Amalgam/prosthodontic courses

INDIAN DENTAL ACADEMY
Leader in continuing Dental Education
www.indiandentalacademy.com

OUTLINE
 INTRODUCTION
 HISTORY
 CLASSIFICATION
 COMPOSITION
LOW COPPER AMALGAM ALLOYS
HIGH COPPER AMALGAM ALLOYS
 PRE AMALGAMATED ALLOY
 MANUFACTURE OF ALLOY PARTICLES-LOW COPPER
-HIGH COPPER
 SETTING REACTION
 PHYSICAL PROPERTIES
-STRENGTH-COMPRESSIVE
-TENSILE

-DIMENSIONAL CNANGES
-FLOW AND CREEP
-CORROSION
 MANIPULATION AND TECHNICAL
CONSIDERATIONS OF DENTAL AMALGAM
 FACTORS CONTROLLING QUALITY OF
DENTAL AMALGAM
 INDICATIONS
 CONTRAINDICATIONS
 ADVANTAGES
 DISADVANTAGES
 CAUSES OF FAILURE OF DENTAL AMALGAM
 MERCURY TOXICITY
 RECENT ADVANCES IN DENTAL AMALGAM

Indian Dental academy
• www.indiandentalacademy.com
• Leader continuing dental education
• Offer both online and offline dental courses

-BONDED AMALGAM RESTORATION
-GALLIUM ALLOYS
-LOW MERCURY AMALGAMS
-INDIUM ALLOYS
-FLUORIDATED AMALGAM
 AMALGAM MYTHS AND FACTS
 REFERENCES
 CONCLUSION

INTRODUCTION

HISTORY
 ORIGIN OF AMALGAM CAN BE TRACED BACK TO
659 AD IN CHINA
 IN 1800’S KNOWN AS MINERAL CEMENT ALSO
CALLED D’ARCETS CEMENT
 FATHER OF AMALGAM-REGNART
 FIRST AMALGAM WAR IN 1843 BY AMERICAN
SOCIETY OF DENTAL SURGEONS
 SECOND AMALGAM WAR IN MID 1920’S BY A
GERMAN DENTIST PROF.A.STOCK
 THIRD AMALGAM WAR BEGAN IN 1980 THROUGH
SEMINARS AND WRITINGS OF DR.HUGGINS

CLASSIFICATION
(MARZOUK)
1) ACCORDING TO NO. OF ALLOY METALS
1) BINARY ALLOYS(SILVER-TIN)
2) TERNARY ALLOYS(SILVER-TIN-COPPER)
3) QUATERNARY ALLOYS(SILVER-TIN-COPPER-
INDIUM
2) ACCORDING TO THE SHAPE OF POWDER
PARTICLES
1)SPHERICAL
2)LATHE CUT
3)ADMIXED

3)ACCORDING TO POWDER PARTICLE SIZE
1)MICROCUT
2)FINE CUT
3)COARSE CUT
4)ACCORDING TO COPPER CONTENT
1)LOW COPPER ALLOYS
2)HIGH COPPER ALLOYS

5)ACCORDING TO ZINC CONTENT
1)ZINC CONTAINING ALLOYS
2)ZINC FREE ALLOYS
6)PRESENCE OF NOBLE METALS
1)NOBLE METAL ALLOYS
2)NON NOBLE METAL ALLOYS

COMPOSITION
LOW COPPER ALLOYS
ACCORDING TO STURDEVANT AND ANUSAVICE-
SILVER 65%
TIN 30%
COPPER 5%
ZINC 1%
ACCORDING TO COMBE-
SILVER 65-74%
TIN 25-27%
COPPER 0-6%
ZINC 0-2%

HIGH COPPER AMALGAM ALLOY-
1.ADMIXED ALLOY POWDER
ACCORDING TO STURDEVANT-
SILVER 60%
TIN 27%
COPPER 13%
ZINC 0%
ACCORDING TO COMBE-
SILVER 69%
TIN 17%
COPPER 13%
ZINC 1%

2.SINGLE COMPOSITION ALLOY-
SILVER 60%
TIN 25%
COPPER 15%

AMALGAM ALLOYS-
ALLOY SILVER TIN COPPER ZINC INDIUM
LOW
COPPER
65-70% 26-28% 2-5% 0-2% 0
ADMIXED 40-70% 26-30% 13-30% 0-1% 0
UNICOMPO
SITIONAL
40-60% 22-30% 13-30% 0 0-5%

PRE AMALGAMATED ALLOYS
In this the surface of alloy particles
have been introduced to mercury by
manufacturer.
Contain upto 35% Hg.

MANUFACTURE OF ALLOY
PARTICLES
LATHE CUT FILINGS
-HOMOGENIZING ANNEAL
-PARTICLE TREATMENT

AMALGAMATION REACTION

HIGH COPPER ALLOYS-
1)ADMIXED ALLOYS
Alloy particles +Ag-Cu eutectic+Hg
Ag2Hg3 + Cu6Sn5 +unconsumed alloy of both type
of particles
2)SINGLE COMPOSITION ALLOYS-
Ag-Sn-Cu alloy particles +Hg
Ag2Hg3 + Cu6Sn5 + unconsumed alloy particles

PROPERTIES
1.STRENGTH-AMALGAM COMPRESSIVE
STENGTH
(MPa)
1hr 7days
CREEP
(%)
TENSILE
STRENGTH
24hrs(MPa)
Low copper 145 343 2 60
Admixed 137 431 0.4 48
Single
composition
262 510 0.13 64

ELASTIC MODULUS-11-12 Gpa
High copper alloys tend to be stiffer than low
copper alloys.
FACTORS AFFECTING STRENGTH OF
AMALGAM ARE-
 TRITURATION
 MERCURY CONTENT
 EFFECT OF CONDENSATION
 EFFECT OT POROSITY
 EFFECT OF AMALGAM HARDENING RATE

2.DIMENSIONAL CHANGES-
When mercury is combined with amalgam it undergoes
three distinct dimensional changes
STAGE 1-INITIAL CONTRACTION
Lasts for about 20 mins
Contraction which occurs is not greater than
4.5µm/cm
STAGE 2-EXPANSION
STAGE 3-LIMITED DELAYED CONTRACTION
EXPANSION IS MORE COPPER FOR LOW COPPER THAN
HIGH ALLOYS.

FACTORS THAT AFFECT THE DIMENSIONAL
CHANGES-
1. Particle size & shape
2. Mercury
3. Manipulation
4. Moisture contamination- this type of
expansion can reach values greater than
400µm.

EXCESSIVE EXPANSION

3.FLOW AND CREEP-
WHEN A METAL IS PLACED UNDER STRESS,IT WILL UNDERGO
PLASTIC DEFORMATION.THIS CHARACTERISTIC IS
REFERRED AS FLOW OR CREEP.
FLOW IS MEASURED DURING SETTING OF AMALGAM
CREEP IS MEASURED AFTER AMALGAM SETTING.
- IT IS DEFINED AS INCREMENTAL DEFORMATION.
-VARY FROM 0.1% TO 4%
HIGH COPPER ALLOYS HAVE LOWER CREEP VALUES THAN
CONVENTIONAL LOW COPPER ALLOYS.

FACTORS INFLUENCING CREEP-
1.Phases of amalgam restorations
2.Manipulation

3.TARNISH AND CORROSION-
TARNISH:Is a surface discolouration on a metal
or even a slight loss or alteration of the
surface finish or luster.
CORROSION:It is the destructive attack of a
metal by chemical or electrochemical
reaction with its environment.

CORROSION OF CONVENTIONAL AMALGAM-
Sn7-8Hg + 1/2 O2+ H2O + Cl-
Sn4(OH)6Cl2 +Hg
Tinoxychloride
CORROSION OF COPPER ENRICHED
AMALGAM-
Cu6Sn5 +1/2 O2 +H2O +Cl-
CuCl2 3Cu(OH)2 +SnO

TYPES OF CORROSION-
1. Chemical corrosion
2. Electrochemical corrosion
a) Galvanic corrosion
b)Crevice corrosion
C) Stress corrosion

4.THERMAL PROPERTIES-
Linear coefficient of thermal expansion of
amalgam is 2.5 times more than the tooth.

MANIPULATION AND TECHNICAL
CONSIDERATIONS OF DENTAL
AMALGAM
• SELECTION OF ALLOY
• MERCURY:ALLOY RATIO-
1) High mercury technique(Increased dryness
technique)
 Initial amalgam mix contains 52-53% Hg
 It is necessary to squeeze the mercury
 Not used these days.

2)Minimal Mercury Technique-
 In 1960,EAMES first promoted this
 Recommended mercury:alloy ratio is 1:1
 Reduces mercury content upto 42 wt% for
spherical alloys.
Mercury and alloy dispenser-

• TRITURATION-
The process of mixing the alloy particles with
mercury.
 Objectives of trituration
 Hand trituration

 Mechanical Trituration
Preproportioned alloy and
Mercury-
Time of trituration ranges from 3-30 sec

 Mulling-It is actually a continuation of
trituration.
o Improves homogenicity of the mass and
texture.
o Done for 2-5 sec.

 Consistency of mix-
Normal mix Undertriturated
grainy mix

 Condensation-
o Objectives of condensation
o Lathe cut alloys employ greater condensation
pressure than spherical alloys.
o Load of upto 4-5 kg is applied to each
increment.

Mechanical Condensation-
o More useful and popular for lathe cut alloys
which require high condensation pressure.
o Not used any more due to introduction of
spherical alloys.
o Ultrasonic condensors are not recommended
as they increase the mercury vapor level
above the safety standards.

 Precarve Burnishing-

 Carving-It is the anatomical sculpturing of the
amalgam material.
o A scraping or ringing sound should be heard
while carving.

 Post carve Burnishing-It is done to remove
scratches,irregularities on the amalgam
surface,facilitating easier and efficient
finishing &polishing.
Burnishing slow setting alloys can damage the
margins of the restoration.

Post carve Burnishing-

 Finishing and Polishing-
o Most important objective is the removal of
superficial scratches and irregularities.
o Minimizes fatigue failure of amalgam
o Polishing can be done using descending
grade abrasive eg. Rubber mounted stone or
rubber cups.
o For obtaining a metallic lusture polishing
agent like precipitated chalk,tin or zinc oxide
are used.

FACTORS CONTROLLING QUALITY
OF DENTAL AMALGAM
I. FACTORS UNDER CONTROL OF
MANUFACTURER
II. FACTORS UNDER CONTROL OF
OPERATOR

I. FACTORS UNDER CONTROL OF
MANUFACTURER-
1) Composition of alloy
2) Heat treatment of alloy
3) Particle size,shape and method of
production
4) Surface treatment of particles,whether
annealing has been performed or not.
5) Form in which alloy is supplied.

II. FACTORS UNDER CONTROL OF
OPERATOR-
1) Selection of alloy
2) Mercury:alloy ratio
3) Proportion of mercury
4) Trituration
5) Condensation technique
6) Marginal integrity
7) Anatomical characteristics
8) Final finishing.

INDICATIONS-

CONTRAINDICATIONS-

ADVANTAGES
1. Ease of use
2. High compressive strength
3. Excellent wear resistance
4. Economic
5. Can be bonded to tooth structure
6. Self sealing ability

DISADVANTAGES
1.Lack of esthetics
2.Less conservative
3.Non insulating

4.Corrosion and galvanism
5.Initial marginal leakage
6.Lack of reinforcement of weakened tooth
structure

7.More difficult tooth preparation-
8.Mercury Toxicity

SIGNS OF FAILURE OF AMALGAM
RESORATIONS-
1) Fracture lines
2)Marginal ditching

3) Proximal overhangs
4) poor anatomic contours
5) marginal ridge incompatibility
6) Incorrect proximal contacts
7) Recurrent caries

8) Amalgam blues-
9) Voids
10) Poor occlusal contacts
11) Bulk fracture of the tooth or amalgam

CAUSES OF FAILURE OF DENTAL
AMALGAM
1.IMPROPER CASE SELECTION

2.IMPROPER CAVITY PREPARATION-
a) Inadequate extensions
b) Overextended cavity preparation
c) Shallow cavity
d) Deep cavity preparation
e) Curve pulpal floor
f) Wide isthmus
g) Narrow isthmus
h) Sharp axiopulpal line angle
i) Lack of butt joint
j) Lack of occlusal convergence
k) Improper convenience form

3.FAULTY SELECTION AND MANIPULATION
OF AMALGAM-
a) Selection of the alloy and mercury
b)Improper trituration
c) Improper condensation
d)Contamination
e) Over & under carving
f) Improper finishing

4.ERRORS IN MATRICING PROCEDURES AND
RESTORATION-
a) Unstable matrix
b)Poor contour
c) Absence of wedges
d)Premature matrix removal

5.POST OPERATIVE FACTORS-
a) Post operative pain or sensitivity
b) Premature fracture

MERCURY MANAGEMENT

CHEMICAL FORMS OF MERCURY-
1. Elemental mercury-
o Highly volatile
o Can be absorbed by lungs upto 80%
o Major route of entry into the human body
from amalgams.
2. Inorganic mercury-
o This is mined as cinnabar ore mercuric sulfide
o Potentially toxic.

3) Organic mercury-
o Found mostly as alkyl mercury salts.
o Methyl mercury is the most common salt
o Used as pesticide
o Highly toxic
Occupational safety & health administration has
set a threshold limit value(TLV) of
0.01mg/cu.mm as maximum amount of
mercury in the work place.
Lowest level of total blood mercury at which
earliest non specific symptoms occur is 35ng/ml

SOURCES OF MERCURY EXPOSURE IN DENTAL
OFFICE-
1) Amalgam raw materials
2) Mixed but unset amalgam
3) Dental amalgam scrap
4) During finishing and polishing
of amalgam.
5) During removal of old amalgam
restorations

MEASURES TO REDUCE MERCURY EXPOSURE IN
THE DENTAL CLINIC-
1. Storage of mercury
2. Office design
3. During trituration of amalgam
4. During insertion of amalgam
5. Disposal of amalgam scrap
6. During polishing of amalgam
7. During removal of old amalgam restorations
8. Care of contaminated instruments
9. Check mercury vapour levels periodically
10. Awareness of mercury toxicity

MERCURY HYPERSENSITIVITY-

MERCURY HYPERSENSIVITY-
This is an immune response to very low levels of
mercury.
It occurs when there is direct skin or mucosal
contact with mercury.
Allergic reactions
Oral signs
All these allergic reactions resolve a few days
after removal of the amalgam restorations.
Allergy to amalgam has been reported in very
small percentage of people.

RECENT ADVANCES IN DENTAL
AMALGAM
1. MERCURY FREE DIRECT FILLING AMALGAM
ALLOYS-
• Developed by ADA at NIST
• They use silver coated Ag-Sn alloy particles that
can be cold welded.
Drawbacks

2. GALLIUM BASED ALLOYS-
• First suggested by Puttkamer in 1928.
• Satisfactory gallium restorations were
developed by Smith & Others in 1956.
• Small amounts of indium &/or tin added to
gallium produces liquid alloy at room
temperature.

Comercially available gallium products-
Gallium Alloy GF:Developed by Horbe & Othe
rs in 1919 & marketed in Japan.
POWDER(w/wt%) LIQUID(w/wt%)
SILVER-60.5 GALLIUM-65
TIN-24.5 INDIUM-18.95
COPPER-12.3 TIN-16
PALLADIUM-2.7

POWDER(wt%) LIQUID(wt%)
SILVER-60.1 GALLIUM-61.98
TIN-28.05 INDIUM-24.99
COPPER-11.80 TIN-12.98
PALLADIUM-0.05 BISMUTH-0.05

Restoration done with gallium alloys-
Advantages-
1. Compressive strength similar to high copper
amalgams.
2. Biocompatibility
3. Good adaptation & reduced marginal
leakage.

4. Low vapour pressure than mercury
Ga-2.06× 10-40 mm Hg at 30C
Hg-0.00278 mm Hg at 30C
5. Creep values as low as 0.09%
6. sets early

Disadvantages-
1. Poor corrosion resistance-
Corrosion poducts-Ga2O3 & SnO2
2. Post operative sensitivity
3. Whitening of margins of restoration-
Due to crystallization of gallium oxy
hydroxide GaO(OH)
4. Stickiness
5. High cost

Studies of biocompatibility & cytotoxicity by
Eakle et al in 1992 & Psarras et al in 1992 have
shown it is not significantly different from
amalgams and composite resins.

3.LOW MERCURY AMALGAMS-
Minimizes the mercury required for
amalgamation to 15-25%
The clinical performance still needs to be
tested…….
4.INDIUM IN MERCURY-
10-15% Indium in admixed alloys reduces the
mercury needed for mixing.
Advantages

Powell et al in 1989 first reported that the
addition of pure indium powder to a high
copper amalgam alloy decreases mercury
vaporization.
This type of amalgam is currently marketed by
INDISPERSE(Indisperse Inc,Canada)

5.BONDED AMALGAM RESTORATIONS-
Adhesive resins contain 4-META,10 MDP & BIS-GMA
phosphonated ester.
Objective-To cause intermingling of amalgam & bonding resin
before they set.
Indications
Amalgam bonding agents-Dual cure/chemically cured.
Systems available are:C & B Meta bond
Panavia 21(Kuraray)
All bond 2(Bisco)
Scotch Bond Multipurpose(3M)
Amalgambond Plus(Parkell),etc

Mechanism of bonding-Micromehanical
Bond strength is around 10 MPa

Advantages
Disadvantages
6.FLUORIDATED AMALGAM-
Stannous Fluoride is added
Exact mechanism of fluoride uptake is not
known.
In vitro studies have shown reduction in
mechanical properties.

REFERENCES

REFERENCES
1.PHILLIPS SCIENCE OF DENTAL MATERAIALS
10th
EDITION
2.COMBE’S NOTES ON DENTAL MATERIALS
5th
EDITION
3.STURDEVANT’S ART AND SCIENCE OF OPERATIVE DENTISTRY
5th
EDITION
4.CLINICAL OPERATIVE DENTISTRY-PRINCIPLES AND PRACTICE
BY RAMYA RAGHU &RAGHU SRINIVASAN
5.MARZOUK’S OPERATIVE DENTISTRY
6.INTERNATIONAL WEB SITE
www.google.com

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