Dental amalgam restorations and children's neuropsychological function: The New England children's amalgam trial

BACKGROUND: A concern persists that children's exposure to mercury vapor from dental amalgams produces neurotoxicicy. OBJECTIVE: Our goal was to compare the neuropsychological function of children, without prior exposure to dental amalgam, whose caries were repaired using either dental amalgam or mercury-free composite materials. METHODS: We conducted a randomized controlled trial involving 534 6- to 10-year-old urban and rural children who were assessed yearly for 5 years using a battery of tests of intelligence, achievement, language, memory, learning, visual-spatial skills, verbal fluency, fine motor function, problem solving, attention, and executive function. RESULTS: Although the mean urinary mercury concentration was greater among children in the amalgam group than the composite group (0.9 vs. 0.6 mu g/g creatinine), few significant differences were found between the test scores of children in the two groups. The differences found were inconsistent in direction. Analyses using two cumulative exposure indices-surface years of amalgam and urinary mercury concentration-produced similar results. CONCLUSIONS: Exposure to elemental mercury in amalgam at the levels experienced by the children who participated in the trial did not result in significant effects on neuropsychological function within the 5-year follow-up period.