Class I Amalgam Restoration

Small/Moderate cavity

Must be in dentine

Minimum 1.5 - 2mm

Flat floor & rounded line angles

No unsupported Enamel

Manipulation of amalgamAims of manipulation:• To mix the alloy with mercury and gain homogenous

plastic mass of amalgam with minimal residual mercury.

• The mercury levels : → 53 % of the final amalgam restoration, considered as dangerous level leading to a) Excessive expansion. b) Drastic loss of strength. c) Increased flow and creep. d) Increased tarnish and corrosion. → 50 % , the maximum safe level. → 47 % , good level.

Manipulation of amalgam

It includes:

• Selection of the alloy.

• Proportioning of alloy to mercury.

• Trituration.

• Condensation.

• Carving.

• Finishing and polishing.

The cavity must be checked for the followings before manipulation of amalgam

• Adequate self-retention.• Proper resistance.• CSA 90.• No caries, debris or moisture.• Pulp is protected with cavity liner or base material

depending on the cavity depth.

1)Selection of alloy

Amalgam alloy could be supplied

in the form of:

A. Powder.

B. Pressed tablets.

C. Pre-weighted capsules.

Selection of alloy

Capsule )pre-weight) The most convenient as it is: a) Properly dispensed and proportioning of Hg/alloy ratio b) More hygienic as it is well sealed and the operator will not subjected to Hg vapors. c) Lesser manipulation procedures → i.e. no need for proportioning and squeezing

2 )Proportioning of alloy and mercury

• Manual : Using volume dispenser.

• Mechanical : -using amalgamator.

-Pre-measured

capsules.

3)Trituration

The process of mixing together Hg and amalgam alloy to produce a coherent plastic and homogenous mass of condensable amalgam.

Trituration Technique:

• Manual → using mortar and pestle with a steady constant force.

• Mechanical → using amalgamator

The resultant mix

2) Over triturated:• Adheres to the mortar.• Faster setting.• Better surface.

3) Properly triturated:• Shiny, smooth and

homogenous

1) Under triturated:• Dull.• Non homogenous.• Friable and non-coherent.• Weak & corrodable

4 .Placement/Condensation

1.Placement of amalgam should complete within 3 minutes of mix

2. Condense with smooth flat plugger

3. Use optimal load at all times

Factors controlling proper condensation

1. Elimination of moisture contamination and debris to avoid:

a) Delayed expansion. b) Loss of strength. c) Excessive corrosion.

2. Size and shape of the condenser/plugger should be of size slightly smaller than the width of the cavity.

3. Addition of mix increment by increment in order to: a) Avoid layering. b) Provide maximum adaptation. c) Remove maximum amount of excess Hg. d) Eliminate voids.

Result of moisture contamination during placement of amalgam into the cavity. “bubbles” on the occlusal surface resulting from gas formation

5. Forceful condensation is necessary in order to:

a) Eliminate voids.

b) Remove excess Hg.

c) Increase adaptation.

d) Increase density of filling.

6. Any old mix, more than 5 minutes should be discarded and replaced by new freshly mixed one, and if used, the restoration will be:

a) Full of voids. b) Corrodable. c) Weak. d) Non coherent i.e. layering.7. The cavity should be over filled in order to: a) Allow proper carving. b) Get the Hg rich layer at the surface that will be removed with carving.

Instruments

1. Amalgam carrier.

2. Condenser/plugger: Should be slightly smaller than the cavity

It may be Smooth.

Serrated.

The condensation force should be directed against cavity walls, line angles and point angles.

The force should be continued until the surface of the increment becomes soft indicating release of excess Hg and a squeezing sound is heard

The cavity must be overfilled in order to allow proper carving and get the Hg rich layer at the surface that will be removed with carving.

5 )CarvingAims: • To reproduce the normal tooth anatomy and contours.• To ensure efficient mastication and tooth function.• To remove the superficial Hg rich layer.Timing of carving:• Carving should be utilized when amalgam starts initial

setting.• This is detected when a slight resistance of carver

movement is felt.Early carving may result in:• Improper reproduction of tooth anatomy.• Formation of sub-margins → i.e. • Amalgam not covering the cavity walls.

Direction of carving:• From tooth structure towards the bulk of amalgam.• Parallel with the cavo-surface outline of the cavity.**If carving is done in a direction from amalgam towards the

tooth structure → there will be a great possibility of exposing cavo-surface margin → i.e. formation of sub-margins.

Double burnishing technique

pre and post carving burnishing

Pre-carving burnishing:Using large sized burnisher with heavy pressure. The

amalgam is pre-carved burnished in a direction from the tooth to amalgam

It provides the followings:• Increased adaptation of amalgam to cavity walls and

margins.• During this, some frictional heat is generated which helps

the excess Hg to be attracted to the surface and easily removed with carving.

• More cohesive amalgam.

Double burnishing technique• The occlusal anatomy is carved

using carver or excavator with proper direction

• All coalesced supplemental grooves that remains at the margins must be carved with probe → other wise, excess amalgam will remain as fine marginal silvery flashes which will fracture under masticatory force leading to formation of → Marginal ditches.

• Marginal ditch → V-shaped notch at tooth /restoration interface.

Double burnishing technique

Post-carving burnishing:• The amalgam is then post-carving burnished with light

pressure until the surface acquires a homogenous stain or velveteen appearance → this will provide surface smoothening.

• The amalgam is then checked for any premature contact using pressure sensitive articulating paper.

• The patient is then instructed not to use this side for the next 24 hours to avoid cracking or fracturing of the restoration.

• Also the patient should be advised to come after 24 hours for finishing and polishing of amalgam.

Finishing and polishingFinishing and polishing

Aims: 1. Removal of any premature contact, marginal flashes or

marginal over hangs.2. Provide a lustrous homogenous amalgam surface.Advantages: 1. Increases corrosion resistance.2. Decreases bacterial plaque retention and liability to

recurrent caries.3. Minimizes gingival irritation.4. Improves strength of amalgam, as it removes the surface

irregularities that act as stress concentration areas. Timing:After 24 hours of carving to avoid disturbing crystallization of

amalgam.

Finishing and polishingFinishing and polishing

Technique :1 .Finishing: Using finishing bur in a direction from the

tooth to restoration. Using sandpaper discs for accessible

surface.2 .Polishing: Using pumice with brush or rubber cup.

3 .Avoid heat generation, as it will lead to attraction of Hg to the surface resulting in:

a) Weakening of the surface. b) Weakening of the bulk due to the formed

porosity.

Finishing and polishingFinishing and polishingUsing 12 bladed finishing bur, amalgam restoration is finished after 24 hours of carving to avoid disturbing crystallization of the set amalgam mass.

Finishing and polishingFinishing and polishingUsing polishing paste or pumice with brush or rubber cup, the amalgam is polished to provide lustrous surface