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?
