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Dental Amalgam dr shabeel pn.

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Presentation on theme: "Dental Amalgam dr shabeel pn."— Presentation transcript:

1 Dental Amalgam dr shabeel pn

2 Official Disclaimer The opinions 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 Click here for briefing on dental amalgam (PDF)
Overview History Basic composition Basic setting reactions Classifications Manufacturing Variables in amalgam performance Click here for briefing on dental amalgam (PDF)

4 History 1833 1895 Crawcour brothers 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 conventional low-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 1980’s 1990’s first single 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 alloy of mercury with another metal.

8 Click here for Talking Paper on Amalgam Safety (PDF)
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 Phillip’s Science of Dental Materials 2003
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 Phillip’s Science of Dental Materials 2003
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 Phillip’s Science of Dental Materials 2003
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 H2O + Zn ZnO + H2 Þ Phillip’s Science of Dental Materials 2003

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 Phillip’s Science of Dental Materials 2003
Basic Composition A silver-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 Conventional Low-Copper Alloys
Dissolution and precipitation Hg dissolves Ag and Sn from alloy Intermetallic compounds formed Ag-Sn Alloy Hg Hg Ag Sn Ag Ag Sn Sn Ag-Sn Alloy Ag-Sn Alloy Mercury (Hg) Ag3Sn + Hg Þ Ag3Sn + Ag2Hg3 + Sn8Hg 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 Hg Ag-Sn Alloy Hg Hg Ag Sn Ag Ag Sn Sn Ag-Sn Alloy Ag-Sn Alloy Mercury Ag3Sn + Hg Þ Ag3Sn + Ag2Hg3 + Sn8Hg 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 Ag-Sn Alloy 1 Ag-Sn Alloy Ag-Sn Alloy Ag3Sn + Hg Þ Ag3Sn + Ag2Hg3 + Sn8Hg Phillip’s Science of Dental Materials 2003 1 2

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 2 Ag-Sn Alloy Ag3Sn + Hg Þ Ag3Sn + Ag2Hg3 + Sn8Hg Phillip’s Science of Dental Materials 2003 1 2

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 Ag-Sn Alloy Mercury Ag Sn Ag-Cu Alloy Hg Ag3Sn + Ag-Cu + Hg Þ Ag3Sn + Ag-Cu + Ag2Hg3 + Cu6Sn5 1 Phillip’s Science of Dental Materials 2003

23 Admixed High-Copper Alloys
Ag-Sn Alloy Ag-Cu Alloy Sn diffuses to surface of Ag-Cu particles reacts with Cu to form (eta) Cu6Sn5 () around unconsumed Ag-Cu particles Ag3Sn + Ag-Cu + Hg Þ Ag3Sn + Ag-Cu + Ag2Hg3 + Cu6Sn5 1 Phillip’s Science of Dental Materials 2003

24 Admixed High-Copper Alloys
Gamma 1 (1) (Ag2Hg3) surrounds () eta phase (Cu6Sn5) and gamma () alloy particles (Ag3Sn) Ag-Cu Alloy Ag-Sn Alloy Ag-Sn Alloy 1 Ag3Sn + Ag-Cu + Hg Þ Ag3Sn + Ag-Cu + Ag2Hg3 + Cu6Sn5 1 Phillip’s Science of Dental Materials 2003

25 Single Composition High-Copper Alloys
Ag-Sn Alloy Gamma sphere () (Ag3Sn) with epsilon coating () (Cu3Sn) Ag and Sn dissolve in Hg Ag-Sn Alloy Ag Ag-Sn Alloy Sn Sn Ag Mercury (Hg) Ag3Sn + Cu3Sn + Hg Þ Ag3Sn + Cu3Sn + Ag2Hg3 + Cu6Sn5 Phillip’s Science of Dental Materials 2003 1

26 Single Composition High-Copper Alloys
Ag-Sn Alloy 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 1 Ag3Sn + Cu3Sn + Hg Þ Ag3Sn + Cu3Sn + Ag2Hg3 + Cu6Sn5 Phillip’s Science of Dental Materials 2003 1

27 Classifications Based on copper content Based on particle shape
Based on method of adding copper

28 Phillip’s Science of Dental Materials 2003
Copper Content Low-copper alloys 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 Lathe cut Admixture Spherical low Cu high Cu low Cu
New True Dentalloy high Cu ANA 2000 Admixture Dispersalloy, Valiant PhD Spherical low Cu Cavex SF high Cu Tytin, Valiant

30 Method of Adding Copper
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 + 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)

34 Admixture: Lathe-cut + Single Composition 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-cut alloys Ag & Sn melted together alloy cooled phases solidify heat treat 400 ºC for 8 hours grind, then mill to microns heat treat to release stresses of grinding Phillip’s Science of Dental Materials 2003

36 Manufacturing Process
Spherical alloys melt alloy atomize spheres form as particles cool sizes range from microns variety improves condensability Phillip’s Science of Dental Materials 2003

37 Material-Related Variables
Dimensional change Strength Corrosion Creep

38 Phillip’s Science of Dental Materials 2003
Dimensional Change Most high-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 Phillip’s Science of Dental Materials 2003
Dimensional Change Net contraction 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 Phillip’s Science of Dental Materials 2003
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 high copper
                                                      Corrosion Reduces strength Seals margins low copper 6 months SnO2, SnCl gamma-2 phase high copper months SnO2 , SnCl, CuCl eta-phase (Cu6Sn5) Sutow J Dent Res 1991

42 Phillip’s Science of Dental Materials 2003
Creep Slow deformation of 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 Click here for table of creep values
High-copper amalgams have 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 Phillip’s Science of Dental Materials 2003
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-cut alloys spherical alloys admixture alloys
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 Post-carve Combined removes excess mercury
improves margin adaptation Post-carve improves smoothness Combined less leakage Ben-Amar Dent Mater 1987

48 Early Finishing After initial 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 Click here for more details
Alloy Selection Handling characteristics 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
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 1Fine Cut, Caulk Dispersalloy, Caulk 3Tytin, Kerr Phillip’s Science of Dental Materials 2003

54 Survey of Practice Types Civilian General Dentists
Amalgam Free Amalgam Users Haj-Ali Gen Dent 2005

55 Frequency of Posterior Materials by Practice Type
Amalgam Users Amalgam Free Haj-Ali Gen Dent 2005

56 Profile of Amalgam Users Civilian Practitioners
Do you use amalgam in your practice? Do you place fewer amalgams than 5 years ago? No No Yes Yes DPR 2005

57 Review of Clinical Studies (Failure Rates in Posterior Permanent Teeth)
% Annual Failure Hickel J Adhes Dent 2001

58 Review of Clinical Studies (Failure Rates in Posterior Permanent Teeth)
% Annual Failure Standard Deviation Longitudinal and Cross-Sectional Data Manhart Oper Dent Click here for abstract

59 Acknowledgements Questions/Comments Dr. David Charlton
Dr. Charles Hermesch Col Salvador Flores Questions/Comments Col Kraig Vandewalle DSN

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