Treatment of dental Treatment of dental caries:caries:

AMALGAM.AMALGAM.Properties, indications, Properties, indications,

inserting, carving, polishing.inserting, carving, polishing.

3.Year - DM

AMALGAMAMALGAM

Amalgam is the most widly used Amalgam is the most widly used permanent filling in dentistry. permanent filling in dentistry. It is It is prepared by mixing the alloy with prepared by mixing the alloy with mercury.mercury.

The reaction between mercury and alloy is The reaction between mercury and alloy is termed an termed an amalgamation reactionamalgamation reaction. .

It results in the formation of a hard It results in the formation of a hard restorative material of silvery – grey restorative material of silvery – grey appearanceappearance

Amalgam Use and BenefitsAmalgam Use and Benefits

Dental amalgam, in widespread use for over 150 Dental amalgam, in widespread use for over 150 years, is one of the oldest materials used in oral years, is one of the oldest materials used in oral health care.health care.

Its use extends beyond that of most drugs, and is Its use extends beyond that of most drugs, and is predated in dentistry only by the use of gold. predated in dentistry only by the use of gold.

Dental amalgam is the end result of mixing Dental amalgam is the end result of mixing approximately equal parts of elemental approximately equal parts of elemental liquid liquid mercurymercury (43 to 54%) and an (43 to 54%) and an alloy powderalloy powder (57 to (57 to 46%)46%)

composed of silver, tin, copper, and sometimes composed of silver, tin, copper, and sometimes smaller amounts of zinc, palladium, or indium. smaller amounts of zinc, palladium, or indium.

AmalgamAmalgam

MERCURY (Hg)MERCURY (Hg) – is a liquid at room – is a liquid at room temperature and it is able to form a workable temperature and it is able to form a workable mass when mixed with the alloy.mass when mixed with the alloy.

The reaction between mercury and alloy is The reaction between mercury and alloy is termed antermed an amalgamation reaction. amalgamation reaction.

Dental amalgam has been used for many years Dental amalgam has been used for many years with a large measure of success. with a large measure of success.

It is the most widely used of all available filling It is the most widely used of all available filling materials.materials.

CompositionComposition The composition of the alloy powder particles The composition of the alloy powder particles

varies from one product to another. varies from one product to another.

Composition of Composition of CONVENTIONAL AMALGAM CONVENTIONAL AMALGAM ALLOY:ALLOY:

Metal: Weight:Metal: Weight: Silver (Ag) .......................... 65% min.Silver (Ag) .......................... 65% min. Tin (Sn) ..............................29% max.Tin (Sn) ..............................29% max. Copper (Cu) ..............................6% max.Copper (Cu) ..............................6% max. Zinc (Zn) ...............................2% max.Zinc (Zn) ...............................2% max. Mercury (Hg) ............................ 3% max.Mercury (Hg) ............................ 3% max.

CompositionComposition

1. 1. SilverSilver - Increases strength, expansion - Increases strength, expansion and reactivity. Decreases creep. Corrosion and reactivity. Decreases creep. Corrosion products are AgCl and AgS. products are AgCl and AgS.

2. 2. TinTin - Increases reactivity and corrosion. - Increases reactivity and corrosion. Decreases strength and hardness. Decreases strength and hardness. Corrosion products are SnO, SnCl, and SnS.Corrosion products are SnO, SnCl, and SnS.

3. 3. CopperCopper - Increases strength, expansion - Increases strength, expansion and hardness. Decreases creep. Corrosion and hardness. Decreases creep. Corrosion products are CuO and CuS.products are CuO and CuS.

CompositionComposition

4. 4. ZincZinc - Increases plasticity, strength - Increases plasticity, strength and the Hg:alloy ratio. Decreases creep. and the Hg:alloy ratio. Decreases creep. Causes secondary expansion. Corrosion Causes secondary expansion. Corrosion products are ZnCl and ZnO.products are ZnCl and ZnO.

5. 5. MercuryMercury - Wets the alloy particles. - Wets the alloy particles. Decreases strength if in excess amounts. Decreases strength if in excess amounts. Implicated in toxic and allergic reactions.Implicated in toxic and allergic reactions.

Effects on properties of an amalgam Effects on properties of an amalgam

restoration imparted by ingredients.restoration imparted by ingredients.

PROPERTY INGREDIENT

  Silver Tin Copper Zinc

Strength Increases      

Durability Increases      

Hardness     Increases  

Expansion Increases Decreases Increases  

Flow Decreases Increases Decreases  

Color Imparts      

Setting time Decreases Increases Decreases  

Workability   Increases   Increases

Cleanliness       Increases

AmalgamAmalgam The role of zinc (Zn) :The role of zinc (Zn) : is as a SCAVENGER during the production of the alloy. is as a SCAVENGER during the production of the alloy.

The alloy is formed by melting all the constituent metals The alloy is formed by melting all the constituent metals together.together.

There are tendency for oxidation to occur.There are tendency for oxidation to occur. OXIDATION OXIDATION of tin (Sn), copper (Cu) or silver would of tin (Sn), copper (Cu) or silver would

seriously affect the properties of the alloy and amalgam.seriously affect the properties of the alloy and amalgam.

Zinc Zinc reacts rapidly and preferentially with the available reacts rapidly and preferentially with the available oxygen, forming a slag of zinc oxide (ZnO) which is oxygen, forming a slag of zinc oxide (ZnO) which is easily removed.easily removed.

Many alloys contain no zinc. They are described as Many alloys contain no zinc. They are described as ZINC- FREE ALLOYS.ZINC- FREE ALLOYS.

Amalgam: propertiesAmalgam: properties

1. DIMENSIONAL CHANGES1. DIMENSIONAL CHANGES 2. STRENGTH2. STRENGTH 3. PLASTIC DEFORMATION (CREEP)3. PLASTIC DEFORMATION (CREEP) 4. CORROSION4. CORROSION 5. THERMAL PROPERTIES5. THERMAL PROPERTIES 6. BIOLOGICAL PROPERTIES6. BIOLOGICAL PROPERTIES

1. DIMENSIONAL CHANGES1. DIMENSIONAL CHANGES

A large A large contractioncontraction would result in a marginal gap would result in a marginal gap

down which fluids could penetrate.down which fluids could penetrate.

A large A large expansionexpansion would result in the protrusion of would result in the protrusion of the filling from the cavity.the filling from the cavity.

Zinc reacts readily with water producing hydrogen:Zinc reacts readily with water producing hydrogen:

Zn + H2O –––––––––––– ZnO + H2Zn + H2O –––––––––––– ZnO + H2

The liberation of hydrogen (H2) causes The liberation of hydrogen (H2) causes a considerable expansion.a considerable expansion.

2. STRENGTH2. STRENGTH

The strength of dental amalgam is developed slowly. The strength of dental amalgam is developed slowly. It may take up to 24 hours to reach a reasonably high It may take up to 24 hours to reach a reasonably high value and continues to increase slightly for some time value and continues to increase slightly for some time after that.after that.

15 – 20 minutes after placing the filling , the AM is 15 – 20 minutes after placing the filling , the AM is relatively weak. I tis necessary, to instruct patients relatively weak. I tis necessary, to instruct patients not to apply undue stress to their freshly placed AM not to apply undue stress to their freshly placed AM fillings.fillings.

There is good correlation between strength and There is good correlation between strength and mercury content. mercury content.

Optimum properties are produced for amalgams Optimum properties are produced for amalgams containing 44-48% mercury.containing 44-48% mercury.

3. PLASTIC DEFORMATION 3. PLASTIC DEFORMATION (CREEP)(CREEP)

Amalgam undergoes a certain amount of plastic Amalgam undergoes a certain amount of plastic deformation or creep when subjected to dynamic deformation or creep when subjected to dynamic intra-oral stresses.intra-oral stresses.

The gamma 2 phase of AM is responsible for the The gamma 2 phase of AM is responsible for the relatively high values of creep.relatively high values of creep.

The copper- enriched amalgams, which contain little The copper- enriched amalgams, which contain little or no gamma 2 in the set material, have significantly or no gamma 2 in the set material, have significantly lower creep values lower creep values

Gamma 2 phase is responsible for high creepGamma 2 phase is responsible for high creep..

4. CORROSION4. CORROSION

Corrosion is a matter which may significantly affect the Corrosion is a matter which may significantly affect the structure and machanical properties. The heterogeneous, structure and machanical properties. The heterogeneous, multiphase structure of AM makes it prone to corrosion.multiphase structure of AM makes it prone to corrosion.

The gamma 2 phase of a conventional AMThe gamma 2 phase of a conventional AM is the most is the most electrochemically reactive and readily forms the anode in an electrochemically reactive and readily forms the anode in an electrolytic cell.electrolytic cell.

The rate of corrosion is accelerated if the AM filling contacts The rate of corrosion is accelerated if the AM filling contacts a gold restoration.a gold restoration.

Smooth surfaces are less prone to concentration cell Smooth surfaces are less prone to concentration cell corrosion.corrosion.

5. THERMAL PROPERTIES5. THERMAL PROPERTIES

AM has a relatively high value of AM has a relatively high value of thermal diffusivitythermal diffusivity Dentine is replaced by a good thermal conductor.Dentine is replaced by a good thermal conductor. The coefficient of thermal expansion value for AM The coefficient of thermal expansion value for AM

is about three times greater than that for dentineis about three times greater than that for dentine..

This results in considerably This results in considerably more expansion and more expansion and contractioncontraction in the restoration than in the surrounding in the restoration than in the surrounding tooth when a patient takes hot or cold food or drink.tooth when a patient takes hot or cold food or drink.

Thermal expansion may cause Thermal expansion may cause microleakage around microleakage around the fillingsthe fillings since is no adhesion between AM and tooth since is no adhesion between AM and tooth substance.substance.

Microleakage plays an important part in initiating such Microleakage plays an important part in initiating such lessions.lessions.

6. BIOLOGICAL PROPERTIES6. BIOLOGICAL PROPERTIES

Certain Certain mercury compoundsmercury compounds are known to are known to have a harmfull effect on the central nervous have a harmfull effect on the central nervous system.system.

Some studies have shown a higher concentration Some studies have shown a higher concentration of mercury in the blood and urine of patients with of mercury in the blood and urine of patients with AM fillings than those without.AM fillings than those without.

Another potential problem concerns allergic Another potential problem concerns allergic reactions, usually manifested as a contact reactions, usually manifested as a contact dermatitis.dermatitis.

Mercury or freshly mixed AM should never be Mercury or freshly mixed AM should never be touched by hand.touched by hand.

Mercury is readily absorbed by the skin.Mercury is readily absorbed by the skin.

Usage and preparation of Usage and preparation of amalgamamalgam

The dental specialist has the direct The dental specialist has the direct responsibilityresponsibility for the correct preparation and for the correct preparation and use of amalgam.use of amalgam.

Incorrect use may produce a faulty restoration Incorrect use may produce a faulty restoration that can cause or contribute to the loss of a tooth. that can cause or contribute to the loss of a tooth.

Therefore, the dental specialist must use Therefore, the dental specialist must use extreme care in preparing a good mix of extreme care in preparing a good mix of amalgamamalgam that will provide the best qualities that will provide the best qualities obtainable from the alloy. obtainable from the alloy.

MANIPULATIVE VARIABLESMANIPULATIVE VARIABLES

The manipulating of AM involves the The manipulating of AM involves the following sequence of events:following sequence of events:

1. Proportioning and dispensing1. Proportioning and dispensing 2. Trituration2. Trituration 3 Condensation3 Condensation 4.Carving4.Carving 5. Polishing5. Polishing

1. PROPORTIONING AND 1. PROPORTIONING AND DISPENSINGDISPENSING

Alloy/mercury ratios vary between 5:8 Alloy/mercury ratios vary between 5:8 and 10:8.and 10:8.

Those mixes containing Those mixes containing greater greater quantities of quantities of mercury are mercury are „wetter“„wetter“ and are generally used and are generally used with hand mixing.with hand mixing.

Those mixes containing Those mixes containing smaller smaller quantities of quantities of mercury are mercury are „drier“„drier“ and are generally used and are generally used with mechanical mixing.with mechanical mixing.

Spherical particle alloys,for example , require less Spherical particle alloys,for example , require less mercury to produce a workable mix.mercury to produce a workable mix.

1. PROPORTIONING AND 1. PROPORTIONING AND DISPENSINGDISPENSING

For optimum properties, the final set For optimum properties, the final set amalgam should contain less than amalgam should contain less than 50% mercury.50% mercury.

The optimal final mercury content The optimal final mercury content ranges from an average of 45% for ranges from an average of 45% for lathe-cut materials to an average of lathe-cut materials to an average of 40% for spherical materials.40% for spherical materials.

2. TRITURATION2. TRITURATION

The mixing or trituration of AM may be The mixing or trituration of AM may be carried out by carried out by hand or in an electrically hand or in an electrically powdered machinepowdered machine which vibrates which vibrates a capsule containing the mercury and alloy.a capsule containing the mercury and alloy.

Trituration by hand is not extensively Trituration by hand is not extensively practised in developed countries nowadays. practised in developed countries nowadays. Mechanical mixing is far more widely used - Mechanical mixing is far more widely used - amalgamator.amalgamator.

Trituration times 5 - 20 seconds are normalTrituration times 5 - 20 seconds are normal..

2. TRITURATION2. TRITURATION

The advantages of The advantages of mechanical triturationmechanical trituration are as follows:are as follows:

1. A uniform and reproducible mix is produced.1. A uniform and reproducible mix is produced. 2. A shorter trituration time can be used.2. A shorter trituration time can be used. 3. A greater alloy/mercury ratio can be used.3. A greater alloy/mercury ratio can be used.

Amalgamator

3. CONDENSATION3. CONDENSATION

Material is condensed into the prepared cavity Material is condensed into the prepared cavity using a flat-ended, steel hand instrument called an using a flat-ended, steel hand instrument called an amalgam condenseramalgam condenser..

The technique chosen for condensation must The technique chosen for condensation must ensure the following.ensure the following.

1. Adequate adaptation of the material to all parts 1. Adequate adaptation of the material to all parts of the cavity base and walls.of the cavity base and walls.

2. Good bonding between the incremental layers of 2. Good bonding between the incremental layers of amalgamamalgam

3. Optimal mechanical properties in the set 3. Optimal mechanical properties in the set amalgam by minimizing porosity and achieving amalgam by minimizing porosity and achieving a final mercury content of 44-48%.a final mercury content of 44-48%.

3. CONDENSATION3. CONDENSATION

There should be a minimal time delay There should be a minimal time delay between trituration and condensation.between trituration and condensation.

If condensation is commended too late, the If condensation is commended too late, the amalgam will have achieved a certain amalgam will have achieved a certain degree of set and adaptation, and final degree of set and adaptation, and final mechanical properties are all affected.mechanical properties are all affected.

There is a good correlation between the There is a good correlation between the quality of an AM restoration and the energy quality of an AM restoration and the energy expended by the operator who condenses it.expended by the operator who condenses it.

It needs to use a It needs to use a high condensating high condensating forceforce..

Lower forces are required to condense Lower forces are required to condense spherical particle amalgams than lathe-cut spherical particle amalgams than lathe-cut materials.materials.

Condensing instrumentsCondensing instruments

Amalgam   carriers   and condensers are used for Amalgam   carriers   and condensers are used for this purpose. this purpose.

4. CARVING4. CARVING

Soon after condensing the AM, the surface Soon after condensing the AM, the surface layer , which is rich in mercury, is carved away layer , which is rich in mercury, is carved away with a sharp instrument.with a sharp instrument.

If carving is delayed too long the material may If carving is delayed too long the material may become too hard to carve and there is a danger become too hard to carve and there is a danger of chipping at the margins.of chipping at the margins.

4. CARVING4. CARVING

Amalgam carversAmalgam carvers

5. POLISHING5. POLISHING

Polishing is carried out in order to achieve Polishing is carried out in order to achieve a lustrous surface having a more acceptable a lustrous surface having a more acceptable appearance and better corrosion resistance.appearance and better corrosion resistance.

The fillings should not be polished untill the The fillings should not be polished untill the material has achieved a certain level of material has achieved a certain level of mechanical strength, otherwisw there is mechanical strength, otherwisw there is a danger of fracture , particularly at the margins.a danger of fracture , particularly at the margins.

Many products require a delay ofMany products require a delay of 24 hours between placing and 24 hours between placing and

polishing.polishing.

5. POLISHING5. POLISHING

AM polishing kitsAM polishing kits

AM polishersAM polishers

BlackDark purpleGreen

Amalgam indicationsAmalgam indications

In primary and permanent dentitionIn primary and permanent dentition In stress bearing areas of the mouthIn stress bearing areas of the mouth Small to moderate - sized cavities in the Small to moderate - sized cavities in the

posterior teethposterior teeth As a foundation to crownsAs a foundation to crowns When oral hygiene is badWhen oral hygiene is bad When moisture control is a problemWhen moisture control is a problem When cost is a concernWhen cost is a concern

Amalgam contraindicationsAmalgam contraindications

When esthetics is importantWhen esthetics is important When pation has a history of allergic When pation has a history of allergic

reactions to the alloyreactions to the alloy When cost is not a concernWhen cost is not a concern

Amalgam fillingAmalgam filling

Amalgam fillingAmalgam filling

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