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Oral biology > OB P9 + 10 : Tooth movements > Flashcards

OB P9 + 10 : Tooth movements Flashcards

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1
Q

where are occlusal forces greater?

A

greater between molars than incisors

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2
Q

what are the physiological chewing forces?

A

– 70-150N dentate (between molars)

– Edentulous 4-55N

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3
Q

what are the maximum clenching forces?

A

– 500-700N between molars

– Up to 1500N – Inuits

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4
Q

what is the load applied in the horizontal and vertical plane in tooth movement?

A
  • Greater movement in horizontal plane (~100μm)

- Lesser movement in the vertical plane (~10μm)

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5
Q

what are the tooth support components?

A
  • bone
  • PDL fibres
  • PDL fluids
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6
Q

what is responsible for the drag response on the movement/time graph?

A

Visco-elastic system

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7
Q

Describe the viscosity of the Visco-elastic tooth support.

A

-extracellular matrix - aggregates at rest-therefore less mobility
-Periodontal fluids:
>interstitial
>blood

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8
Q

Describe the elasticity of the Visco-elastic tooth support.

A
  • collagen
  • bone
  • osseointegrated implants (“pure” elastic support)
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9
Q

what is the difference between teeth and osseous-integrated implant?

A 
Tooth:
-PDL and bone
-Viscoelastic support
Osseointegrated implant :
-no PDL
-Elastic support-bone
-much less movement
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10
Q

what are the 4 types of post -eruptive movements?

A
  • vertical
  • buccal
  • mesial
  • orthodontic
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11
Q

Describe vertical movements.

A

Continued eruption:

  • compensation for wear (occlusal and incisal)
  • bone deposition (apically and cervically)
  • Cementum deposition (increased cementum thickness)
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12
Q

Describe the buccal movements.

A
  • growth of jaws

- bone remodelling

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13
Q

when does medial drift occur?

A

throughout life

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14
Q

what is mesial drift?

A

teeth drift in medial direction -towards arch midline

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15
Q

what is the result of medial drift?

A 
– Compensates for approximal wear
– Incisal crowding
– Shortening of dental arch – may make space for 8’s
– Orthodontic relapse
– Space closure following tooth loss 
• Positive
• Negative
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16
Q

what is approximal surface wear?

A

teeth rub against each other

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17
Q

What are the measurements of medial drift?

A

From 6-18 years : 3-4mm

With hard diet : 7mm

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18
Q

what are the mechanisms for medial drift extrinsic to periodontium?

A
  • Occlusal forces
  • Muscular soft tissue forces
  • Erupting molars
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19
Q

what are the mechanisms for medial drift intrinsic to periodontium?

A
  • Bone remodeling
  • PDL fibres
    > Transeptal fibres
20
Q

what is the evidence for occlusal forces?

A
  • Vertical occlusal load applied:
    > Horizontal vector of force
    > Occlusal load of 9Kg results in a horizontal load of
    • 2.25Kg against the molars
    • 5Kg against the canines
  • Approximal tooth wear must require a force pushing teeth together
21
Q

what is the evidence against occlusal forces?

A

occlusal loads transient

22
Q

what type of force is medial drift?

A

anterior vector to closing force

23
Q

How was medial drift visualised?

A

contact points opened up with cutting disk

24
Q

what was the result from extracting opposing teeth?

A

medial drift was faster

25
Q

what was the result of flattened cusps?

A

medial drift was faster

26
Q

What was the result of reshape cusps ?

A

one side favoured medial drift and other side opposed it

27
Q

what is the conclusion for occlusal forces?

A

– occlusal forces partly involved in mesial drift

– but not the most important factor

28
Q

what are the soft tissue forces?

A

forces from cheeks (buccinator ) and tongue

29
Q

what experiment was used to tests soft tissue forces effect on medial drift?

A

– Cover teeth with acrylic dome
– No opposing teeth
– Still get mesial drift

30
Q

what was the conclusion for soft tissues forces?

A

not likely to play a role

31
Q

what is the evidence for forces from erupting molars?

A

Extraction of premolars:

– Spaces close more rapidly when molars erupting

32
Q

what is the evidence against forces from erupting molars?

A 
> Mesial drift occurs throughout life 
– Even after molars erupted
>  Still get mesial drift:
– If no adjacent tooth contacts 
– Anterior to an ankylosed tooth
33
Q

what is the evidence for bone remodelling?

A

Get remodelling at same time as mesial drift

34
Q

what is the evidence against bone remodelling?

A
  • Marker experiments show that bone fills in

- Effect, not cause

35
Q

Describe the PDL fibres : transeptal fibres affect on medial drift.

A
  • Transeptal fibres maintain tooth contact
  • Stabilise tooth position
  • Less orthodontic relapse if cut
  • mesial drift slows down when fibres are cut
36
Q

what is the summary of the cause of medial drift?

A
  • multifactorial:
    >Greatest factor: PDL -transeptal fibres
    >Other factor: occlusal forces
    (not likely erupting molars)
37
Q

what is the result of orthodontics applying small continuous forces?

A

– Bone remodel
– PDL remodel
– Tooth movement

38
Q

what are the 3 types of orthodontic tooth movement?

A

– Tipping
– Bodily
– rotational

39
Q

During tipping movements , where is the force greatest?

A

Movements and hence forces greater the further away from the fulcrum

40
Q

How much force?

A

> Ideally close to naturally occurring forces (e.g. mesial drift)
Ideally less than the PDL capillary pressure:
– If < capillary pressure – PDL remains normal
– If > capillary pressure - ischaemia
Depends on type of movement and size of tooth

41
Q

what are the forces (g) for different tooth movements?

A

tipping - 30-60g
bodily - 60-120g
rotational - 30-60g
intrusion - 10-20g

42
Q

what is the result of light forces?

A
  • Compression : frontal resorption by osteoclasts

- Tension : deposition by osteoblasts

43
Q

what is the result of heavy forces?

A
  • Compression ++ (capillary pressure exceeded) : undermining endosteal resorption by osteoclasts
  • Tension : deposition by osteoblasts
44
Q

What are the possible effects of excessive forces?

A 
>  Pain
– Ischaemic
– Inflammatory - necrosis
>  Unrepaired hyalinisation
>  Pulp death
– strangulation of vessels at apex
>  Root resorption
– Odontoclasts
– Can self repair – new cementum infill
45
Q

Describe remodelling of principle collagen fibres.

A

– Rapid below alveolar crest
– Slower above alveolar crest • Supralaveolar
• Especially transeptal
• Rotations

46
Q

what is the need for retention?

A

– Long term / permanent e.g.: • Large space closure

• Correction of severe rotations

Oral biology (29 decks)

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