Silver Amalgam Seminar

CONTENTS
2
• Introduction
• Definition
• History
• Classification
• Composition
• Amalgamation
• Properties of amalgam
• Indications and contraindications.

3
•Advantages and disadvantages
•Manipulation
•Failure of amalgam restoration.
•Amalgam waste management
•Repaired amalgam restoration
•Recent advances
•Conclusion
•References

Alloy:
A metal made by combining two or more
metallic elements, especially to give greater
strength or resistance to corrosion.
Amalgam:
Amalgam is an alloy that contain mercury as
on of its constituents.
Phillips science of dental materials 11th edi chp 17 pg no 496
5
INTRODUCTION

Mercury :
ANSI/ADA specification no. 6 for dental
mercury requires that mercury should have
clean reflecting surface that is free from
surface film when agitated in air.
Material used in dentistry, Mahalaxmi chp 12 pg no.195-221.
6
INTRODUCTION

Dental Amalgam:
Dental amalgam is produced by mixing
liquid mercury by solid particles of an alloy
containing pre dominantly silver , tin and
copper.
Phillips science of dental materials 11th edi chp 17 pg no 496
7

9
• Su Kung, China gave the earliest
reference for the use of silver paste for
filling.
659 AD
• Johannes Strokerus,Germany
recommended amalgam as a filling
material
1528
• Li Shihchan ,used dental mixture of 100
parts mercury with 45 parts silver and
900 parts tin.
1578

10
• Traveau described a “silver paste” filling
material
1826
• Crawcours brothers introduced to North
America their “Royal Mineral
Succedaneum”
1833
• “ First Amalgam War and Amalgam
pledge”
1845

11
• End of Amalgam war
1850
• John Tomes, conducted first research
program on amalgam
1861
• Charles Tomes measured the shrinkage
and expansion in amalgam
1871

12
• J. Foster Flagg, managed to change the
attitude toward dental amalgams
1877
• New alloys with 60% of silver and 40%
of tin as major constituents
1881
• G.V.Black, standardized the formulation
of amalgam.
1895, 1896, 1908

13
• Stocker, introduced copper amalgam
1900
• Alfred Stock, published article
condemning amalgam restoration.
• Second Amalgam war
1926
• Dr. Wilmer Eames recommended a 1:1
ratio of mercury to alloy.
1959

14
• Innes & Youdelis, introduced admixed
alloy.
1963
• Hal Huggins,Third Amalgam war
1980
• Safety of dental amalgam as restorative
material was proved.
1997

• In 1845 , American society of dental surgeon
condemned the use of all filling material other
than gold as toxic.
• The society went further and requested to sign a
pledge refusing to use amalgam.
• However , this policy was reconsidered in 1850.
16
FIRST AMALGAM WAR

• The use of amalgam was promoted by work of
F.Flagg.
• Final approval for clinical use came from the
work of G.V. Black.
• Improved handling and performance of
amalgam blocked the criticism and inspired the
use of amalgam.
17
FIRST AMALGAM WAR

• German Dentist Professor Alfred Stock claimed
to have evidence showing that mercury could be
absorbed from dental amalgam, which lead to
serious health problems.
• His writing attracted wide spread attention.
• Charite Hospital in Berlin appointed a committee
to investigate allegation of amalgam toxicity.
18
SECOND AMALGAM WAR

• An account of committee finding was published
in 1930, declare that there was no reason to
condemn newer silver tin amalgam.
19
SECOND AMALGAM WAR

• War began in 1980, primarily through writing of
Dr. Huggins.
• He was convinced that mercury released from
dental amalgam was responsible for human
disease affecting CVS & CNS.
20
THIRD AMALGAM WAR

• But research ,demonstrated that there was no
cause and effect relationship between the dental
amalgam restoration and other health problems.
21
THIRD AMALGAM WAR

• ANSI/ADA Specification no.1 amalgam alloys
should contain predominantly silver and tin.
• The content of the alloy should be at least 65
wt% silver, 29 wt% tin, and less than 6 wt% ,
copper, a composition close to that
recommended by G.V. Black in 1896.
Phillips science of dental material 11th edi chp 17pg no.496-98
23
ALLOY COMPOSITION

1. Powder 2. Liquid
Silver Mercury
Tin
Copper
Zinc
24
COMPOSITION

Amal
gam
alloys
Classi
ficatio
n
Partic
le
type
Ag Sn Cu Zn Other
New
true
dentall
oy
Low
coppe
r
Lathe
cut
70.8 25.8 2.4 1 -
Disper
s alloy
High
coppe
r
Mixed 69.5 17.7 11.9 0.9 -
Aristall
oy
High
coppe
r
Spheri
cal
58.7 28.4 12.9 0 -
Indiloy High
coppe
r
Lathe
cut
60.5 24 12.1 0 3.4
(indiu
m)25
Sturdevant art and science of operative dentistry 6th edition

MANUFACTURE OF
ALLOY POWDER
27

Consituent of metal heated,with
protection from oxidation
Poured into mould to form ingot
(3-4cms in diameter & 20-30
cms in length)
The ingot are cooled relatively
slowly.
28
LATHE CUT FILINGS

This leads to formation of γ
and little amount of ε,η,β
phases.
The ingot is then reduced to
filing
Cut using suitable tool on
lathe and ball milled.
29

Aging of the alloy is a
desirable process during
manufacturing
Which improves the shelf life
of the alloy powder
It is associated with the stress
induced in the particle during
cutting of the ingot
30

The current practise is to age the particles
artificially by subjecting them to controlled
temperature of 60-100°C for 1-6 hours.
31

Spherical powder is produced by
atomization process
All metallic ingredients are melted
together to form a desired alloy.
The liquid alloy is sprayed into a
large chamber through a very fine
crack in a crucible under high
pressure of inert gas32
SPHEROIDALATOMIZED POWDER

Since the chamber is large ,
globules of liquid alloy solidify
before they reach bottom
surface.
Thus preserving its spherical
shape.
Diameter varying from 2 to
43 µm.
33

Particle size range from 15 -35
µm is favored
A smaller particle size is
chosen because it result in
Less mercury content
34
PARTICLE SIZE

Rapid hardness
Early compressive strength
Smoother surface for carving
35

Less corrossion suscepitible.
36

• Amalgams made from lathe-cut powders, or
admixed powders (blend of lathe cut and
spherical powders).
• Resist condensation better than amalgams
made entirely from spherical powders.
37

• Spherical alloys require less mercury than
typical lathe-cut alloys
• Because spherical alloy powder particles
have a smaller surface area per volume than
do the lathe cut alloy particles.
• Amalgams with a low mercury content
generally have better properties.
38

1. Binary alloy (Ag-Sn)
2. Tertiary alloy (Ag-Sn-Cu)
3. Quaternary alloy(Ag-Sn-Cu-Zn)
Sturdevant’s art and science of operative dentistry 5th edi
40
NUMBER OF ALLOYED
METALS:

41
SHAPE OF PARTICLE
ADMIXED
LATHE-CUT SPHERICAL

1. Conventional/Low copper amalgam
( <0-6%)
2. High copper amalgam (>6-13%)
a. High copper admixed alloy
b. High copper uni-compositional
alloy
42
COPPER CONTENT :

Zinc containing alloy ( >0.01%)
Zinc free alloy(<0.01%)
43
ZINC CONTENT :

1st Gen: 3part silver and 1 part tin .
2nd Gen: 3 parts of Ag ,1 part of Sn, 4% Cu to
decrease the plasticity and to increase the
hardness and strength and 1 % zinc
which act as oxygen scavenger and
decreases the brittle ness
44
ADDITION OF GENERATIONS
OF AMALGAM:

3rd Gen: First generation + spherical amalgam
copper eutectic alloy
4th Gen: Adding copper up to 29% to original silver
and tin powder to form ternary alloy so that
tin is bounded to copper
45

5th Gen: Quaternary alloy that is silver ,tin, copper
and indium.
6th Gen : consisting of eutectic alloy containing
silver(62%) , copper (28 %),
palladium (10 %) which is lathe cut
and blend into 1st / 2nd / 3rd gen
amalgam in ratio 1:2
46

AMALGAMATION AND
RESULTING
MICROSTRUCTURE
47

Amalgamation is the process of reaction and
setting when mercury is mixed / amalgamated
with any alloy.
48
AMALGAMATION REACTION

Sturdevant art and science of operative dentistry 6th edition
49
Silver tin phase γ Ag3Sn
Silver mercury
phase
γ1 Ag2Hg3
Tin mercury
phase
γ2 Sn7-8Hg
Copper tin
phase
ε Cu3Sn
Copper tin
phase
η Cu6Sn5
Phases of Amalgam

Amalgamation occur when alloy
is triturate with mercury.
During trituration mercury
diffuses into the γ phase of
alloy particle reacting with
mainly silver and tin
50
LOW COPPER CONVENTIONAL
AMALGAM ALLOYS

Mercury has limited solubility for
silver (0.035%) as compared to
tin (0.6%).
Hence ,tin remains in solution
longer than silver
When this solubility exceeds the
wt %, the silver starts
precipitating first
51

As the remaining mercury
dissolves the alloy particles γ1 &
γ2 crystal grow and amalgam
begins to harden.
There is insufficient mercury to
completely consume all the alloy
particles.
Unconsumed particles around 27
% are present in set amalgam.
53

54
Setting reaction
Ag 3 Sn + Hg Ag2 Hg3 +Sn7-8Hg + Ag3Sn
(γ) (γ1) (γ2) (γ)
(unreacted)

55
Conventional amalgam contain following
component phases
• Gamma(γ)phase (Ag 3 Sn ):
strongest phase
occupy maximum available space in
volume of restoration.
• Gamma-1(γ1) phase :
noblest phase
most resistant to tarnish and corrossion.

56
• Gamma-2(γ2)phase (Ag 3 Sn ):
weakest phase
more prone to tarnish and corrosion.
• Mercury phase :
weakest phase
drastic drop in strength occurs if this
phases exceeds a certain volume limit.

57
• Interphase:
interphase between (γ-γ1) , (γ1-γ2) ,
(γ2-γ)
The closer and continuous they are in
final restoration, the better is the
bonding.
The resultant mass is more cohorent and
more resistant to enviromental variables
the restoration is subjected to.

• In 1963, Innes & Youdelis added spherical
silver copper eutectic alloy
• These alloys are often called admixed alloys
because the final powder is mixture of atleast
2 kinds of particles.
Phillips science of dental material 11th edi chp 17 pg no. 505..
58
HIGH COPPER ADMIXED ALLOY:

 Amalgam made from this powder is stronger,
because of, increase in residual alloy
particle, and resultant decrease in matrix.
 There is elimination of
gamma-2 phase,
which is the weakest phase.
Phillips science of dental material 11th edi chp 17 pg no. 505..
59

60
Setting reaction :
Ag 3 Sn + Hg Ag2 Hg3 +Sn7-8Hg + Ag3Sn
(γ) (γ1) (γ2) (γ)
(unreacted)
Sn7-8Hg +Ag-Cu Cu6 Sn5 + Ag2Hg3 + Ag3Sn
(γ2) (eutectic) (η) (γ1) (γ)

61
Thus , in final set amalgam the γ2 phase is
eliminated.
The γ2 phase is replaced by η phase.
The total copper content should be at least 12 % for
this reaction to occur.

 Unlike admixed alloy powders, each particle of
these alloy has the same chemical
composition.
 εphase is added to provide additional copper
 When triturated with mercury , the silver and
tin Ag-Sn phases dissolve in mercury whereas
copper dissolve in negligible amount.
62
SINGLE- COMPOSITION ALLOY:

As γ1 crystal grows , they form matrix that binds
the partially dissolve particle together
The εphase is converted to η phase
The reaction occur in a ring around the spherical
particles
The ring only consist of γ1 & η
The γ and ε remain in center of the
ring.
63

64
Setting reaction :
Ag-Sn-Cu + Hg Ag2Hg3 + Cu6 Sn5 +
(γ1) (η)
unconsumed alloy particles

ADA specification no.1 for amalgam alloy
contains certain requirement that aid significantly
in controlling the qualities of amalgam.
The specification list three physical properties as
measure of quality of amalgam
• Strength
• Dimensional change
• Creep and flow
Material used in dentistry, Mahalaxmi chp 12 pg no.195-221.66

1. Stage I : Intial Contraction:
Contraction which begins for about 20 minutes
after beginning of trituration is called as intial
contraction.
Occurs as the alloy particles dissolve in
mercury and γ1 phase grow .
67
DIMENSIONAL CHANGE:

2. Stage II : Expansion
As γ1 phase grows– impingement and outward
growth of crystals occur—result expansion.
Occurs when there is adequate mercury to
provide plastic matrix.
DIMENSIONAL CHANGE:

DIMENSIONAL CHANGE:
Excessive
Contraction
Excessive
Expansion
• Micro leakage
• Post operative
sensitivity
• Secondary caries
• Pressure on pulp
• Post operative
sensitivity
• Protrusion of
restoration

ANSI/ADA Specification No 1 requires that
amalgam neither to contract nor to expand
more than 20 µm/cm, measured at 37°C,
between 5 min and 24 hr after the beginning of
trituration.
Phillips science of dental material 11th edi chp 17 pg no. 508-10.70

1.Particle size and shape:
Smaller and regular particles – has more smooth
surface area– mercury reacts faster – γ1 phase
grows faster—intial contraction (stage I) will occur
rapidly and expansion(Stage II) also occur fast to
neutralise the initial contraction.
71
FACTOR AFFECTING
DIMENSIONAL CHANGE:

2. Mercury:
More mercury in amalgam mix– more
expansion—stage II expansion prolonged
72
FACTOR AFFECTING
DIMENSIONAL CHANGE:

3. Manipulation:
During trituration – more energy—particle will
become smaller –mercury will be pushed
between the particles—discouraging the
expansion
73
FACTOR AFFECTING
DIMENSIONAL CHANGE:

3. Manipulation:
More condensation pressure– closer the
particle—more mercury is expressed out–
inducing more contraction.
74
FACTOR AFFECTING
DIMENSIONAL CHANGE:

4.Moisture contaimination:
Zinc containing low copper/ high copper alloy ,
which get contaiminated by moisture during
manipulation– delayed expansion.
75
FACTOR AFFECTING
DIMENSIONAL CHANGE:

Zn + H2O---- ZnO+H2
Complication Of Delayed Expansion:
Protrusion of restoration out of the cavity
Increase in microleakage.
Increase in flow and creep
Pain due to pressure exerted by expansion of
amalgam
76

Dental amalgam is strong in compressive
strength and weak in tensile strength.
.
77
STRENGTH :

Hence if the thickness is inadequate , fracturing
of this thin amalgam even in small area ,
especially at margins expedites corrosion,
secondary caries, subsequent clinical failure.
78

Amalgam Compressive strength(MPa)
1hr 7 days
Low copper 145 343
High copper admixed 137 431
High copper uni-
compositional
262 510
79
COMPRESSIVE STRENGTH :
• 1 hr CS is much less than half the final strength
• Patients are instructed not to use excessive
masticatory forces for at least 6-8 hrs

Amalgam Tensile strength in
24 hrs(MPa)
Low copper 60
High copper admixed 48
High copper uni- compositional 64
80
TENSILE STRENGTH :
• Amalgam is a brittle material
• It cant undergo deformation or elongation on
loading

1. Trituration:
Both under trituration and over trituration
decreases the compressive strength.
Greater trituration energy –even distribution of
matrix– results in improved strength of restoration.
FACTORS AFFECTING THE
STRENGTH :

1. Trituration:
If trituration continued even after formation of
matrix – lead to crack formation – drop in
strength of set amalgam.

2. Mercury content :
The strength of amalgam depends upon each
particles being wetted by mercury.
If mercury too less—dry ,granular mix, rough,
pitted surface that invites corrosion.

2. Mercury content :
Any excess mercury - formation of weaker matrix
–affect the compressive strength.
If mercury content of amalgam mix is more than
53-55% ---drop in compressive strength by 50 %

3. Effect of condensation:
Condensation pressure and technique – depends
on shape of alloyparticles.

For lathe cut alloys– more pressure is required to
pack compactly -- minimize the porosity—express
excess mercury to surface -- higher compressive
strength.

For spherical particles much lighter condensation
pressure is required– as spherical particles tend
to slip under heavy pressure– hence cannot be
compacted properly.

4. Effect of porosity:
Weak areas of restoration –decreases strength of
restoration.
Porosity facilitates:
Stress concentration
Propogation of cracks
Corrosion

Porosity can be due to:
Under trituration
Particle shape(lathe-cut)
Insertion of too large increments
Inadequate condensation pressure

5. Particle size:
Smaller particle size – greater will be strength.

6. Temperature :
Amalgam loses 15% of its strength when
temperature is elevated from room temperature to
mouth temperature.
Loses 50 % of strength when temperature
elevates 60 °C.
91

• Time dependent strain or deformation that is
produced by a stress.
• ANSI/ADA Specification No. 1 specified that
creep rate below 3%.
Phillips science of dental material 11th edi chp 17 pg no. 515-16.92
CREEP :

• Phases of amalgam restoration:
High creep rates are associate with γ2 in low
copper alloy and γ1 in high copper alloy.
93
FACTORS INFLUENCING CREEP
Amalgam Creep(%)
Low copper 2.0
Admix 0.4
Single
composition
0.13

CLINICAL SIGNIFICANCE:
Reduce creep rate is asociate with:
Low mercury: alloy ratio
Increased trituration time
Greater condensation pressure
On non occlusal surface –
restoration appear to be
extruded – producing
esthetic problems /over hangs.
Sturdevants art and science of operative dentistry 6th edi chp 13 pg no.347
94

On occlusal surface-
Occlusal margins become fracture-
susceptible
Ledges elevates above the natural contour
of adjacent enamel.
95

INDICATIONS &
CONTRA -INDICATIONS
OF AMALGAM
96

• Class I, II, V restoration
• Caries-control restoration
• As a foundation for cast-metal, metalceramic,
and ceramic restorations,
• When patient commitment to personal oral
hygiene is poor
• When cost is an overriding patient concern
Sturdevants art and science of operative dentistry 6th edi chp 13 pg no.342-43
97
INDICATIONS OF AMALGAM

• Sometimes can be used for
cuspal
restorations (with pins usually).
• As a core build-up material prior
to cast restoration.
• As a retrograde filling material.
• As a die material.
98

• Pt allergic to alloy component.
• Esthetic areas of tooth.
• Class III & IV restorations.
CONTRA -INDICATIONS OF
AMALGAM

ADVANTAGES &
DISADVANTAGES OF
AMALGAM
100

• Restoration is completed within one sitting
without requiring much chair time.
• Well-condensed and triturated amalgams
have good compressive strengths.
101
ADVANTAGES OF AMALGAM

• Least technique sensitive of all restorative
material.
• Good long-term clinical performance
• Ease of manipulation by dentist
• Economical .
102

• Poor esthetic qualities
• Long-term corrosion at tooth-restoration interface
may result in ditching leading to replacement.
• Galvanic response potential exists
• Local allergic potential
• Concern about possible mercury toxicity
• Marginal breakdown103
DIS-ADVANTAGES OF AMALGAM

Metallic taste and Galvanic shock.
• Marginal leakage.
• Discoloration of the tooth structure.
• Lack of chemical or mechanical adhesion to
the tooth structure.
104

• High rate of secondary caries.
• Thermal conductivity.
• Promotes plaque adhesion.
• Delayed expansion
105

Selection of alloys
Mode of supply
Proportioning of mercury to Alloy
Trituration
Condensation
Pre carve Burnishing
Carving the amalgam restoration
Post carve Burnishing
Finishing Amalgam Restoration
Polishing
107
MANIPULATION

To enable the clinician to select the appropriate
silver amalgam material ,for a particular clinical
situation, difference between various silver alloys
must be considered.
108
SELECTION OF ALLOY

Low copper
• Amalgamation requires
more mercury
• γ1 phase is dominant
• Corrossion due to γ2
phase
• Creep value is high(1-
8%)
• Low compressive
strength
• Marked dimensional
change
High copper
• Less mercury is
required for
amalgamation
• Dominant η phase
• η phase least corrosion-
resistant phase.
• Very low creep
value(0.1-1%)
• High compressive
strength
• Minimal dimensional
change
109

Lathe cut
• Alloy particle have
irregular shape
• Manufactured by
lathe cutting a ingot
• More Hg for mixing
• Poor mechanical
properties
• Mix is less plastic
• Heavy condensation
pressure is required
Spherical
• Spherical smooth
surface
• Manufactured by
process called as
atomization
• Require less mercury
• Better mechanical
properties
• Mix is more plastic
• Less condensation
pressure
110

Admixed
• Cu: 9-20%
• WT is longer & sets
slow
• High condensation
pressure
• High Hg content in
final set amalgam
• Low early strength
• Creep is higher
• Difficult to finish
Spherical
• Cu: 13-30%
• WT is less & sets
faster
• Low condensation
pressure
• Low Hg content in final
set amalgam
• High early strength
• Creep is low
• Easy to finish
111

1. Alloy powder and mercury
2. Disposable capsule with pre-proportioned
alloy powder and mercury
3. Pre-weighted alloy in tube form and mercury
in sachets
112
MODE OF SUPPLY

113
PROPORTIONING OF MERCURY
TO ALLOY
Historical background:
Hand trituration using conventional alloys ,
required a mercury/alloy ratio of 8:5.
After trituration the excess mercury was
squeezed from mix by hand exposing
operator to risk.
Increase in proportion of gamma 2 phase
producing a weaker restoration that was
prone to corrosion.

114
TO ALLOY
Current recommendation:
Intial mercury content between 50-55 % is
still recommended where modern lathe cut
alloy is used.
Spherical alloy require less mercury for
amalgamation as low as 40 %.

115
BY WEIGHT:
CRESCENT AND ASH
BALANCE
BY VOLUME:
BAKER PROPORTIONER

116
MODERN ENCAPSULATED ALLOY AND MERCURY WITH PRESS

• Contain little more
mercury than needed
for powder.
• Continue squeezing of
mercury is necessary.
• Each increments dryer
than previous one.
• Equal amount of
mercury and alloy
powder.
Operative Dentistry Modern Theory and Practise .Marzouk chp 4 111-12.
117
TO ALLOY
High mercury
technique/increasing
dryness technique
Minimal mercury
technique/ Eames
technique

The purpose of trituration is to mix the amalgam
alloy intimately with mercury so as to wet the
surface of powder particles to allow reaction
between liquid mercury and silver alloy.
Operative Dentistry Modern Theory and Practise .Marzouk chp 4 111-12.118
TRITURATION

Objectives of trituration:
1) Workable mass of amalgam
2) Remove oxides from powder particle.
3) To reduce particle size.
4) To dissolve the particles.
Operative Dentistry Modern Theory and Practise .Marzouk chp 4 111-12.119
TRITURATION

• A Pestle and mortar employed hand
trituration.
• Surface texture of mortar and
pestle should be roughened to
maximize the friction
between amalgam and glass
surface.
120
HAND TRITURATION

• Mechanical trituration of encapsulated alloy
and mercury allows a precise , reproducible
technique and minimizes a risk of mercury
contamination.
• Three basic movements :
Back and forth in straight line.
Back and forth in figure 8.
Centrifugal fashion.
Operative Dentistry Modern Theory and Practise .Marzouk chp 4 112-13.
121

• A capsule serves as a mortar.
• A cylindrical metal or plastic piston of smaller
diameter than the capsule is inserted into the
capsule, and this serves as the pestle.
Silver amalgam in clinical practise 3rd edition chp 6 pg 105 to 126
122

• A continuation of trituration.
• Improve homogeneity.
• Assure consistent mix.
• Achieve a single, consistent coherent mass.
Operative Dentistry Modern Theory and Practise .Marzouk chp 4 113.
123
MULLING

The mix is placed in a dry piece of rubber dam
and vigorously rubbed between first finger and
thumb .
This process should not exceed 2-5 seconds.
124

After mechanical trituration, the pestle can be
removed from capsule and the mix is triturated at
low speed for 2-3 sec to achieve mulling
This process allows cleaning of capsule
125

• Under Triturated:
Appears rough, grainy, may crumble easily
Outer surface of alloy particles is not completely
wetted by mercury.
Increases working time
More porosity
Low strength and corrosion resistance.
126

• Normal mix:
Appears shiny and has a smooth surface and
consistency.
127

• Over triturated:
Soupy, difficult to remove from capsule & too
plastic to manipulate.
Decreases working time
Higher contraction with trituration
Decrease the strength
Increases creep.
128

• The condensation of amalgam mass into tooth
cavity is most important steps in amalgam
restoration.
129
CONDENSATION OF AMALGAM

• To adapt the plastic mix to cavity walls and
margins .
• To squeeze the unreacted mercury out of
increments thereby preventing entrapment
of mercury.
130
OBJECTIVES OF CONDENSATION:

• To bring the strongest phase of amalgam
close together thereby increasing the
final strength of restoration.
• To reduce the number of voids and keep
matrix continuous.
131

• Careful condensation of amalgam will force
alloy particles together, force mercury –rich
material to the surface of each increment,
facilitated bonding of successive layers and
ultimately allow removal of excess mercury.
132

• Lathe cut alloys require higher mercury
content for proper amalgamation
• Hence , greater forces of condensation is
required to remove excess mercury.
• With spherical alloy, initial mercury is lower,
the lower condensation pressure is required
133

• Rupp , Paffenbarger and Patel (1980)
Reported “If a delay occurs between
condensation and trituration , less mercury can
be removed from restoration , strength may be
reduced and more creep may result. ”
• Mosteller (1950) “Set the maximum time limit
for safe condensation at 3 mins.”
134

• Ryge et al (1952) demonstrated that method of
mechanical condensation may reduce setting
time and increase the compressive strength of
restoration.
135

• Ryge et al (1952) commented that better
results will be obtained using either hand or
mechanical condensation if multiple small
increments are applied .
136

• Three types:
1. Hand condensation
2. Mechanical condensation
3. Ultrasonic condensation
137

• Amalgam carrier is use to carry increments of
alloy and inserted into cavity.
• Increment should be as small at a time while
condensing , to avoid porous and weak
restoration.
138
HAND CONDENSATION

• Condensing unit is generally contra angled
with serrated ends.
• Most of cavities round condenser is used
• Parallelogram and oval are more effective in
gingival point angles.
139

• Tip size should be small when lathe cut alloys
are condensed .
• For spherical alloys, larger tipped condensers
are used, since smaller tips tend to slip and
spherical particles roll over one another.
140

SPHEROIDING
Ramsay (1941) referred to the spheroiding of
amalgam at sharp line angles.
To overcome this,
line angles be rounded
use of small instrument tips of contour suited to
the anatomy of line angle
is recommended
Silver amalgam in clinical practise 3rd edition chp 6 pg 115

• The area of the condenser point, or face,
and the force exerted on it by the operator
govern the condensation pressure (force per
unit area).
• Forces in the range of 13.3 to 17.8 N (3 to 4
lb) represent the average force employed.
142

 To ensure maximum density and adaptation
to the cavity walls, the condensation force
should be as great as the alloy will allow,
consistent with patient comfort.
143

• Condensation usually starts from the center of
cavity and 45° to walls and floor for non
spherical amalgam.
• Subsequently , condensation should be done
90° to displacement of primary increment.
• The increments are added till the cavity is
overfilled.
144

• After this, the amalgam mix is is condensed
heavily using largest condenser possible
• This is called blotting mix.
• It serves to blot excess mercury from the
margin and surface of restoration and to
adapt amalgam more intimately to cavosurface
anatomy.
145

Mechanical Condensation
The procedures and principles of mechanical
condensation are the same as those for hand
condensation, including the need to use small
increments of amalgam
The only difference is that the condensation of the
amalgam is performed by
an automatic device.
Some provide an impact type of
force , whereas others use
rapid vibration.
Phillips science of dental material 11th edi pg no.530.
146

• Burnishing is defined as plastic deformation
of surface due to rubbing / sliding the contact
with another object.
147
PRE-CARVE BURNISHING

• Burnishing the amalgam immediately after
condensation has been used in an attempt to
increase the packing of particles at surface
and reduce the final mercury content of
restoration.
• Restoration with pre carve burnishing were
superior to those unburnished in terms of
marginal adaptation.
148

• Immediately after condensation a large
round burnisher is used in light strokes from
restoration towards cavosurface margins.
• Beaver tail burnisher is used in inaccessible
areas such as proximal surface of restoration
149

• Objectives Of Pre Carve Burnishing:
To improve marginal adaptation of amalgam
To reduce the number of voids present at the
surface
To bring any further excess mercury on the
surface which can be removed during carving.
To condition the amalgam surface to the carving
procedure.
150

• The carving procedure should be delayed
until the surface offer resistance to
instrumentation.
• A particular “squeaking”(amalgam crying)
sound elicited from the surface.
• A sharp instrument is used to
carve along the amalgam/enamel
junction.
151
CARVING THE AMALGAM
RESTORATION

No underhangs
Physiologic contour
Compatible marginal ridges.
Proper contacts
Amenable for plaque control
152
OBJECTIVES OF CARVING :

• 3 stages:
• Initial carving of accessible areas
• Second involves occlusal re-assessment and
adjustment.
• Third stage defines the final occlusion form.
153
OCCLUSAL CARVING

(a)Incorrect technique-from amalgam to enamel
(b)Incorrect technique –from enamel to amalgam
(c)Correct technique - blade resting on both enamel and amalgam

• The main purpose is to render the smooth
surface, discourage corrosion.
• Post carve burnishing may reduce the size of
marginal gap around restoration and also
reduces the early
micro-leakage.
(Ben-Amar et al,1987).
155
POST-CARVE BURNISHING

The process which continues the carving
objectives , remove flash, overhangs, and
surface irregularities.
156
FINISHING AMALGAM
RESTORATION

• Polishing is the process that removes the
scratches and irregularities from the surface
of restoration leaving , smooth high glazed
surface that is corrosion resisitant.
157
POLISHING

FAILURE OF
AMALGAM
RESTORATION
158

• Fracture lines:
-Visible on occlusal surface
especially in the isthmus region
• Marginal ditching:
-Is the breakdown of the amalgam at
the margins due to wear, fracture or
improper cavosurface margins

• Proximal overhangs:
-Can be confirmed clinically
or radiographically or by
tearing of dental floss when
passed through
interproximal contacts.
-Constitute failure as they
produce gingival
inflammation

• Poor anatomic contours:
-Inadequate embrasure form, flat contours are
defects which require replacement
• Marginal ridge incompatibility:
-Results in poor occlusal embrasure form and
improper clearance of food leading to food
impaction and periodontal disease
• Improper proximal contacts:
-Improper restorations may cause open contact
resulting into food impaction and periodontal
problems

• Recurrent caries:
-Presence of fractures or marginal
gaps indicate recurrent caries
-Probing with explorer and
radiographic examination helps in
diagnosis.
• Amalgam blues:
-Seen as bluish hue through a thin
enamel shell
-Due to leaching of corrosion
products into dentinal tubules

• Voids:
-May be present at the margins due to
improper condensation
-Possess a risk of secondary caries
especially in areas like gingival seat.
• Bulk fracture of tooth or amalgam:
-Bulk fracture of tooth is a sign of
lack of resistance form while bulk
fracture of amalgam indicates lack of
retention form.

• Poor occlusal contacts:
-Lack of occlusal contacts can produce improper
occlusal functioning and undesirable tooth
movement

 Improper case selection
 Improper cavity preparation
• Inadequate extensions
• Over extended cavity preparations
• Shallow cavity preparations
• Deep cavity preparations
• Curved pulpal floor
165
REASON FOR FAILURE OF RESTORATION

• Wide isthmus
• Narrow isthmus
• Sharp axiopulpal line angle
• Lack of butt joint at the cavosurface margins
• Lack of occlusal convergence
• Improper convenience form
166

 Errors in matricing procedures and restoration
• Unstable matrix
• Poor contour
• Absence of wedge
167

 Postoperative factors
• Postoperative pain or sensitivity
• Premature fracture
168

POST OPERATIVE PAIN
Hyperocclusion leading to inflammation of apical
periodontium
Cracks in tooth such cracks cause pain during
chewing because of expansion or contraction of
tooth structure with every bite
Galvanism: may be due to dissimilar adjacent metal
restoration or poorly condensed amalgam due to
variation in silver concentration
Delayed expansion

Inadequate pulp protection leading to conduction
of heat
Varnish should be applied under amalgam
restoration to avoid leakage around restoration
which may lead to post operative sensitivity and
amalgam blues due to penetration of corrosion
products into dentinal tubules
Restoration fracture may occur if patient does not
follow instruction properly and bites on restoration
before it sets

FROM THE MATERIAL SIDE
• Micro leakage:
Percolation of oral fluids
• Dimensional change
Depends on residual mercury
contraction and expansion
May even cause pain

• It is the surface discoloration on metallic surface
without any loss of structure.
• In low copper amalgam γphase is responsible
• In high copper alloy η phase is responsible
172
TARNISH

It is the chemical or electrochemical reaction of metal
with its environment and progressive destruction by
formation of corrosive byproducts.
In low copper alloy :
Sn7-8Hg +1/2 O2+H2O + Cl --------- Sn4(OH)6Cl2 + Hg
(tin oxychloride)
173
CORROSION

In high copper alloy :
Cu6Sn5+1/2 O2+H2O + Cl ---CuCl2.3Cu(OH)2 +SnO.
174
CORROSION

As a result of the corrosion reaction , mercury is
released.
This released mercury then reacts with unreacted γ
particles and produce additional γ1 &γ2 phases ,
resulting in expansion
This results in porosity and reduction in strength of
restoration. Material used in dentistry, Mahalaxmi chp 12 pg no.195-221.
175
MERCUROSCOPIC EXPANSION

• .
176
ELECTROCHEMICAL CORROSION
Occurs when
chemically
different site
act as anode
and cathode
In the presence
of electrolyte
typically saliva
Anode corrodes
producing
soluble and
insoluble
corrossion
reaction product

Galvanic corrosion:
Dental amalgam is in direct contact with an
adjacent metallic restoration such as gold crown
As a result of large difference in electromotive
forces (EMF) of two materials.
The corrosion process can liberate free mercury,
which can contaminate and weaken gold
restoration .
Phillips science of dental material 11th edi chp 17 pg no. 517-19..177
TYPES OF CORROSION:

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.

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
along the margins.
. Phillips science of dental material 11th edi chp 17 pg no. 517-19..179

Amalgam has linear co efficient of thermal
expansion 2.5 times greater than tooth
structure.
During expansion and contraction percolation
occurs along the external walls
180

Percolation owes to difference intra oral
temperature changes .
181

• The amalgam restorations possible only because of
the unique characteristics of mercury.
• The use of mercury in the oral environment has
raised concerns regarding safety for more than 170
yrs.
• To understand the possible side effects of dental
amalgam, the differences between allergy and
toxicity must be discussed.
SIDE – EFFECT OF MERCURY

Typically, allergic responses represent an antigen-
antibody reaction marked by
Itching
Rashes
Swelling
Phillips science of dental material 11th edi chp 17 pg no. 535-40..
184
ALLERGY

• Contact dermatitis or Coombs Type IV
hypersensitivity reactions represent the most
likely physiologic side effect to dental amalgam,
but these reactions are experienced by less
than 1% of the treated population.
185
ALLERGY

• Normal daily intake of mercury is 15µg from food
• 1µg from air
• 0.4 µg from water.
• Maximum allowable limit of mercury in blood is 3µg
TOXICITY

Mercury from dental amalgam is released in the
form of vapors and ions
Mercuric ions are released from corrosion.
MERCURY EXPOSURE IN
DENTISTRY

The amalgam restoration may release mercury in
range 1-3µg/day.
The released mercury is greater for low copper
amalgam than high copper amalgam
MERCURY EXPOSURE IN
DENTISTRY

Minamata disease is methylmercury (MeHg)
poisoning that occurred in humans who
ingested fish and shellfish contaminated by
MeHg discharged in waste water from a
chemical plant.
.
Minamata disease: methylmercury poisoning in Japan caused by environmental pollution. Crit Rev Toxicol.
1995;25(1):1-24
189
MINAMATA DISEASE:

Symptoms :
Sensory disturbances (glove and stocking
type), ataxia, dysarthria, constriction of the
visual field, auditory disturbances and tremor
were also seen.
.
1995;25(1):1-24
190

Urinary mercury
levels (µg)
Symptoms
Up to 25 No side effects
100 Decrease brain activity with verbal
skills
500 Irritability, depression, memory
loss,early symptom ofdisturbed
kidney function.
1000 Kidney inflammation. Swollen
gums, excessive tremors
2000 Joint pain
4000 Hearing loss and death.
.
1995;25(1):1-24
191

• Current limit of mercury vapor established by
OSHA is 50µg/m3 in any 8 hour work shift over
40 – hours work week.
193
AMALGAM WASTE
MANAGEMENT

• Well ventilated.
• Well-sealed containers.
• Proper disposal through reputable dental
vendors is mandatory to prevent environmental
pollution.
194
AMALGAM WASTE
MANAGEMENT

• Increasing legal attention is being focused on
correct disposal of potentially hazardous waste
materials, including dental amalgams and
mercury.
• Amalgam scrap and materials contaminated
with mercury or amalgam should not be
incinerated or subjected to heat sterilization.

• If mercury is spilled, it must be cleaned up as
soon as possible.
• Mercury suppressant powders are helpful, but
these should be considered temporary
measures.

REPAIRED
AMALGAM
RESTORATIONS
197

• Occasionally, when an amalgam restoration
fails, as from marginal fracture, it is repaired.
• A new mix of amalgam is condensed against
the remaining part of the existing restoration.
Phillips science of dental material 11th edi chp 17 pg no. 540..198
REPAIRED AMALGAM
RESTORATIONS

• Thus the strength of the bond between the new
and the old amalgam is important.
• The strength of repaired amalgam is less than
50% of that of unrepaired amalgam.

• The bond is a source of weakness.
• Factors such as corrosion and saliva
contamination at the interface present
formidable barriers that interfere with bonding of
the old and new ,amalgam.

• Another repair option for areas that exhibit
minor marginal breakdown (i.e., gaps that are
250 µm in width) is to etch the enamel adjacent
to the restoration and, after rinsing and drying
the marginal gap area, sealing the gap with a
dentin bonding adhesive.
• However, minimal scientific evidence is
available to prove that this procedure can
prevent secondary caries.

• Amalgam tattoo is an iatrogenic lesion caused
by traumatic implantation of dental amalgam
into soft tissue.
.
Amalgam tattoo of the oral mucosa: clinical manifestations, diagnosis and treatment. Refuat Hapeh
Vehashinayim (1993) 2004 Apr;21(2):19-22, 96.
203
AMALGAM TATTOO

• Amalgam tattoo is the most common localized
pigmented lesion in the mouth .
• Clinically, amalgam tattoo
presents as a dark gray or
blue, flat macule located
adjacent to a restored tooth.
.
Amalgam tattoo of the oral mucosa: clinical manifestations, diagnosis and treatment. Refuat Hapeh
Vehashinayim (1993) 2004 Apr;21(2):19-22, 96.
204
AMALGAM TATTOO

• Most are located on the gingiva and alveolar
mucosa followed by the buccal mucosa and the
floor of the mouth.
• Microscopic examination reveals that amalgam
is present in the tissues in two forms:
• As irregular dark, solid fragments of metal or as
numerous, discrete fine, brown or black
granules dispersed along collagen bundles and
around small blood vessels and nerves.
.
Amalgam tattoo of the oral mucosa: clinical manifestations, diagnosis and treatment. Refuat Hapeh Vehashinayim
(1993) 2004 Apr;21(2):19-22, 96.
205

• Gallium based alloy
• Consolidated silver alloy system
• Indium containing alloy powder
• Fluoride containing amalgam
• Bonded amalgam
• Cermet
• Miracle mixture
207
RECENT ADVANCES

• As early as 1956, Smith and coworkers claimed that
a gallium based alloy could serve as a possible
alternative to dental amalgam.
• They found that mixing gallium with either nickel or
copper and tin produced a pliable mass that could
be condensed into a prepared cavity, which, after
setting, had physical properties suitable for a
restorative material.
Dental amalgam: An update J Conserv Dent. 2010 Oct-Dec13(4): 204–208.
208
GALLIUM BASED ALLOY:

• It uses a fluoro boric 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.
Dental amalgam: An update J Conserv Dent. 2010 Oct-Dec 13(4): 204–208.
209
CONSOLIDATED SILVER
ALLOY SYSTEM

• One problem associated with the insertion of
this material is that the alloy strain hardens, so it
is difficult to compact it adequately to eliminate
internal voids and to achieve good adaptation to
the cavity without using excessive force
210

• Powel et al (1989) added indium powder into
dispersed phase of high copper alloy and
triturate with mercury.
• They found significant difference in mercury
evaporation from amalgam.
• These were marketed as “Indisperse” & “Indiloy”
211
INDIUM CONTAINING ALLOY
POWDER

• Fluoride, being cariostatic, has been included in
amalgam to deal with the problem of recurrent
caries associated with amalgam restorations.
• Several studies concluded that a fluoride
containing amalgam may release fluoride for
several weeks after insertion of the material in
mouth.
212
FLUORIDE CONTAINING
AMALGAM

• As an increase of up to 10–20fold in the fluoride
content of whole saliva could be measured,the
fluoride release from this amalgam seems to be
considerable during the first week.
213

• An anti-cariogenic 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.
214

In recent times, adhesive resins have
been employed to bond amalgam
restorations to tooth surface
The objective is to cause
Intermingling of amalgam and
bonding resin
BONDED AMALGAM RESTORATIONS

Indications:
Extensive caries in posterior teeth when cast
restorations cannot be done
Teeth with short clinical crown height when inlays
or onlays or pin retained amalgam restorations
are not possible
Foundations for full crown restorations

MECHANISM OF BONDING:
In bonded amalgam restorations, the
bonding interface consists of tooth-adhesive
resin-amalgam
The mode of retention is by
micromechanical means due to
microscopic projections of the
resin into the amalgam

ADVANTAGES:
Allows conservative tooth preparation
Reinforces the remaining tooth structure
Better marginal seal
More cost effective
DISADVANTAGES:
Technique sensitive
Incorporation of resin into amalgam can lower down
its mechanical properties
Long term durability of the bond between amalgam
and tooth is not well known

This system consists of
- physically blending of silver alloy powder with
the glass powder in the ratio of 1:7
- Glass ionomer liquid
ADVANTAGES:
- Increase in strength
- Increase in abrasion resistance
SILVER ALLOY ADMIX GLASS
IONOMER CEMENT

• A glass ionomer cement that has been reinforced
with filler particle prepared by fusing silver particle
to glass.
• Radiopaque and grayish in color
• Used as an alternative to amalgam and composite
for posterior restoration.
220
CERMET

• Amalgam restorations have served the
profession well and will continue to do so in the
years to come.
• In terms of longevity, they are probably superior
to composite resins, especially when used for
large restorations and cusp capping.
• The new high copper single composition alloys
offer superior properties.
222

• The use of amalgam can be continued as a
material of choice if esthetics is not a concern.
223

• Phillips science of dental material 11th edi chp
17 .
• Silver amalgam in clinical practise 3rd edition chp
6
• Sturdevants art and science of operative dentistry
6th edi chp 13
• Craig’s restorative dental materials 13th edi.chp10
224
REFERENCES

• Material used in dentistry, Mahalaxmi chp 6, 12
,13 .
• Operative dentistry modern theory and practise
1st edi chapter 4.
• Bharti R, Wadhwani KK, Tikku A, Chandra
A.Dental amalgam: An update J Conserv Dent.
2010 Oct-Dec;13(4): 204–208.
 .
• Amalgam tattoo of the oral mucosa: clinical
manifestations, diagnosis and treatment. Refuat
Hapeh Vehashinayim (1993) 2004 Apr;21(2):19-
22, 96.
225

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