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Muscles of Mastication
ColbyVictoria
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What are the muscles?
Masseter
Temporalis
Medial Pterygoid Lateral Pterygoid
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Masseter
Overlies lateral surface oframus of mandible
Quadrangular shaped
Anchored above to zygomatic
bone & anterior 2/3 of maxilla Superficial origin: Maxillaryprocess of zygomatic bone
Deep origin: medial aspect ofzygomatic arch
Innervated by Masseteric nerve
(from V3) Vascularized by Masseteric
artery (from Maxillary A)
Figure 8.132: Masseter muscle
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Figure 8.135: Nerves and arteries of the temporal fossa
Temporalis
Fan shaped, fills temporal fossa
Origin: from bony surface oftemporal fossa to inferiortemporal line
Anterior fibers vertically
oriented Posterior fibers horizontally
oriented
Fibers form TENDON
Inserts: coronoid process ofmandible
Innervation: Deep temporalnerves (from V3)
Vascularization: Deep temporalarteries (from middle temporal A)
Figure 8.134: Temporalis muscle. Lateral View
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Medial Pterygoid
Quadrangular shaped with 2heads:
Deep head: Origin: Medial surface of lateral
plate of pterygoid process &
pyramidal process of palatinebone
Superficial head: Origin: tuberosity and pyramidal
process of maxilla
Insert the same place: Medialsurface of mandible (near the
angle) Innervation: Nerve to medial
pterygoid (from V3)
Vascularization:Figure 8.137: Medial pterygoid muscle
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Lateral Pterygoid
Thick triangular muscle with 2heads
Upper head: Origin: roof of infratemporalfossa
(lateral to foramen ovale and
spinosum) Lower head: larger
Origin: lateral plate of thepterygoid process (tracksbetween the 2 heads of medialpterygoid)
Insertion: pterygoid fovea of neck
of mandible AND into capsule ofTMJ
Innervation: nerve to lateralpterygoid (from V3)
Vascularization:
Figure 8.138: Lateral pterygoid muscle
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Consequences of Mal-Occlusion
Abfraction:Wedgeshaped loss of toothstructure at cervical due to heavyabnormal occlusalforce.
Tension
ripped apart
Attrition corresponding to
Occlusalforces.Loss of structure due to tooth-tooth contact
Deciduous and permanent dentition
Wear facets correspond to occlusal pattern
Increased likelihood poor quality of
enamel, edge to edge occlusion, prematureocclusion, intraoral abrsives, grinding ofteeth
Shortening of arch length
Pulp exposure and sensitivity are rare
Early diagnosis and intervention
Chronic malocclusion
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2ndmost common source of facialpain
Women are 4 times more likely to
have TMJ disorder
Most common in people 20-40
years old
20-25% of the population have
symptoms of a TMJ disorder
Only 3-4% of the population
seek treatment
About 70% of reported TMJ
disorder cases are attributed topathologies involving the disc
TMJ disorder
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Summary Slide
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