fixed appliances Flashcards
definition
an appliance which is fixed to the teeth and can’t be removed by the patient
consists of brackets, bands, archwires and auxillaries
precision tooth movements
advantages of fixed appliances
3D control
complex tooth movements
control of root movement - root torque
less dependent on compliance
disadvantages of fixed appliances
requires excellent OH
risk of iatrogenic damage - white marks
poor intrinsic anchorage - don’t have palate for anchorage
advantages of removable appliances
less risk of iatrogenic damage - can clean more effectively
good intrinsic anchorage- baseplate
disadvantages of removable appliances
only simple tooth movements- tipping
no control over root movement
greater compliance required
can be lost
indications for fixed appliances
camouflage (correction of mild to mod skeletal discrepancies) alignment of teeth correction of rotations centreline correction OJ and OB reduction closure of spaces/creating spaces vertical movements of teeth
treatment goal - Andrew’s 6 keys
tight approximal contacts, no rotations
class 1 incisors
class 1 molars
flat occlusal plane or slight curve of spee
long axis of teeth have a slight mesial inclination except from the L incisors
the crowns of the canines back to the molars have a lingual inclination
history of fixed appliances
1 - bands made individually for each tooth
2 - direct bonding (brackets) - Edgewise.
- have to put bends in wire - time-consuming and challenging
- spaces closed using springs
3 - pre-adjusted Edgewise “straight wire”
- no longer need to pre-bend wire
- arch wire slot individualised for each tooth
components
bracket/tube band archwire modules auxiliaries anchorage components force generating components
components of bracket
bracket slot
tie wings
bracket base
bracket materials
metal: SS, (CoCr, Au)
polymers: higher friction, not as strong
ceramics: hard to remove post treatment
types of self-ligating bracket
passive
active
passive self-ligating brackets
reduced friction, wire not held in gap, freely moving to slide
active self-ligating brackets
little spring which holds wire in slot
no modules to put on bracket
increased friction so not as good for sliding
how are brackets attached?
connected to bands or directly bonded on the teeth
function of brackets
hold arch wire in place
bands
SS ring which encompasses tooth with pre-welded attachments
- tubes and sometimes lingual/palatal cleats (run elastics)
how do you attach the ortho attachment to the band?
weld/solder
where are bands mostly used and why?
on molars as need increased bond strength
can also use if a tooth is heavily restored
what are bands cemented on with and what need to be done before placement?
GIC
space required - separator visit 5-7 days before
why might pt complain of jag cheeks with a band and how do you treat this?
as teeth align surplus wire may protrude distally out of tubes
cut surplus flush with tube
auxillaries
supplement main components of bands, brackets and archwires
arch wire hooks and stops, cleats, buttons, coil springs, elastomeric, elastics, separators, wire ligatures, TPA, quad helix, headgear
elastomeric modules
secure archwire into arch wire slot
force generating components
sliding mechanisms
- elastic power chain (close spaces and pull ectopic canines)
- NiTi coils
- IO elastics
- active ligature
teeth move by utilising the energy stored in the elastic or spring
- pull/push teeth away/towards each other along the arch wire
class 2 inter maxillary elastics
run from U anteriors to L posteriors
e.g. to reduce OJ
class 3 intermaxillary elastics
run from U molar to L canine
to pull lower labial segment back
what does the bracket prescription determine?
in/out
tip
torque
control
what is the MBT prescription modified for?
to make it suitable to treat the most common malocclusion - class 2
where on the tooth is the MBT prescription for?
at the midpoint of the facial surface
in-out control
relative bucco-lingual position of teeth
e.g. 2 set palatally, 3 set labially
what determines in-out control?
depth of bracket base
tip
the mesio-distal angle of the tooth - the angle the tooth makes to the horizontal along the line of the arch
all teeth tip mesially
what determines tip?
angle of the horizontal slot
what tooth movements can a round AW achieve?
tipping and vertical tooth movements
torque
bucco-lingual angle (inclination) of the tooth
- U incisors inclined labially
- UBS inclined palatally
- all lowers inclined lingually
what determines torque?
angle between the bracket base and slot
when does torque only happen and why?
when you use a rectangular wire
engages wall of slot
the closer the fit between the arch wire and bracket slot the greater the degree of control
get force couple with interaction between arch wire and walls of bracket - apical and rotational movements
composite bonding techniques for brackets and tubes
acid etch technique
self-etching primer (transbond plus)
what does the bracket have to enhance bonding?
mesh base to increase SA
why shouldn’t you really use GI to cement brackets?
decreased bond strength
what is GI used to cement?
molar bands
how does the arch wire shape change throughout tx?
start round them progress to rectangular
arch wire materials
NiTi SS CoCr B-Ti (TMA) composite glass
SS wires
often use early
working AWs to slide teeth (low friction)
hypodontia/to open gaps - slide teeth to create space (then align with NiTi wire)
formable - AW bands, loops
multistrand - flexible
NiTi wires
flexible
light continuous force - low force delivery over large deflection
shape memory - return to original shape, difficult to distort
higher friction than SS - because surface isn’t as highly polished
anchorage
resistance to unwanted tooth movement
Newton’s 3rd law
every force has an equal but opposite reactionary force
what is the first aspect of treatment planning?
anchorage
why are fixed appliances anchorage demanding?
you are just involving teeth
TADs - absolute anchorage
non-osseointegrating mini screw won't move under force major development in ortho - anchorage control - tooth movement mechanics
TADs failure rate
low e.g. comes loose
v few problems
how to use TADs
LA then insert between roots
uses of TADs
retract canine distally (inter-radicular TAD) intrude molars (palatal TAD between 5 and 6s) - close AOB (prev would have required surgery)
cortical anchorage
cortical plates provide increased resistance to tooth movement
- buccal roots start to hit cortical plates as move forward because maxilla gets narrower
prevents mesial molar movement
TPA and lingual arch
maintains intermolar width
also transverse anchorage
Nance palatal button/arch
utilises palatal vault for anchorage reinforcement
stops molars from tipping and prevents mesial drift
can potentially further increase anchorage
headgear
traditional headgear use is in decline sometimes still use protraction gear for class 3 - maxilla more amenable - can disrupt sutures and move forward
headgear safety
must ensure appropriate safety mechanisms to prevent catapult ocular injuries from face bows
- locking devices
- safety release springs
written and verbal instructions
retention
maintaining the final tooth position with a passive orthodontic appliance
what is the aim of retention?
prevent relapse
types of retainers
fixed
removable
consent stage - retention
lifelong retention required
pt decision - wear for as long as you can unless you want to take the risk of relapse
features with high relapse potential
diastema/space closure rotations palatally ectopic canines proclination of L incisors AOB instanding U lateral incisors
what type of retention should be given to high relapse risk patients?
bonded retainers
PFRs
clear overlay retainers
variety of materials and thicknesses
can include prosthetic tooth for aesthetics
well-tolerated
PFRs wear pattern
varies between clinicians
2 weeks full time wear except eating and drinking, night only thereafter
or straight to nights only
types of removable retainer
PFRs
Hawley removable retainer
Hawley retainer
1920s
labial bow to control incisors and canines
not well tolerated in the L arch
can add prosthetic teeth
clinical situations for a fixed retainer
spaced arch diastema proclination of lower labial segment PD cases (can also use as splinting for mobile teeth) ectopic canines instanding U2s
bonded wire retainer maintenance
requires careful monitoring and ID cleaning
ensure composite attachments intact and sound
refer back to orthodontist if problems
Orthoflextech
good for L anteriors
cant use for upper incisors as space between composite bonds too big so can get movement
rigid canine bars
canine to canine
0.032 inch SS
some companies provide preformed
maintain IC width so incisors can’t move
winged retainer
issue if one wing fails
types of fixed retainer
bonded wire retainer
Orthoflextech
rigid canine bars
winged
risks of fixed appliances
decalcification - monitor throughout tx
root resorption
relapse
gingival recession - esp if pre-existing in adult patient
pt journey
assessment and diagnosis - tx aims
tx plan and informed consent
commence tx
average case length
18-24m
hypodontia, ectopic canines, orthognathic case length
24-30m but v variable
frequency of routine adjustments
every 4-8 weeks
initial problems encountered
pain
mucosal irritation
ulceration
appliance breakage
GDP role
continue to see pt for routine care and check ups - reinforce OHI and diet advice
liase with orthodontist if concerns
make appliance safe in case of an ortho emergency
- snipping of jaggy wire
- removal of loose component
