Stainless Steel Flashcards
1
Q
What are some uses of steel in dentistry?
A
- cutting instruments
- forceps
2
Q
what is the meaning of allotropic?
A
in a solid state it can exist in 2 crystalline forms
3
Q
What is an alloy?
A
TWO metals that form a COMMON LATTICE structure that are
- soluble in one another
- form a solid solution
4
Q
When does steel become stainless steel?
A
when Cr is >12%
5
Q
Why is stainless steel corrosion resistant?
A
chromium oxide layer
6
Q
What is the function of nickel in stainless steel?
A
- improves corrosion resistance
- improves fracture strength
7
Q
What are the types of stainless steel?
A
- martensitic
- austenitic
8
Q
What are the uses of austenitic stainless steel?
A
- dental equipment and instruments
- wires (ortho)
- sheet forms for denture bases
9
Q
What is cold working?
A
- work done on metal/allow at LOW TEMPERATURE (below recrystallisation temperature)
- causes SLIP (dislocations collect at grain boundaries)
- stronger/harder material
10
Q
what are the material science requirements of wires?
A
- high springiness
- stiffness
- high ductility
- easily joined without impairing properties (soldered/welded)
- corrosion resistant
11
Q
Why is NiTi rarely used as a wire material?
A
- poor springback ability
- difficulty with ductility/hard to join wires together
12
Q
What are the advantages of having a stainless steel denture base?
A
- thin (0.11mm.. acrylic is 1.52mm)
- light
- fracture resistant
- corrosion resistant
- high polish obtainable
- high thermal conductivity
- high abrasion resistance
13
Q
What are the disadvantages of a stainless steel denture base?
A
- possible dimensional inaccuracy
- elastic recovery of steel leads to inaccuracies
- damage of die under hydraulic pressure
- loss of fine detail due to many stages
- difficult to get uniform distance
