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Dental Materials Part 2 > Final Exam: Amalgams > Flashcards

Final Exam: Amalgams Flashcards

1
Q

What is an amalgam?

A

Alloy of mercury with other metal(s)

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2
Q

What do we use amalgam?

    • What’s the cost like?
    • Easy or difficult to use?
    • What’s the proven track record?
    • Why do we use it over composite?
A
    • Inexpensive
    • Ease of use
    • Proven track record: (x) > 100 years
    • Resin Free: Less allergies than composite
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3
Q

Basic constituents of amalgam:
COPPER (CU)
– What does it tie up? This helps reduce what kind of formation?
– Copper helps increase what in the amalgam?
– What three things does it reduce?
– If you increase CU, what happens?
– How is CU added to amalgam?

A

– ties up tin
– reducing gamma-2 formation
– increases strength
– reduces tarnish and corrosion
– reduces creep: deformation under steady pressure
—reduces marginal deterioration
-High copper = much better
Cu added by epsilon coating

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4
Q

Basic constituents of amalgam:
Zinc (Zn)
– Zinc is used in what and help do what in amalgam?
– What kind of anode is it?
- How does it help in providing better clinical performance?
- Zinc, in the presence of low CU allows, what does it do to the amalgam? …. and under what circumstance?

A
    • Zinc is used in manufacturing
      • Decreases oxidation of other elements (so no rusting)
      • Sacrificial anode
    • Less marginal breakdown
    • Causes delayed expansion with low Cu allows
        • If contaminated with moisture during condensation. ( H2O + Zn –> ZnO + H2 )
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5
Q

Basic composition of amalgam: (single composition)

What are the two matrix present in amalgam?

A

Matrix:

- - Ag2Hg3 called gamma 1
       - - cement 
- - Sn8Hg called gamma 2 
       - - Voids, weak, BAD GUY
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6
Q

Single Composition High-Copper Alloys

In High-Copper Alloys:

    • What kind of sphere is associated with it? Give formula as well.
    • What kind of coating is associate with it? Give formula as well.
    • Silver and Tin dissolves in what element?
    • Tin has affinity for what?
A

– Gamma sphere (g) (Ag3Sn)
– epsilon coating (e) (Cu3Sn)
– Ag and Sn dissolve in Hg
(Silver) (tin)
– Tin has affinity for copper

Gamma Epsilon
Ag3Sn + Cu3Sn + Hg -> Ag3Sn + Cu3Sn + Ag2Hg3 + Cu6Sn5
Gamma Eta

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7
Q

Single Composition Spherical (SCS)

    • Greater or less condensation force?
    • What size of condenser would you use with SCS particles?
    • What kind of sphere is associated with gamma particles?
A
    • Less condensation force
    • Larger condenser
    • Gamma particles as 20 micron spheres
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8
Q

Dimensional Change

    • Most high-copper amalgams undergo what kind of contraction?
    • What do contractions leave?
    • Initial leakages causes what type of sensitivity
  • Over time, the marginal gap is reduced as a result of what?
A
    • Most high-copper amalgams undergo a net contraction
      1) Contraction leaves marginal gap
      a) initial leakage
      - aa)post-operative sensitivity
    • Reduced with corrosion over time seals the marginal gap over time
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9
Q

Dimensional Change

The net contraction of amalgam is dependent on three things. What are they?

A

1) Type of alloy
2) Condensation technique
3) Trituration time

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10
Q

Dimensional Change

    • What type of alloy plays a role in the net contraction?
    • This type of alloy has MORE contraction due to what reason?
A
    • spherical alloys (have more contraction)

- - More contraction due to LESS MERCURY

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11
Q

When using the condensation technique:

By having a greater condensation, what kind of contraction will you have?

A

HIGHER contraction

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12
Q

Trituration time:

Overtrituration (of the amalgam) causes what kind of contraction?

A

Higher contraction

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13
Q

Strength of amalgam:

What two characteristics are used to measure the strength of a particular amalgam?

    • In thin sections of amalgam, what’s the strength like and why?
    • What to do with caution points on amalgam?
A
    • Higher compressive vs. tensile strength
    • Weak in thin sections
        • because UNSUPPORTED EDGES FRACTURE (brittle)
    • Wait till the amalgam completely settles before chewing since there will be caution points after amalgam restoration.
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14
Q

Corrosion:

    • Corrosion of the treated teeth results to what sort of strength?
  • – Corrosion does what to the margins?
  • – Using a low copper or high copper amalgam material, corrosion will last for how long?
    - What phases accompany with these two copper materials.
A
    • Reduces strength
    • Seals margins
      * low copper:
      - - 6 months
      - - SnO2, SnCl
      - - gamma-2 phase
  •   * high copper: 
         - - 6 - 24 months
         - - SnO2 , SnCl, CuCl
         - - eta-phase (Cu6Sn5)
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15
Q

What is Creep?

A

slow deformation of amalgam placed under a constant load.

load less than that necessary to produce fracture

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16
Q

Creep is correlated with what kind of breakdown?

A

Correlates with MARGINAL breakdown.

17
Q

The presence of what kind of copper amalgams have creep resistance?

    • High-copper amalgams prevent the formation of what type of matrix (aka… what kind of phase)?
      • – Requires how much % of Cu in total for prevention of gamma-2 phase
A
    • High-Copper amalgams
    • Prevention of gamma-2 phase
    • (x) > 12%
18
Q

Creep is present more in which gamma phase?

A

a lot more in gamma 2 phase

remember that gamma 2 phase matrix….. are that “bad” guys. This will be on test

19
Q

Trituration:

Name the two types of trituration discussed in class.

A
    • Overtrituration

- - Undertrituration

20
Q

Overtrituration:

    • What kind of mix is associated with an overtrituration mix?
    • This mix would result to an increase or decrease working/setting time?
    • This mix would result to an increase or decrease in setting contraction?
A

Overtrituration:

- - “hot” mix: sticks to capsule kinda like a ball after you "centrifuge" it.
    - - decreases working / setting time
    - - slight increase in setting contraction
21
Q

In undertrituration, what kind of mix do you get from it?

A

– Grainy, crumbly mix

22
Q

Condensation of amalgam:

    • Condensation is said to be a continuation of what?
    • Condensation packs the amalgam to what?
A
    • Continuation of trituration

- - Adapts amalgam to cavity walls

23
Q

Condensation of amalgam:

    • The process of condensation reduces what in restoration?
    • The process of condensation will help eliminate or induce voids?
    • The process of condensation will help increase or decrease the strength and serviceability of restoration?
A
    • Reduces residual Hg in restoration (reduces creep)
    • Eliminates voids
    • Increases strength and serviceability of restoration
24
Q

Spherical alloys have what kind of condensing force?

A

Less condensing forces

25
Q

What kind of copper will corrode faster?

A
  • Low copper corrodes faster (6 months)

- - High copper will still SEAL

26
Q

Stability:
Do all amalgams contract?
– If there are more contraction, what will happen to the sensitivity?
– What type of alloy (shape) will contract more?

A
    • All amalgam contracts a bit
    • More contraction = more sensitivity
    • Spherical alloys contract more

Dental Materials Part 2 (11 decks)

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