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Orthodontics (IODC) > Biomechanics and tooth movement > Flashcards

Biomechanics and tooth movement Flashcards

1
Q

Tooth movement

A

Physiological

Orthodontic

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2
Q

Physiological tooth movement

A

Pre-eruptive
Eruptive
Post-eruptive

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3
Q

Pre-eruptive tooth movements

A

Permanent teeth form lingually to primary teeth

Nearly always erupt lingually

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4
Q

Eruptive movements

A

usually occurs at rate of 1mm per month

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5
Q

Post-eruptive movement

A

Accomodate growing jaws
Compensate for occlusal wear
Compensate for interproximal wear - mesial drift
Infraocclusion due to ankylosis

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6
Q

Growing jaws

A

Teeth move to adapt to gowth

Lower jaw tends to continue to grow anteriorly longer than the top jaw

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7
Q

Occlusal wear

A

Thickening of cementum to account for occlusal wear

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8
Q

Mesial drift

A

Even occurs if wisdom tooth is not there

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9
Q

Orthodontic tooth movement

A

Vital PDL

-don’t need a vital pulp

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10
Q

PDL

A
  1. Cells
    - Obs!!!
    - Ocs!!!
    - fibroblasts
    - epithelial rests of Malassez
    - macrophages
    - undifferentiated mesenchymal cells
    - cementoblasts
  2. Extracellular component
    - fibres (relevant to relapse and retention - about 3 months)
    - ground substance
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11
Q

PDL fibres

A
  1. Collagen fibre bundles
    - alveolar crest fibres
    - horizontal fibres
    - transseptal fibres
    - oblique fibres
    - apical fibres
    - interradicular fibres
  2. Oxytalan fibres
    - elastic in nature
    - inserts into cementum and runs in 2 directions
    - function is thought to maintain the patency of blood vessels during occlusal loading
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12
Q

Ground substance

A
  1. Glycosaminoglycans
  2. Glycoproteins
  3. Glycolipids
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13
Q

Resting forces

A

Very light forces
PDL metabolic activity 5-10g
PIC

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14
Q

Ortho tooth movement

A

‘a pathological process from which the tooth usually recovers’

  • bendy wires
  • spring
  • elastics
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15
Q

Bone resorption removable appliance

A

PIC
Force, tension and pressure at different places
With removable appliance, just able to tip crown one way or other around point of rotation

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16
Q

Pressure side of moving tooth

A

Differentiation of osteoclasts - bone resorption

Collagen fibre remodelling

17
Q

Tension side of moving tooth

A

Bone deposition

Collagen fibre remodelling

18
Q

Rate of movement

A
  1. Initial compression
    - tooth moves through PDL
  2. Delay phase (2-14 days)
    - loss of cells from area (no movement possible)
    - new cells move into area (osteoclasts, fibroblasts)
    - ->osteoclasts from vasculature system
    - collagen fibre remodelling
  3. Tooth movement
19
Q

Duration of force (graph)

A

There is a threshold but we do not know what it is

This must be done ~6hrs/24 to have an effect

20
Q

Force levels

A

Optimum
-Graph
Excessive

21
Q

Optimum force levels graph

A

<1 s: PDL fluid incompressible, alveolar bone bends, piezoelectric signal generated
1-2s: PDL fluid expressed, tooth moves in PDL space
3-5s: BVs compressed on p side, dilated on tension side, PDL fibres and cells distorted
Minutes: blood flow altered, oxygen tension changes, chemicals released
Hours: Metabolic changes, cellular differentiation begins
2 days: tooth movement begins as Ocs/ Obs within PDL remodel bony socket

22
Q

Optimum force

A

Small cell-free zone - osteoclasts recruited from blood vessels in the PDL
Resorption from PDL side of socket

23
Q

Excessive force graph

A

<1s: PDL fluid incompressible, alveolar bine bends, piezoelectric signal generated
1-2s: PDL fluid expressed, tooth moves in PDL space
3-5s: BVs within PDL occluded on p side
Minutes: Blood flow cut off to compressed PDL area
Hours: cell death in compressed area
3-5 days: cell differentiation in adjacent narrow spaces, undermining resorption begins
7-14 days: undermining resorption removes lamina dura adjacent to compressed PDL, tooth movement occurs

24
Q

Excessive force

A 
Complete loss of BVs in PDL
-Ocs recruited from endosteal surface of bone
Delay in tooth movement
Pain
Loss of viltality
Mobility
Root resorption
Loss of anchorage
25
Q

Optimum force depends on

A 
Size of root
Type of movement
Continuous or intermittent better?
20-25g/cm^2
Anchorage also depends on force levels
26
Q

Heavy force

A

Canine does not move at first
Molar moves forward
-loss of anchorage

27
Q

Types of tooth movement

A 
Tipping (removable)
Bodily movement
Rotation
Torque
Vertical movement
-extrusion
-intrusion
28
Q

Types of tooth movement

A 
Tipping (removable)
Bodily movement
Rotation
Torque
Vertical movement
-extrusion
-intrusion
29
Q

Fully controlled movement

A

Need attachment to tooth - full 3D control

30
Q

Light force

A 
Canine moves distally
Anchor tooth (molar) moves forward only slightly
31
Q

Anchorage in orthodontics

A

Control of unwanted tooth movement
Teeth respond to pressure
Pressure = force per unit root area

Orthodontics (IODC) (17 decks)

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