biology of orthodontic tooth movement (dr. sun)

Question 1

the PDL is approx. ____mm in width.

Answer 1

0.5mm

Question 2

what is the effect of tissue fluids in the PDL?

Answer 2

dampening effect/ shock absorber (viscoelastic element)

Question 3

the nerve ending for perception of pain and proprioception in the PDL are __________ (myelinated/ unmyelinated).

Answer 3

unmyelinated

Question 4

the PDL is adapted to resist __________ (short/long) duration forces.

Answer 4

short (seconds)

Question 5

_______________ of ____________ occurs when prolonged forces act on the PDL.

Answer 5

remodeling of bone and adjacent PDL

Question 6

a force magnitude as low as _____gm can induce tooth movement.

Answer 6

2

Question 7

PDL remodeling is caused by _________, which are abundant in the PDL.

Answer 7

fibroblasts

Question 8

PDL fibers have to remodeled in order to induce tooth movement. which fibers are especially important?

Answer 8

Sharpey’s fibers

Question 9

_________ is required for tooth movement beyond the PDL space.

Answer 9

bone resorption

Question 10

osteoclasts originate from _________ cells.

Answer 10

hematopoietic stem cells

Question 11

T/F: osteoclasts are not readily available in the PDL

Answer 11

True, must be recruited from blood vessels or bone marrow

Question 12

the ________ theory of tooth movement states that bony changes are caused by electric signals.

Answer 12

bioelectric theory

Question 13

the __________ theory of tooth movement states that bony changes are caused by chemical signals

Answer 13

pressure-tension theory

Question 14

what are the two principles of the bioelectric theory?

Answer 14

1. force induces piezoelectric signals

2. bioelectric potential changes cell activity

Question 15

what are the three principles of the pressure-tension theory?

Answer 15

1. pressure and tension alter blood flow
2. formation and release of chemical messengers
3. chemical messengers change cell activity

Question 16

____ seconds of light OR heavy pressure causes displacement of PDL within PDL space.

Answer 16

1-2 seconds

Question 17

T/F: 3-5 seconds of heavy pressure occludes blood vessels on the pressure side

Answer 17

True

Question 18

what does minutes of light pressure cause?

Answer 18

oxygen tension at compression side decreases the PG-E and IL-1 release

Question 19

what does hours of light pressure cause?

Answer 19

chemical messengers cause metabolic change–>second messengers release–> osteoclast recruitment from blood flow–> frontal bone resorption

Question 20

what does 2 days of light pressure cause?

Answer 20

tooth movement beyond PDL space

Question 21

when is blood flow cut off to compressed PDL during heavy pressure?

Answer 21

within minutes

Question 22

when does cell death occur in compressed area during heavy pressure?

Answer 22

hours

Question 23

when does tooth movement beyond the PDL occur during heavy pressure?

Answer 23

7-14 days

Question 24

when does osteoclast recruitment and activation–> undermining bone resorption occur during heavy pressure?

Answer 24

3-5 days

Question 25

during light pressure, osteoclasts are recruited from ____________, but from _________ during heavy pressure.

Answer 25

blood flow, bone marrow inside the alveolar bone opposite the PDL

Question 26

______ force is required for tooth movement, but ______ force is not absolutely necessary

Answer 26

sustained, continuous

Question 27

based on clinical experience ____hrs of force is required to see movement.

Answer 27

4-8

Question 28

tipping or translation has the larger compression area

Answer 28

translation, therefore greater force needed to produce the same pressure

Question 29

within jaw bones, _________ may slow tooth movement, while ______ may accelerate it

Answer 29

osteopetrosis, osteoporosis

Question 30

tooth movement is faster in the _______ and slower in the __________ because bone density is lower in the __________.

Answer 30

maxilla, mandible, maxilla

Question 31

what two drug types inhibit tooth movement

Answer 31

prostaglandin inhibitors (NSAID, corticosteroids) and bisphonates

Question 32

what are some methods to accelerate tooth movement?

Answer 32

1. local injury: regional acceleratory phenomenon (RAP) 2. corticotomy assisted tooth movement (Wilckodontics) 3. other: vibration, phototherapy, ultrasound

Question 33

optimal force

Answer 33

the amount of tooth movement increases with pressure only to a certain extent

Question 34

T/F: optimal force varies with teeth and depends on the pressure produced at the PDLs

Answer 34

True

Question 35

using light force is key to which kind of space closure strategy?

Answer 35

differential

Question 36

T/F: no anchorage control is need for reciprocal space closure

Answer 36

True

Question 37

stationary anchorage control

Answer 37

only allow bodily movement of the molars, which requires stronger pressure

Question 38

skeletal anchorage

Answer 38

use temporary anchorage devices (TADs) to prevent unwanted tooth movement

Question 39

regarding pulpal reactions, when should we try to avoid major tooth movements?

Answer 39

for calcium hydroxide filled anterior teeth with open apicies

Question 40

T/F: most ortho patients do NOT experience root resorption, but 1-2% do.

Answer 40

FALSE: most patients do, with 1-2% being severe cases

Question 41

permanent root structure loss usually occurs at the _______.

Answer 41

apex

Question 42

which 2 teeth are more prone to root resorption?

Answer 42

incisors and second premolars

Question 43

apical external root resorption categories

Answer 43

1- slight blunting | 2- moderate 1/4

Question 44

what are the risk factors for excessive root resorption?

Answer 44

abnormal root morphology prolonged tx time (excessive force) genetics history of root resorption

Question 45

usually alveolar bone height is resorbed by ______ during ortho tx