Muscles Of Mastication anatomy orthodontics

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

2. CONTENTS
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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
• Stylohyoid
• 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 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. 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. LATERAL PTERYGOID
UPPER HEAD
Origin-infratemporal surface & crest of greater
wing of sphenoid

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

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 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. 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. Masseter
Superficial Layer
It is the largest component that arises from the anterior
twothirds of the lower border of the zygomaticarch

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