Dental Amalgam Flashcards
(46 cards)
what is dental amalgam a product of
amalgamation
what is amalgamation
alloy + mercury react to form silvery hard grey mass
what makes amalgam unappealing
poor aesthetic
why is dental amalgam use declining
development of viable alternatives
safety and enviro pollution
what are the two compositions of amalagam
conventional
high copper
what is x ray refraction used for
to work out crystal structure a scatters rays to work out distance between etc
what is most common composition of amalagam used today
conventional superseded by high cooper
what si the compositor of conventional
65% Ag (min) 29% Sn (max) 6% Cu (max) 2% Zn (max) 3% Hg (max)
what si the composition of high copper composition
40% Ag (min) 32% Sn (max) 30% Cu (max) 2% Zn (max) 3% Hg (max)
how do variations of alloy morphology come about
lathe cut
spherical
what is a lathe
used to cut off bits of alloy into finer or coarse - changing how much in contact with mercury
what is better about the high copper comp to the conventional
reaction changes gamma 2 slim and replaced
better corrosion resist and less susceptible to creep
what is the effector of a greater amount of Ag(3)Sn
undergoes setting reaction
what effect does copper have on amalgam
strengthening effect
what does Zn act as in alloy production
scavenger which can complex with oxygen - leading to problems
what may be eliminated in an inert atmosphere
Zn
what is mixing termed as
trituration
what are the dimensional changes take pace
30 mins - sell shrink
30-60 mins - expansion
why at 30 mins is there a small shrinkage
Hg diffuses into alloy
why at 30-60 mins expansion
due to crystallation
what is the overall effect of size changes
net expansion/contraction
(+/-) 0.1%
what does it mean hangs is given off
poor moisture control and Zn containing alloy - gas given off = greater expansion
what is the tie of placement to function
15-20 mins
when is final strength of malaga reached
24 hours
