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Procedure for
Amalgam
Restoration
Upload By : Ahmed Ali Abbas
Babylon University College of Dentistry
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theoptimalsmile.wix.com/dentistry
Mercury/alloy ratio• Historically the only way to achieve smooth and plastic
amalgam mixes was to use excess of mercury but this was discarded later considering health hazard.
• for conventional mercury added system two techniques were used for achieving mercury reduction in final restoration, initially it is removed with the help of the cloth by squeezingthrough it.
• Second techqnique- increasing dryness tchnique,duringcondensation of each increment a mercury rich soft layer comes to the surface.
• The most obvious method to reduce mercury content is minimal mercury technique or eamestechnique(mercury:alloy=1:1) ,in which sufficient mercury should be present to form coherent and plastic mass after trituration.
The mercury content of the finished restoration should be comparable to the original mercury/alloy ratio usually 50 wt%
Mercury and alloy
Proportioning • The amount of alloy and mercury to be used can be described as
the mercury/alloy ratio which signifies the parts by weight of
mercury and of alloy to be used.
• The recommended mercury/alloy ratio for the lathe cut alloys is
approximately 1:1 or 50% mercury, in case of spherical alloy
mercury should be 42% because spherical particles have lower
surface/volume ratios.
• Use of little mercury results in dry mix, impairs the strength of
high copper amalgam and also reduces corrosion resistance.
• Dispenser should be held vertically to ensure consistent spills of
the mercury, tilting the bottle 45-degree results in unreliable
mercury/alloy ratios and the dispenser should be half full when
used.
Trituration
• The objective of trituration is to provide proper amalgamation of the mercury and the alloy. The alloy particles are coated with a film of oxide which is removed by abrasion when alloy particles and mercury are triturated
• Types- hand mixing mechanical mixing
Hand mixing
• A glass mortar and pestle are used.
• The mortar has its inner surface roughened to increase
the friction .
• Usually a period of 25 to 45 second is sufficient for
hand mixing.
MORTAR AND PESTLE
Mechanical trituration
The disposable capsule serves as a mortar and the cylindrical metal placed in the capsule serves as the pestle.
The alloy and mercury are dispensed into the capsule ,it is secured in the machine and the machine is turned on. There is an automatic timer for controlling the mixing time.
• Mordern amalgamator has two or more operating speeds.
• The mulling process generally causes the mix to cohere so that it can be readily removed from the capsule.
• Spherical alloy require less amalgamation time than lathe-cut alloys, amalgamation time also depends on the quantity.
• For a given alloy/mercury ratio increased trituration time and speed shortens the working and setting time.
Amalgamat
or
UNDER TRITURATED MIX
rough and grainy and may crumble
tarnish and corrosion can occur
strenght is less
mix hardens too rapidly
excess mercury present
NORMAL MIX
Shiny surface,soft and smooth consistency
Warm when removed from capsule
Best compressive and tensile strenght
Has luster after polishing
Increased resistence to tarnish and corrosion
OVER TRITURATED MIX
Soupy mix,difficult to remove from capsule
Working time increased
Higher contraction of amalgam
Creep is increased
Consistency
• Proper combination of the alloy and mercury is a prime
manipulative consideration, the composition of the final
amalgam is the major determinant of the physical properties.
• Proper mix retains its luster longer after polishing and also
remains warm when it is removed from the capsule.
MULLING
Mulling is actually a continuation of trituration.
It increases the homogenity of the mass and get a single consistent
mix.
The mix is enveloped in dry piece of rubber dam and rubbed
between the first finger and thumb,or the thumb of one hand and the
palm for 2-5 sec.
Armamentarium
Amalgam Condensers
Anatomic Burnishers
Carves
— Cleoid or Discoid
Check condenser fit
condensation• The goal of condensation is to compact
the alloy into the prepared cavity so that the with sufficient mercury present to ensure complete continuity of the matrix phase between the remaining alloy particles.
• After the mix is made condensation of the amalgam should be prompltyinitiated, condensation of partially set material probably fractures and break up the matrix that has already formed.
• Condensation should be as rapid as possible and a fresh mix of amalgam should be made if condensation takes longer than 3-4 mins.
• The field of operation should be dry before application.
Hand condensation• Once the increment of amalgam is inserted into
the cavity preparation it should be condensed with pressure to avoid voids and to adapt the material to the walls, the condenser point is forced into the amalgam mass under hand pressure.
• Condensation is started at the center and then condenser point is stepped little by little towards the cavity wall.
• After condensation of the each increment excess mercury should left over the first increment so that it can bond with the next increment.
• The procedure of adding an increment,condensing it,adding another increment and so forth is continued until the cavity is overfillled.
• In case the cavity is large well condensed amalgam restoration can be achieved when the mix has proper consistency.
Hand condenser
Contd….
• Size of the increments should be small.in larger piece of
increment it is difficult to reduce the voids and to adopt the
alloy to the cavity walls.
• Sufficient condensation force should be used to force the alloy
particles together and to reduce voids,and work mercury to the
surface to achieve bonding between the increments.
Condensation pressureWhen a given force is applied,smaller the condenser greater the pressure exerted on the amalgam.
. For eg-when a thrust of 40N exerted with the help of the 2mm diameter results in condensation pressure 13.8MPa, the same thrust produce by 3.5mm in diameter produces 4.6MPa pressure, although forces as great as 66.7N is acceptable.
• Serrated condenser is preferred than round condenser in case of the corner of the cavity.
• The shape of condenser points should conform to the area under condensation.
• eg- a round condenser is ineffection in the corner of the cavity,atriangular or rectangular is indicated in such areas.
Condensation of amalgam
First increment
Start with the smallest condenser
Step condenser over mass
Continue adding increment
Condense toward walls
Mechanical
condensation
It differs from hand condensation such that it is performed
by an automatic device.
Various mechanics are employed for such instruments-
some provide impact type of force and some use rapid
vibration..
Less energy is required than hand condensation and the
dentist feels less fatigue.
Use alternative instruments
Overpacked
Carving of amalgam
restoration
Carving and finishing
• After amalgam is condensed in cavity it is carved to reproduce
the proper tooth anatomy. It should be started when the
amalgam is hard enough to offer resistance to the carving.
• Burnishing of the occlusal anatomy can be accomplished with
the help of the ball burnisher. A rigid flat-bladed instrument is
best used on the smooth surfaces. Final smoothing can be done
with the help of moist cotton or with the help of prophylaxis
paste. While polishing temp should not raise beyond 60-degree.
• Final finish should be done after the amalgam is fully set,it
should be delayed for at least 24 hr. and a wet prophylaxis
paste should be used .
Create initial grooves
Carve to margin
Remove flash
Final shape and burnishing
Completed restoration
Initial Condensation
Class II restoration
Lateral Condensation
Overpacking
Marginal Ridge Condensation
Condense to Margins
Occlusal Embrasure
Removing wedge
Removing Band
Flash & Excess
Moving Excess
Check with interproximal carve
Completed Restoration
Polishing
Thank you…….