Evaluation of the effect of ultra-high field magnetic resonance imaging on amalgam phase change and mercury release

Objective: Amalgam restorations used in the treatment of dental caries have the potential to cause toxic effects due to mercury in their contents. It is thought that the amount of mercury released from amalgam restorations may change with different physical and chemical conditions. Magnetic resonance imaging (MRI) is often preferred for imaging of soft tissue-related pathologies. Metal objects exposed to the magnetic field exhibit behaviors such as heating and moving within the magnetic field. The aim of this study was to evaluate the phase change and the amount of mercury release in amalgams which exposed to the magnetic field. Method: 60 amalgam discs with 4 mm diameter and 4 mm height were prepared. 30 amalgam discs were selected as control group and 30 amalgam discs were selected as MRI group. The discs were placed in the Fusayama-Meyer solution. Discs in the MRI group were exposed to MRI with 14.1T ultra-high-field magnetic resonance (UHF-MRI) system (EPFL, Lausanne, Switzerland). 2, 12 and 24 hours after UHF-MRI application, all discs were removed from the solutions. Inductively coupled plasma-mass spectroscopy (ICP-MS) analysis was performed to the solutions, while X-ray diffractometry (XRD) analysis was performed on amalgam discs. Differences and interactions between groups were evaluated by two-way ANOVA test. Results: Mercury concentrations in solutions were significantly higher in the MRI group than the control group (p = 0.026). There were no differences between the metallurgical phases of the amalgam discs in the MRI group and the control group. The peak intensity of the amalgam discs in the MRI group obtained by XRD analysis was significantly lower than the peak intensity of amalgam discs in the control group (p = 0.000). Conclusion: It is possible that patients with amalgam restoration who underwent UHF-MRI application may be at risk of mercury toxicity due to the increase in the release of mercury related with the power of magnetic field and and the time of MRI application. UHF-MRI application is thought to have a debilitating effect on the crystal structure in amalgam in relation to the duration of exposure to the magnetic field. Key words: amalgam, MRI, mercury, ICP-MS, XRD