21-tmj jaw bones e-learning
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The Temporomandibular Joint
& Jaw Bones
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TMJ
Type:ginglymoarthrodial synovial
joint
(modified hinge joint)
Ginglymus: hinge
Arthrodial: plane
1st movement: rotational
2nd movement: gliding ortranslational
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Articulations:
Head of mandibular condyle
Ant. Part of Mandibular fossa
Of temporal bone
&
Articular tubercle
of
*articular surfaces
fibrocartilage
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Supporting Ligaments
Main (Intrinsic)
Articular fibrous capsulesurrounds the J.
attached
sup.: margins of themandibular fossa
inf.: neck of the mandibleLat. (TM) Lig.:
runs downwards backwards
between the articulartubercle & the neck of themandible
prevents the posteriordislocation of the joint
protects the structuresbehind the joint(the tympanic plate)
Most of the dislocations of the TMJ
occur anteriorly because there is no
ligament to prevent this
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Accessory (Extrinsic)
Stylomandibular lig.:
extends between the styloidprocess & the angle of the
mandiblethickened part of theinvesting layer of deepcervical fascia
- Determines the extension of
protrusion
Sphenomandibular lig.:
lies on medial side &
extends between the spine ofsphenoid & the lingula
- Protects the inferior alveolarnerve & limits the lateralmovements of the mandible
3. Is there any other lig.??
- The pterygomandibularligament
*define the extents of
Mandibular movements
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The Articular Disc
Oval plate of fibrocartilage that is located between articular
surfaces of TMJ
Ant. & post. Bands
Attachments
periphery: to the fibrouscapsule
ant.: to the lateral pterygoidmuscle & the head of themandible
post.: to the postglenoidtubecle of temporal bone &the neck of the mandible
* The disc divides the Joint cavity into 2 compartments:
Sup. & Inf.
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Additional slide
- The special characteristics of the TMJ :
1- The type of the articular cartilage on the surface of the(mandibular condyle, mandibular fossa & articular tubercle
tubercle) is fibrocartilage rather than hyaline cartilage(becauseof the continuous movement)
2- The articular disc
3- The extrinsic ligaments
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Additional slide
- There are two compartments in the TMJ cavity to specialize themovements of the TMJ (two cavities two differentmovements) :- The rotational movements : in the inferior compartment
- The translational movement : in the superior compartment
- The superior compartment : between the mandibular fossa &the articular disc
- The inferior compartment : between the articular disc & the
mandibular condyle
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Movements
1. Depression of mand.
(mouth opening)3 muscle groups :
- Lateral pterygoid
- Suprahyoid group
- Infrahyoid group
* Main mover : the action ofthe gravity
- Those muscles act againstresistance
2. Elevation:(mouth closing)
3 muscles:
- Masseter
- Medial pterygoid
- The vertical fibers of temporalis
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3. Protrusion:
(forwards)
3 muscles :
- Anterior part of masseter
- Anterior part of medialpterygoid
- Lateral pterygoid
main one : lateral pterygoid
4. Retrusion, Retraction:
(backwards)
by the posterior (horizontal)fibers of temporalis
5. Lat. Movement to the sides:
by the medial & lateralpterygoid muscles of theopposite side
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Movements of Mouth Opening
Involves 2 kinds of movement:
1. Rotation:
condyle & lower surface of
articular disc ( compartment) 20o (hinge)
2. Translation:
condyle & disc
articular tubercle
until the head of the mandible & the articular disc are locatedinferior to the tip of the articular tubercle (gliding)
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Relations of TMJAnt.:
masseteric a. & n.
- artery : from the 2nd part ofthe maxillary artery
- Nerve : from the anteriordivision of the mandibularnerve
- Those go through themandibular notch
Post.:
- glenoid process of theparotid gland
- tympanic plate of EAM
- superfacial temporalartery & vein
- auriculotemporal nerveLat.:
parotid gland
Med.:
max. Vessels &
auriculotemp. N.
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Dislocation of TMJ
The head of the mandible moves ant. To the articular tubercle
mandible is depressed & the pt. cannot close his mouth
Cause:
excessive contraction of lat. Pterygoid m.
as in: taking a large biteover opening for the dentist
Rx.:pressure the mandible inf. Then post.
by grasping the mandible with your thumbs over lowerdentition
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Clicking of TMJ
When the post. Band of articular disc is anteriorly displaced
(in front of mand. Condyle)
*As the pt. opens his mouth:
the displaced disc, at a certain point, returns to its normalposition
producing the click sound in the joint
Ant. Displacement with reduction
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Anterior Displacement WithoutReduction
The disc remains anteriorly displaced as the mouth is opening
- the pt. cannot fully open his mouth
- Grinding sounds are present
- sometimes perforation of the disc may happened
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The Jaw Bones
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Maxilla
Body & 4 Processes
Body
pyramidal
hollow inside (max. sinus)
- Upper surface: the floor of theorbit (infraorbital)
- Anterolateral surface: in theface
- Posterolateral surface: in theinfratemporal fossa
- Medial surface: the lateralsurface of the nasal cavity
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Maxillary Processes
Zygomatic:
projects lat.,
ant. zyg. Arch
Frontal:
sup.,
lat. to nasal bones
Alveolar:
inf.,
contains upper teeth
Palatine:
post.,
ant. 2/3 of hard palate
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Maxillary Foramina
2 foramina:
Infraorbital F.
ant. wall, infraorbital n. & a.
Incisive Foramen:
between palatine processes
post. to central incisors
incisive n. (nasopalatine n.)
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Largest & strongest facial bone
Only movable skull bone beside
The ear ossicles
Horizontal part:
Body
Vertical Parts:
Rami (ramus)
Jxn.:
Angle
Mandible
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Body:
mental foramen (below the 2nd premolar)
alveolar processmental protuberance
sup. & inf. Mental spines
(attached to genioglossus & geniohyoid, respectively)
mylohyoid line (demarcates the floor of the mouth)
Ramus:
mandibular notch
coronoid process
condylar process:
head & neck
lingula & mand. foramen
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Mention 8 muscles attached to the mandible ?
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Mention 8 muscles attached to the mandible ?
-Temporalis
- Masseter
- Medial pterygoid
- Lateral pterygoid
- Genioglossus
- Geniohyoid
- Mylohyoid
- Anterior beally of digastric
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Done by : Muad Al-ZoubiBest wishes
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