3. Why Amalgam?
Inexpensive
Ease of use
Proven track record
- >100 years
Familiarity
Resin-free
- less allergies than composite
4. Composition Of Dental Amalgam
Traditional or Convential amalgam alloys is based
on Black’s composition.
63-70% silver
26-28% tin
Less than 6% Cu &
Sometimes 0-2% Zn.
8. Basic Constituents
Copper (Cu)
Ties up tin
Reducing gamma-2 formation
Increases strength & hardness
Reduces tarnish and corrosion
Reduces creep
Reduces marginal deterioration
9. Basic Constituents
Mercury (Hg)
Activates reaction
Only pure metal that is liquid
at room temperature
Spherical alloys
* Require less mercury
- Smaller surface area easier to wet
40 to 45% Hg
Admixed alloys
Require more mercury
lathe-cut particles more difficult to wet
45 to 50% Hg
10. Other Constituents
Zinc (Zn)
Used in manufacturing
Decreases oxidation of other elements
Sacrificial anode
Provides better clinical performance
less marginal breakdown
Causes delayed expansion with low Cu alloys
If contaminated with moisture during condensation
H2O + Zn ZnO + H2⇒⇒
11. Other Constituents
Indium (In)
Decreases surface tension
Reduces amount of mercury necessary
Reduces emitted mercury vapor
Reduces creep and marginal breakdown
Increases strength
Must be used in admixed alloys
Example
Indisperse (Indisperse Distributing Company)
5% indium
12. Other Constituents
Palladium (Pd)
Reduced corrosion
Greater luster
Whitens the Alloy
Example
Valiant PhD (Ivoclar Vivadent)
0.5% palladium
13. Basic Composition
A silver-mercury matrix containing filler
particles of silver-tin
Filler (bricks)
Ag3Sn called gamma
can be in various shapes
irregular (lathe-cut), spherical,
or a combination
Matrix
Ag2Hg3 called gamma 1
cement
Sn8Hg called gamma 2
voids
15. Conventional Low-Copper Alloys
Dissolution and precipitation
Hg dissolves Ag and Sn
from alloy
Intermetallic compounds
formed
Ag-Sn
Alloy
Ag-Sn
Alloy
Ag-Sn Alloy
Mercury
(Hg)
Ag
AgAg
Sn
Sn
Sn
Hg Hg
AgAg33Sn + HgSn + Hg ⇒⇒ AgAg33Sn + AgSn + Ag22HgHg33 + Sn+ Sn88HgHg
γ γ γ1 γ2
16. Conventional Low-Copper Alloys
Gamma (γ) = Ag3Sn
Unreacted alloy
Strongest phase and
corrodes the least
Forms 30% of volume
of set amalgam
Ag-Sn
Alloy
Ag-Sn
Alloy
Ag-Sn Alloy
Mercury
Ag
Ag
Ag
Sn
Sn
Sn
Hg
Hg
Hg
AgAg33Sn + HgSn + Hg ⇒⇒ AgAg33Sn + AgSn + Ag22HgHg33 + Sn+ Sn88HgHg
γ γ γ1 γ2
18. Conventional Low-Copper
Alloys
Gamma 2 (γ2) = Sn8Hg
weakest and softest phase
corrodes fast, voids form
corrosion yields Hg which
reacts with more gamma (γ)
10% of volume
volume decreases with time
due to corrosion
AgAg33Sn + HgSn + Hg ⇒⇒ AgAg33Sn + AgSn + Ag22HgHg33 + Sn+ Sn88HgHg
γ γ γ1 γ2
γ2
Ag-Sn Alloy
Ag-Sn
Alloy
Ag-Sn
Alloy
19. Admixed High-Copper
Alloys
Ag enters Hg from Ag-Cu spherical
eutectic particles
Eutectic
An alloy in which the elements are
completely soluble in liquid solution
but separate into distinct areas upon
solidification
Both Ag and Sn enter Hg from Ag3Sn
particles
AgAg33Sn + Ag-Cu + HgSn + Ag-Cu + Hg ⇒⇒ AgAg33Sn + Ag-Cu + AgSn + Ag-Cu + Ag22HgHg33 + Cu+ Cu66SnSn55
γ γ γ1 η
Ag-Sn
Alloy
Ag-Sn
Alloy
Mercury
Ag
AgAg
Sn
Sn
Ag-Cu Alloy
Ag
HgHg
20. Admixed High-Copper Alloys
Sn diffuses to surface of
Ag-Cu particles
Reacts with Cu to form
(eta) Cu6Sn5 (η)
Around unconsumed
Ag-Cu particles Ag-Sn
Alloy
Ag-Cu Alloyη
Ag-Sn
Alloy
AgAg33Sn + Ag-Cu + HgSn + Ag-Cu + Hg ⇒⇒ AgAg33Sn + Ag-Cu + AgSn + Ag-Cu + Ag22HgHg33 + Cu+ Cu66SnSn55
γ γ γ1 η
22. Single Composition
High-Copper Alloys
Gamma sphere (γ) (Ag3Sn)
with epsilon coating (ε)
(Cu3Sn)
Ag and Sn dissolve in Hg
Ag-Sn Alloy
Ag-Sn Alloy
Ag-Sn Alloy
Mercury (Hg)
ε
Ag
Sn
Ag
Sn
AgAg33Sn + CuSn + Cu33Sn + HgSn + Hg ⇒⇒ AgAg33Sn + CuSn + Cu33Sn + AgSn + Ag22HgHg33 + Cu+ Cu66SnSn55
γ γ γ1 ηε ε
23. Single Composition
High-Copper Alloys
Gamma 1 (γ1) (Ag2Hg3) crystals
grow binding together partially-
dissolved gamma (γ) alloy
particles (Ag3Sn)
Epsilon (ε) (Cu3Sn) develops
crystals on surface of
gamma particle (Ag3Sn)
in the form of eta (η) (Cu6Sn5)
Reduces creep
Prevents gamma-2 formation
Ag-Sn Alloy
Ag-Sn Alloy
Ag-Sn Alloy
γ1
η
AgAg33Sn + CuSn + Cu33Sn + HgSn + Hg ⇒⇒ AgAg33Sn + CuSn + Cu33Sn + AgSn + Ag22HgHg33 + Cu+ Cu66SnSn55
γ γ γ1 ηε ε
24. Classifications
Based on Cu content
Based on particle shape
Based on Zn content
Based on number of alloyed metals
Based on size of alloy
25. Copper Content
Low-copper alloys
4 to 6% Cu
High-copper alloys
thought that 6% Cu was maximum amount
due to fear of excessive corrosion and expansion
Now contain 9 to 30% Cu
at expense of Ag
26. Particle Shape
Lathe cut
low Cu
New True
Dentalloy
high Cu
ANA 2000
Admixture
high Cu
Dispersalloy, Valiant PhD
Spherical
low Cu
Cavex SF
high Cu
Tytin, Valiant
27. Manufacturing Process
Lathe-cut alloys
Ag & Sn melted together
alloy cooled
phases solidify
heat treat
400 ºC for 8 hours
grind, then mill to 25 - 50 microns
heat treat to release stresses of grinding
More Hg needed – high force needed due to irregular form
28. Manufacturing Process
Spherical alloys
melt alloy
atomize
spheres form as particles cool
sizes range from 5 - 40 microns
variety improves condensability
Spherical particles wet easier
( less Hg is required)
30. Zn content
If the Zn content is greater than 0.01% the
amalgam is called a Zn-containing Amalgam.
If the content is less, then Amalgam is Non-Zn
Amalgam.
31. Number of alloyed metals
Binary alloys : Ag-Sn
Tertiary Alloys : Ag-Sn-Cu
Quaternary alloys : Ag-Sn-Cu-In