Dental amalgam is an alloy used in dentistry as a filling material. It contains mercury and other metals such as silver, tin, and copper. Amalgam is used for fillings in back teeth and to restore crowns. There are different types of amalgam based on their composition and particle shape. The properties and performance of amalgam depend on factors like mercury content, alloy composition, trituration, and condensation technique. While amalgam is inexpensive and durable, it also has disadvantages like poor aesthetics, potential toxicity, and marginal breakdown over time.

1. Presented by--
Hemam Shankar Singh

2. An amalgam is a special type of alloy that
contains mercury as one of its constituents.

3. 1. As permanent filling material for
 Class I and class II cavities, and
 Class V cavities where esthetics is not important
2. In combination with retentive pins to restore a
crown
3. For making dies
4. In retrograde root canal fillings
5. As a core material

4. 1. Silver
2. Tin
3. Copper
4. Zinc
5. Platinum
6. Palladium
7. Indium

5. 1. Based on copper content-
-low copper alloys
-high copper alloys
2. Based on zinc content
-zinc containing (more than 0.01% Zn)
-zinc free (less than 0.01% Zn)
3. Based on shape of the alloy particle
-lathe cut alloys
-spherical alloys
-spheroidal alloys
4. Based on number of alloyed metals
-binary
-ternary
-quaternary
5. Based on size of alloy
-microcut
-macrocut

6. low copper high copper
lathe-cut lathe-cut spherical spherical
or spherical 2/3 1/3
Admixed unicomposition
Silver 63-73% 40-70% 40-65% 40-60%
Tin 26-29% 26-30% 0-30% 22-30%
Copper 2-5% 2-30% 20-40% 13-30%
Zinc 0-2% 0-2% 0 0-40%
Composition

7.  Silver:
 major element in the reaction
 whitens the alloy
 Decrease the creep
 Increase the strength
 Increase the expansion on setting
 Increase the tarnish resistance in the resulting amalgam
 Tin:
 Controls the reaction between silver and mercury
 Reduces strength and hardness
 Reduces the resistance to tarnish and corrosion
 Copper:
 Increases hardness and strength
 Increases setting expansion

8.  Zinc:
 Acts as a scavenger or deoxidizer
 It causes delayed expansion
 Platinum
 Hardens the alloy and increases resistance to
corrosion
 Palladium:
 Hardens and whitens the alloy
 Indium:
 When added reduces mercury vapor and improves
wetting

9. 1. Microleakage
 Dental amalgam has the ability of self sealing to
microleakage
 This may be caused by corrosion products that form in
the interface between the tooth and the restoration,
sealing the interface and thereby preventing
microleakage
 The space between the alloy and the tooth permits
microleakage of electrolyte, and a classic concentration
cell (crevice corrosion) process results.
 The common corrosion products found with traditional
amalgam alloys are oxides and chlorides of tin

10. 2. Dimensional stability
• According to ADA Specification No. 1 amalgam can neither
contract nor expand more than 20µm/cm at 37ºC between 5
minutes to 24hrs.
• Severe contraction can lead to microleakage and to secondary
caries
• Excessive expansion can produce pressure on the pulp and
postoperative sensitivity
 Moisture contamination
moisture contamination during
manipulation causes delayed
expansion due to reaction between
water and zinc present in the
amalgam alloy
this expansion starts after 3-5 days,
reaching values greater than 400µm
(4%)
DIMENSIONALCHANGEINµm/cm

11. 3. Strength
i. Effect of trituration
undertrituration or overtrituration decreases the strength for
both low and high copper amalgams as it affects the reaction
between the matrix phase and the alloy particles
ii. Effect of mercury content
sufficient Hg should be mixed with the alloy to wet each particle
of the alloy
increase in mercury content above approximately 54-55%
markedly reduced the strength
low mercury content may result in a rough, pitted surface that
may lead to corrosion
iii. Effect of condensation
» lathe-cut alloy
greater the condensation pressure, higher the compressive
strength
higher condensation pressure are required to minimized
porosity and to express mercury from lathe-cut amalgam
» spherical alloy
condensation with light pressure produces adequate
strength

12. iv. Effect of porosity
• Voids and porosity are possible factors influencing the
compressive strength of hardened amalgam
• It is related to number of factors including plasticity of the
mix amalgam
• Plasticity decreases over time from the end of trituration
• Undertrituration also decreases plasticity
• Decrease plasticity causes greater porosity resulting in
lower strength of the amalgam
TABLE: comparison of compressive strength of low-copper and high-copper
amalgams
compressive tensile
strength (Mpa) strength—24hr
Amalgam 1hr 7Day (Mpa)
Low copper 145 343 60
Admixed 137 431 48
Single composition 262 510 64

13. 4. Creep
creep rate has been found to correlate with marginal breakdown
of traditional low-copper amalgams, i.e. higher the creep greater
the degree of marginal deterioration
different alloy have different creep value as shown below
TABLE: comparison of creep of low-copper and high-copper
amalgams
Amalgam creep (%)
low copper 2.0
admixed 0.4
single composition 0.13

14. A B

15. 1. Mercury : alloy ratio
2. Trituration
3. Condensation
4. Carving and finishing

16. Mercury : alloy ratio
 Up until the early 1960s it was necessary to use an amount of
mercury considerably in excess of that desirable in the final
restoration to achieve smooth, plastic amalgam mixes.
 because of deleterious effects of an excessive mercury content
procedures were employed to reduce the amount of mercury
left in the restoration to an acceptable level.
 So, in 1959 a new technique was introduced known as
minimal mercury technique , or Eames technique in recognition of
the dentist who developed the concept.
 According to Eames technique mercury should be 50% by
weight or in 1:1 ratio.

17. Figure: Hardening data (BHN= Brinell hardness number) for two alloys (A
and B ) mixed at low, medium, and high settings. Broken lines at 1.0 and
4.5 represent working and carving consistency, respectively.

18.  Under triturated
mix of amalgam.
Such a mix are
grainy and has
low strength and
low resistance to
tarnish.

19.  Aims
 To adapt it to the cavity wall
 Remove excess Hg
 Reduce voids
 Proper condensation increases the
strength and decreases the creep of the
amalgam.
 Failure to use a matrix can result in a
poorly condensed and weak
restoration.
 Mixed materials is packed in
increments.
 Condensation is started at the centre,
and the condenser point is stepped
sequentially towards the cavity walls

20.  Carving and burnishing is done to reproduce the tooth
anatomy and to get a smooth surface respectively
 Carving should not be started until the amalgam is
hard enough to offer resistance to carving instrument
 A scrapping or ringing sound should be heard when it
is carved
 Polishing is also required as it minimizes corrosion and
prevents adherence of plaque
 Final polishing should be delayed at least 24hrs after
condensation

21.  Mercury is absorbed through
 skin, lungs or GIT, most commonly by lungs i.e. vapor phase
 Penetration into the tooth from the restoration
 The threshold limit value of mercury in the air is
0.05mg of Hg/m³ of air, this is the vapor level to which
the average worker can be safely exposed for 8hrs a
day and 5days per week
 Increase in exposure causes toxicity which may
associate with signs and symptoms
 The lowest level of total blood Hg at which the earliest
nonspecific symptoms occur is 35ng/mL
 Weakness, fatigue, anorexia, weight loss, insomnia,
irritability, shyness, dizziness, and tremors in the
extremities are the recognizable symptoms of chronic
Hg poisoning

22.  Mercury should be kept in an unbreakable container that are
tightly sealed
 Spills and leak should be cleaned up immediately by
approved methods
 Water spray and high-volume evacuation should be used when
removing an old amalgam restoration or finishing a new
one
 Glasses and disposable face mask should be worn to reduce
hazards associated with flying particles and the inhalation
of amalgam dust
 Amalgamators that completely enclose the arms and
amalgam capsule during trituration should be used
 Since mercury vaporizes at room temperature, operatories
should be well ventilated to minimize the mercury level in the
air
 Use of gloves is a must

23. 1. Reasonably easy to insert
2. Not overly technique sensitive
3. Maintains anatomic form well
4. Has adequate resistance to fracture
5. After a period of time prevents marginal
leakage
6. Have reasonably long service life
7. Cheaper than other alternative posterior
restorative material like cast gold alloys

24. 1. Color does not match tooth structure
2. More brittle and can fracture if incorrectly
placed
3. They are subject to corrosion and galvanic
shock
4. Show marginal breakdown
5. Do not bond to tooth structure
6. Risk of Hg toxicity