Biology of Orthodontic Tooth Movement

Question 1

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

Answer 1

PDL

Question 2

What are the four things found trapped in the PDL

Answer 2

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

Question 3

The PDL is constantly doing these two things

Answer 3

adapting and remodeling

Question 4

The PDL is adapted to resist these forces

Answer 4

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

Question 5

Prolongued forces induce what to occur

Answer 5

remodeling of the PDL and adjacent bone

6hrs = movement

Question 6

These two things are important in tooth movement

Answer 6

force magnitude and duration

Question 7

The remodeling of the PDL is mainly conducted by what

Answer 7

fibroblasts

Question 8

This is required for tooth movement beyond the PDL space

Answer 8

bone resorption

Question 9

These are required for bone resorption

Answer 9

osetoclasts

Question 10

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

Answer 10

osteoclasts

Question 11

This theory states that bony changes are caused by electrical signals

Answer 11

bioelectric theory

Question 12

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

Answer 12

pressure-tension theory

Question 13

What are the three proponents of the pressure-tension theory

Answer 13

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

Question 14

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

Answer 14

tooth displacement within the PDL space

Question 15

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

Answer 15

blood flow changes

Question 16

What is the response to minutes of sustained light pressure

Answer 16

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

Question 17

What is the response to hours of sustained light pressure

Answer 17

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

Question 18

What is the response to 2 days of sustained light pressure

Answer 18

tooth movement beyond PDL space

Question 19

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

Answer 19

tooth displacement within PDL space

Question 20

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

Answer 20

blood vessels occluded on pressure side

Question 21

What is the response to minutes of sustained heavy pressure

Answer 21

blood flow cut off to compressed PDL

Question 22

What is the response to hours of sustained heavy pressure

Answer 22

cell death in compressed area

Question 23

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

Answer 23

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

Question 24

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

Answer 24

tooth movement beyonds the PDL space

Question 25

What is tooth movement pattern like under heavy forces

Answer 25

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

Question 26

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

Answer 26

sustained force is required | continuous force is not absolutely required

Question 27

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

Answer 27

4-8hr/day | longer duration produces more efficient tooth movement

Question 28

Force application pattern determines what

Answer 28

compression/tension regions

Question 29

The compression area is larger during what than tipping

Answer 29

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

Question 30

Movement is slower in which type of people

Answer 30

adults

Question 31

Children have these two characteristics that allow for faster movement

Answer 31

remaining alveolar growth | relatively less dense bone

Question 32

Generally, tooth movement is faster in which arch

Answer 32

maxilla, because the bone density is lower

Question 33

What are two drugs that may inhibit orthodontic tooth movement

Answer 33

prostaglandin inhibitors; NSAIDs, corticosteriods | bisphosphonates

Question 34

This method to accelerate tooth movement involves making small indentations

Answer 34

local injury; regional acceleratory phenomenon (RAP)

Question 35

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

Answer 35

corticotomy assisted tooth movement (Wilckodontics)

Question 36

What are three additional methods to accelerate tooth movement

Answer 36

vibration, phototherapy, ultrasound

Question 37

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

Answer 37

anchorage

Question 38

What is the goal of efficient orthodontics

Answer 38

maximizing tooth movement and minimizing unwanted "reactionary effects"

Question 39

The amount of tooth movement increases with pressure only to what

Answer 39

a certain extent

Question 40

What is reciprocal space closure

Answer 40

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

Question 41

What is maximum anchorage

Answer 41

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

Question 42

What is minimum anchorage

Answer 42

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

Question 43

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

Answer 43

stationary anchorage control

Question 44

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

Answer 44

skeletal anchorage | easy to remove because not osteointegrated

Question 45

What happens to the pulp during orthodontic movement

Answer 45

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

Question 46

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

Answer 46

root remodeling/resorption

Question 47

Permanent loss of root surface occurs primarily where

Answer 47

at the apex

Question 48

Which teeth are more prone to root resorption

Answer 48

incisors and second premolars

Question 49

**What are four risk factors for excessive root resportion

Answer 49

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

Question 50

What is the effect that orthodontics has on alveolar bone height

Answer 50

<0.5mm height reduction

Question 51

This must be controlled before orthodontic movement

Answer 51

periodontal movement