Biology of Orthodontic Tooth Movement Flashcards

1
Q

This is the soft tissue connecting teeth to the alveolar bone; approximately 0.5mm in width

A

PDL

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2
Q

What are the four things found trapped in the PDL

A

Many parallel collagenous fibers
cells; fibroblasts, osteoblasts, mesenchymal stem cells, and cells from the vascular structures
blood vessels and nerve endings
tissue fluids

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3
Q

The PDL is constantly doing these two things

A

adapting and remodeling

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4
Q

The PDL is adapted to resist these forces

A

short-duration forces; it acts like a “shock absorber”

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5
Q

Prolongued forces induce what to occur

A

remodeling of the PDL and adjacent bone

6hrs = movement

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6
Q

These two things are important in tooth movement

A

force magnitude and duration

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7
Q

The remodeling of the PDL is mainly conducted by what

A

fibroblasts

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8
Q

This is required for tooth movement beyond the PDL space

A

bone resorption

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9
Q

These are required for bone resorption

A

osetoclasts

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10
Q

These cells are not normally available in the PDL; must be recruited from the blood vessels or bone marrow

A

osteoclasts

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11
Q

This theory states that bony changes are caused by electrical signals

A

bioelectric theory

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12
Q

This theory states that bony changes are caused by chemical signals; this theory is accepted

A

pressure-tension theory

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13
Q

What are the three proponents of the pressure-tension theory

A

pressure and tension alter blood flow
formation and release of chemical messengers
chemical messenger change cell activities

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14
Q

What is the response to 1-2 seconds of sustained light pressure

A

tooth displacement within the PDL space

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15
Q

What is the response to 3-5 seconds of sustained light pressure

A

blood flow changes

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16
Q

What is the response to minutes of sustained light pressure

A

oxygen tension at compression side decreases leading to prostaglandins (PG-E) and cytokines (IL-1) release

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17
Q

What is the response to hours of sustained light pressure

A

chemical messengers cause metabolic change; second messengers such as cAMP release recruiting osteoclasts
They mature and are activated leading to frontal bone resorption

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18
Q

What is the response to 2 days of sustained light pressure

A

tooth movement beyond PDL space

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19
Q

What is the response to 1-2 seconds of sustained heavy pressure

A

tooth displacement within PDL space

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20
Q

What is the response to 3-5 seconds of sustained heavy pressure

A

blood vessels occluded on pressure side

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21
Q

What is the response to minutes of sustained heavy pressure

A

blood flow cut off to compressed PDL

22
Q

What is the response to hours of sustained heavy pressure

A

cell death in compressed area

23
Q

What is the response to 3-5 days of sustained heavy pressure

A

osteoclast recruitment from the bone marrow in the alveolar bone; maturation and activation leading to undermining bone resorption

24
Q

What is the response of 7-14 days of sustained heavy pressure

A

tooth movement beyonds the PDL space

25
Q

What is tooth movement pattern like under heavy forces

A

tooth moves quickly, then stops, then moves quickly due to undermining resorption

26
Q

This type of force is required, while this other one is not

A

sustained force is required

continuous force is not absolutely required

27
Q

What is the required time/day needed for efficient tooth movement

A

4-8hr/day

longer duration produces more efficient tooth movement

28
Q

Force application pattern determines what

A

compression/tension regions

29
Q

The compression area is larger during what than tipping

A

translation

with tipping, greater force is needed to produce the same pressure

30
Q

Movement is slower in which type of people

A

adults

31
Q

Children have these two characteristics that allow for faster movement

A

remaining alveolar growth

relatively less dense bone

32
Q

Generally, tooth movement is faster in which arch

A

maxilla, because the bone density is lower

33
Q

What are two drugs that may inhibit orthodontic tooth movement

A

prostaglandin inhibitors; NSAIDs, corticosteriods

bisphosphonates

34
Q

This method to accelerate tooth movement involves making small indentations

A

local injury; regional acceleratory phenomenon (RAP)

35
Q

This method to accelerate tooth movement involves “scoring” between the bony sockets

A

corticotomy assisted tooth movement (Wilckodontics)

36
Q

What are three additional methods to accelerate tooth movement

A

vibration, phototherapy, ultrasound

37
Q

This is resistance to unwanted tooth movement and resistance to the reaction force

A

anchorage

38
Q

What is the goal of efficient orthodontics

A

maximizing tooth movement and minimizing unwanted “reactionary effects”

39
Q

The amount of tooth movement increases with pressure only to what

A

a certain extent

40
Q

What is reciprocal space closure

A

No anchorage is needed; both sides are working equally to move

41
Q

What is maximum anchorage

A

when you don’t want to move the posteriors; anchor there

42
Q

What is minimum anchorage

A

when you don’t want to move the anteriors; anchor there

43
Q

This only allows bodily movement of the molars, which requires stronger pressure

A

stationary anchorage control

44
Q

This is the use of temporary anchorage devices (TADs) to prevent unwanted tooth movement

A

skeletal anchorage

easy to remove because not osteointegrated

45
Q

What happens to the pulp during orthodontic movement

A

pulpal reaction is minimal; loss of vitality may be due to previous trauma

46
Q

This is a constant feature of orthodontic tooth movement; all patients exhibit some of this, 1-2% of them severe

A

root remodeling/resorption

47
Q

Permanent loss of root surface occurs primarily where

A

at the apex

48
Q

Which teeth are more prone to root resorption

A

incisors and second premolars

49
Q

**What are four risk factors for excessive root resportion

A

abnormal root morphology; conical roots, pointed apices, dilaceration
prolonged treatment time, excessive and prolonged orthodontic forces
genetic predisposition
history of root resorption

50
Q

What is the effect that orthodontics has on alveolar bone height

A

<0.5mm height reduction

51
Q

This must be controlled before orthodontic movement

A

periodontal movement