TMJ Flashcards
Where is the Pterygoid fossa of the mandible?
Where is the Coronoid process of the mandible?
Where is the Mylohyoid line
of the mandible?
Where is the Mylohyoid line
of the mandible?
Where is the Digastric fossa
of the mandible
What are the two parts of the Mandibular fossa? What bone is it on?
Dome & Articular eminence, Temporal
Where is the Postglenoid tubercle?
Does the Sphenoid contribute to the structure of the TMJ?
No, Bony prominences serve as muscle attachments:
Medial pterygoid plate
Lateral pterygoid plate
What are the 2 joint cavities of the TMJ
Superior joint cavity & Inferior joint cavity
In which direction is the mandibular condyle longer?
M/L length > AP length
What are the poles of the Mandibular condyle?
Medial and lateral poles
What is the mandibular condyle covered in? What is its significance
fibrocartilage, able to absorb loads and transmit forces better than hyaline cartilage also has a greater capacity for healing
What part of the mandibular fossa is articular?
Anterior
What part of the mandibular fossa is non-articular?
Superior and posterior, very thin
What is the articular disc made of?
Fibrocartilage
What is the articular disc function?
Congruency, stability (guides condyle)
What is the neurovascular supply of the articular disc?
Poor, exception around the periphery
What are the attachments of the articular this?
Posteriorly: Retrodiscal lamina, Inferiorly:
Mandibula condyle,
Superiorly:
articular eminence, Anteriorly:
superior head of lateral pterygoid
muscle
What are the regions of the articular disc?
Anterior, posterior, intermediate,
What are the attachments of the Anterior region of the Articular disc
Several attachments: anterior superior neck, tendon of superior head of lat. Pterygoid, temporal bone anterior to articular eminence
What are the attachments of the Posterior region of the Articular disc of the TMJ
Attaches to retrodiscal laminae
Superior lamina- tympanic plate
Inferior lamina- superior neck of mandible with capsule of TMJ
Space above and below lamina
What is the thinnest region of the articular disc?
Intermediate
What is the fibrous capsule?
Fibrous capsule
Outer fibrous portion and inner synovial lining
Role: Support TMJ
How is the fibrous capsule asymmetrically tight?
It is tighter in the medial lateral direction than the superior and inferior direction
What is the lateral ligament?
What is the primary reinforcement to the TMG?
Lateral ligament
What is the function of the lateral ligament of the TMJ?
Stabilize the joint laterally
Guide movement of the condyle during opening
If torn disc can migrate medially
What are the accessory ligaments of the TMJ?
Stylomandibular ligament
Sphenomandibular ligament
What is the function of this accessory ligaments of the TMJ?
Both medial to the joint capsule and help to suspend the mandible from the cranium
What are theThree primary osteokinematic motions of the TMJ?
Depression & Elevation
Protrusion & Retrusion
Lateral excursion
Movement of the mandible involves what kind of action?
BILATERAL action
With are the two Arthrokinematic motions at the TMJ?
Rotation condyle rotates relative to inferior disc
Translation condyle and disc slide on articular eminence together
What is the range of mandible depression and elevation?
ROM = 45-50mm
Full: 3 fingers (PIP)
Functional range = 18mm (chewing)
What is the first phase of the Arthrokinematics of depression?
Early
Involves primarily rotation
Lower joint cavity
Convex condyle on concave disc
Body of mandible moves inferior and posterior
What is the Second phase of the Arthrokinematics of TMJ depression?
Late
primary translation
Upper joint cavity
Condyle and disc slide together anteriorly and inferiorly along articular eminence
How are the AKs of elevation different from depression?
Reverse arthrokinematics of opening: translation first, followed by rotation
Tension in the retrodiscal lamina is critical for retraction of the disc and helps to initiate the early translational phase of closing
What are the anterior posterior movements of the TMJ called?
Protrusion
Translation of the mandible anteriorly without much rotation
ROM limited by?
Retrusion
Translation of the mandible posteriorly
What is the side to side movement of the TMJ known as?
Lateral Excursion
Side to side translation of the mandible
Disc and condyle slide together within fossa
Which condyle serves as a fixed pivot in lateral excursion?
Ipsilateral condyle serves as fixed pivot
What is the ROM of lateral excursion of the TMJ?
ROM = 11 mm
What are the muscles of mastication?
Masseter
Temporalis
Medial Pterygoid
Lateral Pterygoid
What is the innervation of the muscles of mastication?
mandibular division of the trigeminal nerve
What are the insertions of the masseter muscle?
Zygomatic arch to external surface of the ramus and angle of the mandible
What are the actions of the masseter muscle?
Bilaterally: elevate and slight protrusion of mandible
Unilaterally: ipsilateral lateral excursion
What position is this ability maximized?
What are the insertions of the temporalis muscle?
Temporal fossa passing beneath zygomatic arch inserting on the coronoid process and to medial surface of the mandible
What are the actions of the temporalis muscle?
Bilaterally: elevate mandible; posterior fibers retrude
Unilaterally: slight ipsilateral excursion of mandible
What are the insertions of the medial pterygoid?
Medial aspect of the lateral pterygoid plate (deep head) and the posterior aspect of the maxilla medial aspect of the ramus and angle of the mandible
What are the actions of the medial pterygoid?
Action
Bilaterally: elevate and protrude mandible
Unilaterally: contralateral excursion
Functional Interaction: Masseter & Medial Pterygoid in simultaneous contaction?
Muscles form a functional sling around the angle of the mandible
Simultaneous contraction powerful biting force
Functional Interaction: Masseter & Medial Pterygoid for grinding?
Synergistic action of ipsilateral masseter and contralateral medial pterygoid
What are the insertions of the lateral pterygoid?
Superior head: greater wing of sphenoid medial wall of joint capsule, medial side of articular disc and pterygoid fossa
Inferior head: lateral surface of lateral pterygoid plate neck of mandible and pterygoid fossa
What are the actions of the lateral pterygoid?
Bilaterally: strong protrusion
Unilaterally:
contralateral excursion of mandible
Ipsilateral antero-medial rotation of the condyle
Superior head- eccentric control of disc tension with resisted closing
Inferior head-depressor (resisted)
How do the suprahyoid and infrahyoid muscles assist the muscles of mastication?
Transmits forces directly or indirectly to the mandible
Suprahyoids can assist with depression of the mandible
What is involved in the muscular control of opening?
Gravity
Contraction of inferior head of lateral pterygoid & suprahyoid muscles
Synergistic action produces rotation
Disc and condyle slide anteriorly in late opening
Disc pulled by:
Translating condyle
Increased intra-articular pressure created by activation of inferior head of lateral pterygoid
What is involved in the muscular control of closing the TMJ?
Forceful: masseter, temporalis and medial pterygoid
Superior head of lateral pterygoid eccentrically contracts to stabilize the disc and neck of the mandible to optimize the position of the disc between the condyle and articular eminence
How does upper cervical posture effect the TMJ joint?
Posture of the head and neck can significantly alter TMJ biomechanics and stresses
Mandibular position
Muscular stresses
Joint loading
