Tooth movement and appliances

Question 1

what is described in the aim of an ortho URA prescription sheet

Answer 1

description of what the APPLIANCE is aiming to achieve
Not the aim of the whole treatment

Question 2

what process does tooth movement via orthodontics rely on

Answer 2

bone remodelling by osteoclasts and osteoblasts which is controlled by PDL fibres
if a prolonged force is applied, tooth movement will occur

Question 3

differential pressure theory of orthodontic tooth movement

Answer 3

applying force to the crown creates stresses in the periodontal ligaments
Compression areas see bone resorption and tension areas see bone deposition

Question 4

mechano-chemical theory of orthodontic tooth movement

Answer 4

cells (osteoblasts) undergo shape changes in response to tension and pressure
Compression areas see osteoblasts bunched up exposing osteoid layer to osteoclasts resulting in resorption
Tension areas see osteoblasts stretched and flattened preventing osteoclasts reaching the osteoid layer and allowing for bone deposition to occur

Question 5

what movement can removable appliances create

Answer 5

tipping of teeth

Question 6

example of a functional appliance

Answer 6

twin block

Question 7

what patients might be given a functional appliance

Answer 7

patients with skeletal discrepancies who are still growing
(must be still growing for them to work)

Question 8

what force is required to tip teeth

Answer 8

dependent on size of tooth , 35-60g

Question 9

what is bodily movement of a tooth and how much force is required for this to be done

Answer 9

bodily movement is moving the whole tooth, crown and root, as one. Requires a fixed appliance
force required in 150-200g

Question 10

what force is required to intrude teeth and why is it so low

Answer 10

10-20g
high forces would risk root resorption

Question 11

what force is required to rotate teeth

Answer 11

35-60g

Question 12

what force is required to extrude teeth

Answer 12

35-60g

Question 13

what is torque movement of a tooth and how much force is required to do this

Answer 13

torque refers to moving the root of the tooth with minimal movement of the crown
requires force of 50-100g

Question 14

what change to blood flow is caused by orthodontics using light pressure

Answer 14

hyperaemia in pressure and tension areas
(increased blood flow)

Question 15

what happens to PDL and gingival fibres when a tooth is moved orthodontically using light pressure

Answer 15

the PDLs have enough time to reorganise
Gingival fibres remain distorted and dont reorganise - a main reason for relapse post treatment if a retainer isnt worn

Question 16

what changes to blood flow is seen during orthodontics using moderate forces

Answer 16

sees hyperaemia on tension side but occlusion of blood vessels on the compression side

Question 17

if moderate forces are being used, what occurs on the compression side of a tooth being moved

Answer 17

compression side sees hyalinisation a process seeing cell death due to occlusion creating a cell free zone

Question 18

how does movement occur when moderate forces are used to move teeth

Answer 18

periods of stasis then sudden rapid tooth movements - unideal

Question 19

name 3 possible consequences of using excessive force to move teeth

Answer 19

root resorption , anchorage loss, loss of vitality

Question 20

why do teeth move slower in older patients receiving ortho

Answer 20

bone becomes denser as we age and there is slower cell turnover

Question 21

to promote eruption of a permanent tooth if extracting a deciduous tooth early , what is the ideal time

Answer 21

when one half to two thirds of the permanent root is formed