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BDS3 Orthodontics > Physiology of tooth movement and appliances overview > Flashcards

Physiology of tooth movement and appliances overview Flashcards

1
Q

2 types of tooth movement

A

physiological

orthodontic

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2
Q

physiological tooth movement

A

Tooth Eruption

  • Pre-eruptive tooth movement (small, random)
  • Intra-osseous eruption (after crown forms, slow, 1mm = 3/12-24/12)
  • Mucosal penetration (fast, 1mm = 2/52)
  • Pre-occlusal eruption (slow)
  • Post-occlusal eruption (very slow)

not continuous - changes speeds

use interceptive orthodontics

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3
Q

5 stages in physiological tooth eruption

A
  1. pre-eruptive tooth movement
  2. intra-osseous eruption
  3. muscosal penetration
  4. pre-occlusal eruption
  5. post-occlusal eruption
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4
Q

3 phases in physiological tooth eruption

A

pre-eruptive phase

  • pre-eruptive tooth movement
  • intra-osseous eruption

pre-functional phase

  • muscosal penetration
  • pre-occlusal eruption

fuctional eruptive phase

  • post-occlusal eruption
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5
Q

pre-eruptive phase

A
  • Starts when the crown starts to form and ends when the crown formation complete/root formation about to start

pre-eruptive tooth movement

intra-osseous eruption

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6
Q

pre-functional eruptive phase

A

Starts as soon as the root start to form and ends when the teeth reach the occlusal plane

  • Reduced enamel epithelium fuses with oral mucosa
    • This breaks down and tooth erupts into oral cavity
  • Tooth moves occlusally

muscosal penetration

pre-occlusal eruption

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7
Q

functional eruptive phase

A

Tooth movement/eruption continues as the root forms and throughout life in extremely small increments

  • Tooth reached occlusal plane – appears fully erupted
    • Further small movements
  • Tooth wear, over eruption due to loss occluding

post-occlusal eruption

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8
Q

orthodontic tooth movements from

A

from externally generated forces

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9
Q

orthopantomogram

A

Not a static view

  • Pre-eruptive movement in upper left (27)
    • Rocks in crypt
  • Intra-osseous phase lower left
    • When roots form
    • 1mm 3months-2 years
      • Slow
    • Resorbing bone and deciduous roots above it
  • Mucosal phase
    • Tooth breaches mucosa
      • Fast – 1-2mm a month
      • Wary – can worsen open bites
  • Once the tooth hits something hard, PDL established and post eruption slow
    • Continuing to erupt
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10
Q

how to check OPT systematically

A

right pt,

right way round,

right time taken,

count teeth from back

  • supernumerary in upper right

Caries

  • right upper and lower – need BW

Root pathology - nil

Delayed eruption of upper left 6

  • ALARM
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11
Q

possible tooth eruption theories

A
  • Pulpal pressure
  • Pulpal growth
  • Fibroblast traction – PDL not formed yet
  • Vascular pressure
  • Blood vessel thrust
  • Root elongation
  • Alveolar bone remodel
  • Periodontal ligament formation

Likely many work to erupt teeth – essential for life

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12
Q

3 key things in tooth eruption process

A
  • genes
  • apical blood flow
  • dental follicle
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13
Q

tooth eruption process is

A

unknown exactly how it occurs

But

  • Genes
  • Apical blood flow
  • Dental follicle

Have roles

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14
Q

does tooth eruption involve

bone resorption

A

yes

by dental follicle - mediator to bone resorption

tested - remove tooth and replace with metal replica - still erupts

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15
Q

does tooth eruption involve

deciduous tooth resorption

A

yes

if not cleidocranial dysplasia - affects bone and teeth

  • delayed loss primary teeth
    • shorter teeth
  • no clavicles
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16
Q

does tooth eruption involve

cell proliferation for root lengthing

A

not critical for tooth eruption

  • Remove apical area, tooth still erupts
    • dental follicle pulls tooth
  • Dilacerations occur if obstruction
    • Hit hard then dilaceration
      • Root still forms despite not erupting
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17
Q

does tooth eruption involve

apical blood flow

A

very important

allows tooth to erupt

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18
Q

does tooth eruption involve

collagen fibres cross linking

A

no

only post eruption - when PDL forms

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19
Q

does tooth eruption involve

genes

A

yes

  • Parathyroid hormone receptor gene (PTHR1 and PFE)
    • Primary failure of eruption (OPT of 6 not erupting)

Genetic element

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20
Q

interceptive orthodontic treatment

A
  • Orthodontists can utilise tooth eruption to minimise the impact of a developing malocclusion.
    e. g. ectopic permenant canines
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21
Q

age for ectopic permanent canine interceptive orthodontics

A

ages 10-13

  • Drift into right place
    • If not – need surgical exposure and appliance to move into place 2-3 years
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22
Q

examples of interceptive orthodontic treatment

A

ectopic permanent canines

permanent teeth can be ‘encouraged to erupt’ if the deciduous toothis extracted at the correct stage

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23
Q

stage to remove deciduous tooth to encourage permanent to erupt

interceptive orthodontic

A

when perment root is 1/2 to 2/3 developed

any earlier will delay permanent eruption

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24
Q

key investigation for permanent canines

A

palpate for upper permanent canines from 9 years

check if ectopic

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25
Q

cause and prevalance of ectopic canines

A

genetic

1-2%

variation in difficulty to fix

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26
Q

best imaging technique for ectoptic canines

A

CBCT

check position, damage/resorption (follicle can dissolve away bone and cementum)

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27
Q

treatment for this case

A

Ignore ectopic canines – obvious

  • One thing wrong with development likely to have other issues

go through methodically

  • No additional teeth
  • Caries – BW follow up
  • Roots
    • Lower right E – distal root partly resorbed, mesial root large – take long time to resorb
      • 45 root is ½ - 2/3 formed – extract deciduous
      • Same lower left E

now maxillary ecotopic canines

  • Palatally positioned – magnified (closer to midline)
  • Follicle larger – cystic change
  • No appearance of resorption of lateral – see full lamina dura
  • Remove Cs – come into correct position
    • Follicle pulls through bone
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28
Q

3 things to check on OPT in regards to ectopic canines

A
  • height
  • closeness to midline
  • angle
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29
Q

assess ectopic canines on this OPT

A

High – above central apex

Good angle – compare to mid sagittal line (vertical plane), under 30 degrees = good

Midline - Doesn’t overlap adjacent incisor by more than half

Favourable -> interception will work, lining teeth up more successful

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30
Q

assess ectopic canines on this OPT

A

Still high

Angle now poor

very close to midline – fully covering lateral

no cystic change

  • now need surgery and 2-3 years ortho tx
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31
Q

mesial drift of 6s more problematic in

A

mandible than maxilla

6 drift forward

5, 4, 3 still waiting to erupt – no space, reduced

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32
Q

what is happening in A, B, D, E, F (C ignore occlusal view)

A

Unusual tooth movement following interceptive extraction

Lower right buccal segment

  • 46
  • Submerging 85
  • 45 – horizontal, no hope

Place a space maintainer – band and loop

  • Within 6 months change position
  • 2 years of space maintenance – erupt into space

Follicle pulling tooth through bone – not apical end

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33
Q

physiological basis for orthodontics

A
  • if an external force is applied to a tooth, the tooth will move as the bone around it remodels
    • bony remodelling is mediated by the periodontal ligament
      • If a tooth has no PDL or is ankylosed, it will NOT move
        • Cause intrusion of adj teeth with healthy PDL
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34
Q

cementum Vs bone

resoprtion

A

Cementum is much more resistant to resorption than bone (1mm thick)

  • although some degree of root resorption after orthodontics should be expected
35
Q

orthodontic forces casue

A

osteoclasts (usually in lacunae) and osteoblasts appear

36
Q

orthodontist role (2)

A

Manages the growth and development of the teeth, face and jaws

Corrects irregularities in these structures using

  • Appliances to transmit force to PDL and bone
  • ‘osteoclast herder’
    • Thousands of workers, 24 hour shifts, no pay, no superannuation, no complaints, no sickness…
    • Work not up to standard or any signs of slacking, macrophage will phagocytose!
37
Q

3 theories for orthodontic tooth movement

A
  • Differential pressure theory
  • Piezoelectric pressure theory
  • Mechno-chemical pressure theory
38
Q

differential pressure theory

A

Pressure on tooth (e.g. here retrocline)

Tension on one side of PDL

Compression on other side of PDL

Tension = bone deposition

Compression = bone resorption

39
Q

piezoelectric pressure theory (1)

A

Piezoelectric currents are generated when crystalline structures, such as bone, are deformed

These currents have been suggested as a mechanisms by which tooth movement is modulated

  • Compression = +
  • Tension = -
  • May result in cells being recruited to sites (osteoclasts +, osteoblasts -)

Forces so small – unlikely alone

40
Q

mechano-chemical pressure theory

A

Mechanical stress on tooth and bone ->

Release of neuropeptides from nerve endings ->

Stimulate fibroblasts, endothelial cells and alveolar bone ->

Fibroblast also communicate with osteoblasts and osteoclasts ->

Alveolar bone and periodontal ligament remodelling ->

Tooth movement

41
Q

3 types of orthodontic appliance

A
  • removable (URA)
  • functionals
  • fixed
42
Q

6 types of orthodontic tooth movement

A
  • tipping
  • bodily movement
  • intrusion
  • extrusion
  • rotation
  • torque - root not crown
43
Q

movement in URA

A

tipping

centre of rotation moves up as tipped

44
Q

common use for URA

A

flat anterior bite plane – best, most efficient way at reducing overbite in growing pt

  • Common URA and lower fixed – overbite reduced, and reduced the amount of time with fixed upper as start with URA
45
Q

functional appliance changes (3)

A
  • The mandible is postured away from its normal rest position
    • Skeletal Changes - growth backwards (red arrows)
  • The facial musculature is stretched which generates forces transmitted to the teeth and alveolus
    • Dental changes
      • Careful not to over procline lower anterior
    • Posterior open bite – close naturally
  • There may be an effect on facial growth
    • E.g. class II cases
      • Restrict maxillary growth
      • Promote mandibular growth
      • Remodel the glenoid fossa
46
Q

skeletal changes in functional appliance

A

growth backwards (red arrows)

mandible is postured away from its normal rest position

47
Q

dental changes in functional appliance

A
  • The mandible is postured away from its normal rest position
    • Skeletal Changes - growth backwards (red arrows)
  • The facial musculature is stretched which generates forces transmitted to the teeth and alveolus
    • Dental changes
      • Careful not to over procline lower anterior
    • Posterior open bite – close naturally
48
Q

functional appliances potential affect on facial growth

A

E.g. class II cases

  • Restrict maxillary growth
  • Promote mandibular growth
  • Remodel the glenoid fossa
49
Q

how can functional appliance be used here

A

Significant jaw discrepancy – try and grow their jaw to save from surgery

50
Q

functional appliance use in overjet

A
  • Large 11mm overjet*
  • 9months constant wearing functional appliance*
  • 18 months after start Tx – wearing at night*
51
Q

mode of action of functionals (%)

A
  • Skeletal change (30%), growth of mandible, restraint of maxilla
  • Dentoalveolar change (70%), retroclination of upper teeth, proclination of lower teeth
    • Mesial migration of the lower teeth
    • Distal migration of the upper teeth

Combination of the above achieves class I

52
Q

mechanism of bodily movement

A

Note that there is a coordinated bone modelling and remodelling response leading and trailing the moving tooth.

  • This mechanism allows a tooth to move relative to basilar bone while maintaining a normal functional relationship with its periodontium
  • Osteoclastic and osteoblastic activity are in red and blue, respectively*

More deposition on the outside of alveolus too – distant from tooth

  • Secondary remodelling
53
Q

5 types of tooth movement by fixed appliances specifically

A
  • bodily movement
  • intrusion
  • extrusion
  • rotation
  • torque
54
Q

wire for fixed appliances

A

must be active

cannot be bendy - tooth slides along

55
Q

intrusion

A
  • Pressure on the supporting structures is evenly distributed and bone resorption is necessary, particularly at the apical area at the alveolar crest
56
Q

extrusion

A
  • Tension is induced in the supporting structures and bone deposition is necessary to maintain tooth support
57
Q

rotation

A
  • Need a force couple – 2 forces in opposing directions
58
Q

torque

A
  • Apical root torque
    • Hard to deliver – root moves most
      • root uprighting
59
Q

optimum force

tipping

A

35-60g

60
Q

optimum force

bodily movement

A

150-200g

61
Q

optimum force

intrusion

A

10-20g

62
Q

optimum force

extrusion

A

35-60g

63
Q

optimum force

rotation

A

35-60g

64
Q

optimum force

torque

A

50-100g

65
Q

histological changes during orthodontics

light forces

A

Hyperaemia within the periodontal ligament on both pressure and tension side

  • Appearance of osteoclasts and osteoblasts

Resorption of lamina dura from pressure side (osteoclasts) frontal resorption

Apposition of osteoid on tension side (osteoblasts) deposition

Remodelling of socket – “frontal resorption”

Periodontal fibres reorganise

Gingival fibres appear not to become reorganised but remain distorted

66
Q

histological changes during orthodontics

moderate force

A

Occlusion of vessels of periodontal ligament on pressure side

Hyperaemia of vessels of periodontal ligament on tension side

Cell free areas on pressure side (hyalinisation)

  • Period of stasis
    • not dead - but nothing happening

Increased endosteal vascularity – “undermining resorption”

Relatively rapid movement of tooth with bone deposition on the tension side – tooth may become slightly loose

Healing of periodontal ligament – reorganisation and remodelling

67
Q

histological changes during orthodontics

excessive force

A
  • Necrosis
  • Undermining resorption
  • Resorption of root surfaces
  • Pain
  • Permanent change

Extensive lateral root resorption (RR) and undermining resorption (UR), just to the left of an area of PDL necrosis (N), is associated with the lag phase of tooth movement

68
Q

4 factors affecting respose to orthodontic force

A
  • magnitude
  • duration
  • age
  • anatomy
69
Q

magnitude of orthodontic force impact

A
  • Light forces – consistent movement*
  • Heavy forces – no change for while as undermining resorption and then sudden*
  • moderate and high forces – not wanted, bad histological movement process
  • Main problem of heavy force – anchorage teeth are moving but not desired tooth so excessive movement by them*
70
Q

duration of orthodontic force impact on tooth movement

A

Constant 24hrs of force to prevent teeth moving back into old position

71
Q

age impact on orthodontics

A

works at any age

maybe slower in older ages

72
Q

anatomy impact on orthodontic force

A
  • no bone
    • wasting/cleft
      • e.g. alveolar encking - not possible to do ortho on as thin dence cortical plate bone
  • soft tissues
    • tongue
    • anterior open bite
  • mid-palatal suture
73
Q

alveolar necking

A
  • 7, 5, 4*
  • 6 extracted long time ago*
  • 5 drifted mesial as no 6*
  • Alveolar bone cortex plates together – knife edge*
  • Hard to move through as dense
74
Q

root treated teeth impact on ortho

A

No pathology = no problem as ortho deals with PDL

75
Q

5 deleterious effects of orthodontic force

A
  • Pain and mobility
  • Pulpal changes
  • Root resorption
  • Loss of alveolar bone support
  • relapse
76
Q

ideal rate of tooth movement

A

1mm per month

treatment time 24 months for fixed appliances

77
Q

3 most likely tooth eruption theories

combination of likely

A
  • Remodelling of the alveolar bone
    • Role of dental follicle
  • Elongation of the root
    • Pressure against the root surface in the apical part of the root pushing it towards the oral cavity
  • Reorganisation of the periodontal membrane fibres
    • Role of the fibroblasts both with their contractile properties and their ability to quickly turn over collagen fibres
78
Q

most common and accepted theory of orthodontic tooth movement

A

mechano-chemical theory

79
Q

removable and functional appliance

move teeth by

A

tipping forces

Functional can also act on MOM set up forces that influences dentition and growth of jaws

80
Q

fixed appliances move teeth by

A

all forces

  • tipping
  • bodily movement
  • intrusion
  • extrusion
  • rotation
  • torque (uprighting root on top of crown)
81
Q

tipping Vs bodily movement

A

Bodily 2 sides

  • One deposition one resorption

Tipping

  • Areas – not whole length
82
Q

how long does it take for undermining resorption to be seen

A

7-14 days

83
Q

4 factors on tooth movement and how they impact

A
  • magnitude
    • light - most efficient, get frontal resorption
    • moderate - slower, get undermining resorption
    • heavy/excessive - necrosis, root resorption, pain, loss of vitality (rare), alveolar bone loss (rare)
  • duration
    • most efficient with (light) continuous force
  • age
    • maybe sligtly slower in adults
  • anatomy
    • volume of bone
    • effects of tongue
    • digit habits

BDS3 Orthodontics (13 decks)

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