Amalgam past,present& future-I

POSTGRADUATE DEPARTMENT OF CONSERVATIVE
DENTISTRY AND ENDODONTICS
SEMINAR TOPIC:-
DENTAL AMALGAM-
PAST, PRESENT & FUTURE-I
(EVOLUTION & PROPERTIES)
Presented by-Ashish Choudhary
Pg student
UNDER GUIDANCE OF :-
Prof. Dr Riyaz Farooq (HOD)
Dr Aamir Rashid (lecturer)
Dr Fayaz Ahmed (lecturer)

Contents
 Introduction
 History of amalgam
 Amalgam wars
 Classification
 Components of amalgam
 Basic setting reaction
 Manufacture of alloy powder
 Properties of amalgam
 Manipulation of amalgam
 Recent advances in amalgam
 Side effects of mercury
 Durability of amalgam
 Future of amalgam
 Conclusion

INTRODUCTION
Dental amalgam is one of the
most versatile restorative
materials used in dentistry.
It constitutes approximately 75% of all
restorative materials used by dentists. It has
served as a dental restoration for more than
165 years.
J Conserv Dent. 2010 Oct;13(4):204-8.
Dental amalgam: An update
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

• There is still no adequate economic
alternative for dental amalgam. The
combination of reliable long-term
performance in load bearing situations and
low cost is unmatched by other dental
restorative material. It has a myriad of uses:
rather low technique sensitivity, self-sealing
property and its longevity
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

AMALGAM POPULARITY
Cost effective
and long life
Acceptable
biocompatibility
Less
technique
sensitive
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

Over the last few years improvements in
composition have led to -
Reduced marginal
failure due to
decreased creep
and corrosion
Early seal between
the tooth and
restoration
But development of alternatives based on ceramics and
composites , and questions on its safety have led to its
decline.
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion
Cavity design
& prepation
Selection of
alloy & its
manipulation
with mercury
Contouring &
finishing
procedures
Age of the
restoration &
its
environment
The variables for amalgam’s appearance
Amalgam: past,present & future
JADA,Vol.86,April 1973

What is amalgam????
a·mal·gam: any alloy of
mercury with any another
metal [silver amalgam is
used as a dental filling]
word amalgam is derived from greek name
‘emolient’ which means paste.
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion
Source: Webster’s New World Dictionary of the American Language,
Guralnik DB, Ed., New York: World Publishing Co., 1972

Dental amalgam is an alloy made by
mixing mercury with a silver tin
amalgam alloy (Ag-Sn)
Amalgam alloy is a silver tin alloy to
which varying amounts of copper(Cu)
and small amounts of zinc(Zn) have
been added
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion
Sturdevant’s Art & Science of Operative dentistry..5th ed; 152

INDICATIONS OF AMALGAM
Moderate to large
Class I and Class II
restorations
Class V restorations
in unaesthetic areas
Foundations
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

Esthetics
Small (even
moderate) defects
in posterior teeth
Requirement for
reinforcement of
tooth
CONTRAINDICATIONS OF AMALGAM
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

ADVANTAGES OF AMALGAM
• Cost effective
• Time effective
• Ease of placement
• Wear resistance
• Prevent marginal leakage after a period of
time
• Adequate resistance to fracture
• Maintains anatomical form
• Not overly technique sensitive
• Favourable long term clinical
research results
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

• Aesthetics
• Toxicity
• Corrosion and galvanic action
• Difficult tooth preparation
• Initial marginal leakage
• Technique sensitive if bonded
• Brittle
• Marginal breakdown
• Do not help retain weakened tooth structure
Disadvantages
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

• Less microleakage, interfacial staining.
• Slightly increase strength of remaining tooth
structure.
• Minimal postoperative sensitivity.
• Some retention benefit.
• Esthetic benefit of sealing by not permitting the
Amalgam to discolor the adjacent tooth
structure.
Bonded Amalgams have “Bonding
benefits” :
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

HISTORY OF AMALGAM
A Chinese medical
text(Material medica)
mentions using a
“silver paste”, a type of
amalgam, to fill teeth
in the 7th century
-by Su Kung in 659
AD
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

In Europe, Johannes Stokers, a
municipal physician in Ulm,
Germany, recommended amalgam as
a filling material in 1528.
Later, Li Shihchen (1578) chronicled a
dental mixture of 100 parts mercury
with 45 parts silver and 900 parts tin
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

In the 18th century, John Hill, an Englishman,
described mercury as, “It penetrates the substance
of all metals, and dissolves, and makes them
brittle.”
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion
• In 1818, Louis Nicolas Regnart, a Parisian
physician invented amalgam by the addition
of one-tenth by weight of mercury to another
metal or metals.
Dental silver amalgam was probably introduced in
England by Joseph Bell, a British chemist, in 1819, and
was known as ‘Bell’s putty’.

• Traveau described a “silver paste” filing
material in 1826. He produced
amalgam by mixing the silver coins
with mercury.
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

1833
-- Crawcours brothers introduced their
“Royal Mineral Succedaneum” to America
--mixed shaved French
silver coins and mercury.
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

In 1877, Foster Flagg published the results of his
laboratory tests and 5-year clinical observation of
new alloys with 60% of silver and 40% of tin as
major constituents in 1881 and thus predated by
some 15 years the work of G.V. Black
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

The universal acceptance of amalgam
as a restorative material resulted from
investigations of G V Black in 1895,
1896, 1908
By combining the principles of cavity design,
extension of the cavity into “immune” areas and
the development of an alloy with the composition
of 68.5% silver, 25.5% tin, 5% gold, 1% zinc,
Black advanced amalgams into modern times
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

Traditional or conventional amalgam
alloys were produced by early dental
manufactures (S S White) &
predominated from 1900 untill 1970.the
basic composition was 65%Ag, 30%Sn,
5%Cu,& less than 1%zinc
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion
ADA specification No 1 was adapted for amalgam in
1929.

Extensive studies of the setting reaction of dental
amalgams was performed by Gayler in 1937 & found
that in the coarse filling alloys of that time, copper
contents greater than 6% produced excessive expansion
This was later challenged by Greener in 1970’s
Gayler ML. Dental amalgams. J Inst Metals. 1937;60:407–19
Greener EH. Amalgam-yesterday, today and tomorrow. Oper Dent. 1979;4:24–35.
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

• In 1959, Dr. Wilmer Eames
recommended a 1:1 ratio of
mercury to alloy, thus lowering
the 8:5 ratio of mercury to alloy
that others had recommended.
Eames WB. Preparation and condensation of amalgam with low mercury alloy ratio.
J Am Dent Assoc. 1959;58:78–83
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

In 1962, a spherical particle dental alloy
was introduced by Innes & Youdelis
This was followed in 1963 by a high copper
dispersion alloy system that proved to be
superior to its low copper predecessors
Example; Dispersalloy (Caulk)
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

1970’s
• first single composition spherical
• Tytin (Kerr)
• ternary system (silver/tin/copper)
1980’s- mercury free alloys introduced
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

AMALGAMWARS-thecontroversy
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion
• In 1841, the American Society of Dental
Surgeons declared that
“the use of amalgam constitutes
malpractice”
AMALGAM USE DECLINED
Dr. Christopher S. Brewster (1846) - condemned the use
of amalgam in all cases merely because its use was
abused by some “unprincipled quacks” was unwise.
The amalgam controversy-an evidence based analysis ;
JADA,Vol.132,march 2001

a belief prevailed that amalgam exerted “a
vitiating influence upon the fluids of the mouth and
gives rise to an unhealthy action in the gums.”
- the society’s members were warned that they
were to sign a pledge “NEVER TO USE amalgam” or they
would risk being expelled from the membership.
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

Townsend - gave his personal directions for
preparing the amalgam, known as “Townsend’s
Amalgam”.
In 1858, Townsend reversed his stance on amalgam
and recommended removal of teeth that could not be
saved by gold.
In 1867, the St. Louis Odontological Society
unanimously adopted a resolution to the effect that
amalgam was “injurious and detrimental to health”
AMALGAM
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

1924 - Alfred Stock became poisoned with mercury &
published papers on the dangers of mercury in
dentistry
1934 - German physicians - no health risk from
amalgams
In December 2003, Dr. Frederick Eichmiller,
- Amalgam is a SAFE, AFFORDABLE, AND DURABLE
MATERIAL.”
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

the first one……
• In 1845, American Society of
Dental Surgeons condemned the
use of all filling material other
than gold as toxic, thereby
igniting "first amalgam war'.
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

What ended the amalgam war??
• Professional and consumer demand.
• In 1859, the leaders of the profession regrouped to form the American Dental
Association.
• Between 1860 and 1890, many experiments were done to improve amalgam
filling materials.
• it was the classical work of GV Black in 1895
that a systemic study was done on properties & appropriate manipulation of
amalgam.
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

Then came the second amalgam
war….
• Controversy over amalgam use surfaced
again in 1926 and into the 1930's when
a German physician, Dr. Alfred Stock,
showed that mercury escaped from
fillings in the form of a dangerous vapor
that could cause significant medical
damage.
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

• During this Second Amalgam War,
the American Dental Association
vigorously defended silver amalgam
and its widespread use was continued
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

Remarkably, the Food and Drug
Administration (FDA) has separately
approved the mercury and the alloy powder
for dental use; but the amalgam mixture has
never been approved as a dental device
Unfortunately now came the second world
war over Europe &" the second amalgam
war" fell in forgetfulness
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

3rd amalgam war in 1980s
It was the Neurobiologist Mats
Hanson, Assosiate professor in
physiology at Lund University in
Sweden, who in 1981 started the fight
against the authorities
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

but began primarily through seminars
,writings,& videotapes of Dr HA Higgins, a
dentist from Colarado Springs in the same
year
Pressure from mounting clinical evidence
forced the ADA to finally publicly concede
that mercury vapor does escape from the
amalgam filling into the patients mouth.
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

But the ADA remained adamant that mercury in
patients' mouths is safe, and in 1986 it changed its
code of ethics, making it unethical for a dentist to
recommend the removal of amalgam because of
mercury
but problem flared in 1990’s by the telecast of
television program ‘60 minutes’ in CBC television
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

Current status on the amalgam war
The amalgam war continues to rage on
today. some states have already
appointed holistic/biological dentists to
dental boards, effectively ending
the ADA monopoly on state dental
boards.
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

Current status on the amalgam war
• The problem is so serious that American
Council on Health & Science, has
determined that allegations against
amalgam constitute one of the greatest
“unfounded health scares of recent times”
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

• There is presently a congressional bill
in The United States House of
Representatives (H.R. 4163) introduced
by Rep. Diane Watson (D-CA) and Rep.
Dan Burton (R-IN) to ban the continued
use dental amalgam fillings.
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

STATEMENT ON AMALGAM-ADA
"No controlled studies have been published
demonstrating systemic adverse effects from amalgam
restorations-FDI & WHO;1997
“based on available scientific
information, amalgam continues to
be a safe and effective restorative
material.“-ADA;1998
"There currently appears to be no justification for
discontinuing the use of dental amalgam.“-ADA;1998
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion
American Dental Association (ADA) Council on Scientific
Affairs, “Statement on dental amalgam,” 2011, http://www
.ada.org/1741.aspx

“The current data are insufficient to support
an association between mercury release from
dental amalgam and the various complaints
that have been attributed to this restoration
material”-LSRO &FDA;2004
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion
.ada.org/1741.aspx

“there were no statistically significant
differences in adverse neuropsychological or
renal effects observed over the 5-year period in
children whose caries are restored using dental
amalgam or composite materials- Journal of the
American Medical Association (JAMA)
and Environmental Health Perspectives;2006
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion
.ada.org/1741.aspx

amalgam is a valuable, viable and safe
choice for dental patients-ADA;2009
material is a safe and effective restorative
option for patients-FDA;2009
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion
.ada.org/1741.aspx

Classification of Amalgam
A) According to Alloyed Metals
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion
Sturdevant’s Art & Science of Operative Dentistry;
5th ed
Number
of
alloyed
metal
Binary alloy
(Ag-Sn)
Tertiary
alloy
(Ag-Sn-
Cu)
Quarternary
alloy
(Ag-Sn-
Cu-Zn)

B) According to shape of powdered particle
5th ed
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion
Lathecut spherical
Admixed

C) According to copper content
5th ed
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion
Low copper
amalgam(<0-6%)
High copper
amalgam(>6-
13%)

D)According to zinc content
5th ed
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion
Zinc containing
alloy
(>0.01-2%)
Non zinc
containing alloy
(<0-0.01%)

1st generation
2nd generation
3rd generation
Cu Zn
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion
Ag3Cu
4th generation Ag Sn Cu upto
29%
5th generation Ag Sn Cu In
6th generation
E)Generations based on the
improvement in composition
Ag Cu Pd
Ternary alloy
Quaternary alloy
Eutectic alloy
1st, 2nd, 3rd
generation+

Components of dental amalgam
Other
Zinc
Indium
Palladium
Silver Tin
Copper Mercury
Basic
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion
Phillip’s Science of Dental Materials;11th ed

Silver(Ag)
Decreases creep & setting time
Decreases corrosion
Increases hardness & edge strength
Increase tarnishing
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

Tin(Sn)
Low strength
Larger contraction
Decreases expansion
Increased corrosion
Increased plasticity
Increased setting time
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

Copper(Cu)
Decreases plasticity
Increases hardness strength of alloy
Reduce creep
Reduce tarnish & corrosion
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

Zinc(Zn)
Decreases brittleness
Acts as a deoxidizer
Less marginal breakdown
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

Indium(In)
decreases surface tension
• reduces amount of mercury
necessary
• reduces emitted mercury vapor
reduces creep and
marginal breakdown
increases strength
example
• Indisperse (Indisperse Distributing
Company)
• 5% indium*
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion
operative dentistry journal1992 Sep-Oct;17(5):196-202

`
• Palladium (Pd)
– reduced corrosion
– greater luster
– example
• Valiant PhD (Ivoclar Vivadent)
– 0.5% palladium
Mahler J Dent Res 1990
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

Palladium pellets placed in an amalgam
restoration were effective in reducing the
amount of mercury vapor released in the
7 days following placement.
Dental Materials Volume 15, Issue 6, November 1999, Pages 382-389
The optimal palladium content in γ1 seems to be in
the range between 0.50 and 0.75 wt%.
Biomaterials, Volume 18, Issue 13, July 1997, Pages 939-946
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

Mercury (Hg) - only pure
metal that is liquid at room
temperature
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
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Conclusion

Alloy Powder Composition
Type Ag Sn Cu Zn Other
Low copper 63-72 26-28 2-7 0-2 —
High-Cu admixed lathe-
cut 40-70 26-30 12-30 0-2 —
High-Cu admixed
spherical 40-65 0-30 20-40 0 0-1 Pd
High-Cu single spherical
40-60 22-30 13-30 0
0-5 In,
0-1 Pd
compositions in weight percent
Sturdevant’s Art & Science of Operative Dentistry;5th ed
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

Alloy Powder: Dispersalloy®
Silver
69%
Tin
18%
Copper
12%
Zinc
1%
Mixing proportions: 50% alloy, 50% mercury
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Conclusion

Alloy Powder: Tytin®
Mixing proportions: 57.5% alloy, 42.5% mercury
Silver
59%
Tin
13%
Copper
28%
Zinc
0%
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Conclusion

Phases in Amalgam
Alloys and Set
Dental Amalgams
Formula
g Ag3Sn
g1 Ag2Hg3
g2 Sn7-8Hg
b Ag4Sn (silver-rich)
e Cu3Sn
h Cu6Sn5
Silver-copper
eutectic
Ag-Cu
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BASIC COMPOSITION
Matrix
Ag2Hg3 called gamma 1 - cement
Sn7Hg called gamma 2 - voids
Filler (bricks)
Ag3Sn called gamma can be in various
shapes irregular (lathe-cut), spherical or a
combination of both.
A silver-mercury matrix containing filler
particles of silver-tin.
Ag3Sn
Ag2Hg3
Sn7Hg8
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Basic setting reactions
Ag-Hg
Ag
Hg
Ag4Hg5 (ƴ1 phase)
Initial product
Ag
Hg
Ag5Hg4 (β1 phase)
In p/o excess Ag
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Materials science for dentistry;9th ed
B.W.Darvell

Silver-Tin (Ag - Sn) System
 Most commercial alloys fall within the limited composition range of B to
C i.e (β + γ) and γ
 If Sn > 26.8 wt%  γ + Sn-rich phase is formed.
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• Dissolution and precipitation
• Hg dissolves Ag and Sn
from alloy
• Intermetallic compounds
formed
Ag
Sn
Conventional Low-Copper Alloys
Hg
Ag3Sn + Hg  Ag3Sn + Ag2Hg3 + Sn8Hg
g g g1 g2
CRAIG’s Restorative Dental Materials;12th ed
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• Gamma (g) = Ag3Sn
– unreacted alloy
– strongest phase and
corrodes the least
– forms 30% of volume
of set amalgam
• Gamma 1 (g1) = Ag2Hg3
– matrix for unreacted alloy
and 2nd strongest phase
– 60% of volume
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IMPORTANCE OF γ2 PHASE:-
• Sn8Hg in a set amalgam may be reduced
in quantity or even eliminated by the
presence of ε–phase (Cu3Sn)
• Potentially valuable rxn for several
reasons:-
 tin act as a most electropositive element
present in absence of Zn, so with high activity
in the γ2 phase, it makes the most
electropositive phase, hence the most easily
corroded
B.W.Darvell
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 γ2 phase is extremely weak & soft,
deforming readily & the strength of
amalgam is limited by its presence
Contributes to static creep of amalgam
B.W.Darvell
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Conclusion

Scanning electron microscopic view of SnHg (γ2)
crystals, that occurs in the matrix of set low copper
amalgam
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Improves strength of the resulting
amalgam
But if in excess, leads to expansion on
setting
B.W.Darvell
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Conclusion
COPPER

Depending on its quantity & amt of Sn
in the alloy, it may present as:-
1.Cu3Sn (ε-phase)
2.Cu6Sn (ή-phase)
As solubility of Cu in γ and γ1 phase is
low, thus Cu-Sn phase formed during
setting process will probably be ή
phase
B.W.Darvell
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Conclusion

The reaction rate of β or γ phase Ag-Sn
with Hg is sufficiently fast that the γ2
phase is always formed initially, but
Cu3Sn (ε phase) & γ2 phase cannot
exist together for long & relatively
slow reaction must occur.
ε + γ2 → ή + (Hg)
B.W.Darvell
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SLOW REACTIONS

 This is at relatively low rate because it is a solid
state reaction
 Also the 2 phases will be distributed as small
grains throughout the amalgam without
necessarily touching , & all diffusion of metal
atoms must be through other phases or grain
boundaries
B.W.Darvell
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In the long term the conversion of γ1 to
β1 may occur in the presence of
unreacted γ phase alloy…
γ + γ1 → β1
B.W.Darvell
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Conclusion

In the presence of excess Hg ( in terms
of reaction with Ag-Sn phases),namely
the decomposition of Cu-Sn phases to
give the phase Cu7Hg6 (β2 phase)
occurs….
ε , ή (IN P/O EXCESS Hg) → β2 + γ2
B.W.Darvell
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Conclusion

Added Cu
As >6% Cu may not be included in the
‘conventionally’ formulated alloy because
of excessive expansion
However, if the extra Cu in incorporated
in the form of second alloy powder, mixed
with the first(admixed alloy),the difficulty
may be avoided
B.W.Darvell
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One such second alloy is eutectic of
Ag-Cu system;this corresponds to
composition 3Ag.2Cu
α + α1 + γ2  ή + γ1
The elimination of γ2 phase results in
improved properties, particularly in
the compressive strength.
B.W.Darvell
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Conclusion

High copper admixed alloy
2. Sn8Hg + AgCu  Cu6Sn5 + Ag2Hg3 + Ag3Sn
(g2) (h ) (g1 ) (g )
1. Ag3Sn + AgCu + Hg  Ag2Hg3 + Sn8Hg + Ag3Sn + AgCu
(g ) (g1 ) (g2 ) (g )
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High copper unicompositional
alloy
Ag3Sn + Cu3Sn + Hg  Cu6Sn5 + Ag2Hg3
(g ) ( e ) ( h ) (g1 )
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Microstructure of Set Low Copper
Amalgam.
g(Ag3Sn)
g2(Sn8Hg)
Voids
g1(Ag2Hg3)
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Conclusion

Microstructure of Set High-Copper
Admixed Amalgam.
g1(Ag2Hg3)
g(Ag3Sn)
Eutectic(Ag3Cu2)
h(Cu6Sn5)
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Produced by cooling molten 72% Ag and 28%
Sn and forming an ingot (The ingot may be 3-4
cm in diameter and 20 -30 cm in length)
Alloy is heated for 8 hours at 400°C for
homogeneous distribution of silver and tin
Ingot is lathe-cut to produce the particles, ball-
milled to reduce their size
The particles are 60-120µm in length, 10-70µm in width
& 10-35µm in thickness(Irregular in shape)
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Manufacture of alloy powder
Lathe cut alloy powder
B.W.Darvell

Produced by atomizing the molten alloy in a
chamber filled with an inert gas- argon
Molten metal falls through a distance of
approximately 30 feet and cools
Results in characteristic spherical particle
shapes.
If particles are allowed to cool before they contact
the surface of chamber, they are spherical in
shape. If they are allowed to cool on contact with
the surface they are flake shaped.
Particle size ranges form 5 to 40 microns
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Spherical alloy powder
B.W.Darvell

A. Lathecut alloy
B. Spherical alloy
C. Admixed alloy
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Homogenizing anneal
1. to overcome the coring & segregation
in the solid ingot
2. to reestablish the equilibrium phase
relationship
the ingot is placed in an oven & heated at temp. below
solidus for a sufficient time to allow diffusion of the
atoms to occur.
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Temperature
for Ag-Sn:
480 degree
Celsius
if Cu present:
465 degree
celsius
if Zn present:
lower it further
The time of heat treatment may vary depending on
the temp. used & size of ingot, but 24 hr at the
selected temp.(350 to 450 ͦC) is usual.
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• At the end of heat treatment:-
If rapid quenching
done
• The phase
distribution
remains
unchanged
• e.g. in an Ag-Sn
alloy results in the
formation of
βphase in max.
amount
If allowed to cool
slowly
• The proportion of
phases continue to
adjust towards
room temperature
equilibrium ratio
• e.g. formation of γ
phase
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Conclusion

Particle(surface) treatment
Freshly cut alloys amalgamate & set more
promptly than aged particles, but some aging
of alloy is desirable to improve the shelf life of
product
Amalgams made from acid washed powders
tends to be more reactive than those ,made
from unwashed powders
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• The aging is related to relief of stress in the
particles during the cutting of the ingot
(Phillip’s Science of Dental Materials;11th ed )
• The alloy particles are aged by subjecting
them to a controlled temperature of 60-100
degree celsius for 1-6 hrs
(Craig’s restorative dental materials,12th ed)
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PARTICLE SIZE
• Greater amount of
mercury to form an
acceptable amalgam
Tiny particles
• More rapid hardening
and a greater early
strength
Small-to-
average
particle size
• A rough surface
• Corrosion
Larger
particles
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Conclusion

Properties of amalgam
• ANSI/ADA specification No.1 for amalgam alloy
contains certain requirements:-
1. Maximum creep value of 3%
2. Minimum Compressive strength of 80 MPa at 1 hr
when a cylindrical specimen is compressed at a rate
of 0.25mm/minute
3. Dimensional change between 5 min & 24 hrs after
trituration, should fall within a range of ±20µm/cm
at 37̊ ̊C.
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DIMENSIONAL CHANGES
Amalgam can expand or contract depending on
manipulation
Severe contraction leads to plaque accumulation &
secondary caries
Expansion leads to postoperative pain & splitting of
tooth
B.W.Darvell
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Immediately after packing a rapid
contraction may be observed, followed
by a slower expansion, and then a slight
& slower contraction(amalgam setting
dimensional change curve)
Materials science for dentistry;9th ed B.W.Darvell
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20µm 20µm 20µm 20µm

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High-Cu, admixed
High-Cu, single comp.
Low-Cu

If amalgam expanded during hardening,
leakage around the margins of restorations
would be eliminated.
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Conclusion

 Shrinkage
• when alloy & mercury are mixed
,contraction results as particles begin to
dissolve & ƴ1 crystals grow
• 8Ag3Sn + 31Hg (823.5ml/mol)=6Ag4Hg5 + Sn8Hg
(774.9ml/mol)
• Thereby a decrease of 5.9% by volume, or
2.0% by length (effect of solidification of
mercury)
B.W.Darvell
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Conclusion

Evidently the detrimental effect of shrinkage occurs only
when the amalgam mass shrinks > 50 µm.
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 LOSS OF GLOSS
• Shrinkage due to reaction will initially
cause a decrease in the bulk volume,
but once contacts between alloy
particles or new crystals interfere with
this, there is no choice but for the Hg to
be withdrawn into the mass, leaving
behind outline of the alloy particles.
B.W.Darvell
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The failure of any amalgam to provide a marginal seal is
due to the shrinkage of the liquid mercury on reaction &
surface tension(a,b)
B.W.Darvell
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• The crinkly surface thus produced
clearly cannot be in direct contact with
the cavity wall & a leakage path exists
which survives even if there is
subsequent expansion
B.W.Darvell
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Conclusion

• The effect infact lead to loss of gloss, a
freshly mixed pellet of amalgam is very
smooth & shiny-metallically wet looking,
but as setting proceeds it acquires a
frosted or sand blasted appearance.
• Leakage path can also occur because of
the surface tension of mercury
B.W.Darvell
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 EXPANSION
• The impingement of growing crystals one on
another will cause outward forces which will
result in some expansion (crystal growth
pressure)
• If sufficient Hg is present to produce a plastic
matrix, expansion occurs as a result of
growth of ƴ1 crystals & viceversa
B.W.Darvell
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Conclusion

 DELAYED EXPANSION
Zinc containing low/high copper
amalgam is contaminated by moisture
during trituration or condensation, a
large expansion can take place
This expansion usually starts after 24
hrs, reach at peak within 3-5 days &
may continue for months reaching
values >400µm.
B.W.Darvell
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• Hydrogen is produced by electrolytic
action involving zinc & water
• H2 doesnt combine with the amalgam
rather it collects within amalgam,
increasing internal pressure of amalgam
leading to expansion
B.W.Darvell
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Delayed expansion
B.W.Darvell
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STRENGTH
A) Compressive strength
 Because amalgam is strongest in compression & much
weaker in tension & shear, the prepared cavity design
should take benefit of that
 When subject to a rapid application of stress either in
tension or compression a dental amalgam does not
exhibit significant deformation or elongation & as a
result function as a brittle material
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• High copper single composition materials
have the highest early compressive
strength of more than 250 Mpa at 1 hr
• While it is lowest for the low copper lathe
cut alloy(45 Mpa)
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Conclusion

• High values for early compressive strength are
advantage for an amalgam, because they reduce the
possibility of fracture by application of prematurely
high occlusal forces by the patient before the final
strength is reached
• The compressive strength at 7 days is again highest
for the high copper single composition alloys, with
only modest differences in the other alloys
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B) Tensile strength
• Amalgam cannot withstand high tensile or
bending stresses
• The design of the restoration should include
supporting structures whenever there is
danger that it will be bent or pulled in
tension
• Both low & high copper amalgams have
tensile strength that range between 48-70
MPa
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Conclusion

Factors affecting strength
-depends on the type of amalgam alloy, the
trituration time & the speed of amalgamator
-either under or overtrituration decreases the
strength in both traditional & high copper
amalgams
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Durability
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Conclusion
1) Effect of trituration

2) Effect of mercury content
dry granular
mixrough & pitted
surfacecorrosion
high mercury
contentmore γ2
phase
low mercury
contentmore
unreacted AgSn
particlesimparts
strength to
restoration
sufficient mercury should be
mixed with the alloy to wet
each particle of the alloy
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Sideeffects of
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Durability
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Conclusion

-good condensation techniques express mercury &
results in smaller volume fraction of matrix
phases
-in lathe cut alloys, higher condensation pressure
results in higher compressive strength,
particularly the early strength(at 1 hr)
-on the other hand spherical amalgams condensed
with lighter pressures produce adequate
strength
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3) Effect of condensation

-voids & porosities reduces strength
-porosity is caused by:-
a. decreased plasticity of the mix (due to low
Hg/alloy ratio, delayed condensation,
undertrituration)
b. inadequate condensation pressure(results in
inappropriate adaptation at the margins &
increase number of voids)
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4) Effect of porosity

c. irregularly shaped particles of alloy
powder
d. insertion of too large increments
-fortunately, voids are not the problem
with spherical alloys
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Conclusion

-amalgams do not gain strength as rapidly as
might be desired
-at the end of 20min,compressive strength may
be only 6% of 1 wk strength
-ADA stipulates a min of 80MPa at 1 hr
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5) Effect of rate of hardening

-the 1 hr compressive strength of high Cu
single composition amalgams is relatively
high compared with admixed high Cu
amalgams
-patients should be cautioned not to
subject the restoration to high bitting
stresses for atleast 8 hrs after placement
,by that time a typical amalgam has
reached at least 70% of its strength
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Conclusion

even after 6 months ,some
amalgams may still be increasing in
strength, suggesting that the
reactions between matrix phases
& the alloy particles may continue
indefinitely
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Conclusion

Strength of various phases
• By studying the initiation & propagation of
crack in a set amalgam, the strength of
various phases can be observed
• Possible to view under a conventional
metallographical microscope
• The propagation of the crack can be halted &
the specimen etched to identify the various
phases
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

• Results of such studies have led to the
following ranking of different phases of a set
low copper amalgam from strongest to
weaker:
Ag3Sn(γ),silver-Hg phase(γ1),tin-Hg
phase(γ2) and the voids
• In high copper amalgams, there is
preferential crack propagation through the
γ1 phase & copper containing particle
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

CREEP
• Defined as time dependent strain or
deformation produced by stress(as in
Phillips)
• Creep of dental amalgam is a slow progressive
permanent deformation of set amalgam which
occurs under constant stress(static creep) or
intermittent stress(dynamic creep)
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

• Creep is related to marginal breakdown of low
copper amalgams
• Higher the creep, the greater is the degree of
marginal deterioration(ditching)
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

• According to ADA sp. No.1 creep should
be below 3%
• creep values:-
-low copper amalgam:0.8-8%
-high copper amalgam:0.1-1%
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

Creep rate has been found to correlate with marginal
breakdown of conventional low-copper amalgams.
ADA spec. #1: creep rate < 3%
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

Microstructure Vs. Creep
Low-Cu Larger g1 volume
fraction
Presence of g2
Larger g1 grain
sizes
Single composition
spherical
h(Cu6Sn5) around Ag-Cu
particles improves bonding to
g 1
h (Cu6Sn5) embedded in
g1 grains and interlock
High-copper amalgams have creep resistance:-
lack of gamma-2 phase.
Admixture
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

Factors influencing creep:
Large g1 volume fraction
Larger g1 grain sizes
smaller g1 grain sizes
g2 associated with high
creep rates.
h phase which act as
barrier to deformation of
g1 phase.
Phases of
amalgam
restorations
High CREEP Low CREEP
B.W.Darvell0

For increased strength & low creep values:-
Mercury alloy ratio should be minimum
Condensation pressure should be
maximum for lathe cut or admixed alloys
Careful attention should be given towards
timing of trituration & condensation
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion
Effect of manipulative variables

Compressive
Strength (MPa)
% Creep Tensile Strength
(24 hrs) (MPa)
Amalgam Type 1 hr 7 days
Low Copper1 145 343 2.0 60
Admixture2 137 431 0.4 48
Single Composition3 262 510 0.13 64
Phillip’s Science of Dental Materials 2003
1Fine Cut,
Caulk 2
Dispersalloy,
Caulk
3Tytin, Kerr

MICROLEAKAGE OF AMALGAM
The 2 to
20micron-wide
gap
Poor condensation
techniques -
marginal voids
Lack of corrosion
by-products
Coefficient of
thermal expansion
Single-composition-spherical alloys
which leak more - do not adapt as well
to the margins
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

• Penetration of fluids & debris around the
margins may cause secondary caries
• If the amalgam restoration is inserted properly,
leakage decreases as the restoration ages in
mouth due to the corrosion products that
forms in the tooth-restoration interface
• Thus amalgam is the self sealing restoration
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

• Both low & high copper amalgams are
capable of sealing against microleakage
but the accumulation of corrosion
products is slower with the high copper
alloys*
*Corrosion sealing of amalgam restorations -in vitro study
Oper Dent. 2009 May-Jun;34(3):312-20.
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

• The sealing ability of different types of dental
amalgams when used as retrograde fillings
with and without a cavity varnish was studied.
• Of the materials tested, a copper-containing
spherical amalgam gave the best results.
• Regardless of material used, the apical seal
was significantly improved when a varnish was
applied to the cavity prior to the placement of
the retrograde amalgam filling
Journal of Endodontics
Volume 9, Issue 12 , Pages 551-553, December 1983
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

THERMAL EXPANSION AND
CONDUCTIVITY
Amalgam 22-28 9.4
Composite resin 20-60 0.25
GIC 10-11 0.15-0.35
Tooth 11.4 0.18-0.47
Thermal expansion
coefficient E 10-6 / C
Thermal conductivity
K 10-6 / C(mm2/s)
E = volume expansion for unit rise in temperature
K = quantity of heat passing per s through a block of unit thickness
and cross sectional area for a temp. difference of 1C
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

CHEMICAL PROPERTIES
Dental amalgam restorations undergo both
chemical and electrochemical corrosion.
TARNISH AND CORROSION
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

The degree of tarnish depends on :
i. The oral environment
ii. The type of alloy used
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

In dental practice , a limited amount of corrosion
around the margins of amalgam restorations may
be beneficial, since the corrosion products tends to
seal the marginal gap & inhibit the ingress of fluids
& bacteria
But excessive corrosion can lead to increased
porosity, reduced marginal integrity, loss of strength
& the release of metallic products into the oral
environment
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

GAP
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion
Liberation of corrosion
products

Electrochemical measurements on
pure phases
Ag2Hg3(γ1)
(highest corrosion
resistance)
Ag3Sn(γ) Ag3Cu2
Cu3Sn(ε),Cu6Sn5(ή)
Sn7-8Hg(γ2)
(least corrosion
resistance)

• The p/o small amounts of tin, silver &
copper that may dissolve in various
amalgam phases has a great influence
on their corrosion resistance
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

•The higher content of tin , less
the corrosion resistance
• The tin content of the γ1 phase
is higher for low copper alloys
than for high copper alloys
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

• The p/o a relatively high %age of tin in
low copper alloys reduces the corrosion
resistance of their γ1 phase so its lower
than their γ phase
• This is not true for high copper alloys
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

• Occurs most notably on the
occlusal surface and produces a
black amalgam silver tarnish film
• Corrosion products are mainly
oxides and chlorides of tin.
Chemical Corrosion :
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

Electrochemical corrosion
Chemically different sites act as anode or
cathode.
Electrolyte (saliva)
The anode corrodes, producing soluble and
insoluble reaction products.
Ag2Hg3 phase has the highest corrosion resistance,
followed by Ag3Sn, Ag-Cu, Cu3Sn, Cu6Sn5 and Sn7-8Hg.
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

LOW COPPER ALLOYS – low corrosion
resistance
The average depth of corrosion for most
amalgam alloys is 100-500 m.
Most corrodible phase is tin-mercury or g2
phase
Even though, a relatively small portion (1- 13%)
of the amalgam mass consists of the g2 phase,
in an oral environment, the structure of such an
amalgam will contain a higher percentage of
corroded phase
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

The corrosion results in the formation of tin oxychloride, from
the tin in g2 and also liberates Hg.
Sn7-8Hg + 1/202 + H2O + Cl-  Sn4 (OH) 6 Cl2 +
Tin oxychloride
Additional gl and g2 result in porosity and lower strength.
Unreacted g
Hg
g 1 and g 2
( Mercuroscopic Expansion )

THE HIGH COPPER ADMIXED AND
UNICOMPOSITION ALLOY
• No g2 phase in the final set mass.
• The η phase formed with high copper alloys is not an
interconnected phase such as the g2 phase, and it has better
corrosion resistance.
• η phase is the least corrosion resistant phase in high
copper amalgam - corrosion product CuCl2.3Cu (OH)2
Cu6Sn5 + 1/202 +H2O + Cl-  CuCl2.3Cu (OH)2 + SnO.
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

• Surface tarnish of low copper amalgams is
more associated with γ than γ1 phase,
whereas in high copper amalgams surface
tarnish is related to the copper rich phases,ή
& silver-copper eutectic
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

Galvanic corrosion
If dental amalgam is in direct contact with
an adjacent metallic restoration such as
gold crown, the dental amalgam is the
anode in the circuit.
Between
titanium and
direct filling
alloys
• Small
galvanic
interaction
High copper
dental
amalgams
when in
contact with Ti
• little galvanic
corrosion
Gallium
direct filling
alloys
• galvanic
interaction
more
detrimental
Dental Materials, Volume 15, Issue 5, September 1999, Pages 318-322
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

Local electrochemical cells may arise
whenever a portion of amalgam is covered
by plaque on soft tissue. It behaves
anodically and corrodes. If these occur in
cracks or crevice, it is called crevice
corrosion.
• Regions that are under stress display a greater
probability for corrosion, thus resulting in stress corrosion.
• For occlusal dental amalgam greatest combination of
stress and corrosion occurs along the margins.
Crevice Corrosion:
Stress Corrosion:
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

Factors related to excess tarnish & corrosion
High residual
mercury
Surface texture-
small scratches &
exposed voids
Contact of
dissimilar metals,
eg. gold & amalgam
Moisture
contamination
during
condensation
Type of alloy-low cu
alloy>high cu alloy
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion

• Smoothening & polishing the
restoration
• Correct mercury/alloy ratio & proper
manipulation
• Avoid dissimilar metals including
mixing of high & low copper amalgams
Introduction
History
Amalgam wars
Classification
Components
setting reaction
Manufacture
Properties
Manipulation
Recent advances
Sideeffects of
mercury
Durability
Future
Conclusion
Corrosion of amalgam can be reduced
by:-

REFERENCES
• PHILLIPS’ Science of Dental Materials;11th ed
Kenneth J. Anusavice
• CRAIG’s Restorative Dental Materials;12th ed
John M. Powers, Ronald L. Sakaguchi
• Materials science for dentistry;9th ed
B.W.Darvell
• Sturdevant’s Art & Science of Operative Dentistry; 5th
ed; Roberson, Heymann, Swift
• fundamentals of operative dentistry, a contemporary
approach; 3rd ed
Summitt, Robbins, Hilton, Schwartz
• Essentials of operative dentistry;
I Anand Sherwood

• Dental amalgam: An update
J Conserv Dent. 2010 Oct-Dec; 13(4): 204–208
• The amalgam controversy-an evidence based analysis ;
• Effect of admixed indium on the clinical success of amalgam restorations
. operative dentistry journal1992 Sep-Oct;17(5):196-202
• American Dental Association (ADA) Council on Scientific Affairs, “Statement on dental
amalgam,” 2011,
• Dental Materials Volume 15, Issue 6, November 1999, Pages 382-389
• Biomaterials, Volume 18, Issue 13, July 1997, Pages 939-946
• Journal of Endodontics
Volume 9, Issue 12 , Pages 551-553, December 1983
• Corrosion sealing of amalgam restorations -in vitro study
Oper Dent. 2009 May-Jun;34(3):312-20.

Amalgam past,present& future-I

Amalgam past,present& future-I

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