Stainless Steel

Question 1

What is the composition of stainless steel?

Answer 1

Iron 72%
Carbon
Chromium
Nickel
Titanium

Question 2

What is meant by an allotropic material?

Answer 2

A material that undergoes 2 solid state phase changes with temperature

Question 3

What is an alloy?

Answer 3

Two metals that form a common lattice structure (solid solution).
Are soluble in one another.

Question 4

What is the purpose of nickel in stainless steel?

Answer 4

Improves UTS & corrosion resistance

Lowers austenitic to marten site transition temperature

Question 5

What are the two types of stainless steel?

Answer 5

Austenitic

Martensitic

Question 6

What are the requirements for wires used in dentistry?

Answer 6

High springiness (EL/YM)
Stiffness (YM)
High ductility (bending without fracture)
Easily joined without impairing properties (soldered, weldered)
Corrosion resistance

Question 7

What is weld decay?

Answer 7

When chromium carbides in SS precipitate at grain boundaries.
Occurs between 500-900 degrees C

Question 8

What problems does weld decay cause?

Answer 8

Alloy becomes brittle

More susceptible to corrosion

Question 9

What are wrought alloys?

Answer 9

Alloys that are manipulated/shaped by cold working

Question 10

What are the uses of SS in dentistry?

Answer 10

Orthodontic wires

Partial denture clasps

Question 11

What are the advantages of a SS denture base?

Answer 11

Thin (0.11mm) & light
Fracture & corrosion resistant
High polish obtainable
High thermal conductivity
High impact strength
High abrasion resistance

Question 12

What are the disadvantages of SS as a denture base?

Answer 12

Possible dimensional inaccuracy
Elastic recovery of steel - inaccuracy
Damage of die under hydraulic pressure
Loss of fine detail during the many stages
Difficult to ensure uniform thickness
Uneven pressure on die & counter die -> wrinkling of steel