Fixed Appliances Flashcards
What is a fixed appliance?
An appliance which is fixed to the teeth and cannot be removed by the patient
-> Consists of brackets, bands, archwires and auxillaries
-> Precision tooth movers
What are some of the ADV of fixed appliances?
3D control
Complex tooth movements
Control of root
Less dependant on compliance- not removable
What are some of the DIS of fixed appliances?
Requires excellent oral hygiene
Risk of iatrogenic damage- relapse, decal, root resorption
Poor intrinsic anchorage- lack of baseplate
Longer treatment time- 2-2.5 years
What are some of the ADV of removable appliances?
Used for tipping
Intrinsic anchorage
Easier cleaning
Less risk of iatrogenic damage
What are some of the DIS of removable appliances?
Simple tooth movements only
No control of root movement
Can be lost
Better compliance required
What are the uses of fixed appliances?
Correction of mild to moderate skeletal discrepancies -Camouflage
Alignment of teeth- straightening
Correction of rotations
Centreline correction- align with mid facial-axis
Overbite and overjet reduction
Closure of spaces/creating spaces
Vertical movements of teeth- extrusion/intrusion
What is orthodontic camouflage?
Accepting underlying skeletal base relationship and treat malocclusion to class 1 incisor relationship
When do be people tend to notice a centre line deviation?
If it is greater than 4mm
What are Andrews Six Keys? (treatment aim)
- Tight approximal contacts with no rotations
- Class I incisors
- Class I molars
- Flat occlusal plane or slight curve of Speed
- 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
- Tooth proportion and size must fit within anatomical average to achieve this- very difficult clinically due to subtle differences in individuals
What are the different components that can be used on fixed appliances?
Brackets- precision milled (different sizes for different teeth usually, although some universal brackets exist)
Band- only done on posteriors due to aesthetics (used in heavily restored teeth without sufficient enamel structure to bond to- MIH)
Arch wire- goes through bracket (communicates bracket to tooth to allow force to be exerted allowing tooth movement as per prescription)
Modules-elastic donuts, hold wire to bracket (changed every visit)
Auxiliaries- spring, plastic tubing to protect sites, elastomeric chain to close spaces
Anchorage components- what is the demand?
Force generating components- coils and springs
Why do patients who receive combined orthognathic and orthodontic surgery have their terminal molars banded?
Gives robust end point of appliance- keeps things secure during osteotomy in case of iatrogenic damage
What is straight wire?
Doesn’t require bending (prescription is included)
Why are molar tubes used instead of bands?
More discrete
Less irritating to soft tissue
What are the components of brackets and their function?
Bracket slot (horizontal)- allows arch-wire to run through
Tie wings- 4 on each bracket, modules attach here
Bracket base- part that bonds to tooth
-> angulation is based on prescription (inclination and torque also pre-prescribed)
Why may canine brackets have hooks on them?
Can be used to attach elastics or springs
What materials can brackets be made from?
Metal
-> SS, CoCr, Ti, Au
Polymers
Ceramics
What are the features of bands?
Stock, so size must be estimated
Have pre-welded attachments- tubes and cleats (can be traumatic- press these in to make them flush)
Space prep visit required- as contacts are often very tight
Cemented with GIC (removed with slow speed tungsten carbide bur)
What bracket prescription is used in GDH?
MBT prescription
Helps us get nice occlusal finish
Each tooth has different degree of tip, in/out and torque
How are brackets bonded to teeth?
Using acid etch technique with self etch primers (prevents excess rinsing and drying)
-> failure rate is low
What is the issue with using self etch primers to bond brackets?
Must be well mixed and agitated on tooth
What are the steps in bonding brackets?
Brackets are usually pre-coated in composite and sealed in a pod (individual for each tooth)
Pop pod just after etching
There are orientation marks to help clinician- goes distally gingivally
-> more expensive
If bracket was not pre-coated we would add composite before placing
-> less efficient, slower, more flash to trim away
What are the issues with excess flash when bonding orthodontic brackets?
Staining
Caries risk
Which materials can be used to make archwires?
Stainless Steel (SS)
Nickel Titanium (NiTi)
Cobalt Chromium (CoCr)
Beta-Titanium (TMA)
Composite/glass
What are the ADV/DIS of NiTi Ortho wires?
ADV:
Flexible
Shape memory- produces light force as it tries to rebound to original shape and form from deflections (this is why the wires are not pre-bent)
DIS:
Higher friction- can prevent efficient sliding and tooth movement
What are the advantageous properties of SS wire?
Low friction- good for sliding teeth along wire
Formable- can be bent
-> loops can be created for elastics
What is the normal wire protocol in Fixed appliance treatment?
NiTi- early aligning wire
-> Start of with round light then work up to larger/rectangular
SS- Working wire for moving teeth after initial alignment
What are the function of modules?
Elastomeric bands (typically) that go over tie wings to allow communication of wire and bracket
What are self-ligating appliances?
Appliances with brackets that have gates (that are opened/closed using an instrument) which keep archwire in place
What are the ADV and DIS of self ligating appliances?
ADV:
More efficient movement as no degradation of modules
-> can be combined with elastomeric if required
Lower friction- better sliding
DIS:
Can get fused with plaque and calculus which can block gate closed (bracket need replaced)
What is the function of a nance button?
Prevents mesial migration of posterior movements using palatal vault for anchorage reinforcement
What are examples of force generating components?
Elastic power chain
NiTi coil springs
IO elastics
Active ligatures
What is the function of a spring?
Can be used to push crowded teeth apart or open up space if teeth congenitally missing
What is plastic sheathing used for?
Helps protect spans where extraction has been carried out, preventing deflection of wire due to occlusal forces (trauma to ST)
What is the issue with elastic power chain?
Power chain only works short term until elastic properties degrade (50% as active after 2 weeks- needs replaced every 6 weeks)
-> good for space closing or pulling teeth into arch
What is the function of NiTi coil springs?
Placed between two brackets (cut more than you need to press into space)
This will want to push back to initial length and can be used to distalise teeth creating space
How do intra-oral elastics work? How are they altered for class II/III
Attach from canine to FPM
Class 3- brings lowers back and uppers forward
-> Lower canine to upper FPM
Class II- opposite
What is anchorage?
Resistance to unwanted tooth movement
-> Every force applied has equal but opposite reactionary force
-> First aspect of planning- can be difficult to recover if incorrectly set up
What is simple anchorage?
Smaller tooth vs bigger tooth
Bigger tooth has more root surface area so acts as anchor and when force is applied smaller tooth is likely to be pulled back more
What is compound anchorage?
2 teeth put together to increase size of root area, giving less unwanted and more favourable tooth movement
What is reciprocal anchorage?
Reciprocal = equal (run elastics between to create equal force and equal rate of movement)
-> can be used to fix diastemas
When is absolute anchorage used?
High anchorage demand case (and cant afford any unwanted movement)
How is absolute anchorage achieved?
Using TADs (non-osteointegrating bone screw)- placed in buccal cortex under LA (interradicular)
-> requires careful planning so not to damage roots
What cases are TADs useful for?
Hypodontia
Moderate AOB- placed in palate
How is cortical anchorage achieved?
Using a transpalatal or lingual arch
-> Vertical anchorage when pulling canines from palate
How is inter maxillary anchorage achieved?
Elastics
Why has headgear been replaced by TADs?
Less risk of trauma/occular injury
No compliance issue- patients found it difficult to wear headgear for required 12-14 hours
Why is lifelong retention required following fixed appliance treatment?
Teeth are not stable- relapse will occur as PDL fibres have elastic memory and want to recoil into original position
Which features have highest relapse potential?
Diastema/ space closure
Rotations
Palatally ectopic canines
Proclination of lower incisors
Anterior open bite
Instanding upper lateral incisors
What is the retainer wear protocol for pressure formed?
2 weeks full time (apart from eating and drinking)
-> then night time only
If perforated or worn- can be replaced by GDP
What can be done with pressure formed retainers if patient has hypodontia?
Can add false teeth if hypodontia in aesthetic zone and not had prosthetic treatment yet
What are the features of a Hawley Retainer?
Acrylic baseplate with adam’s clasp on 6s
Labial bow- can help against relapse of proclined upper anteriors (poor aesthetics)
Can add teeth (backed up with metal) into acrylic for hypodontia patients (before prosthetic treatment)
Which cases commonly require fixed retention?
Spaced closure
Diastema
Proclination of lower
labial segment
Periodontal cases
Ectopic canines
Instanding upper 2’s
-> sometimes any case
What are the issues with fixed retainers?
Requires careful monitoring- check looseness
Orthodontist required to fixed breakages
Difficult OH
How does decalcification appear?
Chalky white
Brown mottled
What is the average amount of root resorption during orthodontic treatment?
1mm- can be more if naturally short or spindle shaped roots
-> monitor frequently with radiographs
How long does fix appliance treatment last?
Average case- 18-24 months
Hypodontia case- 24-30 months
Orthognathic case- 24-30 months
How often does a patient need to attend for adjustment of fixed appliance?
Every 4-8 weeks
Which issues may a patient encounter at the start of fixed orthodontic treatment?
Pain
Mucosal irritation
Ulceration
Appliance breakages
