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High-Powered MRI Releases Mercury From Dental Amalgam

NEW YORK (Reuters Health) – Dental amalgam exposed ex vivo to 7.0-T MRI releases potentially toxic mercury, researchers from Turkey report.

Dental amalgam consists of approximately 50% mercury, which can be released during chewing, brushing and corrosion into the saliva (about 40% of the mercury released from amalgam, as metal ions) or into the air (about 60%, as mercury vapor).

About 100 million amalgam filling procedures are performed every year in the U.S. Since 2008, Sweden, Norway, Denmark and Germany have forbidden the use of amalgam fillings.

In light of previous studies showing microleakage of mercury after MRI, Dr. Selmi Yilmaz from Akdeniz University, in Konyaalti/Antalya, and colleagues investigated the mercury release into artificial saliva from 60 caries-free molar or premolar amalgam-filled teeth exposed to 7.0-T and 1.5-T MRI in an ex vivo setting.

The mean mercury values in the artificial saliva medium were 673 mcg/L in the 7.0-T MRI group, 172 mcg/L in the 1.5-T MRI group and 141 mcg/L in the unexposed control group, the team reports in Radiology, online June 26.

The mercury content in the 7.0-T group was significantly higher than that in both of the other groups, whereas mercury content did not differ significantly between the 1.5-T and control groups.

“The World Health Organization estimates that the daily absorbed dose from amalgam is 122 mcg mercury, and the Environmental Protection Agency provides a reference concentration of 0.3 mcg/m3 for inhalation,” the researchers note. “In the present study, the dissolved amount of mercury was observed to be in the range of 325-1000 mcg/L mercury after 7.0-T MRI.”

“Further studies of mercury amalgam with 7.0-T MRI may be warranted to evaluate the relationship between high-field-strength MRI and release of mercury from dental amalgam,” they conclude.

Dr. Jack Krall, chairman of the board of International Academy of Oral Medicine and Toxicology (IAOMT), a global network of dentists, health professionals and scientists who research the biocompatibility of dental products, told Reuters Health by email, “We have been aware of the effect of electromagnetic phenomenon on mercury fillings for some time. For those of us very familiar with mercury fillings as a source of chronic exposure to mercury, our reactions have long ago transformed from ‘interesting’ to disturbing.”

“This study showed a significant increase to the continuous (24/7) and chronic exposure to mercury vapor, a known neurotoxin, that, depending on numerous variables, such as the number of surfaces of mercury amalgam fillings and the individuals’ polymorphisms, will increase the risk of harm,” he said.

Physicians should remind especially unhealthy patients to never allow their dentists to place a new mercury filling in their teeth,” Dr. Krall said. “When having any mercury fillings removed, go to a dentist who will use a safe removal protocol such as SMART, developed by the IAOMT.”

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