Presented By: Dr. Amrita Ghosh (2ND yr PGT)

Guided By :Prof. ( Dr.) D. Mazumder

Principal & H.O.D Dept. Of Conservative Dentistry & Endodontics Dr. R A D C & H , Kolkata.

• DEFINITION

An amalgam is an alloy that contains mercury as one of its constituents.

• DENTAL AMALGAM

An alloy of mercury, silver, copper and tin which may also contain palladium ,zinc and other elements to improve handling characteristics and clinical performance

The general term amalgam is also used as a synonym by the dental professionals

HISTORY•DENTAL AMALGAM APPARENTLY WAS FIRST USED BY CHINESE SU KUNG IN 659AD, AS MENTIONED IN MATERIA MEDICA.

•LATER, LI SHIHCHEN (1578) CHRONICLED A DENTAL MIXTURE OF 100 PARTS MERCURY, WITH 45 PARTS SILVER, 900 PARTS TIN.

• SILVER AMALGAM FIRST INTRODUCED BY BELL (ENGLAND) IN 1819.

•TAVEAU- USED IN PARIS IN 1826 .

•IN 1833- TWO FRENCH RESEARCHERS –CRAWCOUR BROTHERS– INTRODUCED AMALGAM AS ‘ROYAL MINERAL SUCCEDANEUM’ IN U.S.

•AMALGAM AT THIS TIME WAS MADE BY FILING SILVER COINS AND MIXING THIS FILING WITH MERCURY. •THIS COMPOSITION WAS FURTHER IMPROVED BY ADDING TIN TO SILVER OR BY FORMING AN ALLOY OF SILVER – TIN BY FUSING THE METALS.

AMALGAM WAR• INITIATED IN 1841 ALSO KNOWN AS THE ‘FIRST AMALGAM WAR’

• DR. CHAPIN A. HARRIS (1839) SAID AMALGAM IS AN ABOMINABLE ARTICLE

FOR DENTAL FILLING.

• 1843-RESOLUTION BY AMERICAN SOCIETY OF DENTAL SURGEONS THAT

AMALGAM USE IS MALPRACTICE.

• 1845- PLEDGE BY THIS ORGANISATION NOT TO USE AMALGAM.

• 1850-PLEDGE RESCINDED. MARKED END OF AMALGAM WAR OFFICIALY.

• INVESTIGATIONS WERE BEGUN ON AMALGAM COMPOSITION IN

GERMANY ,U.S. & FRANCE.

• THE QUESTION OF AMALGAM COMPOSITION WAS FINALLY SETTLED IN 1895

BY DR. G.V. BLACK . (67.5% Ag; 27.5% Sn; 5% Cu).

• The Second Amalgam War was started by a German chemist, professor Alfred Stock in the mid 1920’s when Stock claimed to have evidence showing that mercury could be absorbed from dental amalgams and that this led to serious health problems. Stock reported that nearly all dentists had excess mercury in their urine.

• He reported that mercury levels in urine of 7 patients with amalgam ranged from 0.1 to 40 mg/L

• The current controversy, sometimes termed the “Third Amalgam War” began primarily through the seminars, writings and videotapes of H.A. Huggins, a dentist from Colorado Springs. He was convinced that mercury released from dental amalgam was responsible for a plethora of human diseases affecting the cardiovascular and nervous systems.

• 1991- Issue reported by a major television

• NIH- NIDR & FDA Reexamined the issue ---- concluded that there is no

basis for the claim

USES

• Moderate to large Class I & II restorations.• Class V restorations• Foundations• Caries control restoration• For making dies.• Earlier as retrograde rootcanal filling

material.

INDICATION

• In clinical situations involving heavy occlusal functioning.

• In less optimum conditions of moisture control.

• Operator ability.

CONTRAINDICATION

• Anterior teeth and clearly visible surfaces of posterior teeth.

• Remaining tooth structure requires support / would require extensive preparation to accommodate amalgam.

• Treatment of incipient / early primary fissure caries.

ADVANTAGES

1. Ease of use2. High compressive strength3. Excellent wear resistance4. Favorable long-term clinical results5. Lower cost than for composite restorations6. Bonded amalgams have "bonding" benefits:• Less microleakage• Less interfacial staining• Minimal postoperative sensitivity• Some retention benefits• Esthetic benefit of sealing by not permitting the amalgam to discolor the

adjacent tooth structure

DISADVANTAGES

1. Noninsulating2. Nonesthetic3. Less conservative (more removal of tooth

structure during tooth preparation)4. More difficult tooth preparation5. Weakens tooth structure (unless bonded)6. More technique sensitive if bonded 7. Initial marginal leakage

DENTAL AMALGAM ALLOY

• An alloy of silver, copper, tin and other elements that is formulated and processed in the form of powder particles or as compressed pellet.

• Also known as alloy for dental amalgam.

GENERATIONS OF AMALGAM ALLOY

• FIRST GENERATION Amalgam that was studied and recommended

by G.V.Black

- Composed of 3 parts silver & 1 part tin.

2ND GENERATION Addition of zinc and copper to the first generation

3RD GENERATION Admixture of spherical Ag ₃ – Cu eutectic alloy to the original alloy powder

4TH GENERATION Alloying of copper to silver and tin , up to 29% form a ternary alloy in which most of the tin is firmly bonded to copper. 5TH GENERATION Alloying of silver, copper , tin and indium creates a true quaternary alloy, in which almost none of the tin is available to react with mercury.

6TH GENERATION Alloying of palladium (10%),silver(62%), copper(28%),to form a eutectic alloy which is lathe cut and blended into 1st , 2nd or 3rd generation amalgam in the ratio of 1:2.

Classification of Amalgam AlloyAccording to no. of alloyed metals

– Binary alloys (Ag-Sn)– Ternary alloys (Ag-Sn-Cu)– Quaternary (Ag-Sn-Cu-In)

Acc to particle size – Microcut– Fine cut– Coarse cut

Acc to copper content– Low copper <6%– High copper >6%

Acc to zinc content– Zinc containing >0.01%– Zinc free <0.01%

Acc to shape of produced particles – Spherical (Smooth-surfaced)– Lathe-cut (Irregular shaped)– Admixed

Acc to alloy Content - Unmixed - Admixed

Acc to presence of noble metals

ALLOY COMPOSITION• ADA Specification No. 1 require that amalgam alloy should be

predominantly silver and tin.

• Unspecified amounts of other elements like copper ,zinc , gold and mercury are allowed in concentration less than silver or tin

• ZINC containing alloy- more than 0.01%

• ZINC free alloy- less than 0.01%

EFFECTS OF VARIOUS COMPONENTS OF AMALGAM

SILVER COPPER TIN

Increases strength Increases Strength Controls reaction rate

Increases Expansion Increases Expansion Decreases strength

Decreases flow Decreases flow Decreases Expansion

Decreases setting time

Decreases setting time

Increases Flow

Increases corrosion resistance

Increases corrosion resistance

Decreases corrosion resistance

Decreases plasticity Increases plasticity

Increases hardness

ZINC INDIUM PALLADIUM

Increases strength Increases strength Increases strength

Increases Expansion Increases Expansion Increases corrosion resistance

Increases Flow Increases Flow

Increases setting time Increases setting time MERCURY

Decreases corrosion resistance

Amalgamation more difficult

Decreases setting time

Increases plasticity Decreases delayed expansion

Decreases brittleness

SCAVENGER

Manufacture of alloy powder

Milling/Lathe cutting Atomizing

Differences between Lathe-cut and Spherical alloys:

Lathe – cut Spherical

1. Require more mercury (50%) 2. Require more condensation force 3. Require smaller condenserpoints 4. Less ease in carving andburnishing 5. Less overhangs and strongproximal contacts

1. Require less mercury (42%) 2. Require less condensation force 3. Require broader condenserpoints 4. Smooth surface duringcarving & burnishing5. Overhangs and weak proximal contacts

METALLURGICAL PHASES IN AMALGAM

• Phases in amalgam alloys and set dental amalgam γ γ ₁ γ₂ є (epsilon) h (eta)

• Stiochiometric formula

Ag₃Sn Ag₂Hg₃ Sn₇₋₈Hg Cu₃Sn Cu₆Sn₅

LOW COPPER ALLOY

• LOWCOPPER contains

SILVER -69.4% TIN -26.2% COPPER - 2-5% ZINC - 0.8% ALSO CALLED CONVENTIONAL AMALGAM ALLOY

SETTING REACTION IN LOW COPPER ALLOYS: Alloy particles ( + ) + b g Hg g₁ + g ₂ + unconsumed alloy particles.

• The physical properties of the hardened amalgam depend on the relative percentage of each of the microstructural phases.

• The more unconsumed Ag-Sn particles found in the final structure , the stronger the amalgam.

• The weakest component is the g₂ phase.

• The hardness of Sn₇₋₈ Hg ( g₂ ) is 10% the hardness of Ag₂ Hg₃ ( g ₁ ).

HIGH COPPER ALLOY

• HIGH CORROSION RESISTANCE

• COPPER content 12 - 30%

• TWO TYPES- ADMIXED - SINGLE COMPOSITION

ADMIXED AMALGAM ALLOY• Introduced in 1963 by INNES AND YOUDELIS.

• Ag-Cu eutectic alloy (71.9% Ag and 28.1% Cu) particles are added to lathe cut low copper amalgam alloy particles.

• STRONGER- Due to increase in residual alloy particle & decrease in matrix.

• Contains 30-55% spherical high copper particle.

• Composition:- Ag-69% Sn-17% Cu-13% Zn-1%

• REACTION :• ALLOY PARTICLES (b+g) + Ag-Cu eutectic + Hg

g₁ + h + UNCONSUMED ALLOY OF BOTH TYPES OF PARTICLES

•When Hg reacts with an admixed powder, Ag

dissolves into the mercury from Ag-Cu alloy

particles .

• Both Ag and Sn dissolve into the Hg from the Ag-

Sn alloy particles.

•The Sn in solution diffuses to the surfaces of the

Ag-Cu alloy and reacts with Cu to form h phase

(Cu₆Sn₅)

• A layer of h crystals forms around unconsumed

Ag-Cu alloy particles.

•The layer also contains some g₁ crystals.

•g₁ forms simultaneously with h on the surface

of h covered Ag-Cu alloy & Ag-Sn lathe cut

alloy particles.

• ELIMINATION OF g 2 PHASE :• REACTION 1 :• Ag₃Sn (Excess γ phase) +Ag-Cu (Silver-Copper Eutectic) + Hg

Ag₂Hg₃ ( g ₁ Phase) + Sn₇₋₈Hg ( g ₂ Phase) +Ag₃Sn ( unreacted γ Phase) + Ag-Cu (unreacted Eutectic phase)

• REACTION 2 :• Ag-Cu (unreacted Eutectic phase) + Sn₇₋₈Hg (γ 2 Phase)

Ag₂Hg₃ + Cu₆Sn₅ ( η phase ) The second reaction occurs at mouth temperature for 1-2 weeks and

γ2 phase is thus nearly eliminated.

UNICOMPOSITIONAL ALLOY• DEVELOPED BY ASGAR IN 1974.

• EACH PARTICLE OF THIS ALLOY HAS THE SAME CHEMICAL COMPOSITION

• SILVER -60% TIN -27% COPPER -13% SMALL AMOUNTS OF INDIUM AND PALLADIUM SEEN IN SOME

ALLOY

• COPPER CONTENT VARIES BETWEEN 13-30%

• REACTION:-• Ag-Sn-Cu ALLOY PARTICLES + Hg

g1 + h+ UNCONSUMED ALLOY PARTICLES.

•When triturted with MERCURY, SILVER

& TIN from Ag-Sn dissolve.

•Little copper dissolve in Hg.

• g1 crystals grow forming a matrix

that binds the unreacted alloy particles

together.

• h crystals(Cu₆Sn₅)- Form a mesh at

the surface of alloy particles and are

also dispersed in the matrix.

FUNCTION OF THE η PHASE

• Strengthen the bond between alloy particles and γ₁ phase.

• Interlocks the γ₁ phase thus improving the amalgams resistance to deformation.

PHYSICAL PROPERTIES OF AMALGAM

DIMENSIONAL STABILITY• ANSI/ADA NO-1 requires that amalgam should

neither contract nor expand more than 20 µm / cm, measured at 37˚C, between 5 mins and 24 hrs after the beginning of trituration , with a device that is accurate to atleast 0.5 μm.

• Classically, amalgam initially undergoes contraction for about 20 min after the beginning of trituration and then begins to expand.

• Initial contraction is due to the dissolving of the alloy particles in Hg and resultant formation of γ₁ phase.

• On availability of sufficient Hg, the γ₁ crystals grow & impinge against each other resulting in expansion.

• Most modern amalgams, exhibit net contraction as their manipulation involves minimum Hg technique.

Factors affecting dimensional change:1) Components:

a) Increased γ phase or β phase, increased expansion

b) Increased traces of Tin, decreased expansion

2) Particle size: Decreased particle size, there is contraction

3) Particle shape: Smoother shape (as in spherical type) there is better wetting with Hg causing in faster amalgamation resulting in contraction.

4) Hg/Alloy ratio: Increased Hg/Alloy ratio -Increased expansion

5) Trituration: Rapid trituration and longer trituration results in contraction because of

– Faster amalgamation

– Decrease in particle size

– Pushing of Hg between particles

– Prevention of outward growth of crystals

6) Condensation: Increased condensation pressure causes closer contact of Hg with alloy particles and squeezing of excess Hg from the mix resulting in contraction.

• Expansion that occurs due to reaction of Hg with alloy components is termed Primary expansion or Mercuroscopic expansion.

• Mercuroscopic Expansion: Release of mercury from γ2 phase during electrochemical corrosion results in additional formation of phases on reaction with unreacted γ phase, causing further expansion.

• Expansion that occurs after 1 to 7 days due to moisture contamination during trituration or condensation before the amalgam mass is set, is termed Secondary expansion or Delayed expansion.

DELAYED EXPANSION

• Alloys containing Zn, if contaminated with moisture during trituration or condensation, a large expansion occurs.

• This is due to release of H₂ gas within the restoration creating an internal pressure of nearly 2,000 psi.

The gas is formed as follows: Zn + H₂O ZnO + H₂

• Starts after 3-5 days , continue for months reaching values greater than 400μm.

Effects of dimensional change

• Expansion >> 4%• Pressure on pulp causing pain • High point leading to occlusal interference causing pain • Pressure on cavity walls resulting in tooth fracture and pain. • Greater susceptibility to corrosion • Expansion over the cavity margins causes fracture of the restoration

("ditched amalgam")• • Contraction >> than 50µ/cm• Microleakage • Secondary caries • Plaque accumulation

STRENGTHAmalgam Compressive strength

(MPa)Tensile

strength(MPa)

ISOCREEP

(%)

1 hr 24 hrs 24 hrs

LOW-Cu 145 343 60 2.0

HIGH-Cu(Admixed)

137 431 48 0.4

HIGH-Cu(Single)

262 510 64 0.13

Factors affecting strength of Dental Amalgam• Trituration: Increased trituration within limits increases strength (due

to increased coherence of matrix crystals). Increased trituration beyond limits decreases strength (

due to cracking of formed crystals decreasing coherence).

• Hg/Alloy ratio: Increased Hg/Alloy ratio, decreased strength, because

increased Hg results in – Decreased unreacted γ phase – Increased γ2 phase – Increased residual Hg (weakest phase) within

amalgam.

• Condensation pressure Increased pressure (3-4lb/ square inch) within limits results in increased strength.

• Microstructure of amalgam: – Increased γ and γ1 phases there is increased strength – Presence of η phase there is increased strength – Increased γ2 phase, there is decreased strength

• Porosity

• Particle size: Decreased size ( 15 -35 ) m results in increased strength (due to increased surface area / unit volume)

• Particle shape: Regular uniform shape result in increased strength (due to more wettability, more coherent mass, less interrupted interphases)

• Effect of amalgam hardening rate: The ADA specification stipulates a minimum compressive strength of 80 Mpa at 1 hour.

CREEPDefn:-Time dependent plastic deformation that is produced by a

stressTYPES : 1) STATIC 2) DYNAMIC SIGNIFICANCE OF CREEP ON AMALGAM : Creep rate has been found to correlate with

marginal breakdown of traditional low-Cu amalgams.

• However for High-Cu amalgams , the Creep rates are less(< 0.1%) .

• Creep occurs because of grain boundary sliding.

• η crystals on γ1 grains prevent grain boundary sliding and therefore are responsible for decreased creep values of high copper alloys.

Factors affecting Creep

• Microstructure of amalgam – Increased γ1 fraction, increased creep – Increased γ2 fraction, increased creep – Increased grain size of γ1, decreased creep – Presence of η phase, decreased creep

• Hg/Alloy ratio: Increased Hg/Alloy ratio, increased creep (due to more residual Hg)

• Condensation pressure: Increased pressure within limits, decreased creep (due to less residual Hg)

• Delay between trituration and condensation: Increased creep

TARNISH & CORROSION• Amalgam undergoes 2 types of corrosion:- Chemical & Electrochemical

• Chemical corrosion results in formation of surface Silver sulfide layer.

• Electrochemical corrosion – Galvanic, Crevice & Stress Corrosion.

• The most common corrosion products of traditional amalgam alloys are oxides & oxychlorides of tin.

• Along the margins SnO helps to seal the space against microleakage. Thus, dental amalgam behaves as a self sealing restoration.

• Electrochemical corrosion of high-copper amalgams produce both Cu & Sn oxides & oxychlorides

MANIPULATION TECHNIQUES

MERCURY : ALLOY RATIO/PROPORTIONING

• A very important factor in the control of strength is the mercury content of the restoration.

• Sufficient mercury should be mixed with the alloy to coat the alloy particles and to allow a thorough amalgamation.

• But, for either low-copper alloys and High – copper alloys , the strength is markedly reduced when the mercury content is more than 54%.

For conventional mercury-added systems , TWO TECHNIQUES are used for achieving mercury reduction in the final restoration:-

i. Squeeze-cloth & increasing dryness techniqueii. Minimal mercury technique / Eames technique (1:1)

Methods of Dispensing Alloy and Hg

A wide variety of mercury and alloy dispensers are available:-

• Automatic mechanical dispensers

• Preweighed pellets- most convenient method of dispensing the alloy.

• Preproportioned capsules -alloy and Hg separated by disk or membrane

Trituration• Objectives:• To dissolve alloy particles in Hg so as to obtain a plastic

mass of amalgam which can be condensed into the cavity. • To remove oxide film coated on the alloy particles. • To pulverize the alloy particles for proper wetting by Hg.

• Methods:• With mortar and pestle (trituration pressure 2-3 psi) • With mechanical amalgamator

• Factors affecting trituration• Speed - number of unit movements/ unit time • Weight of the capsule and the pestle • Duration of trituration • Difference in the size between the pestle and the encasing capsule.

MULLING

• It is a continuation of trituration.

• Can be accomplished in two ways:- a) By kneading the plastic amalgam mix in a piece

of rubber dam.b) By triturating the mix in a pestle free capsule for

2-3 seconds after the specified time.

CONDENSATION• Objectives:• To condense unattacked g particles closely together

• To adapt amalgam to the cavity walls.

• To remove excess Hg.

• To bring Hg on the top of each increment so as to bind the increments to one another (increasing dryness technique).

• To increase the density of the restoration by development of an uniform compact mass with minimal voids.

• To increase the rate of hardening so that carving operation need not be unduly delayed.

• Methods:• Hand condensation • Mechanical condensation( impact type of force , rapid

vibrations)

• Condensation pressure: 3 to 4 lb/sq inch.

CARVING• Objectives: To produce a restoration with - • Proper physiological contours. • Minimal flash (no overhangs). • Functional, non-interfering occlusal anatomy. • Adequate, compatible marginal ridges. • Proper size, location, extent and inter-relationship of contact areas. • Physiologically compatible embrasures. • No interference with integrity of periodontium.

• Method: Performed by using various varieties of amalgam carvers available ( like Hollenbeck's carver). Carving is always from the tooth surface to the restoration surface. This is done to avoid removal of amalgam at the margins.

BURNISHING

• Objectives:• To further decrease the size and number of voids. • To express excess Hg on the surface of the amalgam

restoration. • To adapt amalgam to the cavosurface anatomy.

• Method: Performed using Beaver tail burnisher or Sprately burnisher. From amalgam to tooth.

FINISHING & POLISHING• Objectives:• To remove amalgam flash that has been left behind during

carving. • To remove superficial scratches and irregularities: decreases

fatigue failure, decreases concentration cell corrosion and decreases accumulation or adherence of plaque.

• To make the restoration aesthetically more appealing.

• Method: • Performed with extra fine silex, slurry of tin oxide, or pumice-

wet mix in a paste form to avoid heat generation (If temperature is >> 60°C, release of Hg occurs).

DENTAL MERCURY HYGIENE RECOMMENDATIONS

1) Ventilation: Provide proper ventilation in the work place by having fresh air exchanges and periodic replacement of filters, which may act as traps for mercury.

2) Monitor office: Monitor the mercury vapor level in the office periodically. This may be done by using dosimeter badges(Limit-50μg/m³in 8hr shift over 40hr work week).

3) Monitor personnel: Monitor office personnel by periodic analysis.

4) Office design: Use proper work area design to facilitate spill containment and cleanup.

5) Pre-capsulated alloys: Use pre-capsulated alloys to eliminate the possibility of a bulk mercury spill. Otherwise store bulk mercury properly in unbreakable containers on stable surfaces.

6) Amalgamator cover: Use an amalgamator fitted with a cover.7) Handling care: Use care in handling amalgam. Avoid skin

contact with mercury or freshly mixed amalgam. Avoid dry polishing.

8) Evacuation systems: Use high volume evacuation when finishing or removing amalgam. Evacuation system have traps or filters. Check, clean or replace traps and filters periodically.

9) Masks: Change mask as necessary when removing amalgam restorations.

10) Recycling: Store amalgam scrap under radiographic fixer solution in a covered container. Recycle amalgam scraps through refiners.

11) Contaminated items: Dispose of mercury contaminated items in sealed bags according to applicable regulations.

12) Spills: Clean up spilled mercury properly by using bottles, tapes or fresh mixes of amalgam to pick-up droplets: or use commercial clean up kits. Do not use household vacuum cleaner.

13) Clothing: Wear professional clothing only in dental operatory.

14) Select an appropriate alloy: Proper mercury/alloy ratio to avoid the need to remove excess mercury before packing.

RECENT ADVANCESGALLIUM BASED ALLOY• Gallium was discovered in 1875. It is a metal with similar

atomic structures and characteristics to mercury and has a melting temperature of 29°C. Hence, by 1928 Puttkammer suggested gallium as a substitute for mercury.

• Recently, 2 Gallium based restorative alloys have become available.

1. Gallium Alloy GF II ; 2. GalloyDisadvantages:-• Handling characteristics of this alloy is not favorable.• High level of corrosion is seen which causes loss of strength

marginal disintegration and marginal fracture in chunks.• Dimensional change of 21.5%.• Poor biocompatibility. • Costly.

MERCURY FREE DIRECT FILLING ALLOY:-Ag coated Ag-Sn particles which can be self-compacted.

BONDED AMALGAM RESTORATIONS:

To compensate for some of the disadvantages presented by amalgam a clinical technique that bonds amalgam to enamel and dentin was introduced by Baldwin as long back as 1897.

Advantages:-

I. It permits more conservative cavity preparations because it does not always require additional mechanical retention.

II. It eliminates the use of retentive pinsIII. It reduces marginal leakage to minimum.IV. It reinforces tooth structure weakened by caries and cavity preparation.V. It reduces the incidence of postoperative sensitivityVI. It reduces the incidence of marginal fracture.Disadvantages:-i. It has not been in use long enough to allow a proper evaluation of its clinical performance.ii. It increases the cost of amalgam restorationiii. It increases the time to perform a conventional amalgam and may be technique sensitive.

THANK YOU