Mechanical Properties of Orthodontic Archwires

Question 1

Most orthodontic archwires are what kind of materials

Answer 1

elastic

Question 2

What two phases of archwires are important

Answer 2

elastic and plastic phases

Question 3

What does the force/deflection curve represent

Answer 3

how much the wire will bend before breaking

Question 4

force/deflection curve changes with what

Answer 4

archwire diameters and materials

Question 5

This is force/area (F/A)

units; newton/square mm, pascal, etc.

Answer 5

stress (σ)

Question 6

This is the change in length/original length (ΔL/L)

units; none; described as a percentage

Answer 6

strain (ε)

Question 7

What is the elastic modulus (E)

Answer 7

stress/strain E (σ/ε)

units; newton/square mm, pascal

Question 8

What is the difference between the stress/strain curve and a F/D curve

Answer 8

stress/strain curve removes the geometric factor

Question 9

Which curve, the S/S or F/D includes the includes the geometry of the specimen in the calculation

Answer 9

F/D

Question 10

The stiffness measured by an F/D curve is called what

Answer 10

extrinsic stiffness

Question 11

The stiffness measured by an S/S curve is called what

Answer 11

intrinsic stiffness

Question 12

Which curve will vary depending upon the items size/diameter. For example, if examining the same material with two different diameters, the graph will change

Answer 12

F/D

S/S curve is the same regardless of size

Question 13

How many different curves will one homogenous material of different dimensions have

Answer 13

one S/S curve

many F/D curves

Question 14

This is the slope of the linear portion of the F/D curve or elastic modulus in the S/S curve

Answer 14

stiffness

Question 15

This is 1/stiffness

Answer 15

springiness

Question 16

This is the ability to return to the original shape; clinical useful can be beyond the elastic limit

Answer 16

springback

Question 17

This is the distance a wire can be bent elastically before permanent deformation

Answer 17

range

Question 18

This is the stiffness x range

Answer 18

strength

Question 19

This is the area under the S/S curve out to the proportional limit

Answer 19

resilience

Question 20

This is the amount of permanent deformation a wire can withstand before failure

Answer 20

formability

Question 21

This property of ideal archwires is to produce desired force magnitude without excessively deflecting the AW

Answer 21

high strength

Question 22

This property of ideal archwires is to produce a relatively constant force

Answer 22

low stiffness

Question 23

This property of ideal arch wires is to deflect the arch wire to a great extent without causing permanent deformation

Answer 23

high range

Question 24

This is not a direct mechanical property of ideal archwires

Answer 24

capability of taking weld/solder

Question 25

What are the two arch wire variables affecting mechanical property

Answer 25

size and shape

Question 26

Shape is more important for which property

Answer 26

shear (torsion) force, but not for bending; the diameter is important for bending

Question 27

Tying an arch wire tightly to the brackets increases this, but decreases these two properties

Answer 27

increases strength | decreases springiness and range

Question 28

Adding loops (increase in length) to an arch wire increases what

Answer 28

its range and springiness

Question 29

Which wire has the highest strength, stainless steel, TMA, M-NiTi

Answer 29

Stainless Steel > TMA and M-NiTi

Question 30

Which wire has the highest stiffness, stainless steel, TMA, M-NiTi

Answer 30

Stainess Steel > TMA > M-NiTi

Question 31

Which wire has the highest range, stainless steel, TMA, M-NiTi

Answer 31

M-NiTi >>> TMA > Stainless Steel

Question 32

This wire has low stiffness, good strength, high range, but very poor formability

Answer 32

M-NiTi

Question 33

This is not considered a typical elastic material; a wide range of constant force is produced during austenitic ⇔ martensitic phase transition

Answer 33

Superelastic NiTi (A-NiTi)

Question 34

Which arch wire is chosen for initial alignment

Answer 34

small size NiTi

Question 35

Which arch wire is chosen for the leveling phase

Answer 35

relatively large size TMA or stainless steel

Question 36

What arch wire is chosen for the torquing phase

Answer 36

large size rectangular stainless steel or TMA

Question 37

What arch wire is chosen for the finishing phase

Answer 37

stainless steel or TMA, size can vary depending on the purpose

Question 38

Loops are helices are used in arch wires primarily to A. align teeth B. increase force of the wires C. increase flexibility of the wires D. hold soft tissues away from orthodontic brackets

Answer 38

C. increase flexibility of the wires