Chapter 5: Mandibular positions and movements Flashcards
1
Q
VDR is provided by our _____ _____
A
Myotatic reflex
2
Q
VDR characteristics:
A
- Relaxed
- With head erect (upright position)
- There is no tooth contact
- 2-4mm IFS between the arches from MI
3
Q
If we have contact during VDR what does it mean?
A
That we have malposition
4
Q
IFS if the distance between _____ and _____
A
VDR and VD
5
Q
What is Centric Relation?
A
The most anterior superior position of the condyles in the glenoid fossa
6
Q
What is the most physiological position for the condyles called?
A
CR
7
Q
What muscles do we use to maintain the CR?
A
The internal pterygoid and the masseter (they are contracting muscles)
8
Q
What is Centric Occlusion?
A
It is a position of maximal, bilateral, balanced contact between the cusps of the maxillary and mandibular arches
9
Q
Only 5-10% of the population has CO. True or False
A
True
10
Q
Is CR recordable?
A
Yes
11
Q
Will CR change over the years?
A
No, it is a good reference because it will not change over the years
12
Q
When we swallow, are condyles are in _____
A
CR
13
Q
What happens with the condyles, when we swallow but we have a prematurity?
A
The condyles will not be in CR anymore
14
Q
Definition of Maximum Intercuspation
A
When the cusps of the teeth of both arches fully interpose themselves with the cusps of the teeth of the opposing arch
15
Q
Is there a “maximum” number of teeth contact?
A
Yes
16
Q
MI is dependent of the condylar position. True or False
A
False. MI is independent of the condylar position
17
Q
What is the spatial relationship between the jaw and skull dependent on?
A
Normal function of:
- TMJ
- Muscles
- Neuromuscular system
- Contact between arches
18
Q
We have a 0-25mm opening motion with pure rotation when the mandible is opened in a _____ _____
A
Retroposition
19
Q
CR in MI =
A
CO or THIOP
20
Q
CR coincides with MI for the majority of the population. True or False
A
False, CR coincides with MI only for 5-10% of the population
21
Q
Cases when the condyles are not in CR when there is MI:
A
- MIOP: condyles are both forward, we have prematurities on both sides
- LIOP: 1 condyle is more forward than the other
22
Q
What is more common MIOP or LIOP?
A
MIOP
23
Q
What situation is more pathological for our TMJ’s health, MIOP or LIOP?
A
LIOP
24
Q
What is the first contact between the slope and MI called?
A
Shift
25
Examples of eccentric relations:
- Protrusion
- Laterality
- Lateroprotrusion
26
Match the letters with the numbers:
A. Protrusion
B. Laterality
C. Lateroprotrusion
1. Laterisation + protrusion
2. Anterior condylar position about CR (mandible is forward)
3. Mandibular movement sideways concerning the maxilla
A. 2
B. 3
C. 1
27
Match the letters with the numbers:
A. Laterality
B. Opening
C. Closing
D. Protrusion
1. No teeth contact
2. Teeth contact
A. 2
B. 1
C. 1
D. 2
28
Functional movements can be measured in 3 planes of space:
Sagittal, frontal and horizontal
29
What is a border movement?
A maximum movement, extreme position of the mandible
30
Border movements are functional movements. True or False
False. Intraborder movements are functional movements
31
What are the main directions of movement? Which is the only centric position?
- Opening and Closing (only centric position)
- Protrusion
- Retrusion
- Laterality
- Combined (lateroprotrusion)
32
Types of movements:
- Rotation
- Translation
- Combined (rotation and translation)
33
In a deep bite, the anterior guidance is compromised. True or False
True
34
In what view do we observe the opening and closing movement?
Sagittal view
35
Posterior border opening characteristics:
1st arc:
a. Up to 25mm
b. Condyles are still in CR (pure rotation)
c. It allows the localisation of the axis of rotation
2nd arc:
a. On average 20mm
b. A combination of rotation and translation
36
What is Protrusion?
It is a posterior disocclusion guided by the anterior teeth
37
What measure can the protrusion movement reach.
Normally we are moving 7mm with teeth contact.
But, the movement can go up to 15mm with no teeth contact.
38
"During this movement, both condyles go forward and descend by the articular eminence" What movement are we talking about?
Protrusion
39
Describe the laterality movement
Canines are edge-to-edge and we can go to maximum laterality with no teeth contact
40
What is the Working Side? (in laterality)
- Side to which the jaw moves
- Active cusps
- Rotational/pivoting side
- Rotation + translation
41
What is the Non-Working Side? (in laterality)
- Translational/orbiting side
- Where the condyle moves the most
42
What happens during the postural rest position?
- There is a balancing of the elevators and depressors muscles
- Condyles are forward and downward in relation to the CR
43
Is the postural rest position easily reproducible?
No, because of the hyper activation of the muscles it may vary
44
Normal measure between the 2 arches during posterior rest position
2-4 mm from MI
45
The posterior rest position is a way to measure VDR. True or False
True
46
What is the interocclusal freeway space?
The space between MI and PRP
47
What is the IFS due to?
The myotatic contraction of the elevator muscles to compensate for gravity
48
IFS might be altered due to:
- Bruxism
- Edentulous with an old prosthesis
- Head's position:
a. Forward: IFS decreases
b. Backwards: IFS increases
- Bone classes:
a. Class II: IFS increases
b. Class III: IFS decreases
49
What will the invasion of the IFS cause?
Muscular dysfunction and temporomandibular dysfunction
50
Match the letters with the numbers:
A. VD
B. VR
C. VO
1. It is the height of the lower facial third; the distance between 2 points in mm
2. The distance to the jaw in MI
3. The distance to the jaw at PRP
A. 1
B. 3
C. 2
51
VDR - VDO =
IFS
52
What position is independent of dental contact?
CR
53
CR is restricted to a movement of translation around the terminal hinge. True or False
False, CR is restricted to a movement of pure rotation around the terminal hinge.
54
"It is the optimal position to rehabilitate a patient when they present no stable occlusion" What position are we talking about?
CR
55
All teeth or dentures will be recorded in ____ because it is the most favourable position
CR
56
Techniques for determining the CR:
Unimanual:
- Chin point guide
- In the past: we used to apply strong pressure on the back of the jaw
- Today: we apply a slight pressure
Bimanual:
- Dawson technique
- More complex for beginners
- It is very accurate
57
We need to direct the mandible and do a ______ ______ ______ to get to a CR position
Posterior border movement
58
Normally discrepancy in CR and MI is ______.
Discrepancy up to ______ is considered physiological.
If it is more than ______ the tendency to develop ______ is higher.
1.25 mm
0.2 mm
1.25 mm, TMD
59
Cases in which we need to have CR and MI coinciding at the same point:
- Full dentures
- RPD free end
- Total rehabilitation with fixed prosthesis
- When there is TMD
60
Prematurities are most commonly found in:
Upper 1st premolar palatal cusp (mesiointernal slope) against the distal internal slope of the lower cusp
61
Match the numbers with the letters:
1. MIOP
2. LIOP
A. Jaw moves forward to MI, and both condyles move from CR to the MI position
B. More pathological
C. Jaw deviation towards the side which is in CR
D. Contralateral condyle moves mesially
E. More common
F. The distance of the condyle's movement is 1.5mm approx
J. One of the condyles is in CR and the other one is more advanced forward
H. Mandibular lateral deviation in MI
A. 1
B. 2
C. 2
D. 2
E. 1
F. 1
J. 2
H. 2
62
What is Right LIOP?
The right condyle is in CR, so the jaw diverts to the right to go into MI
63
What is Left LIOP?
The left condyle is in CR, so the jaw diverts to the left to go into MI
64
What is the sagittal condylar path in protrusive movements?
- It is the trajectory describing the condyles during protrusion
- It usually has an italic S form
- It is influenced by the anterior guidance
- It is not a fixed factor
65
What is an anterior guidance?
When the lower incisors slide forward and downward until they reach the edge-to-edge position
66
Value of the incise guidance inclination
50 to 5 degrees ( 5 degrees greater than CPI)
67
What does the anterior guidance cause?
Posterior disocclusion
68
We can study the condyle in a ______ or ______ view but not in a ______ view.
- Sagittal or Horizontal
- Frontal
69
What muscle is the laterality movement produced by?
The external pterygoid (lower head) on the NWS
70
The non-working side, despite its name its condyle works more. True or False
True
71
What is the Bennett angle?
It is the angle formed between the sagittal plane and the average path of the advancing condyle on NWS as viewed in the horizontal plane during lateral mandibular movements.
72
Average of the Bennett angle
- In the very beginning 7.5-12.8 degrees, it will decrease depending on the movement
- When we are edge to edge the value is 15 degrees
73
What is more frequent regarding the working side of the laterality movement; that it only rotates (mediotrusion) or that it rotates and moves outwards (laterotrusion)?
That it rotates and moves outwards, to allow its rotation on a vertical axis
74
What is the Bennett movement?
It is defined as the bodily lateral movement or shift of the mandible resulting from the movements of the condyles along lateral inclines of the mandibular fossa during jaw movement.
75
What are the 2 references to Bennett's movement?
- The bodily lateral movement of both condyles
- The outward movement of the WS
