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Yr 3 Orthodontics > Spring > Flashcards

Spring Flashcards

1
Q

What are the different components of a removable appliance?

A

Active components

Retentive components

Baseplate

Anchorage

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2
Q

Which components should be designed first and why?

A

Active components (because the other components will be influenced by the active components)

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3
Q

What 6 things will an ideal spring do?

A
    • Apply the correct force over a good range
    • Move tooth in the right direction
    • Be difficult to position incorrectly
    • Be resistant to accidental damage
    • Be a-traumatic
    • Be hygienic
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4
Q

What are the 3 parts of the palatal retractor?

A

The arm = not normally straight -> usually sits around the tooth

Coil = extension of the arm

Tag = mechanical retention - the only portion that goes within the acrylic

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5
Q

What is this part?

A

A guard

The horizontal wire stops distortion in the mouth

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6
Q

Why do we have an eyelet on the end of the arm?

A

To stop damage to patient

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7
Q

Which factors determine the force applied by a spring?

A
  1. Length of the spring
  2. Thickness of a wire
  3. Elastic modulus of the wire
  4. Degree of activation
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8
Q

What force do we want the force of a tooth moving spring to apply?

A

A low force over a good range of movement

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9
Q

What does doubling the length of a wire do to a spring?

A

Reduces the stiffness by a factor of 8

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10
Q

What does doubling the radius (thickness) of a wire do to a spring?

A

Increases the stiffness by a factor of 16

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11
Q

What does a lower elastic modulus of wire do to a spring?

A

Lowers the stiffness (listen to 9mins 30)

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12
Q

What does doubling the activation of a wire do to a spring?

A

Doubles the force of the spring

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13
Q

What does the loop in a palatal spring do?

A

It adds length (reduces the force for a given deflection) (listen to 10 mins = slide 15)

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14
Q

What force does an ideal palatal retractor apply and what activation does it have?

A

Force: 20-40 gm (cN) = moves tooth gently & physiologically

Activation: 3mm

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15
Q

Typically for a canine which wire is used to make sure it is the right thickness and elastic modulus?

A

0.5mm stainless steel

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16
Q

What happens if the spring is activated too much (>3mm)?

A

It may self- insert on the wrong side of the tooth (tooth width) and will apply too much force

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17
Q

How do you activate a palatal retractor?

A
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18
Q

What can help ensure the correct amount of activation?

A

Marking the acrylic (on baseplate and bend the wire to this mark)

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19
Q

In which direction will the tooth move to the point of contact?

A

The tooth will move at right angles to the point of contact

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20
Q

What is a common incorrect tooth movement?

A

Point of contact slightly too palatal = rotation and buccal movement

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21
Q

What is a common adjustment that can be used to prevent this rotation?

A
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22
Q

What movements are palatal springs clinically used to achieve?

A

Mesio-distal movement of canines, premolars and molars

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23
Q

When moving a premolar which thickness of wire do we use?

A

Thicker wire (the extra force can be taken due to the wider root)

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24
Q

Which other orthodontic springs exist?

A

The buccal canine retractor (X3)

Z springs

T springs

Auxillary springs (Screws)

25
Q

When is the buccal canine retractor used and what are the 3 types?

A

For moving buccally placed canine teeth :

    • Self supporting
    • Sleeved
    • Reverse loop
26
Q

What is the self supporting retractor?

A

A buccal canine retractor = 0.7mm stainless steel wire n.b there’s not very much sulcal depth in this region (if too long = trauma)

27
Q

What are the advantages of the self supporting retractor?

A

Quite stiff = good control of spring position

28
Q

What are the disadvantages of the self supporting retractor?

A

Activation of stiff wire = high force levels

Sits high in sulcus and can traumatise the mucosa

29
Q

How much are self supporting retractors activated by?

A

1mm only

30
Q

What is a sleeved buccal retractor?

A

The same as the self supporting retractor but the non active part is sleeved = thick and stiff

0.5mm in tubing

31
Q

How are the self supporting retractors and sleeved buccal retractor activated?

A
32
Q

What are the advantages of the sleeved buccal retractor?

A

Flexible with 2mm activation

Good control

33
Q

What are the disadvantages of the sleeved buccal retractor?

A

High in sulcus (can traumatise mucosa)

34
Q

How much are sleeved buccal retractors activated by?

A

2mm

35
Q

What can happen if the sleeved buccal retractor is too high?

A

Ulcer

36
Q

What design can be used to make it lower?

A

= less trauma but stiffer

37
Q

What is the reverse loop buccal retractor?

A

Coil is above the tooth two behind the moving tooth

0.7mm stainless steel

38
Q

How is the reverse loop buccal retractor activated?

A

‘curl and cut’

39
Q

What are the advantages of the reverse loop buccal retractor?

A

Short vertically (less traumatic)

Good lateral control of the spring position (relatively short range of movement -> can only bend a few times before it breaks)

40
Q

What are the disadvantages of the reverse loop buccal retractor?

A

Stiff (short range)

41
Q

How much is a reverse loop buccal retractor activated by?

A

1mm (more than this applies huge pressure to tooth)

42
Q

What does the reverse loop buccal retractor look like when passive and active?

A
43
Q

What type of spring is this?

A

z spring

44
Q

What movement to z springs achieve?

A

Push teeth labially

45
Q

If you have a cross bite (upper incisors behind lowers) how do we use a z spring to treat this?

A

But z spring behind upper incisors and use blocks so no horizontal interference -> can use single spring contacting two teeth to move them but two individual springs is more adjustable

46
Q

What are the advantages of z springs?

A
  • Flexible with 1-2mm activation on a single tooth spring and 3-4 mm activation on a double tooth spring
  • Quite easily adjustable
47
Q

What are the disadvantages of z springs?

A
  • Displaces the appliance = requires very good retention i.e. cribs and labial bows
48
Q

How are z springs activated?

A
49
Q

What type of spring is this?

A

T spring

50
Q

What movement does a T spring achieve?

A

Pushes teeth buccally

51
Q

What are the purpose of the loops on the T spring?

A

Give the wire extra length = reduces the pressure put on the tooth

52
Q

How are T springs activated?

A

Pulled away from acrylic

53
Q

What are the advantages of T springs?

A
  • Easily adjustable
  • Good for buccal segment teeth
54
Q

What are the disadvantages of T springs?

A
  • Displace the appliance and need good retention
  • Limited range of action
55
Q

What movements can screws achieve (with a crib)?

A

Mesio-distal movement and for expansion

56
Q

How do screws work?

A

Patient tightens/ loosens activation wheel once each week = 0.25 mm activation

57
Q

How can screws be used for distal movement?

A

n.b. need lots of retention to keep it in place

58
Q

What is important in screws?

A

Done by patient themselves = should not be able to do it incorrectly = wrong movement!

Yr 3 Orthodontics (4 decks)

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