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Dental Amalgam

Dental Amalgam. Prepared by : Dr.Dalia A. Abu-Alena in MDS,BDS. Dental Amalgam. Amalgam: is an alloy of mercury with one or more other metals.

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Dental Amalgam

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  1. 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% 11-13% 27-35% 1  Hg   2 Hg 2 1+

  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(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 • 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.

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