Mercury Fillings: Autoimmune disorders Health effects for dentists

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 ajority of the amalgam which had contaminated his office had been manufactured by the Kerr Corporation.[60]