14. Amalgam Flashcards
True or false
INDICATIONS of using amalgam
→ primary and permanent teeth
→ moderate to large Class I and II restorations including
restorations that involve:
o heavy occlusion
o cannot be isolated well
o extend onto the root surface
T
True or false
INDICATIONS of using amalgam
Class V restorations including restorations that are:
o not esthetically critical
o cannot be well isolated
o located entirely on the root surface
True
an alloy made by mixing mercury with a silver-tin amalgam alloy
DENTAL AMALGAM
COMPOSITION of dental amalgam
_____+ amalgam alloy = dental amalgam
mercury
COMPOSITION of dental amalgam
(Hg) + (Silver, Tin, Copper,_____) = dental amalgam
Zinc
a _______ amalgam alloy added with varying amounts of mercury and small amount of zin
silver-tin
What is the composition of amalgam alloy?
Silver, Tin, Copper, Zinc
→ 67-70%
→ strength
Silver
Tin
Copper
Zinc
Silver
→ 25-27%
→ workability and strength
Silver
Tin
Copper
Zinc
Tin
→ 6% or less (3-5%)
Silver
Tin
Copper
Zinc
Copper
→ strength and corrosion resistance
Silver
Tin
Copper
Zinc
Copper
→ maximum of 2%
→ may or may not be present
Silver
Tin
Copper
Zinc
Zinc
→ suppress oxidation
Silver
Tin
Copper
Zinc
Zinc
has the potential to be hazardous if not managed properly
MERCURY
the alloying reaction of mercury with the ______ go to completion to ensure that mercury does not diffuse into the oral
environment
Ag-Sn alloy
the critical times are when metallic mercury exists in____ or ____ form rather than bound in a set amalgam
liquid or
vapor
as a vapor, metallic mercury can be inhaled and absorbed
through the alveoli in the lungs at ____ % efficiency
80%
1:1 mercury:alloy ratio
MERCURY-TO-ALLOY RATIOS
this ratio is one portion of mercury to one portion of alloy by
weight
MERCURY-TO-ALLOY RATIOS
Eames Technique
MERCURY-TO-ALLOY RATIOS
DENTAL AMALGAM
classified according to (3)
(1) amalgam alloy particle geometry and size
(2) copper content
(3) zinc content
What are the particle type?
Lathe-Cut Particles
Spherical Particles
Dispersion System
→ regular cut, fine cut and microfine cut
A. Lathe-Cut Particles
B. Spherical Particles
C. Dispersion System
A
→ require much less mercury to make a particular mixture
A. Lathe-Cut Particles
B. Spherical Particles
C. Dispersion System
B
the particles were packed more efficiently
A. Lathe-Cut Particles
B. Spherical Particles
C. Dispersion System
B
increased the fluidity of the mixture by
presenting less resistance to particle sliding
A. Lathe-Cut Particles
B. Spherical Particles
C. Dispersion System
B
mixed geometries
A. Lathe-Cut Particles
B. Spherical Particles
C. Dispersion System
C
dispersed alloy
A. Lathe-Cut Particles
B. Spherical Particles
C. Dispersion System
C
Low-Copper Amalgam Alloy contain?
contain 2-5% copper
High-Copper Amalgam Alloy contain?
contain 12-30% copper
Low-Copper Amalgam Alloy:
Ag percent?
69.4%
Low-Copper Amalgam Alloy:
Sn %?
26.2%
Low-Copper Amalgam Alloy:
Cu %?
3.6%
Low-Copper Amalgam Alloy:
Zn %?
0.8%
High-Copper Amalgam Alloy:
Ag %?
60%
High-Copper Amalgam Alloy:
Sn %?
27%
High-Copper Amalgam Alloy:
Cu%?
13%
High-Copper Amalgam Alloy:
Zn %?
0%
ZINC CONTENT can be:
o zinc containing
o non-zinc containing
𝐴𝑔3𝑆𝑛 + 𝐻𝑔 = 𝐴𝑔3𝑆𝑛 + 𝐴𝑔2𝐻𝑔3 + 𝑆𝑛7𝐻𝑔8
PHASES OF DENTAL AMALGAM
Ag3Sn
Gamma Phase
Ag2Hg3
Gamma 1 Phase
Sn7Hg8
Gamma 2 Phase
strongest phase
Gamma Phase
should occupy the maximum volume in the restoration
Gamma Phase
crystals are small and equiaxed
Gamma 1 Phase
intermediate corrosion resistance
Gamma 1 Phase
crystals are long and blade-like
Gamma 2 Phase
prone to corrosion
Gamma 2 Phase
results in porous spongy amalgam with mechanical
resistance
Gamma 2 Phase
PROPERTIES OF DENTAL AMALGAM
Setting Time
Plasticity
Strength
Creep
Dimensional Change
Corrosion and Tarnish
Tensile Strength
relates to the technique employed to condense it to prepared cavity
A. Setting Time
B. Plasticity
C. Strength
D. Creep
E. Dimensional Change
F. Corrosion and Tarnish
G. Tensile Strength
B
True or false
High plasticity requires greater condensing force
FALSE
LOW plasticity requires greater condensing force
final strength is achieved 24 hours after placement
A. Setting Time
B. Plasticity
C. Strength
D. Creep
E. Dimensional Change
F. Corrosion and Tarnish
G. Tensile Strength
C
amount of Hg present in the final restoration relates to ____
A. Setting Time
B. Plasticity
C. Strength
D. Creep
E. Dimensional Change
F. Corrosion and Tarnish
G. Tensile Strength
C
more than 52% of Hg results in decreased _____
A. Setting Time
B. Plasticity
C. Strength
D. Creep
E. Dimensional Change
F. Corrosion and Tarnish
G. Tensile Strength
C
percentage of flow under pressure at mouth temperature
A. Setting Time
B. Plasticity
C. Strength
D. Creep
E. Dimensional Change
F. Corrosion and Tarnish
G. Tensile Strength
D
deformation with time in response to a constant stress
A. Setting Time
B. Plasticity
C. Strength
D. Creep
E. Dimensional Change
F. Corrosion and Tarnish
G. Tensile Strength
D
high copper alloy decreases corrosion
A. Setting Time
B. Plasticity
C. Strength
D. Creep
E. Dimensional Change
F. Corrosion and Tarnish
G. Tensile Strength
F
polishing reduces corrosion
A. Setting Time
B. Plasticity
C. Strength
D. Creep
E. Dimensional Change
F. Corrosion and Tarnish
G. Tensile Strength
F
loss of material at the margin
A. Setting Time
B. Plasticity
C. Strength
D. Creep
E. Dimensional Change
F. Corrosion and Tarnish
G. Tensile Strength
G
butt joint margin increases tensile strength
A. Setting Time
B. Plasticity
C. Strength
D. Creep
E. Dimensional Change
F. Corrosion and Tarnish
G. Tensile Strength
G
too high Hg content and ultrafine alloy produces
low tensile strength
A. Setting Time
B. Plasticity
C. Strength
D. Creep
E. Dimensional Change
F. Corrosion and Tarnish
G. Tensile Strength
G