Dental Amalgam

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Dental Amalgam

• Dr. Rama Bitar
  

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What is Amalgam?

• Amalgam any alloy of mercury with another metal
  or other metals.
• In dentistry, the other metals are copper, silver
  and tin.
• One of the oldest restorative materials

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Types of Dental Amalgam

• Copper amalgam (no longer used)
• Conventional (low-copper) amalgam formulation
  standardized in 1890s
• High copper amalgam first developed in the 1960s

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Shape of amalgam particles

• Spherical
• Irregular shape known as lathe cut
• Admixed containing both shapes

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Composition

• Silver 60-70
• Tin 27
• Copper 13
• Zinc 0-2

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Reaction Low-Copper Alloys

• Ag3Sn(?) Hg ?Ag2Hg3(?1) Sn7-8Hg(?2)
  Ag3Sn(?)
• This reaction with mercury produces a corrosion
  prone phase Sn7-8Hg(?2)
• Called gamma phase

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Reaction High-Copper Alloys
Ag3Sn(?) Ag-Cu Hg ?Ag2Hg3(?1) Sn7-8Hg(?2)
Ag3Sn(?) Ag-Cu and Sn7-8Hg(?2) Ag-Cu
?Cu6Sn5(?) Ag2Hg3(?1)
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Properties of Amalgam

• Good compressive strength giving amalgam the
  ability to withstand the forces of biting.
• Corrosion is reduced due to the addition of
  copper.

Corrosion
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Amalgam Capsules

• Contain (in separate compartments)
• powdered amalgam alloy
• liquid mercury
• Some are manually activated, others self-activated

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Amalgamator (Triturator)

• Speeds vary
• Times vary from 520 seconds.
• Mix powder and liquid components to achieve a
  pliable mass.
• Reaction begins after components are mixed.

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• If theres less than 50 of mercury in the mix,
  then the amalgam mix is too dry and difficult to
  work with.

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Mercury Evaporation from Amalgam

• Scientists agree that dental amalgam fillings
  leach mercury into the mouth, but studies vary
  widely in the amount and whether such amount
  presents significant health risks.
• The evaporation rate of Hg from amalgam is
  8001500 times lower than from oxidized mercury.

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Mercury Dose from Amalgam

• Person with average number of fillings (7) would
  absorb 1.6 µg/day
• Person with a moderately high number of fillings
  (13) would absorb 3 µg/day

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Jerome Mercury Vapor Analyzer

• Used by many anti-amalgam dentists to measure
  intra-oral mercury vapor
• Differences in sampling volumes and flow rates
  must be taken into account, or gross errors will
  result