Dental amalgam - Recent advances.ppt

1. DENTAL AMALGAM WITH
RECENT ADVANCES

2. Overview
• Introduction
• History
• Indications, Contraindications,
Advantages & Disadvantages
• Basic Composition
• Manufacture of Alloy
• Mode of Supply
• Classification of Alloy
• Technical Considerations
• Properties of Amalgam
• Mercury Toxicity
• Newer Advances
• Controversy of Amalgam
• Conclusion

3. Introduction
Alloy

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

5. Indications, Contraindications,
Advantages & Disadvantages

6. Basic Composition
Alloy Powder:
• Silver
• Tin
• Copper
• Zinc
• Indium
• Platinum & Palladium
• Liquid:
• Mercury

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

9. Particle Shape
• Lathe cut
• Spherical
•Spheroidal

10. Mode of Supply
• Powder & Liquid
• Capsule
• Sachets & Pellets
Alloy

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

13. Conventional Low-Copper Alloys
Ag3Sn + Hg  Ag3Sn + Ag2Hg3 + Sn8Hg
Phillip’s Science of Dental Materials 2003
  1 2
Ag3-Sn Alloy
Mercury (Hg)
+
 2
Ag3-Sn + Ag2-Hg3 + Sn8Hg
1
• Composition:
– Silver – 63-70%
– Tin – 26-28%
– Copper- 2-5%
– Zinc – 0-2%

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 

16. Admixed High-Copper Alloys
• Gamma 1 (1) (Ag2Hg3)
surrounds () eta phase
(Cu6Sn5) and gamma ()
alloy particles (Ag3Sn) Ag-Sn
Alloy
1
Ag-Cu Alloy

Ag-Sn
Alloy
Phillip’s Science of Dental Materials 2003
Ag3Sn + Ag-Cu + Hg  Ag3Sn + Ag-Cu + Ag2Hg3 + Cu6Sn5
  1 

17. Single Composition
High-Copper Alloys
• Gamma sphere () (Ag3Sn)
with epsilon coating ()
(Cu3Sn)
• Ag and Sn dissolve in Hg
Ag-Sn Alloy
Ag-Sn Alloy
Ag-Sn Alloy
Mercury (Hg)

Ag
Sn
Ag
Sn
Ag3Sn + Cu3Sn + Hg  Ag3Sn + Cu3Sn + Ag2Hg3 + Cu6Sn5
Phillip’s Science of Dental Materials 2003
  1 
 

18. Single Composition
High-Copper Alloys
• Gamma 1 (1) (Ag2Hg3) crystals
grow binding together partially-
dissolved gamma () alloy
particles (Ag3Sn)
• Epsilon () (Cu3Sn) develops
crystals on surface of
gamma particle (Ag3Sn)
in the form of eta () (Cu6Sn5)
– reduces creep
– prevents gamma-2 formation
Ag-Sn Alloy
Ag-Sn Alloy
Ag-Sn Alloy
1

Ag3Sn + Cu3Sn + Hg  Ag3Sn + Cu3Sn + Ag2Hg3 + Cu6Sn5
Phillip’s Science of Dental Materials 2003
  1 
 

19. Technical Considerations
• Selection of the alloy
• Proportioning of the alloy
• Trituration
• Condensation
• Precarve burnishing
• Carving
• Burnishing
• Finishing and polishing

20. Selection of the alloy

21. • EAMES Technique
– Alloy & mercury 1:1
Proportioning of the alloy

22. Trituration
• Normal mix
• Overtrituration
• Undertrituration
Phillip’s Science of Dental Materials 2003
Hand mixing
Mechanical mixing

23. Condensation

24. Precarve burnishing

25. Carving

26. Burnishing
Ben-Amar Dent Mater 1987

27. Finishing

28. Polishing

29. Properties of Amalgam
• Dimensional change
• Strength
• Corrosion
• Creep

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

31. Strength
Phillip’s Science of Dental Materials 2003
Compressive
Strength (MPa)
% Creep Tensile Strength
(24 hrs) (MPa)
Amalgam Type 1 hr 7 days
Low Copper1 145 343 2.0 60
Admixture2 137 431 0.4 48
Single Composition3 262 510 0.13 64
Amalgam Properties

32. Corrosion
Sutow J Dent Res 1991

33. Creep
Phillip’s Science of Dental Materials 2003

34. Mercury Toxicity

35. Newer Advances
• High copper amalgam
• Bonded amalgam
• Gallium based alloys
• Direct filling silver
• Powder coated technology
• Alloying additions

36. Controversy of amalgam

37. Conclusion

38. Thank you