Dental Amalgam Dental Amalgam

Kraig

S. Vandewalle, Col, USA
Official Disclaime

•

The opinions expressed in this prese

those of the author and do not necesreflect the official position of the US the Department of Defense (DOD)

•

Devices or materials appearing in th

presentation are used as examples available products/technologies and imply an endorsement by the author USAF/DOD
Overview

• History• Basic composition• Basic setting reactions• Classifications • Manufacturing• Variables in amalgam 

performance

Click here for briefing o
History

• 1833

– Crawcour brothers introduce

amalgam to US

• powdered silver coins mixed with me

– expanded on setting

• 1895

– G.V. Black develops formula 

for modern amalgam alloy

• 67% silver, 27% tin, 5% copper, 1% 

– overcame expansion problems
History

• 1960’s

– conventional low-copper lathe-cu

• smaller particles

– first generation high-copper alloy

• Dispersalloy (Caulk)

– admixture of spherical Ag-Cu

eutectic particles with conventional lathe-cut

– eliminated gamma-2 phase

Ma
History

• 1970’s

– first single composition spherica

• Tytin (Kerr)• ternary system (silver/tin/copper)

• 1980’s

– alloys similar to Dispersalloy an

• 1990’s

– mercury-free alloys

Ma
Amalgam

• An alloy of mercury with ano
Why Amalgam?

• Inexpensive•

Ease of use

•

Proven track record

– >100 years

•

Familiarity

•

Resin-free

– less allergies than composite

Click here for Talking 
Constituents in Ama

•

Basic

–

Silver

– Tin–

Copper

– M

e

r

c

u

r

y

• O

t

h

e

r

– Zin

c

– Indium–

Palladium
Basic Constituen

•

Silver (Ag)

– increases strength– increases expansion

•

Tin (Sn)

– decreases expansion– decreased strength– increases setting time

Phillip’s S
Basic Constituen

•

Copper (Cu)

– ties up tin

•

reducing gamma-2 formation

– increases strength–

reduces tarnish and corrosion

–

reduces creep

•

reduces marginal deterioration

Phillip’s S
Basic Constituen

•

Mercury (Hg)

–

activates reaction

– only pure metal that is liquid 

at room temperature

–

spherical alloys

•

require less mercury

–

smaller surface area easier to wet

» 40 to 45% Hg

– admixed alloys

•

require more mercury

– lathe-cut particles more difficult to wet

» 45 to 50% Hg

Phillip’s S
Other Constituen

•

Zinc (Zn)

–

used in manufacturing

• decreases oxidation of other eleme

– sacrificial anode

–

provides better clinical performan

• less marginal breakdown

– Osborne JW Am J Dent 1992

–

causes delayed expansion with lo

• if contaminated with moisture during 

– Phillips RW JADA 1954

H

2O + Zn ZnO ⇒

+ H

2

Phillip’s S
Other Constituen

• Indium (In)

– decreases surface tension

•

reduces amount of mercury necessa

•

reduces emitted mercury vapor

–

reduces creep and marginal brea

– increases strength–

must be used in admixed alloys

– e

x

a

m

ple

• Indisperse

(Indisperse Distributing C

–

5% indium
Other Constituen

•

Palladium (Pd)

–

reduced corrosion

–

greater luster

– e

x

a

m

ple

•

Valiant PhD (Ivoclar Vivadent)

–

0.5% palladium
Basic Compositio

•

A silver-mercury matrix containing f

particles of silver-tin

•

Filler (bricks)

– Ag

3Sn called gamma

• can be in various shapes

– irregular (lathe-cut), spherical,

or a combination

• M

a

t

rix

– Ag

2Hg

3 called gamma 1

• cement 

– Sn

8Hg called gamma 2 

• voids

Phillip’s S
Basic Setting React

•

Conventional low-copper alloys

•

Admixed high-copper alloys 

•

Single composition high-copper 
Conventional Low-Copp

•

Dissolution and precipitation 

•

Hg dissolves Ag and Sn

from alloy

• Intermetallic compounds

formed Ag-S

Allo

Hg 

Ag

3Sn + Hg Sn + Hg

⇒ Ag

3Sn + Ag Sn + Ag

2Hg

3 + 

Phillip’s S

γ γ

γ

1
Conventional Low-Copp

•

Gamma (

γ) = Ag

3Sn

– unreacted alloy– strongest phase and 

corrodes the least

– forms 30% of volume 

of set amalgam

Ag-Sn

Alloy

Ag

Hg

Hg

Ag

3Sn + Hg Sn + Hg

⇒ Ag

3Sn + Ag Sn + Ag

2Hg

3 + 

Phillip’s S

γ γ

γ

1
Conventional Low-Copp

•

Gamma 1 (

γ

1) = Ag

2Hg

3

– matrix for unreacted

alloy

and 2nd strongest phase

– 10 micron grains

binding gamma 

(

γ

)

– 60% of volume

Ag-Sn

Alloy

Ag

3Sn + Hg Sn + Hg

⇒ Ag

3Sn + Ag Sn + Ag

2Hg

3 + 

Phillip’s S

γ γ

γ

1
Conventional Low-Copp

•

Gamma 2 (

γ

2) = Sn

8Hg

– weakest and softest phase– corrodes fast, voids form– corrosion yields Hg which 

reacts with more gamma 

(

γ

)

– 10% of volume– volume decreases with time 

due to corrosion

Ag-Sn

Alloy

Ag

3Sn + Hg Sn + Hg

⇒ Ag

3Sn + Ag Sn + Ag

2Hg

3 + 

Phillip’s S

γ γ

γ

1
Admixed High-Copper 

•

Ag enters Hg from Ag-Cu 

spherical eutectic particles

– eutectic

• an alloy in which the elements 

are completely soluble in liquid solution but separate into distinc

t

areas upon solidification

•

Both Ag and Sn enter Hg 

from Ag

3Sn particles

Ag-Sn

Alloy

Hg

Ag

3Sn + Ag Sn + Ag

-Cu + Hg Cu + Hg

⇒ Ag

3Sn + Ag Sn + Ag

-Cu + A

Cu + A

γ γ

Phillip’s S
Admixed High-Copper 

•

S

n diffuses to surface of 

Ag-Cu particles 

– reacts with Cu to form 

(eta)

C

u

6Sn5 

(

η

)

• around unconsumed

Ag-Cu particles

Ag-Sn

Alloy

η 

Ag

3Sn + Ag Sn + Ag

-Cu + Hg Cu + Hg

⇒ Ag

3Sn + Ag Sn + Ag

-Cu + A

Cu + A

γ γ

Phillip’s S
Admixed High-Copper 

•

Gamma 1 (

γ

1) (Ag

2Hg

3) 

surrounds 

(

η

) eta phase 

(Cu

6Sn

5) and gamma 

(

γ

)

alloy particles (Ag

3Sn) Ag-Sn

Alloy

η 

Ag

3Sn + Ag Sn + Ag

-Cu + Hg Cu + Hg

⇒ Ag

3Sn + Ag Sn + Ag

-Cu + A

Cu + A

γ γ

Phillip’s S
Single Compositio

High-Copper Allo

•

Gamma sphere (

γ) (Ag

3Sn) 

with epsilon coating (

ε

)

(Cu

3Sn)

•

Ag and Sn dissolve in Hg

Ag-Sn

ε

Ag

3Sn + Cu Sn + Cu

3Sn + Hg Sn + Hg

⇒ Ag

3Sn + Cu Sn + Cu

3Sn + A

Sn + A

Phillip’s Sc

γ γ ε

ε
Single Compositi

High-Copper Allo

•

Gamma 1 (

γ

1) (Ag

2Hg

3) crystals

grow binding together partiallydissolved gamma (

γ) alloy

particles (Ag

3Sn)

•

Epsilon 

(

ε

) (Cu

3Sn) develops 

crystals on surface of gamma particle (Ag

3Sn) 

in the form of eta

(

η) (C

u

6Sn

5

)

– reduces creep– prevents gamma-2 formation

Ag-Sn

All

η

Ag

3Sn + Cu Sn + Cu

3Sn + Hg Sn + Hg

⇒ Ag

3Sn + Cu Sn + Cu

3Sn + A

Sn + A

Phillip’s Sci

γ γ ε

ε
Classifications

•

Based on copper content

•

Based on particle shape

•

Based on method of adding 

copper 
Copper Conten

• Low-copper alloys

–

4 to 6% Cu

•

High-copper alloys

–

thought that 6% Cu was maximum 

• due to fear of excessive corrosion an

–

Now contain 9 to 30% Cu

• at expense of Ag 

Phillip’s S
Particle Shape

• Lathe cut

– low Cu

• New True

Dentalloy

– high Cu

• ANA 2000

•

Admixture

– high Cu

• Dispersalloy, Valiant 

PhD

•

Spherical

– low Cu

• Cavex

– high Cu

• Tytin, V
Method of Adding Co

• Single Composition Lathe-Cut (SC

• Single Composition Spherical (SC• Admixture: Lathe-cut + Spherical 

• Admixture: Lathe-cut + Single Co

Spherical (ALSCS)
Single Composition La

(SCL)

•

More Hg needed than spheric

•

High condensation force need

lathe cut

• 20% Cu• Example

– ANA 2000 (Nordiska

Dental)
Single Composition Sp

(SCS)

•

Spherical particles wet easier 

– less Hg needed (42%)

• Less condensation force, larg•

Gamma particles as 20 micro

– with epsilon layer on surface

• Examples

– Tytin (Kerr)– Valiant (Ivoclar Vivadent)
Admixture: 

Lathe-cut + Spherical E

(ALE)

• Composition

– 2/3 conventional lathe cut (3% Cu– 1/3 high Cu spherical eutectic (28– overall 12% Cu, 1% Zn

• Initial reaction produces gamma 

– no gamma 2 within two years

• Example

– Dispersalloy (Caulk)
Admixture:

Lathe-cut + Single Com

Spherical (ALSCS

• High Cu in both lathe-cut and 

components

– 19% Cu 

• Epsilon layer forms on both co• 0.5% palladium added 

– reinforce grain boundaries on g

• Example

– Valiant PhD (Ivoclar Vivadent)
Manufacturing Proc

• Lathe-cut alloys

– Ag & Sn melted together– alloy is cooled

• phases solidify

– heat treated

• 400 oC for 8 hours

– ground, then milled to 25 - 50 m– heat treated to release stresses 

Phillip’s S
Manufacturing Proc

•

Spherical alloys

– alloy is melted – atomized

• spheres form as particles cool

– sizes range from 5 - 40 microns

• variety improves condensability

Phillip’s S
Material-Related Var

•

Dimensional change

•

Strength

•

Corrosion

•

Creep
Dimensional Chan

•

Most high-copper amalgams un

net contraction

•

Contraction leaves marginal gap

– initial leakage

•

post-operative sensitivity

–

reduced with corrosion over time

Phillip’s S
Dimensional Chan

•

Net contraction

–

type of alloy

•

spherical alloys have more 

contraction

– less mercury

–

condensation technique

•

greater condensation = higher contr

–

trituration time

•

overtrituration causes higher contra

Phillip’s S
Strength

• Develops slowly

– 1 hr: 40 to 60% of maximum– 24 hrs: 90% of maximum 

• Spherical alloys strengthen fast

– require less mercury

• Higher compressive vs. tensile s• Weak in thin sections

– unsupported edges fracture

Phillip’s S
Corrosion

• Reduces strength• Seals margins

– low copper 

• 6 months

– SnO2, SnCl– gamma-2 phase

– high copper

• 6 - 24 months

– SnO2 , SnCl, CuCl

– eta-phase (Cu6Sn5)

Suto
Creep

• Slow deformation of amalgam p

a constant load

– load less than that necessary to p

fracture

• Gamma 2 dramatically affects c

– slow strain rates produces plastic 

• allows gamma-1 grains to slide

• Correlates with marginal breakd

Phillip’s S
Creep

• High-copper amalgams have cr

resistance

– prevention of gamma-2 phase

• requires >12% Cu total

– single composition spherical

• eta (Cu6Sn5) embedded in gamma-

– interlock

– admixture

• eta (Cu6Sn5) around Ag-Cu particle

– improves bonding to gamma 1

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Dentist-Controlled Va

•

Manipulation

– trituration– condensation– burnishing– polishing
Trituration

• Mixing time

– refer to manufacturer

recommendations

• Click here for details

• Overtrituration

– “hot” mix

• sticks to capsule

– decreases working / setting time– slight increase in setting contraction

• Undertrituration

– grainy, crumbly mix

Phillip’s S
Condensation

• F

o

r

c

e

s

– lathe-cut alloys

•

small condensers 

• hig

h f

o

r

c

e

–

spherical alloys

• large condensers • less sensitive to amount of force•

vertical / lateral with vibratory motion

– admixture alloys

• intermediate handling between lathe-
Burnishing

• Pre-carve

– removes excess mercury– improves margin adaptation

• Post-carve

– improves smoothness

• Combined

– less leakage

Be
Early Finishing

•

After initial set

– prophy

cup with pumice

– provides initial smoothness to re– recommended for spherical ama
Polishing

• Increased smoothness• Decreased plaque retention• Decreased corrosion• Clinically effective?

– no improvement in marginal integ

• Mayhew, Oper Dent 1986• Collins, J Dent 1992

– Click here for abstract
Alloy Selection

•

Handling characteristics

•

Mechanical and physical

properties

•

Clinical performance

Click here 
Handling Character

•

Spherical

– advantages

•

easier to condense

–

around pins

•

hardens rapidly

•

smoother polish

–

disadvantages

•

difficult to achieve tight contacts

•

higher tendency for overhangs

Phillip’s S
Handling Character

•

Admixed

– advantages

•

easy to achieve tight contacts

• good polish

–

disadvantages

•

hardens slowly

– lower early strength
Amalgam Propert

Compressive 

Strength (MPa)

% Creep 

Amalgam Type 1 hr 7 daysLow Copper1 145 343 2.0 Admixture

2 137 431 0.4 

Single Composition

3

262 510 0.13 

1Fine Cut, Caulk 2Dispersalloy, Caulk 3Tytin, Kerr Phillip’s S
Survey of Practice T

Civilian General Dentis

32%

Amalgam 

Users

Amalgam 

Free

H
Frequency of Posterior M

by Practice Type

51%

3% 7%

Amal

g

a

m Direct Comp

o

site Indir

e

3%

8%

12%

Amalgam Users

Amalgam Free

Haj-Ali, Gen Dent 2005 
Profile of Amalgam U

Civilian Practitioners

78

%

22

%

Do you use amalgam in 

your practice?

Yes

No

12

%

Do you pla

than 

No
Review of Clinical St

(Failure Rates in Posterior Perma

02468

A

mal

g

a

m

Direct

Co

m

p

Co

m

p

Inlays

Cera

mic

Inla

y

s

CAD/CA

M

Inla

y

s

G

Inl

O

Longi

tudi

n

al C

r

o

ssSectio

n

al

% Annual Failure
Review of Clinical St

(Failure Rates in Posterior Perma

05

1015

Amalgam

Direct Comp

Compomer

Comp Inlays

Ceramic Inlays

CAD/CAM

Cast Gold

GI

% Annual Failure

Standard D

eviati

o

n

Longitudinal and Cross-Sectional Data
Acknowledgemen

•

Dr. David Charlton

•

Dr. Charles Hermesc

•

Col Salvador Flores