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BDS3 Orthodontics > Appliances and Physiology of Tooth Movement > Flashcards

Appliances and Physiology of Tooth Movement Flashcards

1
Q

what are the types of tooth movement

A

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

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2
Q

what is the physiological basis of orthodontics

A

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

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3
Q

what two situations can you not move teeth

A

if a tooth has no PDL or if it is ankylosed

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4
Q

what happens to every tooth you move orthodontically

A

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

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5
Q

what are the two theories for orthodontic tooth movement

A

differential pressure theory
mechano-chemical theory

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6
Q

what is the differential pressure theory

A

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

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7
Q

what is the mechano-chemical theory

A

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

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8
Q

what are cytokines

A

low molecular weight proteins that regulate the actions of target cells

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9
Q

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

A

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

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10
Q

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

A

RANKL and CSF

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11
Q

what happens in areas of compression

A

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

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12
Q

what happens in areas of tension

A

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

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13
Q

what protein do osteoblasts also release

A

OPG

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14
Q

what is the action of OPG

A

prevents osteoclastic differentiation and prevents the activity

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15
Q

what are the types of orthodontic appliances

A

removable
fixed
functional

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16
Q

what type of tooth movement are removable appliances used for only

A

tipping or tilting

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17
Q

what tooth movement do functional appliances use

A

tipping

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18
Q

what are functional appliances used for and indications

A

skeletal problems
used while the patient is still growing

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19
Q

what type of tooth movement do fixed appliances cause

A

bodily movement
intrusion
extrusion
rotation
torque

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20
Q

what is bodily movement

A

crown and root moving at the same time

21
Q

what is torque

A

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

22
Q

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

A

35 -60 grams

23
Q

how do functional appliances work

A

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

24
Q

what changes occur when wearing a twin block

A

retroclination of upper incisors and proclinaiton of lowers

25
Q

how long do patients need to wear a twin block

A

6-12 months continuously

26
Q

what do twin blocks cause posteriorly

A

open bite

27
Q

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

A

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

28
Q

what occurs during bodily movement of a tooth

A

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

29
Q

how much forces is needed for bodily movement

A

100-120 grams

30
Q

what is intrusion of the teeth

A

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

31
Q

what does a high force when trying to intrude teeth cause

A

root resorption
use 10-20 grams

32
Q

what is extrusion

A

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

33
Q

how do you generate torque

A

engage rectangular wire in rectangular bracket

34
Q

what occurs on pressure side of the tooth when moving teeth

A

hyperaemia of blood vessels
osteoclasts increase activity to resorb bone

35
Q

why is there time left between applying force on the teeth

A

so there is time for PDL to remodel

36
Q

what occurs in light forces

A

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

37
Q

what occurs to gingival fibres when moving teeth

A

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

38
Q

what are moderate forces

A

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

39
Q

what do you have to wait for in moderate forces

A

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

40
Q

what are excessive forces

A

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

41
Q

what is anchorage

A

resistance to unwanted tooth movement

42
Q

what are the factors that affect response to orthodontic force

A

magnitude of force
duration
age
anatomy

43
Q

when should appliances be worn ideally

A

24/7

44
Q

when can we not move teeth

A

if there is no bone

45
Q

what is alveolar necking

A

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

46
Q

can we orthodontically treat RCT teeth

A

yes if there is an intact PDL

47
Q

what are side effects of ortho treatment

A

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

48
Q

how much should teeth move between visits

A

1mm per month

BDS3 Orthodontics (9 decks)

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