Dental Anatomy Quiz 6

What is the origin and insertion of the sphenomandibular ligament?

What is the action?

O: Spine of sphenoid

I: lingual

A: no effect on mandibular movement

What is the origin and insertion of the stylomandibular ligament?

What is the action?

O: styloid process

I: angle and posterior border of ramus

A: limits protrusion

What is the action of the digastrics?

Depress the mandible

What is the origin and insertion of the Masseter?

What is the action?

O: Zygomatic Arch

I: Lateral aspect of border of ramus

A: Elevate mandible

What is the origin and insertion of the Temporalis?

What is the action?

O: Temporal Fossa

I: Coronoid Process

A: Elevates and retrudes mandible

What are the 3 divison of the temporalis? What is the action of each of them?

Anterior: raises mandible vertically

Middle: Elevates and retrudes mandible

Posterior: Retrudes mandible

What is the origin and insertion of the Medial Pterygoid?

What is the action?

O: Pterygoid Fossa

I: Medial Surface of Mandibular Angle

A: Elevate and unilateral mediotrusive movement

What is the origin and insertion of the Inferior Belly of the Lateral Pterygoid?

What is the action?

O: Outer surface of lateral pterygoid plate

I: Neck of condyle

A: Protrudes mandible + Unilaterally mediotrusive movement

• Active during opening of mandible

What is the origin and insertion of the Superior Belly of the Lateral Pterygoid?

What is the action?

O: Infratemporal region of greater sphenoid wing

I: Articular capsule, disc, and neck of condyle

A: Active during power stroke

What is the origin and insertion of the posterior belly Digastric?

O: Mastoid Notch

I: Intermediate tendon

What is the origin and insertion of the Anterior belly Digastric?

O: Fossa on lingual surface of mandible

I: Intermediate tendon

What is the function of the Digastrics? (3 functions) **

1. Depresses the mandible and pulls it backward when hyoid is fixed

2. Teeth are brought out of contact

3. When mandible is stabilized, it elevates the hyoid bone during swallowing

What other muscles contribute to mastication? (4)

1. Suprahyoid

2. Infrahyoid

3. SCM

4. Posterior Cervical Muscle

What are the 2 systems of the TMJ?

What are their functions?

Where are they in the synovial cavity?

1. Condyle-Disc Complex

   1. Responsible for rotation

   2. Comprises the inferior synovial cavity

2. Condyle-Disc Complex + Mandibular Fossa

   1. Responsible for translation

   2. Superior synovial Cavity

How is the TMJ kept stable?

What happens with increased and decreased pressure?

• What happens to the disc space

• Constant activity of the elevators even at rest

• No pressure = articular surfaces separate and dislocate

  • Disc space widens

  • Happens during closed rest position

• Increased pressure = interarticular pressure

  • Disc space narrows

What is the function of the superior retrodiscal lamina?

What protects it?

What happens when the mouth is open?

What about closed?

What about protruding?

Retract the disc posteriorly (only structure to do so)

• Elastic fibers allow condyle to move out of the fossa without damaging Superior retrodiscal lamina

When mouth is open: Superior Retrodiscal Lamina = Stretched

When mouth is closed: Elastic traction is minimal

When in full protrusion: Retractive forces are at a maximum

What is dislocation of the TMJ?

How does the body compensate? What muscle?

One side of dentition bites down on something hard and not the other

• TMJ not equally loaded

• Superior lateral pterygoid fights this by becoming activated so thicker part of disc is in contact with TMJ

What muscles elevate the mandible?

Temporal

Masseter

Medial Pterygoid

***Articular surface must always be in constant contact

What are the 2 components of Articular Cartilage?

What comprises them?

Condrocytes: Produce Collagen + Proteoglycans + Glycoproteins

Intracellular Matrix: Proteoglycans = Hyaluronic Acid chain

• Hydrophilic

• Swelling due to High Water content

What is the innervation of the TMJ?

What CN? What branches (3)?

Mandibular Nerve

• Auriculotemporal

• Deep Temporal

• Masseteric

What is the blood supply to the TMJ? (3)

• What parts do the supply blood to?

Superior Temporal Artery = Posterior

Middle Meningeal Artery = Anterior

Inferior Maxillary Artery = Inferior

What is the function of the Collateral Discal Ligaments? (4)

Responsible for Hinge movements

Restricts movement of disc away from condyle

Allows passive movement with condyle during gliding

Permits anterior and posterior rotation of the disc

Divides joint into superior and inferior cavities

What is the function of the oblique portion of the TM Ligament?

Limits extent of mouth opening

• Gliding starts after anterior teeth are 20-25mm apart

Limits rotational and hinge movement

What is the function of the horizontal portion of the TM Ligament? (4)

Limits posterior movement of condyle and disc

Prevents condyle from moving into posterior region of mandibular fossa

Protects retrodiscal tissue from trauma

Protects lateral pterygoid from overlengthening

What is the function of the Stylomandibular Ligament?

When is most relaxed?

Taut with protrusion = limits excessive protrusion

Most relaxed when wide open

What ligament has no function?

Sphenomandibular Ligament