Lecture 4- Biology of orthodontic tooth movement

Question 1

Are osteoblasts in the PDL?

Answer 1

yes

Question 2

Are osteoclasts in the PDL?

Answer 2

no, but can be recruites from blood vessels or bone marrow

Question 3

Origin of osteoblasts?

Answer 3

mesenchymal

Question 4

Origin of osteoclasts?

Answer 4

hematopoietic stem cells

Question 5

How long until tooth movement beyond the PDL space is seen with sustained light pressure?

Answer 5

2 days

Question 6

How long until tooth movement beyond the PDL space is seen with sustained heavy pressure?

Answer 6

7-14 days

Question 7

Is tooth movement faster in maxilla or mandible?

Answer 7

maxilla because less dense bone

Question 8

4 risk factors for excessive root resorption

Answer 8

Abnormal root morphology
Prolonged tx time
Genetic predispos.
Hx of root resorption

Question 9

PDL is … in width

Answer 9

0.5 mm

Question 10

Bone …. is required for tooth movement beyond the PDL space

Answer 10

resorption

Question 11

The … theory says that bony changes are caused by electric signals. it does NOT stimulate nerve endings

Answer 11

bioelectric

Question 12

The bioelectric theory says that force induces …. signals and that bioelectric potential changes …

Answer 12

piezoelectric

cell activity

Question 13

The …. theory says that bony changes are caused by chemical signals

Answer 13

pressure-tension

Question 14

The pressure-tension theory says that pressure and tension alter…. and this causes formation and release of …. which change cell activities

Answer 14

blood flow

chemical messengers

Question 15

Response to sustained light pressure:
1-2 seconds: … within PDL space

3-5 seconds: …. changes

Minutes: O2 tension at compression side decreases leading to … and …. release

Answer 15

tooth displacement

blood flow

Prostaglandins (PGE2) and cytokines release (IL-1)

Question 16

Response to sustained light pressure:

Hours: chemical messengers cause metabolic change; second messengers (such as cAMP) release –> …. recruitment from blood flow, maturation and activation –> …

Answer 16

osteoclasts

frontal bone resorption

Question 17

Drugs that may inhibit orthodontic tooth movement

Answer 17

NSAIDs, corticosteroids and Bisphosphonates (inhibits clasts directly)

Question 18

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

Answer 18

anchorage

Question 19

all patients exhibit some resorption with only …% reaching a severe level

Answer 19

1-2%

Question 20

A maxillary protraction-face mask and reverse pull headgear is usually done before age…. and often lasts …

generally cannot achieve more than … of skeletal movement

Answer 20

10-11

6-8 months

3mm

Question 21

… is the oldest age you can do reverse headgear because sutures fuse

Answer 21

11