Lec 2.2: Physical Properties of Wires

Question 1

Represents the internal stress/strain in the wire.

Answer 1

Elastic behavior

Question 2

Elastic behavior is produced by an external force deflecting the wire:
- ____ = internal load
- ____ = internal distortion

Answer 2

Stress
Strain

Question 3

Two effects under stiffness?

Answer 3

• Pseudoelastic effect
• Thermoelastic effect

Question 4

• When an austenitic wire is placed in the mouth and deformed by forcing it into the misaligned brackets.
• This transforms the austenitic alloy into a martensitic state, which as the teeth align, gradually reverses to the austenitic state.

Answer 4

Pseudoelastic effect

Question 5

Martensitic active alloys are stable at room temperature, but when raised to mouth temperature, the material changes into an austenitic state, which exhibits shape memory.

Answer 5

Thermoelastic effect

Question 6

Nitinol is introduced by?

Answer 6

Andreasen

Question 7

The alloy, introduced in 1970 by Andreasen, is stabilized by introducing a certain amount of work hardening during processing and does not show true memory shape properties.

Answer 7

Martensitic stable alloy (Original Nitinol)

Question 8

• “Active” means that it exhibits the shape memory, in this case of the pseudoelastic type, the shape memory effect being induced by stress distorting the arch wire in malaligned teeth.
• Examples of superelastic NiTi are Titanol from Forestadent and Nitinol SE from Unitek

Answer 8

Austenitic active alloy

Question 9

• This exhibits shape memory, but of the thermally activated variety.
• This alloy is stable at low temperatures but when is placed in the mouth and the temperature increased to mouth temperature, it exhibits the shape memory effect.
• Examples of thermally activated NiTi are Noe-Sentalloy from GAC and Nitinol XL from Unitek

Answer 9

Martensitic active alloy

Question 10

• No memory shape
• Stiff, tough, good formability
• Can form bends

Answer 10

Martensitic

Question 11

• This material has strength, toughness and ductility
• Memory shape

Answer 11

Austenitic

Question 12

• High temperature
• Low stress

Answer 12

Austenitic

Question 13

• Low temperature
• High stress

Answer 13

Martensitic

Question 14

The distance it will bend elastically before permanent deformation occurs. If the wire is deflected beyond its yield point, it will not return to its original shape.

Answer 14

Range of deflection / spring back

Question 15

Exhibited by the more recent nickel titanium wires, has revolutionized the selection of wires for appropriate tooth movement.

Answer 15

Shape memory effect

Question 16

The _____________ effect is brought about by a change in the internal crystal formation from the martensitic phase with a _________ crystal structure to or from the austenitic phase with a ________ crystal structure.

Answer 16

Shape memory
Hexagonal
Cuboid

Question 17

The shape in crystalline structure can be brought about by either:
a. _________, as in the ____________ effect in the austenitic active alloy.
b. _________, as in the ___________ effect in the Martensitic active alloy where the transition temperature is between room and mouth temperatures.

Answer 17

• Stress; pseudoelastic
• Heat; thermoelastic

Question 18

It determines the maximum force it can deliver.

Answer 18

Strength of the wire

Question 19

The amount of permanent deformation a wire can withstand before it breaks.

Answer 19

Formability

Question 20

_______ can be soldered and welded but _______ cannot.

_______ is weldable.

Answer 20

Stainless steel
NiTi
TMA

Question 21

Two components, bracket and wire, may damage each other as they moved across their surfaces.

Answer 21

Friction

Question 22

Any material used for the construction of the wire must be stable in the oral environment. This has been one of the limitations of the esthetics.

Answer 22

Environmental stability