Composite (Plastic) Fillings & Sealants
It is believed that composite (plastic) fillings are much safer than mercury amalgam
fillings over the long run. In some cases, though, there are important allergic sensitivity
issues that need to be considered. It has also been shown in recent research that composite
fillings, when properly placed by an experienced dentist, last nearly as long as
mercury amalgam fillings (on average). Large composite fillings can be successfully
placed by experienced dentists. One of the benefits is that unlike mercury
amalgam fillings, little on no tooth material has to be drilled away to place the
composite filling.
The allergic sensitivity issue can be an important one for some people. These people
can use the Clifford Materials Reactivity Testing
procedure to reduce the likelihood of an allergic reaction to the dental materials.
You can arrange this test yourself or your dentist can arrange for the test for you. My
dentist told me that Conquest brand materials tend to cause fewer reactions than others
he has tried.
The chronic toxicity issue is a complicated one. The composite fillings release estrogenic
chemicals into the body. Significant exposure to estrogenic chemicals can cause health
problems over time. However, after the first few days, the amount of release into the body is
extremely small.
There is something in biological response to some chemicals known as the "U-shaped curve".
As an example, when an exposure is at 100 units, it causes a specific health effect. At
an exposure of 1 unit, it causes no observable effect. But at an exposure of 0.1 units, the
chemical again causes a health effect. This can happen when, for example, the 0.1 dose
causes a health effect, the 1.0 dose is high enough to cause different enzymes to protect the
body and prevent effects, and the 100.0 dose overwhelms the body's defenses. This U-shaped curve
seems to be what in seen in scientific research related to the compounds released from composite
fillings and sealants. However, the dose released from these substances may even be below
the lowest dose ever seen to cause effects (except for the time immediately after filling
replacement).
The results of the these experiments was discussed in the March 24, 1997 issue
of Chemical & Engineering News:
"In late February, researchers at the University of Missouri,
Columbia, led by Frederick S. vom Saal,
reported
that when extremely small doses of bisphenol A are given to pregnant
mice for seven days, the adult male offspring have enlarged prostates.
"Early this month, vom Saal reported in a companion article that the
dose-response curves for natural estradiol, and for the synthetic
estrogen diethylstilbestrol (DES), are shaped like an inverted "U"
[Proc. Natl. Acad. Sci. USA 94, 2056 (1997)]. When pregnant mice
were given either estradiol or DES, the prostate weights in the male
offspring increased up to a certain dose level and then began to
decrease as the doses rose."
In the same Chemical & Engineering News article there is a discussion of the
findings of a researcher researcher who found estrogenic compounds in patients'
saliva soon after placement of composite materials:
"In any event, Soto says, after the sealants were applied in her
study, the patients' saliva was found to be estrogenic in a standard
assay, and it wasn't beforehand. This shows that an estrogenic
compound must be released from the sealants, she says.
The only contraindications I would suggest for placing composite fillings
are during pregnancy and in cases of allergic reactions to the composite
materials. It is possible that one day, new, non-metal materials may be found that
are even safer than composite materials.