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 significantly
amalgam 88.4% of all direct posterior restorations (1990)
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,

4. Amalgam & Resin Composite for posterior restorations – use in the U.S.
71 million posterior amalgams (1999)
46 million posterior resin composites (1999)
amalgam 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,

5. all schools teach Class I resin composites
Amalgam & Resin Composite for posterior restorations – use in the U.S. dental school
all schools teach Class I resin composites
less acceptance as restoration becomes larger and more complex
only 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) 2
1 Mjor IA, Wilson NH. J Am Dent Assoc 1998;129(10):
2 Lynch CD, McConnell RJ, Wilson NH. J Am Dent Assoc 2006;137(5):

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

7. Amalgam & Resin Composite for posterior restorations – use in the English speaking world
Canada very like U.S.
in 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) 2
1 Burke FJ, Wilson NH, Cheung SW, Mjor IA. J Dent 2001;29(5):
2 Burke FJ, McHugh S, Randall RC, Meyers IA, Pitt J, Hall AC.. Aust Dent J 2004;49(4):

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

9. Jordan: amalgam used predominantly Brazil: like North America
Amalgam & Resin Composite for posterior restorations – use in other places
Jordan: amalgam used predominantly
Brazil: like North America
Japan: very few amalgams placed
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):

10. In 2008 Scandinavian countries began banning amalgam.
Amalgam Regulation
In 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. 1,2
In 2008 Scandinavian countries began banning amalgam.
1 Wahl MJ.. Quintessence Int 2001;32(7):
2 Burke FJ. J Dent 2004;32(5):

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 patients with renal impairment (Germany)
in most of the world, dentists have received no such recommendations
Burke FJ. J Dent 2004;32(5):

12. Amalgam Regulation - Norway & Denmark
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.

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 effect
after 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 1999
Burke FJ. J Dent 2004;32(5):

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

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

16. Amalgam - disadvantages
silver color – can tarnish to black
poor initial seal
thermal and electrical conductor
corrodes

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

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

19. Development of amalgam - 2
Crawcours – five brothers & their sons
Poorly educated, claimed to have learned about amalgam in France
1790 – 1830: Crawcours were itinerant dentists in Northern England
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.
1834 they were “chased out” of the U.S.
1843 – 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. Black
The major change was the addition of tin (Sn) to the silver (Ag) in the powder

22. Powder is based on the composition Ag3Sn, an intermetallic compound
Low Copper Amalgam
Powder is based on the composition Ag3Sn, an intermetallic compound
β Ag-Sn
 Ag-Sn

23. intermetallic compound:
usually stable over a narrow range of composition
centered around a composition that is a whole number ratio of the elements (e.g., A3B, A2B, AB, AB2, AB3)
can be thought of as involving a mixture of covalent and metallic bonding
ordered – usually remain ordered from room temperature to their melting temperature

24. Random Solid Solution (Disordered)
Gold
Copper
Random Solid Solution (Disordered)

25. Intermetallic Compound (Ordered)
Gold
Copper
Intermetallic Compound (Ordered)

26. Powder is based on the composition Ag3Sn, an intermetallic compound
Low Copper Amalgam
Powder is based on the composition Ag3Sn, an intermetallic compound
Also contains zinc (Zn)
Mixed with 53 – 60 wt. % mercury
Extra Hg was squeezed out (“expressed”) during condensation.

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

28.  Ag - Sn Ag3Sn b Ag - Sn Ag5Sn  Cu - Sn Cu3Sn phases in particles:
Intermetallic
compound
b Ag - Sn
Ag5Sn
Solid
solution
 Cu - Sn
Cu3Sn
Intermetallic
compound
Intermetallic compounds are brittle. Consequently, the particles are brittle.

29. 1 (Ag - Hg) Ag2Hg3 2 (Sn - Hg) Sn7Hg matrix phases: Intermetallic
compound
2 (Sn - Hg)
Sn7Hg
???
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:
Very plastic
Very plastic
Silver & tin dissolve into liquid
mercury.
After silver reaches saturation,
1 Ag-Hg crystals nucleate & grow.

31. Reaction mechanism – low-copper amalgam:
Plastic
Carveable solid
 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.

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

33.  Ag - Sn Ag3Sn β Ag - Sn Ag5Sn  Cu - Sn Cu3Sn phases in particles:
Intermetallic
compound
β Ag - Sn
Ag5Sn
Solid
solution
 Cu - Sn
Cu3Sn
Intermetallic
compound

34. 1 (Ag - Hg) Ag2Hg3  2 (Sn - Hg) Sn7Hg matrix phases: Intermetallic
compound
1 (Ag - Hg)
Ag2Hg3
 2 (Sn - Hg)
Sn7Hg
???

35. 1 (Ag - Hg) Ag2Hg3 < 60 vol. % 2 (Sn - Hg) Sn7Hg < 10 vol. %
matrix phases:
1 (Ag - Hg)
Ag2Hg3
< 60 vol. %
2 (Sn - Hg)
Sn7Hg
< 10 vol. %

36. High – copper Amalgams

37. High-Cu Amalgams - types:
admixed
single composition

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

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

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

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

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

44. 1 (Ag - Hg) Ag2Hg3 2 (Sn - Hg) Sn7Hg  (Cu-Sn) Cu6Sn5
matrix phases:
corrosion resistant weak
1 (Ag - Hg)
Ag2Hg3
corrodes
very weak
2 (Sn - Hg)
Sn7Hg
 (Cu-Sn)
Cu6Sn5
corrodes less
fairly strong

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

46. 1 (Ag - Hg) Ag2Hg3 < 60 vol. %  (Cu-Sn) Cu6Sn5 < 10 vol. %
matrix phases:
1 (Ag - Hg)
Ag2Hg3
< 60 vol. %
 (Cu-Sn)
Cu6Sn5
< 10 vol. %

47. High-Cu Amalgams - types:
admixed
single composition

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

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

51. Single Composition
High-Copper
Amalgam
Tytin
30 um

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

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

54. Compressive strength after seven days:
low - copper 350 MPa
admixed 430 MPa
single - composition 500 MPa

55. Tensile strength after seven days:
low - copper MPa
admixed MPa
single - composition MPa

56. DB Mahler’s marginal fracture rating system:1 3 5 7 2 4 6 11 7 9 8 10

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

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 diameter
temperature: 37o C
stress: MPa

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

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

63. ADA Creep Values of Amalgam Types

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

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

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.
annual failure rates:
amalgam: 0 – 7.4% / yr
resin composite: 0 – 9.0% / yr
average failure rate of combined studies
amalgam: 3.0% / yr
resin composite: 2.2% / yr
Not statistically different
Manhart J, Chen H, Hamm G, Hickel R. Oper Dent 2004;29(5):

68. Posterior Amalgam Restorations - Longevity
Manhard & Hickel (2004) reviewed 41 clinical studies of amalgam & 50 of resin composite.
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):

69. Longevity Testing – Test settings
general 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 longevity
Wilson NH. Oper Dent 1990;15(4):
Mjor IA, Jokstad A, Qvist V. Int Dent J 1990;40(1):11-17.

70. Longevity Testing – Types of studies
longitudinal 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 practices

71. Longevity Testing – Test settings
general 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 longevity
Wilson NH. Oper Dent 1990;15(4):
Mjor IA, Jokstad A, Qvist V. Int Dent J 1990;40(1):11-17.

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

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

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

75. Class II amalgams: 44.1 years (1213 restora-tions – 15 years) 1
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) 1
Class II amalgams: 25.0 years (469 restora-tions – 9.5 years) 2
Class 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):
2. Jokstad A, Mjor IA. Acta Odontol Scand 1991;49(1):47-63.
3. Smales RJ. Oper Dent 1991;16(1):17-20.

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

77. 19.4 years (194 restorations; 10 years) 1
Longevity Testing – median survival times posterior RCs longitudinal prospective - optimum settings - 2
19.4 years (194 restorations; 10 years) 1
20.2 years (34 restorations; 11 years) 2
35.4 years (100 restorations; 17 years) 3
34.4 years (56 restorations; 11 years) 4
1. Gaengler P, Hoyer I, Montag R. J Adhes Dent 2001;3(2):
2. van Dijken JW.. J Dent 2000;28(5):
3. Wilder AD, Jr., May KN, Jr., Bayne SC, Taylor DF, Leinfelder KF J Esthet Dent 1999;11(3):
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 studies

79. The End