The MRI in discussion here is
the first 7 Tesla (7T) MRI device that was cleared by the U.S. Food and Drug
Administration (FDA) for use in the United States in 2017.
‘MRI scanners with higher magnetic field strengths produce better picture quality for diagnosis. But, a side effect of such high strength MRIs is an increased release of mercury that could occur from amalgam dental fillings.’
magnetic fields and radio waves (radiofrequency energy) to generate images that
provide information that may be useful in determining a diagnosis. The 7T
MRI has more than double the static magnetic field strength
earlier MRIs where increased strength relates to an equally better overall
image quality of MRI. The magnetic field strength in the MRI scanners are
measured in Tesla or "T." Earlier clinical MRI systems were available in field
strengths of 3T and below.
Amalgam fillings are otherwise known as silver fillings
and have been used in dentistry for many years. Amalgam consists
of approximately 50 percent mercury; mercury, as we all know, is a toxin that
can cause a host of harmful effects in humans.
American Dental Association reports that approximately 100 million
amalgam filling procedures are performed every year in the U.S.
the U.S. Food and Drug Administration considers amalgam fillings
safe for adults and children
older than age six, the use of dental
amalgam, however, remains rather controversial due to its high mercury content.
fillings are currently banned or restricted in Sweden, Norway, Denmark,
Germany, Finland, Netherlands, and Japan.
Connection between MRI
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."
However, the magnets in the
stronger scanners cause corrosion in the amalgam, which allows toxic mercury to
fact, studies done earlier have revealed that exposure to the magnetic fields
of MRI could cause mercury to leak from amalgam fillings, with approximately 40
percent of it traveling into saliva and the gastrointestinal system and around
10 percent of the mercury being absorbed. Also, approximately 60 percent is
released as mercury vapor and is either inhaled, entering the lungs, or is
concern increased some more when the ultra-high-strength 7-T scanners were
cleared for use by the FDA in the clinic. Yes, the stronger magnetic field of
7-T MRI yields more anatomical detail, but the question remained as to what
effect these powerful fields will have on amalgam dental fillings.
our knowledge, no previous study has tested the effects of 7-Tesla MRI on
mercury release from amalgam fillings," the authors wrote. "We
hypothesized that 7-Tesla MRI can trigger mercury release."
Study design -
Evaluating mercury released from the dental amalgams after exposure to 7-T and
Yilmaz and Mehmet Zahit Adi, Ph.D., studied the teeth of patients that had been
extracted for clinical indications.
researchers opened two-sided cavities in each tooth and applied amalgam
nine days, two groups of 20 randomly selected teeth were separated and placed
in a solution of artificial saliva
following this, one group was exposed to 20 minutes of 1.5-T MRI while the
other was exposed to 20 minutes of 7-T MRI.
third group was a control group of teeth that was placed in artificial saliva
researchers then analyzed the artificial saliva solution
- The mercury content in the 7-T MRI
group was 0.67 ± 0.18 parts per million (ppm) compared to 0.17 ± 0.06 ppm
in the 1.5-T MRI group
- The mercury content in the control
group was 0.14 ± 0.15 ppm
- This increase of 0.67 ppm in the 7-T
group was approximately four times the levels found in the 1.5-T group and
the control group
our study, we found very high values of mercury after ultra-high-field
MRI," Dr. Yilmaz said. "This is possibly caused by phase change in
amalgam material or by the formation of microcircuits that leads to electrochemical
corrosion, induced by the magnetic field."
the same time, the authors reassure that no evidence of harmful effects was
found in the 1.5-T group and since this is the scanner widely available and
commonly used for patient exams, patients with amalgam fillings should erase
their concerns about having an MRI exam.
are three ongoing projects being planned by, Dr. Yilmaz and his group where
they will focus on phase and temperature changes of dental amalgam across
different magnetic fields.
human is exposed to some level of mercury. However, the type
and severity of health effects that occur depend on the type of mercury, the
dose, the age or developmental stage of the person exposed, the duration of
exposure, and the route of exposure.
is measured as the amount of mercury in the bloodstream (for short-term
exposure) or the amount of mercury excreted in the urine relative to creatine
(for long-term mercury exposure).
is a component of amalgam and is absorbed very differently from the one found
in fish, methylmercury.
How much a person is exposed to mercury
from amalgam restorations depends on the number and size of restorations,
composition, chewing and brushing habits, and many other physiological factors.
is high during filling placement and removal.
Mercury vapors are released
when chewing for more than 30 minutes and then subside approximately 90 minutes
following chewing cessation. Chewing contributes to a daily mercury exposure
for those with amalgam fillings.
- Mortazavi G, Haghani M, Rastegarian N, Zarei S, Mortazavi SMJ. "Increased Release of Mercury from Dental Amalgam Fillings due to Maternal Exposure to Electromagnetic Fields as a Possible Mechanism for the High Rates of Autism in the Offspring: Introducing a Hypothesis." Journal of Biomedical Physics & Engineering. (2016) ;6(1):41-46.