if amalgam contracts too much, it will open gaps at the _______
margins
if amalgam expands excessively, it can put pressure on the cusps, cause _____ when biting or may result in cusp _____
pain
ftr
t/f does the composition of alloy particles, ratio of mercury to alloy powder by weight, and salivary/moisture contamination contribute to dimensional changes?
true
what is the strongest directly placed restorative material?
amalgam
amalgam is strong in compression, but weak in ______ and _____
tension
shear
t/f amalgam resists breaking, the less bulky it is
false! the more bulky
when do some high copper amalgams gain 80% of their strength? ______ hours
8
what kind of particles create a greater surface area which the mercury can react?
spherical
____-copper alloys are mostly admix or spherical types
high
in comparing spherical and admixed amalgam, which one feels soft?
spherical (it has little resistance to the condensation into the cavity)
if amalgam sets too quickly and has a crumbly appearance, it has been:
under-triturated
why would an under-triturated allow be weak?
the components wouldnt be totally mixed, leaving a higher level of unreacted mercury and alloy particles
why does an over-triturated alloy set too quickly?
heat is produced by prolonged mixing
is over-triturated too wet or too dry?
too wet
will an over-triturated alloy be stronger or weaker?
weaker, it forms too many rxn products (silver-mercury, copper-tin)
what does properly triturated alloy look like?
it has a satin
t/f improper mixing can adversely affect the longevity of the restoration
true
when amalgam is condensed, which "steps" should be made with the condenser to avoid voids in the amalgam?
overlapping steps
if amalgam is sitting out for a couple minutes after being triturated, why will it get weaker?
the crystals that are forming will be disrupted during condensation
what is the advantage of burnishing before carving?
it produces a much smoother and denser surface
what will happen if the amalgam restoration hardens and you are trying to carve it?
it can damage margins of the amalgam or cause ftr's
how long should a pt with a newly placed amalgam restoration avoid chewing?
8 hours!
what is complete after 24 hours of a placed amalgam restoration?
crystallization
which amalgam can be lightly polished after initial set?
spherical amalgam
what can happen to the mercury if the restoration is polished without water to cool it (it reaches over 140 degrees F)?
it can come to the surface
which polishing agents are used as polishers?
silux
slurry mix of fine pumice
abrasive-impregnated rubber points/cups
t/f the expansion and corrosion of low copper amalgam helps reduce microleakage at the tooth/amalgam interface
true!
t/f high copper amalgams have more microleakage later on, which can lead to sensitivity
