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Dr. Piyush Verma
Dept of Pedodontics & Preventive
Indications & contraindications
Composition of amalgam & Amalgamation reactions
Properties of amalgam
Manipulation of amalgam
Mercury toxicity & various health hazards
Repair of amalgam restorations
Dental amalgam is an alloy made by mixing mercury
with a silver tin alloy. Dental amalgam alloy is a silver
tin alloy to which varying amount of copper and small
amount of zinc has been added.
According to Skinner’s, amalgam is a special type of
alloy in which one of its constituent is mercury. In
dentistry, it is common to use the term amalgam to
mean dental amalgam.
Amalgam -- First used by Chinese. There is a mention
of silver mercury paste by Sukung (659AD)
in the Chinese medic
1578-lshitichen used 100 parts if Hg, 45 parts of Ag
and 100 parts of Sn
Liu Wen-Thai (1508) and Li Shih-Chen (1578)
discussed its formulation; 100 parts of mercury to 45
parts of silver and 900 parts of tin, trituration of these
ingredients produced a paste said to be as solid as
Introduced in 1800’s in France alloy of bismuth, lead,
tin and mercury plasticized at 100ºC poured directly
1819, Bell advocated the use of a room temperature
mixed amalgam as a restorative material, in England
1826, M.Traveau is credited with advocating the first
form of amalgam paste , in France.
Crawcour brothers introduced
amalgam to US
powdered silver coins mixed with
expanded on setting
To overcome expansion problems
G.V. Black developed a formula
for modern amalgam alloy
67% silver, 27% tin, 5% copper, 1% zinc
Black’s formula was well accepted and not much
changed for nearly sixty years.(1890-1963)
1946 - Skinner, added copper to the amalgam alloy
composition in a small amount. This served to
increase strength and decrease flow.
Traditional or conventional amalgam alloys
predominated from 1900 to 1970.
1960’s - conventional low-copper lathe-cut alloy
1962 - A spherical particle dental alloy was
introduced, by Demaree and Taylor
The work of Innes and Youdeis (1963) has led to the
development of high copper alloys.
Had longer working time, less dimensional change,
easy to finish, set faster, low residual mercury, low
creep & higher early strength
Added spherical silver copper eutectic alloy(71.9wt%
Ag and 28.1wt%Cu)particles to lathe cut low copper
amalgam alloy particles.
These alloys are called admixed alloys
1971 – Johnson designed a spherical particle alloy
having the composition 64% Ag, 26% Sn and 10%
cu by weight, and exhibiting no Sn8Hg after
1973 - first single composition spherical alloy
named Tytin (Kerr) a ternary system
(silver/tin/copper) was discovered by Kamal Asgar
of the University of Michigan
1980’s alloys similar to Dispersalloy and Tytin was
I. According to number of alloy metals:
1. Binary alloys (Silver-Tin)
2. Ternary alloys (Silver-Tin-Copper)
3. Quaternary alloys (Silver-Tin-Copper-Indium).
II.According to whether the powder consist of
unmixed or admixed alloys.
Certain amalgam powders are only made of one alloy.
Others have one or more alloys or metals physically
added (blended) to the basic alloy. E.g. Adding copper
to a basic binary silver tin alloy
III. According to the shape of the powdered
1. Spherical shape (smooth surfaced spheres).
2. Lathe cut (Irregular ranging from spindles to
3. Combination of spherical and lathe cut (admixed).
IV. According to Powder particle size.
1. Micro cut
2. Fine cut
3. Coarse cut
V. According to copper content of powder
1. Low copper content alloy - Less than 4%
2. High copper content alloy - more than 10%
VI. According to addition of Nobel metals
VII. According to compositional changes of
succeeding generations of amalgam.
First generation amalgam was that of G. V Black i.e. 3
parts silver one part tin (peritectic alloy).
Second generation amalgam alloys - 3 parts silver, 1 part
tin, 4% copper to decrease the plasticity and to increase the
hardness and strength. 1 % zinc, acts as a oxygen scavenger
and to decrease the brittleness.
Third generation: First generation + Spherical amalgam –
copper eutectic alloy.
Fourth generation: Adding copper upto 29% to original
silver and tin powder to form ternary alloy. So that tin is
bounded to copper.
Fifth generation. Quatemary alloy i.e. Silver, tin, copper
Sixth generation (consisting eutectic alloy).
According to Presence of zinc.
Zinc containing (more than 0.01%).
Non zinc containing (less than 0.01%).
INDICATIONS OF AMALGAM
Class I and class II cavities.-moderate to large restorations.
As a core build up material.
Can be used for cuspal restorations (with pins usually)
In combination with composite resins for cavities in
posterior teeth. Resin veneer over amalgam.
As a die a material.
Restorations that have heavy occlusal contacts.
Restorations that cannot be well isolated
In teeth that act as an abutment for removable appliances
INDICATIONS OF AMALGAM
Class 3 in unaesthetic areas eg.distal aspect of
Preparation is extensive with minimal facial
Class 5 lesions in nonesthetic areas especially when
access is limited and moisture control is difficult and
for areas that are significantly deep gingivally.
CONTRA INDICATIONS OF AMALGAM
Anterior teeth where esthetics is a prime concern
Esthetically prominent areas of posterior teeth.
Small –to-moderate classes I and II restorations that
can be well isolated.
Small class VI restorations
Ease of use, Easy to manipulate
Excellent wear resistance
Restoration is completed within one sitting without
requiring much chair side time.
Well condensed and triturated amalgam has good
Sealing ability improves with age by formation
of corrosion products at tooth amalgam
Relatively not technique sensitive.
Bonded amalgams have “bonding benefits”.
Slightly increased strength of remaining tooth
Minimal postoperative sensitivity.
Unnatural appearance (non esthetic)
Tarnish and corrosion
Metallic taste and galvanic shock
Discoloration of tooth structure
Lack of chemical or mechanical adhesion to the tooth
Promotes plaque adhesion
Weakens tooth structure (unless bonded).
Composition of amalgam
Conventional Amalgam Alloys: (G.V. Black’s:
Silver- tin alloy or Low copper alloy).
Low copper alloys are available as comminuted
particles (Lathe -cut and Pulverized) and spherical
Low copper composition:
Silver : 63-70%
Tin : 26-28%
Copper : 2- 5%
Zinc : 0-2%
Role of individual component
Constitutes approximately 2/3rd of
conventional amalgam alloy.
Contributes to strength of finished
Decreases flow and creep of amalgam.
Increases expansion on setting and
offers resistance to tarnish.
To some extent it regulates the setting
Second largest component and
contributes ¼th of amalgam alloy.
Readily combines with mercury to form
gama-2 phase, which is the weakest
phase and contributes to failure of
Reduce the expansion but at the same
time decreases the strength of amalgam.
Increase the flow.
Controls the reaction between silver and
Tin reduces both the rate of the reaction
and the expansion to optimal values.
Contributes mainly hardness and strength.
Tends to decrease the flow and increases the
Acts as Scavenger of foreign substances such
Helps in decreasing marginal failure.
The most serious problem with zinc is delayed
expansion, because of which zinc free alloys
are preferred now a days.
Indium/Palladium: They help to increase the
plasticity and the resistance to deformation.
HIGH COPPER AMALGAM ALLOY (COPPER
To overcome the inferior properties of low copper
amalgam alloy -- shorter working time, more dimensional
change, difficult to finish, set late, high residual mercury,
high creep & lower early strength, low fracture resistant
Youdelis and Innes in 1963 introduced high copper
content amalgam alloys. They increased the copper
content from earlier used 5% to 12%.
Copper enriched alloys are of two types:
1) Admixed alloy powder.
2) Single composition alloy powder.
I. Admixed alloy powder:
Also called as blended alloys.
Contain 2 parts by weight of
conventional composition lathe cut
particles plus one part by weight of
spheres of a silver copper eutectic alloy.
Made by mixing particles of silver and
tin with particles of silver and copper.
The silver tin particle is usually formed
by the lathe cut method, whereas the
silver copper particle is usually spherical
I. Admixed alloy powder:
Amalgam made from these powders are stronger than
amalgam made from lathe cut low copper alloys
because of strength of Ag-Cu eutectic alloy particles.
Ag-Cu particles probably act as strong fillers
strengthening the amalgam matrix.
Total copper content ranges from 9-20%.
II. Single composition alloy
It is so called as it contains
particles of same
Usually spherical single
composition alloys are used.
As lathe cut, high copper
alloys contain more than
II. Single composition alloy
1. Ternary alloy in spherical form, silver 60%, tin 25%,
2.Quaternary alloy in spheroidal form containing Silver:
59%, copper 13%, tin: 24%, indium 4%.
AMALGAMATION REACTION/ SETTING
Low copper conventional amalgam alloy
Dissolution and precipitation
Hg dissolves Ag and Sn
Ag3Sn + Hg Ag3Sn + Ag2Hg3 + Sn8Hg
Low copper conventional amalgam alloy
Gamma () = Ag3Sn
strongest phase and
corrodes the least
forms 30% of volume
of set amalgam
Ag & Sn melted together
400 ºC for 8 hours
grind, then mill to 25 - 50 microns
heat treat to release stresses of grinding
Atomizing process produces these
First liquefying the amalgam alloy, it is
sprayed through a jet nozzle under
high pressure in a cold atmosphere.
If particles are allowed to cool before
they contact the surface of chamber,
they are spherical in shape.
If they are allowed to cool on contact
with the surface they are flake shaped.
ADA specification No.1 for amalgam lists following
physical properties as a measure of quality of the
Modulus of elasticity
Amalgam is strongest in compression and weaker in
tension and shear
The prepared cavity design and manipulation should
allow for the restoration to receive compression forces
and minimum tension and shear forces.
The compressive strength of a satisfactory amalgam
restoration should be atleast 310 MPa.
Compressive Strengths of Low-Copper and High
Amalgam Compressive Strength
1 h 7 day
Low copper 145 343
Admix 137 431
Amalgam is much weaker in tension
Tensile strengths of amalgam are only a fraction of
their compressive strengths
Cavity design should be constructed to reduce tensile
stresses resulting from biting forces
High early tensile strengths are important – resist
fracture by prematurely applied biting forces
Product Tensile strength (Mpa)
15min 7 days
LOW COPPER ALLOYS
a) Lathe cut
HIGH COPPER ALLOYS
Tensile strengths of amalgam
The factors affecting strength of amalgam are:
Amalgam looses 15% of its strength when its
temperature is elevated from room temperature to
looses 50% of room temperature strength when
temperature is elevated to 60OC e.g. hot coffee or
Effect of trituration on strength depends on the type
of amalgam alloy, the trituration time and the speed of
Either, under trituration or over-trituration decreases
the strength for both traditional and high copper
More the trituration energy used, more evenly
distributed are the matrix crystals over the amalgam
mix and consequently more the strength pattern in the
Excess trituration after formation of matrix crystals
will create cracks in the crystals, lead to drop in
strength of set amalgam
3) Mercury Content:
Low mercury alloy content, contain
stronger alloy particles and less of the
weaker matrix phase, therefore more
Mercury is too less -- dry, granular mix,
results in a rough, pitted surface that
If mercury content of amalgam mix is
more than 53-55%, causes drop of
compressive strength by 50%.
4) Effect of condensation:
For lathe-cut alloys
Greater the condensation pressure, the higher the
Higher condensation pressure is required to minimize
porosity and to express mercury from lathe-cut
For spherical alloys
Amalgams condensed with lighter pressure produce
5) Effect of Porosity:
Can be due to
Insertion of too large increments into the cavity,
Delayed insertion after trituration,
Non-plastic mass of amalgam.
Facilitate stress concentration, propagation of cracks,
corrosion, and fatigue failure of amalgam restoration.
6) Effect of rate hardening
Patient may be dismissed from the dental chair within 20
min, rate of hardening of the amalgam is of considerable
At the end of 20 min, compressive strength – 6% of the 1
ADA specification stipulates minimum compressive
strength of 80 Mpa at 1 hr
Clinical significance -- Patient should be cautioned not
to subject the restoration for high biting force for 8 hrs
after placement– 70% of its strength is gained
Modulus of elasticity
High copper alloys tend to be stiffer than low copper
When rate of loading increased, values of approx 62
Gpa have been obtained
When mercury is combined with amalgam it
undergoes three distinct dimensional changes.
Stage -1: Initial contraction, occurs for about 20
minutes after beginning of trituration. Contraction
results as the alloy particles dissolve in mercury.
Contraction, which occurs, is no greater than 4.5 µcm.
Stage -2: Expansion- this occurs due to formation and
growth of the crystal matrix around the unconsumed
Stage -3: Limited delayed contraction.
Factors that affect the dimensional changes:
1) Particle size and shape:
More regular the particle shape, more smoother the
Faster and more effectively the mercury can wet the
powder particles and faster amalgamation occurs in all
stages with no apparent expansion.
More mercury , more will be the expansion, as more
crystals will grow.
Low mercury: alloy ratio favors contraction
During trituration, if more energy is used for
manipulation, the smaller the particles will become ,
mercury will be pushed between the particles,
More the condensation pressure used during
condensation, closer the particles are brought
together; more mercury is expressed out of mix
inducing more contraction.
Moisture contamination (Delayed Expansion):
Certain zinc containing low copper or high copper
amalgam alloys which get contaminated by moisture
during manipulation results in delayed expansion or
Occur 3-5 days after insertion and continues for months.
Zinc reacts with water, forming zinc oxide and hydrogen
Complications that may result due to delayed
Protrusion of the entire restoration out of the cavity.
Increased micro leakage space around the restoration.
Increased flow and creep.
Pulpal pressure pain.
Such pain may be experienced 10-12 days after the
insertion of the restoration
Flow and Creep:
Time dependent plastic
When a metal is placed under
stress, it will undergo plastic
The high copper alloys, as
compared with conventional silver
tin alloys, usually tend to have
lower creep values.
Factors influencing creep:
A) Phases of amalgam restorations
Creep rates increases with larger 1 volume fraction
and decreases with larger 1 grain sizes.
2 is associated with high creep rates.
In absence of 2, low creep rates in single composition
alloy may be due to phase which act as barrier to
deformation of 1 phase.
Greater compressive strength will minimize creep
Low mercury: alloy ratio, greater the condensation
pressure and time of trituration, will decrease the
Excessive corrosion can
Reduced marginal integrity.
Loss of strength.
Release of metallic products
in to the oral environment.
Phases in decreasing order of corrosion resistance
Low copper amalgam system:-
Most corrodible phase is tin-mercury or 2 phase.
Neither the nor the 1 phase is corroded as easily.
The corrosion results in the formation of tin
oxychloride, from the tin in 2 and also liberates Hg.
Sn7-8Hg + 1/202 + H2O + Cl- Sn4 (OH) 6 Cl2 + Hg
Reaction of the liberated mercury with unreacted
can produce additional l and 2 (Mercuroscopic
Results in porosity and lower strength.
The high copper admixed and
unicomposition alloy :-
Do not have any 2 phase in the final set mass
The η phase formed has better corrosion resistance.
However, is the least corrosion resistant phase in high
Corrosion product CuCl2.3Cu (OH)2 has been associated
with storage of amalgams in synthetic saliva.
Cu6Sn5 + 1/202 +H2O + Cl- CuCl2.3Cu (OH)2 + SnO.
Types of Corrosion:
1) Galvanic corrosion:
Dental amalgam is in direct contact
with an adjacent metallic
restoration such as gold crown
2) Crevice Corrosion:
Local electrochemical cells may arise
whenever a portion of amalgam is
covered by plaque on soft tissue.
The covered area has a lower oxygen
and higher hydrogen ion
concentration making it behave
anodically and corrode.
Regions within the dental
amalgam that are under stress
display a greater probability for
corrosion, thus resulting in
For occlusal dental amalgam
greatest combination of stress
and corrosion occurs along the
PROPORTIONS OF ALLOY TO
Correct proportioning of alloy and mercury-
essential for forming a suitable mass of amalgam
Some alloys require mercury – alloy ratios in excess
of 1:1 (Eames technique)
whereas others use ratios of less than 1:1 with the
percentage of mercury varying from 43% to 54%.
dispensers for alloy & mercury
have been used in the past
Capsules with pre proportioned
amounts of alloy & mercury
have been substituted
Cross section sketch of a disposable capsule
containing amalgam alloy & mercury
SIZE OF MIX
Manufacturers commonly supply capsules containing
400, 600, or 800 mg of alloy and the appropriate
amount of mercury.
For large size cavities - capsules containing 1200 mg of
all0y are also available.
Process of mixing the amalgam alloy particles with
Originally, the alloy and mercury were mixed, and was
triturated by hand with a mortar and pestle
Mechanical amalgamation saves time and standardizes
Mechanical amalgamators are available in the following
Low speed: 32-3400 cpm.
Medium speed: 37-3800 cpm.
High speed: 40-4400 cpm.
Spherical/irregular low-copper alloys – triturated at
High copper alloys – high speed
Time of trituration on amalgamation ranges from 3-30
seconds. Variations in 2-3 seconds can also produce a
under or over mixed mass.
Over-trituration: Alloy will be hot,
hard to remove from the capsule,
shiny wet and soft.
Under-trituration: Alloy will be
dry, dull and crumbly; will crumble
if dropped from approx 30 cm.
Normal Mix: Shiny appearance
separates in a single mass from the
Objectives of Trituration are:
To achieve a workable mass of amalgam within a
To remove the oxide layer
To pulverize pellets into particles, that can be easily
attacked by the mercury.
To reduce particle size
To keep the amount of 1 or 2 matrix crystal as
minimal as possible, yet evenly distributed
1) Working time & dimensional change
All types of amalgam, spherical or irregular –
decreases with overtrituration
Overtrituration – slightly higher contraction for all
types of alloys
2) Compressive & tensile strength
Irregular shaped alloys – increase by overtrituration
Spherical alloys -- greatest at normal trituration time
Refers to the incremental placement
of the amalgam into the prepared
cavity and compression of each
increment into the others
Amalgam should be condensed into
the cavity within 3 min after
Aims of condensation
Adapt amalgam to the margins, walls and line angles
of the cavity.
Minimize voids and layering between increments
within the amalgam.
Develop maximum physical properties.
Remove excess mercury to leave an optimal alloy:
Purpose of Condensation
To get a continuous homogenous mass that is well
adapted to all margins, walls and line angles.
Best carried out using hand instruments.
Hand condenser :
Should allows a operator to
readily grasp it & exert a force
Size of condenser tip &
direction & magnitude of the
force placed, depends on the
type of amalgam alloy selected
Irregular shaped alloys –
Condensers with relatively small tip, 1 to 2 mm
High condensation forces in vertical direction
As much mercury-rich mass as possible should be
Spherical amalgam alloys
Condensers with large tips are used
Condensed in lateral direction
High copper spherical amalgams – vertical & lateral
direction condensation with vibration
Condensation pressure – load of 15 lb is
recommended to be applied to each increment
Useful for condensing irregular shaped alloys when
high condensation forces are required
Need was eliminated with the advent of spherical
Tend to lead to unreliable condensation as well as
generation of heat and mercury vapor, both of which
Causes the release of considerable quantities of
mercury vapor in the dental office
SPEED OF PLACEMENT
Once amalgam is triturated, phase formation
commences and the setting reaction is underway.
Amalgam must be placed in a plastic state
No amalgam should be placed more than 3 minutes
after the start of mixing.
Attempting to condense a partly set amalgam into a
cavity will result in
Reduced marginal seal and
A weak restoration.
First Burnish (Pre-carve Burnish)
Carried out using a large burnisher
for 15 seconds
Use light force and move from the
center of the restoration outwards to
Objectives of precarve burnishing :
Continuation of condensation, further reduce the size
and number of voids on the critical surface and
marginal area of the amalgam.
Brings any excess mercury to the surface, to be
discarded during carving.
Adapt the amalgam further to cavosurface anatomy.
Using remaining enamel as a guide,
carve gently from enamel towards the
center and recreate the lost anatomy
of the tooth.
Amalgam should be hard enough to
offer resistance to carving instrument
A scarping or "ringing" (amalgam
crying) should he heard.
If carving is started too soon,
amalgam will pull away from margins.
Objectives of carving :
To produce :
A restoration with no underhangs
A restoration with the proper physiological contours.
A restoration with minimal flash.
A restoration with adequate, compatible marginal ridges.
A restoration with proper size, location, extend and
interrelationship of contact areas.
Final Burnish (Post carve burnishing)
Following carving, check the occlusion
and carry out a brief final burnish.
Use a large burnisher at a low load and
burnish outwards towards the margins
Heat generation should be avoided
If temp raises above 60C, causes release of mercury
accelerates corrosion & fracture at margins
Finishing & Polishing
Finishing can be defined as the process, which continues
the carving objectives, removes flash and overhangs and
corrects minimal enamel underhangs.
Polishing is the process which creates a corrosion resistant
layer by removing scratches and irregularities from the
Can be done using descending grade abrasive, eg. rubber
mounted stone or rubber cups.
A metallic lusture, is always done with a polishing agent
(precipitated chalk, tin or zinc oxide).
Objective of finishing and polishing :
Removal of superficial scratches and irregularities
Minimizes fatigue failure of the amalgam under the
cyclic loading of mastication
Minimizes concentration cell corrosion which could
begin in the surface irregularities
Prevents the adherence of plaque
Usually, 24 hours should pass after amalgam insertion
before any finishing and polishing commences.
However, some new alloys can be polished after 8-12
hours still others require only a 30-minute wait after
Primary retention form
Mechanical locking of
inserted amalgam into
surface irregularities to
allow good adaptation
Preparation of vertical
walls that converge
Primary resistance form
For tooth :
Maintaining as much unprepared tooth structure as
Having pulpal & gingival walls perpendicular to
Having rounded internal prepartaion angles
Removing unsupported & weakened tooth structure
Placing pins into the tooth as a part of final stage of
Primary resistance form
For amalgam :
Adequate thickness – 1.5 -2 mm in areas of occlusal
contact, 0.75 mm in axial areas
Marginal amalgam of 90 degrees or greater
Box like preparation form
Rounded axiopulpal line angles in class II
Secondary resistance & retention
resistance/retention forms are
present in tooth, additional
preparation is indicated
Such features include :
Placement of grooves, locks,
coves, pins, slots or amalgam pins
Larger the tooth preparation,
greater the need of secondary
resistance & retention forms
Amalgams have been used for 150 years
About 200 million amalgams are inserted each year in
the United States and Europe
Concern -- mercury in dental amalgam may pose
threats to the health of patients, to the health of
dental care providers and to the environment.
Mercury is available in 3 forms:
Elemental mercury (liquid or vapor).
Absorbed relatively poorly across skin or mucosa.
Most mercury becomes charged (ionized) before it
reaches the blood.
Ionized mercury is excreted well through kidneys and
There is no known risk to patients from liquid
Less benign -- rapidly absorbed into the blood via the
lungs , remains uncharged and therefore highly lipid
soluble, for several minutes.
Can cross the blood-brain barrier where it becomes
charged and exists in extra cellular fluid of the brain
and returns into the blood much more slowly.
High tissue levels- can lead to impaired brain
function, insanity and death may occur at 4000 g/kg.
Low tissue levels- can lead to restlessness, tremors,
and loss of concentration.
Inorganic compounds of mercury
S0urce – Drinking water, food
Amalgam contains several different inorganic mercury
They are of low or very low toxicity and are apparently
harmless when swallowed.
Poorly absorbed, do not accumulate in body tissues
and are well excreted.
Organic compounds of mercury
Source -- Drinking water, food (sea food)
Some organic compounds of mercury are highly toxic
at low concentrations
But none are known to form in the oral environment
through dental amalgam use.
CONCENTRATIONS OF MERCURY
The Occupational Safety & Health Administration
(OSHA) has set a TLV of 0.05 mg/m3 as the maximum
amount of mercury vapor allowed in the work place.
Average Daily dose of mercury from dental amalgam
for patients with more than 12 restored surfaces has
been estimated at up to 3 g.
CONCENTRATIONS OF MERCURY
Clarkson TW (1997) --
Lowest dose of mercury that elicits a toxic reaction –
3to7 g/kg body weight
Paresthesia -- 500 g/kg body weight
Ataxia -- 1000 g/kg body weight
Joint pain -- 2000 g/kg body weight
Hearing loss & death -- 4000 g/kg body weight
CONCENTRATIONS OF MERCURY
Mercury release has been quantified for a number of
Placement of amalgam restoration: 6-8 g.
Dry polishing: 44 g.
Wet polishing: 2-4 g.
Amalgam removal under water spray & high
velocity suction: 15-20 g
CONCENTRATIONS OF MERCURY
The release of mercury is:
Greater for low-copper amalgams, because of
corrosion related loss of tin and increased porosity.
Greater from Unpolished surfaces
Increased by tooth brushing, which removes a
passivating surface oxide film-although this re-forms
Mercury in urine
Body cannot retain metallic mercury, but passes it
Skare I et al (1990) –
urine mercury level peak at 2.54 g/L 4 days after
placing amalgam restorations, return to zero after 7
On removal of amalgam, urine mercury levels reach a
maximum value of 4g/L, return to zero after 7 days
Mercury in blood
Maximum allowable level of mercury in blood is 3
Chang SB et al(1992) showed that freshly placed
amalgam restorations elevated blood mercury
levels to 1 to 2 g/L
As with urine mercury levels, there is first an
increase of around 1.5 g/L, which decreases in
about 3 days
Ott KH et al (1996) monitored blood mercury levels for 1
year, showed that patients with amalgams had lower than
average blood mercury level (0.6 g/L ) than patients
without amalgams (0.8 g/L )
Mackert JR et al(1997) indicated higher blood
mercury levels in dentists, stated that -
elevated blood mercury levels may relate to mercury
spills in the office
Both blood & serum mercury levels seem to correlate
best with occupational exposure, not with number of
amalgam & length of time with amalgam in place
Sensitivity to amalgam restorations
Skin lesions being more common than oral lesions.
An urticarial rash may appear on the face and limbs and
this may be followed by dermatitis.
Long- term response -- oral lichen planus or lichenoid
reactions with erosive areas on the tongue or buccal
mucosa adjacent to an amalgam restoration.
Possible causes are:
Scraps of amalgam may fall into open surgical or
Excess amalgam may be left in the tissues following
sealing the apex of a root canal with a retrograde
Pieces of amalgam may be forced into the mucosa.
Sources of Mercury Exposure in
Dental amalgam raw materials being stored for use.
Mixed but unhardened dental amalgam during
triturations, insertion and intraoral setting.
Dental amalgam scrap that has insufficient alloy to
completely consume the mercury present.
Dental amalgam undergoing finishing and polishing
Dental amalgam restoration being removed.
DENTAL MERCURY HYGIENE
Recommendations from the ADA include the following:
The work place should be well ventilated, with fresh air
exchange and outside exhaust
Use only precapsulated alloy, discontinue use of Bulk
mercury & bulk alloy
Avoid the need to remove excess mercury before or
during packing by selecting an appropriate alloy:
Use an amalgamator with a completely enclosed arm.
Mercury and unset amalgam should not be touched by
the bare hands.
Floor coverings should be non absorbent & easy to
Spilled mercury should be cleaned up using trap
bottles, tape or freshly mixed amalgam to pick up
Do not use a house hold vaccum cleaner to clean
Skin accidentally contaminated by mercury should be
washed thoroughly with soap and water.
If a mercury hygiene problem is suspected, personnel
should undergo urine analysis to detect mercury levels
Remove professional clothing before leaving the work
Scrap amalgam disposal
In a tightly closed container
Under radiographic fixer solution
Dispose mercury contaminated items in sealed bags
Donot dispose mercury contaminated items in
medical waste containers or bags or along with the
waste that will be incenerated
CLINICAL TECHIQUES TO ENHANCE
1) Copal resin varnish:
Apply two thick coats to the cavity walls and margins
before placing the amalgam and it will gradually
dissolve, beginning at the cavosurface, over 2-3
As the varnish dissolves out, the gap will be filled with
corrosion products from the amalgam and dissolution
of the varnish will cease.
CLINICAL TECHIQUES TO ENHANCE
2) Glass-ionomer linings
Placed under an amalgam will seal the dentinal
tubules and release small quantities of fluoride
Will not affect enamel margins or enhance the seal at
CLINICAL TECHIQUES TO ENHANCE
3) Oxalate solutions :
Such as potassium oxalate, can be applied to the
cavity surface to reduce the permeability of the tubules
and possibly seal the dentine.
The crystals this deposited will not wash out but will
allow deposition of corrosion products.
1) BONDED AMALGAMS
During the 1990’s some clinicians began to routinely
bond amalgam restorations to enamel and dentine
After preparation of the cavity, enamel and dentine
etched using a conventional etchant, a chemically
cured resin-bonding agent applied to the walls of the
Amalgam is immediately condensed into the cavity
before the resin bond has cured
Advantages of Bonded-Amalgam :
Conservation of tooth structure.
Fracture strength was as high as for composites
Decreased marginal leakage in class 5 restorations
compared with unbonded amalgams
Some operators claim elimination of post-insertion
Reduces incidence of marginal fracture and recurrent
Can be done in single sitting.
Allows for amalgam repairs.
Disadvantages of Bonded-Amalgam :
Clinical difficulty of application of more viscous bonding
Lightly filled resin bonding agents tend to pool at the
gingival margin resulting in a higher potential for micro
Carving is difficult.
Requires practitioner to adapt to new technique.
Increases cost of amalgam restorations.
2) Gallium alloys
Mercury free metallic restorative materials proposed as
substitute for mercury containing amalgam are gallium
containing materials and pure silver and/or silver based
Puttkammer (1928), suggested the use of gallium in
Attempts to develop satisfactory gallium restorative
materials were unsuccessful until Smith et al in 1956,
showed that improved Pd-Ga and Ag-Ga materials has
physical and mechanical properties that were similar to or
even better than those of silver amalgam.
ADVANTAGES OF GALLIUM BASED ALLOYS:
Good marginal seal by expanding on solidification.
The compressive and tensile strength increases with
time comparable with silver amalgam
Creep value are as low as 0.09%
It sets early so polishing can be carried out the same
They expand after setting therefore provides better
After mixing, the alloy tends to adhere to the walls of
capsule, thus difficult to handle.
Moreover, by adding few drops of alcohol, the problem
of sticking can be minimized.
Biologic considerations of Gallium based alloys :
Surface roughness, marginal discoloration and fracture
were reported. With improvement in composition,
these defects were reduced but not eliminated
Could not be used in larger restorations as the
considerable setting amount of expansion leads to
fracture of cusps and post operative sensitivity.
Cleaning of instruments tips is also difficult
Less popular because it is costlier than amalgam.
3) Fluoride releasing amalgam
Have been shown to have anticaries properties sufficient to
inhibit the development of caries in cavity walls.
Concentration of fluoride is sufficient to enhance
Tviet and Lindh (1980) -- greatest concentration of
fluoride i.e. about 4000µg/mL in enamel surfaces exposed
to fluoride-containing amalgams were found in the outer
0.05µm of the tissue.
In dentin, the greatest concentrations, i.e. about
9000µg/ml were found at a depth of 11.5µm.
However, this release of fluoride decreases to minor
amounts after 1 week.
Forsten L (1976) -- fluoride released from amalgams
loaded with soluble fluoride salts was detectable
within the first month and thereafter fluoride was not
released in measurable amounts.
Garcia Godoy et al( 1990) – fluoride release can
continue as long as 2 years (but at a much lower rate
than that for GIC).
Marginal fracture of amalgam
Referred to as “Marginal
breakdown”, “ditching”, and
Regardless of the type of
amalgam, marginal fracture
increases with time
The rate of increase is greater for
CLINICAL TECHNIQUES TO PREVENT
Excess amalgam, left lying over the occlusal or
proximal surface should be carved correctly
The angle of the carvo-surface margin should be
greater than 70º and the cavity should be designed to
allow for this.
On completion of packing, burnish the margins both
before and after carving to improve marginal
Repair Of Amalgam Restorations
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
The strength of the bond between the new and the old
amalgam is important
Factors contributing to strength of
Presence of porosity and phase at the junction.
Contamination of the surface of the existing amalgam.
Corrosion & contamination from saliva.
Marginal Adaptation And Seal :
Lack of marginal adaptation in first few weeks
May be associated with marginal deterioration,
accumulation of debris, recurrent caries, post-
restoration sensitivity or pulpal reactions.
After 48 hours, “self sealing” occurs
Low-copper amalgam -- seal within 2-3 months
High-copper amalgams -- corrode less and therefore
take 10-12 months to provide a comparable seal.
In 1845, American Society of Dental Surgeons condemned
the use of all filling material other than gold as toxic,
thereby igniting "first amalgam war'. The society went
further and requested members to sign a pledge refusing to
In mid 1920's a German dentist, Professor A. Stock started
the so called "second amalgam war". He claimed to have
evidence showing that mercury could be absorbed from
dental amalgam, which leads to serious health problems.
He also expressed concerns over health of dentists, stating
that nearly all dentists had excess mercury in their urine.
"Third Amalgam War' began in 1980 primarily
through the seminars and writings of Dr.Huggins, a
practicing dentist in Colorado.
He was convinced that mercury released from dental
amalgam was responsible for human diseases affecting
the cardiovascular system and nervous system
Also stated that patients claimed recoveries from
multiple sclerosis, Alzheimer’s disease and other
diseases as a result of removing their dental amalgam
There are certain advantages inherent with amalgam
such as technique insensitive, excellent wear
resistance, less time consuming, less expensive which
are not present in the newer materials, these factors
will continue to make amalgam the material of choice
for many more years to come.
Stephen. C. Boyne, Duane. F. Taylor, “Dental materials”, The Art and
Science of operative Dentistry, Mosby 3rd Edition 1997:219-235.
Kenneth J Anusavice, D.M.D., PhD., “Philip’s Science of Dental
materials”, W.B. Saunders Company, 10th Edition 1996: 361-410.
M.A. Marzouk D.D.S. M.S.D. et al, “Operative Dentistry Modern theory
and Practice”, IEA inc 1997:105-120.
Craig, “Science of Dental Materials”.
Jagannathan, K, “Cruise for Gamma 2 Free Mercury”, “Materials in
Restorative Dentistry”, MADC & H, 1998 66-69.
John F. McCabe, Angus W.G. Walls, “Dental Amalgam”, Applied Dental
Materials, Blackwell Science, 8th Edition, 1998:157-168
Satish Chandra, Shaleen Chandra, “Dental Amalgam”, A Text Book of
Dental materials with Multiple Choice Questions”, Jaypee Brothers; 1st
Vimal. K. Sikri, “Silver Amalgam”, Text book of Operative Dentistry”
CBS publishers, 1st Edition 2002, 204-242.