Proportioning of alloy and mercury is important for proper manipulation and setting of amalgam. The ratio is typically 1:1 or 1:2 by weight of alloy to mercury. Preweighed capsules help standardize the mix.
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Trituration
Purpose: to obtain plastic mass
Hand trituration: alloy and Hg rubbed between fingers
Machine trituration: amalgamator
Factors affecting:
-time of trituration
-speed of machine
-temperature
-type of alloy
-particle size
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Mulling
4. Introduction
Amalgam : alloy that contains mercury as one of its
constituent
Amalgam: derived from greek word
malagma= emollient
malassein= soften
Alloy : latin word
alligare= to combine
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5. History
1ST form of amalgam developed by
M.Taveau( 1826) in Paris.
Crawcour brothers(1833) introduced it in
dental profession . Called Royal Mineral
Succedaneum .
Amalgam War: 1840-1850
Dr.G.V.Black(1896):
ADA Specification 1 in 1929
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6. Advantages
Durable
High compressive strength
Insoluble in the fluids of
mouth
Adaptability to walls of
preparation
Least time consuming to
place
Ability to corrode-
decreased microleakage
Ability to take polish
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7. Disadvantages
Not tooth colored
Does not bond to tooth structure
Lack of edge strength
High conductivity
Mercury toxicity
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8. Classification
No of alloys:
1. Binary alloys– silver and tin
2. Ternary: silver , tin and copper
3. Quarternary: silver ,tin, copper, indium
Powder particle size:
1. Micro cut
2. Fine cut
3. Coarse cut
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9. Based on copper content
1. Low copper: <6%Cu
2. High copper: >6% Cu
admixed: 28%
single composition- 13-30%
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11. Based on addition of noble metals
1st generation: 3 parts silver+1 part tin peritectic
2nd generation: copper is added upto 4%
3rd generation : silver copper eutectic alloy +
original alloy
4th generation : alloying of copper to silver and tin
upto 29%
5th generation : silver, copper ,tin, indium
6th generation: alloying palladium 10%,
silver62%, copper 28%--- eutectic lathecut
blended into 1st gen in ratio of 1:2
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14. Single composition
Each particle has same composition
silver:40-60%
Tin: 22-30%
Copper: 13-30%
Indium: 0-5%
Palladium: 0-1%
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15. Functions of each ingredients
Silver:
1. Increases strength
2. Increase setting expansion
3. Decreases flow
4. Improves color
5. Setting time decreased
6. Resist tarnish and corrosion
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16. Tin
Advantages:
1. Decreases expansion
2. Helps in amalgamation
Disadvantages:
1. Decreases strength
2. Setting will be slow
3. Increases flow
4. Tarnish and corrosion
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17. copper
Advantages:
1. Increases strength and hardness
2. Decreases flow
3. Setting will be quick
Disadvantages:
1. Increases expansion
2. Can be tarnished
3. Brittleness
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18. Zinc
Advantages:
1. Scavenger/ de-oxidiser
2. Helps in workability
3. Quickens the setting time
4. Increases ultimate strength
Disadvantages:
1. Increases expansion in presence of moisture
2. Diminishes edge strength
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19. Mercury
Advantages:
1. Gives plasticity and softness
2. Binds the particles together
3. Essential for setting reaction and hardening
Disadvantages:
1. Mercury toxicity
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20. Selenium: Improves the biocompatability of amalgam
(Sato and Kumei-1982)
Indium: Decreases the mercury vapour released
during mastication( Dowell and Youdelis 1992)
Platinum: Hardens alloy and corrosion resistant
Palladium: Hardens and whitens alloy
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21. Manufacturing of alloy
Lathecut:
Ingot: 20-25 cm long and 3-8 cm diameter
Homogenised anneal of ingot: oven 400C for 6-8 hrs
Ballmilling : to reduce size
particle treatment with acids to improve the reactivity
Aging process to improve shelf life
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22. Spherical alloy
Atomised: liquid alloy
into a closed chamber
filled with inert gas
Size: 2-43 microns
Acid treatment
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31. Single composition
Ag3Sn + Cu3Sn+ HgCu6Sn5 +Ag2Hg3
Core: Ag3Sn and Ag-Cu
Matrix: Ag2Hg3
Cu6Sn5 is present in gamma1 matrix rather
than as halo around Ag-Cu
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34. Dimensional changes
ADA specification1:
-15Micron to + 20
microns at 37c between 5
min and 24hrs after
beginning of trituration
Theory of dim.change:
1. Initial contraction
2. Expansion
3. Delayed contraction
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35. Severe contraction:
1. Microleakeage
2. Plaque accumulation
3. Secondary caries
Excessive expansion
1. Pressure on pulp
2. Post op sensitivity
3. Protrusion of restoration
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37. Factors affecting dimensional
change
Constituents: more gamma- more exp
tin– less exp
Mercury: more ->expansion high
Particle size: smaller size-> more contraction
Trituration:
more energy, longer time-contraction
Condensation: more forces contraction
Particle shape: irregular expansion
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38. Creep
Creep: time dependent plastic strain of
material under static load or constant
stress
ADA specification : 3% or less
Low copper alloys: 0.8% to 8%
High copper alloys: 0.1%
Factors: 1. influence of microstructures
2. manipulative variables
High creep: more marginal detoriation
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41. Compressive strength
Satisfactory compressive strength: 310 MPa
After 7 days , comp strength of high copper
alloys is more than low copper alloys
After 1hr, single composition alloy strength is
double that of other alloys
Amalgam is weak in tension
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44. Rate of attaining strength
Accelerated strength:
1. Decreased particle size.
2. More trituration energy
3. More condensation energy
4. Smooth and regular particles
5. Homogenisation heat treatment
6. Minimum mercury in the mix
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45. Tarnish and corrosion
Tarnish: surface discoloration on metal or even
slight loss or alteration of the surface finish or
luster.
Corrosion: actual detoriation of ametal by
reaction with its environment
Active corrosion: interface between tooth and
restoration crevice corrosion
selfsealing
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47. Both low and high copper corrosion
products are oxides and chlorides of tin
In high copper amalgam: corrosion process is
limited,since n (Cu6Sn5) is least susceptible to
corrosion than gamma2
Gold restoration when placed in contact with
an amalgam,large difference in
EMFcorrosion
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48. Other properties
Effect of moisture contamination:
Zinc-containing amalgam contaminated by
moisture , a large expansiondelayed
expansion or secondary expansion
H2O + Zn ZnO2 +H2 (gas)
This hydrogen gas collects in restoration
expansion, protrusion , increased creep,
increased microleakage, corrosion, pain.
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49. Marginal adaptation
Tendency to minimise microleakeage –self sealing
Due to corrosion products which seals restoration
Low copper alloys–> 2-3 months
High copper alloys10-12 months
Problems due to improper adaptation
1. Marginal detoriation
2. Accumulation of debris
3. Recurrent caries
4. Post op sensitivity
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50. Gallium alloy
Alloy: Liquid:
Silver60%
Tin 25% Gallium 62%
copper 13% Iridium 25%
Palladium 20%
Tin 25%
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51. Gallium alloys
Puttkammer 1928
Comp.strength and tensile strength comparable
to amalgam
Creep—0.09%
Sets early polishing can be done on same
day
They expand after mixing, better marginal seal
Sticks to walls of capsule.
More costly.
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53. Copper amalgam
Copper and mercury
Antiseptic
Composion: 70%Hg , 30% copper- pellet
Heated in a spoon,then triturated
Adv: increased hardeness,
not effected by moisture,
no creep
Disadv: discoloration and shrinkage
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54. Manipulation
1. Choice of alloy and mercury
2. Proportioning
3. Trituration
4. Mulling
5. Condensation
6. Burnishing
7. Carving
8. Finishing and polishing
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55. Choice of alloy and mercury
Selection of alloy depend on:
setting time, particle size and shape, composition,
presence or absence of zinc.
90% amalgams placed are high Cu ,admixed alloys
Adv: no gamma2,
low creep
high early strength
good corrosion resistance
decreased marginal failure
Zinc containing and zinc free:
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56. Proportioning of alloy and mercury
Preferably done by weight rather than volume
Mode of supply: powder particles, pellet ,disposable
capsules, reusable capsules
Dispensers with preweighed tablets and Hg
containers are available
NO TOUCH :preweighed capsules are available with
alloy and Hg seperated by membrane.
Size of mix:400,600,800 +appropriate Hg--- color
coded
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57. Contd
Reusable capsules :1.friction fit
2. screw type—better
Disposable capsules should not be reused
Increasing dryness techique: 52-53% Hg
very plastic mix,
large restorations,
multiple auxillary means of retention
Eames technique: 48-50% Hg
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59. Trituration
Act or rubbing
Objectives:
Achieve workable mass
Removes oxides from powder particles
Pulverize pellets to particles
Dissolve particles of powder in Hg
Reduce particle size
Keep gamma1 matrix crystals minimal and evenly
distribute
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60. Triturators
2 types: hand and mechanical
Hand: mortar and pestle
Mechanical: amalgamators
Has plastic or metal capsule, metal or plastic ball or
pestle.
Hoods.
3 basic movements of pestle:
centrifugal
figure 8
straight line
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61. Contd
Coherence time: minimum mixing time required for an
amlagam to form a single coherent pellet.
Effective trituration depends on duration and speed of mixing.
Duration:
Speed:
low :3200-3400 cycles/ min
medium:3700-3800 cycles /min
high :4000-4400 cycles/min
Spherical or irregular low copper: low speed
High copper alloys: high speed
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64. Trituration energy
Trituration(work) = motor speed *
time * capsule-pestle action
Trituration Energy:
1. Speed or no. of unit movements per unit time
2. Thrust of the movement
3. Weight of the capsule or pestle
4. Difference in size between pestle and capsule
5. Time
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65. Mulling
Continuation of trituration
Provides homogenicity to the mix
2 ways:
1. Mix is enveloped in dry piece of rubberdam and
rubbed betweem 1st finger and thumb.
2. After trituration,pestle is removedfrom capsule and
mix is triturated for 2-3 sec.
This assures cleaning of capsule walls of remnants
of mix and developing a single coherent mix
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66. Type of mix
Test for correct mix:
Normal mix:
May be warm
Smooth and soft
Overtrituration:
Alloy will be hot
Hard to remove from the
capsule
Shiny wet and soft
Undertrituration
1. Alloy will be dry
2. Will crumble if dropped from
approximately 30cm
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68. condensation
Continuation of trituration process
Purpose:
1. Squeezes unreacted Hg out of increments
2. This Hg squeezed to surface binds further sucessive
increments
3. Forces used brings stronger phase together boosting
final strength
4. Adapts plastic mix to the walls of preparation
5. Decreases no. of voids
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69. Condensation
Should start immediately after trituration
3-3 ½ min
Further condensation causes cracks
3 ways: 1. hand condensation
2. mechanical: a. vibratory
b. impact
3. ultrasonic
Pressure inversely proportional to square of surface
area
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72. Round condensors
3 instruments of diameter 15,25,35
Angle 10 degrees to shaft
Nibs 7mm long
15-25 diameter: compressing amalgam in
small pits
35 diameter: final heavy pressure in occlusal
surface of molars
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75. Sweeney’s instruments
has sharp angles
condensing amalgam
into angles
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76. condensation
Face or nib should be flat or smooth
Atleast 6 pounds should be used
Amalgam is inserted into cavity in small
increments and condensed with smaller
instruments.
Minimises voids and adapts to smaller details
Near surface, larger consensors are used.
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77. Nonspherical alloys
Force applied at 45deg
to walls and floor
Next increment at 90
deg to previous one
Centre to periphery
condensation
Excess Hg which comes
to surface is excavated
and discarded.
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78. Spherical alloys
Large increments
Largest condensor that
will fit the cavity, to
prevent lateral escape of
spherical part
Particles have tendency
to roll over
Less energy than
nonspherical
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79. Final appearance
Concave amalgam surface should face
condensor indicating proper angulation and
application of forces
Condensed increment should not be indentented
by further cond. force showing a coherent mass
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80. Blotting mix
An overdried amalgam mix is condensed
heavily on the restoration using large
condensors
Blots excess Hg from critical marginal and
surface area of restoration
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81. Burnishing or surfacing
Process of rubbing, usually performed to make a surface
shiny
Light strokes, from amalgam to tooth surface
Objectives:
1. Dec size and no. of voids on critical areas and margins
2. Brings excess Hg to surface
3. Adapts amalgam to cavosurface anatomy
Precarve and post carve burnishing
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83. carving
Anatomical sculpting of amalgam.
Begins immediately after condensation and precarve
burnishing
Objectives:
1. Produce restoration with no under hangs
2. Proper physiological contours and contacts
3. Adequate and compatible marginal ridges
4. Physiological embrasures
5. Functional non interfering occlusal anatomy
6. Enhance periodontal health and integrity
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84. Carving - steps
Initial carving– discoid carver removes extra bulk
Accessible embrasures : sharp explorer or lateral edge
of hollenback carver
Creating triangular fossa: discoid /cleoid
This coupled with previous procedure will erect
marginal ridges
Margination: discoid /hollenback removes marginal
flash,
from tooth to amalgam
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86. Contd
Facial and lingual grooves: hollenback, chisel,
cleoid /discoid
Cusp ridges and inclined planes: hollenback placed
concurrently on amalgam and adjacent tooth
surface ,lateral movement with intact tooth as guide
Anatomic grooves: anatomic burnisher
Post carve burnishing : light forces
not done in fast setting amalgams
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89. Finishing and polishing
Finishing: process which continues the carving
objectives, removes flash and overhangs , corrects
minimal underhangs
Done at placement appointment
Polishing: smoothing the surface to a point of high
gloss or lusture.
Creates corrosion resistant layer by removing scratches
& irregular surface
After 24hrs preferably
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90. objectives
1. Conversion of superficial amalgam into
relatively inert layer galvanically
2. Removal of superficial scratches and
irregularities
3. Minimises concentration cell corrosion
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91. contd
Gross smoothening: finishing burs
Polishing agents: Tinoxide, Zincoxide ,PPT chalk
Polishing convex surfaces like facial ,lingual
proximal: progressive finer disks, abrasive
impregnated cups
Concave surfaces : Abr impregnated rubber points
Contact areas and gingival embrasures: linen
polishing strips or dental tape
Abundance of air-coolant and intermittent contact
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101. Defective cavity preparation
Insufficient occlusal extension
Under extension of proximal box
Over extended cavity preparation
Cavity depth
Floor
No butt joint
Fracture of isthmus
Sharp axiopulpal line angle
Incomplete removal of caries
Hyperemia of pulp
Additional retentive forms to be in dentin
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102. Defective amalgam manipulation
Improper condensation
Incorrect mercury alloy ratio
Contamination
Defective finishing and polishing
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103. Post operative pain
High points
Delayed expansion
Inadequate pulp protection
Continuous leakage around filling
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104. Finishing and polishing
Overcarving
Failure to polish
Temperatures greater than 65c mercury is
released from amalgam
Amalgam which have greater tendency for
tarnish and corrosion
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105. Amalgam bonding
Amalgam is hydrophobic while enamel and
dentin are hydrophilic.
Wetting agent should have both the properties
4-methyloxy ethyl trimellitic anhydride
Thick layers of bonding agents(10-50 microns)
are applied about 8-10 times
Amalgam bond, scotch bond MP, All Bond 2,
Panavia 21, Clearfill Linerbond 2, Optibond2
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106. Bonding interface
Tag formation
Chemical binding to the inorganic or org
components of dentin
Formation of hybrid layer of reinforced dentin
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107. Advantages
Dentin sealing
Resistance and retention form increased
Improves marginal seal
Use of retention pins eliminated
Microleakeage ,recurrent caries, postoperative
sensitivity reduced
Cavity can be made conservatively
Cost effective for extensively carious tooth
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108. Limitations
Technique sensitive
Bond strength is reduced after some years
Cost of bonded amalgam is more than
nonbonded
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109. Gallium alloy
Alloy: Liquid:
Silver60%
Tin 25% Gallium 62%
copper 13% Iridium 25%
Palladium 20%
Tin 25%
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110. Gallium alloys
Puttkammer 1928
Comp.strength and tensile strength comparable
to amalgam
Creep—0.09%
Sets early polishing can be done on same
day
They expand after mixing, better marginal seal
Sticks to walls of capsule.
More costly.
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