fixed appliances Flashcards
What are the different types of tooth movement?
Tipping
Bodily movement
Rotation
Torque
Vertical movements (extrusion/intrusion)
Removable can do tipping too but none of the other movements
What are problems/risks of fixed appliances?
Demineralisation/caries
Root resorption
Soft tissue lacerations
Perio problems (gingivitis/recession)
Pulp devitalisation
Relapse
Unwanted tooth movements
What are the components?
Brackets
Molar tubes/bands
Archwires
Auxillaries
What are archwire materials?
Nickel Titanium (super elastic/heat activated)
Stainless steel
What are brackets?
Pre adjusted edgewise
Stainless steel or ceramic or even plastic
Has tie wings and a slot (for metal tie/elastic module)
Most common slot size- 0.022’x0.028’
Bracket base- foil mesh for retention with composite
Slot in middle for probe to seat
Specific brackets for every tooth (prescription of tip and torque)
5-5
What is the wire progression?
1. Round wires- initial tooth alignment (flexible NiTi)
2. Increase in rigidity and thickness
3. Rectangular wires- (1925) final alignment and space closure (aka working archwire) this is the aim
What is the maximum dimension of wire?
0.019’x0.025’
What are aesthetic brackets?
Ceramic- fracture in use and debonding/abrasion of other teeth/increased friction/cost
Lingual (SS) - difficult technique/cost/trauma to tongue
Plastic- fracture/distort/discolour
Why is tungsten carbide good for debonding?
Removes composite but not enamel
How should ceramic brackets be used?
Upper arch only to avoid abrasion of other teeth
Lower arch only if no OB
What are molar bands?
Lower- single tube for archwire, hook for auxiliaries
Upper- additional tube for head gear (round, not used for archwire), hook for auxiliaries
Need to place ortho separators for a week
Different sizes, should be close fitting, can be adapted
Place w GIC, pt can bite down on a instrument to help seat
What are the benefits of ortho separation for molar bands?
More comfort for patient
Easier for operator
More accurate band selection
What are molar tubes?
Can bond tube to tooth- has hook and tube- similar to bracket
Don’t need to place separators
Difficult isolation from moisture- more likely to debond
Problem w wire if debonds
Can’t use headgear
What is the function of archwires?
Active- move teeth with wire for alignment- light forces, flexible, NiTi
Passive- teeth move along wire for bodily movement w help of accessory components- rigid, SS
What is the cross section of archwires?
Round wires- 0.012’ to 0.018’ (usually goes up in 2s so 012, 014 etc)
Rectangular wires- 0.019’x0.025’
How is the arch wire attached?
Elastic modules- O shape or figure of 8 for reinforcement
If needs even more reinforcement can use wire ligatures (quick ties)
Self ligating brackets (reduces friction) slot wire in and shut a door- uncomfortable, takes longer, narrower arch and flat profile
What are auxiliaries?
ELASTICS
bands O
power chain ooo
zing string (elastic thread) —
e-links o—o
traction ligatures oxx
SPRINGS
push coil/coil spring —xxx—
closing coil/retraction spring oxxo
What does a fixed appliance kit have?
Weingarts- grips archwires
Tucker- tuck end of quick ties
Adam’s pliers- make bends in archwires or adjust clasp on removable appliances
Light wire plier cutter- cut light wires/elastics
Distal end cutters- right angle, cut end of archwires
Crown shears- cut ends of quick ties
Why is Invisalign not as effective?
Doesn’t allow the same range of movements
Where did the Andrews 6 keys to normal occlusion (1972) come from?
120 sets of models (from local dentists/orthodontists/unis)
Wanted straight teeth, pleasing appearance, correct bite, no need for ortho
Compared w models that had ortho w v good results
What are the 6 keys?
1. Molar relationship (class I)
2. Crown angulation (tip)- root tipped distally by 5 degrees for molars and incisors and 11 for canines
3. Crown inclination (torque)
4. No rotations- molars need more space compared to incisors
5. Tight contacts- no crowding/spacing
6. Flat curve of Spee- flat occlusal plane
What does the straight wire appliance have built in?
Tip (eg. Andrews values- U3 is 11 degrees so angle of slot in bracket is rotated)
Torque (slot in bracket is rotated up or down)
In-out (different bracket base thicknesses, distal offset of upper molars)
For each individual tooth
What are the main stages of tx?
Levelling and alignment (vertical/buccolingual/mesiodistal movements and correct rotations)
Space closure (OJ reduction, centre line correction)
Additional stages (OB/CB correction, finishing and detailing)
What is the choice of initial archwire?
NiTi round wires
Or even beta titanium (TMA) or super elastic or SS (multistrand)
What is the problem of tip in canine brackets?
Crown moves forward
Incisors extruded
Bite deepens
So we use CANINE LACEBACKS (ligature wire under archwire)
Prevents canine moving mesially
Posterior teeth can move forward
What are space closure methods?
NiTi springs
Power chain
Traction ligatures
What are some additional stages?
Make finishing bends in wire as prescription brackets may only go 95% of the way
Box elastics can improve occlusion
What are types of retainers?
Removable
-acrylic (hawley)
-vacuum formed (Essix)
Fixed
-bonded
What are hawley retainers?
Acrylic from palate to palatal surface of incisors (locks posterior teeth)
Cribs on 6s for retention
Adam’s clasps
Labial bows
What is the retention regime?
12hrs/day for first year
Alternate nights for the second year
Gradual withdrawal
Minimum 1x a week indefinitely
What teeth are prone to relapse?
Perio involved teeth due to lack of bone support
Midline diastemas
Severe rotations- pericisions (supracrestal fibres want to pull them back)
Teeth out of zone of stability w soft tissues (eg. proclined lower incisors/OJ reduction w incompetent lips)
What is pericision?
Circumferential supracrestal fibrotomy
