1. Amalgam Flashcards
What is an alloy
A metal made by combining two or more metals together (can also mix in non-metals as well)
Alloys tends to have more advantageous properties such as….
greater strength and resistance to corrosion
(T/F) Dental amalgam is not an alloy
F-it is
What are the components that make up the alloy for the dental amalgam
- silver
- tin
- copper
- (sometimes zinc/palladium)
The alloy is mixed with _ to form dental amalgam
mercury
What are the three types of dental amalgam alloys
- conventional lathe- cut alloy
- spherical alloys
- admix alloys (mixture of lathe-cut and spherical particles)
Conventional lathe-cut amalgam particles are _ shaped
irregular
spherical alloys require (more/less) mercury. This is a (good/bad) thing because…
less… good… Amalgams with lower Hg content have better properties
Why do spherical alloys require less mercury compared to conventional lathe-cut
because the particles have a smaller surface area/volume ratio.
Spherical alloy particles tend to be more (buttery/brittle) due to the lower conc. of mercury
buttery (or plastic)
The most common type of alloy used today is
Admix alloy
(T/F) Admix alloy requires considerable force when condensing
t
An admix alloy is stronger after a (little/lot) of time passes
a lot
An admix alloy can be polished after how long post-setting
24 hours
The main component of dental amalgam is what element?
Silver (70%)
Silver serves to increase the __ of dental amalgam
strength
The next component of dental amalgam that is most abundant next to silver is
tin (16%)
Tin is involved in lowering the _ of dental amalgam
expansion
The metal that has the 3rd highest % composition in dental amalgam is…
Copper (~13%)
The two main roles of copper in dental amalgam is to decrease _ and _
creep and corrosion
The 4th and final element in dental amalgam with the lowest %composition is
zinc (
The roles of zinc in the alloy is to…
- decrease the formation of oxides during melting*
- Increases the wettability of the particles (increased plasticity) –> stronger margins
Having inc in dental amalgam makes the material more prone to…which leads to….
moisture contamination…delayed expansion
Silver and tin are (plastic/brittle) adding copper to the mix makes the material more (plastic/brittle)
brittle…plastic
High copper alloys are also called (2 names)
phase-diapered alloy and admixed high-copper alloy
A high copper amalgam must have between -% Cu in it to be considered high copper
9-30%
High copper amalgams have (better/worse) strength compared to conventional amalgam
better
Why is there better marginal integrity and decreased marginal breakdown for high copper amalgams
because they eliminate the gamma 2 phase
Gamma phase is a reaction product of…
unreacted tin and silver
Gamma 1 phase is a reaction product of…
silver and mercury
Gamma 2 phase is a reaction product of
tin and mercury
Rank the 3 gamma phases in order of increasing strength
gamma2-gamma1-gamma
The gamma phase most susceptible to corrosion is…
gamma 2
What is amalgamation
the process of mixing liquid mercury with alloys
What are the two different techniques used by dentists to amalgamate amalgam
triturator and mortar and pestle
Define creep
time-dependent strain or deformation that is produced by a stress
High copper amalgams (increase/decrease) creep
decrease
Amalgams can undergo dimensional changes- amalgam can expand or contract- how can you minimize these changes
proper usage of alloy and mercury
What types of dimensional changes are commonly seen in Zn-containing amalgams
delayed expansion
what can be used in the alloy to reduce the amount of delayed expansion caused by moisture contamination in a Zn-containing amalgam
tin
Amalgam shows (high/low) compressive strength, (high/low) tensile strength, and (high/low) shear strength
high…low…low
What is tarnish
process which amalgam restoration surface is dulled or discolored due to the formation of oxide layers
What is corrosion
Actual deterioration of a metal caused by the chemical reaction between the metal and its environment (air/water) forming metal compounds or corrosion products
What is percolation
Influx of salivary flow into the microscopic gap between the restoration and the tooth (salivary fluids react with copper, tin, and silver)
High copper amalgams show (slow/fast) rates of percolation because….
slow because they have less gamma 2 phase
(T/F) Amalgam creates a deal dependent of the operator that is user friendly
F- independent of the operator*
Know the table on the 2nd to last slide
ok
Why are amalgam capsules sealed
to prevent evaporation of mercury
Increasing the amount of tin the alloy will (increase/decrease) the amount of corrosion/tarnish
increase
Increasing the amount of copper in the alloy will (increase/decrease) the amount of tarnish/corrosion
decrease
Increasing the amount of silver will (increase/decrease) the strength of the amalgam
increase
Increasing the amount of tin will (increase/decrease) the strength of the amalgam
decrease
Increasing the amount of copper will (increase/decrease) the strength of the amalgam
increase
Increasing the amount of silver will (increase/decrease) the setting expansion of the amalgam
increase
Increasing the amount of tin will (increase/decrease) the strength of the amalgam
decrease
Increasing the amount of copper will (increase/decrease) the strength of the amalgam
increase
Increasing the amount of silver will (increase/decrease) the creep and flow
decrease
Increasing the amount of tin will (increase/decrease) the creep and flow
increase
Increasing the amount of copper will (increase/decrease) the creep and flow
decrease
Increasing the amount of silver will (increase/decrease) the compressive strength
increase
Increasing the amount of tin will (increase/decrease) the compressive strength
decrease
Increasing the amount of copper will (increase/decrease) the compressive strength
increase
Increasing the amount of mercury will (increase/decrease) the setting expansion
increase
Increasing the amount of mercury will (increase/decrease) the compressive strength
decrease
Increasing the amount of mercury will (increase/decrease) the flow
increase
Increasing the amount of copper with (slow/fast) the rate of percolation… because
slow… because the marginal integrity increases in high copper amalgams
