3 - Cobalt Chrome & Stainless Steel Flashcards Preview

DENTAL MATERIALS > 3 - Cobalt Chrome & Stainless Steel > Flashcards

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

co/cr alloys: dental uses?

- connectors for partial dentures
- clasps: retention
- palates in complete denture (sometimes)

2

co/cr: composition?

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

3

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

- alloy becomes too brittle
- max. chromium used to improve corrosion resistance

4

molybdenum: what does it contribute to? x2

- reduce grain size
- improve hardness

5

carbon: what does it contribute to? x3
what happens if there is too much carbon?

- hardness
- strength
- ductility

-too much carbon will make the alloy brittle

6

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

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

7

advantages of co/cr? x5

- 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

problems with co/cr?

- difficult to polish
- cannot be burnished
- clasp can fracture

9

stainless steel:
alloy of?
resistant to?

- iron
- resistant to corrosion

10

dental uses of stainless steel?

- dental instruments
- endodontic files
- hand pieces
- partial denture clasps
- mesh for orthodontics

11

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?

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

12

types of stainless steel and examples of each?

- austenitic: ortho wires, denture clasps
- ferritic: non-cutting instruments
- martenistic: cutting instruments, burs etc

13

amount of chromium (Cr), nickel (Ni) and carbon (C) in
- ferritic s/s?
- austenitic s/s?
- martenistic s/s?

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