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Flashcards in 1. Amalgam Deck (37):
1

History of Dental Amalgam

lDeveloped in France..1800s
lFirst used in US 1833 ____ worked on a balanced formulation of silver and tin in 1896
l1920s Specification #1 of the ADA a standard test for dental amalgam. Amalgam alloy must be mostly Ag and Sn (____% Ag, ____% Sn)

Flagg and Black
65
29

2

History contd.

lln 1940 s and 1950 s changes in the shape of the particles to increase early ____. Lathe-cut alloys become ____-lathe cut alloys. (No improvement clinically
ll____ particles were introduced ll1960 s high-copper amalgams
____ (1963)-Admix High-Copper
Tytin was developed by Kamal Asgar
Single composition; High ____; Spherical

strength
micro
spheical
disperalloy
copper

3

Mercury

lMercury toxicity is a concern in dentistry because of its harmful effects on the kidneys and the ____.
lIts greatest risk is to office staff from mercury ____. It evaporates at room temperature and the lungs absorb most of the vapor.
l Mercury toxicity is not a problem for patients. Dentists who urge patients to replace amalgam restorations to cure medical problems are not practicing ethical dentistry.
l Mercury in the environment is an important problem. The role dentistry plays in contamination is under
investigation.

CNS
vapor

4

What is Dental Amalgam?

l Amalgam is a mixture of ____, tin, ____ and sometimes zinc, or a small amount of other metals with mercury
l Is a ____ alloy
l There are 2 basic particle shapes, lathe cut and spherical used to make three types of alloys: lathe cut, spherical and admixed

silver
copper
metal

5

Classification of Amalgam Alloys
Based on Particle Shape

____ – Irregular particles from filing on a Lathe
____ – Spherical particles from atomizing molten metal
____ – Mixture of spherical and lathe-cut particles

Based on composition High- and Low-Copper Zinc and Non-Zinc

lathe-cute
spherical
admix

6

Particle Classification

In the admix you have spherical and rod shaped particles.
Referring to pics above:
A) ____-cut rod shaped particles
B) ____ particles seen in EM of tytin
C) ____ that you would typically see in a class 2 restoration because the rods here give good packing and condensation in box unlike the spherical shaped particles

lathe
spherical
dispersalloy

7

Amalgam Phases

lGamma----- g ____
lGamma 1------ g1 ____ lGamma 2 ----- g2 ____ lEpisilon --------e
lEta -------- h
lSilver Copper Eutectic

Ag3-Sn
Ag2-Hg3
Sn8-Hg

8

Low Copper Dental Amalgam

llBlack s composition ____% Ag, ____% Sn, less than ____% Cu, and sometimes ____% Zn
llStrictly ____
llCu and Ag- causes setting expansion, ____ strength and corrosion resistance
lSn causes setting contraction and ____ strength and corrosion resistance
llZn-____, makes amalgam less brittle

65
25
6
1
historical
increases
decreases
doxidizer

9

Low Copper Amalgams Process

Setting reaction
llg+Hg = g+g1+g2 Precipitation of
gamma 1 and gamma 2 continues until the mercury is consumed.

llThe bulk of the finished restoration consists of the ____ surrounded by reaction products

llAmalgam with lower ____ generally has better properties

original alloy
Hg

10

High Copper Amalgam Process

llState of the art. Dominate the market because the clinical performance is superior to even the best low copper amalgams.

llPerformance improved by elimination of the weak ____. (g2=Sn8-Hg)
llStrength ____
llCorrosion ____
llMarginal breakdown, ____ creep

gamma 2 phase
increases
decreases
decreases

11

High Copper Amalgam Process

Admix
Ag3Sn( ) + Ag-Cu + Hg = Ag2Hg3 ( 1)
+ Cu6Sn5(η ) + Ag3Sn( ) +Ag-Cu
At least ____ Cu needed to eliminate 2

Single Composition
Ag-Sn-Cu + Hg =Ag2Hg3( 1) +Cu6Sn5(η ) +Ag3Sn( ) +Ag-Sn-Cu

12%

12

High Copper Amalgams

In Admixed (Disperalloy) the ____ Ag3Sn powder and the ____ Ag-Cu eutectic particles are mixed with mercury. When the amalgam sets, the Ag2Hg3 (____ phase) forms as it did when the low-copper containing amalgam also set. However, rather than forming the tin-mercury phase, the tin reacts with copper and form the Cu6Sn5 phase (the eta phase of the Cu-Sn phase diagram).

Some of the dental amalgam alloy particles remain partly ____ after the amalgam has set. These unreacted particle parts ____ the amalgam.

lathe-cut
spherical
gamma-1
unreacted
strengthen

13

High Copper Amalgams

l Spherical: The spherical particles contain both Ag3Sn (the gamma phase of the silver-tin phase diagram) and Cu3Sn (____ phase of the copper-tin phase diagram) phases, and these particles are mixed with mercury. When the amalgam sets, the Ag2Hg3 (____ phase) forms as it did when the low-copper containing amalgam also set. Again, rather than forming the tin-mercury phase, the tin reacts with copper and form the Cu6Sn5 phase (the eta phase of the Cu-Sn phase diagram).

Some of the dental amalgam alloy particles remain partly unreacted after the amalgam has set. These unreacted particle parts ____ the amalgam.

epsilon
gamma-1
strengthen

14

High Copper Amalgams

Two Groups
1)Admix High-Copper Amalgam (Dispersalloy)
Lathe-cut: Ag=____%, Sn=____%,Cu=____%,Zn=____%, Hg=____% with
Spherical: Ag=____%, Cu= ____%

2)Spherical High-Copper Amalgams (Tytin)
Ag=____%, Sn=____%, Cu=____%, Zn=____%

66-73
25-29
0-5
0-1
0-3

72
28

40-60
22-30
13-30
0-1

15

Amalgam Properties
§§ ____
§§ Creep
§§ ____
§§ Dimensional Change
§§ ____

strength
corrosion
working/setting times

16

AMALGAM PROPERTIES

lADA SPECIFICATION NO. 1
- helps control the qualities of dental
amalgam
- three physical properties used as a measure
a) ____
b) ____ (1 hr.-80 MPa)
c) ____

creep
compressive strength
dimensional change

17

Dimensional Stability

lIdeally amalgam should be ____
lNo Severe ____...
lNo Excessive expansion... lGood ____ ratio
lIncreased condensation pressure favors ____

stable
contraction
Hg-Alloy
contraction

18

AMALGAM PROPERTIES Dimensional Change

llInitial contraction – first 20 mins related to the solubility of ____ and ____ particles
llThen ____ – the reaction of Hg with Ag and Sn
ll6-8 hrs ____
ll24 hrs ____
llContamination of Zn containing alloys with H2O results in excessive ____ dimensional change
llADA --- + or – 20 microns/cm

Hg
alloy
expansion
constant
final
delayed

19

Dimensional Change


A is ____, b is ____ and C is ____ amlagam.

Seeing the initial contractions that happens with the low copper amalgams. Has to do with the ____ phase. The low copper amalgam use alot more mercury

In A can see initial contraction but as u condense and remove excess amalgam then u have expansion which cancels each other out - resulting in a ____ amalgam restoration.

admix
spherical
low copper
gamma 2
stable

20

AMALGAM PROPERTIES Compressive Strength

- resistance to compressive forces
- dependent on ____ design
l Variables affecting strength
____
Hg content -weakens
____
Porosity

l High Copper 1hr – 250 MPa
l Lathe Cut 1hr 45 MPa
l Low Copper 1hr – 88MPa
l ADA 80MPa (11000psi)
l Needs support of tooth structure because tensile and shear strengths are low

cavity
trituration
condensation

21

Compressive Strength

llHigh Cu vs. Low Cu Amalgams.
Mercury ____ is very important.
If Hg ____ increases more than ____, strength decreases.

content
content
54%

22

AMALGAM PROPERTIES Tensile strength

llThe high early ____ strengths of the high copper unicompositional alloys resist fracture by premature biting stresses
llCavity designed to reduce ____ stresses
llOver- and under- triturating decrease ____ of spherical alloys

tensile
tensile
strengths

23

Amalgam Fracture
1) The amalgam was not ____ properly.
2) the dovetail is fairly large, the isthmus is narrow and the box is fairly large so you have a narrow ____ supporting a large bulk of amalgam.
3) If the axial pulpal line angle was left very ____
4) Not condensed properly, so when patient tried to function on marginal ridge, stresses occured.

condensed
isthmus
sharp

24

Creep
lTime dependent deformation of a material under a ____ load or stress
lADA requirement:

constant
3
deterioration
delayed
H2

25

Creep
In pic 1 you see that its burnished very well and margins are sealed. Then patient comes back and in pic 2 u see that amalgam is extruding from the restoration.

This suggests that there was ____ contamination when the amalgam was being condensed.

Contamination is not as severe if occurs during burnishing or carving as it is when u r condensing.

moisture

26

Delayed Expansion
This is a ____ restoration and it is very hard to prevent the moisture from the gingival sulcus to coming in contact with the restoration, most of the time u see creep or an extrusion from the restoration its usually in the class 5.

Its even worse if you try to place a ____ in a wet environment. Placing the amalgam is less technique sensitive, it is important to keep it dry, but it is very technique sensitive if you want to place a composite

class V
composite

27

TARNISH AND CORROSION
llAmalgam corrodes in much the same way that ____ rusts. Reaction with environment.
llTarnish – the formation of surface ____ or loss of ____

Low Cu amalgams
Sn7Hg + 1/2O2 + H2O + Cl- = ____ + Hg

High Cu Amalgams
Cu6Sn5 + 1/2O2 + H2O + Cl- = ____ + SnO

iron
discoloration
luster
Sn4(OH)6Cl2
CuCl23Cu(OH)2

28

Corrosion
ll____ reaction
llCorrosion process can liberate free ____ which can contaminate and ____ gold restoration

galvanic
Hg
weaken

29

AMALGAM TRITURATORS
There is a hare and a tortoise button in the preclinical lab - goes on about the hare and tortoise story. Hare is the fast one.

The high copper amalgams need to have ____ speed triturations so you would press the hare button

These can also be used to mix ____ not just amalgam. The speeds are different depending on the type of cement u are mixing

high
cements

30

AMALGAM TRITURATION
Should be familiar with the different types of capsules. 1 is ____ and 2 is ____.

If you under triturate you get a very ____ mix as seen in pic labelled a) on previous slide. You cant pick it up with amalgam carrier. And by the time u get it into the prep and start condensing it will be very dry and they layers wont stick to each other.

Pic labelled b) is an ____ mix

Pic labelled c) is ____. This also weakens the strength. It looks falt , shiny instead of solid round.

dispersalloy
tytin
dry
ideal
over triturated

31

Trituration
lIncreased triturating time and/or speed ____ the working and setting times.
lHigh copper alloys require ____ speed triturating
lOver- and under- triturating reduces ____ and ____ and increases ____

shortens
high
compressive
tensile
creep

32

Amalgam Manipulation
- Select almagam based on ____ time, particle size and shape, composition, and the presence or absence of ____.
l Large restorations....

- Capsule - 400, 600, 800mg of alloy color coded. If large amounts are required several ____ mixes are recommended.
l “a ____ setting amalgam, used by a slow condensing dentist, can result in a ____ amalgam”

setting
Zn
small
fast
weak

33

Amalgam Manipulation
CONDENSATION
The amount of Hg that remains in the restoration influences ____, creep, and ____ strength.
Moisture contamination during mixing and condensation may produce excessive ____ (Zn alloys)

l Condensation pressure influences the amount of ____
l Size of ____ and direction and magnitude of force
lAmalgam should be condensed promptly
after ____.

Condensation of a
partially set amalgam breaks up the ____ already formed.

dimensional change
compressive
expansion

Hg
condenser tip
triturating
matrix

34

Amalgam Bonding
lWith the development of adhesive bonding systems attempts were made to bond amalgam to tooth structure. Adhesive monomers containing ____ are most successful ;

Amalgam to dentin – ____ MPa Composite to Dentin – ____ MPa

4_META (4-methacryloxyethyl trimellitic anhydride)
10
20-22

35

Amalgam Bonding
lIncreased fracture resistance (2x) – dependent on ____ of restoration
lDecreased ____ in Class V restorations compared to not bonding
lThe amalgam restoration is unique in that ____ decreases as the restoration ages. This is due to corrosion products that form between the tooth and the restoration

width
marginal leakage
leakage

36

Uses of Dental Amalgam
ll____ direct restorations
llCore ____
ll____ treatment following an apicoectomy

non-esthetic
build-ups
retrograde endodontic

37

Carving and Finishing
lAfter the amalgam sets carve anatomy when there is some ____. Simulate the ____, not reproduce every minor detail.
lBurnish
lFinal polishing ____ hours later

resistance
anatomy
24