Orthodontics - Fixed Appliances Flashcards
Describe a fixed appliance.
An appliance which is fixed to the teeth and cannot be removed by the patient
- Precision tooth movers as they can move the teeth in 3D planes using varying forces
List the features of a fixed appliance. (7)
- 3D control (crown and root)
- Complex tooth movements
- Control of root
- Less dependent on compliance
- Requires excellent oral hygiene
- Risk of iatrogenic damage (decal, root resorption, relapse)
- Poor intrinsic anchorage as no baseplate
When are fixed appliances used? (7)
- Correction of mild to moderate skeletal discrepancies
- Camouflage: accept the underlying skeletal base and treat the malocclusion to create a class 1 relationship.
- Alignment of teeth
- Correction of rotations
- Centreline correction (correct midline deviations)
- Overbite and overjet reduction
- Closure of spaces/ creating spaces
- Vertical movements of teeth e.g. intrude and extrude
What are the treatment goals of fixed appliances? (7)
Andrews 6 keys:
- Tight approximal contacts with no rotations.
- Class I incisors.
- Class I molars.
- Flat occlusal plane or slight curve of Spee
- Long axis of the teeth have a slight mesial inclination except the lower incisors.
- The crowns of the canines back to the molars have a lingual inclination.
7th key : tooth proportion, sizes and formation must be within normal average.
Describe the advantages of a bracket fixed appliance system.
prescriptions incorporated;
Each bracket will have the inclination, angulation and torque already pre-incorporated into the bracket system
What bracket prescription is used in the GDH?
MBT
How are ortho brackets bonded to teeth?
Bond via composite and an acid etch technique – uses micromechanical retention
Describe how brackets are placed. (5)
- Polish the tooth using pumice and water
- Isolate the tooth
- Tooth prepared with Self etch primers with tooth agitation
- Brackets can be precoated or can manually coat with composite
- Attached to the tooth with the locating dot distal gingivally
In which location should the brackets locating dot be on the tooth?
locating dot distal gingivally
What are the advantages of a precoated bracket?
What is the disadvantage?
- Quicker and efficient
- Less flash to remove
X – more expensive
Where are orthodontic bands placed and why?
on posterior teeth as they are not aesthetic
What material is used to bond ortho brackets?
GIC
Why are ortho bands used? (2)
- when teeth don’t have sufficient enamel for braackets to bond to (i.e. heavily restored)
- provides an end stopping point of the appliance (orthognathic patients)
What is the alternative to a molar band?
List the advantages. (4)
molar tubes;
Advantages of molar tubes:
- More discrete
- Less irritating to the soft tissues
- Less cover-some
- Petite on the tooth
(Can be used on upper and lower 6’s and 7’s)
What material are working archwires made from?
stainless steel
List the properties of a stainless steel working wire. (2)
- low friction = Working arch wires to slide teeth
- Formable = can incorporate arch wire bends and loops
What material are early aligning archwires made from?
NiTi
List the properties of a NiTi early aligning wire. (4)
- flexible
- Applies light continuous force (trying to get back to natural shape)
- Has shape memory (return to normal shape)
Disadvantage: Higher friction than SS (= less tooth slide and movement)
What is the function of an orthodontic module?
helps keep the wire and bracket together
List the types of ortho modules (2)
- Elastomeric
- Self ligating appliance (gate opening appliance) - instrument used to open the gate and the archwire is inserted then the gate is closed again
(lower friction with more slide)
What is a disadvantage of a self ligating module?
can become Fused with plaque and calculus if the px has poor OH
List examples of orthodontic auxillaries. (3)
- Spring
- Plastic tubing
- Elastomeric chain
What kind of mechanics do we use to move teeth?
sliding mechanics
List force generating components used in fixed appliances (4)
describe how these work.
Elastic power chains
NiTi coils
Intra-oral elastics
Active ligatures
The teeth move by using the force stored in the elastic or the spring
What is anchorage?
Resistance to unwanted tooth movement
Newtons 3rd law – for every reaction there is an equal and opposite reaction
List the 3 types of anchorage.
simple
compound
reciprocal
How do we achieve absolute anchorage?
TADs - temp anchorage devices
a non-osseointegrating mini screw
When is absolute anchorage required?
in high anchorage cases where no unfavourable tooth movement can occur
Describe cortical anchorage.
provide an example of a device which provides this.
Where the cortical plates increase the resistance to tooth movement
- Very minimal mesial unfavourable tooth movement occurs
e.g. transpalatal arch
How do we achieve intermaxillary anchorage?
intra-oral elastics (class 2 or class 3)
What is a retainer?
a passive orthodontic appliance used to retain the final tooth position post ortho tx
In which orthodontic patients are fixed retainers used? (7)
- Diastema
- space closure
- Proclined lower labial segment
- Periodontal cases
- Ectopic canines
- AOBS
- In standing upper laterals
However some orthodontists use it for all cases
How long are fixed appliances worn in an average orthodontic case?
18-24 months
How long are fixed appliances worn in a hypodontia orthodontic case?
24 -30 months
How long are fixed appliances worn in a orthognathic orthodontic case?
24-30 months
When are routine adjustments made to fixed ortho applaicnes?
between 4-8 weeks
What are the initial problems that patients experience with fixed appliances? (4)
- Pain
- Mucosal irritation
- Ulceration
- Appliance breakage
What is the GDP’s role in fixed appliance maintenance? (4)
- Routine check ups
- Reinforce OHI and diet advice
- Liaise with orthodontist If required
- Make appliances safe in an orthodontic emergency
List the components of fixed appliances. (6)
brackets/tubes/bands
archwire
auxiliaries
modules
force generating components
anchorage components
