Ortho

Question 1

Springback

Answer 1

Springback is useful because:
It is when the wire is deflected beyond the yield point to the loading point and no longer returns to its original shape BUT there is PARTIAL retention of shape.

If the wire is deflected beyond its yield point, it will NOT return to its original shape, but clinically useful springback will occur (i.e. partial retention of shape, flexibility) until the failure point is reached.

Springback ~ 1) **more resistance to deformation, 2) **more flexibility

• CuNiTi:
  1. Most resistant to permanent deformation
  2. Better springback than other NiTi
  3. More constant forces exerted over smaller activations

*SS has the least resistance to permanent deformation and the lowest springiness. Another wording: SS is most likely to have permanent deformation ~ SS has the best formability.

Springiness is the inverse of stiffness:
Springiness = 1/stiffness = reciprocal of stress/strain curve
Low modulus = low stiffness = high springiness
*Strength = springiness x range

2x diameter = 1/16 springiness, (8x force, 1/2 range)
2x length = 8x springiness, (1/2 force, 4x range)

TMA has the most friction in an SS bracket.
NiTi has the most asperities in an SS bracket

Question 2

Canine substitution

Answer 2

What is not important:

Color and size of the opposite canine

Question 3

Facial Plane
Facial Angle
Facial Axis
Y-Axis
Angle of Convexity

Answer 3

Facial Plane: N-Pog
Facial Angle: FH - NPog (increases with age, 90 normal, >90 protrusive chin)
Facial Axis: BaN - PtGn (stable with age, 90 normal, >90 protrusive chin, )
Y-Axis: FH - S - Gn (stable with age, 60 normal, >60 vertical and backward chin growth)
Angle of Convexity: N-A-Pog (decreases with age, 0 normal, + Class II, - Class III)

Question 4

Centric cusps

Answer 4

Cusps that contact central fossa or marginal ridges
Non-centric cusps in posterior crossbite: LUBL

Working interferences/functional cusps: LUBL
Balancing interferences/nonfunctional cusps: BULL

Question 5

Eligoy

Answer 5

Eligoy components:
Cobalt (40%)
Chromium (20%)
Iron (16%)
Nickel (15%)

Eligoy/CC (at normal temperature) has the same *stiffness as SS. Another wording: without the heat treatment, the stiffness stays the same as SS.

Heat treatment: increases Eligoy’s *strength, *formability, and *resilience.