Appliances and Physiology of Tooth Movement

Question 1

what are the types of tooth movement

Answer 1

physiological (eruption of teeth and mesial drift)
orthodontic tooth movement

Question 2

what is the physiological basis of orthodontics

Answer 2

if an external force is applied to a tooth the tooth will move as the bone around it remodels

Question 3

what two situations can you not move teeth

Answer 3

if a tooth has no PDL or if it is ankylosed

Question 4

what happens to every tooth you move orthodontically

Answer 4

there will be some degree of root resorption (root loss length of like 1-2mm)

Question 5

what are the two theories for orthodontic tooth movement

Answer 5

differential pressure theory
mechano-chemical theory

Question 6

what is the differential pressure theory

Answer 6

in area s of compression bone is resorbed and in areas of tension bone is deposited

Question 7

what is the mechano-chemical theory

Answer 7

a description of what is happening at cell level
cells changing shape in PDL and adjacent alveolar bone which causes release of cytokines
cytokines cause target cells to secrete other mediators

Question 8

what are cytokines

Answer 8

low molecular weight proteins that regulate the actions of target cells

Question 9

what occurs after a force is applied to the tooth in the mechano-chemical theory

Answer 9

mechanical loading causes fluid movement in periodontal ligament membrane and osteocytes detect this and produce cytokines
the cytokines recruit osteoblasts to produce more cytokines which upregulate osteoblasts or RANKL

Question 10

what two molecules act on the blood vessels to cause blood monocytes to fuse and form multinucleated osteoclasts in an area of compression

Answer 10

RANKL and CSF

Question 11

what happens in areas of compression

Answer 11

osteoblasts bunch up together and expose the osteoid layer giving osteoclasts access to absorb the bone

Question 12

what happens in areas of tension

Answer 12

the osteoblasts are flattened covering the osteoid layer and preventing osteoclasts from gaining access to the bone

Question 13

what protein do osteoblasts also release

Answer 13

OPG

Question 14

what is the action of OPG

Answer 14

prevents osteoclastic differentiation and prevents the activity

Question 15

what are the types of orthodontic appliances

Answer 15

removable
fixed
functional

Question 16

what type of tooth movement are removable appliances used for only

Answer 16

tipping or tilting

Question 17

what tooth movement do functional appliances use

Answer 17

tipping

Question 18

what are functional appliances used for and indications

Answer 18

skeletal problems
used while the patient is still growing

Question 19

what type of tooth movement do fixed appliances cause

Answer 19

bodily movement
intrusion
extrusion
rotation
torque

Question 20

what is bodily movement

Answer 20

crown and root moving at the same time

Question 21

what is torque

Answer 21

almost like a tipping movement but the crown doesn’t move - looking for the root to move

Question 22

what is the force you would want to use to tip a tooth

Answer 22

35 -60 grams

Question 23

how do functional appliances work

Answer 23

using blocks to posture the jaws into a better occlusion which stretches facial muscles and transmits force to the teeth and alveolus

Question 24

what changes occur when wearing a twin block

Answer 24

retroclination of upper incisors and proclinaiton of lowers

Question 25

how long do patients need to wear a twin block

Answer 25

6-12 months continuously

Question 26

what do twin blocks cause posteriorly

Answer 26

open bite

Question 27

how would you fix a posterior open bite caused by twin block wear

Answer 27

ask patient to wear twin block only at night for 6 months and hope for continuous eruption sometimes fixed appliances are needed

Question 28

what occurs during bodily movement of a tooth

Answer 28

when fixed appliances are applied there is frontal resorption and then bony deposition on the opposite side

Question 29

how much forces is needed for bodily movement

Answer 29

100-120 grams

Question 30

what is intrusion of the teeth

Answer 30

pressure on the supporting structures evenly and bone resorption apically at alveolar crest

Question 31

what does a high force when trying to intrude teeth cause

Answer 31

root resorption use 10-20 grams

Question 32

what is extrusion

Answer 32

tension is induced in supporting structures and bone deposition is necessary to maintain tooth support

Question 33

how do you generate torque

Answer 33

engage rectangular wire in rectangular bracket

Question 34

what occurs on pressure side of the tooth when moving teeth

Answer 34

hyperaemia of blood vessels osteoclasts increase activity to resorb bone

Question 35

why is there time left between applying force on the teeth

Answer 35

so there is time for PDL to remodel

Question 36

what occurs in light forces

Answer 36

hyperaemia with PDL appearance of osteoclasts and osteoblasts resorption and deposition remodelling of socket PDL fibres reorganise

Question 37

what occurs to gingival fibres when moving teeth

Answer 37

they remain distorted - this is why teeth try to relapse after ortho treatment

Question 38

what are moderate forces

Answer 38

occlusion of vessels on the pressure side - no cells due to this so there is no deposition or resorption - period of stasis

Question 39

what do you have to wait for in moderate forces

Answer 39

osteoclasts coming in to resorb bone - this can take a number of days

Question 40

what are excessive forces

Answer 40

causes pain necrosis and undermining resorption takes place resulting in permanent changes causes root resorption anchorage loss

Question 41

what is anchorage

Answer 41

resistance to unwanted tooth movement

Question 42

what are the factors that affect response to orthodontic force

Answer 42

magnitude of force duration age anatomy

Question 43

when should appliances be worn ideally

Answer 43

24/7

Question 44

when can we not move teeth

Answer 44

if there is no bone

Question 45

what is alveolar necking

Answer 45

when there is not a tooth in that aspect of the bone and the cortical plates of the bone are much closer together in this area

Question 46

can we orthodontically treat RCT teeth

Answer 46

yes if there is an intact PDL

Question 47

what are side effects of ortho treatment

Answer 47

pain and mobility pulpal changes root resorption loss of alveolar bone support relapse

Question 48

how much should teeth move between visits

Answer 48

1mm per month