This document provides an overview of dental amalgam, including: - A brief history of amalgam, noting its first uses dating back to the 7th century and widespread adoption starting in the 19th century. - Details on the "amalgam wars" that occurred over concerns about the safety of mercury in amalgam in the 19th and 20th centuries. - Descriptions of the composition, manufacturing processes, phases and properties of amalgam, as well as newer advances and ongoing controversies. - It concludes by restating amalgam's position as one of the most commonly used dental restorative materials historically, while acknowledging alternatives and declining use due to safety questions.

1. Dr. Anita Dsouza
3rd MDS
Department of Conservative Dentistry and
Endodontics
DENTAL AMALGAM
MATERIAL ASPECTS

2. CONTENTS
• INTRODUCTION
• HISTORY
• AMALGAM WARS
• ADA SPECIFICATION
• CLASSIFICATION
• INDICATIONS AND CONTRAINDICATIONS
• ADVANTAGES AND DISADVANTAGES
• COMPOSITION
• MANUFACTURING PROCESS
• PHASES
• METALLURGIC PROCESSES
• PROPERTIES
• NEWER ADVANCES
• CONTROVERSIES
• CONCLUSION
• REFERENCES

3. 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.

5. • over the last few years, improvements in composition
have led to:
REDUCED
MARGINAL
CORROSION DUE
TO DECREASED
CREEP AND
CORROSION
EARLY SEAL
BETWEEN
TOOTH AND
RESTORATION
But development of alternatives based on ceramics and
composites , and questions on its safety have led to its
decline.

6. AMALGAM
• Amalgam -An alloy containing mercury
• Dental Amalgam – An alloy of mercury silver copper and tin,
which may also contain palladium, zinc and other elements
to improve handling characteristics and clinical
performance
• Dental amalgam Alloy – An alloy of silver copper and tin
that is formulated and processed in the form of powder
particles or compressed pellets.
Phillips’ Science of dental materials, 11/e Anusavice.

7. • Amalgam -- First used by Chinese. There is a mention of
silver mercury paste by Sukung (659AD) in the Chinese
medicine and later by Li schichan
• First use of room temp mixed amalgam- Bell in England
1819 (Bell’s putty)
• Traveau in France (1826) – advocated a mixture of silver
and mercury as a filling material – produced amalgam by
grinding silver coins with mercury.
• 1833 – Introduction of Royal Mineral Succedaneum to USA
as substitute for gold – Crawcour Brothers- “Royal mineral
succedaneum”

8. • 1840s– AMALGAM WAR
• 1859- ADA was formed
• 1860’S -1870’S – Elisa townsend and Flagg did a lot of
work to improve Dental Amalgam
• 1895- To overcome expansion problems G.V. Black
developed a formula for modern amalgam alloy -67%
silver, 27% tin, 5% copper, 1% zinc
• 1920 – Dr Grey – Delayed expansion
• 1926 - Second amalgam war – Europe – as a result of
the writings of Alfred Stock, a professor of Chemistry
published papers on the dangers of mercury vapor

9. • 1937- Gaylerin 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
• 1946 - Skinner, added copper to the amalgam alloy
composition in a small amount. This served to increase
strength and decrease flow
• 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.
• 1962- spherical particle dental alloy was introduced by Innes
& Youdelis

10. • 1963 – Innes and Youdelis – High Cu admixed alloy
• 1970- Change from hand trituration to mechanical trituration
• 1973 - Current controversy – termed Third amalgam war –
due to writings of Dr HA Higgins
• 1973 - First single composition spherical alloy named Tytin
(Kerr) a ternary system (silver/tin/copper) was discovered by
Kamal Asgar of the University of Michigan
• 1979 – Gay and workers found mercury vapor in breath of
patients with amalgam fillings following chewing.

11. • 1984- human autopsy demonstrated the mercury found in brain
and kidneys were related to the amalgam fillings in the teeth.
• 1990- media was involved when the TV show “is there a poison in
your mouth?” came out.
• 1991- Dental amalgam mercury syndrome groups started being
active.
• May 1991- Illinois house of representatives concluded amalgam
was safe.
• August 1991- national institute of health technology concluded
amalgam was safe.

12. AMALGAM WARS

13. WHAT ENDED THE 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.

14. SECOND AMALGAM WAR

15. • During this Second Amalgam War, the American Dental
Association vigorously defended silver amalgam and its
widespread use was continued.
• 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

16. THIRD AMALGAM WAR
But it began primarily through seminars ,writings,&
videotapes of Dr HA Higgins, a dentist from Colorado
Springs

17. • 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.
• 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

18. CURRENT STATUS ON AMALGAM WAR
• The amalgam war continues to rage on today.
• 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
• 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.

21. • Norway banned dental amalgam in 2008
• Sweden banned the use of dental amalgam for almost all
purposes in 2009 and Denmark, Estonia, Finland, and Italy
use it for less than 5% of tooth restorations.
• Japan and Switzerland have also restricted or almost banned
dental amalgam.
• France has recommended that alternative mercury-free dental
materials be used for pregnant women.

22. • In December of 2016, three EU institutions (the European
Parliament, the European Commission and the Council of the
European Union) reached a provisional agreement to ban dental
amalgam fillings for children under 15 and pregnant and
breastfeeding women as of July 1, 2018, and to consider banning
dental amalgam completely by 2030.
• Safe Mercury Amalgam Removal Technique (SMART) should be
used when amalgam fillings are removed. SMART was developed
by IAOMT to mitigate mercury exposures that can occur when the
fillings are taken out of people’s mouths, which often occurs due
to hypersensitivity, and/or patient preference.

23. ADA SPECIFICATION
• SPECIFICATION NO. 1
• ANSI/ADA STANDARD NO. 6—DENTAL
MERCURY: 1987 (REAFFIRMED 2005)

24. CLASSIFICATION BY MARZOUK
According to number of alloy metals:
• 1. Binary alloys (Silver-Tin)
• 2. Ternary alloys (Silver-Tin-Copper)
• 3. Quaternary alloys (Silver-Tin-Copper-Indium).

25. According to the shape of the powdered particles.
• 1. Spherical shape (smooth surfaced spheres).
• 2. Lathe cut (Irregular ranging from spindles to
shavings).
• 3. Combination of spherical and lathe cut (admixed).

26. According to Powder particle size.
• Micro cut
• Fine cut
• Coarse cut
According to copper content of powder
• Low copper content alloy - Less than 4%
• High copper content alloy - more than 10%

27. Based on zinc content-
• Zn containing (>0.01%)
• Zn free (<0.01%)
According to addition of Noble metals
• Platinum
• Gold
• Pallidum

28. According to compositional changes of succeeding generations
of amalgam
• First generation amalgam was that of G. V Black i.e. 3 parts silver one part
tin (peritectic alloy).
• Second generation amalgam alloys - 3 parts silver, 1 part tin, 4% copper to
decrease the plasticity and to increase the hardness and strength. 1 %
zinc, acts as a oxygen scavenger and to decrease the brittleness.
• Third generation: First generation + Spherical amalgam – copper eutectic
alloy.
• Fourth generation: Adding copper upto 29% to original silver and tin
powder to form ternary alloy. So that tin is bounded to copper.
• Fifth generation: Quatenary alloy i.e. Silver, tin, copper and indium.
• Sixth generation: consisting eutectic alloy which includes palladium, silver
and copper.

29. • Class I and class II cavities-moderate to large restorations.
• As a core build up material.
• Can be used for cuspal restorations (with pins usually)
• In combination with composite resins for cavities in posterior
teeth.
• As a die material
• Restorations that have heavy occlusal contacts.
INDICATIONS

30. • Class 3 in unaesthetic areas eg.distal aspect of canine.
especially if preparation is extensive with minimal facial
involvement
• Class 5 lesions in non-esthetic areas especially when
access is limited and moisture control is difficult and for
areas that are significantly deep gingivally.
• Restorations that cannot be well isolated.
• In teeth that act as an abutment for removable
appliances.

31. CONTRAINDICATIONS
• Anterior teeth where esthetics is a prime concern
• Esthetically prominent areas of posterior teeth.
• Small –to-moderate classes I and II restorations that
can be well isolated.
• Small class VI restorations

32. ADVANTAGES
• Ease of use, Easy to manipulate
• Relatively inexpensive
• Excellent wear resistance
• Restoration is completed within one sitting without
requiring much chair side time.
• Well condensed and triturated amalgam has good
compressive strength.

33. • Sealing ability improves with age by formation of
corrosion products at tooth amalgam interface.
• Relatively not technique sensitive.
• Bonded amalgams have “bonding benefits”.
Less microleakage
Slightly increased strength of remaining tooth
structure.
Minimal postoperative sensitivity.

34. DISADVANTAGES
• Unnatural appearance (non esthetic)
• Tarnish and corrosion
• Metallic taste and galvanic shock
• Discoloration of tooth structure
• Lack of chemical or mechanical adhesion to the tooth
structure.
• Mercury toxicity
• Promotes plaque adhesion
• Delayed expansion
• Weakens tooth structure (unless bonded).

35. COMPOSITION

36. • Silver (Ag)
increases strength
increases expansion
Decreases creep &
setting time
Decreases corrosion
Increases hardness
Increases tarnishing
• Tin (Sn)
decreases expansion
decreased strength
increases setting time
Increases corrosion
Increases plasticity

37. • Copper (Cu)
ties up tin thereby reducing gamma-2 formation
increases strength
Increases setting expansion
reduces tarnish and corrosion
reduces creep, flow.
reduces marginal deterioration,
increases edge strength.

38. • Zinc (Zn)
provides better clinical performance
less marginal breakdown
decreases oxidation of other elements
Give plasticity, hastens setting , improves color of mass.
causes delayed expansion - both high & low Cu alloys if
contaminated with moisture.

39. • Indium (In)
decreases surface tension
reduces amount of mercury necessary
reduces emitted mercury vapor
reduces creep and marginal breakdown
increases strength
must be used in admixed alloys

40. • Palladium (Pd)
reduces corrosion
greater luster

41. • Mercury (Hg)
activates reaction
only pure metal that is liquid at room temperature
Spherical alloys
require less mercury
smaller surface area easier to wet
Admixed alloys
require more mercury
lathe-cut particles more difficult to wet

43. MANUFACTURING PROCESS- LATHE CUT
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)

44. PARTICLE TREATMENT
• Acid washed – Preferential dissolution of specific
components – acid washed powders more reactive than
unwashed powders
• Aging is basically a stress relief process.
• It makes the alloy stable in its reactivity and property for
indefinite period of time – improves shelf life.
• Generally done by heating them 60 to 100 ̊c for 1 to 6
hours

45. MANUFACTURING PROCESS- SPHERICAL
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

47. PHASES IN AMALGAM ALLOYS

48. METALLURGICAL PROCESSES IN
AMALGAMATION- LOW COPPER ALLOYS
• Amalgamation occurs when mercury contacts the surface
of the silver-tin alloy particles.
• The silver and tin dissolve into the mercury.
• During the reaction, the formation of body centered
cubic form of Ag2Hg3 and hexagonal Sn7-8Hg occurs.
• Gamma 1 and 2 crystals grow as the remaining mercury
dissolves the alloy particles.
• As the mercury disappears, amalgam hardens.

49. • Alloy is mixed with mercury in the ratio of 1:1
• γ + Hg γ1 + γ2 + Unreacted alloy particles
γ1 - Dominant phase – 54-56%
Unreacted γ - 27- 35%
γ2- 11-13%

50. HIGH COPPER ALLOYS- ADMIXED
• 1963 innes and youdelis added silver copper eutectic alloy
particles ( 71.9% of Ag and 28.1% Cu) to lathe cut low
copper alloys.
• Also called as blended alloys.
• Contain 2 parts by weight of conventional composition lathe
cut particles plus one part by weight of spheres of a silver
copper eutectic alloy.
• The silver tin particle is usually formed by the lathe cut
method, whereas the silver copper particle is usually
spherical in shape
• The AgCu particles acts as strong fillers in strengthening the
amalgam matrix.
• copper content - 9 to 20%.

51. • The mercury dissolved in the Ag-Sn particles forms gamma 1 and
2 phases leaving some unreacted Ag-Sn particles.
• The newly formed gamma 2 around the Ag-Sn particles reacts with
AgCu eutectic alloy particles and forms the η phase (Cu6Sn5)
along with some gamma 1 phase around Ag-Cu particles.
• Ag3Sn + Ag-Cu + Hg Ag3Sn + Ag2Hg3 + Sn8Hg + Ag-Cu
• Sn8Hg + Ag-Cu Cu6Sn5 + Ag2Hg3 + Ag-Cu

52. UNICOMPOSITIONAL ALLOY
• It is so called as it contains particles of same composition
(Asgar – 1974)
• Usually Spherical in nature
• Cu Content 13 – 30 %.
• The particles of unicompositional alloys in very early stages
of setting are surrounded by gamma 1 and 2 phases and the
periphery becomes an alloy of Ag and Cu.
• Gamma 2 reacts with Ag-Cu phase and forms η and more
gamma 1.

53. • The unicompositional alloy reaction with Hg is

54. PROPERTIES
ADA specification No.1 for amalgam lists following
physical properties as a measure of quality of the
amalgam.
• Creep
• Strength
• Dimensional changes
• Modulus of elasticity

55. 1) STRENGTH
A) COMPRESSIVE STRENGTH
• Amalgam is strongest in compression & much weaker in
tension & shear.
• 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 functions as a brittle
material
• 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(145 Mpa)

56. • 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.
• Tooth preparation should be done in such a way that they are
subjected to more of compressive stresses and less of tensile
stresses.
• The compressive strength of a satisfactory amalgam restoration
should be atleast 310 MPa

57. COMPRESSIVE STRENGTHS OF LOW-COPPER AND
HIGH COPPER AMALGAM

58. B) TENSILE STRENGTH
• Amalgam is much weaker in tension
• Tensile strengths of amalgam are only a fraction of their
compressive strengths
• Cavity design should be constructed to reduce tensile
stresses resulting from biting forces
• High early tensile strengths are important – resist fracture by
prematurely applied biting forces
• Both low & high copper amalgams have tensile strength that
range between 48-70 MPa

59. TENSILE STRENGTHS OF AMALGAM

60. FACTORS AFFECTING STRENGTH
A) Effect of Trituration:
• Effect of trituration on strength depends on the type of
amalgam alloy, the trituration time and the speed of the
amalgamator.
• Under trituration or over-trituration decreases the strength for
both traditional and high copper amalgams.
• More the trituration energy used, more evenly distributed are
the matrix crystals over the amalgam mix and consequently
more the strength pattern in the restoration.
• Excess trituration after formation of matrix crystals will create
cracks in the crystals, and lead to drop in strength of set
amalgam

61. • B) Effect of Mercury
• Sufficient mercury should be there to coat the particles.
• Low mercury alloy content, contain stronger alloy particles
and less of the weaker matrix phase, therefore there is more
strength.
• If mercury is too less it leads to a dry, granular mix, which
results in a rough, pitted surface that invites corrosion.
• If the mercury content increases beyond 54% the strength
reduces markedly

62. C) Effect of condensation
• For lathe cut amalgam, greater the condensation pressure
higher the compressive strength. Higher condensation
pressure is required to minimize porosity and to express
mercury.
• Spherical amalgam - light condensation pressure produces
adequate strength.

63. D) Effect of porosity
• Voids & porosities reduces strength
• Porosity is caused by:
a. Decreased plasticity of the mix (due to low Hg/alloy ratio,
delayed condensation, under-trituration)
b. Inadequate condensation pressure (results in inappropriate
adaptation at the margins & increase number of voids)
c. Irregularly shaped particles of alloy powder
d. Insertion of too large increments

64. E) Temperature:
• Amalgam looses 15% of its strength when its temperature
is elevated from room temperature to mouth temperature
• It looses 50% of room temperature strength when
temperature is elevated to 60 deg C e.g. hot coffee or
soup.

65. 2) CREEP AND FLOW
• Creep is 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)
• Creep is related to marginal breakdown of low copper
amalgams
• Higher the creep, the greater is the degree of marginal
deterioration (ditching)
• It is measured after the amalgam has set.

66. • 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%
• Creep rate has been found to correlate with marginal
breakdown of conventional low-copper amalgams.
• High-copper amalgams have creep resistance because of lack
of gamma-2 phase.
FLOW:
Flow refers to the deformation that occurs during the setting of
amalgam.
Greater the flow, greater are chances for restoration failure.

67. FACTORS INFLUENCING CREEP
A) Phases of amalgam restorations
• Creep rate decreases with larger gamma1 grain sizes.
• Gamma 2 is associated with high creep rates.
• In absence of gamma 2, low creep rates in single
composition alloy may be due to eta phase which act as
barrier to deformation of gamma1 phase.

68. B) Manipulations:
• Greater compressive strength will minimize creep rates.
• Low mercury: alloy ratio, greater the condensation
pressure and time of trituration, will decrease the creep
rate.

69. 3) DIMENSIONAL CHANGE
• Severe contraction leads to plaque accumulation &
secondary caries
• Expansion leads to postoperative pain & splitting of tooth
• If amalgam expanded during hardening, leakage around the
margins of restorations would be eliminated.
• Largest dimensional change -19.7µg/cm- low cu lathe cut
alloy.
• Lowest -1.9µm/cm – high cu admixed alloy.

70. • Evidently the detrimental effect of shrinkage occurs only
when the amalgam mass shrinks > 50 µm.
• According to ADA/ANSA SPECIFICATION NO-1.
+-20µm/Cm is allowed.

71. When mercury is combined with amalgam it undergoes three
distinct dimensional changes:
• Stage -1: Initial contraction, occurs for about 20 minutes
after beginning of trituration. Contraction results as the alloy
particles dissolve in mercury. Contraction, which occurs, is
no greater than 4.5 µcm.
• Stage -2: Expansion- this occurs due to formation and
growth of the crystal matrix around the unconsumed alloy
particles.
• Stage -3: Limited delayed contraction.

72. FACTORS THAT AFFECT THE DIMENSIONAL
CHANGES:
1) Particle size and shape:
• More regular the particle shape, more smoother the
surface area.
• Faster and more effectively the mercury can wet the
powder particles and faster amalgamation occurs in all
stages with no apparent expansion.

73. 2) Mercury:
• More mercury , more will be the expansion, as more crystals
will grow.
• Low mercury: alloy ratio favors contraction.
3) Manipulation:
• During trituration, if more energy is used for manipulation,
the smaller the particles will become , mercury will be
pushed between the particles, discouraging expansion.
• More the condensation pressure used during condensation,
closer the particles are brought together; more mercury is
expressed out of mix inducing more contraction.

74. CONTRACTION
Alloys dissolve in mercury and becomes smaller in size.
FACTORS FAVOURING CONTRACTION
• Less mercury content
• Higher condensation pressure
• Over trituration
• Smaller particle size
• Spherical alloys have more contraction
• Low Hg - higher contraction.

75. EXPANSION:
• 16.6% of restorations fail- 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
• According U.S Bureau of standards a dimensional change on
setting, value of 5 - 10µm allowable.

76. DELAYED EXPANSION
• Dr Grey - 1920
• Takes place after 24 hours. Zinc containing amalgam when
contaminated with moisture during trituration or condensation
can result in delayed expansion.
• This expansion can be for 3-5 days to months reaching values
greater than 400µm • Also called as secondary expansion.
• Hydrogen is produced by the electrolytic action involving zinc
and water which does not combine in amalgam but rather
collects within the restoration increasing the internal pressure
causing amalgam to expand.
Zn + H2O  ZnO + H2

77. COMPLICATIONS THAT MAY RESULT DUE TO
DELAYED EXPANSION ARE:
• Protrusion of the entire restoration out of the cavity.
• Increased micro leakage space around the restoration.
• Restoration perforations.
• Increased flow and creep.
• Pulpal pressure pain.
Such pain may be experienced 10-12 days after the insertion of
the restoration

78. 4) TARNISH AND CORROSSION
• Tarnish – surface discolouration on a metallic surface
without the loss of structure. ( sulphide layer)
• It depends on oral environment and type of alloy.
• In case of low copper alloys, gamma phase is responsible.
For high copper alloys, eta and Ag-Cu eutectic are
responsible.
• Does not cause any detrimental effect on the amalgam

79. CORROSION
• Corrosion – actual deterioration of metal by reaction with its
environment.
• Porosity,
• Reduced marginal integrity and
• Loss of strength
• Tin oxychloride is the corrosion product formed. (low copper)
Sn7-8Hg + 1/202 + H2O + Cl- -> Sn4 (OH)6 Cl2 + Hg
• Corrosion product CuCl2.3Cu(OH)2 (high copper)
Cu6Sn5 + 1/202 +H2O + Cl- -> CuCl2.3Cu (OH)2 + SnO.

80. GALVANIC CORROSION:
• If dental amalgam is in direct contact with an adjacent metallic
restoration such as gold crown galvanic corrosion takes place. The
dental amalgam is the anode in the circuit. Saliva being the electrolyte.
STRESS 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:
• 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.

82. Electro chemical studies show
• γ1 phase has the highest corrosive resistance followed by γ,
AgCu, ε and η
• Least resistant to corrosion is the γ2 phase.
• γ2 phase crystals are long and blade like, penetrating throughout
the matrix. They form a penetrating matrix because of the
intercrystalline contact between the blades. Hence this phase is
more prone for corrosion producing penetrating corrosion.
• γ2 is more electronegative than γ and γ1 phases. So this induces
galvanic corrosion.

83. • Corrosion products from the tin in gamma 2 phase include tin
oxychloride. Due to corrosion, mercury gets released.
• This mercury then reacts with unreacted gamma particles and
produces additional gamma 1 and 2 phases which results in
some expansion called as MERCUROSCOPIC EXPANSION.
This results in porosity and reduction in strength.
• Corrosion on surface of amalgam restorations usually occurs
to a depth of about 100 – 500 micrometers.
• Phosphate buffering ability of saliva is known to inhibit this
process and provide protection against corrosion.

84. FACTORS RELATED TO EXCESS TARNISH &
CORROSION
• High residual mercury
• Contact of dissimilar metals, eg. gold & amalgam
• Surface texture- scratches and voids
• Moisture contamination during condensation
• Type of alloy-low cu alloy>high cu alloy

85. CORROSION CAN BE REDUCED BY:
• Smoothening & polishing the restoration
• Correct mercury/alloy ratio & proper
manipulation
• Avoid dissimilar metals including mixing of
high & low copper amalgams

86. SELF SEALING ABILITY OF AMALGAM
• Though corrosion and corrosion products are detrimental
to a restoration, it is advantageous in amalgam
restorations.
• Since amalgam doesn’t bond to the tooth, the corrosion
products seal the amalgam and tooth interference.
• This is seen more in low copper amalgam than high
copper amalgam.

87. RECENT ADVANCES

88. RESIN COATED AMALGAM
• To overcome the limitation of microleakage with
amalgams, a coating of unfilled resin over the restoration
margins and the adjacent enamel, after etching the
enamel, has been tried.
• Although the resin may eventually wear away, it delays
microleakage until corrosion products begin to fill the tooth
restoration interface.

89. FLUORIDATED AMALGAM
• Fluoride, being cariostatic, has been included in amalgam to deal with
the problem of recurrent caries associated with amalgam restorations.
It was proposed by Innes and Youdelis in 1966, Serman in 1970 and
Stone in 1971
• Several studies concluded that a fluoride containing amalgam may
release fluoride for several weeks after insertion of the material in
mouth.
• the fluoride release from this amalgam seems to be considerable during
the first week.

90. • An anticariogenic action of fluoride amalgam could be explained by
its ability to deposit fluoride in the hard tissues around the fillings and
to increase the fluoride content of saliva, subsequently affecting
remineralization.
• In this way, fluoride from amalgam could have a favorable effect not
only on caries around the filling but on any initial enamel
demineralization.
• The fluoride amalgam thus serves as a “slow release device”
• Example: Fluoralloy
• The problem with this method is that the fluoride is not delivered long
enough to provide maximum benefit.
Fluoride release from a fluoride-containing amalgam in vivo. Skartveit L, Tveit AB, Ekstrand J Scand J Dent
Res. 1985 Oct; 93(5):448-52.

91. BONDED AMALGAM
• Since amalgam does not bond to tooth structure, microleakage
immediately after insertion is inevitable.
• So, to overcome these disadvantages of amalgam, adhesive systems
that reliably bond to enamel and dentin have been introduced.
• Amalgam bond is based on a dentinal bonding system developed in
Japan by Nakabayashi and co-workers.
• 4META has been used to bond amalgam to cavity walls.
• The bond strength in admixed alloys was lower than those achieved
with spherical alloys.

92. • One study compared post-insertion sensitivity of teeth with
bonded amalgams to that of teeth with pin-retained amalgams.
After 6 months, teeth with bonded amalgams were less sensitive
than teeth with pin-retained amalgams.
• This difference in sensitivity was not present 1 year after insertion.
This is possibly because of corrosion products in nonbonded
amalgam restorations filling the interface, and thus, decreasing
microleakage and sensitivity.
Summitt JB, Burgess JO, Osborne JW, Berry TG, Robbins JW. Two year evaluation of amalgambond plus
and pin-retained amalgam restorations (abstract 1529) J Dent Res. 1998;77:297.

94. GLASS CERMET
• It is also called as cermet ionomer cements. McLen and
Gasser in 1985 first developed this material. Fusing the
glass powder to silver particles through sintering that can be
made to react with polyacid to form the cement.
• The properties include strength which is both tensile and
compressive strength is greater than conventional glass
ionomer cement. The abrasion resistance is greater than
conventional GIC due to silver particle incorporation.
• The silver cement radiopacity is equal to that of dental
amalgam. The fluoride release for cermet is about 3350
ug in 2 weeks and about 4040 ug in 1 month.

95. GALLIUM – AN ALTERNATIVE TO AMALGAM
• As early as 1956, Smith and Caul and Smith and co-workers
claimed that a gallium based alloy could serve as a possible
alternative to dental amalgam.
• They found that mixing gallium with either nickel or copper and
tin produced a pliable mass that could be condensed into a
prepared cavity, which, after setting, had physical properties
suitable for a restorative material.
• Commercial brands are: Galloy, Bayswater,
Gallium GF, Gallium GF II

97. HOWEVER…

98. INDIUM CONTAINING ALLOY POWDER AND
MERCURY-INDIUM LIQUID ALLOY
• Powell et al in 1989 added pure indium powder with high
copper alloy and triturated it with mercury.
• A significant decrease in mercury evaporation was seen.
• This was marked as : Indisperse and Indiloy
• Youdelis found that less mercury is required for mixing
amalgam when 10% Indium is present.
• Johnson GH et al : indium containing
high copper alloy exhibited low creep
and increase in strength.

100. CONSOLIDATED SILVER ALLOY SYSTEM
• One amalgam substitute being tested is a consolidated silver alloy system
developed at the National Institute of Standards and Technology.
• It uses a fluoroboric acid solution to keep the surface of the silver alloy
particles clean. The alloy, in a spherical form, is condensed into a
prepared cavity in a manner similar to that for placing compacted gold.
• One problem associated with the insertion of this material is that the alloy
strain hardens, so it is difficult to compact it adequately to eliminate
internal voids and to achieve good adaptation to the cavity without using
excessive force.
Bharti R, Wadhwani KK, Tikku AP, Chandra A. Dental amalgam: An update. Journal of conservative
dentistry: JCD. 2010 Oct;13(4):204.

101. MERCURY FREE AMALGAM
• Here, an experimentation was done which involved discarding the
mercury content of amalgam and replacing it with a proprietary
antimicrobial silver solution and unsialinized titanium dioxide ceramic
nanoparticles for strength, with a favorable, easy to manipulate
consistency.
• Prepared maxillary premolar controls were filled with Permite amalgam
and compared to an experimental group filled with the novel material.

102. • Both groups were then thermocycled, cross-sectioned, and
studied through scanning electron microscopy (SEM).
• It was concluded that the addition of the silver solution and
ceramic nanoparticles to mercury-free regular-set Permite alloy
yielded a product that exhibits improved marginal adaptation with
less application of condensation pressure, when compared to
regular-set Permite amalgam.

103. CONTROVERSIES IN AMALGAM
Basun et al. (1991) and Hock et al.
(1998) demonstrated a significant
nearly twofold increase in plasma
and blood Hg levels in AD
patients when compared to the
respective values from age matched
controls.
Ehmann et al. (1986) found higher levels of Hg in the brain of
autopsied AD patients than the control subjects without AD.

104. CONTROVERSIES IN AMALGAM
Mackert and Berglund
concluded that the extremely
low dosage of mercury
attributable to amalgam
restorations
was insufficient to produce any
detectable negative effect on
general health.
Data strongly suggest
that mercury levels
many times higher
than those associated
with a mouth full of
amalgam pose no
risk of adverse
health effects.
Ekstrand and colleagues found no effects on
various parameters of kidney function in humans

105. CONCLUSION:
• Dental amalgam has served as an excellent and versatile
restorative material for many years, despite periods of
controversy.
• It has served as a dental restoration for more than 165 years.
There is still no adequate economic alternative for dental
amalgam.
• Although there is evidence of a decrease in its use in the world,
amalgam’s cost, durability and ease of manipulation have
persuaded many dentists to continue to use it as their first choice
for restoring posterior teeth.

109. • Also, in regards to dental allergies, Dr. Stejskal introduced the
MELISA test in 1994. This is a modified version of the Lymphocyte
Transformation Test designed to test for metal sensitivity type IV
delayed hypersensitivity to metals, including sensitivity to mercury.
• Amalgam will probably disappear eventually, but its
disappearance will be brought about by a better and more esthetic
material, rather than by concerns over health hazards.
• When it does disappear, it will have served dentistry and patients
well for more than 200 years.

110. REFERENCES
• J Conserv Dent. 2010 Oct;13(4):204-8. Dental amalgam: An update
• The amalgam controversy-an evidence based analysis ; JADA,Vol.132,march 2001
• Mertz-Fairhurst EJ, Curtis JW, Jr, Ergle JW, Rueggeberg RA, Adair SM. Ultraconservative
and cariostatic sealed restorations: Results at year 10. J Am Dent Assoc. 1998;129:55–
66.
• Summitt JB, Burgess JO, Osborne JW, Berry TG, Robbins JW. Two year evaluation of
amalgambond plus and pin-retained amalgam restorations (abstract 1529) J Dent Res.
1998;77:297.
• Bharti R, Wadhwani KK, Tikku AP, Chandra A. Dental amalgam: An update. Journal of
conservative dentistry: JCD. 2010 Oct;13(4):204.
• DODES, J. E. (2001). The amalgam controversy. The Journal of the American Dental
Association, 132(3), 348–356. doi:10.14219/jada.archive.2001.0178
• PHILLIPS’ Science of Dental Materials;11th ed Kenneth J. Anusavice
• CRAIG’s Restorative Dental Materials;12th ed John M. Powers, Ronald L. Sakaguchi

111. THANK YOU