Chapter 2 J: Dental Amalgam Flashcards
Amalgam is
An alloy in which mercury appears as a main constituent
Dental amalgam is
Alloy of mercury with silver, tin and varying amounts of copper, zinc, and other minor constituents
Match the finding with the year XVII C:
A: Crawcour brothers crushed silver coins with mercury
B: G.V Black recommended Ag, Sn, Cu, and Zn alloys, and this new alloy was accepted as an obturation material
C: high copper amalgams were introduced, less corrosion and less fractures
D: amalgam was introduced into dentistry
E: towsend added Tin to the mixture improving the mechanical properties
F: Ag introduced into amalgam (pate d’argent)
G: ADA specified percentages of the amalgam components
D
Match the finding with the year XIX C:
A: Crawcour brothers crushed silver coins with mercury
B: G.V Black recommended Ag, Sn, Cu, and Zn alloys, and this new alloy was accepted as an obturation material
C: high copper amalgams were introduced, less corrosion and less fractures
D: amalgam was introduced into dentistry
E: towsend added Tin to the mixture improving the mechanical properties
F: Ag introduced into amalgam (pate d’argent)
G: ADA specified percentages of the amalgam components
F
Match the finding with the year 1833:
A: Crawcour brothers crushed silver coins with mercury
B: G.V Black recommended Ag, Sn, Cu, and Zn alloys, and this new alloy was accepted as an obturation material
C: high copper amalgams were introduced, less corrosion and less fractures
D: amalgam was introduced into dentistry
E: towsend added Tin to the mixture improving the mechanical properties
F: Ag introduced into amalgam (pate d’argent)
G: ADA specified percentages of the amalgam components
A
Match the finding with the year 1855:
A: Crawcour brothers crushed silver coins with mercury
B: G.V Black recommended Ag, Sn, Cu, and Zn alloys, and this new alloy was accepted as an obturation material
C: high copper amalgams were introduced, less corrosion and less fractures
D: amalgam was introduced into dentistry
E: towsend added Tin to the mixture improving the mechanical properties
F: Ag introduced into amalgam (pate d’argent)
G: ADA specified percentages of the amalgam components
E
Match the finding with the year 1908:
A: Crawcour brothers crushed silver coins with mercury
B: G.V Black recommended Ag, Sn, Cu, and Zn alloys, and this new alloy was accepted as an obturation material
C: high copper amalgams were introduced, less corrosion and less fractures
D: amalgam was introduced into dentistry
E: towsend added Tin to the mixture improving the mechanical properties
F: Ag introduced into amalgam (pate d’argent)
G: ADA specified percentages of the amalgam components
B
Match the finding with the year 50’s:
A: Crawcour brothers crushed silver coins with mercury
B: G.V Black recommended Ag, Sn, Cu, and Zn alloys, and this new alloy was accepted as an obturation material
C: high copper amalgams were introduced, less corrosion and less fractures
D: amalgam was introduced into dentistry
E: towsend added Tin to the mixture improving the mechanical properties
F: Ag introduced into amalgam (pate d’argent)
G: ADA specified percentages of the amalgam components
G
Match the finding with the year 60’s:
A: Crawcour brothers crushed silver coins with mercury
B: G.V Black recommended Ag, Sn, Cu, and Zn alloys, and this new alloy was accepted as an obturation material
C: high copper amalgams were introduced, less corrosion and less fractures
D: amalgam was introduced into dentistry
E: towsend added Tin to the mixture improving the mechanical properties
F: Ag introduced into amalgam (pate d’argent)
G: ADA specified percentages of the amalgam components
C
Percentage of silver according to the ADA in the 50’s?
≥ 65
Percentage of tin according to the ADA in the 50’s?
≤29
Percentage of copper according to the ADA in the 50’s?
≤6
Percentage of mercury according to the ADA in the 50’s?
3
Percentage of zinc according to the ADA in the 50’s?
≤2
The two types of amalgam are:
Conventional and high copper
The percentage of copper in conventional amalgam is ?
0-6%
The percentage of copper in high copper amalgam is?
11-22%
Properties of silver include:
- increases resistance, strength, and setting expansion
- reduces shrinkage and setting time
- an excessive amount of Ag can lead to an excessive expansion of the material
What happens to amalgam when it sets in comparison to composite?
Amalgam expands while composite contracts
Properties of tin include:
- reduces strength, hardness, and setting expansion
- increases setting time
Properties of copper include:
- improves hardness and resistance
- reduces tarnish and corrosion
- less fractures and less corrosion
Properties of zinc include:
- its presence is not essential
- improves the color, cleaner aspect
- contaminated with moisture, dissociating H20 into H and O, liberating H as bubbles (secondary expansion)
Properties of mercury include:
Gives the plastic consistency when mixed with other solid crushed metals
Is amalgam soluble or insoluble in the oral cavity?
Insoluble
Corrosion helps in
Cavity sealing
Which type of amalgam has higher corrosion?
Conventional amalgam
What gives the amalgam a blackish and shine-less aspect?
Corrosion
Is there adhesion or chemical retention with amalgam?
No
When does amalgam suffer dimensional changes?
Within the first year when it becomes stable
An excess of silver or mercury leads to:
Expansion
An excess of tin leads to:
Shrinkage
How does amalgam adaption improve over time?
With corrosion and secondary expansion
One of the best advantages of amalgam is:
It’s resistance to compression and the greatest compressive resistance is after 24hrs
It’s resistance to traction is ___ of the compressive resistance
A fifth
What happens if amalgam exceeds the cavosurface margin?
A wedge is formed and easily fractured leading to secondary caries
How is deformation measured? And what’s the value of deformation of amalgam?
Creep: deformation suffered by a viscoelastic material when it is being subjected to tensions under its elastic threshold
3%
Which type of amalgam has higher creeps leading to worse results?
Conventional amalgam
What has a better thermal and electrical conductivity (dental tissues/structures or amalgam)?
Amalgam
Amalgam is ___ times a better thermal conductor than dentin and ___ times better conductor than enamel which makes its highly sensitive to thermal changes
36, 25
Galvanism is defined as:
When two or more of dissimilar metals in dental restorations which are bathed in saliva or a single metal in contact with two electrolytes such as saliva and pulp fluid tissue produces an electric current.
can affect the pulp if done continuously
Amalgam has the highest toxicity when?
- polishing without water
- when removing old amalgam fillings
- high inhalation when recently mixed
When do we polish?
After 24 hours
Biggest disadvantages of amalgam are?
Aesthetics and toxicity
The advantages of amalgam are;
- resistance to occlusal forces
- marginal sealing gets better with time
- not very exigent in its application technique
What kind of walls do we need for amalgam?
Convergent
What happens after 20 minutes ?
Primary contraction
What happens after contraction ?
Crystallisation
