Applied Dental Material Second Year

1. Dental Amalgam
Dr. Hala Bahgat
Dr. Dina Mostafa

2. Amalgam:
Any alloy + Mercury (Hg)
Dental Amalgam:
Dental alloy + Mercury (Hg)
Alloy for Dental Amalgam :
Alloy powder used in dental amalgam
Ag , Sn , Cu
and
Zn
Amalgamation reaction:
Chemical reaction between dental alloy and mercury at room
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temperature
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3. Dental Amalgam
Mode of supply
Hg
Powde
r
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Dr. Dina Mostafa

4. Dental Amalgam
Posterior Direct Filling Materials
USES
1. Better in small
occlusal cavity
Class I
2. Class II with
some
precautions
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Dr. Dina Mostafa

5. 3. Core
material for
crown build
up
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Dr. Dina Mostafa

6. Advantages:
• Ease of manipulation
• High compressive strength
• Low cost
• Marginal leakage decreases
with time
• Long clinical service life
Disadvantages:
• Metallic color
• Brittle and low toughness
• Thermal irritation
•Subject to corrosion and
galvanic action
• subject to creep
• Does not bond to tooth
structure
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Dr. Dina Mostafa

7. Dr. Hala Bahgat
Dr. Dina Mostafa

8. Silver (Ag)
1.
2.
3.
4.
Increases strength and hardness.
Increases setting expansion.
Increases corrosion resistance.
Decreases creep.
Tin (Sn)
1. Decreases strength and hardness.
2. Decreases setting expansion (causes
contraction).
3. Decreases corrosion resistance.
4. Increases creep.
It is a time dependent deformation of a material under its own
weight (below P.L.), having its melting temperature near the
ambient temperature.
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Dr. Dina Mostafa

9. 73.2-80% Ag
20-26.8% Sn
Below 480°C
γ
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Dr. Dina Mostafa

10. Silver
1.Increases strength
and hardness.
2.Increases setting
expansion.
3.Increase corrosion
resistance.
4.Decreases creep.
Tin (Sn)
1. Decreases strength and
hardness.
2. Decreases setting expansion
(causes contraction).
3. Decreases corrosion
resistance.
4. Increases creep.
5. Formation of intermetallic
compound with silver.
6. Increases the rate of
amalgamation.
7. Increases plasticity of
amalgam mass during
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condensation.
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11. Copper (Cu)
1.Increases strength
and hardness.
2.Increases setting
expansion.
3.Increases
corrosion
resistance.
4.Decreases creep.
Zinc (Zn)
1.Deoxidizer
(scavenger) during
the alloy
manufacturing.
2.Increases strength.
3.Increases setting
expansion.
4.Increases plasticity
of amalgam mass
during
condensation.
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Dr. Dina Mostafa

12. + Mercury
Hg
1.Decreases strength and
hardness.
2.Highly increases the setting
expansion.
3.Decreases corrosion resistance.
4.Increases creep.
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Dr. Dina Mostafa

13. Classification of Dental Amalgam
I- According to Zinc Content
Zinc containing amalgams
More than 0.01- 2% mx
Zinc free amalgams
Less than 0.01%
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14. II- According to Particles Shape
Spherical
Lathe Cut
Spheroidal
Advantage of spherical particles
compared to lathe cut:
1- Lower surface area/volume
2- They take less mercury
3- Need less condensation pressure but
larger condenser
4- Fast setting
5-They produce smoother surface
6- They offer superior strength property
Dr. Hala Bahgat
Dr. Dina Mostafa

15. III- According to Particles Size
Coarse Cut
Fine Cut
Microfine Cut
100 – 200 µm
15 – 35 µm
Less than 3 µm
Advantage of fine cut particles compared
to coarce cut:
Disadvantages:
Increase total area/volume
1- More consumption of mercury
2- Fast setting
Will need more Hg
3- They produce smoother surface
4- They offer superior strength property
5- Better adaptation to cavity walls
Less mechanical properties
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Dr. Dina Mostafa

16. IV- According to Copper Content
High Copper Amalgams
Low Copper Amalgams or
Conventional Amalgams
Admixed
amalgams
Less than 6% Cu
Unicompositional
amalgams
More than 6% Cu
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Dr. Dina Mostafa

17. Low Copper
or
Conventional Amalgam
Composition
Silver (Ag)
65%
Tin (Sn)
Lathe coarse cut
29%
Copper (Cu)
Zinc (Zn)
6%
mx 2%
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18. Theory of Setting
Diffusion Theory:
Wetting
Diffusion
Surface
reaction
Ag2Hg3 (γ 1)
Sn8Hg (γ 2)
Hg
γ
Hg
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19. Ag3 Sn
+
Hg
Ag2Hg3
(γ)
(γ 1)
+
Sn8Hg + Ag3Sn + voids
(γ 2)
unreacted (γ)
Ag3Sn (γ
)
Ag2Hg3 (γ 1)
Sn8Hg (γ 2)
voids
Strength
Hg:
Setting expansion
Corrosion resistance
Creep
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20. Ag3Sn (γ
)
Ag2Hg3 (γ 1)
Sn8Hg (γ 2)
voids
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21. High Copper Dental Amalgams
γ 2 Free Amalgams
More than 6% Cu
Admixed
amalgams
Unicompositional
amalgams
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22. Admixed Dental
Amalgams
(9-20% Cu)
Lathe coarse cut
Spherical cut
AgCu
+
50-70%
30-50%
Intermetallic
alloy (lathe cut)
Eutectic alloy
(spherical)
72%Ag
28%Cu
779.4°C
Ag3Sn (γ)
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Dr. Dina Mostafa

23. Setting Reactions of Admixed Amalgam
1- Dissolution of mercury in the alloy powder
[Ag3Sn+ Ag - Cu] + Hg → Ag2Hg3
γ
(eutectic)
(γ )
+ Sn8Hg + [Ag3Sn+ Ag - Cu] + voids
(γ 2)
1
Ag3Sn
Cu6Sn5
(γ
)
Ag2Hg3
(γ 1)
AgCu
Sn8Hg (γ 2)
voids
2- Elimination of γ 2 (Solid State Reaction)
Ag – Cu +
Sn8Hg
(γ 2)
Cu6Sn5 + Ag2Hg3 + Ag-cu unreacted + voids
η
(γ 1)
(eutectic)
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24. Ag3Sn
(γ
)
Ag2Hg3
Cu6Sn5
(γ 1)
(η)
AgCu
voids
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25. Ag3Sn
Cu6Sn5
(γ
)
Ag2Hg3
(γ 1)
AgCu
Sn8Hg (γ 2)
voids
Disadvantages:
1- Sedimentation of one type of the particles
2- Surface oxidation of the silver - copper eutectic
particles during storage
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26. Unicompositional
Dental Amalgams
Composition:
Silver
Tin
Copper 13- 30%.
40-60%.
27 - 30%~
Manufacturing of the powder:
The powder is produced by melting and atomization of
the liquid alloy to produce spherical powder particles.
Each unicompositional spherical powder particle is
composed of γ Ag3Sn phase and ε Cu3Sn (epsilon)
phase which is concentrated near the particle surface.
Ag3Sn
Cu3Sn
Dr. Hala Bahgat
Dr. Dina Mostafa

27. Setting Reaction
[Ag3Sn + Cu3Sn] +
ε
γ
Hg → Ag2Hg3 + Cu6Sn5+ Unreacted Ag Sn + voids
3
Cu6Sn5 γ 1
η
γ
Cu3Sn
Ag2Hg3 (γ 1)
Ag3Sn
Strength
Voids
Corrosion resistance
Creep
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Dr. Dina Mostafa

28. Cu6Sn5
(η)
Ag2Hg3 (γ 1)
Ag3Sn
Voids
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Dr. Dina Mostafa