Class I Amalgam Restoration Small/Moderate cavity

No unsupported Enamel Must be in dentine Minimum 1.5 - 2mm Flat floor & rounded line angles

Manipulation of amalgam Aims 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 3) Properly triturated: Shiny, smooth and homogenous 1) Under triturated: Dull. Non homogenous. Friable and non-coherent. Weak & corrodable 3) Properly triturated: Shiny, smooth and homogenous 2) Over triturated: Adheres to the mortar. Faster setting. Better surface.

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) Carving Aims: 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 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 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 polishing Using 12 bladed finishing bur, amalgam restoration is finished after 24 hours of carving to avoid disturbing crystallization of the set amalgam mass.

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