Amalgam

Question 1

Why use amalgam

Answer 1

Inexpensive
Easy to use
>100 yr history
Familiarity
Resin free this less allergies

Question 2

What are the basic constituents of amalgam

Answer 2

Silver
Tin
Copper
Mercury

Question 3

How does silver affect amalgam

Answer 3

Increases strength and expansion

Question 4

How does tin affect amalgam

Answer 4

Decreases expansion, strength

Increases setting time

Question 5

How does addition of copper affect amalgam

Answer 5

Ties up tin
Decreases gamma 2
Increases strength
Reduces tarnish and erosion
Reduces creep (marginal deterioration)

Question 6

What does mercury do for amalgam

Answer 6

• activates reaction

- liquid at room temp

Question 7

do spherical alloys require more or less mercury than admixed

Answer 7

spherical less (45 vs 50%) because they have smaller surface area and are easier to wet

Question 8

Why is zinc sometimes used in amalgam

Answer 8

Decreases oxidation of other elements and less marginal breakdown

Question 9

Palladium does what to amalgam

Answer 9

reduce corrosion

greater luster

Question 10

What amalgam that we use has palladium

Answer 10

Valiant PhD

Question 11

How much mercury is mixed with alloy

Answer 11

50/50

Question 12

What are the three particle shapes for amalgam

Answer 12

lathe cut, spherical, admix

Question 13

Tytin have what particle shapes

Answer 13

spherical

Question 14

Dispersalloy, Original D, and Valiant PhD has what type of particle shape

Answer 14

admix

Question 15

In amalgam equations what is gamma

Answer 15

the unreacted Alloy

forms 30% of volume of set amalgam

Question 16

What is gamma 1

Answer 16

2nd strongest
60% of volume
Ag2Hg3
creates matrix around unreacted alloy

Question 17

gamma 2

Answer 17

weakest and softestphase
Sn8Hg
as corrodes over time Hg is released which reacts with the alloy so volume of gamma 2 decreases over time

Question 18

Describe admix alloy componets

Answer 18

2 types of particles spherical and lathe cut
spherical Ag-Cu
lathe cut
AG SN
The copper ties up the tin

Question 19

How do single composition high copper alloys differ

Answer 19

the gamma spheres have a copper tin coating that reduce creep and prevents gamma 2 formation

Question 20

What dimensional change do high copper amalgams undergo

Answer 20

net contraction
.3% shrinkage
contraction leaves marginal gap but is reduced overtime with corrosion

Question 21

What factors affect amalgam contraction

Answer 21

type of alloy:spherical have more due to less hg
condensation+more condensation + greater contraction
trituration time
more trituration causes higher contraction

Question 22

Amalgam strength variables

Answer 22

Time: at 1 hr 40-60% at 24 hrs 90%
Spherical alloys strengthen faster
need bulk for strength. Brittle at thinner sections

Question 23

How does corrosion affect amalgam restorations

Answer 23

Reduces strength
acts to seal margins
low copper 6months
high copper up to 24 months

Question 24

Which kinds of Am have been shown to last longest? Shortest

Answer 24

Shortest
low copper zinc free
longest
high copper with zinc

Question 25

Describe an overtrituated mix

Answer 25

hot decreased setting time increased contraction

Question 26

Describe an undertriturated mix

Answer 26

grainy and crumbly

Question 27

What kind of condensation forces do you use on lathe cut

Answer 27

small condensers with high force

Question 28

what kind of condensing do you use for spherical

Answer 28

large condensers using vertical/lateral vibratory motion

Question 29

how do you condense admix

Answer 29

intermediate between spherical and lathe cut

Question 30

Why should you burnish amalgams and when should you

Answer 30

pre carve to remove excess Hg and improve margin post car to improve smoothness doing both gives less leakage

Question 31

Does polishing improve marginal integrity

Answer 31

Collins J Dent 92 say no

Question 32

What are the advantages of spherical alloys

Answer 32

Easier to condense hardens rapidly smoother polish

Question 33

what are the disadvantages of spherical alloy

Answer 33

hardens rapidly hard to get tight proximal contacts higher tendency for overhang higher shrinkage

Question 34

what are the advantages of admixed

Answer 34

easy to achieve tight contacts good polish hardens slowly

Question 35

What are the disadvantages of admix

Answer 35

hardens slowly with lower early strength

Question 36

Should we bond amalgam?

Answer 36

Cochrane: No difference in Am survival or post op sensitivity summit 2004: bonded complex am were as retentive as using pins conclusion: Probably only use for complex

Question 37

whats the avg daily dose from 8-10 Am surfaces of mercury

Answer 37

1-2 micrograms

Question 38

What are the threshold mercury levels for pre clinical effects and dangerous effects

Answer 38

preclinical 30micrograms | dangerous 80 micrograms

Question 39

what is the biologic activity of mercury

Answer 39

binds to sulfhydryl groups | no carcinogenicity but can cause birth defects

Question 40

what form of mercury is most toxic

Answer 40

alylmethyl | minimal bay japan posoning

Question 41

when removing Am how does the Hg vapor release compare to the established exposure level threshold

Answer 41

far below, < 5%

Question 42

any evidence to link Am to diseases

Answer 42

nope

Question 43

what is the exa ruling on Am

Answer 43

install am separators to reduce Am entering sewer prohibit use of oxidizing agents for flushing of vacuum systems prohibit rinsing or flushing of Am waste down a drain

Question 44

Whats the minimata convention

Answer 44

Global agreement to protect human health from releases of Hg. Phase down use of Am

Question 45

What does the ban on Am do to Dental Economics

Answer 45

Increase res price ~19% decrease number of res placed increase in untreated car