Dental amalgam is an alloy used in dental fillings that consists of liquid mercury and a powdered alloy mixture of silver, tin, and copper. It has been used since the 1830s as a dental restorative material. Newer advances include high copper amalgam, bonded amalgam, and gallium-based alloys as alternatives that aim to reduce mercury levels while maintaining strength and durability. However, the use of amalgam remains controversial due to concerns about mercury toxicity.
4. History
• 1833
– Crawcour brothers introduce
amalgam to US
• powdered silver coins mixed with mercury
– expanded on setting
• 1895
– G.V. Black develops formula
for modern amalgam alloy
• 67% silver, 27% tin, 5% copper, 1% zinc
– overcame expansion problems
Sir Regnart is called the father of amalgam.
Amalgam was first introduced in England in 1819
and later in Paris by Taveau in 1826
7. 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
Phillip’s Science of Dental Materials 2003
Manufacture of the Alloy
8. Manufacturing Process
• Spherical alloys
– melt alloy
– atomize
• spheres form as particles cool
– sizes range from 5 - 40 microns
Phillip’s Science of Dental Materials 2003
11. Classification
• Depending upon the copper content.
– Low copper alloy.
– High copper alloy Admixed alloy
Single composition alloy
• Based on zinc content
– Zinc containing alloy
– Zinc free alloys.
• According to the shape of the powder particle
– Lathe cut.
– Spherical.
– Spheroidal
12. • Based on number of alloying metals:
1. Binary.
2. Tertiary.
3. Quarternary.
• Based on noble metal content
• Generations of amalgam
14. 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
Phillip’s Science of Dental Materials 2003
Ag3Sn + Ag-Cu + Hg Ag3Sn + Ag-Cu + Ag2Hg3 + Cu6Sn5
1
Ag-Sn
Alloy
Ag-Sn
Alloy
Mercury
Ag
Ag
Ag
Sn
Sn
Ag-Cu Alloy
Ag
Hg
Hg
High-Copper Alloys
15. Admixed High-Copper Alloys
• Sn diffuses to surface of
Ag-Cu particles
– reacts with Cu to form
(eta) Cu6Sn5 ()
• around unconsumed
Ag-Cu particles
Ag-Sn
Alloy
Ag-Cu Alloy
Ag-Sn
Alloy
Phillip’s Science of Dental Materials 2003
Ag3Sn + Ag-Cu + Hg Ag3Sn + Ag-Cu + Ag2Hg3 + Cu6Sn5
1
30. Dimensional Change
• According to ADA specification
No. 1 Amalgam should not either
contract or expand more than
20µ per cm at 37°C.
– Stage I – Initial contraction for
20mins followed by
– Stage II – Expansion
– Stage III – Delayed contraction.
Phillip’s Science of Dental Materials 2003
