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Flashcards in Amalgam Deck (30)
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1
Q

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

A

amalgam alloy and a metallic liquid of elemental mercury.

2
Q

Dental Amalgam consists of a variety of intermetallic compounds

A

before and after mixing and final setting.

3
Q

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

A

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

4
Q

amalgam alloy powder consists of a metallic phase called

A

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

5
Q

Various alloy particle types include

A

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

6
Q

Spherical alloy requires less mercury

A

to adequately titurate.

7
Q

Spherical alloy easier to

But harder to

A

Condense

Create contact

8
Q

Amalgam Alloy Composition Types:

A

1) LOW COPPER (2-5%);

2) HIGH COPPER (10-30%)

9
Q

CONVENTIONAL AMALGAM (low copper) reaction is a

A

solution precipitation process.

10
Q

GAMMA is

A

SILVER-TIN phase.

11
Q

GAMMA-1

A

SILVER-MERCURY phase.

12
Q

GAMMA-2

A

TIN-MERCURY phase.

13
Q

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

A

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

14
Q

HIGH COPPER AMALGAMS:

A
  • Suppression of gamma-2 phase (Sn-Hg)
  • Preferential formation of Sn-Cu
  • Immediate or delayed gamma-2 suppression
15
Q

ELIMINATION OF GAMMA-2 occurs by two distinct mechanisms:

A

Admixed and unicompositional

16
Q

Admixed

A

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

17
Q

Unicompositional

A

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

18
Q

SOURCE OF COPPER - HIGH COPPER AMALGAM:

A

silver-copper (Cu3Sn) “epsilon” phase

19
Q

HIGH-COPPER ADVANTAGES

A
  • improved strength
  • corrosion resistance
  • marginal integrity
  • less creep
20
Q

DISPERSALLOY High copper

A
  • Blended-Admixed-Dispersion
  • Traditional lathe cut particles
  • Spherical silver-copper eutetic
21
Q

UNICOMPOSITIONAL “HIGH-COPPER” AMALGAM: Reaction Mechanism:

A

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

Alloy particles Mercury Ag-Hg Cu-Sn Alloy particles

22
Q

TRITURATION

A

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

23
Q

CONDENSATION

A

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

24
Q

Working time

A

DECREASED by over-trituration for all types

25
Q

Contraction

A

SLIGHTLY INCREASED by over-trituration for all types

26
Q

Compressive/Tensile strength

A

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

27
Q

Creep

A

Permanent deformation under load in a set material

INCREASED by over-trituration, DECREASED by under-trituration

28
Q

Heating

A

INCREASED by overtrituration, speeding reaction rate

29
Q

Amalgam displays two types of dimensional change:

A

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

30
Q

BEST MANAGEMENT PRACTICES

A
  • 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