MF BIOMECHANICS Flashcards
Which properties are ideal for alignment?
Low load deflection rate (NiTi)
Which properties are ideal for leveling?
High load deflection rate (SS)
Which wire has low modulus of elasticity?
NiTi (more flexible)
Which wire to use for nickel sensitivity?
TMA
What is the composition and properties of SS?
- 18-8 (18% chromium and 8% nickel)
- HIGH modulus of elasticity
________ is defined as the distance that the wire will bend elastically before permanent deformation.
Range
(If deflected past yield point, will not return to original shape)
Still clinically useful until point of arbitrary clinical loading (no hope of going back to original shape); Will work until failure point
Spring back
Which wire has more friction?
TMA
Which wire has more asparities?
NiTi
T/F: properties of SS, TMA, and martensitic NiTI?
- SS has higher strength than TMA
- TMA has a higher strength and stiffness than martensitic NiTI
- SS has a higher stiffness than TMA
- TMA has a wider range than SS
- Martensitic NiTi has a longer range than TMA
All true
What is the equation for strength?
Stiffness x range
What happens to the ability of a rectangular archwire to deflect, if the size is doubled? Strength if diameter is doubled?
- If you double the size of an archwire, the deflection is going to be 1/8.
- If you double the diameter of the wire, you will increase the strength by 8
How is the transformation from A-NiTi to M-NiTi induced?
Thermally induced (phase transformation)
Which NiTi has high stress, low temp (flexible outside the mouth)?
Martensitic
Which NiTi is low stress, high temp (in mouth, restores original shape), good range and constant force, initial wire?
Austentic
What is the effect of 1st, 2nd, and 3rd order bends?
- 1st: in/out (correcting rotations)
- 2nd: up/down (correcting marginal ridges)
- 3rd: torque (correcting marginal ridges)
Does bone increase with intrusion?
No
Where is the center of rotation in uncontrolled tipping?
1/3 from the apex
What does not affect the location of center of resistance of a single tooth?
Magnitude of force application
Optimum force to retract a canine?
100-150g
What is hysteresis?
- Force delivered to the periodontal structures is lower than the force necessary to activate the wire.
- It is the difference in force of a wire between loading and unloading (loading is always higher).
- Low hysteresis is desired.
What is the affect on the wire with lingual crown torque on LR6?
Wire will be above the bracket on the opposite side
What happens to strength, springiness, and range if you double the Diameter? Length?
Diameter:
- Strength: 8
- Springiness: 1/16
- Range: 1/2
Length:
- Strength: 1/2
- Springiness: 8
- Range: 4
