Amalgam Flashcards

1
Q

What is the general setting reaction for amalgams?

A

Alloy + Hg = Dental amalgam

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2
Q

What is the typical mercury/alloy ratio?

A

0.5

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3
Q

What are the major elements in the alloy for dental amalgam?

A

Ag (primary)
Sn (Secondary)
Cu (2-30%)
Zen (0-1%)

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4
Q

How can one obtain a mercury exposure?

A

Skin contact, inhalation of vapor, airborne droplets

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5
Q

T/F: Some patients may exhibit an allergic skin reaction to dental amalgams.

A

True

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6
Q

What are operator precaution when working with amalgam?

A

Wear face mask and use water spray and high vac suction when working with amalgams.

periodically have mercury levels checked by urinalysis

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7
Q

How should scrap dental amalgam be stored?

A

In a cool space in capped, unbreakable jar holding water with finely divided sulfur.

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8
Q

T/F: Spherical particles are wetted with less mercury than lathe-cut particles.

A

TRUE

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9
Q

T/F: Spherical particles resist forces of condensation more than lathe-cut particles.

A

FALSE

Lathe-cut resist condensation better

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10
Q

T/F: Low-copper products have greater clinical longevity in restorations.

A

FALSE.

High-copper is better

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11
Q

What is the major benefit of heat treating the alloy for dental amalgam?

A

Provides manufacturer control of setting time.

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12
Q

What is the general setting reaction for dental amalgam?

A

Gamma (starting alloy particles) + Hg (liquid) -> reaction phases (matrix) + unreacted alloy particles (core)

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13
Q

What would be the bricks in the set amalgam? Mortar?

A

“Bricks” = alloy particles

“Mortar” = reaction phases

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14
Q

What is the major reaction phase in both low and high copper amalgams?

A

Gamma1

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15
Q

What forms instead of gamma2 in high-copper amalgams?

A

n’

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16
Q

Which amalgam has the most contraction over 24 hours?

A

LCL (Low copper, lathe-cut)

17
Q

Which amalgam has a slight expansion during 24 hours of being set?

A

HCB (high-copper blend)

18
Q

What causes expansion in the amalgam?

A

Formation and growth of reaction phases

19
Q

What causes contraction of amalgam?

A

Final absorption of mercury by remaining alloy particles

20
Q

What is the strongest alloy phase?

A

Starting alloy particles (gamma)

21
Q

What is the weakest phase?

A

gamma2 in low-copper amalgams

Most prone to corrosion

22
Q

Why might corrosion occurs?

A

Corrosion can occur do to lower oxygen levels caused by plaque or lower pH of saliva. Crevices, margins, and scratches in amalgam are most prone to corrosion.

23
Q

T/F: Amalgam is a brittle material.

A

True

24
Q

T/F: Amalgam has a high tensile strength.

A

False.

Has a high compressive strength.

25
Q

What type of amalgam is affected by creep?

A

Low copper amalgam

26
Q

What is creep?

A

Scrapping off of gamma2 layer at the margins causing weakened marginal integrity

27
Q

T/F: Moisture contamination is a problem with Zn-containing dental amalgam.

A

True