Dental AmalgamDental AmalgamKraigS. Vandewalle, Col, USAF, DCOfficial Disclaimer•The opinions expressed in this presentation arethose of the author and do not necessarilyreflect the official position of the US Air Force orthe Department of Defense (DOD)•Devices or materials appearing in thispresentation are used as examples of currentlyavailable products/technologies and do notimply an endorsement by the author and/or theUSAF/DODOverview• History•Basic composition•Basic setting reactions•Classifications•Manufacturing•Variables in amalgamperformanceClickhereforbriefing on dental amalgam (PDF)History•1833–Crawcourbrothers introduceamalgam to US•powdered silver coins mixed with mercury–expanded on setting•1895–G.V. Black develops formulafor modern amalgam alloy•67% silver, 27% tin, 5% copper, 1% zinc–overcame expansion problemsHistory•1960’s–conventional low-copper lathe-cut alloys•smaller particles–first generation high-copper alloys•Dispersalloy (Caulk)–admixture of spherical Ag-Cueutectic particles withconventional lathe-cut–eliminated gamma-2 phaseMahler, J Dent Res 1997History•1970’s–first single composition spherical•Tytin (Kerr)•ternary system (silver/tin/copper)•1980’s–alloys similar to Dispersalloy and Tytin•1990’s–mercury-free alloysMahler, J Dent Res 1997Amalgam•An alloy of mercury with another metal.Why Amalgam?•Inexpensive•Ease of use•Proven track record–>100 years•Familiarity•Resin-free–less allergies than compositeClickherefor Talking Paper onAmalgam Safety (PDF)Constituents in Amalgam•Basic–Silver– Tin–Copper– Mercury• Other– Zinc–Indium–PalladiumBasic Constituents•Silver (Ag)–increases strength–increases expansion•Tin (Sn)–decreases expansion–decreased strength–increases setting timePhillip’s Science of Dental Materials 2003Basic Constituents•Copper (Cu)–ties up tin•reducing gamma-2 formation–increases strength–reduces tarnish and corrosion–reduces creep•reduces marginal deteriorationPhillip’s Science of Dental Materials 2003Basic Constituents•Mercury (Hg)–activates reaction–only pure metal that is liquidat room temperature–spherical alloys•require less mercury–smaller surface area easier to wet»40 to 45% Hg–admixed alloys•require more mercury–lathe-cut particles more difficult to wet»45 to 50% HgClickherefor ADA MercuryHygiene RecommendationsPhillip’s Science of Dental Materials 2003Other Constituents•Zinc (Zn)–used in manufacturing•decreases oxidation of other elements–sacrificial anode–provides better clinical performance•less marginal breakdown–Osborne JW Am J Dent 1992–causes delayed expansion with low Cu alloys•if contaminated with moisture during condensation–Phillips RW JADA 1954H2O + Zn ZnO+H2⇒Phillip’s Science of Dental Materials 2003Other Constituents•Indium (In)–decreases surface tension•reduces amount of mercury necessary•reduces emitted mercury vapor–reduces creep and marginal breakdown–increases strength–must be used in admixed alloys– example•Indisperse(IndisperseDistributing Company)–5% indiumPowell, J Dent Res1989Other Constituents•Palladium (Pd)–reduced corrosion–greater luster– example•Valiant PhD (Ivoclar Vivadent)–0.5% palladiumMahler, J Dent Res 1990Basic Composition•Asilver-mercury matrix containing fillerparticles of silver-tin•Filler (bricks)–Ag3Sn called gamma•can be in various shapes–irregular (lathe-cut), spherical,or a combination• Matrix–Ag2Hg3called gamma 1•cement–Sn8Hgcalled gamma 2•voidsPhillip’s Science of Dental Materials 2003Basic Setting Reactions•Conventional low-copper alloys•Admixed high-copper alloys•Single composition high-copper alloysConventional Low-Copper Alloys•Dissolution and precipitation•Hg dissolves Ag and Snfrom alloy•IntermetalliccompoundsformedAg-SnAlloyAg-SnAlloyAg-SnAlloyMercury(Hg)AgAgAgSnSnSnHgHgAg3Sn + HgSn + Hg⇒Ag3Sn + AgSn + Ag2Hg3+ Sn8HgPhillip’s Science of Dental Materials 2003γ γγ1γ2Conventional Low-Copper Alloys•Gamma (γ) = Ag3Sn–unreactedalloy–strongest phase andcorrodes the least–forms 30% of volumeof set amalgamAg-SnAlloyAg-SnAlloyAg-SnAlloyMercuryAgAgAgSnSnSnHgHgHgAg3Sn + HgSn + Hg⇒Ag3Sn + AgSn + Ag2Hg3+ Sn8HgPhillip’s Science of Dental Materials 2003γ γγ1γ2Conventional Low-Copper Alloysγ1•Gamma 1 (γ1) = Ag2Hg3–matrix for unreactedalloyand 2nd strongest phase–10 micron grainsbinding gamma(γ)–60% of volumeAg-SnAlloyAg-SnAlloyAg-SnAlloyAg3Sn + HgSn + Hg⇒Ag3Sn + AgSn + Ag2Hg3+ Sn8HgPhillip’s Science of Dental Materials 2003γ γγ1γ2Conventional Low-Copper Alloys•Gamma 2 (γ2) = Sn8Hg–weakest and softest phase–corrodes fast, voids form–corrosion yields Hg whichreacts with more gamma(γ)–10% of volume–volume decreases with timedue to corrosionγ2Ag-SnAlloyAg-SnAlloyAg-SnAlloyAg3Sn + HgSn + Hg⇒Ag3Sn + AgSn + Ag2Hg3+ Sn8HgPhillip’s Science of Dental Materials 2003γ γγ1γ2Admixed High-Copper Alloys•Ag enters Hg from Ag-Cuspherical eutectic particles–eutectic•an alloy in which the elementsare completely soluble in liquidsolution but separate into distinctareas upon solidification•Both Ag and Snenter Hgfrom Ag3Sn particlesAg-SnAlloyAg-SnAlloyMercuryAgAgAgSnSnAg-Cu AlloyAgHgHgAg3Sn + AgSn + Ag-Cu + HgCu + Hg⇒Ag3Sn + AgSn + Ag-Cu + AgCu + Ag2Hg3+ Cu6Sn5γ γγ1ηPhillip’s Science of Dental Materials 2003Admixed High-Copper Alloys•Sndiffuses to surface ofAg-Cu particles–reacts with Cu to form(eta)Cu6Sn5(η)•around unconsumedAg-Cu particlesAg-SnAlloyAg-Cu AlloyηAg-SnAlloyAg3Sn + AgSn + Ag-Cu + HgCu + Hg⇒Ag3Sn + AgSn + Ag-Cu + AgCu + Ag2Hg3+ Cu6Sn5γ γγ1ηPhillip’s Science of Dental Materials 2003Admixed High-Copper Alloys•Gamma 1 (γ1) (Ag2Hg3)surrounds(η)etaphase(Cu6Sn5) and gamma(γ)alloy particles (Ag3Sn)Ag-SnAlloyγ1Ag-Cu AlloyηAg-SnAlloyAg3Sn + AgSn + Ag-Cu + HgCu + Hg⇒Ag3Sn + AgSn + Ag-Cu + AgCu + Ag2Hg3+ Cu6Sn5γ γγ1ηPhillip’s Science of Dental Materials 2003Single CompositionHigh-Copper Alloys•Gamma sphere (γ) (Ag3Sn)with epsilon coating (ε)(Cu3Sn)•Ag and Sndissolve in HgAg-SnAlloyAg-SnAlloyAg-SnAlloyMercury(Hg)εAgSnAgSnAg3Sn + CuSn + Cu3Sn + HgSn + Hg⇒Ag3Sn + CuSn + Cu3Sn + AgSn + Ag2Hg3+ Cu6Sn5Phillip’s Science of Dental Materials 2003γ γγ1ηεεSingle CompositionHigh-Copper Alloys•Gamma 1 (γ1) (Ag2Hg3) crystalsgrow binding together partiallydissolved gamma (γ) alloyparticles (Ag3Sn)•Epsilon(ε)(Cu3Sn) developscrystals on surface ofgamma particle (Ag3Sn)in the form of eta(η)(Cu6Sn5)–reduces creep–prevents gamma-2 formationAg-SnAlloyAg-SnAlloyAg-SnAlloyγ1ηAg3Sn + CuSn + Cu3Sn + HgSn + Hg⇒Ag3Sn + CuSn + Cu3Sn + AgSn + Ag2Hg3+ Cu6Sn5Phillip’s Science of Dental Materials 2003γ γγ1ηεεClassifications•Based on copper content•Based on particle shape•Based on method of addingcopperCopper Content•Low-copper alloys–4to 6% Cu•High-copper alloys–thought that 6% Cu was maximum amount•due to fear of excessive corrosion and expansion–Now contain 9 to 30% Cu•at expense of AgPhillip’s Science of Dental Materials 2003Particle Shape•Lathe cut–low Cu•New TrueDentalloy–high Cu•ANA 2000•Admixture–high Cu•Dispersalloy, ValiantPhD•Spherical–low Cu•CavexSF–high Cu•Tytin, ValiantMethod of Adding Copper• Single Composition Lathe-Cut (SCL)• Single Composition Spherical (SCS)• Admixture: Lathe-cut + Spherical Eutectic (ALE)• Admixture: Lathe-cut + Single CompositionSpherical (ALSCS)Single Composition Lathe-Cut(SCL)•More Hg needed than spherical alloys•High condensation force needed due tolathe cut•20% Cu•Example–ANA 2000 (NordiskaDental)Single Composition Spherical(SCS)•Spherical particles wet easier with Hg–less Hg needed (42%)•Less condensation force, larger condenser•Gamma particles as 20 micron spheres–with epsilon layer on surface•Examples–Tytin (Kerr)–Valiant (Ivoclar Vivadent)Admixture:Lathe-cut + Spherical Eutectic(ALE)•Composition–2/3 conventional lathe cut (3% Cu)–1/3 high Cu spherical eutectic (28% Cu)–overall 12% Cu, 1% Zn•Initial reaction produces gamma 2–no gamma 2 within two years•Example–Dispersalloy (Caulk)Admixture:Lathe-cut + Single CompositionSpherical (ALSCS)•High Cu in both lathe-cut and sphericalcomponents–19% Cu•Epsilon layer forms on both components•0.5% palladium added–reinforce grain boundaries on gamma 1•Example–Valiant PhD (Ivoclar Vivadent)Manufacturing Process•Lathe-cut alloys–Ag & Snmelted together–alloy is cooled•phases solidify–heat treated•400 oC for 8 hours–ground, then milled to 25 -50 microns–heat treated to release stresses of grindingPhillip’s Science of Dental Materials 2003Manufacturing Process•Spherical alloys–alloy is melted–atomized•spheres form as particles cool–sizes range from 5 -40 microns•variety improves condensabilityPhillip’s Science of Dental Materials 2003Material-Related Variables•Dimensional change•Strength•Corrosion•CreepDimensional Change•Most high-copper amalgams undergo anet contraction•Contraction leaves marginal gap–initial leakage•post-operative sensitivity–reduced with corrosion over timePhillip’s Science of Dental Materials 2003Dimensional Change•Net contraction–type of alloy•spherical alloys have morecontraction–less mercury–condensation technique•greater condensation = higher contraction–triturationtime•overtriturationcauses higher contractionPhillip’s Science of Dental Materials 2003Strength•Develops slowly–1hr: 40 to 60% of maximum–24 hrs: 90% of maximum•Spherical alloys strengthen faster–require less mercury•Higher compressive vs. tensile strength•Weak in thin sections–unsupported edges fracturePhillip’s Science of Dental Materials 2003Corrosion•Reduces strength•Seals margins–low copper•6 months–SnO2, SnCl–gamma-2 phase–high copper•6 -24 months– SnO2, SnCl, CuCl–eta-phase (Cu6Sn5)Sutow, J Dent Res 1991Creep•Slow deformation of amalgam placed undera constant load–load less than that necessary to producefracture•Gamma 2 dramatically affects creep rate–slow strain rates produces plastic deformation•allows gamma-1 grains to slide•Correlates with marginal breakdownPhillip’s Science of Dental Materials 2003Creep•High-copper amalgams have creepresistance–prevention of gamma-2 phase•requires >12% Cu total–single composition spherical•eta(Cu6Sn5) embedded in gamma-1 grains–interlock–admixture•eta(Cu6Sn5) around Ag-Cu particles–improves bonding to gamma 1Clickherefor table of creep valuesDentist-Controlled Variables•Manipulation–trituration–condensation–burnishing–polishingTrituration•Mixing time–refer to manufacturerrecommendations•Clickherefor details•Overtrituration–“hot”mix•sticks to capsule–decreases working / setting time–slight increase in setting contraction•Undertrituration–grainy, crumbly mixPhillip’s Science of Dental Materials 2003Condensation• Forces–lathe-cut alloys•small condensers• highforce–spherical alloys•large condensers•less sensitive to amount of force•vertical / lateral with vibratory motion–admixture alloys•intermediate handling between lathe-cut and sphericalBurnishing•Pre-carve–removes excess mercury–improves margin adaptation• Post-carve–improves smoothness•Combined–less leakageBen-Amar, Dent Mater 1987Early Finishing•After initial set–prophycup with pumice–provides initial smoothness to restorations–recommended for spherical amalgamsPolishing•Increased smoothness•Decreased plaque retention•Decreased corrosion•Clinically effective?–no improvement in marginal integrity•Mayhew, Oper Dent 1986•Collins, J Dent 1992–Clickherefor abstractAlloy Selection•Handling characteristics•Mechanical and physicalproperties•Clinical performanceClickherefor more detailsHandling Characteristics•Spherical–advantages•easier to condense–around pins•hardens rapidly•smoother polish–disadvantages•difficult to achieve tight contacts•higher tendency for overhangsPhillip’s Science of Dental Materials 2003Handling Characteristics•Admixed–advantages•easy to achieve tight contacts•good polish–disadvantages•hardens slowly–lower early strengthAmalgam PropertiesCompressiveStrength (MPa)% CreepTensileStrength(24 hrs) (MPa)Amalgam Type1 hr7 daysLow Copper11453432.060Admixture21374310.448SingleComposition32625100.13641Fine Cut, Caulk2Dispersalloy, Caulk3Tytin, KerrPhillip’s Science of Dental Materials 2003Survey of Practice TypesCivilian General Dentists68%32%AmalgamUsersAmalgamFreeHaj-Ali, Gen Dent 2005Frequency of Posterior Materialsby Practice Type39%51%3%7%AmalgamDirectCompositeIndirectCompositeOther3%77%8%12%Amalgam UsersAmalgam FreeHaj-Ali, Gen Dent 2005Profile of Amalgam UsersCivilian Practitioners78%22%Do you use amalgam inyour practice?YesNoDPR 200588%12%Do you place fewer amalgamsthan 5 years ago?YesNoReview of Clinical Studies(Failure Rates in Posterior Permanent Teeth)02468AmalgamDirectCompCompInlaysCeramicInlaysCAD/CAMInlaysGoldInlays &OnlaysGILongitudinalCrossSectional% Annual FailureHickel, J AdhesDent 2001Review of Clinical Studies(Failure Rates in Posterior Permanent Teeth)051015 Am al ga m D ir e c t C o m p C o m pom e r Co m p Inla ys Ceram i c I n l a y s CA D/ CAM C a s t G o ld GI Tu nne l ART% Annual FailureManhart, OperDent 2004Clickherefor abstractStandard DeviationLongitudinal and Cross-SectionalDataAcknowledgements•Dr. David Charlton•Dr. Charles Hermesch•Col Salvador Flores