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Flashcards in 2) Orthodontic Springs Deck (46):
1

Which elements of the removable appliance are designed first?

Active components - the other components will be designed by the active components

2

What are the active components?

Springs

Bows

Screws

3

What will an ideal spring do?

Apply the correct force over a good range

Move tooth in right direction

Be difficult to position incorrectly

Be resistant to accidental damage

Be atraumatic

Be hygienic

4

What are the 3 parts to the palatal canine retractor?

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Arm

Coil

Tag

5

What are the 2 types of palatal springs?

Guarded and un-guarded palatal springs

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6

Describe the force applied by springs?

Factors determining applied force;

 1) Length of the spring

 2) Thickness of the wire

 3) Elastic modulus of the wire

 4) Degree of activation For a tooth-moving spring we want a low force over a good range of action

7

What are the properties of springs?

Length - double the length of the wire and it will reduce the stiffness by a factor of 8

Thickness - double the radius of a wire will increase the stiffness by a factor of 16

Modulus - the lower the modulus, the lower the stiffness

Activation - double the activation doubles the force

8

What happens if the wrong length/thickness/modulus/activation is provided?

Give too high a force

9

Describe the palatal retractor?

An ideal palatal retractor; - applies a force of 20-40gm (cN) with a 3mm activation - so must be right length, right thickness of wire and material - typically - e.g. for a canine - wire is 0.5mm stainless steel

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10

Describe palatal retractor force?

Force must be 20-40gm to move the single tooth gently and physiologically

11

What happens if the spring is activated >3mm?

It may self-insert on the wrong side of the tooth (as well as apply too much force)

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12

What is occurring in this image?

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When the retractor is activated by 2-3mm it slides down the mesial surface of the canine on insertion

13

What can help ensure the correct amount of activation?

Marking the acrylic

14

What does this diagram show?

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Activating the retractor

15

Is this correct or incorrect tooth movement?

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Correct Tooth will move at right angles to the point of contact

16

Is this correct of incorrect tooth movement?

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Incorrect Tooth will move at right angles to the point of contact - so this would cause rotation and buccal movement

17

What has happened here?

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Force applied incorrectly - causing a rotation

18

Why has this adjustment been made?

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To prevent rotation

19

What are the clinical applications of palatal springs?

Mesio-distal movements of canines, premolars and molars Ideal deflection 2-3mm Ideal force 20-40gms (cN)

20

How do palatal retractors achieve the aim in springs of being atraumatic?

By being in a sheltered position in the mouth

21

What are the other orthodontic springs?

Buccal canine retractor

Z springs

T springs

Auxillary springs

(Screws)

22

Describe the buccal canine retractor?

For buccally placed teeth;

 1) Self supporting - 0.7mm

 2) Sleeved - 0.5mm (in tubing)

 3) Reverse loop - 0.7mm

23

What is this?

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Self supporting retractor in 0.7mm stainless steel wire

24

What are the advantages of the self supporting retractor?

Quite stiff so good control of spring positon

25

What are the disadvantages of the self supporting retractor?

Activation of stiff wire provides high force levels High in sulcus and can traumatise mucosa - 0.7mm wire - activate 1mm only

26

What is this?

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Sleeved buccal retractor - sleeved 0.5mm stainless steel wire in tubing - flexible component with rigid support

27

What are the advantages of the sleeved buccal retractor?

Flexible with 2mm activation

Good control

28

What are the disadvantages of the sleeved buccal retractor?

High in sulcus so can traumatise mucosa

29

What is shown in these images?

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Sleeved buccal retractor

Left - too high - ulcer

Right - lower design - less trauma but stiffer

30

What is shown here?

Q image thumb

Activation of the buccal retractor

31

What does this show?

Reverse loop buccal retractor - made in 0.7mm stainless steel wire

32

How are reverse loop buccal retractors activated?

'Curl and cut'

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33

What does this show?

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Reverse loop buccal retractor

Left - passive, prior to full insertion

Right - ideal position, 1mm active

34

What are the advantages of the reverse loop buccal retractor?

Short vertically, so less traumatic

Good lateral control of spring position

35

What are the disadvantages of the reverse loop buccal retractor?

Stiff so short range of action

36

What are these?

Q image thumb

Z springs

37

What are the advantages of Z springs?

Flexible with 1-2mm activation on a single-tooth spring and 3-4mm on a double-tooth spring

Quite easily adjustable

38

What are the disadvantages of Z springs?

Displaces the appliance so requires very good retention

39

What are these?

T springs

40

What do T springs do?

Push teeth buccally

41

How do you activate T springs?

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42

What are the advantages of T springs?

Easily adjustable

Good for buccal segment teeth

43

What are the disadvantages of T springs?

Displace the appliance and need good retention

Limited range of action

44

What are screws?

Are the only means in a removable appliance of holding on to a tooth for retention (with a crib) and at the same time moving it

For;

 - mesio-distal movement

 - expansion

45

What does this show?

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Screws

One turn = 0.25mm activation, turn once per week

46

What is this screw for?

Q image thumb

Distal movement