1. Prepared by : Dr.Dalia A. Abu-Alena in MDS,BDS
Dental Amalgam
Prepared by :
Dr.Dalia A. Abu-Alena in
MDS,BDS

2. Dental Amalgam
Amalgam:is an alloy of mercury with one or more other metals.
Dental amalgam alloy:is an alloy that contains solid metals of silver,tin, copper and some times zinc.
Dental amalgam: is the alloy that results when mercury is combined with the previously mentioned alloys to form a plastic mass.

3. Amalgam
Advantages
Disadvantages

4. Composition of Dental Amalgam:
Silver
Tin
Copper
Zinc
Indium and Palladium
Mercury

5. Classification of Dental Amalgam Alloys
Conventional (Low Copper )Alloy:
Lathe-cut Particles.
Spherical Particles
(a)
(b)

6. Classification of Dental Amalgam Alloys
High copper alloy:
Admix Alloy.
Unicompositional alloy.
(a)
(b)

7. Silver -Tin Binary System

8. Setting Reactions of Dental Amalgams:
Low Copper Alloy:
Ag3Sn + Hg Ag2Hg3 + Sn8Hg + Ag3Sn
(  ) (1) ( 2) ()
54%-56% % % 1   Hg  2 Hg
1+ 2

9. Setting Reactions of Dental Amalgams:
High copper alloy
Admixed alloy
Ag3Sn + AgCu + Hg Ag2Hg3 + Sn8Hg + Ag3Sn + AgCu
( ) (1 ) (2 ) ( )
Sn8Hg + AgCu Cu6Sn5 + Ag2Hg3 + Ag3Sn
(2) ( ) (1 ) ( )

10. Setting Reactions of Dental Amalgams:
High copper alloy
Unicompositional Alloy:
Ag3Sn + Cu3Sn + Hg Cu6Sn5 + Ag2Hg3
( ) (  ) (  ) (1 )

11. Microstructure of Set Low Copper Amalgam.
(Ag3Sn)
2(Sn8Hg)
Voids
1(Ag2Hg3)

12. Microstructure of Set High-Copper Admixed Amalgam.
1(Ag2Hg3)
Eutectic(Ag3Cu2)
(Cu6Sn5)
(Ag3Sn)

13. Properties of Dental Amalgam

14. Properties of Dental Amalgam
Compressive strength
Tensile Strength
Elastic Modulus
Creep
Dimensional Changes
Tarnish and Corrosion:

15. Properties of Dental Amalgam
Compressive strength
-Amalgam is strongest in compression and much weaker in tension and shear.
-HCU materials have the highest compressive strength.

16. Properties of Dental Amalgam
Tensile Strength:
-Amalgam is strongest in compression and much weaker in tension and shear.
-HCU materials have the highest early tensile strength.

17. Properties of Dental Amalgam
Strength of various phases:
Unreacted Ag3Sn () phase. (strongest)
Ag2Hg3(1)phase.
Sn8Hg (2)phase.(weakest)

18. Properties of Dental Amalgam
Elastic Modulus:
-High- copper alloys are stiffer than low-copper alloys.
-Amalgam are viscoelastic.

19. Properties of Dental Amalgam
Creep
-Low-copper lathe cut alloy has the highest value of creep (6.3%).
-The low creep values of high- copper alloys( %) increase the brittleness of amalgam and decrease the relief of stresses at contact areas under load.

20. Properties of Dental Amalgam
Dimensional Changes:
-Low-copper alloy have the greatest dimensional change(-19.7m/cm).
-High-copper unicompositional alloy have the least dimensional change (-1.9 m/cm).
-Other alloys are ranging from (-8.8 to –14.8 m/cm).

21. Properties of Dental Amalgam
Dimensional Changes:
Delayed Excessive Expansion ?
Zinc – containing alloy + Moisture.

22. Properties of Dental Amalgam
Tarnish and Corrosion:
-Corrosion of various phases:
- Ag3Hg3 ( 1)…..Least corrodible.
-Ag3Sn().
-Ag3Cu2(eutectic).
-Cu3Sn( ).
-Cu6Sn5( ).
-Sn8Hg (2).…….Most corrodible

23. Properties of Dental Amalgam
Tarnish and Corrosion:
Excessive corrosion can lead to :
Increase porosity.
Reduced marginal integrity.
Loss of strength.
Release of metallic products .

24. Manipulation of Dental Amalgam:
Selection of alloy.
Proportioning and dispensing.
Trituration.
Condensation.
Carving.
Finishing and polishing.

25. Manipulation of Dental Amalgam:
Selection of alloy:
It is estimated that the majority of the dental amalgams currently placed are high – copper alloys , spherical- unicopositional or admixed types .

26. Manipulation of Dental Amalgam:
Proportioning and dispensing:
proportioned capsules containing alloy particles and mercury in compartments separated by a disk or membrane are available.

27. Manipulation of Dental Amalgam:
Trituration:
Trituration is the process by which mercury is allowed to react with the alloy powder . This procedure allows the rubbing of the surface oxide on amalgam particles , exposing an active surface to react with mercury .

28. Manipulation of Dental Amalgam:
Trituration:
- Hand Trituration
-Mechanical Trituration

29. Manipulation of Dental Amalgam:
Effect f over-trituration and under-trituration:
Working time decreases with over- trituration.
Setting contraction increases with over- trituration.
Compressive and tensile strengths increase with over-trituration of lath cut alloys;however they decrease with over- and under-trituration of spherical alloys.
Creep increases with over- trituration.

30. Manipulation of Dental Amalgam:
Condensation:
-Hand Condensation.
-Mechanical Condensation.

31. Manipulation of Dental Amalgam:
Carving:

32. Manipulation of Dental Amalgam:
Finishing and polishing:

33. Mercury Toxicity Properties of mercury. Sources of mercury exposure.
Mercury hygiene.

34. Recent Modifications of Dental Amalgam Alloys
Indium containing amalgam.
Palladium containing amalgam.
Copper amalgam.
Mercury free gallium based alloy.