News | Magnetic Resonance Imaging (MRI) | July 05, 2018

High-Strength MRI May Release Mercury from Amalgam Dental Fillings

While new research suggests ultra-high-field 7T MRI could pose problems for people with amalgam fillings, conventional 1.5T scans were found to be safe

High-Strength MRI May Release Mercury from Amalgam Dental Fillings

July 5, 2018 — Exposure to ultra-high-strength magnetic resonance imaging (MRI) may release toxic mercury from amalgam fillings in teeth, according to a new study appearing online in the journal Radiology. The effect was not seen, however, in the lower strength, more commonly used 1.5-Tesla (T) MRI.

Amalgam fillings, also known as silver fillings, have been a staple of dentistry for many years. Amalgam consists of approximately 50 percent mercury, a known toxin that can cause a host of harmful effects in humans. Despite the presence of mercury, the U.S. Food and Drug Administration (FDA) considers amalgam fillings safe for adults and children older than age six.

“In a completely hardened amalgam, approximately 48 hours after placing on teeth, mercury becomes attached to the chemical structure, and the surface of the filling is covered with an oxide film layer,” said the study’s lead author, Selmi Yilmaz, Ph.D., a dentist and faculty member at Akdeniz University in Antalya, Turkey. “Therefore, any mercury leakage is minimal.”

Previous research has found that exposure to the magnetic fields of MRI could cause mercury to leak from amalgam fillings. This concern has been heightened by the recent arrival of ultra-high-strength 7T scanners in the clinic. The stronger magnetic field of 7T MRI yields more anatomical detail, but its effects on amalgam dental fillings have not been studied.

To learn more, Yilmaz and colleague, Mehmet Zahit Adişen, Ph.D., evaluated mercury released from dental amalgam after 7T and 1.5T MRI in teeth that had been extracted from patients for clinical indications. While 7T MRI was approved by the FDA in 2017, it has extremely limited availability. The lower-strength 1.5T MRI is widely available and commonly used for patient exams.

The researchers opened two-sided cavities in each tooth and applied amalgam fillings. After nine days, two groups of 20 randomly selected teeth were placed in a solution of artificial saliva immediately followed by 20 minutes of exposure to 1.5T or 7T MRI. A control group of teeth was placed in artificial saliva only.

When the researchers analyzed the artificial saliva, the mercury content in the 7T, 1.5T and control group was 0.67 ± 0.18, 0.17 ± 0.06 and 0.14 ± 0.15 parts per million (ppm), respectively.  At 0.67 ppm, the mercury content in the 7T group was approximately four times the levels found in the 1.5T group and the control group.

“In our study, we found very high values of mercury after ultra-high-field MRI,” Yilmaz said. “This is possibly caused by phase change in amalgam material or by formation of microcircuits, which leads to electrochemical corrosion, induced by the magnetic field.”

An important point of discrimination concerning safety and hazard to human health is the amount of mercury that is absorbed by the vital tissues.

“It is not clear how much of this released mercury is absorbed by the body,” Yilmaz said.

Further studies may be warranted, Yilmaz added, to evaluate the relationship between high-field MRI and release of mercury from dental amalgam. The researchers have three ongoing projects focused on phase and temperature changes of dental amalgam across different magnetic fields.

As no evidence of harmful effects was found in the 1.5T group, patients with amalgam fillings should not be unduly concerned about having an MRI exam.

For more information: www.pubs.rsna.org/journal/radiology

Reference

Yilmaz S., Adisen M.Z. "Ex Vivo Mercury Release from Dental Amalgam after 7.0-T and 1.5-T MRI," Radiology. June 26, 2018. https://doi.org/10.1148/radiol.2018172597

Related Content

NIH Study of Brain Energy Patterns Provides New Insights into Alcohol Effects

NIH scientists present a new method for combining measures of brain activity (left) and glucose consumption (right) to study regional specialization and to better understand the effects of alcohol on the human brain. Image courtesy of Ehsan Shokri-Kojori, Ph.D., of NIAAA.

News | Neuro Imaging | March 22, 2019
March 22, 2019 — Assessing the patterns of energy use and neuronal activity simultaneously in the human brain improve
Book Chapter Reports on Fonar Upright MRI for Hydrocephalus Imaging

Rotary misalignment of atlas (C1) and axis (C2). Image courtesy of Scott Rosa, DC, BCAO.

News | Magnetic Resonance Imaging (MRI) | March 20, 2019
Fonar Corp. reported publication of a chapter where the physician-author-researchers utilized the Fonar Upright Multi-...
Older Biologic Age Linked to Elevated Breast Cancer Risk
News | Women's Health | March 19, 2019
Biologic age, a DNA-based estimate of a person’s age, is associated with future development of breast cancer, according...
HeartFlow Analysis Successfully Stratifies Heart Disease Patients at One Year
News | CT Angiography (CTA) | March 19, 2019
Late-breaking results confirm the HeartFlow FFRct (fractional flow reserve computed tomography) Analysis enables...
PET Scans Show Biomarkers Could Spare Some Breast Cancer Patients from Chemotherapy
News | PET Imaging | March 18, 2019
A new study positron emission tomography (PET) scans has identified a biomarker that may accurately predict which...
SyncVision iFR Co-registration from Philips Healthcare maps iFR pressure readings onto angiogram.

SyncVision iFR Co-registration from Philips Healthcare maps iFR pressure readings onto angiogram. Results from an international study presented at #ACC19 show that pressure readings in coronary arteries may identify locations of stenoses remaining after cardiac cath interventions.

Feature | Cardiac Imaging | March 18, 2019 | By Greg Freiherr
As many as one in four patients who undergo cath lab interventions can benefit from a technology that identifies the
Non-Contrast MRI Effective in Monitoring MS Patients
News | Neuro Imaging | March 18, 2019
Brain magnetic resonance imaging (MRI) without contrast agent is just as effective as the contrast-enhanced approach...