ortho wire

Question 1

Determine how much stress a material can withstand before it starts permanent deformation.

Answer 1

yield strength

Question 2

Flexibility or stiffness
Basic property of the material, gives its fundamental characteristics of flexibility.

Answer 2

Modulus of Elasticity

Question 3

First permanent deformation
Point at which material starts to deform permanently.

Answer 3

Elastic Proportional Limit

Question 4

Maximum load
Point of clinical loading
SPRINGBACK – maximum load a wire can sustain and still be clinically useful.

Answer 4

Ultimate Tensile Strength

Question 5

Wire breaks
BRITTLE – (materials that do not strain much beyond the elastic limit
DUCTILE – (those that deform a great deal before breakage)

Answer 5

Fracture / Failure Point

Question 6

Maximum force that can be obtained from a wire (S=SxR)

Answer 6

STRENGTH

Question 7

Amount of force produced per activation

Answer 7

STIFFNESS

Question 8

• Ability to apply lower force.
• Greater ease and accuracy in applying force.
• A more constant force over time as the wire deactivates.

Answer 8

LOW STIFFNESS SLOPE

Question 9

• Distance wire will bend elastically before permanent (plastic) deformation occurs.
• Clinically measured to the ultimate tensile strength – spring back / working range

Answer 9

RANGE

Question 10

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

Answer 10

Pseudoelastic effect

Question 11

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 11

Thermoelastic effect

Question 12

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 12

Martensitic stabilized alloy (e.g. Unitek’s Original Nitinol)

Question 13

• “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 13

Austenitic active alloy

Question 14

The range of wire is 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

• The shape-memory effect, exhibited by the more recent nickel titanium wires, has revolutionized the selection of wires for appropriate tooth movement.
• The wires manufactured for orthodontic purposes are composed of an alloy of nearly equal parts of nickel and titanium.
• The shape memory effect is brought about by a change in the internal crystal formation from the martensitic phase with a hexagonal crystal structure to or from the austenitic phase with a cuboid crystal structure.
• The shape in crystalline structure can be brought about by either:
• Stress, as in the pseudoelastic effect in the austenitic active alloy.
• Heat, as in the thermoelastic effect in the Martensitic active alloy where the transition temperature is between room and mouth temperatures.

Answer 15

Shape Memory Effect

Question 16

The strength of a wire is important because it determines the maximum force it can deliver.
The above three properties are related by the formula:
Strength = Stiffness × Range

Answer 16

Strength of the Wire

Question 17

This is the amount of permanent deformation a wire can withstand before it breaks.

Answer 17

Formability

Question 18

Stainless steel can be soldered and welded but NiTi cannot.
Miura recently reported a method of soldering nickel titanium wires. TMA is weldable as described by Burrstone.

Answer 18

Solubility and Weldability

Question 19

The laboratory understanding of friction is not relevant to the clinical situation because every time the patient bites together, the tooth is liable to move a small distance in all three planes of space.
More important is the concept that the two components, bracket and wire, may damage each other as they moved across their surfaces.

Answer 19

Friction

Question 20

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 20

Environmental Stability

Question 21

Gold alloy were used in the manufacture of orthodontic arch wire.
It was intensively used before 1940. Gold and gold alloy arch wire exhibit excellent formability, environmental stability and biocompatibility.
The main drawbacks of these arch wires include high-cost, low-spring back and low-yield.

Answer 21

GOLD

Question 22

Stainless steel was introduced by Wilkinson in 1929. Stainless steel arch wire exhibits adequate strength, high resilience, formability, high stiffness, biocompatibility and are economical.
BASIC COMPONENTS
18% Cr, 8% Ni, 0.2% C, 71% Fe
Cold working (hardens steel)
Annealing (softens steel)
Fully annealed (makes the steel dead soft)
The drawback of these arch wires includes high modulus of elasticity; more frequent activations are required to maintain the same force level.

Answer 22

STAINLESS STEEL

Question 23

Similar to SS
Secret formula of Wilcock in Australia
Key wire to Begg Technique
Excellent working wire
20% stiffer than SS (more stiff – more brittle

Answer 23

AUSTRALIAN WIRE

Question 24

Nickel titanium alloy, also known by nitinol (Nickel Titanium Naval Ordinance Laboratory) was invented by William R Buchler at Naval Ordinance Laboratory.
The main advantage of this alloy over others is the high elasticity and shape-back memory.
The drawback of these arch wires is that they cannot be welded or soldered and cannot receive bends or loops or helices.

Answer 24

NICKEL TITANIUM ALLOYS

Question 25

Andreasen 1978: NITINOl (Nickel Titanium Naval Ordinance Lab)
Poor formability – can’t be bent into loops / stops

Answer 25

First Generation Ni-Ti

Question 26

Shape memory (wire remembers its original shape)
Super elasticity (force stays fairly constant during wire deformation)

Answer 26

Second Generation Ni-Ti

Question 27

Variable temperature activates.
27°C colder state, constant activation, rapid tooth movement
35°C recommended temperature, milder activation, lower force
40°C intermittent activation, mild forces, high canines
Soft, pliable wire for earlier bracket engagement
Enhanced torque control for faster treatment.
Momentary forces applied to teeth early in treatment for reduced chair time

Answer 27

Temperature Activated Ni-Ti