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DENTALDENTALAMALGAMAMALGAM

Stephen C. BayneStephen C. BayneDepartment of Operative DentistryDepartment of Operative DentistrySchool of DentistrySchool of DentistryUniversity of North CarolinaUniversity of North CarolinaChapel Hill, NC 27599Chapel Hill, NC 27599--74507450

DENTAL AMALGAMDENTAL AMALGAM

What is it?What is it?

BEFORE REACTIONBEFORE REACTION AFTER REACTIONAFTER REACTION

AlloyAlloy

MercuryMercury ReactionReactionProductsProducts

AlloyAlloy

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 AgDENTAL AMALGAM = an alloy of Hg with Ag--SnSn..DENTAL AMALGAM ALLOY = a AgDENTAL AMALGAM ALLOY = a Ag--SnSn alloy (to be mixed with Hg).alloy (to be mixed with Hg).

ALLOY PRODUCTIONALLOY PRODUCTION

Melting / Casting / Melting / Casting / ComminutionComminution →→ IRREGULAR ParticlesIRREGULAR Particles

Melting / Spray Atomization Melting / Spray Atomization →→ SPHERICAL PARTICLESSPHERICAL PARTICLES

““Cast ingots Cast ingots ----> filed into powder> filed into powder””Irregular particles = lathe cut = filingsIrregular particles = lathe cut = filingsPolycrystalline particlesPolycrystalline particlesHomogenized by HT to remove coringHomogenized by HT to remove coringAnnealing HT to relieve cold work in filingsAnnealing HT to relieve cold work in filings

Hot alloy sprayed into cold airHot alloy sprayed into cold airParticles Particles spherodizespherodize and solidifyand solidifySpheres are acidSpheres are acid--washedwashedGenerally spheres are HTGenerally spheres are HT

Hg / Alloy RATIOSHg / Alloy RATIOS

50:5050:5042:5842:58

ALLOY MANIPULATIONALLOY MANIPULATION

Manual Trituration Procedures:Manual Trituration Procedures:Alloy + Hg Alloy + Hg →→ mortar + pestle mortar + pestle →→ manual mixingmanual mixing

Mechanical Trituration Procedures:Mechanical Trituration Procedures:Powdered alloy + Hg Powdered alloy + Hg →→ capsule + pestle capsule + pestle →→ amalgamatoramalgamatorPelletedPelleted alloy + Hg alloy + Hg →→ capsule + pestle capsule + pestle →→ amalgamatoramalgamator

Powdered alloy + Hg Powdered alloy + Hg →→ prepre--capsulatedcapsulated →→ amalgamatoramalgamator

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CLASSIFICATION CLASSIFICATION

•• 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 = ZnZinc content = Zn--containing, Zncontaining, Zn--freefree

Application of system of nomenclatureApplication of system of nomenclatureAlloyAlloy CopperCopper ParticleParticle Number ofNumber of ZincZincName:Name: Content:Content: Shape:Shape: Particles:Particles: Content:Content:New True New True DentalloyDentalloy LowLow IrregularIrregular 1 Particle1 Particle NoNoVelvalloyVelvalloy LowLow IrregularIrregular 1 Particle1 Particle NoNo““DispersalloyDispersalloy”” HighHigh BothBoth 2 Particles2 Particles YesYes““TytinTytin”” HighHigh SphericalSpherical 1 Particle1 Particle NoNo

Rx and MICROSTRUCTURE Rx and MICROSTRUCTURE

IrregularIrregularAlloyAlloy

SphericalSphericalAlloyAlloy

AgAg Primary reactantPrimary reactantSnSn Creates solubility, fluidityCreates solubility, fluidityCuCu Reacts with Reacts with SnSnZnZn Alloy processing aidAlloy processing aidHgHg Reactant with Ag (and Reactant with Ag (and SnSn))

SETTING REACTIONS SETTING REACTIONS

LowLow--Copper Dental Amalgam:Copper Dental Amalgam:I/SI/S--AlloyAlloy + Hg + Hg →→ Residual Alloy Residual Alloy + Matrix+ Matrix--1 1 + Matrix+ Matrix--22AgAg--SnSn + Hg+ Hg →→ AgAg--SnSn + Ag+ Ag--HgHg + + SnSn--HgHgAgAg33SnSn + Hg+ Hg →→ AgAg33SnSn + Ag+ Ag22HgHg33 + Sn+ Sn77--88HgHgγγ + Hg+ Hg →→ γ γ + + γ γ 11 + + γ γ 22

22--Particle HighParticle High--Copper Dental Amalgam:Copper Dental Amalgam:II--Alloy Alloy + Hg + Hg →→ Residual Alloy Residual Alloy + Matrix+ Matrix--1 1 + Matrix+ Matrix--22γγ + Hg+ Hg →→ γ (γ (AgAg33SnSn)) + + γ γ 11 + (+ (γ γ 22))SS--Alloy Alloy + Hg + Hg →→ Residual Alloy Residual Alloy + Matrix+ Matrix--1 1 + Matrix+ Matrix--22AlloyAlloy + Hg+ Hg →→ Alloy (Alloy (AgAg--CuCu) ) + + γ γ 11 + + εε + + ηη

11--Particle HighParticle High--Copper Dental Amalgam:Copper Dental Amalgam:SS--Alloy Alloy + Hg + Hg →→ Residual Alloy Residual Alloy + Matrix+ Matrix--1 1 + Matrix+ Matrix--22AgAg33Sn/Cu+ HgSn/Cu+ Hg →→ AgAg33Sn/CuSn/Cu + Ag+ Ag22HgHg33 + + CuSnCuSn + Cu+ Cu33SnSnγγ + Hg+ Hg →→ γ γ + + γ γ 11 + + εε + + ηη

Rx and MICROSTRUCTURE Rx and MICROSTRUCTURE

+ Hg + Hg →→ ++ ++

γγ γγ11 γγ22

BEFORE REACTIONBEFORE REACTION AFTER REACTIONAFTER REACTION

AlloyAlloy

MercuryMercury ReactionReactionProductsProducts

AlloyAlloy

+ Hg + Hg →→ ++ ++

γγ γγ11γγ + spheres+ spheres εε + + ηη

Rx and MICROSTRUCTURE Rx and MICROSTRUCTURE

69 Ag69 Ag18 18 SnSn12 Cu12 Cu

1 Zn1 Zn

DISPERSALLOYDISPERSALLOY

PHASE DIAGRAMS PHASE DIAGRAMS

AgAg HgHg

AgAg33Sn + Hg >>>Sn + Hg >>>AgAg22HgHg33 = = γγ11

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

γγ11γγ + + ββ

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Overview of Manipulation Overview of Manipulation

Selection / Proportioning / Amalgamation / Manipulation / PolishSelection / Proportioning / Amalgamation / Manipulation / Polishinging

Placement andPlacement andCondensationCondensation

CarvingCarving BurnishingBurnishing PolishingPolishing

Onset ofOnset ofMIXINGMIXING

Onset ofOnset ofWORKINGWORKING

Onset ofOnset ofSETTINGSETTING

End ofEnd ofSETTINGSETTING

24 hours24 hours

TIMETIME

Amalgamators Amalgamators

SPEEDSPEED TIMETIME

ENERGY = Speed x TimeENERGY = Speed x Time

Unset amalgamUnset amalgam

AA

Setting amalgamSetting amalgam

BB

Ag-Hg crystalreaction products

Residual alloy

Excess Hg-rich matrixeliminated by condensation.

DIMENSIONAL CHANGES DIMENSIONAL CHANGES

Dimensional changes on setting:Dimensional changes on setting:CONTRACTION during alloy dissolutionCONTRACTION during alloy dissolutionEXPANSION 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 µµmm

AMALGAM PROPERTIES AMALGAM PROPERTIES

2.2. Clinical PerformanceClinical Performancea.a. Longevity = 20Longevity = 20--25 yrs ideally, 825 yrs ideally, 8--12 yrs practically12 yrs practicallyb.b. Modes of failure = caries, marginal fracture, bulkModes of failure = caries, marginal fracture, bulk

UNITEDSTATES

WORLD

ADA FDI

ISOANSI

B.B. Properties:Properties:1.1. PhysicalPhysical2.2. MechanicalMechanical3.3. ChemicalChemical4.4. BiologicalBiological

A.A. Introduction:Introduction:1.1. Specifications for Amalgam PropertiesSpecifications for Amalgam Properties

a.a. ADA / ANSI and ISOADA / ANSI and ISO

Physical Properties Physical 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 25 ppmppm//ººCC[High][High]

[High][High]

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Mechanical Properties Mechanical Properties

Compressive Strength (psi)Compressive Strength (psi) Tensile Strength (psi)Tensile Strength (psi)1515--minmin 11--hrhr 2424--hrhr 1515--minmin 11--hrhr 2424--hrhr

LOW COPPER:LOW COPPER:VelvalloyVelvalloy 5,4005,400 17,40017,400 56,20056,200 625625 1,9001,900 9,0009,000SpheralloySpheralloy 5,8005,800 18,50018,500 56,90056,900 450450 1,5501,550 8,8008,800

HIGH COPPER:HIGH COPPER:OptalloyOptalloy IIII 9,1009,100 23,80023,800 55,90055,900 1,0001,000 2,3502,350 7,2507,250DispersalloyDispersalloy 6,2006,200 22,40022,400 59,90059,900 575575 1,7501,750 6,9906,990IndiloyIndiloy 4,6004,600 26,30026,300 64,50064,500 450450 2,4002,400 6,5006,500SybraloySybraloy 23,80023,800 50,00050,000 72,70072,700 2,1902,190 4,7004,700 6,6006,600TytinTytin 10,20010,200 40,80040,800 79,10079,100 990990 4,0004,000 9,3009,300

Mechanical Properties Mechanical Properties

TYTIN (Kerr Dental Mfg) = TYTIN (Kerr Dental Mfg) = ““tie up the tintie up the tin””HighHigh--Copper, Spherical, 1 Particle, ZnCopper, Spherical, 1 Particle, Zn--freefree42% Hg mixed with alloy42% Hg mixed with alloyFastFast--settingsettingHigh early strengthHigh early strength

PolishedPolishedSurfaceSurface

FractureFractureSurfaceSurface

Chemical Properties Chemical Properties

Clean Surface,High O2 Potential

(CATHODIC)Plaque Buildup,Low O2 Potential

(ANODIC)

(a)

(b)

(a) (b)

PlaqueBuildup

Clean Surface,High O2 Potential

(CATHODIC)Plaque Buildup,Low O2 Potential

(ANODIC)

(a)

(b)

(a) (b)

PlaqueBuildup

ELECTROCHEMICAL CORROSION:ELECTROCHEMICAL CORROSION:

•• Galvanic corrosionGalvanic corrosion•• Local galvanic corrosion (structure selective)Local galvanic corrosion (structure selective)•• Crevice corrosion (concentration cell)Crevice corrosion (concentration cell)•• Stress corrosionStress corrosion

Sn-O-ClSn-O

CHEMICALCHEMICALCORROSION:CORROSION: AgS

Biological Properties Biological Properties

Mercury Toxicity:Mercury Toxicity:OSHA maximum OSHA maximum TLV = 50 TLV = 50 µµg/mg/m33 (vapor) per 40 hr work week(vapor) per 40 hr work weekTransient intraoral release (<35 Transient intraoral release (<35 µµg/mg/m33))

Mercury Hypersensitivity:Mercury Hypersensitivity:Low level allergic reactionLow level allergic reactionEstimated to be Estimated to be < 1 / 100,000,000< 1 / 100,000,000

Amalgam Amalgam TatooTatoo::Can occur during amalgam removal if no rubber damCan occur during amalgam removal if no rubber damEmbedded amalgam particles corrode and locally discolor gumEmbedded amalgam particles corrode and locally discolor gumNo known adverse reactionsNo known adverse reactions

Clinical Performance Clinical Performance

Reasons for Failure:Reasons for Failure:Secondary Secondary cariescaries ---- principally with lowprincipally with low--copper amalgamcopper amalgamMarginal fractureMarginal fracture ---- prevalent with lowprevalent with low--copper amalgamcopper amalgamBulk fractureBulk fracture ---- most common with highmost common with high--copper amalgamcopper amalgam

Jorgensen theory of mercuroscopic expansionJorgensen theory of mercuroscopic expansion

Corrosion at marginsCorrosion at margins

SnSn--OO--ClCl and and SnSn--OO

Internal corrosionInternal corrosion

PENETRATING versus SUPERFICIAL CORROSIONPENETRATING versus SUPERFICIAL CORROSION

Clinical EvaluationClinical Evaluation

Mahler scale:Mahler scale:

??????

HiHi--Cu, no ZnCu, no ZnHiHi--Cu, +ZnCu, +Zn

LowLow--Cu, +ZnCu, +Zn

LowLow--Cu, no ZnCu, no Zn

HiHi--CuCu LowLow--CuCu

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