Ortho Lab Flashcards
What are the components of stainless steel and their percetnages
Iron - 72%
Chromium -18%
Nickel 8%
Titanium 1.7%
Carbon 0.3%
Name 4 advantages of removable orthodontics
Excellent anchorage
Shorter Chairside time
Oral hygiene is easier to maintain
Non destructive to tooth surface
Can be easily adapted for over bite reduction
What are 5 disadvantages of removable appliances
Less precise control of tooth movement ( tipping and tilting limited)
Can be easily removed by the patient - non compliance
Generally only 1-2 teeth can be removed at a time
Specialist technical staff required to construct the appliances
Rotations are very difficult to correct
What diameter is stainless steel in the claps used
0.7mm
What is the active component
Name of components that will be moving the teeth through force
What is retention
Resistance to displacement forces
What are the 5 forces which a removable appliance can be subjected to?
Gravity
Mastication
Speech = vibrations through the palate displace it
Tongue
Active components
What is anchorage
The resistance to unwanted tooth movement
Newtons 3rd law is related to anchorage and can make anchorage difficult.
What is this law?
Every action as an equal and opposite reaction
What is the baseplate of a URAs function
To connect all the components
Retention - adhesion/cohesion
Resistance to unwanted movement - provides anchorage and assists with retention
What is the aim of the appliance design
Description of what the appliance is trying to achieve
What are the 4 advantages of heat cure over self cure PMMA
Heat cure has a better working time
Heat cure is stronger
Heat cure has less residual monomer - self cue has quite a bit
Heat cure is more dimensionally stable. There is more shrinkage in self cure
There are many more advantages to heat cure over self cure PMMA , so why is self cure PMMA used and why is it adequate
Heat cure PMMA has to go though the lost wax technique and this an take up to 15 hours.
Whereas self cure PMMA takes 15 mins.
Self cure PMMA is adequate are these appliances are disposable and aren’t subjected to large forces the same way as dentures are.
How does the baseplate in a URA help with anchorage
Baseplate spreads the load over the other teeth so this helps with anchorage so the hinge movement doesn’t happen.
How many mm of tooth movement would we expect a month from URA
1mm
