**Amalgam Flashcards
Define amalgamation
the reaction between alloys and mercury to make amalgam
Define alloy
a mixture of metallic elements
Define trituration
the mixing of the mercury and alloy powder in the amalgam capsule
Define creep
the slow change in dimensions of the amalgam due to prolonged exposure to stress
What occurs when amalgam slowly moves out over the cavosurface margins under occlusal pressures?
creep
Define corrosion
the process where metal is eaten away by a chemical reaction
Is corrosion due to a chemical or mechanical reaction?
chemical
Define galvanism
an electric current created by a chemical reaction of dissimilar metals
Define tarnish
the discoloration of the surface of the amalgam
List the four major types of alloy in amalgam
silver, copper, tin, and zinc
What type of metal is the highest percentage of the alloy?
Silver
What type of metal is the lowest percentage of the alloy?
zinc
What type of metal in the alloy is used to prevent oxidation during the manufacturing process?
zinc
What type of metal in the alloy forms a metallic compound with the mercury?
silver
List the three types of of size/shapes of the alloy particles in amalgam?
Lathe-cut, spherical-cut, mixture of cuts
What type of alloy particle cut requires the least amount of mercury?
spherical-cut
Amalgams with ____ mercury content generally have better properties.
(low or high)
low
How is mercury absorbs into the human body?
Through the pores in skin or by inhalation
Approximately what percent of mercury is left in a finished amalgam restoration?
3%
During placement of the amalgam restoration, what process allows the mercury-rich layer to rise to the surface and be removed?
Condensing
Is a higher or lower ratio of mercury a quicker setting time?
Lower
What percentage of mercury ratio is considered a “mercury-rich” amalgam?
More than 54%
What causes the Gamma 2 phase?
inadequate condensation of amalgam during placement of the restoration
What metal in an alloy can help reduce problems with the Gamma 2 phase?
high amounts of copper
The Gamma 2 phase of a combination of what two materials in amalgam that decreases the strength of the final restoration?
tin and mercury
What is inside each amalgam capsule?
a pre-measured amount of alloy and mercury
Define pestle
a metal or plastic piece placed inside the amalgam capsule to aid in the mixing process
What is a spill of amalgam?
the amount of material inside each amalgam capsule
The settings on the amalgamator that determine the quality of the amalgam capsule’s mixture includes what?
mixing time, speed, force
How will an overtriturated mix appear?
crumbly and dull
How will an undertriturated mix appear?
soupy
Where are amalgam scraps stored?
Regulated waste amalgam containers
Define burnishing
the process of using a ball burnisher instrument to lightly rub over the surface of the amalgam restoration to smooth it and achieve a dull luster (optional procedure)
When an amalgam restoration is successfully burnished, how will it appear?
smooth, dull luster
Define: flash
excess
Define: overhang
excess restorative material that has leaked under and out of the matrix band
Define: open margins
a space left between a tooth and the restorative material due to inadequate condensing of the material
Define: ditching
creation of scratches or concave areas due to excessive finishing of the amalgam
In a Class 2 restoration, it is indicated to place the first increment of amalgam in the least accessible area of the prep. Where would this be?
the proximal box
When carving anatomy in an amalgam restoration, what type of motion will you use to activate the instrument?
pulling motion
How long after placing an amalgam restoration should you wait to finish and polish the restoration, if needed?
24-48 hours, per manufacturer’s instructions
Why can amalgam not be finished/polished the same day as the restoration is placed?
premature finishing and polishing will disturb the crystalline structure of the hardened amalgam, and will weaken the restoration
