Fall Lecture 1: Dental Amalgam: Physical and Mechanical Properties, Composition, and Handling

Question 1

Alloy:

Answer 1

2 or more metals to give greater strength or resistance to corrosion, 2 or more metals with non-metals

Question 2

2 examples of alloys:

Answer 2

bronze, brass

Question 3

Bronze:

Answer 3

copper, tin, and other metals (aluminium, etc.) and non-metals such as arsenic, phosphorus, or silicon

Question 4

Brass:

Answer 4

copper, zinc

Question 5

Dental amalgam alloy:

Answer 5

silver, tin, copper, zinc

Question 6

Which metal is kept separate from the rest in the amalgam capsules?

Answer 6

mercury

Question 7

Dental amalgam alloy:

Answer 7

silver, tin, copper, mercury (may also contain: zinc, palidium)

Question 8

When does dental amalgam become an amalgam?

Answer 8

when it mixes with mercury

Question 9

3 types of dental amalgam alloy:

Answer 9

Conventional lathe-cut alloy, spherical alloy, admix alloy (mixture of lathe-cut and spherical particles)

Question 10

Formulation of alloy we use is based on:

Answer 10

what G.V. Black Presented in 1885

Question 11

How did dental alloys change in the 60’s?

Answer 11

high copper content and spherical particles

Question 12

Lathe-cut alloys:

Answer 12

irregularly shaped particles produced by milling or lathe cutting of cast of _?___ amalgam alloy

Question 13

Spherical alloys:

Answer 13

made in a gas chamber, less mercury than lathe cut = better props, low mercury helps the spherical powder, smaller volume ratio than lathe powder

Question 14

Alloys w buttery/soft consistency:

Answer 14

spherical

Question 15

Issue with filing Class 2 resto with spherical alloy:

Answer 15

buttery, soft, very plastic, good proximal (Class 2) contact can be tough to get, need great clinical technique

Question 16

Why can spherical be used for core build up material?

Answer 16

high early strength, strong after 10-15m

Question 17

Which have higher final strength, admix alloys or spherical alloys?

Answer 17

spherical, core build up must be strong

Question 18

Benefit of admix:

Answer 18

denser final amalgam

Question 19

Most common material in dental amalgam:

Answer 19

admix alloy

Question 20

Admix alloy requires:

Answer 20

more force, better for proximal contacts, stregnth is time dependent, initially relatively weak, delay final polishing at least 24h

Question 21

These alloys have low copper:

Answer 21

lathe-cut and spherical

Question 22

These alloys have high copper:

Answer 22

admix and spherical

Question 23

Does spherical have low or high copper?

Answer 23

can be either

Question 24

Silver provides:

Answer 24

strength

Question 25

Fxn of tin in amalgam:

Answer 25

dec expansion

Question 26

Composition of dental amalgam, high to low:

Answer 26

Ag, Sn, Cu, Zn (STCZ)

Question 27

TF? It is important that the amalgam expand after it is set.

Answer 27

F. should not expand (tin)

Question 28

Copper fxn:

Answer 28

strength, (low to high range)

Question 29

Low copper percentage:

Answer 29

3%

Question 30

High copper

Answer 30

up to 30%

Question 31

Copper decreases corrosion by:

Answer 31

decreasing gamma 2 phase

Question 32

What eliminates the gamma 2 phase?

Answer 32

copper

Question 33

Zinc fxn:

Answer 33

scavenger, deoxidizer during melting, inc plasticity, more susceptible to moisture contamination, delayed expansion

Question 34

TF? Zn free amalgam is better, than with Zn.

Answer 34

F.

Question 35

These alloys are brittle and difficult to blend uniformly

Answer 35

sliver/tin alloys (copper replaces the silver to increase strength)

Question 36

First silver/copper alloy was made in:

Answer 36

early 60's

Question 37

Silver/ copper alloy is aka:

Answer 37

dispersed phase or admix high-copper alloy

Question 38

Amalgam we use:

Answer 38

Valiant PHD XT, phase dispersed (Ivoclar Vivadent), low mercury, high copper, extended stetting time (7-10min)

Question 39

State of the art amalgam:

Answer 39

high copper amalgam

Question 40

% Cu required to be a high copper amalgam:

Answer 40

9-30%

Question 41

Benefits of high copper amalgam:

Answer 41

inc strength and marginal integrity, elimination of gamma 2 phase

Question 42

Is an 8% copper amalgam considered a 'high copper' amalgam?

Answer 42

no

Question 43

Why does high copper amalgam perform the best in clinic?

Answer 43

elimination of gamma 2 phase

Question 44

Gamma phase:

Answer 44

unreacted particles (sliver, tin particles, strong, suspended in matrix of gamma 1 phase, reaction product of silver and mercury, less strong and more corrosion susceptible (?)

Question 45

Which amalgam reaction has a gamma 2 phase?

Answer 45

conventional or low copper amalgam reaction, weakest, most corrosion susceptible phase

Question 46

Phases, strong to weak:

Answer 46

gamma, 1, then 2

Question 47

If a tin/mercury compound is present is this low copper or high copper reaction?

Answer 47

low copper

Question 48

What compound is eliminated with the elimination of the gamma 2 phase?

Answer 48

Sn7Hg (weakest compound eliminated, high copper reaction stronger)

Question 49

Low copper amalgam development:

Answer 49

dissolution, precipitation of g1 crystals, Hg consumption and growth of g1 and g2, final set

Question 50

Greater unconsumed silver tin will lead to greater/decreased strength:

Answer 50

greater

Question 51

Creep:

Answer 51

low creep, better restoration, time dependent deformation due to stress on material (high Cu amalgam: improved marginal integrity, decreased breakdown in margin, less creep)

Question 52

Amalgams w delayed expansion after moisture contamination:

Answer 52

zinc-containing amalgams, tin helps to reduce expansion (wks to mths)

Question 53

___ gas causes the restoration to expand after wks to mths

Answer 53

hydrogen

Question 54

When to use zinc-free amalgam?

Answer 54

moisture control difficult

Question 55

compressive strength of amalgam, high or low?:

Answer 55

very high

Question 56

tensile and shear strength of amalgam are higher/lower than its compressive:

Answer 56

lower

Question 57

Tarnish:

Answer 57

amalgam surface is dulled or discolored, formation of oxide layers

Question 58

Corrosion

Answer 58

actual deterioration of a metal, chemical rxn bw metal and env (H20, air, saliva) forming metal compounds or corrosion products

Question 59

Zinc works as:

Answer 59

scavenger, deoxidizes

Question 60

increase tin:

Answer 60

increase tarnish and corrosion

Question 61

Increased copper

Answer 61

decrease tarnish and corrosion

Question 62

percolation of amalgam:

Answer 62

influx of salivary fluid bw microscopic gap bw resto and tooth

Question 63

High copper amalgams have fast/slow rate of percolation:

Answer 63

slow, no g2 phase in high copper amalgam

Question 64

this phase corrodes the most

Answer 64

g2 phase

Question 65

Percolation takes (this long) in high copper amalgams:

Answer 65

6 mo

Question 66

These metals have all the opposite effects as each other:

Answer 66

Sn and Cu

Question 67

Effects of Sn:

Answer 67

dec strength, dec setting expansion, inc creep, inc flow, dec compressive strength, inc tarnish and corrosion

Question 68

Which metal has all the same properties as Cu except for tarnish and corrosion?

Answer 68

Ag

Question 69

Which amalgam has more copper?

Answer 69

admix

Question 70

What causes the delayed expansion?

Answer 70

zinc

Question 71

What reduces the oxide layer?

Answer 71

zinc

Question 72

__ increases corrosion, while __ decreases corrosion:

Answer 72

tin, copper

Question 73

This helps to create self sealing:

Answer 73

percolation

Question 74

This is (basically) the corrosive phase:

Answer 74

g2 phase