Muscles of mastication


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Muscles Of Mastication anatomy orthodontics

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Muscles of mastication

  1. 1. MUSCLES OF MASTICATION Dr. Arif Ismail Dept. Of orthodontics
  2. 2. CONTENTS • • • • • • Introduction Development Anatomy ACTIONS Innervation & Vasculature Clinical Significance & Applied Aspects • Conclusion
  3. 3. INTRODUCTION Traditionally four powerful muscles – Masseter, Temporalis, Medial Pterygoid & Lateral pterygoid are called the “Muscles of Mastication”
  4. 4. Accessory Muscles Suprahyoid muscles • Mylohyoid • Geniohyoid • Stylohyoid • Digastric Infrahyoid Muscles • Sternothyroid • Omohyoid • Thyrohyoid • Sternohyoid
  5. 5. DEVELOPMENT Muscles of mastication develops from the mesoderm of the first brachial arch that is also called the Mandibular Arch
  6. 6. Pterygoid Muscle • Differentiate in the 7th week • It is related to the cartilage of the cranial base and the condyle initially • Later as the bony skull appears and increases in width and length, the muscle expands rapidly
  7. 7. Temporalis muscle • Begins lateral development in the 8th week, occupying the space anterior to the otic capsule • As the temporal bone begins to ossify in the 13th week, the muscle attaches to it Masseter muscle • Begins attachment to the zygomatic arch as it undergoes lateral growth, providing space for muscle development
  8. 8. LATERAL PTERYGOID UPPER HEAD Origin-infratemporal surface & crest of greater wing of sphenoid
  9. 9. Lower head Origin- lateral surface of the lateral pterygoid plate
  10. 10. ACTION Superior Head • active during the power stroke.Power stroke refers to movement that involves closure of the mandible against resistent such as in chewing or clenching the teeth together. Inferior Head • Depression(bilateral): depresses the mandible along with suprahyoid and infrahyoid muscles to open the mouth • Protrusion(bilateral): the lateral pterygoid acting together are the prime protractors of the mandible. • Contralateral excursion(unilateral): the medial and lateral pterygoid muscle of the two sides contact alternately to produce side to side movement of the mandible(as in chewing
  11. 11. Nerve Supply The nerve to the lateral pterygoid muscle branches off from the masseteric or buccal nerve, which is the branch of the anterior trunk of the mandibular nerve Blood Supply Pterygoid vessels from Maxillary artery
  12. 12. Superficial head Maxillary tuberosity & pyramidal process of palatine bone
  13. 13. Deep Head Medial surface of the Lateral plate of Pterygoid process and Pyramidal process of Palatine bone
  14. 14. ACTION • Elevation (bilateral) : The medial pterygoid acting along with the masseter muscle are powerful elevators of the mandible • Protrusion( bilateral): The insertion of the muscle is posterior to its origin and therefore it helps in protrusion of mandible • Contralateral excursion: The medial and lateral pterygoid muscle of two sides contract alternately to produce Side-to-Side movement of Mandible
  15. 15. Nerve Supply The never supplying the medial pterygoid muscles is the medial pterygoid nerve branch of the mandibular nerve Blood Supply The artery supplying the medial pterygoid muscles is a branch of the maxillary artery
  16. 16. TEMPORALIS ORIGIN Floor of temporal fossa(inferior temporal line) Overlying temporal fascia of the side of skull
  17. 17. Insertion Margins & deep surface of coronoid process Anterior Border of Ramus
  18. 18. Action It can be divided into 3 distinct areas according to fiber direction and function • The Anterior fibers are directed almost verticallyelevation of mandible • The middle fibers run obliquely forward as they pass downward -elevate and retrude the mandible • The posterior fibers are aligned almost horizontally retrusion of mandible
  19. 19. Nerve Supply Deep temporal branches of the anterior trunk of the mandibular nerve Blood Supply This is furnished by the middle & deep temporal arteries. The middle temporal artery is a branch of the superficial temporal artery & the deep temporal arteries are branches of the maxillary artery
  20. 20. Masseter Superficial Layer It is the largest component that arises from the anterior twothirds of the lower border of the zygomaticarch
  21. 21. Middle Layer The middle layer takes its orgin from the medial surface of the anterior twothirds and the lower border of posterior one third of the arch
  22. 22. Deep Layer The deep layer arises from the whole length of medial surface of the zygomatic arch
  23. 23. Action • Elevation(bilateral):masseter elevates the mandible to occlude the teeth in mastication. • Ipsilateral excursion(unilateral): as the origin of the masseter muscle is slightly lateral to its insertion , a single masseter muscle can move the mandible to the same side. • Retrusion: (bilateral): when the mandible is in a protruded position the deep fibers are in a position to retrude the mandible
  24. 24. Nerve supply Supplied by Masseteric nerve a branch of anterior division of Mandibular nerve Blood Supply Supplied by masseteric artery branch of maxillary artery
  25. 25. Muscle as an etioogy of malocclusion Muscle dysfunction Facial asymmetry in a eleven yr old boy whose masseter muscle was missing on left side
  26. 26. MPDS • Pain disorder in which unilateral pain is referred from trigger points in myofacial structure • Constant pain, dull ache Laskin’s Cardinal Signs • Muscle tenderness • Pain • Clicking or propping noise in TMJ • Limited Jaw Movement
  27. 27. Trismus • Inability to normally open the mouth due to one of the many causes • Inflammation of muscles of mastication • Pericoronitis • Peritonsillar abscess • Temperomandibular joint Disorder(TMD) • Submucous Fibrosis
  28. 28. Temporal Tendonitis • Chronic strain from temporalis muscle pulling on tendon that attaches to mandible • Causes sharp headaches in temple just to side of the eyes
  29. 29. Conclusion • The masticatory muscles include a vital part of the oro-facial structure and are important both functionally and structurally • 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