1. Dental Amalgam

2. Status of Dental Amalgam in 2009

3. Amalgam & Resin Composite for posterior restorations – use in the U.S. use of amalgam has declined significantlyuse of amalgam has declined significantly amalgam 88.4% of all direct posterior restorations (1990)amalgam 88.4% of all direct posterior restorations (1990) amalgam 60.6% of all direct posterior restorations (1999)amalgam 60.6% of all direct posterior restorations (1999) Berthold M. Restoratives Trend data shows shift in use of materials. ADA News. Vol 33; 2002:1, 10-11.

4. Amalgam & Resin Composite for posterior restorations – use in the U.S. 71 million posterior amalgams (1999)71 million posterior amalgams (1999) 46 million posterior resin composites (1999)46 million posterior resin composites (1999) amalgam is still by far the most widely used material for posterior restorationsamalgam is still by far the most widely used material for posterior restorations Berthold M. Restoratives Trend data shows shift in use of materials. ADA News. Vol 33; 2002:1, 10-11.

5. Amalgam & Resin Composite for posterior restorations – use in the U.S. dental school all schools teach Class I resin compositesall schools teach Class I resin composites less acceptance as restoration becomes larger and more complexless acceptance as restoration becomes larger and more complex only 30% teach resin composite for 3-surface Class II in molars (1997) 1only 30% teach resin composite for 3-surface Class II in molars (1997) 1 68% teach resin composite for 3-surface Class II in molars (2005) 268% teach resin composite for 3-surface Class II in molars (2005) 2 1 Mjor IA, Wilson NH. J Am Dent Assoc 1998;129(10):1415-1421. 2 Lynch CD, McConnell RJ, Wilson NH. J Am Dent Assoc 2006;137(5):619-625.

6. Amalgam & Resin Composite for posterior restorations – use in the U.S. dental school 80% of schools: amalgam is taught first (2005)80% of schools: amalgam is taught first (2005) 60% of posterior restorations placed by students are amalgam (2005)60% of posterior restorations placed by students are amalgam (2005) Lynch CD, McConnell RJ, Wilson NH. J Am Dent Assoc 2006;137(5):619-625.

7. Amalgam & Resin Composite for posterior restorations – use in the English speaking world Canada very like U.S.Canada very like U.S. in UK 16% of 654 general dentists ‘often’ or ‘always’ used resin composite in posterior restorations (2001) 1in UK 16% of 654 general dentists ‘often’ or ‘always’ used resin composite in posterior restorations (2001) 1 In Australia 41% of 560 general dentists ‘often’ or ‘always’ used resin composite in posterior restorations (2002) 2In Australia 41% of 560 general dentists ‘often’ or ‘always’ used resin composite in posterior restorations (2002) 2 1 Burke FJ, Wilson NH, Cheung SW, Mjor IA. J Dent 2001;29(5):317-324. 2 Burke FJ, McHugh S, Randall RC, Meyers IA, Pitt J, Hall AC.. Aust Dent J 2004;49(4):185-191.

8. Amalgam & Resin Composite for posterior restorations – use in the Scandinavia Many dentists don’t use amalgam at all (2002 data)Many dentists don’t use amalgam at all (2002 data) 72% of Finnish dentists72% of Finnish dentists 60% of Swedish dentists60% of Swedish dentists 12% of Danish dentists12% of Danish dentists 8% of Norwegian dentists8% of Norwegian dentists Ylinen K, Lofroth G. Acta Odontol Scand 2002;60(5):315-320.

9. Amalgam & Resin Composite for posterior restorations – use in other places Jordan: amalgam used predominantlyJordan: amalgam used predominantly Brazil: like North AmericaBrazil: like North America Japan: very few amalgams placedJapan: very few amalgams placed Other countries: little in the published literature; guess is that most of the world uses amalgam like U.S.Other countries: little in the published literature; guess is that most of the world uses amalgam like U.S. Ylinen K, Lofroth G. Acta Odontol Scand 2002;60(5):315-320.

10. Amalgam Regulation In 1990s, anti-amalgam websites and newsletters rumor that amalgam had been banned in Europe, especially in Sweden and GermanyIn 1990s, anti-amalgam websites and newsletters rumor that amalgam had been banned in Europe, especially in Sweden and Germany Not true. Until 2008 there was very little legislation limiting the use of amalgam anywhere in the world. 1,2Not true. Until 2008 there was very little legislation limiting the use of amalgam anywhere in the world. 1,2 In 2008 Scandinavian countries began banning amalgam.In 2008 Scandinavian countries began banning amalgam. 1 Wahl MJ.. Quintessence Int 2001;32(7):525-535. 2 Burke FJ. J Dent 2004;32(5):343-350.

11. Amalgam Regulation - recommendations to dentists that amalgam not be placed in pregnant women (Sweden, Norway, Austria, and Germany)that amalgam not be placed in pregnant women (Sweden, Norway, Austria, and Germany) that amalgam not be placed in patients with renal impairment (Germany)that amalgam not be placed in patients with renal impairment (Germany) in most of the world, dentists have received no such recommendationsin most of the world, dentists have received no such recommendations Burke FJ. J Dent 2004;32(5):343-350.

12. Amalgam Regulation - Norway & Denmark Norway banned dental amalgam beginning 1/1/08. Ban by regulation – a bit surprising.Norway banned dental amalgam beginning 1/1/08. Ban by regulation – a bit surprising. Denmark is phasing out amalgam – allow only in permanent molar teeth where there is evidence that amalgam will outlast a resin composite. New regulation were to take effect in October of 2008.Denmark is phasing out amalgam – allow only in permanent molar teeth where there is evidence that amalgam will outlast a resin composite. New regulation were to take effect in October of 2008.

13. Amalgam Regulation - the situation in Sweden Sweden is making an all out effort to outlaw all use of mercury – regulations to do this are already in effectSweden is making an all out effort to outlaw all use of mercury – regulations to do this are already in effect after delaying including dental amalgam in the ban several times, the ban dental amalgam was finally set to go into force 6/1/09after delaying including dental amalgam in the ban several times, the ban dental amalgam was finally set to go into force 6/1/09 not too big a change; amalgam is already used very little. The Swedish National Health system has not reimbursed dentists for amalgam restorations since 1999not too big a change; amalgam is already used very little. The Swedish National Health system has not reimbursed dentists for amalgam restorations since 1999 Burke FJ. J Dent 2004;32(5):343-350.

14. Amalgam - advantages strong enoughstrong enough wear resistant enoughwear resistant enough leakage decreases with timeleakage decreases with time simple to placesimple to place durable (1/2 fail in 7 – 15 years)durable (1/2 fail in 7 – 15 years) initially inexpensive – cost effectiveinitially inexpensive – cost effective

15. Leakage of amalgam restorations with time 24 h 1 mo 3 mo 6 mo This self sealing behavior may be one of the reasons for the success of amalgam restorations.

16. Amalgam - disadvantages silver color – can tarnish to blacksilver color – can tarnish to black poor initial sealpoor initial seal thermal and electrical conductorthermal and electrical conductor corrodescorrodes

17. margins fracturemargins fracture bulk fracture can occurbulk fracture can occur Weak in tension & shear Amalgam - disadvantages

18. Development of amalgam 1818 – Paris dentist Louis Regnart suggests use of amalgam to restore teeth1818 – Paris dentist Louis Regnart suggests use of amalgam to restore teeth Another Parisian dentist, August Omesine Taveau popularized itAnother Parisian dentist, August Omesine Taveau popularized it

19. Development of amalgam - 2 Crawcours – five brothers & their sonsCrawcours – five brothers & their sons Poorly educated, claimed to have learned about amalgam in FrancePoorly educated, claimed to have learned about amalgam in France 1790 – 1830: Crawcours were itinerant dentists in Northern England1790 – 1830: Crawcours were itinerant dentists in Northern England Claimed to be able to save teeth with a new material “Royal Mineral Succedaneum”Claimed to be able to save teeth with a new material “Royal Mineral Succedaneum”

20. Development of amalgam - 3 1833 two of the Crawcour brothers travel to the U.S.1833 two of the Crawcour brothers travel to the U.S. 1834 they were “chased out” of the U.S.1834 they were “chased out” of the U.S. 1843 – American Society of Dental Surgeons declares use of amalgam malpractice1843 – American Society of Dental Surgeons declares use of amalgam malpractice

21. Development of amalgam - 3 1843 – 1895 alloy powder gradually improved, culminating with the research of G.V. Black1843 – 1895 alloy powder gradually improved, culminating with the research of G.V. Black The major change was the addition of tin (Sn) to the silver (Ag) in the powderThe major change was the addition of tin (Sn) to the silver (Ag) in the powder

22. Low Copper Amalgam Powder is based on the composition Ag 3 Sn, anPowder is based on the composition Ag 3 Sn, an intermetallic compound  Ag-Sn β Ag-Sn

23. intermetallic compound: usually stable over a narrow range of compositionusually stable over a narrow range of composition centered around a composition that is a whole number ratio of the elements (e.g., A 3 B, A 2 B, AB, AB 2, AB 3 )centered around a composition that is a whole number ratio of the elements (e.g., A 3 B, A 2 B, AB, AB 2, AB 3 ) can be thought of as involving a mixture of covalent and metallic bondingcan be thought of as involving a mixture of covalent and metallic bonding ordered – usually remain ordered from room temperature to their melting temperatureordered – usually remain ordered from room temperature to their melting temperature

24. Random Solid Solution (Disordered) Gold Copper

25. Intermetallic Compound (Ordered) Gold Copper

26. Low Copper Amalgam Powder is based on the composition Ag 3 Sn, anPowder is based on the composition Ag 3 Sn, an intermetallic compound Also contains zinc (Zn) Mixed with 53 – 60 wt. % mercury Extra Hg was squeezed out (“expressed”) during condensation.

27. low - copper amalgam: (Ag - Sn alloys particles) =  1 (Ag - Hg) (partially consumed particles) + + +Hg   2 (Sn - Hg)

28. phases in particles:  Ag - Sn Ag 3 Sn Intermetallic compound  Ag - Sn Ag 5 Sn Solid solution  Cu - Sn Cu 3 Sn Intermetallic compound Intermetallic compounds are brittle. Consequently, the particles are brittle.

29. matrix phases:  1 (Ag - Hg) Ag 2 Hg 3 Intermetallic compound  2 (Sn - Hg) Sn 7 Hg ??? The predominant matrix phase,  1, is intermetallic and, consequently, is brittle. Since both the partially consumed particles and matrix phase are brittle, amalgam will be brittle.

30. Reaction mechanism – low-copper amalgam: Silver & tin dissolve into liquid mercury. After silver reaches saturation,  1 Ag-Hg crystals nucleate & grow. Very plastic

31. Reaction mechanism – low-copper amalgam:   crystal continue to grow. As they grow they consume the liquid Hg. When tin reaches saturation in Hg,  2 crystals nucleate & grow. Both types of crystals continue to grow until all the mercury is con- sumed. Matrix is mostly  1, but also contains  2 and voids. Plastic Carveable solid

32. Microstructure – low-Cu amalgam: G1 -  1 (Ag-Hg) G2 -  2 (Sn-Hg) P - Ag-Sn E -  Cu-Sn V - voids

33. phases in particles:  Ag - Sn Ag 3 Sn Intermetallic compound β  Ag - Sn Ag 5 Sn Solid solution  Cu - Sn Cu 3 Sn Intermetallic compound

34. matrix phases:  1 (Ag - Hg) Ag 2 Hg 3 Intermetallic compound  2 (Sn - Hg) Sn 7 Hg ???

35. matrix phases:  1 (Ag - Hg) Ag 2 Hg 3  2 (Sn - Hg) Sn 7 Hg < 10 vol. % < 60 vol. %

36. High – copper Amalgams

37. High-Cu Amalgams - types: admixedadmixed single compositionsingle composition

38. Development of High-Cu Amalgams: admixed amalgam invented – Innes & Youdelis 1962admixed amalgam invented – Innes & Youdelis 1962 less marginal fracture in admixed high Cu amalgam restorations – Mahler et al., 1970.less marginal fracture in admixed high Cu amalgam restorations – Mahler et al., 1970.

39. low copper amalgam low copper amalgam admixed high-Cu amalgam after 8 years; Osborne et al. 1980 fractured margins less marginal fracture

40. Admixed High-Cu Amalgams – Powder Types: irregular (Ag-Sn alloy) + spherical (Ag-Cu)irregular (Ag-Sn alloy) + spherical (Ag-Cu) irregular (Ag-Sn alloy) + spherical (Ag-Sn-Cu)irregular (Ag-Sn alloy) + spherical (Ag-Sn-Cu)

42. 30 um Admixed High-Cu Amalgam powder Dispersalloy spherical particles lathe-cut particles Au-Cu Ag-Sn

43. admixed amalgam: (Ag - Sn alloy particles) (Ag - Cu alloys particles) =  1 (Ag - Hg)  (Cu-Sn) + (partially consumed particles) + ++Hg

44. matrix phases:  1 (Ag - Hg) Ag 2 Hg 3 corrosion resistant weak  2 (Sn - Hg) Sn 7 Hg corrodes very weak  (Cu-Sn) Cu 6 Sn 5 corrodes less fairly strong

45. G1 -  1 (Ag-Hg) P - Ag-Sn E -  Cu-Sn V - voids R -  +   D – Ag-Cu alloy Microstructure – Admixed High-Cu Amalgam:

46. matrix phases:  1 (Ag - Hg) Ag 2 Hg 3  (Cu-Sn) Cu 6 Sn 5 < 10 vol. % < 60 vol. %

47. High-Cu Amalgams - types: admixedadmixed single compositionsingle composition

48. Single Composition High-Cu Amalgams: Invented by Kamal Asgar in 1974

49. Single Composition High-Cu Amalgam – types: Spherical – Ag-Sn-CuSpherical – Ag-Sn-Cu Irregular – Ag-Sn-CuIrregular – Ag-Sn-Cu

51. Single Composition High-Copper Amalgam Tytin 30 um

52. single - composition amalgam: (Ag - Sn - Cu alloys particles) =  1 (Ag - Hg)  (Cu-Sn) + (partially consumed particles)+ +Hg

53. Microstructure of single-composition high-copper amalgam: unconsumed alloy (Ag-Cu-Sn) particles  (Cu-Sn) particles  1 (Ag - Hg) – the matrix phase

54. Compressive strength after seven days: low - copper 350 MPalow - copper 350 MPa admixed430 MPaadmixed430 MPa single - composition500 MPasingle - composition500 MPa

55. Tensile strength after seven days: low - copper 50 - 75 MPalow - copper 50 - 75 MPa admixed50 - 75 MPaadmixed50 - 75 MPa single - composition50 - 75 MPasingle - composition50 - 75 MPa

56. DB Mahler’s marginal fracture rating system:            

57. Marginal Fracture of Amalgam Restorations Mahler et al. J Oral Rehab 1979;6:391-398.

58. Creep Test - ADA Specification No. 1

59. Static creep: Time-dependent plastic deformation that occurs when a material is placed under a constant load that is less than the its yield strength.

60. Creep Test - ADA Specification No. 1 cylinder: 8 mm high by 4 mm in diametercylinder: 8 mm high by 4 mm in diameter temperature:37 o Ctemperature:37 o C stress:35.85 MPastress:35.85 MPa

61. Creep Test - ADA Specification No. 1 % creep = (height 4th hr) - (height 1st hour) initial height x 100

62. ADA Creep Beech & Brockhurst. Aust Dent J 1982; 27:306-309.

63. ADA Creep Values of Amalgam Types

64. Correlation between marginal fracture & creep ( 10 - 6 / sec ) Vrijhoef & Letzel J Oral Rehab 1986;13:299 - 303.

65. one-hour compressive strength Beech & Brockhurst. Aust Dent J 1982; 27:306-309.

66. One-hour Compressive Strength of Amalgam Types

67. Posterior Amalgam Restorations - Longevity Manhard & Hickel (2004) reviewed 41 clinical studies of amalgam & 50 of resin composite.Manhard & Hickel (2004) reviewed 41 clinical studies of amalgam & 50 of resin composite. annual failure rates:annual failure rates: amalgam: 0 – 7.4% / yr resin composite: 0 – 9.0% / yr average failure rate of combined studiesaverage failure rate of combined studies amalgam: 3.0% / yr resin composite: 2.2% / yr Manhart J, Chen H, Hamm G, Hickel R. Oper Dent 2004;29(5):481-508. Not statistically different

68. Posterior Amalgam Restorations - Longevity Manhard & Hickel (2004) reviewed 41 clinical studies of amalgam & 50 of resin composite.Manhard & Hickel (2004) reviewed 41 clinical studies of amalgam & 50 of resin composite. problems:problems: too many short terms studies – exclude failure mechanisms whose probability increases with time (e.g. caries, bulk fracture, marginal fracture) combine studies performed in general practice with studies performed in optimum settings. Manhart J, Chen H, Hamm G, Hickel R. Oper Dent 2004;29(5):481-508.

69. Longevity Testing – Test settings general practice – dental offices, public health clinics, lots of clinicians, operators uncalibrated, patients from everywhere – works against longevitygeneral practice – dental offices, public health clinics, lots of clinicians, operators uncalibrated, patients from everywhere – works against longevity optimum settings – often dental schools, few operators, operators calibrated, selected patients – promotes longevityoptimum settings – often dental schools, few operators, operators calibrated, selected patients – promotes longevity Wilson NH. Oper Dent 1990;15(4):149-155. Mjor IA, Jokstad A, Qvist V. Int Dent J 1990;40(1):11-17.

70. Longevity Testing – Types of studies longitudinal studieslongitudinal studies prospective – can tightly control variables; often optimum settings; can study aspects of general practice too retrospective – rely of patient charts or insurance databases; often used in general practice settings cross sectional – a ‘snap shop’ of restorations placed or replaced over a short period; usually used to study general practicescross sectional – a ‘snap shop’ of restorations placed or replaced over a short period; usually used to study general practices

71. Longevity Testing – Test settings general practice – dental offices, public health clinics, lots of clinicians, operators uncalibrated, patients from everywhere – works against longevitygeneral practice – dental offices, public health clinics, lots of clinicians, operators uncalibrated, patients from everywhere – works against longevity optimum settings – often dental schools, few operators, operators calibrated, selected patients – promotes longevityoptimum settings – often dental schools, few operators, operators calibrated, selected patients – promotes longevity Wilson NH. Oper Dent 1990;15(4):149-155. Mjor IA, Jokstad A, Qvist V. Int Dent J 1990;40(1):11-17.

72. Longevity Testing – median survival times posterior amalgams longitudinal prospective - optimum settings 65.8 years (3244 restorations; combined studies; 5 – 15 years) 165.8 years (3244 restorations; combined studies; 5 – 15 years) 1 57.5 years (181 restorations; 13 years) 257.5 years (181 restorations; 13 years) 2 69.0 years (53 restorations; 8 years) 369.0 years (53 restorations; 8 years) 3 1. Letzel H, van 't Hof MA, Marshall GW, Marshall SJ.J Dent Res 1997;76(11):1787-1798. 2. Osborne JW, Norman RD. Dent Mater 1990;6(3):189-194. 3. Collins CJ, Bryant RW, Hodge KL. J Dent 1998;26(4):311-317.

73. Longevity Testing – median survival times posterior amalgams longitudinal retrospective - general practice settings 14.4 years (1345 restorations; 0 – 17 years) 114.4 years (1345 restorations; 0 – 17 years) 1 11.9 years (76,418 restorations; 0 - 12 years) 211.9 years (76,418 restorations; 0 - 12 years) 2 1. Dawson AS, Smales RJ. Aust Dent J 1992;37(3):196-200. 70. 2. Lucarotti PS, Holder RL, Burke FJ. J Dent 2005;33(10):805-815.

74. Longevity Testing – median survival times posterior amalgams longitudinal retrospective general practice 1990 - 2001 data from UK’s General Dental Service’s database:1990 - 2001 data from UK’s General Dental Service’s database: Single surface amalgams: 11.9 years (16,680 restorations) 1Single surface amalgams: 11.9 years (16,680 restorations) 1 DO & MO amalgams: 9.8 years (16,680 restorations) 1DO & MO amalgams: 9.8 years (16,680 restorations) 1 MOD amalgams: 8.8 years (147,087 restorations) 1MOD amalgams: 8.8 years (147,087 restorations) 1 1. Lucarotti PS, Holder RL, Burke FJ. J Dent 2005;33(10):805-815.

75. Longevity Testing – median survival times posterior amalgams longitudinal prospective optimum settings – Class II only - Class II amalgams: 44.1 years (1213 restora- tions – 15 years) 1Class II amalgams: 44.1 years (1213 restora- tions – 15 years) 1 Class II amalgams: 25.0 years (469 restora- tions – 9.5 years) 2Class II amalgams: 25.0 years (469 restora- tions – 9.5 years) 2 Class II amalgams: 27.6 years (664 restora- tions – 15 years) 3Class II amalgams: 27.6 years (664 restora- tions – 15 years) 3 1. Gruythuysen RJ, Kreulen CM, Tobi H, van Amerongen E, Akerboom HB. Community Dent Oral Epidemiol 1996;24(3):207-210. 2. Jokstad A, Mjor IA. Acta Odontol Scand 1991;49(1):47-63. 3. Smales RJ. Oper Dent 1991;16(1):17-20.

76. Longevity Testing – median survival times posterior RCs longitudinal prospective - optimum settings - 1 44.3 years (~ 80 restorations; 10 years) 144.3 years (~ 80 restorations; 10 years) 1 24.4 years (55 restorations; 8 years) 224.4 years (55 restorations; 8 years) 2 26.0 years (52 restorations; 8 years) 226.0 years (52 restorations; 8 years) 2 43.0 years (54 restorations; 8 years) 243.0 years (54 restorations; 8 years) 2 1.Lundin SA, Koch G. Swed Dent J 1999;23(5-6) 2.3. Collins CJ, Bryant RW, Hodge KL. J Dent 1998;26(4):311- 317.

77. Longevity Testing – median survival times posterior RCs longitudinal prospective - optimum settings - 2 19.4 years (194 restorations; 10 years) 119.4 years (194 restorations; 10 years) 1 20.2 years (34 restorations; 11 years) 220.2 years (34 restorations; 11 years) 2 35.4 years (100 restorations; 17 years) 335.4 years (100 restorations; 17 years) 3 34.4 years (56 restorations; 11 years) 434.4 years (56 restorations; 11 years) 4 1. Gaengler P, Hoyer I, Montag R. J Adhes Dent 2001;3(2):185- 194. 2. van Dijken JW.. J Dent 2000;28(5):299-306. 3. Wilder AD, Jr., May KN, Jr., Bayne SC, Taylor DF, Leinfelder KF J Esthet Dent 1999;11(3):135-142. 4. Pallesen U, Qvist V. Clin Oral Investig 2003;7(2):71-79.

78. Longevity Testing – median survival times posterior RCs longitudinal retrospective general practice settings No long term studiesNo long term studies