Orthodontics Lab Flashcards
What metal is used for orthodontic appliances?
Stainless steel 18/8 austentitic
What are the components of stainless steel?
72% Iron
18% Chromium
8% Nickel
1.7% Titanium
0.3% Carbon
Why might fractures of stainless steel occur?
Overworked- bending and straightening in the same spot
Mechanical abrasion- by burs
Fatigue- Repeated straining action.
Weld decay
What are the uses of study casts?
Monitor treatment over time
Treatment plan
Patient and parent motivation
Legal requirement
Construction of appliances
Design of appliance
Teaching
Forensics
What are Adam’s clasps used for?
Retentive component that engages the medial and vital undercuts on the buccal surface of teeth.
What diameter of wire are retentive components made with?
0.7mm HSSW.
What diameter of wire are active components made with?
0.5mm HSSW.
What is the acronym for the prescription of a URA?
ARAB
Active component
Retention
Anchorage
Baseplate
What is the active component?
Component of the URA that is applying force to the tooth to cause it to move.
What is a retentive component?
Resistance to displacement.
What is anchorage?
Resistance to unwanted tooth movement.
What is the baseplate?
Connects all the components together and also assists with anchorage.
How much tooth movement is expected per month?
1mm
What material is used for the baseplate and why?
Heat-cured PMMA
Less shrinkage than self cure, so is dimensionally stable.
Stronger
Less free radicals, less unreacted monomer (less irritant for the patient).
Name some advantages of Adam’s clasps?
Clasp is small, neat and unobtrusive.
Can be placed on any tooth- permanent or deciduous (0.6mm HSSW).
Can be modified in a number of ways.
Highly retentive
Aids removal of appliance
What retentive components may be employed?
Southend clasp (anteriors)
Labial bow
Adam’s clasp (posteriors)
Both in 0.7mm HSSW.
What active components may be employed to retract canines that are in line with the arch?
Palatal finger springs and guards- 0.5mm HSSW.
What active components may be employed to retract canines that are buccally placed?
Buccal canine retractor- 0.5mm HSSW with 0.5mm tubing.
What is a flat anterior bite plane used for?
Reduce the overbite.
How does a FABP work?
Placed anteriorly to disocclude posterior teeth- allows them to continue to erupt, reducing the overbite.
What are the purpose of guards?
Prevent components of the URA from going into the soft tissue.
When prescribing the FABP, you have to say overjet + 3mm, why?
To prevent lower anteriors from tilting backwards.
The baseplate usually extends from 7-7, why is this the case?
Too far back- gag reflex
Too far forward- expose the wire work
What are the advantages of a URA?
Tipping of teeth
Excellent anchorage
Cheaper than fixed
Shorter chair side time
Oral hygiene is easier to maintain
Non-destructive to tooth surface
Less specialised training required to manage
Can achieve block movements.
What are the disadvantages of a URA?
Patient compliance
Requires specialist labs to construct
Less precise tooth movement
Only 1-2 teeth can be moved at a time.
How long does it take before a URA becomes passive?
1 month.
Why would a FABP not work in a adult?
Over-eruption of posterior teeth, rather than continuing to erupt.
What active component would be utilised for reducing an overjet?
Robert’s retractor- 0.5mm HSSW with 0.5mm internal tubing.
What are medial stops used for?
Prevents teeth moving in the opposite direction to what you want it to.
Describe the process of fitting a URA.
- Check patient details match the details supplied for the appliance.
- Check the appliance matches the design specifications.
- Inspect appliance, run finger around wire work and fitting surface.
- Check integrity of wire work.
- Insert the appliance into the mouth and observed blanching.
- Check posterior retention.
- Check anterior retention.
- Activate the appliance.
- Demonstrate to the patient how to take the appliance in and out.
- Book review appointment for 4-6 weeks later.
What patient information should be given when the URA is fitted?
- Appliance will feel big and bulky.
- May cause increased salivation.
- May impair speech for a short time
- May cause initial discomfort or ache
- Must be worn 24/7 including meal times and sleep.
- Remove after a Mel and clean with a soft brush.
- Remove during contact sports.
- Avoid hard and sticky foods.
- Missing appointments and non-compliance will significantly lengthen the treatment time.
- Provide emergency contact details incase problems arise.
What component is utilised when you wish to correct an anterior cross bite?
Posterior bite plane
Z-spring- 0.5mm HSSW.
What component might you utilise to expand the upper arch?
Midline palatal screw (active component).
To correct a posterior cross bite, what appliance might you utilise?
URA with midline palatal screw and posterior bite plane.
What type of retainers might you employ?
Conventional removable retainer
Thermoplastic retainer
Bonded retainer
What is a transpalatal arch used for?
Anchorage
Rotation
Limited widening or contraction
Most commonly attached to the upper 6’s with orthodontic stainless steel bands.
The wire is attached tot he bands by weldering/soldering.
What thickness of wire is used for a transpalatal arch?
0.9mm HSSW
What is a palatal arch with a nance button used for?
Anchorage
Most commonly attached to the first permanent molars Sith the use of stainless steel bands.
What thickness of wire is used for a palatal arch with nance button?
0.9mm HSSW
What is a quadhelix used for?
Bilateral expansion
Asymmetrical expansion
Fan style expansion
Rotation of molars
Expansion in cleft palate
Modified to proline incisors
Assist in habit breaking
What thickness of wire is used for a Quadhelix?
0.9mm HSSW
What are the advantages of fixed orthodontics?
Bodily tooth movement can occur
Rotations easily fixed
Can be used as easily in the lower arch as the upper arch
Individual forces can be applied to every tooth
Not easily removed by the patient
Works 24 hours a day, 7 days a week
Precise 3D movement of teeth
Less invasive of tongue space
Minimal palatal coverage
What are the disadvantages of fixed appliances?
Not as easy to clean- plaque retentive factor.
Increased risk of root resorption
Decalcification
Can be perceived as visually unattractive
Can cause soft tissue trauma
Poor anchorage
Etching teeth is a destructive procedure
Highly trained specialist training required
What are the advantages of removable orthodontics?
OH is easier because it can be removed from the mouth
Tipping of teeth
Excellent anchorage
Cheaper than fixed
Non-destructive to tooth surface
Less specialised training required to manage
Can be easily adapted for overbite reduction
Can achieve block movements
What are the disadvantages of removable appliances?
Less precise control of tooth movement
Can be easily removed by the patient
Only 1-2 teeth can be moved at one time
Rotations very difficult to correct
Specialist technical staff required to construct the appliances
What type of arch wire is utilised initially for fixed ortho?
Nickel Titanium- has good shape memory.
Then move to stainless steel wires and work up the sizes throughout treatment.
What are the advantages and disadvantages of a thermoplastic retainer?
Advantages
- Cheap
- Aesthetically better than conventional
- Easily tolerated by the patient
- Easily taken out to perform OH
Disadavntages-
- Easily broken/snapped
- Easily lost
- Compliance can be an issue
What are the indications for a bonded retainer?
Diastema
Rotations
Instanding laterals
