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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

Dental Amalgam

Prepared by :

Dr.Dalia A. Abu-Alena in

MDS,BDS

dental amalgam1
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.
slide3

Amalgam

Advantages

Disadvantages

composition of dental amalgam
Composition of Dental Amalgam:
  • Silver
  • Tin
  • Copper
  • Zinc
  • Indium and Palladium
  • Mercury
classification of dental amalgam alloys
Classification of Dental Amalgam Alloys
  • Conventional (Low Copper )Alloy:
    • Lathe-cut Particles.
    • Spherical Particles

(a)

(b)

classification of dental amalgam alloys1
Classification of Dental Amalgam Alloys
  • High copper alloy:
    • Admix Alloy.
    • Unicompositional alloy.

(a)

(b)

setting reactions of dental amalgams
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+

setting reactions of dental amalgams1
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) ( )
setting reactions of dental amalgams2
Setting Reactions of Dental Amalgams:
  • High copper alloy
    • Unicompositional Alloy:

Ag3Sn + Cu3Sn + Hg Cu6Sn5 + Ag2Hg3

( ) (  ) (  ) (1)

microstructure of set low copper amalgam
Microstructure of Set Low Copper Amalgam.

(Ag3Sn)

2(Sn8Hg)

Voids

1(Ag2Hg3)

microstructure of set high copper admixed amalgam
Microstructure of Set High-Copper Admixed Amalgam.

1(Ag2Hg3)

Eutectic(Ag3Cu2)

(Cu6Sn5)

(Ag3Sn)

properties of dental amalgam1
Properties of Dental Amalgam
  • Compressive strength
  • Tensile Strength
  • Elastic Modulus
  • Creep
  • Dimensional Changes
  • Tarnish and Corrosion:
properties of dental amalgam2
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.

properties of dental amalgam3
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.

properties of dental amalgam4
Properties of Dental Amalgam
  • Strength of various phases:
    • Unreacted Ag3Sn () phase. (strongest)
    • Ag2Hg3(1)phase.
    • Sn8Hg (2)phase.(weakest)
properties of dental amalgam5
Properties of Dental Amalgam
  • Elastic Modulus:

-High- copper alloys are stiffer than low-copper alloys.

-Amalgam are viscoelastic.

properties of dental amalgam6
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.

properties of dental amalgam7
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).

properties of dental amalgam8
Properties of Dental Amalgam
  • Dimensional Changes:

Delayed Excessive Expansion ?

Zinc – containing alloy + Moisture.

properties of dental amalgam9
Properties of Dental Amalgam
  • Tarnish and Corrosion:

-Corrosion of various phases:

- Ag3Hg3 ( 1)…..Least corrodible.

-Ag3Sn().

-Ag3Cu2(eutectic).

-Cu3Sn( ).

-Cu6Sn5( ).

-Sn8Hg (2).…….Most corrodible

properties of dental amalgam10
Properties of Dental Amalgam
  • Tarnish and Corrosion:

Excessive corrosion can lead to :

  • Increase porosity.
  • Reduced marginal integrity.
  • Loss of strength.
  • Release of metallic products .
manipulation of dental amalgam
Manipulation of Dental Amalgam:
  • Selection of alloy.
  • Proportioning and dispensing.
  • Trituration.
  • Condensation.
  • Carving.
  • Finishing and polishing.
manipulation of dental amalgam1
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 .

manipulation of dental amalgam2
Manipulation of Dental Amalgam:
  • Proportioning and dispensing:

proportioned capsules containing alloy particles and mercury in compartments separated by a disk or membrane are available.

manipulation of dental amalgam3
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 .

manipulation of dental amalgam4
Manipulation of Dental Amalgam:
  • Trituration:

- Hand Trituration

-Mechanical Trituration

manipulation of dental amalgam5
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.
manipulation of dental amalgam6
Manipulation of Dental Amalgam:
  • Condensation:

-Hand Condensation.

-Mechanical Condensation.

manipulation of dental amalgam8
Manipulation of Dental Amalgam:
  • Finishing and polishing:
mercury toxicity
Mercury Toxicity
  • Properties of mercury.
  • Sources of mercury exposure.
  • Mercury hygiene.
recent modifications of dental amalgam alloys
Recent Modifications of Dental Amalgam Alloys
  • Indium containing amalgam.
  • Palladium containing amalgam.
  • Copper amalgam.
  • Mercury free gallium based alloy.