Lecture 5- mechanical properties of orthodontic archwires Flashcards
Force/Deflection (F/D) curve changes with archwire … and …
diameters and materials
What does the Stress/Strain (S/S) curve account for that Force/Deflection (F/D) does not?
area
Stress= …
Force/Area
F/D …. include geometry of specimen in the calculation so the stiffness measured by an F/D curve is called…
DOES NOT
Extrinsic stiffness
S/S curve … the geometry out so the stiffness measured by an S/S curve is called…
normalizes
Intrinsic stiffness
… is the slope of linear portion of the F/D curve or elastic modulous in S/S curve
Stiffness
… is the distance a wire can be bent elastically before permanent deformation
Range
Strength =
Stiffness x Range
… is the area under the S/S curve out to the proportional limit
Resilience
… is the amount of permanent deformation of a wire can withstand before failure
Formability
Ideal orthodontic archwires will have
... strength ... stiffness ... range ... formability capability of taking ...
HIGH strength
LOW stiffness
HIGH range
HIGH formability
Capability of taking weld/solder
If you increase the diameter of a wire then you…
.. strength
… springiness
… range
increase strength
decrease springiness
decrease range
If you increase length of a wire then you…
… strength
… springiness
… range
decrease strength
increase springiness
increase range
adding loops to an archwire increases … and …
range
springiness
NiTi wires have... ... stiffness .... strength ... range .... formability
LOW stiffness
GOOD strength
HIGH range
POOR formability
Loops and helices are used in arch wires primarily to…. (4)
align teeth
increase force of the wires
increase flexibility of the wires
hold soft tissues away from brackets
Center of resistance is NOT at the center of gravity, rather it is the approximate midpoint of … (or halfway between the … and …)
embedded portion of root
halfway btn apex and alveolar crest
The center of resistance of a tooth varies with … and …
alveolar bone height
and
root length
T/F the center of resistance varies with an orthodontic force
False
If there is alveolar bone loss, center of resistance moves…
apically
If there is root resorption, center of resorption moves…
coronally
If the line of action of a force does NOT pass through the center of resistance, the force will produce some … of the tooth. This potential for… is measured as a ….
rotation
rotation
moment
A … is two forces that are equal magnitude, parallel and mom-collinear and opposite direction
couple
A couple produces…
a pure rotation
… produces bodily tooth movement which means all points on an object move in the same direction at the same rate
Translation
To produce translation, the line of action of a single force needs to pass through
the center of resistance
The center of rotation for translation is…
infinity
The center of rotation for uncontrolled tipping is…
slightly apical to the center of resistance (one third root length from the apex)
The center of rotation for controlled tipping is the…
apex
The center of rotatin for root movement (torque) is the …
incisal edge
The center of rotation for pure rotation is …
the center of resistance
Herbst and MARA are … appliances for growth modification to correct…
fixed
class 2
Forsus is a … appliance to correct …. occlusion but only correct dentally
fixed
class 2
Are fixed or removable more commonly used?
fixed
