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TEMPOROMANDIBULAR JOINT AND MASTICATION
Mr. P Mazengenya
Room 2B04, Tel 72204
AIMS
• Descibe the TMJ
– Articulation
– Stabilizers
– Movements
– Apply information to mastication
– Clinically – dislocation of the mandible
TMJ
• TMJ
o Joint between mandible and temporal bone
o In chewing or speaking, it is only the mandible or lower jaw that moves;
o The upper jaw or maxilla remains stationary
• Articulation:
o condylar process of mandible
o Articular tubercle of temporal bone
o and mandibular fossa
Joint type Modified hinge-type
synovial joint
• Divided into 2 compartments: o Fibrocartilagenous disc
• Hence o Gliding movements
(protrusion and retrusion/retraction) occur in upper compartment
o Hinge movements (depression and elevation) occur in lower compartment
• Stabilized by three ligaments:
o Lateral temporomandibular ligament Lateral thickened parts of
articular capsule
Prevent posterior dislocation of joint
o Sphenomandibular ligament Primary passive support
Runs from spine of sphenoid to lingulae of mandible
Serves as swinging hinge and check ligament
o Stylomandibular ligament • Thickening of the capsule
of parotid gland
• Runs from styloid process to angle of mandible
MOVEMENTS OF TMJ
o Depression Suprahyoid
infrahyoid muscles
gravity
• Elevation
o Temporalis
o masseter
o medial pterygoid muscles
o Protrusion- o lateral pterygoid
o masseter
o medial pterygoid
o Retraction/retraction Temporalis
masseter
Diagastic, geniohyoid
• Side to side grinding-
o retractors of same side
o protruders of opposite side
• Stability of TMJ
o Shape of the bones
o The articulating disc (though controversial)
o Ligaments
o Muscle tone
Lymph
MASTICATION
• Muscles of mastication:
o Derivatives of 1st pharyngeal arch
o Innervated by the mandibular division (v3)
o All supplied by branches of the maxillary artery
Recap
• Muscles of mastication:
o Temporalis
o Massetor
o Medial and lateral pterigoid
Chewing
• Lateral movements (grinding and chewing)
o Temporal of same side,
o pterygoids of opposite side,
o and masseter
Summary- dislocation
• Sometimes during yawning or taking a large bite, excessive contraction of the lateral pterygoids may cause the heads of the mandible to dislocate anteriorly (pass anterior to the articular tubercles) In this position, the mandible remains wide open and the person is unable to close.
Thank you
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