dental materials ch 9
Card Set Information
dental materials ch 9
ch 9 dental materials
what is the most widely used material in restorative dentistry historically and currently?
amalgams _________ _______ and _________ strength makes it superior to composite resin
what alloy (mix of metals) is in amalgam? (5)
silver (most of the alloy)
t/f mercury is a liquid metal
silver alloy becomes a dental amalgam once it goes through the _________ reaction with mercury
______ is susceptible to corrosion
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?
what are 6 undesirable features of amalgam?
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)
to remove surface tarnish, stains, flash, and roughness, a _____ agent and then a ______ agent should be used when polishing
bur = ______
pumice = _______
tin oxide =________
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?
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
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?
what can be added to the alloy to reduce tarnish? what can be done to the restoration after it is placed to reduce tarnish?
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 _____
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 ______
a chemical rxn btw the amalgam and substances in saliva or food, resulting in oxidation of the amalgam is called ________
an electrical current generated between metals (similar to a battery) is called ________
t/f corrosion can occur when two dissimilar metals interact in a solution (saliva) containing electrolytes
what is the result of a galvanic rxn?
oxidation of one of the metals
what three things can galvanism cause over time with amalgam?
stain the surrounding tooth as the corrosion enters the dentinal tubules
high copper vs low copper, high copper has: (3)
less marginal deterioration
t/f a galvanic rxn may occur when a newly placed amalgam comes in contact with a gold crown
what does a pt experience with galvanic rxn?
mild electrical shock
t/f a pt will know when corrosion occurs with their amalgam restorations
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 _______