dental amalgam
DESCRIPTION
dental education ebookTRANSCRIPT
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Dental AmalgamDental Amalgam
Prepared by : Dr.Dalia A. Abu-Alena in
MDS,BDS
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I.I. Dental AmalgamDental 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.
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II.II. Composition of Dental Composition of Dental Amalgam:Amalgam:
SilverTin CopperZincIndium and PalladiumMercury
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III.III. Classification of Dental Classification of Dental Amalgam AlloysAmalgam Alloys
1. Conventional (Low Copper )Alloy:
a. Lathe-cut Particles.
b. Spherical Particles
(a)
(b)
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Classification of Dental Classification of Dental Amalgam AlloysAmalgam Alloys
2. High copper alloy:
a. Admix Alloy.
b. Unicompositional
alloy.
(a)
(b)
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IV.IV. Silver -Tin Binary SystemSilver -Tin Binary System
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V.V. Setting Reactions of Setting Reactions of Dental Amalgams:Dental Amalgams:
1) Low Copper Alloy:
Ag3Sn + Hg Ag2Hg3 + Sn8Hg + Ag3Sn ( ) (1) ( 2) () 54%-56% 11-13% 27-35%
Hg 12
Hg
1+ 2
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Setting Reactions of Dental Setting Reactions of Dental Amalgams:Amalgams:
2) High copper alloya) Admixed alloy
1. Ag3Sn + AgCu + Hg Ag2Hg3 + Sn8Hg + Ag3Sn + AgCu ( ) (1 ) (2 ) ( )
2. Sn8Hg + AgCu Cu6Sn5 + Ag2Hg3 + Ag3Sn (2) ( ) (1 ) ( )
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Setting Reactions of Dental Setting Reactions of Dental Amalgams:Amalgams:
2) High copper alloyb) Unicompositional Alloy:
Ag3Sn + Cu3Sn + Hg Cu6Sn5 + Ag2Hg3
( ) ( ) ( ) (1 )
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Microstructure of Set Low Microstructure of Set Low Copper Amalgam.Copper Amalgam.
(Ag3Sn)
2(Sn8Hg)
Voids
1(Ag2Hg3)
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Microstructure of Set High-Microstructure of Set High-Copper Admixed Amalgam.Copper Admixed Amalgam.
1(Ag2Hg3)
(Ag3Sn)
Eutectic(Ag3Cu2)(Cu6Sn5)
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VI.VI. Properties of Dental Properties of Dental AmalgamAmalgam
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VI.VI. Properties of Dental Properties of Dental AmalgamAmalgam
1. Compressive strength2. Tensile Strength3. Elastic Modulus4. Creep5. Dimensional Changes6. Tarnish and Corrosion:
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VI.VI. Properties of Dental AmalgamProperties of Dental Amalgam
1. Compressive strength-Amalgam is strongest in compression
and much weaker in tension and shear.
-HCU materials have the highest compressive strength.
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Properties of Dental AmalgamProperties of Dental Amalgam
2. Tensile Strength:-Amalgam is strongest in compression
and much weaker in tension and shear.
-HCU materials have the highest early tensile strength.
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Properties of Dental AmalgamProperties of Dental Amalgam
Strength of various phases:1. Unreacted Ag3Sn () phase.
(strongest)
2. Ag2Hg3(1)phase.
3. Sn8Hg (2)phase.(weakest)
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Properties of Dental AmalgamProperties of Dental Amalgam
3. Elastic Modulus:-High- copper alloys are stiffer than
low-copper alloys.
-Amalgam are viscoelastic.
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Properties of Dental AmalgamProperties of Dental Amalgam
4. 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.
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Properties of Dental AmalgamProperties of Dental Amalgam
5. Dimensional Changes:-Low-copper alloy have the greatest
dimensional change(-19.7m/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).
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Properties of Dental AmalgamProperties of Dental Amalgam
5. Dimensional Changes:
Delayed Excessive Expansion ?
Zinc – containing alloy + Moisture.
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Properties of Dental AmalgamProperties of Dental Amalgam
6. Tarnish and Corrosion:-Corrosion of various phases:
- Ag3Hg3 ( 1)…..Least corrodible.
-Ag3Sn().
-Ag3Cu2(eutectic).
-Cu3Sn( ).
-Cu6Sn5( ).
-Sn8Hg (2).…….Most corrodible
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Properties of Dental AmalgamProperties of Dental Amalgam
6. Tarnish and Corrosion:
Excessive corrosion can lead to : Increase porosity. Reduced marginal integrity. Loss of strength. Release of metallic products .
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VII.VII. Manipulation of Dental Manipulation of Dental Amalgam:Amalgam:
1) Selection of alloy.
2) Proportioning and dispensing.
3) Trituration.
4) Condensation.
5) Carving.
6) Finishing and polishing.
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Manipulation of Dental Amalgam:Manipulation of Dental Amalgam:
1) Selection of alloy:
It is estimated that the majority of the dental amalgams currently placed are high – copper alloys , spherical- unicopositional or admixed types .
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Manipulation of Dental Amalgam:Manipulation of Dental Amalgam:
2) Proportioning and dispensing:
proportioned capsules containing alloy particles and mercury in compartments separated by a disk or membrane are available.
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Manipulation of Dental Amalgam:Manipulation of Dental Amalgam:
3) 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 .
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Manipulation of Dental Amalgam:Manipulation of Dental Amalgam:
3) Trituration:
- Hand Trituration
-Mechanical Trituration
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Manipulation of Dental Amalgam: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.
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Manipulation of Dental Amalgam:Manipulation of Dental Amalgam:
4) Condensation:
-Hand Condensation.
-Mechanical Condensation.
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Manipulation of Dental Amalgam:Manipulation of Dental Amalgam:
5) Carving:
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Manipulation of Dental Amalgam:Manipulation of Dental Amalgam:
6) Finishing and polishing:
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Mercury ToxicityMercury Toxicity
Properties of mercury.
Sources of mercury exposure.
Mercury hygiene.
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Recent Modifications of Dental Recent Modifications of Dental Amalgam AlloysAmalgam Alloys
Indium containing amalgam.Palladium containing amalgam.Copper amalgam.Mercury free gallium based alloy.