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2ND Year - CSA clinical aspects > Amalgam > Flashcards

Amalgam Flashcards

1
Q

Define amalgam

A

Any alloy of mercury with another metal other metals

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2
Q

Defne dental amalgam

A

Essentially an alloy of silver =, mercury and tin with some other metals aded to modify the properties

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3
Q

State the chemical reaction that forms amalgam

A

Ag + Sn=> Ag3Sn

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4
Q

What shapes can the alloy powder particles be in?

A

Lathe cut

Spherical

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5
Q

What is amalgam made up f?

A

Amalgam powder (made up of silver , copper etc)
AND
liquid mercury

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6
Q

Let the 3 possible reagins the can occur when liquid mercury and amalgam powder are mixed together?

A
  1. 3Ag+Sn=>Ag3Sn
  2. 2Ag+3Hg=>Ag2Hg3
  3. Hg+7Sn=>Sn7Hg
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7
Q

State the gamma reaction that occurs when liquid mercury and amalgam powder are mixed together

A

3Ag + Sn => Ag3Sn

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8
Q

State the gamma 1 reaction that occurs when liquid mercury and amalgam powder are mixed together

A

2Ag + 3Hg => Ag2Hg3

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9
Q

State the gamma 2 reaction that occurs when liquid mercury and amalgam powder are mixed together

A

Hg + 7Sn => Sn7Hg

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10
Q

Which of the 3 reactions that occur in amalgam the most problematic?

A

The gamma 2 reaction :

Sn7Hg

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11
Q

What is the gamma 2 reaction responsible for?

A
  1. Corrosion
    2, Creep
  2. Decrease in strength
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12
Q

What do we ad to amalgam to reduce the gamma 2 phase?

A

Copper

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13
Q

State the gamma 2 reaction when copper I added

A

AgCu + Sn7Hg => Cu6Sn5 + Ag2Hg3

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14
Q

Name the 4main ingredients that makeup modern amalgam powder

A
  1. SIlver
    2, Tin
  2. Copper
  3. Zinc
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15
Q

State the percentage weight of silver in modern amalgam powder

A

65%

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16
Q

State the percentage weight of tin in modern amalgam powder

A

29%

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17
Q

State the percentage weight of copper in modern amalgam powder

A

6-13%

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18
Q

State the percentage weight of zinc in modern amalgam powder

A

2%

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19
Q

What is the IDEAL ratio of powder to liquid in amalgam

A

Ideally final amalgam restoration should contain less than 50% mercury

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20
Q

What is the problem with trying to mix powder with less than 50% mercury?

A

It is very difficult as the mixture is too dry

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21
Q

How do we overcome the problem of too dry amalgam mix?

A

By increasing the amount of mercury BUT then later removing in when we are packing

22
Q

How do we remove the excess mercury the setting our amalgam filling?

A

During packing the excess mercury indrawn to the top and hen we scrape it away during carving

23
Q

Describe spherical amalgam powder particles

A

They are softer and more flowable

24
Q

Describe lathe cut amalgam powder particles

A

Less flowable

Good for building up late amounts missing tooth structure

25
Q

Give some advantages of amalgam

A
  1. Has good compressive strength
  2. Good wear resistance
  3. Kind to opposing teeth
  4. Easy to use
  5. chemically set
  6. Cheap
  7. Radio-opaque so can be seen on radiographs
26
Q

What are the disadvantages of amalgam

A
  1. It is non-adhesive
  2. It’s weak in thin sections
  3. It’s a thermal conductor
    4 It’s Unaesthetic
  4. Can become a plaque retentive factor
27
Q

Give some properties of amalgam

A
  1. Non adhesive
  2. Weak in thin sections
  3. Thermal conduction / expansion
  4. Corrosive
  5. Unaesthetic
    6 Reactions (lichenoid reactions)
28
Q

When would we place an amalgam filling?

A
  1. Class I and class II caries
  2. Areas where heavy occlusal forces are encountered
  3. Where aesthetics are not important
  4. Building up broken teeth prior to crowning
29
Q

What qualities must our cavity have before we place an amalgam filling

A
  1. Clean walls
  2. No unsupported enamel prisms
  3. Undercut
  4. Cavosurface angle greater than 90
  5. Amalgam-margin angle greater than 70
  6. Cavity must be greater than 2mm
30
Q

What is an undercut ?

A

When the base of the cavity wider than the top

31
Q

What is retention?

A

The prevention of the amalgam filling from being puled out vertically

32
Q

What type of retention is displayed in amalgam?

A

Retention is macro molecular

33
Q

When may an undercut not be sufficient ?

A

When a cusp of the tooth is completely missing

34
Q

What do we NOT use anymore to keep amalgam in place if a cusp is missing?

A

Pins

35
Q

Why do we no longer use coins when placing an amalgam restoration?

A

The pins can:
Go into the pulp
Weaken the tooth

36
Q

What do we do instead of placing pins?

A

Create pits and grooves

37
Q

Does phishing improve the life expectancy of amalgam restorations?

A

NO

38
Q

What is the problem with polishing amalgam?

A

Amalgam takes 24 hrs to set so you can’t polish straight away
Also polishing generates heat which may irritate the pulp

39
Q

Compare he median age of replacement of amalgam with composite

A 
Amalgam = 15 yrs
Composite = 8 yrs
40
Q

Compare the average life span of amalgam and composite

A 
Amalgam = 12 yrs
Composite = 5 yrs
41
Q

What is the main reason for failure for both amalgam and composite?

A

Secondary caries

42
Q

Does amalgam or composite have a greater risk of developing secondary caries

A

Risk of secondary caries was 3.5 times greater in composite than amalgam

43
Q

Does amalgam perform better in large or small restorations?

A

Large

44
Q

How much of amalgam is made up of mercury|

A

Approx 50%

45
Q

What state of mercury is toxic?

A

Mercury vapours is highly toxic

46
Q

When are mercury vapours released in dentistry?

A

Mercury vapours are released from amalgam fillings during chewing and toothbrushing

47
Q

What has amalgam been blamed for?

A
  1. Neurotoxicity
  2. Kidney disfunction
  3. Reduced immunocompetence
  4. Birth defects
  5. Effects on oral & intestinal bacteria
48
Q

What has reared shown on the effect f amalgam on our health?

A

It has never been convincingly show that the negligible levels of mercury entering the body from amalgam fillings have any impact on general health

49
Q

What is the main reason mercury is being phased out?

A

Due to its detrimental affect on the environment

50
Q

What happens when mercury enters the environment?

A

It s converted by bacteria into Methy mercury in fresh and salt water

51
Q

Why is methyl mercury dangerous?

A

It is highly poisonous

52
Q

How do we dispose of amalgam in the clinical skills labs?

A

Put empty capsules and waste amalgam in the receptacles provided ◦ Clean the heads into the designated sink (This has a separator on it)
Report any spillages

2ND Year - CSA clinical aspects (4 decks)

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