Amalgam Filling in Dentistry

An amalgam filling – colloquially called a filling – is a dental filling material that is usually an alloy of mercury with silver, copper, indium, tin and zinc. Amalgam has been used worldwide for many decades as a very durable filling material due to its good mechanical material properties. It is the only filling material paid for by statutory health insurers in the posterior region, except for plastic fillings in exceptional cases such as kidney dysfunction and proven amalgam allergy. Advantages

  • Good mechanical properties, thus strong load capacity.
  • Many years of lying in the mouth
  • Relatively inexpensive
  • Simpler processing and handling than plastic filling; thus requires not so high compliance (ability of the patient to cooperate), which may be reduced, for example, by a restricted mouth opening, strong salivation or the impossibility of relative or absolute drainage by rubber dam, etc.
  • With the natural tooth substance comparable abrasion behavior.

Disadvantages

  • The potential danger of amalgam due to its mercury content has been increasingly pointed out by some scientists in recent years. Amalgams used today have a high oral stability. Nevertheless, it must be assumed that minimal amounts of mercury are constantly released from an amalgam filling.According to the report of an EU commission, however, amalgam fillings do not pose any significant health and ecological risks. A possible ban on amalgam was rejected on the basis of current studies. It should also be noted that the amount of mercury absorbed through food (especially fish), breathing air and drinking water exceeds the daily amount released from fillings.
  • The removal of an old amalgam filling is also associated with increased exposure to mercury and should therefore be carried out under certain precautions that minimize the potential exposure of the patient and the treatment team.
  • Amalgam tattoos: carryover of amalgam particles from filling areas close to the mucosa can cause gingiva (gums) or oral mucosa to take on blackish discolorations that are aesthetically disturbing but harmless.
  • Insufficient aesthetics

Indications (areas of application)

  • Occlusal, occlusal-approximal and cervical (located on the occlusal surface, on the contact surface with the adjacent tooth or in the cervical area) fillings in the posterior region.
  • In the anterior region for aesthetic reasons only on oral tooth surfaces (surfaces facing the oral cavity).
  • In case of allergy to plastic filling material

Contraindications

Contraindications take into account the discussed health risks from mercury released as a purely precautionary measure, without relying on any proven evidence in this regard.

  • Placement of an amalgam filling in gravidity (pregnancy) or lactation phase (breastfeeding)* .
  • Direct contact in the mouth with gold alloys: no amalgam fillings next to gold inlays or crowns or as core build-ups under planned gold crowns, because the differences between base and noble metal build up an electrical potential that removes material from the amalgam filling, while the gold alloy takes on an unaesthetic-looking dark filmy coating
  • Renal dysfunction
  • Careful consideration in the care of children and adolescents* ; contraindicated in adolescents < 15 years of age.
  • Proven allergy to amalgam – very rare; immediately after application (placing the filling) urticaria (hives), eczematous distant reactions, very rarely local (local) manifestations; subsiding after two to three weeks.

* From July 2018, the mercury-containing amalgam may no longer be used as a dental filling in pregnant or lactating women and adolescents under 15 years of age (adopted regulation of the European Parliament, 14.3.2017).The U.S. Food and Drug Administration (FDA) advises against the use of amalgam in high-risk groups due to an increased health risk, due to mercury vapors emitted by the filling:

  • Women who plan to become pregnant
  • Pregnant
  • Breastfeeding women
  • Children under 6 years
  • People with pre-existing neurological conditions such as multiple sclerosis (MS), Alzheimer’s disease or Parkinson’s disease.
  • Patients with impaired renal function
  • Persons with known increased sensitivity (allergy) to to mercury or other components of dental amalgam.

The procedure

Amalgam is a material produced by trituration (mixing) of pure mercury and a powdery metal mixture usually of silver–tin alloy (Ag3Sn) and silver-copper alloy immediately before application (placing) of the filling. The freshly mixed material, which is still plastic, is inserted into the tooth under the highest possible tamping pressure in order to achieve a high material quality and the lowest possible mercury content through strong compaction, since the mercury collects on the surface of the filling during tamping with special amalgam condensers. This is deliberately “overplugged” in height, and the mercury-rich low-grade excess is removed when the filling is modeled (finished). The process steps in detail:

  • Excavation (caries removal).
  • Cavity preparation (grinding of the tooth defect): undercuts required, as the filling is anchored purely mechanically
  • Reworking the enamel margins: removing the marginal enamel prisms loosened by the preparation, whose retention would result in a qualitatively inferior marginal finish of the filling
  • Placement of a pressure-stable subfilling (e.g. glass ionomer or zinc phosphate cement).
  • Relative draining (e.g., with saliva ejector and cotton rolls).
  • In the case of approximal fillings (in contact with the adjacent tooth), application of a screwable matrix that resists the tamping pressure
  • Fixing the matrix termination in the approximal space by means of a wedge.
  • Trituriation: mixing of the material in pre-dosed disposable capsules in the mechanical vibrator for a few seconds according to the manufacturer’s instructions; the result is a kneadable and malleable, not too dry, still matt silvery shiny material with the characteristic “snowball crunch” when processing.
  • Stuffing and condensing (compacting) of the filling under maximum stuffing pressure for material optimization either manually or with mechanical condenser; “overstuffing” of the filling.
  • Finishing, “carving” of the filling: the mercury-rich filling material of the excess surface is removed with hand instruments, the filling is adapted to the tooth contours by “carving” the material losing its plasticity within three to five minutes

After the procedure

  • Application of varnish (e.g. fluoride varnish).
  • The patient should be instructed to refrain from eating and otherwise stressing the filling for about two hours, because the amalgam has only reached approximately its final hardness after ten hours.
  • Therefore, polishing the filling is not yet possible in the first session, it can be done after 24 hours at the earliest. In the process, the filling margins are driven to the enamel margins, taking into account the direction of travel of the polishing instruments, fine polishing is done with polishing pastes. It is essential to ensure that enough paste material is applied to avoid overheating of the amalgam.

Possible complications

  • Filling fracture with premature loading
  • Allergic reactions in previously unknown amalgam allergy.
  • Amalgam tattoo
  • Overstuffing of filling material into the approximal space when the matrix band is insufficiently tight.
  • Formation of a corrosion element in the direct contact of more noble gold alloys with the less noble amalgam.