Spring

Question 1

What are the different components of a removable appliance?

Answer 1

Active components

Retentive components

Baseplate

Anchorage

Question 2

Which components should be designed first and why?

Answer 2

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

Question 3

What 6 things will an ideal spring do?

Answer 3

• • 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

Question 4

What are the 3 parts of the palatal retractor?

Answer 4

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

Question 5

What is this part?

Answer 5

A guard

The horizontal wire stops distortion in the mouth

Question 6

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

Answer 6

To stop damage to patient

Question 7

Which factors determine the force applied by a spring?

Answer 7

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

Question 8

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

Answer 8

A low force over a good range of movement

Question 9

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

Answer 9

Reduces the stiffness by a factor of 8

Question 10

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

Answer 10

Increases the stiffness by a factor of 16

Question 11

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

Answer 11

Lowers the stiffness (listen to 9mins 30)

Question 12

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

Answer 12

Doubles the force of the spring

Question 13

What does the loop in a palatal spring do?

Answer 13

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

Question 14

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

Answer 14

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

Activation: 3mm

Question 15

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

Answer 15

0.5mm stainless steel

Question 16

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

Answer 16

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

Question 17

How do you activate a palatal retractor?

Answer 17

Question 18

What can help ensure the correct amount of activation?

Answer 18

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

Question 19

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

Answer 19

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

Question 20

What is a common incorrect tooth movement?

Answer 20

Point of contact slightly too palatal = rotation and buccal movement

Question 21

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

Answer 21

Question 22

What movements are palatal springs clinically used to achieve?

Answer 22

Mesio-distal movement of canines, premolars and molars

Question 23

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

Answer 23

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

Question 24

Which other orthodontic springs exist?

Answer 24

The buccal canine retractor (X3)

Z springs

T springs

Auxillary springs (Screws)

Question 25

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

Answer 25

For moving buccally placed canine teeth : * - Self supporting * - Sleeved * - Reverse loop

Question 26

What is the self supporting retractor?

Answer 26

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)

Question 27

What are the advantages of the self supporting retractor?

Answer 27

Quite stiff = good control of spring position

Question 28

What are the disadvantages of the self supporting retractor?

Answer 28

Activation of stiff wire = high force levels Sits high in sulcus and can traumatise the mucosa

Question 29

How much are self supporting retractors activated by?

Answer 29

1mm only

Question 30

What is a sleeved buccal retractor?

Answer 30

The same as the self supporting retractor but the non active part is sleeved = thick and stiff 0.5mm in tubing

Question 31

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

Answer 31

Question 32

What are the advantages of the sleeved buccal retractor?

Answer 32

Flexible with 2mm activation Good control

Question 33

What are the disadvantages of the sleeved buccal retractor?

Answer 33

High in sulcus (can traumatise mucosa)

Question 34

How much are sleeved buccal retractors activated by?

Answer 34

2mm

Question 35

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

Answer 35

Ulcer

Question 36

What design can be used to make it lower?

Answer 36

= less trauma but stiffer

Question 37

What is the reverse loop buccal retractor?

Answer 37

Coil is above the tooth two behind the moving tooth 0.7mm stainless steel

Question 38

How is the reverse loop buccal retractor activated?

Answer 38

'curl and cut'

Question 39

What are the advantages of the reverse loop buccal retractor?

Answer 39

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)

Question 40

What are the disadvantages of the reverse loop buccal retractor?

Answer 40

Stiff (short range)

Question 41

How much is a reverse loop buccal retractor activated by?

Answer 41

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

Question 42

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

Answer 42

Question 43

What type of spring is this?

Answer 43

z spring

Question 44

What movement to z springs achieve?

Answer 44

Push teeth labially

Question 45

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

Answer 45

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

Question 46

What are the advantages of z springs?

Answer 46

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

Question 47

What are the disadvantages of z springs?

Answer 47

- Displaces the appliance = requires very good retention i.e. cribs and labial bows

Question 48

How are z springs activated?

Answer 48

Question 49

What type of spring is this?

Answer 49

T spring

Question 50

What movement does a T spring achieve?

Answer 50

Pushes teeth buccally

Question 51

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

Answer 51

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

Question 52

How are T springs activated?

Answer 52

Pulled away from acrylic

Question 53

What are the advantages of T springs?

Answer 53

- Easily adjustable - Good for buccal segment teeth

Question 54

What are the disadvantages of T springs?

Answer 54

- Displace the appliance and need good retention - Limited range of action

Question 55

What movements can screws achieve (with a crib)?

Answer 55

Mesio-distal movement and for expansion

Question 56

How do screws work?

Answer 56

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

Question 57

How can screws be used for distal movement?

Answer 57

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

Question 58

What is important in screws?

Answer 58

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