Orthodontic Springs

Question 1

3 active components of a removable appliance

Answer 1

spings
bows
screws

Question 2

4 elements of a removable appliance and examples

Answer 2

• active components: springs, bows, screws
• retentive components: adams crib, southend clasp, reversed loop of labial bow, baseplate
• baseplate
• anchorage

Question 3

which of these should be designed first and why

Answer 3

active components–> influences other components

Question 4

6 requirements of a spring

Answer 4

• apply correct force over good range
• move tooth in right direction
• be difficult to position incorrectly
• be resistant to accidental damage
• be atraumatic
• be hygienic

Question 5

3 parts of palatal retractor

Answer 5

arm
coil
tag

Question 6

what does ‘guarded’ palatal spring protect against?

Answer 6

being bent in mouth (but not in pockets etc)

Question 7

4 factors determining force applied by springs

Answer 7

1. length: double length of wire reduces stiffness x 8
2. thickness of wire: double radius of wire increases stiffness x 16
3. elastic modulus of wire: lower modulus, lower stiffness
4. degree of activation: double activation doubles force

Question 8

function of loop in palatal retractor

Answer 8

adds length –> reduces force for given deflection

Question 9

palatal retractor:

a) force
b) activation
c) wire thickness

Answer 9

a) force: 20-40g (cN)
b) activation: 3mm
c) wire thickness: 0.5mm stainless steel

Question 10

why should low force be used

Answer 10

to move tooth gently and physiologically

Question 11

why is max activation 3mm?

Answer 11

• may self-insert on wrong side of tooth

- may apply too much force

Question 12

how does palatal retractor line up to various points on the tooth?

Answer 12

(pencil line down long axis of tooth)
arm and coil anterior to line
arm contacts tooth on point at 90 degrees to contact point to apply load

Question 13

what movement are palatal springs used for?

Answer 13

mesio-distal movement of canines, premolars, molars

Question 14

name other orthodontic springs

Answer 14

-buccal canine retractor
-Z springs
-T springs
auxillary springs

Question 15

3 types of buccal-canine retractor and their wire thickness and activation amont

Answer 15

• self-supporting (0.7mm, activate 1mm)
• sleeved (0.5mm in tubing, activate 2mm)
• reverse loop (0.7mm, activate 1mm)

Question 16

advantages of self-supporting retractor

Answer 16

stiff–> good control of spring position

Question 17

disqadvantages of self-supporting retractor

Answer 17

• activation of stiff wire –> high force

- high in sulcus –> can traumatise mucosa –> activate 1mm only

Question 18

how to activate self-supporting and sleeved buccal retractor

Answer 18

deflect arm so when in place, unit springs forward –> drags tooth back

Question 19

advantages of sleeved buccal retractor

Answer 19

flexible within 2mm activation

good control

Question 20

disadvantages of sleeved buccal retractor

Answer 20

high in sulcus –> traumatise mucosa

Question 21

how to activate reverse loop buccal retractor

Answer 21

curl (bend hook further back) and cut

Question 22

where does the reverse loop buccal retractor attach?

Answer 22

1 tooth further back than the one you’re moving

Question 23

advantages of reverse loop buccal retractor

Answer 23

short vertically so less traumatic

good lateral control of spring position

Question 24

disadvantages of reverse loop buccal retractor

Answer 24

stiff –> short range

Question 25

function of Z spring

Answer 25

push teeth labially (tilts teeth, rather than move them)

Question 26

how to activate Z spring

Answer 26

pull arm in desired direction

Question 27

advantages of Z springs

Answer 27

• flexible (1-2mm activation on single tooth spring, 3-4mm activation on double tooth spring)
• easily adjustable

Question 28

disadvantages of Z springs

Answer 28

displaces appliaces –> needs good retention

Question 29

function of T springs

Answer 29

push teeth bucally

Question 30

activation of T springs

Answer 30

pull away from acrylic towards tooth

Question 31

advantages of T springs

Answer 31

easily adjustable

good for buccal segment teeth

Question 32

disadvantages of T springs

Answer 32

displace appliance –> need good retention

limited range of action

Question 33

3 functions of a screw

Answer 33

• expansion
• mesio-distal movement
• only method of removable appliance holding on to tooth for retention and moving it at the same time