PFMs Flashcards
noble metal copings must be ___ mm
0.3-0.5 mm
base metal copings must be ___ mm
0.2 mm
opaquing porcelain thickness
0.2-0.3 mm
porcelain thickness
0.5-2.0 mm
metal alloys have a high ___ ___ and ___ ___
elastic modulus
yield strength
high noble metal criteria
> /= 60%
at least 40% gold
more gold = ___ alloy
softer
gold-platinum-palladium contains up to ___ gold
88%
___ causes greening
silver
our PFM metal alloy
gold-palladium
(44-55% gold, 35-45% palladium)
sag
resistance to deformation @ high temperatures
high elastic modulus and yield strength
noble metal criteria
> /= 25% noble metals
(not having to be gold)
PFMs are layered with ___ ___
feldspathic porcelain
___ ___ is a particle-filled glass ceramic
lithium disilicate
polycrystalline ceramic = ___
zirconia
feldspar = ___ ___
glass matrix
strong oxide that increases strength
increases viscocity
alumina
alkali fluxes are ___ ___
glass modifiers
includes opacifiers and colorants
increases coefficient of thermal expansion
glass modifiers
brings ceramic coefficient of thermal expansion closer to metal coefficient of thermal expansion
leucite
compressive forces = ___ ___
thermal contraction
___ increase the wettability of the metal
microabrasions
___ ___ forms oxide bond with oxide layer of metal coping
opaque porcelain
the more ___, the lower the melting temperature
gold
ceramic ___ is greater than metal ___
CTE (x2)
contacts are made in ___
porcelain
finish lines must be ___ away from occlusal contacts
1.5 mm
porcelain shoulder requirements (2)
high fusing aluminous porcelain
2 additional firings
metal copings are often overcontoured and thick at the gingival area
disappearing margin
bond failure = ___ fracture
cohesive
(due to occlusion)
de-lamination = ___ fracture
adhesive
(due to incorrect oxidation)
1 reason for porcelain fracture
poor design
2 reason for porcelain fracture
occlusion
PFM strength comes from what?
bond between metal and ceramic
