Lecture 6 - Mechanics of Mandibular Movement

Question 1

what are the four anatomic determinants of movement

Answer 1

-right TMJ
- left TMJ
- teeth/occlusion
-neuromusculature

Question 2

where does rotational movement occur

Answer 2

in the inferior joint compartment

Question 3

where does translational movement occur

Answer 3

in the superior joint compartment

Question 4

when does rotation occur

Answer 4

when the mouth opens and closes around a fixed point or axis within the condyles

Question 5

where does the condyle rotate in rotation

Answer 5

on the inferior aspect of the articular disk

Question 6

when does rotation vs translation occur

Answer 6

rotation occurs for the first 20-25 mm of opening then further opening translation occurs

Question 7

what 3 reference planes may rotational movement occur in the mandible

Answer 7

-rotation in the sagittal plane around a horizontal axis
- rotation in the horizontal plane around a vertical axis
- rotation in the frontal plane around a sagittal axis

Question 8

what is the horizontal axis that passes through both R and L condyles called

Answer 8

-terminal hinge axis
- transverse hinge axis
- horizontal hinge axis

Question 9

What is the only rotational movement that can be isolated clinically and recorded and identifiable

Answer 9

rotation in the sagittal plane around a horizontal axis

Question 10

when does rotation in the horizontal plane around a frontal axis occur

Answer 10

during lateral movement

Question 11

where is the frontal axis located in rotation in the horizontal plane around a frontal axis

Answer 11

in the working side condyle

Question 12

where does the non-working side condyle move in rotation in the horizontal plane around a frontal axis

Answer 12

medially and forward in the horizontal plane orbiting around this frontal axis

Question 13

when does rotation in the vertical plane around a sagittal center of rotation occur

Answer 13

during lateral movement

Question 14

where is the sagittal axis located in rotation in the vertical plane around a sagittal center of rotation

Answer 14

working side condyle

Question 15

where does the non-working side condyle move in in the vertical plane around a sagittal center of rotation

Answer 15

inferiorly in the frontal plane around the sagittal axis

Question 16

what is the point called where are three axes (horizontal, vertical, and sagittal) meet

Answer 16

the rotational center of the condyle

Question 17

what is translation defined as

Answer 17

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

Question 18

when does translation occur

Answer 18

depression of the mandible beyond 25 mm, and in protrusion

Question 19

what do the working side condyle and non working side condyle do in lateral translational movement

Answer 19

working side: move downwards, forwards, and medially
non-working side: may shift laterally, called the Bennett movement

Question 20

what is the working side of the mandible in lateral movement and the non working side and what are the both called

Answer 20

-working side: the condyle on the side towards which the mandible moves- called the rotating condyle
- non- working side: condyle on the side opposite to which the mandible moves - called the orbiting condyle

Question 21

what do the working side and non working side do in lateral movement

Answer 21

-working side: condyle rotates around a vertical axis
- non-working side: condyle moves downwards, forwards, and medially through a series of rotations

Question 22

what is the condylar angle defined as

Answer 22

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

Question 23

how can the condylar angle be recorded on a patient

Answer 23

via a protrusive movement or via lateral movements

Question 24

what is the condylar angle influenced by in protrusive movement

Answer 24

the posterior slope of the articular eminence

Question 25

is the angle of the posterior slope of the articular eminence the same in everyone

Answer 25

no

Question 26

what is the condylar angle measured via lateral movement influenced by

Answer 26

the steepness of the medial wall of the articular fossa - non-working side

Question 27

is the condylar angle slightly steeper when recorded in protrusion or lateral movement

Answer 27

lateral movement

Question 28

what is fischers angle defined as

Answer 28

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

Question 29

what is fischers angle the difference between

Answer 29

the condylar angle recorded with a protrusive and lateral record

Question 30

medial wall of the articular fossa is generally steeper than ____

Answer 30

the posterior slope of the articular eminence

Question 31

what is fischers angle usually

Answer 31

5-10 degrees

Question 32

what is bennett angle

Answer 32

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

Question 33

what is bennett movement

Answer 33

bodily movement of the mandible during lateral excursive movement

Question 34

what happens in bennett movement

Answer 34

the working side condyle rotates and also shifts laterally during the lateral movement, this lateral movement of the working side condyle is the bennet movement

Question 35

what happens in protrusion

Answer 35

-both condyles translate
- condyles move forwards and downwards
- condyles move down the posterior slope of the articular eminence (condylar guidance angle can be calculated from this)