21-tmj jaw bones e-learning

8/2/2019 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

21-tmj jaw bones e-learning

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