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| IMC Wiki | Amalgam filling

Amalgam filling

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Composition of amalgam

In the past, amalgam used to be the classical filling material for lateral teeth; nowadays, however, composites are increasingly used.

Pursuant to the chemical definition, amalgam is a liquid, malleable or solid alloy of mercury and other metals.
In dental medicine, powders made of metal alloys consisting mainly of silver, tin, and copper are mixed with mercury in a 1:1 ratio and referred to as 'silver amalgam'.
Thus, 50 % of amalgam consists of mercury and 50 % of metal filings (alloy). The exact composition of the alloy varies; it has been changed in the course of technical development:
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Conventional amalgam

Formation of the gamma-2 phase (γ-2) is a disadvantage of amalgam used in the past (= conventional amalgam). The γ-2 phase results from the hardening/setting reaction of mercury with the metal powder and consists of a mixture of tin and mercury (Sn8Hg). Sn8Hg (γ-2 phase) is relatively unstable and decomposes following contact with saliva (corrosion); tin and mercury are then released. Corrosion results in bending and distortion of the edges of the amalgam filling which will eventually lead to breakdown of those edges. This results in small gaps around the edges of what now becomes a defective filling requiring replacement.

Gamma2-free (non-γ-2) amalgam

The composition of the alloy of the new amalgam type referred to as gamma2-free (non-γ-2) was improved so as to prevent formation of the γ-2 phase. Nowadays, only gamma2-free (non-γ-2) amalgam should be used.
This will usually contain:
  • 40 - 70 % silver (Ag)
  • 12 - 30 % copper (Cu)
  • up to 32 % tin (Sn)
Pursuant to the German DIN 13904, the following simple categorisation of amalgam types may be used:

Silver-rich amalgam
silver (Ag) 65 % min.
tin (Sn) 29 % max.
copper (Cu) 15 % max.

Copper-rich amalgam
silver (Ag) 40 % min.
tin (Sn) 32 % max.
copper (Cu) 30 % max.

Amalgams vary not only with regard to their composition but also the morphology of their alloy, ie the form of the metal filings:
  • filings or splinters
  • balls
  • filing / ball mix
  • ball-like drop-shaped (spheroidal) particles
When the alloy is mixed with mercury, a plastic mass forms that will set within 10 minutes at room temperature. During this time, the amalgam must be placed into, condensed and carved within the cavity. The setting time of amalgam depends on the composition of the alloy, the shape and size of the particle and the mixing time. 90 % of the final hardness will be reached after 10 - 12 hours.

Forms of application of amalgam

Amalgam is available in three different forms of application, regardless of its composition:
  • capsules for triturators (mixing devices),
  • powder for dosing and mixing devices (amalgators), and
  • tablets for special 'dispersers' (dosing appliance).
The big disadvantage of powder and tablets is that free mercury has to be dealt with when they are refilled. These open mixing devices in which mercury and metal filings are mixed unprotected should no longer be used because they put the health of the user at risk due to the developing mercury vapours; the MAC (maximum allowable concentration) for mercury is exceeded. Only amalgam ready for use and pre-packaged in plastic capsules should be used. One half of the capsule contains the mercury, the other half the metal powder. Both halves are separated by a membrane that is destroyed during the mixing procedure in the triturator. The metal powder is then thoroughly mixed with the mercury and is flexible at first but will soon start to harden.

Three different capsule sizes are available:
  • capsules for fillings with one surface,
  • capsules for fillings with two surfaces, and
  • capsules for fillings with three surfaces.
The selection of capsule size depends on the size of the defect.

Mixing (trituration)

A capsule with the necessary size is fixed into a suitable mixing device (triturator). The secure fastening of the capsule must be checked prior to initiation of the mixing procedure. The mixing time must be individually adapted to any device. Frequently it is 5 - 10 seconds. The ideal mixing time will result in a silvery, shiny amalgam ball that will completely and cleanly detach from the capsule shell. Mixing for too long will lead to sticking (especially to the membrane foil) and will shorten the time available for processing; for too short a period it will lead to a pale appearance and may result in insufficient amalgamation of the component metals.


Residual amalgam and empty amalgam capsules must be disposed of separately in special containers. These containers contain fixing salts or other chemical substances to bind mercury vapours. These containers must be disposed of according to legal requirements, returning them to the respective manufacturer. Local/regional instructions for waste disposal must be observed.

Placing of an amalgam filling

Instruments and materials required

  • 2 ml syringe with local anaesthetic, long injection cannula for regional block anaesthesia, short injection cannula for infiltration anaesthesia
  • red high-speed angle handpiece
  • rotary instruments:
    • pear-shaped diamond polisher,
      normal grain (without colour mark),
      fine / finest grain (with red or yellow colour mark),
    • hard metal instrument interlocking crosswise, if required (to remove old amalgam fillings)
  • green right angle
  • rose-head burs in different sizes (e.g. ISO 010-018)
  • multi-functional syringe (air/water)
  • large and small saliva ejector
  • cotton wool rolls (ca. 10 pieces)
  • cotton wool pellets (ca. 5 pieces)
  • Dappen glass with e.g. H2O2 (3 %) or CHX (2%) or NaOCl (5%)
  • phosphate cement (powder and liquid)
  • glass plate
  • cement spatula
  • cement condenser
  • calcium hydroxide preparation for treatment of deep caries, indirect or direct pulp capping

  • matrix holder with suitable matrix band (e.g. Tofflemire's)
  • suitable inter-dental wedge made of maple wood, colour-coded according to size
    (one inter-dental wedge is required for each approximal space to be filled
  • amalgam in capsules
  • amalgam mixing device for trituration
  • amalgam dispenser
  • amalgam gun
  • condensation instruments (amalgam condenser)
    • machines for condensation, if necessary, e.g. Bergendahl's vibrator
  • amalgam carving instruments, e.g.
    • cleoid/cleoid (clover leave shape)
    • discoid/cleoid (disk and clover leave shape)
    • Wieland instruments
    • Sprengel instruments
  • 2 flag holders with occlusal foil in different colours, e.g. black and red
  • dental floss
  • amalgam burnisher for adaptation of amalgam to the edges of the cavity
  • fluoride (e.g. Duraphat toothpaste)

Treatment overview

  • anaesthesia
  • removal of old fillings and/or primary preparation
  • caries excavation
  • cavity disinfection
  • base lining
  • finishing of the edges of the filling and base
  • insertion of matrix and inter-dental wedge
  • insertion of amalgam into the cavity
  • carving of the amalgam filling
  • occlusal control
  • burnishing of the amalgam filling
  • fluoridation of the tooth

Case description

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Polishing of an amalgam filling

Amalgam fillings must be polished but not until 24 hours have passed after the insertion.

Instruments and materials required

  • large and small saliva ejector
  • rotary instruments for polishing the amalgam (examples):
    • hard metal finisher
    • Arkansas stones
    • AABA universal polisher - dark
    • AABA universal polisher - light
    • Brownie
    • Greenie
    • Super Greenie