TMJ Flashcards
What two bones make up the TMJ
The temporal bone of the skull (squamous portion) and the condyle of the mandible
What limits the glenoid fossa?
The glenoid fossa is limited anteriorly by the articular eminence and posteriorly by the tympanic plate and postglenoid tubercle
What is the superior TMJ joint capsule attachment?
The circumference of the glenoid fossa but extending to the anterior of the articular eminence and posterior to the petrotympanic fissure
The temporal bone, superiorly, has to enclose the articular eminence
What is the inferior attachment of the TMJ joint capsule?
The neck of the mandible
The capsule encloses the joint space all the way around
Synovial membrane of the TMJ
Lines the entire joint space EXCEPT the articular surfaces
What is the function of the synovial membrane
It lubricates the joint, and provides nutrients to avascular parts of the joint
What covers the articular surfaces of the TMJ?
Dense, fibrous connective tissue
What is the benefit of having dense fibrous connective tissue instead of cartilage?
It is much more dynamic and can adapt
When may there be fibrocartilage in the articular surface of the TMJ?
Stress bearing areas may have fibrocartilage or fibrous connective tissue with cartilage cells but there will not be fibrocartilage in a mature TMJ
What is the blood supply to the articular surface?
No blood supply - it is an avascular surface
What is the primary nerve of the TMJ?
Auriculotemporal nerve
Where are the nerve endings in the TMJ?
The auriculotemporal nerve has sensory nerve endings in the joint capsule and the retrodiscal pad, pain fibers and some proprioception are supplemented by fibers in the periodontal ligament
What is the primary blood supply to the TMJ?
Branches of the superficial temporal and maxillary arteries
The most important is the anterior tympanic branch of the maxillary artery
Maxillary artery provides for the deep side of the TMJ, and the superficial temporal provides for the more lateral side of the TMJ
What is the intrinsic ligament of the TMJ?
The lateral ligament of the TMJ, which is also called the temporomandibular ligament.
Where does the lateral ligament of the TMJ attach?
From the articular tubercle to the neck of the mandible
What is the function of the lateral ligament of the TMJ?
It helps to limit posterior and inferior movement, and is part of the joint capsule itself
What are the extrinsic, or accessory, ligaments of the TMJ?
The sphenomandibular ligament and the stylomandibular ligament
Where does the sphenomandibular ligament attach?
From the spine of the sphenoid bone to the lingula of the mandible (remnant of meckel’s cartilage) - it surrounds the opening of the mandibular foramen
Where does the stylomandibular ligament attach?
From the styloid process to the angle of the mandible
What do the extrinsic ligaments of the TMJ collectively do?
Limit inferior and anterior movement
Which is the more important of the extrinsic ligaments of the TMJ?
The sphenomandibular ligament
Articular disc/meniscus of the TMJ
Dense fibrous connective tissue with areas of stress sometimes made up of fibrocartilage, it is there for stability and to fill in the incongruities of the joint
What makes up the articular part of the disc?
anterior and posterior bands and an intermediate zone. between bones during movement
Articular part of disc = avascular
Where is the disc attached?
The disc is attached to the medial and lateral poles of the condyle of the mandible, and the attachment is very very tight
These attachements are called collateral ligaments
Where does the disc merge?
Into a capsule around the entire circumference
What is the posterior disc (non articular part) called?
Retrodiscal pad, or bilaminar zone
What part of the disc has nerve endings and vascular tissue?
The retrodiscal pad/posterior disc/bilaminar zone/non-articular part of the disc
What part of the disc is always thicker?
The medial part of the disc is always thicker than the lateral part of the disc
What is the most common part of the disc for perforation?
Lateral part of the intermediate zone
How does the disc fit onto the condyle?
Fits onto the condyle like a swim cap
What joint space is tight, and what is loose?
The lower joint space is tight and allows for rotational movement
The upper joint space is looser and allows for translational movement
What compartment between disc and condyle is the site for rotational movement?
The inferior compartment
What compartment between disc and fossa is the site for translational movement?
The superior compartment
What is the movement within the joint?
The initial opening (first few mm) is rotational, or hinge movement. It is limited by the tympanic plate, the parotid gland, and the retrodiscal pad.
Further opening - the condyle and disc translate anteriorly as a unit onto and down the articular eminence
What muscle contracts to allow the mouth to START opening?
The lateral pterygoid
What is the axis of rotation for the initial opening of the mouth?
the axis is IN the condyle
Where is “translation” occurring?
Between the disc and the articular eminence
Where is “rotation” occurring?
Between the condyle and the disc
What happens to the center of rotation when you want to translate farther?
The center of rotation changes from the condyle to the center of the ramus in order to translate farther
What is the sequence of moving in opening?
Lateral pterygoid contracts to initiate opening; the shortening pulls on the neck of the mandible and starts the rotational movement with the axis of rotation through the condyle
When rotational opening is hindered, the lateral pterygoid pulls the mandible forward onto the articular eminence and down it. The disc moves along with the condyle.
As the stylomandibular and sphenomandibular ligaments are pulled tight, the mandible rotates downward around an axis through the mandibular foramen (i.e. depression - and the sphenomandibular ligament acts as a swinging hinge). There is a shift in axis of rotation - it allows the inferior alveolar nerve and vessels to remain static
What is unique about the mandible?
It is one bone with two more or less symmetrical joints - the angle allows for lateral movements of the TMJ
A working movement means that it is moving TOWARD that side.
Differentiate between what is the rotating condyle and what is the orbiting condyle
If you are moving your mandible to the right, the rotating condyle is the RIGHT condyle, and the orbiting condyle is the LEFT condyle
What are the changes in the TMJ associated with age?
Loss of teeth may lead to perforations of the disc, and flattening of the condyle and eminence
Dislocation of the joint - luxation or subluxation
Always occurs anteriorly
Locked open, and you cannot move the mandible
Can happen from over-opening, blow to the side of the mandible when the mouth is open
Unilateral dislocation
Mandible will deviate to one side, away from the effected side
How can you decide if it is a bilateral or unilateral dislocation?
If the midline of the mandibular incisors is in the right spot, the mandible is dislocated on both sides.
If the mandibular midline is deviated from the maxillary midline, it is unilateral.
If the mandible is deviated toward the right, the dislocation is on the left side
You can reposition by forcing the mandible inferiorly (downward pressure) in order to get it below the eminence
Ankylosis
fusion of the mandibular condyle to the fossa
fairly uncommon, happens most commonly in kid due to trauma, causes inflammation of the joint and condyle, causing it to fuse together due to inflammation
This is a LONG TERM CONDITION
Deviation in midline due to the fusion, growth on one side has stopped - the deviation is toward the ankylo side
TMD - Temporomandibular dysfunction or disorder
Symptoms include: headache pain, in joint and muscles clicking joints earache
40-60% of people probably have symptoms, so it is a common problem but only 5% think it is severe enough to seek treatment
Majority of those who seek treatment are women in late teens, early twenties, and postmenopausal
