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amalgam presentation conservative and ENDODONTIC
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- 2. Official Disclaimer • Theopinions expressed in this presentation are those of the author and do not necessarily reflect the official position of the US Air Force or the Department of Defense (DOD) • Devices or materials appearing in this presentation are used as examples of currently available products/technologies and do not imply an endorsement by the author and/or the USAF/DOD
- 3. Overview • History • Basiccomposition • Basic setting reactions • Classifications • Manufacturing • Variables in amalgam performance Click here for briefing on dental amalgam (PDF)
- 4. History • 1833 – Crawcourbrothers introduce amalgam to US • powdered silver coins mixed with mercury – expanded on setting • 1895 – G.V. Black develops formula for modern amalgam alloy • 67% silver, 27% tin, 5% copper, 1% zinc – overcame expansion problems
- 5. History • 1960’s – conventionallow-copper lathe-cut alloys • smaller particles – first generation high-copper alloys • Dispersalloy (Caulk) – admixture of spherical Ag-Cu eutectic particles with conventional lathe-cut – eliminated gamma-2 phase Mahler J Dent Res 1997
- 6. History • 1970’s – firstsingle composition spherical • Tytin (Kerr) • ternary system (silver/tin/copper) • 1980’s – alloys similar to Dispersalloy and Tytin • 1990’s – mercury-free alloys Mahler J Dent Res 1997
- 7. Amalgam • An alloyof mercury with another metal.
- 8. Why Amalgam? • Inexpensive •Ease of use • Proven track record – >100 years • Familiarity • Resin-free – less allergies than composite Click here for Talking Paper on Amalgam Safety (PDF)
- 9. Constituents in Amalgam •Basic – Silver – Tin – Copper – Mercury • Other – Zinc – Indium – Palladium
- 10. Basic Constituents • Silver(Ag) – increases strength – increases expansion • Tin (Sn) – decreases expansion – decreased strength – increases setting time Phillip’s Science of Dental Materials 2003
- 11. Basic Constituents • Copper(Cu) – ties up tin • reducing gamma-2 formation – increases strength – reduces tarnish and corrosion – reduces creep • reduces marginal deterioration Phillip’s Science of Dental Materials 2003
- 12. Basic Constituents • Mercury(Hg) – activates reaction – only pure metal that is liquid at 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% Hg Click here for ADA Mercury Hygiene Recommendations Phillip’s Science of Dental Materials 2003
- 13. Other 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 1954 Phillip’s Science of Dental Materials 2003 H2O + Zn ZnO + H2
- 14. Other 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 (Indisperse Distributing Company) – 5% indium Powell J Dent Res 1989
- 15. Other Constituents • Palladium(Pd) – reduced corrosion – greater luster – example • Valiant PhD (Ivoclar Vivadent) – 0.5% palladium Mahler J Dent Res 1990
- 16. Basic Composition • Asilver-mercury matrix containing filler particles of silver-tin • Filler (bricks) – Ag3Sn called gamma • can be in various shapes – irregular (lathe-cut), spherical, or a combination • Matrix – Ag2Hg3 called gamma 1 • cement – Sn8Hg called gamma 2 • voids Phillip’s Science of Dental Materials 2003
- 17. Basic Setting Reactions •Conventional low-copper alloys • Admixed high-copper alloys • Single composition high-copper alloys
- 18. • Dissolution andprecipitation • Hg dissolves Ag and Sn from alloy • Intermetallic compounds formed Ag-Sn Alloy Ag-Sn Alloy Ag-Sn Alloy Mercury (Hg) Ag Ag Ag Sn Sn Sn Conventional Low-Copper Alloys Hg Hg Ag Ag3 3Sn + Hg Sn + Hg Ag Ag3 3Sn + Ag Sn + Ag2 2Hg Hg3 3 + Sn + Sn8 8Hg Hg Phillip’s Science of Dental Materials 2003 1 2
- 19. Conventional Low-Copper Alloys •Gamma () = Ag3Sn – unreacted alloy – strongest phase and corrodes the least – forms 30% of volume of set amalgam Ag-Sn Alloy Ag-Sn Alloy Ag-Sn Alloy Mercury Ag Ag Ag Sn Sn Sn Hg Hg Hg Ag Ag3 3Sn + Hg Sn + Hg Ag Ag3 3Sn + Ag Sn + Ag2 2Hg Hg3 3 + Sn + Sn8 8Hg Hg Phillip’s Science of Dental Materials 2003 1 2
- 20. Conventional Low-Copper Alloys •Gamma 1 (1) = Ag2Hg3 – matrix for unreacted alloy and 2nd strongest phase – 10 micron grains binding gamma () – 60% of volume 1 Ag Ag3 3Sn + Hg Sn + Hg Ag Ag3 3Sn + Ag Sn + Ag2 2Hg Hg3 3 + Sn + Sn8 8Hg Hg Phillip’s Science of Dental Materials 2003 1 2 Ag-Sn Alloy Ag-Sn Alloy Ag-Sn Alloy
- 21. Conventional Low-Copper Alloys •Gamma 2 (2) = Sn8Hg – weakest and softest phase – corrodes fast, voids form – corrosion yields Hg which reacts with more gamma () – 10% of volume – volume decreases with time due to corrosion Ag Ag3 3Sn + Hg Sn + Hg Ag Ag3 3Sn + Ag Sn + Ag2 2Hg Hg3 3 + Sn + Sn8 8Hg Hg Phillip’s Science of Dental Materials 2003 1 2 2 Ag-Sn Alloy Ag-Sn Alloy Ag-Sn Alloy
- 22. Admixed High-Copper Alloys •Ag enters Hg from Ag-Cu spherical eutectic particles – eutectic • an alloy in which the elements are completely soluble in liquid solution but separate into distinct areas upon solidification • Both Ag and Sn enter Hg from Ag3Sn particles Phillip’s Science of Dental Materials 2003 Ag Ag3 3Sn + Ag-Cu + Hg Sn + Ag-Cu + Hg Ag Ag3 3Sn + Ag-Cu + Ag Sn + Ag-Cu + Ag2 2Hg Hg3 3 + Cu + Cu6 6Sn Sn5 5 1 Ag-Sn Alloy Ag-Sn Alloy Mercury Ag Ag Ag Sn Sn Ag-Cu Alloy Ag Hg Hg
- 23. Admixed High-Copper Alloys •Sn diffuses to surface of Ag-Cu particles – reacts with Cu to form (eta) Cu6Sn5 () • around unconsumed Ag-Cu particles Ag-Sn Alloy Ag-Cu Alloy Ag-Sn Alloy Phillip’s Science of Dental Materials 2003 Ag Ag3 3Sn + Ag-Cu + Hg Sn + Ag-Cu + Hg Ag Ag3 3Sn + Ag-Cu + Ag Sn + Ag-Cu + Ag2 2Hg Hg3 3 + Cu + Cu6 6Sn Sn5 5 1
- 24. Admixed High-Copper Alloys •Gamma 1 (1) (Ag2Hg3) surrounds () eta phase (Cu6Sn5) and gamma () alloy particles (Ag3Sn) Ag-Sn Alloy 1 Ag-Cu Alloy Ag-Sn Alloy Phillip’s Science of Dental Materials 2003 Ag Ag3 3Sn + Ag-Cu + Hg Sn + Ag-Cu + Hg Ag Ag3 3Sn + Ag-Cu + Ag Sn + Ag-Cu + Ag2 2Hg Hg3 3 + Cu + Cu6 6Sn Sn5 5 1
- 25. Single Composition High-Copper Alloys •Gamma sphere () (Ag3Sn) with epsilon coating () (Cu3Sn) • Ag and Sn dissolve in Hg Ag-Sn Alloy Ag-Sn Alloy Ag-Sn Alloy Mercury (Hg) Ag Sn Ag Sn Ag Ag3 3Sn + Cu Sn + Cu3 3Sn + Hg Sn + Hg Ag Ag3 3Sn + Cu Sn + Cu3 3Sn + Ag Sn + Ag2 2Hg Hg3 3 + Cu + Cu6 6Sn Sn5 5 Phillip’s Science of Dental Materials 2003 1
- 26. Single Composition High-Copper Alloys •Gamma 1 (1) (Ag2Hg3) crystals grow binding together partially- dissolved gamma () alloy particles (Ag3Sn) • Epsilon () (Cu3Sn) develops crystals on surface of gamma particle (Ag3Sn) in the form of eta () (Cu6Sn5) – reduces creep – prevents gamma-2 formation Ag-Sn Alloy Ag-Sn Alloy Ag-Sn Alloy 1 Ag Ag3 3Sn + Cu Sn + Cu3 3Sn + Hg Sn + Hg Ag Ag3 3Sn + Cu Sn + Cu3 3Sn + Ag Sn + Ag2 2Hg Hg3 3 + Cu + Cu6 6Sn Sn5 5 Phillip’s Science of Dental Materials 2003 1
- 27. Classifications • Based oncopper content • Based on particle shape • Based on method of adding copper
- 28. Copper Content • Low-copperalloys – 4 to 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 Ag Phillip’s Science of Dental Materials 2003
- 29. Particle Shape • Lathecut – low Cu • New True Dentalloy – high Cu • ANA 2000 • Admixture – high Cu • Dispersalloy, Valiant PhD • Spherical – low Cu • Cavex SF – high Cu • Tytin, Valiant
- 30. Method of AddingCopper • Single Composition Lathe-Cut (SCL) • Single Composition Spherical (SCS) • Admixture: Lathe-cut + Spherical Eutectic (ALE) • Admixture: Lathe-cut + Single Composition Spherical (ALSCS)
- 31. Single Composition Lathe-Cut (SCL) •More Hg needed than spherical alloys • High condensation force needed due to lathe cut • 20% Cu • Example – ANA 2000 (Nordiska Dental)
- 32. 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)
- 33. Admixture: Lathe-cut + SphericalEutectic (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)
- 34. Admixture: Lathe-cut + SingleComposition Spherical (ALSCS) • High Cu in both lathe-cut and spherical components – 19% Cu • Epsilon layer forms on both components • 0.5% palladium added – reinforce grain boundaries on gamma 1 • Example – Valiant PhD (Ivoclar Vivadent)
- 35. Manufacturing Process • Lathe-cutalloys – Ag & Sn melted together – alloy cooled • phases solidify – heat treat • 400 ºC for 8 hours – grind, then mill to 25 - 50 microns – heat treat to release stresses of grinding Phillip’s Science of Dental Materials 2003
- 36. Manufacturing Process • Sphericalalloys – melt alloy – atomize • spheres form as particles cool – sizes range from 5 - 40 microns • variety improves condensability Phillip’s Science of Dental Materials 2003
- 37. Material-Related Variables • Dimensionalchange • Strength • Corrosion • Creep
- 38. Dimensional Change • Mosthigh-copper amalgams undergo a net contraction • Contraction leaves marginal gap – initial leakage • post-operative sensitivity – reduced with corrosion over time Phillip’s Science of Dental Materials 2003
- 39. Dimensional Change • Netcontraction – type of alloy • spherical alloys have more contraction – less mercury – condensation technique • greater condensation = higher contraction – trituration time • overtrituration causes higher contraction Phillip’s Science of Dental Materials 2003
- 40. Strength • Develops slowly –1 hr: 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 fracture Phillip’s Science of Dental Materials 2003
- 41. Corrosion • 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 1991
- 42. Creep • Slow deformationof amalgam placed under a constant load – load less than that necessary to produce fracture • Gamma 2 dramatically affects creep rate – slow strain rates produces plastic deformation • allows gamma-1 grains to slide • Correlates with marginal breakdown Phillip’s Science of Dental Materials 2003
- 43. Creep • High-copper amalgamshave creep resistance – 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 1 Click here for table of creep values
- 44. Dentist-Controlled Variables • Manipulation –trituration – condensation – burnishing – polishing
- 45. Trituration • Mixing time –refer to manufacturer recommendations • Click here for details • Overtrituration – “hot” mix • sticks to capsule – decreases working / setting time – slight increase in setting contraction • Undertrituration – grainy, crumbly mix Phillip’s Science of Dental Materials 2003
- 46. Condensation • Forces – lathe-cutalloys • small condensers • high force – spherical alloys • large condensers • less sensitive to amount of force • vertical / lateral with vibratory motion – admixture alloys • intermediate handling between lathe-cut and spherical
- 47. Burnishing • Pre-carve – removesexcess mercury – improves margin adaptation • Post-carve – improves smoothness • Combined – less leakage Ben-Amar Dent Mater 1987
- 48. Early Finishing • Afterinitial set – prophy cup with pumice – provides initial smoothness to restorations – recommended for spherical amalgams
- 49. Polishing • Increased smoothness •Decreased plaque retention • Decreased corrosion • Clinically effective? – no improvement in marginal integrity • Mayhew Oper Dent 1986 • Collins J Dent 1992 – Click here for abstract
- 50. Alloy Selection • Handlingcharacteristics • Mechanical and physical properties • Clinical performance Click here for more details
- 51. Handling Characteristics • Spherical –advantages • easier to condense – around pins • hardens rapidly • smoother polish – disadvantages • difficult to achieve tight contacts • higher tendency for overhangs Phillip’s Science of Dental Materials 2003
- 52. Handling Characteristics • Admixed –advantages • easy to achieve tight contacts • good polish – disadvantages • hardens slowly – lower early strength
- 53. Amalgam Properties Compressive Strength (MPa) %Creep Tensile Strength (24 hrs) (MPa) Amalgam Type 1 hr 7 days Low Copper1 145 343 2.0 60 Admixture2 137 431 0.4 48 Single Composition3 262 510 0.13 64 Phillip’s Science of Dental Materials 2003 1 Fine Cut, Caulk 2 Dispersalloy, Caulk 3 Tytin, Kerr
- 54. Survey of PracticeTypes Civilian General Dentists 68% 32% Amalgam Users Amalgam Free Haj-Ali Gen Dent 2005
- 55. Frequency of PosteriorMaterials by Practice Type 39% 51% 3% 7% Amalgam Direct Composite Indirect Composite Other 3% 77% 8% 12% Amalgam Users Amalgam Free Haj-Ali Gen Dent 2005
- 56. Profile of AmalgamUsers Civilian Practitioners 78% 22% Do you use amalgam in your practice? Yes No DPR 2005 88% 12% Do you place fewer amalgams than 5 years ago? Yes No
- 57. Review of ClinicalStudies (Failure Rates in Posterior Permanent Teeth) 0 2 4 6 8 Amalgam Direct Comp Comp Inlays Ceramic Inlays CAD/CAM Inlays Gold Inlays & Onlays GI Longitudinal Cross-Sectional Hickel J Adhes Dent 2001 % Annual Failure
- 58. 0 5 10 15 A m a l g a m D i r e c t C o m p C o m p o m e r C o m p I n l a y s C e r a m i c I n l a y s C A D / C A M C a s t G o l d G I T u n n e l A R T % Annual Failure ManhartOper Dent 2004 Click here for abstract Standard Deviation Longitudinal and Cross-Sectional Data Review of Clinical Studies (Failure Rates in Posterior Permanent Teeth)
- 59. Acknowledgements • Dr. DavidCharlton • Dr. Charles Hermesch • Col Salvador Flores Questions/Comments Col Kraig Vandewalle – DSN 792-7670 – ksvandewalle@nidbr.med.navy.mil