Orthodontic Springs Flashcards
3 active components of a removable appliance
spings
bows
screws
4 elements of a removable appliance and examples
- active components: springs, bows, screws
- retentive components: adams crib, southend clasp, reversed loop of labial bow, baseplate
- baseplate
- anchorage
which of these should be designed first and why
active components–> influences other components
6 requirements of a spring
- 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
3 parts of palatal retractor
arm
coil
tag
what does ‘guarded’ palatal spring protect against?
being bent in mouth (but not in pockets etc)
4 factors determining force applied by springs
- length: double length of wire reduces stiffness x 8
- thickness of wire: double radius of wire increases stiffness x 16
- elastic modulus of wire: lower modulus, lower stiffness
- degree of activation: double activation doubles force
function of loop in palatal retractor
adds length –> reduces force for given deflection
palatal retractor:
a) force
b) activation
c) wire thickness
a) force: 20-40g (cN)
b) activation: 3mm
c) wire thickness: 0.5mm stainless steel
why should low force be used
to move tooth gently and physiologically
why is max activation 3mm?
- may self-insert on wrong side of tooth
- may apply too much force
how does palatal retractor line up to various points on the tooth?
(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
what movement are palatal springs used for?
mesio-distal movement of canines, premolars, molars
name other orthodontic springs
-buccal canine retractor
-Z springs
-T springs
auxillary springs
3 types of buccal-canine retractor and their wire thickness and activation amont
- self-supporting (0.7mm, activate 1mm)
- sleeved (0.5mm in tubing, activate 2mm)
- reverse loop (0.7mm, activate 1mm)
advantages of self-supporting retractor
stiff–> good control of spring position
disqadvantages of self-supporting retractor
- activation of stiff wire –> high force
- high in sulcus –> can traumatise mucosa –> activate 1mm only
how to activate self-supporting and sleeved buccal retractor
deflect arm so when in place, unit springs forward –> drags tooth back
advantages of sleeved buccal retractor
flexible within 2mm activation
good control
disadvantages of sleeved buccal retractor
high in sulcus –> traumatise mucosa
how to activate reverse loop buccal retractor
curl (bend hook further back) and cut
where does the reverse loop buccal retractor attach?
1 tooth further back than the one you’re moving
advantages of reverse loop buccal retractor
short vertically so less traumatic
good lateral control of spring position
disadvantages of reverse loop buccal retractor
stiff –> short range
function of Z spring
push teeth labially (tilts teeth, rather than move them)
how to activate Z spring
pull arm in desired direction
advantages of Z springs
- flexible (1-2mm activation on single tooth spring, 3-4mm activation on double tooth spring)
- easily adjustable
disadvantages of Z springs
displaces appliaces –> needs good retention
function of T springs
push teeth bucally
activation of T springs
pull away from acrylic towards tooth
advantages of T springs
easily adjustable
good for buccal segment teeth
disadvantages of T springs
displace appliance –> need good retention
limited range of action
3 functions of a screw
- expansion
- mesio-distal movement
- only method of removable appliance holding on to tooth for retention and moving it at the same time
