Dental amalgam

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

2. I. 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.

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

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

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

7. IV. Silver -Tin Binary System

8. V. Setting Reactions of
Dental Amalgams:
1) Low Copper Alloy:
Ag3Sn + Hg Ag2Hg3 + Sn8Hg + Ag3Sn
(  ) (1) ( 2) ()
54%-56% 11-13% 27-35%
 Hg  
1
2
Hg
1+ 2

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

10. Setting Reactions of Dental
Amalgams:
2) High copper alloy
b) 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)
(Ag3Sn)
Eutectic(Ag3Cu2)
(Cu6Sn5)

13. VI. Properties of Dental
Amalgam

14. VI. Properties of Dental
Amalgam
1. Compressive strength
2. Tensile Strength
3. Elastic Modulus
4. Creep
5. Dimensional Changes
6. Tarnish and Corrosion:

15. VI. Properties of Dental Amalgam
1. 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
2. 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:
1. Unreacted Ag3Sn () phase.
(strongest)
2. Ag2Hg3(1)phase.
3. Sn8Hg (2)phase.(weakest)

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

19. Properties of Dental Amalgam
4. Creep
-Low-copper lathe cut alloy has the highest
value of creep (6.3%).
-The low creep values of high- copper
alloys(0.05-0.09%) increase the
brittleness of amalgam and decrease the
relief of stresses at contact areas under
load.

20. Properties of Dental Amalgam
5. 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
5. Dimensional Changes:
Delayed Excessive Expansion ?
Zinc – containing alloy + Moisture.

22. Properties of Dental Amalgam
6. 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
6. Tarnish and Corrosion:
Excessive corrosion can lead to :
 Increase porosity.
 Reduced marginal integrity.
 Loss of strength.
 Release of metallic products .

24. VII. Manipulation of Dental
Amalgam:
1) Selection of alloy.
2) Proportioning and dispensing.
3) Trituration.
4) Condensation.
5) Carving.
6) Finishing and polishing.

25. Manipulation of Dental Amalgam:
1) 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:
2) 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:
3) 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:
3) 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:
4) Condensation:
-Hand Condensation.
-Mechanical Condensation.

31. Manipulation of Dental Amalgam:
5) Carving:

32. Manipulation of Dental Amalgam:
6) 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.