dental mat cont
Card Set Information
dental mat cont
ch 9 dental mat
if amalgam contracts too much, it will open gaps at the _______
if amalgam expands excessively, it can put pressure on the cusps, cause _____ when biting or may result in cusp _____
t/f does the composition of alloy particles, ratio of mercury to alloy powder by weight, and salivary/moisture contamination contribute to dimensional changes?
what is the strongest directly placed restorative material?
amalgam is strong in compression, but weak in ______ and _____
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
what kind of particles create a greater surface area which the mercury can react?
____-copper alloys are mostly admix or spherical types
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:
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?
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
when amalgam is condensed, which "steps" should be made with the condenser to avoid voids in the amalgam?
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?
what is complete after 24 hours of a placed amalgam restoration?
which amalgam can be lightly polished after initial set?
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?
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
t/f high copper amalgams have more microleakage later on, which can lead to sensitivity
false! more microleakage INITIALLY