Muscles of mastication

Muscles Of Mastication anatomy orthodontics

1. MUSCLES OF MASTICATION Dr. Arif Ismail Dept. Of orthodontics

2. CONTENTS Introduction Development Anatomy ACTIONS Innervation & Vasculature Clinical Significance & Applied Aspects Conclusion

3. INTRODUCTION Traditionally four powerful muscles – Masseter , Temporalis, Medial Pterygoid & Lateral pterygoid are called the “ Muscles of Mastication ”

4. Accessory Muscles Suprahyoid muscles Mylohyoid Geniohyoid S tylohyoid Digastric Infrahyoid Muscles Sternothyroid Omohyoid Thyrohyoid Sternohyoid

5. DEVELOPMENT Muscles of mastication develops from the mesoderm of the first brachial arch that is also called the Mandibular Arch

6. Pterygoid Muscle Differentiate in the 7 th 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. Temporalis muscle Begins lateral development in the 8 th week , occupying the space anterior to the otic capsule As the temporal bone begins to ossify in the 13 th 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. UPPER HEAD Origin- infratemporal surface & crest of greater wing of sphenoid LATERAL PTERYGOID

9. Lower head Origin- lateral surface of the lateral pterygoid plate

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. 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. Superficial head Maxillary tuberosity & pyramidal process of palatine bone

13. Deep Head Medial surface of the Lateral plate of Pterygoid process and Pyramidal process of Palatine bone

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. 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. ORIGIN Floor of temporal fossa(inferior temporal line) Overlying temporal fascia of the side of skull TEMPORALIS

17. Insertion Margins & deep surface of coronoid process Anterior Border of Ramus

18. Action It can be divided into 3 distinct areas according to fiber direction and function   The Anterior fibers are directed almost vertically- elevation 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. 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. Superficial Layer It is the largest component that arises from the anterior twothirds of the lower border of the zygomaticarch Masseter

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. Deep Layer The deep layer arises from the whole length of medial surface of the zygomatic arch

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. 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. 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. 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. 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. 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. 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