Physiology of Tooth Movement and Appliances

Question 1

what is bone remodelling mediated by

Answer 1

PDL

Question 2

what happens if a tooth has no PDL or is ankylosed

Answer 2

will not move

Question 3

what is the mechano-chemical theory

Answer 3

cell shape changes within the PDL and adjacent alveolar bone which initiates signalling interactions between cells

Question 4

what happens in the mechano-chemical theory

Answer 4

mechanical loading
stretching and compression of PDL fibres
osteocytes detect bone distortion and produce cytokines to recruit osteoblasts and clasts for bone resorption
macrophages produce IL1
osteoblasts produce prostaglandins and leukotrienes
fibroblasts produce MMPs

Question 5

on a cellular level what happens in areas of compression

Answer 5

osteoblasts bunch up together and expose the osteoid layer giving osteoclasts access to resorb the bone
osteoblasts send signals to osteoclasts to recruit and activate osteoclasts

Question 6

on a cellular level what happens in areas of tension

Answer 6

osteoblasts are flattened covering the osteoid layer and prevents osteoclasts from gaining access to the bone
osteoblasts secrete collagen and other proteins which secrete hydroxyapatite crystals which forms new bone

Question 7

what does osteoprotegerin do

Answer 7

prevents osteoclastic differentiation and suppresses their activity

Question 8

what regulates bone remodelling

Answer 8

amount of RANKL produced and amount of OPG produced

Question 9

what is the role of orthodontists

Answer 9

utilise inflammatory response which occurs in PDL
use appliances to transmit force to PDL and bone
manage patient carefully through periods of resorption and repair of bone

Question 10

what are the types of orthodontic appliances

Answer 10

removable
functional
fixed

Question 11

what are the types of tooth movement

Answer 11

tipping
bodily movement
intrusion
extrusion
rotation
torque

Question 12

how do functional appliances work

Answer 12

mandible postured away from normal rest position
facial musculature stretched which generates forces to teeth and alveolus

Question 13

what effect can functional appliances have on facial growth

Answer 13

restrict maxillary growth
promote mandibular growth
remodel glenoid fossa

Question 14

what is the skeletal change with functionals

Answer 14

30% change - growth of mandible and restraint of maxilla

Question 15

what is the dentoalveolar change with funtionals

Answer 15

70% change - retroclination of upper teeth, proclination of lower teeth

Question 16

what is the mode of action with functionals

Answer 16

skeletal change
dentoalveolar change
mesial migration of lowers
distal migration of uppers
achieving class 1

Question 17

what does secondary remodelling allow

Answer 17

tooth to retain PDL width and stability

Question 18

what is bodily movement

Answer 18

moving the tooth as a whole

Question 19

what happens with intrusion

Answer 19

pressure on supporting structures evenly distributed and bone resorption necessary at apical area and alveolar crest

Question 20

what happens with extrusion

Answer 20

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

Question 21

what is the force needed for tipping a tooth

Answer 21

35-60g

Question 22

what is the force needed for bodily movement

Answer 22

150-200g

Question 23

what is the force needed for intrusion

Answer 23

10-20g

Question 24

what is the force needed for extrusion

Answer 24

35-60g

Question 25

what is the force needed for rotation

Answer 25

35-60g

Question 26

what is the force needed for torque

Answer 26

50-100g

Question 27

what type of resorption does light force movement result in

Answer 27

frontal resorption

Question 28

when applying light force to a tooth what happens to the PDL

Answer 28

hyperaemia (increased blood flow)

Question 29

what happens on the pressure side when applying light force

Answer 29

resorption of lamina dura

Question 30

what happens on tension side when applying light force

Answer 30

apposition of osteoid on tension side

Question 31

what is the remodelling of the socket in light force movement driven by

Answer 31

frontal resorption

Question 32

what happens to periodontal fibres during light force

Answer 32

reorganise

Question 33

when applying a moderate force what happens to the blood vessels

Answer 33

occlusion of vessels of PDL on pressure side
hyperaemia of vessels of PDL on tension side

Question 34

what is hylinisation

Answer 34

cell free areas

Question 35

when does hylinisation occur

Answer 35

during moderate forces

Question 36

what type of resorption happens with moderate forces

Answer 36

undermining resorption

Question 37

what is undermining resorption

Answer 37

increased endosteal vascularity

Question 38

what is the movement of the tooth during moderate force movement

Answer 38

rapid movement with bone deposition on tension side - tooth can loosen

Question 39

what does light force movement allow for

Answer 39

slow continuous tooth movement

Question 40

what does moderate force movement mean for tooth movement overall

Answer 40

rapid movement initially then 10-14 days with little movement while undermining resorption occurs

Question 41

what are the unwanted side effects of excessive forces

Answer 41

pain
necrosis and undermining resorption
root resorption
anchorage loss
possible loss of tooth vitality

Question 42

what factors affect the response to orthodontic force

Answer 42

magnitude
duration
age
anatomy

Question 43

what anatomical structures affect response to force

Answer 43

no bone
soft tissues
mid palatal suture

Question 44

what are the deleterious effects of orthodontic force

Answer 44

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

Question 45

how much movement do we want to see per month

Answer 45

one mm

Question 46

how long is treatment for fixed appliances

Answer 46

24 months