A descriptive presentation on the material aspect of dental amalgam and mercury toxicity.

1. By:
Dr. Harshita Lath
1st yr PGT

2. Index
 Introduction
 History
 Amalgamwars
 Classification
 Indications & contraindications
 Advantages/disadvantages
 Composition of amalgam & Amalgamationreactions
 Manufacturing process
 Properties of amalgam
 Manipulation of amalgam

3.  Recentadvances
 Repair of amalgamrestorations
 Clinical considerations
 Mercury toxicity & various healthhazards
 Conclusion

4. Introduction
Dental amalgam (silver amalgam or simply amalgam) is a
metallic, polycrystalline restorative material originally
composed of a mixture of silver–tin alloy and mercury.
- Sturdevant
Word “amalgam” is derived from the latin word “amalgama”.
It has been used more than any other material in restorative
dentistry.


5. History
 Amalgam -- First used by Chinese medic, Sukung as a silver
mercury paste (659 AD)
 Introduced in 1800’s in France: alloy of bismuth,lead, tin and
mercury plasticized at 100ºC poured directly into cavity
 1818, Louis Regnart “father of amalgam”—credited for
lowering the temperature of D’Arcet’s Mineral Cementa by
adding more mercury to it.
 1819, Bell introduced amalgam in England as “Bell’s Putty”

6.  1833
 Crawcour brothersintroduced
amalgam toUS
 powdered silver coins mixedwith
mercury
 expanded on setting
 1895
 Toovercome expansionproblems
 G.V. Black developed a formula
for amalgamalloy
 67% silver, 27% tin, 5% gold, 1% zinc

7.  Black’s formula was well accepted and notmuch
changed for nearly sixtyyears.(1890-1963)
 1946 - Skinner, added copper to the amalgamalloy
composition in a small amount. This served to
increase strength and decreaseflow.
 The work of Innes and Youdeis (1963) has led to
the development of high copperalloys.

8. Amalgam wars
 In 1845, American Society of Dental Surgeons condemned the
use of all filling material other than gold as toxic, thereby
igniting "first amalgam war'. The society went further and
requested members to sign a pledge refusing to use amalgam.
 In mid 1920's a German dentist, Professor A. Stock started
the so called "second amalgam war". He claimed to have
evidence showing that mercury could be absorbed from
dental amalgam, which leads to serious health problems. He
also expressed concerns over health of dentists, stating that
nearly all dentists had excess mercury in their urine.

9.  "Third Amalgam War' began in 1980 primarily through the
seminars and writings of Dr.Huggins, a practicing dentist in
Colorado.
 He was convinced that mercury released from dental
amalgam was responsible for human diseases affecting the
cardiovascular system and nervous system
 Also stated that patients claimed recoveries from multiple
sclerosis, Alzheimer’s disease and other diseases as a result
of removing theirdental amalgam fillings.
 But research in United States and other First World countries
clearly demonstrated that there is no cause-and-effect
relationship between the dental amalgam restoration and
other health problems.

11. CLASSIFICATION (Marzouk)
I. According to the number of alloy metals
A. Binary alloys (silver–tin)
B. Ternary alloys (silver– tin–copper)
C. Quaternary alloys (silver–tin–copper–indium)
II. According to whether the powder consists of unmixed or admixed
alloys
A. Admixed/dispersion or blended alloys
B. Single compositional/unicompositional alloys
III. According to the shape of the powdered particles
A. Spherical shape (smooth-surfaced spheres)
B. Lathe-cut (irregular, ranging from spindles to shavings)
C. Combination of spherical and lathe cut (admixed)

12. IV. According to the powder’s particle size
A. Microcut
B. Fine cut
C. Coarse cut
V. According to the copper content of powder
A. Low copper content alloy: Less than 4%
B. High copper content alloy: 10%–30%
VI. According to the addition of noble metals
A. Platinum
B. Gold
C. Palladium
VII. According to the presence of zinc
A. Zinc containing (more than 0.01%)
B. Non–zinc containing (less than 0.01%)

13.  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 most of the tin is firmly bonded to
copper.
 Fifth generation. Quaternary alloy i.e. Silver, tin, copper and indium.
None of the tin is available to react with mercury.
 Sixth generation consisting of eutectic alloy containing silver (62%), copper
(28%), and palladium (10%), which is lathe-cut and blended into the first-,
second-, or third-generation amalgam in the ratio of 1:2. Exhibits highest
nobility.
GENERATIONS OF AMALGAM

14. INDICATIONS OF AMALGAM
 Class I and class II cavities.-moderate to large restorations.
 Class 5 cavities where esthetics is not important.
 As a core build up material.
 For cuspal restorations (with pins usually)
 As a die a material.
 Restorations that have heavy occlusal contacts.
 Restorations that cannot be well isolated
 In teeth that act as an abutment for removable appliances

15. CONTRA INDICATIONS OF AMALGAM
 Anteriorteethwhereesthetics isa primeconcern
 Estheticallyprominentareasof posteriorteeth.
 Small –to-moderateclasses I and II restorationsthat can be well
isolated.

16. Advantages
• Ease of use
• High compressive strength
• Excellent wear resistance
• Favorable long-term clinical results
• Lower cost than for composite restoration
• Restoration is completed within one sittingwithout requiring
much chair sidetime.

17. Disadvantages
• Non-insulating
• Unaesthetic
• Less conservative (more removal of tooth structure during
tooth preparation)
• Lack of chemical or mechanical adhesion to the tooth
structure.
• Mercury toxicity
• Promotes plaqueadhesion
• Delayed expansion
• Weakens tooth structure (unlessbonded).
Amalgam blues

18. COMPONENTS OF
DENTAL
AMALGAM

19. Silver:
 Constitutes approximately 2/3rdof
conventional amalgam alloy.
 Contributes to strength offinished
amalgam restoration.
Silver whitens the alloy.
 Decreases flow and creep ofamalgam.
 Increases expansion on settingand
offers resistance totarnish.
 Tosome extent it regulates the setting
time.

20. Tin:
 Second largest component and
contributes ¼th of amalgamalloy.
 Readily combines with mercuryto form
gama-2 phase, which is the weakest
phase and contributes to failure of
amalgam restoration.
 Reduce the expansion but at the same
time decreases the strength ofamalgam.
 Increase the flow.
 Controls the reaction between silverand
mercury.
 Tin reduces both the rate of the reaction
and the expansion to optimalvalues.

21. Copper:
 Contributes mainly to hardness and strength.
 Tends to decrease the flow and increases the setting
expansion
Zinc:
 Acts as Scavenger of foreign substances such as oxides.
 Helps in decreasing marginal failure.
 The most serious problem with zinc is delayed expansion,
because of which zinc free alloys are preferred now a
days.
Indium/Palladium:
• They help to increase the plasticity and the resistance to
deformation; and whitens the alloy.
• Decrease marginal breakdown.

22. METALLURGICAL PHASES IN
AMALGAM
• Phases in amalgam alloys
and set dental amalgam
γ
γ ₁
γ₂
є (epsilon)
 (eta)
• Stiochiometric formula
Ag₃Sn
Ag₂Hg₃
Sn₇₋₈Hg
Cu₃Sn
Cu₆Sn₅

23. COMPOSITION
OF
ALLOYS

24. Low Copper Alloys:
 Silver
 Tin
 Copper
 Zinc
: 63-70%
: 26-28%
: 2- 5%
: 0-2%
•G.V. Black’s: silver- tinalloy or low copper alloy.
•Also called conventional amalgam alloy

25. HIGH COPPER AMALGAM ALLOY (COPPER ENRICHED
ALLOYS)
 Toovercome the inferior properties of low copper amalgam alloy -
- shorterworking time, more dimensional change, difficult to
finish, set late, high residual mercury, high creep & lowerearly
strength, low fracture resistant.
 Youdelis and Innes in 1963 introduced high copper content
amalgam alloys. They increased the copper content from
earlier used 5% to12%.
 Copperenriched alloys are of two types:
1) Admixed alloypowder.
2) Single composition alloypowder.

26. I. Admixed alloy powder:
 Also called as blendedalloys.
 Contain 2 parts by weight of lathe cut particles
plus one part by weight of spherical silvercopper
eutecticalloy.
 Amalgam made from these powdersare stronger
than amalgam made from lathe cut low copper
alloys because of strength of Ag-Cueutecticalloy
particles.
 Total copper content ranges from9-20%.
Composition:
 Silver-69 %
 Tin-17 %
 Copper-13 %
 Zinc-1 %

27. II. Single composition alloy
(Unicomposition):
 It is socalled as each particle in the
alloy powder has the same
composition.
 Usually spherical single composition
alloys areused.
 Contain copper in the range of
13%–30%.

28. Different types of single compositional alloys
are available:
• Ternary alloy in spherical form –
•Silver: 60%
•Tin: 25%
•Copper: 15%
•Ternary alloy in spheroidal form –
• Composition same as for ternary alloy in spherical
form
•Quaternary alloy in spheroidal form –
•Silver: 59%
•Copper: 13%
•Tin: 24%
•Indium: 4%

29. Zinc containing alloy
•Alloys containing more than 0.01% zinc :zinc-containing alloys
•Less than 0.01% zinc :non– zinc-containing alloys.
•Zinc aids in the manufacturing process by producing clean, sound castings
of the ingots by its scavenging or deoxidizing action.
•Alloys without zinc are more brittle and less plastic.
•However, zinc can cause an abnormal expansion of the amalgam over time
when water contamination of the amalgam occurs during its manipulation.
This is known as delayed expansion.

30. Pre-amalgamated alloys
•In these, the surface of the alloy particles is treated with mercury by the
manufacturer for rapid amalgamation after trituration to make
precompacted pellets.
•Contain up to 35% mercury.
•Mercury is incorporated into the alloy by treating with mercuric chloride.
•It is then treated with acids, to remove the chloride content.
•In this process, along with chloride, zinc also gets eliminated.

31. AMALGAMATION REACTION/
SETTING REACTION

32. During trituration mercury
diffuses into the gamma
phase of the alloy particles
reacting with mainly silver
and tin.
Mercury has a lower
solubility for silver (0.035
wt%) as compared to tin (0.6
wt%). Hence, tin remains in
solution longer than silver.
silver starts precipitating first
and the g1 phase is then
formed and the g2 phase
precipitates later.
As the remaining mercury
dissolves the alloy particles,
g1 and g2 crystals grow and
the amalgam begins to
harden.
As the particle becomes
covered with newly formed
crystals, mostly g1, the
reaction rate decreases
Low copper conventional amalgam alloy

33. A, Dissolution of silver
and tin into mercury.
B, Precipitation of γ1
crystals in the mercury.
C, Consumption of the
remaining mercury by
growth of γ1 and γ2
grains.
D, The final set
amalgam.
Ag3Sn + Hg  Ag3Sn + Ag2Hg3 +Sn8Hg
 1 2


34. PHASES
Gamma () = Ag3Sn
 unreacted alloy
 strongest phaseand
corrodes the least
 forms 30% ofvolume of
set amalgam
Gamma 1 (2)= Ag2Hg3
 Noblest phase
 Most resistant to tarnish and
corrosion
 Body centered cubic
Gamma 2 ( 2) = Sn8Hg
 weakest phase
 Most prone to corrosion and creep
 Hexagonal close packed

35. Mercury phase:
•A very small amount of unreacted residual mercury will be present within
the amalgam mass.
•Since it is the weakest phase, a drastic drop in the strength of amalgam
occurs if this phase exceeds a certain volume limit.
Interphase:
•This phase applies to the interphases between the main components: g–g1,
g1 –g2, and g2–g.
•The closer and continuous they are in the final restoration, the better is the
bonding.

36. •Both γ1 and γ2 crystals form, as in lathe-cut alloys.
• The tin in mercury diffuses to the surfaces of the ag-cu alloy particles and reacts
with the copper to form a layer of η′ phase crystals on the surface.
•As in the low-copper amalgams, γ1 is the matrix phase .
•γ2 phase does form along with the η′ phase but later reacts with copper from Ag-Cu
particles, yielding additional η′ phase.
•The γ2 phase can be eliminated with at least 11.8% of copper by weight in the alloy
powder.
High Copper Admixed Alloy

37. The set amalgam consists of
core particles of unreacted
Ag–Cu (eutectic) which is
surrounded by a halo of eta
(Cu6Sn5) phase.

38. High Copper Unicompositional Alloy
•Every particle has all the phases in very small amounts.
•When triturated with mercury, the silver and tin from the Ag–Sn phases dissolve
in mercury.
•Very little copper dissolves in mercury.
•As the g1 crystals start to grow, they form the matrix that binds the partially
dissolved alloy particles together.
• The η′ crystals are found as meshes of rod like crystals at the surfaces of alloy
particles, dispersed in the matrix.
•In most single-composition amalgams, little or no γ2 forms .

39. The set amalgam consists of core particles of unreacted
phase which are surrounded by a mesh of rod-shaped eta
phase, embedded in the matrix of g1.

40. Function of the η phase
• Strengthen the bond between alloy particles and γ₁ phase.
• Interlocks the γ₁ phase thus improving the amalgams resistance to
deformation.
Epsilon phase:
•Silver-tin alloys are quite brittle and difficult to blend uniformly unless
a small amount of copper is substituted for silver.
•This atomic replacement is limited to 4-5 wt% above which Cu3Sn is
formed within the limited range of copper solubility.

41. PROPERTIES OF AMALGAM

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

43. Compressive Strengths of Low-Copper andHigh
Copper Amalgam
Amalgam Compressive Strength
(MPa)
1 h 7 day
Low copper 145 343
Admix 137 431
Single
Composition
262 510
 Since 1-hour
compressive strength
is much less than half
the final strength, the
patients are warned
not to use excessive
masticatory forces for
at least 6–8 hours
after the restoration,
the time during which
70%–80% of the total
strength is attained.
 The compressive strengthof a satisfactoryamalgam restoration should
be atleast 310MPa.
STRENGTH

44. Product Tensile strength (Mpa)
15min 7 days
LOW COPPER ALLOYS
a) Lathe cut 3.2 51
b) spherical 4.7 55
HIGH COPPER ALLOYS
a) Admixed 3.0 43
b) Unicompositional 8.5 56
Tensile strengths ofamalgam
 Both low & high copper amalgams have tensile strength that range
between 48-60 MPa

45. The factors affecting strength of amalgam are:
1) Temperature:
 Amalgam looses 15% of its strength when its
temperature is elevated from room temperature to
mouth temperature
 looses 50% of room temperature strength when
temperature is elevated to 60OC e.g. hot coffeeor
soup.

46. 2) Trituration:
 Effect of trituration on strength depends on the type of
amalgam alloy, the trituration time and the speed of the
amalgamator.
 Either, under trituration or over-trituration decreases
the strength for both traditional and high copper
amalgams.
 Excess trituration will create cracks in the crystals.

47. 3) Mercury Content:
 Low mercury alloy content, contain
strongeralloy particles and less of the
weaker matrix phase, therefore more
strength
 Mercury is too less -- dry, granular mix,
results in a rough, pitted surface that
invites corrosion.
 If mercury content of amalgam mixis
more than 53-55%,it causes drop of
compressive strength by50%.

48. 4) Effect of condensation:
 For lathe-cut alloys
Greater the condensation pressure, the higher the
compressive strength
Higher condensation pressure is required tominimize
porosity and to express mercury from lathe-cut
amalgam.
 For spherical alloys
Amalgams condensed with lighter pressureproduce
adequate strength.

49. 5) Effect of Porosity:
 Can be dueto
 Under trituration,
Particle shape,
Insertion of too large increments into the cavity,
Delayed insertion aftertrituration,
 Non-plastic mass ofamalgam.
 Facilitate stress concentration, propagation ofcracks,
corrosion, and fatigue failure of amalgamrestoration.

51. Modulus of elasticity
 High copper alloys tend to be stiffer than low copper alloys
 When rate of loading increased, values of approx62 Gpa
have beenobtained
Knoop Hardness
 110 kg/mm2

52. 1. Stage 1—Contraction:
• Contraction which occurs for about 20 minutes after the beginning of trituration
is called initial contraction.
• It results as the alloy particles dissolve in mercury and the g1 phase grows.
• It is no greater than 4.5 mm.
• Contraction continues as long as there is growth of the g1 phase.
2. Stage 2— Expansion:
• As the g1 crystals grow, they start impinging against each other.
• When adequate crystals are formed, this impingement and outward pressure will
counteract the initial contraction and result in expansion.
• This expansion occurs only when there is adequate liquid mercury to provide a
plastic matrix. Once a rigid g1matrix is formed, there is no more expansion.
3. Stage -3: Limited delayedcontraction
• Final dimensional change can never reach zero.
• Expansion is more for low copper than high copper alloys.
• Modern amalgams on the contrary show a net contraction
DIMENSIONAL CHANGES:
Ada no.1 requires that amalgam should neither contract nor
expand more than 20um/cm at 37 degree Celsius, between
5mins-24hrs after the beginning of trituration.

53. Moisture contamination (Delayed
Expansion):
 When a zinc-containing, low-copper or high-copper amalgam is
contaminated by moisture during trituration or condensation, a large
expansion can take place.
 Usually starts 3 to 5 days after placement
 May continue for months, reaching values greater than 400 µm/cm
(4%).
 The effect is caused by the hydrogen produced by electrolytic action
involving zinc and water.
 The hydrogen does not combine with the amalgam but, rather, collects
within the filling, increasing the internal pressure to levels high enough
to cause the amalgam to creep, thus producing the observed expansion.
 The main source of contamination is saliva.

54. Complications that may resultdue todelayed expansionare:
 Protrusionof the entire restoration outof the cavity.
 Increased micro leakage space around therestoration.
 Restoration perforations.
 Increased flow andcreep.
 Pulpal pressurepain.
Such pain may beexperienced 10-12 days after the insertion of the
restoration

55. Flow and Creep:
 Time dependent plastic
deformation
 When a metal is placed under stress,
it will undergo plastic deformation.
 constant stress (static creep)
intermittent stress (dynamic creep)
 The high copper alloys, as compared with
conventional silver tin alloys, usually tend to
have lower creep values.
 Higher the creep, the greater is the degree
of marginal deterioration (ditching)

56. Factors influencing creep:
A) Phases of amalgam restorations
 g2 is associated with high creep rates.
B) Manipulations:
 Greater compressive strength will minimize creep rates.
 Low mercury: alloy ratio, greater the condensation
pressure and time of trituration, decrease in creep rate.

57. TARNISH
•Tarnish is surface discoloration on a metallic surface without any
loss of structure.
• Formation of a protective oxide layer on the surface of iron is
one form of tarnish.
• In case of low copper alloys, the g phase is responsible for
surface tarnish, while in high copper alloys, the copper rich
phases eta and silver–copper eutectic are responsible.

58. Corrosion
Corrosion is the chemical or
electrochemical reaction of a metal
with its environment and its
progressive destruction by formation
of corrosive byproducts
Excessive corrosion can lead to:
o Increased porosity.
o Reduced marginal integrity.
o Loss of strength.
o Release of metallic products into the oral
environment.
o Phases in decreasing order of corrosion resistance:
g> g1> Ag-Cu eutectic> epsilon> eta> g2

59. Low copper amalgam system:-
 Most corrodible phase is tin-mercury or 2 phase.
 Neither the  nor the 1 phase is corroded as easily.
 The corrosion results in the formation of tin oxychloride, from the
tin in 2 and also liberates Hg.
Sn7-8Hg + ½ 02 + H2O + Cl- Sn4 (OH) 6 Cl2 + Hg
 Reaction of the liberated mercury with unreacted  can produce
additional l and 2 (Mercuroscopic Expansion).
 Results in porosity and lower strength.

60. The high copper admixed and
unicomposition alloy :-
 Do not have any 2 phase in the final set mass
 The η phase formed has better corrosion resistance.
 However,  is the least corrosion resistant phase in high copper
amalgam
 Corrosion product CuCl2.3Cu (OH)2 , copper hydroxychloride has been
associated with storage of amalgam in synthetic saliva.
Cu6Sn5 + 1/202 +H2O + Cl- CuCl2.3Cu (OH)2 + SnO.

61. Types of Corrosion
1) Galvanic corrosion:
Dental amalgam is in direct contact with an
adjacent metallic restoration such as gold crown
2) Crevice Corrosion:
 Local electrochemical cells may arise whenever a
portion of amalgam is covered by plaque on soft
tissue.
 The covered area has a lower oxygen and higher
hydrogen ion concentration making it behave
anodically and corrode.
 Aka concentration cell corrosion.

62. Stress Corrosion:
 Regions within the dental
amalgam 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 alongthe
margins.

64. SELF SEALING ABILITY
•Since amalgam does not bond to the tooth, the corrosion products seal
the amalgam–tooth interface.
•The self-sealing ability of low copper amalgams is better than that of
high copper amalgam as the rate of corrosion is more in low copper
amalgam

65. CLINICAL CONSIDERATIONS OF
DENTAL AMALGAM

66. SELECTION OF ALLOY
•Low copper alloys have the disadvantages of g2 phase.
•High copper alloys :high early strength, low creep, better marginal
adaptation, and good resistance to corrosion.
•Lathe-cut alloys require almost 50% or more mercury to obtain adequate
plasticity during trituration.
•Spherical alloys require less mercury (about 42%) for trituration. They donot
offer much resistance to the condensation pressure.

67. Differences between Lathe-cut
and Spherical alloys
Lathe – cut Spherical
1. Require more mercury (50%) 1. Require less mercury (42%)
2. Require more condensation
force
2. Require less condensation
force
3. Require smaller condenser 3. Require broader condenser
points points
4. Less ease in carving and 4. Smooth surface during
burnishing carving & burnishing
5. Less overhangs and strong
proximal contacts
5. Overhangs and weak
proximal contacts

69. MODE OF SUPPLY
Silver amalgam is commercially available in various forms:
1. Alloy powder and mercury
2. Disposable capsules with preproportioned alloy powder and mercury
3. Preweighted alloy in tube form and mercury in sachets.

70. PROPORTIONS OF ALLOY TO MERCURY
 Correct proportioning of alloy and mercury- essential
for forming a suitable mass of amalgam
 The mercury: alloy ratio refers to the amount of alloy
powder and the mercury in wt% that is required for
trituration.
 There are two mercury: alloy ratio techniques
employed:
1. High mercury technique
2. Minimal mercury technique

71. High mercury technique :
• Aka increasing dryness technique
• Initial mix contains more mercury which is then
squeezed out.
• 52-53% mercury
• Produces a very plastic mix
• Ideal for pin retained amalgam restorations and
very large restorations.
Minimal mercury technique:
• aka Eames technique
• Ratio 1:1
• Equal amounts of mercury and powder
• Final restoration has 50% or less mercury.

72. SIZE OF MIX
 Manufacturerscommonlysupplycapsulescontaining 400, 600, or 800 mg
of alloy and the appropriate amount of mercury.
 For large size cavities - capsulescontaining 1200 mg of alloy are also
available.

73. TRITURATION
 Purpose: mix the amalgam alloy intimately with mercury so as to wet
the surface of the powder particles to allow the reaction between
liquid mercury and silver alloy.
 Objectives of trituration:
1. To remove the oxide layer
2. To pulverize pellets into particles, which can be easily wetted by the
mercury.
3. To reduce the particle size since this increases the surface area
4. To provide proper amalgamation and to achieve a workable mix of
amalgam within a short time, leaving more working time for the
insertion, condensation, and carving of the restoration

74. MANUAL TRITURATION
•A mortar and pestle is used.
•The inner surface of the mortar is roughened to maximize the friction
between amalgam and the glass surface.
•Both the mortar and pestle can be made from either glass or ceramic.
•In hand trituration, if excessive force is
employed, it can lead to splintering of
alloy particles and weakening of the
matrix.
•A trituration pressure of 2–3 psi is
required for proper mixing.

75. Amalgamator
MECHANICAL TRITURATION

76. There are three basic movements of a mechanical triturator, which are as
follows:
1. The mixing arm carrying a capsule moves back and forth in a straight line.
Such movements can occur at varying speeds.
2. The mixing arms travel back and forth in a figure of 8, also at varying
speeds.
3. The mixing arm travels in a centrifugal fashion.
ADVANTAGES
1. Uniform and reproducible mix can be attained.
2. Minimal trituration time is required.
3. A greater alloy: mercury ratio is used for preparing the mix as they are
proportioned by the manufacturer.
4. Atmospheric mercury contamination is reduced

77. Mechanical amalgamators are available in the following speeds:
 Low speed: 32-3400 cpm.
 Medium speed: 37-3800 cpm.
 High speed: 40-4400 cpm.
 Spherical/irregular low-copper alloys – triturated at low speed
 High copper alloys – high speed
 Time of trituration on amalgamation ranges from 3-30 seconds.
Variations in 2-3 seconds can also produce a under or over mixed mass.
The mixing time may vary depending upon the
speed and a parameter known as coherence
time (tc), which is defined as the minimum
time required for mixing to form a single
coherent pellet of amalgam.
Effective trituration depends upon a combination of the duration and speed of
the mixing.

78. MULLING
• It is a continuation of trituration.
• Can be accomplished in two ways:-
a) By kneading the plastic amalgam mix in a piece of
rubber dam.
b) By triturating the mix in a pestle free capsule for 2-3
seconds after the specified time.
• It is mainly done to improve the homogeneity of the
mass, assure improved texture, and achieve a single,
consistent coherent mass.
• Also removes excess mercury.
Compressive strength is decreased by 1%
if the residual mercury content is
increased by 1%.
Residual mercury content also contributes
to increased expansion and creep rate.

79. •Appears rough and grainy and may crumble
easily.
•The outer surface of the alloy particles is
not completely wetted by the mercury.
•This results in an incomplete reaction.
• The mix remains plastic longer, increasing
the working time.
•Has more porosity and is low in strength
and corrosion resistance.
Under Trituration

80. Normal Mix
•The normal mix appears shiny and has a smooth surface and
consistency.
•It separates as a single mass from the capsule.

81. The over mixed amalgam appears soupy, difficult to remove from
the capsule, and too plastic to manipulate.
Effects :
1. Working time: Working time for both spherical alloys and low
copper alloys decreases with overtrituration.
2. Dimensional changes: Both spherical alloys and low copper alloys
show higher contraction with overtrituration.
3. Compressive and tensile strength: Compressive and tensile
strength of high copper, admixed, and spherical alloys are
maximum at normal trituration time. Overtrituration decreases
the strength.
4. Creep: Overtrituration increases creep and undertrituration
decreases it.
Over Trituration

82. Condensation
 The method of packing the amalgam mix in its
plastic state into the prepared cavity so as to
achieve the greatest possible density of the
material when set.
 Aim of condensation:
1. To adapt amalgam tothe margins, wallsand line
angles of thecavity.
2. Minimize voids and microleakage.
3. To bring the strongest phases of amalgam
close together, thereby increasing the final
strength of the restoration
4. Removeexcess mercury to leavean optimal
alloy: mercuryratio.
For every 1% of porosity, the compressive
strength decreases by 1%.

83. Condensation Procedure
•Usually started at the center, and then incrementally toward the cavity walls.
•After condensation of each increment, the surface should be shiny in
appearance. This indicates that there is sufficient mercury present at the surface
to diffuse into the next increment so that each increment is added, it will bond to
the preceding one.
 Irregular shaped alloys require condensers with relativelysmall tip, 1 to 2 mm.
 Spherical amalgam alloys require condensers with large tips.
Condensation Pressure
•The smaller the condenser, the greater is the pressure exerted on the amalgam.
•A study of 30 practitioners showed that condensation forces average between
13.3 and 17.8 N (3 to 4 lb) employed.
HAND CONDENSATION

84. Mechanical Condensers:
 Useful forcondensing irregularshaped alloyswhen high condensation
forces arerequired
 Need was eliminated with the adventof spherical alloys
 Tend to lead to unreliable condensation as well as generation of heat
and mercury vapor, both ofwhich are undesirable.
Ultrasonic Condensers:
 Not recommended
 Causes thereleaseof considerable quantitiesof mercuryvapor in the dental office

85. BURNISHING
•Burnishing is defined as the plastic deformation of a surface due to
rubbing/sliding contact with another object.
Pre carve burnishing
Post carve burnishing
Objectives of pre carve burnishing:
 Continuation of condensation, to further reduce the size and number
of voids on surface of theamalgam.
 Bringsanyexcess mercury to the surface, which can be
removed duringcarving.
 Improve marginal adaptation

86. •Ball burnisher (fig 1) is used.
•Beaver tail burnisher (fig 2) is used in inaccessible areas
such as proximal surfaces of the restoration.

87. CARVING
Carving is the anatomical sculpturing of the amalgam material.
The objective of carving is to produce a restoration:
1. With proper anatomical contours
2. With no underhangs,
3. No extra flash of material
4. With proper occlusal anatomy and
occlusal contact points
5. With proper size, location, tightness
of contact areas
6. With adequate embrasures that
are compatible with
the periodontal structures

88.  Using remaining enamel as a guide, carving is donegently from enamel
towards the center to recreate the lost anatomy of the tooth.
 Amalgam should be hard enough to offer resistance to carving
instrument
 A scarping or "ringing"(amalgam crying) should he heard.
 If carving is started too soon, amalgam will pull away from the margins.

89. POST CARVE BURNISHING
 Done to remove scratches and irregularities on the amalgam
surface, facilitating easier and efficient finishing and polishing.
 The combination of frictional heat and pressure of the burnisher
achieves the desired results.
 Similar to pre-carve burnishing, this is also accomplished by a ball
burnisher with gentle strokes from the amalgam surface to the
tooth surface.
If temp raises above 60C,it causes release of mercury accelerates
corrosion & fracture at margins

90. Finishing & Polishing
 Finishing can be defined as the process, which continues the
carving objectives, removes flash and overhangs and
corrects minimal enamel underhangs.
 Polishing is the process which creates a corrosion resistant
layer by removing scratches and irregularities from the
surface.
 Can be done using descending grade abrasive, eg. rubber
mounted stone or rubbercups.
 A metallic lusture, is always done with a polishing agent
(precipitated chalk, tin or zincoxide).

91. Advantages:
 Minimizes fatigue failure of the amalgam under the cyclic loading of
mastication
 Prevents the adherence of plaque
•Finishing should be done intermittently to avoid too much friction that
can produce overheating.
•Polishing should be done 24 hours after condensation.
•Wet polishing is preferable, where a wet abrasive powder is made into
a paste for polishing.
•Dry polishing is not advocated because it increases the temperature
above 60°c resulting in corrosion and fracture at the margins.
• Usually amalgam restoration should be finished after 24 hours.
However, spherical high copper alloys can be polished after 8–12 hours
but others still require only a 30-minute wait after insertion.

92. CLINICAL TECHIQUES TO ENHANCE
MARGINAL SEAL
1) Copal resin varnish:
 Apply two thick coats to the cavity walls and margins before placing the
amalgam and it will gradually dissolve, beginning at the cavosurface,
over 2-3 months.
 As the varnish dissolves out, the gap will be filled with corrosion products
from the amalgam and dissolution of the varnish will cease.

93. 3) Oxalate solutions :
 Such as potassium oxalate, can be applied to the cavity surface to
reduce the permeability of the tubules and possibly seal the dentine.
 The crystals this deposited will not wash out but will allow deposition
of corrosion products.
2) Glass-ionomer linings
 Placed under an amalgam will seal the dentinal tubules and
release small quantities of fluoride
 Will not affect enamel margins or enhance the seal at the margin.

94. Condensation
 The method of packing the amalgam mix in its
plastic state into the prepared cavity so as to
achieve the greatest possible density of the
material when set.
 Aim of condensation:
1. To adapt amalgam tothe margins, wallsand line
angles of thecavity.
2. Minimize voids and microleakage.
3. To bring the strongest phases of amalgam
close together, thereby increasing the final
strength of the restoration
4. Removeexcess mercury to leavean optimal
alloy: mercuryratio.

95. Condensation Procedure
•Usually started at the center, and then incrementally toward the cavity walls.
Condensation Pressure
•The smaller the condenser, the greater is the pressure exerted on the amalgam.
•A study of 30 practitioners showed that condensation forces average between
13.3 and 17.8 N (3 to 4 lb) employed.
•*Spherical: 1.7±0.6 MPa
•Lathe cut:4.1 ±1.2 MPa
•Admixed: 2.4±1.0 MPa
HAND CONDENSATION
*Lussi A, Brunner M, Portmann P, Bürgin W. Condensation pressure during amalgam placement in patients. European
journal of oral sciences. 1995 Dec;103(6):388-93.
Mechanical Condensers
•Useful forcondensing irregularshaped alloyswhen high condensation forces are
required

96. BURNISHING
•Burnishing is defined as the plastic deformation of a surface due to
rubbing/sliding contact with another object.
Pre carve burnishing
Post carve burnishing
Objectives of pre carve burnishing:
 Continuation of condensation, to further reduce the size and number
of voids on surface of theamalgam.
 Bringsanyexcess mercury to the surface, which can be
removed duringcarving.
 Improve marginal adaptation

97. POST CARVE BURNISHING
 Done to remove scratches and irregularities on the amalgam
surface, facilitating easier and efficient finishing and polishing.
If temp raises above 60C,it causes release of mercury which accelerates
corrosion & fracture at margins

98. CARVING
Carving is the anatomical sculpturing of the amalgam material.
The objective of carving is to produce a restoration with:
1. Proper anatomical contours
2. No extra flash of material
3. Proper occlusal anatomy
and contact points
4. Proper size, location, tightness
of contact areas
 A scarping or "ringing"(amalgam cry) should he heard.

99. Finishing & Polishing
 Finishing can be defined as the process, which continues the
carving objectives, removes flash and overhangs and
corrects minimal enamel underhangs.
 Polishing is the process which creates a corrosion resistant
layer by removing scratches and irregularities from the
surface.
.

100. •Finishing should be done intermittently to avoid too much friction that
can produce overheating.
•Polishing should be done 24 hours after condensation.
•Wet polishing is preferable, where a wet abrasive powder is made into
a paste for polishing.
•Dry polishing is not advocated because it increases the temperature
above 60°c resulting in corrosion and fracture at the margins.

101. CLINICAL TECHIQUES TO ENHANCE
MARGINAL SEAL
1) Copal resin varnish:
 Apply two thick coats to the cavity walls and margins before placing the
amalgam and it will gradually dissolve.
 As the varnish dissolves out, the gap will be filled with corrosion products
from the amalgam and dissolution of the varnish will cease.

102. 3) Oxalate solutions :
 Such as potassium oxalate, can be applied to the cavity surface to
reduce the permeability of the tubules and possibly seal the dentine.
2) Glass-ionomer linings
 Placed under an amalgam will seal the dentinal tubules and
release small quantities of fluoride
 Will not affect enamel margins or enhance the seal at the margin.

103. WHAT NEW IN AMALGAM ?
Gallium
based
Alloys
Indium
containing
alloy
powder and
binary Hg-
Indium
liquid alloy Low
mercury
amalgam
alloy
Consolida
ted silver
alloy
system
Flouride
containin
g
amalgam
Bonded
amalgam

104. Bonded Amalgam
Concept was introduced by Baldwin in 1897
here amalgam was condensed onto zinc phosphate cement
Utilizes bonding agents to seal the dentin and “bond” the
amalgam to the prepared tooth.
The amalgam is condensed into a polymerizing dual cure
resin.
It chemically binds to the resin, which in turn is bonded to
the tooth structure primarily by micromechanical retention.
Thus the resin will partially retain the amalgam in place,
reducing the need to create retentive features in the tooth.
Recently, 4META has been used for bonding amalgam to
cavity walls

105. • The bond strengths recorded in studies have varied, approximately 12–15
MPa, Summitt and colleagues reported mean bond strength of 27 MPa.
• Bond strengths achieved with admixed alloys tend to be slightly lower than
those with spherical alloys.
•Clinical research thus far has shown that bonded and non bonded amalgams
perform equally well. There seems to be little advantage to bonding amalgams,
and the technique is more complex and time consuming.

106. Gallium Amalgam
To conquer the harmful effects of mercury, gallium metal
which has second lowest melting point (next to mercury) has
been tried.
1920s, Gallium (Ga) was one of the substitutes suggested for
Hg (Putt Kammer, 1928)
Composition:
Powder –
Silver (Ag) - 55 to 65%
Tin (Sn) - 20 to 30%
Copper (Cu) - 10 to 16%
Palladium (Pd) - 10 to 15%
Liquid –
Gallium (Ga) - 57 to 67%
Indium (In) - 15 to 25%
Tin (Sn) - 15 to 25%

107. Setting Reaction
Reaction between powder AgSn particles and liquid gallium results into formation of
AgGa phase and a pure tin phase.
AgSn + Ga → AgGa + Sn
Properties of Gallium Amalgam Restorations
• Compressive strength: Gallium alloys have sufficient strength for small restoration.
• Setting expansion: In initial stages, controlled expansion occurs but if contaminated,
uncontrolled expansion can result. This excessive expansion can cause cuspal fracture,
and postoperative sensitivity.
• Creep value: In gallium alloys, creep value is less.
• Gallium amalgam has very high wetting ability, hence the final restoration is highly
resistant to microleakage.
• Time consuming: Since their handling is difficult because of being sticky, it takes
more time for condensation and matrix band has to be removed very carefully to
avoid fracture of restoration.
• Expensive: Gallium amalgam is about 16 times costlier than the silver mercury
amalgam.

108. Indium containing alloy powder and
binary Hg-Indium liquid alloy
•Developed by Powell et al 1989
•10-15% indium in admixed alloy reduces the mercury
needed for manipulation.
•Marketed as: Indisperse, Indiloy
•Reaction: indium oxide and tin oxide are rapidly formed.
•Reduction in mercury release
•Long term clinical performance needs further evaluation.

109. Fluoridated amalgam
Addition of fluoride to amalgam proposed by Innes and Youdelis 1966,
Serman 1970, Stone 1971.
Fluoride, being cariostatic, has been included in amalgam to deal with the
problem of recurrent caries associated with amalgam restorations.
 However, this release of fluoride decreases to minor amounts after 1
week.
 Fluoride is released as a slow releasing device.
 Increase of up to 10–20-fold in the fluoride content of whole saliva
could be measured.

110. 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.
Exhibited superior clinical performance and longevity compared with
unsealed amalgam restorations over a period of 10 years

111. MERCURY FREE DIRECT FILLING
ALLOY
Developed by ADA at National Institute on Standard
and Technology NIST
They use silver coated Ag-Sn particles
To keep the surface of alloy particles clean, a
fluoroboric acid solution is used.
Condensed in the same manner as direct filling gold
restoration.
Disadvantages :
Poor adaptation to preparation walls
Material hardens and becomes brittle during condensation
Presence of internal voids

112. LOW MERCURY ALLOY
In this approach, alloy particles are carefully selected so that
they can be packed well.
This reduces the need of mercury for amalgamation around 15
to 25%.
However, the clinical properties of these alloys are not yet
known.

113. May 2020
Journal of the Pakistan Medical Association

115. FORMS OF MERCURY
 Elemental mercury
 Inorganic mercury
 Organic mercury

116. Most volatile
Exist in liquid/vapor form
Inhaled and absorbed into lungs(80%) and
GIT(0.01%)
Most common form: amalgam restoration
Exposure to this form can occur due to accidental
spillage of mercury in dental office
Can cross the blood-brain barrier and placenta
Denature biological proteins, inhibit enzymes,
interrupt membrane transport and release of
neurotransmitters
Elemental Mercury

117. Inorganic Mercury
 Safest
 Source – drinking water,food
 They are of low or very low toxicity and are apparently
harmless whenswallowed.
 Poorlyabsorbed, do not accumulate in body tissues and
are wellexcreted.

118. Organic Mercury
 Source -- sea food
 Formed when mercury combines with carbon.
 Usually an environmental hazard and not related to dental
hazard.
 Most common form is methyl mercury, which is considered
to be most toxic since it is readily absorbed from food and
passes up the food chain.

119. Exposure to mercury
Can be not only from dental amalgam(occupational exposure) but also diet,
water, air.
WHO has estimated that eating seafood once a week raises
urine Hg levels to 5-20 µg/L,i.e. 2-8 times the level of exposure from
amalgam
Mercury blood levels :
patients with amalgam: 0.7ng/ml
subjects with no amalgam: 0.3ng/ml

120. OSHA
RECOMMENDED
TLV=0.05mg/m³
MOST Dental office mercury level lie below 0.05mg/m³

121. Source g Hg vapour g inorganic Hg g methyl Hg
Atmosphere 0.12 0.038 0.034
Drinking Water --- 0.05 ---
Food & Fish 0.94 --- 3.76
Food & Non-Fish --- 20.00 ---
ESTIMATED DAILY INTAKE OF MERCURY

126. • Allergy responses represent an antigen-antibody reaction marked by
itching, rashes, sneezing, or other symptoms
 Contact dermatitis or Comb's type IV hypersensitivity reaction represent
the most likely physiologic side effect to dental amalgam.
 Usually small percentage of people are allergic to mercury
 Reaction is self limiting (usually within 2 Wks)

127. Mercury Toxicity
Mainly seen because of chronic exposure of mercury which can be in
form of food, restorations or other sources.
Usually mercury gradually accumulates in the body over a period of
time, contributes to chronic mercury poisoning.
Factors Affecting Toxic Effects of Mercury
• Amount of exposure
• Length of exposure
• Location of mercury accumulation in body
• Amount of accumulated mercury
• Overall health of the patient (for detoxification).

130. • Bleeding gums
• Alveolar bone loss
• Loosening of teeth
• Excessive salivation
• Foul breath
• Metallic taste
• Burning sensation, with tingling of lips, face
• Tissue pigmentation(amalgam tattoo of gum)
• Stomatitis (sore in the mouth)
• Ulceration of gingiva, palate, tongue
SYMPTOMS IN THE ORAL CAVITY

131. CASE STUDIES

132. •First discovered in the city of minamata, japan,
in 1956.
• It was caused by the release of methyl
mercury in the industrial waste water from a
chemical factory.
•This highly toxic chemical biomagnified in
shellfish and fish in minamata bay and
the shiranui sea, which, when eaten by the local
population, resulted in mercury poisoning.

135. 1971 Iraq poison grain disaster
It was a mass methyl mercury poisoning incident that began in
late 1971.
Grain treated with a methyl mercury fungicide was consumed
as food by Iraqi residents in rural areas.
People suffered from paresthesia, ataxia and vision loss,
symptoms similar to those seen when Minamata
disease affected Japan.
The recorded death toll was 459 people, but figures at least ten
times greater have been suggested.
The 1971 poisoning was the largest mercury poisoning disaster
when it occurred.

137. Minamata Convention
The Minamata Convention on Mercury is
an international treaty designed to protect
human health and the environment from
mercury and mercury compounds.
It provides controls over a myriad of
products containing mercury
Dental fillings which use
mercury amalgam are also regulated under
the Convention.

138. MERCURY HYGIENE

139. Steps to Reduce Mercury Exposure in
the Dental Clinic
Storage of Mercury
Precapsulated alloys should be preferred for avoiding mercury spill
If bulk mercury is purchased, store it in tight container with tight lid in closed
cabinets.
Location of storage should be near the window/exhaust vent.
Trituration of Amalgam
Use precapsulated alloy in amalgamator
Avoid manual mixing
small covers are used over the amalgamator to contain the aerosol in that area
Air flow should be reasonably high in dental office to minimize air contamination
Avoid direct exposure of the mercury with skin as it may cause hypersensitivity
reactions.

140. •Designing of Office
•Proper ventilation of the dental office
• Avoid carpeting/floor coverings in dental office as there is no way of
removing mercury from the carpet.
•Insertion and Condensation of Amalgam
• Proper aseptic techniques such as use of mouth masks, gloves and
protective eyeglasses should be done.
• Avoid direct exposure of mercury with skin.
• Use rubber dam to isolate the tooth.
•Use high volume evacuation system to control the mercury level in air.
•Polishing of Amalgam
•Polishing should be done with coolant to decrease heat and vapors present
in atmosphere.
•Cleaning of Mercury Contaminated Instruments
•amalgam material left on the instrument surface, heated during sterilization
can release mercury vapor in atmosphere.
• Isolation of the area along with proper ventilation of sterilization area is
preferred.

141. •Disposal of Mercury Contaminated Waste
•should be disposed in tightly closed plastic container/plastic bag which can be
placed into sanitary landfill for disposal.
•Scrap amalgam should be carefully collected and stored under water, glycerin
or spent X-ray fixer solution in tightly capped jar.
•Spent X ray fixer is preferred for storage of amalgam scrap because it is a
source of both silver and sulfide ions which react with mercury present in
scrap amalgam to form solid product and decrease the mercury vapor
pressure.
•Removal of Old Amalgam Restorations
•Rubber dam and high volume evacuator should be used to decrease mercury
vapor.
•Water cooling should also be used
•Monitoring of Mercury Vapors
•The accepted threshold limit for exposure to mercury vapor for a 40-hour
work per week is 50 µg/m3 (given by OSHA).
•Periodical monitoring of mercury vapor in dental office should be done and
carefully recorded.

142. Mercury Exposure In Dental Clinic

143. Bulletin of World Health Organization, 2018
Fisher
J,
Varenne
B,
Narvaez
D,
Vickers
C.
The
Minamata
Convention
and
the
phase
down
of
dental
amalgam.
Bulletin
of
the
World
Health
Organization.
2018
Jun
1;96(6):436.

144. Jan’29, 2020

146. Alkaline bulk fill composite
Can be cured in increments of upto 4-5mm thickness
Designed for temporary restoration and for permanent restorations
of nature class I, II or V
There’s no necessity to place a bonding agent
Can be used with or without an adhesive; (adhesive could be
avoided but it requires a retentive preparation)
Monomer: UDMA
Moderate viscosity
This alkasite is chemical cured but it also has optional light
curing.
Setting time: 4mins for self cure

149. FUTURE OF AMALGAM
The prediction that amalgam would not last until the end
of the 20th century was wrong.
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.
J Conserv Dent. 2010 Oct;13(4):204-8. 124 Dental
amalgam: An update

150. References
•Phillip’s science of dental materials
•Sturdevant’s art and science of operative dentistry
•Marzouk
•Materials used in dentistry by S. Mahalaxmi