Reference- Skinners 11th edition

1. Presented by
Sneha Singh
JR-1
1

2. Contents
• Introduction
• Alloy composition & classification
• Metallurgic phases in Dental Amalgams
• Manufacture of alloy particles
• Amalgamation and resulting microstructures
• Dimensional stability
• Strength
• Creep
• Clinical performance of Amalgam restorations
• Factors affecting the success of Amalgam restorations
• Mercury/Alloy ratio
• Mechanical trituration
• Condensation
• Carving and finishing
• Clinical significance of dimensional change
• Side effects of mercury
• Marginal deteriotion
2

3. 3

4. Definitions
• Amalgam
An amalgam is an alloy that contains mercury as one
of its constituents.
• 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, tin and other elements that
is formulated and processed in the form of
powder particles or as compressed pellets.
4

5. Definitions
• Creep:
Time dependent strain or deformation that is
produced by a stress.
• Delayed Expansion:
The gradual expansion of zinc-containing amalgam
over weeks to months, which is associated with
hydrogen gas development caused by
contamination of the plastic mass with moisture
during its manipulation in a cavity preparation.
• Marginal Breakdown:
The gradual fracture of the perimeter or margin of a
dental amalgam restoration that leads to the
formation of gaps or ditching at the external interfacial
region between the amalgam and the tooth.
5

6. Definitions
• Trituration:
The process of grinding powder especially within a
liquid.
• Amalgamation:
The process of mixing liquid mercury with one or more
metals or alloys to form an amalgam.
6

7. Amalgamator (Triturator)
• Speeds vary upward
from 3000 rpm
• Times vary from 5–20
seconds
• Mix powder and liquid
components to
achieve a pliable mass
• Reaction begins after
components are mixed
7

8. History
• 1833
– Crawcour brothers introduce
amalgam to US
• powdered silver coins mixed with mercury
– expanded on setting
• 1895
– G.V. Black develops formula
for modern amalgam alloy
• 67% silver, 27% tin, 5% copper, 1% zinc
– overcame expansion problems
8

9. History
• 1960’s
– conventional low-copper lathe-cut alloys
• smaller particles
– first generation high-copper alloys
• Dispersalloy (Caulk)
– admixture of spherical Ag-Cu
eutectic particles with
conventional lathe-cut
– eliminated gamma-2 phase
9

10. • 1970’s
– first single composition spherical
• Tytin (Kerr)
• ternary system (silver/tin/copper)
• 1980’s
– alloys similar to Dispersalloy and Tytin
• 1990’s
– mercury-free alloys
10

11. The Amalgam wars
• Amalgam war initiated in 1841 also known as the ‘first
amalgam war’
• Dr. Chapin A. Harris (1839) said amalgam is an abominable
article for dental filling.
• 1843-resolution by american society of dental surgeons
that amalgam use is malpractice.
• 1845- pledge by this organisation not to use amalgam.
• 1850-pledge rescinded. Marked end of amalgam war
officialy.
• Investigations were begun on amalgam composition in
germany ,u.S. & France.
• The question of amalgam composition was finally settled in
1895 by dr. G.V. Black . (67.5% ag; 27.5% sn; 5% cu).
11

12. • The Second Amalgam War was started by a German chemist,
professor Alfred Stock in the mid 1920’s when Stock claimed to
have evidence showing that mercury could be absorbed from
dental amalgams and that this led to serious health problems. Stock
reported that nearly all dentists had excess mercury in their urine. •
He reported that mercury levels in urine of 7 patients with amalgam
ranged from 0.1 to 40 mg/L
• The current controversy, sometimes termed the “Third Amalgam
War” began primarily through the seminars, writings and videotapes
of H.A. Huggins, a dentist from Colorado Springs. He was convinced
that mercury released from dental amalgam was responsible for a
plethora of human diseases affecting the cardiovascular and nervous
systems.
• 1991- Issue reported by a major television
• NIH- NIDR & FDA Reexamined the issue ---- concluded that there is
no basis for the claim
12

13. Uses of Amalgam
• ANTERIOR TEETH –
Class III = distal surfaces of Canine .
• POSTERIOR TEETH –
Class I & Class II
• OTHER USES –
Retrograde root canal filling ,
Post & Core preparation
13

14. Indication
• In clinical situations involving heavy occlusal
functioning.
• In less optimum conditions of moisture
control.
• Operator ability.
14

15. Contra-indication
• Anterior teeth and clearly visible surfaces of
posterior teeth.
• Remaining tooth structure requires support /
would require extensive preparation to
accommodate amalgam.
• Treatment of incipient / early primary fissure
caries.
15

16. 16

17. Alloy composition
Basic
– Silver
– Tin
– Copper
Other
– Zinc
– Indium
– Palladium
17

18. Basic Constituents
• Silver (Ag)
– increases strength
– increases expansion
• Tin (Sn)
– decreases expansion
– decreased strength
– increases setting time
18

19. Basic Constituents
• Copper (Cu)
– ties up tin
• reducing gamma-2 formation
– increases strength
– reduces tarnish and corrosion
– reduces creep
• reduces marginal deterioration
19

20. Basic Constituents
• Mercury (Hg)
– activates reaction
– only pure metal that is liquid
at room temperature
spherical alloys
• require less mercury
– smaller surface area easier to wet
» 40 to 45% Hg
– admixed alloys
• require more mercury
– lathe-cut particles more difficult to wet
» 45 to 50% Hg
20

21. Other constituents
• Zinc (Zn)
– used in manufacturing
• decreases oxidation of other elements
– sacrificial anode
– provides better clinical performance
• less marginal breakdown
– Osborne JW Am J Dent 1992
– causes delayed expansion with low Cu alloys
• if contaminated with moisture during condensation
– Phillips RW JADA 1954
• H2O + Zn ZnO + H2
21

22. Other constituents
• 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
– example
• Indisperse (Indisperse Distributing Company)
– 5% indium
22

23. Other constituents
• Palladium (Pd)
– reduced corrosion
– greater luster
– example
• Valiant PhD (Ivoclar Vivadent)
– 0.5% palladium
23

24. Alloy 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 unicomp-
ositional spherical
40-60 22-30 13-30 0
0-5 In,
0-1 Pd
compositions in weight percent
24

25. Classifications
Based on Cu
Content
High Cu (>6%)
Admixed
Regular
Unicomposition
Single
Compositon
Low Cu (<6%)
25

26. BASED ON Zn CONTENT
Zn CONTAINING Zn FREE ALLOY
> 0.01% Zn < 0.01% Zn
Classifications
26

27. Classifications
BASED ON SHAPE OF ALLOY
LATHECUT SPHERICAL ADMIXED
27

28. Classifications
BASED ON NUMBER OF ALLOY METAL
BINARY TERTIARY QUATERNARY
Ag,Sn Ag,Sn,Cu Ag,Sn,Cu,Zn
28

29. Classifications
BASED ON SIZE OF ALLOY
MICROCUT FINE CUT MACROCUT COURSE CUT
29

30. 30

31. Metallurgical Phases
Phases – Greek symbols Stoichiometric formula
γ (Greek small letter - Gamma) Ag3Sn
γ1 Ag2Hg3
γ2 Sn7-8Hg
ε (Greek small letter – Epsilon) Cu3Sn
η (Greek small letter – Eta) Cu6Sn5
Silver-Copper eutectic Ag-Cu
31

32. Metallurgical Phases
Equilibrium phase diagram of silver-tin system
Ag- 961.8°C
Sn-231.9°C
α - Silver
β - Silver rich
γ – Ag3Sn
δ – Tin
32
Narrow range of
compositions that fall
within the β + γ and
the γ areas
These areas enclosed
by the lines ABCDE
At point C is the
intermetallic
compound Ag3Sn
The more silver rich β
Phase is
crystographically
similar to the γ phase

33. Influence of Ag-Sn Phases on
Amalgam Properties
• In the range of compositions near the γ phase,
increase or decrease of silver influences the amounts
of β and γ phases formed and the properties of the
amalgam.
• Most Commercial alloys fall within the limited
composition range of B to C and are not exactly at
the peritectic composition (Point C).
• The effect of these phases is relatively pronounced,
thus their control is essential
33

34. Influence of Ag-Sn Phases on
Amalgam Properties
• If the tin concentration exceeds 26.8 wt%, a mixture
of γ and tin-rich phase (γ+δ) is formed.
• Presence of tin-rich phase increases the amount of
the tin-mercury phase formed when the alloy is
amalgamated.
• The tin-mercury phase lacks corrosion resistance and
is the weakest component of the dental amalgam.
34

35. Influence of Ag-Sn Phases on
Amalgam Properties
• Silver-tin alloys are quite brittle and difficult
to communicate uniformly unless a small
amount of copper is substituted for silver.
• This atomic replacement is limited to about
4 to 5 wt%, above which Cu3Sn formed.
Within the limited range of copper solubility,
an increased copper content hardens and
strengthens the silver-tin alloy
35

36. Influence of Ag-Sn Phases on
Amalgam Properties
• The use of Zinc in an amalgam alloy is a subject of
controversy.
• Zinc is seldom present in an alloy to an extent greater than
1wt%.
• Alloys without zinc are more brittle and their amalgams tend
to be less plastic during condensation and carving
• The chief function of zinc in amalgam alloys is that of a
deoxidizer.
• It acts as a scavanger during melting, uniting with oxygen to
minimize the formation of other oxides.
• Zinc may have some beneficial effects related to early
corrosion and marginal integrity, as shown in clinical trials
• Disadvantage  Delayed expansion 36

37. Influence of Ag-Sn Phases on
Amalgam Properties
• The ANSI/ADA specification for Amalgam alloys allows
mercury to be incorporated in the alloy powder.
• Some pre amalgated alloys are sold in Europe.
37

38. 38

39. Manufacture of alloy powder
• Lathe-cut powder
• Homogenizing Anneal
• Particle treatments
• Atomized powder
39

40. Lathe-cut powder
• To produce lathe-cut powder, an annealed
ingot of alloy is placed in a milling machine or
in a lathe and is fed into a cutting tool or bit.
The chips removed are often needle like and
some manufacturers reduce the chip size by
ball-milling.
40

41. Particles of a conventional lathe-cut amalgam alloy (×100)
41

42. Homogenizing Anneal
• Because of the rapid cooling conditions from
the as-cast state, an ingot of a silver-tin alloy
has a cored structure and contains non-
homogenous grains of various composition.
• A homogenizing heat treatment is performed
to re-establish the equilibrium phase
relationship.
42

43. Homogenizing Anneal
• The ingot is placed in an oven and heated at a
temperature below the solidus for a sufficient
time to allow diffusion of the atoms to occur
and the phases to reach equilibrium.
• The time of heat treatment may vary
depending on the temperature used and the
size of the ingot, but 24hrs at the selected
temperature is not unusual.
43

44. Homogenizing Anneal
• At the conclusion of the heating cycle, the ingot is
brought to room temperature for the succeeding
steps in manufacture.
• The manner in which the ingot is cooled
influences the proportion of phases present in
the ingot after cooling.
• If the ingot is permitted to cool very slowly, the
proportions of phases continue to adjust toward
the room temperature equilibrium ratio.
44

45. Homogenizing Anneal
• At the conclusion of the heating cycle, the ingot is
brought to room temperature for the succeeding steps
in manufacture.
• The manner in which the ingot is cooled influences the
proportion of phases present in the ingot after cooling.
• If the ingot is permitted to cool very slowly, the
proportions of phases continue to adjust toward the
room temperature equilibrium ratio.
• For example, in an Ag-Sn alloy, rapid quenching results
in the maximum amount of β phase retained, whereas
slow cooling results in the formation of the maximum
amount of the γ phase.
45

46. Particle treatments
• Once the alloy ingot has been reduced to lathe-cut
segments, many manufacturers perform some type of
surface treatment of the particles. Although specific
treatment are proprietary, treatment of the alloy
particles with acid has been a manufacturing practice
for many years.
• The exact function of this treatment is not entirely
understood, but it is probably related to the
preferential dissolution of specific components from
the alloy. Amalgams made from acid washed powders
tend to be more reactive than those made from
unwashed powder.
46

47. Particle treatments
• The stresses induced into the particle during
cutting and ball-milling must be relieved or they
will slowly decrease over time, causing a change
in the alloy characteristics, particularly in the
amalgamation rate and the dimensional change
occurring during hardening.
• The stress relief process involves an annealing
cycle at a moderate temperature, usually for
several hours at approximately 100°C. The alloy is
generally then stable in its reactivity and
properties when its stored for an indefinite time.
47

48. Atomized Powder
• Atomized powder is made by melting together
the desired elements. The liquid metal is
atomized into fine spherical droplets of
metals.
• If the droplets solidify before hitting a surface,
the spherical shape is preserved. These
atomized powders are frequently called
spherical powders.
48

49. Particles of a spherical amalgam alloy (×500)
49

50. Atomized Powder
• Like the lathe cut powders, spherical powders
are given a heat treatment that coarsens the
grains and slows the reaction of the particles
with mercury.
• As with the lathe-cut alloys, spherical powders
are usually washed with acid.
50

51. Particle Size
• Maximum particle size and the distribution of
sizes within an alloy powder are controlled by the
manufacturer.
• The average particle size of modern powder
range between 15 and 35 µm.
• The most significant influence on amalgam
properties is the distribution of sizes around the
mean value. For example, very small particle (less
than 3 µm) greatly increases the surface area per
unit volume greater amount of mercury
required.
51

52. Particle Size
• In producing lathe cut alloys, the cutting rate
is precisely controlled to maintain the desired
average particle size and size distribution.
• Similarly, parameters of the atomizing process
are controlled to produce the desired particle
sizes of spherical alloys.
• The particles may be graded according to size
and the graded particles remixed to produce
with an optimum size distribution.
52

53. Particle Size
• The current trend in amalgam technique favours the
use of small average particle size, which tends to
produce a more rapid hardening of the amalgam with
greater early strength.
• The bulk of the finished restoration is composed of
particles of the original alloy surrounded by reaction
products. The particle size distribution can affect the
character of the finished surface.
• During the carving, the larger particles may be pulled
out of the matrix, producing a rough surface
(probably) more susceptible to corrosion.
53

54. Lathe-cut compared to Atomized
Lathe cut alloy powder Atomized alloy powder
Resist condensation better
than (purely) spherical powders
Very plastic a contoured and
wedged matrix band is
essential to prevent flat
proximal contours, overhanging
cervical margins and improper
contacts.
More mercury required Less mercury required (smaller
surface area per volume) 
better properties
54

55. 55

56. Based on Cu
Content
High Cu (>6%)
Admixed
Regular Unicomposition
Single
Compositon
Low Cu (<6%)
56

57. Low copper alloys
• Amalgamation occurs when the mercury contacts
the surface of the silver-tin alloy particles.
• When powder is triturated, the silver and tin in
the outer portion of the particle dissolve into
mercury.
• At the same time mercury diffuses into the alloy
particles.
• The mercury has a limited solubility for silver
(0.035wt%) and tin (0.6 wt%)
57

58. Development of amalgam microstructure
Schematic illustration
Dissolution of silver and tin into mercury 58

59. Low copper alloys
• When the solubility in mercury is exceeded,
crystals of two binary metallic compounds
precipitate into the mercury.
• These are the
– body- centered cubic  Ag2Hg3 (γ1) phase
– and the hexagonal  Sn7-8Hg (γ2) phase
• Solubility of silver in Hg is much lower than
tin, the γ1 phase precipitates first.
59

60. Development of amalgam microstructure
Schematic illustration
Precipitation of γ1 phase crystals in the mercury60

61. Development of amalgam microstructure
Schematic illustration
Consumption of the remaining mercury by growth of γ1 & γ2 grains
61

62. Low copper alloys
• Immediately after trituration, the alloy
powder coexists with the liquid mercury giving
the mix a plastic consistency.
• As the mercury disappears, the amalgam
hardens.
• As the particles get covered with newly
formed crystals, mostly the γ1 phase, the
reaction rate decreases.
62

63. Low copper alloys
• The alloy is usually mixed in a 1:1 ratio.
• This is insufficient mercury to consume the
original alloy particles completely;
consequently, unconsumed particles are
present in set amalgam.
• Alloy particles (smaller now, because their
surfaces have dissolved in mercury) are
surrounded and bound together by solid γ1
and γ2 crystals.
63

64. Development of amalgam microstructure
Schematic illustration
The final set amalgam
Thus a typical low-copper amalgam is a composite
in which the unconsumed particles are embedded
in γ1 and γ2 phases.
64

65. Low copper alloys
65
A scanning electron micrograph of low copper
(lathe-cut) silver-tin amalgam (×1000)
• P – remaining alloy
particles of β and γ
(Ag-Sn) phase.
• E - ε phase (Cu3Sn)
• G1 - γ1 (Ag2Hg3) phase
• G2 – γ2 (Sn7-8Hg)
phase
• V- Voids (always
formed during γ1 and
γ2 crystal growth
when amalgam is
condensed

66. Low copper alloys
66
Alloy particles + Hg
(β +  )
Ag2Hg3 + Sn7-8Hg + Unconsumed alloy particles
(1) ( 2) (β + )
• The physical properties of the hardened amalgam
depend on the relative percentages of each of the
microstructural phases.
• The more unconsumed Ag-Sn particles that are
retained stronger the amalgam
• Weakest phase is γ2 (Sn7-8Hg) phase. (hardness is ~10%
of γ1)
• γ2 is also the least stable in corrosive environment
corrosion attack, especially in crevices of restoration.
• The interface between the γ and γ1 matrix is important.

67. High copper alloys
• Compared with traditional low copper
amalgams, high copper amalgams have
become the material of choice because of
their improved mechanical properties,
corrosion characteristics, better marginal
integrity and improved performance in clinical
trials.
• Admixed and single-composition alloy powder
available.
67

68. Admixed - High copper alloys
• In 1963, Innes and Youdelis added speherical
silver-copper eutectic alloy (71.9 wt% Ag and
28.1 wt% Cu) particles to lathe-cut low copper
amalgam alloy particles. This was the first
majjjor change in the composition of alloys for
dental amalgam since Black’s formulation
introduced in the late 1800s.
68

69. Admixed - High copper alloys
• These alloys are often called admixed alloys because the
final powder is a mixture of at least 2 kinds of particles.
69
Typical admix high copper alloy powder showing
the lathe cut silver-tin particles and the silver-
copper spheres (×500)
SEM micrograph of admixed high copper amalgam

70. Admixed - High copper alloys
• Amalgams made from these alloys is stronger
because of increase in residual alloy particles
and resultant decrease in matrix rather than
the dispersion strengthening mechanism
originally suggested.
• Clinically superior to conventional amalgams
(better resistance to marginal breakdown)
• The admixed alloy powders usually contain 30
to 55 wt% spherical high-Cu powder.
• The total Cu content is 9 to 20 wt%
70

71. Admixed - High copper alloys
• Amalgams made from these alloys is stronger
because of increase in residual alloy particles
and resultant decrease in matrix rather than
the dispersion strengthening mechanism
originally suggested.
• Clinically superior to conventional amalgams
(better resistance to marginal breakdown)
• The admixed alloy powders usually contain 30
to 55 wt% spherical high-Cu powder.
• The total Cu content is 9 to 20 wt%
71

72. Admixed - High copper alloys
• The phases present in the Cu-containing
particles depend on their composition.
• The Ag-Cu alloy consist of 2 phases:
– Silver rich phase
– Copper rich phase
with the crystal structures of pure silver and
pure copper, respectively.
• Each phase consists a small amount of the
other element.
72

73. Admixed - High copper alloys
• In the atomized powder (which is fast cooled),
the eutectic two-phase mixture forms very
fine lamellae.
• Compositions on either side of the eutectic
form relatively large grains of copper rich
phase or silver rich phase amid the eutectic
mixture.
73

74. A copper-silver alloy (1%) as cast and the same after
homogenization heat treatment (×100)
74

75. Admixed - High copper alloys
• When mercury reacts with an admixed powder,
silver dissolves into the mercury from the silver
copper alloy particles and both silver and tin
dissolve into the mercury from the silver-tin alloy
particles.
• The tin in solution diffuses to the surfaces of the
silver copper alloy particles and reacts with the
copper to form the η phase (Cu6Sn5)
• A layer of η crystals forms around unconsumed
silver-copper alloy particles.
• The η layer on Ag-Cu alloy particles also contain
some γ1 crystals
75

76. Admixed - High copper alloys
• The γ1 phase forms simultaneously within the
η phase and surrounds both the η-covered
silver copper spherical alloy particles and the
silver-tin lathe-cut alloy particles.
• As in the low copper amalgams, γ1 is the
matrix phase.
76

77. Admixed - High copper alloys
• ε Cu3Sn
• γ Ag3Sn
• η Cu6Sn5
• γ1 Ag2Hg3
77
Scanning electron micrograph of an
admixed high-copper amalgam. The
various phases and reaction layer
are labeled. The small, very light,
drop-shaped areas are high in
mercury owing to the freshly
polished specimen (×1000)

78. Admixed - High copper alloys
• Note that the γ2 phase has been eliminated in this
reaction.
• The γ2 phase actually forms at the same time as η but
is later replaced by it.
• There is no precise definition for an amalgam alloy to
qualify as a ‘high copper’ system, but it is generally
accepted that it is a formulation whereby the γ2 is
virtually eliminated during the hardening reaction.
(~12% in the alloy powder)
• Some set amalgams do contain γ2 , although the % is
lower that in low-Cu amalgams.
78
Alloy particles + Ag-Cu eutectic + Hg
(β +  )
Ag2Hg3 + Cu6Sn5 + Unconsumed alloy particles of both types
(1) (η) (β +  + Ag-Cu)

79. Single composition - High copper alloys
• Success of the admixed amalgams has led to the
development of another type of high Cu alloy.
• Unlike admixed, each particle of this alloy has the
same chemical composition.
– 60 wt% Ag,
– 27 wt% Sn,
– 13 wt% Cu.
• The Cu content may range from 13 to 30 wt%.
• Small amounts of indium and palladium are
included in some of the currently marketed single
compositon alloys
79

80. Single composition - High copper alloys
• A number of phases are found in each single
composition alloy particle, including the
– β phase (Ag-Sn)
– γ phase (Ag3Sn)
– ε phase (Cu3Sn)
• Atomized particles have dendritic
microstructures, consisting of fine lamellae.
80

81. 81
• P – unconsumed
alloy particles
• G1 - γ1 (Ag2Hg3)
phase
• H – η phase
A scanning electron micrograph
of a high copper single
composition amalgam. A relief
polish technique was used to
reveal the structure (×560)
Single composition - High copper alloys

82. Single composition - High copper alloys
• When triturated with mercury, silver and tin from
the Ag-Sn phases dissolve in the mercury.
• Very little Cu dissolves in the Hg.
• The γ1 crystals grow, forming a matrix that binds
together the partially dissolved alloy particles.
• The η crystals are found as meshes of rod-like
crystals at the surfaces of alloy particles, as well
as dispersed in the matrix.
• These are much larger than the η crystals found
in the reaction layers surrounding Ag-Cu particles
in admixed amalgams.
82η-Cu6Sn5, γ1 - Ag2Hg3

83. Single composition - High copper alloys
• The undesirable γ2 phase can also form in
single composition amalgams.
• This is particularly true if the atomized powder
has not been treated or if the powder has
been treated for too long at too high a
temperature.
• Nevertheless, in most single composition
amalgams, little or no γ2 forms.
83η-Cu6Sn5, γ1 - Ag2Hg3, γ2 - Sn7-8Hg
Ag-Sn-Cu ALLOY PARTICLES + Hg Ag2Hg3 + Cu6Sn5 + UNCONSUMED ALLOY PARTICLES
(1) (η)

84. 84
• γ (arrow A) and η (arrow B) (×1000)
η-Cu6Sn5, γ1 - Ag2Hg3
Single composition - High copper alloys
Scanning electron micrograph of a
high-copper single-composition
amalgam fractured shortly after
condensation, when amalgamation
reaction is still taking place, showing
reaction products being formed.
Two kinds of crystals are seen on the
surface: Polyhedral crystals (arrow
A) b/w the unconsumed alloy
particles & meshes of η crystals
(arrow B) which cover the
unconsumed alloy particles.

85. Scanning electron micrograph of a
high-copper single-composition
amalgam fractured shortly after
condensation, when amalgamation
reaction is still taking place, showing
reaction products being formed.
In addition to a mesh of η crystals
(arrow B) that formed on
unconsumed alloy particle, η rods
(arrow C) are seen embedded in a
γ1 crystal (arrow A).
85
η-Cu6Sn5, γ1 - Ag2Hg3
Single composition - High copper alloys
Higher magnification of marked area. η rod
embedded in γ; crystals can be identified
(arrow C) (×5000)

86. Single composition - High copper alloys
• Meshed η crystals on unconsumed alloy
particles may strenthen bonding between the
alloy particles and γ1 grains, and η crystals
dispersed between γ1 grains may interlock
the γ1 grains.
• This interlocking is believed to improve the
amalgam’s resistance to deformation.
86η-Cu6Sn5, γ1 - Ag2Hg3

87. 87

88. Dimensional Change
• Contraction microleakage, plaque
accumalation, secondary caries.
• Expansion  pressure on pulp and post
operative sensitivity
• Protrusion of a restoration may also result
from excessive expansion.
88

89. Dimensional Change
• ANSI/ADA Specfication No. 1 requires that
amalgam neither contract nor expand more
than 20 µm/cm, measured at 37°C, between 5
min and 24 hr after the beginning of
trituration, with a device that is accurate to
atleast 0.5 µm.
• The specimen size is essentially equivalent to
the bulk used in large amalgam restorations.
89

90. Theory of dimensional change
• The classic picture of dimensional change is
one in which the specimen undergoes an
initial contraction for approximately 20 min
after the beginning of trituration and then
begins to expand.
• Most modern amalgams exhibit a net
contraction when triturated with a mechanical
amalgamator and evaluated by the ADA
procedure.
90

91. 91

92. • When the alloy and mercury are mixed,
contraction results as the particles begin to
dissolve(hence become smaller) and the γ1
grows.
• Calculations show that the final volume of the
γ1 phase is less than the sum of initial
volumes of dissolved silver and liquid mercury
that are used to produce the γ1 phase
92
Theory of dimensional change

93. • Therefore, contraction continues as long as
growth of the γ1 phase continues.
• As γ1 crystals grow, they impinge against one
another.
• If conditions are appropriate, this
impingement of γ1 can produce an outward
pressure, tending to oppose the contraction.
93
Theory of dimensional change

94. • If there is sufficient liquid mercury present to
provide a plastic matrix, expansion will occur
when γ1 crystals impinge upon one another.
• After a rigid γ1 matrix has formed, growth of
γ1 crystals cannot force the matrix to expand.
• Instead γ1 crystals grow into interstices
containing Hg, consuming Hg, and producing a
continued reaction.
94
Theory of dimensional change

95. • According to this model, if sufficient Hg is present
in the mix when the measurement of the
dimensional change begins, expansion will be
observed. Otherwise contraction will occur.
• Therefore, manipulation that results in less
mercury in the mix, such as lower mercury/alloy
ratio and higher condensation pressures, favour
contractio.
• Higher condensation pressure squeeze Hg out of
the alloy  low powder/hg ratio  contraction.
95
Theory of dimensional change

96. • In addition, manipulative procedures that
accelerate setting and consumption of Hg also
favour contraction.
• Including longer trituration times and use of
small size alloy particles.
• Smaller particle size accelerates the
consumption of Hg because smaller particle
size has a larger surface area per unit mass
96
Theory of dimensional change

97. • The reason for
– Modern amalgam  net contraction
– In the past  expansion
is that
- older amalgam contained larger alloy particles
- higher mercury/alloy ratios
- hand trituration and amalgamator
97
Theory of dimensional change

98. • All the observations thus far presented have been
concerned with the dimensional change during the first
24 hrs only.
• Some admixed amalgams continue to expand for at
least 2 yr.
• This expansion may be related to the disappearance of
some or all of the γ2 phase in these high copper
amalgams or other solid state transformation that
continue to occur for long periods.
• Nevertheless, if they are manipulated properly, most
amalgams exhibit little further dimensional change
after 24 hr.
98
Effect of moisture contamination

99. • How ever, if a zinc containing low copper or
high copper amalgam is contaminated by
moisture during trituration or condensation, a
large expansion can take place.
• This expansion usually starts after 3 to 5 days
and may continue for months, reaching values
more than 400 µm (4%).
• This type of expansion is known as delayed
expansion or secondary expansion.
99
Effect of moisture contamination

100. • This effect is caused by the reaction of zinc with
water and is absent in non-zinc amalgams.
• Hydrogen is produced by electrolytic action
involving zinc and water.
• The hydrogen does not combine with the
amalgam; rather, it collects within the
restoration, increasing the internal pressure to
levels high enough to cause the amalgam to
creep, thus producing the observed expansion.
100
Effect of moisture contamination

101. • The contamination of the amalgam can occur
at almost any time during manipulation and
insertion into the cavity.
• It should be noted that the contamination
must occur during trituration or condensation.
• After the amalgam is condensed, the external
surface may come in contact with the saliva
without the occurrence of delayed expansion.
101
Effect of moisture contamination

102. Delayed expansion of an amalgam.
102

103. Strength
• Traditionally, the strength of dental amalgam has
been measured under compressive stress using
specimens of dimensions comparable to the
volume of typical amalgam restorations.
• When strength is measured in this manner, the
compressive strength of a satisfactory amalgam
may be at least 310 MPa. When they are
manipulated properly, most amalgams exhibit a
compressive strength in excessive of this value.
103

104. Comparison of compressive strengths and creep of a
low copper silver-tin amalgam and high copper
amalgams
Amalgam
Compressive strength
Creep (%)
Tensile
strength
– 24 hrs (Mpa)1 hr 7 days
Low Cu 145 343 2.0 60
Admix 137 431 0.4 48
Single Compo 262 510 0.13 64
104

105. Strength
• Tensile stresses can easily be produced in
amalgam restoration.
• For eg. A compressive stress on the adjacent
restored cusp introduces complex stresses that
result in tensile stresses in the isthumus area.
• Because dentin has a relatively low elastic
modulus, as much tooth structure as possible
should be preserved to prevent the dentin from
bending away from the restoration, or fracturing
under masticatory forces.
105

106. Strength
• It is important to reemphasize that the 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.
• Use of a high copper amalgam does not help.
• The tensile strengths of high copper amalgams
are not significantly different from those of the
low Cu amalgams.
106

107. Effect of Trituration
• The effect of trituration on strength depends
on
– the type of amalgam alloy,
– the trituration time
– the speed of the amalgamator.
• Either under-trituration or over-trituration
decreases the strength in both traditional and
high-Cu amalgams
107

108. Effect of mercury content
• Sufficient Hg should be mixed with the alloy to
coat the alloy particles and allow a thorough
amalgamtion.
• Each particle of the alloy must be wet by the
mercury; otherwise a dry, granular mix results.
– Such a mix results in a rough, pitted surfaces that
may lead to corrosion.
• Excess mercury left in the restoration 
Marked reduction in strength.
108

109. Effect of mercury content
• Add graph
• For either Low-Cu or High-Cu admixed
amalgam, if the Hg content increases more
than 54%, the strength is markedly reduced.
• Similar decrease in strength with increased
final Hg content are observed for spherical
high-Cu amalgams, except that the critical Hg
content at which the strength occurs is less.
109

110. Effect of mercury content
• The strength of an amalgam is a function of the
volume fractions of unconsumed alloy particles
and Hg containing phases.
• Low mercury content amalgams contain more
of the stronger alloy particles  less of the
weaker matrix phases.
• Increasing the final Hg content increases the
volume fraction of the matrix phases at the
expense of the alloy particles.
• As a result amalgams containing higher Hg 
weaker.
110

111. Effect of condensation
• Condensation pressure, technique and alloy particle
shape affect the amalgam properties
• Typical condensation techniques + lathe cut alloys 
greater the condensation pressure = higher the
compressive strength
– Particularly the early strength (eg. at 1 hr)
• Good condensation technique expresses mercury and
result in a smaller volume fraction of matrix phases.
• Higher condensation pressure  minimize porosity
• On the other hand, spherical amalgams condensed
with lighter pressures produce adequate strength.
111

112. Effect of porosity
• Voids and porosity are possible factors
influencing the compressive strength of set
amalgam.
• Porosity is related to a number of factors,
including the plasticity of the mix.
• Plasticity of amalgam decreases with increased
time (delayed condensation) and undertrituration
• Under such conditions  porosities greater,
strength lower.
• Increasing condensation improves adaptation at
the margins and decreases the number of voids.
112

113. • For spherical alloys, the condensor simply
punches through the amalgam if heavy
pressures are employed.
• It is fortunate that voids are not such a
problem with these alloys.
• Thus lighter pressure can be employed
without danger of sacrificing properties.
113

114. Comparison of compressive strengths and creep of a
low copper silver-tin amalgam and high copper
amalgams
Amalgam
Compressive strength
Creep (%)
Tensile
strength
– 24 hrs (Mpa)1 hr 7 days
Low Cu 145 343 2.0 60
Admix 137 431 0.4 48
Single Compo 262 510 0.13 64
114

115. Effect of amalgam hardening rate
• Amalgam do not gain strength as rapidly as
may be desired.
• For eg. at the end of 20 min, compressive
strength may only be 6 % of the 1 wk strength.
• The ANSI/ADA specification stipulates a
minimum comprehensive strength of 80 Mpa
at 1 hr.
115

116. Effect of amalgam hardening rate
• The 1 hr compressive strength of high Cu single
composition is relatively high compared with admixed
high Cu amalgams after 24 hr
• This strength may have some advantages clinically.
• For eg fracture is less probable if the patient accidently
bites on the restoration soon after leavin the dentists
office.
• Also, these amalgams may be strong enough shorlty
after placement to permit amalgam build ups to be
prepared for crowns and to permit taking impressions
for crowns
116

117. Effect of amalgam hardening rate
• Even if a fast hardening amalgam is used, its
strength is likely to be low initially.
• Patients should be cautioned not to subject
the restoration to high biting stresses for
atleast 8 hr after placement.  70% of
strength.
117

118. CREEP
Creep:
Time dependent strain or deformation that is
produced by a stress.
• Creep rate has been found to correlate with
marginal breakdown of traditional low Cu
amalgams; that is; the higher the creep
magnitude, the greater the degree of marginal
detoriation.
118

119. CREEP
• However, for high Cu amalgams, creep is not
necessarily a good predictor of marginal
fracture.
• Many of these amalgams have creep rates of
0.4% or less.
• It is prudent to select a commercial alloy that
has creep rate below the level of 3% specified
in ANSI/ADA specification No. 1
119

120. CREEP
• There is no data available that suggest that
reducing creep value below approximately 1%
influences marginal breakdown.
120
Amalgam
Compressive strength
Creep (%)
Tensile
strength
– 24 hrs (Mpa)1 hr 7 days
Low Cu 145 343 2.0 60
Admix 137 431 0.4 48
Single Compo 262 510 0.13 64

121. Influence of microstructure on Creep
• The γ1 phase has been found to exert primary
influence on low Cu amalgam creep rates.
• ↑ γ1 phase volume fraction = ↑ Creep rate
• ↑ γ1 grain size = ↓ Creep rate
• The presence of γ2 phase also associated with
higher creep rates
• In addition to absence of γ2 phase, the
presence of η rods in single compo high Cu
amlgamsa  low creep rates
121

122. Effect of manipulative variables on
Creep
• These manipulative factors discussed
previously that maximize strength also
minimize creep rate for any given type of
amalgam.
• Thus, mercury alloy ratio should be minimized
and condensation pressure maximized for
lathe-cut or admixed alloys and careful
attention should be paid to the timing of
trituration and condensation.
122

123. Clinical performance of amalgam
restorations
• The small amount of leakage under amalgam
restorations is unique.
• If the restoration is properly inserted, the
leakage decreases as the restoration ages in
the mouth.
• This may be formed by the corrosion products
that form along the interface between tooth
and restoration, sealing the interface and
thereby preventing leakage
123

124. Clinical performance of amalgam
restorations
• The ability to seal against micro-leakage is
shared by both the low-Cu and High-Cu
• However, the accumulation of corrosion
products is slower for the high-Cu alloys.
124

125. Clinical performance of amalgam
restorations
• Many amalgam restorations must be replaced
because of problems, including secondary
caries, gross fracture, “ditched” or fractured
margins, and excessive tarnish and corrosion.
• The ultimate life time of an amalgam
restoration is determined by a number of
factors: material, skill, patient factors.
125

126. Tarnish and Corrosion
• Tarnish is observable as a surface discoloration
on a metal, or as a slight loss or alteration of the
surface finish or lustre.
– Process by which a metal surface is dulled or
discolored when a reaction with a sulfide, oxide,
chloride or other chemical causes a thin film to form.
– Electrochemical studies indicate that some passivation
offering partial protection against further corrosion
occurs as result of tarnish
– Unaesthetic (black silver sulfide) but does not imply
failure
126

127. Tarnish and Corrosion
• Corrosion is chemical or electrochemical
process in which a solid, usually a metal, is
atacked by an environment agent, resulting in
partial or complete dissolution.
– Although glasses and other nonmetals are
susceptible to environmental degradation, metals
are generally more susceptible to attack because
of electrochemical reactions.
127

128. Tarnish and Corrosion
• Active corrosion of a newly placed restoration
occurs on the metal surface along the interface
between the tooth and the restoration.
• The space between the alloy and the tooth
permits the micro-leakage of electrolytes and a
classic concentration cell (crevice corrosion)
process results.
• The build-up of corrosion products gradually seals
this space, making dental amalgam a self sealing
restoration.
128

129. Tarnish and Corrosion
• The most common corrosion products in
traditional amalgam alloys are chlorides and
oxides of tin.
• Corrosion products containing Cu can also be
found in high-Cu restoration.
• However the corrosion process is more limited
because the η is less susceptible to corrosions
129

130. Tarnish and Corrosion
• Whenever a gold restoration is placed in
contact with an amalgam, corrosion of the
amalgam is expected because of the large
differences in their E.M.F.
• A high Cu amalgam is cathodic with respect to
low Cu amalgam leading to accelerated
corrosion of the latter. Thus use of both in the
same mouth should be avoided.
130

131. Tarnish and Corrosion
• γ2 phase is the most anodic phase, thus more
corrosion.
• This phase eliminated in high Cu amalgams,
thus better clinical performance.
• However, high Hg/alloy ratio may lead to
formation of γ2 phase even in high-Cu
Amalgams.
131

132. Compositional effect on the survival of
Amalgam restorations
132

133. Factors affecting the success of
amalgam restorations
• Selection of material:
– Low Cu alloys are still available and acceptable
amalgam restorations, but it is obvious that the
high-Cu alloy is the material of choice
– For Hg, only requisite is purity. Contamination
with arsenic can lead to pulpal damage. Also, any
impurity can adversely affect the physical
properties of the amalgam.
133

134. Hg/Alloy ratio
Eames technique or the Minimal Hg Technique:
• Sufficient Hg must be present in the original mix to
provide a cohesive and plastic mass after
trituration.
• However the Hg level should also be low enough,
so that Hg content of the restoration is at a
acceptable level without the need to remove an
appreciable amount during condensation
About 50 wt% for lathe cut and admix
42 wt% for spherical
Any addition of mercury after trituration is
contraindicated. 134

135. Mechanical Trituration
• The objective of the trituration is to provide
proper amalgamation of the Hg and alloy.
• The alloy particles are coated with a film of
oxide which is difficult for Hg to penetrate.
• This film must be rubbed off in some manner
so that Hg can come in contact with the alloy
• The oxide layer is removed by abrasion when
the Hg and alloy particles are triturated.
135

136. Use of amalgamators
• Capsule serves as a mortar
• A cylindrical metal or plastic piston of smaller
diameter than the capsule inserted in it,
serves as the pestle
136

137. Use of amalgamators
Capsules can be reusable or disposable
• Reusable capsules: friction fit or screw-cap lids
– The alloy and mercury are dispensed into the capsule
– It should be cleaned and free of previously mixed,
hardened alloy
– Mulling process- causes the mix to cohere – easy
removal and cleaning
• Disposable capsules: it may require activation
before use
Pestles : the diameter and length of the pestle
should be considerably less than the capsule.
137

138. 138

139. Use of amalgamators
• When the capsule has been secured in the
machine and turned on, the arms holding the
capsule oscillate at high speed, thus trituration is
accomplished.
• Some amalgam alloys and certain types of pre-
proportioned capsules systems have specific
recommendations for trituration speeds.
• New amalgamators may have hoods to confine
Hg from escaping into the room and to prevent
capsule from being ejected from the amalgamtor
139

140. 140

141. Consistency of mix
141

142. Condensation
Objectives:
• To condense unattacked alloy particles closely together
• To adapt amalgam to the cavity walls.
• To remove excess Hg.
• To bring Hg on the top of each increment so as to bind the increments
to one
another (increasing dryness technique).
• To increase the density of the restoration by development of an
uniform
compact mass with minimal voids.
• To increase the rate of hardening so that carving operation need not be
unduly delayed.
Delayed condensation / Early condensation - not advisable.
142

143. Condensation
Methods:
• Hand condensation
• Mechanical condensation( impact type of
force , rapid
vibrations)
Condensation pressure: 3 to 4 lb/sq inch.
143

144. Hand Condensation
• The amalgam mixture should never be mixed
with bare hands.
• Increments can be inserted into the cavity
through small forceps or amalgam carriers.
• Once the increment of amalgam is inserted into
the cavity, it should be immediately condensed
with sufficient pressure
• Start at the centre and then the condenser is
stepped little by little towards the cavity walls.
• The pressure required depends on the shape of
alloy particles.
144

145. Hand Condensation
• After condensation of an increment, surface
should be shiny in appearance
• This indicates that there is sufficient Hg to diffuse
into the next increment.
• Even with the minimal Hg technique, it is
probably desirable to remove some of the soft or
mushy material that is brought to the surface of
each increment.
• The last increment should slightly overfill the
cavity, the Hg rich layer removed by carving.
145

146. Condensation pressure
• Condensation pressure governed by the
– Area of condenser point
– Force applied
• It is doubtful that a condenser more than 2mm in
diameter will produce enough pressure (for lathe-
cut)
• Force as great as 66.7 N (15 lb) are
recommended.
To ensure maximum density and adaptation, the
force should be as great as the alloy will allow,
consistent with patient’s comfort
146

147. Mechanical Condensation
Automated device for condensation
– Impact type of force
– Rapid vibrations
• Less fatiguing to the dentist
• Similar clinical results as compared to hand
condensation
147

148. 148

149. Carving and Finishing
Objectives:
To produce a restoration with -
• Proper physiological contours.
• Minimal flash (no overhangs).
• Functional, non-interfering occlusal anatomy.
• Adequate, compatible marginal ridges.
• Proper size, location, extent and inter-relationship
of contact areas.
• Physiologically compatible embrasures.
• No interference with integrity of periodontium.
149

150. Carving and Finishing
• Carving should not be started until the amalgam is hard
enough to offer resistance to the carving instrument.
• After carving is finished, surface should be smoothened by
burnishing.
• Final smoothening can be concluded by rubbing the surface
with a moist cotton pellet or rubber polishing cup and
extremely fine prophylaxis paste.
• Burnishing slow setting amalgams can damage the margins
of the restoration.
• Undue pressure and heat generation should be avoided
• Temperature above 60°C cause a significant release of Hg
• Final finish should not be carried out until the amalgam has
set and be delayed for at least 24 hrs or longer.
150

151. 151

152. Clinical Significance of Dimensional
Change
• Expansion
– Insufficient trituration and condensation
– Delayed expansion
– Formation of cracks due to reducing too much
tooth structure. ‘Hooding’ of the weakened cusp
should be done.
If cracks are minor and do not threaten the
vitality of tooth  etching and bonding of the
fissure may provide a sufficient interim solution
152

153. Clinical Significance of Dimensional
Change
• Contraction
– Slight contraction occurs in properly triturated
amalgams.
– Not clinically significant
153

154. Side effects of Hg
• To understand the possible side effects of
dental amalgam, the differences b/w allergy
and toxicity needs to be understood.
154

155. Allergy
• Allergic responses represent an antigen-antibody
reaction marked by itching, rashes, sneezing,
difficulty in breathing, swelling or other symptoms.
• Contact dermatitis or Coombs’ Type IV
hypersensitivity reactions represent the most likely
physiologic side effect to dental amalgam, but these
reactions are experienced by less than 1% of the
treated population
155

156. Allergy
• Allegations of signs of symptoms of dental amalgams have been
made in recent years, causing some health professionals to
mistakenly conclude that certain patients are ‘hypersensitive’ to Hg
based on symptoms that mimicked those of various diseases such
as multiple sclerosis, epilepsy and arthritis
• This misconception prompted a few dentists to request a
dermatologic test for this hypersensitivity. Because the classic signs
and syptoms of Type IV hypersensitivity are hyperemia, edema,
vescicle formation and itching, the term hypersensitivity was
incorrectly applied to these cases.
• Inappropriate usage of patch test kits with instructions for
additional analysis of blood pressure, pulse rate, indigestion,
blurred vision, headaches, irritability, fatigue, depression and
redness of the eyes has lead to an erroneously high estimate of
25% positive responses in one report
156

157. Allergy
• To confirm suspicions of true hypersensitivity,
especially when a reaction has sustained for 2wks or
more, patient should be referred to an allergist.
• When such a reaction has been documented by a
dermatologist or allergist, an alternative material
must be used unless the reaction is self limiting.
157

158. Toxicity
• Hg toxicity ↓ in the past few years because of
• Encapsulation technology
• Capsule design
• Scrap storage methods
• Elimination of carpets and other Hg retention sites.
• In some countries amalgam particle collectors with
efficiencies greater than 99% are required in dental
clinics.
158

159. 159

160. Toxicity
• Undoubtedly, Hg penetrates from the restoration into
tooth structure
• An analysis of dentin underlying amalgam restorations
reveals the presence of Hg which in part causes
discoloration
• Use of radioactive Hg in silver amalgam has also
revealed that some Hg might even reach the pulp
• Small amount of Hg also released during mastication
However, possibility of toxic reaction from these in the
pt is slight
160

161. Toxicity
• Hg vapour detectors inhaled over a 24hr period -
1.7 µg per day
• For a pt. with 8 to 10 amalgam restorations is
1.1 to 4.4 µg per day
• The threshold value for workers in Hg industry is
350 to 500 µg per day. (established by the US
federal government for occupational
environments)
161

162. Toxicity
• Dentists and auxiliaries are exposed daily to the risk of
Hg intoxication.
• Hg  absorbed through skin, ingestion, inhalation
• Safe  50 µg of Hg per cubic meter of air per day
• Hg is volatile at room temperature and has a vapor
pressure of 20 mg per cubic meter of air  about 400
times the acceptable amount.
• Liquid Hg is 14 times denser than water  a small
amount of spill is significant
• An eye dropper sized spillage of Hg can saturate the
air in average operatory.
162

163. Toxicity
• Hg blood levels
• Pts with amalgam restoration  0.7 ng/mL
• Without  0.3 ng/mL
• P = 0.01
• However, the normal daily intake of Hg is 15µg from
food, 1µg from air and 0.4µg from water.
163

164. Toxicity
• Precautionary methods
• Well ventilated operatory
• All excess Hg  collected in well sealed containers
• Proper disposal
• If spilled cleaned up ASAP (ordinary vacuums disperse the Hg through
exhaust)
• Hg suppressant powders  temporary solution
• Materials contaminated with amalgam should not be incinerated or
subjected to heat sterilization
• If Hg comes in contact with skin, wash with soap and water.
• Well fitting capsules to be used
• When grinding amalgam, a water spray and suction should be used.
• Eye protection, disposable mask and gloves  Mandatory
• Use of ultrasonic amalgam condensers NOT advisable
164

165. 165

166. Toxicity
• Periodic monitoring procedure – annually
• Various instruments can be used
• Instruments that yield a time weighed average measurement for
Hg exposure.
• Film badges (similar to radiation exposure badges)
– Biological determinations can be performed on office staff
to measure Hg levels in blood and urine
166

167. 167

168. Repaired amalgam restorations
• The flexural strength of repaired amalgam is 50% of that of
unrepaired amalgam
• The bond is a source of weakness
• Factors like corrosion and saliva contamination at the interface
present formidable barriers that interfere with bonding of the old
and new amalgam
• Repair should be attempted only if the area is not subjected to high
stresses or the two restoration parts are adequately supported and
retained.
• Another repair option are for areas that exhibit minor marginal
breakdown(i.e. gaps that are 250µgm in width) is to etch the
enamel adjacent to restoration and after rinsing and drying the
marginal gap area, sealing the gap with a dentin bonding adhesive
168

169. Amalgam removal protocol
• Considerations prior to amalgam removal
– Thorough Medical and dental history
– Physician evaluates the overall health and ability
of the individual to eliminate toxins (eg Leaky gut)
– If woman is pregnant / lactating  amalgam
removal not advisable
– Vit C intake prior to and following amalgam
removal
169Colson DG .A Safe Protocol for AmalgamRemoval. J Environ and Pub Health.2012, Article ID 517391,

170. Amalgam removal protocol
• Chair side procedure
– Rubber dam
– Underneath the dam, acivated charcoal or
chlorella is placed along with cotton roll and gauze
– Patients face is draped under the dam with a liner
– Patient is given protective eye wear and head
cap/bonnet
– Oxygen supplied with a nasal mask and Vapour
ionizer is turned on.
170Colson DG .A Safe Protocol for AmalgamRemoval. J Environ and Pub Health.2012, Article ID 517391,

171. Amalgam removal protocol
• Chair side procedure
– A new bur is used
– High volume suction and continuous addition of
water spray
– If possible, amalgam is sectioned and scooped
out.
171Colson DG .A Safe Protocol for AmalgamRemoval. J Environ and Pub Health.2012, Article ID 517391,

172. Thank you.
172