3 - Cobalt Chrome & Stainless Steel Flashcards Preview

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Flashcards in 3 - Cobalt Chrome & Stainless Steel Deck (13)
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1
Q

co/cr alloys: dental uses?

A
  • connectors for partial dentures
  • clasps: retention
  • palates in complete denture (sometimes)
2
Q

co/cr: composition?

A

cobalt 55-65%
chromium 30%
molybdenum 4-5%
carbon (small amnt)

3
Q

co/cr: what happens when there is too much chromium in the composition?
max. amnt of chromium used to improve what?

A
  • alloy becomes too brittle

- max. chromium used to improve corrosion resistance

4
Q

molybdenum: what does it contribute to? x2

A
  • reduce grain size

- improve hardness

5
Q

carbon: what does it contribute to? x3

what happens if there is too much carbon?

A
  • hardness
  • strength
  • ductility

-too much carbon will make the alloy brittle

6
Q

properties of co/cr? will it be enough for crowns/bridges?

A
  • high casting temperature, 1500-1550deg
  • casting shrinkage ~2%
  • not accurate enough for crowns/bridges
7
Q

advantages of co/cr? x5

A
  • strong
  • can be made thinner than gold for partial denture
  • half density of gold
  • low corrosion
    high biocompatability, but some alloys contain nickel -> can produce allergic response
8
Q

problems with co/cr?

A
  • difficult to polish
  • cannot be burnished
  • clasp can fracture
9
Q

stainless steel:
alloy of?
resistant to?

A
  • iron

- resistant to corrosion

10
Q

dental uses of stainless steel?

A
  • dental instruments
  • endodontic files
  • hand pieces
  • partial denture clasps
  • mesh for orthodontics
11
Q

stainless steel:
huge variety of properties can be obtained by?
steel is an alloy of?
cast iron has how much carbon?
stainless steel - minimum of how many % chromium?
what is formed in exposed SS?

A
  • by small changes in composition
  • carbon (max 2%) and iron
  • greater than 2% carbon
  • 11% chromium
  • a layer of chromium oxide formed
12
Q

types of stainless steel and examples of each?

A
  • austenitic: ortho wires, denture clasps
  • ferritic: non-cutting instruments
  • martenistic: cutting instruments, burs etc
13
Q

amount of chromium (Cr), nickel (Ni) and carbon (C) in

  • ferritic s/s?
  • austenitic s/s?
  • martenistic s/s?
A

Ferritic: 11.5-27% Cr
0% Ni
0.2% C

Austenitic: 16-22% Cr
7-22% Ni
0.25% C

Martenistic
11-17% Cr
0.2-5% Ni
0.15-0.25% C