Fixed Appliance Flashcards
What is a fixed appliance
An appliance which is fixed to the teeth and cannot be removed by the patient
What does a fixed appliance consist of
brackets, bands, archwires and auxillaries
What are the features of fixed appliances
o 3D control
o Complex tooth movements
o Control of root
o Less dependant on compliance
o Requires excellent oral hygiene
o Risk of iatrogenic damage
o Poor intrinsic anchorage
What are the features of removable appliance
o Simple tooth movements (tipping/tilting)
o No control over root movement
o Greater compliance required
o Less risk of iatrogenic damage
o Good instrinic anchorage - due to baseplate covering palate
When do we use fixed
- Correction of mild to moderate skeletal discrepancies (camouflage)
- Alignment of teeth
- Correction of rotations
- Centreline correction
- Overbite and overjet reduction
- Closure of spaces/creating spaces
- Vertical movements of the teeth (extrusion/intrusion)
What are andrew’s 6 keys
- Tight approximal contacts with no rotation
- Class 1 incisors
- Class 1 molars
- Flat occlusal plane or slight curve of spee
- Long axis of the teeth have slight mesial inclination except the lower incisors
- The crowns of the canines back to the molars have a lingual inclination
What are andrew’s 6 keys
- Tight approximal contacts with no rotation
- Class 1 incisors
- Class 1 molars
- Flat occlusal plane or slight curve of spee
- Long axis of the teeth have slight mesial inclination except the lower incisors
- The crowns of the canines back to the molars have a lingual inclination
What is the 7th key of occlusion
Bolton’s ratio
relates to tooth proportions, sizes and formation so everything fits together
What are the components of a fixed appliance
bracket/tube
band
archwire
modules
auxillaries
anchorage components
force generating components
What are the components of the bracket
bracket slot
tie wing
bracket base
What are the different bracket materials
stainless steel, CoCr, Ti, Au
What does the bracket prescription determine
o Bracket prescription determines the tip, torque and in/out control
o MBT prescription used
How are brackets bonded on
o Acid etch technique
o Used for brackets and tubes but not bands
o Photoinitiation reaction using light cure 440-480nm wavelength of light
o Utilises micromechanical retention
o The brackets come in sealed pods and they have a dot marker which is a clinical indicator to help with orientation, they go towards the gingiva distally
o Don’t want much flash caries risk
What are bands
- Made of stainless steel with prewelded attachments: cleats or tubes
- Requires space prior to placement so requires a separator visit
Where are orthodontic bands placed
- Tend to be placed only on posterior teeth due to aesthetics
- Also consider use if needing to involve heavily restored teeth with not enough enamel to bond to
- Orthognathic patients will often have terminal molars banded as they are more robust and harder to dislodge
How are bands bonded
GI cement
What are the various arch wire materials
stainless steel
niti
cocr
beta titianium
composite/glass
What are the features of stainless steel wire
o Working archwires to slide teeth
o Used for moving teeth
o Low friction
o Formable so can put archwire bends and loops
What are the features of nickel titanium wire
o Flexible
o Light continuous force - wire tries to return to original shape
o Shape memory - wants to return to original shape and cannot bend
o Higher friction than stainless steel- undesirable, slower tooth movement
o Start with round NiTi then onto rectangular Niti then stainless steel
How do force generating components work
Teeth move by utilising the energy stored in the elastic or spring
sliding mechanism utilised
What are the different force generating components
elastic power chain
niti coils
intra-oral elastics
active ligature
What are elastic power chains
Elastic chain running from hook to appliance on anterior tooth to posterior tooth and it helps pull the buccal segment together
Elastic loses its properties so the elastic chain will only be 50% as active weeks later so by the time they come back, the elastic needs to be replaced
What are ni-ti coils
Still have elastic memory but in coil form so when we stretch the coil and works continuously to close the space
Better than elastic as elastic properties degrade
What are intra-oral elastics
Can be used for class 3 or class 2 malocclusions
The patient changes them at home
Provides specific direction of force and helps guide teeth into ideal position
Where are intra oral elastics placed for class 3
anterior tooth on lower jaw (usually canine) attached to posterior tooth on upper jaw (usually a 6)
Where are intra oral elastics placed for class 2
anterior tooth on upper jaw (usually a canine) attached to a posterior tooth on lower jaw (usually a 6)
Useful for reducing OJ and OB at the same time
What is anchorage
resistance to unwanted tooth movement
What theory is anchorage based on
newton’s third law which is every force has an equal but opposite reactionary force
What is simple anchorage
o This is one tooth against the other
o E.g trying to move back a canine against a molar
o The molar has a bigger root surface therefore the canine will move more than the molar and so the molar is the anchor
What is compound anchorage
More than one tooth used as the anchor
Trying to increase the size and surface area against the tooth we are trying to move
What is reciprocal anchorage
Equal forces in both directions
E.g diastema closure, two central incisors are of equal weighting and so will move the same way
What are the types of anchorage
absolute anchorage
cortical anchorage
intermaxillary anchorage
headgear
What is absolute anchorage
This is defined as no movement of the anchorage unit (hence zero anchorage loss) as a consequence of the reaction forces applied to move teeth
What is absolute anchorage
This is defined as no movement of the anchorage unit (hence zero anchorage loss) as a consequence of the reaction forces applied to move teeth
How can absolute anchorage be obtained
use of ankylosed teeth or implants
What are temporary anchorage devices
non-osseointigrating mini screw
Why are TADs useful
Revolutionised notoriously difficult cases e.g hypodontia cases
Can be placed into interradicular bone and placed in the palate
Can be used in the palate when there is a moderate anterior open bite and you are trying to prevent a surgical treatment pathway
What is cortical anchorage
Cortical plates provide increased resistance to tooth movement
What is an example of cortical anchorage
transpalatal arch
How does cortical anchorage work
It moves the roots torwards the cortical plate to dercease the tendency of the molars to move mesially in response to orthodontic force
Nance button uses palatal vault for more anchorage reinforcement
What is intermaxillary anchorage
Defined as anchorage in which the resistance units situated in one jaw are used to effect tooth movement in the opening jaw
Uses intra-oral elastics
What is headgear
Can be used for anchorage reinforcement
Not used much anymore
Comes with risk of ocular injuries hence safety mechanisms must be ensured
What is retention
maintaining the final tooth position with a passive orthodontic appliance
What are features with high relapse potential
o Diastema/space closure
o Rotations
o Palatally ectopic canines
o Proclination of lower incisors
o Anterior open bite
o Instanding upper lateral incisors
What are the 2 types of removable retainers
PFR
hawley
What are the features of PFR
Variety of materials and thicknesses
Can include prosthetic tooth for aesthetics
Well tolerated
Usually 2 wks full time wear and then night only there after
How does hawley retainer work
Labial bow to control incisors and canines
Not well tolerated in the lower arch
What are the indications of fixed retainers
- Spaced closure
- Diastema
- Proclination of lower labial segment
- Periodontal cases
- Ectopic canines
- Isntanding upper 2s
What are the features of bonded wire retainer
- Requires careful monitoring and interdental cleaning
- Ensure composite attachments intact and sound
- Refer back to the orthodontist if any problems
What are the main risks of fixed appliance
Decalcification
Root resorption
Relapse
Enamel Wear
What is the average root resorption
on average 1mm of root length per teeth, importance of pre-op radiograph to ensure adequate root length prior
What increases risk of root resorption
Higher risk roots are narrow/tapered roots
Spindly roots
Shorter roots
Describe the patient journey
assessment/diagnosis
tx plan
commence tx
routine adjustments
How long does the average ortho case take
18-24 months
How long does a hypodontia & orthognathic case take
24-30 months
How long does a hypodontia & orthognathic case take
24-30 months
How often are routine adjustments made
4-8 wks
What are the initial problems encountered
o Pain
o Mucosal irritation
o Ulceration
o Appliance breakage
