Dental
amalgam is the oldest and the most useful filling material. To date,
extensive research has failed to establish any links between amalgam
use and general ill health.
Most dentists are continuing to use amalgam for cavities where a very
durable material is needed - especially in the chewing surfaces of posterior
teeth. In many respects amalgam is an ideal filling material. As well
as being very durable, it expands and contracts with temperature change
at the same rate as the surrounding natural tooth. Like most biomaterials,
dental amalgam is not inert. Amalgam fillings release mercury vapor,
especially when teeth are chewed on or brushed. Some of the vapor is
exhaled but some reaches the rest of the body through inhalation. Part
of it also dissolves in saliva and is swallowed. Much of the mercury
entering the body is excreted but some accumulates in certain organs
- especially the kidneys but also, to a very much lesser extent, in
the brain, lungs, liver and gastrointestinal tract.
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However, experts
do not believe that the levels of mercury exposure resulting from amalgam
fillings are of any general health significance. The amount of mercury
that reaches the rest of the body is very small. Whether the amount
is related to the number of fillings is unclear. But mercury is toxic,
isn't it? Mercury is certainly toxic at large enough doses but the research
does not indicate that the small exposures, which result from the use
of dental amalgam, are harmful. Many substances are toxic at certain
dose levels and for certain people, depending on individual susceptibility.
Some people are even allergic to ingredients in foods such as bread
and milk. Reactions sometimes occur in the soft tissues of the mouth
next to fillings, not only with amalgam but with other restorative materials
too. Amalgam is not especially allergenic and true sensitivity reactions
are very rare. They may resolve spontaneously or after a change of restorative
material. Suspected allergies are investigated by dermatologists/allergists
and by oral medicine departments of dental hospitals, on referral from
the dentist.
Should amalgam
be used during pregnancy? It is known that mercury can cross the
placenta from mother to foetus and can also be detected in breast milk
but there is no evidence of any link between amalgam use and birth defects
or still births. Generally, it is sensible to minimize health interventions
during pregnancy. The 1998 report from the Committee on Toxicity already
referred to say that there was no reason to think that the placement
or removal of amalgam fillings during pregnancy was harmful. Committee
on Toxicity agreed with the European Commission's expert group, however,
that 'it may be prudent to avoid, where clinically reasonable, the placement
or removal of amalgam fillings during pregnancy. More research was recommended.
This does not constitute a ban on the use of dental amalgam during pregnancy.
There will be occasions when patients will decide, on advice from a
dentist, that the benefit of using amalgam (in terms of permanency,
for example) outweigh the as yet theoretical risk of systemic toxicity.
Dentists must always have a patient's informed consent before undertaking
any treatment.
Should amalgam
be used for children? Children who have a good diet and oral hygiene
can usually be treated successfully using sealant resins and glass ionomer
cements. But once posterior cavity approaches one third of the occlusal
width and once any mesial or distal extension is not bound by enamel,
glass ionomer fillings are not normally recommended and amalgam is an
acceptable restorative material.
Is there any
group for whom amalgam should not be used? Patients with proven
amalgam sensitivity are the only group for whom the placement of new
amalgam fillings is not advised.
Should dentists
explain current concerns about amalgam safety when suggesting its use?
Law and medical ethics require that patients be told enough about a
proposed treatment and any associated material risks to enable them
to reach an informed decision on whether to accept the treatment. The
information given by the dentist will be a matter for personal judgement.
In the case of a child with multiple allergies, the possibility of mercury
or amalgam hypersensitivity might be raised, for example. However, based
on recent legal decisions about the requirements for consent, dentists
are advised that it is not necessary to discuss the alleged links between
amalgam use and health problems with generally healthy patients, except
in relation to pregnancy. Until there is a reputable body of opinion,
which believes that there are material risks in amalgam use, consent
given without discussion of side effects can be regarded as 'informed'.
Dentists should, of course, always be prepared to answer patients' questions
about the safety of dental amalgam.
Bojadziski
Darko