Orthodontic Materials / Physical Principles 8% 5Q

Question 1

Equation for stress =

Answer 1

force / area

Question 2

Equation for strain =

Answer 2

deflection / unit strength

Question 3

Equation for strength =

Answer 3

stiffness x range

Question 4

Equation for springiness =

Answer 4

1 / stiffness

Question 5

The stress strain curve shows the __________ behavior of a material

Answer 5

elastic

Question 6

the point at which any permanent deformation is first observed:

Answer 6

elastic limit / proportional limit

Question 7

Deformation of 0.1% is observed

Answer 7

yield strength

Question 8

Maximum Load / Ultimate Tensile Strength

Answer 8

maximum load the wire can sustain after some permanent deformation

Question 9

area of the curve up to the proportional limit. (Energy Storage)

Answer 9

Resilience

Question 10

amount of permanent bending a wire can stand before breaking

Answer 10

Formability

Question 11

distance a wire will bend elastically before permanent deformation

Answer 11

Range

Question 12

Ideal AW properties:

( High / Low ) strength

( High / Low ) Stiffness

( High / Low ) Range

( High / Low ) Formability

Answer 12

High strength

Low Stiffness

High Range

High Formability

Question 13

In terms of surface roughness which AW materials have the most asperities

Answer 13

NiTi > TMA > SS

Question 14

Which AWs have the most friction to sliding mechanics

Answer 14

TMA > NiTi > SS

Question 15

Frictionless mechanics with closing loops is done with which material?

Answer 15

TMA

Question 16

An increase in wire length x 2 has what effect on strength?

Answer 16

decrease x 2

1/X

Question 17

An increase in wire length x 2 has what effect on stiffness?

Answer 17

decrease x 8

1/X³

Question 18

An increase in wire length x 2 has what effect on springiness?

Answer 18

increase x 8

X³

Question 19

An increase in wire length x 2 has what effect on range?

Answer 19

increase x 4

X²

Question 20

An increase in wire diameter x 2 has what effect on range?

Answer 20

decrease x 2

1/X

Question 21

An increase in wire diameter x 2 has what effect on strength?

Answer 21

increase x 8

X³

Question 22

An increase in wire diameter x 2 has what effect on stiffness?

Answer 22

increase x 16

X⁴

Question 23

An increase in wire diameter x 2 has what effect on springiness?

Answer 23

decrease x 16

1/X⁴

Question 24

what is another name for the material Elgiloy

Answer 24

cobalt chromium

Question 25

Elgiloy can be softer and thus more:

Answer 25

formable

Question 26

Elgiloy can be heat treated, which would increase its strength to that of _________________ by increasing the UTS and resilience

Answer 26

stainless steel

Question 27

Nitinol has no phase change, is not superplastic and is also known as

Answer 27

M-NiTi

Question 28

NiTi is superplastic, meaning it has shape \_\_\_\_\_\_\_\_\_\_\_; it ( does / does not ) have the ability to change molecular structure

Answer 28

memory does

Question 29

Name the 2 ways to get a phase change in NiTi

Answer 29

**Pseudoelasticity/Superelasticity** **Thermoelasticity**

Question 30

Due to the thermoelasticity of NiTi, heat induces change from the ___ → ___ state while cold induces change from the ___ → ___ state.

Answer 30

heat: M → A cold: A → M

Question 31

Due to the superelasticity of NiTi, stress induced martensite (SIM) induces change from the ___ → ___ state while deactivation induces change from the ___ → ___ state.

Answer 31

SIM A → M Deactivation M → A

Question 32

NiTi is formed at high temps (state ___ ), when cooled (state ___ ) can then be plastically deformed. This means its original shape restored when ( cooled / heated )

Answer 32

A M heated

Question 33

* ( A / M ) NiTi is the stabilized form of NiTi with **no** application of phase transition effects

Answer 33

M (Martensitic)

Question 34

Flexibility: A-NTi ___ M-NiTi

Answer 34

A \< M

Question 35

Stiffness: A-NTi ___ M-NiTi

Answer 35

A \> M

Question 36

**what** is manifested by very large reversible strains and a non-elastic stress-strain or force-deflection curve

Answer 36

superelasticity

Question 37

In A-NiTi wires, the initial archwire should exert (more / less / same ) force whether it were deflected a relatively small or large distance

Answer 37

the same

Question 38

The unique force-deflection curve for A-NiTi wire occurs because of a ______________________ in grain structure from austenite to martensite in response to an applied force (not to a temperature change).

Answer 38

phase transition

Question 39

Beta NiTi is aka

Answer 39

Copper NiTi

Question 40

which material guarantees Temperature Transition Range (TTR) so you know exactly at what temperature the phase transition occurs?

Answer 40

Beta NiTi

Question 41

the ideal temperature for the phase transition of Beta NiTi

Answer 41

35**°** C

Question 42

Bending moment vs deflection plot for 16 mil orthodontic wires Note that after an initial force is reached, \_\_\_-NiTi has a considerably flatter load-deflection curve and greater springback than \_\_\_-NiTi, which has greater springback than steel

Answer 42

A M

Question 43

The concept that the unloading force is different (less) than the loading force. After untyting, retying increases the amount of force delivered.

Answer 43

Hystersis

Question 44

Small-round NiTi wires should be \_\_\_-NiTi, while larger rectangular ones often perform better if made from \_\_\_-NiTi. M-NiTi which remains useful, primarily in the later stages of treatment when flexible but larger and somewhat stiffer wires are needed

Answer 44

A M

Question 45

TMA is aka

Answer 45

Titanium Molybdenum

Question 46

Compared to Nitonol, TMAis, ( smoother / rougher ), ( can / cannot ) be welded, has good formability

Answer 46

smoother can

Question 47

What AW material offers remarkable strength and springiness, making it an excellent choice for auxiliary springs and for intermediate and finishing wires

Answer 47

TMA