Dental Amalgam Guide

CONTENTS
Introduction
Definition
History
Material aspects:
- Mercury
- Alloy powder
Composition
Manufacture of alloy powder
Phases in the structure of amalgam
Amalgamation and microstucture
Properties of amalgam
Manipulation
- Selection of alloy
- Proportioning

- trituration
- Condensation
- Burnishing
- Carving
- Finishing and polishing
 Indications and contraindications
 Advantages and disadvantages
 Harmful effects of mercury
 Mercury management
 Controversies
 Advances in amalgam
 Conclusion
 References

INTRODUCTION
Dental amalgam has served as an excellent & versatile restorative material for many years
despite periods of controversy.
Acceptance & usage have been based on the biomechanical properties, clinical characteristics,
versatility in application & a long experience relating to the serviceability of amalgam in the
oral environment.
Through the years amalgam has survived despite political discussion
such as amalgam war, economic & availability crisis & challenges by
comparable alternative restorative materials.

DEFINITION
The word “Amalgam” is derived from Greek work “emollient” meaning paste
An Amalgam is an alloy that contains mercury as one of it’s constituents
- Phillips
Dental amalgam is a metal like restorative material composed of a mixture of silver/tin/
copper alloy and mercury
- Sturdevants
Dental Amalgam Alloy – an alloy of silver copper and tin that
is formulated and processed in the form of powder particles or
compressed pellets.
- Phillips

HISTORY
659AD - First used by Chinese. There is a mention of silver-mercury paste by SuKung
in the Chinese materia medica
- The first book on remedies for holes in the teeth were published. The decayed
tooth was cauterized with a gold instrument .Vitriol+ strong acid + mercury
were boiled .The mercury will transform itself into an amalgam which was
poured into the cavity
- Li Shitichen used 100parts of Hg, 45parts of Ag &
100 parts of Sn
- In southern Germany, Johannes recommended amalgam
for the purpose of restoration
1528
1578
1601

1800 - D ‘arcets mineral cement –earliest dental amlgam used in France
1818 - First dental silver amalgam is supposed to have been introduced into England by
Bell – “Bell’s Putty”
1826 - Introduction of silver mercury paste by Peter.O.Taveou of Paris (french silver
coin filings & Hg)
1833 - Introduced to the North American continent by Cawcour brothers termed as
“Royal Mineral Succedaneum”or substitute for gold
1841 - Lefoulon introduced amalgam ,but it was rejected because of black discoloration
porosity and shrinkage
1843 - Resolution passed by the American Society of Dental Surgeons
(the first organised Dental Society in the U.S.A declaring
the use of amalgam a “Malpractice”).
Thus the Amalgam War began (1840-1850)

1845 - “Amalgam Pledge” was adopted by the society
1848 - Thomas W Evancs in Paris added calcium to Tin-Silver mixture
1861 - First research programme was conducted by John Tomes Who measured
shrinkage of a number of amalgams
1870
1895
1896
1928
- Elish Townsend & J.I Flagg improvised amalgam alloy composition
- Dr G.V Black gave composition for low copper alloy
- Formula for “Conventional Amal Circa”. This contains
- 72.5% silver and 27.5% tin-mercury
- The use of gallium in direct restorative materials was first
suggested by Puttkammer

1930 - A.D.A specification No. 1 for amalgam
1951 - Markley published a classic article advocating constricted occlusal preparations
He designed pear shaped burs (No 330 and 329)
1963
1970
1976
1980
1997
- Innes and Youdelis added Spherical particles of silver copper eutectic, 39%
copper to silver ,to particles of lathe cut low copper alloy
- Change from hand trituration to mechanical trituration
- Introduction of non zinc and zinc free alloys
- Bonded amalgam restorations was introduced
- Third amalgam war
- WHO Consensus Statement on Dental Amalgam considering
amalgam to be safe

MATERIAL ASPECT
Mercury :
 ADA Specification No.- 6
 Silvery white mirror like surface
 Atomic no. - 80
 Specific gravity - 13.55gm/cm2
 Freezing point - -38.8°c
 Boiling point - 356.9°c
 Tends to form globules when dropped on a surface due to high
surface tension of 465 dynes/cm at 20 deg C.(Water- 72.8 dynes/cm)
 Being liquid in nature, binds with the alloy particles to form amalgam
 Almost 50% of amalgam is Elemental Mercury by wt

CLASSIFICATION
According to Sturdevant
Based on particle shape:
SPHERICAL LATHE CUT ADMIXED

• Regular cut
• Fine cut
• Microfine cut
Based on
particle size
• Low copper alloy (<6%)
• High copper alloy (>6%)
Based on
copper content
• Zinc alloys
• Non-zinc alloys
Based on zinc
content

According to Marzouk
According to the no. of alloyed metals:
 Binary alloys (e.g.: silver-tin)
 Ternary alloys (e.g.: silver-tin-copper)
 Quaternary alloys (eg: silver-tin-copper-indium)
According to whether the powder consists of unmixed or admixed alloys:
Certain amalgam powders are only made of one alloy while others have one or more alloys or
metals physically added to the basic alloy

According to the shape of the particle:
 Spherical
 Irregular
 Combined
According to the size:
 Micro cut
 Fine cut
 Coarse cut
According to the copper content:
 Low copper
 High copper

According to the addition of noble metals:
Metals such as pd, Au or pt are alloyed to the powder the resulting amalgams may be classified
as “noble metal alloys
Can also be classified according to dispensing:
 As powder and liquid in separate bottles
 As pre weighed capsules of powder and liquid separated by a thin membrane
 As pellets,capsules(of the powder)
 As pre-amalgamated powder(around 2% of Hg is mixed by manufacturer)

According to compositional changes of succeeding generations of amalgam
1st generation – 3 parts silver + 1 part tin peritectic
2nd generation – copper is added upto 4%
3rd generation – silver copper eutectic alloy + original alloy
4th generation – alloying of copper to silver and tin upto 29%
5th generation – silver, copper, tin, indium
6th generation – alloying palladium 10%, silver 62%, copper 28% -
eutectic lathecut blended into 1st generation in ratio
of 1:2

COMPOSITION
ALLOY PARTICLE
SHAPE
Ag Sn Cu Zn
Low Cu
Lathe cut+
Spherical
63-70% 26-28% 2-5% 0-1%
High Cu
- Admixed
Lathe cut +
Spherical 60-65% 15-25% 9-13% 0-2%
- Single
composition
Spherical 60-65% 15-25% 13-30% 0-2%

Zinc
- acts as a deoxidizer
- makes alloy particles less
brittle and contributes to
the workability of the
amalgam
- Zinc causes delayed
expansion, if
contaminated.
Tin
- decreases strength &
hardness
- decreases expansion of
Amalgam
- increases flow
- greater affinity for Hg-
helps in amalgamation
Copper
- hardens & strengthens
Ag- Sn alloy
- decreases flow
- increases setting
expansion
Silver
-whitens the alloy
-increases strength
-increases expansion
-decreases flow of amalgam
-decreases setting time
-resists tarnish & corrosion

Platinum
Hardens the alloy
Increases resisitance to
corrosion
Palladium
Hardens the alloy
Whitens the alloy
Indium
• Increases strength
• Improved resistance to
creep and corrosion
• Reduces dimensional
changes
Other constituents include

MANUFACTURING
Lathe-cut Alloy Powder:
(1) Mixing:
 The ingredient metals are mixed in definite proportion and melted in a graphite crucible.Then
poured into a mould to form an ingot(cylinder) of dimension 4cm diameter and 20-25 cm length.
(2) Homogenisation:
 The ingot has cored structure(difference in composition within the alloy)
with β and ɣ phases in homogeneously distributed.
 Then the ingot is heated for various periods of time (usually 6 to 8 hrs)
at 400ºC to produce homogenous distribution of Ag3Sn.
It is slowly cooled.

(3) Lathe milling:
 The ingot is then reduced to filings by being cut on a lathe & ball
milled to form powder.
 The particles are passed through a fine sieve & then ball milled to form
the proper size.
 The average particle size of modern powders range between 15-35µm.

(4) Ageing & Particle treatment:
 The alloy particles are aged by subjecting them to a controlled temp of 60ºC to 100ºC for
1 to 6 hrs & washed with acid.
 The aging is related to relief of stress in the particles produced during the cutting of the
ingot.
 Acid washed powders tend to be more reactive than those made from unwashed powders.

Spherical alloy powder
 The spherical particles are prepared by an atomization process.
 All the desired elements are melted together.
 The liquid alloy is then sprayed under high pressure of an inert gas, through a fine crack in a
crucible into a large chamber.
 If the droplets solidify before hitting a surface, the spherical shape is
attained.
 They are seperated into different sizes by seiving and then homogenized
to remove cored structure.

Lathe cut alloys Spherical alloy
Alloy particles have irregular shape Alloy particles have spherical shape
Alloy particles are manufactured by milling Alloy particles are produced by atomization
Requires more mercury for mixing and have poor
properties
Requires less mercury and have better properties
Mix is less plastic and heavy condensation
pressure is required
Mix is more plastic and it is not sensitive to
condensation pressure
Cu content is 9-20% Cu content is 13-30%
Creep is high due to high mercury content Creep is low due to low mercury content
Difficult to finish Easy to finish
LATHE CUT VS SPHERICAL ALLOYS

Factors governing the quality of a Dental Amalgam Restoration
1) Those that can be controlled by the dentist:
- Selection of an alloy
- Mercury / Alloy ratio
- Trituration procedures
- Condensation technique
- Marginal integrity
- Anatomical characteristics
- Final finish

2) Those that are under the control of the manufacturer:
- The composition of the alloy
- The heat treatment of the alloy
- The size, shape and method of production of the alloy particles.
- The surface treatment of the particle.
- The form in which the alloy is supplied.

SYMBOLS & STOICHIOMETRY OF PHASES THAT ARE INVOLVED IN THE
SETTING OF DENTAL AMALGAM
Phases in Ag-Sn alloy system Stoichiometric formula
 Ag3Sn
1 Ag2Hg3
2 Sn7-8Hg
Є Cu3Sn
η Cu6Sn5
Silver-copper eutectic Ag-Cu

AMALGAMATION AND RESULTING MICROSTRUCTURES
AMALGAMATION AND RESULTING MICROSTRUCTURES
Low copper alloys-(setting reaction)
 Amalgamation occurs when alloy powder and mercury are triturated ,the silver and tin in outer
portion of the particles dissolve into mercury . Simultaneously the mercury diffuses into the
alloy particles and start reacting with silver and tin within forming crystals of silver –mercury
and tin mercury compounds.
 Silver tin compound (unreacted alloy powder )is known as gamma
phase()silver mercury compound is known as gamma 1 phase (1)
and tin mercury as gamma 2 phase (2)

Setting Reaction:
 The alloy particles do not react completely with mercury
 About 27%of original Ag3Sn remains as unreacted particles - which is called as gamma
phase.
 1 2

Microstructure of set Amalgam:
Set mass consists of unreacted particles () surrounded
by a matrix of the reaction products (1+2).
More the unconsumed Ag-Sn phase () present in final
structure – more stronger the amalgam will be.
2 is the weakest component & is least stable to
corrosion process.
The high proportion of the unconsumed  phase will not
strengthen the amalgam unless the particles are bound
to the matrix.

High copper alloys
 Contain more than 6 wt% copper.
 High copper alloys have become the materials of choice because of their improved
mechanical properties, resistance to corrosion, better marginal integrity and improved
performance in clinical trials as compared with low copper alloys.
 2 types of high copper alloy powders:
- Admixed alloy powder
- Single-composition alloy powder.

Admixed alloys
 The admixed alloys was introduced in 1963 and were orignally made by mixing 1 part of silver
copper eutectic alloy(high copper spherical particles)with 2 parts of silver tin alloy (low copper
lathe cut alloy)
 An eutectic alloy is one in which the components exhibit complete liquid solubility but limited
solid solubility)

Greater residual filler
content thereby changing
the filler to matrix ratio
Silver copper particles
are present in greater
amounts
Reduction in gamma 2
phase
Admixed alloys are
better than lathe cut
alloys

Setting reaction in admixed alloys
 When mercury reacts with an admixed powder, silver in Ag-Cu spheres and silver and tin from
Ag-Sn particles dissolve into the mercury.
 Whereas 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.
 The η′ layer on the surface of Ag-Cu alloy particles also contains γ1 crystals, since γ1 and η′
phases form simultaneously.
 As in the low-copper amalgams, γ1 is the matrix phase (i.e., the phase
that binds the unconsumed alloy particles together).

 In this reaction, the γ2 phase does form along with the η′ phase but later reacts with copper from Ag-Cu
particles, yielding additional η′
 The γ2 phase can be eliminated with at least 11.8% of copper by weight in the alloy powder.

Microstructure of set Amalgam:
 The Cu6Sn5 (η) is present as a “halo” surrounding the Ag-Cu particles.
 The ɳ phase is also found as a mesh of rod crystals
binding the matrix of gamma1 crystals together
contributing to the strength.
 Final set material consists of:
Core of
1) Ag3Sn ()
2) Ag-Cu surrounded by a halo of Cu6Sn5 (η)
Matrix of 1 (Ag2Hg3)

Single-Composition Alloys
 The major components of single-composition particles are usually silver, copper, and tin.
 The copper content of various single-composition alloys ranges from 13% to 30% by weight.
 In addition, small amounts of indium or palladium are included in some of the single-
composition alloys.
 A number of phases are found in each single-composition alloy particle, including the β phase
(Ag-Sn), γ phase (Ag3Sn), and ε phase (Cu3Sn).
 Some of the alloys may also contain some η′ phase

Setting reaction
 When triturated with mercury, silver and tin from the Ag-Sn phases dissolve in mercury.
 Very little copper dissolves in mercury.
 The γ1 crystals grow, forming a matrix that binds together the partially dissolved alloy
particles.
 The η′ crystals are found as meshes of rodlike crystals at the surfaces of alloy particles,
dispersed in the matrix.
 In most single-composition amalgams, little or no γ2 forms

Microstructure of set amalgam
Set material consists of:
- a core of Ag3Sn & Ag-Cu
- a matrix of 1 (Cu6Sn5 is present in the 1 matrix)

PROPERTIES
 Dimensional stability
 Strength
 Creep and flow
 Tarnish and corrosion
 Thermal properties

1. DIMENSIONAL STABILITY
• Amalgam can expand or contract, depending on its manipulation.
• ADA Specification No. 1 requires that the dimensional change of amalgam be in the range of
15 to 20 µm/cm measured at 37 °C between 5 min and 24 h after the beginning of trituration.
Severe contraction can lead to microleakage, plaque
accumulation, and secondary caries.

Excessive expansion can produce pressure on the pulp and postoperative
sensitivity
Protrusion of a filling can also result from excessive expansion.

MECHANISM OF DIMENSIONAL CHANGE
Steps Involved:-
1. Initial contraction
2. Expansion
3. Slight contraction
Mechanism involved
When the alloy and mercury are mixed, contraction results as the particles dissolve (and hence
become smaller). Since the final volume of the γ1 phase is less than the sum of the silver and
liquid mercury volume needed to produce the γ1 phase, contraction continues as long as the γ1
phase keeps growing.
As γ1 crystals grow, they will impinge against one another.
When there is sufficient liquid mercury present to provide a plastic matrix,
expansion will occur when γ1 crystals impinge on each other

After a rigid γ1 matrix has formed, growth of γ1 crystals cannot force the matrix to expand further.
The reaction continues with γ1 crystals growing into interstices containing mercury, thereby
resulting in slight contraction
NET RESULT WITH MODERN AMALGAM IS SMALL AMOUNT OF CONTRACTION of
about 0.3 % by volume.

More Expansion observed in-
High Hg : alloy ratio
Less condensation pressure
Too little Sn in composition
Large particle size of alloy
Under trituration
Moisture contamination
More Contraction
 Lower mercury/alloy ratios
 Higher condensation pressures
 Manipulative procedures that accelerate setting
and consumption of mercury also favor
contraction, including
 Longer trituration
 Smaller particle size
M.A. Marzouk et al. Operative dentistry Modern Theory & Practice

EFFECT OF MOISTURE CONTAMINATION
When 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 3 to 5 days after
placement and may continue for months, reaching
values greater than 400 µm/cm (4%).
This type of expansion is known as delayed
expansion or secondary expansion.

Mechanism of Delayed Expansion
• The effect is caused by the hydrogen produced by electrolytic action involving zinc and
water.
Zn + H2O ZnO + H2
• 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.

Source of Contaminants
Saliva
Blood
skin Secretions (zinc containing alloys is touched with bare hand )
 Other sources
-Moisture contamination of the alloy and mercury during storage
-Moisture contamination of the equipment used for trituration and condensation
-Moisture contamination of the instruments used for trituration and condensation

Complications due to delayed expansion
 Protrusion of the entire restoration out of the cavity
 Increased microleakage around the restoration
 Restoration perforations
 Increased flow and creep
 Pulpal pressure pain

MERCUROSCOPIC EXPANSION
• Originally proposed by Jorgensen (1965)
• Extrusion of the margins is promoted by
electrochemical corrosion ,during which the mercury
from the Sn-Hg phase reacts with remaining
unreacted alloy i.e Ag Sn particles and produce
further expansion during the new reaction
• This mechanism – Mercuroscopic expansion
This expansion of the amalgam against the cavity wall
results in an unsupported wedge at the margin of the
restoration
Jorgensen theory of
mercuroscopic expansion

Relative weakness of this wedge is due to
 High mercury content
 Presence of porosities due to corrosion
 Smaller cavosurface angles
This leads to marginal breakdown under the influence of the forces acting in the oral cavity
This theory of Jorgensen is one of the arguments to prepare a cavosurface angle of 90° as well as
possible

2. STRENGTH
 Strength of dental amalgam has been measured under the compressive stress.
 By this manner compressive strength of a satisfactory amalgam should be atleast 310mpa
(45,000 psi) or more.
 When they are manipulated properly, compressive strength ranges from 380 - 550 mpa
(55,000 - 80,000 psi ) which is similar to enamel & dentine
Amalgam is brittle material i.e. HIGH COMPRESSIVE & LOW TENSILE
STRENGTH.
Tensile strength of amalgam is 1/5th—1/8th of compressive
strength.

Insufficient mercury between particles yields a dry, granular mix. Such a mix results in
a rough, pitted surface that promotes corrosion. Thereby resulting in decreased
strength
Increasing the final mercury content increases the volume fraction of the matrix phases
at the expense of the alloy particles.
A higher mercury content promotes the formation of γ2 phase, even
in a high-copper amalgam. This in turn decreases the strength
of the amalgam
1. Effect of Mercury Content (Marzouk)

2. Effect of Trituration
The effect of trituration depends on
 Type of amalgam alloy
 The trituration time, and
 The speed of the triturator
More the triturition energy, the more continuous are the interphase between amalgam matrix
and alloy particles and more evenly distribution of matrix, thereby providing strength
But in case of overtriturition, excess energy will create cracks in the matrix and interphase
causing lowering of strength
Undertrituration also decrease the strength of both conventional and
high-copper amalgams.

3. Effect of Condensation
Good condensation techniques will express mercury and result in a smaller volume fraction of
matrix phase.
Ideal condensation pressure for amalgam with a small head condenser is 13.3-17.8N
(3– 4 lb)
Higher condensation pressures are required to minimize porosity and express mercury from
lathe-cut amalgams.
On the other hand, spherical amalgams condensed with lighter pressures
produce adequate strength.

LATHE CUT
PARTICLES
Greater
condensation
pressure
SPHERICAL
PARTICLES
Lesser
condensation
pressure

3. Effect of Porosity
• Porosity & voids reduces strength
• Porosity is related to plasticity of mix
Reduced plasticity
More porosity
More area for stress concentration
Propagation of cracks & corrosion
Less strength
In lathe cut alloys
more condensation pressure required for well adaptation to walls
This results in less voids and porosity More strength

Porosity can be due to
 Undertrituration
 Particle shape
 Insertion of too large increments into the cavity
 Delayed insertion after trituration
 Non plastic mass of amalgam

4. Effect of temperature
Amalgam loses 15% of strength when its temperature is elevated from room temperature to
mouth temperature
Looses 50% of room temperature strength when temperature is elevated to 60°C e.g: hot coffee
or soup

3. CREEP
Creep is defined as time dependent plastic deformation
Amalgam Creep has been defined as plastic deformation due to slow metallurgic phase
transformations that involve diffusion-controlled reactions and produce volume expansion
(Sturdevant )
The associated expansion makes the amalgam protrude from the tooth preparation.

 According ADA specification creep value – less than 2%
Low copper alloy - 0.8 to 8%
High copper alloy - 0.4 to 0.1%
 When an amalgam creeps, it is the γ1 phase that deforms plastically. That is higher creep
rates for low copper amalgam with higher γ1 volume fractions and vice versa. Also, the
presence of the γ2 phase increases the creep rate.
 In addition to the absence of the γ2 phase, the very low creep rates in single-composition
high-copper amalgams may be associated with η′ phase rods, which act as barriers to
deformation of the γ1 phase.

 The creep of dental amalgam is a continued deformation ,that occurs under constant stress
(static creep) or under intermittent masticatory stresses (dynamic creep )
 Responsible for the marginal break down
 Higher the creep, greater is the degree of marginal deterioration

Increased creep Decreased creep
Effect of microstructure
and composition
• Large gamma 1 volume
fractions
• Presence of gamma2
• Excess mercury in the
amalgam
• Larger gamma 1 grains
• Complete elimination of
gamma 2
• Presence of eta crystals
Effect of manipulative
variables
• Under or over trituration
• Increased mercury to alloy
ratio
• Increased condensation
pressure
• All manipulative factors
that affect maximize the
strength also minimizes
the creep
FACTORS AFFECTING CREEP

5. TARNISH AND CORROSION
TARNISH
It is the surface discoloration of a metal or a slight loss or alteration of the surface finish or luster due to
formation of thin layer of oxides, chloride or other chemicals
CORROSION
It is a process in which deterioration of a metal is caused by the reaction of metal with its environment
Amalgam restorations often tarnish and corrode in the oral environment.
The degree of tarnish depends on:
(I) the oral environment
(II) the type of alloy used

 Tarnish of amalgam restorations is due to the formation of black silver sulfide
 Corrosion products – oxides and chlorides of tin
Corrosion products of Cu is also found in the high copper amalgam
Corrosion results in the formation of tin oxychloride from the tin in the gamma 2 phase and
also liberates mercury
Sn 7-8 Hg + H2O + Cl Sn 4 (OH )6 Cl2 + Hg
The liberated mercury reacts with unreacted gamma can produce additional gamma 1 and
gamma 2. the presence of gamma 2 phase is responsible for tarnish and corrosion
High copper amalgam is more resistant to tarnish and corrosion due
to the absence of gamma 2 phase

Types of corrosion
1. Chemical corrosion or Dry corrosion
2. Electrochemical or Wet corrosion
a. Galvanic corrosion
b. Concentration cell corrosion
c. Stress corrosion
Chemical Corrosion
It is the direct combination of metallic and nonmetallic elements to yield a chemical compound
through oxidation reactions.
E.g :- discoloration of silver by sulfur, where silver sulfide forms by chemical corrosion.
Electrochemical Corrosion

Galvanic Corrosion
When the two dissimilar metals are brought in contact ,there
is sudden short circuit through two alloys ,which may result
in the patient experiencing a sharp pain.
E.g. An amalgam restoration on the occlusal surface of
lower molar opposing a Gold inlay in an upper tooth
Concentration cell Corrosion
Accumulations of food debris in the inter-proximal
Areas produces an electrolyte which is different
from the electrolyte produced by normal saliva
at the occlusal surface.
Electrochemical corrosion of the alloy surface
underneath the layer of food debris will
take place in this situation.

A similar type of attack may occur from differences in the oxygen concentration between parts
of the same restoration, with the greatest attack at the areas containing the least oxygen (the
anode).
Irregularities—such as pits, scratches, and cracks—in restoration surfaces are important
examples of this phenomenon. The region at the bottom of such a defect is oxygen-deprived and
becomes the anode and thereby undergoes corrosion
A pit on a dental alloy as a corrosion cell.
The region at the bottom of the pit is an anode, and the surface around
the rim of the pit is the cathode

Examples of sites susceptible to electrochemical and chemical corrosion on amalgams:
galvanic corrosion (a) at interproximal contact with metallic restoration such as gold casti ng alloy; local galvanic
(b) corrosion on occlusal surface at grain boundaries between different metallic phases; crevice corrosion (c) at
margin due to lower pH and oxygen concentration of saliva; crevice corrosion (d) under retained interproximal
plaque due to lower local pH; crevice corrosion (e) within unpolished scratches or detailed secondary anatomy;
chemical corrosion (f) of occlusal surface with sulfide ions in saliva, producing surface tarnish.

Stress Corrosion
Small surface irregularities, such as notches or pits, act as sites of stress concentrations.
More deformed areas act as anode and undergo electrochemical corrosion
Corrosion can lead to:
 Reduced strength i.e.. a corroded amalgam restoration is predisposed to fracture;
 Marginal degradation (“ditching”) which is a stress/corrosion type of degradation
 Dimensional changes i.e.. a corroding amalgam restoration increases in size
 Increased internal porosities and surface roughness
 Discoloration
 Galvanic effects, rarely including a metallic taste;
 Biological effects, including allergy to corrosion products and possible
toxic reaction in extreme situations.

6. THERMAL PROPERTIES
Thermal diffusivity
 Dental amalgam is a conductor of heat
 Consequently, large amalgam restorations are usually lined with a thermal insulating
cements to protect the pulp from the temperature changes in the mouth caused by hot and
cold food and liquids
Thermal expansion
 The coefficient of thermal expansion is about 25 ppm which is almost double of the tooth
-results in microleakage
 Prevented by application of cavity varnish

MANIPULATION OF AMALGAM
Selection of
alloy
Mercury Alloy
ratio
Proportioning Condensation
Mulling
trituration Carving
Burnishing
Finishing and
polishing

SELECTION OF ALLOY
1. Particle size:
Micro cut or smaller particles are used because they are:
-easy to condense
-greater strength
-easy to carve
-smooth finish
-less marginal failure
-faster setting time
-good adaptation
Larger particles lead to porous fillings and decreased strength.

2. Shape of alloy:
Spherical alloys are preferred because it:
-gives better finish
-good marginal adaptation
-good strength
-requires less condensation forces
-carving is easier
-requires less mercury (42% conc of Hg ) due to low surface area compared to lathe cut which
requires 50% or more Hg.
Lathe cut particles gives a rough surface and has poor corrosion resistance.

3. Unicompositional alloys are preferred compared to admixed
• High early strength(1st and 7th hr)
• Consumes less mercury and hardens faster
• Requires less condensation forces
• Easier to polish
However admixed has the advantages of less dimensional changes and longer working time.
4. High Cu is preferred over low Cu
• Less creep due to absence of gamma2 phase
• Better corossion resistance.
• Cheaper

MERCURY ALLOY RATIO
 Sufficient mercury must be present in the original mix to provide a coherent and plastic
mass after trituration, but it must be low enough that the mercury content of the
restoration is at an acceptable level without the need to remove an appreciable amount of
mercury during condensation.
 The mercury content of the lathe-cut alloy is about 50% by weight and that for spherical
alloys is 42% by weight.

For conventional mercury added systems 2 techniques were used for mercury reduction:
 By squeezing or wringing the mixed amalgam in a squeeze cloth before insertion into the
prepared cavity.
 Mercury rich amalgam was worked to the top during condensation
of each increment, and this excess was removed as the amalgam mix
was built up to form a restoration

The present day alloys are designated for manipulation with reduced mercury / alloy ratios just
enough to get a coherent plastic mass.
This method is known as the minimal mercury technique or the Eames technique(1959)
It is a technique for mixing dental amalgam in 1:1 ratio of mercury and alloy to
minimize free mercury in the unset mass
Certain manufacturers use ratios less than 1:1 with the percentage of mercury varying from
43% to 54%

PROPORTIONING
There are different ways of proportioning:
 Weighing and triturating:this is ideal but time consuming
 Volume dispensing(Graviometry):Widely used-however it is difficult to dispense any
powder accurately by volume
 Pre-weighed capsules of alloy powder and Hg seperated
by a membrane: Disposable capsules containing pre-
proportioned amounts of mercury and alloy are widely used.
Just before the mix is triturated the membrane is ruptured
by compression of the capsule.

Preproportioned capsules
The older types of preproportioned capsules require activation before trituration to allow the
mercury to enter the compartment with the alloy.
Some alloys are now available in self-activating capsules, which bring the alloy and
mercury together automatically during the first few oscillations of the triturator.
Advantages
 More convenient
 Eliminates the chance of mercury spills during proportioning
 Result in a reliable mercury/alloy ratio
Disadvantages
 Expensive
 These capsules do not provide an opportunity to make minor
adjustments in the mercury/alloy ratio to accommodate personal
preferences

TRITURATION
trituration is the process of mixing alloy particles with mercury
Objectives of trituration (Marzouk)
1. To achieve a workable mass of amalgam within a minimum time, leaving sufficient time
for its insertion into a cavity preparation and carving the tooth anatomy.
2. To remove oxides from the powder particle surface, facilitating direct contact between the
particles and the mercury.
3. To pulverize pellets into particles that can be easily attacked by the
mercury.
4. To reduce particle size so as to increase the surface area of the alloy
particles per unit volume , leading to a faster and more complete
amalgamation.

5. To dissolve the particles or part of the particles of the powder in mercury , which is a
prerequisite for the formation of the matrix crystals.
6. To keep the gamma1 matrix crystals as minimal as possible yet evenly distributed
throughout the mass for proper binding and consistent adequate strength

Hand mixing by the Mortar and Pestle
 In this a glass mortar and a pestle is used
 The time of mixing is 30-40sec with a force of 800-900 gm being applied.
 The mixed mass should be homogeneous,smooth,should not stick to walls of mortar and
pestle and should form a lump.
 Extra mercury can be removed by squeezing the mass with a dental floss.
Factors affecting it include:
• pressure exerted on the mix,
• no. of revolutions per minute,
• inclination of the pestle relative to the mortar
• surface roughness of both mortar and pestle

Mechanical trituration
A capsule serves as a mortar. A cylindrical metal or plastic piston of smaller diameter than the
capsule is inserted into the capsule which serves as the pestle.
There are three basic movements of mechanical trituritors:
1.The mixing arm carrying a capsule moves back and forth in a straight line.
2.The mixing arm travels back and forth in a figure of 8 motion.
3.The mixing arm travels in centrifugal fashion.
The main mixing mechanism of a mechanical triturator is a reciprocating arm that holds the
capsule under a protective hood.
The purpose of the hood is to confine mercury that might escape into the
room or to prevent a capsule from being accidentally ejected from the
triturator during trituration. (Philips)

Types of capsules
A. Reusable capsules with pestle.
B. Preproportioned capsule with pestle.
C. Preproportioned capsule without pestle.
• A reusable capsule should be clean and free of previously mixed, hardened alloy.
• At the end of each trituration procedure, one should quickly remove the pestle from the
capsule, replace the lid, reinsert the capsule in the triturator, turn it on for a second or two,
and then remove the amalgam.
• This mulling process generally causes the mix to cohere so that it can be
readily removed from the capsule with minimal residue in the capsule.
• It minimizes the need of scraping out partially hardened alloy, which
usually produces scratches in the capsule.

Spherical alloys often do not need a pestle
Pestels may be plastic or metal.
The diameter and length of the pestle should be considerably less than the capsule.
If the pestel is too large,the mix is not homogeneous.
a. Satisfactory size relationship between capsule
and pestle
b. Unsatisfactory pestle size
a b

A commonly used older model is a single-speed
device with an automatic timer for controlling the
length of the mixing time.
Later models have multiple speed settings.
A modern triturator is often microprocessor
controlled and contains preset trituration programs
for a number of materials. It can also be programmed
by the operator to include other materials

Mechanical Amalgamators are available in the following speeds:-
Low speed : 3200-3400 cpm
Medium speed : 3700-3800 cpm
High speed : 4000-4400 cpm
Time of trituration on amalgamator ranges from 3-30 seconds.
Variations in 2-3 seconds can also produce a under or overtriturited mass.
For a given alloy and mercury, increased trituration time and /or speed shortens the working
and setting times.

CONSISTENCY OF MIX
Normal mix:
• Has maximum strength.
• Mix may be warm (not hot),when it is removed from the capsule.
• The smooth carved surface will retain its luster longer after polishing
Under trituration:
• Rough & grainy mix, difficult to manipulate
• Rough surface after carving, less resistance to tarnish & corrosion
• Compressive & tensile strength reduced
• Mix will harden too rapidly & excess mercury will be left in the
restoration

Over trituration:
• Mix will be soupy, too plastic to manipulate
• Working time decreased
• Creep is increased
• Increased contraction of amalgam
• Compressive & tensile strength increased for lathe cut alloys, reduced for spherical

MULLING
Mulling is actually a continuation of trituration.
The step can still be used following mechanical trituration to improve the homogeneity of the
mass and to assure a consistent mix.
It can be accomplished in two ways:
1. The mix is enveloped in a dry piece of rubber dam and
vigorously rubbed between the first finger and thumb;
or the thumb of one hand and palm of another hand.
The process should not exceed 2 to 5 seconds.
2. After trituration the pestle can be removed from the
capsule, and the mix triturated in the pestle-free capsule
for additional 2 to 3 seconds. This will also assure cleaning
of the capsule walls of remnants of the amalgam mix,
thereby delivering the mix in one single, coherent, and
consistent mass.

CONDENSATION
Condensation is used to compact the alloy into the prepared cavity so that the greatest possible
density is attained with sufficient mercury present to ensure complete continuity of the matrix
phase (Ag2Hg3) between the remaining alloy particles.
Objectives of condensation:
• To remove any excess mercury from each increment as it is worked to the top by the
condensing procedure.
• Adapt the amalgam to the margins, walls and line angles of the cavity
• Minimize voids
• Acquire maximum physical properties

The longer the time that elapses between mixing and condensation, the weaker the amalgam will be
Effect of elapsed time between trituration and
condensation on the strength of the hardened
amalgam.
The greater the elapsed time, the lower is the
strength
Condensation should be as rapid as possible
and a fresh mix of amalgam should be made if
condensation takes longer than 3-4 minutes.

Condensation Procedure (Hand Condensation )
 The condenser tip, or face, is forced into the amalgam mass under hand pressure.
 Condensation is usually started at the center, and then the condenser point is stepped
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.
 The procedure of adding an increment, condensing it, adding another
increment, and so forth is continued until the cavity is overfilled.
 Any mercury-rich material at the surface of the last increment will be
removed when the filling is carved.

 Small increments of amalgam should be used throughout the condensation procedure to
reduce void formation and to obtain maximum adaptation to the cavity.
 After completely filling the cavity, an overdried amalgam mix(made by sqeezing off mercury
in a cloth) is condensed heavily over the restoration using the largest condensers possible for
the involved tooth. This mix is called the blotting mix.
 This serves to blot excess mercury from the critical marginal and surface area of the
restoration and to adapt amalgam more intimately to the cavosurface anatomy.The mix is
excavated and discarded after it achieves these two functions

1.
Amalgam
carried
into the
prepared
cavity
2.
Amalgam
condensed
4.
Final
condensation
3.
Blotting mix
placed on the
restoration

The condensation of spherical alloy amalgam differs from the non spherical ones in two ways:
 It is necessary to use increments large enough to fill the entire cavity or a large part of the
cavity.In this situation the condenser acts as a moving roof against the amalgam confined
within the cavity with the condenser moving towards the floor.
 It is necessary to use the largest condenser that will fit the cavity or part of it preventing the
lateral escape of the spherical particles during condensation. (Marzouk)

Mechanical Condensation:
 Condensation of the amalgam can be performed by an automatic device.
 Useful for irregular shaped alloys when high force is used
 Some provide an impact type of force, whereas others use rapid vibration.
Advantages are:
a) less energy is needed than for hand condensation.
b) the operation may be less fatiguing to the dentist.
Ultrasonic condensers are not recommended since they increase the mercury vapour level to
above the safety level

Condensation Pressure
• The area of the condenser tip and the force exerted on it by the operator govern the
condensation pressure (force per unit area).
• The smaller the condenser, the greater is the pressure exerted on the amalgam.
• If the condenser point is too large, the operator cannot generate sufficient pressure to condense
the amalgam adequately and force it into retentive areas.
A study of 30 practitioners showed that condensation forces average between 13.3 and 17.8 N (3
to 4 lb) employed.
To ensure maximum density and adaptation to the cavity walls, the condensation force should be
as great as the alloy will allow, and consistent with patient comfort.

Many of the spherical alloys have little “body” and offer only minimal resistance to the
condensation force. Therefore, the strength properties of spherical amalgam alloys tend to be less
sensitive to condensation pressure.
The potential disadvantages of a spherical alloy are the tendency for overhangs in proximal areas
and weak proximal contacts.
The shape of the condenser tips should conform to the area under condensation.
For example, a round condenser tip is ineffective adjacent to a corner or angle of a prepared
cavity; a triangular or square tip is indicated in such an area.

PRECARVE BURNISHING
 After condensing with amalgam condensers, the amalgam maybe further condensed and
shaping of the occlusal anatomy begun with a large burnisher such as an ovoid burnisher.
 This is done with use of heavy strokes, made in mesiodistal and faciolingual directions.
 This produces denser amalgam at the margins of the restorations.
 Mainly useful for high copper amalgams.

The objectives of burnishing are: (Marzouk)
1. It is a continuation of condensation, in that it will further reduce the size and number of
voids on the critical surface and marginal areas of the amalgam.
2. It brings any excess mercury to the surface, to be discarded during carving.
3. It will adapt the amalgam further to cavosurface anatomy.
4. It conditions the surface amalgam to the carving step.

CARVING
After the amalgam has been condensed into the prepared cavity, it is carved to reproduce the
proper tooth anatomy.
The objective of carving is to simulate the anatomy rather than to reproduce extremely fine
details (Philips)
Objectives of Carving (Marzouk)
1. To produce a restoration with no underhangs,ie.,all marginal details of the cavity
preparation are completely covered with amalgam.
2. To produce a restoration with the proper physiological contours.
3. To produce a restoration with minimal flash
(Flash is the thin portion of amalgam extending beyond the margins)

4. To produce a restoration with functional, non interfering occlusal anatomy.
5. To produce a restoration with adequate, compatible marginal ridges.
6. To produce a restoration with the proper size, location, extent and interrelationship of
contact areas.
7. To produce a restoration with physiological compatible embrasures.
8. To produce a restoration not interfering in any way with the integrith of the periodontium,
enhancing its health and amenable for plaque control.

Deep occlusal grooves should not be carved into the restoration because these may thin the
amalgam at the margins, invite chipping and weaken the restoration.
Undercarving leaves thin portions of amalgam subject to fracture on the tooth surface. Such
margins give the appearance that the amalgam has extended beyond the preparation.
The mesial and distal fossae should be carved slightly deeper than the proximal marginal
ridges.
A scraping or ringing sound should be heard when it is carved(amalgam cry).
After carving, the outline of the amalgam margin should reflect the contour and location of
the prepared cavosurface margin, revealing a regular(not ragged outline) with gentle curves.
An amalgam restoration that is more than minimally overcarved
(ie.,a submarginal defect > 0.2mm) should be replaced.

POSTCARVE BURNISHING
 After carving is completed, the surface of the restoration should be smoothed. This may be
accomplished by judiciously burnishing the surface and margins of the restoration.
 Burnishing of the occlusal anatomy can be accomplished with a ball burnisher
 Clinical data on performance of restorations support the desirability of burnishing the fast
setting, high-copper systems.
 Burnishing slow-setting alloys can damage the margins of the restoration.
 Undue pressure should not be exerted in burnishing, and heat generation
should be avoided.
Temperatures above 60 °C (140 °F) cause a significant release of mercury

FINISHING AND POLISHING
This step is necessary to
1. Complete the carving
2. Refine the anatomy, contours and marginal integrity.
3. Enhance the surface texture of the restoration.
4. To remove superficial scratches, pits & irregularities which in turn minimizes corrosion &
prevents adherence of plaque.
The final finishing of the restoration should be delayed until the
amalgam develops sufficient strength to resist the pressure of
polishing.
Generally, the recommendation is to wait for at least 24 h or until
the next
appointment

The area may be further smoothened using light pressure with a suitably shaped round
finishing bur. This bur removes the scratches from the green or white stone.
Polishing is initiated with coarse abrasive rubber point at slow speed and an air water spray.
Diminishing grades (increased fineness) of abrasives are used for polishing.
Final polishing may be accomplished by using a rubber cup with a flour of pumice or tin oxide
followed by a high lustre agent like precipitated chalk

(A) When necessary, a
carborundum or fine-grit
alumina stone is used to
develop continuity of surface
from the tooth to the
restoration;
(B) The restoration is surfaced
with a round finishing bur
(D) Polishing is initiated with a
coarse rubber abrasive point
at
low speed
(F) a high polish is obtained with
medium- grit and fine-grit
abrasive points and

After carving After final
finishing

INDICATIONS AND CONTRAINDICATIONS
INDICATIONS:
 Moderate to large class I & class II restorations(specially those with heavy occlusion,that
cannot be isolated well or which extends into the root surface)
 Class V restorations those that are not esthetically critical.
 Cuspal restorations (usually amalgam pins)
 Class III in unesthetic areas (e.g : distal aspect of canine) especially in extensive preparation
with minimal facial involvement
 Class V lesions in non esthetic areas where access is limited and moisture control is difficult
and for areas that are significantly deep gingivally

 Foundations(including badly broken down teeth that requires increased retention and
resistance form in anticipation of the subsequent placement of a crown)
 As a die material
 In teeth that act as abutment for removable appliances
 In combination with composite resins for cavities in posterior teeth (Resin veneer over
Amalgam)
 Restorations that have heavy occlusal contacts
 Temporary caries control restorations.

CONTRAINDICATIONS:
 Anterior teeth where esthetic is of prime concern
 Esthetically prominent areas of posterior teeth
 Small to moderate class I & class II restorations that can be well isolated (a composite may be
preferred since tooth preparation will be less)
 Small class VI restorations.
 Allergy to any component of amalgam
 Patients with proven amalgam induced lichenoid reactions
 Treatment of incipient or early primary fissure caries
 Remaining tooth structure which requires extensive tooth preparation
to accommodate amalgam

ADVANTAGES AND DISADVANTAGES
ADVANTAGES:
• Ease of handling
• Economical
• High compressive strength
• Excellent wear resistance
• Durability : Favourable long term clinical results
• Restoration is completed within one sitting without requiring much chairside time
• Not technique sensitive

• Optimal dimensional changes: ADA specification no. 1 permits + 0.2% expansion/contraction
during setting.(amalgam is within that range)
• Self Sealing ability - Sealing improves with age by formation of corrosion products at tooth
amalgam interface
• Modern alloys used in amalgam undergo less dimensional changes when compared to GIC
and Composite
• Recurrence of caries around amalgam restoration is low. This is proven
clinically but poorly understood

DISADVANTAGES:
 Non esthetic
 Less conservation of tooth structure. Amalgam requires adequate depth and width during
cavity preparation for proper retention
 Weakens tooth structure
 Technique sensitive
 More difficult tooth preparation
 Does not bond to the tooth structure. Lack of chemical or mechanical adhesion to the tooth
structure
 Amalgam is a good thermal conductor-thus base is required.
 Less tensile strength
 Galvanic currents produced in certain cases
 Undergoes tarnish and corrosion

 Delayed expansion. Restoration may protrude from the tooth structure
 Occurrence of secondary caries.
 Postoperative sensitivity. Patients are usually asked to avoid extremely hot or cold
food for 24hrs of amalgam placement
 May cause discoloration of the tooth structure (Amalgam blue)
 Amalgam tattoo. Mostly due to amalgam scraps left in the open surgical or
extraction wounds or into the gingival tissue
 Not biocompatible. May cause allergic reactions in certain patients.
 Cause environmental hazards

ALLERGY/
HYPERSENSITIVITY
MERCURY
TOXICITY
Mercury may cause injury to
biological tissues in the form
cell destruction, organ
damage and even death
1. Immediate
Hypersensitivity
reactions
2. Delayed Hypersensitivity
reactions
Syed Kashif Abrar SKA et al. Dental amalgam : A controversial filling material.
Acta Scientific Dental Sciences, 2019

IMMEDIATE HYPERSENSITIVITY REACTION
- Skin lesion more common than oral lesions
- Urticarial rash on the face and limbs followed by dermatitis.
OTHER SYMPTOMS:
• Itching
• Rashes
• Sneezing
• Difficulty in breathing
• Swelling

DELAYED HYPERSENSITVITY REACTIONS
• Contact Dermatitis or Coomb’s Type IV hypersensitivity
• Erosive lesion on the tongue or buccal mucosa adjacent to amalgam restorations
• Causes eczematous reaction on skin and mucosa
• A long term response in the form of erosive lichen planus or lichenoid reaction

MERCURY TOXICITY
TOXIC EFFECTS OF MERCURY DEPENDS ON
 Amount of exposure
 Length of exposure
 Length of mercury accumulation in body
 Amount of mercury accumulated
 Overall health of patient (detoxification)

1. Elemental
Mercury vapor (Hg),
a stable monoatomic gas
Dental amalgams
(inhaled and absorbed into
lungs)
2. Inorganic Divalent mercury (Hg2+)
2 forms : Mercuric and Mercurous
Least Toxic
(inhaled into lungs)
3. Organic
Methyl mercury (CH3Hg+)
Ethyl mercury (CH3CH3Hg+)
Most Toxic
Fish, sea mammals
(absorbed into the gut)
CHEMICAL FORMS OF MERCURY

CONCENTRATIONS OF MERCURY
The Occupational Safety and Health Administration (OSHA) has set a Threshold
Limit Value of 0.05 mg/m3 as the maximum amount of mercury vapour allowed in the
workplace
It has been estimated that a patient with 9 amalgam occlusal surfaces will inhale daily only
about 1% of the amount the Occupational Safety and Health Administration
(OSHA) allows to be inhaled in the workplace.
Lowest dose of mercury that elicits a toxic reaction – 3 to 7 µg/kg body weight
Paresthesia – 500 µg/kg body weight
Ataxia – 1000 µg/kg body weight
Joint pain – 2000 µg/kg body weight
Hearing loss and death – 4000 µg/kg body weight

AMOUNT OF MERCURY RELEASED DURING MANIPULATION OF AMALGAM

1.PRIOR TO USE:
 During storage of raw materials of dental amalgam
2.DURING USE:
 During trituration, insertion, condensation
3.POST USAGE:
 Amalgam scrap
MERCURY EXPOSURE IN DENTAL OFFICE

4.POST RESTORATION:
Finishing and polishing, removal of old restoration
5. MERCURY SPILLS:
Anytime during usage
JAIN RIMJHIM ET AL. MERCURY TOXICITY AND ITS MANAGEMENT.
INT.RES J. PHARM 2016;4(8):38-41.

MERCURY HAZARDS IN DENTAL OFFICE

RESIDUAL MERCURY CONTENT
Residual mercury refers to the amount of mercury present in the fully reacted alloy.
Residual mercury levels are highest on the surface and margins of the restoration
The ideal range of residual mercury is from 44-48%
This concentration should not exceed 55% as this leads to
• Decrease in strength
• Decreased resistance to tarnish and corrosion
• Increased creep as the mercury converts gamma to gamma1
and gamma 2 phases
• Marginal breakdown
• Surface roughness

Factors that lead to increased residual mercury levels :
 Alloys that contain high mercury- alloy ratio (lathe cut alloys)
 Poor condensation
 Delay between trituration and condensation
Effect of residual mercury content on Creep
(Rupp -Paffenbarger-Patel: Effect of mercury content on creep in amalgams. JADA;2003)
According to a study, silver-tin , spherical-particle alloys with low copper content had relatively low
creep values when packed quickly. Creep and residual mercury content, however, increased when
compaction was delayed.
The effect was comparatively less with the amalgam made from Non-Zinc alloys.

Amalgams made with copper-rich alloys, also had relatively low creep values for the early
compacted specimens
In clinical practice, small amounts of amalgam should be mixed and used immediately after
trituration. If the delay between trituration and compaction is longer than three minutes, additional
mixes are required.
Effect on compressive strength
(SWARTZ AND RALPH W. PHILLIPS. Residual mercury content of amalgam restorations and its influence on
compressive strength. Journal of Dental Research)
 compressive strength of amalgam increased from 53,000 psi to approx 59,000 psi when the
residual mercury fell from 48 to 35 per cent. However, they found no correlation between
strength and residual mercury within limits of 45-50 per cent.
 The use of extremely high condensation pressures (256,000 psi) reduced the residual mercury
to 28.3 per cent and the compressive strength rose to 73,000 psi

Although the average residual mercury content of the entire restoration may be less than 55%
it is quite common to find certain areas which may exceed that figure.
Certainly those areas of high mercury, and hence low strength, would be more vulnerable to
fracture if subjected to stress.
Care must be exerted in adhering to the recommended ratio and using adequate condensation
pressure(13.3 and 17.8 N) and technic to minimize residual mercury and possible fracture.

CARVERS USED IN AMALGAM
• Discoid and Cleoid: large and small
• Hollenback carver
• Proximal carver (CVWI 8)
Discoid and Cleoid
• Initially, Discoid and cleoid (discoid side) is used to remove excess amalgam from the occlusal
surface. Use Discoid/cleoid (cleoid side) to develop a continuous (smooth) surface from the
enamel to the restoration
• Occlusal carving is done with "pull stroke", however, the "push stroke" can also be suitable in
developing occlusal anatomy (grooves)
• The first decision is to place the central groove. The central groove is found by continuing the
central grooves of the teeth mesial and distal to the restoration. This is carved with the discoid
end of a discoid-cleoid carving instrument

• The next steps are to place the marginal grooves and the buccal and lingual
grooves. These grooves are placed again with the discoid end of the discoid-
cleoid carver in its proper position. Marginal fossae are formed by these
grooves
• Using the cleoid end of the carver, place the tip in the central groove, orient
the blade at approximately 45 degrees to the occlusal surface, and develop
the shape of the occlusal surface
• The cleoid is placed in the proximal with the tip forming the marginal
groove. The instrument is moved distally, forming a raised, rounded
marginal ridge.
• The occlusal table can be refined and secondary anatomy applied if desired,
using the cleoid or the half-Hollenback.

• Using a half-Hollenback carving instrument, start to define and
shape these grooves. Continue to carve the surface until all flash is
removed from the cavo-surface margin.
• Place the Hollenback carver obliquely across the cavity margins
with its tip resting against the adjacent tooth (matrix band) and
its blade resting on the enamel adjacent to the proximal cavity
margins. The proximal contour of the adjacent tooth is used as a
guide to develop the restoration’s proximal contour
Proximal carver (CVWI 8) is used mainly in
difficult access areas

Other carvers include:
WARDS CARVER : it is used for carving occlusal surfaces and for carving proximal
surfaces in class II restoration
FRAHMS CARVER : (diamond shaped)used for carving occlusal surfaces

FUNCTIONS OF BURNISHING
Precarve Burnishing
• Form of condensation that ensures dense amalgam at the margins
• It is used to remove excess mercury
• Done by using heavy strokes with large burnishers moving from centre of restoration
outwards beyond the margins
Postcarve Burnishing
• This is done to adapt the material to the walls
• Promote sealing of amalgam at margins
• Provide smoothness and produce a shiny appearance
• Accomplished by light rubbing of carved surface with small ball burnishers

DIMENSIONAL CHANGES IN AMALGAM
Stage 1 – initial contraction results from absorption of
mercury into the interparticular spaces of the alloy
powder
Stage 2 –expansion due to growth of crystals. This
expansion reaches a plateau phase with cessation of
crystal formation
Stage 3 – limited delayed contraction resulting from
absorption of unreacted mercury
Net result with modern amalgam is SMALL AMOUNT OF CONTRACTION of about 0.3 % by
volume

Factors affecting dimensional changes of amalgam:
1. Constituents : greater the gamma phase, greater will be the expansion. Greater traces of tin produces less expansion
2. Mercury content – More mercury in the amalgam produces more prolonged stage of amalgamation. Hence, greater the
mercury content, greater is expansion. Therefore, lathe cut alloys exhbit more expansion than spherical alloys
3. Particle size – greater particle size result in marked contraction.
4. Triturition – more the triturition energy, greater distribution of matrix over the mix, preventing outward growth of
crystals. Furthermore, faster the amalgamation proceeds, so plateau phase occur before completely filling the cavity. This
results in no expansion but limited contraction
5. Condensation – More the energy used for condensing the amalgam, closer the original particles of the powder are brought
together. Also, increased condensation squeezes mercury out of the mix. This leads to less formation of matrix crystals,
therby contraction
6. Particle shape – more regular the particles, faster and more effectively mercury can wet the alloy particles. This makes
amalgamation process faster in all stages. Therefore, maximum expansion occurs before filling the cavity with no apparent
expansion.
7. Moisture contamination

MERCURY POISONING
ACUTE MERCURY
POISONING
• Sudden exposure of high
levels of mercury especially
from elemental mercury or
organic mercury.
• It results in immediate and
severe symptoms requiring
urgent medical attention.
CHRONIC MERCURY
POISONING
• HYDRARGYRISM
• Mercury exposure for a prolonged
period
• Workers may get poisoned due to
vapors or dust.
• The lowest level of total blood
mercury at which the earliest
nonspecific symptoms occur is 35
ng/ml.

Inhalation of mercury vapor causes:
 Chemical pneumonia
 Pulmonary edema
 Gingivostomatits
 Increased salivation
 CNS symptoms like:
• Ataxia
• Restriction of field of vision
• Delirium
• Polyneuropathy
Bernhoft RA. Mercury toxicity and treatment: a review of the literature.
Journal of environmental and public health. 2012

Ingestion of mercury causes:
 Acrid metallic taste in mouth.
 Feeling of constriction or choking of throat.
 Hoarseness of voice.
 Difficulty in breathing
 Hot burning pain in mouth, stomach and abdomen.
 Stools are blood stained , urine is suppressed and scanty, contain blood and albumin is
accompanied by necrosis of renal tubules and damage to the glomeruli.
 Pulse is quick small and irregular
 Thrombocytopenia and bone marrow depression
Houston MC. Role of mercury toxicity in hypertension, cardiovascular disease, and
stroke.
The journal of clinical hypertension. 2011 aug 1;13(8):621-7

Other conditions associated with mercury poisoning
 MINAMATA DISEASE
 PINK DISEASE
 HUNTER -RUSSELL SYNDROME
 ERETHISM

MERCURY MANAGEMENT
ADA Council On Scientific Affairs. JADA, Vol. 134, Issue.11November 2003:1498-99.
A Review of the ADA Mercury Hygiene Recommendations.Dentistry Today :January 2003.
ADA recommendations No. 109
1. Train all personnel involved in the handling of mercury or dental amalgam regarding the
potential hazard of mercury vapor and the necessity of observing good hygiene practices.
2. Work in well-ventilated spaces, with fresh air exchanges and outside exhaust. If the spaces are
air-conditioned, air-conditioning filters should be replaced periodically.
3. Periodically check the dental operatory atmosphere for mercury vapour

4. Make personnel aware of the potential sources of mercury vapor in the operatory – that is,
spills; open storage of used capsules; trituration of amalgam; placement, polishing or removal
of amalgam; heating of amalgam-contaminated instruments; leaky capsules; and leaky bulk
amalgam dispensers. Personnel also should be knowledgeable about the proper handling of
amalgam waste and be aware of environmental issues. Some state dental societies have
published waste management recommendations applicable to their state.
5. Use proper work area design to facilitate spill contamination and cleanup. Flooring covering
should be nonabsorbent, seamless and easy to clean
6. Use only precapsulated alloys; discontinue the use of bulk mercury and bulk alloy

7. If possible, recap single-use capsules from precapsulated alloy after use. Properly dispose of
them according to applicable waste disposal laws
8. Use high-volume evacuation when finishing or removing amalgam. Evacuation systems should
have traps or filters
9. Salvage and store all scrap amalgam (that is, noncontact amalgam remaining after a
procedure) in a tightly closed container, either dry or under radiographic fixer solution

10. Use care in handling amalgam. Avoid skin contact with mercury or freshly mixed amalgam
11. Use an amalgamator with a completely enclosed arm
12. Where feasible, recycle amalgam scrap and waste amalgam. Otherwise, dispose of amalgam
scrap and waste amalgam in accordance with applicable laws
13. Dispose of mercury-contaminated items in sealed bags according to applicable regulations
14. Clean up spilled mercury properly using trap bottles, tapes or freshly mixed amalgam to pick up
droplets, or use commercial cleanup kits. Do not use a household vacuum cleaner.
15. Remove professional clothing before leaving the workplace.

MANAGEMENT OF MERCURY SPILLS
 Never use a vacuum cleaner of any type to clean up the mercury.
 Never use household cleaning products to clean up the spill,
particularly those containing ammonia or chlorine.
 Never pour mercury, or allow it to go, down the drain.
 Never use a broom or a paintbrush to clean up the mercury.
 Never allow people whose shoes may be contaminated with mercury to walk around or leave
the spill area until the mercury-contaminated items have been removed.

MANAGEMENT OF SMALL MERCURY SPILLS
• A spill is considered small if there are less than 10 grams of
mercury present (a pool no larger than the size of a quarter).
• Small spills can be cleaned safely using commercially available
mercury cleanup kits.
ADA Council On Scientific Affairs. JADA, Vol. 134, Issue.11November 2003:1498-99.

MANAGEMENT OF LARGE MERCURY SPILLS
 A mercury spill is considered large if there are more than 10 g of
mercury present (a pool larger than the size of a quarter).
 Cleanup of large mercury spills requires the use of an
experienced environmental contractor who specializes in toxic
spill cleanup.

MANAGEMENT OF MERCURY VAPOUR RELEASE IN
DENTAL OFFICE
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
• High vibrations during mixing can create aerosols of liquid droplets and these vapors may
extend up to 6-12 ft from the amalgamator. So, to minimize the risk, 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

Designing of Office
Office should be designed so as to reduce mercury contamination.
Following points are to be kept in mind while designing:
• Proper ventilation of the dental office
• Avoid carpeting/floor coverings in dental office as there is no way of removing mercury
from the carpet.
Scrap amalgam on carpeted treatment-room floor (bur
shown for scale). Over time, scrap and waste amalgam
becomes imbedded in the carpet and breaks into smaller
and smaller particles. Carpet scuffed by foot traffic or
wheels on an operatory stool releases mercury vapor into
the breathing zone of dental personnel. Vacuuming
brings mercury vapor into the breathing zone of cleaning
staff

Insertion and Condensation of Amalgam
• Use rubberdam to isolate the tooth.
• Use high volume evacuation system to control the mercury
level in air.
Polishing of Amalgam
The mercury is tightly bound when amalgam is set. Polishing should be done with coolant to
decrease heat and vapors present in atmosphere.

Disposal of Scrap Amalgam
Scrap amalgam during insertion and condensation 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.

Disposal of Mercury Contaminated Waste
• Disposal of spent capsules, mercury contaminated cotton rolls and paper napkins should be
done properly.
• These items should be disposed in tightly closed plastic container/plastic bag which can be
placed into sanitary landfill for disposal.
Removal of Old Amalgam Restorations
• Rubberdam and high volume evacuator should be used to decrease mercury vapor.
• Watercooling should also be used as high rotary instruments used without water, increase the
temperature of filling and increase the mercury vapors in that area.

Cleaning of Mercury Contaminated Instruments
• Clean the mercury contaminated instrument used during insertion, finishing and polishing
and during removal of restoration as 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.

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.

Methods to detect mecury vapour release
1. Mercury thermometer
2. Jerome mercury vapours detectives
3. Gold film mercury vapour detectives
4. Twin cell photo acoustic mercury detector
5. Atomic absorption mercury detector
6. Scanning electron microscopy (SEM) and Energy dispensive X-ray analysis (EDXA) of
sections teeth with amalgams
7. Perkins Elmer flow infection mercury system

GOLD FILM MERCURY VAPOUR
DETECTIVES
PHOTOACOUSTIC
SPECTROSCOPY
PHOTOIONIZATION
DETECTORS
COLD VAPOUR MERCURY
ANALYSIS
DOSIMETER

SAFE MERCURY AMALGAM REMOVAL TECHNIQUE (SMART)
Recommendations given by the International Academy of Oral Medicine and Toxicology
(IAOMT):
• An amalgam separator should be properly installed, utilized
and maintained to collect mercury amalgam waste
• Protective gowns and covers
• Face shields and hair/head coverings
• Proper handling, cleaning and/or disposal of mercury contaminated
components, equipment, surfaces of the room and flooring in the
dental office.

CONTROVERSIES
AMALGAM WARS
First Amalgam War – 1845 – American Society of Dental Surgeons
• They condemned the use of all filling material other than gold as toxic
• They further requested members to sign a pledge refusing the use of amalgam
Second Amalgam War – 1920 – Dr Alfred Stock
• He claimed to have evidence showing mercury absorbed from dental amalgam leads to serious
health problems
• He also expressed concerns over health of dentists, stating that nearly all dentists had excess
mercury in their urine

Third Amalgam War – 1980 – Dr Huggins
• He convinced that mercury released from dental amalgam was responsible for human
diseases affecting cardiovascular and nervous system
• Also stated that patients claimed recoveries from multiple sclerosis, alzheimers disease
and other diseases as a result of removing their dental amalgam fillings
But ADA remained adamant that mercury in patients mouth is safe and in 1986 it changed its
code of ethics, making it unethical for a dentist to recommend the removal of amalgam filling
because of mercury

CURRENT STATUS OF AMALGAM WAR
• Amalgam war continues to rage on today
• The problem is so serious that American Council of Health and Science has determined that
allegations against amalgam constitute one of the greatest unfounded health scares of recent
times.
• There is presently a congressional bill in the United States House of Representatives (HR
4163) to ban the continued use of amalgam fillings

MERCURY PHASE OUT
There is a global effort spearheaded by the United
Nations Environment Programme (UNEP) to reduce
mercury usage
By the end of 2011, United Nations Environment Program (UNEP)’s Intergovernmental
Negotiating Committee formalized a global, legally-binding treaty named “Minamata Convention
on Mercury” to protect human health and environment from the adverse effects of mercury.
Thus a proposal for “phase -down” of dental amalgam was supported.

• The requirements of this Convention includes minimizing the usage of amalgam, promotion
of alternatives, and development of mercury free alternatives
• In 2012, United Nations adopted a legislation at the Minamata Convention against mercury
pollution.
• The legislation will phase out the use of mercury in dental amalgam by 2030.
• The Convention now has over 105 parties and 128 signatories
• ADA, FDI, International Association of Dental Research and WHO as leading authorities on
the oral health of public demands reduction of amalgam in order to safeguard public health

 But at the third meeting of Conference of the parties(COP3) to the Minamata Convention
on Mercury in November 2019 held at Geneva, Switzerland, six African countries proposed
to amend phase out of Dental amalgam which triggered debate. The proposed amendment
sought to phase out amalgam in deciduous teeth, children under 15yrs, pregnant women and
breastfeeding women by 2021, and ending all amalgam use by 2024 only when mercury free
alternatives are available.
 COP3 delegates rejected the proposal and agreed to accelerate the phase down of dental
amalgam
 During this conference, delegates representing 113 parties renewed their commitment to
“phasing out the use of products containing mercury and promote alternatives”

ADVANCES IN AMALGAM
RECENT ADVANCES AND MODIFICATIONS OF DENTAL RESTORATIVE MATERIALS - A REVIEW
International Journal of Recent Advances in Multidisciplinary Research. 2016
1. Resin coated amalgam
2. Consolidated silver alloy system
3. Fluoridated amalgam
4. Gallium based alloys
5. Indium based alloy
6. Bonded amalgams
7. Glass cermet

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.

Consolidated silver alloy systems
Developed at the National Institute of Standards and Technology.
• It uses a fluoroboric acid solution to keep the surface of the silver alloy particles clean.
• The alloy, in a spherical form, is condensed into a prepared cavity in a manner similar to that
for placing compacted gold.
Disadvantage:-
Difficult to compact it adequately to eliminate internal voids and to achieve good adaptation to
the cavity without using excessive force

Fluoridated amalgam
• Fluoride, being cariostatic, has been included in amalgam to deal with the problem of recurrent
caries associated with amalgam restorations.
• Fluoride containing amalgam may release fluoride for several weeks after insertion of the
material in mouth. An increase of up to 10-20-fold in the fluoride content of whole saliva could
be measured during the first week.
• An anticariogenic action of fluoride amalgam could be explained by its ability to deposit
fluoride in the hard tissues around the fillings and to increase the fluoride content of plaque
and saliva, subsequently affecting remineralization.
• In this way, fluoride from amalgam could have a favorable effect not only
• on caries around the filling but on any initial enamel demineralization.
The fluoride amalgam thus serves as a "slow release device"

Gallium based alloys
Gallium is used as a substitute for mercury in mercury free amalgam
Ag3Sn + Ga = Ag3Ga + Sn
Advantages:
• Rapid solidification
• Adapts well to the cavity walls
• Good marginal seal by expanding on solidification
• Heat resistant
• Strength increases with time
• Creep value is as low as 0.09%
• Sets early so polishing can be carried out the same day
• Toxicity was minimal

Disadvantages:
• Alloy tends to adhere to the walls of capsule. By adding few drops of alcohol, sticking can be
minimized
• Cleaning of instrument tips difficult. Teflon coated instruments can be used.
• Increased chances of corrosion
• Increased expansion may cause fracture or postoperative sensitivity
• Costly
• Surface roughness, marginal discoloration and fracture reported
• Could not be used in larger restorations

Indium based alloys/ Mercury indium liquid alloy
• Introduced by POWELL
• He added pure indium powder with high copper alloy and triturated with mercury
• A significant decrease in mercury evaporation was seen due to the formation of indium
oxide and tin oxide
• This was marked as Indisperse and Indiloy
• Youdelis found that less mercury is need for mixing amalgam when
10% indium is added
• They also exhibited low creep and increase in strength
• Less cytotoxic than amalgam

Bonded Amalgams
Introduced by BALWIN
The provision for adequate resistance and retention form for amalgams may require removal of
healthy tooth structure. Further, since amalgam does not bond to tooth structure, microleakage
immediately after insertion is inevitable. So, to overcome these disadvantages of amalgam,
adhesive systems that reliably bond to enamel and dentin have been introduced.
After cavity preparation, enamel and dentin etched with a
conventional etchant, then a chemically cured bonding agent
applied o the walls of the cavity. Amalgam is immediately
condensed into the cavity before the resin bond has cured
4-META is used for bonding amalgam to cavity walls

Advantages:
• Treatment option for extensive carious lesions with low cost than either cast metal or metal
ceramic crowns
• It allows use of amalgam in teeth with low gingivo – occlusal height
• Permits more conservative preparation
• Reduced marginal leakage
• Less postoperative sensitivity
• Reinforces tooth structure weakened by caries and
cavity preparation
• Reduced incidence of marginal fracture
• Reduced incidence of recurrent caries
• Allows biological sealing of pulpodentinal complex

Disadvantages:
• Increased time
• May be technique sensitive
• Increased cost
• Requires practitioners to adapt to a new technique

Microleakage of bonded amalgam restorations using different adhesive agents with dye
under vacuum : an invitro study
Indian Journal of Dental Research, 2011
Bonded amalgam with type 1 GIC is a better alternative to amalgam with resin cement and
amalgam with varnish for larger restorations.
GIC Type 1 under amalgam allows chemical bonding between amalgam and tooth structure
Thus reduced microleakage
A systematic review of amalgam bonded restorations : Invitro and Clinical findings.
The Journal of Contemporary Dental Practice, 2018
Bonded amalgam restorations reduced the need for mechanical retention thus conserving tooth
structure and reducing adverse effects of microleakage.
Bonded amalgam can be considered as the material of choice for large restorations

GLASS CERMET
• Also called Cermet ionomer cements
• Introduced by McClean and Gasser
• It involves fusing the glass powder to silver particles through sintering that can be made
to react with polyacid to form the cement
Properties:
• Both tensile and compressive strength is greater than conventional glass ionomer cement
• Abrasion resistance is greater
• Radiopacity equal to amalgam
• Fluoride release is about 3350 µg in 2 weeks and about 4040 µg in 1 month

Here, an experimentation was done which
involved discarding the mercury content of
amalgam and replacing with proprietary
antimicrobial silver solution and
unsialinized titanium dioxide ceramic
nanoparticles for strength, with a favourable
easy to manipulate consistency
Prepared maxillary premolar controls were
filled with Permite amalgam and compared to
experimental groups filled with novel material.
Both groups were thermocycled, cross sectioned
and studied through SEM

Results:
It was concluded that addition of silver solution and ceramic nanoparticles to mercury free
regular set Permite alloy yielded a product that exhibits improved marginal
adaptation with less application of condensation pressure, when compared to
regular set Permite alloy

CONCLUSION
Dental amalgam has served as an excellent and versatile restorative material for many years
despite periods of controversy.
It has served as a dental restoration for more than 165 years
There is still no adequate economic alternative for dental amalgam
Amalgam is safe and can be used if mercury hygiene recommendations are properly followed in
order to get minimal mercury vapor exposure. Although small amounts of mercury release from
amalgam is known to occur, it does not cause any major health problems. However it might cause
allergic reactions in some patients

Despite the long history and popularity of dental amalgam as a restorative material, its use has
been reducing in clinical practice due to the esthetic requirements of the patients.
Although there are other alternatives to amalgam, amalgams cost, durability and
ease of manipulation have persuaded many dentist to continue its use as their first
choice for restoring posterior teeth.
32
%

REFERENCES
• Kenneth J Anusavice. PHILLIPS’ Science Of Dental Materials, Eleventh Edition
• Sturdevant’s Art & Science Of Operative Dentistry, Seventh Edition
• Robert G. Craig & John M. Powers. Science of Dental Materials, Eleventh Edition
• M.A. Marzouk et al. Operative dentistry Modern Theory & Practice
• James B. Summitt, Fundamentals Of Operative Dentistry, Second Edition
• Vimal K Sikri. “Silver Amalgam” Textbook of operative dentistry. CBS Publishers, 1st edition
• John F McCabe, Angus W.G Walls. “Dental Amalgam”, Applied Dental materials, 8th edition, 1998

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