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Dentistry > Dental Amalgam > Flashcards

Dental Amalgam Flashcards

1
Q

An alloy, one of the constituents of which is mercury

A

Silver Paste

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2
Q

An alloy made by mixing Hg with Ag-Sn dental amalgam alloy

A

Silver Paste

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3
Q 
Increases expansion
Retards setting time
Enhances strength
Decrease flow
Resist tarnish/corrosion
A

Silver

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4
Q 
Unites with Hg with difficulty
Reduces setting time
Increases expansion
Increases strength and hardness
Reduces flow
A

Copper

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5
Q 
Combines readily with Hg
Retards setting time
Improves platsicity
Reduces expansion
Increases flow
A

Tin

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6
Q 
Combines readily with Hg
Causes expansion increases setting time
Increases flow
Inhibits oxidation 
Decreases porosity
Provides better clinical performance
A

Zinc

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7
Q

Other Constituents of Dental Amalgam

A

Indium (In)
Palladium (Pd)
Mercury (Hg)

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8
Q 
Decreases surface tension
Reduces amount of mercury necessary
Reduces emitted mercury vapor
Reduces creep and marginal breadown
Increases strength
Must be used in admixed alloys
5%
A

Indium (In)

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9
Q

Reduces corrosion
Greater luster
e.g. Vallant PhD (Ivoclar Vivadent)
0.5%

A

Palladium (Pd)

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10
Q

Activates reaction

Only pure metal that is liquid at room temperature

A

Mercury (Hg)

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11
Q

Classification of Amalgam

A

Amalgam alloy particle geometry and size
Copper content
Zinc content

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12
Q 
Irregular particle pack poorly and require a large amount of Hg (50-60%)
Precapsulated amalgam (spherical) has 42-45% Hg
A

Alloy-Mercury ratio

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13
Q

Require less Hg
Smaller surface area, easier to wet
40 to 45%

A

Spherical Alloys

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14
Q

Reaction of Amalgam

A

Mercury + Silver-Tin -> Silver-Tin phase + Silver-Mercury phase + Tin-Mercury Phase

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15
Q

Called the gamma phase

Composed of unreacted alloy particle

A

Silver-Tin Phase

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16
Q

Ag3Sn
Unreacted alloy
Strongest phase and corroded the least
Forms 30% of volume set amalgam

A

Gamma

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17
Q

The amount of mercury needed to wet all particles and occupy the space between the particles range from ____________ mercury by weight

A

40-60%

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18
Q

Called the gamma one

A

Silver-Mercury Phase

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19
Q 
Ag2Hg3
Matrix for unreacted alloy
Second strongest phase
10 micron grains binding gamma
60% of volume
A

Gamma 1

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20
Q

Called the gamma two

A

Tin-Mercury Phase

21
Q

Sn8Hg
Weakest and softest phase
Corrodes fast,
Voids from corrosion yeilds Hg which reacts with more gamma
10% of volume
Volume decreases with time due to corrosion

A

Gamma 2

22
Q

2 phenomenon during hardening of amalgam

A

Solution

Crystallization

23
Q

When Hg comes in contact with amalgam alloy, the particles are wt by mercury and begins to absorb it
The solution of mercury into silver-tin particles leads to the formation of the surface of Ag-Hg and Sn-Hg phases
The crystallisation of the gamma1 and 2 phases and their subsequent growth leads to hardening of amalgam

A

Crystallisation

24
Q

Factors affecting Setting Time (4)

A

Effect of alloy/mercury ratio
Condensation pressure
Particle size
Particle shape

25
Q

More mercury increases expansion - as well as setting time

A

Effect of alloy/mercury ratio

26
Q

As the condensation pressure increases, the tendency for shrinkage increases. Increased condensation pressure results in removal of more excess mercury and a faster setting reaction

A

Condensation Pressure

27
Q

As the particle size decreases, the total particle surface area increases. This results in a faster setting reaction, as long as no additional mercury is added. Amalgams made from smaller dental amalgam alloy particles shrink more as long as the mercury ratio is not high

A

Particle size

28
Q

Spherical particles need less mercury because of the smaller total surface area. Thus, spherical amalgams often set faster than lathe-cut amalgams. Because of the lower mercury ratio, spherical amalgams often shrink more than lathe-cut alloys

A

Particle Shape

29
Q

Properties of amalgam

A

Dimensional change

Strength

30
Q

Causes amalgam to expand and contract
Diffusion of mercury into alloy particles causes an expansion
Spherical alloys have more contraction (less Hg)
Greater condensation = higher contraction

A

Dimensional Change

31
Q

Amalgam does not develop sufficient strength to resist the forces pf mastication
Tensile strength - 7100 psi
Compressive strength - 45,500 psi
Develops slowly

A

Strength

32
Q

Dentist Controlled Variable

A

Manipulation

33
Q

4 properties under manipulation

A

Trituration
Condensation
Burnishing
Polishing

34
Q

Process of manual mixing of alloy with Hg
Done by proportioning Hg and alloy into a mortar grinding the mixture with a pestle
Mixing time refer to manufacturers recommendation

A

Trituration

35
Q

Sticks to capsule
Decrease working and setting time
Causes higher contraction

A

Overtrituration

36
Q

Grainy, crumbly material

A

Undertrituration

37
Q

Types of trituration

A

Hand

Mechanical

38
Q

Done by proportioning Hg and alloy into a mortar and grinding the mixture with a pestle

A

Hand trituration

39
Q

Use of amalgamator

A

Mechanical trituration

40
Q

A hallow tube with rounded ends constructed as two pieces that could friction fit or screwed together

A

Reusable capsule

41
Q

Pre-proportioned

A

Precapsulated

42
Q

Phases of Burnishing

A

Pre-carve
Post-carve
Combined

43
Q

Removes excess mercury

Improves margin adaptation

A

Pre-carve

44
Q

Improves smoothness

A

Post-carve

45
Q

Less leakage

A

Combined

46
Q

Increased smoothness
Decreased plaque retention
Decreased corrosion
Clinically effectivev

A

Polishing

47
Q

Uses squeeze cloth to remove excess mercury

A

Mercury rich mixtures

48
Q

Illness associated with mercury

A

Allergies, chronic fatigue, depression, GI disorders, immune system suppression, endocrine disorders, periodontal disease, neurological problems, reproductive disorders, birth defects, kidney disease, heart problems, hypertension, repiratory disorder, cancer, and skin disease

49
Q

Sources of mercury

A

Mercury vapours released from stored materials
Amalgamator aerosols
Spillage during restoration procedure
Amalgam and mercury in plumbing and sewer system
Amalgam scrap container

Dentistry (1 decks)

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