The effect of magnetic resonance imaging on mercury release from dental amalgam at 3T and 7T

Abstract

The effect of magnetic resonance imaging on mercury release from dental amalgam at 3T and 7T James R. Allison, Karthik Chary, Chris Ottley, Quoc C. Vuong, Matthew J. German, Justin Durham, Peter Thelwall. The effect of magnetic resonance imaging on mercury release from dental amalgam at 3T and 7T. Journal of Dentistry. 127, 2022, doi: 10.1016/j.jdent.2022.104322. Abstract Objectives To measure mercury release from standardised hydroxyapatite/amalgam constructs during MRI scanning and investigate the impact of static field strength and radiofrequency (RF) power on mercury release. Methods Amalgam was placed into 140 hydroxyapatite disks and matured for 14-days in artificial saliva. The solution was replaced, and samples split into five groups of 28 immediately prior to MRI. One group had no exposure, and the remainder were exposed to either a 3T or 7T MRI scanner, each at high and low RF power. Mercury concentration was measured by inductively coupled plasma mass spectrometry. Groups were compared using one-way ANOVA, and two-way ANOVA for main effects/ interaction of field strength/ RF power. Results Mercury concentration was increased in the 7T groups (high/ low: 15.43/ 11.33 ng mL−1) and 3T high group (3.59) compared to control (2.44). MRI field strength significantly increased mercury release (p < .001) as did RF power (p = .030). At 3T, mercury release was 20.3 times lower than during maturation of dental amalgam, and for the average person an estimated 1.50 ng kg−1 of mercury might be released during one 3T investigation; this is substantially lower than the tolerable weekly intake of 4,000 ng kg−1. Conclusion Mercury release from amalgam shows a measurable increase following MRI, and the magnitude changes with magnetic field strength and RF power. The amount of mercury released is small compared to release during amalgam maturation. Amalgam mercury release during MRI is unlikely to be clinically meaningful and highly likely to remain below safe levels. sciencedirect.com

AI evidence extraction

Main findings

In standardized hydroxyapatite/amalgam constructs, mercury concentration increased after MRI exposure in the 7T groups (high/low RF power: 15.43/11.33 ng mL−1) and the 3T high RF power group (3.59) compared with control (2.44). MRI field strength significantly increased mercury release (p < .001) and RF power also increased release (p = .030); estimated mercury released during an average 3T investigation was 1.50 ng kg−1, substantially below the tolerable weekly intake cited (4,000 ng kg−1).

Outcomes measured

• Mercury concentration (ng mL−1) released from hydroxyapatite/amalgam constructs during/after MRI exposure

Limitations

• In vitro construct model (hydroxyapatite disks in artificial saliva) rather than human participants
• Exposure duration and specific RF parameters (e.g., SAR) not reported in abstract
• Clinical outcomes not assessed; outcome limited to measured mercury concentration in solution

Suggested hubs

• who-icnirp (0.2)
  Study concerns RF exposure and safety context (tolerable intake mentioned), but no direct WHO/ICNIRP policy focus stated.

{
    "study_type": "other",
    "exposure": {
        "band": "RF",
        "source": "MRI scanner",
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": null
    },
    "population": null,
    "sample_size": 140,
    "outcomes": [
        "Mercury concentration (ng mL−1) released from hydroxyapatite/amalgam constructs during/after MRI exposure"
    ],
    "main_findings": "In standardized hydroxyapatite/amalgam constructs, mercury concentration increased after MRI exposure in the 7T groups (high/low RF power: 15.43/11.33 ng mL−1) and the 3T high RF power group (3.59) compared with control (2.44). MRI field strength significantly increased mercury release (p < .001) and RF power also increased release (p = .030); estimated mercury released during an average 3T investigation was 1.50 ng kg−1, substantially below the tolerable weekly intake cited (4,000 ng kg−1).",
    "effect_direction": "mixed",
    "limitations": [
        "In vitro construct model (hydroxyapatite disks in artificial saliva) rather than human participants",
        "Exposure duration and specific RF parameters (e.g., SAR) not reported in abstract",
        "Clinical outcomes not assessed; outcome limited to measured mercury concentration in solution"
    ],
    "evidence_strength": "low",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "MRI",
        "3T",
        "7T",
        "radiofrequency power",
        "static magnetic field strength",
        "dental amalgam",
        "mercury release",
        "artificial saliva",
        "inductively coupled plasma mass spectrometry"
    ],
    "suggested_hubs": [
        {
            "slug": "who-icnirp",
            "weight": 0.200000000000000011102230246251565404236316680908203125,
            "reason": "Study concerns RF exposure and safety context (tolerable intake mentioned), but no direct WHO/ICNIRP policy focus stated."
        }
    ]
}

Comments

Log in to comment.

No comments yet.