. 29. • Opening wide activates the muscles of pterygomandibularrapheby stretching, whichthereby defines the most distal extension• Instructing the patient to close against your fingers on the tray handle causes masseter muscle to contract and push against the medially situated buccinator muscle• .•
  30. 30. LITERATURE REVIEW• According to Garrett NR, Kaurich M et. al a cross- sectional study on Masseter muscle activity in denture wearers with superior and poor masticatory performance was done. JProsthetDent 1995 Dec vol74 (6) 628-36• The results indicated that application of more equivalent force by the right and left masseter muscles during unilateral chewing is consistent with improved chewing ability indenture wearers
  31. 31. Lateral Pterygoid Muscle:
  32. 32. Lateral Pterygoid Muscle:• It is divided into 2 heads• Origin:• Upper head – infratemporal surface & crest of greater wing of sphenoid bone• Lower head – lateral pterygoid plate• Insertion :• Pterygoid fovea on the anterior surface of neck of mandible• Anterior margin of articular disc & capsule of TMJ
  33. 33. • Nerve Supply:• Pterygoid branch of Trigeminal nerve.• Arterial supply:• Pterygoid branch of Maxillary artery.• Functions:• Depresses the mandible• Protrudes it forward for opening of the jaw• Side Movements
  35. 35. • 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
  36. 36. Clinical Importance of Lateral Pterygoid Muscle:• Most commonly involved muscle in 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•
  37. 37. LITERATURE REVIEW• R. Johnstoneand Mc cormick templetonstudied the feasibility of palpating the lateral pterygoid muscle ( JProsthetDent Vol44 (3) Sept 1980 Pg 318-23) and came to a conclusion through dissections and lateral head radiographs that it is not possible to palpate the lateral pterygoidmuscle directly by conventional clinical techniques without applying pressure through the overlying superficial head of medial pterygoid muscle
  38. 38. Medial Pterygoid muscle
  39. 39. Medial Pterygoid muscle:• It is a thick muscle of mastication.• Origin and Insertion :• It Arises lateral pterygoid plate, and from the maxillary tuberosity.• Insertion is seen on the Medial angle of the Mandible
  40. 40. • Arterial supply:• Pterygoid branch of Maxillary artery.• Nerve Supply:• Mandibular nerve through the medial pterygoid.
  41. 41. • Functions:• Elevates the mandible,• Closes the jaw,• Helps in side to side movement.
  42. 42. Palpation of medial pterigoid
  43. 43. • gently palpate them on the medial aspect of the jaw,• simultaneously from both inside and outside the mouth
  44. 44. Clinical Importance of Medial Pterygoid Muscle:• Medial Pterygoid muscle can be palpated only intraorally• Most commonly involved in MPDS• Trismus following inferior alveolar nerve block is mostly due to involvement of medial pterygoid muscle
  45. 45. LITERATURE REVIEW• Wodd WW studied the medial pterygoid muscle activity during chewing and clenching. J ProsthetDent.1986 May;Vol 55 ( 5):615-21• Patterns of medial pterygoidmuscle activity were consistentfor ipsilateralchewing• Intercuspal clenching initiated less activity when force was directed posteriorly and more activity when directed anteriorly
  46. 46. Accessory muscles
  47. 47. Accessory Muscles Of Mastication• Suprahyoid • Infrahyoid muscles• Digastric • Sternohyoid• Stylohyoid • Thyrohyoid• Mylohyoid • Omohyoid• Geniohyoid
  48. 48. Digastric• Origin anterior belly - digastric fossa (mandible); posterior belly -mastoid process of temporal bone• Insertion Intermediate tendon (hyoid bone)
  49. 49. • Artery• anterior belly - Submental branch of facial artery;• Posterior belly -occipital artery• Nerve• anterior belly - mandibular division (V3) of the trigeminal(CN V) via the mylohyoid nerve; posterior belly - facial nerve (CN VII)
  50. 50. Stylohyoid Muscle
  51. 51. Origin and insertion
  53. 53. • Artery• Mylohyoid branch of inferior alveolar artery• Nerve• mylohyoid nerv e, from inferior alveolar branch of mandibular nerve• Actions• Raises oral cavity floor, elevateshyoid, elevates tongue, depresses mandible
  55. 55. • Artery : Facial artery• Nerve : C1 via hypoglossal nerve• Action: carry hyoid bone and the tongue upward during deglutition
  57. 57. • Artery : Superior Thyroid Artery• Nerve : C1-C3 by a branch of Ansa cervicalis• Action : Depress Hyoid bone
  59. 59. • Artery : Superior Thyroid Artery• Nerve : C1 via of Ansa cervicalis• Action : Elevates thyroid Depress Hyoid bone
  61. 61. • Artery• Infrahyoid artery from the superior thyroid artery, suprahyoid branch of the lingual artery.• Nerve• Ansa cervicalis (C1-C3)• Actions• Depresses the larynx and hyoid bone. Also carries hyoid bone backward and to the side.
  62. 62. Features of Masticatory muscle• Have shorter contraction times than most other body muscles• Incorporate more of muscle spindles to monitor their activity• Do not have golgi tendon organs to monitor tension• Elevators predominantly white fibrous which perform fast twitching• Do not get fatigued easily• Psychological stress increases the activity of jaw closing muscles• Occlusal interferences cause a hypertonic synchronous muscle activity• Closing movement also determined by the height of the teeth
  63. 63. SUMMARY
  64. 64. Primary Muscles Of Mastication• Temporalis• Masseter• Lateral Pterigoid• Medial pterigoid
  65. 65. Accessory Muscles Of Mastication• Suprahyoid • Infrahyoid muscles• Digastric • Sternohyoid• Stylohyoid • Thyrohyoid• Mylohyoid • Omohyoid• Geniohyoid
  66. 66. CONCLUSION• The masticatory muscles include a vital part of the orofacial structure and are important both functionally and structurally• It can be influenced by a variety of factors many of which are controlled by the practicing prosthodontist
  67. 67. • During functional impression making• Accurate recording of various clinical parameters like vertical dimension, centric relation• Morphology of artificial tooth• Maintenance of arch form• The proper management and periodical self - examination of the muscles may provide a greater chance of catching the disease process at an early stage which may be useful for its better prognosis.
  68. 68. REFERENCES• Human anatomy A K Dutta -#rd Edition• Grays Anaatomy• Burkitsoral medicine diagnosis & treatment 10 th edition• Textbook of Complete dentures by Charles M Heartwell• Journal Refernces
  69. 69. Thank You