have been used in dentistry for the past 160 years as restorative
fillings. The use of dental amalgams is decreasing nowadays,
but it continues to be the material of choice among many dentists
in providing inexpensive restoration of posterior teeth.
Dental amalgams are made of metal alloys. Amalgams are prepared
from alloys of mercury and metals. These metals are platinum,
gold, zinc, cadmium, antimony, and bismuth. A high dispersion
copper alloy was developed in 1963. This dispersion copper alloy
is more corrosion resistant than earlier copper alloys.
Today the amalgams are made from mercury and alloys that are
composed of silver, tin, and copper. Other metals like zinc,
indium, and palladium may also be present in small amounts of
1% or less of the alloy. It is believed that zinc improves the
clinical performance of the amalgam by the preventing corrosion.
This modern amalgam is made by mixing 43% to 50% mercury by weight
with the alloy.
Amalgams are available as irregular practices. They are small
spheres or a mixture of the two. Handling characteristics of
the alloy depends upon its formulation, shape, and size. But
the clinical performance remains the same. Spherical alloys are
easily adaptable to cavity walls because they are less resistant
to condensation. But an actual experience showed that the spherical
alloys exhibit microleakage due to poor adaptation.
In order to seal the margin between the tooth and the amalgam,
cavity varnishes are needed to reduce the leakage. Before, copal
varnishes were used, it lasted only for a few months. Nowadays,
the replacement of the traditional varnishes by bonding resins
that provide a better initial seal of the cavity walls is happening
gradually. The use of varnish is not advised when an amalgam
is used with bonding resins.
The major problem with amalgam restorations is recurrent caries.
A retrospective survey was done by clinics and private practitioners.
The survey showed that in half of the cases of replacement, restoration
was done in teeth with recurrent caries. In this study, it was
believed that some cases were wrongly identified as recurrent
caries and that the first amalgam restoration was not done properly
and the caries remained underneath the first filling.
If the tooth is not correctly prepared and cleanded before a
filling this often leaves a residual caries that later becomes
a bigger problem. In other
are also wrongly diagnosed as caries, especially when there
is debris found in the area.
Recurrent caries can be minimized by the following ways:
- use topical fluoride applications
- good oral hygiene
- careful amalgam placement
- placement of an unfilled resin
to seal restoration margins
Improvements and new studies have led to a changed cavity design.
Preserving the tooth structures with minimal intervention is
the key. The amalgam fillings should be extended to carious fissures
and not to adjacent non-carious fissures. Studies have revealed
that smaller restorations last longer, and retaining as much
sound tooth as possible also reduces the chances of cusp fracture.
When the tooth has been destroyed by caries and/or trauma, large
restorations are needed. The retention of large restorations
requires further measures such as the use of retentive pins.
These retentive pins are not sufficient to combat the pressure
exerted during placement. This can cause fractures in surrounding
tooth structure. In these cases, dentists create amalgam pins
by cutting channels in the teeth and filling them with amalgam.
Amalgam pins also require removal of tooth structure in an already
No long-term studies were made to show how good amalgam bondings
are. But short term studies and an increasing evidence showed
that amalgams are effective over the years. Only a successful
long term bonding can eliminate mechanical bondings like the
retentive and amalgam pins. Reducing the chances of more damage
to the tooth and enabling better cavity design that would preserve
more sound structures is achieved through the elimination of
Problems with amalgam fillings
Amalgams have adverse effects. Alloy components present in the
amalgams can cause oral lesions, although this occurrence is
rare. This problem affects not only the patients but also the
involved in restoration. To resolve the problem, removing the
offending restoration is done. Patients may show sensitivity
or allergies to the resins.
Another disadvantage of amalgams
is aesthetic problems, as they can cause tooth discoloration.
Mercury toxicity, neuro toxicity, birth defects, and compromised
health are some of the allegations against the use of amalgams.
These have no supporting scientific evidence, but should not
Mercury is one of the metals used in amalgams. Mercury in large
amounts can have adverse effects on people.
There are studies that have revealed that the small amount of
mercury vapor released by amalgams does not pose a health hazard.
With all these allegations thrown at the use ofamalgams, its
ironic that the dental staff, who are most exposed to these amalgams,
have higher life expectancies than others have. There is no evidence
that dental staff develop diseases or die from coauses that are
different from the general population - they are affected by
the same diseases seen in the general population.