Mandibular Movement

Question 1

What are the four anatomic determinants of mandibular movement?

Answer 1

1. right TMJ
2. left TMJ
3. Teeth/occlusion
4. Neuromusculature

Question 2

What are the two different types of movements within the TMJ?

Answer 2

• rotational movement (inferior joint compartment)
• translational movement (superior joint compartment)

Question 3

What is rotation within the TMJ?

Answer 3

• process of turning about the axis
• mouth opens and closes around a fixed point or axis within the condyles

Question 4

Where does rotation occur?

Answer 4

within the inferior joint compartment (on the articular disk)

Question 5

How far (mm) does rotation occur before translation begins?

Answer 5

20-25 mm of opening

Question 6

What are the three reference planes that rotational movements of mandbile may occur in?

Answer 6

sagittal plane - horizontal axis
horizontal plane - vertical axis
frontal plane - sagittal axis

Question 7

What is the horizontal axis that passes through both right and left condyles called?

Answer 7

terminal hinge axis
transverse hinge axis
horizontal hinge axis

Question 8

What movement of the mandible only occurs when in CR?

Answer 8

rotation in the sagittal plane around a horizontal axis

Question 9

What movement causes rotation in the horizontal plane around the frontal axis?

Answer 9

lateral movement

Question 10

What does the working side and non working side do during rotation in the horizontal plane around the frontal axis?

Answer 10

working side - frontal axis is in it
nonworking side - medially in the horizontal plane

Question 11

What movement causes rotation in the vertical plane around the sagittal axis?

Answer 11

lateral movement

Question 12

What does the working side and non working side do during rotation in the vertical plane around the sagittal axis?

Answer 12

working side - sagittal axis is in it
nonworking side - inferiorly in the frontal plane

Question 13

What is the rotational center of the condyle?

Answer 13

where all three axes (horizontal, vertical, sagittal) meet

Question 14

What is translation?

Answer 14

Defined as every point in an object
(mandible) simultaneously moving in the same direction with the same velocity

Question 15

What movements cause translation?

Answer 15

• depression of the mandible
• protrusion
• lateral movement

Question 16

In lateral movement with translation what do the working and nonworking condyles do?

Answer 16

working - shift laterally (bennett movement)
nonworking - moves down, forward, and medial

Question 17

What is the bennet movement?

Answer 17

the lateral movement of the working side condyle in translation movements

Question 18

During a lateral movement, this is the condyle on the side towards which the mandible moves is the…

Answer 18

working side condyle
- rotating

Question 19

During a lateral movement, this is the condyle on the side opposite to which the mandible moves…

Answer 19

non-working side condyle
- orbiting

Question 20

Working side condyle mainly rotates around a _______ axis

Answer 20

vertical

Question 21

Non-working side condyle moves ________ ________ ________ through a series of rotations

Answer 21

downwards, forwards and medially

Question 22

What is the condylar angle?

Answer 22

Angle at which the condyle moves away from a horizontal reference plane

Question 23

How can you measure the condylar angle?

Answer 23

recorded via protrusive movement or lateral movements

Question 24

During PROTRUSIVE MOVEMENT, the angle is influenced by the…

Answer 24

posterior slope of the articular eminence

Question 25

What is fischer’s angle?

Answer 25

The angle formed by the intersection of the protrusive and non-working condylar paths as viewed in the sagittal plane.

Question 26

What is the difference between the condylar angle recorded with a protrusive and lateral recor?

Answer 26

fischer’s angle (5-10 degrees)

Question 27

What is bennett angle?

Answer 27

The angle at which the NWS condyle moves medially away from a sagittal reference plane as viewed in the horizontal plane during a lateral movement