Amalgam

Question 1

Dental Amalgam, prior to mixing, consists of a powder of

Answer 1

amalgam alloy and a metallic liquid of elemental mercury.

Question 2

Dental Amalgam consists of a variety of intermetallic compounds

Answer 2

before and after mixing and final setting.

Question 3

intermetallic, also called an intermetallic compound, or an intermetallic alloy, or an ordered intermetallic alloy, or a long-range-ordered alloy

Answer 3

is a solid-state compound exhibiting metallic bonding, defined stoichiometry and ordered crystal structure

Question 4

amalgam alloy powder consists of a metallic phase called

Answer 4

gamma (γ), a silver-tin alloy consisting of the intermetallic compound, Ag3Sn

Question 5

Various alloy particle types include

Answer 5

Comminuted (lathe-cut or pulverized)
• Spherical
• Blended: comminuted + spherical

Question 6

Spherical alloy requires less mercury

Answer 6

to adequately titurate.

Question 7

Spherical alloy easier to

But harder to

Answer 7

Condense

Create contact

Question 8

Amalgam Alloy Composition Types:

Answer 8

1) LOW COPPER (2-5%);

2) HIGH COPPER (10-30%)

Question 9

CONVENTIONAL AMALGAM (low copper) reaction is a

Answer 9

solution precipitation process.

Question 10

GAMMA is

Answer 10

SILVER-TIN phase.

Question 11

GAMMA-1

Answer 11

SILVER-MERCURY phase.

Question 12

GAMMA-2

Answer 12

TIN-MERCURY phase.

Question 13

Gamma-2 is a problem in low copper alloys bc:

Answer 13

1) corrosion-prone;
2) weakest component;
3) connecting blade-like geometry
4) penetrating corrosion

Question 14

HIGH COPPER AMALGAMS:

Answer 14

• Suppression of gamma-2 phase (Sn-Hg)
• Preferential formation of Sn-Cu
• Immediate or delayed gamma-2 suppression

Question 15

ELIMINATION OF GAMMA-2 occurs by two distinct mechanisms:

Answer 15

Admixed and unicompositional

Question 16

Admixed

Answer 16

gamma-2 forms around silver-tin (gamma) particles and is eliminated around silver-copper particles

Question 17

Unicompositional

Answer 17

Ag-Sn-Cu particles first function like Ag-Sn particles, then they function like Ag-Cu particles, above.

Question 18

SOURCE OF COPPER - HIGH COPPER AMALGAM:

Answer 18

silver-copper (Cu3Sn) “epsilon” phase

Question 19

HIGH-COPPER ADVANTAGES

Answer 19

• improved strength
• corrosion resistance
• marginal integrity
• less creep

Question 20

DISPERSALLOY High copper

Answer 20

• Blended-Admixed-Dispersion
• Traditional lathe cut particles
• Spherical silver-copper eutetic

Question 21

UNICOMPOSITIONAL “HIGH-COPPER” AMALGAM: Reaction Mechanism:

Answer 21

Ag-Sn-Cu + Hg Gamma-1 + Eta + Ag-Sn-Cu

Alloy particles Mercury Ag-Hg Cu-Sn Alloy particles

Question 22

TRITURATION

Answer 22

Combining amalgam alloy with mercury by vigorous mixing to form a plastic mass of dental amalgam

Question 23

CONDENSATION

Answer 23

Adaptation of the plastic dental amalgam mass into the cavity preparation by compressing with pressure

Question 24

Working time

Answer 24

DECREASED by over-trituration for all types

Question 25

Contraction

Answer 25

SLIGHTLY INCREASED by over-trituration for all types

Question 26

Compressive/Tensile strength

Answer 26

INCREASED by over-trituration for lathe-cut MAXIMUM by normal trituration for spherical

Question 27

Creep

Answer 27

Permanent deformation under load in a set material

INCREASED by over-trituration, DECREASED by under-trituration

Question 28

Heating

Answer 28

INCREASED by overtrituration, speeding reaction rate

Question 29

Amalgam displays two types of dimensional change:

Answer 29

1) initial or setting change; 2) delayed or secondary.

Question 30

BEST MANAGEMENT PRACTICES

Answer 30

• use precapsulated alloys
• recycle used capsules
• salvage contact amalgam / recycle
• use chairside traps / recycle
• recycle vacuum filter contents
• DON’T incinerate extracted teeth with amalgam restorations
• DON’T use bleach in suction lines