what is the most widely used material in restorative dentistry historically and currently?
amalgam
amalgams _________ _______ and _________ strength makes it superior to composite resin
wear resistance
compressive strength
what alloy (mix of metals) is in amalgam? (5)
mercury
copper
zinc
tin
silver (most of the alloy)
t/f mercury is a liquid metal
true
silver alloy becomes a dental amalgam once it goes through the _________ reaction with mercury
amalgamation
______ is susceptible to corrosion
silver
what is added to silver to minimize corrosion?
copper (gamma phase 2 eliminated)
what is durable, similar in compressive strength to enamel, and relatively inexpensive?
amalgam
what are 6 undesirable features of amalgam?
unattractive
high thermal conductivity
dimensionally unstable (creep)
delayed expansion if contaminated with water
requires tooth support
ftr by excessive occlusion
t/f polishing can reduce the rate of corrosion (less surface area)
true
to remove surface tarnish, stains, flash, and roughness, a _____ agent and then a ______ agent should be used when polishing
course
fine
bur = ______
pumice = _______
tin oxide =________
course
fine
finest
what is a way to avoid overhangs?
use properly placed band and wedge
how is an overhang detected?
with an explorer
over how many years has dental amalgam been used?
over 170 years!
is amalgam a direct or indirect placement?
DIRECT
what is tin used for?
to control the rate of set of the amalgam
t/f copper reacts with the tin to keep it from being available for the gamma 2 phase
true
do high copper amalgams have a gamma 2 phase?
NO! they are far too superior for that
the rougher or smoother the surface, is more likely to tarnish?
ROUGHER
what can be added to the alloy to reduce tarnish? what can be done to the restoration after it is placed to reduce tarnish?
palladium
polishing
when is it BEST to polish amalgams?
after it has set for 24 hours (although some do it after 20 minutes of placement)
if an amalgam is polished right after placement, it will not have a high _____
shine
do high or low copper amalgams have a smoother surface after carving?
HIGH (they tarnish less too)
excessive heat during polishing can lead to a release of ____ from the silver mercury phase that results in a mercury ____ surface that will corrode more readily and deteriorate at the ______
mercury
rich
margins
a chemical rxn btw the amalgam and substances in saliva or food, resulting in oxidation of the amalgam is called ________
corrosion
an electrical current generated between metals (similar to a battery) is called ________
galvanism
t/f corrosion can occur when two dissimilar metals interact in a solution (saliva) containing electrolytes
true
what is the result of a galvanic rxn?
oxidation of one of the metals
what three things can galvanism cause over time with amalgam?
weaken amalgam
stain the surrounding tooth as the corrosion enters the dentinal tubules
deteriorate margins
high copper vs low copper, high copper has: (3)
less marginal deterioration
less corrosion
higher strength
t/f a galvanic rxn may occur when a newly placed amalgam comes in contact with a gold crown
true
what does a pt experience with galvanic rxn?
mild electrical shock
metallic taste
t/f a pt will know when corrosion occurs with their amalgam restorations
false
galvanism may persist until the amalgam ________ its setting time, oxides build up on one of the metals, or until the opposing/adjacent restoration is replaced with a similar metal or _______
