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AMALGAM

AMALGAM. Dr shabeel pn. DEFINITION. Dental amalgam is a metal like restorative material composed of a mixture of silver/tin/copper alloy and mercury. . HISTORY. Amalgam has been primary restorative material for more than 150 yrs.

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AMALGAM

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  1. AMALGAM Dr shabeel pn

  2. DEFINITION • Dental amalgam is a metal like restorative material composed of a mixture of silver/tin/copper alloy and mercury.

  3. HISTORY • Amalgam has been primary restorative material for more than 150 yrs. • Initially, amalgam restorations were made by dentists filing silver coins and mixing the filings with mercury. • This was made to a putty like mass that was placed into the defective tooth.

  4. USES • AS CLASS 1,2,5 RESTORATION. • AS FOUNDATION- IN COMBINATION WITH RETENTIVE PINS TO RESTORE CROWN. • FOR MAKING DIES. • FOR RETROGRADE ROOT CANAL FILLING. • AS CARIES CONTROL RESTORATION.

  5. Components of dental amalgam 1)Amalgam alloy 2)Mercury

  6. CLASSIFICATION

  7. Classification of dental amalgam alloys

  8. MANUFATURE OF ALLOY POWDER • 1)LATHECUT ALLOY POWDER • 2)SPHERICAL ALLOY POWDER

  9. COMPARISON OF LATHECUT WITH ATOMIZED SPHERICAL POWDER • AMALGAM FROM LATHECUT \ ADMIXED POWDER,TEND TO RESIST CONDEN-SATION BETTER THAN AMALGAM MADE ENTIRELLY FROM SPHERICAL POWDER. • AMALGAM OF SPHERICAL POWDER ARE VERY PLASTIC-CANNOT RELY ON PRESSURE OF CONDENSATION TO ESTABLISH PROXIMAL CONTOUR. • SPHERICAL ALLOYS REQUIRE < Hg THAN LATHECUT ALLOY DUE TO SMALL SURFACE AREA PER VOLUME . • AMALGAM WITH LOW Hg CONTENT –BETTER PROPERTIES.

  10. COMPOSITION

  11. COMPOSITION Low Copper: Silver - 63-70% Tin - 26-29% Copper - 2-5% Zinc – 0-2%

  12. Admixed: Silver – 40-70% Tin - 26-30% Copper-13-30% Zinc - 0-1%

  13. Unicompositional : Silver- 40-60% Tin - 22-30% Copper-13-30% Zinc -0%

  14. FUNCTION OF EACH CONSTITUENT • SILVER:- • MAJOR ELEMENT. • WHITENS ALLOY. • DECREASES CREEP. • INCREASES STRENGTH. • INCREASES EXPANSION ON SETTING. • INCREASES TARNISHING RESISTANCE IN RESULTING AMALGAM.

  15. TIN:- • CONTROLS THE REACTION BETWEEN Ag & Hg. • REDUCES STRENGH & HARDNESS. • REDUCES RESISTANCE TO TARNISH & CORROSION. • COPPER:- • INCREASES HARDNESS & STRENGTH. • INCRESES SETTING EXPANSION.

  16. ZINC:- • SMALL AMOUNT –NOT AFFECT SETTING REACTION \ PROPERTIES OF AMALGAM. • ACT AS A SCAVENGER \ DEOXIDISER. • WITHOUT Zn ALLOYS ARE MORE BRITTLE & AMALGAM FORMED LESS PLASTIC. • CAUSES DELAYED EXPANSION , IF CONTAMINATED WITH MOISTURE DURING MANIPULATION. • BENEFICIAL EFFECT ON CORROSION & MARGINAL INTEGRATION.

  17. PLATINUM:- • HARDENS THE ALLOY & INCREASES THE RESISTANCE TO CORROSION. • PALLADIUM:- • HARDENS THE ALLOY. • WHITENS THE ALLOY. • PRE AMALGAMATED ALLOYS:- SMALL AMOUNT UPTO 3% OF Hg IS ADDED TO THE ALLOY BY MANUFACTURER.

  18. RECENT DEVELOPMENT OF D.AMALGAM • Mercury free direct filling amalgam alloys • Gallium based alloys • Low mercury amalgams • Indium in mercury

  19. AMALGAMATION

  20. AMALGAMATION AND RESULTING MICROSTRUCTURE. • DURING TRITURATION Ag & Sn IN THE OUTER PORTION OF THE PARTICLES DISSOLVE INTO Hg . Hg DIFFUSES INTO ALLOY PARTICLES. • Hg HAS LIMITED SOLUBILITY FOR Ag (.035WT%) & Sn (.6wt%). • AMALGAMATION OCCURS WHEN Hg CONTACTS THE SURFACE OF Ag-Sn ALLOY PARTICLES. • WHEN THE SOLUBILITY IN Hg EXEEDED- CRYSTALS OF 2 BINARY METTALIC COMPOUND PRECIPITATE INTO Hg. THESE ARE BCC Ag2Hg3 & HEXAGONAL Sn7-8Hg.

  21. Low copper Alloys • Ag3Sn+Hg > Ag2Hg3 + Sn8Hg + Ag3Sn (r) (r1) (r2) (unreacted)

  22. High Copper Alloys • Admixed alloys Ag3Sn + Ag-Cu +Hg>Ag2Hg3 + Sn8Hg + Ag3Sn + AgCu LATER, Sn8Hg + AgCu > Cu6Sn5 + Ag2Hg3 (r2) (eutectic) (n) (r1)

  23. Single Composition AgSnCu+ Hg > Cu6Sn5 + Ag2Hg3 +AgSnCu

  24. PROPERTIES OF SET AMALGAM. • MICROLEAKAGE. • DIMENSIONAL CHANGES. • STRENGTH. • CREEP. • TARNISH & CORROSION.

  25. MICROLEAKAGE. • OCCURS DUE TO PENETRATION OF FLUIDS OR DEBRIS AROUND THE MARGINS THAT CAN LEAD TO SECONDARY CARIES. AMALGAM HAS GOT A SELF SEALING PROPERTY – CORROSION PRODUCT WILL FILL THE TOOTH RESTORATION INTERFACE & PREVENT MICROLEAKAGE.

  26. ACCORDING TO ADA SPECIFICATION ,IT SHOULD NOT EXPAD OR CONTRACT MORE THAN 20u\cm AT 37 degree celcious BETWEEN 5min AND 24hrs AFTER BEGINNING OF TRITURATION. MODERN AMALGAM ALWAYS SHOWS CONTRACTION. OLDER AMALGAM SHOWS EXPANSION.

  27. CONTRACTION. • RESULT IN MICROLEAKAGE & SECON –DARY CARIES. • FACTORS FAVOURING CONTRACTION • LONGER TRITURATION TIME. • HIGHER CONDENSATION PRESSURE. • SMALL PARTICLE SIZE. • Hg ALLOY RATIO.

  28. EXPANSION. • IF A Zn CONTAINING LOW Cu \ HIGH Cu IS CONTAMINATED DURING TRITURATION \ CONDENSATION ,A LARGE EXPANSION TAKE PLACE.IT USUALLY STARTS FROM 3-5 DAYS AND CONTINUE FOR MONTHS CREATING VALUES UPTO MORE THAN 400um – DELAYED EXPANSION. • H2O + Zn ZnO + H2 • PROTRUSION OF RESTORATION OUT OF CAVITY • INCREASE CREEP • INCREASE MICROLEAKAGE • PITTED SURFACE OF RESTORATION & CORROSION.

  29. STRENGTH. • AMALGAM IS SRONGEST IN COMPRE-SSION & MUCH WEAKER IN TENSION & SHEAR , THE PREPARD CAVITY DESIGN SHOULD MAXIMIZE THE COMPRESSION FORCES IN SERVICE & MINIMIZE TENSION \ SHEAR FORCES.

  30. CREEP. • DEFINED AS A TIME DEPENDENT PLASTIC DEFORMATION UNDER CONSTANT STRESS. • ACCORDING TO ADA SPECIFICATION NO 1 CREEP SHOULD BE BELOW 3%. • CREEP OF LOW Cu AMALGAM IS 0.8-8% & HIGH Cu IS 0.4-1%.

  31. MANIPULATION

  32. MANIPULATION (1) Selection of materials (2) Mercury:Alloy ratio (3) Trituration (4) Mulling (5) Condensation (6) Shaping & finishing

  33. SELECTION OF MATERALS • ALLOY • MERCURY • DISPENSORS • PRE PROPOTION CAPSULE

  34. MERCURY: ALLOY RATIO • Squeezing cloth • Increased dryness technique • EAMES technique

  35. TRITURATION (1)Hand mixing (2)Mechanical

  36. MULLING • Improve homogenity of mass & get a single consistent mix

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