Other alloys used in restorative dentistry Flashcards
What does cobalt add to the co-cr?
increased elastic nodules
increased strength
increased hardness
What are the most common alloys for denture substructures?
co-chromium
nickel-chromium
pure titanium
titanium
What is chromium good at?
good passivator
What does a good passivator mean?
forms a surface oxide layer that conveys corrosion and tarnish resistance to the alloy
What is the max percent of chromium un the alloy? and why?
29% - makes alloy very difficult to cast as a brittle phase is formed
What is the role of molybdenum? (co-cr)
solid solution hardening effect
What is the role of carbon of carbon in co-cr?
added in very little quantities
carbides formed
increase the strength and hardness of the alloy
What is the downside to too much C added to co-cr?
increase brittleness
casting porosity and components of denture can fracture, e.g. clasp
What are the properties of co-cr?
thin layer on pallet
tensile strength i significantly higher than the high noble alloys
yield strength is in the region of 60% higher
final polished surface is highly scratch resistant and durable
low density of chrome-cobalt alloys means that castings are lighter and better tolerated
What are clinical notes for co-cr?
What are properties of titanium, why is it used?
able to passivate if scratched as the surface is normally covered by a thin oxide layer, if scratched a new oxide fil is formed
what do ytou do if tiutanium is scratched?
able to passivate if scratched as the surface is normally covered by a thin oxide layer, if scratched a new oxide fil is formed
What are alloys manufactured?
cast
wrought
swaged
what temp does co-cr require to be cast?
13-1400 dc
need induction casting
What temp is wrought allows altered?
cold state (cold working)
When would you use wrought alloys?
Does swaging require heat?
no
cold worked
How do you mould the swaging allow?
explosion forming: force applied to the alloy controlled
hydraulic forming: sudden hydraulically applied pressure
what metal is often swaged?
stainless steel
Why is stainless steel advantageous?
lightweight
