Appliance Design (Labs) Flashcards
What are the main components of stainless steel and their %s?
- Iron -72%
- Carbon 0.3%
- Chromium - 18%
- Nickel - 8%
- Titanium - 1.7%
What are the properties of stainless steel that makes it good for use in ortho?
- non-corrosive
- can bend without fracturing
- cheap
- flexible
- non-toxic
- strong
- biocompatible
- ductile
What are the advantages of study casts?
- Good for record keeping
- Good to see the improvements/progress
- Good motivation for patients (can cut teeth off and put wax in place (don’t make too realistic)
- Can look when patient isnt there
- design appliances on it
- more information for a more informed decision
- teaching purposes
- retrospective studies
What are the 3 main aims of ortho treatment?
- good aesthetic outcome
- functional
- stable occlusion
What type of action/movement can removable ortho appliances do? (how do they move teeth?)
they can tip/tilt teeth
Where is the fulcrum in terms of the tooth when using a removable appliance?
at the midpoint of the tooth (between the crown and root)
[we dont bend teeth]
What are the advantages of removable appliances?
- Tipping of teeth (able to move teeth)
- fundamental change. In restorative and dentures we are stabilising teeth
- Give excellent anchorage
- Generally cheaper than fixed orthodontics. Fixed involves attaching brackets on every tooth. URA’s are better tolerated than lowers as tongue
- Shorter chairside time required
- Oral hygiene is easier to maintain (can take them out and clean)
- Non-destructive to tooth surface and no tooth prep required (Composite is used to bond to the teeth - need to etch which is destructive - fixed)
- Less specialised training required to manage
- Can be easily adapted for overbite reduction
- Can achieve block movements (segment and entire section of teeth and move it in one - bit of a problem but will be discussed later)
What are the disadvantages of removable appliances?
- Less precise control movement of teeth (aka limited to just tipping/tilting)
- Can be easily removed by patient (can forget to put back in or not compliant)
- Generally only 1-2 teeth can be moved at one time (fixed can move multiple)
- Specialist technical staff required to construct the appliances
- Rotations very difficult to correct (aka tooth rotated mesially or distally)
What is the acronym used for appliance design?
ARAB:
- Active component
- Retentive
- Anchorage
- Baseplate
What is the active component of a removable appliance?
Any component that will move the teeth through the application of force
When writing the active component on a design sheet, what do you need to state?
- The teeth
- The component
- The wire thickness
What kind of stainless steel wire is used in ortho?
Hard stainless steel wire (soft is never used)
What is the thickness of stainless steel wire used for active components?
0.5mm
What is the thickness of stainless steel wire used for retentive components?
0.7mm
What is the definition of anchorage?
the resistance to unwanted tooth movement (Making sure the teeth we want to move do move and the ones we don’t want to move stay in the same place)
Anchorage is resisting displacement forces. What are 5 examples of the displacement forces that will be experienced in the mouth?
- forces from the tongue (click it on and off)
- mastication
- speaking
- gravity
- the active component - is applying forces to the teeth which will bounce out and can cause the appliance to pop out
Newton’s 3rd law makes anchorage hard. What is Newton’s 3rd law?
for every action, there is an opposite and equal action
What are the 3 functions of the baseplate?
- hold all the components together
- assists with retention (adhesion and cohesion)
- Gives a lot of anchorage
What material is the baseplate made from?
Self-cure PMMA
What thickness of HSSW would be used for an Adam’s clasp on a deciduous tooth?
0.6mm HSSW
What baseplate modification is used to help correct overbites? How does it work?
Flat anterior bite plane
- props open mouth and creates posterior open bite
- Lower teeth continue to erupt and new bone is formed around them
- When FABP is removed the overbite will be reduced
Note: cant be done in older patients as teeth would just over-erupt
What is the size of the FABP and why do we make it this size?
OJ + 3mm
If didnt add extra 3mm then patient would change bite and bite behind the plane - result in the lower anterior teeth proclining and increasing the overjet
How do you resolve an anterior crossbite?
Z-spring and a posterior bite plane to give anterior open bite to allow movement of the tooth in crossbite
How many posterior teeth need to be incorporated to a posterior bite plane and why?
All of them otherwise they will continue to erupt
Why will using a posterior bite plane not cause the patients anterior teeth to continue to erupt?
The anteriors dont occlude naturally
Note: sometimes in restorative dentistry a posterior bite plane is used to get the anteriors to erupt - this is for PARTIALLY erupted anterior teeth
Why do we continue to reduce an overbite when moving onto the next appliance? (e.g. retracted canines and now retracting the 22-12)
- The canines will retract quicker than the lower teeth erupt and when new bone is formed it is less dense than normal bone.
- The flat anterior bite plane allows this new bone to become dense. Otherwise, the teeth could intrude again.
- As the incisors are tipped back, they will drop ‘lower’ which therefore would increase the overbite
Describe the steps in fitting an URA.
Before fitting the appliance should always check that the patient’s medical history has not changed and that the appliance has been disinfected and is ready to fit.
- Ensure the patients details match the details supplied for the appliance (Right Appliance-Right patient).
- Check the appliance matches the design specifications.
- Inspect the appliance and run your finger over all surfaces looking for sharp or potentially traumatic areas.
- Check the integrity of the wirework (Damage or work-hardening).
- Work hardening would happen if the wire was bent one way then realised it was wrong and bent the other way. Any force on this area would cause it to break
- Can identify these areas as they will be dark (not shiny like normal)
- Chromium is what makes the metal shiny and prevents corrosion. If there is damage or work hardening then the chromium will have been removed and the area is prone to corrosion and fracture (will be sharp in the patients mouth if it fractures).
- Insert the appliance into the patient’s mouth, immediately looking for areas of blanching or soft tissue trauma.
- If the appliance causes ulceration etc then the patient will not wear it
- Check the posterior retention (Adam’s clasp. Firstly, check the flyovers aren’t interfering with occlusion, then that the arrowheads are correctly engaging the appropriate undercuts.)
- Apply the same principles to the anterior retention.
- Activate the appliance (1mm movement approximately per month).
- We receive the appliances in a passive state.
- Demonstrate to the patient the correct procedure for insertion and removal of the appliance (Ensure that the patient demonstrates this correctly).
- Book a review appointment 4-6 weeks
What information and instructions would you give to a patient after fitting an URA?
- Appliance will feel big & bulky (this is perfectly normal and they will get used to it quickly).
- My cause initial excessive salivation (this will pass in 24 hours).
- May impinge speech for a short period of time (practise reading a book aloud at home and this will subside).
- May cause initial discomfort or ache (this is perfectly normal, and indicates that the appliance is working).
- To be worn 24/7 including meal times & sleep.
- Remove after every meal and clean with a soft brush.
- Remove and store in a protective container when participating in contact or active sports.
- Avoid hard or sticky foods that may damage the appliance and be cautious with hot food or drinks.
- Missing appointments and non-compliance will significantly lengthen the treatment time.
- Provide emergency contact details in case any problems arise.
What is the active component when simply just retracting the canines
palatal finger spring and guard
What would be the retention on an appliance that is made to only retract canines
adams clasp
southend clasps
For reduction of an overbite, what would have to be added to an appliance
flat anterior bite plane
What is the active component in an appliance for the retraction of buccally placed canines
buccal canine retractor + ID tubing
What is the active component in an appliance that is correcting an anterior crossbite
z spring
What addition has to be added to an appliance that is made to correct anterior crossbite
posterior bite plane
What would the retention be on an appliance made to retract buccally placed canines
adams clasps and southend clasps
What would the retention be on an appliance that is correcting an anterior crossbite
adams clasps on 4s and 6s
no southend clasp (would inhibit movement)
What is the active component in an appliance made for correcting an overjet
roberts retractor (ID tubing required)
What is the retention for an active component that is made to correct an overjet
adams clasps only
no anterior retention required - roberts retractor sits in undercut
What else is required that is not part of ARAB in an appliance made to correct overjet
mesial stops
to prevent movement of teeth back to original position
What is the active component in an appliance that is made to expand the upper arch
midline palatal screw
What is the retention on an appliance that is made to expand the upper arch
adams clasps on 4s and 6s
What addition does an appliance made to expand the upper arch require
posterior bite plane
What are the different components of an adams clasp
- tag
- baseplate
- leg
- flyover
- arrowhead
Where would you adjust an adams clasp
flyover first
What problems can an overjet create
- Trauma, speech, functional, aesthetics and sometimes can get a lip trap or incompetent lips
How can we make space in the mouth
- Extraction or widen the arch
What is the definition of retention
- he resistance to displacement forces
Why do we use self cure over heat cure
- Because self cure takes about 15 minutes but takes about 15 hours if using heat cure
- Heat cure has better properties but self cure has acceptable properties
How much tooth movement do we want a month
1 mm of tooth movement per month
How do you activate a component
- want to uncoil the wire
What are flat anterior bite planes used for
- correction of an overbite ONLY
When can you use a posterior bite plane
anterior crossbite
expanding upper arch
What components require ID tubing
roberts retractor
buccal canine retractor
Why do roberts retractors and buccal canine retractors need ID tubing
they are bucally placed
function is to prevent wire from distorting
What 3 things in relation to the coil affect displacement of the tooth
- The size of the coil
- The thickness of the wire
- The length of the wire
Why does the wire move away from the tooth in a palatal finger spring
- The tooth is moving closer to the coil
- The wire is uncoiling so it is getting longer
What is reciprocal anchorage
- When we have the same force going in both directions (because of Newtons first law)
- An example of when this is used is in a URA with a midline palatal screw
What are the 2 pliers we use in ortho
no 64 universals
no 65 coil formers
Compare heat cure PMMA with self cure
- Self-cure has shorter working time
- Heat cure PMMA is stronger
- Residual monomer is burnt off in heat cure. There is therefore more residual monomer in self-cure (allergic reaction)
- Heat cure doesn’t shrink as much as self-cure
- Sefl-cure takes 15 minutes
- Same amount of money for self-cure and heat cure
- Self-cure is satisfactory = only wearing it for 6 months anyway
