Nearly 150 years since dentists started using mercury in fillings, researchers at the University of Washington School of Dentistry are beginning one of the first studies specifically aimed at determining whether such fillings are safe for children.
The study, supported by a $4.1 million grant from the National Institute of Dental Research, will be performed by UW and University of Lisbon researchers in Lisbon, Portugal, and involve testing 500 children – patients most likely to be affected by low-level mercury exposure.
Principal Investigator Timothy DeRouen, chair of Dental Public Health Sciences and professor of biostatistics at the UW, said by monitoring a wide range of possible health effects and using a well-suited study population, the study will provide the first reliable findings about the safety of mercury amalgams, a topic scientists have been debating for decades.
“This study is designed to settle the controversy over whether the most commonly-used dental material in the world, mercury amalgam, has even subtle health effects associated with its use in children,” DeRouen said.
DeRouen notes that sparse research into mercury amalgams is of concern since millions of people are being exposed to a known toxin. Yet, since dental amalgam is the least expensive, longest lasting dental filling material for chewing surfaces, banning its use without good reason would have severe consequences, including an increase in cost of dental care and, consequently, a likely decrease in dental care for the poor.
Children involved in the study will be students aged 8 to 10 enrolled in the Casa Pia School System in Lisbon, which serves disadvantaged children. The school was selected as an ideal site since children tested will have no prior exposure to levels of mercury or lead that might interfere with study results, are in need of substantial dental care and can be easily tracked during the study period. Additionally, the study will draw on the UW’s longstanding collaboration with University of Lisbon researchers, who will assist in the study.
The known effects of high-level exposure to mercury include kidney damage and a variety of neurological problems such as decreased verbal skills, insomnia, fatigue, gastrointestinal problems, muscle tremors, mood swings and memory disturbances. Little is known about health effects of low-level exposure to mercury.
To assess possible health effects on study participants, a team of UW experts in fields including dentistry, toxicology, biostatistics, oral medicine, neurology and epidemiology will administer extensive behavioral and neurological tests before and after subjects receive dental treatment either with or without mercury amalgams. Additionally, urine samples will be collected on a regular basis and examined for mercury level. The study will follow subjects for five years.
Dental amalgam, which is approximately 50 percent mercury, is the standard material used for dental restorations. Approximately 100 million persons have amalgam fillings in the United States alone. Some controversial studies have suggested dental amalgams could be the cause for various diseases, ranging from mild skin conditions to debilitating neuromuscular diseases. However, reports from the Public Health Service (1993) and Food and Drug Administration Panel (1991) found no reliable evidence suggesting a harmful effect of amalgams; although they stressed the need for research programs looking for long-term biological effects.
“Because there has been a lack of clear and consistently demonstrated health effects, dental amalgams are assumed to be safe; however, this safety issue continues to be hotly debated,” DeRouen said.
In addition to the UW School of Dentistry, the NIH awarded a similar study grant to the New England Research Institutes in Boston, Mass.