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Orthodontics > Exam 2 - Biological Response to Force > Flashcards

Exam 2 - Biological Response to Force Flashcards

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1
Q

movement of the teeth from alveolar bone modification

A

orthodontics

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2
Q

modification of facial growth

A

dentofacial orthopedics

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3
Q

What are the biological structures for modifications in dentofacial orthopedics?

A

maxilla - suture
mandible - secondary cartilage

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4
Q

What is tooth movement based on?

A

the principle that pressure applied to a tooth is transmitted through the PDL to surrounding bone which remodels in such a manner that the socket migrates, carrying the tooth with it

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5
Q

What are the components of the tooth-bone attachment/PDL?

A
  1. collagenous fibers: sling-like shock absorber
  2. cellular elements
    - vascular
    - neural
    - mesenchymal
  3. tissue fluids
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6
Q

How thick is the PDL?

A

.5 mm thick

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7
Q

What is the sling-like shock absorber of the PDL?

A

collagenous fibers

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8
Q

What are the mesenchymal cells and their progeny?

A

connective tissue cells
- fibroblasts & fibroclasts (collagen and matrix materials)

bone cells
- osteoblasts & osteoclasts (remodelling of alveolar socket)

*blast = build
* clast = chew or breakdown

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9
Q

What is the range of masticatory lodges?

A

2-50 kg

2 = soft food
50 = hard food

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10
Q

Describe the events that happen at <1, 1-2 and 3-5 seconds with regards to the PDL

A
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11
Q

What are the gram forces during active stabilization/resting pressures? Are these forces in equilibrium?

A

not in equilibrium

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12
Q

What two things are required for tooth movement?

A
  1. stimulus
    - biologic electricity theory
    - pressure: tension theory
  2. cell differentiation
    - osteoclasts
    - osteoblasts
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13
Q

What is biological electricity?

A

an electrical signal which can be described by the piezoeletric effect

*once off the force is the same but reverse

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14
Q

What are three characteristics of the piezoelectric effect?

A
  1. small charge differences
  2. quick decay
  3. opposite streaming with release of force
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15
Q

What is the pressure-tension theory?

A

a chemical signal

pressure side = compression
tension side = expansion

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16
Q

This theory is a chemical signal

A

pressure-tension theory

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17
Q

This theory is an electrical signal

A

Biological electricity

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18
Q

What things will happen from the pressure-tension theory?

A
  1. alteration in blood flow from pressure in the PDL
  2. formation and release of chemical messengers
  3. activation of cells
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19
Q

What is the physiological response to sustained light pressure on the PRESSURE side?

A
  1. 3-5 seconds
    - alteration in blood flow
  2. minutes
    - 02 levels change
    - increase in prostaglandins and cytokines
  3. hours
    - histologic changes in PDL cells
  4. 2 days
    - osteoclasts/blasts begin “frontal resoprtion”
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20
Q

What is the physiological response to sustained heavy pressure on the PRESSURE side?

A
  1. minutes
    - blood flow stops
  2. hours
    - cell death from compression
  3. days
    - osteoclasts/osteoblasts begin remodeling adjacent marrow spaces
  4. weeks
    - “undermining resorption”
    - removes dead bone
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21
Q

Describe this image of the physiologic response to sustained heavy pressure

A

PDL necrosis

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22
Q

Describe this picture of the physiological response to light force

A
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23
Q

frontal resorption is in response to

A

light force

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24
Q

undermining resorption is in response to

A

heavy force

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25
What is better at controlling the positional movement of bone, heavy or light force?
heavy force because you can put the tooth where it needs to go
26
Describe the tooth movement (mm) vs. time (days) for frontal and undermining resorption
FRONTAL - light wire - continuous tooth movement UNDERMINING RESPORPTION - heavy wire - force dissipates to 0 and the tooth will move, after the tooth moves the bracket will have to be moved for this to happen again so the patient will have to come in
27
What occurs during tooth tipping (biomechanics)?
1. only 1/2 PDL loaded 2. forces must be light ~ 50 gm
28
Where is the center of resistance during the tipping movement?
apical 1/3
29
What happens during tooth translation?
- crown and root move concurrently - whole PDL loaded - more force required ~ 70-120 gm
30
What is a force couple? When is it used?
placing a bracket wire 1. 2 forces equal in magnitude but opposite in direction 2. allows a moment vector of force in any direction
31
How many forces are required for tooth translation?
2 1. a moment force 2. a force couple
32
What occurs during tooth intrusion?
1. only apex PDL loaded 2. forces must be very light 3. ~ 10-20 gm
33
What is the threshold that must be met for the force (hrs/day) to get the effect you want?
need a minimum threshold met of 6 hours
34
What are the three force decays?
1. continuous force 2. interrupted force 3. intermittent force: patient puts it in and takes it out
35
Will an increase in pressure always can an increase in tooth movement?
No. There is an optimal force in which an increase in pressure will cause no more increase in tooth movement past this optimal force.
36
What occurs during simple space closure?
distribution of force over equal PDL areas results in reciprocal tooth movement
37
Is there reciprocal tooth movement during tipping and translation?
there is NOT reciprocal tooth movement so need to do a two stage space closure to fix the teeth (pull the anterior mandibular teeth posterior)
38
Which tooth has the largest anchorage (hardest tooth to move)?
maxillary first molar
39
Which tooth has the lowest anchorage (easiest tooth to move)?
mandibular central incisor
40
What occurs during two stage space closure?
1. canine retraction - using elastics to move canine into 1st premolar position - omega loop on 2nd molar which causes mandibular anterior teeth to join the anchorage to help move the canines into place 2. incisor retraction **6 teeth anchoring posteriorly = 1st and second molar, 2nd premolar
41
What is the result of excessive force on the PDL?
root resorption
42
Does resorption occur during most treatments? How?
Yes. moderate resorption during most treatments generalized osteoclastic activity which shortens roots
43
Does resorption occur during most treatments? How?
Yes. moderate resorption during most treatments generalized osteoclastic activity which shortens roots
44
a fibrous union between two or more bones
suture
45
Where are sutures found
midface of skull
46
What do sutures start as before the mature
fontanelles (in skull)
47
Sutures ___ bone in joint with tension and ____ bone in joint with pressure
deposit resorb
48
grows in response to changes in surrounding tissues
growth site
49
As an individual matures, what happens to the development of the palatal suture?
suture becomes more tortuous (curving like a river)
50
What is use to treat a cross bite malocclusion? How long does it take?
- rapid palatal expansion - 60 days
51
What are extraoral force applications to midfacial sutures?
headgear
52
When is headgear used?
sutural compression to treat class II malocclusions when maxilla is large
53
Palatal expansion is an example of what kind of force?
interrupted force
54
Extraoral force via headgear is an example of what kind of force?
intermittent force
55
cartilagenous head of mandible composed of secondary cartilage capped by fibrocartilage
mandibular condyle
56
growth plates of long bones are known as
growth centers
57
What is the growth potential of secondary cartilage?
intrinsic growth potential, but may be modified by changes in surrounding tissue
58
Is the mandibular condyle different than cartilagenous growth plates of long bones?
Yes. it has secondary cartilage which is able to be modified by changes in surrounding tissues
59
Epiphysial growth plate is an example of what type of cartilage?
primary cartilage
60
Mandibular condyle is an example of what type of cartilage?
secondary cartilage
61
How is growth of the suture regulated?
by surrounding tissues
62
How is the growth of the mandibular condyle regulated?
by surrounding tissues and genetic growth potential
63
How is the growth of the epiphyseal growth plate regulated?
by genetic growth potential
64
What does the shape of the mandibular condyles look like?
"like" a long bone with the epiphysis removed
65
In what direction does the condyle grow?
backwards, away from the ramus
66
In what direction does the body of the mandible grow?
like an "expanding V"
67
What kind of growth increases ramus height?
condylar growth
68
Describe condyle growth. What does condyle growth cause?
- may grow forward or backward relative to the ramus - mandibular growth rotations
69
Forward growth rotation of condyle causes
class II deep bite
70
Backward growth rotation of condyle causes
class II open bite
71
What do functional appliances do? What is an example
- apply force to teeth, mandibular condyle & sutures - dentofacial orthopedic treatment: bionator appliance worn over 16 hours/day
72
What does a bionator appliance require?
bite construction from forward posture of mandible
73
What is an extraoral force to the mandible
74
What happens to growth potential as you age?
decreases with age
75
Which tooth in the maxilla has the highest anchorage value?
maxillary first molar

Orthodontics (7 decks)

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