amalgam for par test[1]

8/4/2019 Amalgam for Par Test[1]

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DENTAL AMALGAMDENTAL AMALGAM

Where is it?Where is it?


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Elemental Mercury

Un-ionized mercury

High vapor pressure

significant to dentistry Absorption

readily from lungs

poorly from GI and skin < 0.1%

not toxic when swallowed

Clarkson Crit Rev Clin Lab Sci 1987


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Inorganic Mercury

Highly toxic as inorganic salts

Hg2+ mercuric ionmercuric oxide

swallowed batteries by childrenmercuric sulfide

red tattoos

Hg1+ mercurous ionmercurous chloride

laxatives

teething powderWands Am J Med 1974 Litovitz

Pediatrics 1992
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Organic Mercury

Alkyl methyl - most toxic form

95% absorbed in gut

responsible for several masspoisonings

Minamata Bay, Japan - 1950 inorganic mercury dumped in bay

methylated by aquatic organisms

concentrates up food chain

ethyl preservative

Thimerosal anti-microbial in pharmaceuticals

Aryl highly toxic antifungal on seeds

Renzoni Environ Res 1998


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Mercury Monitoring

Exhalation

difficult to perform reliably

Urinebest method for chronic

exposure

symptoms 300 g/L normal < 25 g/L

Goldfranks Toxicologic Emergencies 1990


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Mercury Monitoring

Blood

normal < 6 g/L

reflects recent exposure

3-day half-life

reliable measurement of methylmercury

exposure Hair

not a reliable method

WHO Environmental Health Criteria


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Dental Occupational Exposure

Higher mercury level found in providers

with poor mercury hygiene

screening of dentists 2% had elevated urinary

mercury levels

avg. 36 g/L

evidence of adverse preclinical effects Echeverria Neurotoxicol Teratol 1995


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Comparison of Toxic Effects

Amalgam Composite Glass Ionomers

Systemic Toxicity

- acute

- chronic

None None None

Not verified Not verified Not verified

Allergic Reactions Rare Rare, but manycomponents haveallergic potential

Extremely rare

Anaphylaxis None so far Isolated cases None so far

Cytotoxicity Low Slight to high Slight to high

Mutagenicity or

Carcinogenicity

None Certain componentsmutagenic in vitro

Slight mutagenicity

Lichenoid reactions Yes Yes None

WHO 1997


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AMALGAM TERMINOLOGYAMALGAM TERMINOLOGY

AMALGAMAMALGAM = an alloy containing Hg as the major ingredient.= an alloy containing Hg as the major ingredient.

DENTAL AMALGAM = an alloy of Hg with Ag-Sn.DENTAL AMALGAM = an alloy of Hg with Ag-Sn.

DENTAL AMALGAM ALLOY = a Ag-Sn alloy (to be mixed with Hg).DENTAL AMALGAM ALLOY = a Ag-Sn alloy (to be mixed with Hg).


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ALLOY PRODUCTIONALLOY PRODUCTION

Melting / Casting / ComminutionMelting / Casting / Comminution IRREGULAR ParticlesIRREGULAR Particles

Melting / Spray AtomizationMelting / Spray Atomization SPHERICAL PARTICLESSPHERICAL PARTICLES

Cast ingots --> filed into powderCast ingots --> filed into powderIrregular particles = lathe cut = filingsIrregular particles = lathe cut = filings

Hot alloy sprayed into cold airHot alloy sprayed into cold airParticles spherodize and solidifyParticles spherodize and solidify

Polycrystalline particlesPolycrystalline particlesHomogenized by HT to remove coringHomogenized by HT to remove coring

Annealing HT to relieve cold work in filingsAnnealing HT to relieve cold work in filings

Spheres are acid-washedSpheres are acid-washedGenerally spheres are HTGenerally spheres are HT


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Hg / Alloy RATIOSHg / Alloy RATIOS

50:5050:5042:5842:58


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ALLOY MANIPULATIONALLOY MANIPULATION

Manual Trituration Procedures:Manual Trituration Procedures:

Alloy + HgAlloy + Hg mortar + pestlemortar + pestle manual mixingmanual mixing

Mechanical Trituration Procedures:Mechanical Trituration Procedures:

Powdered alloy + HgPowdered alloy + Hg capsule + pestlecapsule + pestle amalgamatoramalgamator

Pelleted alloy + HgPelleted alloy + Hg capsule + pestlecapsule + pestle amalgamatoramalgamator

Powdered alloy + HgPowdered alloy + Hg pre-capsulatedpre-capsulated amalgamatoramalgamator


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Dispersion Hardening

A crack will dead end or terminate on a

sphere that is dispersed in the matrix,

preventing a fatal crack of the material


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Propagation of a dental amalgam

crack

i di i h d i i


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To incorporate dispersion hardening into

dental amalgams: Conventional amalgam mixed small spheres of the

eutectic of AgCu in the powder, the phase

The eutectic was used for the low melting point.


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Final composition of the dispersion

strengthened amalgam (admixed alloy)

Ag 71 % 69.7 % Sn 26 % 17.7 %

Cu 2 % 12 %

Zn 1 % 0.9%

Sphere size ranged from 20-60m diameter

Before adding spheres After adding spheres


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Dispersion Hardened Amalgam

Clinical experience showed that the

amalgam performed well and showed little

corrosion.

The amalgam contained no 2

phase

The spheres were disappearing from the

amalgam


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Setting Reaction

Sn7Hg + Ag3Cu Sn5Cu6 + Ag3Hg

2 1

The 2 phase is converted to the and the 1phase

The Cu is the active metal in the conversion

This reaction is slow, taking months to go to completion

Cu could be added to the alloy The Cu must replace the Ag not the Sn

The addition of spheres for dispersion hardening doesnot produce the intended result


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High Cu single composition alloys

The development of making spheres of

eutectics produced the technology of

making spheres of ternary alloys, producingall-spherical alloys

Most high copper alloys are spherical single

composition alloys Particle sizes are below 30 m for most of

these compositions


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Single composition all-spherical alloys

The advantages of the all spherical particles is

that

Close dense packing can be achieved

Less Hg is required ( 40 - 45 % by wt )

The amalgam sets faster (more surface area

of the particles)


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CLASSIFICATIONCLASSIFICATION

Copper content = low copper, high copperCopper content = low copper, high copper Particle size (and shape) = irregular, sphericalParticle size (and shape) = irregular, spherical Number of particle types = 1 or 2Number of particle types = 1 or 2 Zinc content = Zn-containing, Zn-freeZinc content = Zn-containing, Zn-free

Application of system of nomenclatureApplication of system of nomenclature

AlloyAlloy CopperCopper ParticleParticle Number ofNumber of ZincZincName:Name: Content:Content: Shape:Shape: Particles:Particles: Content:Content:

New True DentalloyNew True Dentalloy LowLow IrregularIrregular 1 Particle1 Particle NoNo

VelvalloyVelvalloy LowLow IrregularIrregular 1 Particle1 Particle NoNoDispersalloyDispersalloy HighHigh BothBoth 2 Particles2 Particles YesYesTytinTytin HighHigh SphericalSpherical 1 Particle1 Particle NoNo


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Rx and MICROSTRUCTURERx and MICROSTRUCTURE

IrregularIrregularAlloyAlloy

SphericalSphericalAlloyAlloy

AgAg Primary reactantPrimary reactant

SnSn Creates solubility, fluidityCreates solubility, fluidity

CuCu Reacts with SnReacts with Sn

ZnZn Alloy processing aidAlloy processing aid

HgHg Reactant with Ag (and Sn)Reactant with Ag (and Sn)


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SETTING REACTIONSSETTING REACTIONS

Low-Copper Dental Amalgam:Low-Copper Dental Amalgam:

2-Particle High-Copper Dental Amalgam:2-Particle High-Copper Dental Amalgam:

1-Particle High-Copper Dental Amalgam:1-Particle High-Copper Dental Amalgam:

S-AlloyS-Alloy + Hg+ Hg Residual AlloyResidual Alloy + Matrix-1+ Matrix-1 + Matrix-2+ Matrix-2AgAg33Sn/Cu+ HgSn/Cu+ Hg AgAg33Sn/CuSn/Cu + Ag+ Ag22HgHg33 + CuSn + Cu+ CuSn + Cu33SnSn

+ Hg+ Hg ++ 11 ++ ++

I-AlloyI-Alloy + Hg+ Hg Residual AlloyResidual Alloy + Matrix-1+ Matrix-1 + Matrix-2+ Matrix-2 + Hg+ Hg ( (AgAg33Sn)Sn) ++ 11 + (+ ( 22))

S-AlloyS-Alloy + Hg+ Hg Residual AlloyResidual Alloy + Matrix-1+ Matrix-1 + Matrix-2+ Matrix-2AlloyAlloy + Hg+ Hg Alloy (Ag-Cu)Alloy (Ag-Cu) ++ 11 ++ ++

I/S-AlloyI/S-Alloy + Hg+ Hg Residual AlloyResidual Alloy + Matrix-1+ Matrix-1 + Matrix-2+ Matrix-2Ag-SnAg-Sn + Hg+ Hg Ag-SnAg-Sn + Ag-Hg+ Ag-Hg + Sn-Hg+ Sn-HgAgAg33SnSn + Hg+ Hg AgAg33SnSn + Ag+ Ag22HgHg33 + Sn+ Sn7-87-8HgHg

+ Hg+ Hg ++ 11 ++ 22


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+ Hg+ Hg ++ ++

11 22

Penetrating CorrosionPenetrating Corrosion


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+ Hg+ Hg ++ ++

11 + spheres+ spheres ++


69 Ag69 Ag

18 Sn18 Sn

12 Cu12 Cu

1 Zn1 ZnDISPERSALLOYDISPERSALLOY


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PHASE DIAGRAMSPHASE DIAGRAMS

AgAg HgHg

AgAg33Sn + Hg >>>Sn + Hg >>>

AgAg22HgHg33 == 11

(26Ag-74Hg)(26Ag-74Hg)

11 ++


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Overview of ManipulationOverview of Manipulation

Selection / Proportioning / Amalgamation / Manipulation / PolishingSelection / Proportioning / Amalgamation / Manipulation / Polishing

Placement andPlacement and

CondensationCondensationCarvingCarving BurnishingBurnishing PolishingPolishing

Onset ofOnset of

MIXINGMIXINGOnset ofOnset of

WORKINGWORKINGOnset ofOnset of

SETTINGSETTINGEnd ofEnd of

SETTINGSETTING24 hours24 hours

TIMETIME


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AmalgamatorsAmalgamators

SPEEDSPEED TIMETIME

ENERGY = Speed x TimeENERGY = Speed x Time


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Unset amalgamUnset amalgam

AA

Setting amalgamSetting amalgam

BB

Ag-Hg crystalreaction products

Residual alloy

Excess Hg-rich matrixeliminated by condensation.


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DIMENSIONAL CHANGESDIMENSIONAL CHANGES

Dimensional changes on setting:Dimensional changes on setting:

CONTRACTION during alloy dissolutionCONTRACTION during alloy dissolution

EXPANSION during impingement of reaction product crystalsEXPANSION during impingement of reaction product crystals

(EXPANSION if side reactions due to H(EXPANSION if side reactions due to H22O contamination)O contamination)

EXP (+)EXP (+)

CONT (--)CONT (--)

TIMETIME

Dimensional changes on depend on reaction variables:Dimensional changes on depend on reaction variables:

Particle size, Hg/alloy ratio, trituration time, condensation, ...Particle size, Hg/alloy ratio, trituration time, condensation, ...

ADA =ADA =

20 20 mm


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AMALGAM PROPERTIESAMALGAM PROPERTIES

2.2. Clinical PerformanceClinical Performance

a.a. Longevity = 20-25 yrs ideally, 8-12 yrs practicallyLongevity = 20-25 yrs ideally, 8-12 yrs practicallyb.b. Modes of failure = caries, marginal fracture, bulkModes of failure = caries, marginal fracture, bulk

UNITED

STATES

WORLD

ADA FDI

ISOANSI

B.B. Properties:Properties:

1.1. PhysicalPhysical

2.2. MechanicalMechanical3.3. ChemicalChemical4.4. BiologicalBiological

A.A. Introduction:Introduction:

1.1. Specifications for Amalgam PropertiesSpecifications for Amalgam Propertiesa.a. ADA / ANSI and ISOADA / ANSI and ISOb.b. Determination of safety and efficacyDetermination of safety and efficacy


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Physical PropertiesPhysical Properties

1.1. Thermal conductivity =Thermal conductivity =

2.2. Electrical conductivity =Electrical conductivity =

3.3. Coefficient of thermal expansion =Coefficient of thermal expansion =

4.4. Radiopacity =Radiopacity =

5.5. Color =Color =

[>2 mm Aluminum][>2 mm Aluminum]

[Lustrous, shiny, white][Lustrous, shiny, white]

25 ppm/25 ppm/CC[High][High]

[High][High]


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Mechanical PropertiesMechanical Properties

Compressive Strength (psi)Compressive Strength (psi) Tensile Strength (psi)Tensile Strength (psi)

15-min15-min 1-hr1-hr 24-hr24-hr 15-min15-min 1-hr1-hr 24-hr24-hr

LOW COPPER:LOW COPPER:

VelvalloyVelvalloy 5,4005,400 17,40017,400 56,20056,200 625625 1,9001,900 9,0009,000

SpheralloySpheralloy 5,8005,800 18,50018,500 56,90056,900 450450 1,5501,550 8,8008,800

HIGH COPPER:HIGH COPPER:

Optalloy IIOptalloy II 9,1009,100 23,80023,800 55,90055,900 1,0001,000 2,3502,350 7,2507,250

DispersalloyDispersalloy 6,2006,200 22,40022,400 59,90059,900 575575 1,7501,750 6,9906,990

IndiloyIndiloy 4,6004,600 26,30026,300 64,50064,500 450450 2,4002,400 6,5006,500

SybraloySybraloy 23,80023,800 50,00050,000 72,70072,700 2,1902,190 4,7004,700 6,6006,600

TytinTytin 10,20010,200 40,80040,800 79,10079,100 990990 4,0004,000 9,3009,300


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Mechanical PropertiesMechanical Properties

TYTIN (Kerr Dental Mfg) = tie up the tinTYTIN (Kerr Dental Mfg) = tie up the tin

High-Copper, Spherical, 1 Particle, Zn-freeHigh-Copper, Spherical, 1 Particle, Zn-free

42% Hg mixed with alloy42% Hg mixed with alloy

Fast-settingFast-setting

High early strengthHigh early strength

PolishedPolishedSurfaceSurface

FractureFracture

SurfaceSurface


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Biological PropertiesBiological Properties

Mercury Toxicity:Mercury Toxicity:OSHA maximumOSHA maximum TLV = 50TLV = 50 g/mg/m33 (vapor) per 40 hr work week.(vapor) per 40 hr work week.Transient intraoral release (


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Clinical PerformanceClinical Performance

Reasons for Failure:Reasons for Failure:Low-copper amalgam marginal fracture and secondary caries.Low-copper amalgam marginal fracture and secondary caries.High-copper amalgam marginal fracture and bulk fracture.High-copper amalgam marginal fracture and bulk fracture.

Jorgensen theory of mercuroscopic expansion (and marginal fracture)Jorgensen theory of mercuroscopic expansion (and marginal fracture)

Internal corrosionInternal corrosion

PenetratingPenetratingCorrosionCorrosion

Corrosion at marginsCorrosion at margins

SuperficialSuperficialCorrosionCorrosion

Sn-O-Cl and Sn-OSn-O-Cl and Sn-O

CorrosionCorrosionProductsProducts


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Clinical EvaluationClinical Evaluation

Mahler scale:Mahler scale:

Hi-Cu, no ZnHi-Cu, no Zn

Hi-Cu, +ZnHi-Cu, +Zn

Low-Cu, +ZnLow-Cu, +Zn

Low-Cu, no ZnLow-Cu, no Zn

Hi-CuHi-Cu

Low-CuLow-Cu

amalgam for par test[1]

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