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Nancy Nairi Maserejian,¹ Felicia L. Trachtenberg,¹ Susan F. Assmann,¹ and Lars Barregard²

¹New England Research Institutes, Watertown, Massachusetts, USA; ²Department of Occupational and Environmental Medicine, Sahlgrenska University Hospital and Academy, Gothenburg, Sweden

Abstract
Background: Urinary mercury (U-Hg) excretion is a commonly used biomarker for mercury exposure from dental amalgam restorations.

Objectives: Our goal was to determine the most efficient measure of dental amalgam exposure for use in analyses concerning U-Hg in children.

Methods: We analyzed time-sensitive longitudinal amalgam exposure data in children randomized to amalgam restorations (n = 267) during the 5-year New England Children's Amalgam Trial. We calculated 8 measures of amalgam, evaluating current versus cumulative exposure, teeth versus surfaces, and total versus posterior occlusal amalgams. Urine samples collected during follow-up years 3–5 were analyzed for mercury excretion. Multivariate models for current and cumulative U-Hg excretion estimated associations between exposures and U-Hg.

Results: At the end of follow-up, the average (± SD) cumulative exposure was 10.3 ± 6.1 surfaces and 5.7 ± 2.9 teeth ever filled with amalgam, corresponding to 30 ± 21 surface-years. Amalgam measures and U-Hg were moderately correlated. Of amalgam exposure measures, the current total of amalgam surfaces was the most robust predictor of current U-Hg, whereas posterior occlusal surface-years was best for cumulative U-Hg. In multivariate models, each additional amalgam surface present was associated with a 9% increase in current U-Hg, and each additional posterior occlusal surface-year was associated with a 3% increase in cumulative U-Hg excretion (p < 0.001) .

Conclusions: One single measure of amalgam exposure is insufficient. Studies of cumulative effects of mercury from amalgam exposure in children are likely to have improved validity and precision if time-sensitive amalgam exposure measures are used. In contrast, simple counts of current amalgam fillings are adequate to capture amalgam-related current U-Hg.

Key words: children, dental amalgam, creatinine/urine, environmental exposure, mercury, mercury/urine. Environ Health Perspect 116:256–262 (2008) . doi:10.1289/ehp.10440 available via http://dx.doi.org/ [Online 12 November 2007]

Address correspondence to N. Maserejian, New England Research Institutes, 9 Galen St., Watertown, MA 02472 USA. Telephone: (617) 923-7747. Fax: (617) 926-0144. E-mail: nmaserejian@neriscience.com

We thank T. Clarkson and E. Cernichiari from the Department of Environmental Medicine, University of Rochester School of Medicine, Rochester, New York, for their contributions in the laboratory methods and analysis.

This research was funded by a cooperative agreement (U01 DE11886) between the New England Research Institutes and the National Institute of Dental and Craniofacial Research.

The authors declare they have no competing financial interests.

Received 7 May 2007 ; accepted 11 November 2007.