Procedure for Amalgam Restoration

Presented by-

Paramita Brahmachari (P.R.C.A)

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 squeezing through it.

• Second techqnique- increasing dryness tchnique,during condensation 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 eames technique(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.

Amalgamator

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 promplty initiated, 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,a triangular 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…….