Alloys for Cast Metal Restorations Flashcards
what is compressive strength
stress required to cause fracture
what is elastic modulus
stress/strain ratio
what is brittleness/ductility
dimensional change experienced before fracture
what is hardness
resistance of surface to indentation or abrasion
what information does the stress strain curve give
rigidity, ductility, and strength
what are the characteristics of porcelain
rigid
hard
strong - high compressive, low tensile
forms surface defects
leads to fracture at low stress
brittle
what does bonding of metal oxide to porcelain help to eliminate
defects/cracks on porcelain surface
what do alloys do for porcelain
acts as a support and limits the strain that porcelain experiences
what are the required property of an alloy to bond to porcelain
form good bond to porcelain
thermal expansion co-efficient similar
avoid discolouration of porcelain
bond strength
hardness
elastic modulus - high to prevent fracture
melting point higher than fusion temperature of porcelain
what is creep
gradual increase in STRAIN experienced under prolonged application of stress
what metal causes green discolouration
silver in silver palladium
copper
what is the problem with high gold alloys
melting range may be too low
youngs modulus too low
what are the advantages of low gold alloys
increased melting temperature
slightly better mechanical properties
what are the advantages of silver palladium alloys
high melting point
what are the advantages of nickel chromium alloys
high melting point
high youngs modulus
high casting shrinkage
low-ish bond strength
