Dental amalgam is an alloy used as a dental restorative material. It consists of mercury combined with other metals like silver, tin, and copper. Amalgam undergoes a setting reaction when mixed with liquid mercury to form a hard material. It is indicated for restoring cavities. While it has advantages like strength and cost-effectiveness, it lacks esthetics and can release low levels of mercury vapor. Modern amalgams have improved properties like reduced creep and shrinkage. Careful manipulation is required to achieve optimal physical properties and reduce risks.

1. DENTAL AMALGAM

2. DEFINITION
“Amalgam is a special type of alloy in
which mercury is one of the
component”

3.  Mercury is liquid at room temperature , it
reacts with other metals that are in solid
state, to form a plastic mass, which can be
conveniently packed into a prepared
tooth preparation. This plastic mass
hardens by the formation of solid reaction
product phases.

4. INDICATIONS
 As a permanent restorative material in
class I, class II, class V, class VI caries
 Cuspal restorations
 Pin retained restorations
 As a foundation
 Post-endodontic access filling and core
 Die preparation
 Retrograde root canal filling material
 Teeth with questionable prognosis
(interim restoration)
 Economic status

5. CONTRAINDICATIONS
 Esthetics
 Extensive loss of tooth structure
 Small class I and class II cavities

6. ADVANTAGES
 Ease of use
 High compressive strength
 Excellent wear resistance
 Favorable long-term clinical results
 Economic
 Can be bonded to tooth structure
 Self-sealing ability

7. DISADVANTAGES
 Lack of esthetics
 Less conservative
 Non-insulating
 Corrosion and galvanism
 Lack of reinforcement of weakened tooth
structure
 Difficulty in restoring proper tooth
anatomy

8. COMPOSITION
 (I) LOW COPPER ALLOYS:
Silver -- 63-70%
Tin -- 26-28%
Copper -- 2-5%
Zinc-- 0 -2%
Setting reaction :
Ag3Sn + Hg = Ag2Hg3 + Sn8Hg+ Ag3Sn
(unreacted)

9.  (II) HIGH COPPER ALLOYS :
Silver -- 69%
Tin -- 17%
Copper -- 13%
Zinc -- 1%
Setting reaction :
Ag3Sn + Ag-Cu + Hg = Ag2Hg + Sn8Hg
+Ag3Sn (unreacted)

10. CLASSIFICATION
Based on copper content :
 Low copper alloy -- < 6% copper
(conventional alloy)
 High copper -- 6-30% copper
(1) admixed alloy
(2) single composition alloy
Based on zinc content :
(1) zinc containing alloy -- > 0.01% zinc
(2) zinc free alloy -- < 0.01 zinc

11. Based on shape of alloy particles :
(1) lathe cut alloy
(2) spherical alloy
(3) admixed alloy
Based on size of alloy particles :
(1) microcut
(2) fine-cut
(3) coarse-cut

13. Based on number of alloy metals :
(1) binary alloy (silver-tin)
(2) ternary alloy (silver-tin-copper)
(3) quaternary alloy
(silver-tin-copper-indium)
Based on presence of noble metals
:
(1) noble metal alloys (palladium,
platinum, gold)
(2) non-noble metal alloys

14.  Based on the generations :
(1) Basic silver-tin alloy
(2) Low copper alloys (silver, tin, copper and
zinc, Cu<4%)
(3) High copper alloys (admixed alloys)
(4) High copper alloys (single composition
alloys)
(5) Gallium based alloys
(6) Noble metal alloys

15. FUNCTION OF EACH CONSTITUENT
SILVER
Whitens the alloy
Decreases creep
Increases strength
Increases the expantion on setting
Increases resistance to tarnis

16. TIN
Reduce tarnish and corrosion
Reduce strength and hardness
COPPER
Increases hardness and strength
Increases setting expansion

17. ZINC
Acts as a deoxidizer and scavenger
Causes delayed expansion in amalgam

18. PROPERTIES
DIMENSIONAL CHANGES :
 Most modern amalgams exhibit a very minor
degree of contraction or expansion on
hardening if they are properly handled
By ensuring proper mercury
content, plasticity of the mix, good
condensation, burnishing, the amalgam can
be well adapted to the prepared cavity
Excessive contraction can lead to
microleakage and secondary caries
Excessive expansion can produce pressure on
the pulp and post-operative sensitivity,or
protrusion of restoration

19. Excessive delayed expansion can occur if a
zinc-containing amalgam is contaminated
by saliva or moisture during trituration
or condensation
This delayed expansion can start 3-5days
after the restoration is placed and
continue for several months
(400micronm)
Zn+H2O=ZnO+H2(gas)

20. MICROLEAKAGE :
Dental amalgam has a tendency to
minimize microleakage
If the restoration is properly
inserted, leakage decreases as the
restoration ages in the mouth
This is due to the formation of corrosion
products which forms at the interface
between the tooth and the restoration.
(copper and tin corrosion products)
This corrosion products seals the interface
and prevent the microleakage

21. STRENGTH
Exhibits high compressive strength and
poor tensile and shear strength
Compressive strength – 380 to 550 Mpa
Tensile strength – 48 to 64 Mpa
Amalgam is brittle when placed inn thin
sections, because of its low edge strength
Hence amalgam should have adequate
bulk
Increase in mercury , decreases the
strength of amalgam

22. CREEP
 Creep is progressive permanent
deformation of set amalgam under
dynamic loading during function
 Low copper amalgam – 2.5% creep (>Y2)
 High copper amalgam – 0.2% creep (<Y2)
 Clinically creep lead to protrusion of
restoration making the amalgam more
prone to fracture, overhangs

23. THERMAL PROPERTIES
 LCTE of amalgam is 2.5 times more than
the tooth and amalgam is a good thermal
conductor
 Hence pulp should be protected with
either varnish, liners or bases

24. RIGIDITY
 MOE of high copper amalgam is 55
GPa(close to enamel). This increases the
longivity of amalgam restoration

25. BIOCOMPATIBILITY
 It is related to the mercury vapour
released during manipulation, placement
and removal of amalgam
 However the amount is minimal and the
possibility of toxic reactions in patients is
less
 Careful handling of mercury reduces the
risk to dentist or dental assistant

26. METALLURGIC REACTIONS
(AMALGAMATION
REACTIONS)

27. LATHE CUT LOW COPPER AMALGAM
 Y(Ag3Sn)+Hg----
Y1(Ag2Hg3)+Y2(Sn7Hg8)+unconsumed
alloy particles +unreacted mercury

30. ADMIXED HIGH COPPER AMALGAM
 Stage 1
Y(Ag3Sn)+Ag-Cu(eutectic)+Hg----
Y1(Ag2Hg3)+Y2(Sn7Hg8)+Ag-
Cu(unreacted)+Y(Ag3Sn)excess
Stage 2
Y2(Sn7Hg8)+Ag-Cu(eutectic)----
n(Cu6Sn5)+Y1(Ag2Hg3)+Ag-Cu excess

32. SINGLE COMPOSITION ALLOYS
(Ag-Sn-Cu)alloy particles+Hg----
Y1(Ag2Hg3)+n(Cu6Sn5)+unconsumed alloy
particles

33. MANIPULATION OF AMALGAM
(1) Selection of alloy and mercury
(2) Mercury alloy ratio (Proportioning)
(3) Trituration (Mechanical and hand)
(4) Mulling
(5) Condensation (Hand and mechanical)
(6) Pre-carve burnishing
(7) Carving
(8) Post-carve burnishing
(9) Polishing

38. THANK YOU