MECHANISMS OF MANDIBULAR MOVEMENT

Question 1

Mandible has 2 main movements

Answer 1

Rotation and Translation

Question 2

Translation

Answer 2

movement in which each point of the moving object has simultaneously the same velocity (speed and direction)
* When the mandible is in protrusive movement (or retrusion)

Question 3

What is responsible for path of translation?

Answer 3

Articular Eminence in the TMJ

Question 4

Most complex movements in the masticatory system are a combination of

Answer 4

Rotation and Translation

Question 5

Border Movements studies

Answer 5

in the outer range of mandibular movements (based on TMJ morphology)

Question 6

Border movements are described in

Answer 6

the 3 planes that the mandible moves - frontal, sagittal, horizontal

Question 7

4 sagittal border movements

Answer 7

posterior opening border
anterior opening border
superior opening border
typical function (not border movement)

Question 8

Anterior and posterior movements are limited by

Answer 8

TMJ morphology and ligaments

Question 9

Superior contacts are limited by

Answer 9

teeth (occlusal and incisal)

Question 10

Functional movements are not considered a border movement because:

Answer 10

minimal movement of jaw

Question 11

Superior contact border movements are determined by:

Answer 11

• Variation between CR and ICP
• Anatomy and steepness of inclines of posterior teeth
• OB (overbite) and OJ (overjet) of anterior teeth
• Lingual surfaces of max anterior teeth
• Interarch relationships

Question 12

In the maxilla - CR contacts of posterior teeth have ______ inclines

Answer 12

mesial

Question 13

In the mandible - CR contacts of posterior teeth have ______ inclines

Answer 13

distal

Question 14

When elevator muscles contract

Answer 14

there is usually a 1.25mm Superior/Anterior Slide (+/- lateral movement)

Question 15

Force applied to the teeth when the condyles are in centric relation (CR) will create ______ to ______

Answer 15

superoanterior shift to the mandible in intercuspal position (ICP)

Question 16

The superior contact border movement when the condyles are in centric relation position (CR) is the same as

Answer 16

the maximum ICP of the teeth

Question 17

postural position (PP) is _____mm below ICP

Answer 17

around 2-4

Question 18

T/F: Postural position (PP) is a border movement

Answer 18

F - habitual but not “repeatable” in a border sense

Question 19

T/F: Postural position (PP) is a true rest position

Answer 19

F

Question 20

Clinical rest position

Answer 20

when muscle activity is least when mandible is 8mm inferior and 3mm anterior to ICP

Question 21

PP is a “_____” position - balance between ____ and ______

Answer 21

ready - muscle tonus and gravity

Question 22

PP is an efficient position to

Answer 22

quickly bring mandible into function

Question 23

Contraction of R inferior lateral pterygoid will move jaw to

Answer 23

left

Question 24

What will move jaw to left?

Answer 24

Contraction of R inferior lateral pterygoid

Question 25

What condyle will cover greatest distance during left lateral border movement?

Answer 25

R condyle

Question 26

If L inferior lateral pterygoid doesn’t contract

Answer 26

stays in CR and becomes the axis of rotation

Question 27

During the Left lateral border movement - which condyle is the working and which is non-working? What are the technical names for these condyles?

Answer 27

L condyle - ROTATING CONDYLE (“working condyle” – WS)
R condyle – ORBITING CONDYLE (“non-working condyle” – NWS)

Question 28

Once left lateral border movement is achieved - what brings mandible back to midline?

Answer 28

R inferior lateral pterygoid remains contracted while the L inferior lateral pterygoid is now contracted

Question 29

functional range within the horizontal border movements

Answer 29

CR, EC, EEP, ICP, LC

Question 30

What area is used in early stages of mastication?

Answer 30

EC - horizontal border movements

Question 31

What area is used in the later stages of mastication just before swallowing occurs?

Answer 31

LC - horizontal border movements

Question 32

Frontal border movements

Answer 32

1. Left Lateral Superior Border
2. Left Lateral Opening Border
3. Right Lateral Superior Border
4. Right Lateral Opening Border

Question 33

What shape is produced by frontal border movements?

Answer 33

shield

Question 34

What motion occurs during L lateral superior border movement - frontal border movement

Answer 34

concave

Question 35

Shape of L lateral superior border movement - frontal border movement - is determined by

Answer 35

o Morphology of max and mand teeth (in contact)
o Morphology and relationships of condyle/disc/fossa
o Ligaments determine maximum lateral movement

Question 36

What pattern is noted during left lateral opening border movement - frontal border movements?

Answer 36

convex

Question 37

As maximum opening is approached in left lateral opening border movement - what happens?

Answer 37

ligaments begin to tighten and a medial shift back to midline is noted