Fixed Appliance Seminar Flashcards
Orthodontic force required to move teth?
50 to 70 grams
Rotation extrusion 50 too 100 gms
Intrusion 15 to 25 grams
What is biomechanics?
The control of orthodontic force.
To enable an adde
How to generate these forces?
Right kind of wire for springs
Right size of wire
Vary. Type and length of springs
What kind of wires and springs are there?
Stainless steel replaced precious metals around mid 50s
Gold requires larger bars to have the same amount of strength
Steel is inherently stronger and stiffer than gold meaning a smaller and meater kind of appliance
Chromium cobalt - eygloy, has properties very similar to stainless steel but easier to form than stainless steel
Nitinol - nickel titanium alloy
Titianium molybdenum alloy
Titanium alloys more similar to gold than steel
What are the edsential differences between these materials?
Using the force dflection curve
Stainless steel, almost straight and then plateaus out. Good for maintaining arch shape. After initial with niti, ss can be used to create arch form.
NiTi, almost flat deflection curve over considerable distance and will spring back into initial shape. Good for initial wire (alignment phase) as it can be deflected all the way and applies light forces for a long period of time (can review less often). Easier to put in and maintain. Can be used to attach impacted canines during open reduction. Howeve, they dont maintain the arch shape of the patient.
TMA - used as an intermediate wire or finishing stage but has the disadvantage of high flexion. Properties btwn ss and niti.
Eygloy has a practicality disadvantage of having to cook it to get ss like strength but easy to manipulate before.
What kind of material is required?
You want a light force without considerable force blding up over time. Niti is better than ss at this.
How does the size of wire affect the force defletion curve?
(20/14) to the fourth power = 4.2 (in mils)
As a wire gets thinnere it loses strength but gains elasticity and springiness
What is strenght?
Resistance to permanent deformation.
What is stiffness?
Reprsentedd by linear portion of curve.
What is rnage?
The distance of elastic deformation.
What kind of beams are us for orthodontic purposes?
Cantilever beam
- spring support on one end. Has considerable length.
- length influences springiness. The longer the beam, the springier.
Supportive beam
Tends to be very short, hence the wire needs to be thin or too muh force will be used
How to choose size of wire?
1) select cost effective material
Most of the time the stainless steel material will be used
2) use smallest size that gives adequate strength
3) increase the length of span to obtain more springiness if necessary (loops or circles of wire)
How can inches be converted to mm?
0.22 is about 0.5mm
How to sequence wires?
Basicallly, what the patient needs at the time and what is trying to be achived.
Normally 2-3 wires should be the average amount of wires to be used throuout the whole case.
Normally niti for initial arch shape and individual tooth movement later on using ss.
What is the advantage of using tip edge brackets?
Minimisation of deflection of arch wire
