silver mercury alloys are commonly used restorative materials in dentry. they are one of the self sealing long lasting restorative material in dentistry
6. HISTORY
ORIGIN OF AMALGAM CAN BETRACED BACKTO
659 AD IN CHINA
IN 1800’S KNOWNAS MINERAL CEMENT ALSO
CALLED D’ARCETS CEMENT
FATHER OF AMALGAM-REGNART
FIRST AMALGAM WAR IN 1843 BY AMERICAN
SOCIETY OF DENTAL SURGEONS
SECOND AMALGAMWAR IN MID 1920’S BY A
GERMAN DENTIST PROF.A.STOCK
THIRD AMALGAMWAR BEGAN IN 1980THROUGH
SEMINARS ANDWRITINGS OF DR.HUGGINS
21. ELASTIC MODULUS-11-12 Gpa
High copper alloys tend to be stiffer than low
copper alloys.
FACTORSAFFECTING STRENGTH OF
AMALGAM ARE-
TRITURATION
MERCURY CONTENT
EFFECT OF CONDENSATION
EFFECT OT POROSITY
EFFECT OF AMALGAM HARDENING RATE
22. 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 COPPERTHAN
HIGHALLOYS.
25. 3.FLOW AND CREEP-
WHEN A METAL IS PLACED UNDER STRESS,ITWILL 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 CREEPVALUESTHAN
CONVENTIONAL LOW COPPER ALLOYS.
27. 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.
31. 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.
32. 2)Minimal MercuryTechnique-
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-
33. • TRITURATION-
The process of mixing the alloy particles with
mercury.
Objectives of trituration
Hand trituration
37. 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.
38.
39. 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.
41. Carving-It is the anatomical sculpturing of the
amalgam material.
o A scraping or ringing sound should be heard
while carving.
42. 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.
44. 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.
45. FACTORS CONTROLLING QUALITY
OF DENTAL AMALGAM
I. FACTORS UNDER CONTROL OF
MANUFACTURER
II. FACTORS UNDER CONTROL OF
OPERATOR
46. 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.
47. 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.
50. 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
58. 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
59. 3.FAULTY SELECTIONAND 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
60. 4.ERRORS IN MATRICING PROCEDURESAND
RESTORATION-
a) Unstable matrix
b) Poor contour
c) Absence of wedges
d) Premature matrix removal
63. 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.
64. 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
65. 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
66. 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
68. 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.
69.
70. 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
71. 2. GALLIUM BASEDALLOYS-
• 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.
72. 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
74. Restoration done with gallium alloys-
Advantages-
1. Compressive strength similar to high copper
amalgams.
2. Biocompatibility
3. Good adaptation & reduced marginal
leakage.
75. 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
76. 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
77. 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.
78. 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
79. 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)
80. 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
86. 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.INTERNATIONALWEB SITE
www.google.com