Amalgam

DEFINITION

Dental amalgam is a metal like restorative material composed of a mixture of silver/tin/copper alloy and mercury.

HISTORYAmalgam has been primary restorative

material for more than 150 yrs.Initially, amalgam restorations were made by

dentists filing silver coins and mixing the filings with mercury.

This was made to a putty like mass that was placed into the defective tooth.

USES AS CLASS 1,2,5 RESTORATION. AS FOUNDATION- IN COMBINATION WITH

RETENTIVE PINS TO RESTORE CROWN. FOR MAKING DIES. FOR RETROGRADE ROOT CANAL FILLING. AS CARIES CONTROL RESTORATION.

Components of dental amalgam

1)Amalgam alloy2)Mercury

COMPOSITION

COMPOSITION Low Copper:

Silver - 63-70% Tin - 26-29% Copper - 2-5% Zinc – 0-2%

Admixed: Silver – 40-70% Tin - 26-30% Copper-13-30% Zinc - 0-1%

PROPERTIES OF SET AMALGAM. MICROLEAKAGE. DIMENSIONAL CHANGES. STRENGTH. CREEP. TARNISH & CORROSION.

MANIPULATION

MANIPULATION Selection of materials Mercury:Alloy ratio Trituration Condensation Shaping & finishing

MERCURY: ALLOY RATIO(1) Squeezing cloth

(2) Increased dryness technique

(1) EAMES technique

TRITURATION(1)Hand mixing

(2)Mechanical

CONDENSATION(1) Hand condensation(2) Mech.condensation

SHAPING & FINISHING.

CARVING. BURNISHING. POLISHING.

PRECAUTIONSVentilationDisposalSealed containersVaccum cleaners

INDICATIONS(1) Moderate to Large Class I & Class II

Restorations(2) Class V Restorations(3) Temporary Caries Control Restorations(4) Foundations

CONTRAINDICATIONS(1)Esthetics(2)Extensive tooth destruction(3)Small Class I & II Cavities

CAVITY PREPARATIONS

FOR

AMALGAM RESTORATION

What is a Cavity Preparation? It is a mechanical alteration of a defective,

injured, or diseased tooth to receive a restorative material that re-establishes a healthy state for the tooth, including esthetics corrections where indicated & normal form & function.

The important factors to consider in preparing a tooth for amalgam restoration are tooth anatomy and material requirements. Aspects of preparation due to tooth anatomy .

STEPS IN CAVITY PREPARATION(1) Initial Cavity preparation

(2) Final Cavity Preparation

Initial…1. Outline form & initial depth2. Primary Resistance form3. Primary Retention form4. Convenience form

Final…1. Removal of any remaining defective Enamel

or Dentin on Pulpal floor2. Pulp protection 3. Finishing External Walls4. Final Cleaning & Inspection

TThe he TType ype OOf f RResrorationesroration

CLASS I They are restorations on occlusal surfaces of

premolars & molars, occlusal 2/3rd of facial & lingual surface of molars & lingual surface of maxillary incisors

Class II Amalgam Preparation and Restoration

The foundations of Class II amalgam preparation are placed by G.V. Black in 1908. These G.V. Black’s principles are: outline form, resistance form, retention form, convenience form, caries removal, finish walls, “toilet of the cavity”.

CLASS II They are reostorations on the proximal

surfaces of posterior teeth- mesio occlusal , disto occlusal, mesio occluso distal.

1. B/L contacts just broken, Gingival contact broken

Both buccal and lingual contacts are broken just to allow the very tip of the explorer to pass thru. Gingival contact opened just to see the rubber-dam. The rationale for braking contact is to allow self-cleansing of the cavosurface margins. Breaking contacts was not necessary on distal proximal surface since the adjacent tooth is missing.  

2. All cavosurfaces margins are smooth and 90°

Due to amalgam physical properties and tooth anatomy (position of enamel rods) it is important to always have approximately 90° angle at the cavosurface margin. This provides strength to both the amalgam and enamel and prevents enamel not supported by sound dentin being left at the margins of the restoration.

3. All walls are convergent Retention form of the preparation is obtained by

convergence of all walls. A very simple way to provide convergent walls is to use 330 bur which has a pear-shaped design with rounded corners and can provide convergent walls to the preparation. The convergent walls can not be seen when looking from the occlusal surface of the preparation.

4. Rounded internal lines and anglesThe axiopulpal line angle is rounded in order to reduce stress concentration on amalgam. Other rounded internal angels have important role in reducing stress concentration on tooth structure.

5. Gingival cavosurface beveled and parallel to axiopulpal wall Due to orientation of enamel rods at gingival cavosurface it is necessary to bevel this surface in order to eliminate unsupported enamel. Parallelism of axiopulpal wall to gingival cavosurface margin is essential in protecting the pulpal chamber. 

6. Extension for prevention It is important to have the pulpal depth just into the dentin due to

extension for prevention, there is also a minimum depth of 1mm required for amalgam restoration because of its lack of compressive forces. Extension for prevention principle is also applied on outline form whish means that central groove is included in the preparation, width of the preparation is determined by the width of the condenser in order to allow proper condensation of amalgam and should not exceed 1/3 the occlusal width.

7. Reverses In the preparation of a Class II amalgam restoration, extension of

the preparation in the proximal area is important for elimination of caries and breaking proximal contacts. This convenience form includes arbitrary extension of the outline form into a reverse-S shape to both widen the box yet remove less tooth structure and is required only when necessary to open the contact. In the 35 MOD preparation reverse S is not present on distal. The reason is there was no need to break contact with adjacent tooth.

8. No iatrogenic flawsThe adjacent teeth should be protected from any iatrogenic

flaw. One way to achieve that is to place matrix band around the neighboring teeth.

CLASS III: They are restorations on the proximal surface of anterior teeth that that

do not involve incisal angle.

CLASS V: They are restorations on gingival 1/3rd of facial & lingual surface of all teeth.

CLASS VI: They are restorations on incisal edge of anterior teeth or cusp tip region of

posterior teeth.

FAILURES OF AMALGAM RESTORATIONS

Signs of failures :1. Fracture Lines2. Marginal Ditching3. Proximal Overhangs4. Poor anatomic contours5. Marginal Ridge incompatibility6. Improper Proximal Contacts7. Recurrent Caries8. Poor occlusal Contacts9. Amalgam Blues

Reasons For Failures:1. Improper Case Selection2. Improper Cavity Preparation3. Faulty Selection & manipulation of

Amalgam 4. Errors in Maricing Procedures 5. Post Operative Factors

AMALGAM TATOO “ Accidental implantation of silver

containing compounds into oral mucosal tissue”

Occur:1. Removal of old amalgam2. Broken Pieces-socket-tooth extraction3. Particles entering surgical wound4. Amalgam dust in oral fluids- abrasion areas Seen as – Grayish black pigmentation Com. Sites- Gingiva, buccal mucosa,

alveolar mucosa

CONCLUSIONClass I & II Restorations are still common

procedures performed by general Dentists.Class VI are used infrequentlyIt is important for practitioners to

understand the indications, advantages, techniques & limitations of these restorations.

When used correctly & properly selected cases, these restorations have the potential to serve for many years