Stainless steel and wrought alloys Flashcards
wrought alloys
alloy that is manipulated/ shaped by cold working
cold working
work at a low temperature
process causes slip (dislocations move to grain boundaries creating stronger materials)
what is steel made of
iron and carbon
(less than 2% carbon)
solid solution
2 metals that form a common lattice
can be either substitutional (random or ordered)
Interstitial (different sizes)
what makes steel stainless
contains more than 12% chromium
why is nickel included in stainless steel
improves strength and aids chromium in corosion resistance
what are the 2 types of stainless steel and what are they used for
martensitic: dental instruments (used where hardness critical e.g knifes)
austenitic: dental instruments and equipment e.g wires (corrosion resistance more important than hardness)
material requirements of orthodontic wires
high ductility
corrosion resistant
easily joined to other components
(springiness and stiffness dependent on use)
why is cobalt chrome not used for dental wires
difficult to join to
weld decay and stainless steel
occurs to stainless steel at temps between 500 and 900 degrees celsius causes alloy to become brittle and more susceptible to corrosion
what are the pros and cons of using stainless steel as a denture base
pros: thin, light, fracture and corrosion resistant, polishable, withstands large impacts
cons: difficult to ensure uniform thickness, potential for innacuracies e.g due to many stages fine detail may be lost
18 - 8 stainless steel
austenitic stainless steel
used for ortho wires and springs and RPD clasps and rests
74% iron , 18% chromium, 8% nickel, 0.1% carbon
what type of metal/alloys may be used for partial dentures
CoCr, AgPd, type IV gold
what type of metal/ alloy may be used for porcelain fused cast metal restorations
low gold
high gold
CoCr
AgPd
what type of metal/alloy may be used to make wires
CoCr, NiTi, stainless steel
