Dental amalgam has been found to
be a frequent contributor to oral
lichenoid lesions[52] (PMID 15529127) and a
possible contributor to other autoimmune conditions such as mutiple sclerosis,
lupus, thyroiditis and eczema.[53]
Among modern dentists who are
exposed to mercury amalgam and vapor on a daily basis, no evidence of mercury
poisoning has been demonstrated. Some studies have indicated that mercury from
amalgams affects some dentists mildly. Dentists in several large-scale studies
performed multiple cognitive and behavioural tests and, compared to a normal
population, lagged behind in many areas. In one study this included 14% worse
scores in memory, co-ordination, motor speed and concentration.[54] The study did not demonstrate any link between mercury
exposure and these lagging scores, however. A newer study[55] also found a link between cognitive impairment (including
mood) and dental work, even though "exposure among these dental personnel
are not much greater than exposures to the general population through the
dental amalgam in their fillings" as shown by urinary studies. Twelve of
13 symptoms were correlated with greater mercury exposure.
A study examining the health
effects of mercury on dentists in the UK published in the Occupational and
Environmental Medicine Journal[56] concluded that 180 dentists had on average 4 times the
urinary mercury excretion levels of 180 people in a control group. Dentists
were significantly more likely than control subjects to have had disorders of
the kidney or memory disturbance. No direct correlation between urinary mercury
levels and the disability, however, was found. Urine testing is unreliable for
showing lifetime mercury accumulation rather than recent exposure.
In the 2005 lawsuit Barnes vs.
Kerr, the dentist David Barnes brought action against the Kerr Corporation, a
major manufacturer of dental amalgams.[57] This suit was originally decided in the Circuit Court
for Bedford County and reviewed by Sixth Circuit of the United States Court of
Appeals.[57] Barnes argued that his alleged mercury poisoning was
caused by exposure to toxic mercury vapors, and that Kerr Corporation's
amalgams were the major source of this poisoning.[58]
Barnes' suit alleged that his
exposure came from three sources.[59] The first was "mercury vapor and mercury contained
in amalgam particulate inhaled when removing existing amalgam from the teeth of
patients". The second was "contaminated office air due to a variety
of sources, including mercury released during trituration of capsules, opening
of triturated capsules, free mercury that may have leaked during transport, and
particulate released into the office air during amalgam removal". The
third source was "was mercury vapor and mercury particulate generated during
the placement of new amalgams".
Barnes' office was found to be
contaminated with mercury by the Tennessee Occupational Health and Safety
Administration (TOHSA) , even after it had been thoroughly cleaned, and mercury
droplets were found in the machine he had used to mix amalgam capsules.[59] An industrial hygienist found that "89% of the
surfaces in Barnes’s office still showed traces of mercury", even after
two intensive cleanings.[59]
Kerr Corporation argued that they
had not manufactured a majority of the amalgams Barnes had removed, that the
contamination of Barnes' office, "could have come from sources other than
leaking capsules", and that Barnes could not have been exposed to mercury
during the placement of amalgams because of the methods he used.[59]
Kerr Corporation's amalgam
capsules bore prominent warning labels in capital letters stating that they
"CONTAIN[ED] METALLIC MERCURY" and featured a skull and crossbones
next to the word "POISON".[60] A detailed warning enclosed with the amalgam capsule
described mercury as a "hazardous ingredient" and listed potential
health hazards associated with exposure including nervous irritability,
weakness, tremors, gingivitis, erethism, greying of the lens of the eye,
nephrotoxic effects, and aggravation of kidney disorders.[60] This full text of the warning read, "WARNING ...
Alloy amalgam capsule products contain mercury. Since mercury is a potentially
hazardous substance, proper care should be taken to prevent exposure to
mercury. These preventative measures include the wearing of gloves, good
ventilation, the use of an enclosed amalgamator, proper disposal of capsules
once they have been activated and used, and the use of HGX or similar-type
mercury absorbing chemicals in the event of spillage. Infrequently capsules may
leak mercury and, as a consequence, the above precautionary measures should
always be utilized".[61]
The district court held that the
testimony of Barnes' expert witnesses in support of "a strong minority
view that dental amalgam containing mercury is both unreasonably dangerous and
hazardous to human health" was admissible.[60] The district court decided in favor of Kerr Corporation
because Barnes had "not demonstrated that his injuries would have occurred
‘but for’ exposure to Kerr’s dental amalgam product".[60] They also ruled that the numerous warnings provided by
Kerr "more than adequate [because] ...[r]easonable minds could not differ
as to their sufficiency".[60] Barnes' suit against Kerr Corporation was dismissed
because he had been warned that amalgam was poisonous and that its use could
result in the contamination of his office, and because he could not prove that
the m http://en.wikipedia.org/wiki/Dental_amalgam_controversy#Autoimmune_disorders
ajority of the amalgam which had contaminated his office had been manufactured
by the Kerr Corporation.[60]
http://en.wikipedia.org/wiki/Dental_amalgam_controversy#Autoimmune_disorders